Torque limiter

The torque limiter includes a flywheel, a clutch plate, a spline hub, a clutch disc assembly and a transmission torque limiting part. The flywheel includes a friction coupling surface. The clutch plate includes plural axial through holes. Plural friction members are respectively attached to the through holes. The spline hub can be engaged with a transmission-side shaft. The clutch disc assembly circumferentially elastically couples the clutch plate and the spline hub. The transmission torque limiting part limits torque to be transmitted from the flywheel to the transmission-side shaft while the friction members are interposed and held between the transmission torque limiting part and the friction coupling surface of the flywheel.

CROSS-REFERENCE TO THE RELATED APPLICATIONS

This U.S. National Stage Application claims priority under 35 U.S.C. §119(a) to Japanese Patent Application Nos. 2009-140027, 2009-140028, and 2009-140031, all of which were filed on Jun. 11, 2009. The entire content of Japanese Patent Application Nos. 2009-140027, 2009-140028, and 2009-140031 is hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a torque limiter, particularly to, a torque limiter configured to limit torque transmitted from a crankshaft of an engine to a transmission-side shaft.

BACKGROUND ART

Some vehicles are provided with a torque limiter for preventing components such as a transmission from being damaged or broken by excessive torque transmitted thereto from an engine. The torque limiter is normally disposed between the engine and the transmission for limiting torque transmitted thereto. In the torque limiter, for instance, at least one friction facing is interposed and held between a pair of plates at a predetermined holding force. Further, the input side of the torque limiter is coupled to engine-side members (e.g., a flywheel), while the output side of the torque limiter is coupled to transmission-side components (e.g., an input shaft).

The torque limiter of the aforementioned type includes a drive plate, a transmission torque limiting part, a driven-side member and a damper mechanism (see e.g., Patent Literature 1). The drive plate includes a friction coupling portion on the radial outer portion thereof. The transmission torque limiting part has a structure that the friction coupling portion of the drive plate is interposed and held between a pair of plates at a predetermined holding force. The driven-side member is coupled to an input shaft of a transmission. The damper mechanism is disposed among the aforementioned components. In the torque limiter, the paired plates that the friction coupling portion is interposed and held therebetween (or a damper cover disposed radial outwards of the friction coupling portion) are coupled to the flywheel.

In the torque limiter, engine torque is transmitted from the flywheel to the drive plate via the friction coupling portion and is further transmitted to the driven-side member and the input shaft of the transmission via the damper mechanism. When the engine torque then exceeds a predetermined level, slippage occurs between the plate and the friction coupling portion. Excess of the torque, exceeding the limit imposed by the transmission torque limiting part, is accordingly prevented from being transmitted to the transmission. Therefore, the transmission can be prevented from being damaged or broken by the excessive torque.

Japan Laid-open Patent Application Publication No. JP-A-2006-017226 (Patent Literature) is an example of the related art.

SUMMARY

Technical Problems

In the well-known torque limiters, a friction member is fixed to a cushioning plate fixed to a clutch plate as similarly seen in the normal clutch discs for the automobiles. Further, the following exemplary methods have been employed for fixing the friction member to the cushioning plate: (a) rivet swaging; (b) adhesion by means of an adhesive material; and (c) integration by means of molding.

In the rivet swaging as an exemplary fixing method, however, it is required to prepare rivets and form counter bores in the friction member for preventing the heads of the rivets from being protruded out of the surface of the friction member. Further in the rivet swaging, the friction (burn-off) length of the friction member is reduced. Further, in the adhesion by means of an adhesive material as an exemplary fixing method, the number of processing steps is increased and this results in cost increase. Yet further, in the integration by means of molding as an exemplary fixing method, the available cushioning shapes are limited and its cost is high.

Further, the well-known torque limiters as described above are normally fixed to the flywheel by means of bolts. The flywheel has been preliminarily attached to the axial end of the crankshaft of the engine. In other words, the flywheel is firstly fixed to the axial end of the crankshaft and the torque limiter is then fixed to the flywheel.

As described above, the well-known power transmission devices with the torque limiter require a flywheel attachment step and a torque limiter attachment step. Further, the torque limiter is coupled to the input shaft of the transmission through a spline joint portion formed on the driven-side member. Therefore, an axis misalignment between the spline joint portion and the flywheel is required to fall in a predetermined range under the condition that the torque limiter is secured to the flywheel. It is herein required to provide either a spigot ferrule or a pair of a knock pin and a pin hole for appropriately positioning both of the torque limiter and the flywheel. Further, an axis-aligning tool for radial positioning is required to be used for setting the axis misalignment between the flywheel and the spline joint portion of the driven-side member to fall in a predetermined range. The axis-aligning tool is herein fitted into, for instance, the spline coupling portion and the holes of the crankshaft.

