Sludge adhesion inhibiting structure for internal combustion engine

A sludge adhesion inhibiting structure for an internal combustion engine according to the present invention is characterized in that a sludge inhibiting layer inhibiting generation or adhesion of sludge is formed on a surface of an area inside the internal combustion engine into which oil as a liquid does not always spread and which is contacted by oil mist as a gas. Preferably, the sludge inhibiting layer is made up of a solid alkali substance. Furthermore, the sludge inhibiting layer is provided in a head cover and formed on an inner surface of an oil separator chamber separating the oil from a blow-by gas.

TECHNICAL FIELD

The present invention relates to a sludge adhesion inhibiting structure for an internal combustion engine, and in particular, to a structure that inhibits possible adhesion of sludge to a particular area of the internal combustion engine.

BACKGROUND ART

It is known that in an internal combustion engine of an automobile or the like, oil as a lubricant may be deteriorated to generate sludge, which may affect relevant parts of the engine in various ways. The sludge contains olefin contained in the oil, NOx and SOx contained in a blow-by gas, and water as main components. The main components react in the presence of heat or acid to change to a precursor such as a sludge precursor or a sludge binder. Thus, the sludge is generated. The sludge appears to be mud or a slime-like substance. The sludge may disadvantageously deposit in, for example, a passage in the internal combustion engine to close the passage.

In particular, water generated inside the internal combustion engine by condensation or the like reacts with NOx and SOx contained in the blow-by gas to generate an acid substance. The acid substance serves as a catalyst for generation of sludge. Mixture of the acid substance into the oil promotes the generation of sludge, accelerates the deterioration of the oil, and degrades the functions of the lubricant.

In connection with the generation of the acid substance, conventional means adds an additive called a metal cleaning agent to the lubricant to neutralize the acid substance generated in the oil to inhibit the generation of sludge. Alternatively, a weak cationic surfactant is added to the oil to enhance the function of the oil for dispersion of the oil in the sludge (see, for example, Japanese Patent Application Laid-Open No. H9-13066(1997)).

The conventional art neutralizes and removes the acid substance contained in the oil to inhibit the generation of sludge. In other words, the main objective of the conventional art is to reduce the amount of sludge dispersed or diffused in the oil to inhibit the deterioration of the oil.

On the other hand, the sludge may disadvantageously adhere to or deposit in an area inside the internal combustion engine into which the oil does not always spread. That is, in an area into which the oil always spreads, even if sludge is generated, the sludge is washed away by the oil and is thus unlikely to adhere or deposit. However, in the area into which the oil does not always spread, the effect of washing away the sludge is not expected to work. Consequently, the adhesion or deposition may disadvantageously occur.

In view of these problems, an object of the present invention is to provide a sludge adhesion inhibiting structure for an internal combustion engine which can prevent the generation or adhesion of sludge in the area into which the oil does not always spread.

DISCLOSURE OF THE INVENTION

The present invention provides a sludge adhesion inhibiting structure for an internal combustion engine characterized in that a sludge inhibiting layer inhibiting generation or adhesion of sludge is formed on a surface of an area inside the internal combustion engine into which oil as a liquid does not always spread and which is contacted by oil mist as a gas.

According to the present invention, the sludge inhibiting layer enables inhibition of generation or adhesion of sludge on or to the surface of the area into which the oil does not always spread and which is contacted by the oil mist.

Preferably, the surface of the area is an inner surface of an area having an outer surface exposed to outside air.

As described above, water reacts with NOx and SOx to generate an acid substance, which then serves as a catalyst promoting the generation of sludge. On the other hand, condensed water is likely to be generated on the inner surface of the area having the outer surface exposed to the outside air. Thus, sludge is likely to be generated on or adhere to the inner surface. However, according to the second invention, the sludge inhibiting layer is formed on the inner surface of the area. This enables the effective inhibition of generation or adhesion of sludge on or to the surface on which the generation or adhesion of the sludge is inherently likely to occur.

