Internal combustion engine

Abstract

To prevent leakage of blow-by gas from a crank chamber to a timing chain arrangement space by using a simple structure in an internal combustion engine.SOLUTION: A turning flow 40 flowing from a rear side to a front side on one side wall (for example, exhaust side wall part) 23 of a crank case 2b is observed in the crank case 2b. A front part of an oil pan 5 fixed to a lower surface of the crank case 2b (cylinder block 2) serves as an oil tank part 5a, and an oil level gauge insertion hole 29 is opened on the one side wall 23 of the crank case 2b. The oil level gauge insertion hole 29 communicates with a groove-shaped gauge guide boss part 37 formed in the crank case 2b. A blow-by gas exhaust passage 30 is opened on the other side wall (for example, intake side wall part) 24 of the crank case 2b. A rear side wall of the gauge guide boss part 37 is formed to be a wide width wall body so as to change a direction of the turning flow 40 toward the other side wall 24 of the crank case 2b.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an internal combustion engine characterized by a ventilation function for a crankcase. [Background technology]

[0002] In reciprocating internal combustion engines, a small amount of burned gas (and unburned gas) can blow through between the piston (and piston ring) and the cylinder bore into the crankcase as blow-by gas, and if this is left unchecked, it can have adverse effects such as oil deterioration. Therefore, the blow-by gas that has blown through into the crankcase is sucked into the blow-by gas discharge passage (PCV passage), where the oil is removed in the oil separator chamber before being returned to the intake system.

[0003] To be precise, blow-by gas diffuses in the crankcase and mixes with oil mist, so the gas containing the blow-by gas and oil mist is sucked up into the PCV passage, the oil mist is collected by the oil separator, and the gas containing the blow-by gas is returned to the intake system. Therefore, a PCV valve that opens due to intake negative pressure is located downstream of the oil separator in the PCV passage. Fresh air is introduced into the crankcase.

[0004] There are various configurations and arrangements for the PCV passage and oil separator chamber, but they can be roughly divided into two types: one where the oil separator chamber is located in the cylinder block, and one where the oil separator chamber is located in the head cover. Furthermore, when the oil separator chamber is located in the head cover, there is a configuration in which blow-by gas is guided to the oil separator chamber through a dedicated passage (i.e., a configuration in which the PCV passage is formed in the cylinder block, cylinder head, and head cover), and a configuration in which the timing chain arrangement space doubles as the PCV passage, and blow-by gas is guided to the oil separator via the timing chain arrangement space and the valve train chamber.

[0005] However, using the timing chain space as a PCV passage is not desirable from the viewpoint of preventing oil deterioration because it increases the chances of blow-by gas coming into contact with oil mist, and it is therefore preferable to provide a dedicated PCV passage in the cylinder block. In this case, if a dedicated PCV passage is provided in the cylinder block, it is necessary to prevent blow-by gas from flowing into the valve train chamber via the timing chain space.

[0006] From this perspective, Patent Document 1 discloses, for an internal combustion engine for an automobile, that a partition plate that leads to an oil reservoir of an oil pan is fixed to the underside of the front end of the crankcase that is closest to the timing chain (the underside of the crank cap located at the front end). This structure allows oil to flow from the timing chain arrangement space into the oil pan, but prevents blow-by gas from flowing from the crankcase into the timing chain arrangement space. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 08-93435 Summary of the Invention [Problem to be solved by the invention]

[0008] While the structure of Patent Document 1 can prevent blow-by gas from leaking from the crankcase into the timing chain arrangement space, it also has some problems. For example, the need for a dedicated partition plate increases costs. In particular, during the internal combustion engine assembly process, the partition plate must first be fixed to the crankcase (crank cap), and then the oil pan must be attached carefully to avoid damaging the partition plate, making the engine assembly process extremely troublesome. Drilling the tapped holes is also time-consuming, and there is also concern that drilling the tapped holes in the crank cap may weaken the crank cap's strength.

