Patent Application
20170203652
The present disclosure relates generally to power transfer systems for controlling the distribution of drive torque from a powertrain to front and rear drivelines of a four-wheel drive motor vehicle. More particularly, the present disclosure is directed to a compact transfer case configured to integrate a sprocket of a chain drive transfer assembly with a clutch drum of an actively-controlled multi-plate friction clutch assembly.
This section provides background information which is not necessarily prior art to the inventive concepts associated with the present disclosure.
Interest in four-wheel drive vehicles has led to development of power transfer systems configured to selectively and/or automatically direct rotary power (i.e. drive torque) from the powertrain to all four wheels of the vehicle. In many four-wheel drive vehicles, the power transfer system includes a transfer case configured to drivingly interconnect the powertrain to front and rear drivelines. More particularly, a majority of current transfer cases are configured to include a mainshaft or rear output shaft interconnecting the powertrain to the rear driveline, a front output shaft interconnected to the front driveline, a transfer assembly drivingly interconnected to the front output shaft, a mode clutch for selectively coupling the transfer assembly to the rear output shaft, and a clutch actuator for controlling actuation of the mode clutch. The mode clutch is operable in a first or “released” state to disconnect the front output shaft from the rear output shaft and establish a two-wheel drive mode (2WD) with all drive torque transmitted from the powertrain to the rear driveline. The mode clutch is also operable in a second or “engaged” state to drivingly connect the front output shaft (via the transfer assembly) to the rear output shaft and establish a four-wheel drive mode (4WD) with drive torque transmitted from the powertrain to both of the front and rear drivelines. Additionally, some two-speed transfer cases are equipped with a geared reduction unit operably disposed between the powertrain and the rear output shaft, and a range clutch that can be actuated for selectively establishing a direct ratio drive connection and a reduced ratio drive connection therebetween for providing four-wheel high-range and low-range drive modes.
Some “part-time” transfer cases are equipped with a positive-locking type of mode clutch, such as a dog clutch, which can be selectively actuated to shift between the two-wheel drive mode (2WD) and a locked four-wheel drive mode (LOCK-4WD). As an alternative, “active” transfer cases are equipped with an on-demand mode clutch, such as an adaptively-controlled multi-plate friction clutch, configured to automatically control the drive torque distribution between the front and rear drivelines without any input or action on the part of the vehicle operator so as to provide an on-demand four-wheel drive mode (AUTO-4WD) in addition to the two-wheel drive mode (2WD). Typically, active transfer cases also include a power-operated clutch actuator that is interactively associated with an electronic traction control system having a plurality of vehicle sensors. The power-operated clutch actuator regulates the magnitude of a clutch engagement force applied to the multi-plate friction clutch based on vehicular and/or road conditions detected by the sensors, thereby adaptively regulating the drive torque distribution ratio between the front and rear drivelines. This adaptive clutch control system can also be used in actively-controlled full-time transfer cases to automatically bias the torque distribution across an interaxle differential.
A majority of current transfer cases are also equipped with a chain and sprocket type of transfer assembly which typically includes a first sprocket rotatably supported on the rear output shaft, a second sprocket fixed for common rotation with the front output shaft, and a continuous chain encircling and drivingly interconnecting the first sprocket for common rotation with the second sprocket. The mode clutch is typically axially offset with respect to the first sprocket and disposed to surround the rear output shaft. Functionally, the mode clutch is operable to selectively/automatically couple the first sprocket to the rear output shaft so as to transfer drive torque to the front output shaft through the chain and sprocket transfer assembly. Thus, the axial dimensions of the first sprocket and the components of the mode clutch, as well as other components associated with the rear output shaft, largely dictate the overall axial length of the transfer case.
In the past, the vehicle ride height and suspension configuration for traditional four-wheel drive vehicles (i.e. trucks and sport utility vehicles) provided sufficient packaging volume to accommodate conventional part-time and active transfer cases. However, in view of increased demand for smaller four-wheel drive vehicles, the packaging volume allocated to the powertrain and the transfer case has been significantly reduced. To accommodate reduced packaging space requirements, alternative transfer case configurations have been developed. For example, commonly-owned U.S. Pat. No. 8,316,783 discloses an active transfer case having a traditional rear output shaft and mode clutch configuration now associated with a beveloid gearset type of transfer assembly and an angulated front output shaft arrangement. Alternatively, some transfer cases have been developed which locate the mode clutch and actuator components on the front output shaft as shown, for example, in U.S. Pat. No. 8,157,072.
