JP3168140B2 - Engine cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an engine body having an ignition plug screwed to a top wall of a cylinder, and a shroud defining a cooling air passage between the engine body and an outer surface thereof, which is supported by the engine body. The present invention relates to a cooling device for an engine, in which a rotor having cooling blades for generating a flow of cooling air in a cooling air passage by rotation thereof is fixed to an outer end of a crankshaft.

[0002]

2. Description of the Related Art In an air-cooled engine, it is generally widely practiced to integrally form cooling fins on the outer surface of an engine body so as to face a cooling air passage for cooling the engine.

[0003]

When a cooling fin is provided in a small hand-held type engine used for a power source such as a trimmer or a chain saw, the ventilation around the head becomes particularly poor, and the exhaust valve and the spark plug are overheated. easy.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has a good ventilation around the head and is capable of effectively cooling the intake and exhaust ports, the valve operating chamber, and the spark plug. It is intended to provide a device.

[0005]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides an engine body having a cooling air passage penetrating through an internal valve operating chamber and passing between intake and exhaust ports therein. And a supplementary air passage that intersects the main air passage and guides the cooling air introduced into the inlet at both ends from the cooling air passage to the main air passage. During the operation of the engine,
Enter each of the auxiliary air ducts and join them in the middle of the main air duct.
Valve chamber, suction and exhaust ports, top of cylinder and spark plug
Shut the outlet of the cooling air passage, where the cooling air
The first feature resides in the provision in the loud .

According to the present invention, in addition to the above features, substantially rhombic first and second mounting seats for mounting a carburetor and an exhaust muffler respectively connected to an intake port and an exhaust port are provided on both outer surfaces of the engine body. The second feature is that the first and second mounting seats are formed so as to be adjacent to the inlets at both ends of the auxiliary air guide path, and the major axes of the first and second mounting seats are inclined with respect to the cylinder axis of the engine body.

Further, the present invention has a third feature in that, in addition to the second feature, the vaporizer is provided with a priming pump at a lower portion.

[0008]

According to the first feature of the present invention, during operation of the engine, cooling air generated in the cooling air passage by the cooling blades of the rotor flows into the main air passage and the auxiliary air passage of the engine body. Merges in the middle of the main wind path to the spark plug. Thereby, the valve train, the suction and exhaust ports, and the spark plug are sequentially and effectively cooled. Therefore, the lubricating oil is cooled in the valve operating chamber, the charging efficiency is improved at the intake port due to the decrease in the intake air temperature, and the exhaust valve and the spark plug can be prevented from overheating.

According to the second feature, by inclining the substantially rhombus-shaped mounting seat, mutual interference between the adjacent mounting seat and the auxiliary airflow passage is minimized to sufficiently secure a sectional area of the auxiliary airflow passage. This can further enhance the cooling effect.

According to a third feature of the present invention, the carburetor is mounted on the mounting seat in a posture in which the carburetor is tilted with the inclination of the mounting seat, and the priming pump below the carburetor is directed outward of the engine body. Therefore, the operability is improved.

[0011]

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

FIG. 1 is a plan view of a small four-stroke engine of a hand-held type used as a power source of a trimmer or a chain saw, FIG. 2 is a sectional view taken along line 2-2 of FIG. 1, and FIGS. FIG. 5 is a side view of the engine viewed from a carburetor, FIG. 6 is a side view of a cylinder block of the engine viewed from a mounting seat side of an exhaust muffler, and FIG. 6 is a sectional view taken along the line 7-7, and FIGS.
9 is a sectional view taken along lines 8-8 and 9-9 of FIG.

First, referring to FIG. 1, an engine body 1 of a small four-stroke engine E of a handheld type has a carburetor 2 and an exhaust muffler 3 attached to the left and right sides, respectively. Is attached.
Further, a fuel tank 5 is attached to a lower portion of the engine body 1. The carburetor 2 is provided with a diaphragm pump that pumps up fuel from the fuel tank 5 using pressure pulsation in the crankcase of the engine E and returns excess fuel to the tank 5. Fuel can be supplied to the intake port. Further, the carburetor 2 is provided with a priming pump 35 (refer to FIG. 5) which is manually operated mainly at the time of starting the engine in a cold region.