[0009] Furthermore, the need for a partition plate and fastening bolts increases the weight of the internal combustion engine, resulting in a deterioration in fuel efficiency. Furthermore, the partition plate is likely to interfere with other components such as the oil strainer and baffle plate, reducing the design flexibility of the oil pan. Furthermore, there is concern that the partition plate may move and cause noise due to vibrations from the internal combustion engine or the vehicle body during driving.

[0010] The present invention was made against the background of the current situation, and aims to disclose a technique that can suppress the leakage of blow-by gas with a simple structure. [Means for solving the problem]

[0011] In internal combustion engines, a rod-shaped or strip-shaped oil level gauge is used as a means for detecting the oil level in the oil pan, and an oil level gauge insertion hole is formed in the cylinder block. On the other hand, the oil pan is open across the entire underside of the crankcase, but it is necessary to prevent air from getting into the oil when it is sucked up through the strainer. Therefore, part of the oil pan is deepened to form an oil reservoir, and a strainer connected to an oil pump is immersed in this oil reservoir.

[0012] The oil pump is generally driven by the crankshaft, but due to space constraints, it is usually driven by the front end of the crankshaft near the timing chain, and therefore the oil reservoir of the oil pan is also located at the front, closer to the timing chain.The oil level gauge detects the amount of oil in the oil reservoir of the oil pan, so the oil level gauge insertion hole is also located at the end of the cylinder block closer to the timing chain.

[0013] The inventors of the present application focused on the structure of such internal combustion engines and realized that the structure formed for the oil level gauge could be used as a means for rectifying blow-by gas, and after repeated research and analysis, they completed the present invention.

[0014] That is, the internal combustion engine of the present invention first comprises: "It comprises a cylinder block in which a plurality of cylinder bores are formed in a line in the crankshaft direction and the lower part of which is a crankcase, an oil pan fixed to the lower surface of the cylinder block, and a chain cover fixed to one end surface of the cylinder block and covering the timing chain, A blow-by gas discharge passage is formed in the crankcase so as to open downward, and a vertically elongated groove-shaped gauge guide boss portion having a vertically elongated opening positioned inside the crankcase is formed concentrically with an oil level gauge insertion hole in a portion of one side wall of the crankcase that is long in the crank axial direction and is close to the chain cover. This is the basic structure.

[0015] In the above basic configuration, "The portion of the gauge guide boss portion opposite the chain cover across the vertically elongated opening is formed on a wide wall that protrudes farther toward the inside of the crankcase than the portion on the chain cover side across the vertically elongated opening." It has the following characteristics.

[0016] In the present invention, the portion of the gauge guide boss located on the chain cover side across the vertically elongated opening may be a narrow wall, or may not have any wall at all. Furthermore, the inner surface of the gauge guide boss is flush with the inner surface of the oil level gauge insertion hole, since it functions as a guide for inserting and removing the oil level gauge. Therefore, it can have a shape such as an arc, ellipse, or rectangle.

[0017] The cross-sectional shape of the outer surface of the wide wall may be substantially the same as or different from the shape of the inner surface of the gauge guide boss. Furthermore, in the present invention, it is preferable that the blow-by gas discharge passage is provided in a portion of the crankcase opposite the gauge guide boss (the other side wall). [Effects of the Invention]

[0018] Complex air flows are generated inside the crankcase, including swirling flows caused by the rotation of the crankshaft, flows caused by the introduction of fresh air, flows caused by suction from the blow-by gas exhaust passage, and flows caused by the rotation of the timing chain.However, analysis by the inventors of the present application revealed that there is a tendency for air to flow along the longitudinal side of the crankcase (the side that is long in the crank axis direction) from the rear where the transmission case is located to the front where the timing chain is located.

[0019] The exact reason why this flow from back to front is not clear, but it is possible that the open space in which the timing chain is located makes it easier for air to escape into the timing chain space, and that the oil pan is deep at the front, so the pressure caused by the swirling flow caused by the rotation of the crankshaft is high at the rear of the oil pan and low at the front of the oil pan. It may also be related to pressure fluctuations caused by the up and down movement of the piston and the shape of the oil pan (or the shape of the baffle plate, etc.).

