FIELD OF THE INVENTION
The present invention relates to automobile clutches in general and more particularly to a system and method for manufacturing wet friction clutch plate having a friction material on the surface of the wet friction clutch plate.
BACKGROUND OF THE INVENTION
Modern day wet friction clutch plate includes a plurality of spaced adjacent segments made of a suitable friction material that is adhesively bonded on to the two annular surfaces of the friction clutch plate (also known as core). The wet friction clutch plate further includes channels or grooves between edges of adjacent segments to provide passageways for oil that transfers heat from the friction plates. The segments can be asymmetric or symmetric in shape and arrangement.
Many methods are known for manufacturing a wet friction clutch plate. One such conventional method includes subjecting a sheet or a strip of friction material to a cutting operation to provide a predetermined sized cut. The method further includes subjecting the cut to a punching operation to provide an annular friction segment and bonding the annular friction segment to an annular core on the clutch plate.
Existing cutting process involves feeding one or more strips of friction material at a tangential or radial direction with respect to the clutch plate. For instance, the apparatus for manufacturing clutch friction plate as disclosed in US patent no. 5571372 includes a feeding mechanism for feeding friction material tape. Accordingly, the feeding mechanism includes a reel disposed in the vicinity of a turntable with the friction material tape wound there around. A guide member is disposed to locate the tip end of the friction material strip near the contact

portion of a cutting roller and a receiving roller. The guide member is provided with a through hole through which the friction material tape is inserted. A feed roller pair as a feeding member is disposed at the upstream of the guide member in the supplying direction (towards the cutting roller) of the friction material tape. Accordingly, the friction material tape is unwound from the reel by the aid of the feed roller, through the through hole in the guide member, and fed into between the cutting roller and the receiving roller. Such a feeding mechanism results in low productivity, as the number of strips fed are limited to one due to complexity in the feeding mechanism. In addition, there is a time lag between the cutting of friction material segment from the strip and pasting/bonding the segment onto the friction clutch plate. Such a time lag is undesirable considering operation cost, adhesive dry time, and efficiency of the complete process.
In addition, such an apparatus has inherent disadvantage of misalignment in the position of segments while placing them onto the friction clutch plate. In other conventional methods and systems such as disclosed in US patent no. 7434300, the feeding operation includes subjecting a band shaped friction material to a cutting operation to result in a 5 strips of friction material spaced apart by a width equal to the intended width of the oil grooves. The strips of friction material are simultaneously subjected to one or more rollers (e.g. cutting roller, positioning rollers, etc.) to obtain segments of friction material out of the strips being fed in parallel. Again, in such methods and apparatuses, the number of strips that can be fed is limited and increasing the number of strips beyond a certain limit can lead to inaccuracies in the cutting and positioning of the friction material segments.
In addition, in all the above methods, the cutting and bonding operation is performed sequentially wherein a strip of friction material is cut into segments and each segment is placed on the annular surface of the friction clutch plate. The manufacturing time becomes almost double considering the time taken for similar operation on both the annular surfaces of the friction clutch plate which results in increased manufacturing time and cost.
In cases, where a single apparatus performs the cutting, positioning, and bonding operations, the accuracy tends to be poor due to physical vibrations of the apparatus during the cutting operation. Moreover, the existing methods and systems provide for few degrees of freedom to choose for different segment shapes.
In certain scenarios, it may be desirable to utilize segments of different shapes and sizes without adding to the cost and complexity of the feeding, cutting, and bonding mechanisms. Most importantly, the efficiency of the apparatus and the method depends heavily on the cutting operation that produces segments to be placed over the surface of clutch plate. Hence, it is desirable to devise a cutting process and a bonding process in manner such that the manufacturing time is considerably reduced and the yield/efficiency of the method and associated apparatus is further improved.
In order to obviate at least one or more of the aforementioned problems, there is a well-felt need to provide an improved method and system for manufacturing wet friction clutch plate that at least reduces the manufacturing time, increases yield of the process, and provides consistently a high quality clutch plate.