It is an object of the present invention to provide a torque limiter achieving fixation of a friction member with a simple structure at a low cost.

It is another object of the present invention to provide a torque limiter that can be easily attached to the engine and does not require an axis-alignment operation for radial positioning thereof after being attached to the engine.

Solution to Problems

In the clutch disc assemblies embedded in the clutch devices for automobiles and so forth, the aforementioned well-known methods of fixing the friction member are used for switching the clutch devices between a turned-on state (i.e., permission of power transmission) and a turned-off state (prevention of power transmission). In the torque limiters, by contrast, it is not required to turn on and off (i.e., activate and deactivate pressure of) the friction member. In addition, it is not required to axially fix the friction member. Further, the amount of abrasion of the friction members in the torque limiters is less than that of the friction members to be used in the clutch devices for automobiles and so forth.

In view of the above, the following torque limiters of the present invention have been produced. A torque limiter according to a first aspect of the present invention is a torque limiter configured to limit a torque to be transmitted from an engine-side member to a transmission-side shaft. The torque limiter includes a drive member, a friction coupling plate, an output-side member, a damper mechanism and a transmission torque limiting part. The drive member is coupled to the engine-side member and includes a friction coupling surface. The friction coupling plate includes a plate body and a single or plurality of friction members. The plate body includes a single or plurality of holes axially penetrating therethrough. Further, the plate body axially has a first thickness. The single or plurality of friction members is attached to the single or plurality of holes of the friction coupling plate on a one-to-one basis. Further, the single or plurality of friction members respectively has a second thickness greater than the first thickness. The output-side member is allowed to be engaged with the transmission-side shaft. The damper mechanism circumferentially elastically couples the friction coupling plate and the output-side member. The transmission torque limiting part is configured to limit a torque to be transmitted from the drive member to the transmission-side shaft while the single or plurality of friction members being interposed and held between the transmission torque limiting part and the friction coupling surface of the drive member.

According to the torque limiter of the first aspect of the present invention, the torque transmitted to the drive member is transmitted to the output-side member through the single or plurality of friction members of the friction coupling plate and is further transmitted to the transmission-side shaft. When excessive torque is inputted from the engine side, the transmitted torque is limited at the single or plurality of friction coupling members and the periphery thereof by the action of the transmission torque limiting part.

Further, the single or plurality of friction members is herein respectively fixed to the single or plurality of holes of the friction coupling plate on a one-to-one basis. Accordingly, the single or plurality of friction coupling members can be fixed to the plate at a lower cost than the well-known fixation method using rivets, adhesive material or molding. Yet further, the torque limiter can be formed with a simple structure. In particular, the axial size of the torque limiter can be reduced.

A torque limiter according to a second aspect of the present invention relates to the torque limiter according to the first aspect of the present invention. In the torque limiter, the damper mechanism includes an input-side plate, an output-side plate and a plurality of torsion springs. The output-side plate is coupled to the transmission-side shaft. The plurality of torsion springs is disposed between the input-side plate and the output-side plate for elastically coupling the input-side plate and the output-side plate. Further, the friction coupling plate is a radial outer portion of the input-side plate.

According to the torque limiter of the second aspect of the present invention, the input-side plate of the damper mechanism and the friction coupling plate are integrated as a single member. Therefore, the torque limiter can be formed with a simpler structure. In particular, the axial size of the torque limiter can be more reliably reduced.

A torque limiter according to a third aspect of the present invention relates to the torque limiter according to the first aspect of the present invention. In the torque limiter, the holes and the friction members of the friction coupling plate are respectively circumferentially disposed at equal angular intervals.

A torque limiter according to a fourth aspect of the present invention relates to the torque limiter according to the third aspect of the present invention. In the torque limiter, each of the friction members is press-fitted in the corresponding one of the holes without producing a circumferential clearance therein.

A torque limiter according to a fifth aspect of the present invention relates to the torque limiter according to the first aspect of the present invention. In the torque limiter, the transmission torque limiting part includes a pressure ring pressing the single or plurality of friction members onto the friction coupling surface of the drive member. Further, at least either of the pressure ring and the friction coupling surface of the drive member includes a protrusion disposed radial inwards of the single or plurality of friction members. The protrusion is protruded closer to the corresponding one of faces of the friction coupling plate.

According to the torque limiter of the fifth aspect of the present invention, the protrusion, protruded from at least either of the drive member and the pressure ring, is disposed radial inwards of the single or plurality of friction members. With the single or plurality of protrusions, foreign substance such as mud and water can be inhibited from entering the friction material side.

A torque limiter according to a sixth aspect of the present invention relates to the torque limiter according to the first aspect of the present invention. The torque limiter further includes an urging member disposed between the drive member and the friction coupling plate for urging the friction coupling plate in a direction away from the drive member.