[0020] In any case, inside the crankcase, with the timing chain side at the front and the transmission case side at the rear, air containing blow-by gas tends to flow from back to front along one inner surface of the crankcase. However, in the present invention, a wide wall is formed on the gauge guide boss portion provided on one inner surface of the crankcase, and the wide wall can prevent the air flow containing blow-by gas from heading toward the timing chain arrangement space.

[0021] In other words, the flow direction of the air flow containing blow-by gas is deflected (changed) toward the center of the crankcase due to the straightening action of the wide wall body, making it easier for the air flow to flow into the blow-by gas discharge passage.

[0022] Furthermore, the present invention has a simple structure in which a wide wall is formed by effectively utilizing the boss portion that exists for guiding the oil level gauge, so no additional members are required and there are no problems such as increased costs or weight, thus completely resolving the problems of Patent Document 1. Therefore, it is highly practical and adaptable to actual equipment. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic side view of an internal combustion engine. [Figure 2] FIG. 2 is a partial bottom view of the cylinder block (crankcase). [Figure 3] FIG. 2 is a perspective view of the front part of the internal combustion engine as seen from the bottom. [Figure 4] FIG. 3 is an enlarged view of a main part of FIG. 2. [Figure 5] FIG. [Figure 6] FIG. 10 is a perspective view of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0024] Next, an embodiment of the present invention will be described with reference to the drawings. This embodiment is applied to a three-cylinder gasoline engine for an automobile. Hatching is used in Figures 2 to 6, but the hatching at the bottom end of the chain cover in Figures 4 to 6 represents a cross section, and the other hatching represents a flat surface.

[0025] In the following, the terms "front-rear" and "left-right" are used to specify directions, but as already mentioned, the front-rear direction is the crankshaft direction, with the side where the timing chain is located being the front and the side where the transmission case is located being the rear. The left-right direction is the direction perpendicular to the crankshaft and the cylinder bore axis. The up-down direction is more accurately the cylinder bore axis direction, but since the internal combustion engine of this embodiment is vertical, the up-down direction is the same as the vertical direction.

[0026] (1) Basic structure of an internal combustion engine The basic structure of an internal combustion engine is the same as that of a conventional engine, and the internal combustion engine comprises a cylinder block 2 in which a plurality of cylinder bores 1, into which pistons are inserted, are formed and lined up in the crankshaft direction, and a cylinder head 3 fixed to the upper surface of the cylinder block 2 via a gasket, with a head cover 4 fixed to the upper surface of the cylinder head 3 and an oil pan 5 fixed to the lower surface of the cylinder block 2. The cylinder block 2 is made up of a cylinder section 2a in which the cylinder bores 1 are formed and a crankcase 2b located below it, and a lower deck section (lower rail section) 2c is formed at the lower end of the crankcase 2b.

[0027] A chain cover (front cover) 6 that covers the timing chain is fixed to the front surface (one end surface) of the cylinder head 3, cylinder block 2, and bend cover oil pan 5, and a transmission case 7 is fixed to the rear surface (other end surface) of the cylinder head 3 and oil pan 5. In Figures 1 and 2, the axis of the crankshaft is schematically indicated by reference numeral 8. The crankshaft 8 rotates clockwise when viewed from the front.

[0028] The internal combustion engine of this embodiment is arranged in the engine compartment of the vehicle in a horizontal orientation with the crankshaft 8 elongated in the vehicle width direction. Also, while Fig. 1 is a side view of the internal combustion engine viewed from the direction facing the front of the vehicle body, the exhaust side of the cylinder head 3 on which the exhaust collection outlet 9 opens faces the front of the vehicle body. Therefore, the internal combustion engine is mounted on the vehicle body in a horizontal orientation with front exhaust.

[0029] Furthermore, in the internal combustion engine of the present invention, the cylinder bore axis is tilted forward by a slight angle (about 5 to 10 degrees) with respect to the vertical line. In other words, although the engine is basically vertical, it is tilted forward (slanted) at an angle that is noticeable to the naked eye.

[0030] The front of the oil pan 5 is formed as a deep oil reservoir 5a, and the rear is formed as a shallow bottom 5b where oil does not accumulate, with the exhaust pipe 10 passing through the space below the shallow bottom 5b. Needless to say, the oil pan 5 has a flange 5c at its top end that is fixed to the underside of the cylinder block 2 with a group of bolts.

