# US 7,608,983 B2 · Piezoelectric actuator, liquid transporting apparatus, and liquid-droplet jetting apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,608,983 B2 - Document ID: US7608983B2 - Status: Granted - Kind: B2 - Application number: 11/879,110 - Filed: 2007-07-16 - Published: 2008-01-24 - Granted: 2009-10-27 - Earliest claimed: 2006-07-18 - Assignees: Brother Kogyo Kabushiki Kaisha - Inventors: Hiroto Sugahara - Web page: https://patentgrep.com/patent/US7608983B2 ## CPC - B41J 2/14233: {of film type, deformed by bending and disposed on a diaphragm} - H10N 30/2047: {Membrane type} - B41J 2002/14266: {Sheet-like thin film type piezoelectric element} - B41J 2002/14491: {Electrical connection} - B41J 2202/11: characterised by specific geometrical characteristics - B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR ## Abstract A piezoelectric actuator includes a piezoelectric layer, a vibration plate, a supporting member which has an relief portion. A thin wall portion is provided in a first area, of one of the piezoelectric layer and vibration plate, facing one end portion in a longitudinal direction of the relief portion. A thickness of the thin wall portion is smaller than a thickness of areas, of one of the piezoelectric layer and vibration plate, facing the central portion and one end portion in a width direction of a pressure chamber, respectively. This makes it possible to provide a piezoelectric actuator which is capable of increasing an amount of displacement of the vibration plate. ## Claims ### Claim 1 A piezoelectric actuator which applies a pressure to an object, comprising: a vibration plate; a piezoelectric layer arranged on one surface of the vibration plate; a supporting member supporting the vibration plate and the piezoelectric layer, the supporting member having a relief portion which is long in a predetermined longitudinal direction and which releases a deformation of the vibration plate and the piezoelectric layer, and a joining portion which is arranged to surround the relief portion and is joined to one of the vibration plate and the piezoelectric layer; and a first electrode and a second electrode which are arranged on both surfaces of the piezoelectric layer respectively, each of the first and second electrodes being arranged at an area facing the relief portion; wherein a bending-stiffness lowering portion is formed in one of the vibration plate and the piezoelectric layer at a first area facing one end of the relief portion in the longitudinal direction; and wherein a first bending stiffness of the bending-stiffness lowering portion is lower than a second bending-stiffness of an other portion of the one of the vibration plate and the piezoelectric layer in which bending-stiffness lowering portion is formed, at a second area facing one end of the relief portion in a width direction orthogonal to the longitudinal direction. ### Claim 2 (depends on 1) The piezoelectric actuator according to claim 1, wherein the bending-stiffness lowering portion includes a first bending-stiffness lowering portion and a second bending-stiffness lowering portion; and wherein the first bending-stiffness lowering portion and the second bending-stiffness lowering portion are provided, on one of the vibration plate and the piezoelectric layer, at the first area facing the one end in the longitudinal direction and a third area facing the other end in the longitudinal direction of the relief portion, respectively. ### Claim 3 (depends on 1) The piezoelectric actuator according to claim 1, wherein the bending-stiffness lowering portion is a first thin wall portion having a wall thickness smaller than a thickness of a fourth area, of one of the vibration plate and the piezoelectric layer, facing a central portion of the relief portion. ### Claim 4 (depends on 3) The piezoelectric actuator according to claim 3, wherein the first thin wall portion is a recess formed locally on a surface, of the piezoelectric layer, on a side opposite to the vibration plate, the recess being formed at another area of the piezoelectric layer facing the one end in the longitudinal direction of the relief portion; and wherein the piezoelectric actuator further includes a predetermined wiring portion which is connected to one of the first electrode and the second electrode arranged on a surface, among the both surfaces of the piezoelectric layer, on a side opposite to the vibration plate, the wiring portion being arranged avoiding the first thin wall portion. ### Claim 5 (depends on 3) The piezoelectric actuator according to claim 3, wherein a second thin wall portion having a wall thickness smaller than a thickness of the fourth area of one of the vibration plate and the piezoelectric layer is formed on the second area of one of the vibration plate and the piezoelectric layer. ### Claim 6 (depends on 5) The piezoelectric actuator according to claim 5, wherein the first thin wall portion is thinner than the second thin wall portion. ### Claim 7 (depends on 5) The piezoelectric actuator according to claim 5, wherein a ratio of an area of the first thin wall portion with respect to the first area of one of the vibration plate and the piezoelectric layer is greater than a ratio of an area of the second thin wall portion with respect to the second area of one of the vibration plate and the piezoelectric layer. ### Claim 8 (depends on 1) The piezoelectric actuator according to claim 1, wherein the bending-stiffness lowering portion is a first through hole formed in the first area of one of the vibration plate and the piezoelectric layer. ### Claim 9 (depends on 8) The piezoelectric actuator according to claim 8, wherein a second through hole is formed in the second area of one of the vibration plate and the piezoelectric layer; and wherein a ratio of an opening area of the first through hole with respect to the first area of one of the vibration plate and the piezoelectric