Brief Description of the drawings:
To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings in which:
Fig. 1 illustrates an isometric view of system for manufacturing wet friction clutch plate before cutting of friction segments according to an embodiment of the present invention;
Fig. 2 illustrates an isometric view of a system for manufacturing wet friction clutch plate during cutting of friction segments according to an embodiment of the present invention; and
Fig. 3 illustrates an isometric view of a system for manufacturing wet friction clutch plate during pasting of friction segments according to an embodiment of the present invention; and
Fig. 4 illustrates an isometric view of a system for manufacturing wet friction clutch plate after pasting of friction segments according to an embodiment of the present invention.
Description:
The principal object of the present invention is to reduce manufacturing time and cost for wet friction clutch plates.
It is yet another object of the present invention to provide accurate spacing between adjacent segments of frictional material.
Still further object of the present invention is to provide an improved mechanism to feed a plurality of friction material strips in a cost and time effective manner.
Methods and systems for manufacturing a wet friction clutch plate are disclosed. A friction plate typically includes a clutch core and a large number of friction material segments adhered to the annular bonding surface in the circumferential direction of the core. Between the adjacent frictional material segments are provided a gap typically referred to as “oil grooves”.
Fig. 1, fig. 2, fig.3, and fig. 4 illustrate a system 100 for manufacturing wet friction clutch plates according to various embodiments of the present invention. As would be clear in the forthcoming sections, the figures illustrate isometric views of the system 100 before cutting, during cutting, during pasting and after pasting of friction material segments respectively.
Referring to fig. 1, the system 100 includes a stationary or movable index table 102 disposed at a height appropriate for easy working. The index table 102 may also correspond to a turntable capable of being rotated about the center. The system 100 further includes a friction clutch plate 104 fixed onto the index table 102 by a clutch plate holder (not marked).
It may be appreciated that a typical process of manufacturing involves application of adhesive material on annular surfaces of the friction clutch plate, pasting or placing or bonding friction material segments onto the annular surfaces and pressing the friction material segments onto the annular surface to firmly affix the segments onto the clutch plate. The steps and apparatus involved in the application of adhesive material onto the annular surfaces are well known in the art and will not be explained in the context of the present invention. However, it may be understood that any adhesive application mechanisms may be implemented for applying the adhesive without deviating from the scope of the present invention.
An example adhesive applying mechanism may include an adhesive discharging member that sprays a suitable adhesive through a nozzle onto an annular surface of the clutch plate 104. The application of adhesive includes rotating the clutch plate (and the index table 102) in a clockwise or an anti-clock wise direction. During such a rotation, the nozzle may remain stationary or may be in motion in a direction opposite to the direction of rotation of the clutch plate 104. This may be followed by an adhesive spreading step by suitable means. In some embodiment, the adhesive spreading step may be avoided by suitable modification in the adhesive spraying mechanism and the nozzle in particular.
In a successive progression, the friction clutch plate 104 with adhesive is subjected to the bonding operation in which a plurality of friction material segments is bonded onto the annular surface of the friction clutch plate 104.
Turning back to fig. 1, the system 100 further includes a plurality of rollers 106 disposed in a circumferential manner around the clutch plate holder on which the friction clutch plate 104 is mounted. As shown in the figure, a plurality of friction material strips 108 is fed into the rollers 106. Each friction material strip 108 is fed to a pair of rollers rotating in opposite direction with respect to each other thereby generating a “drawing in” tension in the friction material strip 108. Such a tension pulls the friction material strip 108 towards the friction clutch plate 104 in a radial direction.
