JP5617785B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine that is excellent in both heat insulation and knock resistance.

  An internal combustion engine such as a gasoline engine or a diesel engine is mainly composed of an engine block and a cylinder head, and its combustion chamber has a bore surface of the cylinder block, a piston top surface incorporated in the bore, and a cylinder head. It is defined by the bottom surface and the bottom surfaces of the intake and exhaust valves provided in the intake and exhaust ports provided in the cylinder head. It is important to reduce the cooling loss with the increase in output required for recent internal combustion engines. As one of the measures to reduce this cooling loss, the inner wall of the combustion chamber is shielded from ceramics. A method of forming a hot film can be mentioned.

  However, the ceramics mentioned above generally have a low thermal conductivity and a high heat capacity, so that the intake efficiency decreases and knocks due to a steady increase in surface temperature (knocking abnormal combustion due to heat generated in the combustion chamber). As a result, the present situation is that it is not widely used as a coating material on the inner wall of the combustion chamber.

  For this reason, it is desirable that the thermal barrier film formed on the wall surface of the combustion chamber is made of a material having low heat conductivity and low heat capacity as well as heat resistance and heat insulation. Furthermore, in addition to the low thermal conductivity and low heat capacity, a thermal barrier film is formed from a material that can withstand repeated stresses of explosion pressure, injection pressure, thermal expansion and thermal contraction during combustion in the combustion chamber. It is desirable that the thermal barrier film is formed from a material having high adhesion to a base material such as a cylinder block.

  When knocking occurs in the internal combustion engine in which the heat insulating film with high heat insulation and low heat capacity is provided on the wall surface of the spark ignition type combustion chamber, the heat shielding film at the knocking occurrence site or its peripheral part is generated by the shock wave. There is a risk of damage.

  In the combustion chamber, in particular, a flame spreads concentrically from the vicinity of the ignition plug on the bottom surface of the cylinder head provided with the ignition plug, for example, concentrically, and knocking easily occurs at a position away from the ignition plug. In particular, the vicinity of the bore in the area on the intake valve side is the part where this knocking is most likely to occur.If knocking occurs at this part and the heat shield film in that part is damaged, the damage to the heat shield film is caused by the surrounding shield. It will proceed to the hot film.

  The reason why knocking is likely to occur in the vicinity of the bore in the region on the intake valve side is that the flame propagation speed started from the spark plug (ignition plug) becomes faster in the region on the exhaust valve side where the temperature is relatively high, Because the flame propagation speed is relatively slow in the relatively cooler intake valve area, the combustible mixture remains in the intake valve area, and this end gas is adiabatically compressed and self-ignited. This is because knocking occurs.

  Here, turning to the conventional published technique, Patent Document 1 discloses an internal combustion engine that can suppress the occurrence of knocking while adopting a heat insulating structure. Specifically, a cooling means is disposed around the combustion chamber and a heat insulating layer is disposed on an inner wall surface forming the combustion chamber, and an intake valve and an exhaust valve that open and close a port opened to the combustion chamber, and the exhaust valve In a spark ignition type internal combustion engine provided with a spark plug disposed facing the combustion chamber, the heat insulation capacity of the heat insulation layer disposed in the vicinity of the portion farthest from the spark plug at a linear distance is other than the heat insulation layer. This is lower than the heat insulating ability of the heat insulating layer disposed in the part.

  In the internal combustion engine disclosed in Patent Document 1, the heat insulation capability of the heat insulation layer disposed in the vicinity of the portion farthest from the spark plug at a linear distance is made lower than the heat insulation capability of the heat insulation layer disposed in another portion. However, considering that the flame spreads concentrically from the spark plug, knocking suppression at the midway position is sufficiently suppressed even if only the heat insulation capacity near the part farthest from the spark plug at a linear distance is lowered. It is unclear whether or not it can be achieved, and at least it is unclear whether or not the above-described problem, that is, knocking that tends to occur in the region on the intake valve side, can be effectively suppressed.

