JPH063126Y2 - Engine cylinder block structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an engine cylinder block structure in which an oil return passage for returning oil accumulated in a cylinder head to the crank chamber side is formed.

(Prior Art) A cylinder block of an engine usually has a blow-by passage for guiding blow-by gas in a crankcase from above a cylinder head to an intake system, as described, for example, in Japanese Utility Model Publication No. 61-36115. It is provided in the cylinder axis direction. Further, the cylinder block must be provided with an oil return passage for returning the oil accumulated in the cylinder head to the crank chamber side. Normally, these blow-by passage and oil return passage are located outside the water jacket around the cylinder bore. It is distributed to the left and right.

However, when the blow-by passage and the oil return passage are arranged outside the water jacket in this way, the openings of these passages to the crank chamber are located in the vicinity of just above the counterweight locus of the crank. There are problems that the oil that is scraped up by the crank interferes with the oil return function and that a large amount of oil enters the blow-by passage. In particular, at the rear end of the cylinder block to which the transmission case is connected, it is difficult to provide the blow-by passage and the oil return passage with openings completely hidden behind the main bearing because of the structure. It will be affected by the oil scraped up by the crank.

(Object of the Invention) The present invention has been made in view of the above problems, and it is an object of the present invention to prevent the function of the oil return passage from being deteriorated and the oil to be drawn into the blow-by passage from coming into the blow-by passage as the crank is raised. .

(Configuration of the Invention) The present invention focuses on the mounting seat surface of the oil jet that is mounted at the crankpin side position in the piston ascending stroke with respect to the cylinder axis and sprays cooling oil on the back surface of the piston. The inventors have found means for also using the bulging portion of the lower deck where the surface is formed as a barrier for blocking the oil for scraping up the crank, and the structure is as follows. That is, in the cylinder block structure of the engine according to the present invention, in the cylinder block structure of the engine in which the oil return passage opening to the crank chamber is formed outside the water jacket when viewed from the cylinder axial direction, The bulging portion is provided at a position on the crankpin side in the piston ascending stroke with respect to the shaft center, and the lower deck at the lower end position of the cylinder bore is provided with a bulging portion bulging to a position facing the opening of the oil return passage. The lower surface of the lower deck including the lower surface of the section is characterized in that an oil jet mounting seat surface for spraying oil is formed on the rear surface of the piston.

(Operation) Oil accumulated in the cylinder head by lubricating the valve mechanism and the like enters the oil return passage and returns to the crank chamber side.
The oil scraped up by the counter weight of the crank during the piston lowering stroke does not reach the opening of the oil return passage because it is blocked by the bulging portion of the lower deck. Therefore, the function of oil return does not deteriorate due to the effect of the scraped oil.

Further, the oil jet is provided at a position where the oil is ejected in the same direction as the scraped oil, and moreover, it has a sufficient mounting seat surface for that purpose. Therefore, the function of the oil jet for cooling the rear surface of the piston can be improved.

By disposing the oil return passage on the crank pin side in the piston ascending stroke in this way, the blow-by passage can be provided on the side that is not affected by the oil scraping by the crank. Therefore, the oil does not enter the blow-by passage. Can be prevented.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a bottom view of a cylinder block showing an embodiment of the present invention applied to a 4-cylinder engine, and FIG.
It shows a cross section in the -A direction.

In this embodiment, the cylinder block 1 is provided with four cylinder bores 4, 5, 6, 7 which penetrate vertically from the upper deck 2 to the lower deck 3, and between the upper deck 2 and the lower deck 3 the cylinder bores 4 to 7 are provided. A water jacket 8 is formed so as to surround the circumference. Further, skirt portions 9 and 10 are formed in the lower part of the cylinder block 1 from the position of the lower deck 3 to the left and right, and are located at positions between the front and lower ends of the cylinder block 1 and the cylinder bores 4 to 7. Is a main bearing portion 11, 12, 13, 1 which is hung from the lower surface of the lower block 3 and whose left and right ends are connected to the skirt portions 9, 10.
4, 15 are formed. A coupling portion 16 for coupling a transmission case (not shown) is formed at the lower end of the cylinder block 1, and the lower end surfaces 17 and 18 of the skirt portions 9 and 10 are oil pans (not shown). ) Forming a mating surface.