2 to 4, the engine body 1
A crankcase 6 formed by joining a pair of upper and lower case halves 6a and 6b with bolts;
And a cylinder block 7 integrated with a head fitted on one side wall thereof. The crankcase 6 and the cylinder block 7 are fixed to the former 6 and are provided with four stud bolts 36 penetrating through four corners of the latter 7. And a nut 37 screwed to them.

The two case halves 6a, 6 of the crankcase 6
b supports a crankshaft 8 and a piston 10 connected to a crankpin of the crankshaft 8 via a connecting rod 9.
Is slidably fitted to a cylinder 7a formed in the cylinder block 7.

On the top wall of the cylinder 7a, there are formed an intake port 11 and an exhaust port 12 connected to the carburetor 2 and the exhaust muffler 3, respectively.
Suction and exhaust valves 13 and 14 for opening and closing the valves 1 and 12 are provided. A valve train 15 for driving the intake and exhaust valves 13 and 14 is disposed in a valve train chamber 16 formed on one side of the crankcase 6 and the cylinder block 7. The valve chamber 16 can be opened and closed by a head cover 21 joined to the head of the cylinder block 7.

The valve gear 15 is supported by a drive timing gear 17 fixed to the crankshaft 8 and a support shaft 19 attached to the crankcase 6 at an intermediate portion of the valve gear chamber 16 so that the drive timing gear 17 A driven timing gear 18 driven at a reduction ratio of 1/1, a cam 20 integrally connected to one end of the driven timing gear 18,
0, a pair of cam followers 23 and 24 supported on a cam follower shaft 22 provided on the cylinder block 7 and a rocker shaft 25 provided on the head of the cylinder block 7 and one end of each. A pair of rocker arms 26 and 27 that contact the valve heads of the suction and exhaust valves 13 and 14, and a pair of push rods 28 and 29 that connect the cam followers 23 and 24 to the other ends of the rocker arms 26 and 27, respectively. Intake and exhaust valve 1
Valve springs 30 and 3 for urging the valves 3 and 14 in the valve closing direction, respectively.
The intake valve 13 is opened during the intake stroke of the piston 10, and the exhaust valve 14 is opened during the exhaust stroke.

As shown in FIG. 2, a known recoil starter 43 capable of cranking the crankshaft 8 is mounted on the upper part of the crankcase 6. Also the crankshaft 8
A rotor 46 with cooling blades 45 of a flywheel magneto 44 is fixed to the lower end of the flywheel, and an ignition coil 47 cooperating with the rotor 46 is fixed to the cylinder block 7.

A centrifugal clutch 49 is interposed between the rotor 46 and the working machine drive shaft 48. The centrifugal clutch 49 includes a plurality of clutch shoes 50 pivotally supported by the rotor 46, a clutch spring 51 for urging the clutch shoes 50 in the diameter reducing direction, and a drive shaft 48 surrounding the clutch shoes 50.
When the rotation of the rotor 46 rises above a predetermined number of revolutions, the clutch shoe 50 expands in diameter and presses against the inner peripheral surface of the clutch drum 52, and the output of the crankshaft 8 is increased. The torque can be transmitted to the drive shaft 48.

The engine body 1 has a shroud 53 covering one side and a head together with a flywheel magneto 44.
Is attached, and a cooling air passage 54 is defined between the engine and the engine body 1. Inlet 54a of this cooling air passage 54
Is a ventilation passage 5 between the engine body 1 and the fuel tank 5.
6, and the outlet 54b thereof is connected to the shroud 53.
And is open to the starter 43 side.