While such alternative transfer case configurations attempt to address the recognized need for reduced packaging requirements, a need continues to exist to advance the technology and structure of transfer cases in a manner which provides enhanced configurations that improve upon otherwise conventional packaging arrangements.
This section provides a general summary of the inventive concepts associated with the present disclosure and is not intended to be interpreted as a complete and thoroughly comprehensive disclosure of all of its aspects, features, advantages and objectives.
It is an aspect of the present disclosure to provide a transfer case having reduced packaging requirements associated with a compact mode clutch and power transfer arrangement.
It is another aspect of the present disclosure to provide a transfer case for use in a four-wheel drive vehicle that is configured to provide a reduced axial length requirement by integrating components of a transfer assembly with components of a mode clutch to provide the compact mode clutch and power transfer arrangement.
It is a related aspect of the present disclosure to provide an active transfer case configured to integrate a clutch drum of an actively-controlled multi-plate mode clutch with a drive sprocket of a chain and sprocket type of transfer assembly to define an integrated torque transfer component.
It is another related aspect of the present disclosure to provide a part-time transfer case configured to integrate a clutch ring of a mechanically-actuated mode clutch with a drive sprocket of a chain and sprocket type of transfer assembly to define another integrated torque transfer component.
It is another aspect of the present disclosure to provide a transfer case having the integrated mode clutch and power transfer arrangement associated with the rear output shaft. In an alternative aspect, the transfer case of the present disclosure has the integrated mode clutch and power transfer arrangement associated with the front output shaft.
In accordance with these and other aspects, the present disclosure is directed to a transfer case for use in four-wheel drive motor vehicles to interconnect the powertrain to first and second drivelines. The transfer case is constructed to include a first shaft configured to transmit drive torque from the powertrain to the first driveline, a second shaft adapted for connection to the second driveline, and an integrated mode clutch and power transfer arrangement configured to selectively and/or automatically transmit drive torque from the first shaft to the second shaft. The integrated mode clutch and power transfer arrangement combines a clutch component of a mode clutch with a transfer component of a transfer assembly to define an integrated torque transfer component.
In accordance with an embodiment of the present disclosure, the integrated torque transfer component combines a clutch drum of a multi-plate friction mode clutch with a sprocket of a chain and sprocket type of transfer assembly to define a sprocket drum. The sprocket drum includes an axially-extending drum segment having sprocket teeth formed on its outer surface and spline teeth formed on its inner surface. The sprocket teeth are configured to be encircled and meshed with a chain of the chain and sprocket transfer assembly while the spline teeth are configured to engage clutch plates associated with a clutch pack of the mode clutch.
Further areas of applicability will become apparent from the description provided herein. As noted, the description and specific embodiments disclosed in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are only for purposes of illustrating selected embodiments and not all implementations or variations thereof. As such, the drawings are not intended to limit the scope of the inventive concepts associated with the present disclosure. In the drawings:
Corresponding reference numerals are used throughout the various views provided in the above-noted drawings to identify common components.
Example embodiments of a transfer case for use in four-wheel drive vehicles having a compact mode clutch and power transfer arrangement will now be described. However, these specific example embodiments are provided so that this disclosure will be thorough and will fully convey the intended scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known device structures and well-known technologies are not described in detail.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
Referring initially to
Front driveline 16 is the secondary driveline and is shown in
Powertrain 12 is also shown in
The power transfer system is shown to also include a power-operated clutch actuator 74 for controlling actuation of mode clutch 70, and a power-operated disconnect actuator 76 for controlling actuation of disconnect coupling 60. Controller 68 controls coordinated actuation of actuators 74, 76 in response to input signals from vehicle sensors 64 and mode signals from mode select mechanism 66. Vehicle sensors 64 are arranged and configured to detect certain dynamic and operational characteristics of vehicle 10 and/or current weather or road conditions.
To establish the 2WD mode, clutch actuator 74 is controlled to shift mode clutch 70 into a first or “released” mode while disconnect actuator 76 is controlled to shift disconnect coupling 60 into its disconnected mode. With mode clutch 70 in its released mode, no drive torque is transmitted through transfer assembly 72 to front output shaft 56 such that all drive torque generated by powertrain 12 is delivered to rear wheels 24 via rear driveline 14.
