FLUID TYPE POWER TRANSMISSION DEVICE

A fluid type power transmission device in which a torque transmission path for transmitting torque from a vehicular engine is provided with a dynamic damper mechanism formed by disposing a plurality of damper springs between an inertial rotating body and a rotation-transmitting member forming part of the torque transmission path. An elastic member always linked to one of the rotation-transmitting member and the inertial rotating body is added to the dynamic damper mechanism. Play occurs in a torque direction between the elastic member and the other of the rotation-transmitting member and the inertial rotating body at a time of low speed rotation, but the elastic member exhibits resilient force between the rotation-transmitting member and the inertial rotating body in response to deformation due to centrifugal force at a time of high speed rotation that is a predetermined rotational speed or greater.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2015-204205 filed on Oct. 16, 2015 the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a fluid type power transmission device in which a torque transmission path for transmitting torque from a vehicular engine is provided with a dynamic damper mechanism formed by disposing a plurality of damper springs between an inertial rotating body and a rotation-transmitting member forming part of the torque transmission path.

Description of the Related Art

A torque converter, which is a fluid type power transmission device, in which a torque transmission path is provided with a dynamic damper mechanism in a state in which a pump impeller and an output shaft are directly coupled using a lockup clutch is known from Japanese Patent Application Laid-open No. 2009-293671, but in such an arrangement the damping rate of the dynamic damper mechanism is uniquely determined, the rotational speed region in which there is a large damping effect due to the dynamic damper mechanism is limited, and the damping effect over a wide rotational speed region is insufficient.

When solving such a problem, obtaining a damping effect over a wide rotational speed region by changing a spring rate of the dynamic damper mechanism according to a rotational speed could be considered, and such a dynamic damper mechanism is known from for example Japanese Patent Application Laid-open No. 2001-263424 and Japanese Patent Application Laid-open No. 2004-239323.

However, in the arrangement disclosed in Japanese Patent Application Laid-open No. 2001-263424 described above, an inertial rotating body and a drive shaft are linked by means of two link mechanisms, the spring rate is changed by changing an attitude of the two link mechanism accompanying a change in the rotational speed, a structure for changing the spring rate is complicated, the number of components is large, and it is difficult to reduce the cost.

Furthermore, in the arrangement disclosed in Japanese Patent Application Laid-open No. 2004-239323 described above, a damping effect is obtained over a wide region by linking a plurality of dynamic dampers in tandem to a structure that is subjected to damping, but when this technique is applied to a fluid type power transmission device without modification, it leads to an increase in the number of components, thus causing an increase in the cost.

SUMMARY OF THE INVENTION

The present invention has been accomplished in light of such circumstances, and it is an object thereof to provide a fluid type power transmission device that enables a spring rate of a dynamic damper mechanism to be changed according to a rotational speed by means of a simple structure in which any increase in the number of components is suppressed.

In order to achieve the object, according to a first aspect of the present invention, there is provided a fluid type power transmission device in which a torque transmission path for transmitting torque from a vehicular engine is provided with a dynamic damper mechanism formed by disposing a plurality of damper springs between an inertial rotating body and a rotation-transmitting member forming part of the torque transmission path, wherein an elastic member that, while being capable of deforming when subjected to a centrifugal force, is always linked to either one of the rotation-transmitting member and the inertial rotating body is added to the dynamic damper mechanism, and the elastic member is disposed between the rotation-transmitting member and the inertial rotating body so that play occurs in a torque direction between the elastic member and the other one of the rotation-transmitting member and the inertial rotating body at a time of low speed rotation where torque variation can be absorbed by the damper spring but so that a resilient force is exhibited between the rotation-transmitting member and the inertial rotating body in response to deformation due to centrifugal force at a time of high speed rotation that is a predetermined rotational speed or greater.

In accordance with the first aspect of the present invention, since the elastic member, which is always linked to either one of the rotation-transmitting member and the inertial rotating body while being capable of deforming when subjected to a centrifugal force, is added to the dynamic damper mechanism, and play occurs in the torque direction between the elastic member and the other one of the rotation-transmitting member and the inertial rotating body at the time of low speed rotation where torque variation can be absorbed by the damper spring but the elastic member exhibits a resilient force between the rotation-transmitting member and the inertial rotating body in response to deformation due to centrifugal force at the time of high speed rotation that is a predetermined rotational speed or greater, the spring force of the elastic member is applied to the damper spring at the time of high speed rotation, a resonant frequency of the dynamic damper mechanism shifts toward the high speed rotation side, the spring rate of the dynamic damper mechanism can be changed according to the rotational speed, and in order to realize this only the elastic member is added, thus enabling a simple structure in which any increase in the number of components is suppressed to be achieved.

According to a second aspect of the present invention, in addition to the first aspect, a spring rate of the dynamic damper mechanism having the elastic member is set so that a ratio of the spring rate at the time of high speed rotation relative to the spring rate at the time of low speed rotation is greater than 1 but no greater than 4.

In accordance with the second aspect of the present invention, since the spring rate of the dynamic damper mechanism having the elastic member is set so that the ratio of the spring rate at the time of high speed rotation relative to the spring rate at the time of low speed rotation is greater than 1 but no greater than 4, a damping performance can be enhanced over a wide range of a common rotational speed region of the vehicular engine. That is, since low frequency vibration excited in a low speed rotation region is easily perceived, and an abnormal noise due to the vibration tends to be easily heard, it is possible, by setting the spring rate at a value corresponding to the low speed rotation region, to obtain an effective damping performance over a wide range of the common rotational speed region of the vehicular engine while suppressing the occurrence of low frequency vibration in the low speed rotation region.