[0031] The chain cover 6 is secured to the front of the cylinder block 2, cylinder head 3, and head cover 4, and an oil filter 11 is attached to an oil filter mounting seat 11a at the bottom by screwing it in from below. The space between the chain cover 6 and the cylinder block 2 / cylinder head 3 forms a timing chain arrangement space 12 in which a timing chain (not shown) is arranged.

[0032] In the internal combustion engine of this embodiment, an oil pump (not shown) that draws oil from the oil pan 5 is driven by the crankshaft, and the portion of the chain cover 6 through which the crankshaft passes doubles as a pump housing, with the pump cover secured from the inside. An oil passage communicating with the pump chamber and oil filter 11 is formed in the chain cover 6. An oil strainer 13 connected to the oil pump is immersed in the oil tank 5a of the oil pan 5. A baffle plate can be placed inside the oil pan 5, at least in the oil tank 5a, but the oil strainer 13 penetrates the baffle plate and is immersed in the oil tank 5a.

[0033] In the embodiment, the upper end of the chain cover 6 overlaps the front surface of the head cover 4 and is provided with a VVT control protrusion 6a at the top, but it is also possible to form the upper end of the chain cover 6 flush with the upper end of the cylinder head 3 and secure the front of the chain cover 6 to the upper surface of the chain cover 6. There is also another embodiment in which the lower end of the chain cover 6 is secured to the front surface of the oil pan 5. In Figure 1, reference numeral 14 denotes a crank pulley and reference numeral 15 denotes a water pump.

[0034] Since the internal combustion engine of this embodiment has three cylinders, the crankshaft is rotatably held by four crank journals arranged inside the crankcase 2b: a front journal 16, two intermediate journals 17, and a rear journal 18, and four pairs of crank caps: a front cap 19, an intermediate cap 20, and a rear cap 21. In the crankcase 2b, the portion where the crank journals 16, 17, and 18 are provided is plate-shaped (see FIG. 4), and the intermediate journal 17 is located between the bores.

[0035] (2) Oil level gauge insertion hole and boss As can be easily understood from Figure 2, the crankcase 2b includes an exhaust side wall (one side wall) 23, an intake side wall (the other side wall) 24, a front wall 25, and a rear wall 26 (see Figure 1). The front journal 16 is formed on the front wall 25, the rear journal 18 is formed on the rear wall 26, and the intermediate journal 17 is formed on an intermediate wall (partition wall) 27 connecting the exhaust side wall 23 and the intake side wall 24.

[0036] An oil level gauge insertion hole 29 is formed in the front of the cylinder block 2 and the cylinder head 3, allowing an oil level gauge 28 to be inserted into the oil reservoir 5a of the oil pan 5. Since the internal combustion engine of this embodiment is horizontally mounted with front exhaust, the oil level gauge insertion hole 29 is located on the exhaust side of the cylinder block 2 and the cylinder head 3, and is also located in a portion of the exhaust-side wall 23 close to the front wall 25 of the crankcase 2b.

[0037] As can be seen from the handle 28a of the oil level gauge 28 shown in solid lines in Figure 1, the upper end of the oil level gauge insertion hole 29 may open on the top surface of the cylinder head 3, or may open at the middle of the cylinder block 2 (the upper end of the crankcase 2b) as shown by the dashed dotted line in Figure 1, but the present invention is applicable to either case.

[0038] 1 and 2, a blow-by gas discharge passage (PCV passage) 30 that opens downward is formed in the front intermediate wall portion 26. The blow-by gas discharge passage 30 extends to the middle of the height of the cylinder block 2, and the upper end of the blow-by gas discharge passage 30 communicates from below with an oil separator chamber 31, the outline of which is shown in Fig. 3. The oil separator chamber 31 is formed in the exhaust side wall of the cylinder portion 2a, and is internally provided with a number of ribs (not shown) for collecting oil mist.

