Patent Application
20150308571
The present invention relates to automatic transmissions and in particular to shift-by-wire transmissions.
A traditional automatic transmission includes a transmission control device employed to control the transmission of a motor vehicle. The transmission control device is used to select several ranges, such as Park, wherein the transmission is locked to prevent the vehicle from moving, Neutral, wherein the transmission allows the vehicle to be moved freely, such as when being towed, Reverse, wherein the transmission allows the vehicle to move backwards, and one or more Drive ranges that enable forward motion of the vehicle. Usually, the transmission control device is in the form of a lever connected to the transmission via a mechanical connection, such as a cable. Typically, the lever is also connected to an indicator. As the transmission control mechanism is moved from one range to another, the mechanical connection physically shifts the transmission to the selected setting and the indicator moves to show the driver which range has been selected. Even if the vehicle is turned off, the driver is able to determine the current transmission range from the indicator and, in some cases, is able to move the transmission control mechanism to Neutral if, for example, the vehicle is to be towed.
The traditional automatic transmission utilizes multiple friction elements for automatic gear ratio shifting. Broadly speaking, these friction elements may be described as torque establishing elements although more commonly they are referred to as clutches or brakes. The friction elements function to establish power flow paths from an internal combustion engine to a set of vehicle traction wheels. During acceleration of the vehicle, the overall speed ratio, which is the ratio of a transmission input shaft speed to a transmission output shaft speed, is reduced during a ratio upshift as vehicle speed increases for a given engine throttle setting. A downshift to achieve a higher speed ratio occurs as an engine throttle setting increases for any given vehicle speed, or when the vehicle speed decreases as the engine throttle setting is decreased. Various planetary gear configurations are found in modern automatic transmissions. However, the basic principle of shift kinematics remains similar. Shifting an automatic transmission having multiple planetary gear sets is accompanied by applying and/or releasing friction elements to change speed and torque relationships by altering the torque path through the planetary gear sets. Friction elements are usually actuated either hydraulically or mechanically based on the position of the transmission control device.
In a shift-by-wire transmission arrangement, the mechanical connection between the transmission control device and the transmission is eliminated. Instead, the transmission control device transmits an electrical signal to an electronic controller, which directs separate actuators to apply or release the various friction elements to obtain a desired gear ratio. The control device is no longer necessarily in the form of a lever because the control device is no longer moving a mechanical connection for controlling the transmission. Instead, the control device is typically an electro-mechanical interface (e.g., a series of buttons, lever or knob) that is used to instruct the transmission to switch between the transmission ranges.
A shift-by-wire transmission according to the present disclosure includes a shiftable member that is selectively engageable with a park gear gear to put the vehicle in PARK. The transmission additionally includes a first intermediate member that is coupled with the shiftable member. The first intermediate member has an engaged position and a disengaged position and is biased toward the engaged position. The engaged position corresponds with the shiftable member being engaged with the gear, and the disengaged position corresponds with the shiftable member being disengaged from the gear. The transmission additionally includes an actuator coupled with the shiftable member via the first intermediate member. The transmission further includes a second intermediate member. The second intermediate member has a nominal position and an override position. In the nominal position the second intermediate member does not move in response to the first intermediate member moving between the engaged position and disengaged position. In addition, moving the second intermediate member from the nominal position to the override position moves the first intermediate member from the engaged position to the disengaged position.
In some embodiments, the first intermediate member includes a first hub and the second intermediate member includes a second hub. The first and second hubs are pivotable about a common axis. Moving the first intermediate member from the engaged position to the disengaged position includes pivoting the first hub about the axis, and moving the second intermediate member from the nominal position to the override position includes pivoting the second hub about the axis. In one such embodiment, the second hub is coupled to and configured to jointly pivot with a flange. The flange has a plane of pivoting motion. The first hub has an outer face and a pin extending from the outer face through the plane of pivoting motion, such that pivoting the second intermediate member from the nominal position to the override position engages the flange with the pin to pivot the first intermediate member from the engaged position to the disengaged position. In some embodiments, the transmission additionally includes a fastener removably retaining the second intermediate member in the nominal position.
