JP2005344575A - Forced air-cooled engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forced air-cooled engine with reduced weight and cost, for effectively reducing blowing noise of a cooling fan. <P>SOLUTION: In the forced air-cooled engine, a shroud 10 is attached to an engine body 1 for guiding cooling air generated by the cooling fan 9 disposed at an end of a crankshaft 6 to a cylinder part 3. The shroud 10 comprises: a scroll type inner shroud 11 made of steel plate, surrounding the cooling fan 9 and having an intake port 11a facing an intake face of the cooling fan 9 and a discharge port 11b opened to the cylinder part 3; and an outer shroud 12 made of synthetic resin, housing inner shroud 11 and guiding the cooling air discharged from the discharge port 11b to the cylinder part 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  According to the present invention, cooling air generated by a cooling fan attached to one end of a crankshaft supported by the crankcase is supplied to the engine body having a crankcase and a cylinder portion protruding from the crankcase. It is related with the improvement of the forced air cooling engine which attached the shroud which guides to a part.

Such a forced air cooling engine is known, for example, as disclosed in Patent Document 1 below.
No. 7-670 Japanese Utility Model Publication No. 4-79929

  In recent years, there has been an increasing demand for noise reduction of work machines, and there is a demand for reduction of blowing noise by cooling fans even in forced air-cooled engines.

  Therefore, in the conventional forced air-cooled engine, in order to meet the above requirements, the shroud is made of a damping steel plate (see Patent Document 1), the shroud has an inner shroud having a wind guide function, and has a wind guide function. 2. Description of the Related Art There is known a complete double structure (see Patent Document 2) in which a non-outside shroud is arranged in an inner and outer double.

  However, if the shroud is made of a damping steel plate, the formability of the damping steel plate is poor, and its weight is heavier than that of ordinary steel plates, so there are disadvantages that increase the weight of the engine and increase the cost. Even a double structure has the same disadvantages as described above.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a forced air cooling engine that is lightweight and low in cost and can effectively reduce the blowing noise of a cooling fan. .

  In order to achieve the above object, the present invention provides a cooling fan attached to one end of a crankshaft supported by the crankcase on an engine body including a crankcase and a cylinder portion protruding from the crankcase. In a forced air-cooled engine equipped with a shroud for guiding the generated cooling air to the cylinder part, the shroud surrounds the cooling fan, and faces the suction port and the cylinder part facing the suction surface of the cooling fan. A scroll-type steel plate inner shroud having an outlet opening that opens and a synthetic resin outer shroud that houses the inner shroud and guides the cooling air discharged from the outlet to the cylinder portion. This is the first feature.

  According to the second aspect of the present invention, in addition to the first feature, the inner shroud is fixed to the engine body, and a starter support member for supporting the recoil-type engine starter is attached to the periphery of the inlet of the inner shroud. It is characterized by.

  The starter support member corresponds to an intake louver 17 in an embodiment of the present invention described later.

  According to the first feature of the present invention, even if the air supply noise caused by the cooling fan is radiated from the inner shroud, it can be blocked by the outer shroud and the silence of the engine can be improved.

  In particular, since the inner shroud made of steel plate constitutes only the scroll portion from the suction port to the discharge port, the press molding is extremely easy and can contribute to cost reduction and weight increase suppression. Further, since the inner shroud made of steel plate only overlaps the outer shroud made of synthetic resin at the scroll portion surrounding the cooling fan, the overall weight of the shroud is light and can contribute to the weight reduction of the engine.

  In addition, the outer shape of the outer shroud made of synthetic resin can be given a desired shape without being restricted by the shape of the inner shroud, so that the degree of freedom in design can be expanded.

  According to the second feature of the present invention, the high-strength inner shroud made of a steel plate fixed to the engine body serves as a bracket for attaching a starter support member for supporting the engine starter. It is no longer necessary to provide the engine body, and the structure can be simplified and the weight can be further reduced.

  Embodiments of the present invention will be described based on preferred embodiments of the present invention shown in the accompanying drawings.

