JP7157011B2 - Engine with blow-by gas recirculation device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine with a blow-by gas recirculation device configured to recirculate blow-by gas to an intake passage, such as a diesel engine applied to agricultural machinery and construction machinery, and an automobile engine.

The various engines described above are generally equipped with a blow-by gas recirculation device for returning the blow-by gas to the intake passage. That is, the blow-by gas from the crankcase is guided to the intake passage through the in-cover gas passage formed inside the head cover.

The gas passage inside the cover of the head cover has a structure in which a special box for blow-by gas flow is installed inside the head cover, and a partition wall is provided to divide the internal space of the head cover vertically, and the upper side of the partition wall is used as a passage for blow-by gas. There are many structures. As such a conventional example, one disclosed in Patent Document 1 is known.

The blow-by gas contains oil in the form of mist (including moisture), and if it is returned to the intake passage as it is, the engine oil will be quickly reduced, which is inconvenient. Therefore, the blow-by gas passage is provided with an oil recovery section such as a filter or separator for capturing and recovering the oil components in the blow-by gas, and an oil return section for returning the recovered oil to the engine. ing.

In Patent Document 1, a partition plate (4) is provided to partition the interior of the head cover into upper and lower parts, an in-cover gas passage is formed above the partition plate (4), and an oil separator section (5) is formed above the partition plate (4). ing. The oil caught in the gas passage inside the cover is discharged from the drain valve (43) provided in the partition plate (4) and the collection cylinder (49) protruding downward, and is returned to the inside of the engine (into the nine-rank case). be able to

JP 2019-27342 A

The oil mist (mist-like oil) in the blow-by gas in the gas passage inside the cover is gas-liquid separated by a filter or a separator, or by colliding with the inner wall of the head cover, and is recovered as oil. However, the collected oil tends to accumulate in various places in the gas passage inside the cover, such as the upper part of the shield. There is a risk that the amount of oil carried away will suddenly increase.

Since it has been found that an increase in the amount of oil carried away, which causes an early decrease in engine oil, may occur even if an oil recovery unit such as a drain valve or a recovery cylinder is provided as in the case of Patent Document 1, It is becoming necessary to take some countermeasures.

An object of the present invention is to reduce or eliminate the possibility of an increase in the amount of oil carried away by further devising the internal structure of the head cover, and to prevent early reduction of engine oil even if the air cleaner is clogged. An object of the present invention is to provide an engine with a blow-by gas recirculation device.

The present invention provides an engine with a blow-by gas recirculation device,
configured to guide blow-by gas from the crankcase to the intake passage through an in-cover gas passage formed inside the head cover;
The gas passage in the cover is provided with a cylindrical ascending passage open at the top and bottom for vertically rising and flowing the blow-by gas,
The ascending passage is provided with a pair of labyrinth pieces arranged opposite to each other and protruding from a side wall of the ascending passage,
The tips of the pair of labyrinth pieces are arranged so that they are laterally close to each other within a range in which they do not overlap each other when viewed in the vertical direction, and are apart in the vertical direction ,
The ascending passage and the pair of labyrinth pieces are integrally formed as part of the head cover .

It is convenient that the tip portions of the pair of labyrinth pieces are vertically close to each other to the extent that a gap is secured between the top and bottom of the labyrinth pieces to allow the flow of blow-by gas. Further, it is convenient that both or one of the pair of labyrinth pieces is angled downward such that the distal end portion thereof is located below the base end portion on the side of the side wall.

Both or one of the pair of labyrinth pieces may have ribs formed along the direction of projection from the side wall of the labyrinth pieces, and the ribs may have a projection height from the labyrinth pieces of the rib. Advantageously, it is formed in a slanted rib that lowers towards the tip.

The lower edge of the slanted rib is preferably angled upward so that the tip of the rib is higher than the base of the rib. Advantageously, a gas outlet is provided at a point.

