JPH0419944B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a differential amplitude expansion mechanism.

Conventionally, the mechanical displacement generated by a drive source is magnified and transmitted by two levers, and the couple differentially transmitted by these two levers is applied to a movable member.
There is a differential amplitude expansion mechanism for obtaining displacement with expanded amplitude.

FIG. 1 is a side view showing a conventional differential amplitude expansion mechanism. In the figure, a piezoelectric body 2 whose one end is fixed to a metal mounting member 1 is a driving source. Piezoelectric body 2
When a driving voltage is applied to the electrode (not shown), the piezoelectric body 2 expands and causes dimensional distortion, and this dimensional distortion is transmitted to the metal first and third coupling members 3 and 5 via the metal first and third coupling members 3 and 5. and second movable members 7 and 8
are transmitted to give mechanical displacements in the directions indicated by dashed arrows A and B, respectively. The lower ends of the first and second movable members 7 and 8 connect second and fourth metal coupling members 4 and 6 at a predetermined distance from the first and third coupling members 3 and 5, respectively. It is connected to the mounting member 1 through the connector. Mechanical displacements in the directions of dashed arrows A and B are the first
When this is transmitted to the second movable members 7 and 8, the second and fourth coupling members 4 and 6 bend in response, producing a rotational moment in the first and second movable members 7 and 8. As a result, the upper ends of the first and second movable members 7 and 8 undergo enlarged displacements in the directions indicated by dashed arrows C and D, respectively. One ends of fifth and sixth coupling members 9 and 10 made of metal plates are fixed to the upper ends of the first and second movable members 7 and 8, respectively. The other ends of members 9 and 10 are connected to a third movable member 11 of metal. The third movable member 11 includes fifth and sixth movable members.
Displacements in the directions of dashed arrows C and D are transmitted via coupling members 9 and 10, respectively. Since these two displacements are in opposite directions, the third movable member 11 receives a couple of differential displacements and causes an enlarged displacement in the direction indicated by the dashed arrow E at its tip end. arise.

FIG. 2 is a partial side view showing a conventional differential amplitude amplification mechanism, illustrating the directions of forces acting on the fifth and sixth coupling members 9 and 10 during operation.
The piezoelectric body 2 extends and the first movable member 7 shows the broken line arrow A.
When the displacement in the direction is transmitted, the first movable member 7 rotates around the axis P passing through the center of the second coupling member 4 as the central axis. Along with this, the joint between the first movable member 7 and the fifth coupling member 9 is arranged in the direction shown by the broken line arrow F, that is, in the direction perpendicular to the line segment connecting the joint and the axis P. The force of is applied. This force acts in the direction shown by the dashed arrow C to pull the fifth coupling member 9 along the plate surface, and acts perpendicularly to the plate surface of the fifth coupling member 9 as shown by the broken arrow G. and the fifth
The plate surface of the connecting member 9 is bent. Similarly, the displacement in the direction of the dashed arrow B is transmitted to the second movable member 8, and the second movable member 8 rotates around the axis Q passing through the center of the fourth coupling member 6. As a result, a force in a direction perpendicular to the line segment connecting the joint location and the axis Q acts on the joint between the second movable member 8 and the sixth coupling member 10, as shown by a broken arrow H. This force pushes the sixth coupling member 10 along the plate surface as shown by the broken line arrow D, and acts perpendicularly to the plate surface of the sixth coupling member 10 as shown by the broken line arrow J, causing bending. .

In this way, in the conventional differential amplitude expansion mechanism,
In operation the fifth and sixth coupling members 9 and 10
This produces tensile stress and compressive stress, respectively, as well as bending stress. For this reason, especially when applied to equipment that undergoes a large number of repetitive operations, such as the print head of a dot impact printer, the magnitude of the stress that repeatedly acts on the fifth and sixth connecting members 9 and 10 may exceed the fatigue limit. There is a disadvantage that the fifth and sixth coupling members 9 and 10 are easily broken.

An object of the present invention is to provide a differential amplitude amplification mechanism that eliminates the above-mentioned drawbacks and reduces the bending stress acting on the plate-shaped coupling member that transmits the force couple compared to the conventional one, thereby preventing breakage. There is a particular thing.