Preferably, the surface of the area is an inner surface of a head cover covering a cylinder head.

Preferably, the surface of the area is an inner surface of a chain cover covering a timing chain.

Preferably, the surface of the area is an inner surface of an oil separator chamber separating oil from a blow-by gas.

For all of the head cover, the chain cover, and the oil separator chamber, the outer surface is likely to be exposed to the outside air and thus cooled. Consequently, condensed water is thus likely to be generated inside the head cover, the chain cover, and the oil separator chamber. Thus, for the head cover, the chain cover, and the oil separator chamber, the sludge inhibiting layer is provided on at least one of the inner surfaces. This enables the inhibition of generation or adhesion of sludge on or to the surface on which the generation or adhesion of sludge is inherently likely to occur.

Preferably, the sludge inhibiting layer comprises a solid alkali substance.

Thus, an acid substance generated on the surface of the area can be allowed to react chemically with the alkali substance for neutralization. Consequently, the acid substance, serving as a catalyst promoting the generation of sludge, can be neutralized and removed. Therefore, the generation or adhesion of sludge can be inhibited.

Preferably, the alkali substance comprises calcium carbonate.

Preferably, a surface of the sludge inhibiting layer is formed to have recesses and protrusions.

Compared to a construction in which the surface of the sludge inhibiting layer is flat, the present construction enables a substantial increase in the surface area of the sludge inhibiting layer, promoting a neutralizing reaction of the acid substance.

Preferably, the sludge inhibiting layer comprises at least one of an aggregate of a large number of particles and a foaming substance.

In this case, the contact area or reaction area between the sludge inhibiting layer and the acid substance can be increased to promote the neutralizing reaction of the acid substance. Furthermore, the acid substance can be physically absorbed or adsorbed and removed.

Preferably, the sludge inhibiting layer is formed by coating.

Thus, the sludge inhibiting layer can be relatively easily formed.

The present invention is very effective for inhibiting the generation, adhesion, or deposition of sludge on the area into which the oil does not always spread.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1shows an internal combustion engine to which the present invention is applied, particularly a blow-by gas circulating apparatus for the internal combustion engine. As shown inFIG. 1, an engine1includes a cylinder block2, a piston3, a crank case4, a cylinder head5, a head cover6that covers the cylinder head5from above, and an oil pan7. The blow-by gas is a gas leaking out into the crank case4through the gap between a piston ring and a cylinder bore in the cylinder block2. The blow-by gas contains a large amount of hydrocarbon and moisture. Thus, an excessively large amount of blow-by gas causes engine oil to be deteriorated early or causes the interior of the engine to be rusted. Furthermore, releasing the blow-by gas, containing hydrocarbon, to the atmosphere intact is not environmentally preferable. Thus, the blow-by gas is forcibly returned to an intake system through a path described below, utilizing an intake negative pressure. Arrows in the figure show the flow of the blow-by gas and fresh air observed when a light load is imposed on the engine.

An intake passage8includes a throttle valve9. A part of the intake passage8located downstream of the throttle valve9communicates with the interior of the head cover6via a PCV passage10. Here, PCV is an abbreviation of a Positive Crankcase Ventilation. A part of the intake passage8located upstream of the throttle valve9communicates with the head cover6via an air passage11. A PCV valve12is provided in the PCV passage10to open and close the PCV passage10. The PCV valve12is opened and closed depending on the magnitude of an intake negative pressure, to change flow rate. In the present embodiment, the PCV valve12is fixedly provided on the head cover6.

An oil drop passage13is formed in the cylinder block2and the cylinder head5to allow the interior of the head cover6to communicate with the interior of the crank case4. The oil drop passage13according to the present embodiment allows oil remaining on the cylinder head5after lubrication of a valve operating system to fall onto the oil pan7. The oil drop passage13also allows the blow-by gas in the crank case4to move upward to the interior of the head cover6. The blow-by gas moving upward from the crank case4to the head cover6contains oil mist generated by agitation and evaporation of the oil in the crank case4.