According to the present invention, since the ascending passage is formed with a pair of labyrinth pieces and a passage (gap) formed between them, it serves as a gas passage for upward movement of blow-by gas and downward movement of oil. It functions as an oil drop part. Due to the presence of the pair of labyrinth pieces, a labyrinth structure is formed in which the trapped oil is permitted to flow downward, but the oil and oil mist are less likely to flow backward from the bottom to the top. Due to this labyrinth, even if the intake negative pressure suddenly becomes excessively large, the oil will not be sucked up in the ascending passage, making it possible to reduce the amount of oil carried away.

Therefore, even if the intake negative pressure becomes excessive due to clogging of the air cleaner, the oil will not be sucked up as it flows back from the check valve, and oil will not accumulate in the gas passage inside the cover. Therefore, it is possible to eliminate the possibility that the amount of oil carried away to the intake passage increases.

As a result, by further devising the internal structure of the head cover, it was possible to reduce or eliminate the possibility of an increase in the amount of oil carried away, and even if the intake negative pressure became excessive, the engine oil would not decrease early, resulting in an improvement. An engine with a blow-by gas recirculation device can be provided.

Left side view of an industrial diesel engine Front view of the engine shown in FIG. Right side view of the engine shown in FIG. A plan view of the engine shown in FIG. Rear view of the engine shown in FIG. Top view around the front part of the head cover Partially cut left side view showing head cover and cover intake passage Plan view of head cover Bottom view of head cover FIG. 9 is a front view showing the head cover and the gas outlet cover in the cross-sectional view taken along the line XX of FIG. 8; The gas outlet cover is shown, (A) is a top view, (B) is a bottom view. A blow-by gas outlet and a valve train are shown, (A) is a cross-sectional view, and (B) is a vertical cross-sectional view of the main part. (A) Side view of discharge reed valve, (B) Side view of return reed valve (A) Top view of gasket, (B) Cross-sectional view of gasket and its upper and lower parts (A) A cross-sectional view from the front of the main part of the head cover showing the structure of the ascending passage, (B) An enlarged cross-sectional view of the main part showing the tips of the left and right labyrinth pieces. Sectional view cut left and right in the ascending passage showing the mold for the head cover Cross-sectional view from the left of the main part of the head cover showing another structure of the ascending passage Sectional view seen from the front of the main part of the head cover showing another structure of the ascending passage

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an engine equipped with a blow-by gas recirculation device according to the present invention will be described below with reference to the drawings for a case where it is applied to an industrial diesel engine. First, the engine and the basic blow-by gas recirculation system will be described, and then the ascending passage 50, which is the gist of the present invention, will be described.

As shown in FIGS. 1 to 5, an industrial diesel engine (hereinafter simply referred to as an engine) E has a cylinder head 2 mounted on the top of a cylinder block 1 and a head cover 3 on the top of the cylinder head 2. An oil pan 4 is assembled to the lower part of the cylinder block 1. - 特許庁A transmission case 5 is attached to the front end of the cylinder block 1 , an engine cooling fan 6 is arranged in front of the transmission case 5 , and a flywheel 7 is arranged in the rear of the cylinder block 1 . The upper half of the cylinder block 1 is composed of a cylinder 1A, and the lower half thereof is composed of a crankcase 1B.

In the front part of the engine E, a drive pulley 8 attached to the shaft end of a crankshaft (not shown), a drive fan pulley 6A for the engine cooling fan 6, and a transmission belt 10 spanning the passive pulley 9A for the dynamo (alternator) 9, A water flange 21 and the like are provided. On the left side of the engine E, an exhaust manifold 11, a supercharger 12, a starter 13, an oil filter 14 and the like are installed. An intake manifold 15, a fuel injection pump housing 16, a stop solenoid 17, etc. are installed on the right side of the engine E, and three injectors 18, a compressor upstream intake passage 19, a compressor downstream intake passage 20, etc. are arranged above. there is

The compressor downstream side intake passage 20 includes a starting end side pipe 20A that is connected to the compressor housing 12A and arranged across the head cover 3 directly above, and a terminal end side pipe 20B that connects the starting end side pipe 20A and the intake manifold 15. configured as follows. As shown in FIG. 4, in a plan view, the start end pipe 20A is arranged along the rear side of the cover intake passage 19A. The bent tube 19B, the start side tube 20A, and the end side tube 20B may be made of a flexible material such as rubber or a metal pipe.