According to a third aspect of the present invention, in addition to the first or second aspect, at least two types of elastic members, as said elastic member, are added to the dynamic damper mechanism so that the spring rate of the dynamic damper mechanism is changed for at least two different rotational speeds.

In accordance with the third aspect of the present invention, since at least two types of the elastic members are added to the dynamic damper mechanism, and the spring rate of the dynamic damper mechanism is changed for at least two different rotational speeds by means of these elastic members, it is possible to obtain more effective damping performance in a driving rotational region of the vehicular engine.

According to a fourth aspect of the present invention, in addition to the first aspect, the elastic member is disposed within the inertial rotating body.

In accordance with the fourth aspect of the present invention, since the elastic member is disposed within the inertial rotating body, it is possible to avoid any increase in the dimensions of the dynamic damper mechanism due to addition of the elastic member.

According to a fifth aspect of the present invention, in addition to the first aspect, a pair of rotation-transmitting members, as said rotation-transmitting member, sandwiching at least part of the inertial rotating body from opposite sides are relatively non-rotatably linked so as to form a spring holder holding the damper spring disposed between the rotation-trasmitting members and the inertial rotating body, and the elastic member is disposed within the spring holder.

In accordance with the fifth aspect of the present invention, since the spring holder is formed from the pair of rotation-transmitting members sandwiching at least part of the inertial rotating body from opposite sides, and the elastic member is disposed within the spring holder, it is possible to avoid any increase in the dimensions of dynamic damper mechanism due to the addition of the elastic member.

According to a sixth aspect of the present invention, in addition to the first aspect, the elastic member is formed by bending a plate spring.

According to a seventh aspect of the present invention, in addition to the first aspect, either one of the rotation-transmitting member and the inertial rotating body is always linked to a middle part of the elastic member along a peripheral direction around a rotational axis of the dynamic damper mechanism in a natural state of the elastic member, the elastic member extending in the peripheral direction around the rotational axis, a housing part housing at least part of the elastic member is formed on the other one of the rotation-transmitting member and the inertial rotating body, the housing part is formed from an inner housing portion and an outer housing portion connected to the inner housing portion from an outside along a radial direction with the rotational axis as a center, a length along the peripheral direction of the inner housing portion is set so as to be longer in the peripheral direction than the elastic member in the natural state so as to avoid contact of opposite end parts along the peripheral direction of the inner housing portion with opposite end parts along the peripheral direction of the elastic member at the time of low speed rotation, and a length along the peripheral direction of the outer housing portion is set so as to be shorter in the peripheral direction than the inner housing portion so that opposite end parts along the peripheral direction of the outer housing portion make contact with the opposite end parts along the peripheral direction of the elastic member when the elastic member has been deformed by being subjected to a centrifugal force at the time of high speed rotation.

The above and other objects, characteristics and advantages of the present invention will be clear from detailed descriptions of the preferred embodiments which will be provided below while referring to the attached drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are explained below by reference to the attached drawings.

A first embodiment of the present invention is explained by reference toFIG. 1toFIG. 9; first, inFIG. 1, a torque converter, which is a fluid type power transmission device, includes a pump impeller11, a turbine runner12disposed so as to oppose the pump impeller11, and a stator13disposed between inner peripheral parts of the pump impeller11and the turbine runner12, and a circulation circuit15through which hydraulic oil is circulated as shown by an arrow14is formed between the pump impeller11, the turbine runner12, and the stator13.

The pump impeller11has a bowl-shaped pump shell16, a plurality of pump blades17provided on an inner face of the pump shell16, a pump core ring18linking these pump blades17, and a pump hub19fixed to an inner peripheral part of the pump shell16by for example welding, and an oil pump (not illustrated) for supplying hydraulic oil to the torque converter is operatively linked to the pump hub19.

Furthermore, a bowl-shaped transmission cover20covering the turbine runner12from the outside is joined to an outer peripheral part of the pump shell16by welding, a ring gear21is fixed to an outer peripheral part of the transmission cover20by welding, and a drive plate22is fastened to the ring gear21. Moreover, a crankshaft23of a vehicular engine E is coaxially fastened to the drive plate22, and rotational power is inputted into the pump impeller11from the vehicular engine E.

The turbine runner12has a bowl-shaped turbine shell24, a plurality of turbine blades25provided on an inner face of the turbine shell24, and a turbine core ring26linking these turbine blades25.

An end part of an output shaft27that transmits the rotational power from the vehicular engine E to a transmission, which is not illustrated, is supported via a bearing bush28on a bottomed cylindrical support tube portion20aintegrally provided on a center part of the transmission cover20. The output shaft27is spline joined to an output hub29disposed at a position spaced in the axial direction from the pump hub19, and a needle thrust bearing30is disposed between the output hub29and the transmission cover20.

The stator13has a stator hub31disposed between the pump hub19and the output hub29, a plurality of stator blades32provided on the outer periphery of the stator hub31, and a stator core ring33linking the outer peripheries of the stator blades32, a thrust bearing34is disposed between the pump hub19and the stator hub31, and a thrust bearing35is disposed between the output hub29and the stator hub31.

A one-way clutch37is disposed between the stator hub31and a stator shaft36relatively rotatably surrounding the output shaft27, which rotates together with the output hub29, and a transmission case (not illustrated) is non-rotatably supported on the stator shaft36.

Formed between the transmission cover20and the turbine shell24is a clutch chamber38communicating with the circulation circuit15, and housed within the clutch chamber38are a lockup clutch40, an inertial rotating body65rotatably supported on the outer periphery of the output hub29, and a spring holder42holding at least part of the inertial rotating body65from opposite sides while being capable of rotating in a restricted range relative to the inertial rotating body65.

