Welding machine and welding method

A welding machine for inserting a first cylinder member into a second cylinder member and for welding the cylinder members together around their circumference, the welding machine comprising:

• an energy source for generating energy, the energy being used for melting the cylinder members at a portion to be welded and for welding the cylinder members together;
• and
• energy-applying units for applying the energy to the cylinder members, wherein:
• the energy-applying units are disposed outside the cylinder members at three or more positions;
• and
• when a number of the energy-applying units is defined by “n” and an angle, by which the neighboring energy-applying units are separated from each other in a circular direction about the cylinder members, defined by θ degrees, [(360/n)−10]≦θ≦[(360/n)+10].

An injector to be assembled by welding, the injector comprising:

• a valve body including a valve seat;
• a valve member for stopping fuel injection when seated on the valve seat, and for permitting fuel injection when separated from the valve seat;
• a movable core connected to the valve member at an opposite side of the valve seat, the movable core reciprocating together with the valve member;
• a fixed core disposed opposite the valve member relative to the movable core, the fixed core facing the movable core;
• an electromagnetic driving device for generating magnetic force by which the movable core is attracted to the fixed core;
• and
• a housing member of which an inner peripheral wall is connected to an outer peripheral wall of the valve body, the housing member containing the movable core so as to reciprocate therein, wherein:
• each of the housing member and the valve body is a cylinder member;
• and
• the valve body is inserted into the housing member, and they are welded to each other by melting them about a circumference of the housing member.

A welding method for welding cylinder members together using a welding machine, the welding method comprising the steps of:

• rotating a first cylinder member and a second cylinder member about a center axis located inside of the first and second cylinder members;
• providing a first energy applying unit disposed outside of the first cylindrical member and the second cylindrical member;
• providing a second energy applying unit disposed outside of the first cylindrical member and the second cylindrical member;
• providing an energy source for generating energy for the energy applying units;
• applying energy to the first cylindrical member and the second cylindrical member through the first energy applying unit;
• melting the first cylindrical member and the second cylindrical member a first time with the first energy applying unit as the cylindrical members are rotated;
• and
• welding the first cylindrical member and the second cylindrical member a first time with the first energy applying unit as the cylindrical members are rotated;
• melting the first cylindrical member and the second cylindrical member a second time with the second energy applying unit as the cylindrical members are rotated;
• and
• welding the first cylindrical member and the second cylindrical member a second time with the second energy applying unit as the cylindrical members are rotated;