JPH0221567Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to a cooling structure for the camshaft bearing of an engine, and more specifically, to a cooling structure that protects the camshaft bearing from the high heat of exhaust gas flowing through the exhaust gas recirculation passage. be.

(Prior technology) Conventionally, an engine exhaust passage is connected to an intake passage via an exhaust gas recirculation passage, and a portion of the exhaust gas is added to the intake air to lower the engine combustion temperature, thereby suppressing the generation of _NOx . The technical idea to do so has become publicly known. By the way, if the exhaust gas recirculation passage is formed as a conduit outside the engine body, the structure around the engine body becomes complicated. It is considered to be provided within the cylinder head.

When an exhaust gas recirculation passage is formed in the cylinder head in this way, the passage is generally cast integrally with the cylinder head, but in consideration of workability and processability during casting, it is usually formed at the side end of the cylinder head. (the end in the cylinder arrangement direction), and is set near the outermost end, avoiding the intake and exhaust valves of the cylinders at this end.

If the engine is a so-called OHC type engine with a camshaft located inside the cylinder head,
The above-mentioned exhaust gas recirculation passage is provided closer to the cylinder block than the camshaft insertion part, but this passage is designed so as not to obstruct the flow of engine cooling water that flows through the cooling passage around the cylinder and flows from the cylinder block into the cylinder head. The exhaust gas recirculation passage is often formed integrally with the lower wall surface of the camshaft insertion portion away from the cylinder block.

However, since a camshaft bearing part is formed near the most side end of this camshaft insertion part, the exhaust gas recirculation passage is continuous with this bearing part via the partition wall, and the high temperature exhaust gas flowing through the exhaust recirculation passage is The gas causes the camshaft bearing to be heated. In particular, if this camshaft bearing is on the side where a winding member (timing belt or timing chain) that transmits the rotation of the crankshaft to the camshaft is arranged, the bearing part receives the tension of the winding member. In particular, since a large load is applied to the bearing, the lubricating oil film tends to be thin in the bearing. Therefore, when the camshaft bearing section is heated to a high temperature, the lubricating oil in the bearing section may run out of oil film, causing the bearing to seize, or the bearing section may become thermally deformed, causing uneven wear of the camshaft. Occur.

(Purpose of the invention) As described above, even if the camshaft bearing on the winding member side and the exhaust gas recirculation passage are formed continuously, the present invention is designed to transfer the high heat of the exhaust gas flowing through the exhaust gas recirculation passage to the bearing. It is an object of the present invention to provide a cooling structure for a camshaft bearing portion of an engine, which is difficult to solve and thus can eliminate various problems such as those described above.

(Structure of the invention) In the engine camshaft bearing cooling structure of the invention, as described above, the camshaft and the exhaust gas recirculation passage are arranged in the cylinder head, and the winding member that transmits the rotation of the crankshaft to the camshaft is arranged. In an engine in which a camshaft bearing part and an exhaust gas recirculation passage formed near the outermost end in the cylinder arrangement direction are continuous through a partition wall, a heat insulating layer made of, for example, air or ceramic is formed on the partition wall. It is characterized by:

(Effect of the invention) If a heat insulating layer is provided on the partition wall between the camshaft bearing and the exhaust gas recirculation passage, the high heat of the exhaust gas flowing through the exhaust gas recirculation passage will be difficult to conduct to the camshaft bearing, and the temperature of the bearing will be reduced. This will eliminate the above-mentioned problems.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a cooling structure for a camshaft bearing of an engine according to an embodiment of the present invention, and FIGS. 2 and 3 show cylinder heads shown in FIG. 1 and 2, respectively. - It is shown by cutting along the line. A cylinder 2 is formed in the cylinder block 1, and a piston 3 is slidably disposed within the cylinder 2. A cylinder head 5 is fixed to the cylinder block 1 via a gasket 4, and an engine combustion chamber 6 is defined by the cylinder head 5, the cylinder 2, and the piston 3.

A camshaft insertion portion 7 extending in the cylinder arrangement direction is formed in the cylinder head 5, and a camshaft bearing portion 8 is formed at both ends and a central portion (not shown) of the cylinder head 5.
is provided. A camshaft 10 having cams 10a and 10b for opening an intake valve 9 and an exhaust valve (not shown) has a camshaft insertion portion when a bearing 11 attached to the camshaft 10 is fitted into the bearing portion 8. It is rotatably supported within 7. As an example, the camshaft 10 is
A pulley 12 fixed to one end of the pulley 12 is rotated by an engine crankshaft (not shown) via a timing belt 13, thereby rotating synchronously with the engine crankshaft. Cylinder head 5
A cylinder head cover 14 is attached to the upper part of the cylinder block 1 and a timing belt cover 15 that covers the timing belt 13 is attached to the sides of the cylinder block 1 and the cylinder head 5.

