Electromagnetic proportional control valve system

An electromagnetic proportional control valve system comprising:

• a three position proportional control valve having a main spool;
• and
• left and right position control apparatuses provided on left and right ends of the main spool to perform stroke control of the main spool in the three position proportional control valve,
• wherein:
• the left position control apparatus comprises a left compressible position feedback spring confronting the left end of the main spool, a left pilot control valve having a left pilot spool, which has left and right ends, and is disposed so that the right end of the left pilot spool confronts the left end of the main spool via the left position feedback spring, and a left proportional solenoid being configured to provide electromagnetic force to the left end of the left pilot spool against the left position feedback spring;
• the left pilot spool is configured to be moved in response to compression force of the left position feedback spring and electromagnetic force of the left proportional solenoid, and further in response to output pressure of the left pilot control valve applied on the left and right ends of the left pilot spool, in order to control position of the left pilot spool operatively;
• a pressure receiving area of the output pressure in the left end of the left pilot spool for pressing the left pilot spool toward the right is larger than a pressure receiving area in the right end of the left pilot spool for pressing the left pilot spool toward the left, in order to make a biasing force by the left output pressure applied on the left end of the left pilot spool larger than a biasing force by the right output pressure applied on the right end of the left pilot spool, so that a position control in the left pilot control valve is performed to generate the output pressure with an inverse proportional relationship against the electromagnetic force of the left proportional solenoid;
• the right position control apparatus comprises a right compressible position feedback spring confronting the right end of the main spool, a right pilot control valve having a right pilot spool, which has left and right ends, and is disposed so that the left end of the right pilot spool confronts the right end of the main spool via the right position feedback spring, and a right proportional solenoid being configured to provide electromagnetic force to the right end of the right pilot spool against the right position feedback spring;
• the right pilot spool is configured to be moved in response to compression force of the right position feedback spring and electromagnetic force of the right proportional solenoid, and further in response to output pressure of the right pilot control valve applied on the left and right ends of the right pilot spool, in order to control position of the right pilot spool operatively;
• a pressure receiving area of the output pressure in the right end of the right pilot spool for pressing the right pilot spool toward the left is larger than a pressure receiving area in the left end of the right pilot spool for pressing the right pilot spool toward the right to make a biasing force by the right output pressure applied on the right end of the right pilot spool larger than a biasing force by the left output pressure applied on the left end of the right pilot spool, so that a position control in the right pilot control valve is performed to generate the output pressure with an inverse proportional relationship against the electromagnetic force of the right proportional solenoid;
• when the main spool is moved rightward from a neutral position, the right position feedback spring is compressed by the main spool, and the main spool is stepped away from the left position feedback spring;
• and
• when the main spool is moved leftward from a neutral position, the left position feedback spring is compressed by the main spool, and the main spool is stepped away from the right position feedback spring.