1. Field of the Invention
The present invention relates to a common rail that is mounted to a pressure accumulation fuel injection system and accumulates high-pressure fuel.
2. Description of Related Art
A common rail 101 of a related art will be described with reference to FIG. 14. The common rail 101 is a pressure accumulator for accumulating high-pressure fuel pumped from a high-pressure fuel pump (supply pump or the like) and has an accumulation chamber (central hole) 123 formed therein for accumulating the high-pressure fuel therein. The common rail 101 has pipe joints 121 to be connected with external pipes (a high-pressure pump pipe, an injector pipe, and the like). A center portion of an outer end of the pipe joint 121 communicates with the accumulation chamber 123 through an inside-outside communication hole 124 (branch hole).
An orifice 130 for reducing pressure pulsation caused by an injection operation of an injector or an orifice 130 for reducing pressure pulsation caused by pumping operation of the high-pressure fuel pump is formed in the inside-outside connection hole 124. The orifice 130 of the related art is formed by directly drilling a main body 120 (hereinafter referred to as a rail main body) of the common rail 101. The orifice 130 is formed in the deepest portion of the inside-outside connection opening 124 because of constraints concerning the drilling. That is, as shown in FIG. 14, the orifice 130 opens in the accumulation chamber 123.
High-pressure fuel is accumulated in the accumulation chamber 123 and therefore high pressure is applied to the inner peripheral surface of the accumulation chamber 123. The orifice 130 having a small diameter opens in and crosses the inner peripheral surface of the accumulation chamber 123. A portion of the opening that crosses the inner peripheral surface is hereinafter referred to as a crossing hole. As the crossing hole becomes smaller, a larger stress is concentrated at the edge of the opening of the crossing hole. Therefore, a common rail, in which the orifice 130 is integrally formed in the rail main body 120 by the drilling, is used for a pressure accumulation fuel injection system of a small size vehicle or the like, in which accumulation pressure of the accumulation chamber 23 is comparatively low (for example, 180 MPa or under).
In recent years, it has been required to increase the common rail pressure to 180 MPa or over also in the small size vehicle for the purpose of improving exhaust performance and the like. However, a common rail having the orifice 130 integrally formed in the rail main body 120 by the drilling has the small crossing hole, which is formed by the orifice 130, and therefore has difficulty in securing a safety factor concerning fatigue strength. Therefore, not only in a large size vehicle but also in the small sized vehicle, for the purpose of securing the safety factor concerning the fatigue strength, as shown in FIG. 3, there has been proposed a common rail 1, in which an orifice 30 is formed in a bush 31 separate from a rail main body 20 and the bush 31 is fixed in an inside-outside communication hole 24 to enlarge the crossing hole (for example, as described in Patent document 1: JP-A-2002-322965) in place of forming the orifice 130 directly in the rail main body 120.
A technology of the related art that fixes the bush 31 having the orifice 30 in the inside-outside communication hole 24 press-fits an outer peripheral surface of the bush 31 into the inside-outside communication hole 24. When the bush 31 is inserted into the inside-outside communication hole 24, there is a possibility that a press-fitting burr A is produced at an end portion (hereinafter referred to as a press-fitting end portion) of the bush 31 opposite to the press-fitting direction of the bush 31 as shown in FIG. 4A.
When the engine is driven in a state where the press-fitting burr A is produced as shown in FIG. 4A, there is a possibility that the press-fitting burr A is dropped by an action of the flow of the fuel and flows as a foreign matter to the injector. When the press-fitting burr A is dropped and flows to the injector, the press-fitting burr A clogs a filter disposed in the injector. When a small press-fitting burr A passes through the mesh of the filter of the injector, there is a possibility that the burr A enters the injector having high accuracy and causes malfunctions such as faulty sliding and faulty sealing.