JP5984428B2 - Blow-by gas passage structure - Google Patents

Description

  The present invention relates to a blow-by gas passage structure formed using a baffle plate or the like between a cylinder head and a head cover, and in particular, an intake on the cam chamber side of a blow-by gas passage through which both fresh air and blow-by gas pass. Concerning structure.

  In an internal combustion engine of a type in which a piston is moved up and down in a cylinder to burn fuel, unburned gas that escapes from the combustion chamber through the gap between the cylinder and the piston is generated. This is called blow-by gas, and contains components such as hydrocarbons. If released as it is, it will lead to environmental pollution. Further, if blowby gas is stored in the crank chamber, it becomes a movement resistance of the piston, leading to output loss.

  Therefore, blow-by gas is again returned to the intake side and recombusted. Further, when the blowby gas is recirculated from the crank chamber to the intake side, PCV (Positive Crankroom Ventilation) is performed in which fresh air is introduced from the intake side to the crank chamber side and the crank chamber is actively ventilated. The parts related to the PCV in the entire engine system are collectively called a PCV system.

  The blow-by gas leaking into the crank chamber passes through the environment in which the balance weight and the like are scooping up the oil in the oil pan, and therefore contains not only unburned gas but also mist of engine oil. As a result, the engine oil mixed in the blow-by gas is recombusted. This promotes the consumption of engine oil, which is not preferable.

  In view of this, a device called oil drop (oil separator) has been devised for removing engine oil in a blow-by gas passage for moving blow-by gas from the crank chamber to the head cover.

  In Patent Document 1, in the blow-by gas passage formed in the head cover from the cylinder head in which the cam chamber is formed, since the conventional blow-by gas passage is directly above the cam shaft, the oil droplets scraped by the rotation of the cam are blow-by. A solution to the problem that oil separation is not performed efficiently by entering the gas passage is disclosed.

  More specifically, in an oil separator of a PCV system provided in a head cover of a DOHC engine, an ignition plug tube adjacent to the blow-by gas inlet of the oil separator is located at an intermediate position between the In-side and Ex-side camshafts. The guide plate is provided at the lower part of the blow-by gas inlet and the blow-by gas intake direction of the guide plate is parallel to the camshaft and opposite to the position of the blow-by gas hole. An oil separator for the system is disclosed.

Japanese Utility Model Publication No. 62-1111916

  In Patent Document 1, since the intake on the cam chamber side opens in parallel with the camshaft and opens only on the side opposite to the position of the blowby gas hole, oil enters the oil separator portion provided in the blowby gas passage. There is a temporary effect in that the oil separation is not performed efficiently.

  However, the flow of blow-by gas flow in the cam chamber is poor, and there remains a problem that the ventilation performance on the cam chamber side is not sufficient. In addition, since the opening on the cam chamber side is opened in a direction parallel to the camshaft, when the pressure on the cam chamber side increases or when the pressure on the blow-by gas passage side suddenly decreases, the cam chamber side opening There was also a problem in that oil splashes were sprayed out to the blow-by gas passage side, resulting in blowback.

  The present invention has been conceived in view of the above problems, and reduces the intrusion of oil from the cam chamber, enters the blow-by gas passage provided in the cylinder head and the head cover through the cam chamber from the crank chamber side. A blow-by gas passage structure is provided for preventing the coming blow-by gas from bringing in oil as much as possible, and for facilitating the flow of fresh air from the fresh air supply side to the cam chamber side.

More specifically, the blow-by gas passage structure according to the present invention is:
A passage through which blow-by gas and fresh air are provided in a space between a cylinder head having a cam chamber containing a cam shaft and a head cover covering the cylinder head;
A first opening communicating with said passage and the fresh air supply is provided before Kihe head cover,
A second opening communicating the cam chamber side and the passage;
The second opening is
In a part of the bottom surface constituting the part where the flow passage cross-sectional area of the blow-by gas passage provided at a position not directly above the cam shaft expands toward the cam chamber side ,
It opens toward the cam chamber side.

