Rotary coupling for an all-wheel drive vehicle

A rotary coupling (200) for an all-wheel drive vehicle includes a housing (210), an input part (212), an output part (214), and a clutch (220) disposed within a clutch area (222) of the housing (210) and is movable between an engaged position and a disengaged position to change an amount of torque transferred from the input part (212) to the output part (214). A fluid reservoir (260) is defined in the housing (210). A lubrication valve (250) is movable between an open position and a closed position for controlling supply of a fluid from the fluid reservoir (260) to the clutch area (222) of the housing (210). An actuator (238) is connected to the clutch (220) to move the clutch (220) between the engaged position and the disengaged position and connected to the lubrication valve (250) to move the lubrication valve (250) between the open position and the closed position.

BACKGROUND

This application claims the benefit of U.S. Provisional Application No. 62/100,123, which was filed on Jan. 6, 2015.

BACKGROUND

All-wheel drive drivetrains for vehicles allow driving power to be delivered to all four wheels of the vehicle. By delivering driving power to all four wheels, vehicle performance is improved when surface conditions are poor. As examples, all-wheel drive systems can improve vehicle performance when road surfaces are slippery as a result of rain or snow, and when the road surface itself is of poor quality, such as dirt or gravel road surfaces.

In all wheel-drive vehicles with a transversely mounted front engine layout, a transaxle is typically utilized to provide a desired gear ratio and to distribute driving power to the left and right front wheels by way of a front differential and a front axle. A power transfer unit receives driving power from the front axle and transfers driving power to the rear wheels of the vehicle by way of a driveshaft, a rear differential, and a rear axle. In some implementations, a rotary coupling is provided to connect and disconnect power transfer to the rear wheels, and/or to prevent rotation of driveline components such as the drive shaft when power is not being supplied to the rear wheels. Some rotary couplings are also able to vary the amount of torque provided to the rear wheels of the vehicle.

One design for a rotary coupling uses a hydraulic clutch to connect and disconnect torque transmission between an input part and an output part. The terms “input part” and “output part” are used for convenience, and are not intended to imply that torque is always applied at the input part, as this can vary based on the configuration of a vehicle and the circumstances under which it is operated. When the clutch is engaged to transfer torque between the input part and the output part, hydraulic fluid within the clutch is utilized to lubricate and cool the clutch pack. When the clutch is disengaged, however, the presence of hydraulic fluid within the clutch pack can cause unintended partial engagement of the clutch, resulting in parasitic losses.

SUMMARY

A rotary coupling for an all-wheel drive vehicle includes a housing, an input part, an output part, and a clutch disposed within a clutch area of the housing and is movable between an engaged position and a disengaged position to change an amount of torque transferred from the input part to the output part. A fluid reservoir is defined in the housing. A lubrication valve is movable between an open position and a closed position for controlling supply of a fluid from the fluid reservoir to the clutch area of the housing. An actuator is connected to the clutch to move the clutch between the engaged position and the disengaged position and connected to the lubrication valve to move the lubrication valve between the open position and the closed position.

A drivetrain for an all-wheel drive vehicle includes an engine, a transmission, at least a first wheel, and a rotary coupling (200) that is operable to selectively deliver driving power to the first wheel. The rotary coupling includes a housing (210), an input part (212), an output part (214), and a clutch (220) that is disposed within a clutch area (222) of the housing (210) and is movable between an engaged position and a disengaged position to change an amount of torque transferred from the input part (212) to the output part (214). The rotary coupling also includes a fluid reservoir defined in the housing, and a lubrication valve that is movable between an open position and a closed position for controlling supply of a fluid from the fluid reservoir to the clutch area of the housing. The rotary coupling also includes an actuator that is connected to the clutch to move the clutch between the engaged position and the disengaged position and connected to the lubrication valve to move the lubrication valve between the open position and the closed position.

DETAILED DESCRIPTION

The disclosure herein is directed to a rotary coupling for an all-wheel drive vehicle.

FIG. 1shows a drivetrain100for an all-wheel drive vehicle that includes a rotary coupling200. It should be understood that the drivetrain100ofFIG. 1is an example of an application in which the rotary coupling200can be utilized. The rotary coupling200can also be utilized in other drivetrains of various configurations for the same purpose of for a different purpose.

