The present invention claims priority under 35 USC §119 based on Japanese patent application No. 2008-146531 filed Jun. 4, 2008. The subject matter of this priority document is incorporated by reference herein.
1. Field of the Invention
The present invention relates to an improvement of a V-type engine in which first and second banks arranged in a V-shape are provided continuously to a crankcase, and in which a carburetor is placed at a valley between the first and second banks, the carburetor communicating with intake ports of the respective banks.
2. Description of the Related Art
Immediately after such a V-type engine stops its operation, cooling air stops flowing. Consequently, heat of the banks easily stays in a valley between the first and second banks, which can cause percolation in a carburetor placed in the valley. The percolation makes it difficult for the V-type engine to restart in a high-temperature state. To this regard, the following conventional measure is known. Specifically, an insulator is provided at a joint part between each of the banks and the carburetor, and a heat shield flange is integrally formed on the insulator in such a manner as to extend vertically, thereby the heat between the bank and the carburetor is shielded (see, for example, Japanese Patent Application Laid-open No. 58-53640).
However, in the above conventional measure, the carburetor is joined to the banks with the relatively-thin insulators in between, and such thin insulators have a limited heat shield capability. Accordingly, when the V-type engine in a high-temperature state stops its operation, the heat from the banks might be conducted to the carburetor through the insulators to cause percolation.
The present invention has been made in consideration of such circumstances, and has an objective of providing a V-type engine that can have excellent restartability in a high-temperature state by surely preventing heat from banks from affecting a carburetor in order to prevent percolation in the carburetor even in the case where the engine stops its operation in a high-temperature state.
In order to achieve the above object, according to a first feature of the present invention, there is provided a V-type engine in which first and second banks arranged in a V-shape are provided continuously to a crankcase, and in which a carburetor is placed at a valley between the first and second banks, the carburetor communicating with intake ports of the respective banks, wherein the carburetor is placed spaced from the first and second banks and connected to the intake ports of the first and second banks via first and second intake pipes, respectively, and first and second heat shield plates each made of synthetic resin are attached to side faces of the respective first and second banks, the side faces facing the carburetor, each of the first and second heat shield plates covering a corresponding one of the side faces and defining a cooling air passage between the heat shield plate and the corresponding side face.
According to the first feature of the present invention, the first and second heat shield plates each define the cooling air passage between the heat shield plate and the corresponding side face of the first and second banks B1 and B2, and cooling air is guided into the cooling air passage while the V-type engine is in operation. Thereby, the banks can be cooled. When the V-type engine in a high-temperature state stops its operation, the first and second heat shield plates interposed between the corresponding first and second banks and the carburetor shield the carburetor from radiation heat from the banks. Furthermore, the carburetor is placed at the valley between the first and second banks while being spaced from the banks, and connected to the banks with the intake pipes, respectively. Accordingly, heat radiation effects of the intake pipes allow less heat to be conducted from the banks to the carburetor. The carburetor can thus be prevented from heating up. Accordingly, percolation in the carburetor can be prevented, and this can contribute to improvement of the restartability of the engine in a high-temperature state.
As described, the first and second heat shield plates play two functions: guidance of cooling air to the surrounding of the first and second banks while the V-type engine E is in operation; and shielding of the carburetor from radiation heat from the banks when the V-type engine E stops its operation. This can contribute to simplification of the structure around the V-type engine.
Further, according to a second feature of the present invention, in addition to the first feature, the first and second heat shield plates attached to the respective side faces of the first and second banks are integrally connected to each other by a bottom plate covering a bottom face of the valley, whereby the first and second heat shield plates and the bottom plate form a single component.
According to the second feature of the present invention, the first and second heat shield plates are integrally connected to each other by the bottom plate to form the single component. Since the single component is integrally formed, not only can the heat shield plates be manufactured at once, this synthetic resin member can be attached to the V-type engine easily and speedily.
Further, according to a third feature of the present invention, in addition to the first or second feature, a holding part for holding a linear member is integrally formed to the single component.
According to the third feature of the present invention, the holding part holding the linear member is integrally formed to the single component. Accordingly, a holding member dedicated to the linear member does not need to be attached to the V-type engine. This can contribute to reduction in the number of components.
The above description, other objects, characteristics and advantages of the present invention will be clear from detailed descriptions which will be provided for the preferred embodiment referring to the attached drawings.
An embodiment of the present invention will be explained below with reference to
In
The first and second banks B1 and B2 each include a single cylinder 7. A piston 9 is fitted into the cylinder 7, while being connected to the crankshaft 1 via a connecting rod 8. Intake pipe attachment flanges 12 and 12 are formed on the head parts, at respective corner parts on the front side, which are opposite to each other, of the respective first and second banks B1 and B2. Each intake port 13 opens to an end face of a corresponding one of the intake pipe attachment flanges 12 and 12. First and second intake pipes 16a and 16b are attached to the intake pipe attachment flanges 12 and 12, respectively. The carburetor 14 is placed at a center part of a valley 10 between the banks B1 and B2. The first and second intake pipes 16a and 16b connect first and second intake paths 15a and 15b of the carburetor 14 to the intake ports 13 and 13 of the first and second banks B1 and B2, respectively. Being placed at the center part of the valley 10, the carburetor 14 is spaced from the banks B1 and B2 by an equal distance.
