Patent Publication Number: US-2002010028-A1

Title: Torsional vibration damper

Description:
BACKGROUND OF THE INVENTION  
       [0001] The present invention relate in general to torque transmitting devices, particularly for motor vehicles for transmitting torque from engines to transmissions. More particularly, the present invention relates to torsional vibration dampers of the kind suited for use with motor vehicle engines.  
       [0002] An example of this kind of torsional vibration damper is disclosed in Japanese Patent Provisional Publication No. 63-26423. The torsional vibration damper includes a flywheel element drivingly connected to an input side element, i.e., a crankshaft of an engine, a damper hub rotatable relative to the flywheel element and drivingly connected to an output side element, i.e., a transmission side element, the damper hub having a plurality of radial hub arms, and a plurality of compression springs disposed circumferentially between the flywheel element and the hub arms of the damper hub for resiliently and drivingly connecting between the crankshaft and the transmission side element.  
       [0003] The flywheel element has a spring retaining portion in the form of an annular chamber in which the compression springs are disposed.  
       SUMMARY OF THE INVENTION  
       [0004] In operation, the compression springs are held out of contact from an inner surface of the spring retaining portion when the deflection of each compression spring is small. However, when the compression springs are compressed to have a large deflection, they are bent radially outward and brought into contact with the inner surface of the spring retaining portion. By such contact or engagement with the compression springs, the inner surface of the spring retaining portion is liable to be worn. Particularly, when the flywheel element driven by the crankshaft at high speed, the compression springs are subjected to a large centrifugal force, therefore tend to be bent further outward and urged against the inner surface of the spring retaining portion with a larger force, thus causing a further accelerated wear of the inner surface of the spring retaining portion.  
       [0005] As a result, the space between the compression springs and the inner surface of the spring retaining portion of the flywheel element is increased so that the compression springs cannot be held stable within the spring retaining portion, thus lowering the torsional vibration absorbing efficiency by the compression springs and the durability of the torsional vibration damper itself. Further, when the compression springs are urged against the inner surface of the spring retaining portion of the flywheel element with an excessively large force, there is a possibility that a large hysteresis in the torsional vibration damping action is caused, thus disabling the torsional vibration damper from attaining stable torsional vibration damping characteristics.  
       [0006] An object of the present invention is to provide a torsional vibration damper which is free from the above described hysteresis in the torsional action or torsional vibration damping action and can attain stable torsional vibration damping characteristics.  
       [0007] Another object of the present invention is to provide a torsional vibration damper which has a good durability and can effect an efficient torsional vibration damping action over an elongated period of usage.  
       [0008] To achieve the above object, there is provided according to an aspect of the present invention a torsional vibration damper comprising a pair of first and second torque transmitting elements rotatable relative to each other, a damper hub operatively connected to the first torque transmitting element and having a plurality of circumferentially equally spaced radial hub arms, a plurality of compression springs extending between the second torque transmitting element and the respective hub arms, and a ring member disposed radially outside the compression springs and having an inner circumferential surface held in contact with radially outer boundaries of the compression springs.  
       [0009] According to another aspect of the present invention, there is provided a torsional vibration damper comprising a pair of first and second torque transmitting elements rotatable relative to each other, a damper hub connected to the first torque transmitting element for rotation therewith and having a plurality of circumferentially spaced radial hub arms, a plurality of compression springs disposed between the second torque transmitting element and the hub arms, a drive plate assembly connected to the second torque transmitting element for rotation therewith and having an annular chamber in which the compression springs are disposed, and an endless ring member disposed within the annular chamber and radially outside the compression springs, the ring member having an inner circumferential surface held in contact with radially outer boundaries of the compression springs, a predetermined space being provided between an outer circumferential surface of the ring member and an inner circumferential surface of the annular chamber which is located opposite to the outer circumferential surface of the ring member.  
       [0010] According to a further aspect of the present invention, there is provided a torsional vibration damper comprising an input element, an output element, a damper hub connected to the output element for rotation therewith and having a plurality of circumferentially equally spaced, radial hub arms, a drive plate assembly connected to the input element for rotation therewith and having an annular chamber and a plurality of circumferentially equally spaced retaining sections which are formed by narrowed parts of the annular chamber, a plurality of compression springs disposed in the annular chamber and extending between the retaining sections and the hub arms, and a ring member rotatable relative to the input member and the output member, disposed radially outside the compression springs and having an inner circumferential surface held in contact with radially outer boundaries of the compression springs.  