According to the torque limiter of the sixth aspect of the present invention, the axial movement of the friction coupling plate is inhibited. Therefore, it is possible to inhibit abrasion and production of abnormal sounds in the respective members that may be caused by the axial movement (i.e., vibration) of the friction coupling plate.

A torque limiter according to a seventh aspect of the present invention relates to the torque limiter according to the first aspect of the present invention. In the torque limiter, the transmission limiting part includes a pressure ring, a cone spring and a support member. The pressure ring holds the single or plurality of friction members with the friction coupling surface of the drive member while the single or plurality of friction members is interposed therebetween. The cone spring is a ring-shaped member including a radial inner portion pressing the pressure ring towards the drive member. The support member is attached to the drive member for supporting a radial outer portion of the cone spring.

A torque limiter according to an eighth aspect of the present invention is a torque limiter configured to limit a torque to be transmitted from a crankshaft of an engine to a transmission-side shaft. The torque limiter includes a disc-shaped drive member, an input-side member, an output-side member, a damper mechanism and a transmission torque limiting part. The disc-shaped drive member includes a friction coupling surface. The disc-shaped drive member is allowed to be coupled to an end of the crankshaft. The disc-shaped drive member includes a plurality of attachment holes circumferentially aligned on a radial inner portion thereof. The attachment holes allow a plurality of fasteners for fixation to be inserted therein on a one-to-one basis. The input-side member includes a friction member on a radial outer portion thereof. The output-side member includes an engaging portion allowed to be engaged with the transmission-side shaft. The damper mechanism circumferentially elastically couples the input-side member and the output-side member. The transmission torque limiting part is configured to limit a toque to be transmitted from the drive member to the transmission-side shaft while the friction member of the input-side member is interposed and held between the transmission torque limiting part and the friction coupling surface of the drive member.

According to the torque limiter of the eighth aspect of the present invention, the torque transmitted to the drive member is transmitted to the output-side member through the friction member of the input-side member and is further transmitted to the transmission-side shaft. When excessive torque is inputted from the engine side, the transmitted torque is limited at the friction member and the periphery thereof by the action of the transmission torque limiting part.

Further, the drive member (e.g., a flywheel) has been preliminarily embedded in the torque limiter. Therefore, the entire torque limiter, including the drive member and the output-side member, can be attached onto the end of the crankshaft while the axis misalignment between the drive member and the engaging portion of the output-side member is set to be in a predetermined range. The attachment work will be thereby easily done. Further, a work is not required for aligning the axes of the crankshaft and the output-side member.

A torque limiter according to a ninth aspect of the present invention relates to the torque limiter according to the eighth aspect of the present invention. In the torque limiter, the drive member includes a positioning portion for executing radial positioning thereof with respect to the crankshaft.

According to the torque limiter of the ninth aspect of the present invention, the axis of the drive member can be aligned with that of the crankshaft by means of the positioning portion of the drive member. Therefore, no structure and no work are required for aligning the axes of the engaging portion of the output-side member and the crankshaft.

A torque limiter according to a tenth aspect of the present invention relates to the torque limiter according to the ninth aspect of the present invention. In the torque limiter, the engaging portion of the output-side member has an axis misalignment of less than or equal to 1.0 mm with respect to the positioning portion of the drive member.

A torque limiter according to an eleventh aspect of the present invention relates to the torque limiter according to the eighth aspect of the present invention. In the torque limiter, the input-side member and the damper mechanism are disposed radial outwards of a pitch circle diameter of the attachment holes of the drive member. Further, no other member excluding the output-side member is disposed radial inwards of the pitch circle diameter.

According to the torque limiter of the eleventh aspect of the present invention, members are concentratedly disposed on the radial outer side while no member is disposed on the radial inner side. Therefore, the torque limiter can be formed with a lightweight structure. Further, the torque limiter can obtain relatively large inertia of moment in spite of the lightweight structure thereof.

A torque limiter according to a twelfth aspect of the present invention relates to the torque limiter according to the eighth aspect of the present invention. The torque limiter further includes the fasteners for fixation inserted into the attachment holes of the drive member on a one-to-one basis.

According to the torque limiter of the twelfth aspect of the present invention, the fixing fasteners such as bolts have been preliminarily attached to the drive member. Therefore, no space is required for inserting the fixing fasteners into the attachment holes of the drive member in the post-processing steps. Accordingly, the axial size of the toque limiter can be reduced.

A torque limiter according to a thirteenth aspect of the present invention relates to the torque limiter according to the twelfth aspect of the present invention. In the torque limiter, the output-side member includes a boss and a flange. The boss has a spline joint portion in a center part thereof. The flange is extended radial outwards from the boss. Further, the flange includes a tool inserting hole allowing a tightening tool to be inserted therein for fixing the fasteners for fixation respectively inserted into the attachment holes of the drive member to the crankshaft by means of the tightening tool.

