Method of producing piezoelectric actuator

A plurality of drive sections are defined by forming a plurality of slits in a plate-shaped member. Then, a plurality of piezoelectric layers are formed in the drive sections respectively by depositing particles of a piezoelectric material onto the plate-shaped member. Subsequently, after forming individual electrodes on the piezoelectric layers respectively, the drive sections are bent in a direction orthogonal to a plane direction of the plate-shaped member. Thus, there is provided a method of easily producing a piezoelectric actuator including the drive sections which are bent-shaped and on which the piezoelectric layers are formed respectively.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of producing a piezoelectric actuator used in a transporting apparatus or the like.

2. Description of the Related Art

A transporting apparatus which includes a transporting roller and a drive motor which drives the transporting roller has been hitherto generally used for transporting a paper or the like to be recorded in a recording apparatus. However, in recent years, a technology for applying a piezoelectric actuator, having a piezoelectric element made of a ceramics material such as lead zirconate titanate (PZT), to a variety of usages has been studied, and in particular, a technology for transporting an object (transportation object) by utilizing a deformation which is developed when a voltage is applied to the piezoelectric element has been proposed. For example, Japanese Patent Application Laid-open Publication No. 2003-111456 describes a piezoelectric actuator which has a plurality of piezoelectric actuator elements each of which includes a substrate in the form of a plate, piezoelectric elements provided to both surfaces of the substrate respectively, and a plurality of electrodes formed on surfaces of the piezoelectric elements respectively. This piezoelectric actuator is structured such that a front tip portion of the substrate is caused to be deformed due to bending deformation of the piezoelectric element, and an object which is cylindrical or tubular in shape can be transported by being moved by a very small amount in a longitudinal direction of the object by a ciliary movement of a plurality of substrates arranged in a circumferential direction of the cylindrical or tubular object. However, this transporting apparatus is structured to transport an object which is mainly cylindrical or tubular in shape, and thus there is a restriction on the shape of the object which can be transported. Accordingly, it is difficult to use this piezoelectric actuator for transporting an object which has a shape other than the cylindrical or tubular shape, such as a paper.

In view of this situation, the inventor of the present application invented a piezoelectric actuator which is capable of transporting objects which have various shapes along a predetermined transportation plane, by a minute feed amount (U.S. patent application Ser. No. 11/235,313 filed on Sep. 27, 2005, published on Mar. 30, 2006 as US 2006/0066177 and corresponding to Japanese Patent Application No. JP 2004-278911). In the piezoelectric actuator, each of the actuator elements has a drive section (bent thin plate section) which projects in a direction orthogonal to a transporting plane, and a piezoelectric layer arranged in the drive section. The drive section has a contact section which makes contact with an object and two inclined sections extending from the contact section, and the piezoelectric layer, made of a ferroelectric substance such as lead zirconate titanate, is formed as two piezoelectric layers arranged in the two inclined sections respectively. When an electric field acts on the piezoelectric layer of the piezoelectric actuator, the piezoelectric layer is deformed to cause the inclined section to deform to be bent. The contact section between the two inclined sections is displaced by this bending deformation, thereby making it possible to transport the object by a minute feed amount.

When the piezoelectric actuator capable of realizing transportation by a minute feed amount is manufactured, it is necessary to form the drive sections of the actuator elements to be bent in a projecting manner, and to form piezoelectric layers in the two inclined sections respectively of each of the drive sections. However, with a conventional method of forming a piezoelectric layer entirely on the plate-shaped member and then processing the plate-shaped member so that the actuator elements are formed in a divided manner, it is difficult to form the actuator elements having a bent shape, and also disadvantageous in view of producing cost. Accordingly, there has been a demand for a method with which a piezoelectric actuator having such a structure can be produced more easily.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of producing a piezoelectric actuator with which a piezoelectric actuator having a drive section in a bent shape and a piezoelectric layer arranged in the drive section can be produced more easily.

According to a first aspect of the present invention, there is provided a method of producing a piezoelectric actuator having an actuator element, the method including: a step for providing a plate-shaped member; a drive section forming step of forming a slit in the plate-shaped member to define a drive section; a piezoelectric layer forming step of forming a piezoelectric layer in the drive section by depositing particles of a piezoelectric material onto one surface of the plate-shaped member; an electrode forming step of forming, in the piezoelectric layer, an electrode for applying electric field in a thickness direction of the piezoelectric layer; and a bending step of bending the drive section.

According to the first aspect of the present invention, a plate-shaped member is firstly prepared, and a drive section is defined by forming a slit in the plate-shaped member. Next, after forming a piezoelectric layer in the drive section by depositing particles of a piezoelectric material onto one surface of the plate-shaped member, the drive section is bent such that the drive section is made to project in a direction different from the plane direction of the plate-shaped member (alternatively, after bending the drive section, the piezoelectric layer is formed in the drive section by depositing the particles of piezoelectric material onto the plate-shaped member). In this case, when the particles of piezoelectric material are deposited onto the plate-shaped member, the particles of piezoelectric material do not deposit onto a part of the plate-shaped member at which the slit is formed. Accordingly, it is easy to form the piezoelectric layer only on the surface of drive section. This makes it possible to produce the piezoelectric actuator having the bent-shaped drive section and the piezoelectric layer arranged in the drive section easily, and also to lower the producing cost.

In the method of producing the piezoelectric actuator, the bending step may be performed after the piezoelectric layer forming step. In this case, the piezoelectric layer is formed by depositing the particles of piezoelectric material onto the surface of drive portion which is still flat before being subjected to the bending processing. Accordingly, a piezoelectric layer with uniform thickness can be easily formed on the surface of the drive section.

In the method of producing the piezoelectric actuator, the plate-shaped member may be made of a metallic material. In this case, even when a plurality of slits are to be formed, the slits can be easily formed by etching or the like. Also, the bending processing of the driving section can be performed easily.