As shown inFIG. 1, while a light load is imposed on the engine, the PCV valve12is opened to return the blow-by gas in the crank case4to the intake passage8through the oil drop passage13, the interior of the head cover6, and the PCV passage10in this order. The blow-by gas is thereafter combusted in a combustion chamber in the cylinder block2. On the other hand, air is introduced into the head cover6through an air passage11. The air appropriately dilutes the blow-by gas in the head cover6.

On the other hand, although not shown in the drawings, when a heavy load is imposed on the engine, the PCV valve12is closed to return the blow-by gas in the head cover6to the intake passage8through the air passage11.

As described above, the blow-by gas in the crank case4is introduced into the head cover6and then returned to the intake passage8for combustion. The blow-by gas contains not only HC (HydroCarbon) that is a fuel component, NOx and SOx contained in a combusted gas, and moisture but also the oil mist, that is, a gas generated by the agitation and evaporation of the oil in the crank case4. Thus, when the blow-by gas is simply circulated to the intake side, the oil is simultaneously combusted. Consequently, oil consumption increases, and the combusted oil may disadvantageously produce white fume.

Thus, an oil separator chamber, described below in detail, is partitioned and formed in the head cover6to separate the oil from the blow-by gas. The oil separator chamber allows the oil to be separated from the blow-by gas and collected before the blow-by gas is returned to the intake system. As a result, the above-described problem can be solved.

FIG. 2shows the appearance of the engine1. As shown inFIG. 2, at one end of the engine1in the direction of a crank shaft, two cam shafts, that is, an intake side cam shaft14I and an exhaust side cam shaft14E, are rotationally driven by the crank shaft (not shown in the drawings) via a timing chain15. The timing chain15is supplied with oil injected by an oil jet16provided in the cylinder block2. The timing chain15is laterally covered with a chain cover17. The chain cover17is fastened to the cylinder block2and the crank case4. The head cover6is partly fastened to the upper end surface of the chain cover17. The oil pan7is partly fastened to the lower end surface of the chain cover17. Thus, a space partitioned from the exterior is formed in the chain cover17.

The head cover6has plug holes20provided along the longitudinal direction thereof and the number of which is the same as that of cylinders (in the present embodiment, four cylinders), and an oiling port21that is openably closed by a cap (not shown in the drawings). The PCV valve12is attached to the head cover6, and a pipe joint22to which piping making up the air passage11is attached is also attached to the head cover6.

FIG. 3is a perspective view of the head cover6as viewed from behind. As shown inFIG. 3, two grooves23A and23B are formed in the upper part of the rear side of the head cover6to partition and form the oil separator chamber. The grooves23A and23B extend in the longitudinal direction L of the head cover6and are formed on one side and the other side, respectively, of the plug holes20in a width direction W. The side in the width direction W on which the groove23A is formed is hereinafter referred to as the “front” side. The side in the width direction W on which the groove23B is formed is hereinafter referred to as the “rear” side. These directions correspond to the front-back direction of the vehicle observed when the engine1is transversely placed in the vehicle as shown inFIG. 2.

The front and rear grooves23A and23B are closed by two substantially rectangular baffle plates24A and24B as shown inFIG. 4. Thus, one oil separator chamber25A partitioned by the groove23A and the baffle plate24A is formed in the front of the head cover6. One oil separator chamber25B partitioned by the groove23B and the baffle plate24B is formed in the rear of the head cover6. The front and rear oil separator chambers25A and25B are separate from and independent of each other.

The baffle plates24A and24B are inverted in both vertical direction and lateral direction. The peripheral parts of the baffle plates24A and24B are joined to junction surfaces26A and26B, respectively, formed on the peripheral parts of the grooves23A and23B in the head cover6and shaped like rectangular frames. The baffle plates24A and24B are then fixed to the head cover6by fastening means such as welding or bolting. The baffle plates24A and24B are aligned with each other using aligning pins27A and27B provided on the junction surfaces26A and26B, respectively, and aligning holes28A and28B formed in the baffle plates24A and24B, respectively. The oil separator chambers25A and25B thus formed are essentially closed spaces except for a gas inlet and a gas outlet described below.

