1. Field of the Invention
The present invention relates to a small-size engine having a forced air cooling system for cooling a cylinder block and a cylinder head with a cooling air induced by a cooling fan.
2. Description of the Prior Art
A small-size engine having a forced air cooling system is known in which a cylinder block of an engine body has a longitudinal axis inclined relative to a horizontal direction and also to a vertical direction, and in which a fan housing is provided on one side of the engine body to cover a cooling fan mounted on one end of a crankshaft so that a cooling air induced by the cooling fan can be guided through the fan housing towards the cylinder block and a cylinder head of the engine body. In such arrangement, an air cleaner and a carburetor defining an air intake passage of the engine are mounted so as to protrude outwardly of the fan housing to secure a cooling air passage within the fan housing. See, for example, the Japanese Laid-open Patent Publication No. 10-227214. In this engine, in order to avoid interference between the carburetor and an ignition unit that is disposed at a location level with the carburetor and offset from the carburetor towards a longitudinal axis of a crankshaft, the air cleaner and the carburetor are so disposed as to protrude diagonally outwardly relative to the longitudinal axis of the crankshaft to thereby separate them away from the longitudinal axis of the crankshaft.
However, it has been found that since in the engine of the structure described above the air cleaner and the carburetor protrude a substantial amount outwardly from the engine body, the space required for an installation of the engine to various work units has been limited. Also, the engine operation tends to be irregular when the carburetor is strongly affected by an external heat, for example, radiant heat generated from the work unit.
In view of the foregoing, the present invention has for its object to provide a small-size engine having a forced air cooling system, wherein an amount of protrusion of an air intake system of the engine outwardly from the engine body can be minimized and a limitation on a space required for various work units to be mounted on the engine body can be alleviated.
In order to accomplish this object, the present invention provides a small-size engine having a forced air cooling system, including a cooling fan mounted on one end of a crankshaft and a longitudinal axis of a cylinder body inclined relative to a horizontal direction and also to a vertical direction. This engine includes a cylinder head mounted atop the cylinder block, and a fan housing for guiding a cooling air, induced by the cooling fan, towards the cylinder block and the cylinder head, a carburetor including a float chamber. The fan housing has a cutout defined therein, and the float chamber of the carburetor is positioned inside the fan housing through the cutout.
According to such a structure, since the float chamber of the carburetor is positioned within the fan housing through the cutout defined in the fan housing, the carburetor can be positioned at a location close to the engine body as compared with the design in which the carburetor in its entirety is positioned outside the fan housing and, therefore, an amount of protrusion of the carburetor outwardly of the engine body can be reduced, making it possible to assemble the engine in a compact size. Consequently, limitations on a space available for installing the engine to various work units can be minimized correspondingly. Also, since the float chamber is effectively and sufficiently cooled by the cooling air guided thereto through a cooling air passage defined by the fan housing, it is possible to avoid the irregularity of the engine operation which would result from influences brought about by external heat, for example, heat from the work unit.
In a preferred embodiment, the engine also includes an ignition unit for driving an ignition plug. This ignition unit is preferably positioned within the fan housing at a location below the carburetor.
Disposition of the ignition unit within the fan housing at a location below the carburetor allows the ignition unit to be positioned at a location in the vicinity of the cylinder head, that is, the ignition plug without interfering the carburetor while securing a sufficient cooling capability.
In another preferred embodiment, the float chamber is positioned in a cooling air passage, defined in the fan housing, at a location upstream of the cylinder block and the cylinder head.
With the float chamber so positioned, the float chamber can be effectively cooled by the cooling air of a low temperature before the cylinder block and the cylinder head are cooled thereby.
In a further preferred embodiment, the engine also includes an air cleaner fluid coupled with an upstream portion of the carburetor in an air intake passage of the engine. This air cleaner is preferably positioned outside the fan housing. According to this feature, an undesirable increase in temperature of the air cleaner which would result from the radiant heat from the cylinder block and the cylinder head can be prevented advantageously.
In a further preferred embodiment, the engine, furthermore includes a drain discharge operating member, an idling setting member, a pilot setting member and/or an air vent passage, for the carburetor and at least one of them is positioned outside the fan housing. According to this feature, adjustment and servicing of those members can easily be performed from outside the fan housing.
According to another aspect of the present invention, the present invention also provides a small-size engine having a forced air cooling system, including a crankshaft having a longitudinal axis and a cooling fan mounted on one end of the crankshaft and a longitudinal axis of a cylinder body inclined relative to a horizontal direction and also to a vertical direction so as to be diagonally upwardly oriented, which engine includes an air intake passage; a fuel supply device; an air cleaner fluid coupled with an upstream portion of the fuel supply device in the air intake passage; and an ignition unit for driving an ignition plug of the engine. A major portion of the air intake passage ranging at least from the air cleaner to a downstream end of the fuel supply device extends parallel to the longitudinal axis of the crankshaft, and the ignition unit is disposed below the fuel supply device.
According to such a structure, since the major portion of the air intake passage is so disposed as to extend parallel to the longitudinal axis of the crankshaft, the amount of respective portions of the air cleaner and the fuel supply device that protrude laterally and rearwardly from the engine body can be advantageously reduced and, therefore, the engine can be assembled compact. As a result thereof, the limitation on the space available for installation of the engine to the various work units can be alleviated. Yet, since the ignition unit for driving the ignition plug is positioned below the fuel supply device, the fuel supply device and the ignition unit do not interfere with each other. It is to be noted that the fuel supply device referred to above may be a carburetor or a fuel injection device.