The method of producing the piezoelectric actuator may further include, before the piezoelectric layer forming step, an insulating layer forming step of forming an insulating layer on the one surface of the plate-shaped member; wherein in the electrode forming step, the electrode and a wiring which is to be connected to the electrode may be formed on a surface of the insulating layer. Although the electrode formed on the piezoelectric layer needs to be electrically connected to a drive circuit for supplying drive voltage, it is difficult to connect the electrode arranged on the surface of the bent-shaped drive section to the drive circuit, and the structure for electrical connection between the electrode and drive circuit tends to be complex as a wiring member such as FPC (Flexible Printed Circuit) or the like is required. According to the method of producing the piezoelectric actuator, however, the electrode is arranged on the surface of the plate-shaped member via the insulating layer, and the wiring to be connected to the electrode can be wired freely on the surface of this insulating layer. Accordingly, it is possible to simplify the structure for electric connection between the electrode and the drive circuit. In addition, when the drive circuit is arranged on the surface of the insulating layer, it is possible to connect the drive circuit directly to the electrode by the wiring on the surface of the insulating layer, thereby omitting the wiring member such as FPC.

In the method of producing the piezoelectric actuator, in the piezoelectric layer forming step, the piezoelectric layer may be formed by one of an aerosol deposition method, a chemical vapor deposition method and a sputtering method. By forming the piezoelectric layer by means of the aerosol deposition method, the chemical vapor deposition method or the sputtering method, it is possible to easily form the piezoelectric layer with a desired thickness.

The method of producing the piezoelectric actuator may include, before the bending step, a recess forming step of forming a recess in the plate-shaped member at a portion which is to be bent in the bending step. Accordingly, the bending of the drive section in the bending step can be performed more easily.

In the method of producing the piezoelectric actuator, in the drive section forming step, the slit may be formed as a plurality of individual slits which extend in a first direction, and aligned in a second direction different from the first direction; and the drive section may be defined, by the individual slits, as a plurality of individual drive sections which are aligned along the second direction. In this case, a piezoelectric actuator having a plurality of individual drive sections can be produced easily.

In the method of producing the piezoelectric actuator, in the drive section forming step, the individual slits may be formed such that each of the individual drive sections is connected, at both ends thereof in the first direction, to the plate-shaped member; and in the bending step, each of the individual drive sections may be bent at the both ends thereof in the first direction and at a middle portion thereof located between the both ends. In this case, a piezoelectric actuator having a plurality of drive sections each of which projects, in the direction different from the direction of the plane of the plate-shaped member, at a middle portion thereof can be produced easily.

In the method of producing the piezoelectric actuator, in the drive section forming step, the individual slits may be formed such that each of the individual drive sections is connected, only at one end thereof in the first direction, to the plate-shaped member; and in the bending step, each of the individual drive sections may be bent at the one end thereof in the first direction such that each of the individual drive sections is parallel to a direction different from a direction of a plane of the plate-shaped member. In this case, a piezoelectric actuator having a plurality of drive sections each of which is bent at one end thereof and extends in a direction different from the direction of the plane of the plate-shaped member can be produced easily.

In the method of producing the piezoelectric actuator, the first direction may be orthogonal to the second direction. In this case, it is possible to perform the bending step for the plurality of drive sections easily.

In the method of producing the piezoelectric actuator, the plate-shaped member may serve as a common electrode. In order to make an electric field act in the piezoelectric layer in its thickness direction so as to deform the piezoelectric layer, it is necessary to arrange electrodes on both sides of the piezoelectric layers respectively. However, with a construction in which the drive section made of a metallic material serves also as one of the electrodes, it is possible to omit a step for forming the one of the electrodes.

In the method of producing the piezoelectric actuator, the piezoelectric actuator may be provided in a transporting apparatus which transport an object in a predetermined transporting direction. In this case, it is possible to easily produce a piezoelectric actuator applicable to a transporting apparatus capable of transporting objects having various shapes by a minute feed amount.

According to a second aspect of the present invention, there is provided a method of producing a movable apparatus which moves with respect to an object, the method including the steps of: providing a plate-shaped substrate; producing a piezoelectric actuator with the method according to the first aspect of the present invention; and joining the substrate and the piezoelectric actuator at the other surface of the plate-shaped member of the piezoelectric actuator. In this case, it is possible to easily produce a piezoelectric actuator applicable to a movable apparatus movable by a minute feed amount.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiments of the present invention will be explained. The first embodiment is an example in which the present invention is applied to a piezoelectric actuator for transporting a paper in an ink-jet printer. First, the ink-jet printer will be explained briefly. As shown inFIG. 1, an ink-jet printer100includes a carriage1which is movable in a scanning direction (left and right direction) inFIG. 1, an ink-jet head2of a serial type which is provided to the carriage1and which discharges ink onto a recording paper P, a paper transporting apparatus3which transports or feeds the recording paper P in a forward direction (forward in a transporting direction) inFIG. 1. The ink-jet head2moves integrally with the carriage1in the scanning direction, and discharges ink onto the paper P, which is transported in the forward direction by the paper transporting apparatus3, from ejecting ports of nozzles formed in the lower surface of the ink-jet head2.

Next, the paper transporting apparatus3will be explained. As shown inFIGS. 1 and 2, the paper transporting apparatus3includes a substrate25forming a horizontal bottom surface (plane), two actuators5provided in the substrate25, and a guide member11which is arranged horizontally above each of the actuators5to face the actuator5. The piezoelectric actuators5are arranged such that one of the piezoelectric actuators5is on an upstream side (toward the rear inFIG. 1) and the other of the piezoelectric actuators5is on a downstream side (toward the front inFIG. 1) of the ink-jet head2, in the transporting direction. Further, each of the piezoelectric actuators5has a plurality of actuator elements10which are aligned in two rows in the scanning direction (left and right direction inFIG. 1) along the horizontal plane.