As shown in FIGS. 4, 6, 7, and 10, the engine E has a blow-by gas recirculation mechanism configured to guide the blow-by gas in the crankcase 1B through the inside of the head cover 3 to the intake passage k. Device A is equipped. The head cover 3 is a bottomless box-like (upper lid-like) component assembled to the cylinder head 2 across the valve gear B, and a plurality of ribs 3a extending left and right are formed inside the cover. An engine oil supply hole 22 is provided in the rear portion of the head cover 3 .

The intake passage k has a cover intake passage 19A provided in the blow-by gas outlet portion 3A of the head cover 3, and includes an outlet space portion 26 (in-cover gas passage W), which is an internal space of the blow-by gas outlet portion 3A, and the cover intake passage. 19A are communicated. The cover intake passage 19</b>A is configured as part of the compressor upstream side intake passage 19 that connects the air cleaner 23 (see FIGS. 4 and 6 ) and the supercharger 12 . In other words, the compressor upstream side intake passage 19 includes a cover intake passage 19A and a bent pipe 19B that connects the cover intake passage 19A and the compressor housing 12A of the supercharger 12 . Note that the intake passage k is a concept that includes all passages such as the air cleaner 23 and the intake manifold 15 for sending the air a to the combustion chamber (not shown).

Here, a brief description will be given of the major functions of the blow-by gas recirculation device A (recirculation portion to the intake passage k). As shown in FIGS. 6 and 7, the blow-by gas g flowing from the cylinder block 1 into the internal space of the head cover 3 passes through the discharge reed valve 31 and passes through the outlet space portion which is the blow-by gas passage of the blow-by gas outlet portion 3A. Enter 26. The blow-by gas g that has entered the outlet space 26, which is also called a CCV (crankcase ventilation) chamber, passes through the communication hole 38 of the gasket 35 and the communication passage 40 (described later) into the cover intake passage 19A, that is, into the intake passage k. be reimbursed. The space inside the head cover 3 excluding the outlet space 26 also corresponds to the "inside cover gas passage W" through which the blow-by gas g flows (see FIG. 7).

Next, the head cover 3 and the cover intake passage 19A will be described.
As shown in FIGS. 6 to 10, the head cover 3, which has a rounded square shape (elliptical shape) in plan view, has a top wall 3C at the front end thereof, and an upwardly open blow-by gas outlet 3A is formed. . The blow-by gas outlet portion 3A is formed in the head cover 3 as an open box-like portion having an outlet space portion 26 surrounded by a vertical partition wall 24 and a bottom wall 25, and a joint surface 27 as an upper surface. .

The outlet space 26, which is a blow-by gas passage, is a trapezoidal portion having a short side on the right side in plan view, and the bottom wall 25 has a shallow main bottom surface 25A and a different depth in the front-rear direction. It has sink bottom surfaces 25B, 25B respectively formed on the front and rear of the main bottom surface 25A. A discharge reed valve 31 for discharging the blow-by gas g from the inside of the head cover 3 is provided in a sideways (leftward) posture at the front-rear central portion of the main bottom surface 25A which exhibits a sideways T-shape in plan view.

As shown in FIGS. 7 to 10, 12 and 13, the discharge reed valve 31 includes a thin discharge valve body 31A arranged on the main bottom surface 25A and a thick discharge valve guide 31B. It is constructed by bolting to the bottom wall 25 at the base side of the . A round tip portion 31a of the discharge valve body 31A is arranged above a discharge valve hole 31C formed in the bottom wall 25 so as to open to the main bottom surface 25A, and normally serves as a cover for the discharge valve hole 31C (valve closed). situation). The portion of the discharge valve hole 31C in the bottom wall 25 is formed in a projecting hole wall 25a projecting downward in a circular shape concentric with the discharge valve hole 31C when viewed from the top and bottom direction.

