JPH0413174Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a mechanical amplification mechanism that amplifies and drives the motion of an electrical/mechanical transducer, and more specifically, it relates to a mechanical amplification mechanism that amplifies and drives the motion of an electrical or mechanical transducer. The present invention relates to mechanical amplification mechanisms mainly applied to printing devices such as printers or switches such as relays.

(Prior Art and its Problems) Conventionally, drive devices using electromechanical transducers have been used in printing devices such as printer print heads, and switches such as relays and switches. For example, most dot impact printer print heads use electromagnets or permanent magnets as their driving source. However, this method has the disadvantage that there is copper loss and iron loss during driving, it is necessary to provide a large amount of input energy relative to the required energy, and the energy conversion efficiency is low. Therefore, in recent years, mechanisms have been considered that use electrostrictive elements or piezoelectric elements as drive sources to reduce power consumption and heat generation and enable high-speed operation. However, in this method, the displacement of the driving source and the electrostrictive or piezoelectric element is 0.005~
Because it is as small as 0.01 mm, it is 0.3 mm to 0.5 mm, which is required for normal printer print heads and relay mechanism operating elements.
It is necessary to amplify the displacement of the electrostrictive or piezoelectric element to obtain a displacement of . One example of what has been proposed in the past in response to this requirement is a mechanism as shown in FIG. In FIG. 1, both ends of a curved spring 2 curved upward (in the printing direction) by an adjusting screw 1 are fixed to a holding element 3, and one of the holding elements 3 is seated on a piezoelectric crystal device 4, and the other is a fixed holding part. Sit down at 5. In this structure, the excitation of the piezoelectric crystal device 4 causes the bending spring 2 to
is bent to drive the printing needle 6 provided at the center of the curved spring 2. In such a system, when a displacement is applied to the curved spring 2 in the axial direction, a deflection occurs as shown in the well-known buckling theory, and a large amount of deflection can be easily obtained, and the structure is simple. However, in a mechanism using such a buckling spring, in order to prevent the snap action phenomenon of the buckling spring or deflection in the opposite direction, and to ensure stable operation, the buckling spring must be adjusted by means such as an adjusting screw as described above. It is necessary to bend it in one direction. However, on the other hand, these mechanical amplification mechanisms such as printer print heads and relays are required to be driven at high speed, made smaller and lighter, and to achieve this, it is necessary to improve the natural frequency of the buckling spring itself and to reduce the length of the buckling spring. Shortening is necessary. However, as the rigidity of the buckling spring increases, the stress acting on the buckling spring also increases.
Fatigue limits may be exceeded. In particular, when the initial displacement is large as mentioned above, the stress during driving is equal to the initial displacement, causing a problem that greatly exceeds the fatigue limit of the buckling spring, making it difficult to speed up and downsize the amplification mechanism. .

(Purpose of the invention) The object of the present invention is to eliminate such conventional drawbacks and provide a mechanical amplification mechanism that is small, can be driven at high speed, and is highly reliable.

(Structure of the invention) According to the invention, the expansion and contraction motion of the electrostrictive or piezoelectric element is transmitted in the axial direction of the buckling spring, the displacement is expanded by the deflection of the buckling spring, and the action element provided on the buckling spring is In the mechanical amplification mechanism that obtains an output, there is obtained a mechanical amplification mechanism characterized in that the buckling spring is a shaped spring that maintains a constant curved shape even in a state where no external force is applied.

(Detailed explanation of configuration) The present invention solves the conventional problems by adopting the above-mentioned configuration. In order to increase the speed and reduce the size of a mechanism using a buckling spring, it is first necessary to increase the natural frequency of the buckling spring. Now, let the length of the leaf spring be, and let the length be t, then the natural frequency f has the relationship f∝t/ ² , so in order to increase f, it is necessary to decrease and increase t. be. On the other hand, δ ₀ is the initial displacement of the buckling spring, and δ ₁ is the amount of deformation of the buckling spring due to electrostriction or excitation of the piezoelectric element.
Then, the maximum stress σ caused by the deflection of the buckling spring has a relationship of σ∝(δ ₀ +δ ₁ )t/ ² , where is small, and when t is large, the stress increases. Under these circumstances, as mentioned above, it is normal for _δ1 to be 0.3 to 0.5 mm for printer print heads, relays, etc.
In this case, even if the initial displacement δ ₀ is made equivalent to δ ₁ , half of the total stress is occupied by the initial displacement. Furthermore, since there are variations in the initial displacement in manufacturing the amplification mechanism, δ ₀ must be made as large as possible in order to shorten the adjustment time. That is, by increasing δ ₀ , manufacturing costs can be reduced. Therefore, 60 to 80% of the total stress is accounted for by the initial displacement, making it difficult to increase the natural frequency f.

