Ratchet one-way clutch assembly

Abstract: A ratchet one-way clutch assembly (50) has an inner member (54), an outer member (52) with pockets (66) and pawl members (56) positioned in the pockets for engagement with the notches (68). The pawl members have a pivot ridge (74) which mates with a peak (76) in the pockets (66). The pawl (56) centre of mass (CM) can be selectively positioned so that the pawl (56) can have a tendency to engage or disengage the notches (68). At least one garter spring (58) positioned between the inner (54) and outer (52) race members is used to provide a tilting force on the pawls (56). Axial retainment members (62,64) having axially extending flanges (118) can also be used with the present invention for improved radial bearing capability.

Description: Technical Field The invention relates to ratchet one-way clutch assemblies. Background Art There are various types of one-way clutch assemblies in use today. Such clutch assemblies include sprag-type, roller-type, and pawl ratchet-type assemblies. All of these one-way clutch assemblies work satisfactorily depending upon the particular application in which they are used. In certain transmissions, increased torque capacity is needed for one-way clutch assemblies. Space constraints also require that the size of the clutch assembly be retained within certain limits. Current one-way clutch assemblies with sprags or rollers are often insufficient to add increased load carrying capacity and still maintain the space constraints. Pawl one-way clutch assemblies can add in-creased nominal load capacity for a given package size. The design limits of a ratchet-type pawl clutch assembly are dictated by contact stress between the pawls and the races and/or bending, shear, and hoop stresses generated within the races. Ratchet clutch assemblies have at least one pawl which acts to lock two notched or pocketed races together in one direction and rotate freely in the other direction. In general, the differences between known ratchet clutch assemblies relate to the control of the movement of the pawls and the effect on that movement by centrifugal forces. Ratchet clutch assemblies are shown, for example, in U.S. Patent Nos. 2,226,247, 3,554,340, and 5,449,057. Another ratchet clutch assembly is shown in British Patent No. 2116. The '340 patent discloses a free-wheeling bicycle hub assembly with a ratchet clutch. Under the action of centrifugal forces at high speed, the pawls can be thrown out of the joints and suffer extreme wear. The '247 patent discloses another bicycle free-wheeling hub assembly with a ratchet clutch assembly. The pawls have a rectangular cross-section and are positioned loosely in the pockets in order to move freely. The looseness makes the position of the pawl center of mass and thus the movement of the pawl uncontrollable. In the '057 patent, the motion of the pawls is controlled by pivoting axles that pass through the pawls. The axles are positioned on a retainer and add complexity and cost to the design. It is also difficult to position the holes in the pawls for the axles with sufficient precision for high speed operation. In the British 2116 patent, the pawls are mounted on axles positioned on a retainer. The axles again add complexity and cost to the design. Also, centrifugal loading during high speed operation will create high forces on the axles and could adversely affect the operation of the clutch. Other known ratchet clutch mechanisms are shown in EP 0471 349 and DE 375 047. In EP0471349, there is disclosed a mechanism comprising inner and outer race members between which a plurality of pawl members are situated, the pawls being biased towards engagement by a circular spring member. It is an object of the present invention to provide generally improved ratchet one-way clutch assemblies and to provide assemblies which have improved operation at high speeds. In accordance with the present invention there is provided a one-way ratchet clutch assembly comprising: an outer member with a plurality of pockets; an inner member with a plurality of notches; a plurality of pawl members positioned in said pockets; spring means positioned between the inner and outer members and biasing said pawl members towards engagement with said notches; characterised in that the spring means comprise a pair of garter spring members in contact with each of the pawl members. In one particular embodiment of the present invention the ratchet one-way clutch assembly includes a plurality of pawls positioned in pockets in the outer race of a clutch assembly. A plurality of corresponding notches are positioned on the outer circumference of the inner race to mate with the pawls in locking engagement during relative rotation of the races in one direction. The pawls have peaks or ridges on one side which mate with pivot ridges or recesses in the pockets in the outer race. Forces tilting or biasing the pawls towards engagement are exerted by the pair of garter springs. . The assembly may include one or more axial retainment devices. These devices include pairs of washers, or plastic retainers with axial extending flange members. The devices retain the pawls axially and also hold the races in axial radial alignment, while allowing