The sink bottom surface 25B includes an inclined surface 32 that becomes lower from the front and rear of the discharge reed valve 31 toward the front or rear, and a lowest surface 33 continuing to the lower side of the inclined surface 32 (see FIG. 8). The lowest surface 33 is positioned to the left of the inclined surface 32 . Each of the lowest surfaces 33, 33 of the bottom wall 25 is formed with a return valve hole 33a penetrating vertically, and a return reed valve 34 is provided for the return valve hole 33a.

As shown in FIGS. 7 to 10, 12 and 13, the return reed valve 34 includes a return valve body 34A in contact with the bottom surface 33A of the bottom wall 25 opposite to the bottom surface 33, and a thick return valve body 34A. The valve guides 34B are bolted to the bottom wall 25 at their root sides. The return reed valve 34 is provided in an upside-down posture with respect to the discharge reed valve 31, and normally, the return valve hole 33a is lightly closed by the tip portion 34a of the return valve body 34A, or the return valve body 34A is closed. It is in an extremely slightly open state due to a slight drooping displacement.

Each of the return reed valves 34, 34 is arranged in a horizontal orientation with the tip portion 34a on the left side, and is a portion that returns the oil mist captured from the blow-by gas g in the outlet space portion 26 to the internal space of the head cover 3. . The diameter of each return valve hole 33a is smaller than the diameter of the discharge valve hole 31C. It is convenient if the discharge valve body 31A and the return valve body 34A, and the discharge valve guide 31B and the return valve guide 34B are the same parts.

As shown in FIGS. 6 to 8 and 11, a gas outlet cover 3B is bolted onto the blow-by gas outlet portion 3A, and the gas outlet cover 3B includes a lid cover portion 36 and a cover intake passage 19A. is configured with The lid cover portion 36 has the same contour shape as the blow-by gas outlet portion 3A in plan view, and is fixed to the head cover 3 by bolting at three locations with a gasket 35 interposed therebetween.

As shown in FIGS. 11(A) and 11(B), the cover intake passage 19A has a passage end portion 19b of the cover intake passage 19A which is positioned outwardly in the longitudinal direction of the head cover 3 with respect to the passage start portion 19a of the cover intake passage 19A. It is formed in a meandering path that is bent in a state of leaning toward. More specifically, the cover air intake passage 19A includes a passage starting end portion 19a and a passage end portion 19b extending in a direction orthogonal (an example of crossing) to the head cover longitudinal direction (front-rear direction) and parallel to each other; It has an oblique passage intermediate portion 19c that connects with the starting end of the terminal portion 19b, and is formed into a meandering passage having a crank shape (substantially Z shape) in a plan view.

The passage intermediate portion 19c is formed in a groove-like passage portion having a downward U-shaped cross section, and an opening 37 at the lower end thereof has a shape similar to that of the passage intermediate portion 19c in a plan view and opens downward. formed. Further, the lid cover portion 36 is formed with a gas passage recess 36a which is located behind the opening 37 and opens downward, and is formed with three bolt holes 3b.

As shown in FIG. 14A, the gasket 35 is a thin plate (sheet-like) having one communication hole 38 and three bolt insertion holes 39 . As shown in FIG. 14B, the gasket 35 is sandwiched between the joint surface 27, which is the upper surface of the blow-by gas outlet portion 3A, and the joint lower surface 36b of the lid cover portion 36 (of the gas outlet cover 3B). provided in the state. The contour shape of the joint surface 27 of the blow-by gas outlet portion 3A, the contour shape of the gasket 35, and the contour shape of the lid cover portion 36 are the same, but not limited to this.

As shown in FIG. 6, the outlet space portion 26 of the blow-by gas outlet portion 3A has an upper surface opening covering substantially the entire surface of the opening 37 of the lid cover portion 36, and the communication hole 38 of the gasket 35 serves as the outlet. This is the only place where the space 26 and the opening 37 are communicated. In other words, the communication hole 38 is a hole that determines the area of communication between the intermediate passage portion 19c (opening 37) and the outlet space portion 26 and the position of communication with respect to the intermediate passage portion 19c.

