JPS62178712A - Forcedly air-cooled engine - Google Patents

Abstract

PURPOSE:To balance cooling air and to effectively cool an engine by providing a partition wall for partitioning the interior of a shroud into a fan chamber and a cylinder chamber with a large opening opposite to a cylinder head and with a small opening opposite to a cylinder. CONSTITUTION:A shroud 40 covers a cooling air blowing fan 34 fixed to a crankshaft 18 of an engine and forms an air conducting path to a cylinder 15 and a cylinder head 16. The shroud 40 comprises a side shroud 40a and an upper shroud 40b for covering the outsides of the cylinder 15 and the cylinder head 16. A partition wall 50 for partitioning the interior of the shroud 40 is disposed between the side shroud 40a and the upper shroud 40b. A large upper opening 52 is provided at a part of the partition wall which is opposite to the cylinder head 16, and a small lower opening 53 is provided at a part thereof which is opposite to the cylinder 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a forced air-cooled engine used, for example, to drive a scooter type vehicle.

[Conventional technology]

This type of forced air-cooled engine has a shroud that covers the cooling fan attached to the crankshaft and the outside of the engine cylinder, and cools the engine by blowing air generated by the fan. While this has the advantage of being able to cool the engine well even at low temperatures, there is a loss in fan drive output. Therefore, from the viewpoint of reducing this loss, it is desired to utilize the cooling air effectively, and conventionally, a baffle plate is provided to change the direction of the cooling air.

[Problem that the invention seeks to solve]

However, such a baffle plate has a problem in that the cooling air cannot necessarily be used effectively because the air volume cannot be controlled. That is, a large amount of cooling air flows toward the cylinder side near the cooling fan, and the amount of air flowing toward the cylinder head side, which requires more cooling than the cylinder, becomes smaller.

[Means for solving problems]

The present invention has been made in view of these circumstances, and it is an object of the present invention to provide a forced air-cooled engine that can effectively utilize cooling air. The forced air-cooled engine according to the present invention is provided with a partition wall that divides the inside of the shroud into a fan chamber and a cylinder chamber, and a portion of the wall that communicates between the two chambers and faces the cylinder head is large and faces the cylinder. The opening is relatively small.

[Effect]

In the present invention, the amount of cooling air is controlled by the opening, so that more cooling air flows through the cylinder head side, which requires higher cooling, and less cooling air flows through the cylinder side, which requires lower cooling compared to the cylinder head. .

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view taken along line I-1 in FIG. 2 showing a forced air-cooled engine according to the present invention, and FIG. 2 is a side view showing a motorcycle equipped with a forced air-cooled engine. 1
2 indicates a square-type motorcycle, which has a low-floor footrest 4 between the handlebar 2 and the seat 3, and a rear cover that covers the lower part of the seat 3 at the rear. 5 are arranged.

Reference numeral 10 denotes a forced air-cooled engine housed in the rear cover 5, which constitutes a drive unit together with a transmission case 12 that houses a power transmission mechanism 11 that extends integrally on the side and transmits engine power rearward. It functions as a component that suspends 13.

The engine 10 is a two-stroke engine with precompression in the crank chamber, and a cylinder 15 having a cooling fin 15a extending horizontally in front of the rear wheel 13 is disposed substantially vertically. A cylinder head 16 closes the upper part of the cylinder 15 and holds the spark plug 17, and is provided with cooling fins 16a that protrude vertically and extend in the vehicle width direction. 16b is a cooling pace fin provided at the lower part of the cylinder head 16, and extends upwardly to the left. Reference numeral 18 denotes a crankshaft connected to a piston 20 via a connecting rod 19, which rotates forward in a clockwise direction in FIG. 21 is a crank case defining a crank chamber, and a partition wall 22a.

Right and left crankcases 21a having 22b.

21b. The crankshaft 18 is mounted in the vehicle width direction via bearings 24 and 24 that are press-fitted into cylinders 23a and 23b provided on the partition wall. Reference numeral 25 denotes an exhaust pipe extending obliquely downward from the front surface of the cylinder 15 for discharging exhaust gas in the same direction as the direction of rotation of the crankshaft 18. The exhaust pipe 25 extends rearward under the engine 10, and is located below the rear cover 5 and supported on the side of the rear wheel 13 by a muffler 2.
6.

Reference numeral 30 denotes a boss keyed to one end of the crankshaft 18. A rotor 31a of a generator 31 is fixed to this boss 30 with a rivet 32, and a cooling fan 34 is attached to the outside of the rotor 31a. It is attached with screws 35.