2, 4 and 7 to 9, the valve chamber 16 is a gear chamber 1 for accommodating the drive, driven timing gears 17 and 18, and intake and exhaust cam followers 23 and 24.
6a, a rocker chamber 16c accommodating the suction and exhaust rocker arms 26 and 27, and the gear chamber 16a and the rocker chamber 16
ｃc is divided into two hands and communicates, suction and exhaust push rod 2
A pair of rod chambers 16b and 16 for individually storing
The main guide passage 55 is formed in the cylinder block 7 so as to pass between the rod chambers 16b, 16b and the suction and exhaust ports 11, 12. The inlet 55a of the main air passage 55 opens on one side of the cylinder block 7 so as to face the cooling air passage 54, and the outlet 55b opens toward the ignition plug 32 screwed to the top wall of the cylinder 7a.

The rocker chamber 1 is provided in the cylinder block 7.
Auxiliary air guides 57 are formed below the air intake / exhaust ports 11 and 12 and the rod chambers 16b and 16b and intersect with the main air guides 55 below the air guide ports 6c and 16c. Intake and exhaust ports 1 as inlets 57a, 57a
The cooling air passage 54 opens on the same side as the outer end openings of the cooling air passages 1 and 12.

Further, the cylinder block 7 includes a pair of stud bolts 36, 36 on the valve operating chamber 16 side and a pair of rod chambers 16b, 16b adjacent to the stud bolts 36, which intersect with the auxiliary air guide path 57. Are formed, and these inlets 58a, 58a are connected to the main guide passage 55.
And opens toward the cooling air passage 54 on the same side as the inlet 55a.

When the rotor 46 rotates together with the crankshaft 8 during the operation of the engine E, the air generated by the cooling blades 45 flows through the ventilation passage 56 and the cooling air passage 54, and the crankcase 6, the fuel tank 5. Cool the valve chamber 16 and the like.

A part of the air flowing through the cooling air passage 54 is
The air enters the main guide passage 55, the auxiliary air guide passage 57, and the second auxiliary air guide passages 58, 58 of the cylinder block 7. The exhaust ports 11 and 12, the top of the cylinder 7 a, and the spark plug 32 are sequentially cooled, and then go to the outlet 54 b of the cooling air passage 54. As a result, the internal lubricating oil is cooled in the valve chamber 16, the filling efficiency is improved at the exhaust port 11 due to a decrease in the intake air temperature, and the exhaust valve 1 is
4 can be prevented from overheating, and the ignition plug 32 can avoid its high temperature deterioration.

On the left and right outer surfaces of the cylinder block 7,
A substantially diamond-shaped mounting seat 59 for mounting the carburetor 2 and the exhaust muffler 3 connected to the suction and exhaust ports 11 and 12, respectively.
60 are formed. At this time, these mounting seats 59, 60
Are arranged such that the long axis B is inclined with respect to the axis A of the cylinder 7a so as to minimize the cross-sectional area of the auxiliary air guide path 57. The carburetor 2 and the exhaust muffler are mounted on the mounting seats 59 and 60 by a pair of bolts 61, 61; 62, 62 arranged on both sides of the outer openings of the exhaust ports 11, 12 on the major axis B. 3 is fixed. As a result, the carburetor 2 is also inclined with respect to the axis A of the cylinder 7a, whereby the priming pump 35 faces the outside of the cylinder block 7, and the operability is improved.

In the above embodiment, various design changes can be made without departing from the gist of the present invention. For example, the cylinder block 7 may be configured as a head-separated type.

[0028]

As described above, according to the first aspect of the present invention, the engine body penetrates the valve operating chamber inside the engine body and passes between the intake and exhaust ports inside the engine body, and the cooling air passage from the cooling air passage. A main airflow path for guiding the introduced cooling air toward the ignition plug, and an auxiliary airflow path intersecting with the main airflow path and guiding the cooling air introduced from the cooling air passage to the inlets at both ends to the main airflow path are provided. , Engine
From the cooling air passage to the main and auxiliary air passages during
Each enters and joins in the middle of the main wind path, and the valve train chamber, suction,
The exhaust port, the top of the cylinder and the spark plug were sequentially cooled
An outlet for the cooling air passage to which the cooling air is directed is provided in the shroud
It was so, cooling air flows vertically and horizontally engine body head, the valve operating chamber, intake, exhaust ports and spark plugs sequentially can be effectively cooled, thus preventing overheating of the exhaust valve, and high temperature deterioration of the spark plug In addition to preventing lowering, lubricating oil cooling and filling efficiency can be improved.