The lockup clutch40has a clutch piston43that can be frictionally connected to the transmission cover20, and can switch between a connected state in which the clutch piston43is frictionally connected to the transmission cover20and a disconnected state in which the frictional connection is released, and an inner peripheral part of the clutch piston43formed into a disk shape is slidably supported on the output hub29so that it can move in the axial direction.

The interior of the clutch chamber38is partitioned by means of the clutch piston43into an inner chamber38aon the turbine runner12side and an outer chamber38bon the transmission cover20side, an oil groove44formed in the output hub29so as to be adjacent to the needle thrust bearing30is made to communicate with the outer chamber38b,and the oil groove44communicates with the interior of the output shaft27, which is cylindrical. Furthermore, an oil passage45communicating with an inner peripheral part of the circulation circuit15is formed between the pump hub19and the stator shaft36. Connected to the oil groove44and the oil passage45alternately are the oil pump and an oil reservoir (not illustrated).

When the vehicular engine E is idling or in a very low speed operating region, hydraulic oil is supplied from the oil groove44to the outer chamber38b,and hydraulic oil is guided out from the oil passage45; in this state the outer chamber38bhas a higher pressure than that of the inner chamber38a,the clutch piston43is pushed toward the side on which it moves away from an inner face of the transmission cover20, and the lockup clutch40is in the disconnected state. In this state, relative rotation of the pump impeller11and the turbine runner12is allowed, and rotating the pump impeller11by means of the vehicular engine E makes hydraulic oil within the circulation circuit15circulate within the circulation circuit15in the sequence: pump impeller11, turbine runner12, and stator13as shown by the arrow14, the rotational torque of the pump impeller11being transmitted to the output shaft27via the turbine runner12, the spring holder42, and the output hub29.

In a state in which a torque-amplifying action occurs between the pump impeller11and the turbine runner12, a reaction force accompanying it is borne by the stator13, and the stator13is fixed by means of a locking action of the one-way clutch37. Furthermore, when torque amplification is completed, the stator13rotates in the same direction together with the pump impeller11and the turbine runner12while making the one-way clutch37idle by reversing the direction of the torque that the stator13receives.

When such a torque converter attains a coupled state or comes close to the coupled state, the connected state between the oil groove44and oil passage45and the oil pump and oil reservoir is switched over so that hydraulic oil is supplied from the oil passage45to the outer chamber38band the hydraulic oil is guided out through the oil groove44. As a result, the pressure in the clutch chamber38becomes higher in the inner chamber38athan in the outer chamber38b,the clutch piston43is pushed toward the transmission cover20side by means of the pressure difference, the outer peripheral part of the clutch piston43is pressed against the inner face of the transmission case20and is frictionally connected to the transmission case20, and the lockup clutch40attains the connected state.

When the lockup clutch40attains the connected state, the torque transmitted from the vehicular engine E to the transmission cover20is transmitted mechanically to the output hub29via a torque transmission path46that includes the clutch piston43and the spring holder42, and a damper mechanism47is disposed in this torque transmission path46.

The damper mechanism47is formed by disposing a plurality of, for example four, first damper springs49between the clutch piston43and the spring holder42, which can rotate relative to each other around the rotational axis, at equal intervals in the peripheral direction.

An annular housing recess50is formed in a face, on the side opposite to the transmission case20, of an outer peripheral part of the clutch piston43, and a retainer51sandwiching between itself and the clutch piston43the first damper springs49housed within the housing recess50at equal intervals in the peripheral direction is fixed to the clutch piston43.

The retainer51is formed so as to integrally have a ring plate portion51adisposed coaxially with the clutch piston43while having an outer periphery substantially corresponding to the inner periphery of the housing recess50, a spring cover portion51bformed with an arc-shaped cross section so as to cover the inner side of the first damper spring49along the radial direction of the clutch piston43, provided so as to be connected to four positions at equal intervals in the peripheral direction on the outer periphery of the ring plate portion51a,and formed lengthwise along the peripheral direction of the clutch piston43, and a first spring abutment portion51cdisposed between the spring cover portions51band provided so as to be connected to the outer periphery of the ring plate portion51a,the ring plate portion51abeing fixed to the clutch piston43by means of a plurality of first rivets52.

Furthermore, the first spring abutment portion51cis disposed between the four first damper springs49, and when the lockup clutch40is in the disconnected state, the first spring abutment portion51cabuts against an end part of each of the first damper springs49on opposite sides thereof.

The spring holder42is formed from first and second retaining plates54and55, which are rotation-transmitting members forming part of the torque transmission path46; the first retaining plate54is fixed to the output hub29together with an inner peripheral part of the turbine shell24by means of a plurality of third rivets59, and the second retaining plate55spaced from the first retaining plate54in a direction along the axis of the output shaft27is relatively non-rotatably linked to the first retaining plate54by means of a plurality of second rivets56.

Moreover, second spring abutment portions55bare integrally and connectedly provided at a plurality of, for example four, locations spaced at equal intervals in the peripheral direction of the outer periphery of the second retaining plate55, the second spring abutment portion55bprojecting into the housing recess50so as to sandwich the first damper spring49between itself and the first spring abutment portion51cof the retainer51, and an opening61is formed in the spring cover portion51bof the retainer51, the second spring abutment portion55bbeing inserted through the opening61so as to allow relative rotation in a restricted range between the spring cover portion51band the second spring abutment portion55b,that is, the spring holder42.