As shown inFIGS. 2B and 3A, each of the actuator elements10has a drive section20which is formed, in a plate-shaped member24made of a metallic material such as an iron-based alloy, titanium-based alloy, aluminum-based alloy or nickel-based alloy, such that the drive section20projects upwardly (in a direction orthogonal to a plane direction of the plate-shaped member24), and a drive section20of one actuator element10and a drive section20of another actuator element adjacent to the drive section in the scanning direction are connected with each other by a base section (base)23. As shown inFIG. 2A, in the plate-shaped member24, the drive sections20extend in a transporting direction (first direction) respectively, and the drive sections20are defined by a plurality of slits28formed to be aligned in two rows in the scanning direction (second direction). Each of the drive sections20includes a contact section21disposed in an upper edge and capable of making contact with the paper P from a lower side, and two inclined sections22each extending from the contact section21in a direction parallel to the transporting direction (left and right direction inFIG. 2A) in a plan view. In addition, the base sections23, which extend in the scanning direction (up and down direction inFIG. 2A), are connected to the two inclined sections22, and each of the drive sections20is connected to another drive section20, which is adjacent thereto in the scanning direction, at both ends of the drive section20via the base sections23respectively. Further, as shown inFIG. 2B, the base sections23are fixed to the horizontal substrate25. The drive sections20and the base sections23are formed as an integrated body by one plate-shaped member24made of a metal. Therefore, the number of components of the piezoelectric actuators5is reduced.

As shown inFIG. 3A, the contact section21is formed to have somewhat round shape and an upper surface of the contact section21is roughened by a sand blast, a micro blast or the like. Piezoelectric layers26, mainly composed of lead zirconate titanate (PZT) which is a solid solution of lead titanate and lead zirconate and is a ferroelectric substance, are formed on upper surfaces of the inclined sections22, respectively.

In each of the actuator elements10, individual electrodes27are formed entirely on the upper surfaces (surfaces on a side opposite to the inclined section22) of the two piezoelectric layers26, respectively. These two individual electrodes27are connected electrically to a driving circuit (not shown) via a wiring member (not shown) such as a Flexible Printed Circuit (FPC), and a drive voltage is applied to the individual electrodes27by the driving circuit. On the other hand, the metallic inclined sections22positioned at a lower side of the piezoelectric layers26are always maintained at ground potential via the base sections23. In other words, each of the inclined sections22serves also as a common electrode which generates an electric field in the piezoelectric layer26sandwiched between the inclined section22and the individual electrode27when the drive voltage is applied to the individual electrode27by the driving circuit. Accordingly, there is no need to form the common electrode separately from the inclined section22.

When the drive voltage is applied to the individual electrode27by the driving circuit, there is a difference in electric potential between the individual electrode27and the inclined section22which serves as the common electrode maintained at the ground potential, and an electric field is generated in the piezoelectric layer26in a direction of thickness thereof, the piezoelectric layer26being sandwiched between the individual electrode27and the inclined section22. At this time, when the direction in which the piezoelectric layer26is polarized is same as the direction of electric field, the piezoelectric layer26expands in the thickness direction, and thus contracts in a direction orthogonal to the thickness direction, that is a plane direction of the piezoelectric layer26. With this contraction of the piezoelectric layer26, the inclined section22is deformed so as to project inwardly.

Therefore, as shown inFIGS. 4 to 6, by applying the drive voltage by the drive circuit on both or any one of the individual electrodes27of one actuator element10to deform the inclined section or sections22in a bending or bowing manner, it is possible to move the contact section21by a minute amount (about several tens of μm, for example) in the transporting direction (towards right side inFIG. 4toFIG. 6). InFIGS. 4 to 6, “+” denotes a state when the drive voltage is applied and “GND” denotes a state when the ground potential is maintained (state when no drive voltage is applied).

To start with, in a state when the drive voltage is not applied to any of the two individual electrodes27, the two inclined sections22are not deformed. The contact section21between these two inclined sections22is at a position projecting upwardly over a position of an under surface of the paper P (seeFIG. 3A), and when the paper P is transported or conveyed, the contact section21cannot be switched to this state (in other words, when the paper P is transported, the voltage is applied to at least one of the two individual electrodes27of each of the actuator elements10). From this state, as shown inFIG. 4, when the drive voltage is applied to both of the individual electrodes27, both of the inclined sections22are deformed so as to project inwardly, and the contact section21moves to a position where the contact section21does not make a contact with the paper P (stand-by position). A point of intersection A of two chain lines denotes a position of a tip of the contact section21while at the stand-by position.

On the other hand, as shown inFIG. 5, when the drive voltage is applied only to the individual electrode27on an upstream side in the transporting direction (left side inFIG. 5), only the inclined section22on the upstream side in the transporting direction is deformed so as to project inwardly. Therefore, the contact section21moves to a position (transporting-preparation position) at which the contact section21can make a contact with the paper P and which is positioned on the upstream side (left side) of the stand-by position in the transporting direction. Further, as shown inFIG. 6, when drive voltage is applied only to the individual electrode on the downstream side in the transporting direction (right side inFIG. 6), only the inclined section22on the downstream side in the transporting direction is deformed so as to project inwardly. Therefore, the contact section21moves to a position (transporting-end position) at which the contact section can make a contact with the paper P and which is positioned on the downstream side of the stand-by position in the transporting direction (right side).

The actuator element10is capable of transporting the paper P, which is in contact with the contact section21, by a minute feed amount in the transporting direction, by moving the contact section21in an order of the stand-by position (FIG. 4), then to the transporting-preparation position (FIG. 5), then to the transporting-end position (FIG. 6), and then to stand-by position (FIG. 4). When the contact section21is moved from the transporting-end position to the transporting-preparation position, the contact section21is once returned from the transporting-end position to the stand-by position at which the contact section21does not make a contact with the paper P. Therefore, the paper P and the contact section21do not make a contact and the paper P can be transported smoothly.

As shown inFIG. 3, grooves22aare formed each in a lower surface side of an edge of each of the inclined sections22on a side of the contact section21, and grooves22bare formed each in an upper surface side of an edge of each of the inclined sections22on a side of the base section23. The stiffness of the drive section20is lowered partially at the grooves22aand22b. Therefore, between the inclined sections22and the contact section21, and between the inclined sections22and the base sections23, the deformation bending of the drive section20is easily caused, and thus it is possible to displace the contact section21even with a low voltage, thereby improving the driving efficiency of the actuator element10. In addition, as will be explained later, the drive section20is easily bent when the contact section21and the two inclined sections22are formed by bending the drive section20.

