# US 12,181,043 B2 · Hydromechanical transmission and warm-up method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,181,043 B2 - Document ID: US12181043B2 - Status: Granted - Kind: B2 - Application number: 18/326,788 - Filed: 2023-05-31 - Published: 2023-09-28 - Granted: 2024-12-31 - Earliest claimed: 2021-03-31 - Assignees: Dana Italia S.R.L. - Applicants: Dana Italia S.R.L. - Inventors: Giacomo Faggiani; Mario Gelmini - Web page: https://patentgrep.com/patent/US12181043B2 ## CPC - F16H 63/48: Signals to a parking brake {or parking lock; Control of parking locks or brakes being part of the transmission} - F16H 47/04: the mechanical gearing being of the type with members having orbital motion - F16H 61/0059: {Braking of gear output shaft using simultaneous engagement of engaging means, e.g. clutches or brakes, applied for different gear ratios} - F16H 2037/088: {Power-split transmissions with summing differentials, with the input of the CVT connected or connectable to the input shaft} - F16H: GEARING ## Abstract Methods and systems for a hydromechanical transmission are provided. In one example, the method includes responsive to rotation of a portion of a mechanical assembly induced by cranking of an engine, blocking an output shaft of the hydromechanical transmission via joint engagement of a forward drive clutch and a reverse drive clutch. The method further includes pressurizing a hydrostatic assembly while the forward drive clutch and the reverse drive clutch remain jointly engaged, where the mechanical assembly is coupled in parallel with the hydrostatic assembly. ## Claims ### Claim 1 A hydromechanical variable transmission (HVT) comprising: a hydrostatic unit coupled in parallel with a mechanical branch; wherein the mechanical branch includes a first planetary gear set that is coupled to a forward drive clutch and a reverse drive clutch; a parking brake mechanism coupled to an output shaft; and a controller that comprises: instructions that when executed, during cranking of an engine coupled to the mechanical branch, cause the controller to: synchronously engage the forward drive clutch and the reverse drive clutch; and increase a pressure differential in the hydrostatic unit via adjustment of a displacement of a hydraulic pump in the hydrostatic unit; and instructions that when executed, subsequent to the synchronous engagement of the forward drive clutch and the reverse drive clutch, cause the controller to: disengage the parking brake mechanism. ### Claim 2 (depends on 1) The HVT of claim 1, wherein the controller further comprises: instructions that when executed, prior to engagement of the forward drive clutch and the reverse drive clutch, cause the controller to: operate the hydrostatic unit in a speed control mode to synchronize the forward drive clutch and the reverse drive clutch. ### Claim 3 (depends on 1) The HVT of claim 1, further comprising a second planetary gear set rotationally coupled to the first planetary gear set. ### Claim 4 (depends on 3) The HVT of claim 3, wherein the second planetary gear set is a simple planetary gear set. ### Claim 5 (depends on 1) The HVT of claim 1, wherein the HVT is configured to rotationally couple to the engine. ### Claim 6 (depends on 1) The HVT of claim 1, wherein the forward drive clutch and the reverse drive clutch are friction clutches. ### Claim 7 (depends on 1) The HVT of claim 1, wherein the hydrostatic unit includes a hydraulic motor. ### Claim 8 (depends on 1) The HVT of claim 1, wherein the forward drive clutch and the reverse drive clutch are synchronously engaged during cranking of an internal combustion engine that is coupled to the HVT. ### Claim 9 (depends on 1) The HVT of claim 1, wherein the forward drive clutch and the reverse drive clutch are coaxially arranged. ### Claim 10 (depends on 1) The HVT of claim 1, further comprising an output shaft rotationally coupled to multiple drive axles. ### Claim 11 A method for operation of a hydromechanical variable transmission (HVT), comprising: synchronously engaging a forward drive clutch and a reverse drive clutch; increasing a pressure differential in a hydrostatic unit via adjustment of a displacement of a hydraulic pump in the hydrostatic unit; and subsequent to the synchronous engagement of the forward drive clutch and the reverse drive clutch, disengaging a parking brake mechanism coupled to an output shaft; wherein the HVT includes: the hydrostatic unit coupled in parallel with a mechanical branch; wherein the mechanical branch includes a planetary gear set that is coupled to the forward drive clutch and the reverse drive clutch; and wherein the forward drive clutch and the reverse drive clutch are coaxially arranged. ### Claim 12 (depends on 11) The method of claim 11, further comprising, prior to the synchronous engagement of the forward drive clutch and the reverse drive clutch, operating the hydrostatic unit in a speed control mode to synchronize the forward drive clutch and the reverse drive clutch. ### Claim 13 A transmission system, comprising: a first planetary gear set; a hydrostatic assembly coupled in parallel with the first planetary gear set; a forward drive clutch and a reverse drive clutch coupled to the first planetary gear set and an output shaft; a parking brake mechanism coupled to the output shaft; and a controller comprising: instructions that when executed, while the first planetary gear set is receiving rotational input from a motive power source, cause the controller to: block the output shaft of the transmission system via joint engagement of the forward drive clutch and the reverse drive clutch; and pressurize the hydrostatic assembly while the forward drive clutch and the reverse drive clutch remain jointly engaged; and instructions that when executed, prior to the joint engagement of the forward drive clutch and the reverse drive clutch, cause the controller to: engage the parking brake mechanism; and instructions that when executed, subsequent to the joint engagement of the forward drive clutch and the reverse drive clutch, cause the controller to: disengage the parking brake mechanism. ### Claim 14 (depends on 13) The transmission system of claim 13, wherein the motive power source is an internal combustion engine. ### Claim 15 (depends on 13) The transmission system of claim 13, wherein the output shaft is coupled to a drive axle.