  In the blow-by gas passage structure of the present invention, the opening from the cam chamber side to the blow-by gas passage side is formed at a position avoiding the position directly above the cam shaft, so that the oil scraped by the cam shaft can be prevented from entering the blow-by gas passage. can do.

  In addition, since the periphery of the opening provided at a position not directly above the camshaft is formed so as to enlarge the cross-sectional area of the flow path, when the gas flow rate decreases and blow-by gas enters the blow-by gas passage, Oil mist inhalation can be reduced.

  In addition, since the opening that connects the blow-by gas passage and the cam chamber is formed so as to face directly to the cam chamber side, when fresh air flows into the cam chamber, the flow of fresh air becomes smooth, and the ventilation performance of the cam chamber Has the effect of improving.

It is an assembly drawing explaining the external appearance of the blowby gas passage concerning the present invention. It is a figure explaining the 2nd opening which connects a cam chamber and a blow-by gas passage.

  The present invention will be described below with reference to the drawings. The following description exemplifies an embodiment of the present invention, and the following embodiment may be modified without departing from the gist of the present invention.

  FIG. 1 shows a blow-by gas passage structure 1 according to the present invention. The blow-by gas passage structure 1 according to the present invention is formed in the cylinder head 20 and the head cover 24. In FIG. 1, the cylinder block connected to the lower side of the cylinder head 20 and the oil pan connected to the lower side of the cylinder block are omitted.

  In the cylinder head 20, a cam chamber 22 is formed which houses a camshaft 2 (2a, 2b) for opening and closing the intake and exhaust valves of the combustion chamber. A baffle plate 4 is disposed on the cam chamber 22. A groove structure 5 for forming a blow-by gas passage is formed in the baffle plate 4.

  On the other hand, a rib structure 9 for forming a blow-by gas passage is formed on the inner surface of the head cover 24. In the figure, the rib structure 9 is hidden and cannot be seen. The rib structure 9 formed on the inner surface of the head cover 24 and the groove structure 5 of the baffle plate 4 are formed at corresponding positions, and the lower end of the rib structure 9 is fitted into the groove structure 5 of the baffle plate 4, thereby The gas passage is formed as a closed space in the space between the cylinder head 20 and the head cover 24. This space is a space forming a blow-by gas passage (also simply referred to as a passage).

  The head cover 24 is formed with a first opening 8 communicating with at least the fresh air supply side. In addition, the head cover 24 may be formed with a communication port with the return path for returning the blow-by gas to the intake side separately from the first opening 8. The first opening 8 is an opening that communicates the blow-by gas passage and the fresh air supply side.

  The blow-by gas passage according to the present invention is formed from the first opening 8 to the communication passage to the crank chamber side. A plurality of protrusion shapes may be formed in the blowby gas passage. In the blow-by gas passage communicating with the fresh air supply side, fresh air flows toward the crank chamber when the load is low, but blow-by gas rises from the crank chamber when the load is high. This is to separate the blowby gas oil. In FIG. 1, the groove 7 that receives the protrusion shape on the baffle plate side is shown.

  FIG. 2 shows an enlarged view of the vicinity of the second opening 12. A rib structure 9 extending from the head cover 24 is fitted into the groove structure 5 formed on the baffle plate 4. Therefore, although not shown, it may be considered that the side wall of the blow-by gas passage is formed.

  Further, FIG. 2 shows an example of a route through which the fresh air 15 flowing from the first opening 8 flows. The fresh air 15 flowing in from the first opening 8 once crosses the baffle plate 4 and returns to the first opening 8 again, and communicates from the second opening 12 provided in the baffle plate 4 to the cam chamber 22 side. Here, between the first opening 8 and the second opening 12, the rib structure 9 extends from the inner surface side of the head cover 24 to the baffle plate 4 side, so that the fresh air 15 meanders to the second opening. Proceed to 12.