Three oil return passages 20, 21, 22 extending in the cylinder axial direction are formed on the crankpin 19 side in the piston upward stroke with respect to the cylinder axial center, at a position outside the water jacket 8 when viewed from the cylinder axial direction. There is. The first oil return passage 20 is provided at a position opened right above the main bearing portion 11 at the front end, and the second oil return passage 21 is provided at the straight end of the fourth main bearing portion 14. It is provided so as to open upward. Furthermore, the third oil return passage 2
2 is provided at a position where the opening is half hidden behind the main bearing portion 15 at the rear end when viewed from the cylinder axis direction. Then, on the lower surface of the lower deck 3 on the same side, oil jet mounting seat surfaces 23, 24, 25, 26 are formed at outer positions adjacent to the rear main bearing portions with respect to the cylinder bores 4 to 7, respectively. ing. These mounting seat surfaces 23 to 26 are formed in such a manner that the lower deck 3 is partially bulged toward the skirt portion 9 side, and at the rear side end portion thereof, as shown in FIG. No. 3 oil return passage 22 overlaps with the opening. At the rear end, the lower deck 3 is the second
As shown in the figure, the lower surface of the lower deck, which is formed to bulge outward on the side of the third oil return passage 22 and includes the lower surface of the bulging portion 27, is raised downward to lower the oil jet mounting seat surface 2
6 is formed. The mounting seat surface 26 is provided with a bolt hole 29 for fixing the oil jet 28 and a positioning hole 30, and the oil jet 28 has the protrusion 3
1 is fitted into the positioning hole 30 and is fixed on the mounting seat surface 26 by the bolt 32. Oil gallery 33
The oil supplied from the nozzle is ejected from the nozzle portion 34 of the oil jet 28 to cool the back surface of the piston 35.

On the crankpin 19 side in the piston descending stroke with respect to the cylinder axis, that is, on the opposite side of the oil return passages 20 to 22, there are three axially extending positions outside the water jacket 8 when viewed from the cylinder axial direction. Two blow-by passages 30, 37, 38 are formed. The first blow-by passage 36 is located directly above the second main bearing portion 12 from the front side, and the second blow-by passage 37 is located directly above the fourth main bearing portion 14. In addition, the third blow-by passage 38
Like the third oil return passage 22, is provided at a position where the opening is half hidden behind the main bearing portion 15 at the rear end when viewed from the cylinder axial direction.

Since the crank chamber side openings of the first and second oil return passages 20 and 21 are hidden behind the main bearing portions 11 and 14, the counterweight 39 is blocked by the oil scraped up. There is no. Also, the crank chamber side opening of the third oil return passage 22 is
Since the bulging portion 27 of the lower block 3 in which the oil jet mounting seat surface 26 is formed becomes an obstacle to the remaining portion, it is hidden halfway behind the main bearing portion 15.
It can be prevented from being blocked by the oil that has been scraped up.

Further, the blow-by passages 36, 37, 38 are all
Since the counterweight 39 is on the side opposite to the oil scraping position, the scraping oil does not enter these passages.

(Effect of the Invention) Since the present invention is configured as described above, it is possible to prevent the function of the oil return passage from being deteriorated due to the scratching of the crank with a simple structure, and at the same time, to prevent the oil jet from spraying oil to the back surface of the piston Performance can be improved. In addition, the blow-by passage can be provided at a position that is not affected by the oil scraping to prevent the scraping oil from entering.

[Brief description of drawings]

FIG. 1 is a bottom view of a cylinder block according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line AA of FIG. 1: Cylinder block, 3: Lower deck, 8: Water jacket, 20, 21, 22: Oil return passage,
23, 24, 25, 26: mounting seat surface, 27: bulging portion, 2
8: Oil jet, 36, 37, 38: Blow-by passages.

Claims (1)

[Scope of utility model registration request] 1. A cylinder block structure of an engine in which an oil return passage opening to a crank chamber is formed outside a water jacket when viewed from the cylinder axis direction.
The oil return passage is arranged at a position on the crankpin side in the piston ascending stroke with respect to the cylinder axis, and the lower deck at the lower end of the cylinder bore is swollen to a position facing the opening of the oil return passage. A cylinder block structure for an engine, characterized in that an oil jet attachment seat surface for injecting oil is formed on the lower surface of the lower deck including the lower surface of the bulging portion.