JPH0439059A - Impact print head - Google Patents

Abstract

PURPOSE:To obtain a good printing quality and prevent a printing noise by a method wherein an antiresonance frequency of a parallel circuit consisting of a reactance component of an electromechanical conversion element and an impedance element is made substantially coincide with a mechanical vibration frequency of a printing head. CONSTITUTION:An inductance of a variable coil 4 of a vibration isolator part 2 provided on a printing head part 1 is previously adjusted so that an antiresonance frequency fa (Hz) of a parallel circuit 35 is made coincide with a mechanical vibration frequency of the printing head part 1. In this manner, an electric current flowing to an electrostatic capacity 3 has a phase 90 degree leading to a change of a voltage output of a force factor 32. On the other hand, an electric current flowing to the variable coil 4 has a phase 90 degree lag from a change of a voltage output the force factor 32. Therefore, an electric current does not flow if the force factor 32 outputs a voltage with the mechanical vibration of the printing head part 1, and the mechanical amplitude of a piezoelectric element 3 cannot be converted to a current output. Therefore, the mechanical vibration of a printer part can be inhibited regardless of the number of the mechanical vibration frequency of the printing head part 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an impact print head, and more particularly to an impact print head with reduced printing noise.

[Prior Art] There are two typical types of conventional impact printing devices as follows. The first type has a hammer, etc. as a movable printing part, and an ink ribbon, type, platen, etc. as a printing medium, and the second type has a built-in number of printing wires, armatures, etc. as a movable printing part. However, it is an impact dot printer that has an ink ribbon, platen, etc. as a printing medium. During the printing operation of these impact dot printers, movable parts such as hammers, printing wires, and armatures collide with other parts, causing damage.
This collision generates vibrations in the print head. Vibration noise caused by this vibration is the main cause of printer noise.

In order to reduce the above-mentioned printing noise, the following method of reducing the vibration of the print head can be easily considered. For example, if it is a hammer type printer, there is a method to reduce the impact force that drives the hammer, or if it is an impact dot printer, there is a method to reduce the impact force that drives the printing wire, or there is a method to increase the rigidity of the print head. It is.

[Problems to be Solved by the Invention] However, the above-mentioned means for reducing the impact force weakens the force of striking the printing medium such as the ink ribbon by the printing movable part such as the hammer or printing wire, and the impact force is insufficient for the ink or paper. There was a problem that the image was not transferred and the print quality deteriorated. Furthermore, if means for increasing the rigidity of the print head are adopted, the weight of the print head increases, making it difficult to reduce the size and weight of the print head.

The present invention has been made to solve the above-mentioned problems, and its purpose is to provide an impact printer that has good print quality, can be easily made small and lightweight, and can easily reduce printing noise. The purpose of the present invention is to provide a system print head.

[Means for Solving the Problems] In order to achieve this object, the impact type print head of the present invention uses a reciprocating motion of a movable printing part such as a hammer or a printing wire to A print head that performs printing by colliding its tip with a print medium such as an ink ribbon, type, or a platen, the print head comprising an electromechanical transducer mounted on at least a portion of the surface of the print head, and the electromechanical transducer. an impedance element connected to the electromechanical transducer and forming a closed circuit together with the electromechanical transducer; The vibration frequency is approximately equal to that of mechanical vibration.

[Function] According to the impact type print head of the present invention having the above configuration, impact When the electromechanical transducer attached to the print head deforms and attempts to generate an electrical output with the same frequency as the vibration of the print head, the electromechanical transducer and impedance element attached to the print head deform. behaves as follows. The parallel circuit made up of the reactance component of the electromechanical transducer and the impedance element has its anti-resonance frequency approximately matched to the frequency of the vibration of the print head that is to be suppressed, so that the parallel circuit composed of the reactance component of the electromechanical transducer and the impedance element is roughly matched to the frequency of the vibration of the print head that is to be suppressed. The mechanical amplitude of the electromechanical transducer generated by the electromechanical transducer cannot be converted into a current output. The amount of deformation of the electromechanical transducer is proportional to the magnitude of the current at its output end, but as a result of no current flowing as described above, deformation of the electromechanical transducer is prohibited and no vibration occurs in the print head. Therefore, it is possible to easily suppress the occurrence of printing noise mainly caused by vibration noise caused by vibration of the printing head.