The valve train B will be briefly described. As shown in FIGS. 8, 10, and 12, the valve train B includes a rocker arm shaft 28 that is supported at a plurality of locations on a shaft support portion 2a erected on the cylinder head 2 and extends in the front-rear direction, and a rocker. It comprises a plurality of (six in total) rocker arms 29 and 30 for air supply and exhaust which are rotatably supported on an arm shaft 28 .

The rocker arms 29, 30 have driving end portions 29a, 30a for operating supply and exhaust valves (not shown) and passive end portions 29b, 30b driven by push rods (not shown). The cylinder head 2 is formed with a push rod hole (not shown) through which the push rod passes, and as shown in FIG. sent to

In the blow-by gas recirculation device A, the inside of the head cover 3 and the outlet space 26 are partitioned by a bottom wall 25 having a discharge reed valve 31 and two return reed valves 34, 34. is communicated with the cover intake passage 19A through a communicating hole 38 of a gasket 35. As shown in FIG. Therefore, when the internal pressure of the head cover 3 is higher than the pressure of the cover intake passage 19A, the exhaust reed valve 31 is opened, and the blow-by gas g inside the head cover 3 passes through the exhaust reed valve 31, the outlet space 26, and the communication hole 38. and enters the passage intermediate portion 19c, and is recirculated to the intake passage k.

When the internal pressure of the head cover 3 and the pressure of the cover intake passage 19A are the same, or when the internal pressure of the head cover 3 is lower than the pressure of the cover intake passage 19A, the pair of return reed valves 34, 34 are opened to open the outlet space. The oil trapped in the blow-by gas g at the portion 26 drops into the head cover 3 through the return valve holes 33a, 33a. The dripping oil from the return valve hole 33a is not only returned to the inside of the engine, but also has a good lubricating function that is supplied to the valve train B such as the sliding portion (not shown) between the rocker arm shaft 28 and the rocker arm 29. is also obtained.

In this engine with a blow-by gas recirculation device, a cover intake passage 19A, which is a part of the compressor upstream side intake passage 19, is attached to the head cover 3, and an outlet space 26 of the blow-by gas outlet portion 3A and an intermediate portion of the cover intake passage 19A are provided. The portion 19c communicates with the portion 19c through the communicating hole 38 of the gasket 35. As shown in FIG. The head cover 3 is a portion that becomes warm due to heat conduction from the cylinder head 2, and the blow-by gas g is returned to the cover intake passage 19A that is part of the head cover 3 that becomes warm.

Therefore, even if the air a taken in is cold due to extremely cold weather, etc., the temperature of the air a flowing through the cover intake passage 19A is increased (see FIG. 11A), so that the blow-by gas is returned to the passage intermediate portion 19c. Freezing of water in g is eliminated or suppressed. As a result, it is possible to provide an engine equipped with a blow-by gas recirculation system which is improved so that the end portion connected to the intake system in the outlet space 26 is less likely to be frozen, and inconvenience caused by freezing at low temperatures is minimized. .

The cover air intake passage 19A is formed such that the passage terminal portion 19b is shifted outward (front side) in the longitudinal direction of the head cover with respect to the passage start portion 19a. More specifically, the cover intake passage 19A includes a passage starting end portion 19a and a passage terminal end portion 19b extending in a direction (horizontal direction) intersecting the longitudinal direction (front-rear direction) of the head cover 3 and parallel to each other, and a terminal end of the passage starting end portion 19a. It is formed to have a passage intermediate portion 19c that connects with the starting end of the passage terminal portion 19b.

As shown in FIGS. 6 and 11, the cover intake passage 19A is set as a meandering passage that is approximately Z-shaped (crank-shaped or bent-shaped) in plan view. Due to the meandering of the cover air intake passage 19A, as shown in FIG. There is an advantage that the anti-freezing action is strengthened.