A shift-by-wire transmission assembly according to the present disclosure includes a first member that is moveable between engaged and disengaged positions and a second member that is moveable between nominal and override positions. The first member is biased to the engaged position. The transmission assembly additionally includes an actuator configured to move the first member from the engaged to the disengaged positions while the second member remains stationary. Moving the second member from the nominal to override positions moves the first member from the engaged to disengaged positions.
In one embodiment, the first member and second member are pivotable about a common axis. The first member is moveable between the engaged and disengaged positions by pivoting about the axis and the second member is movable between the nominal and override positions by pivoting about the axis.
In an additional embodiment, moving the second member from the nominal to override positions moves the first member from the engaged to disengaged positions, and further to a first member override position. Some such embodiments additionally include a controller. The controller is configured to, in response to the first member being moved to the first member override position, signal an alert to a driver indicating that a transmission override mode is enabled.
Some embodiments additionally include a fastener removably retaining the second member in the nominal position. Various other embodiments additionally include a spring biasing the second member in the nominal position. Some embodiments include a parking pawl coupled with the first member selectively engageable with a gear. In such embodiments, the first member engaged position corresponds with the parking pawl being engaged with the gear, and the first member disengaged position corresponding with the parking pawl being disengaged from the gear.
An override system for a transmission according to the present disclosure includes a first hub coupling a hydraulic or electric actuator with a parking pawl. The parking pawl is selectively engaged with a gear. The first hub is configured to pivot about an axis, with an engaged position corresponding with the parking pawl being engaged with the gear and a disengaged position corresponding with the parking pawl being disengaged from the gear. The override system additionally includes a second hub that is configured to pivot about the axis. The second hub has a nominal position and an override position. When in the nominal position, the second hub does not move in response to the first hub moving between the engaged and disengaged positions. Furthermore, moving the second hub from the nominal position to the override position moves the first hub from the engaged position to the disengaged position.
In one embodiment, the override system additionally includes a finger member coupled with the second hub and configured to pivot with the second hub. The finger member has a pivot plane. The override system additionally includes a pin extending from a face of the first hub through the pivot plane, such that moving the second hub from the nominal position to the override position engages the finger member with the pin and moves the first hub from the engaged position to the override position.
Some embodiments additionally include a fastener removably retaining the second hub in the nominal position. In one embodiment, moving the second hub from the nominal position to the override position moves the first hub from the engaged position to the disengaged position, and further to a first hub override position. Such an embodiment may additionally include a controller configured to, in response to the first hub being moved to the first hub override position, signal an alert to a driver indicating that a transmission override mode is enabled.
Embodiments according to the present disclosure provide a number of advantages. For example, the present disclosure provides an override for shifting a transmission out of park in the absence of engine power. Systems and methods according to the present disclosure may avoid routing override cables to a passenger cabin, thus reducing packaging complexity and cost. Furthermore, systems and methods according to the present disclosure provide an externally accessible lever that remains stationary during normal operating conditions, and thus is less susceptible to damage due to mud or ice buildup on the lever.
The above advantage and other advantages and features of the present disclosure will be apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings.
As required, detailed embodiments of the present invention are disclosed herein; however, it is to 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. Therefore, 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 to variously employ the present invention.
A shift-by-wire transmission refers to an arrangement having no mechanical connection between a transmission control device and the transmission. Instead, a user-operated gear shift module transmits an electrical signal to an electronic controller, which directs separate actuators to apply or release the various friction elements, such as clutches or brakes, to obtain a desired gear ratio. In some embodiments, the transmission may be provided with a parking pawl that is operated by one of the actuators. The parking pawl may engage with at least one gear in the transmission to inhibit vehicle motion or release from the at least one gear to permit vehicle motion. The parking pawl may be engaged in response to a driver shifting the transmission to PARK. Of course, various other parking elements may also be used to inhibit vehicle motion, such as a parking brake.
