Abstract:
A planar overrunning coupling assembly for a geared transmission. The coupling assembly has a circular pocket plate, a notch plate, and torque transmitting struts in pockets formed in the pocket plate. The geometry of the pockets prevents displacement of the struts toward the notch plate under the influence of centrifugal force when the pocket plate overruns the notch plate. The pocket plate and the notch plate define in part friction disc coupling assemblies.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a division of U.S. application Ser. No. 10/869,583 filed Jun. 16, 2004; 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     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.  
         [0004]     2. Background Art  
         [0005]     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.  
         [0006]     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.  
         [0007]     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.  
         [0008]     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.  
         [0009]     Another example of an overrunning planar clutch is disclosed in U.S. Pat. No. 5,597,057. Both the &#39;331 and &#39;057 patent are assigned to the assignee of the present invention.  
         [0010]     In a transmission gearing installation that includes a planar clutch of know design, such as the clutch disclosed in the &#39;331 patent and in the &#39;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.  
         [0011]     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.  
         [0012]     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.  
         [0013]     A one-way planar clutch assembly of the kind disclosed in the &#39;331 patent and in the &#39;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.  
       SUMMARY OF THE INVENTION  
       [0014]     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.  
         [0015]     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.  
         [0016]     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.  
         [0017]     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. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is a partial cross-sectional view of a gearing system that includes the planar one-way clutch assembly of the invention in combination with two friction clutch assemblies;  
         [0019]      FIG. 2  is an enlarged detail view of a portion of the cross-sectional view of  FIG. 1  wherein the elements of the planar one-way clutch assembly of the invention are emphasized;  
         [0020]      FIG. 3   a  is an isometric view of a pocket plate, which forms an element of the planar one-way clutch assembly of the invention;  
         [0021]      FIG. 3   b  is an isometric view of a notch plate for use with the pocket plate of  FIG. 3   a  in the assembly of  FIG. 2 ;  
         [0022]      FIG. 3   c  is an isometric view of a torque transmitting strut located in a pocket of the pocket plate of  FIG. 3   a;    
         [0023]      FIG. 3   d  is a cross-sectional view of one of the pockets of the pocket plate of  FIG. 3   a  as seen from the plane of section line  3   d - 3   d  of  FIG. 3   a;    
         [0024]      FIG. 4  is a plan view of the planar surface of the pocket plate of  FIGS. 1, 2  and  3   a;    
         [0025]      FIG. 5  is a plan view of the planar surface of the notch plate of  FIGS. 1, 2  and  3   b;    
         [0026]      FIG. 6  is a cross-sectional view of the pocket plate of  FIG. 4  as seen from the plane of section line  6 - 6  of  FIG. 4 ; and  
         [0027]      FIG. 7  is a cross-sectional view of a pocket plate similar to the pocket plate disclosed in prior art U.S. Pat. No. 5,964,331, wherein a positive draft angle is present at a radially outward wall of the pocket. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     An automatic transmission gear system incorporating the invention is shown in the partial cross-sectional view of  FIG. 1 . It includes a planetary gearing arrangement  10 , which comprises three simple planetary gear units  12 ,  14 , and  16 . Gear unit  12  includes a sun gear  18 , a ring gear  20 , and a planetary carrier  22 . Gear unit  14  comprises a sun gear  24 , a ring gear  26 , and a planetary carrier  28 . Gear unit  16  comprises a sun gear  30 , a ring gear  32 , and a planetary carrier  34 .  
         [0029]     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 .  
         [0030]     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.  
         [0031]     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 .  
         [0032]     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 .  
         [0033]     Clutch element  66  is connected drivably to friction brake discs  68 , which register with friction plates  70  of a multiple disc brake assembly  72 .  
         [0034]     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.  
         [0035]     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 .  
         [0036]     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 .  
         [0037]     The planar clutch assembly of the invention is illustrated in  FIG. 1  at  92 . It comprises a notch plate  94 , which envelopes pocket plate  96 . The planar annular surface  98  provides a brake disc reaction surface, which is engaged by an adjacent brake disc of the brake disc assembly  84 . Clutch plates of the brake disc assembly  84  are externally splined to the transmission housing  74 , as shown at  100 .  
         [0038]     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 .  
         [0039]     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 .  
         [0040]     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 .  