       [0011] The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012]FIG. 1 is a sectional view taken on the line I-I in FIG. 2, showing a torsional vibration damper according to an embodiment of the present invention;  
     [0013]FIG. 2 is a partially cutaway plan view of the torsional vibration damper of FIG. 1;  
     [0014]FIG. 3 is a view similar to FIG. 1 but shows a second embodiment;  
     [0015]FIG. 4 is a view similar to FIG. 1 but shows a third embodiment;  
     [0016]FIG. 5 is a view taken in the direction indicated by the arrow V in FIG. 4;  
     [0017]FIG. 6 is a view similar to FIG. 1 but shows a fourth embodiment; and  
     [0018]FIG. 7 is a view taken in the direction indicated by the arrow VII in FIG. 6.  
     [0019]FIG. 8 is a sectional view taken on the line VIII-VIII in FIG. 9, showing a torsional vibration damper according to a fifth embodiment of the present invention;  
     [0020]FIG. 9 is a partly cutaway plan view of the torsional vibration damper of FIG. 8; and  
     [0021]FIG. 10 is an elevational view of a ring member utilized in the torsional vibration damper of FIG. 9. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0022]FIGS. 1 and 2 show a torsional vibration damper according to an embodiment of the present invention which is adapted to constitute a flywheel of an internal combustion engine, i.e., adapted to be operatively connected to a crankshaft  1  of the engine. The torsional vibration damper includes a drive plate assembly  4  connected to an end  1   a  of the crankshaft  1  with a plurality of bolts  3 , with a reinforcement plate  2  being interposed therebetween, and a damper hub  6  splined to an end portion  5   a  of an output member  5  which also serves as a transmission side input member. The damper hub  6  is disposed so as to be rotatable relative to the drive plate  4 .  
     [0023] The drive plate assembly  4  includes a pair of first and second annular drive plates  41  and  42  having radially outer portions  41   a  and  42   a  which are axially spaced from each other and connected by means of a plurality of stopper pins  8 . Between the radially outer portions  41   a  and  42   a  is defined an annular chamber  9  within which four compression coil springs  10  are disposed in an circular array and at equal intervals, i.e., the compression springs  10  are disposed in such a manner that respective circumferentially central portions thereof are positioned at intervals of 90 degrees. The radially outer portions  41   a  and  42   a  of the first and second drive plates  41  and  42  are respectively formed with seat sections  11   a  and  11   b  which protrude into the annular chamber  9  in a way as to be opposed to each other. The compression springs  10  have arcuated center axes and are disposed between the seating sections  11   a  and  11   b  and hub arms  6   a  of the hub  6 .  
     [0024] The radially outer portion  42   a  of the second drive plate  42  has a nearly L-like cross section and welded at an end to a mating end of the radially outer portion  41   a  of the first drive plate  41 . Further, the radially outer portion  42   a  of the second drive plate  42  has an outer circumferential surface to which are welded a ring gear  12  and an annular mass  13 . In the meantime, the first and second drive plates  41  and  42  have at radially inner potions thereof opposite inner surfaces between which is interposed a sealing member  20  for providing a seal between each of the inner surfaces and the damper hub  6 .  
     [0025] The damper hub  6  is formed with a plurality of arcuated holes  14  which are arranged in a circular array and at equal intervals. Within the arcuated holes  14  are disposed friction material members  15  which are shaped and sized so as to allow the arcuated holes  14  to have spaces at opposite circumferential ends of the friction materials  15 , i.e., so as to allow the arcuated holes  14  to have spaces provided in the circumferential or torsional direction of the damper hub  6 . Each friction material member  15  has an end in contact with an inner surface of the radially inner portion of the second drive plate  42  and another end in engagement with a Belleville spring  17  by way of a friction plate  16 . By this, each friction material member  15  is urged by the spring  17  against the inner surface of the radially inner portion of the second drive plate  42 , i.e., in the left-hand direction in FIG. 1. The friction material members  15  are connected circumferentially with one another by a friction material holder  18 . Further, to a radially inner portion of the damper hub  6  is fixedly attached by means of rivets  30  a guide member  19  which has a radially inner end portion opposed to the radially inner portion of the first drive plate  41  and which cooperates with the reinforcement plate  2  to center the damper hub  6 .  
