JPH0532753U - Cylinder block structure of air-cooled engine - Google Patents

Abstract

(57) [Abstract] [Purpose] Cylinder liner 5 and push rod space 18
Since there is a curved cooling air passage 11 between them, the cylinder liner 5 and the push rod space 18 can be configured to bite into each other, and a sufficient cooling air passage space can be provided, and the thickness of the cylinder wall can be increased. Can be taken sufficiently. [Structure] Cylinder liner 5 and push rod space 18
Only the portion forming the central cooling air passage 11 at the closest portion of the cylinder 17 has a structure in which the upper mold 14 is pulled upward, and the cooling air passage 11 is opened on the upper surface,
The curved shape along the line is possible.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a structure of a cooling air passage of an air-cooled overhead valve engine.

[0002]

[Prior Art]

 Conventionally, regarding the structure of the cooling air passage of the air-cooled overhead valve engine, the technique described in Japanese Patent Publication No. 61-33985 is known. Since the space formed between the push rod space 18 and the cylinder liner 5 is narrow, there is a problem that the cooling air does not reach the side opposite to the fan side and the part gets high heat. This problem is solved. For this reason, in the above-mentioned conventional technique, a cooling air guide for covering the circumference of the cylinder is provided, and the cooling air is guided by the cooling air guide.

Further, in the above-mentioned conventional technique, the cooling air passage formed between the cylinder liner and the push rod space 18 is formed by removing the casting mold in the left-right direction of the cylinder liner. With such a conventional configuration, the upper surface of the cylinder block is closed, and the narrowest part between the cylinder liner and the push rod space is configured in a substantially straight line, so that a particularly narrow part occurs. Even if the front and rear of that portion are wide, the air volume is limited by the narrowest portion, so that there is a problem that sufficient cooling air does not reach the portion of the cylinder on the side opposite to the fan.

Further, as described above, when die-cutting is performed to form the cooling air passage from the left and right, the cooling air passage has a linear shape, and therefore, when the minimum cylinder wall is to be obtained, the cylinder liner There is a problem in that the space between the No. 5 and the push rod space 18 becomes large and the air-cooled overhead valve engine cannot be made compact.

[0005]

[Problems to be solved by the device]

 The present invention solves the above-mentioned problems of the prior art. Only the portion forming the cooling air passage 11 at the closest portion of the cylinder liner 5 and the push rod space 18 is configured so that the mold is pulled out upwards. By opening 11 on the upper surface, a curved shape is possible, and therefore, since there is a curved cooling air passage 11 between the cylinder liner 5 and the push rod space 18, the cylinder liner 5 and the push rod space 18 are Can be configured so as to bite into each other, a sufficient cooling air passage space can be secured, and a sufficient thickness of the cylinder wall can be secured.

[0006]

[Means for Solving the Problems]

 The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described. That is, in the cylinder block 1 of the air-cooled engine, the central cooling air passage 11 in the narrowest part between the cylinder liner 5 and the push rod space 18 is opened on the upper surface of the cylinder block 1, and the cooling air passage 11 is connected to the cylinder 17. It has an arc shape curved in the direction along the outer periphery of the.

[0007]

[Action]

 Next, the operation will be described. Cooling air is blown from a cooling fan provided on the front side of the air-cooled overhead valve engine. However, the cooling air needs to be uniformly blown around the cylinder 17, so that the cylinder 17 and the push rod are connected. A certain amount of cooling air also needs to pass through the spaces between the spaces 18. In the present invention, the cooling air passage is composed of the cooling air passages 12 and 13 and the central cooling air passage 11, and the central cooling air passage 11 has a curved shape along the outer periphery of the cylinder 17, The central cooling air passage 11, which has been the narrowest portion in the past, can be configured to have a passage of the same width, and there is no longer a bottleneck in the passage of cooling air. Further, since the outer periphery of the cylinder 17 is along the curved central cooling air passage 11, even when the diameter of the cylinder 17 is increased, the thinnest portion of the cylinder wall is unlikely to occur.

[0008]

EXAMPLE Next, an example will be described. 1 is a front sectional view showing the overall structure of an air-cooled engine of the present invention, FIG. 2 is a plan view showing the upper surface of a cylinder block 1 orthogonal to the sliding direction line of a piston 3, and FIG. 3 is a camshaft 10 and a cam follower. 21 and 22 are side sectional views, FIG. 4 is a plan sectional view of the cooling air passages 11, 12, and 13 of the cylinder block 1, and FIG. 5 is a side sectional view of the cooling air passages 11, 12, and 13 as well. is there.

The overall configuration will be described with reference to FIG. The air-cooled overhead valve engine includes a cylinder block 1, a crankshaft 4, a piston 3 connected to the crankshaft 4 by a connecting rod, a cylinder liner 5 on which the piston 3 slides, a cylinder head 2 and a camshaft 10. It is composed of a balancer shaft 25.