In an exemplary embodiment, the rollers 106 are rotated by means of a plurality of stepper motors disposed inside the rollers 106. A stepper motor (or step motor) corresponds to a brushless, synchronous electric motor that can divide a full rotation into a large number of steps. The motor''s position can be controlled precisely without any feedback mechanism, as long as the motor is carefully sized to the application. In various other embodiments, the stepper motor may be outside of the roller 106. Each roller pair may have a single or two stepper motors that drives the roller pair. Suitable mechanisms can be implemented to generate a clockwise and an anti-clockwise rotation in the roller pair 106 for generating the “drawing in” tension.
The clutch plate holder may include sensing mechanisms that sense the position of the friction material strip 108 with respect to the clutch plate holder. Sensing mechanisms may include, but not limited to, an infrared sensor. Upon detection of a desirable position of the friction material strip 108 over the clutch plate holder, the stepper motors or the rollers 106 may be configured to stop feeding the friction material strips. In an embodiment, a single “step” of the stepper motor corresponds to an exact positioning of the friction material strip 108 over the clutch plate holder. The “steps” of all the stepper motors used in the system can be time synchronized to simultaneously feed a plurality of friction material strips 108 to the friction clutch plate 104. As shown in the figure, the friction material strips are ready for a cutting operation.
The system 100 further includes a punching mechanism 110 configured to cut friction segments from the plurality of friction material strips 108. The punching mechanism 110 includes grooves or slots 112 around its lower cutting portion as shown. The grooves are spaced apart by a width equal to the intended space or width of the oil grooves on the friction clutch plate 104. The punching mechanism 110 also includes a top member connected to the lower cutting portion by a spring 114 fixed there between. The spring can be made of suitable material as per the restoration force requirement of the punching mechanism 110. In an embodiment, the restoration force of the spring 114 can be adjusted by varying the stiffness (spring constant) of the springs for proper bonding and appropriate pressing force.
In an embodiment, the punching mechanism 110 is configured to cut a plurality of friction material segments from the plurality of friction material strips 108 positioned over the friction clutch plate 104.
To this end, fig. 2 illustrates an isometric view of the system 100 during the cutting operation. Accordingly, the punching mechanism 110 is lowered by suitable mechanisms in such a manner that the ends of the friction material strips 108 positioned above the friction clutch plate 104 fits into the grooves or slots 112 as shown in the figure. It is noteworthy here that the number of grooves 112 is exactly equal to the maximum number of friction material strips 108. In addition, the relative orientation of the friction material strips 108 and the punching mechanism 110 is such that the ends of the friction material strips are exactly below the grooves 112. Moreover, the width of the grooves 112 is equal to the width of the friction material strip 108.
In an exemplary implementation, an edge of each of the grooves 112 that faces the friction material strips 108 and is parallel to the friction clutch plate 104 is configured with a cutting blade. The cutting blade can be made of materials known in the art.
In operation, as shown in fig. 2, the punching mechanism 110 is lowered further to enable the cutting blades of the grooves 112 to cut the plurality of friction material segments from the plurality of friction material strips 108. It may be noted that the length of the friction material segment cut from the friction material strip 108 is equal to the width of the annular surface of the friction clutch plate 104. The cutting operation involves pressing the cutting edge of the grooves 112 against the clutch plate holder with the friction material strip 108 there between. The friction material segments thus cut out from the friction material strips 108 remain fixed in the grooves 112 subsequent to the cutting operation.
Fig. 3 illustrates an isometric view of a system for manufacturing wet friction clutch plate during pasting of friction segments according to an embodiment of the present invention. As shown, the punching mechanism 110 moves down further to place the cut segments of friction material on the friction clutch plate. As described earlier, the punching mechanism 110 also includes a spring 114 fixed between the upper part and the lower cutting portion. During the pasting phase of the process, the lower cutting portion of the punching mechanism 110, after placing the segments on the friction clutch plate, comes to a temporary halt. The surface of the friction clutch plate facing the punching mechanisms has pre-applied adhesive. Moreover, in an embodiment, the lower surface of the segments of friction material may also have pre-applied adhesive. Due to adhesives applied on either the friction clutch plate or the friction material segment or both, the segments are placed onto the friction clutch plate due to the force applied by the punching mechanism 110 before coming to a halt.