A torque limiter according to a fourteenth aspect of the present invention is a torque limiter configured to limit a torque to be transmitted from a crankshaft of an engine to a transmission-side shaft. The torque limiter includes a disc-shaped drive member, a disc-shaped input-side member, an output-side member, a damper mechanism and a transmission torque limiting part. The disc-shaped drive member includes a friction coupling surface on a radial outer portion thereof. The disc-shaped drive member is allowed to be coupled to an end of the crankshaft. The disc-shaped input-side member includes a friction member on a radial outer portion thereof. The output-side member includes an engaging portion allowed to be engaged with the transmission-side shaft. The damper mechanism circumferentially elastically couples the input-side member and the output-side member. The transmission torque limiting part is configured to limit a torque to be transmitted from the drive member to the transmission-side shaft while the friction member of the input-side member is interposed and held between the transmission torque limiting part and the friction coupling surface of the drive member. Further, the drive member includes an axially extended abutment portion on the radial outer portion thereof for executing radial positioning thereof. An outer peripheral edge of the input-side member is abutted to the abutment portion of the drive member for executing radial positioning of the input-side member, the output-side member and the damper mechanism.

According to the torque limiter of the fourteenth aspect of the present invention, the torque transmitted to the drive member is transmitted to the output-side member through the friction member of the input-side member and is further transmitted to the transmission-side shaft. When excessive torque is inputted from the engine side, the transmitted torque is limited at the friction member and the periphery thereof by the action of the transmission torque limiting part.

Further, the drive member (e.g., a flywheel) has been herein preliminarily embedded in the torque limiter. Therefore, the entire torque limiter, including the drive member and the output-side member, can be attached onto the end of the crankshaft while the axis misalignment between the drive member and the engaging portion of the output-side member is set to be in a predetermined range. The attachment work will be thereby easily done. Further, no work is required for aligning the axes of the crankshaft and the output-side member.

Yet further, the outer peripheral edge of the input-side member is abutted to the abutment portion of the drive member for executing radial positioning of the respective members. Therefore, the respective members (e.g., the input-side member) are not required to be extended to the inner radial part of the drive member. As a result, a small number of members are disposed on a transmission-side part of the inner radial part of the drive member. Accordingly, it is possible to easily form the structure for fixing the entire torque limiter including the drive member to the engine-side member.

A torque limiter according to a fifteenth aspect of the present invention relates to the torque limiter according to the fourteenth aspect of the present invention. In the torque limiter, the drive member includes a tubular inner peripheral surface axially extended. Further, the abutment portion for executing radial positioning is formed on the tubular inner peripheral surface.

According to the torque limiter of the fifteenth aspect of the present invention, the abutment portion is formed on the tubular inner peripheral surface formed in the drive member. Further, the outer peripheral edge of the input-side member is abutted to the abutment portion. Therefore, radial positioning of the input-side member can be done with a simple structure.

A torque limiter according to a sixteenth aspect of the present invention relates to the torque limiter according to the fifteenth aspect of the present invention. In the torque limiter, the tubular inner peripheral surface includes a first engaging portion on an axial transmission side of the abutment portion. Further, the transmission toque limiting part includes a pressure ring, a cone spring and a support member. The pressure ring holds the friction member with the friction coupling surface of the drive member while the friction member is interposed therebetween. The cone spring is a ring-shaped member including a radial inner portion pressing the pressure ring towards the drive member. The support member is attached to the drive member for supporting a radial outer portion of the cone spring. Yet further, the pressure ring includes a second engaging portion on a radial outer portion thereof. The second engaging portion is engaged with the first engaging portion for preventing the pressure ring from rotating relative to the drive member.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Entire Structure

FIG. 1illustrates a cross-sectional view of a torque limiter with a flywheel according to an exemplary embodiment of the present invention. Further,FIG. 2is a front view of a part of the torque limiter with a flywheel. Although not being illustrated inFIG. 1, the structure assumed inFIG. 1is that an engine is disposed on the left side of the torque limiter while a transmission is disposed on the right side of the torque limiter.

A torque limiter1is disposed between a crankshaft2of the engine and an input shaft3of the transmission for limiting torque to be transmitted from the engine to the transmission. Further, the torque limiter1includes a flywheel5as a drive member, a clutch disc assembly6and a transmission torque limiting part7including a part of the clutch disc assembly6.

