# US 2008/0185938 A1 · Monolithic Piezo Actuator With a Change in the Electrode Structure in the Junction Region, and Use of the Piezo Actuator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2008/0185938 A1 - Document ID: US20080185938A1 - Status: Published application - Kind: A1 - Application number: 11/996,601 - Filed: 2006-07-26 - Published: 2008-08-07 - Earliest claimed: 2005-07-26 - Assignees: Siemens Aktiengesellschaft - Inventors: Harald Johannes Kastl; Carsten Schuh - Web page: https://patentgrep.com/patent/US20080185938A1 ## CPC - H10N 30/045: by polarising - H10N 30/053: by integrally sintering piezoelectric or electrostrictive bodies and electrodes - H10N 30/508: {adapted for alleviating internal stress, e.g. cracking control layers} - H10N 30/871: {Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes} - Y10T 29/42: Piezoelectric device making - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A piezo actuator in a monolithic multilayer design, has at least one piezoelectrically active stack element, wherein the stack element has stacked piezoceramic layers made of piezoceramic material and electrode layers arranged between the piezoceramic layers, at least one piezoelectrically inactive terminating region arranged above the stack element, and at least one junction region arranged between the stack element and the terminating region, wherein the stack element, the terminating region and the junction region are connected to one another to form a monolithic total stack. The junction region has stacked piezoceramic layers and electrode layers arranged between the piezoceramic layers, and the piezoceramic layers and the electrode layers are in a form and are arranged on one another such that in the stack direction of the junction region one piezoelectrically active area per junction piezoceramic layer is successively changed from piezoceramic layer to piezoceramic layer. ## Claims ### Claim 1 A piezo actuator in a monolithic multilayered design, comprising: at least one piezoelectrically active stack, wherein the stack comprises stacked piezoceramic layers and electrode layers arranged between the piezoceramic layers, at least one piezoelectrically inactive terminating region arranged above the piezoelectrically active stack, and at least one transition region arranged between the piezoelectrically active stack and the terminating region, wherein the piezoelectrically active stack, the terminating region and the transition region are joined together to form a monolithic total stack, and wherein the transition region comprises stacked transition-region piezoceramic layers and transition-region electrode layers arranged between the transition-region piezoceramic layers, and the transition-region piezoceramic layers and the transition-region electrode layers are in a form and are arranged on one another such that from transition-region piezoceramic layer to transition-region piezoceramic layer in the stack direction of the transition region, one piezoelectrically active area per transition piezoceramic layer is successively changed. ### Claim 2 (depends on 1) The piezo actuator according to claim 1, wherein the structure parallel to the lateral dimension of the respective transition-region electrode layer is formed like a comb. ### Claim 3 (depends on 1) The piezo actuator according to claim 1, wherein the structure parallel to the lateral dimension of the respective transition-region electrode layer is shaped like a ring. ### Claim 4 (depends on 1) The piezo actuator according to claim 1, wherein adjacent transition-region electrode layers form an interdigital structure. ### Claim 5 (depends on 1) The piezo actuator according to claim 1, wherein the active sub-stack and/or the terminating region has a sub-stack height selected from the range 1 mm to 10 mm inclusive. ### Claim 6 (depends on 1) The piezo actuator according to claim 1, wherein the transition region sub-stack has a transition-stack height selected from the range 0.2 mm to 5.0 mm inclusive. ### Claim 7 (depends on 1) The piezo actuator according to claim 1, wherein the total stack has a total-stack height that is selected from the range 10 mm to 200 mm inclusive. ### Claim 8 A method for providing a piezo actuator, comprising the steps of: providing at least one piezoelectrically active stack, wherein the stack comprises stacked piezoceramic layers and electrode layers arranged between the piezoceramic layers, arranging at least one piezoelectrically inactive terminating region above the piezoelectrically active stack, and arranging at least one transition region between the piezoelectrically active stack and the terminating region, joining the piezoelectrically active stack, the terminating region and the transition region together to form a monolithic total stack, wherein the transition region comprises stacked transition-region piezoceramic layers and transition-region electrode layers arranged between the transition-region piezoceramic layers, and the transition-region piezoceramic layers and the transition-region electrode layers are in a form and are arranged on one another such that from transition-region piezoceramic layer to transition-region piezoceramic layer in the stack direction of the transition region, one piezoelectrically active area per transition piezoceramic layer is successively changed. ### Claim 9 (depends on 8) The method according to claim 8, further comprising the step of forming the structure parallel to the lateral dimension of the respective transition-region electrode layer like a comb. ### Claim 10 (depends on 8) The method according to claim 8, further comprising the step of shaping the structure parallel to the lateral dimension of the respective transition-region electrode layer like a ring. ### Claim 11 (depends on 8) The method according to claim 8, wherein adjacent transition-region electrode layers form an interdigital structure. ### Claim 12 (depends on 8) The method according to claim 8, wherein the active sub-stack and/or the terminating region has a sub-stack height selected from the range 1 mm to 10 mm inclusive. ### Claim 13 (depends on 8) The method according to claim 8, wherein the active sub-stack and/or the terminating region has a sub-stack height selected from the range 3 mm to 5 mm inclusive. ### Claim 14 (depends on 8) The method according to claim 8, wherein the transition region sub-stack has a transition-stack height selected from the range 0.2 mm to 5.0 mm inclusive. ### Claim 15 (depends on 8) The method according to claim 8, wherein the transition region sub-stack has a transition-stack height selected from the range 0.5 mm to 2.0 mm inclusive. ### Claim 16 (depends on 8) The method according to claim 8, wherein the total stack has a total-stack height that is selected from the range 10 mm to 200 mm inclusive. ### Claim 17 (depends on 8) The method according to claim 8, further comprising the step of operating a valve with said piezo actuator. ### Claim 18 (depends on 16) The method according to claim 16, wherein the valve is an injection valve of an internal combustion engine. ### Claim 19 (depends on 1) The piezo actuator according to claim 1, wherein the active sub-stack and/or the terminating region has a sub-stack height selected from the range 3 mm to 5 mm inclusive. ### Claim 20 (depends on 1) The piezo actuator according to claim 1, wherein the transition region sub-stack has a transition-stack height selected from the range 0.5 mm to 2.0 mm inclusive.