The drivetrain100includes an engine110that is coupled to a transmission112. The engine110is the prime mover of the drivetrain100and can be, as examples, an internal combustion engine, an electric motor/generator, or a combination of the two. Other types of prime movers can be utilized as the engine110to provide driving power (e.g. via a rotating output shaft) to the transmission112. The transmission112includes components operable to convert the speed and torque of the driving power provided by the engine110, such as by a gear train that provides multiple gear ratios. As examples, the transmission112can be a manual transmission, an automatic transmission, a semi-automatic transmission, a continuously variable transmission, or a dual clutch transmission. In the illustrated example, the engine110is front-mounted in a transverse configuration and the transmission112is an automatic transaxle.

The transmission112provides driving power to a front axle114and to a power transfer unit116. The front axle114can be, as examples, a solid axle or a pair of independent half axles. The front axle114drives a pair of wheels115that are fitted with tires.

The power transfer unit116is operable to transfer a portion of the driving power from the transmission112to a driveshaft118. The power transfer unit116can also be operable to connect and disconnect transmission of driving power to the driveshaft118, such as by incorporating a clutch.

The driveshaft118extends from the power transfer unit116to the rotary coupling200. The rotary coupling200is operable to connect and disconnect transmission of torque using a clutch (not shown inFIG. 1). This allows the driveshaft118to be disconnected from the rear wheels of the vehicle when the power transfer unit116is disengaged to prevent rotation of the driveshaft118via the rear wheels of the vehicle. The rotary coupling200can also be operable to transmit driving power of a desired degree, such as by slipping engagement of the clutch, to allow variable distribution of driving power to the front and rear wheels of the vehicle.

A rear differential122receives driving power from the rotary coupling200and distributes the driving power to a rear axle124. The rear axle124can be, as examples, a solid axle or a pair of independent half axles. The rear axle124provides driving power to a pair of rear wheels125that are fitted with tires.

As seen inFIGS. 2-4, the rotary coupling200includes a housing210that surrounds and encloses some of the components of the rotary coupling200. An input part, such as an input flange212, and an output part, such as an output hub214, are accessible from outside of the housing210. Thus, the input flange212and the output hub214are connectable to other components of a vehicle drivetrain, such as the driveshaft118and the rear differential122of the drivetrain100for receiving and/or supplying driving power.

The input flange212is connected to an input shaft216, which is supported for rotation with respect to the housing210by bearings218. The input flange212rotates in unison with the input shaft216, such as by a splined connection.

The input shaft216is connected to the output hub214by a clutch220. The clutch220is disposed within a clutch area222of the housing210and is disposed radially around the input shaft216and the output hub214. The clutch220is movable between an engaged position and a disengaged position to change an amount of torque transferred from the input flange212and the input shaft216to the output hub214.

The clutch220includes a clutch drum224. The clutch drum224is connected to the output hub214for rotation in unison with the output hub214. The clutch drum224has a radial wall226that is disposed in the clutch area222of the housing. The radial wall226of the clutch drum and the clutch area222are both generally circular when viewed along the axis of the input shaft216, with a maximum outside diameter of the radial wall226being slightly smaller than an inside diameter of the clutch area222.

The clutch220includes a clutch pack228. The clutch pack228includes a plurality of interleaved clutch plates that are engageable with one another to cause torque transmission from the input shaft216to the clutch drum224. A first group of the interleaved plates of the clutch pack228is connected to the input shaft216. A second group of the interleaved plates of the clutch pack228is connected to an interior surface of the radial wall226of the clutch drum224.

The clutch220includes an apply plate230that is connected to the input shaft216for rotation in unison with the input shaft216but is able to slide axially with respect to the input shaft216. For example, the apply plate230can be connected to the input shaft216by axially extending splines.

The apply plate230is operable to apply pressure to the clutch pack228by moving axially toward and away from the clutch pack228. Application of pressure to the clutch pack228by the apply plate230moves the clutch220from a disengaged position toward an engaged position by increasing the degree by which torque is transmitted between the first and second groups of interleaved plates of the clutch pack228. The apply plate230may be biased away from engagement with the clutch pack228by one or more springs232, such that the clutch220moves toward the disengaged position as a result of the force applied by the springs232absent actuation of the clutch220by an external actuator. In this example, actuation is provided by an apply collar234that, when rotated, applies pressure to the apply plate230via a cam mechanism236.