The flywheel5is a disc-shaped member. The flywheel5includes a hole5aand a disc portion10. The hole5ais formed in the center of the flywheel5, while the disc portion10is formed from the radial inner part to the radial intermediate part of the flywheel5. Further, the flywheel5includes a mass portion11on the radial outside of the disc portion10. The hole5a, formed in the center of the flywheel5, is fitted onto a spigot ferrule2aformed on the axial end face of the crankshaft2. Accordingly, the flywheel5and the crankshaft2are appropriately positioned in the radial direction.

The disc portion10includes a plurality of through holes5bcircumferentially aligned on the radial inner part thereof. A plurality of bolts12is respectively inserted into the through holes5bon a one-to-one basis. The bolts12are respectively screwed into a plurality of screw holes of the crankshaft2on a one-to-one basis. Accordingly, the flywheel5can be fixed to the axial end face of the crankshaft2. Further, the axial thickness of the entire disc portion10is roughly constant in the radial direction. It should be noted that each bolt12is a hexagon socket bolt including a hexagon socket on the head thereof for allowing a tightening tool to be inserted therein.

The mass portion11has an axial thickness greater than that of the disc portion10. As illustrated in an enlarged view ofFIG. 3, the mass portion11includes an accommodation portion14on the transmission-side face thereof. The accommodation portion14is recessed towards the engine. The accommodation portion14includes a radial positioning surface14aon the outer periphery thereof as an axially extended tubular inner peripheral surface. Further, the accommodation portion14includes a friction coupling surface14bon a part corresponding to the bottom surface thereof (i.e., an engine-side wall surface).

Further, the flywheel5includes a plurality of recesses15in a boundary part between the disc portion10and the mass portion11on the engine-side face thereof. The recesses15are recessed towards the transmission. The recesses15are aligned in the circumferential direction of the flywheel5. Each of the recesses15is formed in a circular-arc shape. Yet further, the flywheel5includes a plurality of through holes16bored from the face thereof opposite to the engine-side face thereof. The through holes16are respectively arranged to be matched with the recesses15on a one-to-one basis. The through holes16penetrate to the recesses15. It should be noted that each through hole16is herein shaped for preventing the engine side from being seen from the transmission side in the axial direction. More specifically, the inner diameter of the friction coupling surface14bis less than the outermost diameter of the disc portion10in the part that the through holes16are formed.

Clutch Disc Assembly

The clutch disc assembly6mainly includes a pair of a clutch plate20and a retaining plate21, a spline hub22and a plurality of torsion springs (damper mechanism)23elastically coupling the spline hub22and the pair of the clutch plate20and the retaining plate21

Each of the clutch plate20and the retaining plate21is an annular member made of, for instance, a sheet metal. The clutch plate20and the retaining plate21are axially separated at a predetermined interval. The clutch plate20is disposed on the engine side, while the retaining plate21is disposed on the transmission side. The radial outer portion of the retaining plate21is partially bent towards the clutch plate20and is further bent radial inwards. The radial-inwardly bent portions of the retaining plate21are respectively fixed to the radial outer portion of the clutch plate20by means of rivets24. Accordingly, the clutch plate20and the retaining plate21are configured to be unitarily rotated.

Further, each of the clutch plate20and the retaining plate21includes four window holes on the radial outer portion thereof. The window holes are disposed at equal intervals along the rotary direction. The window holes respectively supports the torsion springs23on a one-to-one basis. Further, the clutch plate20includes a hole20ain the center part thereof, while the retaining plate21includes a hole21ain the center part thereof. The diameters of the holes20aand21aof the plates20and21are both greater than an attachment pitch circle P (seeFIG. 1) of the bolts12for fixing the flywheel5to the crankshaft2. Therefore, no other component excluding the spline hub22is disposed radial inwards of the clutch disc assembly6.

The outer periphery of the clutch plate20is extended to the friction coupling surface14bof the flywheel5. The outer peripheral edge of the clutch plate20is disposed adjacent to the radial positioning surface14aof the accommodation portion14of the flywheel5. The clutch plate20is appropriately positioned in the radial direction by the radial positioning surface14a.

Further, a plurality of friction members26is disposed on the radial outer portion of the clutch plate20. In other words, the radial outer portion of the clutch plate20functions as a friction coupling plate. More specifically, the clutch plate20includes a plurality of circular-arc holes20bon the radial outer portion thereof, as illustrated inFIG. 2. The circular-arc holes20bare aligned along the circumferential direction of the clutch plate20. The circular-arc shaped friction members26are respectively attached to the circular-arc holes20bon a one-to-one basis. Specifically, the circumferential end surfaces of each friction member26are press-fitted and attached into a corresponding one of the holes20b. It should be noted that a clearance is produced between each friction member26and a corresponding one of the holes20bin a radial direction. Each friction member26has a thickness greater than that of the clutch plate20.