[Example] Hereinafter, an example embodying the present invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view of an impact type print head according to an embodiment of the present invention. 2 is a partially sectional front view of the print head shown in FIG. 1, FIG. 3 is a left side view of the print head, and FIG. 4 is a right side view of the print head. First, the configuration of the main parts of the impact type print head of this embodiment will be explained based on FIG. In FIG. 1, 1 is a print head section. Further, 2 is a vibration isolator section, which is composed of a piezoelectric element 3 and a variable coil 4. The piezoelectric element 3 is attached to the side surface of the print head section 1 by adhesive or the like, one end of the variable coil 4 is directly connected to one surface of the piezoelectric element 3, and the other end is connected to the print head section 1. It is electrically connected to the other surface of the piezoelectric element 3 via 1. The variable coil 4 is a coil equipped with a variable mechanism that changes the inductance by adjusting the insertion and removal of the core.

Furthermore, the detailed structure of the print head section 1 of the impact type print head according to the embodiment of the present invention will be explained based on FIGS. 2 to 4. In FIGS. 2 to 4, 11 is a yoke that forms the main part of the print head, and 12 is an armature 1.
Back stopper for positioning when resetting 8, 1
3 is a nose that holds the wire guide 14. The printing movable section 10 consists of a printing wire 15 and an armature 18, and the base of the printing wire 15 is fixed to the tip of the armature 18 by silver soldering or the like.

16 is a frame spring that holds the backstopper 12 and damper 17; 19 is an armature return spring that returns the armature 18 to the reset position; and 20 is a rubber sheet that prevents dust from entering the inside of the print head. 21
is a coil attached to a core pole 22 formed on the yoke 11, and when electricity is passed through the coil 21, a magnetic attraction force is generated between the core pole 22 of the yoke 11 and the armature 18. 22 constitute an electromagnet.

Next, the operation of the impact type print head of this embodiment configured as described above will be explained based on FIGS. 1 to 4 and FIG. 5. Here, FIG. 5 is a circuit diagram showing an electrical equivalent circuit of the vibration isolator section 2 attached to the print head section 1. As shown in FIG.

First, the operation of the print head section 1 will be explained in FIGS. 1 to 4.
Outline based on the diagram. When the coil 21 is energized, a magnetic flux force is generated in the coil 21, and this magnetic flux passes through the core pole 22 and enters the armature 18.
The air flows from the armature 18 through the yoke 11 to the core pole 22. At this time, the armature 18
A magnetic attraction force acts on the core pole 22 side, and due to this magnetic attraction force, the printing wire 15 fixed to the tip of the armature 18 moves in the direction of arrow a in FIG. It collides with the ribbon 23 and platen 24, and prints on paper (not shown). Thereafter, by the force of the armature return spring 19, the printing wire 15
is returned in the direction of the arrow in FIG.
8 collides with the backstop 12 and returns to the reset position. Due to the above-described collision between the armature 18 and the nozzle stopper 12 or the reciprocating movement of the printing wire 15 and the armature 18, vibrations of a certain frequency f[H2] are excited in the printing head section 1. try However, the print head section 1 is provided with the vibration isolator section 2 which is made up of the piezoelectric element 3 and the variable coil 4, and the vibration isolator section 2 generates vibrations in the print head section 1. It works to prevent it from happening. Here, the operation of the vibration isolator section 2 will be explained based on FIG. 5. The piezoelectric element 3 has mechanical compliance 3
1, a parallel circuit 3 represented by a force coefficient 32 and a capacitance 33, and constituted by the capacitance 33 and the variable coil 4;
The antiresonance frequency fa [Hz] of No. 5 is given by the following equation.

fa= [Hz co2π (LC
)1/2 Here, L is the inductance of the variable coil 4, and C is the capacitance. However, in the variable coil 4,
- the energy stored by its inductance component is greater than the energy consumed by its resistance component during a cycle;

In the impact type print head of this embodiment configured in this way, the frequency f [Hz] of the print head section 1 is
The piezoelectric element 3 receives vibrations of the same frequency f[
Hz]. Here, the inductance of the variable coil 4 is determined by the capacitance 33 of the piezoelectric element 3 and the anti-resonance frequency fa [Hz] of the parallel circuit 35 constituted by the variable coil 4 or the vibration of the print head section 1. If adjusted in advance to match the frequency f [Hz], the current flowing through the capacitance 33 will have a force coefficient of 32
The current flows through the variable coil 4 with a force coefficient of 32.
Since the current is delayed in phase by 90 degrees with respect to the change in the voltage output, energy is only exchanged between these two elements.

Therefore, even if a voltage output is generated due to the mechanical vibration of the print head 1, the force coefficient 32 is determined by the piezoelectric element 3, which is generated due to the vibration of the print head 1, because no current flows. Unable to convert mechanical amplitude to current output.

In other words, at this time, the piezoelectric element 3 is prohibited from being deformed, and the print head section 1 is affected by the collision between the armature 18 and the back stopper 12 or the reciprocating movement of the print wire 15 and the armature 18. No mechanical vibrations occur. Therefore, noise mainly caused by vibration noise caused by the vibration of the print head section 1 is not generated.

