JP5804710B2 - Cylinder block structure - Google Patents

Description

  The present invention relates to a structure of a cylinder block, and more particularly to a structure for easily discharging blow-by gas of an engine having a plurality of cylinders.

  In an internal combustion engine that obtains rotational force by moving a piston up and down in a cylinder, types other than the two-cycle engine preferably recirculate blow-by gas, which is unburned gas stored in the crank chamber, to the intake side. This is because blow-by gas contains hydrocarbon or the like and causes deterioration of engine oil in the crank chamber. Moreover, if it is discharged as it is, there will be a negative effect that the effect on the environment remains. In order to suck out blow-by gas from the crank chamber, it is necessary to secure a blow-by gas passage.

  FIG. 3 shows a blow-by gas passage disclosed in Patent Document 1. Patent Document 1 discloses an oil return hole that is formed in a cylinder block and returns to the crankcase the oil received by the upper surface of the cylinder head discharged from the valve mechanism, and a blowby that guides blowby gas in the crankcase to the rocker cover. In an engine having a gas rising hole, a blow-by gas rising hole 112 having an opening for positively receiving the air flow generated in the crankcase, and an opening for preventing the air flow in the crankcase from entering the engine. An oil return structure provided with an oil return hole 111 having a portion is disclosed.

  Here, there is disclosed a projection 114 that actively guides the blow-by gas 117 to the blow-by gas rising hole 112 in order to discharge the blow-by gas in the crank chamber. The protrusion 114 is similar in shape to the shielding member 113 that prevents the blow-by gas from entering the oil return hole 111 due to the rotation of the counterweight or the connecting rod, but the role is different. That is, the rotation of the counterweight and the connecting rod causes the blowby gas 116 flowing in the direction of the arrow to recirculate along the skirt portion in the crank chamber and return to the blow-by gas rising hole 112 instead of returning to the crank chamber.

  In patent document 1, since the blow-by gas rising hole 112 is formed in the side wall of the cylinder, there arises a problem that it is difficult to cool with an increase in size of the cylinder portion.

  Patent Document 2 does not mention blow-by gas directly, but discloses an invention in which communication holes are provided in a partition wall between cylinders as a structure for eliminating a pumping loss due to compression of air in a crank chamber. The air in the crank chamber may be considered to contain blow-by gas. Therefore, patent document 2 has shown an example of the method of ventilation of blow-by gas.

  Patent Document 2 discloses an invention in which communication holes capable of flowing blow-by gas are provided in partition walls between cylinders arranged side by side, and the timing at which the counterweight closes the communication holes and the timing at which blow-by gas flows are disclosed. .

Japanese Utility Model Sho 62-175205 JP 2010-084560

  Since the engine disclosed in Patent Document 1 is provided with a blow-by gas passage in the side wall of the cylinder block, the size of the engine is increased. Further, the protrusion 114 (FIG. 3) as in Patent Document 1 is not easy to be cast at the time of casting such as aluminum die casting. In this regard, it can be said that the structure for flowing blow-by gas disclosed in Patent Document 2 is suitable for downsizing the engine. However, as in Patent Document 2, just by providing a vent hole in the partition wall between the cylinders, blow-by gas cannot be efficiently exhausted for the following reason.

  The flow of the blow-by gas in the crank chamber is the rotational movement of members such as counterweights, crank arms, and connecting rods. However, the vent holes provided in the partition walls between the cylinders as in Patent Document 2 are formed in parallel to the flow given to the blow-by gas in these crank chambers. Therefore, it cannot be said that blow-by gas efficiently flows into the vent hole.

  That is, as in Patent Document 2, in the case where communication holes are provided between the cylinders, it is necessary to provide a measure that allows the blow-by gas to flow through the communication holes more positively. Also, such measures should not hinder the ease of forming the cylinder block. This is because if the cylinder block cannot be formed, the engine cannot be manufactured with a high yield.

The present invention is a cylinder block structure conceived in view of the above problems. More specifically, the structure of the cylinder block according to the present invention is as follows:
A partition wall is provided at a skirt portion between a plurality of cylinders, a communication hole is provided above the skirt portion of the partition wall to communicate between the cylinders, blow-by gas from each cylinder flows toward one end of the cylinder, A cylinder block structure of a multi-cylinder internal combustion engine in which a blow-by gas discharge port is provided only in the cylinder,
A side inner wall surface of the skirt portion that is in contact with the partition wall between a cylinder in a direction in which blow-by gas flows and a cylinder in a direction in which blow-by gas flows out of the plurality of cylinders. Only , a projection is formed in which the outer surface of the cylinder block is recessed into the inner surface.

