1. Field of the Invention
The invention relates to a planar coupling assembly for establishing and disestablishing a torque flow path in a geared multiple-ratio transmission for an automotive vehicle powertrain.
2. Background Art
Prior art U.S. Pat. No. 5,964,331 discloses a one-way clutch comprising a pocket plate and a notch plate situated in a juxtaposed adjacent relationship. One-way clutches of this kind are sometimes referred to as planar clutches because the adjacent juxtaposed surfaces are situated in radial planes with respect to the axis of the clutch.
For purposes of this disclosure, the term coupling should be interpreted to include clutches or brakes wherein one of the plates is drivably connected to a torque delivery element of a transmission and the other plate is drivably connected to another torque delivery element or is anchored and held stationary with respect to a transmission housing. The terms coupling, clutch and brake may be used interchangeably.
The pocket plate is provided with angularly disposed recesses or pockets about the axis of a one-way clutch. The pockets are formed in the planar surface of the pocket plate. Each pocket receives a torque transmitting strut, one end of which engages an anchor point in a pocket of the pocket plate. An opposite edge of the strut, which may hereafter be referred to as an active edge, is movable from a position within the pocket to a position in which the active edge extends outwardly from the planar surface of the pocket plate. The struts may be biased away from the pocket plate by individual springs.
The notch plate is formed with a plurality of recesses or notches located approximately on the radius of the pockets of the pocket plate. The notches are formed in the planar surface of the notch plate.
Another example of an overrunning planar clutch is disclosed in U.S. Pat. No. 5,597,057. Both the '331 and '057 patent are assigned to the assignee of the present invention.
In a transmission gearing installation that includes a planar clutch of know design, such as the clutch disclosed in the '331 patent and in the '057 patent, the pocket plate will rotate relative to the notch plate as the notch plate is held stationary by a spline connection between the periphery of the notch plate and a transmission housing. A friction disc assembly selectively anchors the pocket plate when a torque reaction point for the transmission gearing is desired.
During operation of a planar clutch of known design in selected transmission gear ratios, it is necessary to anchor the pocket plate to provide a torque reaction for an associated torque transmitting gear element of the transmission. The springs that act on the individual torque transmitting struts then urge the struts toward the notch plate to effect engagement of the active edge of the struts with the notches of the notch plate, thus establishing a torque reaction point for the torque transmitting gear element. If the pocket plate rotates at the initiation of a ratio shift that requires a torque reaction on the one-way clutch assembly, a centrifugal force is developed on each torque transmitting strut, causing it to engage at its radially outward active edge with an edge of its pocket. When the overrunning clutch is in its overrunning mode and is operated at high speeds, centrifugal force developed due to the mass of the rotating strut tends to cause unwanted movement of the strut.
Typically, the pocket has a radially outward edge that is formed with a positive angularity or draft angle with respect to the axis of rotation. The centrifugal force acting on the strut then will have an axial component that may cause the strut to shift into engagement with the notch plate. This interferes with the effective overrunning action of the one-way clutch and causes wear and undesirable noise. This disadvantage is of significance since continuous overrunning of the one-way clutch occurs during a high percentage of the overall operating time of the transmission.
A one-way planar clutch assembly of the kind disclosed in the '331 patent and in the '057 patent typically is used in combination with at least one friction disc assemblies, the friction disc assembly defining a brake or a clutch that establishes a torque flow path that is parallel to the torque flow path established by the one-way planar clutch assembly. Thus, multiple clutch assemblies are required, which complicates the overall transmission design and increases cost and transmission assembly time.
According to one feature of the one-way clutch assembly of the present invention, provision is made for eliminating the adverse effects of centrifugal force acting on the one-way clutch torque transmitting struts, thereby improving the freewheeling performance of the clutch assembly, especially at high overrunning clutch speeds. This is done by providing a 0° draft angle on the radially outward edge of the pockets in which the struts are situated. The pockets may be designed also with a negative draft angle to further enhance the beneficial holding effect that overcomes the adverse effect of centrifugal force acting on the struts.