The cylinder head 5 that is cast as clearly shown in FIG. 2 has an exhaust gas recirculation passage 18 that communicates with the exhaust port 16 and opens at the end 5a on the side where the intake port 17 is opened, which is integral with the cylinder head 5. is formed. The exhaust gas recirculation passage 18 opens into an intake manifold (not shown) that communicates with the intake port 17, and is adapted to recirculate a portion of the exhaust gas discharged into the exhaust port 16 to the intake system. .

The exhaust gas recirculation passage 18 has intake and exhaust ports 1
The cylinder head 5 is formed so that its central portion extends near the outermost end of the cylinder head 5, avoiding the intake and exhaust valves disposed at the cylinder head 7 and 16. The exhaust gas recirculation passage 18 also allows engine cooling water pumped by a cooling water pump 19 to rise in a cooling water passage 20 (see FIG. 2) formed around the cylinder 2 and reach the cylinder head 5. The camshaft insertion portion 7 is provided adjacent to the camshaft insertion portion 7 apart from the lower end surface 5b on the cylinder block 1 side so as not to prevent the camshaft from flowing into the cylinder block 1 side.
Therefore, the central portion of the exhaust gas recirculation passage 18 is continuous with the camshaft bearing portion 8 formed at the end of the camshaft insertion portion 7 via the partition wall 21. A camshaft 1 is attached to this partition wall 21.
A gap 22 is provided which extends in the axial direction of the bearing part 8 and communicates between the front and rear parts of the bearing part 8.

Since the exhaust gas that recirculates to the intake system through the exhaust gas recirculation passage 18 has an extremely high temperature, the passage 18
The peripheral wall of the exhaust gas is heated to a high temperature. Further, since a particularly large load is applied to the camshaft bearing portion 8 on the side where the timing belt 13 is disposed due to the tension of the timing belt 13, the thickness of the lubricating oil film in the bearing portion 8 tends to be thin. . However, here, the lubricating oil that is supplied to the valve train lubricating parts such as the cams 10a and 10b of the camshaft 10 and the bearings 11, received on the camshaft insertion part 7, and then collected in, for example, an oil pan, is provided in the partition wall 21. Since it flows in the space 22 that is
The heat of the exhaust gas is radiated to the lubricating oil through the peripheral wall of the passage 18, so that the bearing portion 8 does not become high in temperature due to the heat of the exhaust gas. In this way, the bearing part 8
However, it is insulated by lubricating oil that acts as a heat insulating layer.
By being cooled, the bearing 11 of the camshaft 10 does not become hot, and the bearing 11 is prevented from seizing or
This prevents thermal deformation from causing uneven wear of the camshaft 10.

Note that even if the gap 22 provided in the partition wall 21 is set at a height that prevents the flow of valve train lubricating oil,
Since the air within the gap 22 acts as a heat insulating layer, an effect of cooling the bearing portion 8 can be obtained.

Furthermore, in addition to providing the above-mentioned voids 22 in the partition wall 21, a heat insulating layer may be formed using a heat insulating material such as ceramic to prevent the bearing portion 8 from becoming hot due to the high heat of the exhaust gas.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing one embodiment of the present invention, and FIG. 2 is a first cross-sectional view of the cylinder head in the above embodiment.
FIG. 3 is a sectional view taken along the line -- of FIG. 2. 5... Cylinder head, 8... Camshaft bearing portion, 10... Camshaft, 13... Timing belt, 18... Exhaust gas recirculation passage, 21... Partition wall, 22... Gap.

Claims (1)

[Scope of Claim for Utility Model Registration] A camshaft shaft and an exhaust gas recirculation passage are arranged in the cylinder head, and the camshaft bearing portion on the side where the wrapping member for transmitting the rotation of the crankshaft to the camshaft is disposed, and the vicinity of the outermost end in the cylinder arrangement direction. 1. A camshaft bearing cooling structure for an engine in which an exhaust gas recirculation passage formed in an engine is connected to an exhaust gas recirculation passage through a partition wall, the partition wall being provided with a heat insulating layer.