JP 2010-222984 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an internal combustion engine that is excellent in both heat insulation and knock resistance.

  In order to achieve the above object, an internal combustion engine according to the present invention includes a bottom surface of a cylinder head, bottom surfaces of an intake valve in an intake port and an exhaust valve in an exhaust port provided in the cylinder head, and a bore of a cylinder block. And a top surface of the piston sliding in the bore, a combustion chamber is formed, and a heat shielding film is formed on a part or all of the wall surface constituting the combustion chamber, and the intake piston and exhaust gas are formed on the bottom surface of the cylinder head. An internal combustion engine in which an ignition plug is positioned between pistons and faces a combustion chamber, and the intake valve is separated when the combustion chamber is divided into an intake valve side region and an exhaust valve side region with the ignition plug as a boundary. The heat insulation performance of at least a part of the heat shield film on the wall surface in the region on the side is higher than that on the heat shield film on the wall surface in the region on the exhaust valve side.

  The internal combustion engine of the present invention is intended for a spark ignition type internal combustion engine, and its combustion chamber is divided into two regions, an intake valve side region and an exhaust valve side region, with an ignition plug as a boundary, and an intake valve side region. The heat insulation performance of at least a part of the heat shield film on the wall is relatively higher than at least the heat shield film in the region on the exhaust valve side.

  The internal combustion engine may be intended for either a gasoline engine or a diesel engine, and the configuration thereof is mainly composed of an engine block and a cylinder head, as described above, and the combustion chamber of the cylinder block A bore surface, a piston top surface incorporated in the bore, a bottom surface of the cylinder head, and a bottom surface of an intake valve and an exhaust valve disposed in the cylinder head are defined.

  Here, “at least a part of the wall surface of the intake valve side region” means the region on the intake valve side of the top surface of the piston, in addition to the region on the intake valve side of the bottom surface of the cylinder head and the bottom surface of the intake valve, In addition to these, it means that the area on the intake valve side of the bore surface is included.

  Examples of the base material constituting the combustion chamber of the internal combustion engine include aluminum and its alloys, titanium and its alloys, and the thermal barrier film can be formed from an anodized film. For example, when a thermal barrier film made of an anodized film is formed on a wall surface made of aluminum or an alloy thereof, the anodized film becomes anodized.

  Here, as an embodiment of “relatively higher heat insulation performance of at least part of the heat shield film on the wall surface of the intake valve side region than at least the heat shield film of the region on the exhaust valve side”, The following two forms can be mentioned.

  One form is that the thermal conductivity of the heat shield film in the region on the intake valve side is lower and the volume specific heat is higher than the heat shield film in the region on the exhaust valve side.

  Simply lowering the thermal conductivity alone will increase the temperature fluctuation range, and the wall temperature during combustion will rise too much compared to other parts, making it difficult to balance the combustion rate. In addition, the condition is that the volume specific heat is increased. By increasing the volume specific heat, the temperature fluctuation range can be kept constant, and the combustion speed balance with other parts can be kept. Here, “temperature fluctuation” refers to the followability of the wall surface temperature to the gas temperature in the combustion chamber. By keeping the temperature fluctuation range as constant as possible, the followability to the gas temperature is improved and the combustion is performed. It becomes easy to balance speed.

  In another embodiment, the heat shield film in the region on the intake valve side is thicker than the heat shield film in the region on the exhaust valve side.

  By simply increasing the thickness of the heat shield film on the intake valve side, the heat insulation performance can be relatively improved.

  Regardless of the form of the heat shield film described above, the heat insulation performance of a part or all of the heat shield film in the region on the intake valve side of the wall surface constituting the combustion chamber is the heat shield film in the region on the exhaust valve side. It is possible to adjust the wall surface temperature in the intake valve side region to the same level as the wall surface temperature in the exhaust valve side region by making it relatively higher than The propagation speed can be made uniform. Since the flame propagation speed is uniform throughout the combustion chamber in this way, combustion within the combustion chamber is completed simultaneously and more quickly, and end-gas self-ignition hardly occurs and knocking is suppressed. Will be.