  In the present invention, since a protrusion is formed on the inner wall surface of the side wall of the skirt portion of the partition wall between the cylinders provided in the cylinder block, the outer surface of the cylinder block is recessed to the inner surface. A narrow portion is formed between the inner wall surface of the skirt portion. Therefore, when the blow-by gas passes through the gap, the pressure on the upstream side rises, and therefore, the blow-by gas is forced to flow through the communication hole formed in parallel with the flow.

  Further, since the protrusion formed on the inner wall surface of the side portion of the skirt is a protrusion formed by recessing from the outer surface of the cylinder block to the inner surface, even if the protrusion is formed, casting is easy during casting, and Since the outer surface of the cylinder block is recessed, the mold can be cooled down to the recessed portion on the mold. Therefore, even if a thick part is provided near the skirt of the cylinder block, effective mold cooling can be achieved. It is possible to prevent adverse effects such as sink marks and cracks during casting, and a cylinder block can be formed with a high yield.

It is a figure which shows sectional drawing of the cylinder block of this invention. It is a perspective view of the cylinder block containing the AA cross section of FIG. It is a figure which shows the example which has a processus | protrusion in a skirt part with the conventional engine.

  FIG. 1 is a sectional view of a cylinder block 1 of the present invention. More specifically, it is a cross section in which a partition wall between one cylinder is cut in a direction perpendicular to the crankshaft 20. FIG. 2 is a perspective view including a cut surface AA of FIG.

  Referring to FIG. 1, a cylinder block 1 of the present invention is formed of a cylinder portion 2 and a skirt portion 3. Throughout this specification, the cylinder block 1 has the direction of the crankshaft 20 as front and rear, the direction in which the cylinder portion 2 is formed as the upper side, and the opposite side as the lower side, and further perpendicular to the crankshaft 20 and the vertical direction. The right direction is the left-right direction. In the cylinder block 1 of the present invention, the side portion refers to the left-right direction. Further, the cylinder block 1 of the present invention has a plurality of cylinders, and each cylinder is arranged in parallel (see FIG. 2). This is because it is not easy to provide a communication hole between the cylinders in the V type or horizontally opposed.

  The cylinders are separated by a partition wall 4 in the skirt portion 3. In FIG. 1, the partition wall 4 is omitted because it covers the entire cross section, and only the reference numeral 4 is shown. Of course, the crankshaft 20 and the like are connected by a through hole 5 formed in the partition wall 4. A cylinder head is coupled to the upper side of the cylinder block 1, and a lower block or an oil pan is coupled to the lower side of the cylinder block 1.

  In the cylinder part 2, the piston 21 moves in the vertical direction. The piston 21 is connected to the crankshaft 20 by a connecting rod 22, and the linear motion of the piston 21 is converted into the rotational motion of the crankshaft 20.

  One connecting rod 22 is preferably provided with one or more counterweights 23. This is because it is possible to reduce the vibration at the time of converting the motion from the straight line to the rotation. The counterweight 23 is a weight provided on the opposite side of the crank arm 24 where the crank pin 24 is disposed in order to cancel vibration caused by a crank arm (not shown) or the connecting rod 22. A crank web in which the crank arm and the counterweight 23 are integrated may be used. The outermost circumference of the rotation locus of the counterweight 23 or the crank arm (hereinafter referred to as “counterweight 23 etc.”) is referred to as a crank locus 6.

  The skirt portion 3 has a shape in which the width increases toward the lower side following the upper cylinder portion 2. This is because the crank locus 6 must be secured. The lower end of the skirt portion 3 is preferably formed so as to have the maximum width. This is because it is easy to remove the mold during casting.

  A gap 8 having a predetermined width is formed on the side inner wall surface 7 of the skirt portion 3 so as not to interfere with the crank locus 6. In the cylinder block 1 of the present invention, a protrusion 9 is formed on the side inner wall surface 7 of the skirt portion 3 so as to be recessed from the outer surface 1a of the cylinder block 1 to the inner surface. That is, a recess 1d is formed on the outer surface 1a of the cylinder block 1, and the protrusion 9 is formed by projecting the recess 1d inward. The protrusion 9 is formed so as not to interfere with the crank locus 6. Therefore, in the side inner wall surface 7 of the skirt portion 3, the gap 8n between the projection 9 and the crank locus 6 forms the narrowest gap.

  Here, “the protrusion 9 recessed from the outer surface 1a of the cylinder block 1 to the inner surface” does not necessarily require that the protrusion 9 on the inner surface and the recess 1d on the outer surface have the same shape. That is, the amount of protrusion of the inner surface protrusion 9 and the amount of depression of the outer surface recess 1d may not be the same. This is because the protrusion 9 on the inner surface and the recess 1d on the outer surface have different roles as described later. Therefore, the mold of the cylinder block 1 of the present invention not only forms a mold without projections 9 on the inner surface and forms a recess 1d from the outer surface 1a toward the inner surface, but also creates a mold with projections 9 on the inner surface, Then, the outer surface may be scraped off, or conversely, a mold having a dent 1d on the outer surface may be produced, and the protrusion 9 may be formed on the inner surface later.