When the lockup clutch40attains the connected state and the clutch piston43and the retainer51rotate, the first spring abutment portion51ccompresses the first damper spring49between itself and the second spring abutment portion55b,and power is transmitted from the first damper spring49to the output hub29via the spring holder42connected to the second spring abutment portion55b.That is, torque is transmitted mechanically between the clutch piston43and the output hub29via the torque transmission path46, the torque transmission path46being formed from the clutch piston43, the retainer51, the first damper spring49, and the spring holder42.

A dynamic damper mechanism64is attached to the torque transmission path46, this dynamic damper mechanism64being formed by disposing a plurality of, for example six, second damper springs53between the inertial rotating body65and the first and second retaining plates54and55, which are rotation-transmitting members forming part of the torque transmission path46, that is, the spring holder42.

At least part (part in this embodiment) of the inertial rotating body65is formed from a disk-shaped inertia plate41sandwiched between the first and second retaining plates54and55forming the spring holder42and having its inner peripheral part rotatably supported on the output hub29, and a weight-adding member66fixed to the outer periphery of the inertia plate41.

A cylindrical collar57is disposed between the first and second retaining plates54and55, the cylindrical collar57being inserted through an elongated hole58provided at a plurality of, for example six, locations spaced at equal intervals in the peripheral direction of the inertia plate41, and the first and second retaining plates54and55are linked by means of the second rivets56, which extends through the collars57. That is, the inertia plate41can rotate relative to the spring holder42in only the restricted range through which the collar57moves within the elongated hole58.

Referring in addition toFIG. 2, spring-retaining portions54afor retaining the second damper springs53are formed at a plurality of, for example six, locations spaced at equal intervals in the peripheral direction of the first retaining plate54so that part of the second damper spring53is exposed to the outside. Furthermore, a spring-retaining portion55afor retaining the second damper spring53is formed in a portion, corresponding to the spring-retaining portion54aof the first retaining plate54, of the second retaining plate55so that part of the second damper spring53is exposed to the outside.

A spring housing hole60housing part of the second spring53is formed in portions, corresponding to the spring-retaining portions54aand55a,of the inertia plate41so that in the disconnected state of the lockup clutch40opposite end parts of the spring housing hole60along the peripheral direction of the inertia plate41abut against opposite end parts of the second damper spring53.

The inertia plate41is formed so that its outer peripheral part projects further radially outward than the first and second retaining plates54and55forming the spring holder42, and the weight-adding member66is fixed to an outer peripheral part of the inertia plate41.

The weight-adding member66is formed with a substantially L-shaped cross-section while integrally having a ring plate portion66aopposing an outer peripheral part of the first retaining plate54from the turbine runner12side across a gap and a tubular portion66bextending from the outer periphery of the ring plate portion66atoward the outer peripheral part side of the inertia plate41, and is fixed to the outer peripheral part of the inertia plate41by means of a plurality of fourth rivets67having a large diameter portion67adisposed between the ring plate portion66aand the inertia plate41so that the tubular portion66babuts against the inertia plate41.

When the vehicle is traveled at a low engine rotational speed in order to reduce the fuel consumption of the vehicular engine E, there are problems with the suppression of muffled sound, vibration, etc. due to torque variation of the vehicular engine E. Such problems are intended to be solved by the dynamic damper mechanism64, but the damping rate of the dynamic damper mechanism64is determined uniquely, and as shown by the broken line inFIG. 3the operating rotational speed of the dynamic damper mechanism64is usually set on the slowest rotational speed side (800 to 1500 rpm) in the connected region of the lockup clutch40. By so doing, the engine rotational speed region that can give a large damping effect is limited, and as shown by dots inFIG. 3a region in which a sufficient damping effect cannot be obtained sometimes occurs.

Obtaining a damping effect over a wide rotational speed region as shown by the solid line inFIG. 3by changing the spring rate of the dynamic damper mechanism64according to the engine rotational speed could therefore be considered, and in accordance with the present invention an elastic member70that, while being capable of deforming when subjected to a centrifugal force, always links to either one of the inertial rotating body65and the first retaining plate54of the spring holder42of the dynamic damper mechanism64is added to the dynamic damper mechanism64.

In this embodiment, the elastic member70is always linked to the inertial rotating body65via the fourth rivet67, and this elastic member70is disposed between the first retaining plate54and the inertial rotating body65while being disposed within the inertial rotating body65so that at a time of low speed rotation when the second damper spring53can absorb the torque variation no resilient force is exhibited between the elastic member70and the first retaining plate54but a resilient force is exhibited between the first retaining plate54and the inertial rotating body65in response to a deformation due to centrifugal force at a time of high speed rotation that is a predetermined rotational speed or greater.

Projecting portions54bprojecting in a radially outward direction are formed integrally with a plurality of, for example four, locations spaced at equal intervals in the peripheral direction on the outer periphery of the first retaining plate54so as to project into an annular recess71formed between the inertia plate41and the weight-adding member66, and the elastic member70enables a resilient force to be exhibited between the projecting portion54bof the first retaining plate54and the inertial rotating body65.

The elastic member70is formed into a wave shape by bending a plate spring so that it extends in the peripheral direction around the rotational axis of the dynamic damper mechanism64, and the large diameter portion67aof the fourth rivet67of the inertial rotating body65is always linked to a middle part, along the peripheral direction, of the elastic member70in its natural state.