In the head cover6, a plurality of baffle boards29A and29B are integrally provided upright at the bottom positions of the grooves23A and23B at predetermined intervals in the longitudinal direction. A plurality of baffle boards30A and30B are also provided upright on the top surfaces of the baffle plates24A and24B, respectively, at predetermined intervals in the longitudinal direction. Referring toFIG. 5, the upper and lower baffle boards29A,29B and30A,30B are alternately arranged in the longitudinal direction L when the baffle plates24A and24B are assembled together. Thus, a meandering passage is defined through which the blow-by gas flows in the longitudinal direction L. Consequently, while flowing in the longitudinal direction of the oil separator chambers25A and25B, the blow-by gas is bent, thus promoting the separation of the oil from the blow-by gas. Various passage structures for the oil separator chamber are known. Besides the vertically meandering structure, any of the following may be used: a laterally meandering structure, a structure obtained by combining the vertically meandering structure and the laterally meandering structure, and a more complicated labyrinth structure. Regardless of whichever passage structure is adopted, the present invention is applicable.

As shown inFIG. 3, in the front oil separator chamber25A, an air entry31A is formed at a right end surface of the groove23A. The air entry31A is connected to the pipe joint22to serve as an air intake port. Furthermore, as shown inFIG. 4, an air outlet hole32A is formed at the left end (the right end inFIG. 4) of the baffle plate24A in the attached state.

Thus, to be introduced into the head cover6, air flows, as shown by white arrows inFIGS. 3 and 4, first from the air entry31A into the front oil separator chamber25A, then from right to left (inFIGS. 3 and 4) in the front oil separator chamber25A, and finally out from the outlet hole32A. Furthermore, with a heavy load imposed on the engine, when the blow-by gas is returned to the intake side through the front oil separator chamber25A, the flows direction is reversed. The blow-by gas flows from the outlet hole32A into the oil separator chamber25A and then from left to right (inFIGS. 3 and 4) in the oil separator chamber25A. At this time, the oil is separated from the blow-by gas. The blow-by gas from which the oil has been separated flows out from the air entry31A to the air passage11. The separated oil is dropped from the outlet hole32A.

On the other hand, in the rear oil separator chamber25B, as shown inFIG. 4, a blow-by gas inlet groove31B is formed at the right end (inFIG. 4, the left end) of the baffle plate24B in the attached state. The inlet groove31B also serves as a drop hole for the oil collected in the oil separator chamber25B. Furthermore, as shown inFIG. 3, an outlet hole32B for the blow-by gas flowing backward is formed at the left end of the groove23B. The outlet hole32B is connected to the PCV valve12.

Thus, to return to the intake side, the blow-by gas flows, as shown by black arrows inFIGS. 3 and 4, first from the inlet groove31B into the rear oil separator chamber25B and then from right to left in the rear oil separator chamber25B. At this time, the oil is separated from the blow-by gas. The blow-by gas from which the oil has been separated flows out from the outlet hole32B to the PCV passage10. The separated oil is dropped from the inlet hole31B.

The oil mist as a gas contained in the blow-by gas is present in the oil separator chambers25A and25B. The inner walls of the oil separator chambers25A and25B are contacted by the oil mist. However, the oil does not always spread into the oil separator chambers25A and25B. In other words, the oil is not positively allowed to flow through the oil separator chambers25A and25B. Thus, sludge is likely to be generated and to adhere to or deposit on the inner surfaces of the oil separator chambers25A and25B.