relative rotation. The retainment devices also act as thrust bearings and can retain required lubrication to prevent excessive wear of the pawls. Further embodiments of the present invention incorporate the pawl pockets directly in a stator or reactor mechanism, or other similar member. The elimination of a separate outer race member can save expenses in materials and manufacturing procedures. Similarly, a separate inner race member can be eliminated and the notches incorporated directly into a central shaft member or the like. Again, this could cause savings in materials, manufacturing time and expense. The present invention ratchet one-way clutch assembly has particular use in vehicle transmissions and can be used in environments where both inner and outer members rotate or where one of the members is fixed. The invention can also be used in any mechanism where a positive backstop is desired to prevent undesired reverse or backward rotation, such as in an escalator mechanism or the like. Other features, benefits and advantages of the present invention will become apparent from the following description of the invention, when viewed in accordance with the attached drawings and appended claims. Brief Description Of The Drawings FIGURE 1 illustrates a ratchet one-way clutch assembly which utilises centrifugal force to engage the clutch; FIGURE 2 is an enlarged view of a portion of the clutch assembly shown in Figure 1; FIGURES 3 and 4 illustrate a ratchet one-way clutch assembly in accordance with the present invention which utilizes garter spring members, with Figure 4 being an elevational view and Figure 3 being an exploded view thereof; FIGURES 5 and 6 show partial cross-sectional views of the embodiment shown in Figure 4, the cross sectional views being taken along lines 5-5 and 6-6, respectively, in Figure 4 and in the direction of the arrows; FIGURE 7 is an enlarged view of a portion of the clutch assembly embodiment shown in Figure 4; FIGURE 8 illustrates an embodiment of the present invention; FIGURES 9 and 10 illustrate pawl members not embodying the invention FIGURES 11 and 12 illustrate another clutch assembly not embodying the invention with Figure 12 being an elevational view and Figure 11 being an exploded view thereof; FIGURES 13 and 14 show partial cross-sectional views of the clutch assembly shown in Figure 12, the cross-sectional views being taken along lines 15-15 and 16-16, respectively, in Figure 12 and in the direction of the arrows; FIGURE 15 is an enlarged view of a portion of the clutch assembly embodiment shown in Figure 12; FIGURE 16 illustrates an assembly usable with the invention wherein the pawl pockets are incorporated directly in a stator/reactor assembly; FIGURE 17 is a cross-sectional view of the assembly of Figure 16, the cross-sectional view being taken along line 23-23 in Figure 16 and in the direction of the arrows; FIGURE 18 shows an alternative construction of the assembly shown in Figures 16-17; FIGURE 19 is an enlarged view of a portion of the assembly shown in Figure 18; FIGURE 20 is a perspective view of the reinforcing members utilized in the construction shown in Figures 18-19; FIGURE 21 illustrates a construction usable with the invention wherein the engaging notches for the pawl members are incorporated directly on a shaft member; FIGURE 22 illustrates a construction of pawl and pocket members for use with the present invention; and FIGURE 23 depicts another construction for use with the invention. Best Mode(s) For Carrying Out The Invention Figure 1 schematically illustrates a ratchet one-way clutch assembly 20. The assembly 20 includes an inner race 22, an outer race 24, and a plurality of individual pawl members 25. The pawl members 25 are positioned in pockets 26 in the outer race member. A plurality of notches 28 are positioned in the outer circumference or periphery of the inner race 22. When the motion of the inner race 22 relative to the outer race member 24 is in the clockwise direction in Figure 1, the inner race rotates freely. When the relative motion of the inner race member 22 relative to the other race member 24 is counter-clockwise, the inner race and outer race are locked together by one of the pawls 25. In this regard, in Figure 1, the locked pawl is indicated by the reference numeral 25'. The pawl 25' transmits force through pocket 26 in the outer race and notch 28 in the inner race. In the clutch assembly shown in Figure 1, ten pockets 26 and ten pawl members 25 are shown, together with eleven notches 28 in the inner race 22. Although the embodiment shown in Figure 1 only shows one pawl 25' in engagement, more than one pawl can be engaged at one time if the number of pawls and notches are both wholly divisible by a common denominator other than one. Figure 2 is an enlarged view of a portion of the clutch assembly shown in Figure 1. The pawl 25 shown in Figure 2 is depicted in the free-wheeling position. In accordance with the present invention, the cross-section of the pawl 25 has a peak or pivot ridge 30 formed by the intersection of two substantially flat sides 32 and 34. The peak 30 of the cross-section forms a pivot ridge with the outer race pocket 26 which is shaped to receive the pawl. In this regard, the pocket 