Electromagnetic pump

An electromagnetic pump, comprising:

• a piston that is slidably provided in a cylinder and the piston oriented in the cylinder so as to partition a first fluid chamber and a second fluid chamber connected to an object to be operated;
• an elastic member oriented in the first fluid chamber and configured to move the piston backward by applying an elastic force;
• an electromagnetic portion configured with a plunger that is connected by a shaft to the piston in an axial direction of the piston, the electromagnetic portion and plunger arranged outside of the cylinder, and the electromagnetic portion configured to move the plunger, shaft and piston forward by an electromagnetic force in a direction opposite to that of the elastic force of the elastic member;
• a first on-off valve that allows working fluid to flow from outside into the first fluid chamber and prevents working fluid from flowing from the first fluid chamber to the outside;
• and
• a second on-off valve that is provided in a connecting flow passage that connects the first fluid chamber and the second fluid chamber to each other, allows working fluid to flow from the first fluid chamber into the second fluid chamber, and prevents working fluid from flowing from the second fluid chamber into the first fluid chamber, wherein
• a capacity of the first fluid chamber reduces and a capacity of the second fluid chamber increases when the piston is moved forward, and the capacity of the first fluid chamber increases and the capacity of the second fluid chamber reduces when the piston is moved backward, and
• a change in capacity of the first fluid chamber is larger than a change in capacity of the second fluid chamber in a reciprocating motion of the piston.