As detailed above, in the impact type print head of this embodiment, the vibration isolator section 2 is attached to the print head section 1, and the inductance of the variable coil 4 of the vibration isolator section 2 is adjusted in advance. Then, the anti-resonant frequency f of the parallel circuit 35
If a [Hz] is made to match the frequency f [Hz] of the mechanical vibration of the print head section 1, the mechanical vibration of the printer section will be This has the effect of inhibiting vibration.

Furthermore, according to the vibration isolating device section 2 of this embodiment, the inductance of the variable coil 4 can be adjusted even if the frequency of mechanical vibration occurring in the print head section 1 is not accurately known. Therefore, the anti-resonant frequency fa of the parallel circuit is
[Hz] is the frequency f of mechanical vibration of the print head section 1
Since it is possible to match the frequency with [Hz], the effect is that it is extremely easy to use.

Note that the present invention is not limited to the embodiments described above, and various changes can be made without departing from the spirit thereof.

For example, in the above-described embodiments, an impact type print head is described in detail, in which a driving force is generated in the armature using magnetic attraction force, and the printing wire is reciprocated by this driving force to perform printing. The present invention is not limited to this method, and similar effects can be obtained even when applied to an impact type print head in which printing is performed by driving a printing hammer using a mechanical driving force.

Further, in the above embodiment, the piezoelectric element is attached to a part of the surface of the print head, but the same effect can be obtained even if the piezoelectric element is attached to the entire surface of the print head. . In addition, in this embodiment, the vibration isolator section is
Although the impact type print head equipped with a set has been described, it goes without saying that vibrations of a plurality of frequencies can be suppressed at the same time by installing a plurality of sets of vibration isolating device sections. Alternatively, it may be provided on the back side of the print head.

Further, the impedance element may be formed by connecting a variable capacitance to a coil, or the impedance element may include a small resistance component.

Furthermore, in this example, a piezoelectric element is used as the electromechanical conversion element, but the invention is not limited to this, and other elements that can convert electrical energy into mechanical energy, such as an electrostrictive element, a magnetostrictive element, etc. may also be used.

Various modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] As is clear from the above detailed description, according to the present invention, the anti-resonance frequency of the parallel circuit constituted by the electromechanical transducer and the impedance element attached to the print head can be adjusted by impact printing. By matching the frequency of the mechanical vibration of the head, the vibration of the impact print head can be reliably and easily prevented, so the impact force can be reduced without degrading print quality, and the rigidity of the print head can be improved. It is possible to reliably prevent the noise generated by this vibration without increasing the weight. Furthermore, since the vibration of the print head, which is the main cause of noise in impact printers, is directly suppressed, there is no need to provide a soundproof cover around the print head or to increase the degree of airtightness of the body of the printer. In addition, since the vibration isolation mechanism consists of only an electromechanical transducer and an impedance element, there is no need to increase the number of parts or complicate the structure, resulting in low manufacturing costs, a small size, and a low-noise impact print head. This has the effect that it becomes possible to easily obtain the following.

Furthermore, since the circuit constituted by the electromechanical transducer and the impedance element does not consume power, there is also the advantage that a power supply circuit is not required.

[Brief explanation of the drawing]

1 to 5 show embodiments embodying the present invention. FIG. 1 is a schematic perspective view of an impact type print head according to an embodiment of the present invention, and FIG. FIG. 3 is a front view showing a part of the print head in cross section, FIG. 3 is a left side view, and FIG. 4 is a right side view. Moreover, FIG. 5 is an electrical equivalent circuit diagram of the vibration isolator section of the embodiment of the present invention. In the figure, 1 is a print head, 3 is a piezoelectric element which is an electromechanical transducer, and 4 is a variable coil which is an impedance element. Further, 10 is a printing movable part, 15 is a printing wire which is an example of the printing movable part, and 18 is an armature which is an example of the printing movable part. Furthermore, 23 and 24 are an ink ribbon and a platen, which are printing media, respectively. Furthermore, 35 is a parallel circuit constituted by the reactance component of the piezoelectric element 3 and the variable coil 4. Patent Applicant Brother Industries, Ltd. President Yoshihiro Yasui Figure 2 Figure 4 Figure 3 @ Figure 5

Claims (1)

[Scope of Claims] An impact type print head that performs printing by colliding the tip of a movable printing part with a print medium, comprising: an electromechanical transducer mounted on at least a portion of the surface of the print head; an impedance element connected to the electromechanical transducer and forming a closed circuit together with the electromechanical transducer;
An impact type print head characterized in that the vibration frequency of the mechanical vibration of the print head is made substantially equal to the vibration frequency of the mechanical vibration of the print head.