  As can be understood from the above description, according to the internal combustion engine of the present invention, the heat insulation performance of at least a part of the thermal barrier film in the wall surface in the region closer to the intake valve than the spark plug is at least in the region on the exhaust valve side. The wall surface temperature in the intake valve side region and the wall surface temperature in the exhaust valve side region can be adjusted to approximately the same temperature by being higher than the heat shield film on the wall surface. The flame propagation speed over the entire region is made as uniform as possible, and combustion in the combustion chamber is completed simultaneously and more quickly in the entire region, so that knocking is effectively suppressed.

(A) is a longitudinal cross-sectional view of one Embodiment of the internal combustion engine of this invention, (b) is b arrow line view of FIG. 1a. It is a longitudinal cross-sectional view of other embodiment of a thermal barrier film. (A) is a longitudinal cross-sectional view of other embodiment of the internal combustion engine of this invention, (b) is b arrow line view of FIG. 3a. It is a longitudinal cross-sectional view of further another embodiment of the internal combustion engine of the present invention. It is a graph which shows the physical property of the thermal barrier film formed in the wall surface of the combustion chamber of the internal combustion engine of this invention.

Hereinafter, an embodiment of an internal combustion engine of the present invention will be described with reference to the drawings.
(Embodiment 1 of an internal combustion engine)
FIG. 1a is a longitudinal sectional view of Embodiment 1 of an internal combustion engine, and FIG. 1b shows a view (plan view of a piston top surface) in FIG.

  The illustrated internal combustion engine 10 is intended for a gasoline engine, a cylinder block 2 in which a cooling water jacket (not shown) is formed, a cylinder head 1 disposed on the cylinder block 2, An exhaust port 1b and an intake port 1c defined in the cylinder head 1, an exhaust valve 1d and an intake valve 1e mounted so as to be movable up and down in an opening facing the combustion chamber NS, and a central position of a bottom surface 1a of the cylinder head 1 Alternatively, it is generally composed of a spark plug 4 facing the combustion chamber NS at a substantially central position and a piston 3 formed so as to be movable up and down from the lower opening of the cylinder block 2. Of course, the internal combustion engine of the present invention may be intended for a diesel engine.

  Each component constituting the internal combustion engine 10 is made of aluminum or an alloy thereof. The constituent member may be formed of a material other than aluminum or an alloy thereof, and the surface of the constituent member may be aluminized with aluminum or an alloy thereof.

A combustion chamber NS is defined by the bore surface 2 a of the cylinder block 2, the bottom surface 1 a of the cylinder head 1, and the top surface 3 a of the piston 3 that constitute the internal combustion engine 10. Here, the combustion chamber NS as a boundary boundary line L which passes through the spark plug 4, has been tentatively divided into regions A _EX between the region A _IN of the intake valve side exhaust valve side. The boundary line L is set at a position where knocking can be more effectively suppressed according to the position of the ignition plug 4 and the number and position of the intake valve 1e and the exhaust valve 1d. .

In the internal combustion engine 10 shown in the figure, a heat shield film 5 is formed on the top surface 3 a of the piston 3. More specifically, of the top surface 3a of the piston 3, and Saeginetsumaku 5 is composed of Saeginetsumaku 5b regions A _EX of Saeginetsumaku 5a and the exhaust valve side of the area A _IN of the intake valve side The heat insulation performance of the heat shield film 5a is adjusted to be relatively higher than that of the heat shield film 5b.

  Regarding the heat insulation performance, the thermal conductivity of the heat shield film 5a in the region on the intake valve side is lower and the volume specific heat is higher than the heat shield film 5b in the region on the exhaust valve side.