     [0026] On the radially outer side of the compression springs  10  is disposed a circular ring member  21  which is endless or seamless. The circular ring member  21  is formed from a sheet metal by pressing and is so sized as to have an inner diameter which is a little larger than the diameter of the radially outer boundaries or peripheries of the compression springs  10 , i.e., the diameter of a circle with which each of the compression springs  10  is brought into contact at a radially outer boundary or periphery thereof. Further, the ring member  21  has such a width W as to cover about one fourth of the external surface of each compression spring  10 . Further, the ring member  21  has an inner circumferential surface  21   a  which is part-circular in cross section and extends axially along the external surface of each of the compression springs  10 . The radius of curvature of the part-circular cross section of the inner circumferential surface  21   a  is nearly equal to that of a circular cross section of the external surface of each compression spring  10 . By this, in operation of the compression springs  10 , i.e., when the coil springs  10  are compressed or expanded, they are moved along in line contact with the inner circumferential surface  21   a  of the ring member  21 .  
     [0027] Accordingly, by this embodiment, a torque supplied from the crankshaft  1  to the drive plate assembly  4  during the operation of the engine causes the seating sections  11   a  and  11   b  to push an end of each of the compression springs  10 . By this, each compression spring  10  is compressed between the seating sections  11   a  and  11   b  and the hub arm  6   a  of the damper hub  6 . In this instance, the compression springs  10  are subjected to a force directed radially outward and thus held in contact at the radially outer boundaries or peripheries  10   a  with the inner circumferential surface  21   a  of the ring member  21 . By such compression, a force is stored in each compression spring  10  and then transmitted to the output member  5 , i.e., the transmission side element by way of the damper hub  6  and the radially inner splined portion  5   a  thereof.  
     [0028] In this instance, the compression springs  10  perform a vibration absorbing action by the effect of a long torsional amplitude, whereas the ring member  21  is caused to move circumferentially due to a frictional resistance between the ring member  21  and the compression springs  10 .  
     [0029] Further, as described above, when the drive plate assembly  4  and damper hub  6  are rotated relative to each other, each friction member  15  having been disposed so as to provide a space at one end is brought into contact with the corresponding circumferential end of each arcuated hole  14  and is moved relative to the friction plate  16  and the drive plate assembly  4 , thus causing a hysteresis torque.  
     [0030] As mentioned above, when the compression springs  10  are compressed and deflected, they are brought into contact at the radially outer boundaries or peripheries  10   a  thereof with the inner circumferential surface  21   a  of the ring member  21 . In this instance, since the ring member  21  is not pushed against any one of other constituent parts of the torsional damper, there is not caused a large hysteresis even when the compression springs  10  are subjected to a centrifugal force. Accordingly, stable torsional vibration damping characteristics are attained.  
     [0031] Furthermore, the inner circumferential surface  21   a  of the ring member  21  is formed so as to have a part-circular cross sectional shape which corresponds in radius of curvature to the cross sectional shape of the external surface of each compression spring  10 , and the compression springs  10  are disposed so as to be partly covered by the ring member  21 . In this instance, since the compression springs  10  are not brought into point contact but into line contact with the inner circumferential surface  21   a  of the ring member  21 , the contact pressure with which the compression springs  10  are brought into contact with the inner circumferential surface  21   a  of the ring member  21  can be reduced or made smaller and therefore the friction between the both  21  and  10  can be made smaller.  
     [0032] Further, the inner circumferential surface  21   a  of the ring member  21  is entirely formed into a circular ring and there does not exist any projection at any place of the inner circumferential surface  21   a . By this, assembling of the torsional vibration damper can be made irrespective of the positions of the ring member  21  and the compression springs  10  relative to each other, thus enabling the assembly work to be done with a good efficiency. Namely, the compression springs  10  can be installed in place all at once by holding them all together, the assembly work can be done very easily. Further, even when the positions of the compression springs  10  in operation are varies relative to the ring member  21 , there is not caused any variation in support or holding of the compression springs  10  by the ring member  21 , thus enabling the compression springs  10  to execute a stable operation.  
