Method for shifting an electronically shifted transmission without engine power

Abstract

Vehicle (10), comprising: an internal combustion engine (12); an electronically shifted transmission (14) comprising a hydraulic actuator (18) coupled to a shift element configured to selectively shift the transmission (14) into the PARK position; a pressure source in fluid communication with the hydraulic actuator (18) and configured to selectively provide pressure in the absence of engine power; and a controller (28) configured to control the pressure source to provide hydraulic pressure to the hydraulic actuator (18) in response to a first driver input when the engine (12) is off, and wherein, in response to a second driver input when the engine (12) is off, the transmission (14) is shifted out of the PARK position without starting the engine (12), wherein the first driver input is a key-on event or an actuation of a brake pedal (22) by the driver.

Description

[0001] The present invention relates to automatic transmissions and, in particular, to electronically shifted transmissions.

[0002] A conventional automatic transmission includes a transmission control device, which is used to control the transmission of a motor vehicle. The transmission control device is used to select various ranges, for example, Park, where the transmission is locked to prevent the vehicle from moving; Neutral, where the transmission allows the vehicle to move freely, such as when towing; Reverse, where the transmission allows the vehicle to move backward; and one or more Drive ranges, which allow the vehicle to move forward. Typically, the transmission control device takes the form of a lever connected to the transmission via a mechanical linkage, such as a cable or hydraulic line. Typically, the lever is also connected to an indicator.When the transmission control mechanism is moved from one range to another, the mechanical linkage physically shifts the transmission to the selected setting, and the indicator moves to show the driver which range has been selected. Even when the vehicle is off, the driver can determine the current transmission range via the indicator and, in some cases, move the transmission control mechanism to neutral, for example, if the vehicle is towed.

[0003] The conventional automatic transmission uses multiple friction elements to automatically shift transmission gears. Generally speaking, these friction elements can be described as torque-producing elements, although they are more commonly referred to as clutches or brakes. The friction elements serve to establish power flow paths from an internal combustion engine to a set of vehicle drive wheels. During vehicle acceleration, the overall gear ratio, which is the ratio of a transmission input shaft speed to a transmission output shaft speed, is decreased during a gear ratio upshift as the vehicle speed increases for a given engine throttle setting.A downshift to achieve a higher gear ratio occurs when an engine throttle setting increases for any given vehicle speed, or when the vehicle speed decreases as the engine throttle setting decreases. Various planetary gearset configurations are found in modern automatic transmissions. However, the basic principle of shift kinematics remains similar. Shifting an automatic transmission with multiple planetary gearsets is accompanied by the application and / or release of friction elements to change the speed and torque relationships by altering the torque path through the planetary gearsets. Friction elements are typically actuated either hydraulically or mechanically based on the position of the transmission control device.

[0004] In an electronically shifted transmission arrangement, the mechanical connection between the transmission control device and the transmission is removed. Instead, the transmission control device takes the form of a gearshift module designed to transmit an electrical signal to an electronic controller. The controller commands separate actuators to apply or release the various friction elements to achieve a desired gear ratio. The gearshift module is not necessarily in the form of a lever, as the control device no longer moves a mechanical linkage to control the transmission. Instead, the gearshift module is typically an electro-mechanical interface (e.g., a series of buttons, lever, or knob) used to command the transmission to shift between gear ranges.

[0005] DE 10 2012 222 221 A1 discloses a method and system providing a selector lock deactivation mode in a vehicle including a shift-by-wire transmission. With the power and ignition on, a driver presses and holds a deactivation switch for a calibrated time. While the deactivation switch is pressed, the driver presses an out-of-park button for a further calibrated time. This results in the vehicle being placed in the selected range, with the transmission not automatically shifting into park upon detection of a trigger event.

[0006] The objective technical problem to be solved can be seen as eliminating or at least mitigating the disadvantages of the prior art. This problem is solved by the subject matter of the independent patent claims.

[0007] A vehicle according to the present disclosure includes an electronically shifted transmission, a pressure source configured to selectively provide hydraulic pressure in the absence of engine power, an internal combustion engine, and a controller. The electronically shifted transmission includes a hydraulic actuator coupled to a shift element configured to selectively place the transmission in the PARK position. The pressure source is in fluid communication with the actuator. The controller is configured, in response to driver input and the internal combustion engine being off, to control the pressure source to provide hydraulic pressure to the hydraulic actuator.

