There is provided a common rail which can reduce a maximum stress value generated in an inner peripheral edge portion of a lower end of a branch hole and can further improve an internal pressure fatigue strength. In the common rail comprising at least one branch hole provided on a peripheral wall portion of a main pipe rail having a communication passage inside an axial core, a pressure receiving seat surface communicating with a branch pipe having a communication passage communicating with the communication passage in a peripheral surface portion of the branch hole and open to an outer portion, thereby bringing a pressing seat surface portion constituted by a connection head portion disposed in an end portion of the branch pipe into contact and engaging therewith, and a joint portion integrally or separately provided in the main pipe rail and a nut previously assembled in the branch pipe end which are meshed with each other so as to be pressed under a neck portion of the connection head portion, thereby being fastened and connected, the main pipe rail has an outer peripheral surface substantially formed in a circular shape, and at least an adjacent portion to the branch hole of the inner peripheral surface is slightly projected or flattened so as to be formed in a vertical cross section of a not complete round shape.
A common rail housing for a common rail injection system is composed of a pressure accumulation pipe whose outer circumference is formed in complete round shape in cross section and which is provided inside with a pressure accumulation chamber having oval cross section and a plurality of blanch pipes each of which is provided inside with a fuel conduit bore. Outer circumference of the oval cross section has a specified portion whose curvature is smaller than that of complete round shape having an area equal to that of the oval cross section. Each of the blanch pipe is connected to the pressure accumulation pipe so that the fuel conduit bore and the pressure accumulation chamber intersect nearly perpendicularly to each other at the specified portion. Accordingly, when fuel is supplied to the pressure accumulation chamber, not only the stresses concentrated on the specified portion are limited but also wall strength of the pressure accumulation pipe at the specified portion is reinforced.
A method is provided for manufacturing common rails, such as a high-pressure fluid manifold or a block rail that may be use in an accumulator fluid injection system. The method includes providing a main tubular rail with a flow passage extending in an axial direction. A bottomed lower hole is formed generally transverse to the axial flow passage. A pressing force is applied to the bottomed lower hole to generate a residual compressive stress in a circumferential part of the end portion of the bottom hole. The bottom lower hole then is made to communicate with the flow passage in the main rail. Defects that may have been caused by the application of the pressing force then are cut off. The removal of the defects improves an internal pressure fatigue strength, achieves high durability and ensures freedom from leakage.
A tube connection device for connecting motor vehicle tubes, a tube having a front element on at least one end, this front element being equipped with a frontal sealing surface. A fitting enclosing the tube is provided, which presses the frontal sealing surface against a connection surface of a connection element. At least one separate pressure element, which at least partially surrounds the tube, is provided between fitting and front element. The fitting acts on the front element through the pressure element and the sealing surface is pressed against the connection surface in this way.
In a high pressure fuel injection pipe, pipe extension and heat treatment are repeated by using a header manufactured by transformation induced plastic type strength steel. A process for depositing residual austenite is then performed, after which a final pipe extension process is performed, and the joint portion is molded and bending processing is performed without performing perfect annealing at the size of a product.
A connection head at a connection end of a thick wall steel pipe has an outer end face formed as a truncated cone or a truncated sphere. A lower neck portion is formed at the rear of the connection head and has a cylindrical outer surface and a taper to the outer surface of the pipe. A connection washer covers the lower neck portion of the connection head. A shallow gently sloping annular groove is produced inside the connection head as a result of a press forming. The above structure can prevent fatigue fracture due to stress concentration at the annular groove inside the head and sticking of a nut to the washer due to excessive tightening torque.