Since the passage end portion 19b is closer to the front side (the outer side in the longitudinal direction of the head cover) than the passage start portion 19a, if the cover intake passage 19A formed by the gas outlet cover 3B of the molded part is made into a meandering passage, the structure can be simplified to the upstream side of the compressor. There is an advantage that the shape of the suction passage 19 can be made into a non-straight passage. Further, since the downstream side (passage end portion 19b) is closer to the front than the confluence point (passage intermediate portion 19c) of the blow-by gas g in the compressor upstream side intake passage 19, the cooling effect of the cooling air from the engine cooling fan 6 is reduced to the passage. There is also the advantage that the temperature of the air supplied to the intake manifold 15 can be lowered because it is stronger than the starting end 19a.

Additional description of the gas outlet cover 3B and its vicinity will be given. As shown in FIGS. 10 and 11, the outlet space 26 and the cover air intake passage 19A are communicated with each other through a communication hole 38 and a labyrinthine communication passage 40. As shown in FIGS. The communication passage 40 is composed of a gas passage recess 36a of the gas outlet cover 3B and a gasket 35 serving as a lid for closing the opening of the recess 36a. The gas passage recess 36a of the gas outlet cover 3B communicates with the downstream end of the passage intermediate portion 19c in the direction of gas flow.

As shown in FIGS. 11A and 11B, the gas passage recess 36a has a right end located above the communication hole 38 of the gasket 35, and a narrow front-to-rear portion connected to the passage intermediate portion 19c. It has an oriented end recess 42 . The gas outlet cover 3B has a left protruding wall 43 protruding rearward toward the gas passage recess 36a along the terminal recess 42, and a right side of the left protruding wall 43 protruding forward toward the gas passage recess 36a. A right projecting wall 44 is formed. Therefore, the blow-by gas g flowing from the communication hole 38 is made to pass through the connecting passage 40, which is a path bent in a labyrinth shape (crank shape) by the right protruding wall 44 and the left protruding wall 43, and then proceed to the intermediate passage portion 19c. is configured to

As shown in FIGS. 11A and 11B, between a portion of the communication passage 40 excluding the intake passage side end (terminating recess 42) and the cover intake passage 19A, more specifically, the passage intermediate portion 19c. A heat insulating portion D is provided. The heat insulating portion D is composed of a curved elongated hole (an example of a recess or hole) 41 formed in the gas outlet cover 3B in a state of opening to the side surface of the gasket of the gas outlet cover 3B. , covered by a gasket 35 .

The curved elongated hole 41 is formed between the passage intermediate portion 19c and the gas passage recess 36a so as to be partitioned by thin front and rear rib-like walls 45, 45, respectively. Due to the presence of the gasket 35, the curved long hole 41 becomes a closed space, so that the space becomes an air layer to form the heat insulation portion D. As shown in FIG. Although the depth of the curved long hole 41 is formed deeper than the depth of the gas passage recess 36a, the depth is not limited to this.

The communication passage 40 connecting the outlet space 26, which is a blow-by gas passage, and the passage intermediate portion 19c is not a straight passage, but a labyrinthine passage bent in a zigzag manner. There is an effect that droplets (moisture etc.) from (passage intermediate portion 19c) are less likely to enter the inside of head cover 3 . In addition, the oil component in the blow-by gas is less likely to be drawn into the communication passage 40, and even if it is drawn in, it is shaken off by the labyrinth-like passage, and an effect of exhibiting an oil removing action can also be achieved.

In addition, the communication passage 40 and the passage intermediate portion 19c are shaped so as to follow each other, but since the heat insulating portion D is formed between the two 40 and 19c, the blow-by gas outlet portion 3A is In particular, the temperature in the vicinity of the communication passage 40 is less likely to drop due to intake air, and the effect of further reducing the possibility of freezing is obtained.

Next, the ascending passage 50 will be described. In the engine with a blow-by gas recirculation device according to the present invention, the blow-by gas outlet 3A (reference embodiment) shown in FIGS. 7 to 10 and FIGS. It has a head cover 3 with a closed structure. Accordingly, the following description will be directed to its replaced structure, the ascending passageway 50 .

