Valve assembly for an injection valve and injection valve
The present disclosure relates to valves. Some embodiments may include solenoid injection valves with a valve body; a valve needle with a needle shaft, an upper retaining element, and a lower retaining element; an electro-magnetic actuator comprising a pole piece and an armature spaced from the pole piece by a first axial gap when de-energized. The armature slides on the valve needle between the upper retaining element and the lower retaining element. The valve may include a calibration spring and a spring element arranged between the armature and the upper retaining element. The armature compresses the spring element and travels at least 50% of the first axial gap before an opening force of the valve assembly becomes larger than a total needle closing force. An opening force for displacing the valve needle away from the closing position is transferred from the armature to the valve needle completely through the spring element and a second axial gap between the armature and the upper retaining element is maintained throughout the operation of the valve assembly.
1. An injection valve comprising:
a valve body having a longitudinal axis and a cavity with a fluid inlet portion and a fluid outlet portion;
a valve needle axially moveable in the cavity to prevent a fluid flow through the fluid outlet portion in a closing position and releasing the fluid flow through the fluid outlet portion in further positions;
the valve needle comprising a needle shaft, an upper retaining element and a lower retaining element both fixedly connected to the needle shaft;
the upper retaining element extending in a radial direction and disposed in a first axial region of the valve needle facing away from the fluid outlet portion;
the lower retaining element extending in the radial direction and arranged in a second axial region of the valve needle facing the fluid outlet portion;
an electro-magnetic actuator unit to actuate the valve needle, the electro-magnetic actuator unit comprising a pole piece and an armature spaced from the pole piece by a first axial gap when the electro-magnetic actuator unit is de-energized;
the armature axially movable in the cavity and joined to the valve needle by form-fit;
the armature sliding on the valve needle between the upper retaining element and the lower retaining element;
a calibration spring preloaded to bias the valve needle towards the closing position; and
a spring element arranged between the armature and the upper retaining element which biases the armature towards the lower retaining element;
wherein the spring element and the calibration spring are adapted to one another such that the armature compresses the spring element and travels at least 50% but no more than 70% of the first axial gap before an opening force for displacing the valve needle away from the closing position becomes larger than a total needle closing force, thereby initiating a displacement of the valve needle away from the closing position before the armature comes into contact with the pole piece;
the opening force for displacing the valve needle away from the closing position is transferred from the armature to the valve needle completely through the spring element throughout a full range of axial displacement of the armature during the operation of the valve assembly; and
the armature and the upper retaining element remain spaced apart from each other throughout the full range of axial displacement of the armature during the operation of the valve assembly.
2. An injection valve according to claim 1 , wherein the spring element allows the armature to travel 70% of the first axial gap before the opening force of the valve assembly becomes larger than the total needle closing force.
3. An injection valve according to claim 1 , wherein the spring element has a higher stiffness than the calibration spring.
4. An injection valve according to claim 1 , wherein the spring element comprises a coil spring.
5. An injection valve according to claim 1 , wherein, in a fully open configuration of the valve assembly, the armature abuts the pole piece and the lower retaining element and the upper retaining element are axially spaced apart from the armature.
6. An injection valve according to claim 1 , wherein the spring element has a stiffness between 2 and 10 times a stiffness of the calibration spring.