According to another feature of the invention, the pocket plate is provided with an externally-splined extension formed integrally with the pocket plate itself. The extension is adapted to carry clutch plates or discs that form a part of a friction clutch assembly in a gearing system for an automatic transmission. In a transmission environment that requires the use of a friction clutch assembly in combination with an overrunning clutch or brake, the one-way planar clutch assembly of the invention makes it possible to integrate the torque transmitting elements of the friction clutch assembly with the overrunning coupling elements of the planar one-way clutch assembly. This simplifies the design and provides an economy of space in an automatic transmission gear system.
Another feature of the invention includes a planar friction surface on the notch plate, which may form a friction disc clutch or brake reaction surface for a secondary friction clutch assembly. Thus, the planar overrunning clutch assembly of the invention can be integrated with two friction clutch assemblies in an automatic transmission system thereby further simplifying the overall design and effecting a further reduction in the space required for the transmission friction elements. An additional benefit of the integration of the friction clutch assemblies and the overrunning clutch assembly is a further reduction in the number of elements and a further reduction in manufacturing costs including reduced assembly time and cost.
It is possible to provide multiple engagements of the torque transmitting struts for each relative angular position of the pocket plate with respect to the notch plate. The backlash inherent in the planar one-way clutch assembly thus can be reduced and the torque capacity of the one-way clutch assembly can be increased by the multiple engagements.
a is an isometric view of a pocket plate, which forms an element of the planar one-way clutch assembly of the invention;
b is an isometric view of a notch plate for use with the pocket plate of
c is an isometric view of a torque transmitting strut located in a pocket of the pocket plate of
d is a cross-sectional view of one of the pockets of the pocket plate of
An automatic transmission gear system incorporating the invention is shown in the partial cross-sectional view of
Carrier 28 is drivably connected to sun gear 32, as shown at 36. Carrier 22 is drivably connected to ring gear 26, as shown at 38. Ring gear 20 is drivably connected to planetary carrier 34 by a torque transfer member 40.
A torque input shaft, which corresponds to the turbine shaft of a hydrokinetic torque converter (not shown), is designated by reference numeral 42. It is splined to sun gear 24. Torque output sleeve shaft 44 is splined to carrier 34, and carrier 22 is splined to friction clutch element 46 of a multiple disc clutch assembly 48, which is engaged during operation of the transmission in the fourth, fifth and sixth speed ratio.
Clutch plates register with clutch discs of the clutch assembly 48. Clutch plates are connected to clutch member 50, which defines in part spaced annular clutch cylinders, as shown at 52 and 54. An annular piston 56 is disposed in clutch cylinder 52 and an annular piston 58 is disposed in annular cylinder 54. The pistons 56 and 58 are biased to a clutch release position by clutch return springs 60 and 62, respectively. The cylinder 52 and the piston 56 define a pressure chamber, which, when pressurized causes piston 56 to frictionally engage the clutch plates and clutch discs of the multiple disc clutch assembly 48 to establish a driving connection between carrier 22 and clutch element 50.
Internally splined clutch plates of a multiple disc clutch assembly 64 are splined to the clutch element 50. Externally splined clutch plates of multiple disc clutch assembly 64 are drivably connected to sun gear 18 by clutch element 66.
Clutch element 66 is connected drivably to friction brake discs 68, which register with friction plates 70 of a multiple disc brake assembly 72.
Clutch disc assembly 64 is engaged during operation in the third and fifth speed ratio, as well as in reverse drive. Brake disc assembly 72 is engaged during operation in second ratio and sixth ratio.
The stationary transmission housing 74 rotatably supports turbine shaft 42, as shown at 76. Housing 74 defines an annular brake pressure chamber 78 in which is situated annular piston 80. A brake actuator element 82 carried by the piston 80 is engageable with the brake disc assembly 72 to establish a torque reaction point for sun gear 18.
Sun gear 16 is drivably connected to brake disc assembly 84 by means of torque transfer element 86. Housing 74 defines an annular cylinder 88, which receives annular piston 90.
The planar clutch assembly of the invention is illustrated in
The brake disc assembly 84 is frictionally engaged when pressure is applied the piston 90, which actuates pressure plate 102 of the brake disc assembly 84.