Further, as described earlier, the upper surface of the contact section21is roughened. Accordingly, when the contact section21is moved in the transporting direction with the contact section21being in contact with the paper P, the frictional force acting between the paper P and the contact section21is increased. Therefore, the paper P hardly slips on the contact section21and can be transported assuredly by the contact section21.

As shown inFIGS. 2 to 6, the guide member11is arranged horizontally above the plurality of actuator elements10to face the actuator elements10. The guide member11has guide sections11a. Each of the guide sections11ais formed to face one of the contact sections21of the plurality of actuator elements10, and each of the guide sections11ais formed to project towards one of the contact sections21, so as to guide the paper P which is transported in the transporting direction by the contact section21. Therefore, the paper P can be guided and transported while being pinched from both the upper and the lower sides by the contact section21and the guide section11aprojecting towards the contact section21. Thus, it is possible to transport the paper P stably in the transporting direction.

Next, a method of producing the piezoelectric actuator5will be explained with reference toFIGS. 7 to 12. First, as shown inFIG. 7, a plurality of drive sections20aligned along the scanning direction (up and down direction inFIG. 7A(second direction)) are formed in a divided manner in a metallic plate-shaped member24, by forming, with a method such as etching processing, a plurality of slits28extending in the transporting direction (left and right direction inFIG. 7A(first direction)) in the metallic plate-shaped member24(drive section forming step). At this time, the slits28are formed such that the slits28do not extend up to the both end portions of the plate-shaped member24in the left and right directions inFIG. 7A. In other words, the slits28are formed such that the slits28are divided by base sections23extending in the up and down direction, and that each of the drive sections20is formed such that the drive section20is connected, at its both ends in the left and right direction, to other drive sections20which are adjacent to the drive section20in the up and down directions respectively. In addition, with a method such as half etching and/or press processing, grooves22aare formed at portions in a lower surface (lower surface inFIG. 7B) of each of the drive sections20, the portions being in the vicinity of the central portion in the left and right direction of the drive section20; and grooves22bare formed at portions in an upper surface (upper surface inFIG. 7B), the portions being at both ends in the left and right directions, respectively (groove forming step). Accordingly, portions (portions each of which is between one of the grooves22aand one of the grooves22b) which are to be two inclined sections22a, respectively, of each of the drive sections20, are formed to have a same length in the left and right direction inFIG. 7A(first direction).

Next, as shown inFIGS. 8A and 8B, a mask30is placed on the upper surface of the plate-shaped member24. The mask30covers an area which is outside of the area formed with the drive sections20and slits28and which include the base sections23, and covers the central portions (portions to be the contact sections21) of the drive sections20. At this time, as shown inFIG. 8B, the portions of the plate-shaped member24formed with the grooves22bare also covered by the mask30. Next, as shown inFIGS. 9A and 9B, piezoelectric layers26are formed at portions (portions which are to be the inclined sections22), of each of the drive sections20, which are other than the central portion and the portions of the drive section20formed with the grooves22b, by depositing particles of a piezoelectric material such as PZT onto the upper surface of the plate-shaped member24(piezoelectric layer forming step).

As a method for depositing the particles of piezoelectric material onto the plate-shaped member24, it is possible to use, for example, an aerosol deposition method (AD method) in which very fine particles of a piezoelectric material are blown onto a substrate to be collided to the substrate (base-plate member24) at a high velocity and to be deposited onto the substrate. Alternatively, the piezoelectric layers26can be formed by a method such as a sputtering method and a chemical vapor deposition method (CVD method). In this manner, when the particles of piezoelectric materials are deposited onto the upper surface of the plate-shaped member24by the AD method, the sputtering method or the CVD method, the particles are not deposited onto the inner surfaces, of the plate-shaped member24, which defines the slits28. In other words, there is no need to use a mask having a complicated configuration for covering each of the slits28so that the piezoelectric layers26are not formed at the portions formed with the slits28. Accordingly, by using the mask30having a relatively simple configuration as shown inFIGS. 8 and 9, the piezoelectric layers26can be formed only on the upper surfaces of the both side portion (portions which are to be the inclined sections22) in the left and right direction of each of the drive sections20, thereby making it easy to form the piezoelectric layers26in the drive sections20. Subsequently, as shown inFIG. 10, after removing the mask30from the plate-shaped member24, then a plurality of individual electrodes27are formed on the upper surfaces of the piezoelectric layers26respectively, with a method such as screen printing method (individual electrode forming step). Alternatively, the individual electrodes27can be formed with the sputtering method or the like. In this case, the mask30also serves as a mask for sputtering, the individual electrodes27may be formed in a state that the mask30is attached, and the mask30may be removed after the formation of individual electrodes.

Next, as shown inFIG. 11, the central portion and the both end portions in the left and right direction of each of the drive sections20are bent with a press processing or the like to cause the central portions of the plate-shaped member24in which the piezoelectric layers26are not formed to project upward (in the direction orthogonal to the plane direction of the plate-shaped member24), thereby forming the contact sections21and the inclined sections22(bending step). Here, since the plate-shaped member24is a metallic plate, the bending can be easily performed by the press processing or the like. In addition, the grooves22aare formed in the lower surface of the central portion of the drive section20and the groove22bare formed in the upper surfaces of the both end portions of the drive section20respectively in the groove forming step as described above, and the piezoelectric layers26are not formed in the grooves22bformed in the upper surface. Accordingly, the drive section20can be bent further easily at the central portion and the both end portions. In addition, since the drive sections20are aligned in the direction (second direction) which is orthogonal to the direction (first direction) in which the drive sections20extend, the grooves22aformed in each of the drive sections20are located in a same position with respect to the first direction, and the grooves22bformed in each of the drive sections20are located in a same position with respect to the first direction. Accordingly, since the grooves22a,22bare aligned along the second direction, the drive sections20can be easily bent in sequence or at once.