More specifically, NOx and SOx contained in the blow-by gas reacts with water resulting from condensation to generate an acid substance. The acid substance serves as a catalyst for the generation of sludge. On the other hand, the blow-by gas in the oil separator chambers25A and25B contains NOx and SOx. Furthermore, transmitting heat from the engine to the head cover6is difficult. The outer surface of the head cover6is exposed to outside air and cooled by cooling wind. Thus, condensed water is likely to be generated on the inner surface of the head cover6. Consequently, an acid substance is likely to be generated in the oil separator chambers25A and25B. As a result, sludge is likely to be generated and the adhesion or deposition thereof is likely to occur. Additionally, the oil is not positively allowed to flow through the oil separator chambers25A and25B. Thus, the sludge generated is not expected to be washed away.

When the sludge adheres to or deposit on the inner surfaces of the oil separator chambers25A and25B, the blow-by gas passages formed in the oil separator chambers25A and25B are substantially closed, thus degrading oil separation performance. Consequently, a large amount of oil mist in the blow-by gas is returned to the intake side. This disadvantageously increases the oil consumption and causes white fume to be generated as a result of combustion of the oil.

Thus, in the present embodiment, to inhibit sludge from being generated in or adhering to an area such as the oil separator chambers25A and25B into which the oil does not essentially spread, a sludge inhibiting layer is formed on the surface of the area. The sludge inhibiting layer is shown by dotted parts inFIGS. 3 and 4.

The sludge inhibiting layer is preferably made up of a solid alkali substance. For example, calcium carbonate (CaCO3) is used as the alkali substance. For example, in the rear oil separator chamber25B, a sludge inhibiting layer35B is formed on the bottom surface of the groove23B, which corresponds to the inner surface of the head cover6, and on the top surface of the baffle plate24B. That is, as also shown inFIG. 5, the sludge inhibiting layer is formed on the top surface (ceiling layer)36B and bottom surface (floor surface)37B in the oil separator chamber25B.

In the present embodiment, the sludge inhibiting layer35B is formed all over the top surface36B and bottom surface37B in the oil separator chamber25B but may be provided exclusively on a part of the top surface36B and bottom surface37B. The formation of the sludge inhibiting layer35B reduces the area of the passages in the chambers by an amount corresponding to the thickness of the sludge inhibiting layer35B. To minimize the reduction in passage area, the present embodiment avoids forming the sludge inhibiting layer35B on the baffle boards29B and30B. However, forming the sludge inhibiting layer35B on the baffle boards29B and30B is optional. As shown inFIG. 4, the sludge inhibiting layer is not formed in the peripheral part of the top surface of the baffle plate24B, which part is joined to the junction surfaces26A and26B of the head cover6.

The top surface36B of the oil separator chamber25B is located on the back of or inside the outer surface of the head cover, which is exposed to the outside air. Thus, as shown by dotted lines inFIG. 5, water M is likely to be generated on the top surface36B by condensation and then to fall onto the bottom surface37B. Then, as a result of the reaction between the water M and NOx and SOx, an acid substance is likely to be generated on the top surface36B and the bottom surface37B. However, in the present embodiment, a sludge inhibiting layer35A is formed on the top surface36B and the bottom surface37B. Thus, the acid substance generated on the top surface36B and the bottom surface37B can be effectively neutralized, thus inhibiting the generation and adhesion of sludge.

On the other hand, the front oil separator chamber25A is similarly constructed. The sludge inhibiting layer35A is formed only all over the top surface (ceiling surface)36A and bottom surface (floor surface)37A of the oil separator chamber25A.

As described above, the sludge inhibiting layers35A and35B, made up of the alkali substance, is provided on the inner surfaces of the oil separator chambers25A and25B, respectively, into which the oil does not always spread and which is contacted by the oil mist. Then, the acid substance generated can be allowed to reach with the alkali substance and thus neutralized. This enables removal of the acid substance, which promotes the generation of sludge, thus allowing inhibition of generation and adhesion or deposition of sludge.

