Normally-closed electromagnetic valve and manufacturing method for the same

1. A manufacturing method for a normally-closed electromagnetic valve, the electromagnetic valve including:

a body member having a receiving space and communication holes communicating with the receiving space;

a moving core disposed within the receiving space so as to move in an axial direction of the receiving space;

a valve seat which has a flow hole constituting a part of a flow passage of a fluid circuit, and is accommodated within the receiving space of the body member so as to be fixed to the body member;

a valve element fixed to an end portion of the moving core, and located in the flow passage for closing the flow hole;

a resilient member urging the valve element toward the valve seat; and

a fixed core fixed to an end portion of the body,

wherein the moving core to which the valve element is fixed and the resilient member are disposed in the receiving space of the body member so that the valve element is sandwiched between the valve seat and the resilient member,

the manufacturing method comprising the steps of:

press-fitting the fixed core into the receiving space of the body member so as to oppose to the moving core and the resilient member;

locating the moving core and the fixed core within a magnetic circuit;

applying a magnetic field by the magnetic circuit to generate electromagnetic attracting force so that the moving core together with the valve element are attracted toward the fixed core and separating the valve element from the valve seat;

detecting a physical quantity of the fluid and controlling an inserting length of the fixed core while applying fluid to the flow passage so as to flow pass through the communicating hole and the flow hole in such a manner that:

inserting the fixed core further toward the valve element against the urging force of the resilient member when the detected physical quantity still surpasses or under runs a predetermined value; and

stopping to insert the fixed core when the detected physical quantity reaches the predetermined value.

2. The manufacturing method for the normally-closed electromagnetic valve according to claim 1 , wherein the physical quantity of the fluid is flow rate detected at the communicating hole or the flow hole, and

the controlling of the inserting length of the fixed core step is performed such that:

inserting the fixed core further toward the valve element against the urging force of the resilient member when the detected flow rate still surpasses the predetermined value; and

stopping to insert the fixed core when the detected flow rate reaches the predetermined value.

3. The manufacturing method for the normally-closed electromagnetic valve according to claim 1 , wherein the physical quantity of the fluid is a pressure differential of the fluid, which is defined between an upstream region and a downstream region of the flow hole, and

the controlling of the inserting length of the fixed core step is performed such that:

inserting the fixed core further toward the valve element against the urging force of the resilient member when the detected pressure differential still under runs the predetermined value; and

stopping to insert the fixed core when the detected pressure differential reaches the predetermined value.

4. The manufacturing method for the normally-closed electromagnetic valve according to claim 1 , wherein:

the moving core has a through hole; and

the manufacturing method further comprises a step of fixing the valve element to the moving core comprising the steps of:

press-fitting the valve element into the through hole;

inserting the resilient member into the through hole; and

detecting a load applied by the compressed resilient member and controlling an inserting length of the valve element while inserting the valve element into the through hole so that the resilient member is compressed in such a manner that: continuing to insert the valve element when the detected load under runs a predetermined value; and

stopping to insert the valve element when the detected load reached the predetermined value.

5. The manufacturing method for the normally-closed electromagnetic valve according to claim 1 , wherein after stopping to insert the valve element, the fixed core is fixedly secured to the body member by welding.

6. A manufacturing method for a normally-closed electromagnetic valve, comprising:

press-fitting a fixed core into a receiving space of a body member;

genreating an electromagnetic attracting force to attract a moving core with a valve element toward a fixed core and separating a valve element from a valve seat;

applying fluid to a flow passage in such a manner that the fixed core is inserted toward a valve element against an urging force of a resilient member; and

stopping to insert the fixed core when a detected physical quantity of the fluid reaches a predetermined value.

7. The manufacturing method for the normally-closed electromagnetic valve according to claim 6 , further comprising controlling the inserting length of the fixed core while applying the fluid to the flow passage.

8. The manufacturing method for the normally-closed electromagnetic valve according to claim 6 , wherein a physical quantity of the fluid is flow rate detected at a communicating hole of a body member of the normally-closed electromagnetic valve or flow hole of the valve seat.

9. The manufacturing method for the normally-closed electromagnetic valve according to claim 7 , wherein the controlling of the inserting length of the fixed core is performed such that:

inserting the fixed core further toward the valve element against an urging force of the resilient member when a detected flow rate surpasses the predetermined value; and

stopping to insert the fixed core when the detected flow rate reaches the predetermined value.

10. The manufacturing method for the normally-closed electromagnetic valve according to claim 6 , wherein a physical quantity of the fluid is a pressure differential of the fluid, which is defined between an upstream region and a downstream region of a flow hole of the valve seat, and

controlling of the inserting length of the fixed core by:

inserting the fixed core further toward the valve element against the urging force of the resilient member when the detected pressure differential under runs the predetermined value; and

stopping to insert the fixed core when the detected pressure differential reaches the predetermined value.