     [0033] Further, since the ring member  21  supports the compression springs  10  in such a manner that the radially outer boundaries  10   a  of the compression springs  10  are partly enclosed or sheathed in the ring member  21 , it can assuredly and stably support the compression springs  10  at all times even if the compression springs  10  in operation are circumferentially moved relative to the ring member  21 , and stable operation of the compression springs  10  can be attained.  
     [0034] Further, since the inner circumferential surface  21   a  of the ring member  21  is par-circular in cross section, the ring member  21  has a high modulus of section and a large strength against a radial force applied thereto. As a result, the ring member  21  can sustain a pushing force resulting from a centrifugal force of the compression springs  10  when the crankshaft  1  is driven at a higher speed. Further, the ring member  21  can sustain a larger radial pushing force caused by the compression springs  10  having a higher spring constant.  
     [0035] Since the inner circumferential surface  21   a  of the ring member  21  is shaped so as to be part-circular in cross section, it becomes possible to store or hold lubrication oil such as grease inside thereof, thus making it possible to attain smooth expanding and contracting action of the compression springs  10 .  
     [0036] Further, as mentioned above, since the inner circumferential surface  21   a  of the ring member  21  is disposed so as to fit on the radially outer boundaries  10   a  of the compression springs  10 , the ring member  21  is axially located in position by the compression springs  10  and has a least possibility of inclining axially. For this reason, it is less possible that the ring member  21  is abuttingly engaged with the first and second drive plates  41  and  42  of the drive plate assembly  4 . As a result, noises resulting from such abutment and wear of such constituent parts can be reduced.  
     [0037] Since the ring member  21  can be formed from a sheet metal by pressing, the ring member  21  can be manufactured with an efficient work and therefore at low cost. FIG. 3 shows another embodiment of the present invention. In FIG. 3, like parts and portions to those of the embodiment of FIGS. 1 and 2 are designated by the like reference characters and will not described again. In this embodiment, the ring member  121  has at the opposite axial ends thereof a pair of integral reinforcement ribs  122  and  122  in the form of radially outward flanges. By the reinforcement ribs  122  and  122 , the overall strength of the ring member  121 , particularly the strength or rigidity against a radial force can be increased. By this, the ring member  121  can support the compression springs  10  with an increased rigidity, particularly radially, and therefore with an increased assuredness. Further, the ring member  121  can have an improved durability.  
     [0038] Except for the above, this embodiment is substantially similar to the previous embodiment of FIGS. 1 and 2 and can produce substantially the same effect.  
     [0039]FIGS. 4 and 5 show a further embodiment. In FIGS. 4 and 5, like parts and portions to those of the embodiment of FIGS. 1 and 2 are designated by the like reference characters and will not described again. In FIG. 3, like parts and portions to those of the embodiment of FIGS. 1 and 2 will be designated by the like reference characters and will not described again. In this embodiment, the hub arm  206   a  of the damper hub  206  is extended radially more outward than the radially outer boundaries  10   a  of the compression springs  10 . Further, the ring member  221  is not in the form of a thin, circular strip but a relatively thicker, circular strip. Namely, the ring member  221  is formed relatively thicker and have a generally rectangular cross section. At the inner circumferential surface and at the axially central portion thereof, the ring member  21  is formed with a groove  223  in which the radially outer end potions  206   b  of the hub arms  206   a  are fitted.  
     [0040] The groove  223  is formed throughout the inner circumferential surface of the ring member  221  so as to have a circular configuration or shape. The groove  223  has such a depth and width that allow the radially outer end portions  206   b  of the hub arms  206  are slidable therewithin.  
     [0041] Accordingly, by this embodiment, the ring member  221  has a larger rigidity in its entirety and thus can support the compression springs  10  more stably and assuredly.  
     [0042] Further, the ring member  221  is fitted at the groove  223  on the radially outer end portions  206   b  of the hub arms  206   a  and thereby supported by the damper hub  206 . By this, the ring member  221  is assuredly prevented from inclining axially of the torsional vibration damper during operation, thus being assuredly prevented from abutting engagement with the first and second drive plates  41  and  42  of the drive plate assembly  4 .  
     [0043] Except for the above, this embodiment is substantially similar to the previous embodiment of FIGS. 1 and 2 and can produce substantially the same effect.  