According to the piezoelectric actuator5and the method for producing the piezoelectric actuator of the first embodiment as explained above, the following effects can be obtained. The actuator elements10, of the piezoelectric actuator5of the first embodiment, has the plurality of drive sections20bent so as to project in the direction orthogonal to the plane direction of the plate-shaped member24; and the piezoelectric layers26arranged in the inclined sections22respectively of each of the drive sections20. Accordingly, it is possible to transport the paper P which is contact with the contact section21of each of the drive sections20by a minute feed amount, by making the electric field acting in the piezoelectric layer26in its thickness direction to form the piezoelectric layer26.

Further, upon producing the piezoelectric actuator5, the drive sections20are defined by forming the slits28in the plate-shaped member24; then the piezoelectric layers26are formed in the drive sections20by depositing the particles of piezoelectric material onto the upper surface of the plate-shaped member24; and then the contact sections21and the inclined sections22are formed by bending the drive sections20. In this case, when the particles of piezoelectric material are deposited onto the upper surface of the plate-shaped member24, the particles are not deposited in the portions of the plate-shaped member24at which the slits28are formed. Accordingly, it is possible to easily form the piezoelectric layers26in the plate-shaped member24only on the upper surfaces (portions which are to be the inclined sections22) of each of the drive sections20. Accordingly, the piezoelectric actuator5which has the bent-shaped drive sections20and the piezoelectric layers26arranged at the inclined sections22of each of the drive sections20, and which is capable of realizing transport by a minute amount utilizing the bending of the drive sections20, can be produced easily, thereby lowering the production cost.

In addition, since the piezoelectric layers26are formed before performing the bending step in which the drive sections20are bent, the particles of piezoelectric material can be deposited onto the flat, upper surfaces of the drive sections20. Accordingly, the piezoelectric layers26having a uniform thickness can be formed easily. In this embodiment, although the grooves22aare formed at both sides in the lower surface of the contact section21respectively, the grooves22amay be formed as one groove which span across the entire lower surface of the contact section21.

Next, modified embodiments, in which various modifications are added to the first embodiment described above, will be explained. Same reference numerals will be used for components which have a structure similar to those in the first embodiment described above and the description of these similar components will be omitted as deemed appropriate.

First Modified Embodiment

In the above first embodiment, the drive sections20are bent such that the central portions of the drive sections20(portions which are to be the contact sections21) project in the direction orthogonal to the plane direction of the plate-shaped member24. However, the central portions may project in a direction which is inclined to some extent with respect to the direction orthogonal to the plate direction, provided that the inclined direction is different from the plane direction. In other words, in the first embodiment, the central portion (contact section21) of each of the drive sections20is formed such that the central portion projects toward the direction orthogonal to the plane direction of the plate-shaped member24, because the portions of each of the drive sections20, which are to be the two inclined sections22, are same in length in the extending direction of the slit28(first direction). However, the direction in which the central portion protrudes may be inclined to some extent from the direction orthogonal to the plane direction of the plate-shaped member24, by bending each of the drive sections20at a position deviated or shifted to one side from the center of the first direction so as to form two inclined sections22which are mutually different in length with respect to the first direction.

Second Modified Embodiment

In the first embodiment, although the drive sections20are bent after forming the piezoelectric layers26on the upper surfaces of the drive sections20(seeFIG. 11), the piezoelectric layers26may be formed by depositing the particles of piezoelectric material onto the surface of the plate-shaped member24after bending the drive sections20.

Third Modified Embodiment

In the first embodiment, the metallic inclined sections22serve as a common electrode, and the electric field is applied to the piezoelectric layer26sandwiched between the inclined section22and the individual electrode27by applying voltage between the inclined section22and individual electrode27. However, a common electrode may be provided separately from the inclined section22. For example, when the plate-shaped member24is made of a metallic material, as shown inFIG. 12, an insulating layer40made of an insulating material may be formed on upper surfaces of the drive sections20and base sections23in the plate-shaped member24, and a common electrode41may be formed on the upper surface of this insulating layer40. Alternatively, the plate-shaped member24can be formed of an insulating material. In this case, no insulating layer40is required, and the common electrode41is formed directly on the upper surface of the plate-shaped member24.

Fourth Modified Embodiment

The individual electrode27, to which the drive voltage is applied, may be arranged on the lower surface of the piezoelectric layer, and the common electrode41, which is kept at ground potential, may be arranged on the upper surface of the piezoelectric layer. For example, as shown inFIG. 13, insulating layers40made of an insulating material may be formed on the upper surface of a metallic plate-shaped member24A, individual electrodes27and wirings42connected to the individual electrodes27respectively may be formed on the upper surfaces of the insulating layers40(on the lower surfaces of piezoelectric layers26A) respectively, and common electrodes41may be formed on the upper surfaces of the piezoelectric layers26A respectively. Each of the piezoelectric layers26A extends, from the left or right end of each of drive sections20A, further up to the upper surface of a base section23A, and a plurality of common electrodes41aligned in a direction orthogonal to the sheet surface ofFIG. 13are connected with each other via a conductive layer43formed the surface of this portion of the piezoelectric layer26A extending up to the base section23A (hereinafter referred also to as “piezoelectric base section26a”).

A method of producing a piezoelectric actuator5A which has actuator elements10A as shown inFIG. 13will be explained with reference toFIGS. 14A to 20B. First, as shown inFIGS. 14A and 14B, a plurality of drive sections20A aligned along the scanning direction (up and down direction inFIG. 14A) are defined in the metallic plate-shaped member24by forming, by etching processing or the like, a plurality of slits28A extending in the transporting direction (left and right direction inFIG. 14A) in the metallic plate-shaped member24A (drive section forming step). In addition, grooves22aare formed, by a method such as half-etching and press processing, at portions in the lower surface of each of the drive sections20A, the portions being in the vicinity of the central portion in the left and right direction of the drive section20A (groove forming step). The grooves22aare for facilitating the bending of the drive sections20A in a bending step as will be explained later. In the fourth modified embodiment, the piezoelectric layer26A (piezoelectric base section26a) is formed in an area ranging from each of the drive sections20to a base section23A. Accordingly, unlike in the first embodiment, no grooves are formed in the upper surface at both ends of each of the drive sections20A.