In some configurations, the actuators operating the friction elements and parking pawl are hydraulic actuators. Under normal vehicle operation, an engine drives a transmission pump to supply hydraulic pressure to the actuators and enable application or release of the friction elements or parking brake. Because there is not a mechanical connection between the gear shift module and the transmission, in the absence of hydraulic pressure to the actuators, a driver will be unable to shift the transmission between gears. When the engine is off, the gear shift module may not be usable to shift gears.
Under some circumstances, however, it may be desirable to shift the vehicle from PARK to another gear without the engine running. For example, if the engine is inoperable, it may be desirable to shift the transmission out of PARK to facilitate towing. As an additional example, it may be desirable to roll the vehicle to a new location without running the engine. Using the standard gear shift module, shifting out of PARK without operating the engine is not possible. Consequently, the transmissions may be provided with a manual override mechanism. This may include a mechanism available under the vehicle hood or a cable mechanism available within the cabin. Such solutions may be difficult for a user to access, difficult to route through a vehicle, and also add complexity and cost to the vehicle. In addition, known override mechanisms that are accessible under the vehicle hood include an external override lever that moves during normal transmission operation. Such external moving parts are susceptible to mud, snow, ice, or other debris accumulating and inhibiting transmission operation.
Referring now to
The vehicle 10 additionally includes a sensor 20 configured to detect a position of the parking override device 18. The sensor 20 is in communication with or under the control of at least one controller 22. In various embodiments, the controller or controllers 22 may be a vehicle system controller or a plurality of controllers in communication with each other. The controller or controllers 22 may, of course, be in communication with various other sensors and vehicle components not illustrated in
Referring now to
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The parking override assembly additionally includes an override lever 50 that is also configured to pivot about the pivot axis 42. The override lever 50 is configured to pivot between various positions, including a first position, which may be a “nominal” position for normal operation, and a second position, which may be an “override” position. The override lever 50 is positioned outside the case for ease of access. The override lever 50 is configured to pivot separately from the inner lever 40, such that as the inner lever 40 pivots between the “PARK” and “not PARK” positions during normal operation, the override lever remains stationary. The override lever 50 is coupled with an actuating arm or finger 52, such that the override lever 50 and actuating arm 52 pivot together about the pivot axis 42. The actuating arm 52 is preferably retained within a transmission case. The actuating arm 52 defines a plane of pivoting motion that passes through the pin 46 of the inner lever 40. The override lever 50 includes a first fastener hole 54 with an associated fastener securing the override lever 50 to the transmission case. The override lever 50 additionally includes a second fastener hole 55. The override lever 50 may also include an extension spring 56 coupled to the actuating arm 52 and biasing the override lever 50 toward the nominal position.
Referring now to
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In
In
In a preferred embodiment, β degrees is a greater angular displacement than required to move the inner lever 40 from the “PARK” position to the “not PARK” position. In such an embodiment, pivoting the inner lever β degrees moves the inner lever 40 from the “PARK” position to a third position, which may be an override position. Preferably a sensor, such as sensor 20 illustrated in
Variations on the above are, of course, possible. For example, in some embodiments, a cabling system may be provided from the override lever into a vehicle cabin, enabling a driver to manually shift the vehicle out of PARK without accessing the engine compartment. Additionally, in some embodiments, no extension spring is included to bias the override lever toward the nominal position. In such embodiments, only a fastener is included to maintain the override lever in the nominal position.
As may be seen from the above description, the present disclosure provides an override for shifting a transmission out of park in the absence of engine power, where the override includes an override lever that remains stationary during normal operating conditions and thus is less susceptible to damage due to mud or ice buildup on the lever. Furthermore, systems and methods according to the present disclosure may avoid routing override cables to a passenger cabin, thus reducing packaging complexity and cost.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.