[0039] The oil separator chamber 31 is closed by a cover plate (not shown), and a PCV valve is provided on the cover plate. One end of a PCV hose is connected to the PCV valve, and the other end of the PCV hose is connected to an intake system component such as a surge tank. When negative pressure occurs downstream of the throttle valve, the PCV valve opens, allowing blow-by gas to return to the intake system. Note that the present invention can also be applied to a type in which the oil separator chamber is provided in the head cover 4.

[0040] For example, in FIG. 2, reference numeral 32 denotes a tapped hole for fixing the oil pan 5 with a bolt, reference numeral 33 denotes a tapped hole for fixing the crank caps 19 to 21 with a bolt, and reference numeral 34 denotes an oil dropping passage.

[0041] 3 and 42, the walls 25, 27, and 26 on which the crank journals 16, 17, and 18 are mounted are located a certain distance (approximately the height of the crank cap) above the lower end surface of the crankcase 2b. The lower end of the oil level gauge insertion hole 29 is located at the same height as the lower end of the front wall 25, and below the lower end of the front wall 25 is formed a vertically elongated gauge guide boss 37 that is concentric with the oil level gauge insertion hole 29 and has a vertically elongated opening 36.

[0042] The vertically elongated opening 36 of the gauge guide boss 37 is cut toward the center of the crankcase 2b and is formed across the entire vertical height of the gauge guide boss 37. Because the gauge guide boss 37 opens toward the inside of the crankcase 2b in this manner, the oil level gauge 28 can be flexibly deformed to enter the vertically elongated opening 36. This allows the oil level gauge 28 to be smoothly inserted into and removed from the oil reservoir 5a of the oil pan 5. In other words, the oil level gauge 28 is guided by the gauge guide boss 37 and smoothly inserted into and removed from the oil reservoir 5a.

[0043] 3 and 4, the lower portions of the front wall 25 and the intermediate wall 27 form a step 39 that recesses further into the crankcase than the reference inner surfaces 38 of the exhaust-side wall 23 and the intake-side wall 24, and the gauge guide boss 37 protrudes from the step 37 into the crankcase. The gauge guide boss 39 has the vertically elongated opening 36 formed therein, and thus has a front wall 37a located on the side of the chain cover 6 with the vertically elongated opening 36 in between, and a rear wall 37b located on the opposite side of the chain cover 6 with the vertically elongated opening 36 in between, with the rear wall 37b being a wide wall with a large lateral width and the front wall 37a being a narrow wall with a small lateral width.

[0044] The gauge guide boss 37 is basically circular, and the vertically elongated opening 36 is formed by cutting out a portion of it with an end mill or the like, so that both the inner and outer surfaces of the rear wall 37b are arc-shaped. The same is true for the front wall 37a. The gauge guide boss 37 protrudes from the step 39, so the outer surface of the rear wall 37b of the gauge guide boss 37 smoothly connects with the rear surface of the step 39.

[0045] Fresh air is introduced into the crankcase 2b, and a fresh air introduction passage may be provided in any part of the wall of the crankcase 2b, or the timing chain arrangement space 12 may also serve as the fresh air introduction passage. It is also possible to form the fresh air passage with a pipe that is attached later, rather than forming it in the cylinder block 2. If a dedicated passage is provided, it is preferable to provide it in the rear wall 26.

[0046] (3) Summary In this embodiment, airflow is generated in the crankcase due to various factors, but as shown by the dotted arrows in Figure 2, a large swirling flow 40 can be seen running along the inner circumferential surface of the crankcase 2b from back to front on the exhaust-side wall 23 and from front to back on the intake-side wall 24. In other words, the swirling flow 40 is observed circulating along the inner circumferential surface of the crankcase 2b.

[0047] The reason why such a swirling flow 40 is generated has not been fully elucidated, but it is speculated that the reason why a flow (vertical flow) from the back to the front is generated on the exhaust side is due to the fact that the oil pan 5 is deep at the front and shallow at the rear, and that air can easily escape from the timing chain arrangement space 12.

[0048] On the other hand, the reason why the air flows along the inner surface of crankcase 2b is presumably due to the influence of the swirling flow caused by the rotation of crankshaft 8 becoming a lateral flow from the intake side to the exhaust side in the area below intermediate wall portion 27, and the tendency of the air to flow lateral to the exhaust side due to the slant of the internal combustion engine. It is presumed that the combination of such longitudinal flow and lateral flow generates swirling flow 40 that flows from back to front on the exhaust side and from front to back on the intake side.