The mechanism of the present invention includes: a columnar drive member having one end fixed to a mounting member and the other end for generating displacement in a predetermined direction; and a first coupling having one end connected to the other end of the drive member. and a second coupling member, one end of which is connected to one end of the mounting member, and one end of which is connected to the other end of each of the second coupling members, the second coupling member having one end connected to the one end of the mounting member, the second coupling member having one end connected to the other end of the second coupling member, the second coupling member having one end connected to the one end of the mounting member. A first rotating member that rotates about a central axis passing through a second coupling member to produce a first angular displacement.
a third coupling member having one end connected to the other end of the driving member, and a fourth coupling member having one end connected to the other end of the mounting member, one end of which is connected to the other end of each of the movable member; a second movable member that rotates around a central axis passing through the fourth coupling member in response to the displacement transmitted via the third coupling member and produces a second angular displacement; , a fifth plate-shaped fifth member having one end joined to the other end of the first movable member and transmitting the first angular displacement;
a connecting member, and a plate-shaped sixth member, one end of which is connected to the other end of the second movable member, for transmitting the second angular displacement.
a coupling member connected to the other end of each of the fifth and sixth coupling members, and a third angular displacement according to the first and second angular displacements transmitted through the fifth and sixth coupling members; and a third movable member that generates an arcuate motion, wherein at least one of the fifth and sixth coupling members is connected to the joint portion of the coupling member. and the central axis of rotation of the movable member to which the coupling member joins among the first and second movable members, the plate surface of the coupling member makes a substantially right angle. It is characterized by being arranged as follows.

Next, the present invention will be explained in detail with reference to the drawings.

FIGS. 3a and 3b are a partial perspective view and a characteristic diagram, respectively, for explaining the principle of the present invention. In the same figure a, the force in the direction of the broken line arrow F acting on the joint J1 between the first movable member 7 and the fifth coupling member 9 is also expressed as f, and this force is applied to the plate of the fifth coupling member 9. It is decomposed into two component forces oriented parallel and perpendicular to the plane, that is, in the directions of dashed arrows C and G, and the magnitudes of the respective component forces are defined as f ₁ and f ₂ . If expressed using the angle θ between the dashed arrows F and C, it is clear that f ₁ = f cos θ and f ₂ =
fsinθ holds true. Let the plate thickness of the fifth coupling member 9 be t, and the plate width be w. Also, a joint J2 and a joint J2 between the fifth coupling member 9 and the third movable member 11
Let the length between 1 and 1 be l. When a force f acts on the joint J1 in the direction of the dashed arrow, the joint J1
A tensile stress corresponding to the force f ₁ and a bending stress corresponding to the force f ₂ are generated in the fifth coupling member 9 between J2 and J2. If the magnitude of this tensile stress is σ ₁ , then σ ₁ =
f ₁ /wt holds true. Also, the bending stress is maximum on the plate surface, and if we take its magnitude as σ ₂ , then σ ₂ = f ₂ ×tl/4I, where I is the moment of inertia of area, and I = wt ³ /12, so σ ₂ = f ₂ ×3l/wt ² . Therefore, if the maximum stress occurring in the fifth coupling member 9 is σ, then σ=σ ₁ +σ ₂ = (f ₁ /wt) + (f ₂ ×3l/wt ² ) = (f/wt) {cosθ+ (3l/t)×sinθ}……(1
) holds true.

FIG. 3b shows the relationship between the angle θ and the stress σ when the numerical values of one design example are substituted into the above equation (1). In this design example, f=2Kg, l=10mm, w=2mm, t
= 0.3mm, and by substituting this into equation (1), σ=
3.33×(cosθ+66.6×sinθ), however, the unit of σ is
The following relational expression is obtained: Kg/mm ² . This relational expression is illustrated in Figure 3b, and since l≫t,
As the angle θ increases, the bending stress σ ₂ increases rapidly;
It can be seen that the stress σ increases rapidly along with this. In this design example, if steel with a fatigue limit of about 40 kg/mm ² is used as the material for the fifth connecting member 9, it must be designed so that the angle θ is 5° or less to prevent breakage. . Of course, the upper limit of the angle θ that does not cause damage will vary depending on the above values and how the materials used are selected, but in normal design l≫t, the upper limit of the angle θ will increase as the angle θ increases. In many cases, it is unavoidable that the bending stress σ ₂ increases rapidly. In the mechanism of the present invention, by configuring the angle θ to be substantially 0°, excessive bending stress is not generated in the couple transmission coupling member, thereby preventing breakage and breakage.