26 has substantially straight sides 36, 37, 38 and 39. Preferably, in accordance with the present invention, the center of mass (CM) of the pawl 25 is positioned to the left of the pivot ridge 30 as viewed in accordance with Figure 2. In this manner, as the clutch assembly 20 rotates, a centrifugal force (CF) on the center of mass (CM) causes the pawl 25 to move toward the engaged position, that is, the position where it would be engaged with notch 28 in the inner race 22. The torque on the pawl 25 is proportional to the tangential distance of the CM away from the ridge 30. Although the embodiment of the invention shown in Figures 1 and 2 shows a pawl member with the center of mass positioned, together with the pocket in the outer race, such that the pawl has a tendency to move toward the engaged position, other arrangements are possible. For example, the geometry of the pawl can be changed to provide a pawl with a disengaging tendency. In this manner, the CM could be positioned to the right of the pivot ridge 30. The pocket 26 in the outer race also has a peak or recess 40 which mates with the pivot ridge 30 of the pawl member 25. The peak 40 in the pocket holds the pawl 25 in the proper circumferential location for free movement in the pocket. This prevents the ends 41 and 43 of the pawl member 25 from coming in contact with the sides 36 and 39, respectively, of the pocket. If the ends of the pawl were to contact the adjacent areas of the outer race pocket, friction could slow the movement 30 of the pawl toward engagement. In accordance with the preferred use of the present invention, it is necessary for the pawls to rotate into engagement with the inner race as quickly as possible. The ridge on the pawl is precisely located relative to the center of mass of the pawl, regardless of the exact location of the pawl with respect to the outer race. This allows precise control of the engaging force, which is preferred for high speed operation. This is also accomplished with a relatively simple geometry which does not include an axle, separate pivot member, or the like. Moreover, the outer race pocket is shaped such that it also has a corresponding peak or recess, which retains the pawl in a precise location in the pocket. This location prevents the pawl from contacting the sides or ends of the pocket as it rotates toward engagement. Preferably, the pawl members 25 are made of a hardened steel material and formed by pieces cut from a drawn wire. This allows precise control of the geometry of the pawl, and also allows precise control of the center of mass relative to the peak or pivot ridge 30. In this regard, with the present invention, it is possible to control the center of mass within a tolerance of 0.001 inches (0.0025cm). The clutch as described above does not embody the invention claimed herein because it does not have any garter spring members. An embodiment of the present invention is shown in Figures 3-8. This embodiment is referred to generally by the reference numeral 50 in the drawings. In the one-way ratchet clutch assembly 50, a spring is used to provide a tilting force on the pawl members 30 toward engagement. A spring is particularly needed for pawls which are disengaged centrifugally, as well as for engaging pawls that must engage when the outer race is stationary. In Figures 3-8, the assembly 50 includes an outer race member 52, an inner race member 54, a plurality of pawl members 56, and a pair of garter springs 58 and 60. A pair of retainment washers 62 and 64 are also provided in the embodiment shown in Figure 3 and are discussed further below. As shown more particularly in Figure 7, the pawl members 56 are positioned in pockets 66 in the outer race members 52 and are adapted to engage with notches 68 in the inner race 54. The garter springs 58 and 60, only one of which is shown in Figure 7, are made from a small coil of wire and are commonly available. For the embodiment shown in Figure 3 which utilizes two garter springs 58 and 60, pawl member 56 is utilized as shown in Figure 8. The pawl member 56 has a pair of recesses or side grooves 70 and 72. The garter springs 58 and 60 are positioned in the grooves 70 and 72 when the pawl members are positioned in the outer race. The remainder of the pawl members 56 have sizes and shapes similar to pawl members 25 described above with respect to Figures 1 and 2. In this regard, the pawl members have a pivot ridge 74 which mates with a peak or recess 76 in the pocket 66. The operation of the spring members 58 and 60 is shown with reference to spring 58 and pawl members 56 in Figure 7. In this regard, when the pawl members are in their disengaged position, the garter spring 58 provides a force toward outer race member (24) and thus toward the engaging position of the pawl member. This spring provides a force F (as shown in Figure 7) against surface 80 of each of the pawl members. When the pawl members 56 are in their engaged positions, that is mated with notches 68 in the inner race, the spring member 58 is relaxed and does not provide a spring force on the pawl members. This is shown with respect to the center pawl member 56 in Figure 7. The spring force can also be arranged to act on a single side groove or a center groove of