[0049] 6 as a comparative example, if the front wall 37a and rear wall 37b of the gauge guide boss 37 are the same height, the swirling flow 40 passes through the gauge guide boss 37 and is more likely to escape from below the front cap 19 into the timing chain arrangement space 12. However, if the gauge guide boss 37 is formed as a complete cylinder, the oil level gauge 28 will be less likely to bend and deform, making it difficult to insert and remove.

[0050] In contrast to this, in this embodiment, by providing a vertically long opening 36 in the gauge guide boss portion 37 and forming the gauge guide boss portion 37 in a groove shape, ease of insertion and removal (flexural deformation) of the oil level gauge 28 is ensured, while the rear side wall 37b of the gauge guide boss portion 37 is formed into a wide wall body, which gives it a straightening function (flow direction changing function) for the swirling flow 40, thereby changing the direction of the swirling flow 40 so that it faces the intake side wall portion 24, preventing the blow-by gas from leaking from the timing chain arrangement space 12 and directing the blow-by gas toward the blow-by gas discharge passage 30.

[0051] The cylinder block 2 is made by die-casting or casting using aluminum as the material, but if the gauge guide boss portion 37 is formed into a complete cylinder and then the vertically elongated opening 36 is formed by cutting with a cutting tool such as an end mill, the intermediate product of the cylinder block 2 can be a conventional one, so there is no increase in costs.

[0052] On the other hand, the outer surface of rear wall 37b may be formed flat, as shown as a modified example in Fig. 5, or may be curved in the opposite direction to the inner surface, as shown as another modified example by the dashed line in Fig. 5. In this way, by changing the shape of rear wall 37b, it is possible to further improve the effect of changing the direction of the swirling flow.

[0053] Although the preferred embodiment of the present invention has been described above, the present invention can be embodied in a variety of other ways. For example, in the case of a horizontally mounted, front-intake internal combustion engine, an oil level gauge insertion hole and a gauge guide boss can be formed in the intake side wall. The gauge guide boss is preferably located between the front wall and the adjacent intermediate wall, but it can also be located midway between the two or closer to the intermediate wall. [Industrial Applicability]

[0054] The present invention can be embodied in an internal combustion engine and is therefore industrially applicable. [Explanation of symbols]

[0055] 1 Cylinder bore 2 Cylinder block 2a Cylinder section 2b crankcase 5 Oil pan 5a Oil tank section 5b Shallow bottom 6 Chain cover 12 Timing chain placement space 16 Front journal 17 Interim Journal 18 rear journal 19 Front cap 20 Intermediate Cap 21 Rear cap 23 Exhaust side wall (one side wall) 24 Intake side wall (other side wall) 25 Front wall 27 Intermediate wall (partition wall) 28 Oil level gauge 29 Oil level gauge insertion hole 30 Blow-by gas exhaust passage 36 Vertical opening 37 Gauge guide boss 37a Front wall (narrow wall) 37b Rear wall (wide wall) 38 Reference Inner Surface 39 Step part 40 Swirling flow

Claims

[Claim 1] The engine is equipped with a cylinder block in which a plurality of cylinder bores are formed in a line in the crank axial direction and whose lower part forms a crankcase, an oil pan fixed to the lower surface of the cylinder block, and a chain cover fixed to one end surface of the cylinder block and covering a timing chain, an internal combustion engine in which a blow-by gas discharge passage is formed in the crankcase so as to open downward, and a groove-shaped gauge guide boss portion having a vertically elongated opening positioned inside the crankcase and concentric with an oil level gauge insertion hole is formed in a portion of one side wall of the crankcase that is long in the crank axial direction and is close to the chain cover, a portion of the gauge guide boss portion opposite the chain cover across the vertically elongated opening formed on a wide wall that protrudes farther toward the inside of the crankcase than a portion of the gauge guide boss portion on the chain cover side across the vertically elongated opening; Internal combustion engine.

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