In the present invention, the buckling spring is a molded spring that maintains its curved shape even without external force so that the initial displacement is equivalent to that required under normal conditions. The shaped spring of the present invention can be obtained, for example, by pressing and heat straightening, or it can also be made of plastic or composite material, as long as it has the shape of a beam and has spring properties, and can be obtained by injection molding. According to the present invention, the stress at the initial displacement is eliminated from the stress equation, so that the stress σ that ultimately acts on the shaped spring can be considered as σ∝δ ₁ t/ ² . In other words, if the amount of displacement δ ₁ when the formed spring operates is the same as before, the stress will be at least half less, and if t is increased and t is made smaller so that the stress is the same as before, the natural vibration will be doubled. You can get a few springs. Therefore, according to the present invention, a mechanical amplification mechanism that is compact and can be driven at high speed can be obtained.

(Example) Examples of the present invention will be described below with reference to the drawings. FIG. 2 is a perspective view of a molded spring showing an embodiment of the present invention. In FIG. 1, the molded spring 7 has been bent by pressing or heat straightening, and a printing needle 8, which is an operating element serving as an output, is provided in the center. As mentioned above, the shaped spring 7 does not need to be plate-shaped as long as it is in the form of a beam, and as long as there is an initial displacement in one direction, it does not have to be in the arcuate shape of FIG. 1. FIG. 3 is a side view showing a print head configuration according to an embodiment of the present invention. In FIG. 3, one end of the electrostrictive or piezoelectric element 9 is fixed to a base 10, and the other end is connected to the base 10. At this time, since the shaped spring 7 has a curved shape even in the absence of an external force, no stress is acting on the shaped spring 7. Further, a backstop 11 is provided at the rear of the printing needle 8 on the molded spring 7 to attenuate the impact of the return movement of the molded spring 7. By applying a voltage to the electrostrictive or piezoelectric element 9, the electrostrictive or piezoelectric element 9 extends in the axial direction, and the displacement 12 is transmitted to the shaped spring 7 in the axial direction. Therefore, according to the well-known buckling theory, the shaped spring 7 causes deformation 13 in the initial displacement direction, that is, in the direction of the printing needle 8, in response to the displacement given in the axial direction, and the maximum deformation occurs at the printing needle 8 in the center of the shaped spring 7. displacement is obtained. Therefore, the printing needle 8 passes through the ribbon guide 14,
Ink ribbon 15, printing paper 16, platen 17
The printing operation is performed by hitting the . Furthermore, when the applied voltage is stopped, the electrostrictive or piezoelectric element 9 returns to its original length, and at the same time, the shaped spring 7 also returns, and thereafter its operation is damped by the backstop 11.

Next, other embodiments of the present invention are shown in FIGS. 4 and 5. In FIG. 4, it is composed of two lever arms 18 for transmitting and amplifying the displacement of an electrostrictive or piezoelectric element 9, and a molded spring 7 supported so as to be sandwiched between the lever arms 18. A printing needle 8 is provided as an active element.
Even in such a system, the present invention can be applied and produce effects. FIG. 5 also shows an electrostrictive or piezoelectric element 9.
two lever arms 1 for displacement amplification, one end of which is connected in common in the expansion/contraction direction, and the other end of the electrostrictive or piezoelectric element 9 is connected by a fulcrum, respectively;
9 and a molded spring 7 supported by a lever arm 19, and a printing needle 8 is provided on the molded spring 7. The present invention can also be applied to this method.

In the embodiments of the present invention described above, the molded spring can be supported either fixedly or rotatably. Furthermore, although it is applied to a printer print head, a relay contact is provided in place of the printing needle on a molded spring, and it is applied as a movable contact, and by adding a fixed contact, it can also be applied to relays, switches, etc. Furthermore, although stacked electrostrictive or piezoelectric elements are exemplified as drive sources in the above embodiments, electrostrictive or piezoelectric elements having transverse or longitudinal effects may also be used.

(Effects of the invention) According to the invention, the conventional large print head measuring 70 mm in length and 40 mm in width can be reduced in size to half, and the driving frequency can be increased to about twice as much. Furthermore, even if the initial displacement of the molded spring is large, the stress is small, so the manufacturing cost is low, and a printing head with a long life and high reliability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a conventional embodiment, and FIG. 2 is a perspective view showing a molded spring that is an embodiment of the present invention.
FIG. 3 is a side view showing one embodiment of the invention, FIG. 4 is a side view showing another embodiment of the invention, and FIG. 5 is a side view showing another embodiment of the invention. Each symbol in the figure indicates the following. 1...
Adjustment screw, 2... Curved spring, 3... Holding element, 4
... Piezoelectric crystal device, 5 ... Fixed holding part, 6 ... Printing needle, 7 ... Molded spring, 8 ... Printing needle, 9 ... Electrostrictive or piezoelectric element, 10 ... Base, 11 ...
Back stop, 12... Displacement of electrostrictive or piezoelectric element, 13... Deformation of formed spring, 14... Ribbon guide, 15... Ink ribbon, 16... Print paper, 17... Platen, 18... Lever arm, 19...Lever arm.

Claims (1)

[Scope of utility model registration request] In the mechanical amplification mechanism, the expansion and contraction motion of the electrostrictive or piezoelectric element is transmitted in the axial direction of the buckling spring, the displacement is expanded by the deflection of the buckling spring, and an output is obtained by an operating element provided on the buckling spring. A mechanical amplification mechanism characterized in that the buckling spring consists of a shaped spring that maintains a constant curved shape even in the absence of external force.