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Secondary air supply for engine exhaust systemRelated Patent Categories: Power Plants, Internal Combustion Engine With Treatment Or Handling Of Exhaust Gas, By Means Producing A Chemical Reaction Of A Component Of The Exhaust Gas, Condition Responsive Control Of Reactor Feed, Pressure, Or By-pass, Air Feed To Reactor Modulated Or Diverted By ControlSecondary air supply for engine exhaust system description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060037311, Secondary air supply for engine exhaust system. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is based on and claims priority under 35 U.S.C. .sctn. 119 (a)-(d) to Japanese Patent Application No. 2004-237338, filed Aug. 17, 2004, the entire contents of which is hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an engine having a secondary air supply system for supplying secondary air to an exhaust system. [0004] 2. Description of the Related Art [0005] There are proposed devices for supplying secondary air to an exhaust system to burn HC and CO contained in exhaust gas and thus to purify the exhaust gas. Conventional devices for supplying secondary air to an exhaust system of this type include the one in which a reed valve device is integrally provided on a head cover mounted on a cylinder head of the engine. See Japanese Patent Publication No. JP-A-2003-56647 as an example of such device. SUMMARY OF THE INVENTION [0006] An aspect of the present invention involves the recognition that this enhanced-combustion technology can be difficult to employ on certain types of engine. For example, in the case of a center-chain-type engine, in which a timing chain for rotationally driving a camshaft is disposed between first and second cylinders, the first and second cylinders are spaced apart from each other by the width of a chain chamber. Accordingly, a first-cylinder valve chamber and a second-cylinder valve chamber for the corresponding reed valve must also be spaced apart from each other. This results in an increased in the number of parts, such as secondary air introduction hoses connected to the valve chambers, cover members for opening and closing openings of the valve chambers, and bolts for securing the cover members. Also, since there are a number of seal mating faces, the sealing structure may become complex. [0007] Accordingly, there is provided an engine comprising a cylinder block that defines at least two adjacent cylinders. A cylinder head is fastened to the cylinder block and supports at least one camshaft. A head cover is mounted to the cylinder head, and a cam chain drives the camshaft. A chain chamber houses the cam chain and is formed generally between the adjacent cylinders. The chain chamber also has a longitudinal axis that lies substantially parallel to axes of the adjacent cylinders. A first-cylinder valve chamber and a second-cylinder valve chamber each are sized to accommodate a valve for supplying secondary air to an exhaust system of the engine. The first-cylinder and second-cylinder valve chambers are disposed in a manner whereby at least portions of the first-cylinder valve chamber and the second-cylinder valve chamber lie to one side of the chain chamber as viewed in a direction along the longitudinal axis of the chain chamber. [0008] This construction reduces the number of engine parts associated with a secondary air system and simplifies the sealing structure of secondary air introduction hoses and cover members. Additionally, while the cylinders are located on opposite sides of the chain chamber, the first-cylinder and second-cylinder valve chambers can adjoin each other, which allows the first and second valve chamber covers to be integrally formed. Therefore, only a single secondary air hose for introducing air to the first and second valve chambers is required, and the number of fastening bolts can be reduced, so that the structure is simplified. [0009] In a preferred mode, the head cover has a breather chamber for separating oil mist from blow-by gas. The breather chamber is disposed such that at least a portion of the breather chamber overlies the chain chamber as seen in the direction along the longitudinal axis of the chain chamber. The breather chamber also preferably lies adjacent to at least one of the first-cylinder and second-cylinder valve chambers. [0010] The inclusion of the breather chamber at this location provides an ample size without increasing the side of the engine as at least a portion of the breather chamber overlaps the chain chamber. In other words, when the adjacent cylinders are located on opposite sides of the chain chamber, the capacity and space for the breather chamber can be obtained without difficulty. Further, the breather chamber can lie adjacent to the first-cylinder and second-cylinder valve chambers. Thus, the breather chamber cover can be integrally formed with the first and second valve chamber covers. Therefore, the mating faces (seal faces) of the openings are flush with each other, so that the number of fastening bolts is reduced and the structure is simplified. [0011] In a further preferred mode, a secondary air hose connects the air cleaner and the first-cylinder and second-cylinder valve chambers, and a breather hose connects the breather chamber with the air cleaner. Because of the close proximity of the valve chambers and the breather changers, thee hoses preferably are bundled together. Thus, the routing structure of the hoses can be simplified, and hence the vicinity around the head covers can be simplified. BRIEF DESCRIPTION OF THE DRAWINGS [0012] The above-mentioned and other features of the invention disclosed herein are described below with reference to the drawings of a preferred embodiment. The illustrated embodiment is intended to illustrate, but not to limit, the invention. The drawings include the following six figures. [0013] FIG. 1 is a sectional side view of a chain chamber of an engine in accordance with a preferred embodiment of the present invention. [0014] FIG. 2 is a partially sectional side view of the engine in FIG. 1. [0015] FIG. 3 is a plan view of a forward cylinder head of the engine in FIG. 1, shown with a head cover removed from the cylinder head. [0016] FIG. 4 is a plan view of the forward head cover of the engine in FIG. 1, shown with the valve chamber covers removed. [0017] FIG. 5 is a plan view of the forward head cover of the engine in FIG. 1. [0018] FIG. 6 is a sectional side view, showing reed valves of the engine in FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0019] An embodiment of the present invention will be described below with reference to accompanying drawings. FIGS. 1 through 5 are explanatory views of the engine configured in accordance with a preferred embodiment of the present invention. The following description of the engine and the present secondary air supply will describe the components of the engine, including the secondary air supply, in the orientation shown in the accompanying drawings. The engine, however, can be used in other orientations depending upon the particular application of the engine. Continue reading about Secondary air supply for engine exhaust system... Full patent description for Secondary air supply for engine exhaust system Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Secondary air supply for engine exhaust system patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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