This application is a national stage of, and claims priority to, Patent Cooperation Treaty Application No. PCT/IB2019/000437, filed on Mar. 26, 2019, which application is hereby incorporated herein by reference in its entirety.
The disclosure herein relates to a disconnectable coupling device with lubrication control applicable to a final drive unit in an AWD vehicle.
In an all-wheel drive (AWD) vehicle, a torque generated by an engine and/or an electric motor is transmitted through a transmission to main driving wheels and is partly extracted and transmitted through a power transfer unit (PTU) to other driving wheels. A final drive unit (FDU) receives and distributes the extracted torque to the right and left wheels. A clutch system can be included as part of the FDU or provided as an external device to cut off torque transmission in order to form a part-time or on-demand AWD system. A wet multi-plate clutch is applicable to this clutch system and may be preferable as it allows limited slippage available for absorbing shocks at a time of drive mode changes. PCT Publications WO2018/031016 and WO2017/141829 disclose related arts.
Wet multi-plate clutches require moderate lubrication because otherwise adhesion or sticking between adjacent plates would occur. The inventors have found typically there is some difficulty in lubrication in a system in which a common housing accommodates both a differential and the multi-plate clutch and rotation of the differential is used for supplying lubricant to all of the accommodated elements. It has been found that the rotation of the differential does spread the lubricant but is not enough to generate a driving force against intervening obstacles such as a partition in the housing. The device described hereinafter addresses this problem.
According to an aspect, a disconnectable coupling device rotatable about an axis is provided with a first shaft having an end and a hub formed on the end, the hub including a flange extending radially from the end, and a round wall projecting axially from the flange and defining a hollow; a second shaft aligned with the first shaft and opposed to the end of the first shaft, the second shaft having a drum overhanging the hub; a multi-plate clutch held between the hub and the drum to disconnectably connect the hub with the drum; a cup so fixed with the hub so as to define a gutter around the first shaft; and one or more perforations axially passing through the flange to establish fluid communication between the gutter and the hollow.
Exemplary embodiments will be described hereinafter with reference to
In these drawings, a reference sign F denotes forward, A aftward, R rightward, and L leftward, respectively. These designations are, however, merely for convenience of explanation, and modified embodiments by interchanging the right and the left, or the front and the rear, are possible.
Any disconnectable coupling device disclosed hereinafter could include, without limitation, a vehicle driveline, particularly to a final drive unit (FDU) in an all-wheel drive (AWD) vehicle exemplarily illustrated in
A disconnectable coupling device 11 of the present embodiment is installed in the FDU 9 and used in combination with the differential 9D. Needless to say, the device 11 may be installed anywhere and used in combination with any device in the vehicle. Referring to
The disconnectable coupling device 11 is generally provided with a first shaft 13 with a hub 31, a second shaft 15, a multi-plate clutch 17 for disconnectably connecting the first shaft 13 with the second shaft 15, a cup 19 fixed with the hub 31, and an actuator 25 for applying a pressure force on the clutch 17. These elements are carried by a housing typically, but not necessarily, made up of a first portion 41 and a second portion 43, which may further compose a part of a housing of the FDU 9.
The first portion 41 thus partly, but not entirely, obstructs fluid communication between the differential 9D and the device 11. Lubricant spread by the differential 9D mainly flows through a limited space around the first shaft 13 into the device 11. The cup 19 by itself, or in combination with the hub 31, defines a gutter 21 for collecting and guiding a considerable amount of lubricant from the first shaft 13 through the inside of the hub 31 to the multi-plate clutch 17. Details of the cup 19 and the gutter 21 will be described later.
The first shaft 13 is a shaft rotatable about a rotational axis C. The first shaft 13 is led out, i.e., extends, through an opening in the first portion 41 toward the differential 9D, and around its led-out end any structure can be formed for linking with the differential 9D, such as splines. There may be some space between the first shaft 13 and the opening on the first portion 41, as described already.