layer is greater than a ratio of an opening area of the second through hole with respect to the second area of one of the vibration plate and the piezoelectric layer. ### Claim 10 (depends on 8) The piezoelectric actuator according to claim 8, wherein a thin wall portion, of which thickness is smaller than a thickness of the vibration plate and the piezoelectric layer in the fourth area, is formed in the second area of one of the vibration plate and the piezoelectric layer. ### Claim 11 (depends on 1) The piezoelectric actuator according to claim 1, wherein the bending-stiffness lowering portion is a first cavity formed in a portion between the vibration plate and the piezoelectric layer, the portion facing the one end in the longitudinal direction of the relief portion. ### Claim 12 (depends on 11) The piezoelectric actuator according to claim 11, wherein a second cavity is formed in another portion between the vibration plate and the piezoelectric layer, the another portion facing the one end in the width direction of the relief portion; and wherein a depth of the first cavity is greater than a depth of the second cavity. ### Claim 13 (depends on 11) The piezoelectric actuator according to claim 11, wherein a filling material having an elastic coefficient smaller than an elastic coefficient of each of the vibration plate and the piezoelectric layer is filled in the first cavity. ### Claim 14 (depends on 1) The piezoelectric actuator according to claim 1, wherein the bending-stiffness lowering portion is formed only at the first area of at least one of the vibration plate and the piezoelectric layer. ### Claim 15 A piezoelectric actuator which applies a pressure to an object, comprising: a vibration plate; a piezoelectric layer arranged on one surface of the vibration plate; a supporting member which supports the vibration plate and the piezoelectric layer, the supporting member having a relief portion which is long in a predetermined longitudinal direction and which releases a deformation of the vibration plate and the piezoelectric layer, and a joining portion which is arranged to surround the relief portion and which has a wall facing one end of the relief portion in the longitudinal direction; and a first electrode and a second electrode which are arranged on both surfaces of the piezoelectric layer respectively, each of the first and second electrodes being arranged at an area facing the relief portion; wherein a bending-stiffness lowering portion, which lowers a bending stiffness of the wall, is formed in the wall of the joining portion. ### Claim 16 (depends on 15) The piezoelectric actuator according to claim 15, wherein the bending-stiffness lowering portion is a groove formed in the wall along the one end in the longitudinal direction of the relief portion. ### Claim 17 (depends on 15) The piezoelectric actuator according to claim 15, wherein the bending-stiffness lowering portion is formed only in a portion, of the wall, facing the one end in the longitudinal direction of the relief portion. ### Claim 18 (depends on 1) A liquid transporting apparatus which transports a liquid, comprising: the piezoelectric actuator as defined in claim 1; and a channel unit in which a liquid channel is formed, and which is joined to the supporting member to form a pressure chamber, as the relief portion, in the liquid channel; wherein the vibration plate covers the pressure chamber, and the piezoelectric actuator applies a pressure to the liquid in the pressure chamber. ### Claim 19 (depends on 18) The liquid transporting apparatus according to claim 18, wherein the bending-stiffness lowering portion is formed only in the first area, of at least one of the vibration plate and the piezoelectric layer, facing the one end in the longitudinal direction of the pressure chamber. ### Claim 20 (depends on 1) A liquid-droplet jetting apparatus which jets a droplet of a liquid, comprising: the piezoelectric actuator as defined in claim 1; and a channel unit in which a nozzle and a liquid channel is formed, and which is joined to the supporting member to form a pressure chamber, as the relief portion, in the liquid channel, the pressure chamber communicating with the nozzle; wherein the vibration plate covers the pressure chamber, and the piezoelectric actuator applies a pressure to the liquid in the pressure chamber. ### Claim 21 (depends on 20) The liquid-droplet jetting apparatus according to claim 20, wherein the one end in the longitudinal direction of the pressure chamber communicates with the nozzle. ### Claim 22 (depends on 20) The liquid-droplet jetting apparatus according to claim 20, wherein the bending-stiffness lowering portion is formed only at the one end, of at least one of the vibration plate and the piezoelectric layer, in the longitudinal direction of the pressure chamber, the one end being on a side of the nozzle. ### Claim 23 (depends on 15) A liquid-droplet jetting apparatus which jets a droplet of a liquid, comprising: the piezoelectric actuator as defined in claim 15; and a channel unit in which a nozzle and a liquid channel are formed, and which is joined to the supporting member to form a pressure chamber, as the relief portion, in the liquid channel, the pressure chamber communicating with the nozzle; wherein the vibration plate covers the pressure chamber, and the piezoelectric actuator applies a pressure to the liquid in the pressure chamber. ### Claim 24 (depends on 23) The liquid-droplet jetting apparatus according to claim 23, wherein one end in the longitudinal direction of the pressure chamber communicates with the nozzle. ### Claim 25 (depends on 23) The liquid-droplet jetting apparatus according to claim 23, wherein the bending-stiffness lowering portion is formed only at one end, of the one of the vibration plate and the piezoelectric layer, in the longitudinal direction of the pressure chamber, the one end being on a side of the nozzle.