Referring in addition toFIG. 4, formed in the projecting portion54bas a through hole that opens on opposite faces of the projecting portion54bis a housing part72housing at least part (part in this embodiment) of the elastic member70. The housing part72is formed from an inner housing portion72aand an outer housing portion72bconnected to the inner housing portion72afrom the outside along the radial direction with the rotational axis of the dynamic damper mechanism64as the center. As is clearly shown inFIG. 4a length L1along the peripheral direction of the inner housing portion72ais set so as to be longer in the peripheral direction than the elastic member70in its natural state so as to avoid contact of opposite end parts along the peripheral direction of the inner housing portion72awith opposite end parts along the peripheral direction of the elastic member70at a time of low speed rotation of the vehicular engine E.

Furthermore, a length L2along the peripheral direction of the outer housing portion72bis set so as to be shorter in the peripheral direction than the inner housing portion72aso that opposite end parts along the peripheral direction of the outer housing portion72bmake contact with opposite end parts along the peripheral direction of the elastic member70that has been deformed by being subjected to centrifugal force at a time of high speed rotation of the vehicular engine E.

Such behavior of the elastic member70is explained by reference toFIG. 5. In a state in which the rotational speed of the vehicular engine E is low, the relative rotational angle between the first retaining plate54and the inertial rotating body65is small, and the centrifugal force acting on the elastic member70is small; as shown inFIG. 5A, the elastic member70is at a position corresponding to the inner housing portion72aof the housing part72, play73in the torque direction occurs between the first retaining plate54and the elastic member70, and the elastic member70is in a non-operational state between the first retaining plate54and the inertial rotating body65.

In a state in which the centrifugal force acting on the elastic member70is still small even though the rotational speed of the vehicular engine E has increased and the relative rotational angle between the first retaining plate54and the inertial rotating body65is large, as shown inFIG. 5Bthe elastic member70is at a position corresponding to the inner housing portion72aof the housing part72, the play73in the torque direction between the first retaining plate54and the elastic member70remains, and the elastic member70is in the non-operational state between the first retaining plate54and the inertial rotating body65.

When the relative rotational angle between the first retaining plate54and the inertial rotating body65increases and the centrifugal force acting on the elastic member70increases as the rotational speed of the vehicular engine E increases, as shown inFIG. 5Cthe elastic member70deforms so that its opposite end parts enter the outer housing portion72bof the housing part72, and the elastic member70operates so that a resilient force is exhibited between the first retaining plate54and the inertial rotating body65. That is, the spring force of the elastic member70is applied to the dynamic damper mechanism64, and the resonant frequency of the dynamic damper mechanism64shifts to the high rotation side. As a result, as shown by the solid line inFIG. 3the frequency characteristics change to the side on which the damping rate becomes high at an operating rotational speed at which the elastic member70starts operating, and the damping range increases.

In a state in which the centrifugal force acting on the elastic member70has increased in response to an increase in the rotational speed of the vehicular engine E, as shown inFIG. 5Dthe opposite end parts of the elastic member70abut against the projecting portion54bof the first retaining plate54in a state in which the elastic member70is housed in the outer housing portion72bof the housing part72, but due to the characteristic of the dynamic damper mechanism64that the relative rotational angle decreases on the side where the rotational speed is higher than the resonant frequency, the relative rotational angle between the first retaining plate54and the inertial rotating body65becomes small, and the elastic member70is not subjected to a load that is larger than necessary.

When the damping rate of the dynamic damper mechanism64disposed in the torque transmission path46of the torque converter provided between the transmission and the crankshaft23of the vehicular engine E whose common rotational speed range is 800 to 2500 rpm is calculated using a usual vehicle vibration model as a reference, the results shown inFIG. 6are obtained. When the result obtained by calculation with a resonant frequency of 1000 rpm is shown by the solid line inFIG. 6, the result obtained when the spring rate of the dynamic damper mechanism64is twice the reference example where the resonant frequency is 1000 rpm is shown by the broken line inFIG. 6.

When, with the frequency characteristics of the spring rate at a time of low speed rotation as the reference example, the spring rate at a time of high rotational speed where the added elastic member70operates is set to twice that at a time of low rotational speed, the dynamic damper mechanism64to which the elastic member70is added can give the frequency characteristics shown by the solid line inFIG. 7. That is, it follows the frequency characteristics of the reference example before the elastic member70operates, and it follows the frequency characteristics where the spring rate is double in the high rotational speed region in which the added elastic member70operates. Here, the most advantageous method for setting the operating rotational speed of the elastic member70is an intersection point present between the resonance points of one dynamic damper; when the operating rotational speed is set in that way, the resonance points of the dynamic damper are present on opposite sides of the operating rotational speed, and a more advantageous operating rotational speed range is 800 to 2000 rpm, which is close to the common rotational speed region of the vehicular engine E.

The frequency characteristics when, with the frequency characteristics of the spring rate at a time of low speed rotation as a reference example, the spring rate at a time of high rotational speed where the added elastic member70operates is set to twice, three times, four times, and five times that at a time of low rotational speed changes as shown inFIG. 8, and the resonant frequency of the dynamic damper is shifted to the high speed side by setting the spring rate high, but since low frequency vibration excited in a low speed rotation region is easily perceived, and an abnormal noise due to the vibration tends to be easily heard, it is desirable to set the spring rate at a value corresponding to the low speed rotation region (800 to 1500 rpm), thus suppressing the occurrence of low frequency vibration in the low speed rotation region (800 to 1500 rpm).