  1 is a front view of a forced air cooling engine according to the present invention, FIG. 2 is a plan view of the engine, FIG. 3 is a side view of the engine, FIG. 4 is a sectional view taken along line 4-4 of FIG. 6 is a front view of the outer shroud in an exploded state, FIG. 6 is a plan view of the outer shroud in an assembled state, FIG. 7 is a view corresponding to FIG. 1 showing the engine in a state where the outer shroud is removed, and FIG. FIG. 9 is a view corresponding to FIG. 2 with the tank, air cleaner and exhaust muffler removed, FIG. 9 is a sectional view taken along line 9-9 of FIG. 7, FIG. 10 is a sectional view taken along line 10-10 of FIG. FIG. 11 is a sectional view taken along line 11-11.

  1 to 3, the forced air cooling engine E in the illustrated example is a single cylinder general purpose engine. The engine body 1 includes a crankcase 2 having a mounting flange 2a on the lower surface and supporting the crankshaft 4 horizontally, and a cylinder portion 3 protruding obliquely upward from one side of the crankcase 2. A large number of radiating fins 3 a, 3 a... Protrude from the outer peripheral surface of the cylinder portion 3. A fuel tank T is disposed above the crankcase 2, and an air cleaner A and an exhaust muffler M with a cover are disposed above the cylinder portion 3. A carburetor 4 communicating with an intake port opened there is attached to a side surface of the cylinder portion 3, and the air cleaner A is connected to the carburetor 4 via an intake duct 5. Further, the exhaust muffler M communicating with the exhaust port opened there is attached to the upper surface of the cylinder portion 3. As described above, the fuel tank T, the air cleaner A, and the exhaust muffler M are intensively arranged horizontally above the engine body 1 to reduce the protrusions to the side of the cylinder portion 3 and to make the engine E compact. Can be achieved.

  As shown in FIG. 4, a flywheel 7 is fixed to one end portion of the crankshaft 6 supported by the crankcase 2 with bolts 8, and a centrifugal cooling fan 9 is attached to the outer end surface of the flywheel 7. The A shroud 10 that guides the cooling air generated by the cooling fan 9 to the cylinder portion 3 or the like is attached to the engine body 1.

  The shroud 10 will be described with reference to FIGS.

  4 to 7, a shroud 10 includes a steel plate inner shroud 11 surrounding the cooling fan 9, and a synthetic resin outer shroud 12 that accommodates the inner shroud 11 and covers each part of the engine body 1. Consists of

  As shown in FIGS. 4 and 7, the inner shroud 11 is formed in a scroll type so that the suction air can be efficiently boosted by the centrifugal cooling fan 9, and the cooling fan 9 is provided on the outer end wall thereof. A circular suction port 11a facing the suction surface and a discharge port 11b opening toward the cylinder part 3 are opened on the peripheral wall. Further, a mounting flange 11c is formed at the inner end of the inner shroud 11 facing the engine body 1, and this is fixed to the engine body 1 by a plurality of bolts 13, 13,. Thus, the inner shroud 11 is supported by the engine body 1.

  The outer shroud 12 houses the inner shroud 11 as shown in FIG. 4, and the shroud side portion 14 covering the side surface of the engine main body 1 on the cooling fan 9 side as shown in FIGS. A shroud upper portion 15 that covers an upper surface facing the fuel tank T, an air cleaner A, and an exhaust muffler M, and covers an upper half portion of the side surface of the cylinder portion 3 opposite to the cooling fan 9, a lower surface of the cylinder portion 3, and The cylinder portion 3 is divided into a shroud lower portion 16 that covers the lower half portion of the side surface opposite to the cooling fan 9 and is individually molded with a synthetic resin.

  4, the side surface of the shroud side portion 14 is provided with an opening 14a aligned with the suction port 11a, and a cup-shaped intake louver 17 having a number of vent holes 17a, 17a,. It is attached to the outer surface of the side portion 14 so as to overlap. The intake louver 17 is provided with a mounting flange 17b that is overlapped with the shroud side portion 14. On the other hand, a plurality of welding nuts 19, 19,... Surrounding the intake port 11a are provided on the inner surface of the inner shroud 11. The mounting flange 17b and the shroud side portion 14 are fixed to the inner shroud 11 by a plurality of bolts 20, 20. Therefore, the outer shroud 12 and the intake louver 17 are firmly supported by the engine body 1 via the highly rigid steel plate inner shroud 11.