Thus in addition to the thermal conductivity of the Saeginetsumaku 5a relatively low, by relatively high volume specific heat, Saeginetsumaku 5a regions A _IN of the intake valve side in the combustion chamber NS And the temperature fluctuation width of the heat shield film 5b in the region A _EX on the exhaust valve side can be kept constant, and the balance of the combustion speed between them can be kept.

  Here, regarding the followability to temperature fluctuation, in the state where the wall surface of a metal base material such as aluminum is exposed without the presence of a thermal barrier film, one cycle of the combustion chamber during engine operation such as intake, compression, combustion, and exhaust is performed. In this case, the wall surface temperature is kept almost constant in the range of about 100 to 200 ° C., and even if the gas temperature changes rapidly in the combustion chamber, the wall surface temperature cannot follow this change. On the other hand, when a thermal barrier film made of ceramics such as zirconia is formed on the wall surface, the wall surface temperature also rises with changes in gas temperature (for example, an increase in gas temperature), but the wall surface temperature is It does not lead to change so as to follow the change in gas temperature.

  On the other hand, in the internal combustion engine 10 provided with the illustrated heat shield film 5 provided on the wall surface of the combustion chamber NS to reduce the heat loss, the followability to a sudden change in the gas temperature is improved. It is evaluated as the followability to the temperature fluctuation of the wall surface with the followability to the temperature change.

  If a thermal barrier film with low thermal conductivity and low heat capacity is formed on at least a part of the wall facing the combustion chamber NS, the temperature of the surface of the thermal barrier film will follow the change of the combustion gas temperature in one cycle. As a result, the temperature difference between the combustion gas temperature and the wall surface temperature is reduced as compared with the case where there is no thermal barrier film, and the heat loss is reduced. This decrease in heat loss results in an increase in piston work and an increase in exhaust temperature, and the increase in piston work leads to improved fuel efficiency.

  Here, it is preferable that the thickness of the anodic oxide coating 5 which is a heat shielding film is, for example, in the range of 100 to 500 μm. If the thickness of the anodic oxide coating having the heat insulation performance is less than 100 μm, the temperature rise of the coating surface during the combustion cycle is insufficient and the heat insulation performance becomes insufficient, and a sufficient fuel economy improvement effect cannot be expected. On the other hand, if the thickness of the anodic oxide coating exceeds 500 μm, the heat capacity will be increased, and the anodic oxide coating itself will easily accumulate heat. However, the characteristic that the temperature of the heat shield film follows the gas temperature in the combustion chamber is hindered.

  Next, a method for forming the anodic oxide coating 5 on the top surface 3a of the piston 3 will be outlined. First, of the top surface 3a of the piston 3, masking is performed on the heat shield film 5b in the exhaust valve side region, and the acidic electrolyte for the heat shield film 5a is accommodated in a container (not shown). 3a is immersed here to serve as an anode. Next, a separate cathode is formed in the acidic electrolytic solution, and the acidic electrolytic solution is sequentially discharged and injected to circulate the acidic electrolytic solution, thereby forming the thermal barrier film 5a while promoting anodized growth. Next, the masking is peeled off, the formed heat shield film 5a is masked and immersed in an acidic electrolyte for the heat shield film 5b, and the heat shield film 5b is formed by the same method as that for the heat shield film 5a. Thus, the heat shield film 5 including the heat shield film 5 a on the intake valve side and the heat shield film 5 b on the exhaust valve side is formed on the top surface 3 a of the piston 3.

  Further, as another embodiment of the heat shield film, a heat shield film 5a on the intake valve side as compared with the heat shield film 5b '(thickness t2) on the exhaust valve side as in the heat shield film 5A shown in FIG. The thickness t1 of 'may be relatively thick.

  In the formation of the heat shield film 5A shown in the figure, the same acidic electrolyte can be used when forming both the heat shield films 5a 'and 5b', and the alumite growth of the heat shield film 5a 'is relatively promoted. By increasing the thickness, the thermal barrier film 5A can be obtained.