The spline hub22includes a boss28and a hub flange29. The boss28is an axially extended tubular portion, whereas the hub flange29is a disc-shaped portion extended from the boss28in the radial direction. The boss28and the hub flange29are integrally formed. The boss28includes a spline hole28ain the inner periphery thereof. The input shaft3of the transmission is fitted into the spline hole28a. On the other hand, the hub flange29includes a plurality of notches aligned along the rotary direction. The notches respectively accommodate the torsion springs23on a one-to-one basis. The hub flange29includes a plurality of holes29ain the radial intermediate part thereof. The holes29aare positioned to be matched with the bolts12. A tool for tightening the bolts12is herein allowed to be inserted into the holes29a. It should noted in the present exemplary embodiment that the axis misalignment of the spline hole28awith respect to the spigot ferrule2aof the crankshaft2is reduced to be equal to or less than 1.0 mm, and specifically, falls in a range of 0.2 mm to 0.3 mm.

Further, one of bushes30is disposed between the hub flange29of the spline hub22and the clutch plate20, while the other of the bushes30is disposed between the hub flange29of the spline hub22and the retaining plate21. The bushes30are respectively fixed to the clutch plate20and the retaining plate21are configured to produce hysteresis torque in relative rotation to the faces of the hub flange29.

Transmission torque limiting part

As illustrated inFIGS. 1 to 3, the transmission torque limiting part7includes the aforementioned friction members26, a pressure ring32, a cone spring33and a cover member34as a support member. The pressure ring32herein holds the friction members26with the friction coupling surface14bof the flywheel5while the friction members26are interposed therebetween. The pressure ring32and the cone spring33, together with the friction members26, are accommodated in the accommodation portion14of the flywheel5.

The pressure ring32is a ring-shaped plate member. The pressure ring32includes a plurality of radial-outwardly protruded engaging protrusions32aon the radial outer portion thereof. On the other hand, the accommodation portion14of the flywheel5includes a plurality of engaging recesses14con the outer peripheral surface thereof, as illustrated in an enlarged view ofFIG. 4. The engaging recesses14care aligned at equal intervals along the circumferential direction of the accommodation portion14. The engaging protrusions32aof the pressure ring32are respectively engaged with the engaging recesses14cof the flywheel5on a one-to-one basis. Accordingly, the pressure ring32is prevented from rotating relatively to the flywheel5but is allowed to move in the axial direction.

As described above, the cone spring33is accommodated in the accommodation portion14of the flywheel5, while the radial inner portion thereof presses the pressure ring32towards the flywheel5.

The cover member34is a ring-shaped plate member fixed to the transmission-side end surface of the mass portion11of the flywheel5by means of a plurality of rivets36. Further, the cover member34supports the radial outer portion of the cone spring33. In other words, the inner diameter of the cover member34is less than the outer diameter of the cone spring33.

The cover member34and the pressure ring32are herein made of a single ring-shaped plate member. Therefore, the cover member34includes a plurality of radial-outwardly directed recesses34a(seeFIG. 2) on the inner peripheral edge thereof. Specifically, the pressure ring32is punched from the single ring-shaped plate member by means of stamping. Accordingly, the remaining part (i.e., the cover member34) of the single-shaped plate member includes the recesses34aarranged to be matched with the engaging protrusions32a. The recesses34afunction as flow paths40(seeFIG. 4) communicating the outside of the torque limiter1and the radial outer portion of the clutch plate20that the friction members26are disposed. Therefore, it is possible to discharge mud water and the like, entering the radial outer portion of the clutch plate20, to the outside through the flow paths40.

In the aforementioned structure, transmittable torque is determined by the urging force of the cone spring33, the friction coefficients of the friction members26, and the effective radius of the friction coupling portion. When a torque greater than the transmittable torque is inputted from the engine side, slippage occurs in the friction coupling portion and the transmission torque is thereby limited to a predetermined torque.

Assembling and Attachment of Torque Limier

In assembling the aforementioned torque limiter, the clutch disc assembly6is required to be preliminarily assembled. Next, the bolts12are inserted into the bolt attachment holes of the flywheel5. Subsequently, the clutch disc assembly6, the pressure ring32and the cone spring33are sequentially disposed in this order in the accommodation portion14of the flywheel5. Finally, the cover member34is fixed to the flywheel5by means of the rivets36.

The torque limiter with the flywheel is thus obtained. The clutch disc assembly6and the flywheel5, forming the main body of the torque limiter, are appropriately positioned in the radial direction by the outer peripheral edge of the clutch plate20and the radial positioning surface14aof the flywheel5. In other words, the axes of the flywheel5and the spline engaging hole28aof the clutch disc assembly6are aligned before the flywheel5and the clutch disc assembly6are fixed onto the crankshaft2.