Next, as shown inFIGS. 15A and 15B, an insulating layer40formed of an insulating ceramic material such as alumina or zirconia is formed on the upper surface of the plate-shaped member24with a method such as the AD method, the sputtering method or the CVD method (insulating layer forming step). Then, as shown inFIGS. 16A and 16B, two individual electrodes27are formed in portions (portions which are to be inclined sections22A), of the surface of the insulating layer40, respectively, the portions being on both left and right sides of each of the drive sections20A and other than the central portions of the drive section20A (individual electrode forming step). At this time, a plurality of wirings42connected to the individual electrodes27respectively are also formed on the surface of portions of the insulating layer40, the portions being formed in the base sections23A. Further, wirings44,45for maintaining common electrodes41(to be explained later) at ground potential are also formed on the surface of the insulating layer40. A conductive pattern, configured of the individual electrodes27and wirings42acorresponding to the drive sections20A respectively and the wirings44,45corresponding to the common electrodes41, can be formed at a time on the upper surface of the plate-shaped member24by screen printing, for example.

Further, as shown inFIGS. 17A and 17B, a mask50is placed on the upper surface of the plate-shaped member24. The mask50covers an area which is outside of the area formed with the drive sections20A and slits28A, and covers the central portions (portions to be the contact sections21A) of the drive sections20A. Here, as shown inFIG. 17A, a portion of the base section23A, connected to the drive sections20A, are not covered by the mask50.

Next, as shown inFIGS. 18A and 18B, piezoelectric layers26A are formed at portions (portions which are to be the inclined sections22), of each of the drive sections20, which are other than the central portions covered by the mask50, by depositing particles of a piezoelectric material such as PZT onto the upper surface of the plate-shaped member24A (piezoelectric layer forming step). In this case, since the portions of the base section23A connected to the drive sections20A respectively are not covered by the mask50, the piezoelectric layers26A (piezoelectric base sections26a) are also formed in these portions.

Further, as shown inFIGS. 19A and 19B, after removing the mask50, common electrodes41corresponding to the two individual electrodes27respectively are formed, by a method such as screen printing method or the like, on the upper surfaces of the individual electrodes26A arranged in each of the drive sections20A (common electrode forming step). Alternatively, since the mask50also serves as a mask for sputtering, the common electrodes41may be formed in a state that the mask50is attached, and the mask50may be removed after the formation of common electrodes41by the sputtering method or the like. At this time, the conductive layer43is also formed on the upper surfaces of the piezoelectric base sections26a, thereby connecting the common electrodes41with each other, the common electrodes41corresponding to the individual electrodes27respectively and aligned in the scanning direction (up and down direction inFIG. 19A). Further, by connecting and the wirings44,45, formed on the upper surface of the insulating layer40, and the common electrodes41with a conductive material, all of the aligned common electrodes41are maintained at ground potential via the wirings44,45. Furthermore, as shown inFIGS. 20A and 20B, the central portions and the both end portions of the drive sections20A are bent with a press processing or the like to cause the central portions to project upward, thereby forming the contact sections21A and the inclined sections22A (bending step). Thus, the producing process of the piezoelectric actuator5A is completed.

As shown inFIG. 20A, in this piezoelectric actuator5A, the wirings42, which are to be connected to the individual electrodes27respectively, can be wired or drawn freely on the upper surface of the plate-shaped member24A via the insulating layer40. Accordingly, the wirings42are drawn up to the both end portions (both end portion in the up and down direction inFIG. 20A) of the plate-shaped member24A, and wiring members such as FPC and the wirings42can be connected at a time. Thus, the construction for electrical connection is more simplified than a case in which terminals of the FPC or the like are directly connected to the individual electrodes27respectively, and the reliability of electrical connection is also improved. Further, when the drive circuit is arranged on the upper surface of the insulating layer40, it is possible to directly connect the drive circuit and the individual electrodes27with the wirings42on the upper surface of the insulating layer40. Accordingly, the number of components can be reduced since the wiring member such as FPC can be omitted. In the fourth modified embodiment, although the grooves22aare formed at both sides in the lower surface of the contact section21A respectively, the grooves22amay be formed as one groove which span across the entire lower surface of the contact section21A.

Fifth Modified Embodiment

In the first embodiment, the drive sections20extending in the first direction corresponding to the transporting direction are aligned along the second direction corresponding to the scanning direction. However, it is not necessarily indispensable that the second direction is orthogonal to the first direction in such a manner, and it is enough that the second direction is different from the first direction.

Next, a second embodiment of the present invention will be explained. As shown inFIGS. 21A and 21B, a piezoelectric actuator65of the second embodiment has a plurality of actuator elements70aligned in two rows, in the scanning direction (up and down direction inFIG. 21A) along the plane of a substrate75provided horizontally.

Each of the plurality of actuator elements70has a drive section80which is formed in a plate-shaped member74made of a metallic material, and a drive section80of one actuator elements70and another drive section80of another actuator element70adjacent to the drive section80in the scanning direction are connected with each other by a base section83. The drive sections80are formed by being bent upwardly by an angle of 90 degrees with respect to the plane of the substrate75. Namely, the drive sections80are bent parallel to a direction orthogonal to the plane direction of the plate-shaped member74. Each of the drive sections80is connected, at one end (left end inFIG. 21A) thereof, to another drive section80adjacent thereto in the scanning direction (up and down direction inFIG. 21A), via one of the base sections83. The base sections83are fixed to the horizontal substrate75.

Piezoelectric layers81, mainly composed of lead zirconate titanate (PZT) which is a solid solution of lead titanate and lead zirconate and is a ferroelectric substance, are formed on the left side surfaces inFIG. 21Brespectively of the drive portions80formed in an upright manner. In addition, individual electrodes82are formed on the left side surfaces of the piezoelectric layers81, respectively, and the individual electrodes82are connected to a drive circuit (not shown). Each of the metallic driving sections80serves also as a common electrode, and is always kept at ground potential.