In order to actuate movement of the clutch220between the engaged and disengaged positions, the rotary coupling200includes an actuator238, such as an electrical motor that is operable to rotate an actuator shaft240. In the illustrated example, the actuator238is connected to the apply collar234by engagement of a first sector gear235with a drive gear242. The first sector gear235is attached to or formed on the apply collar234and extends outward with respect to a nominal diameter of the apply collar234. The drive gear242is attached to or formed on the actuator shaft240. Thus, rotation of the actuator shaft240by the actuator238is operable to apply pressure to the clutch pack228via the drive gear242, the first sector gear235, the apply collar234, the cam mechanism236, and the apply plate230.

In the illustrated example, the clutch220and a lubrication valve250are both driven between their respective positions by rotation of the actuator shaft240by the actuator238. Thus, a single actuator is operable to control both the clutch220and the lubrication valve simultaneously with a rotational action. This arrangement eliminates the need for separate actuators and in some implementations can reduce the need for multiple electrical and/or hydraulic connections that may be required for separate actuators.

As best seen inFIGS. 5-8, the actuator238moves the lubrication valve250between open and closed positions to control flow of a lubricating fluid to the clutch220. As examples, the lubricating fluid can be hydraulic fluid or automatic transmission fluid. In the illustrated example, a plurality of gear teeth244are formed on the apply collar234and thus rotate when the apply collar234is rotated by the actuator via the first sector gear235and the drive gear242. A second sector gear246is connected to the lubrication valve250such that the second sector gear246and the lubrication valve250rotate on a common axis of rotation. The gear teeth of the second sector gear246mesh with the plurality of gear teeth244on the apply collar234such that the second sector gear246rotates in response to rotation of the apply collar234.

In order to store the lubricating fluid, the housing210defines a fluid reservoir260. One end of the fluid reservoir260is sealed from a remainder of the interior of the housing210by a cover plate261. The lubrication valve250extends into the fluid reservoir260, for example, by extending through or adjacent to the cover plate261.

The fluid reservoir260has an inlet262that is in communication with the clutch area222of the housing210. Thus, the fluid reservoir260receives the lubricating fluid from the clutch area222via the inlet262. The inlet262is positioned above the clutch area222, at the top of the circular shape defined by the clutch area222. The angular orientation of the rotary coupling200shown inFIGS. 5-8is representative of the angular orientation at which the rotary coupling200will be installed when utilized in a vehicle. Thus, as will be explained further herein, the lubricating fluid enters the inlet262from the clutch area222upon being pumped to the top of the clutch area222. The lubricating fluid exits the fluid reservoir260and is directed to the clutch220via a first fluid supply path270and a second fluid supply path272, with the lubrication valve moving between open and closed positions to permit or block fluid from the fluid reservoir260to the first fluid supply path270and the second fluid supply path272.

The lubrication valve250is a rotary valve that moves between various positions by rotating with respect to the housing210along its axis. As previously described, the lubrication valve250is rotated by the second sector gear246. Movement of the lubrication valve250is constrained to axial rotation by engagement with surfaces of the housing210that engage the lubrication valve250. It should be understood, however, that other types of valves and actuators could be used.

In order to selectively block and establish fluid flow to the first fluid supply path270and the second fluid supply path272, the lubrication valve250defines one or more passages that block or permit fluid flow dependent upon the rotational position of the lubrication valve250with respect to the housing210. In the illustrated example, a first passage252and a second passage254are formed on the lubrication valve250.

The first passage252of the lubrication valve250allows selective fluid supply from the fluid reservoir260to the first fluid supply path270. Rotation of the lubrication valve250moves the first passage252between an open position and a closed position. In the open position, fluid flow from the fluid reservoir260to the first fluid supply path270is permitted, with the first passage252being at least partially in registration with the fluid reservoir260. In the closed position, the outer surface of the lubrication valve250abuts the fluid reservoir260in the area adjacent to the first fluid supply path270, thereby blocking fluid flow from the fluid reservoir260to the first fluid supply path270.

The second passage254of the lubrication valve250allows selective fluid supply from the fluid reservoir260to the second fluid supply path272. Rotation of the lubrication valve250moves the second passage254between an open position and a closed position. In the open position, fluid flow from the fluid reservoir260to the second fluid supply path272is permitted, with the second passage254being at least partially in registration with the fluid reservoir260. In the closed position, the outer surface of the lubrication valve250abuts the fluid reservoir260in the area adjacent to the second fluid supply path272, thereby blocking fluid flow from the fluid reservoir260to the second fluid supply path272.

