242 – Solenoid Valve Attractive Force Analysis Taking into Account Movable Part Motion

Application Note / Model Data


Solenoid valves are used to adjust the inflow or outflow of liquids or gases by translational movement of the iron core. If an electric current is passed through the coil, an electromagnet is created and an electromagnetic attractive force is generated between the moving part and the fixed parts. Since high responsiveness is required for valve opening and closing, an important item to consider is whether or not the power source used for driving and the solenoid valve used satisfy the required responsiveness and attractive force.
Solenoid valves are often used for hydraulic valves and injectors, and the mover itself is placed in high pressure liquid and encounters flow resistance. Since the mover employs a guide to move, it has positional error and it has the possibility of causing inclination.
It is beneficial to examine in advance whether a change in attractive force when inclination occurs or whether an unbalanced force generated in the mover effects the alignment and contributes to worsening the alignment.
In this example, the influence on the electromagnetic force for various positions of the mover from the presence or absence of inclination is confirmed.

Mover Position and Inclination

Fig. 1 shows the position and inclination of the mover. The position of the mover is considered for three gap lengths – 3.6 mm, 1.9 mm, and 0.2 mm. At each position, there is an inclination of the mover. Comparisons to the situation of having no inclination is carried out. The center axis of the inclination is not dependant on the position of the mover and has fixed coordinates. The inclination is 2 deg.

Effect on Electromagnetic Force

Fig. 2 shows the attractive force from the inclination for each mover position, and Fig. 3 shows the torque about the center axis of the inclination.
From Fig. 2, it can be seen that the inclination has almost no effect on the attractive force when the gap length is 3.6 mm, but the attractive force increases by 20 % at 1.9 mm and decreases by 3 % at 0.2 mm.
From Fig. 3, it can be seen that the torque becomes larger as the gap length becomes shorter. In this example, since the positive direction of the torque and the direction of the center axis of inclination are made to coincide with each other, it is seen that the unbalanced force generated in the mover acts in a direction to increase the inclination.

Electromagnetic Force Distributions

Fig. 4 to Fig. 6 show the electromagnetic force distributions in the vicinity of the moving part for each position.
From Fig. 4, when the gap length is 3.6 mm, almost no change in the electromagnetic force from the inclination is observed.
From Fig. 5, for gap length 1.9 mm, it can be seen that the electromagnetic force increases at the points where the fixed iron core and movable iron core are closer because of the inclination. On the other hand, you can see that the electromagnetic force decreases at the points where the fixed iron core and movable iron core move away because of the inclination. The total increase / decrease of the electromagnetic force is determined by these balances.
For the gap length of 0.2 mm shown in Fig. 6, the electromagnetic force is not in the moving direction but perpendicular to the moving direction due to the inclination of the mover. It can be seen that this is the reason for the decrease in attractive force.

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