When the drive voltage is applied to the individual electrode82from the driving circuit, there is a difference in electric potential between the individual electrode82and the drive section80which serves as the common electrode and is maintained at the ground potential, and an electric field is generated in the piezoelectric layer81in a direction of thickness thereof, the piezoelectric layer81being sandwiched between the individual electrode82and the drive section80. At this time, when the direction in which the piezoelectric layer81is polarized is same as the direction of electric field, the piezoelectric layer81expands in the thickness direction, and thus contracts in a direction orthogonal to the thickness direction, that is a plane direction of the piezoelectric layer81. Accordingly, with this contraction of the piezoelectric layer81, the drive section80is deformed so as to bend or bow leftward, thereby displacing a tip portion, as a free end of the drive section, leftward by a minute amount.

In other words, when the drive voltage is applied to an individual electrode82, the piezoelectric actuator65causes the tip portion of the drive section80, corresponding to this individual electrode82, to be displaced leftward, and thus the piezoelectric actuator is capable of transporting the paper P which is guided by the guide member71by a minute feed amount while supporting the paper P from below with the tip portion of the drive section80.

Next, a method of producing the piezoelectric actuator65will be explained with reference toFIGS. 22A to 26B. As shown inFIGS. 22A and 22B, a plurality of drive sections80aligned along the scanning direction (up and down direction inFIG. 22A) are defined in a metallic plate-shaped member74, by forming, with a method such as etching processing, a plurality of slits88extending in the transporting direction (left and right direction inFIG. 22A) in the metallic plate-shaped member74(drive section forming step). At this time, by also forming slits89each of which extends in the up and down direction inFIG. 22Aand connects the slits88with each other, the drive sections80are defined such that each of the drive sections80is connected to another drive section80adjacent thereto only at its left end inFIG. 22A, and is divided from other drive section80at its right end inFIG. 22A.

Next, as shown inFIGS. 23A and 23B, a mask90is placed on the upper surface of the plate-shaped member74. The mask90covers an area which is outside of the area formed with the drive sections80and slits88and which includes the base sections83. Next, as shown inFIGS. 24A and 24B, piezoelectric layers81are formed in the drive sections80respectively, by depositing particles of a piezoelectric material such as PZT onto the upper surface of the plate-shaped member74(piezoelectric layer forming step).

Further, as shown inFIGS. 25A and 25B, after removing the mask90, then individual electrodes82are formed on the upper surfaces of the piezoelectric layers81respectively, with a method such as screen printing method (individual electrode forming step). Alternatively, the individual electrodes82may be formed by a method such as the sputtering method before removing the mask90, and the mask90may be removed after forming the individual electrodes82. Then, as shown inFIGS. 26A and 26B, the left end portions of the drive sections82, connected to the base sections83, are bent upwardly in an upright manner by a press processing or the like (bending step). Thus, the production of the piezoelectric actuator65is completed.

In this second embodiment, similarly in the first embodiment, the driving section80are firstly defined by forming the slits88in the plate-shaped member74; then the piezoelectric layers81are formed in the driving sections80respectively, by depositing the particles of piezoelectric material onto the upper surface of the plate-shaped member74; and then the drive sections80are bent. Here, when the particles of piezoelectric material are deposited onto the upper surface of the plate-shaped member74, the particles of piezoelectric material are not deposited onto portions of the plate-shaped plate74at which the slits88are formed respectively. Accordingly, the piezoelectric layers81can be easily formed in the plate-shaped member only on the upper surfaces of the drive sections80, respectively. In addition, according to this producing method, the piezoelectric actuator65which has the bent-shaped drive sections80and the piezoelectric layers81arranged the drive sections80respectively, and which is capable of realizing transport by a minute amount utilizing the bending of the drive sections80, can be produced easily, thereby lowering the production cost.

Also in the second embodiment, changes similar to those added to the first embodiment can be added to the second embodiment. Namely, the piezoelectric layers81may be formed in the drive sections80after bending the drive sections80in advance. Alternatively, common electrodes may be formed separately from the drive sections80. Still alternatively, the individual electrodes82may be arranged on surfaces (right side surfaces inFIG. 21B) of the piezoelectric layers81respectively, the surface being on the side of the drive sections80; and the common electrodes may be arranged on the other surfaces (left side surfaces inFIG. 21B) of the piezoelectric layers81respectively, the other surfaces being on the side opposite to the drive sections80. Further, it is not necessarily indispensable that the direction in which the drive sections80are aligned is orthogonal to the direction in which the drive sections80extend, and it is enough that the alignment direction is different from the extend direction.

In this second embodiment, as explained above, the particles of the piezoelectric material such as PZT are deposited onto the upper surface of the plate-shaped member74to form the piezoelectric layer81in each of the drive sections80(in this case, the upper surface of each of the drive sections80inFIGS. 24A,24B), and further the individual electrodes82are formed in the piezoelectric layers81respectively (in this case, the upper surfaces the piezoelectric layers81inFIGS. 25A,25B). However, in the piezoelectric layer forming step, the particles of the piezoelectric material may be deposited onto both surfaces of the plate-shaped member74so as to form the piezoelectric layers81on the both surfaces, respectively, of each of the drive sections80; then in the individual electrode forming step, the individual electrodes82may be formed in the piezoelectric layers81formed in the both surfaces, respectively, of each of the drive sections80; and in the bending step as explained above, the left end portions of the drive sections80may be bent upwardly in an upright manner by a press processing or the like.

In this case, when drive voltage is alternately applied to the individual electrodes82formed on the both surfaces, respectively, of each of the drive sections80, the piezoelectric layers81, each formed in the left side surface or the right side surface of each of the drive sections80, contract alternately in the plane direction which is orthogonal to the thickness direction of the piezoelectric layer. Accordingly, with this alternate contraction of the piezoelectric layers81, the drive section80is deformed so as to bend or bow alternately leftward or rightward, thereby displacing a tip portion, as a free end of the drive section, in both of leftward and rightward direction by a greater amount.

