JPH0453951Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a wire dot printing head used in, for example, a dot printer.

(Prior Art) FIG. 3 is a half-sectional view showing a conventional wire dot printing head of this type. In FIG. 3, a core 3 is provided on the negative pole side of the permanent magnet 1 via a first yoke 2, and a coil 4 is installed in this core 3 for generating a magnetic field to cancel the magnetic flux of the permanent magnet 1. A ferromagnetic residual sheet 6 made of a thin metal plate made of a ferromagnetic material is provided with grease 5 applied to the upper surface of the core. On the other pole side of the permanent magnet 1, a second yoke 7, a third yoke 9 holding the fixed end of the leaf spring 8, a fourth yoke 10, and a fifth yoke 11 are arranged in succession in this order. The leaf spring 8 supports at its free end an armature 13 to which the printing wire 12 is fixed, and this armature 13 is arranged opposite to the core 3 with the residual sheet 6 in between.
The printing wire 12 passes through an intermediate guide 14 and reaches a tip guide 15. These intermediate guides 14 and tip guides 15 are provided, and the fifth yoke 1
A head frame 16 is provided in contact with the wire dot printing head 1 and for supporting the wire dot printing head configured as described above.

In addition, in the spring-charged wire dot printing head having such a configuration, strain energy is stored in the leaf spring 8 by bending the leaf spring 8, so that the upper surface of the core 3 is at the fixed end of the leaf spring 8. There must be a step higher than the top surface of a certain yoke 9. This step difference is the thickness of the ferromagnetic residual sheet 6. Therefore, in order to increase the strain energy or spring force of the leaf spring 8, the thickness of the ferromagnetic residual sheet 6 must be increased.

Next, the operation will be explained. First, coil 4
When is in a non-energized state, the magnetic flux of permanent magnet 1 is
Yoke 2 → Core 3 → Ferromagnetic residual sheet 6
→ Armature 13 → Fifth yoke 11 → Fourth yoke 10 → Leaf spring 8 → Third yoke 9 → Second yoke 7
pass through. Of course, at this time, a magnetic attraction force is generated between the core 3 and the armature 13 due to the magnetism of the permanent magnet 1, the armature 13 is attracted to the core 3 via the ferromagnetic residual sheet 6, and the leaf spring 8 is bent. In this state, when the coil 4 is energized, the magnetic flux of the coil 4 is generated in the opposite direction to the magnetic flux generated by the permanent magnet 1, and the armature 13 uses a ferromagnetic resin to cancel the magnetic flux. The sheet 6 is released from the core 3. Therefore, the strain energy accumulated in the leaf spring 8 is released due to the action of the armature 13 being attracted to the core 3 side, and the armature 13 fixed to one end of the leaf spring 8 is released from the ferromagnetic resin at the edge of the core 3. The printing wire 12, which is fixed to the armature 13, protrudes from the tip guide 15 in the direction of the arrow A shown in the figure. An unmarked ink ribbon and print medium are struck to record pixels on the print medium.

(Problem to be solved by the invention) However, in the device with the above configuration, the ferromagnetic residual sheet 6 maintains the attraction force from the permanent magnet 1, but significantly prevents the progress of wear from the core 3 side. However, if the thickness of the ferromagnetic residual sheet 6 is increased, the attractive force of the permanent magnet 1 to the armature 13 decreases, and the cross section shown in FIG. As shown, the magnetic flux attracting the armature 13 flows into the adjacent armature-core pair through the ferromagnetic residual sheet 6, resulting in a decrease in the attractive force, and furthermore, the demagnetizing flux also interferes with each other, causing so-called magnetic flux. There was a problem in that interference increased, and as a result, it was necessary to increase the demagnetizing current flowing through the coil 4.

Therefore, the print head disclosed in Japanese Patent Application Laid-Open No. 59-202863 has fins radially provided inside a ring-shaped ferromagnetic residual sheet to separate the cores, and separate each core-armature pair individually. Even if the ferromagnetic residual sheet is made thicker by dividing the core into two, the magnetic flux is prevented from flowing out to the neighboring core-armature pair.

However, in the print head configured as described above, when the armature separates from the core, that is, the ferromagnetic residual sheet, due to the restoring force of the leaf spring, the fins of the ferromagnetic residual sheet cling to the armature and turn up. If this operation is repeated, there is a problem in that the fins of the ferromagnetic residential sheet may break or the ferromagnetic residual sheet may be damaged due to metal fatigue.

The purpose of this invention is to eliminate the above-mentioned problems and to provide a wire dot printing head that can prevent magnetic flux from flowing out to areas other than its own armature-core pair using the special structure of the ferromagnetic residual sheet. do.

(Means for Solving the Problems) The wire dot printing head according to this invention is made of a thin metal plate made of ferromagnetic material, and a ferromagnetic residual sheet inserted between a core and an armature is magnetically connected between the cores by a hole. It is divided into two parts.