[0008] The driver input is a key-on event. Alternatively, the driver input is a brake pedal application by the driver.

[0009] In one embodiment, the transmission comprises at least one gear set. In such an embodiment, the shift element comprises a parking pawl that can selectively engage the gear set. When the parking pawl engages the gear set, it restricts the movement of the vehicle.

[0010] In some embodiments, the pressure source comprises an electric motor. In various other embodiments, the pressure source comprises a pressure accumulator.

[0011] A method of controlling a vehicle, the vehicle including an internal combustion engine, an electronically shifted transmission including a parking lock and an engine-driven transmission pump, and an accumulator in fluid communication with the parking lock, includes controlling the transmission pump to provide hydraulic pressure to the transmission in response to the internal combustion engine being engaged. The method additionally includes controlling the accumulator to provide hydraulic pressure to the parking lock in response to a driver input and the internal combustion engine being disengaged.

[0012] In one embodiment, the driver input is a key-on event. In another embodiment, the driver input is driver application of a brake pedal. In some embodiments, the parking lock includes a parking mechanism configured to selectively restrict movement of the vehicle while the vehicle is unattended. The parking lock further includes a hydraulic actuator in fluid communication with the accumulator and configured to selectively disengage the parking mechanism. One embodiment further includes shifting the transmission to NEUTRAL in response to a second driver input and the transmission being in PARK.

[0013] A method of controlling a vehicle according to the present disclosure, the vehicle including an electronically shifted transmission with a park pawl and an electric pump in fluid communication with the park pawl, includes controlling the pump to provide hydraulic pressure to the park pawl. Controlling the electric pump is performed in response to the transmission being in PARK, a first driver input, and the engine being off. The method further includes shifting the transmission out of PARK in response to a second driver input.

[0014] In one embodiment, the first driver input is a driver application of a brake pedal. In another embodiment, the first driver input is a key-on event.

[0015] Embodiments according to the present disclosure offer a number of advantages. For example, the present disclosure provides a system and method for shifting an electronically shifted transmission out of PARK while an internal combustion engine in the vehicle is not running. Furthermore, systems according to the present disclosure provide a means for a driver to do this from inside the vehicle cabin, avoiding accessing a transmission overrunning clutch under a vehicle hood. Furthermore, the present disclosure operates without additional cost and without the complexity associated with a manual transmission overrunning clutch.

[0016] The above advantage and other advantages and features of the present disclosure will become apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings. Fig. 1 is a schematic illustration of a vehicle including an electronically shifted transmission in accordance with the present disclosure; Fig. 2 is a schematic representation of another embodiment of a vehicle in accordance with the present disclosure; and Fig. 3 illustrates a method of controlling a vehicle including an electronic circuit according to the present disclosure in flowchart form.

[0017] As required, detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to variously employ the present invention.

[0018] An electronically shifted or parked transmission refers to an arrangement that has no mechanical connection between a transmission controller and the transmission. Instead, a gearshift module transmits an electrical signal to an electronic controller, which instructs separate actuators to apply or release the various friction elements, such as clutches or brakes, to achieve a desired gear ratio. In some embodiments, the transmission may be provided with a parking pawl actuated by one of the actuators. The parking pawl may engage at least one gear in the transmission to prevent movement of a vehicle, or it may be released from the at least one gear to permit movement of a vehicle. In some embodiments, the parking pawl may engage in response to a driver shifting the transmission into the PARK position.In further embodiments, the parking pawl may engage in response to a driver engaging a parking brake. Of course, various other parking elements may also be used to prevent movement of a vehicle.

[0019] In some configurations, the actuators that operate the friction elements and the parking pawl are hydraulic actuators. During normal vehicle operation, an internal combustion engine drives a transmission pump to provide hydraulic pressure to the actuators and enable application or release of the friction elements or parking brake. Because there is no mechanical connection between the gearshift module and the transmission, the driver cannot shift the transmission between gears in the absence of hydraulic pressure to the actuators. When the internal combustion engine is off, the gearshift module may not be usable to shift gears.

[0020] However, under some circumstances it may be desirable to shift the vehicle from PARK to another gear without the engine running.