         [0041]     Pocket plate  96  has an axial extension  116 , best seen in  FIG. 2 , which is externally splined to internally splined friction brake discs  110  of a multiple disc brake assembly  112 . Splined clutch plates, as seen in  FIGS. 1 and 2 , are connected to transmission housing  74 . Brake pressure plate  114  is engaged by an actuator element  117 , which in turn is carried by brake actuator piston  119 . The pocket plate extension  116  has internal splines  108  to establish a splined driving connection to carrier  22 , as best seen in  FIG. 1 .  
         [0042]     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 .  
         [0043]      FIG. 2  is an enlarged detail view of the planar clutch assembly  92  and the friction brake assembly  84 . The piston  90 ′ of  FIG. 2  corresponds to the piston  90  of  FIG. 1 , the later being formed as a steel stamping whereas the piston  90 ′ is a machined part. In each instance, when the piston or the multiple disc brake assembly  84  is subjected to brake actuating pressure, a force is applied to the pressure plate  102 . The reaction for that actuating force on the pressure plate is accommodated by the notch plate  94 . The reaction force is transmitted to the transmission housing through snap ring  104 .  
         [0044]     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  FIGS. 1 and 2  to provide a separate backup plate for the friction brake assembly. The integrated design illustrated in  FIGS. 1 and 2  incorporates common features for the planar clutch assembly  92  and the friction brake assembly  84 , thereby eliminating components and reducing the packaging space for the torque transmitting elements of the transmission.  
         [0045]     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 .  
         [0046]     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 .  
         [0047]     The stationary externally splined notch plate, as best seen in  FIG. 3   b  and in  FIG. 5 , includes a plurality of ramped recesses or notches  118  throughout the entire periphery of the notch plate. These notches are situated in juxtaposed adjacent relationship with respect to pockets  120  formed in the planar annular surface  122  of the pocket plate. The pockets  120  are disposed about the periphery of the pocket plate, as seen in  FIG. 3   a.    
         [0048]     A torque transmitting strut  124  is situated in each pocket. The struts are best seen in  FIG. 3   c . They include a notch engaging active edge  126  and an anchor edge  128 . The edge  128  is elongated in a tangential direction to provide anchor shoulders  132  and  132 ′, which are received in a radially enlarged portion of the pockets  120 .  
         [0049]      FIG. 3   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  FIG. 3   d  at  130 , is supported by a base surface  134  of the pocket  120 . The spring engages the underside of the torque transmitting strut  124 , as best seen in  FIG. 3   d , and urges the strut  124  in a radially outward direction. This causes the strut to pivot about anchor edge  128 . The active notch plate engaging edge  126  is moved outwardly so that it is engageable with the notches  118  as the pocket plate moves rotatably relative to the notch plate.  
         [0050]     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.  
         [0051]     When the pocket plate moves rotatably in the direction of the directional vector FW in  FIG. 3   d , the torque transmitting strut  126  will ratchet across the notches  118 . If the relative motion of the pocket plate is zero, the notch plate engaging active edge  126  of the struts  124  will engage an edge of the notches  118  thereby preventing reverse motion of the pocket plate relative to the notch plate.  
         [0052]     When the planar one-way clutch assembly is freewheeling, a centrifugal force is developed on the torque transmitting struts  124 , as indicated in  FIG. 6  by the force vector  136 .  
         [0053]     In  FIG. 6 , the spring force acting on the torque transmitting strut  124  is represented by the force vector  138 . The fluid pressure force created by the effect of the strut displacing transmission fluid when moving into the notch plate is represented by the vector  140 . Based upon empirical data, this force  140  has been shown to have a minimal effect, and for all practical purposes it can be ignored.  
         [0054]     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 .  
         [0055]     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.  
         [0056]     In contrast to the design of  FIG. 6 ,  FIG. 7  illustrates a planar overrunning clutch design of the kind shown in U.S. Pat. No. 5,918,715. When the planar overrunning clutch assembly is in a freewheeling state, the centrifugal force vector F C  will create a “push-out” force component F P . When combined with fluid pressure force F L  and spring force F S , the resultant force F R  is developed, which tends to move the torque transmitting strut  124 ′ outwardly where it can interfere with the freewheeling action of the strut plate relative to the pocket plate. The draft angle θ is a positive value in the case of the design of  FIG. 7 , whereas the draft angled for the design of  FIG. 6  is negative. In some instances, the angle θ shown in  FIG. 6  can be near or at a zero value. The actual negative draft that can be used depends upon design characteristics of the gearing with which the planar overrunning clutch is used.  
         [0057]     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.