# US 2014/0196528 A1 · System and Method for Detecting Clutch-Related Faults in an Automatic Transmission > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0196528 A1 - Document ID: US20140196528A1 - Status: Published application - Kind: A1 - Application number: 14/216,122 - Filed: 2014-03-17 - Published: 2014-07-17 - Earliest claimed: 2010-12-01 - Assignees: Allison Transmission, Inc. - Applicants: Allison Transmission, Inc. - Inventors: Charles F. Long; Darren J. Weber; John William Edward Fuller - Web page: https://patentgrep.com/patent/US20140196528A1 ## CPC - G01M 13/02: Gearings; Transmission mechanisms - F16H 61/12: Detecting malfunction or potential malfunction, e.g. fail safe (in control of hydrostatic gearing F16H61/4192) {; Circumventing or fixing failures} - F16H 37/086: {CVT using two coaxial friction members cooperating with at least one intermediate friction member} - F16H 61/6648: {controlling of shifting being influenced by a signal derived from the engine and the main coupling} - F16H 2061/1208: {with diagnostic check cycles; Monitoring of failures} - F16H 2061/6601: {with arrangements for dividing torque and shifting between different ranges} - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR - F16H: GEARING ## Abstract A fault diagnostic method for an automatic transmission may include monitoring an operating state of a trim system configured to selectively supply clutch engagement pressure and exhaust to at least one clutch control valve, determining an expected operating state of the trim system based on current operating conditions of the transmission, and generating a fault signal if the monitored operating state of the trim system is different from the expected operating state of the trim system. ## Claims ### Claim at position 1 1-20. (canceled) ### Claim 21 A system for an automatic transmission, the system comprising: a trim system configured to selectively (i) supply clutch engagement pressure to at least one clutch control valve via first and second fluid passageways and (ii) exhaust the first and second fluid passageways; and a first pressure switch fluidly coupled to the trim system, wherein the first pressure switch is (i) in a first operating state when the trim system supplies the clutch engagement pressure to the first and second fluid passageways and (ii) in the first operation state when the trim system exhausts both the first and second fluid passageways. ### Claim 22 (depends on 21) The system of claim 21, wherein the trim system comprises a first trim valve having (i) a first operating state in which the first trim valve supplies clutch engagement pressure to at the least one clutch control valve via the first fluid passageway and (ii) a second operating state in which the first trim valve exhausts the first fluid passageway. ### Claim 23 (depends on 22) The system of claim 22, wherein the trim system comprises a second trim valve having (i) a first operating state in which the second trim valve supplies the clutch engagement pressure to the at least one clutch control valve via the second fluid passageway and (ii) a second operating state in which the second trim valve exhausts the second fluid passageway. ### Claim 24 (depends on 23) The system of claim 23, further comprising a transmission control circuit including a memory having instructions stored therein that are executable by the transmission control circuit to monitor the operating state of the first pressure switch, to determine an expected operating state of the first pressure switch based on current operating conditions of the transmission, and to generate a fault signal if the monitored operating state of the first pressure switch is different from the expected operating state of the first pressure switch. ### Claim 25 (depends on 24) The system of claim 24, wherein the instructions stored in the memory further include instructions executable by the transmission control circuit to store a trim system fault code in the memory in response to a determination that the monitored operating state of the first pressure switch is different from the expected operating state of the first pressure switch. ### Claim 26 (depends on 24) The system of claim 24, wherein the instructions stored in the memory further include instructions executable by the transmission control circuit to determine the expected operating state of the first pressure switch based on current operating conditions of the transmission based on a determination that the expected operation state of the first pressure switch is the first operating state when the transmission is in true neutral, in-range neutral or transitioning between adjacent ones of a number of different operating modes of the transmission. ### Claim 27 (depends on 23) The system of claim 23, wherein the at least one clutch control valve comprises: a first control valve fluidly coupled to the first trim valve via the first fluid passageway and to first and second friction engagement devices, and a second control valve fluidly coupled to the first and second trim valves via the first and second fluid passageways and to a third friction engagement device. ### Claim 28 (depends on 27) The system