The first and second intake pipes 16a and 16b are joined, at their upstream ends, to a single large joint flange 17, and thus connected to each other integrally. The carburetor 14 is joined, at its downstream end face, to the large joint flange 17 by bolts. Small joint flanges 18 and 18 are formed to the respective first and second intake pipes 16a and 16b at their downstream ends. These small joint flanges 18 and 18 are joined to the respective intake pipe attachment flanges 12 and 12 by bolts 19.
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Further, a holding part 34 is integrally formed to the single component 25 (i.e., in the illustrated example, one of the heat shield plates, 29b). The holding part 34 holds linear members 33 such as an electric wire for control of the V-type engine E, an operation cable, and a hose.
Referring back to
Next, operations of this embodiment will be explained.
The first and second heat shield plates 23a and 23b made of synthetic resin are attached to the side faces of the first and second banks B1 and B2, which face the carburetor 14. Each of the first and second heat shield plates 23a and 23b covers the corresponding side face and defines a corresponding one of the cooling air passages 22 and 22 between the heat shield plate and the side face. The end parts of the first and second heat shield plates 23a and 23b at the cooling fan 4 side are continuous with the end parts of the fan cover 5 which are located at the downstream side of the cooling air. Accordingly, while the V-type engine E is in operation, cooling air taken in and sent under pressure by the cooling fan 4 that rotates with the crankshaft 1 is guided into the cooling air passages 22 and 22 around the respective banks B1 and B2. Thereby, the banks B1 and B2 can be cooled. Especially because the many cooling fins 29, 29 of each of the banks B1 and B2 face a corresponding one of the cooling air passage 22 and 22, the banks B1 and B2 can have improved cooling capability. Furthermore, part of the cooling air sent under pressure by the cooling fan 4 is also supplied to the carburetor 14 side, and cools the carburetor 14.
Moreover, the curved part 30 at the rear end of each of the heat shield plates 23a and 23b bends the pathway of the cooling air flowing through a corresponding one of the cooling air passage 22 and 22 of the bank B1 or B2, and the cooling air thereby travels to the back face side of the corresponding bank B1 or B2. Accordingly, the back face side of the banks B1 and B2 can be cooled well.
When the V-type engine E stops its operation in a high-temperature state, the cooling fan 4 stops rotating, and consequently the cooling air stops flowing. Accordingly, the banks B1 and B2 dissipate heat peripherally. However, the carburetor 14 can be prevented from heating up because the heat shield plates 23a and 23b interposed between the corresponding bank B1 or B2 and the carburetor 14 shield the carburetor 14 from radiation heat from the banks B1 and B2.
Furthermore, the carburetor 14 is placed at the center part of the valley 10 between the first and second banks B1 and B2 and is spaced from the banks B1 and B2. The carburetor 14 is therefore connected to the banks B1 and B2 via the relatively-long intake pipes 16a and 16b, respectively. Accordingly, heat radiation effects of the intake pipes 16a and 16b allow less heat to be conducted from the banks B1 and B2 to the carburetor 14. The carburetor 14 can thus be prevented from heating up. Percolation in the carburetor 14 can be prevented in this way, and this can contribute to improvement of the restartability of the V-type engine E in a high-temperature state.
As described, the first and second heat shield plates 23a and 23b play two functions: guidance of cooling air to the surrounding of the first and second banks B1 and B2 while the V-type engine E is in operation; and shielding of the carburetor 14 from radiation heat from the banks B1 and B2 when the V-type engine E stops its operation. This can contribute to simplification of the structure around the V-type engine E.
In addition, the paired heat shield plates 23a and 23b are integrally connected to each other by the bottom plate 24 which covers the bottom face of the valley 10 between the first and second banks B1 and B2, and thereby the first and second heat shield plates and the bottom plate form the single component 25. Since the single component 25 is integrally formed, not only can the heat shield plates 23a and 23b be manufactured at once, the single component 25 can be attached to the V-type engine E with a small number of the bolts 28. This can contribute to improvement of installation work efficiency.
Additionally, the holding part 34 is integrally formed to the single component 25 to hold the linear members 33 such as an electric wire for control of the V-type engine E, an operation cable, and a hose. Accordingly, the V-type engine E does not need to be installed with a holding member dedicated to the linear members 33. This can contribute to reduction in the number of components.
The present invention is not limited to the above-mentioned embodiment and may be modified in a variety of ways as long as the modifications do not depart from its gist. As the carburetor 14, independent first and second carburetors may be individually connected to the first and second intake pipes 16a and 16b, respectively. The present invention can be applied to a general-purpose V-type engine of a vertical type in which the crankshaft is placed upright.
Number | Date | Country | Kind |
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2008-146531 | Jun 2008 | JP | national |