[0021] For example, if the engine is inoperable, it may be desirable to shift the transmission out of PARK to enable towing. As another example, it may be desirable to roll the vehicle to a new location without the engine running. Using the standard gearshift module, shifting out of PARK without running the engine is not possible. As a result, transmissions are being provided with a manual overrun mechanism. This may include a mechanism available under the vehicle hood or a cable-operated mechanism available in the cabin. Such solutions can be difficult for a user to access, difficult to maneuver through a vehicle, and also add complexity and cost to the vehicle.

[0022] Now referring to Fig. 1, a vehicle 10 is illustrated in schematic form. The vehicle 10 includes an internal combustion engine 12 and an electronically shifted transmission 14. The transmission 14 includes an associated transmission pump 16 operatively coupled to and driven by the internal combustion engine 12. The transmission further includes at least one actuator 18. The actuator 18 is configured to selectively engage or disengage a vehicle parking mechanism. In some embodiments, the vehicle parking mechanism includes a pawl that engages or disengages a gear in the transmission to restrict movement of a vehicle. Additional actuators (not shown) may control various other friction devices, such as clutches and brakes, to selectively transfer power from the internal combustion engine 12 to the vehicle wheels (not shown).The transmission pump 16 is in fluid communication with the actuator 18 and, when active, provides hydraulic pressure to the actuator 18 and other components.

[0023] The vehicle 10 further includes a battery 18 and an auxiliary pump 20. The auxiliary pump 20 is an electric pump that is in fluid communication with the transmission 14, and in particular with the actuator 18. The auxiliary pump 20 is configured to provide hydraulic pressure to the transmission 14 using electrical power from the battery 18. Such pumps may be provided, for example, in stop-start vehicles configured to automatically stop a vehicle engine in response to a first set of predetermined operating conditions and restart the vehicle engine in response to a second set of predetermined operating conditions. Stop-start vehicles may be equipped with such auxiliary pumps to maintain hydraulic pressure in the transmission while the internal combustion engine 12 has been automatically stopped.Other vehicles that are not equipped with a start-stop function can also be equipped with an electric auxiliary pump.

[0024] The vehicle 10 includes a brake pedal 22 and an associated brake pedal sensor 24. The brake pedal sensor provides a signal in response to driver application of the brake pedal. The vehicle 10 also includes a driver ignition interface 26. The driver ignition interface 26 may, in various embodiments, comprise a key interface, a button, or other suitable interface. The driver ignition interface 26 provides a signal in response to driver input. The vehicle 10 further includes a gearshift interface 27. The gearshift interface 27 provides controls for receiving instructions for shifting between different gears. In various embodiments, the gearshift interface 27 may comprise a lever with PRND indicators, a rotary selector, or push buttons.

[0025] The internal combustion engine 12, the transmission 14, the auxiliary pump 20, the brake sensor 24, and the driver ignition interface 26 are all in communication with or controlled by at least one controller 28. In various embodiments, the controller or controllers 28 may be a vehicle system controller or multiple controllers that communicate with each other. The controller or controllers 28 may, of course, be in communication with various other sensors and vehicle components that may be Fig. 1 are not shown.

[0026] Now referring to Fig. 2, another embodiment of a vehicle according to the present disclosure is illustrated in schematic form. The vehicle 10' includes an internal combustion engine 12' and an electronically shifted transmission 14' with a transmission pump 16' and at least one actuator 18'. The vehicle 10' further includes a brake pedal 22' with an associated pedal sensor 24', a driver ignition interface 26', and a gearshift interface 27'. The vehicle further includes a hydraulic accumulator 30. The hydraulic accumulator 30 is in fluid communication with the transmission, in particular with the at least one actuator 18'. The accumulator 30 may be a spring-loaded accumulator, a pressurized gas-loaded accumulator, or any suitable mechanism for storing hydraulic fluid under pressure.

[0027] The internal combustion engine 12', the transmission 14', the accumulator 30, the brake sensor 24', the driver ignition interface 26', and the gearshift interface 27' are all in communication with or controlled by at least one controller 28'. In various embodiments, the controller or controllers 28' may be a vehicle system controller or multiple controllers that communicate with each other. The controller or controllers 28' may, of course, be in communication with various other sensors and vehicle components that are included in Fig. 2 are not shown.

[0028] In various other embodiments, other pressure sources may be used instead of an accumulator or electric motor. Generally speaking, any suitable pressure source designed to operate in the absence of engine power may be similarly installed in fluid communication with the transmission and used in conjunction with the system described below with reference to Fig. 3 described procedures can be used.