When the resonant frequency of the dynamic damper in the low speed rotation region is set at 1000 rpm as in the reference example ofFIG. 8, in order to improve the damping performance over a wider range of a range of 800 to 2500 rpm, which is the common rotational speed region of the vehicular engine E, it is desirable to set the spring rate of the high rotational speed region due to operation of the elastic member70to at least three times, and the frequency characteristics shown by the solid line inFIG. 9are obtained when the spring rate is three times. In addition, when the spring rate of the high rotational speed region is set to five times that of the low rotational speed region, the frequency characteristics become those shown by the dotted line inFIG. 9, and the damping performance around the rotational speed (around1200to1700inFIG. 9) where the added elastic member70starts operating becomes insufficient; taking this into consideration it is desirable to set the spring rate of the dynamic damper mechanism64having the elastic member70so that the ratio of that at a time of high speed rotation relative to that at a time of low speed rotation is greater than 1 but no greater than 4.

The operation of this first embodiment is now explained. The torque transmission path46for transmitting the torque from the vehicular engine E is provided with the dynamic damper mechanism65formed by disposing the plurality of second damper springs53between the inertial rotating body65and the spring holder42formed from the first and second retaining plates54and55forming part of the torque transmission path46. The elastic member70which, while being capable of deforming when subjected to a centrifugal force, is always linked to the inertial rotating body65, which is either one of the spring holder42and the inertial rotating body65, is added to the dynamic damper mechanism64. The elastic member70is disposed between the spring holder42and the inertial rotating body65so that the play73in the torque direction occurs between itself and the spring holder42, which is the other one of the spring holder42and the inertial rotating body65, at a time of low speed rotation when torque variation can be absorbed by the second damper spring53, but a resilient force is exhibited between the spring holder42and the inertial rotating body65in response to deformation due to centrifugal force at a time of high speed rotation that is a predetermined rotational speed or greater.

Therefore, in the dynamic damper mechanism64, the spring force of the elastic member70is applied to the second damper spring53at a time of high speed rotation, the resonant frequency of the dynamic damper mechanism64shifts toward the high speed rotation side, the spring rate of the dynamic damper mechanism64can be changed according to the rotational speed, and in order to realize this only the elastic member70is added, thus enabling a simple structure in which any increase in the number of components is suppressed to be achieved.

Furthermore, since the spring rate of the dynamic damper mechanism64having the elastic member70is set so that the ratio of that at the time of high speed rotation relative to that at the time of low speed rotation is greater than 1 but no greater than 4, the damping performance can be enhanced over a wide range of the common rotational speed region of the vehicular engine E. That is, since low frequency vibration excited in a low speed rotation region is easily perceived, and an abnormal noise due to the vibration tends to be easily heard, it is possible, by setting the spring rate at a value corresponding to the low speed rotation region, to obtain an effective damping performance over a wide range of the common rotational speed region of the vehicular engine E while suppressing the occurrence of low frequency vibration in the low speed rotation region.

Furthermore, since the elastic member70is disposed within the inertial rotating body65, it is possible to avoid any increase in the dimensions of the dynamic damper mechanism64due to addition of the elastic member70.

A second embodiment of the present invention is explained by reference toFIG. 10toFIG. 12B; parts corresponding to those of the first embodiment shown inFIG. 1toFIG. 9are denoted by the same reference numerals and symbols, and detailed explanation thereof is omitted.

When the lockup clutch40attains a connected state, torque that is transmitted from the vehicular engine E to the transmission cover20is transmitted mechanically to the output hub29via a torque transmission path78that includes the clutch piston43and a spring holder76, the damper mechanism47being disposed in the torque transmission path78.

The damper mechanism47is formed by disposing the plurality of, for example four, first damper springs49spaced at equal intervals in the peripheral direction between the spring holder76and the clutch piston43, which can rotate relative to each other around the rotational axis.

The spring holder76is formed from first and second retaining plates80and81, which are rotation-transmitting members forming part of the torque transmission path78; the first retaining plate80is fixed to the output hub29together with an inner peripheral part of the turbine shell24by means of the plurality of third rivets59, and the second retaining plate81spaced from the first retaining plate80in a direction along the axis of the output shaft27is relatively non-rotatably linked to the first retaining plate80by means of a plurality of rivets, which are not illustrated.

Furthermore, a second spring abutment part81cis integrally and connectedly provided on the outer periphery at a plurality of, for example four, locations spaced at equal intervals in the peripheral direction of the second retaining plate81, the second spring abutment part81cpenetrating into the housing recess50so as to sandwich the first damper spring49between itself and the first spring abutment portion51cof the retainer51fixed to the clutch piston43. The opening61is formed in the spring cover portion51bof the retainer51, the second spring abutment part81cbeing inserted through the opening61so as to allow relative rotation in a restricted range relative to the second spring abutment part81c,that is, the spring holder76.

When the lockup clutch40attains a connected state and the clutch piston43and the retainer51rotate, the first spring abutment portion51ccompresses the first damper spring49between itself and the second spring abutment part81c,and power is transmitted from the first damper spring49to the output hub29via the spring holder76connected to the second spring abutment part81c.That is, torque is transmitted mechanically between the clutch piston43and the output hub29via the torque transmission path78, the torque transmission path78being formed from the clutch piston43, the retainer51, the first damper spring49, and the spring holder76.

The torque transmission path78is provided with a dynamic damper mechanism84. This dynamic damper mechanism84is formed by disposing a plurality of, for example six, second damper springs53between the spring holder76and an inertial rotating body85.

The inertial rotating body85is formed from a disk-shaped inertia plate77and a weight-adding member86. At least part (part in this embodiment) of the inertia plate77is sandwiched between the first and second retaining plates80and81forming the spring holder76, and an inner peripheral part of the inertia plate77is rotatably supported on the output hub29, the weight-adding member86being fixed to the outer periphery of the inertia plate77by means of a plurality of fifth rivets87.

