Vehicle roll-away prevention

• US 10,302,195 B2
• Filed: 11/10/2016
• Issued: 05/28/2019
• Est. Priority Date: 11/10/2016
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Ulrey, Joseph Norman, Pursifull, Ross Dykstra
• Primary Examiner(s): Young, Edwin A
• Application Number:
  US15/348,161
• Publication Number:
  US 20180128371A1
• Time in Patent Office: 929 Days
• CPC Class Codes: F16H 2059/663 Road slope
• CPC Class Codes: F16H 2059/746 Engine running state, e.g. on-off of ignition switch
• CPC Class Codes: F16H 2061/223 Electrical gear shift lock, e.g. locking of lever in park or neutral position by electric means if brake is not applied; Key interlock, i.e. locking the key if lever is not in park position
• CPC Class Codes: F16H 2312/022 Preparing to drive off
• CPC Class Codes: F16H 61/22 Locking of the control input devices constructional features of locking or disabling mechanisms F16H63/34
• CPC Class Codes: F16H 63/483 Circuits for controlling engagement of parking locks or brakes

Abstract

A brake interlock feature prevents release of the park mechanism unless a driver is depressing the brake pedal. This is intended to prevent the vehicle from rolling following park release. An enhanced brake interlock feature also checks to ensure that adequate brake boost is available to prevent vehicle roll before releasing the park mechanism. The feature may directly measure brake boost or may measure a quantity indirectly related to the availability of brake boost such as engine speed.

Claims

1. A vehicle comprising:

a transmission having a park mechanism;

a transmission mode selector for accepting user requests to release or engage the park mechanism;

an engine configured to provide brake force assistance; and

a controller programmed to inhibit release of the park mechanism in response to a level of available brake force assistance being less than a threshold,

wherein the threshold varies depending on road grade.

2. The vehicle of claim 1 wherein the controller inhibits release of the park mechanism in response to an ignition state indicating that the engine is not running.

3. The vehicle of claim 1 further comprising a shift lock override control and wherein the controller is programmed to release the park mechanism in response to selection of Neutral via the mode selector while the shift lock override control is activated regardless of the level of available brake force assistance.

4. The vehicle of claim 1 wherein the transmission mode selector includes buttons for selecting modes and the controller is programmed to release the park mechanism in response to depression of one of the buttons corresponding to Drive, Reverse, or Neutral only if the level of available brake force assistance exceeds the threshold.

5. The vehicle of claim 1 wherein the transmission mode selector includes a shift lock and the controller is programmed to engage the shift lock in response to the level of available brake force assistance being less than the threshold.

6. The vehicle of claim 5 further comprising a shift lock override control and wherein the controller is programmed to release the park mechanism in response to activation of the shift lock override control regardless of the level of available brake assistance.

7. The vehicle of claim 1 wherein the controller is further programmed to display a message to a driver upon inhibiting release of the park mechanism.

8. A transmission control method comprising:

releasing a park mechanism in response to a user request if an engine is running and a brake pedal is pressed;

preventing release of the park mechanism in response to the engine being stopped; and

releasing the park mechanism in response to the user request if the engine is stopped, the brake pedal is pressed and a grade is less than a threshold.

9. The method of claim 8 further comprising:

releasing the park mechanism in response to the user request if the engine is stopped, the brake pedal is pressed and a shift lock override control is activated.

10. The method of claim 8 further comprising:

displaying a message to a driver in response to an attempt to disengage the park mechanism with the engine stopped.

11. A transmission control method comprising:

measuring a quantity indicative of available brake boost; and

preventing release of a park mechanism in response to the quantity being less than a threshold,

wherein the threshold varies based on grade.

12. The method of claim 11 wherein release of the park mechanism is prevented by engaging a shift lock.

13. The method of claim 11 wherein the quantity is engine speed.