# US 10,308,251 B2 · Transmission engagement control system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,308,251 B2 - Document ID: US10308251B2 - Status: Granted - Kind: B2 - Application number: 15/676,297 - Filed: 2017-08-14 - Published: 2019-02-14 - Granted: 2019-06-04 - Earliest claimed: 2017-08-14 - Assignees: Ford Global Technologies, LLC - Applicants: Ford Global Technologies, LLC - Inventors: Scott Joseph Gittins; Ryan Eggebrecht; Timothy Fedullo; Samuel Glauber - Web page: https://patentgrep.com/patent/US10308251B2 ## CPC - B60W 30/18054: {at stand still, e.g. engine in idling state (hill holding B60W30/18118)} - B60W 10/115: with planetary gears - B60W 10/196: acting within the driveline, e.g. retarders - B60W 30/19: Improvement of gear change, e.g. by synchronisation or smoothing gear shift - F16H 3/663: {with conveying rotary motion between axially spaced orbital gears, e.g. a stepped orbital gear or Ravigneaux} - F16H 61/0021: {Generation or control of line pressure} - F16H 61/12: Detecting malfunction or potential malfunction, e.g. fail safe (in control of hydrostatic gearing F16H61/4192) {; Circumventing or fixing failures} - F16H 63/3425: {characterised by pawls or wheels} - F16H 63/3483: {with hydraulic actuating means} - B60W 2510/108: pressure of control fluid - B60W 2510/188: Parking lock mechanisms - B60W 2540/12: Brake pedal position - B60W 2540/16: Ratio selector position - B60W 2710/1083: pressure of control fluid - B60W 2710/188: Parking lock mechanisms - F16H 3/666: {with intermeshing orbital gears (F16H3/663 takes precedence)} - F16H 2061/0075: {characterised by a particular control method} - F16H 2061/1276: {the failing part is a friction device, e.g. clutches or brakes} - F16H 2200/006: the gear ratios comprising eight forward speeds - F16H 2200/201: with three sets of orbital gears - F16H 2200/2046: with six engaging means - F16H 2200/2069: using two freewheel mechanism - F16H 2200/2084: two freewheel mechanisms - B60W: CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT - F16H: GEARING ## Abstract A transmission park mechanism is hydraulically actuated. Specifically a controller releases the parking pawl by commanding engagement of particular shift elements at an elevated line pressure. The process of transitioning from Park to a Drive or Reverse condition may involve several sequential steps. To reduce the delay between driver selection of Drive or Reverse and completion of the engagement, it is advantageous to raise the line pressure in response to depression of a brake pedal, prior to movement of the shift lever. To limit the adverse fuel economy impact of increased line pressure, the line pressure is lowered again if the driver does not move the shift lever soon after depressing the brake pedal. ## Claims ### Claim 1 A transmission comprising: a parking pawl engageable to hold an output shaft stationary; a hydraulic control system having a line pressure circuit; a pump configured to supply pressurized fluid to the line pressure circuit; and a controller configured to increase a pressure in the line pressure circuit in response to depression of a brake pedal while the parking pawl is engaged to decrease a time required to engage a drive ratio. ### Claim 2 (depends on 1) The transmission of claim 1 wherein the hydraulic control system further comprises a plurality of clutch apply circuits and wherein engaging the drive ratio comprises permitting fluid flow from the line pressure circuit to a first subset of the clutch apply circuits. ### Claim 3 (depends on 2) The transmission of claim 2 wherein the hydraulic control system in configured to release the parking pawl in response to fluid pressure in a second subset of the clutch apply circuits. ### Claim 4 (depends on 1) The transmission of claim 1 wherein the controller is further programmed to reduce the pressure in the line pressure circuit if the brake pedal is depressed for longer than a threshold time while a shifter remains in a park position. ### Claim 5 (depends on 1) The transmission of claim 1 wherein the controller is further programmed to reduce the pressure in the line pressure circuit in response to release of the brake pedal. ### Claim 6 (depends on 1) The transmission of claim 1 wherein the controller is further programmed to inhibit the increase in line pressure in response to detection of a clutch failure. ### Claim 7 A vehicle comprising: a parking mechanism configured to selectively hold the vehicle stationary; a transmission pump configured to supply pressurized fluid to a line pressure circuit; and a controller programmed to increase a pressure in the line pressure circuit in response to depression of a brake pedal while the parking mechanism is engaged to decrease a time required to engage a transmission drive ratio. ### Claim 8 (depends on 7) The vehicle of claim 7 further comprising a plurality of shift elements and wherein engaging the transmission drive ratio comprises engaging a first subset of the shift elements. ### Claim 9 (depends on 8) The vehicle of claim 8 wherein engaging the transmission drive ratio further comprises engaging a second subset of the shift elements to release the parking mechanism. ### Claim 10 (depends on 7) The vehicle of claim 7 wherein the controller is further programmed to reduce the pressure in the line pressure circuit if the brake pedal is depressed for longer than a threshold time while a shifter remains in a park position. ### Claim 11 (depends on 7) The vehicle of claim 7 wherein the controller is programmed to reduce the pressure in the line pressure circuit in response to release of the brake pedal. ### Claim 12 (depends on 7) The transmission of claim 7 wherein the controller is further programmed to inhibit the increase in line pressure in response to detection of a clutch failure. ### Claim 13 A method of controlling a transmission comprising: with the transmission in Park and a brake pedal released, controlling a pressure in a line pressure circuit to a first pressure level; and in response to depression of the brake pedal with the transmission in Park, increasing the pressure in the line pressure circuit to a second pressure level. ### Claim 14 (depends on 13) The method of claim 13 further comprising: in response to the brake pedal being depressed for a threshold time with the transmission in Park, decreasing the pressure in the line pressure circuit to the first pressure level. ### Claim 15 (depends on 13) The method of claim 13 further comprising: in response to a shifter being moved from a Park position, engaging a first shift element to release a parking pawl in the transmission. ### Claim 16 (depends on 15) The method of claim 15 further comprising: after the parking pawl is released, engaging a second shift element to establish a power flow path between a transmission input shaft and a transmission output shaft. ### Claim 17 (depends on 16) The method of claim 16 further comprising: after the parking pawl is released and before engaging the second shift element, decreasing the line pressure and releasing at least one shift element. ### Claim 18 (depends on 17) The method of claim 17 wherein the at least one shift element includes the first shift element.