A spring-retaining portion80afor retaining the second damper spring53is formed at a plurality of, for example six, locations spaced at equal intervals in the peripheral direction of the first retaining plate80, part of the second damper spring53being exposed to the outside. Furthermore, a spring-retaining portion81afor retaining the second damper spring53is formed in a part, corresponding to the spring-retaining portion80aof the first retaining plate80, of the second retaining plate81so that part of the second damper spring53is exposed to the outside.

Formed in a part, corresponding to the spring-retaining portions80aand81a,of the inertia plate77is a spring housing hole82housing part of the second damper spring53. In a disconnected state of the lockup clutch40, opposite end parts of the spring housing hole82along the peripheral direction of the inertia plate77abut against opposite end parts of the second damper spring53.

The inertia plate77is formed so that its outer peripheral part projects further radially outward than the first and second retaining plates80and81forming the spring holder76, and the weight-adding member86is fixed to the outer peripheral part of the inertia plate77.

An elastic member88is added to the dynamic damper mechanism84so that it is always linked to either one of the first retaining plate80and the inertial rotating body85of the spring holder76of the dynamic damper mechanism84and can deform when subjected to a centrifugal force.

The elastic member88is always linked to the inertia plate77forming part of the inertial rotating body85, and this elastic member88is disposed between the spring holder76and the inertial rotating body85while being disposed within the spring holder76so that a resilient force is not exhibited between itself and the spring holder76formed from the first and second retaining plates80and81at a time of low speed rotation when torque variation can be absorbed by the second damper spring53but a resilient force is exhibited between the spring holder76and the inertial rotating body85in response to deformation due to centrifugal force at a time of high speed rotation that is a predetermined rotational speed or greater.

Spring housing holes89that are long along the peripheral direction of the inertia plate77are formed at a plurality of locations spaced at equal intervals in the peripheral direction of part of the inertia plate77that are positioned further radially outward than the second damper spring53and that are positioned further radially inward than a fifth rivet87for fixing the weight-adding member86.

The elastic member88is formed into a wave shape by bending a plate spring so as to extend in the peripheral direction around the rotational axis of the dynamic damper mechanism84, and is housed in the spring housing hole89so that opposite end parts of the elastic member88in the natural state abut against opposite end parts in the longitudinal direction of the spring housing hole89. A projecting portion77ais linked to a middle part along the peripheral direction in the natural state of the elastic member88, the projecting portion77abeing projectingly provided integrally with the inertia plate77so as to project into the spring housing hole89from a middle part along the peripheral direction of the spring housing hole89.

On the other hand, formed as a through hole opening on opposite faces of the retaining plates80and81in each of the first and second retaining plates80and81disposed on opposite sides of the inertia plate77is a housing part92housing part of the elastic member88. Formed in parts, corresponding to the housing part92, of the first and second retaining plates80and81are spring-retaining portions80band81bfor retaining the elastic member88, part of the elastic member88facing the outside.

The housing part92is formed from an inner housing portion92aand an outer housing portion92bconnected to the inner housing portion92afrom the outside along the radial direction with the rotational axis of the dynamic damper mechanism84as the center. As clearly shown inFIG. 12Aa length L3along the peripheral direction of the inner housing portion92ais set so as to be longer in the peripheral direction than the elastic member88in the natural state so as to avoid contact of opposite end parts along the peripheral direction of the inner housing portion92awith opposite end parts along the peripheral direction of the elastic member88at a time of low speed rotation of the vehicular engine E. Furthermore, a length L4along the peripheral direction of the outer housing portion92bis set so as to be shorter in the peripheral direction than the inner housing portion92aso that opposite end parts along the peripheral direction of the outer housing portion92bmake contact with opposite end parts along the peripheral direction of the elastic member88that has been deformed by being subjected to centrifugal force at a time of high speed rotation of the vehicular engine E.

In accordance with the elastic member88and the housing part92, in a state in which the rotational speed of the vehicular engine E is low and the centrifugal force acting on the elastic member88is small, as shown inFIG. 12A, the elastic member88is present at a position corresponding to the inner housing portion92aof the housing part92, play93in the torque direction occurs between the first and second retaining plates80and81and the elastic member88, and the elastic member88is in a non-operational state between the first and second retaining plates80and81and the inertial rotating body85.

When the rotational speed of the vehicular engine E increases and the centrifugal force acting on the elastic member88increases, as shown inFIG. 12B, the elastic member88deforms so that its opposite end parts enter the outer housing portion92bof the housing part92, and the elastic member88operates so that a resilient force is exhibited between the first and second retaining plates80and81and the elastic member88. That is, the spring force of the elastic member88is applied to the dynamic damper mechanism84.

Moreover, it is desirable that the spring rate at a time of high speed rotation of the dynamic damper mechanism84having the elastic member88is set so that the ratio of that at a time of high speed rotation relative to that at a time of low speed rotation is greater than 1 but no greater than 4 as in the first embodiment.

In accordance with this second embodiment, the same effects as those of the first embodiment described above can be exhibited and, moreover, since the elastic member88is disposed within the spring holder76, it is possible to avoid any increase in the dimensions of dynamic damper mechanism84due to the addition of the elastic member88.

A third embodiment of the present invention is explained by reference toFIG. 13toFIG. 15; parts corresponding to those of the first embodiment shown inFIG. 1toFIG. 9and those of the second embodiment shown inFIG. 10toFIG. 12Bare denoted by the same reference numerals and symbols, and detailed explanation thereof is omitted.