of claim 27, further comprising a second pressure switch fluidly coupled to the first control valve such that the second pressure switch is in a first operating state when the first control valve is de-stroked and is in a second operating state when the first control valve is stroked. ### Claim 29 (depends on 28) The system of claim 28, further comprising a transmission control circuit including a memory having instructions stored therein that are executable by the transmission control circuit to monitor the operating state of the second pressure switch, determine an expected operating state of the second pressure switch based on current operating conditions of the transmission, and generate a first control valve fault signal in response to a determination that the monitored operating state of the second pressure switch is different from the expected operating state of the second pressure switch. ### Claim 30 (depends on 29) The system of claim 29, further comprising a third pressure switch fluidly coupled to the second control valve such that the third pressure switch is in a first operating state when the second control valve is de-stroked and is in a second operating state when the second control valve is stroked. ### Claim 31 (depends on 30) The system of claim 30, wherein the instructions stored in the memory further include instructions that are executable by the transmission control circuit to monitor the operating state of the third pressure switch, determine an expected operating state of the third pressure switch based on current operating conditions of the transmission, and generate a second control valve fault signal in response to a determination that the monitored operating state of the third pressure switch is different from the expected operating state of the third pressure switch. ### Claim 32 A system for detecting clutch-related faults in an automatic transmission, the system comprising: a trim system configured to selectively (i) supply clutch engagement pressure to a first fluid passage and (ii) exhaust the first fluid passageway; a first control valve fluidly coupled to the trim system via the first fluid passageway; a first pressure switch fluidly coupled to the first control valve such that the first pressure switch is in a first operating state when the first control valve is de-stroked and is in a second operating state when the first control valve is stroked; and a transmission control circuit to monitor the operating state of the first pressure switch, determine a predefined operating state of the first pressure switch based on current operating conditions of the transmission, and generate a first control valve fault signal in response to a determination that the monitored operating state of the first pressure switch is different from the predefined operating state of the first pressure switch. ### Claim 33 (depends on 32) The system of claim 32, wherein the trim system comprises a first trim valve having a first operating state in which the first trim valve supplies clutch engagement pressure to the at least one clutch control valve via the first fluid passageway and a second operating state in which the first trim valve exhausts the first fluid passageway. ### Claim 34 (depends on 33) The system of claim 33, wherein the trim system is configured to selectively (i) supply clutch engagement pressure to a second fluid passageway and (ii) exhaust the second fluid passageway. ### Claim 35 (depends on 34) The system of claim 34, wherein the trim system comprises a second trim valve having a first operating state in which the second trim valve supplies the clutch engagement pressure to the at least one clutch control valve via the second fluid passageway and a second operating state in which the second trim valve exhausts the second fluid passageway. ### Claim 36 (depends on 35) The system of claim 35, comprising a second control valve fluidly coupled to the trim system via the first and second fluid passageways. ### Claim 37 (depends on 36) The system of claim 36, comprising a second pressure switch fluidly coupled to the second control valve such that the second pressure switch is in a first operating state when the second control valve is de-stroked and is in a second operating state when the second control valve is stroked. ### Claim 38 (depends on 37) The system of claim 37, wherein the instructions stored in the memory further include instructions that are executable by the transmission control circuit to monitor the operating state of the second pressure switch, determine a predefined operating state of the second pressure switch based on current operating conditions of the transmission, and generate a second control valve fault signal in response to a determination that the monitored operating state of the second pressure switch is different from the predefined operating state of the second pressure switch. ### Claim 39 (depends on 38) The system of claim 38, wherein the first control valve is fluidly coupled to first and second friction engagement devices. ### Claim 40 (depends on 39) The system of claim 39, wherein the second control valve is fluidly coupled to a third friction engagement device.