The notch plate 94 acts as the reaction element for the brake disc assembly 84. It is splined to the transmission housing 74 and is secured within the transmission housing against axial displacement by snap ring 104 located in a snap ring groove in the transmission housing 74.
The pocket plate 96 is held fast within the notch plate 94 by a snap ring 106 situated in a snap ring groove formed in the pocket plate 94.
Pocket plate 96 has an axial extension 116, best seen in
An annular cylinder 121 formed in the transmission housing 74 receives a piston 119. Internal fluid pressure passages provide actuating pressure to the cylinder 121 to create a brake actuating force on the piston 119. That force is transmitted through the actuator element 117, which engages pressure plate 114 to apply the brake disc assembly 112. This anchors the carrier 22 of the planetary gear unit 12.
The surface 98 on the notch plate is fully precision ground prior to assembly so that it can act as a backing plate for the friction disc pack. It thus is not necessary with the design illustrated in
As previously mentioned, the brake disc assembly 84 is applied during operation in the first, second, third and fourth speed ratios for the transmission. This provides a coast braking torque for the transmission during forward drive. Reaction torque is transmitted from the sun gear 30 and from the torque transfer element 86 through the engaged brake disc assembly 84. During forward drive, reaction torque on the sun gear 30 is accommodated by the planar one-way clutch assembly 92.
When the planar one-way clutch assembly is active, forward driving torque is transmitted from the carrier 22 to the transmission housing through the pocket plate during first, second, third and fourth gear ratio operation. When the transmission is operating in the fifth and sixth speed ratio, pocket plate 96 will assume a freewheeling condition whereby the pocket plate will overrun the stationary notch plate. Coast braking during low speed ratio operation and reverse drive operation can be achieved by engaging multiple disc brake assembly 112, which includes friction brake discs 110 that are splined to extension 116 on the pocket plate 96.
The stationary externally splined notch plate, as best seen in
A torque transmitting strut 124 is situated in each pocket. The struts are best seen in
d shows the anchor edge 128 engaged with one edge of the pocket 120. A spring, preferably a leaf-type or hairpin-type spring, as shown in
The number of pockets may be different than the number of pockets to reduce backlash. They may be arranged relative to the pockets to effect multiple strut engagements, thereby increasing coupling torque capacity.
When the pocket plate moves rotatably in the direction of the directional vector FW in
When the planar one-way clutch assembly is freewheeling, a centrifugal force is developed on the torque transmitting struts 124, as indicated in
In
The centrifugal force shown by force vector 136 acting on the strut creates a centrifugal force component vector 142 that tends to resist displacement of the strut out of the pocket 120 when the planar one-way clutch assembly is freewheeling. Force vector 142 is created by reason of a negative draft angle 144 formed at the radially outward edge of the pocket 120. The negative draft angle is created during manufacture of the pocket plate. A negative draft angle can be achieved by upsetting the metal at the radially outward wall of a pocket 120, as shown at 146. A punching tool may be used during the manufacture of the pocket plate to upset the metal at the radially outward edge of the pocket 120.
Preferably, the pocket plate and the notch plate can be formed using powder metal technology. During the sintering operation in the powder metal casting technique, the notches 146 can be formed readily when the pocket plate still is in its heated state while it is most malleable. It has been demonstrated that the negative draft angle on the pockets 120 will resist displacement of the struts 124 even when the pocket plate rotates at high speeds; for example, speeds greater than 2500 rpm. This greatly improves the overrunning clutch performance, reduces wear on the struts, and avoids any tendency of the struts to create noise due to ratcheting of the struts across the pockets of the pocket plate when the planar overrunning clutch assembly is freewheeling.
In contrast to the design of
Although an embodiment of the invention has been disclosed, it will be apparent to persons skilled in the art that modifications may be made without departing from the scope of the invention. All such modifications and equivalents thereof are intended to be covered by the following claims.
This application is a division of U.S. application Ser. No. 10/869,583 filed Jun. 16, 2004;
Number | Date | Country | |
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Parent | 10869583 | Jun 2004 | US |
Child | 11480809 | Jul 2006 | US |