the pawl geometry. This is shown in Figures 9 and 10, respectively, where the pawl members are referred to by the reference numbers 82 and 84. The garter spring is indicated in phantom lines and is referred to by reference numeral 86. If either of the pawl assemblies shown in Figures 9 and 10 are utilized with the embodiment of the invention shown in Figures 3-7, then the position of the garter spring and the number of garter springs provided is adjusted accordingly. Opening or aperture 81 in the drawings (Figure 6) provides an access hole for lubrication for the transmission or other mechanism in which the one-way clutch assembly 50 is utilized. Preferably, several access holes are provided in the clutch assembly, such as the three openings 81 shown in Figure 12. The washers 62 and 64 are also known as axial retainment devices or members and can be used to improve or enhance the operation of the present invention. The members 62 and 64 retain the pawl members axially (longitudinally) in the clutch assemblies. The retainment members also hold the inner and outer races in axial alignment, while allowing free relative rotation. Moreover, the axial retainment members act as thrust bearings between the clutch assembly and external parts of the mechanism that are rotating relative to the clutch assembly and must carry an axial load through the assembly. Finally, the axial retainment members (washers) 62 and 64 can retain lubrication in the clutch assembly which is required to prevent excess wear of the pawl members. The washers 62 and 64 can be connected to the outer race through a press-fit arrangement, staking, welding, or mechanical fastening in any conventional manner. An injection molded plastic retainer member can also be utilized. Such a member 100 is shown in Figures 11-15. In these Figures, the one-way ratchet clutch assembly is referred to generally by the reference numeral 102. Together with the retainer member 100, the assembly 102 includes an outer race member 104, an inner race member 106, a plurality of pawl members 108, a garter spring member 110 and a second retainment member 112. In this regard, in the assembly shown in Figures 11-15, the pawl members 108 can be of any of the types shown and described earlier. In addition, the pawl members 108 are contained in pockets 120 in the outer race member and engage notches 122 in the inner race member, in the same manner described above with reference to the other Figures. The retaining member 100 has a plurality of flanges or upstanding arcuate shaped guide members 118 situated to be positioned within the annular space between the inner and outer races 106 and 104, respectively. The member 100 is a radial bearing retainer for the pawls and the race members, and also acts as a lube dam for lubrication. The retainer members 100 and 112 are preferably attached together to retain the clutch assembly together axially. The retainer members also act as thrust bearings between the assembly and external parts of the mechanism that are rotating relative to the clutch assembly and carry axial loads through the assembly. Preferably, the retainer member 100 is made from an injection molded plastic material, and also preferably has a low friction coefficient so that it can provide improved bearing performance over regular steel-on-steel bearings. The retainer members 100 and 112 can be connected together in any conventional manner, such as a press-fit arrangement, staking, ultrasonic welding, mechanical fastening, and the like. Alternative constructions for use with the present invention are shown in Figures 16-22. These assemblies can provide improved economies in cost, manufacture and assembly improved procedures, as well as improved performance. As shown in Figures 16-17 the pawl pocket members are incorporated directly as part of a stator or reactor member 150 for a torque converter or the like. The member 150 can be any integral part which would require a one-way clutch mechanism. Preferably, the member 150 is made from an aluminum, plastic or another material which can be cast and machined relatively easily. A plurality of pocket members 152 are formed and/or machined directly into the inner diameter surface 154 of the member 150. The pawl members 156, which are positioned in the pockets 152, can be of any of the types shown and described herein, and can be urged toward the engaged position by one of the various types of spring members or mechanisms, as discussed herein. The inner member 160 can be any typical inner race member of the type discussed above with a plurality of locking notches 162 positioned around its outer circumference 164. Alternatively, the central shaft member which typically mates with the inner race member by mating teeth or spline members 166 or the like, can have the notches machined or formed directly on the outer circumference of the shaft, thereby eliminating the inner race member. Such an assembly is shown in Figure 21 wherein a plurality of notches 162' are provided on shaft member 170, which typically is hollow, and the shaft member is then mated with member 172 which can be an outer race member, a stator or reactor member, or the like. Shaft member 170 can be, for example, part of a vehicle transmission. Any