FIG. 4 is a side view showing the first embodiment of the present invention. In the mechanism shown in the figure, the plate surface of the fifth coupling member 19 rotates in the direction shown by the broken line arrow F, that is, the joint location of the first movable member 17 and the fifth coupling member 19, and the rotation of the first movable member 17. The plate surface of the sixth coupling member 20 is configured to be parallel to the direction perpendicular to the line segment connecting the central axis, and the plate surface of the sixth coupling member 20 is oriented in the direction indicated by the dashed arrow H, that is, the second movable member 18 and the sixth The second movable member 18 is configured to be parallel to a direction perpendicular to a line connecting the joint portion of the connecting member 20 and the central axis of rotation of the second movable member 18 . Therefore, displacements in the directions of broken line arrows A and B are transmitted to the first and second movable members 17 and 18, respectively, and a displacement that is expanded is transmitted to the third movable members 17 and 18 via the fifth and sixth coupling members 19 and 20. movable member 21 of
When the angle θ is 0° in FIGS. 3a and 3b, an excessive bending stress is not generated in the fifth and sixth coupling members 19 and 20. As a result, even when applied to equipment such as a print head that is operated repeatedly many times, it does not break or break, and its service life can be significantly longer than that of the prior art.

FIG. 5 is a side view showing a second embodiment of the invention. Similar to the first embodiment, when the angle θ is 0° in FIGS. 3a and 3b, the mechanism of this embodiment
The third
The direction of displacement obtained by the movable member 31 is different from that in the first embodiment. That is, the first and second
By changing the shape of the movable members 27 and 28, displacements in the directions indicated by broken line arrows A and B are transmitted,
This is the fifth and sixth coupling members 29 and 30.
When the signal is transmitted to the third movable member 31 via the broken line arrows A and B, as shown by the broken line arrow E,
The structure is such that displacement in a direction parallel to the direction of is obtained. In the first embodiment, as shown in FIG. 4, the direction of the displacement transmitted from the piezoelectric body 2,
The directions of displacement transmitted to the third movable member 21 are orthogonal to each other, and the angle between these two directions of displacement can be set as desired by appropriately changing the first and second movable members. The size can be selected. In this case as well, the structure can be configured to perform the operation corresponding to the case where the angle θ is 0° in FIGS. It is possible to prevent breakage and breakage by not generating excessive bending stress.

Note that in both the first and second embodiments,
The angle θ of both the fifth and sixth coupling members is 0°
Although it is configured so that
Since the width and length of both plates are not necessarily equal, bending stress exceeding the fatigue limit may not be generated in one of them even if the angle θ is not set to substantially 0°. In such a case, the angle θ for only the other one of the two is substantially
If configured so that the angle is 0°, the desired effect can be obtained.

As is clear from the above explanation, the present invention can realize a differential amplitude expansion mechanism that reduces the bending stress acting on the plate-like coupling member for couple transmission more than before and prevents breakage and breakage. This effect is particularly noticeable when applied to equipment that operates repeatedly many times.

[Brief explanation of drawings]

Figures 1 and 2 are a side view and a partial side view, respectively, of a conventional differential amplitude amplification mechanism;
Figures a and b are a partial perspective view and a characteristic diagram for explaining the principle of the present invention, respectively, and Figures 4 and 5 are side views showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Mounting member, 2... Piezoelectric body, 3... First coupling member, 4... Second coupling member, 5... Third coupling member, 6... Fourth coupling member, 7, 17,2
7...First movable member, 8, 18, 28... Second
movable member, 9, 19, 29... fifth coupling member, 10, 20, 30... sixth coupling member, 1
1, 21, 31...Third movable member.

Claims (1)

[Scope of Claims] 1. A columnar drive member having one end fixed to a mounting member and the other end for generating a predetermined directional displacement, and a first coupling having one end connected to the other end of the drive member. and a second coupling member, one end of which is connected to one end of the mounting member, and one end of which is connected to the other end of each of the second coupling members, the second coupling member having one end connected to the one end of the mounting member, the second coupling member having one end connected to the other end of the second coupling member, the second coupling member having one end connected to the one end of the mounting member. A first rotating member that rotates about a central axis passing through a second coupling member to produce a first angular displacement.
a third coupling member having one end connected to the other end of the driving member, and a fourth coupling member having one end connected to the other end of the mounting member, one end of which is connected to the other end of each of the movable member; a second angular displacement that rotates around a central axis passing through the fourth coupling member in response to the displacement transmitted via the third coupling member;
a fifth plate-shaped movable member whose one end is connected to the other end of the first movable member and which transmits the first angular displacement.
a connecting member, and a plate-shaped sixth member, one end of which is connected to the other end of the second movable member, for transmitting the second angular displacement.
a coupling member connected to the other end of each of the fifth and sixth coupling members, and a third angular displacement according to the first and second angular displacements transmitted through the fifth and sixth coupling members; and a third movable member that generates an arcuate motion, wherein at least one of the fifth and sixth coupling members is connected to the joint portion of the coupling member. and the central axis of rotation of the movable member to which the coupling member joins among the first and second movable members, the plate surface of the coupling member makes a substantially right angle. A differential amplitude amplification mechanism characterized by being arranged as follows.