When the lockup clutch40attains a connected state, torque transmitted from the vehicular engine E to the transmission cover20is transmitted mechanically to the output hub29via a torque transmission path98that includes the clutch piston43and a spring holder96, this torque transmission path98having the damper mechanism47disposed therein.

The damper mechanism47is formed by disposing the plurality of, for example four, first damper springs49spaced at equal intervals in the peripheral direction between the clutch piston43and the spring holder96, which can rotate relative to each other around the rotational axis.

The spring holder96is formed from first and second retaining plates100and101, which are rotation-transmitting members forming part of the torque transmission path98; the first retaining plate100is fixed to the output hub29together with an inner peripheral part of the turbine shell24by means of the plurality of third rivets59, and the second retaining plate101, which is spaced from the first retaining plate100in a direction along the axis of the output shaft27, is relatively non-rotatably linked to the first retaining plate100by means of the plurality of second rivets56.

A second spring abutment part101bis integrally and connectedly provided with the outer periphery at a plurality of, for example four, locations spaced at equal intervals in the peripheral direction of the second retaining plate101, the second spring abutment part101bpenetrating into the housing recess50so as to sandwich the first damper spring49between itself and the first spring abutment portion51cof the retainer51fixed to the clutch piston43, and the opening61is formed in the spring cover portion51bof the retainer51so as to allow relative rotation in a limited range between the spring cover portion51band the second spring abutment part101b,that is, the spring holder96, the second spring abutment part101bbeing inserted through the opening61.

When the lockup clutch40attains a connected state and the clutch piston43and the retainer51rotate, the first spring abutment portion51ccompresses the first damper spring49between itself and the second spring abutment part101b,and power is transmitted from the first damper spring49to the output hub29via the spring holder96connected to the second spring abutment part101b.That is, torque is transmitted mechanically between the clutch piston43and the output hub29via the torque transmission path98, the torque transmission path98being formed from the clutch piston43, the retainer51, the first damper spring49, and the spring holder96.

Attached to the torque transmission path98is a dynamic damper mechanism104. This dynamic damper mechanism104is formed by disposing the plurality of, for example four, second damper springs53between an inertial rotating body105and the first and second retaining plates100and101, which are rotation-transmitting members forming part of the torque transmission path98, that is, the spring holder96.

The inertial rotating body105is formed from an inertia plate97and the weight-adding member66fixed to the outer periphery of the inertia plate97, the inertia plate97having at least part thereof (part in this embodiment) sandwiched between the first and second retaining plates100and101forming the spring holder96and having its inner peripheral part rotatably supported on the output hub29.

The cylindrical collar57is disposed between the first and second retaining plates100and101, the cylindrical collar57being inserted through the elongated hole58provided at a plurality of, for example six, locations spaced at equal intervals in the peripheral direction of the inertia plate97. That is, the spring holder96can rotate relative to the inertia plate97only in a limited range via which the collar57moves within the elongated hole58.

Formed at a plurality of, for example four, locations spaced at equal intervals in the peripheral direction of the first retaining plate100are spring-retaining portions100afor retaining the second damper spring53, part of the second damper spring53being exposed to the outside. Furthermore, formed in a part, corresponding to the spring-retaining portion100aof the first retaining plate100, of the second retaining plate101is a spring-retaining portion101afor retaining the second damper spring53, part of the second damper spring53being exposed to the outside.

The inertia plate97is formed so that its outer peripheral part projects further radially outward than the first and second retaining plates100and101forming the spring holder96, and the weight-adding member66is fixed to an outer peripheral part of the inertia plate97.

Formed in a part, corresponding to the spring-retaining portions100aand101a,of the inertia plate97is a spring housing hole (not illustrated) housing part of the second spring53, this spring housing hole being formed so that opposite end parts of the spring housing hole along the peripheral direction of the inertia plate97abut against opposite end parts of the second damper spring53in a disconnected state of the lockup clutch40.

At least two types of elastic members are added to the dynamic damper mechanism104so that the spring rate of the dynamic damper mechanism104can be changed between at least two different rotational speeds. In this third embodiment, the elastic member70and the elastic member88are added to the dynamic damper mechanism104.

The elastic member70is always linked to the inertia body105via the fourth rivet67as in the first embodiment, and is disposed between the first retaining plate100and the inertial rotating body105while being disposed within the inertial rotating body105.

Furthermore, the elastic member88is, as in the second embodiment, always linked to the inertia plate97forming part of the elastic rotating body105, and is disposed between the spring holder96and the inertial rotating body105while being disposed within the spring holder96.

As described above, due to the elastic members70and88being added, the dynamic damper mechanism104exhibits the frequency characteristics shown inFIG. 15. That is, when one of the elastic members70and88operates and exhibits a spring rate that is twice that at a time of low speed rotation, operating at an operating rotational speed of for example1100rpm creates a dynamic damper resonance point P around for example 1350 rpm, and when the other of the elastic members70and88operates and exhibits a spring rate that is four times that at a time of low speed rotation, operating at an operating rotational speed of for example 1500 rpm creates a dynamic damper resonance point Q around for example 1900 rpm.

In accordance with this third embodiment, in addition to the effects of the first and second embodiments described above, since the two types of elastic members70and88are added to the dynamic damper mechanism104, and the spring rate of the dynamic damper mechanism104is changed for two different rotational speeds by means of these elastic members70and88, it is possible to obtain more effective damping performance in a driving rotational region of the vehicular engine E.

Embodiments of the present invention are explained above, but the present invention is not limited to the above-mentioned embodiments and may be modified in a variety of ways as long as the modifications do not depart from the gist of the present invention.