Because the first passage252and the second passage254are both formed on the lubrication valve250, the geometry of the first passage252and the second passage254dictates the relative timing of opening and closing of the first passage252and the second passage254. For example, by forming the first passage252and the second passage254on the lubrication valve250at similar angles and geometries, rotation of the lubrication valve250can cause the first passage252and the second passage254to open and close concurrently. As an alternative, forming the first passage252and the second passage254on the lubrication valve250at different angles and/or geometries will result in rotation of the lubrication valve250causing the first passage252and the second passage254to open and close at different times. For example, the first passage252could open slightly prior to opening of the second passage254.

The first fluid supply path270is operable to supply the lubricating fluid to a first pumping mechanism that is defined by a plurality of channels282that are formed in the apply plate230. The channels282extend inward from an outer periphery of the apply plate230at an angle with respect to a radial direction, as best seen inFIG. 7. In an alternative implementation, the first pumping mechanism can be formed separately from the apply plate230, as a disk-shaped member that incorporates the channels282.

As the apply plate230rotates in unison with the input shaft216, the fluid supplied by the first fluid supply path270enters the channels282and is pressurized and forced radially inward along the channels282toward a plurality of axial flow paths284that are defined in the input shaft216, as shown inFIG. 8. The lubricating fluid exits the input shaft216via radial ports (not shown) that are formed in the input shaft216into the clutch pack228. The lubricating fluid then exits the clutch pack228via radial ports (not shown) that are formed through the radial wall226of the clutch drum224into the clutch area222.

The second fluid supply path272is operable to supply the lubricating fluid to the clutch area222of the housing adjacent to the radial wall226of the clutch drum224. Here, the lubricating fluid from the second fluid supply path272joins the lubricating fluid that exits the clutch pack228via the radial ports that are formed through the radial wall226of the clutch drum224.

A plurality of features such as axially extending ridges290(which may also be referred to as corrugations) are formed on the exterior of the radial wall226of the clutch drum224. Because axially extending ridges290are positioned closely to the interior wall of the clutch area222of the housing210, they define a second pumping mechanism that is operable to pump fluid from the clutch area222of the housing to the inlet262of the fluid reservoir260. In particular, the axially extending ridges290create a variable distance between the clutch drum224and the interior wall of the clutch area222. A portion of the lubricating fluid that is present in the clutch area222of the housing210becomes captured in the valley between successive ones of the axially extending ridges290, and enters the reservoir upon reaching the inlet262. Other types of features can be utilized to define the second pumping mechanism on the clutch drum224instead of the axially extending ridges290.

In operation, the actuator238moves the clutch220between an engaged position and a disengaged position. Movement of the actuator also moves the first passage252and the second passage254of the lubrication valve250between open and closed positions. When the actuator moves the clutch220toward the engaged position (for example, in response to signals from an external control computer), pressure applied to the clutch pack228by the apply plate230causes the output hub214to rotate in response to rotation of the input flange212. At the same time, the lubrication valve250rotates to move the first passage252and the second passage254to their respective open positions. Fluid from the fluid reservoir260is thereby supplied to the clutch pack228and the clutch area of the housing210via the first fluid supply path270and the second fluid supply path272. While the clutch220remains in its engaged position, the lubricating fluid is pressurized by the first pumping mechanism defined by the channels282and is also pressurized by the second pumping mechanism defined by the axially extending ridges290. As a result, the lubricating fluid cycles through the clutch pack and/or the clutch area222before repeating the process.

When the actuator moves the clutch220to the disengaged position, the clutch pack228releases the connection between the input flange212and the output hub214. The lubrication valve250also moves the first passage252and the second passage254to their respective closed positions. Continued motion of the clutch drum224(such as parasitic motion or motion driven by the rear wheels125of the drivetrain100) causes the second pumping mechanism to pump a portion of the remaining fluid from the clutch area222to the fluid reservoir260. Because fluid is no longer being supplied via the first fluid supply path270and the second fluid supply path272, the amount of fluid present in the clutch drum224and the clutch area222is reduced. By reducing the amount of fluid present in the clutch drum224and the clutch area222, parasitic losses are reduced.

While the disclosure has been made in connection with what is presently considered to be the most practical and preferred embodiment, it should be understood that the disclosure is intended to cover various modifications and equivalent arrangements.