Furthermore, the acid substance generated is neutralized and removed. Thus, simultaneously with the inhibition of generation and adhesion or deposition of sludge, possible dissolution of the acid substance into the oil can be inhibited, which may deteriorate the oil.

In the present embodiment, as shown inFIG. 3, a sludge inhibiting layer35C is also formed on a part of the inner surface of the head cover other than the front and rear oil separator chambers25A and25B. The head cover6is likely to be entirely cooled. Thus, the sludge inhibiting layer35C is preferably formed on the inner surface of the head cover except for the front and rear oil separator chambers25A and25B, as in the case of the present embodiment.

As is appreciated from the above description, in the present embodiment, the sludge inhibiting layer, which neutralizes the acid substance, is provided on the surface of the area into which the oil does not always spread and which is contacted by the oil mist. Thus, the present embodiment is essentially different from such a conventional technique as described in Japanese Patent Application Laid-Open No. H9-13066(1997) in which an additive is mixed into oil in order to neutralize an acid substance mixed into the oil.

Examples of a method for forming sludge inhibition layers35A and35B will be described below. For example, as shown inFIG. 6A, a large number of particles38made up of an alkali substance are distributively arranged on a target surface. The particles are fixedly bonded to the target surface39with an adhesive. Thus, the sludge inhibiting layers35A and35B are made up of an aggregate of the large number of particles. In the illustrated example, the particles38are solid. However, the particles38may be hollow. Another method is as follows. As shown inFIG. 6B, the alkali substance is dispersed in a solution, which is then coated on the target surface in the form of foam or mousse. The solution is then dried to immobilize the alkali substance42to the target surface39. In this case, the sludge inhibiting layers35A and35B are made up of a foaming substance. Yet another method is as follows. As shown inFIG. 6C, a plate41(for example, a pumice plate) of an alkali substance with a large number of holes40formed inside is produced and then fixed to the target surface39. Also in this case, the sludge inhibiting layers35A and35B are made up of a foaming substance. Still another method is as follows. As shown inFIG. 6D, a solution with an alkali substance dispersed therein is coated on the target surface39with a brush or by spraying. The solution is then dried to immobilize the alkali substance42to the target surface39. In this case, each of the sludge inhibiting layers35A and35B is made up of a single layer with substantially no hole and can thus be relatively easily formed. The surface of each of the sludge inhibiting layers35A and35B is formed to have recesses51and protrusions52in the structures shown inFIGS. 6A to 6Cand to be flat in the structure shown inFIG. 6D. As shown inFIG. 6E, the sludge inhibition layers may also comprise a sponge53.

At least any two of the above-described methods and structures obtained by the methods can be combined together depending on the target area. In particular, compared to the structure shown inFIG. 6D, the structures shown inFIGS. 6A to 6Cenable a substantial increase in the surface area of the sludge inhibiting layers. The structures shown inFIGS. 6A to 6Calso enable an increase in the contact area or reaction area between the acid substance and the sludge inhibiting layers to promote the neutralizing reaction of the acid substance. Furthermore, the structures shown inFIGS. 6A to 6Callow the acid substance to be physically absorbed or adsorbed. Furthermore, the sludge inhibiting layers composed of a sponge53containing an alkali substance facilitates the absorption and adsorption. This also enables the removal of the acid substance and the inhibition of generation and adhesion of the sludge.

The forming methods for and the structures of the sludge inhibiting layers are not limited to those described above. For example, such a single layer structure as shown inFIG. 6Dmay be formed such that the surface thereof has recesses51and protrusions52to substantially increase the surface area thereof.

The present inventors carried out comparative experiments on the present embodiment. Then, when the sludge inhibiting layer was not provided on the top and bottom surface of the oil separator chamber, a significant amount of slime-like sludge adhered to and deposited on the top and bottom surfaces of the oil separator chamber. In contrast, when the sludge inhibiting layer was provided on the top and bottom surfaces of the oil separator chamber, almost no sludge adhered to the top and bottom surfaces of the oil separator chamber. Thus, the effects of the present invention were confirmed.

