Chain case structure of engine

Abstract

A chain case structure of an engine includes an oil pump is disposed in a chain case and driven by a crankshaft of the engine and an oil pump case. The oil pump case includes an oil strainer mounting portion, an oil suction passage communicating the oil strainer mounting portion with a pump chamber, and a chain guide portion protruding toward the one end in the crankshaft direction of the engine and extending along an outer periphery of a timing chain. The oil strainer mounting portion is disposed below the chain guide portion, the oil suction passage portion is expanded from a wall surface of the oil pump case toward the engine and extended toward the chain guide portion, and the oil strainer mounting portion and the chain guide portion are connected by the oil suction passage portion.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a chain case structure of an engine particularly capable of preventing a timing chain of the engine from falling off or being disengaged during assembling of the timing chain.[0003]2. Description of the Related Art[0004]In an engine of a vehicle provided with a cam-drive structure with a timing chain and an oil pump directly driven by a crank, it is generally required to remove a cam sprocket with a chain case being mounted as it is at a time of maintenance in the market. In this removing operation, the timing chain loses its mounting tension, and it is therefore necessary to locate a member for holding the timing chain so as to prevent tooth skipping of the timing chain on a wrapping portion of a crank sprocket.[0005]For this purpose, one of conventional techniques is a method of providing a fall-off (disengagement) preventing rib for holding a timing chain in a lower portion of a crank...

AI Technical Summary

Benefits of technology

[0012]The present invention was conceived in consideration of the circumstances of the conventional art mentioned above, and an object of the present invention is to provide a chain case structure of an engine having a simplified structure of an oil pump case with considerable rigidity being maintained.

[0021]The chain case structure of an engine according to the preferred aspect of the present invention mentioned above can simplify a structure of the oil pump case arranged in the chain case and also enhance the rigidity of the chain guide portion protruding from an inner wall of the oil pump case toward the engine.

Problems solved by technology

However, in a conventional structure, in order to a defect mentioned above, a fall-off preventing rib having a certain length or more is disposed on a back surface of a wrapping portion of a crank sprocket so as to cover a timing chain in a width direction only for the purpose of achieving a fall-off prevention function, which causes an increase in weight.

Furthermore, in a case where it is required to form such rib with minimum thickness, the rib takes an arcuate shape having a large area with less rigidity, and because of this reason, the rib generates radiation sound, that is, acoustic radiation efficiency becomes adversely high, constituting engine noise generation source.

In the structure of the Patent Document 1, it is necessary to locate a dedicated member for preventing disengagement of a timing chain, which may provide a complicated structure, thus being disadvantageous.

However, the projecting portion is provided in a cantilevered manner projecting from a wall surface of the oil pump case in the chain chamber, which may provide insufficient rigidity of the protrusion portion, increase acoustic radiation efficiency, and adversely affect engine noise or vehicle vibration.

Moreover, an oil suction passage and this projecting portion are provided in different positions, and the location of these portions provides a complicated structure and configuration of the oil pump case, and hence, an oil pump, thus being also disadvantageous.

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