[0029] Now referring to Fig. 3, a method for controlling a vehicle according to the present disclosure is illustrated in flowchart form. The method begins with the engine 12 off and the transmission in PARK, as illustrated in block 40. In some embodiments, this may include engaging a parking pawl with a gear in the transmission.

[0030] Subsequently, a first driver input is received, as illustrated at 42. In various embodiments, the first driver input may include a key-on event or a brake pedal application, as illustrated at block 44. In further embodiments, other suitable driver inputs may be used. Generally speaking, a suitable first driver input confirms the driver's presence in the vehicle, thus preventing an inadvertent shift of the transmission out of PARK when no occupant is present.

[0031] In response to a first driver input, a pressure source is controlled to provide hydraulic pressure to the transmission, as shown at block 46. In one embodiment, the pressure source is an electric motor, as shown at number 20 in Fig. 1. In another embodiment, the pressure source is a pressure accumulator, as shown at number 30 in Fig.2. In further embodiments, other suitable pressure sources configured to selectively provide pressure in the absence of engine power may be used. Providing hydraulic pressure to the transmission includes providing hydraulic pressure to at least one actuator. The actuator is coupled to a parking pawl or other braking element.

[0032] A second driver input is received, as illustrated at block 48. The second driver input may be, for example, a driver selection of NEUTRAL on a gearshift module, as illustrated at block 50. In further embodiments, the second driver input may be another suitable input indicating the driver's intent to shift the vehicle out of PARK, such as a driver release of a parking brake.

[0033] The transmission is then shifted out of the PARK position, as illustrated at block 52. In embodiments that include a parking pawl selectively engaging a gear in the transmission, shifting the transmission out of the PARK position includes controlling an associated actuator to disengage the parking pawl from the gear in the transmission.

[0034] As can be seen from the various embodiments, the present invention provides a system and method for shifting an electronically shifted transmission out of the PARK position when an internal combustion engine 12 in the vehicle is off. Furthermore, the present invention provides such a system and method without the increased cost, complexity, and difficulty of access associated with a manual transmission overrun system.

[0035] Although the best mode has been described in detail, those skilled in the art will recognize various alternative concepts and embodiments within the scope of the following claims. As will be appreciated by those skilled in the art, while various embodiments have been described as being advantageous or preferred over other prior art embodiments with respect to one or more characteristics, trade-offs may be made between one or more characteristics to achieve desired system features, depending on the particular application and implementation. These features include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc.Thus, embodiments discussed herein that are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for certain applications.

Claims

[1] Vehicle (10), comprising: an internal combustion engine (12); an electronically shifted transmission (14) comprising a hydraulic actuator (18) coupled to a shift element configured to selectively shift the transmission (14) into the PARK position; a pressure source in fluid communication with the hydraulic actuator (18) and configured to selectively provide pressure in the absence of engine power; and a controller (28) configured to control the pressure source to provide hydraulic pressure to the hydraulic actuator (18) in response to a first driver input when the engine (12) is off, and wherein, in response to a second driver input when the engine (12) is off, the transmission (14) is shifted out of the PARK position without starting the engine (12), wherein the first driver input is a key-on event or an actuation of a brake pedal (22) by the driver. [2] A method of controlling a vehicle (10), the vehicle (10) comprising an electronically shifted transmission (14) having a parking lock and an electric auxiliary pump (20) in fluid communication with the parking lock, and comprising controlling the auxiliary pump (20) to provide hydraulic pressure to the parking lock, wherein controlling the electric auxiliary pump (20) is performed in response to the transmission (14) being in PARK, a first driver input, and the engine (12) being turned off, further comprising, without starting the engine (12), shifting the transmission (14) out of the PARK position in response to a second driver input, the first driver input being a key-on event or driver application of a brake pedal (22). [3] The vehicle (10) of claim 1, wherein the transmission (14) comprises a gear set and the shifting element comprises a parking pawl selectively engageable with the gear set to restrict movement of a vehicle (10). [4] The vehicle (10) of claim 1, wherein the pressure source comprises an electric motor. [5] Vehicle (10) according to claim 1, wherein the pressure source comprises a pressure accumulator (30). [6] The method of claim 2, wherein the parking lock comprises a parking mechanism configured to selectively restrict movement of the vehicle (10) while the vehicle (10) is unattended, and the parking lock further comprises a hydraulic actuator (18) in fluid communication with the accumulator (30) and configured to selectively disengage the parking mechanism.

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