To establish the LOCK-4WD mode, disconnect actuator 76 is controlled to shift disconnect coupling 60 into its connected mode and clutch actuator 74 is controlled to shift mode clutch 70 into a second or “fully-engaged” mode. With mode clutch 70 operating in its fully-engaged mode, rear output shaft 36 is, in effect, drivingly coupled to front output shaft 56 via transfer assembly 72 such that drive torque is equally distributed (i.e. 50/50) therebetween. With disconnect coupling 60 in its connected mode, shaft segments 46A, 46B are drivingly coupled together such that drive torque delivered to front output shaft 56 is transferred via front driveline 16 to front wheels 44.
To establish the AUTO-4WD mode, disconnect coupling 60 is shifted into, or maintained in, its connected mode and clutch actuator 74 operates to adaptively regulate the drive torque distribution between rear output shaft 36 and front output shaft 56 by varying operation of mode clutch 70 between its released and fully-engaged modes. The torque distribution ratio is based on and determined by control logic associated with controller 68 which is configured to determine a desired or “target” amount of the total drive torque to be transmitted to front output shaft 56 based on the operating characteristics and/or road conditions detected by sensors 64.
Referring now to
In addition to first sprocket 82, transfer assembly 72 also includes a second transfer member or second sprocket 84 that is fixed to, or formed integrally with, front output shaft 56, and a continuous power chain 86 encircling and meshed with first sprocket teeth 88 formed on first sprocket 82 of sprocket drum 100 and with second sprocket teeth 90 formed on second sprocket 82. In the non-limiting embodiment shown, transfer assembly 72 is of the chain and sprocket type of drive torque transfer arrangement. Transfer case 22, as shown in
With continued attention to
Power-operated clutch actuator 74 is schematically shown in
Referring now to
With continued reference to
Force generating mechanism 74B is shown in the non-limiting embodiment disclosed in
Second cam ring 172 is configured to be both rotatably moveable and axially moveable relative to first cam ring 170 to create and transfer a clutch engagement force through pressure plate 74A to clutch pack 96. Second cam ring 172 is shown to include a sector-shaped extension 190 having gear teeth 192 formed along its peripheral edge surface. Rotation of second cam ring 172 relative to first cam ring 170 is caused by rotation of a toothed output component of powered driver unit 74C that is meshed with sector gear teeth 192. As a result of rotation of second cam ring 172 relative to first cam ring 170, second cam ring 172 translates axially in one of a first or “engaging” direction toward clutch pack 96 and a second or “releasing” direction away from clutch pack 96 based on the direction of rotation provided by the powered driver unit 74C.
Rotation of worm 200 in a first direction causes rotation of second cam ring 172 in a first rotary direction which, in turn, causes corresponding axial movement of second cam ring 172 in its releasing direction (right in drawings) to permit a biasing spring (not shown) to move pressure plate 74A in a releasing direction and placing mode clutch 70 in its released mode. In contrast, rotation of worm 200 in a second rotary direction causes rotation of second cam ring 172 in a second rotary direction which, in turn, causes corresponding axial movement of second ram ring 172 in its engaging direction (left in drawings) for forcibly moving pressure plate 74A in an engaging direction and shifting mode clutch 70 from its released mode into its engaged mode. The configuration of the aligned pairs of first and second cam tracks 176, 178 acts to coordinate the relationship between rotation and axial translation of second cam ring 172 relative to first cam ring 170.
As noted, the combination of clutch drum 92 associated with mode clutch 70 and drive sprocket 82 associated with transfer assembly 70 in a radially stacked arrangement provides transfer case 22 with a compact mode clutch and power transfer configuration. Sprocket teeth 88 (formed on exterior surface of sprocket/drum segment 156) and spline teeth 160 (formed on interior surface of sprocket/drum segment 156) can include complimentary profiles or, in the alternative, be formed with non-complimentary profiles. Sprocket drum 100 can be a net formed component or a machined component. The radial dimension of transfer case 22 is not detrimentally impacted since chain 86 encircles and rides directly on sprocket teeth 88 formed directly on the external surface of sprocket drum 100.
Referring to
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