number of pockets and notches can be provided as desired by the clutch designer and/or in accordance with the operating specifications and parameters for the clutch mechanism. In the assembly shown in Figures 16-17, three pockets and pawl members are provided and uniformly spaced around the inner circumference/diameter of the outer member 150. In order to effectively and efficiently mate with this number of pawl members and to allow the clutch mechanism to lock-up in the desired time with limited backlash (e.g. seven degrees), preferably seventeen notches are provided in the inner member. Figures 18-20 depict an alternative construction in which insert members 180 are provided. The insert members 180 are made from steel or another hard or hardened material and are used to prevent damage to softer materials which might be utilized for the outer stator, reactor or other member 150 when the clutch mechanism is utilized. The inserts can be made of stamped steel or the like. The pocket members 182 in the member 150 are provided with a larger space or area, to allow positioning of the insert members 180 therein. The insert members are press fit, wedged or otherwise permanently secured in the pockets 182. The pawl members 156 are positioned inside the cupped insert members as shown. Another assembly is shown in Figure 22. In this construction, 25 the pawl member 200 has a different size and shape from the pawl members shown above. In particular, the pawl members 200 have a greater height H in the radial direction. This is to increase the load-carrying capacity of the clutch mechanism. As with the other assemblies presented above, the pawl member 200 is positioned in a pocket 202 in an outer member 204, which can be an outer race, a stator or reactor, or the like. The center of mass CM of the pawl member 200 is preferably positioned as shown relative to the peak or pivot ridge 206 such that a pawl engaging force is generated upon rotation of the outer member 204. Similarly, a plurality of notches 210 are formed in the inner member 212, which can be an inner race, a shaft member, or the like. It is possible to utilize one of the spring members or mechanisms of the types and embodiments discussed above in order to assist in providing a tilting force on the pawl members 200 toward engagement. The use of retainment washers or thrust bearings on one or more sides of the ratchet one-way clutch mechanism shown in Figure 22 could also be provided. Appropriate lubrication channels and openings could further be provided as are conventionally utilized in the clutch art. As an additional feature it is also possible to provide the outer member as an insert which is combined with a stator, reactor or other mechanical member. This is shown in Figure 23. The outer member 220 has an annular shape and is adapted to fit within cavity or recess 222 in the stator, reactor or other member 224. The outer member 220, which preferably is made from a metal material, can be press fit or keyed by key member 226 into the member 224. In this manner, the member 224 can be made from a lower cost material, such as a plastic material. The other portion of the clutch mechanism, including the inner member 160, pawl members 156 and the like are the same as those set forth above.

Claims: A one-way ratchet clutch assembly (50; 102) comprising: an outer member (52; 104; 150; 204; 220) with a plurality of pockets (66; 120; 182); an inner member (54; 106; 160; 212) with a plurality of notches; a plurality of pawl members (56; 108; 156; 200) positioned in said pockets; spring means positioned between the inner and outer members and biasing said pawl members (56; 108; 156; 200) towards engagement with said notches; characterised in that the spring means comprise a pair of garter spring members (58, 60) in contact with each of the pawl members (56; 108; 156; 200). A one-way ratchet clutch assembly (50; 102) according to claim 1, wherein each pawl member has recesses (70, 72) for positioning of the garter spring members (58, 60) A one-way ratchet clutch assembly (50; 102) according to claim 2, wherein the recesses comprise a pair of grooves (70, 72) for receiving the garter springs. A one-way ratchet clutch assembly according to claim 2 or 3, wherein a pair of disc-shaped retention members (62, 64; 100, 112) are positioned on opposite sides of said assembly. A one-way ratchet assembly according to claim 4, wherein one of said pair of retention members (100, 112) includes a plurality of guide members (118) thereon, said guide members being positioned between said inner and outer races (104, 106). A one-way ratchet clutch assembly according to any one of claims 1 to 5 wherein the number of notches (68; 122; 162; 210) provided is different to the number of pawl members (56; 108; 156; 200). A one-way ratchet clutch assembly according to any one of claims 1 to 6 wherein the pawl members (56; 108; 156; 200) each have a ridge member (74; 206), the pockets each have a recess member (76) and said ridge and recess members co-operate to define a pivot.

Inventors: BACON DUANE A, COSTIN DANIEL P, BACON, DUANE A., COSTIN, DANIEL P.
Applicants: BORG WARNER INC, BORGWARNER INC.
Application year: 1997
Main classification: F16D41
IPC codes: F16D41