A method of producing a piezoelectric actuator having such drive sections80will be explained. Firstly, as explained with reference toFIGS. 22A,22B, a plurality of drive sections80aligned along the scanning direction are defined in a metallic plate-shaped member74, by forming, with a method such as etching processing, a plurality of slits88extending in the transporting direction in the metallic plate-shaped member74(drive section forming step).

Next, as explained with reference toFIGS. 23A,23B, a mask90is placed on the upper surface of the plate-shaped member74. The mask90covers an area which is outside of the area formed with the drive sections80and slits88and which includes the base sections83. Next, as shown inFIGS. 24A and 24B, piezoelectric layers81are formed on the upper surfaces, respectively, of each of the drive sections80, by depositing particles of a piezoelectric material such as PZT onto the upper surface of the plate-shaped member74. Afterward, a mask90is placed on the lower surface of the plate-shaped member74. The mask90covers an area which is outside of the area formed with the drive sections80and slits88and which includes the base sections83. Next, as shown inFIGS. 24A and 24B, piezoelectric layers81are formed on the lower surfaces, respectively, of each of the drive sections80, by depositing particles of a piezoelectric material such as PZT onto the lower surface of the plate-shaped member74. Accordingly, the piezoelectric layers81are formed on both surfaces of each of the drive sections80(piezoelectric layer forming step).

Subsequently, as explained with reference toFIGS. 25A,25B, after removing the mask90from the upper surface of the plate-shaped body74, then individual electrodes82are formed on the upper surfaces of the piezoelectric layers81respectively, with a method such as screen printing method. Then, after removing the mask90from the lower surface of the plate-shaped body74, then individual electrodes82are formed on the lower surfaces of the piezoelectric layers81respectively, with a method such as screen printing method. Accordingly, the individual electrodes82are formed on both surfaces of the piezoelectric layers81which are formed on both surfaces, respectively, of each of the drive sections80(individual electrode forming step).

Then, as explained with reference toFIGS. 26A,26B, the left end portions of the drive sections82, connected to the base sections83, are bent upwardly in an upright manner by a press processing or the like (bending step). Thus, the production of the piezoelectric actuator65, in which the piezoelectric layers and the individual electrodes are formed on both surfaces, respectively, of each of the drive sections80, is completed.

In the second embodiment, although the drive sections80are bent in an upright manner such that the drive sections80project in a direction orthogonal to the plane direction of the plate-shaped member74, the drive sections80may project in a direction which is inclined to some extent with respect to the direction orthogonal to the plate direction of the plate-shaped member74, provided that the inclined direction is different from the plane direction.

Sixth Modified Embodiment

In each of the first and second embodiment, the method of producing a piezoelectric actuator having a plurality of piezoelectric actuator elements is explained. The present application, however, is also applicable to a piezoelectric actuator having a single piezoelectric actuator element. In this case, a plate-shaped member corresponding to an area surrounded by a dotted line X1inFIG. 7Aor to an area surrounded by a dotted line X2inFIG. 22Ais prepared, and by forming the slit, drive section, piezoelectric layer or the like in accordance with the steps as explained in the first or second embodiments, the piezoelectric actuator having a single actuator element can be produced.

Although the first and second embodiment as explained above are examples in which the present invention is applied to a paper transporting apparatus for a printer, the present invention is also applicable to a paper transporting apparatus usable in an apparatus or device other than printer such as a facsimile machine, a photocopy machine, a scanner or the like. In addition, the aspect to which the present invention is applicable is not limited to a transporting apparatus which transports a transporting object having a sheet-like shape such as paper, and the present application is also applicable to a transporting apparatus which transports transporting objects having various shapes such as cylinder-shaped, plate-shaped, box-shaped or tube-shaped.

Further, the present invention is applicable also to a usage other than for the transporting apparatus. For example, the present invention is applicable to a video projector including a plurality of actuators of which number corresponds to pixels, and a plurality of mirrors arranged in the actuators respectively, wherein each of the actuators configures its mirror to be displaceable between a projection-possible position and a non-projection position, and a mirror which is arranged in an actuator included in the plurality of actuators and is positioned at the projection-possible position reflects a light to project the light onto a screen, thereby forming an image. In addition, the present invention is applicable also to an optical switch which includes a plurality of actuators, and a plurality of mirrors arranged corresponding to the actuators respectively; and in which the actuators displaces the mirrors so as to selectively reflect light beams, irradiated from terminals of a plurality of optical fibers respectively, thereby guiding the light beams to terminals of a plurality of optical terminals different from the plurality of optical terminals.

Further, the piezoelectric actuator produced with the production method of the present invention can be applied also to a movable apparatus which moves with respect to an object. A movable apparatus200as shown inFIGS. 27A and 27Bhas a plurality of actuator elements10provided to a rear surface of a substrate125. The actuator elements10are arranged in the rear surface of the substrate125such that three of the actuator elements10are provided for each of rows in a front side and a rear side, in a direction of advancement M of the movable apparatus. The contact section (apex section)21of the actuator element10is arranged in downward direction and makes a contact with a floor surface. In other words, while the actuator element10of the first embodiment interacts with the paper P and transports the paper P, the actuator element10of the movable apparatus200interacts with an installation surface (floor surface) or an object surface, and the actuator element10(and the substrate25on which the actuator element10is mounted) itself moves on the installation surface or the object surface. An element91which has a built-in charge coupled device (CCD) is mounted on the substrate125.

This movable apparatus200is suitable for an application of taking images in extremely narrow gaps, holes, in a tough environment of low temperature or high temperature, and in the space. In this example, the element91with the built-in charge coupled device (CCD) is mounted on the substrate125. However, any object according to the application, such as a mirror, a temperature sensor, a micro tool, a micro robot arm can be mounted on the substrate125. Particularly, in the producing method of the present invention, the piezoelectric actuator element10, in which the apex section (contact section) is supported by two inclined surfaces, can be formed easily. Accordingly, the piezoelectric actuator element produced with the producing method of the present invention can be applied to a movable apparatus which is capable of mounting a comparatively heavy object on the substrate125, and of transporting the object.