  A support shaft 21 is fixed at the center of the inner end wall of the intake louver 17, and a known recoil-type engine starter 24 including a starter pulley 23 around which a starter rope 22 is wound is attached to the support shaft 21. Reference numeral 22 a is a knob connected to the outer end of the starter rope 22 and gripped during the towing operation. The starter pulley 23 is provided with a number of through holes 23 a that allow the air flow that has passed through the intake louver 17.

  As shown in FIGS. 7 and 10, around the cylinder portion 3, an air guide duct portion 25 (see FIG. 10) is constituted by the shroud upper portion 15, the shroud upper portion 15 and the shroud lower portion 16, and the inner shroud 11. Cooling air from the discharge port 11 b is guided around the cylinder portion 3. The shroud upper portion 15 is provided with an exhaust port 26 that opens the air guide duct portion 25 toward the exhaust muffler M. The head cover 3b of the cylinder portion 3 is exposed to the outside of the air guide duct portion 25 (see FIG. 1), and reference numeral 27 in FIG. 6 indicates an opening portion of the outer shroud 12 that exposes the head cover 3b.

  As shown in FIG. 10, the shroud upper portion 15 and the shroud lower portion 16 are provided with mounting bosses 15 a and 16 a at portions facing the cylinder portion 3, and these are provided on the cooling fins 3 a and 3 a from the outer surface of the cylinder portion 3. ... Are fixed to the longer-projecting support bosses 30, 30 with bolts 31, 31. As shown in FIGS. 7 and 11, the shroud upper portion 15 is formed with a plurality of mounting bosses 15 b, 15 b... At a portion facing the crankcase 2, and these are formed on the upper surface of the crankcase 2. Are fixed to the supporting bosses 40, 40... By bolts 32, 32. Thus, the shroud upper portion 15 and the shroud lower portion 16 are supported by the engine body 1.

  Further, a plurality of tank stays 33, 33... Are integrally formed in the shroud upper portion 15 immediately above the crankcase 2. A bracket 34 having welding bolts 35, 35,... Corresponding to the bolt holes of the tank stays 33, 33, and welding nuts 36, 36, is fixed to the bottom wall of the fuel tank T. The bracket 34 is fixed to the tank stays 33, 33 ... by nuts 37, 37 ... and bolts 38, 38 ... which are screwed and tightened to the 35, 35 ... and welding nuts 36, 36 .... Thus, the fuel tank T is supported by the shroud upper portion 15.

  Next, the operation of this embodiment will be described.

  During the operation of the engine E, the cooling fan 9 that rotates together with the crankshaft 6 sucks the air that has passed through the numerous air holes 17a, 17a... Of the intake louver 17 into the inner shroud 11 from the suction port 11a. Since the inner shroud 11 is formed in a scroll type, the intake air can be efficiently boosted and a large amount of cooling air can be discharged from the discharge port 11b toward the cylinder portion 3. In particular, since the inner shroud 11 made of steel plate constitutes only the scroll portion from the suction port 11a to the discharge port 11b, the press molding is extremely easy and contributes to cost reduction and suppression of weight increase. Can do.

  Since the outer shroud 12 forms an air guide duct portion 25 around the cylinder portion 3, the cooling air is guided to the air guide duct portion 25 and flows through the entire circumferential surface of the cylinder portion 3. The portion 3 can be effectively cooled, and not only the synthetic resin air guide duct portion 25 can absorb and block the radiated sound from the cylinder portion 3 to improve the silence of the engine E.

  Further, since the wind guide duct portion 25 is provided with an exhaust port 26 that opens toward the exhaust muffler M, the cooling air that has cooled the cylinder portion 3 inevitably comes out from the exhaust port 26. Therefore, the exhaust muffler M hits the exhaust muffler M and can be effectively cooled. At the same time, the exhaust muffler M can attenuate the exhaust noise.

  By the way, since the inner shroud 11 is accommodated in the outer shroud 12 made of synthetic resin, even if air supply noise from the cooling fan 9 is radiated from the inner shroud 11, this is blocked by the outer shroud 12, and the engine E Can improve the silence.

  In addition, the outer shape of the outer shroud 12 made of synthetic resin can be given a desired shape without being constrained by the shape of the inner shroud 11, so that the degree of freedom in design can be expanded.

  Further, the outer shroud 12 made of synthetic resin is lighter than that made of steel plate, and the inner shroud 11 made of steel plate only overlaps with the outer shroud 12 at the scroll portion surrounding the cooling fan 9, so that the shroud 10 as a whole. Is light and can greatly contribute to the weight reduction of the engine E.

