JPH0748966Y2 - Crankcase ventilation system for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a crankcase ventilation device for forcibly introducing fresh air into a crankcase of an internal combustion engine to discharge blow-by gas.

BACKGROUND ART There are various types of blow-by gas treatment devices for internal combustion engines, but in general, they are generally introduced into the crankcase from an upstream side of the throttle valve in the intake passage through an oil separator located inside the cylinder head cover or the like. With the introduction of fresh air,
The blow-by gas pushed out by this fresh air is guided to the downstream side of the intake passage through an oil separator also located inside the cylinder head cover or the like.

For example, in Japanese Unexamined Patent Publication (Kokai) No. 58-143109, a crankcase is provided at two front and rear positions of the crankcase, which communicate with the inside of the cylinder head cover so that fresh air is introduced from one side and blow-by gas is taken out from the other side. A ventilator is disclosed.

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention However, in the above-described conventional configuration, since fresh air is introduced into the crankcase and blow-by gas is discharged simply by the pressure difference between the upper and lower sides of the throttle valve, efficient ventilation of the crankcase is required. I can't. In particular, the fresh air inlet on the cylinder head cover side and the blow-by gas outlet connected to the intake system communicate with each other through the inside of the cylinder head, and the introduction of fresh air on the crank case side and the discharge of blow-by gas are almost natural ventilation. It will be done in shape, so it is very inefficient.

Means for Solving the Problems Therefore, the present invention is designed to forcibly introduce fresh air into the crankcase by utilizing local pressure fluctuations in the crankcase due to vertical movement of the piston. .
That is, the present invention relates to a multi-cylinder 4-cycle internal combustion engine in which a bulkhead is formed on the upper part of the crankcase so as to partition the inside of the crankcase into a plurality of compartments.
In the crankcase, a fresh air introduction port is formed in the vicinity of the peripheral surface or the side surface of the counterweight of the crankshaft, and at the position closed by the counterweight when the volume of the section including the fresh air introduction port is reduced, It is characterized in that the fresh air inlet is provided.

Operation The crankcase is integrated as a whole, but is divided into a plurality of sections by the bulkhead to some extent. Therefore, when the piston moves up and down at a high speed, a local pressure fluctuation occurs.

When the volume of the compartment including the fresh air inlet increases as the piston moves, the pressure near the compartment in the crankcase decreases. At this time, the fresh air introduction port is not covered with the counterweight and is open, so that the fresh air is taken into the crankcase.

When the volume of the compartment including the fresh air inlet decreases with the piston movement, the pressure in the vicinity of the compartment increases, but the fresh air inlet is blocked by the counterweight, so that the reverse flow of fresh air hardly occurs. . Therefore, fresh air is forcibly introduced as the piston moves up and down.

Embodiment Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

1 and 2 show an embodiment in which the present invention is applied to an in-line 4-cylinder 4-cycle internal combustion engine.

In the figure, 1 is a cylinder block, 2 is an oil pan mounted on the lower surface of the cylinder block 1 to define a crankcase 3, and 4 is supported on each main bearing portion 5 of the cylinder block 1 via a bearing cap 6. 2 shows a crankshaft that is driven.

The cylinder block 1 is integrally cast from cast iron or the like, and four cylinder bores # 1 to # 4 are formed therethrough, and deep skirt type skirt portions 8 are formed on both lower sides. There is. A bulkhead 9 is formed in the skirt portion 8 so as to partition the cylinders from each other, and the main bearing portion 5 is provided at the center of the lower edge of the bulkhead 9. That is, in this embodiment, one section is formed for each cylinder.

The oil pan 2 is attached to the lower edge of the skirt portion 8, an oil sump portion 10 is provided at the front end portion thereof, that is, the end portion on the # 1 cylinder side, and the crankshaft 4 is provided at other portions. It is formed relatively shallow so that it approaches.

As shown in FIG. 2, the crankshaft 4 includes a journal portion 11 supported by a main bearing portion 5, a crankpin 14 connected to a piston 12 of each cylinder via a connecting rod 13, and a crankpin 14 of this crankpin. 14 and the journal department
It is composed of a crank arm 15 for connecting 11 and a counter weight 16 formed integrally with the crank arm 15. The counter weight 16 is attached to the crank arm 15 on the opposite side of the crank pin 14,
The peripheral surface 16a is formed along an arc centered on the axis of the crankshaft 4 and has a fan shape over an angular range of about 120 °. In addition, the crank pins 14 of the # 2 and # 3 cylinders are 180 ° with respect to the crank pins 14 of the # 1 and # 4 cylinders.
Counterweight 16 is the same because it is in a different position #
The positions of the # 1 and # 4 cylinders and those of the # 2 and # 3 cylinders are 180 ° different.