Referring to
The structure as described above is beneficial in forming the first shaft 13 and the hub 31 in a unitary body by casting, forging, cutting out from a bulk ingot, or any suitable forming method. The first shaft 13 and the hub 31 may be nonetheless formed in separate bodies and thereafter unitized by engaging, press-fitting, welding or any unitization method.
The hub 31 may have any structure such as openings for allowing the lubricant to flow from around the first shaft 13 into the multi-plate clutch 17.
Referring again to
The second shaft 15 may be formed as a tubular structure and the interior thereof may have any structure such as splines for linking with an axle or a shaft to the axle. A flange radially projects from the shaft 15 exterior, and a drum 37 is fixed or formed as a unitary, i.e., single, part with the flange. The drum 37 overhangs the hub 31 and thereby forms an external structure of the clutch 17. The inner periphery of the drum 37 has any structure such as keys or lugs for engaging with outer plates of the multi-plate clutch 17.
Inner and outer plates of the clutch 17 are alternately arranged and are respectively engaged with the lugs of the hub 31 and the drum 37. The multi-plate clutch 17 is thereby held between the hub 31 and the drum 37. When a sufficient thrust force is applied thereto, the clutch 17 connects the hub 31 with the drum 37 and then transmits the torque from the first shaft 13 to the second shaft 15.
The actuator 25 is a device for exerting the thrust force on the multi-plate clutch 17. Applicable devices include, without limitation, a hydraulic actuator, a pneumatic actuator, an electromagnetic actuator, and a cam mechanism 25 as illustrated in
The cam mechanism 25 is a device for converting a torque into a thrust force. The cam mechanism 25, as best understood from
The cup 19 may be formed in a relatively broad and shallow cup-like or pan-like shape with an opened bottom 19B, as best seen in
The outer wall of the cup 19 is fitted on or fixed with the hub 31, particularly on the outer periphery of the flange 31F and/or its wall 31W for instance. The outer wall extends in the direction opposite to the wall 31W relative to the flange 31F and the first shaft 13 passes through the opening of the bottom 19B. The fitting or fixation may be created by press-fitting, and correspondingly the wall 31W may include a stepwise narrowed portion to receive the fitted-on cup 19 as shown in
The device 11 may, although does not necessarily, have another lubricant pathway. One example thereof is a passage 45 as shown in
In any of these cases, the gutter 21 pools a considerable amount of the lubricant therein and the rotating cup 19 in turn exerts a centrifugal force on the pooled lubricant but dams it radially, thereby creating an axial driving force that urges the lubricant to flow beyond the adjacent perforations 23 into the hollow 33.
To pool a sufficient amount of the lubricant and/or promote the axial flow toward the perforations 23, as shown in
Referring again to
In contrast, when the device 11, particularly the first shaft 13, stops rotating, the lubricant supply would concurrently halt as the centrifugal forces no longer act thereon. This is beneficial in getting the clutch 17 connected because excessive lubricant would not intrude into the mutually parted clutch plates. It is additionally noted that disconnection of the clutch 17 and suspension of rotation of the first shaft 13 would concurrently occur particularly in a case where the PTU 5 includes the cut-off device to stop the propshaft 7 as described earlier. The device disclosed herein thus provides necessary and sufficient lubrication control automatically.
It is additionally noted that, absent the structures described above, the hollow 33 might be hardly usable as a main route for the lubricant because the hollow 33 is hidden behind the hub 31 and the drum 37 but the above embodiments can impel a sufficient amount of the lubricant through the perforations 23 and use centrifugal force in the hollow 33 for feeding the lubricant to the clutch 17.
Although certain exemplary embodiments are described above, modifications and variations of the embodiments will occur to those skilled in the art, in light of the above teachings.
Filing Document | Filing Date | Country | Kind |
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PCT/IB2019/000437 | 3/26/2019 | WO |
Publishing Document | Publishing Date | Country | Kind |
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WO2020/194020 | 10/1/2020 | WO | A |
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Entry |
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International Search Report and Written Opinion dated Nov. 19, 2019 for PCT/IB2019/000437 (10 pages). |
Number | Date | Country | |
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20220120322 A1 | Apr 2022 | US |