In a preferred embodiment of the second aspect of the present invention, the engine further includes a fan housing for guiding a cooling air from the cooling fan towards the cylinder block and the cylinder head, and the fuel supply device referred to above may be a carburetor having a float chamber, and the fan housing is formed with a cutout through which the float chamber of the carburetor is positioned inside the fan housing.
According to the above described construction, the cooling air guided through a cooling air passage formed by the fan housing can cool the float chamber satisfactorily and, therefore, the possibility of the engine operation being irregular under the influence of an external heat can be avoided.
In any event, the present invention will become more clearly understood from the following description of preferred embodiments thereof, when taken in conjunction with the accompanying drawings. However, the embodiments and the drawings are given only for the purpose of illustration and explanation, and are not to be taken as limiting the scope of the present invention in any way whatsoever, which scope is to be determined by the appended claims. In the accompanying drawings, like reference numerals are used to denote like parts throughout the several views, and:
With reference to accompanying drawings, a preferred embodiment of the present invention will now be described.
A small-size engine shown in
A cooling fan 9 is fixedly mounted on one end of the crankshaft 4 that is located on a rear side of the engine body 1, that is, a right-hand end of the crankshaft 4 as viewed in
Also as shown in
The fan housing 17 for guiding a cooling air W from the cooling fan 9 towards the cylinder block 5 and the cylinder head 6 is fitted to a rear side surface of the engine body 1 as shown in
As best shown in
The air cleaner 14 referred to hereinbefore is fluid connected with an upstream portion of the fuel supply device 15 in the air intake passage and is exposed to the outside of the fan housing or cooling housing 17. As shown in
In the small-size engine having the forced air cooling system of the structure described hereinabove, as shown in
Particularly in this engine the float chamber 23 of the carburetor 15 which is the fuel supply device is positioned inside the fan housing 17 through the cutout 22 defined in the fan housing 17. Accordingly, as compared with a design in which the carburetor 15 in its entirety is positioned outside the fan housing 17, the carburetor 15 can be positioned at a location close to the engine body 1 and, therefore, the amount of protrusion of the carburetor 15 and the air cleaner 14 coupled with this carburetor 15 that protrude outwardly of the engine body 1 can be reduced, making it possible to assemble the engine in a compact size. In view of this, limitations on the space available for installing the engine to various work units can be minimized correspondingly.
Also, since the float chamber 23 of the carburetor is positioned within the fan housing 17 through the cutout 22, the float chamber 23 is effectively and sufficiently cooled as well by the cooling air W induced by the cooling fan 9 and, therefore, it is possible to avoid irregularity of the engine operation which would result from influences brought about by an external heat, for example, heat from the work units, transmitted to the float chamber 23. Moreover, since the float chamber 23 is positioned within the cooling air passage 28, defined by the fan housing 17, upstream of the cylinder block 5 and the cylinder head 6, the float chamber 23 can be effectively cooled by the cooling air W of a low temperature before the cylinder block 5 and the cylinder head 6 are cooled.
In addition, since the major portion 13a of the air intake passage 13 of the air intake system 12 ranging at least from the air cleaner 14 to the downstream end of the fuel supply device 15 is so designed as to extend parallel to the longitudinal axis C of the crankshaft 4, as compared with the conventional case in which it is inclined as shown by the double-dotted line in
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings which are used only for the purpose of illustration, those skilled in the art will readily conceive numerous changes and modifications within the framework of obviousness upon the reading of the specification herein presented of the present invention. For example, although in the foregoing embodiment the fan housing 17 has been shown and described as having the cutout 22 formed therein so that the float chamber 23 of the carburetor 15 can be positioned within the fan housing 17, the fan housing 17 may be formed with a recess of a configuration following the contour of the float chamber 23 so that a portion of the float chamber 23 can be accommodated within this recess. In this case, a portion of the fan housing 17 aligned with the recess may have an air guide outlet for allowing the cooling air W to be drawn outwardly so that a portion of the cooling air W can be guided towards the float chamber 23 and its surroundings. It is, however, to be noted that when no cooling of the float chamber 23 is needed, the air guide outlet for the cooling air W may not be formed.
Also, although the fuel supply device 15 has been shown and described as used in the form of a carburetor, a fuel injection device may be employed in place of the carburetor. In such case, the fuel injection device is to be disposed outside the fan housing 17.
Accordingly, such changes and modifications are, unless they depart from the scope of the present invention as delivered from the claims annexed hereto, to be construed as included therein.
Number | Date | Country | Kind |
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2002-042828 | Feb 2002 | JP | national |
Number | Name | Date | Kind |
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4261302 | Sheldon | Apr 1981 | A |
4548167 | Tamba et al. | Oct 1985 | A |
4692123 | Tada et al. | Sep 1987 | A |
4907546 | Ishii et al. | Mar 1990 | A |
5960751 | Isoshima | Oct 1999 | A |
6227162 | Dahlberg et al. | May 2001 | B1 |
6378467 | Kobayashi et al. | Apr 2002 | B1 |
6378469 | Hiranuma et al. | Apr 2002 | B1 |
Number | Date | Country |
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10-227214 | Aug 1998 | JP |
Number | Date | Country | |
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20030154934 A1 | Aug 2003 | US |