  However, if the protrusion 9 on the inner surface is formed by recessing the outer surface 1a, the protrusion 9 can be formed while the thickness of the skirt portion 3 of the cylinder block 1 is kept constant.

  The protrusions 9 need not be formed uniformly in the front-rear direction of the cylinder. Rather, it may be formed on the partition wall 4 with the cylinder in the direction in which blow-by gas flows. Reference is now made to FIG. Assume that there are three cylinders (30a, 30b, 30c). The blow-by gas flows from the cylinder 30a to the cylinder 30c through the communication hole 4h formed in the partition wall 4. The cylinder 30c is provided with a blow-by gas discharge port upward or downward. The fact that the protrusions 9 do not need to be formed uniformly in the front-rear direction means that the protrusions 9 of the cylinder 30a need only be provided in the vicinity of the partition wall 4 adjacent to the cylinder 30b through which blow-by gas flows.

  Thus, it is not necessary to provide the protrusion 9 uniformly in the front-back direction of the cylinder block 1 for the following reason. As will be described later, the protrusion 9 according to the present invention facilitates the discharge of blow-by gas from the communication hole 4h disposed in the vicinity thereof. Therefore, if it forms in the partition wall 4 with the cylinder of the side which receives blow-by gas, it will return the blow-by gas which has flowed back to the cylinder which flowed again.

  Referring again to FIG. 1, the communication hole 4 h is provided in the partition wall 4 between the cylinders, and may be the cylinder part 2, the skirt part 3, or both. It may be. However, even if the piston 21 reaches the lowest point in the cylinder part 2, the gas from the combustion chamber (the space formed by the piston, cylinder, and cylinder head) does not escape from the center of the cylinder part 2 to the extent that it does not escape. It must be formed at a remote location. This is because if the combustion gas in the combustion chamber has escaped, the engine output will decrease.

  Further, it must be formed at a position that can be separated from the crankshaft 20 rather than a position where the entire area of the communication hole 4 h covers the crank locus 6. This is because blow-by gas is difficult to escape if the entire area of the communication hole 4h covers the crank locus 6.

  Therefore, the positions of the communication holes 4h and the protrusions 9 formed on the side inner wall surface 7 of the skirt portion 3 cannot be determined by only one point. However, the communication hole 4h is formed above the skirt portion 3, and the protrusion 9 is the same height as the communication hole 4h or the lower end side of the skirt portion 3 with respect to the communication hole 4h, and the crank locus 6 has the entire area. It will be formed at a position where it is not completely covered. Here, the “height” is a height based on the lower end 3u of the skirt portion.

  The side inner wall surface 7 of the skirt portion 3 from the lower end 3u of the skirt portion 3 to the protrusion 9 on the inner surface is preferably formed in an arc shape along the crank locus 6 or with a larger curvature. This is because if the curvature is decreased toward the lower end 3u of the skirt portion 3, it is not easy to remove from the mold. Moreover, the width of the cylinder block 1 becomes wider than necessary, and the engine cannot be downsized.

  The upper surface (up to the front of the cylinder portion) from the protrusion 9 on the inner surface of the skirt portion 3 is preferably formed as a standing wall close to a straight. This is because, by using the standing wall, it is possible to provide the surplus portion 10 that has higher rigidity than the arc-shaped aspect and can reduce the thickness. If such an extra portion 10 can be provided, it is possible to reduce the weight of the engine and improve fuel efficiency.

  Next, the effect of the cylinder block 1 of the present invention will be described. As already described, in the cylinder part 2, the piston 21 moves up and down by compressing and exploding the fuel. The up and down linear motion is converted into the rotational motion of the crankshaft 20 through the connecting rod 22. A counterweight 23 or the like is formed on the crankshaft 20 and rotates in a certain direction. Accordingly, the blow-by gas 12 flows along the side inner wall surface 7 of the skirt portion 3 according to the rotation of the counterweight 23 and the like.

  Here, when the counterweight 23 or the like passes through the portion of the side inner wall surface 7 facing the protrusion 9, the gap 8 n between the counterweight 23 and the inner wall of the skirt portion 3 is narrowed. Accordingly, the pressure on the upstream side 8b such as the counterweight 23 becomes higher than this portion. This is because the blow-by gas 12 flowing along with the counterweight 23 and the like becomes difficult to pass through because the gap 8 is narrowed.