     [0044]FIGS. 6 and 7 show a further embodiment. In FIGS. 6 and 7, like parts and portions to those of the embodiment of FIGS. 1 and 2 are designated by the like reference characters and will not be described again. In this embodiment, the damper hub  306  is formed from a pair of hub plates  306   b  and  306   b  which are joined together. The hub arms  306   a  are extended radially more outward than the radially outer boundaries  10   a  of the compression springs  10 . The radially outer end portion  306   c  of each hub plate  306   b  is bent so as to have an L-shaped section so that a groove  324  of a rectangular cross section is formed between the radially outer end portions  306   c  and  306   c  of the hub plates  306   b  and  306   b , i.e., at the radially outer end portion of each hub arm  306   a . On the other hand, the ring member  221  is shaped so as to have a relatively smaller cross sectional area and be slidably received in the groove  324  of each of the hub arms  306   a.    
     [0045] Accordingly, by this embodiment, the ring member  321  is held assuredly and stably within the grooves  324  and is prevented from inclining axially, thus being assuredly prevented from abutting engagement with the first and second drive plates  41  and  42  of the drive plate assembly  4 .  
     [0046] Except for the above, this embodiment is substantially similar to the previous embodiment of FIGS. 1 and 2 and can produce substantially the same effect.  
     [0047] FIGS.  8  to  10  show a further embodiment. In FIGS.  8  to  10 , like parts and portions to those of the embodiment of FIGS.  1  and  2  are designated by the like reference characters and will not described again. In this embodiment, a space or clearance C is provided between the radially outer circumferential surface  421   b  of the ring member  421  and the associated inner circumferential surface of the drive plate assembly  404  as shown in FIG. 8.  
     [0048] More specifically, the radially outer end portion  441   a  of the drive plate  441  has an L-shaped cross section and includes a radially extending circumferential wall section  441   b  and an axially extending circumferential wall portion  441   c  extending from the radially outer end of the circumferential wall section  441   b . The axially extending circumferential wall section  441   c  is generally uniform in diameter. The radially outer end portion  442   a  of the drive plate  442  has a radially extending circumferential wall section  442   b  generally in parallel with the radially extending circumferential wall section  441   b  of the drive plate  441 . The radially extending circumferential wall section  442   b  of the drive plate  442  has a radially outer end  442   c  connected to an end  441   d  of the axially extending circumferential wall section  441   c  of the drive plate  441  by caulking. The above described predetermined space C is thus defined between the outer circumferential surface  421   b  of the ring member  421  and the inner circumferential surface of the axially extending circumferential wall section  441   c  of the drive plate  441 .  
     [0049] Further, a plurality of friction members  440  are arranged in a circular array and along the same circle as that along which the friction members  15  are disposed.  
     [0050] By the provision of the predetermined space C between the outer circumferential surface  421   b  of the ring member  421  and the axially extending circumferential wall section  441   c  of the drive plate  441  surrounding the ring member  421 , the outer circumferential surface  421   b  of the ring member  421  is assuredly prevented from being brought into contact with the axially extending circumferential wall section  441   c  of the drive plate  441  even when the compression springs  10  are moved relative to the ring member  421  to perform a vibration damping action while being held in contact with the inner circumferential surface  421   a  of the ring member  421 . Accordingly, since the ring member  421  is not pushed against any constituent part, it is not causative of a large hysteresis in the torsional damping action. Therefore, the embodiment can attain stable torsional vibration damping characteristics.  
     [0051] Except for the above, this embodiment is substantially similar to the previous embodiment of FIGS. 1 and 2 and can produce substantially the same effect.  
     [0052] From the foregoing, it will be understood that according to the present invention the compression springs in operation are caused to contract and expand to perform a vibration damping action while be held in contact with the inner circumferential surface of the ring member. By this, the compression springs are prevented from protruding radially outward excessively. Further, the ring member is adapted so as not to be pressed against any other constituent part so that the torsional vibration damper of this invention does not cause any hysteresis in a vibration damping action.  
     [0053] The entire contents of Japanese Patent Applications P2000-222914 (filed Jul. 24, 2000) and P2000-353724 (filed Nov. 21, 2000) are incorporated herein by reference.  
     [0054] Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings. The scope of the invention is defined with reference to the following claims.