In an exemplary embodiment, the top member of the punching mechanism 110 continues to move down even after the lower cutting portion has come to a halt. The downward displacement of the top member is determined by the spring constant of the spring used. Due to downward movement of the top member, the spring is compressed and the top member exerts a pressure on the lower cutting portion. The pressure thus exerted presses the friction material segments onto the friction clutch plate thereby bonding/pasting the segments firmly.
The disclosed spring- enabled pasting provides for flexible options of applying different pressures for different kinds and sizes of friction material segments. For example, a thicker friction material segment may require a larger pressing force and consequently a larger spring constant. When the spring is compressed to a maximum distance, the top member of the punching mechanism 110 also comes to a halt and spring exerts maximum pressure onto the friction material segments. In an embodiment, the punching mechanism 110 may remain in this position for a little while to continue applying pressure on the friction material segments.
Subsequent to the pasting operation described above, the top member moves up thereby relaxing the spring to restore its normal position. Once the spring retains its normal position, the lower cutting member also moves up thereby moving the punching mechanism 110 away from the friction clutch plate 104.
Fig. 4 illustrates an isometric view of the system 100 subsequent to the above-described pasting operation.
The friction material segments thus pasted conform to high accuracies with regard to positioning of the segments. In addition, the time lag between the cutting and pasting operation is reduced. Since a plurality of friction material segments is cut and pasted simultaneously, the manufacturing time and cost is reduced significantly.
As described earlier, the cutting and pasting operation is carried out subsequent to the application of a suitable adhesive material onto the annular surfaces of the friction clutch plate 104. The friction material may include known materials such as, but not limited to, fiber, cellulose strip, etc. Existing methods and systems may be used for obtaining friction material strips from friction material bands. It is desirable that the friction material strip has width that is equal to the annular width of the friction clutch plate 104 to avoid wastage of friction material.
In an alternative implementation, the friction material strip 108 may have adhesive material pre-applied on one side (that faces the friction clutch plate 104). In such implementations, the step of applying adhesive material onto the friction clutch plate can be eliminated thereby saving manufacture time and cost. Various methods known in the art can be used to manufacture such friction material strips with pre-applied adhesive.
In an alternative embodiment, the punching mechanism simultaneously carries out the pasting and pressing operation.
In yet another implementation, the system 100 may have the rollers 106 above and below the friction clutch plate 104 thereby enabling a simultaneous cutting and pasting operation onto both the annular surfaces thereby further saving manufacturing time and cost. In such an embodiment, the one or more punching mechanisms 110 can cut, paste and bond (e.g. by applying pressure) a plurality of segments on both the annular surfaces simultaneously. The timing of the bonding on the opposite annular surfaces can be so configured to have simultaneous placing and pressing of two segments on the opposite annular surfaces by two punching mechanisms 110.
The disclosed system follows an easier, faster, and economic method for manufacturing a friction plate. The disclosed method uses a friction material strip, tape, or band 108 with a pre-determined dimension that matches the annular width thereby increasing the yield and eliminating wastage of friction material. Further, the automated and independent positioning of the punching mechanism 110 and the rotation (if required) of the clutch plate 104 provides for a precise pre-determined control of placement and profiling of the segments.
Due to a possible automation of the cutting and feeding mechanism, no damage occurs to the profile of oil grooves between the adjacent segments. Moreover, the profiles can be modified by changing the shape of the segments and precisely controlling the positioning of the segments without having to change the punching mechanism 110. In addition, the proposed method provides for a higher degree of freedom to choose for different shapes of the segment.
Since, the number of steps is less; the whole process is faster. As discussed earlier, employing a plurality of punching mechanisms brings down the manufacturing time. The steps or processes in the disclosed methods can include partial or complete automation. Such automation results in very high accuracies in the profiling and placing of the segments and the oil grooves. Moreover, the disclosed method does not need very high operating temperature and hence the working environment is cool and healthy. In an exemplary embodiment, the method can be performed at room temperature.