  Therefore, the blow-by gas 12y whose pressure has increased passes through the communication hole 4h and is sent to the next cylinder. As described above, blow-by gas flows to the next cylinder through the communication hole 4h formed in the partition wall 4 between the cylinders. Therefore, in order to facilitate the flow of blow-by gas to the next cylinder, it is preferable to form the protrusion 9 in the vicinity of the communication hole 4h in the direction in which the blow-by gas flows (see FIG. 2).

  Further, if the projections 9 are formed on both side surfaces of the skirt portion 3 regardless of the rotation direction of the counterweight 23, there is no place for the blow-by gas to escape further, and the projections 9 can easily pass through the communication holes 4h. Therefore, the protrusions 9 are preferably provided on both side surfaces.

  On the contrary, it is desirable not to provide the protrusion 9 in the vicinity of the communication hole 4h on the side where blow-by gas flows from the adjacent cylinder. This is because the blowby gas 12y that has flowed with great effort returns to the original cylinder. This will be described with reference to FIG. As already described, the protrusion 9 is provided in the cylinder 30a in the vicinity of the partition wall 4 adjacent to the cylinder 30b through which blow-by gas flows. On the other hand, in the cylinder 30b in which blow-by gas flows from the cylinder 30a, the projection 9 is not provided on the side of the partition wall 4 adjacent to the cylinder 30a. This is because blow-by gas is not returned to the cylinder 30a.

  Since the cylinders are arranged side by side, the blow-by gas gathers in the cylinder formed at either end. The cylinder is separately provided with a blow-by gas discharge port and recirculated to the intake side. By doing so, it is not necessary to provide blow-by gas extraction means for each cylinder, and the engine itself can be reduced in size and weight.

  Next, the effect of the outer shape of the cylinder block 1 of the present invention will be described. FIG. 2 is a perspective view including a cross section taken along line AA of FIG. A recess 1 d corresponding to the protrusion 9 formed on the side inner wall surface 7 of the skirt portion 3 is formed on the outer surface 1 a of the cylinder block 1. The recess 1d forms a gap 14 between the cylinders 2 to the cylinder portion 2. The gap 14 is formed by a protrusion in the mold of the cylinder block 1. Then, in the casting_mold | template, the part used as the protrusion means that the dent which cools from the outer surface of a casting_mold | template can be formed.

  That is, in the mold, the portion between the cylinders is often thick, but the thickened portion or its vicinity can be cooled. When producing with a mold like the cylinder block 1, it forms by pouring the molten metal into a mold. When the casting is cooled in the mold, it is ideal that the temperature of each part is uniformly reduced. However, the thick part is less likely to cool than the thin part. If the cooling temperature is too different in the casting, damage such as sink marks and cracks will occur in the casting.

  Therefore, if the thickened portion or the vicinity thereof can be cooled, it is difficult to cause damage during cooling, and a cylinder block with a high yield can be formed.

  As described above, the cylinder block 1 according to the present invention has a configuration in which the partition wall 4 is provided between the cylinders, and the communication hole 4h is provided in the partition wall 4, and the gap 8 between the crank locus 6 is narrow in the vicinity of the communication hole 4h. The blow-by gas in the cylinder block 1 increases the pressure on the upstream side 8b of the blow-by gas every time the counterweight 23 or the like passes through the position facing the protrusion 9, and the communication hole The blow-by gas can be suitably exhausted by flowing from 4h to the adjacent cylinder.

  Further, since the projection 9 is formed by a recess 1d provided on the outer surface 1a of the cylinder block 1, the casting can be easily cooled from the outside of the mold when the cylinder block 1 is cast. In particular, since this dent 1d can be formed between the cylinders which are likely to be thick, the cylinder block 1 free from sink marks and cracks can be manufactured with a high yield.

  The present invention can be suitably used for forming a cylinder block of an engine.

DESCRIPTION OF SYMBOLS 1 Cylinder block 1a Outer surface 1d Depression 2 Cylinder part 3 Skirt part 4 Partition wall 4h Communication hole 5 Through-hole 6 Crank locus 7 Side inner wall surface 8 Crevice 9 Protrusion 10 Dumpling part 12, 12y Blow-by gas 20 Crankshaft 21 Piston 22 Connecting・ Rod 23 Counterweight 24 Crankpin 30a, 30b, 30c Cylinder

Claims (1)

A partition wall is provided at a skirt portion between a plurality of cylinders, a communication hole is provided above the skirt portion of the partition wall to communicate between the cylinders, blow-by gas from each cylinder flows toward one end of the cylinder, A cylinder block structure of a multi-cylinder internal combustion engine in which a blow-by gas discharge port is provided only in the cylinder,
A side inner wall surface of the skirt portion that is in contact with the partition wall between a cylinder in a direction in which blow-by gas flows and a cylinder in a direction in which blow-by gas flows out of the plurality of cylinders. The cylinder block structure is characterized in that a projection is formed by recessing the outer surface of the cylinder block into the inner surface.