A fresh air introduction port 21 is formed at a side surface of the rear end portion of the cylinder block 1, more specifically, at a position facing the peripheral surface 16a of the counter weight 16 at the rearmost end. The fresh air introduction port 21 is formed so as to penetrate the skirt portion 8 at a height position near the axis of the crankshaft 4, and is opened at a position sufficiently close to the peripheral surface 16a of the counterweight 16. . For example, the gap with the peripheral surface 16a is set to about 3 to 4 mm. The fresh air introduction port 21 is provided on the side of the left and right skirt portions 8 through which the counterweight 16 passes when the piston 12 of the # 4 cylinder descends. That is, in this embodiment, the crankshaft 4 moves forward (#
Since it rotates clockwise when viewed from the 1st cylinder side), it is arranged in the skirt portion 8 on the left side when viewed from the front (the left and right sides are inverted due to the inverted state in FIG. 2).

Further, a gas discharge port 22 is formed in an opening at a side surface of the front end portion of the cylinder block 1, more specifically, at a position facing the peripheral surface 16a of the counter weight 16 at the front end. The gas discharge port 22 penetrates the skirt portion 8 at a height position near the axial center of the crankshaft 4 similarly to the fresh air introduction port 21, and is located sufficiently close to the peripheral surface 16a of the counterweight 16. It is open. Contrary to the fresh air inlet 21, the gas outlet 22 is provided on the side of the left and right skirts 8 through which the counterweight 16 passes when the piston 12 of the # 1 cylinder rises. There is. That is, it is arranged in the skirt portion 8 on the right side when viewed from the front, as opposed to the fresh air introduction port 21.

As shown in the explanatory view of FIG. 3, the fresh air introduction port 21 is connected to a fresh air introduction portion 25 of a cylinder head cover 24 via a fresh air passage 23 formed of an external pipe. The gas outlet 22 is connected to the gas outlet 27 of the cylinder head cover 24 via a gas passage 26 formed of an external pipe. The fresh air introducing section 25 and the gas outlet section 27 each include an oil separator (not shown). The fresh air introducing section 25 communicates with the upstream side of the throttle valve 29 of the intake passage 28, and the gas outlet section.
27 communicates with the throttle valve 29 downstream. The fresh air introducing section 25 and the gas outlet section 27 communicate with each other through the inside of the cylinder head 30 at the same time, and the inside of the cylinder head 30 is scavenged by the introduction of fresh air.

Next, the operation of the above configuration will be described.

Skirt part 8 and oil pan 2 of the cylinder block 1
The crankcase 3 defined by and is integrally communicated with the engine as a whole, but the upper part thereof is partitioned by the bulkhead 9 to a considerably lower position for each cylinder. Therefore, when the piston 12 moves up and down at high speed, Local pressure fluctuations occur between the cylinders. That is, if the piston 12 of a cylinder rises, the pressure in the section corresponding to the piston 12 decreases, and conversely, if the piston 12 descends, the pressure rises.

Therefore, the piston 12 of the # 4 cylinder in which the fresh air inlet 21 is located
Rises, the pressure around the fresh air inlet 21 locally drops, but at this time, the fresh air inlet 21 has the counterweight.
Since it is not covered with 16 and is open, fresh air is taken into the crankcase 3 as the pressure drops. When the piston 12 of the # 4 cylinder turns downward, the pressure around the fresh air inlet 21 locally rises. However, during the most part of the piston down stroke, the fresh air inlet 21 moves around the counterweight 16. Since it is blocked by the surface 16a, the reverse flow of fresh air hardly occurs. Then, when the piston 12 of the # 4 cylinder descends, the pistons 12 of the # 3 and # 2 cylinders adjacent to each other are in an upward stroke, so that due to the pressure difference between the two, fresh air is further drawn from the # 4 cylinder portion to # 3, #. It flows to the 2 cylinder part.

That is, by repeating the vertical movement of the piston 12, a kind of pumping action is performed, and fresh air is forcibly introduced through the fresh air introduction port 21 and is sequentially pumped forward.

When the piston 12 of the # 4 cylinder descends, the peripheral surface 16a of the counterweight 16 passes through the front surface of the fresh air introduction port 21 at high speed, which causes a pressure drop at the opening of the fresh air introduction port 21.
A suction effect of fresh air is obtained. Therefore, the fresh air inlet 21
By bringing as close as possible to the circumferential surface 16a of the counterweight 16, fresh air can be introduced more effectively.

On the other hand, the gas outlet 22 at the front end of the engine is opened while the piston 12 of the # 1 cylinder descends, that is, when the pressure rises, and the counterweight when the piston 12 rises, that is, the pressure decreases.
Blocked by 16.

Therefore, the pump action is exerted from the inside of the crankcase 3 to the outside, and the blow-by gas inside the crankcase 3 is forced out through the gas discharge port 22.

Therefore, even if there is almost no pressure difference between the upstream and downstream of the throttle valve 29, a large amount of fresh air is forcibly introduced from the fresh air introduction port 21 at the rear end of the engine, Since the blow-by gas is forcibly taken out from the gas discharge port 22 at the front end of the engine, the inside of the crankcase 3 can be effectively ventilated.

Further, in the configuration of the above-described embodiment, since fresh air and blow-by gas flow from the rear to the front in the crankcase 3, the lubricating oil dropped on the oil pan 2 is pushed by the gas flow, and the oil is collected in the oil sump 10. Good return.