As shown in FIGS. 15(A) and 15(B), the cover internal gas passage W is provided with an ascending passage 50 for vertically rising and flowing the blow-by gas. The ascending passage 50 is provided with a pair of left and right labyrinth pieces 51 and 52 which are arranged to face each other and protrude from the side wall 50 a of the ascending passage 50 . The left and right labyrinth pieces 51 and 52 are configured so that their distal ends 51a and 52a are laterally close to each other within a range in which they do not overlap each other when viewed in the vertical direction, and are separated in the vertical direction. there is The upper end of the ascending passage 50 , that is, the upper end opening of the ascending passage 50 serves as a gas outlet 46 through which blow-by gas exits the head cover 3 . 3L and 3R are the left side wall and the right side wall of the head cover 3, respectively.

The tip portions 51a and 52a of the pair of labyrinth pieces 51 and 52 are vertically brought close to each other to the extent that a gap s (see FIG. 15(B)) that allows the flow of blow-by gas is secured between them. there is Both of the pair of labyrinth pieces 51 and 52 are provided with a downward angle θ such that their distal end portions 51a and 52a are positioned below base end portions 51b and 52b on the side of the side wall 50a. Both the left downward angle θ1(θ) and the right downward angle θ2(θ) with respect to the horizontal are the lines of the vertical thickness centers of the left and right labyrinth pieces 51 and 52 . Therefore, the downward angles of the upper and lower surfaces of the left labyrinth piece 51 are θ1(θ)+α and θ1(θ)−α, respectively, and the downward angles of the upper and lower surfaces of the right labyrinth piece 52 are θ2(θ)+β and θ2( θ)-β. Note that α and β are predetermined angles such as 3 degrees and 5 degrees.

As shown in FIGS. 15(A) and 15(B), on the lower surfaces of both the left and right labyrinth pieces 51 and 52, in the projecting direction (rightward or leftward direction) from the side wall 50a of the labyrinth pieces 51 and 52. Left and right ribs 51r and 52r are formed along the edge. Each of the ribs 51r, 52r is formed as an inclined rib in which the downward projection height from the labyrinth pieces 51, 52 decreases toward the tip of the rib. The lower edges of the slanted ribs 51r, 52r are provided with an upward angle τ such that the height level at the distal end portions 51a, 52a is higher than the height level at the proximal end portions 51b, 52b. The upward angle τ1 on the left side and the upward angle τ2 on the right side are both upward angles based on the horizontal.

In FIG. 15, the tips of the left and right labyrinth pieces 51 and 52 are aligned in the left-right direction, but they may be slightly apart. The rightward projection length of the left labyrinth piece 51 is longer than the leftward projection length of the right labyrinth piece 52, but the length conditions may be the same or opposite. . In addition, the inclination angle of the protruding direction of the left and right labyrinth pieces 51 and 52 may be horizontal or upwardly angled. Thicker shapes are also possible.

As described above, the ascending passage 50 is formed with a pair of labyrinth pieces 51 and 52 and a gap s therebetween, so that the oil drop hole is open in the vertical (vertical) and horizontal (horizontal) directions. It functions as a part and as an in-cover gas passage for the blow-by gas g. Since the left and right labyrinth pieces 51 and 52 are inclined at a downward angle θ so that the tip portions 51a and 52a are lowered, they have an "oil return" shape, so that the captured oil easily flows downward. , a labyrinth structure is formed from the bottom to the top to prevent backflow of oil mist. That is, since the labyrinth pieces 51 and 52 of the oil return structure are provided, even if the intake negative pressure suddenly becomes excessive, the oil will not be sucked up in the ascending passage 50, thus reducing the amount of oil carried away. it becomes possible to

By reducing the amount of oil carried away, the following effects (1) to (3) are obtained.
(1) Oil consumption can be reduced. (2) Performance degradation due to oil adhesion inside the intake port and oil intrusion into the engine can be suppressed. (3) Air cleaner is completely clogged. It is possible to reduce or eliminate the amount of oil carried away

In addition, as shown in FIG. 16, the head cover 3 including the ascending passage 50 has a two-split structure in which an upper mold 53 and a lower mold 54 are vertically split at a horizontal mold parting surface 56. 55 can be produced with high productivity. In this two-split structure, the left and right labyrinth pieces 51 and 52 are laterally close to each other within a range in which their tip portions 51a and 52a do not overlap each other when viewed in the vertical direction, and are separated in the vertical direction. This is possible by adopting the ascending passage 50 configured as above.

