JPH0430351B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printing element, and particularly to a printing element for performing dot printing using a piezoelectric material as a driving source.

FIG. 1 is a perspective view illustrating the structure of a printing element according to the present invention. A piezoelectric body 2 whose lower end is fixed to a metal mounting member 1 is a driving source for printing operation. The upper end of the piezoelectric body 2 is fixed to a metal coupling member 3. Both of the metal movable members 4 and 5 are provided to act as levers to magnify and transmit the displacement when they receive displacement from the piezoelectric body 2. The lower end portions of the movable members 4 and 5 are respectively connected to the mounting member 1 and the coupling member 3 via plate-shaped connecting portions. Furthermore, a transmission member 6 of a metal plate is provided at the upper end of each of the movable members 4 and 5.
and 7 are fixed, and the other ends of the transmission members 6 and 7 are fixed to desired locations on the movable member 8, respectively. A metal rod wire 9 for dot printing is attached and fixed to the tip of the movable member 8.

When a driving voltage is applied through the lead 11 between the pair of electrodes 10 provided on both sides of the piezoelectric body 2 , the piezoelectric body 2 expands due to the electrostrictive effect, causing dimensional distortion, pushing up the coupling member 3 and causing the movable member 4 to move. and give a displacement to 5. In response to this displacement, movable members 4 and 5 each act as a lever, causing displacement in the directions indicated by broken line arrows A and B at their respective upper ends. When these two displacements in opposite directions are transmitted via the transmission members 6 and 7, the movable member 8 causes a rotational movement, and the wire moves in the direction of the dashed arrow C to perform the dot printing operation. I do.

In the conventional printing element, spring steel is used as the metal material for the mounting member 1, the movable members 4 and 5, and the transmission members 6 and 7. When the printing operation is performed many times, large stresses are concentrated especially at the connection parts between the transmission members 6 and 7 and the movable members 4 and 5 and the mounting member 1 and the coupling member 3 because they are plate-shaped. Therefore, we select and use steel materials for springs that have high durability against this repeated stress.

However, conventional printing elements using such materials suffer from temperature fluctuations as the ambient temperature changes during operation.
Breakage and destruction of transmission members 6 and 7 or piezoelectric body 2
There are disadvantages in that peeling and breakage may occur, and the position of the tip of the wire 9 may shift, preventing normal printing operation. First, when brazing is performed to fix each end of the transmission members 6 and 7 to the movable members 4 and 5 or the movable member 8, the welding heat causes a heat-affected zone to occur at the brazed locations. As a result, the fatigue strength of each end of the transmission members 6 and 7 deteriorates due to causes such as embrittlement and cracking. For example, if the original fatigue limit was about 80Kg/mm ² , after welding it deteriorates to half that, 40Kg/mm ² or even lower. In particular, when downsizing the element, the plate thickness of the transmission members 6 and 7 must be made thinner accordingly in order to obtain smooth repetitive motion, and as a result, the magnitude of the stress that repeatedly acts on the transmission members 6 and 7 is reduced. Since it exceeds 40Kg/ ^mm2 , it is likely to break and break during operation. Furthermore, the thermal expansion coefficient of the piezoelectric body 2 is approximately (0 to 2) × 10 ^-6 /°C, whereas the thermal expansion coefficient of the spring steel material is approximately (10 to 2) × 10 -6 /°C.
20)×10 ^-6 /°C. For example, when using a piezoelectric body 2 with a length of 30 mm as a drive source, if the ambient temperature changes by 30°C after both ends of the piezoelectric body 2 are fixed to the coupling member 3 and the mounting member 1 with adhesive, the piezoelectric body 2 Change in length of connecting member 3 and mounting member 1
A difference of about 10 μm occurs between the length changes. This difference in the amount of thermal expansion causes compressive or tensile stress to act on the piezoelectric body 2, but since the piezoelectric body 2 has low strength against tensile stress, cracks occur in the piezoelectric body 2 due to the tensile stress especially when the temperature rises and the piezoelectric body 2 peels off. Easy to cause destruction. Furthermore, as mentioned above, the length of the piezoelectric body 2 changes as the temperature changes, but the magnitude of this change is approximately the same as the amount of change in length due to dimensional distortion that occurs when the piezoelectric body 2 is driven. There is. In such a case, the tip position of the wire 9 may shift depending on the change in the length of the piezoelectric body 2, and the wire 9 may no longer impact the paper surface when driven, or conversely, the wire 9 may not impact the paper surface even when not driven. It came into contact with the paper,
Normal printing operation becomes impossible. In addition, displacement occurs in the movable members 4 and 5 in accordance with a change in the length of the piezoelectric body 2, and this is transmitted to the transmission members 6 and 7.
Even when not driven, stress of the same magnitude as when driven acts on the transmission members 6 and 7, and if the stress generated when driven is further superimposed, the fatigue limit will be exceeded and breakage will occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a printing element and a method for manufacturing the same, which eliminates the above-mentioned drawbacks and prevents breakage of the transmission member, peeling and destruction of the piezoelectric body, and displacement of the wire tip during operation.

The element of the present invention includes a piezoelectric body that generates dimensional distortion in response to an applied voltage, and a mounting member fixed to one end of the piezoelectric body and made of a metal material having substantially the same coefficient of thermal expansion as the piezoelectric body. and a first one connected to the other end of the piezoelectric body and the mounting member via a plate-like member, and oriented in opposite directions in response to the dimensional strain applied from the piezoelectric body through the plate-like member. and first and second movable members that produce a second angular displacement, and first and second transmission of age hardenable metal plates having one end of each fixed to the first and second movable members. a member, and the other ends of the first and second transmission members are fixed to each other, and one end is fixed to produce a rotational movement in response to the first and second angular displacements transmitted through both. and a third movable member that applies a printing operation to a certain thin rod-shaped wire.