  The inner shroud 11 made of steel plate and rigidly fixed to the engine body 1 serves as a bracket for attaching the shroud side portion 14 of the outer shroud 12 and the intake louver 17 that supports the engine starter 24, so that the shroud side It is no longer necessary to provide the engine body 1 with a bracket dedicated to supporting the portion 14 and the intake louver 17, thereby simplifying the structure and further reducing the weight. In addition, in this case, since the shroud side portion 14 made of synthetic resin is interposed between the inner shroud 11 and the intake louver 17, the shroud side portion 14 exhibits a vibration damping function, and the intake louver for engine vibrations. 17 and transmission to the engine starter 24 can be suppressed, and the durability of the engine starter 24 can be improved.

  On the other hand, a plurality of tank stays 33, 33... Are integrally formed on a synthetic resin shroud upper portion 15 fixed to the upper surface of the crankcase 2 of the outer shroud 12, and the fuel tank T is supported by these tank stays. The resin shroud upper portion 15 and the tank stays 33, 33... Exhibit a vibration damping function to absorb vibrations of the engine E and suppress vibration transmission to the fuel tank T.

  Further, the shroud upper portion 15 also serves as a heat insulating and sound insulating plate for blocking the radiant heat and radiated sound from the crankcase 2 and can prevent the fuel tank T from being heated and resonated. In addition, since it is not necessary to attach a dedicated support member for supporting the fuel tank T to the engine body 1, the support structure can be simplified.

  In this case, since the tank stays 33, 33... Are formed in the outer shroud 12, particularly in the shroud upper portion 15 facing the fuel tank T, the tank stays 33, 33. Thus, the fuel tank T can be firmly supported.

  Eventually, the engine noise is blocked by the inner shroud 10 and the shroud side portion 14 which are arranged inside and outside the cooling fan 9, and the transmission of the radiated sound from the crankcase 2 to the fuel tank T is transmitted to the upper portion of the shroud. 15, the radiated sound from the cylinder portion 3 is blocked by the air guide duct portion 25, and the exhaust sound from the exhaust port 26 of the air guide duct portion 25 is attenuated by the exhaust muffler M. Can be effectively increased.

  The present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the invention.

1 is a front view of a forced air cooling engine according to the present invention. The top view of the engine. The side view of the engine. FIG. 4 is a sectional view taken along line 4-4 of FIG. The disassembled state front view of the outer shroud of the engine. The assembly state top view of an outer side shroud. FIG. 2 is a view corresponding to FIG. 1 showing the engine with the outer shroud removed. Fig. 3 is a view corresponding to Fig. 2 showing the engine with the fuel tank, air cleaner and exhaust muffler removed. FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 7. FIG. 10 is a sectional view taken along line 10-10 in FIG. 7; FIG. 11 is a sectional view taken along line 11-11 in FIG. 7.

Explanation of symbols

E ... Engine 1 ... Engine body 2 ... Crankcase 3 ... Cylinder 6 ... Crankshaft 9 ... Cooling fan 10 ... .... Shroud 11 ... Inner shroud 11a ... Suction port 11b ... Discharge port 12 ... Outer shroud 17 ... Starter support member (intake louver)

Claims (2)

An engine body (1) having a crankcase (2) and a cylinder portion (3) protruding from the crankcase (2) is attached to one end of a crankshaft (6) supported by the crankcase (2). In a forced air cooling engine equipped with a shroud (10) for guiding cooling air generated by an attached cooling fan (9) to the cylinder part (3),
The shroud (10) surrounds the cooling fan (9), and the suction port (11a) facing the suction surface of the cooling fan (9) and the discharge port (11b) opening toward the cylinder part (3) ) And a steel plate inner shroud (11), and the inner shroud (11) are accommodated, and the cooling air discharged from the discharge port (11b) is guided to the cylinder part (3). A forced air-cooled engine characterized by comprising an outer shroud (12) made of resin. In the forced air-cooled engine according to claim 1,
The inner shroud (11) is fixed to the engine body (1), and a starter support member (17) for supporting the recoil-type engine starter (24) is attached to the periphery of the inlet (11a) of the inner shroud (11). A forced air-cooled engine.

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