Moreover, in such ventilation of the crankcase 3,
Taking out the lubricating oil poses a problem, but in the above configuration, the counterweight 16 approaches the gas discharge port 22 in the form of proceeding from top to bottom, so the lubricating oil lifted up by the counterweight 16 directly flows into the gas discharge port 22. Will not flow into the pipe, and the carry-out of lubricating oil will be relatively small.

Next, in the embodiment shown in FIG. 4, a fresh air introduction port 21A is formed inside the rear end wall 1a of the cylinder block 1, and
A gas outlet 22A is formed inside the front end wall 1b. The fresh air inlet 21A is opened and closed by the side surface 16b (see FIG. 1) of the counterweight 16 at the rearmost end of the crankshaft 4, and the gas discharge port 22A is formed by the side surface 16b of the counterweight 16 at the frontmost end of the crankshaft 4. It is opened and closed. The fresh air inlet 21A and the gas outlet 22A are formed by drilling from the outside of the cylinder block 1 and closing the outside with plugs, and are formed at the rear and front of the cylinder block 1. It communicates with the fresh air passage 23A and the gas passage 26A.

According to the configuration of this embodiment, the lubricating oil droplets scattered from the counterweight 16 in the circumferential direction by the centrifugal force are discharged from the gas discharge port 22A.
It does not jump into the fresh air introduction port 21A and the carry-out of the lubricating oil is further suppressed. In addition, the fresh air passage 23A and the gas passage 26A
Can be formed inside the cylinder block 1, and the external piping can be reduced.

The embodiment in which the present invention is applied to the in-line four-cylinder engine has been described above, but the present invention can be similarly applied to other V-type internal combustion engines and the like.

FIG. 5 shows, as an example, an embodiment in which a fresh air introduction port 21 is provided on the side of the cylinder block 1 of a V-type 8-cylinder internal combustion engine. In such a V-type internal combustion engine, since the pair of pistons 12 in the left and right banks are connected to one crank pin 14, the interior of the crankcase 3 is partitioned into two cylinders by the bulkhead 9 and the bearing cap 6. It has become a shape. In other words, # 1 and # 2 cylinder sections, # 3,
It is divided into four sections, a section for # 4 cylinders, a section for # 5 and # 6 cylinders, and a section for # 7 and # 8 cylinders. The fresh air introduction port 21 is provided so as to face the peripheral surface 16a of the counterweight 16 located at the rearmost end, that is, the end on the # 8 cylinder side.

Therefore, the fresh air introduction port 21 is the last end section, that is, # 7,
The pressure fluctuation of the section including the cylinder bore 7 of the # 8 cylinder is mainly received. The volume of this compartment is 14
Shows the maximum when it is located at the lowest point as shown in FIG. 5, and it becomes the minimum when it is located at an upper point that is different from this by 180 °. To do. On the other hand, the peripheral surface 16a of the counterweight 16 opens and closes the fresh air introduction port 21 with the characteristic shown in Fig. 6B, so that the forced introduction of fresh air is possible as in the above-described embodiment. Can be achieved. In this embodiment, in order to realize the above-mentioned opening / closing timing, the counterweight 16 (arrow ω indicates the direction of rotation) for opening / closing the fresh air introduction port 21 has an asymmetrical shape as shown in FIG. Therefore, the angle θ ₁ and the angle θ ₂ divided by the center line passing through the crank pin 14 have a relationship of θ ₂ > θ ₁ .

Effects of the Invention As is clear from the above description, according to the crankcase ventilation device for an internal combustion engine of the present invention, the fresh air is forcibly introduced into the crankcase by utilizing the pressure fluctuation associated with the vertical movement of the piston. Since this is done, it is possible to reliably ventilate the inside of the crankcase without depending on the pressure difference above and below the throttle valve.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an internal combustion engine showing an embodiment of a ventilation device according to the present invention, FIG. 2 is a perspective view of a cylinder block and a crankshaft, and FIG. 3 is an explanation showing a passage structure of this embodiment. FIG. 4 is a perspective view of a cylinder block showing a different embodiment of the present invention, FIG. 5 is a sectional view showing an embodiment applied to a V-type 8-cylinder internal combustion engine, and FIG. 6 is its volume fluctuation and fresh air. It is a characteristic view showing the relationship with the introduction opening and closing timing. 1 ... Cylinder block, 2 ... Oil pan, 3 ... Crank case, 4 ... Crank shaft, 9 ... Bulkhead, 16
… Counterweight, 21… fresh air inlet, 22… gas outlet.

Claims (1)

[Scope of utility model registration request] 1. A multi-cylinder four-cycle internal combustion engine in which a bulkhead is formed in the upper part of the crankcase so as to divide the interior of the crankcase into a plurality of compartments, and in the crankcase, a peripheral surface of a counterweight of a crankshaft or A fresh air introduction port is formed adjacent to the side surface, and the fresh air introduction port is arranged at a position where it is closed by a counterweight when the volume of the compartment including the fresh air introduction port is reduced. Crankcase ventilation system for internal combustion engine.