Thus obtained torque transmitter with the flywheel is attached onto the crankshaft2. Specifically, the spigot ferrule2aof the crankshaft2is fitted into the hole5aformed in the center of the flywheel5. Accordingly, the torque limiter is entirely set on the crankshaft2. Next, the plural bolts12are respectively screwed into the screw holes formed on the axial end surface of the crankshaft. The tightening tool is then inserted into each of the holes29aformed in the hub flange29of the spline hub22and the tip thereof is locked with the hexagon socket formed on the head of each bolt12for receiving the tightening tool. Each bolt12is thus tightened and fixed therein by means of the tightening tool.

Detachment of Torque limiter

Thus attached torque limiter can be detached in the following procedure. It should be noted that the hub flange29of the spline hub22includes four holes29bthat a pin is inserted for detaching the attached torque limiter as illustrated in diagrams ofFIG. 7Aand thereafter. The holes29bare herein arranged at equal intervals of 90 degrees. Likewise, the flywheel5includes four holes5carranged to be matched with the holes29b. InFIG. 7A, “tool inserting holes” to be described correspond to the aforementioned holes29aformed in the hub flange20of the spline hub22for allowing the tool to be inserted. As is obvious fromFIG. 7A, when the phase of the pin inserting holes29band that of the pin inserting holes5cof the flywheel5are matched (i.e., their circumferential positions are matched), the phase of the tool inserting holes29aand that of the bolts12are also matched.

First,FIG. 7Aillustrates a state immediately after attachment of the torque limiter. Under the condition, the phase of the tool inserting holes29aof the spline hub22and that of the bolts12are matched. In other words, each bolt12can be screwed by means of the tool inserted through the corresponding one of the tool inserting holes20a.

As illustrated inFIG. 7B, on the other hand, the phase of the tool inserting holes29band that of the bolts12are misaligned (i.e., their circumferential positions are not matched) when the clutch disc assembly6is rotated with respect to the flywheel5in conjunction with activation of the torque limiter. In this case, two pins50are firstly inserted into two of the pin inserting holes29b. The pins50are herein kept inserted into the holes29bwithout being deeply inserted therein for avoiding the tips thereof from making contact with the bolts12even when the clutch disc assembly6is rotated.

Next, a jig51is prepared as illustrated inFIG. 7C. The jig51includes a flanged portion52, a spline shaft53and a nut portion54. The spline shaft53is formed on one face of the flanged portion52. The nut portion54is formed on the other face of the flanged portion52. The flanged portion52includes four holes for allowing the pins50to pass therethrough. Further, an alignment pin55is fixed to the flanged portion52. The alignment pin55can be inserted into each tool inserting hole29a. The outer diameter of the pin55is roughly the same as the inner diameter of each hole29a.

The aforementioned jig51is set as illustrated inFIG. 7Cand the nut portion54is rotated by means of a tool56. The damper disc assembly6is accordingly rotated. Rotation of the damper disc assembly6is then stopped under the condition that positions of the pins50are matched with two of the pin inserting holes5cof the flywheel5. The pins50are herein deeply inserted and fitted into two of the pin inserting holes5cof the flywheel5.

It is judged whether or not the positions of the pins50are matched with those of two of the pin inserting holes5cof the flywheel by observing the pin inserting holes5cof the flywheel5through the remaining pairs of the hole of the flanged portion52cand the pin inserting hole29bof the spline hub22in which the pins50are not inserted.

Further, the flywheel5includes alignment markings5dformed or attached thereon. It is also possible to judge that the positions of the pins50are matched with two of the pin inserting holes5cof the flywheel by matching the phase of the alignment markings5dand that of the pin inserting holes29b.

The jig51is detached under the condition that the phase of the pins50and that of the pin inserting holes5cof the flywheel5are matched as described above.FIG. 7Eillustrates the state of the torque limiter that the jig51is detached. The phase of the clutch disc assembly6is herein locked by means of the pins50. Therefore, the phase of the flywheel5and that of the clutch disc assembly6are prevented from being misaligned even when the jig51is detached therefrom. Under the condition, each bolt12is loosened by means of the tool inserted through the corresponding one of the tool inserting holes29a. The torque limiter with the flywheel is then detached from the crankshaft2.

Features

(1) The friction members26are attached and fixed in the holes20bformed in the clutch plate20. Therefore, the friction members can be fixed to the plate at a lower cost, compared to the well-known fixing methods using rivets, adhesive materials or molding. Further, the axial size of the torque limiter can be reduced.

(2) The radial outer portion of the clutch plate20functions as a friction coupling plate. Therefore, the torque limiter can be more simply structured. Especially, the axial size of the torque limiter can be further reduced.