  In addition to the anodized film, the heat shield film formed on the wall surface facing the combustion chamber NS may be a heat shield film formed by laminating a number of hollow beads with, for example, a silica-based adhesive. .

(Embodiment 2 of an internal combustion engine)
FIG. 3a shows a longitudinal sectional view of the second embodiment of the internal combustion engine, and FIG. 3b shows a view (a plan view of the bottom surface of the cylinder head) in FIG.

  In the internal combustion engine 10A shown in the figure, a thermal barrier film 5 made of an alumite film is formed on the top surface 3a of the piston 3 in the same manner as the internal combustion engine 10 shown in FIG. 1 among the wall faces facing the combustion chamber NS. In addition, a heat shield film 6 made of an alumite film is formed on the bottom surface 1a of the cylinder head 1, and a heat shield film 7 made of an alumite film is formed on the bottom surfaces of the exhaust valve 1d and the intake valve 1e.

More specifically, of the bottom surface 1a of the cylinder head 1, the intake valve side in the region A _IN Saeginetsumaku 6a to, Saeginetsumaku 6b is formed in the region A _EX of the exhaust valve side, the intake valve 1e A heat shield film 7a is formed on the bottom surface and a heat shield film 7b is formed on the bottom surface of the exhaust valve 1d so that the heat insulation performance of the heat shield films 6a and 7a is relatively higher than that of the heat shield films 6b and 7b. It has been adjusted.

  That is, the heat conductivity of the heat shield films 6a and 7a in the intake valve side region is adjusted to be lower and the volume specific heat is higher than the heat shield films 6b and 7b in the exhaust valve side region. However, as shown in FIG. 2, the heat insulating films 6a and 7a may be made thicker than the heat insulating films 6b and 7b to relatively increase the heat insulating performance.

  In the internal combustion engine 10A, in addition to the top surface 3a of the piston 3, the bottom surface 1a of the cylinder head 1 is formed with a heat insulating film having high heat insulation performance in the region on the intake valve side compared to the region on the exhaust valve side. Therefore, the knocking suppression effect is higher than that of the internal combustion engine 10.

(Third embodiment of internal combustion engine)
FIG. 4 shows a longitudinal sectional view of Embodiment 3 of the internal combustion engine. The internal combustion engine 10B shown in the figure has a heat shield film 8 made of an alumite film on the bore surface 2a of the cylinder block 2 on the wall surface facing the combustion chamber NS in addition to the heat shield film described in the internal combustion engine 10A. It is those which are formed, more specifically, of the bore surface 2a, Saeginetsumaku 8a in the region a _iN of the intake valve side, Saeginetsumaku 8b is formed in the region a _EX of the exhaust valve side ing.

In all of the wall facing this way in the combustion chamber NS of the engine 10B, a thermal barrier heat insulating performance is high Saeginetsumaku region A _IN of the intake valve side than the thermal barrier film in a region A _EX of the exhaust valve side By forming the film, it is possible to make the temperature of all the walls facing the combustion chamber NS of the internal combustion engine 10B as uniform as possible, thereby achieving a uniform combustion rate in the combustion chamber NS. As a result, an extremely high knocking suppression effect can be achieved.

  Here, with reference to FIG. 5, the material property values targeted by the heat shielding film formed on the wall surface facing the combustion chamber of the internal combustion engine of the present invention will be considered.

  This figure shows a coordinate system with the vertical axis representing the thermal conductivity and the horizontal axis representing the volume specific heat.It consists of aluminum and iron that can form the base material that constitutes the wall facing the combustion chamber, and a conventional thermal barrier film. A certain zirconia (an example of a ceramic film), and further, physical properties of air are plotted as a reference.