The manufacturing method of the present invention includes welding one end of a first and second transmission member of a metal plate to first and second movable members made of low expansion steel, respectively, and After each other end is welded to a third movable member made of low expansion steel, the method includes the step of heat treating at a predetermined temperature for a predetermined period of time.

Next, the present invention will be explained in detail.

In the present invention, the materials for the mounting member and the transmission member in a printing element for dot printing using a piezoelectric body as a driving source are selected to effectively prevent damage to the piezoelectric body and the transmission member. An embodiment of the present invention will be described below. In the printing unit having the structure as illustrated in FIG. 1, the mounting member 1 and the movable members 4 and 5 are integrally formed of a low expansion alloy, and the transmission members 6 and 7 are made of age-hardening martensitic aged steel ( MA steel). For example, Nickel 36 is used as a low expansion alloy.
% steel material (Invar) has a coefficient of thermal expansion of (0 to 1) ppm/°C. Therefore, the difference in length change between the piezoelectric body 2, the mounting member 1, and the connecting member 3 due to temperature changes is as follows. Reduced to less than 1/10 of the previous level. Therefore, when the ambient temperature changes, especially when the temperature rises, the stress acting on the piezoelectric body 2 is reduced to 1/10 or less of that of the conventional one, which prevents peeling failure of the piezoelectric body 2 and the position of the tip of the wire 9 as in the conventional case. Misalignment and generation of stress in the transmission members 6 and 7 when not driven can be prevented.

FIG. 2 is a characteristic diagram showing changes in the fatigue limits of the transmission members 6 and 7 for each manufacturing process in this example. As mentioned above, the transmission members 6 and 7 are made of MA steel, and both ends of the transmission members 6 and 7 are connected to the movable member 4,
The predetermined locations of 5 and 8 are brazed with a brazing material having a welding temperature set within the range of 820 to 900°C. After that, heat treatment is performed at 480°C for 3 hours. Movable members 4 and 5 have been solution-treated at 820°C before brazing, and their fatigue limit when cooled at room temperature is approximately 40 kg/mm ² , but they are age-hardened by heat treatment after brazing. The fatigue limit of approximately 80Kg/ ^mm2 is reached. Therefore, the fatigue limit of the welded parts of the transmission members 6 and 7 does not deteriorate after welding as in the past, but the fatigue limit of the welded parts of the transmission members 6 and 7 is about twice that of the conventional one due to age hardening due to heat treatment, and breakage during operation is prevented. Destruction can be prevented. Furthermore, this improved fatigue limit makes it possible to downsize the printing element. Invar is a low-carbon steel and does not undergo phase transformation at high temperatures to form a gallox structure unlike conventionally used spring steels with a high carbon content, and has the advantage of being suitable for the heat treatment in this example. have

Note that the structure of the printing element to which the present invention can be applied is not limited to that illustrated in FIG. Element,
If the printing element is equipped with a plate-shaped transmission member that transmits the displacement to the wire, the member that fixes both ends of the piezoelectric body is made of a metal material whose thermal expansion coefficient is substantially the same as that of the piezoelectric body, and Using age-hardening metal material as the material of the transmission member,
It is clear that the same effects as in this embodiment can be obtained.

As is clear from the above description, the present invention has the effect of providing a printing element and a method for manufacturing the same that prevent damage to the transmission member during operation, peeling and destruction of the piezoelectric body, and displacement of the tip of the wire.

[Brief explanation of drawings]

FIG. 1 is a perspective view illustrating the structure of a printing element according to the present invention, and FIG. 2 is a characteristic diagram for explaining one embodiment of the present invention. 1... Mounting member, 2... Piezoelectric body, 3, 4, 8...
...Movable member, 6, 7...Transmission member, 9...Wire.

Claims (1)

[Claims] 1. A piezoelectric body that generates dimensional distortion in response to an applied voltage, and a metal material having one end fixed to the piezoelectric body and having substantially the same coefficient of thermal expansion as the piezoelectric body. The mounting portion is connected to the other end of the piezoelectric body and the mounting member through a plate-like member, and in response to the dimensional strain applied from the piezoelectric body through the plate-like member, the piezoelectric body rotates in opposite directions. first and second movable members that produce first and second angular displacement; first and second age-hardenable metal plates having one end of each fixed to the first and second movable members; a transmission member, and each other end of the first and second transmission members is fixed, and rotational movement is generated in response to the first and second angular displacements transmitted through both, and one end is fixed. and a third movable member that applies a printing operation to a thin rod-shaped wire. 2. A mounting member for fixing one end of a piezoelectric body that generates dimensional distortion in response to an applied voltage; and a mounting member that is connected to the other end of the piezoelectric body and the mounting member via a plate member, and is connected to the other end of the piezoelectric body and the mounting member through a plate member, First and second movable members that produce first and second angular displacements in opposite directions in response to the dimensional strain applied via the plate member are heated to substantially the same temperature as the piezoelectric body. One end of the first and second transmission members of a metal plate formed of a metal material having a coefficient of expansion and having age hardening properties is welded to the first and second movable members, respectively, and the other end is attached to a printing wire. A method for manufacturing a printing element, comprising the step of age-hardening the first and second transmission members by heat treatment after welding them to the third movable member.