JPH0395902A - Hammer solenoid - Google Patents

Abstract

PURPOSE: To realize a solenoid hammer of large impact force and movement and small bounce and oscillation by providing a spring device, making a magnetic flux booster slide separately from the magnetic center of a coil when the coil is de-energized. CONSTITUTION: A spring 90, arranged between the front end of a plunger 40 and a housing former-half part 20, pushes the plunger backward. In order to buffer the impact of the plunger when the plunger returns to its still state, plastic and rubber damping member 100 and 110 are arranged at the rear end of a housing latter-half part 30. A ferromagnetic body piece 120 operates as a magnetic flux booster, deviating the magnetic center of the plunger backward and increasing the force and movement of the plunger, when a coil is operated. The thickness of a side wall 130 is reduced sufficiently so that the coil may magnetically be saturated when being energized by a desired operating current by a current source 140, e.g. The magnetic center of the plunger is additionally deviated backward for increasing the operating force and movement.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electromagnetic actuator. More particularly, the present invention relates to a solenoid actuator specifically adapted for striking the tie bar of an impact printer.

BACKGROUND OF THE INVENTION Electromagnetic solenoids are used in many impact printers to drive tie bars and print bins. Ideally, a printer solenoid actuator should exert a relatively large mechanical force to produce sharp prints and should have low inertia to allow fast printing speeds. Additionally, the actuator mechanism must be mechanically damped to prevent bounce and vibrations that could distort the printed characters or create multiple images.

JP-A-61-194802 describes a solenoid designed to reduce bounce of a plunger. In this solenoid, the impact target body is movably arranged, the impact surface of the impact target body is formed into a spherical shape, and the plunger end facing the impact target body is shaped into a concave shape. However, said sphere is relatively insignificant in terms of the magnetic mass of the plunger and has little effect on its magnetic properties.

(Problems to be Solved by the Invention) An object of the present invention is to obtain a solenoid hammer that has a large impact force and movement, and has little bounce and vibration.

(Means for Solving the Problems) In order to achieve the above object, the hammer solenoid of the present invention includes a coil, a first end portion and a second end portion slidably disposed inside the coil. a hollow cylindrical ferromagnetic plunger having an actuator attached to a first end of the plunger and extending axially from the coil; and an actuator attached to a second end of the plunger. A ferromagnetic flux booster and a spring device that exerts an axial force on the plunger to slide the flux booster away from the magnetic center of the coil when the coil is deenergized. It is something to do.

The hollow plunger structure is relatively "dead" in reducing hammer bounce and vibration. In a preferred embodiment of the plunger of the invention, the walls of the hollow cylinder are made sufficiently thin so that they become magnetically saturated when the coil is actuated. This further shifts the magnetic mass of the plunger rearward, increasing the impact force.

In another embodiment of the invention, the ferromagnetic piece has a permanent magnet that is attracted by the magnetic field of the solenoid coil.

(Example) FIG. 1 shows the hammer solenoid of the present invention.

A hollow coil 10 is provided in a cylindrical ferromagnetic housing, and the ferromagnetic housing has a front half 2 of the housing.
0 and a housing rear half 40. A hollow cylindrical ferromagnetic plunger 40 is provided within the hollow coil 10 and flux return ring 50. hammer actuator 70
is attached to the front end of the plunger 40, and the bushing 60
is slidably supported by. The front end of this hammer actuator 70 includes a surface 8 adapted to impact the anvil of a type bar on, for example, a printer display wheel.
0 is set. A spring 90 disposed between the front end of the plunger 40 and the housing half 20 pushes the plunger rearward so that the magnetic center of the plunger is moved away from the center of the coil 10 when the coil is inactive. Plastic and rubber damping members 100, 110 are disposed at the rear end of the housing rear half 30 to cushion the impact of the plunger as it returns to its resting state. According to the invention, a ferromagnetic piece 120 is provided within the rear end of the hollow plunger 40. This ferromagnetic piece 120, compressed or glued to the hollow plunger, acts as a flux booster to shift the magnetic center of the plunger rearward, increasing the force and movement of the plunger when the coil is actuated.

In one preferred embodiment of the invention, sidewall 130 is made sufficiently thin so that the coil is magnetically saturated when energized with the desired actuation current, such as by current source 140. The magnetic center of the plunger is thus shifted further rearward to increase actuation force and movement.

In another embodiment of the invention, said sidewall is permanently magnetized;
The permanent magnetic field is polarized to attract the magnetic field of the energized coil, thus further increasing the force and movement of the plunger. A further embodiment of the invention provides for the magnetic field generated in the plunger sidewall by the permanent magnet to be sufficient to magnetically saturate the sidewall.

The solenoid of the present invention provides a relatively vibration-free and bounce-free printing hammer that has high impact force and travel and is suitable for printing applications.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of one embodiment of the hammer solenoid of the present invention. DESCRIPTION OF SYMBOLS 10...Hollow coil 20...Housing front half 30...Housing back half 40...Plunger 70...Hammer actuator 90...Spring 100.110...Damping member

Claims (9)

[Claims] 1. a coil; a hollow cylindrical ferromagnetic plunger having a first end and a second end slidably disposed within the coil; and a hollow cylindrical ferromagnetic plunger having a first end and a second end attached to the first end of the plunger. an actuator extending axially from the coil;
a ferromagnetic flux booster mounted on a second end of said plunger and exerting an axial force on said plunger to cause said flux booster to move away from the magnetic center of said coil when said coil is deenergized; and a spring device for sliding away. 2. 2. The solenoid of claim 1, wherein the actuator includes a marking hammer. 3. Claim 1: The magnetic flux booster is a solid piece of soft magnetic material.
Solenoid listed. 4. 4. The solenoid of claim 3, further comprising means for energizing the coil. 5. 5. The solenoid of claim 4, wherein the means for energizing the coil causes the coil to generate a magnetic flux that saturates the wall of the hollow plunger. 6. Claim 1: The plunger has a wall containing a permanent magnet.
Solenoid listed. 7. 7. The solenoid of claim 6, wherein the permanent magnet generates a magnetic flux that saturates the wall of the hollow plunger. 8. 8. A solenoid as claimed in claim 7, including means for energizing a coil to generate a magnetic field, the polarity of the permanent magnet being attractive to the magnetic field generated by said coil. 9. 7. The solenoid of claim 6 further comprising means for energizing a coil to generate a magnetic field, the polarity of the permanent magnet being attractive to the magnetic field generated by said coil.