For John Deere solenoid valve AL177192 Construction machinery accessories Excavator accessoriesvalve

            A proportional solenoid valve is a special type of solenoid valve that provides smooth

and continuous changes in flow or pressure depending on the electrical input. This type can

be classified as a control valve. In order for the solenoid valve to be proportional, the plunger

position must be controlled. It is achieved by balancing the plunger with an external force

usually done by a spring. The spring will compress until the external force equals the electromagnetic

force of the solenoid. If the position of the plunger must be controlled, the current must be changed,

resulting in an imbalance of forces on the spring. The spring will compress or stretch until a force

balance is established.

             One problem with this type is the effect of friction. Friction disrupts the smooth balance

between electromagnetic and spring forces. To eliminate this effect, special electronic controls

are used. A common method used for the proportional control characteristics of solenoid valves

is pulse width modulation or PWM. Applying a PWM signal as the control input causes the solenoid

to power on and off continuously at a very fast rate. This puts the plunger in an oscillating state and

thus into a stable position. To change the position of the plunger. The on and off state of the solenoid,

also known as the duty cycle, is controlled.

              Unlike ordinary on/off solenoid valves, proportional solenoid valves are used in applications

that require automatic flow control, such as proportional pneumatic actuators, throttle valves, burner

control, etc.