Although the methods and systems have been described with reference to fig. 1, fig. 2, and fig. 3, in the context of system 100, it may be appreciated that the components such as, the index table 102, the punching mechanism 110, the rollers 106 can be integrated into a single system for manufacturing friction clutch plate. Therefore, it is to be understood that figures 1, 2, and 3 are illustrative embodiments and a single system 100 may perform all the steps as disclosed.
The disclosed design of the apparatus eliminates any vibrations thus resulting in consistent high quality wet friction clutch plates. The disclosed apparatus also eliminates any chance of deposition of dusts thus resulting in proper bonding and better oil grooves. The disclosed design also incorporates auto sensors that avoid wastage of material or the clutch plate (under process) during the changing of strip.
While this provisional patent application contains the description of the principal inventive concepts. The complete patent application pursuant here to, will fully and particularly describe the preferred embodiments of the present invention.
Dated this 23rd Day of March, 2011


We Claim:
1. A system for manufacturing a wet friction clutch plate, the wet friction clutch
plate having a core plate (104) and a plurality of friction material segments adhered to an annular
section of the core plate in a circumferential direction, such that a gap is provided between the
consecutive segments, the system comprising:
a clutch plate holder (116) for holding the core plate (104);
one or more adhesive discharging member for applying adhesive on the core plate (104);
a plurality of pair of rollers (106) for feeding one or more strip (108) of friction material, such that the pair of rollers (106) are disposed in a circumferential manner around the clutch plate holder (104) equidistant from each other and arranged to feed simultaneously one strip (108) of friction material by each pair of roller on the core plate (104); and
a punching mechanism (110) for cutting friction segments from the plurality of friction material strips (108), and pressing the segments on the core plate (104) such that a gap is maintained between the consecutive segments.
2. The system as claimed in claim 1, wherein the punching mechanism comprises of a top member and a cutting member, the top member being connected to the cutting member by a spring (114) fixed there between.
3. The system as claimed in claim 1 and 2, wherein the punching mechanism has a plurality of groves or slots (112) at a bottom end of the cutting member and configured to cut friction segments from the plurality of friction material strips.
4. The system as claimed in claim 3, wherein the grooves (112) are spaced apart by a width equal to the gap between the consecutive segments.
5. The system as claimed in claim 3, wherein the number of grooves (112) is equal to the number of friction material strips (108).
6. The system as claimed in claim 1, further comprising one or more stepper motors for controlling the rotation of the rollers.
7. The system as claimed in claim 1, further comprising a sensing mechanism for controlling the motion of the rollers by sensing the position of the friction material strip (108) with respect to the core plate (104).
8. The system as claimed in claim 7, wherein the sensing mechanism is an infrared sensor.
9. The system as claimed in claim 1, wherein the adhesive discharging member is configured to sprays a suitable adhesive through a nozzle onto the annular surface of the core plate (104).
10. The system as claimed in claim 1, wherein the application of adhesive includes rotating the clutch plate along with the clutch plate holder (116).
11. A method for manufacturing a wet friction clutch plate, the wet friction clutch plate having a core plate (104) and a plurality of friction material segments adhered to an annular section of the core plate in a circumferential direction, such that a gap is provided between the consecutive segments; the method comprising steps of:
applying adhesive on the core plate (104) by one or more adhesive discharging member;
simultaneously feeding one or more strips (108) of friction material from different directions by a plurality of pair of rollers (106) wherein the pair of rollers (106) are positioned around the circumference of the core plate (104) equidistant from each other;
cutting a friction segment from one or more strips (108) of friction material and pressing the segments on the circumference on the core plate (104) by a punching mechanism (110) such that a gap is maintained between the consecutive segments,
such that at least the feeding, cutting and pressing steps are performed without rotating the core plate (104).