(Function) The wire dot printing head in this invention is
Since the ferromagnetic residual sheet is magnetically separated by the hole between the cores, it is possible to prevent the magnetic flux in the magnetic path passing through the core-armature pair from flowing out into other magnetic paths through the ferromagnetic reastic sheet. This prevents the ferromagnetic resiliency sheet from partially sticking to the armature and turning upward.

(Example) Hereinafter, an example of this invention will be described based on the drawings. FIG. 1 is a partial view of a ferromagnetic residual sheet used in a wire dot print head according to an embodiment of the invention. The ferromagnetic residual sheet 17 according to this embodiment is a ring-shaped thin ferromagnetic metal plate with radial holes 17c and a positioning margin protruding outward from the outer periphery. . This ferromagnetic residual sheet 17 can be similarly used in place of the ferromagnetic residual sheet 6 shown in FIG. 3 to construct a wire dot printing head.

A hole 17c of a ferromagnetic residual sheet 17 incorporated in the wire dot print head is provided on a surface other than the face where the core 3 and the armature 13 face each other, and exists between the cores 3, that is, between adjacent cores 3. Since each core 3 to armature 13 pair is magnetically separated from each other by the hole 17c in this way, magnetic flux is difficult to flow out to neighboring core to armature pairs. In addition, since the ferromagnetic resiliency sheet 17 is connected at the inner and outer ends, even if the ferromagnetic resiliency sheet 17 partially sticks to the armature 13 due to the printing operation and attempts to turn it up, It is pulled by other parts and does not roll upwards. Other operations are the same as those of the conventional example, and will therefore be omitted.

Note that, as described above, since there is a positional relationship between the hole 17c and the core 3, the so-called magnetic assemblies indicated by symbols 1 to 4, 7, and 9 and the ferromagnetic residual sheet 17 need to be positioned. however,
If the dimensional relationship between the core 3 and the hole 17c is designed with a margin, precise positioning is not necessary, so positioning may be performed using a simple structure using a positioning allowance.

As described above, according to this invention, the wire dot printing has a structure that almost eliminates the magnetic flux that wraps around from one magnetic path to another through the ferromagnetic residual sheet 17, and also prevents the ferromagnetic residual sheet from being turned up by the armature. Since the head is used as a head, it is possible to prevent a decrease in the attractive force caused by increasing the thickness of the ferromagnetic sheet 17, prevent magnetic interference, and prevent the ferromagnetic sheet from breaking or being damaged.

Figure 2 is a comparison example of the case where this invention is implemented and the conventional example in which the magnetic separation is not performed.
L _A shows this example of the invention, and straight line L _B shows the conventional example.
For conventional products, the thickness of the ferromagnetic residual sheet is
If you increase 0.18mm from 0.1mm to 0.28mm, the suction force will go from 320g to 240g, which is about a 25% reduction.
On the other hand, in the case of the ferromagnetic residual sheet of this invention, the attractive force is
Only about 6% down from 340g.

(Effects of the invention) As explained in detail above, according to this invention, the ferromagnetic residual sheet has a structure in which holes are provided between the cores to almost eliminate the magnetic flux that goes around to other magnetic paths. Even if the residual sheet is made thicker and the spring force is increased, the attractive force hardly decreases.Therefore, there is no need to increase the total magnetic flux by increasing the size of the permanent magnet, which reduces the cost of the wire dot printing head and makes it more compact. can be converted into Furthermore, since magnetic interference is reduced, current consumption is also reduced. In addition, since the ferromagnetic residual sheet does not partially stick to the armature and roll up, there is no possibility of the ferromagnetic sheet being bent or damaged due to fatigue, resulting in a long-life wire dot printing head. .

[Brief explanation of drawings]

Figure 1 is a partial diagram of a ferromagnetic residual sheet according to an embodiment of this invention, Figure 2 is a diagram showing the relationship between the thickness of the ferromagnetic residual sheet and the attractive force, and Figure 3 is a diagram of a wire dot. FIG. 4 is a half-sectional view of the printing head, and is a partial cross-sectional view showing the relationship between the conventional ferromagnetic residual sheet and the core. In the figure, 1... Permanent magnet, 3... Core, 4... Coil, 8... Leaf spring, 12... Printing wire, 13
... Armature, 17... Ferromagnetic residual sheet, 17c... Hole.

Claims (1)

[Claims for Utility Model Registration] An armature with a printing wire fixed to its end and supported on the free end side of a leaf spring is made of ferromagnetic material by the magnetic force of a permanent magnet against the elastic force of the leaf spring. When a magnetic flux is generated that cancels the magnetic flux generated by the permanent magnet by attracting the core through a ferromagnetic residual sheet made of a thin metal plate and energizing the coil wound around the core, the armature is released from the attraction to drive the printing wire, the wire dot printing characterized in that the ferromagnetic residual sheet is provided with a hole for magnetically separating the adjacent cores. Head.