(3) The flywheel5has been preliminarily embedded in the torque limiter. Therefore, the entire torque limiter, including components such as the flywheel5and the spline hub22, can be attached onto the crankshaft2while the axis misalignment between the flywheel5and the spline hole28aof the spline hub22is set to fall in a predetermined range. Therefore, the attachment work of the torque limiter can be easily done. In addition, no work is required for aligning the axes of the crankshaft2and the spline hub22.

Specifically, the axis of the flywheel5can be aligned with the axis of the crankshaft2by means of the hole5aformed in the center of the flywheel5. Further, the axes of the flywheel5and the spline hole28aof the spline hub22are aligned. Therefore, no structure and work is required for aligning the axes of the crankshaft2and the spline hole28aof the spline hub22.

(4) In the transmission torque limiting part7, the torsion springs23and the pair of the clutch plate20and the retaining plate21are disposed radial outwards of the pitch circle of the bolts attached to the flywheel5. In other words, components are concentratedly disposed on the radial outer side. Therefore, the torque limiter can be formed in a lightweight structure. Further, the torque limiter can obtain relatively large inertia of moment in spite of the lightweight structure thereof.

(5) The bolts12have been preliminarily attached to the flywheel5. Therefore, no space is required for inserting the bolts12into the attachment holes of the flywheel5in the post-processing steps. Accordingly, the axial size of the toque limiter can be reduced.

(6) The axis of the clutch disc assembly6is aligned with the crankshaft2while the outer peripheral edge of the clutch plate20is abutted to the radial positioning surface14aof the flywheel5. Therefore, it is not required to extend the radial inner portion of the clutch plate20to the boss28of the spline hub22as structured in the well-known torque limiters. Accordingly, only the spline hub22is disposed radial inwards of the flywheel5on the transmission side. In other words, the flywheel5can be fixed onto the crankshaft2with a simple structure.

Other Exemplary Embodiments

The present invention is not limited to the aforementioned exemplary embodiment, and a variety of changes and modifications can be made without departing from the scope of the present invention.

(a) As illustrated inFIG. 5, the friction coupling surface14bof the flywheel5may include an annular protrusion42on the inner peripheral edge thereof. Likewise, the pressure ring32may include an annular protrusion43on the inner peripheral edge thereof. The protrusions42and43are disposed adjacent to the inner peripheral edges of the friction members26. Further, the protrusions42and43are disposed adjacent to the faces of the clutch plate20while being separated at a predetermined interval. It should be noted that at least one of the flywheel5and the pressure ring32may include the protrusion.

The aforementioned protrusions42and43can inhibit mud water and the like, moving from the inner peripheral side, from entering the parts including the friction members26. Therefore, abrasion and slippage of the friction members26can be inhibited.

(b)FIG. 6illustrates yet another exemplary embodiment of the present invention. In this case, the friction coupling surface14bof the flywheel5includes an annular notch44on the inner peripheral edge thereof. Further, a wave washer45is disposed on the notch44. In other words, the wave washer45is disposed radial inwards of the friction members26while being interposed between the flywheel5and the clutch plate20. The wave washer45urges the clutch plate20in a direction away from the flywheel5(i.e., towards the pressure ring32).

The axial movement of the clutch plate20can be herein inhibited by the urging force of the wave washer45. It is thereby possible to inhibit abrasion and abnormal noise production of the respective components that may be caused by the axial movement (i.e., vibrations) of the clutch plate20.

It should be noted that the member for urging the clutch plate20is not limited to the wave washer and may be an elastic member made of resin or the like.

(c) The hole5a, formed in the center of the flywheel5, is engaged with the spigot ferrule2aof the crankshaft2in aligning the axis of the flywheel5with that of the crankshaft2. However, a knock pin may be used for aligning the axes of the flywheel5and the crankshaft2.

(d) It is not required to preliminarily attach the bolts12to the flywheel5when larger holes than the holes29aof the aforementioned exemplary embodiment can be formed in the hub flange29of the spline hub22.

(e) The shape and the number of the friction members are not limited to those in the aforementioned exemplary embodiment. For example, a plurality of friction members may be respectively formed in a circular shape.

INDUSTRIAL APPLICABILITY

According to the aforementioned present invention, the friction members can be fixed in the torque limiter with a simple structure at a low cost.

Advantageous Effects of the Invention

According to the aforementioned present invention, the single or plurality of friction members can be fixed in the torque limiter with a simple structure at a low cost. Further, according to the present invention, the obtained torque limiter can be easily attached to the engine side and does not require an axis-aligning work for post-attachment radial positioning. Yet further, according to the present invention, the torque limiter includes the drive member preliminarily attached thereto and the entire torque limiter is designed to be fixed to the engine-side member. Therefore, the torque limiter can be easily attached onto the crankshaft. In addition, radial positioning of the torque limiter can be appropriately done.