Then, the cam followers 21 and 22 contact the cam shaft 10, and the vertical slide of the cam followers 21 and 22 is transmitted to the intake valve and the exhaust valve of the cylinder head 2 by the push rod. The push rod space 18, which is the portion through which the push rod passes, passes through the side of the cylinder block 1 into which the cylinder liner 5 is fitted, and it is difficult to cool the cylinder 17 in that portion. Conventionally, a cooling air passage is formed between the push rod space 18 and the cylinder 17, but if the cooling air passage 11 is made too large, the space between the cylinder and the push rod space becomes too wide. However, there was a problem that the cylinder block could not be made compact.

On the contrary, if the cooling air passage between the cylinder 17 and the push rod space 18 is made too narrow, the cooling air from the cooling fan passing through this portion becomes difficult to pass and the narrowest portion can be cooled. Not only that, but it becomes impossible to cool the outer circumference of the cylinder on the side opposite to the cooling fan, and the temperature of that part rises too much, which causes the engine performance to deteriorate.

In addition, in order to improve the horsepower, the design of the cylinder 17 is changed by opening the large diameter cylinder 17 in the cylinder block 1 made of the same material and increasing the diameter of the cylinder liner 5. However, if the insertion hole of the cylinder liner 5 is machined to have a large diameter in order to increase the diameter of the cylinder 17, the thinnest portion is between the push rod space 18 and the thinnest cylinder wall. is there. This is because the cooling air passage 11 between the cylinder 17 and the push rod space 18 is formed by inserting a mold into the cylinder 17 from the left and right in the past, so that it is linear in a plan view. This is a cooling air passage, and since the circular cylinder 17 having a large diameter is brought closer to this linear cooling air passage, the portion of the cooling air passage is thinnest.

In the present invention, in order to solve the above-mentioned problems of the conventional technology, the shape of the cooling air passage 11 between the cylinder 17 and the push rod space 18 is curved along the outer circumference of the cylinder 17. It has a shape. In this way, the curved shape along the outer periphery of the cylinder 17 can be constituted only by the cooling air passages 12 and 13 in the conventional method of inserting the molds 15 and 16 from the left and right sides of the cylinder 17 as shown in FIG. Therefore, only the cooling air passage 11 at the center is constructed by inserting the upper mold 14 which is taken in and out from above. When the central cooling air passage 11 is formed by the upper mold 14, a hole for removing the upper mold 14 is inevitably formed in a portion of the upper surface of the cylinder 17 on which the cylinder head 2 is mounted. Is configured to be closed by mounting the cylinder head 2.

In FIG. 4, the shape of the present invention is clearly illustrated. That is, the cooling air passage between the cylinder 17 and the push rod space 18 is constituted by the left and right cooling air passages 12 and 13 and the central central cooling air passage 11, and only the central cooling air passage 11 is provided. Is constituted by a curved concave portion along the outer circumference of the cylinder 17. Inside the push rod space 18, cam follower holes 19 and 20 through which the cam followers 21 and 22 pass are opened.

[0015]

[Effect of the device]

 Since the present invention is configured as described above, it has the following effects. That is, firstly, the central cooling air passage 11 formed between the cylinder 17 and the push rod space 18 does not form the narrowest portion at the maximum diameter portion of the cylinder 17, and the central cooling air passage 11 is formed. Since the passages can have the same width, the width of the narrowest part does not restrict the passage of the cooling air as in the conventional case.

Secondly, by providing the curved central cooling air passage 11 along the outer periphery of the cylinder 17, even when the diameter of the cylinder 17 is increased to increase the horsepower, the punching of the cylinder 17 is performed to the maximum extent. It was possible to perform the installation work, and the cylinder wall at the narrowest part, which would occur when the central cooling air passage was straight as in the past, was eliminated.

Thirdly, since the central cooling air passage 11 is opened upward, the cooling air in that portion can reach the upper portion of the cylinder 17, and up to the joint surface between the cylinder 17 and the cylinder head 2. Therefore, the cooling air efficiency of the portion of the central cooling air passage 11 can be improved.

[Brief description of drawings]

FIG. 1 is a front sectional view showing the overall configuration of an air-cooled engine of the present invention.

FIG. 2 is a plan view orthogonal to a sliding direction line of a piston 3 showing an upper surface of a cylinder block 1.

FIG. 3 is a side sectional view of a cam shaft 10 and cam followers 21 and 22.

FIG. 4 is a cooling air passage 11, 12 of the cylinder block 1.
FIG. 13 is a plan sectional view of a portion 13;

FIG. 5 is a side sectional view of a portion of the cooling air passages 11, 12, and 13 as well.

[Explanation of symbols]

 1 Cylinder Block 2 Cylinder Head 3 Piston 4 Crank Shaft 5 Cylinder Liner 11 Central Cooling Air Passage 12, 13 Cooling Air Passage 14 Upper Mold 15, 16 Left and Right Mold 17 Cylinder 18 Push Rod Space

Claims (1)

[Scope of utility model registration request] 1. In a cylinder block 1 of an air-cooled engine, a central cooling air passage 11 in a narrowest portion between a cylinder liner 5 and a push rod space 18 is opened on an upper surface of the cylinder block 1, and the cooling air passage 11 is opened. Is a circular arc shape curved in a direction along the outer periphery of the cylinder 17, a cylinder block structure of an air-cooled engine.