In addition, the wall temperature fluctuation ranges of 200 ° C, 500 ° C, 1000 ° C, and 1200 ° C on the wall surface are shown in the figure.
And when the thermal barrier film of a ceramic material (zirconia) is formed, it can be seen that the volume specific heat is larger although the thermal conductivity is lower than when the metal base material on the wall surface is exposed.

On the other hand, among the heat shield films formed on the wall facing the combustion chamber of the internal combustion engine of the present invention, the physical property value of the heat shield film formed in the region on the exhaust valve side is a plot P. in in the 500 ° C. of the wall temperature variation width on the line, the thermal conductivity is 0.5 W / mK, volume specific heat is 300kJ / m ³ K.

  First, it can be seen that the thermal conductivity of the thermal barrier film formed in the region on the exhaust valve side is much lower than that of a ceramic thermal barrier film having a conventional structure.

In this example, the heat shield film formed in the exhaust valve side region and the heat shield film formed in the intake valve side region are placed on the same wall temperature fluctuation width line, so that Concerning the physical properties of the thermal barrier film formed in the region, by reducing the thermal conductivity to 0.1 W / mK and increasing the volume specific heat to 1500 kJ / m ³ K, the temperature fluctuation width of the entire wall facing the combustion chamber is constant. (In this case, both the intake valve side and the exhaust valve side have a wall temperature fluctuation range of 500 ° C.), and the entire wall surface is an internal combustion engine with a good balance of combustion speed.

  In addition, simply reducing the thermal conductivity of the thermal insulation film on the intake valve side to 0.1 W / mK only shifts the physical properties of the thermal insulation film on the intake valve side to the wall temperature fluctuation line at 1000 ° C. The wall surface temperature will be too high compared to the heat shield film on the exhaust valve side, and it will be difficult to balance the combustion speed between the two, so in addition to lowering the thermal conductivity, increasing the volume specific heat It can be understood from FIG.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Cylinder head, 1a ... Bottom surface, 1b ... Exhaust port, 1c ... Intake port, 1d ... Exhaust valve, 1e ... Intake valve, 2 ... Cylinder block, 2a ... Bore surface, 3 ... Piston, 3a ... Piston top surface, 4 ... Spark plugs, 5, 6, 7, 8 ... Thermal barrier films (anodized coatings, anodized coatings), 5a, 5a ', 6a, 7a, 8a ... Thermal barrier films on the intake valve side, 5b, 5b', 6b, 7b, 8b ... heat shield film on the exhaust valve side, NS ... combustion chamber, L ... boundary line

Claims (6)

A bottom surface of the cylinder head, a bottom surface of each of the intake valve in the intake port and the exhaust valve in the exhaust port established in the cylinder head, a bore of the cylinder block, and a top surface of the piston sliding in the bore A combustion chamber is formed, a thermal barrier film is formed on part or all of the wall surface constituting the combustion chamber, and a spark plug is positioned between the intake piston and the exhaust piston on the bottom surface of the cylinder head and faces the combustion chamber. An internal combustion engine
When the combustion chamber is divided into a region on the intake valve side and a region on the exhaust valve side with the spark plug as a boundary, the heat insulation performance of at least a part of the wall surface of the wall in the region on the intake valve side is at least on the exhaust valve side An internal combustion engine that is higher than the thermal barrier film on the wall surface in the region.   The internal combustion engine according to claim 1, wherein the at least part of the wall surface is a top surface of a piston.   2. The internal combustion engine according to claim 1, wherein the at least some of the wall surfaces are a top surface of a piston, a bottom surface of a cylinder head, and a bottom surface of an intake valve.   The thermal conductivity of the heat shield film in the region on the intake valve side is lower and the volume specific heat is higher than the heat shield film in the region on the exhaust valve side. Internal combustion engine.   The internal combustion engine according to any one of claims 1 to 3, wherein a film thickness of the heat shield film in the region on the intake valve side is thicker than a heat shield film in the region on the exhaust valve side.   The internal combustion engine according to any one of claims 1 to 5, wherein the thermal barrier film is an alumite coating.

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