[Another embodiment 1]
As shown in FIG. 17, the head cover 3 may have an ascending passage 50 having front and rear side walls 50b, 50b on which a pair of front and rear labyrinth pieces 57, 58 are formed. 15 except that the projecting directions of the labyrinth pieces 57 and 58 have changed from the lateral direction to the longitudinal direction. The above description is omitted. Although illustration is omitted, the head cover 3 according to this alternative embodiment 1 can also be manufactured by molding with a structure divided into upper and lower halves.

[Another embodiment 2]
As shown in FIG. 18, the ascending passage 50 may be configured such that the left and right side walls 3L, 3R of the head cover 3 are also used as the side walls 50a, 50a. The lower edge of the left rib 59r of the left labyrinth piece 59 is angled downward so that the height level at the tip portion 59a is lower than the height level at the base end portion 59b. The lower edge of the right labyrinth piece 60 is formed in a horizontal state so that the height level at the tip portion 60a and the height level at the base end portion 60b are the same.

Otherwise, the configuration is basically the same as that of the ascending passage 50 shown in FIG. 15, and corresponding portions are denoted by corresponding reference numerals, and further explanation is omitted here. Although illustration is omitted, the head cover 3 according to the second embodiment can also be manufactured by molding with a structure divided into upper and lower halves.

1B Crankcase 3 Head cover 46 Gas outlet 50 Ascending passage 50a Side wall 51 Labyrinth piece 51a Tip part 51b Base part 51r Rib (inclined rib)
52 labyrinth piece 52a distal end 52b proximal end 52r rib (inclined rib)
W Cover gas passage k Intake passage s Gap θ Downward angle τ Upward angle

Claims (7)

configured to guide blow-by gas from the crankcase to the intake passage through an in-cover gas passage formed inside the head cover;
The gas passage in the cover is provided with a cylindrical ascending passage open at the top and bottom for vertically rising and flowing the blow-by gas,
The ascending passage is provided with a pair of labyrinth pieces arranged opposite to each other and protruding from a side wall of the ascending passage,
The tips of the pair of labyrinth pieces are arranged so that they are laterally close to each other within a range in which they do not overlap each other when viewed in the vertical direction, and are apart in the vertical direction ,
An engine with a blow-by gas recirculation device, wherein the ascending passage and the pair of labyrinth pieces are integrally formed as a part of the head cover .

2. An engine with a blow-by gas recirculation device according to claim 1, wherein the top and bottom ends of said pair of labyrinth pieces are positioned close to each other such that a gap is secured between them to allow the flow of blow-by gas. 3. The blow-by gas recirculation device according to claim 1, wherein one or both of the pair of labyrinth pieces is angled downward so that the tip end portion thereof is located below the base end portion on the side of the side wall. engine. An engine with a blow-by gas recirculation device according to any one of claims 1 to 3, wherein ribs are formed on both or one of the lower surfaces of said pair of labyrinth pieces along the direction in which said labyrinth pieces protrude from the side wall. . 5. An engine with a blow-by gas recirculation system according to claim 4, wherein said rib is formed as an inclined rib in which the height of protrusion from said labyrinth piece decreases toward the tip of said rib. 6. An engine with a blow-by gas recirculation system according to claim 5, wherein the lower edge of said inclined rib is angled upward such that the tip of the rib is higher than the base of the rib. The engine with a blowby gas recirculation device according to any one of claims 1 to 6, wherein the upper end of the rising passage is provided with a gas outlet where the blowby gas is discharged from the head cover.

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