  The passage enlarged portion 10 is a portion where the cross-sectional area of the blow-by gas passage is enlarged, and has a shape that is intentionally formed to provide the second opening 12. Here, the ceiling that forms the blow-by gas passage is the inner surface of the head cover 24. That is, by forming a concave shape protruding downward from the baffle plate 4 forming the blow-by gas passage, a portion (passage enlargement portion) 10 in which the cross-sectional area of the passage is enlarged can be formed in the blow-by gas passage. it can. Note that the cross-sectional area of the blow-by gas passage can be further increased by raising the ceiling of the blow-by gas passage at the passage enlarged portion 10. The second opening 12 is formed in the passage enlarged portion 10.

  Furthermore, the passage enlarged portion 10 is formed to include a position that is not directly above the camshaft. FIG. 2 shows an example in which the passage enlarged portion 10 is formed so as to include a position where the second opening 12 can be formed between the two camshafts (2a, 2b) on the intake side and the exhaust side. The second opening 12 is formed at a position not directly above the camshaft 2.

  The second opening 12 is formed to open directly toward the cam chamber. That is, the second opening 12 is not formed on a surface that is substantially perpendicular to the baffle plate 4 in the concave shape, including a concave side surface (surface illustrated by reference numeral 13) that forms the passage expanding portion 10.

  The operation of the blow-by gas passage structure 1 formed as described above will be described. When the engine has a low load, fresh air 15 is introduced from the first opening 8 into the blow-by gas passage. The fresh air 15 flows through the blow-by gas passage along the side wall formed by the rib structure 9 extending from the inner surface of the head cover 24.

  When the passage enlargement portion 10 is reached, the flow speed decreases. This is because the fresh air 15 is released from the narrow space to the wide space. At this time, since the second opening 12 between the cam chamber 22 side and the cam chamber 22 is directly open, the second chamber 12 can smoothly flow into the cam chamber 22. The fresh air 15 flowing into the cam chamber 22 flows toward the crank chamber while pushing back the blow-by gas in the cam chamber 22 toward the crank chamber.

  On the other hand, when the engine load is high, blow-by gas rises from the crank chamber side. Of course, a blow-by gas passage having a PCV valve and a PCV pipe for discharging blow-by gas is formed elsewhere. However, even in a fresh air passage, blow-by gas flows backward at high loads.

  At this time, blow-by gas from the cam chamber 22 passes through the second opening 12 and flows into the passage enlarged portion 10 that secures a relatively large space, so that the flow velocity is relatively low. Therefore, it is possible to prevent oil from the cam chamber 22 from entering the blow-by gas passage.

  The second opening 12 opens directly to the cam chamber 22 side, but is not formed immediately above the camshaft 2 as a position. For this reason, the oil pumped up by the camshaft 2 is prevented from entering the blow-by gas passage.

  As described above, in the blow-by gas passage structure 1 according to the present invention, the second opening 12 for communicating the cam chamber 22 and the blow-by gas passage is formed in the passage enlarged portion 10 formed at a position not directly above the cam shaft 2. Therefore, the ventilation performance of the cam chamber 22 and the flow of the fresh air 15 to the crank chamber can be made smooth while preventing oil from entering the blow-by gas passage.

  The blow-by gas passage structure according to the present invention can be suitably used as a passage for introducing fresh air in a PCV system.

DESCRIPTION OF SYMBOLS 1 Blow-by gas passage structure 2 (2a, 2b) Camshaft 4 Baffle plate 5 Groove structure 7 Groove corresponding to protrusion shape 8 1st opening 9 Rib structure 10 Passage expansion part 12 2nd opening 13 Recessed side surface 20 Cylinder head 22 Cam chamber 24 Head cover

Claims (1)

A passage through which blow-by gas and fresh air are provided in a space between a cylinder head having a cam chamber containing a cam shaft and a head cover covering the cylinder head;
A first opening communicating with said passage and the fresh air supply is provided before Kihe head cover,
A second opening communicating the cam chamber side and the passage;
The second opening is
In a part of the bottom surface constituting the part where the flow passage cross-sectional area of the blow-by gas passage provided at a position not directly above the cam shaft expands toward the cam chamber side ,
A blow-by gas passage structure having an opening toward the cam chamber.