According to a second feature of the present invention, a substantially rhombus-shaped first and second mounting seat for mounting a carburetor and an exhaust muffler respectively connected to an intake port and an exhaust port on both outer surfaces of the engine body. Are formed adjacent to the inlets at both ends of the auxiliary air guide path, and the major axes of the first and second mounting seats are inclined with respect to the cylinder axis of the engine body. The cross-sectional area of the air guide path is ensured, and the head of the engine body can be cooled reliably.

Further, according to the third feature of the present invention, since the carburetor is provided with the priming pump at the lower portion, the priming pump of the carburetor inclined together with the mounting seat is directed outward of the engine body. Operability can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a small four-stroke engine of a handheld type according to one embodiment of the present invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG. 2;

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a sectional view taken along line 4-4 in FIG. 2;

FIG. 5 is a side view of the engine as viewed from a carburetor.

FIG. 6 is a side view of the cylinder block of the engine as viewed from a mounting seat side of the exhaust muffler.

FIG. 7 is a sectional view taken along line 7-7 of FIG. 6;

8 is a sectional view taken along line 8-8 in FIG. 7;

9 is a sectional view taken along line 9-9 in FIG. 7;

[Explanation of symbols]

 Reference Signs List A cylinder axis B mounting seat long axis E engine 1 engine body 2 carburetor 3 exhaust muffler 8 crankshaft 11 intake port 12 exhaust port 16 valve operating chamber 32 ignition plug 35 priming pump 45 cooling blade 46 rotor 53 shroud 54 cooling air passage 55 Main air duct 55a Inlet 55b Exit 57 Auxiliary air duct 57a Inlet 59 First mounting seat 60 Second mounting seat

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02B 29/04 F02B 29/04 L (56) References JP-A 64-53416 (JP, U) JP-A 56-129540 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) F01P 1/02 F01P 1/08 F01P 1/10 F01P 5/06 502

Claims (3)

(57) [Claims] An ignition plug (3) is provided on a top wall of a cylinder (7a).
A shroud (53) defining a cooling air passage (54) is provided between the engine body (1) screwed with 2) and the outer surface thereof, and a crankshaft (8) supported by the engine body (1). ), A rotor (46) having a cooling blade (45) for generating a flow of cooling air in a cooling air passage (54) by rotation of the rotor (46) is fixed to the engine body (1). The cooling air introduced from the cooling air passage (54) penetrates through the valve operating chamber (16) and passes through the suction and exhaust ports (11, 12) in the interior thereof, and receives the cooling air from the cooling air passage (54).
The main airflow path (55) that is guided toward 2) and the cooling air that intersects with the main airflow path (55) and is introduced from the cooling air passage (54) to the inlets (57a) at both ends are supplied to the main airflow path (55). And an auxiliary air guide path ( 57) for guiding the cooling air path (54) from the cooling air path (54) during operation of the engine.
(55) and auxiliary wind guideway (57)
Merges in the middle of the air path (55), and the valve train chamber (16)
Air ports (11, 12), top of cylinder (7a) and
Cooling air that is directed by cooling air that has cooled the spark plugs (32) sequentially
Exit (54b) of passage (54) to shroud (53)
An engine cooling device, comprising: 2. The intake port according to claim 1, wherein the intake ports are provided on both outer surfaces of the engine body.
And a carburetor (2) connected to the exhaust port (12), respectively.
And first and second substantially rhombic mounting seats (59, 60) for mounting the exhaust muffler (3) are formed adjacent to the inlets (57a) at both ends of the auxiliary air guide path (57). A cooling device for an engine, wherein a long axis (B) of the first and second mounting seats (59, 60) is inclined with respect to a cylinder axis (A) of the engine body (1). 3. A cooling device for an engine according to claim 2, wherein the carburetor (2) is provided with a priming pump (35) in a lower part.