The area on which the sludge inhibiting layer is formed is not limited to the oil separator chambers or any part of the head cover other than the oil separator chambers. The sludge inhibiting layer is preferably formed in an area enclosed by an alternate long and short dash line inFIG. 2. However, the area includes not only the head cover6but also the chain cover17, particularly the upper part thereof. Like the head cover6, the chain cover17has an outer surface exposed to the outside air and is thus likely to be cooled. Furthermore, the upper part of the chain cover17is unlikely to receive heat from the engine, and the low temperature of the engine is transferred to the upper part of the chain cover17. Thus, water is likely to be generated on the chain cover17, particularly the inner surface of the upper part thereof by condensation. Furthermore, in the space inside the chain cover17, the blow-by gas contained in the oil is dissipated and the oil mist is present. Thus, the oil as a liquid is prevented from flowing. Only an amount of oil required and sufficient for lubrication is supplied by the oil jet16. Consequently, the oil does not flow in the chain cover17. Therefore, the sludge inhibiting layer is preferably formed on the chain cover17, particularly the inner surface of the upper part thereof.

In addition, the following area is suitable for the formation of the sludge inhibiting layer.FIG. 7schematically shows a dry sump engine100. The dry sump engine100does not have an oil pan serving as an oil reservoir, on an engine main body101side. Instead, oil is sucked from the bottom of the engine main body101using a scavenging pump102. The oil is then collected in a separately and independently installed oil tank103. The oil stored in the oil tank103circulatively fed to each of the circulating portions of the engine100using a feed pump109.

A blow-by gas is mixed into the oil collected in the oil tank103. Consequently, the blow-by gas and oil mist are generated in the oil tank103. Thus, as described above, an oil separator chamber104is formed at the upper end of the oil tank103to separate the oil from the blow-by gas. The sludge inhibiting layer is also preferably formed on the inner surface of the oil separator chamber104, particularly the inner top and bottom surfaces thereof. The blow-by gas from which the oil has been separated in the oil separator chamber104of the oil tank103is returned to the intake side through a PCV valve108.

Alternatively, the oil separator chamber may be installed adjacent to a crankcase or a cylinder block. Also in this case, the sludge inhibiting layer is preferably formed on the inner surface of the oil separator chamber.

The preferred embodiment of the present invention has been described. However, according to the present invention, any other embodiment may be adopted. For example, as the alkali substance making up the sludge inhibiting layer, any alkali substance other than calcium carbonate may be used. Furthermore, the sludge inhibiting layer may be formed on any of various other areas.

In the above-described embodiment, the sludge inhibiting layer is formed on each of the top and bottom surfaces of the oil separator chamber. However, the sludge inhibiting layer may be formed exclusively on the top or bottom surface of the oil separator chamber. Furthermore, in the above-described embodiment, the oil separator chamber is provided in the head cover so that the inner surface of the head cover also serves as the top surface of the oil separator chamber. However, if the oil separator chamber is not provided in the head cover, the sludge inhibiting layer may independently be formed on the inner surface of head cover. Alternatively, if the oil separator chamber is provided in the head cover, the sludge inhibiting layer may be formed on any part of the inner surface of the head cover other than the oil separator chamber. The position at which the oil separator chamber is installed is not particularly limited. In particular, if the oil separator chamber has an outer surface exposed to the outside air, the sludge inhibiting layer is preferably installed on the inner surface of the oil separator chamber, which is positioned on the back of the outer surface thereof.

The embodiment of the present invention is not limited to the one described above. The present invention includes any variations, applications, and equivalents embraced in the concept of the present invention specified in the claims. Thus, the present invention should not be limitedly interpreted but is applicable to any other technique belonging to the scope of the present invention.

INDUSTRIAL APPLICABILITY

The present invention is applicable to an internal combustion engine for which generation or adhesion of sludge is desirably inhibited.