A resin shroud 40 covers the outside of the cooling fan 34 and the outside of the cylinder 15 to form a cooling air guide path, and extends from the periphery of the cooling fan 34 upward to the side of the cylinder 15. Extended side shroud 4
0a, and an upper shroud 4 extending in the vehicle width direction from the upper part of the side shroud 40a and covering the outside of the cylinder 15.
0b. The side shroud 40a has an air intake 41 at a portion facing the cooling fan 34. Upper shroud 40. As shown in FIG. 3 in a plan view and in FIG. 4 as a side view, b is formed into a box shape that opens downward, and a peripheral wall 42 provided on the side is connected to the edge of the side shroud 40a. They are integrally connected by engaging in the matching groove 43. Reference numeral 44 denotes an exhaust port provided on the back surface of the upper shroud 40b for discharging air that has cooled the cylinder 15 and the cylinder head 16, and extends toward the rear and right side toward the muffler 26.

50 is a partition wall that divides the inside of the shroud 40 into two parts, a fan chamber 51 and a cylinder chamber 52;
It is formed integrally with the side surface of 0b and extends in the front-rear direction.

53 and 54 are upper and lower openings opened in the front part of the partition wall 50 and having a rectangular shape in side view and communicating between the two units, which face the cylinder head 16 which is easily heated to form the upper surface of the combustion chamber. The opening area of the upper opening 53, which is opened in the area where the opening is made, is made large. On the other hand, the opening area of the lower opening 54 opened in a portion facing the cylinder 15 is relatively smaller than that of the upper opening 53.

In a forced air-cooled engine configured in this way,
When the engine 10 is started and the crankshaft 18 rotates,
The cooling fan 34 is driven to rotate. Therefore, the cooling fan 34 takes in external air from the air intake port 41 and increases the pressure to generate cooling air. After the cooling air is guided upward by the side shroud 40a, it passes through the upper and lower openings 53 and 54, flows into the upper shroud 40b, and flows along the cooling fins 15a and 16b while contacting the cylinder 15 and the cylinder. Cool the head 16.

After cooling, the cooling air flows along the peripheral wall of the upper shroud 40b and is blown out from the exhaust port 44.

Here, the upper opening 53 has a large opening area, and the lower opening 5
Since the opening 4' is relatively small compared to the upper opening 53, the amount of cooling air passing through the partition wall 50 and flowing into the cylinder chamber 52 can be controlled. That is, more cooling air flows through the cylinder head 16 side, which requires relatively high cooling, and less cooling air flows through the cylinder 15 side, which requires lower cooling compared to the cylinder head 16. In other words, the amount of cooling air can be changed according to the amount of heat generated by the part to be cooled, and effective cooling can be performed.

In addition, since the cooling base fins 16b of the cylinder hood 16 are inclined upward to the left, the cooling air can be directed upward and directed efficiently to the cooling surface.

〔Effect of the invention〕

As explained above, according to the present invention, a partition wall is provided that divides the inside of the shroud into a fan chamber and a cylinder chamber, and the part of this wall that communicates between the two units and faces the cylinder head is thick ( Since the part facing the cylinder has a relatively small opening, the cooling air volume can be controlled by the opening.
It is possible to increase the amount of cooling air flowing through the cylinder head side, which requires relatively high cooling, and to reduce the amount of cooling air flowing through the cylinder side, which requires lower cooling than the cylinder head.

Therefore, it is possible to flow cooling air that is balanced according to the parts to be cooled, so that the cooling air can be effectively used to cool the engine.

[Brief explanation of drawings]

FIG. 1 is a sectional view taken along the line 1-1 in FIG. 2 showing a forced air-cooled engine according to the present invention, FIG. 2 is a side view showing a motorcycle equipped with a forced air-cooled engine, and FIG. 3 is an upper shroud. FIG. 4 is a side view as well. 15...Cylinder, 16...Cylinder head,
34...Cooling fan, 40...Shroud, 50...Partition wall, 51...Fan chamber, 52...
...Cylinder chamber, 52, 53...Top and bottom openings.

Claims (1)

[Claims] In a forced air-cooled engine in which an engine cylinder and a cooling fan are covered with a shroud that forms an air guide path, a partition wall is provided to divide the inside of the shroud into a fan chamber and a cylinder chamber, and this wall is provided with a partition wall that separates the two chambers. A forced air-cooled engine with a large opening in the area facing the communicating cylinder head and a relatively small opening in the area facing the cylinder.