Patent Publication Number: US-2012031722-A1

Title: Hydraulic transmission apparatus

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2010-178752 filed on Aug. 9, 2010 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to hydraulic transmission apparatuses including a damper mechanism having an input element that is coupled to a turbine runner capable of rotating together with a pump impeller connected to an input member, and a lockup clutch capable of performing lockup in which the input member is engaged with the input element of the damper mechanism, and also capable of releasing the lockup. 
     DESCRIPTION OF THE RELATED ART 
     Hydraulic transmission apparatuses that have been conventionally proposed as this type of hydraulic transmission apparatus include: a lockup clutch coupled to a front cover that is coupled to a crankshaft of an engine; a fluid coupling that is formed by a pump impeller integral with the front cover and a turbine; and a damper having an input-side member connected to both the lockup clutch and the turbine and an output-side member connected to an input shaft of a transmission (see, e.g., Japanese Patent Application Publication No. JP-A-2007-309334). In this hydraulic transmission apparatus, the turbine is coupled to the input-side member of the damper to form a so-called turbine damper. When a rotational force is applied from the lockup clutch, that is, when the lockup is being performed, the turbine that is heavy in weight is positioned on the upstream side in a power transmission path to shift a resonance point out of a normal region, thereby enhancing a damping effect. 
     SUMMARY OF THE INVENTION 
     However, in the above conventional hydraulic transmission apparatus, torque from the fluid coupling (the turbine) is transmitted to the transmission side via a damper mechanism, even when the lockup is being released. Thus, the torque from the fluid coupling is damped by the damper mechanism, and required torque may not be able to be transmitted to the transmission side. 
     It is therefore a primary object of a hydraulic transmission apparatus of the present invention to improve torque transmission capability obtained when lockup is being released and damping capability obtained when the lockup is being performed, in a hydraulic transmission apparatus including a damper mechanism having an input element that is coupled to a turbine runner capable of rotating together with a pump impeller connected to an input member, and a lockup clutch capable of performing lockup in which the input member is engaged with the input element of the damper mechanism, and also capable of releasing the lockup. 
     The hydraulic transmission apparatus of the present invention uses the following means in order to achieve the above primary object. 
     A hydraulic transmission apparatus according to a first aspect of the present invention includes: a pump impeller connected to an input member that is coupled to a motor; a turbine runner capable of rotating together with the pump impeller; a damper mechanism having an input element that is coupled to the turbine runner, an elastic body that engages with the input element, and an output element that engages with the elastic body and that is coupled to an input shaft of a transmission device; a lockup clutch capable of performing lockup in which the input member is engaged with the input element of the damper mechanism, and capable of releasing the lockup; and an engagement mechanism that engages the turbine runner with the output element of the damper mechanism so that the turbine runner and the output element of the damper mechanism rotate integrally, when the lockup is being released by the lockup clutch, and that does not engage the turbine runner with the output element of the damper mechanism so that the turbine runner and the output element of the damper mechanism do not rotate integrally, when the lockup is being performed by the lockup clutch. 
     In the hydraulic transmission apparatus according to the first aspect, when the lockup is being released by the lockup clutch, the engagement mechanism engages the turbine runner with the output element of the damper mechanism, and the turbine runner and the output element of the damper mechanism rotate integrally. Thus, when the lockup is being released by the lockup clutch, the turbine runner is directly coupled to the output element of the damper mechanism. This can suppress damping of torque transmitted from the pump impeller to the turbine runner by the elastic body of the damper mechanism. When the lockup is being performed by the lockup clutch, the engagement mechanism does not engage the turbine runner with the output element of the damper mechanism, and the turbine runner and the output element of the damper mechanism do not rotate integrally. Thus, when the lockup is being performed by the lockup clutch, the turbine runner is capable of swinging with respect to the output element of the damper mechanism, and forms a so-called turbine damper. Accordingly, vibration can be satisfactorily damped by the turbine damper. Thus, the torque transmission capability obtained when the lockup is being released, and the damping capability obtained when the lockup is being performed can be improved in the hydraulic transmission apparatus. 
     According to a second aspect of the present invention, the turbine runner and the input element of the damper mechanism may be coupled together via a second elastic body that engages with both the turbine runner and the input element of the damper mechanism. Thus, when the lockup is being performed by the lockup clutch, the turbine runner is capable of swinging with respect to the output element of the damper mechanism, and forms together with the second elastic body a so-called dynamic damper. Accordingly, in the hydraulic transmission apparatus according to the second aspect, vibration is absorbed by the dynamic damper on a more upstream side in a power transmission path to the transmission device to which power from the input member is to be transmitted. Thus, vibration that is transmitted from the motor side to the hydraulic transmission apparatus, that is, the input member, is effectively absorbed (damped) by the dynamic damper before being damped by elements located on the downstream side of the input element of the damper mechanism, whereby transmission of the vibration to the downstream side of the input element can be satisfactorily suppressed. Note that in the case where the input element of the damper mechanism is formed by a plurality of members, the dynamic damper need only be configured to absorb vibration from any one of the plurality of members that form the input element. 
     Moreover, according to a third aspect of the present invention, the engagement mechanism may include a plurality of male-side engagement portions that are provided on one side of the turbine runner and the output element of the damper mechanism, and a plurality of female-side engagement portions that are provided on the other side of the turbine runner and the output element of the damper mechanism, and that are capable of engaging with the male-side engagement portions, respectively, and the male-side engagement portion and the female-side engagement portion may engage with each other with a clearance in a rotational direction, which is determined so that the male-side engagement portion contacts the female-side engagement portion in the rotational direction when the lockup is being released by the lockup clutch, and that the male-side engagement portion does not contact the female-side engagement portion in the rotational direction when the lockup is being performed by the lockup clutch. Thus, the turbine runner and the output element of the damper mechanism can be made to rotate integrally when the lockup is being released by the lockup clutch, and the turbine runner and the output element of the damper mechanism can be made not to rotate integrally when the lockup is being performed by the lockup clutch. 
     According to a fourth aspect of the present invention, the clearance may be determined so that the male-side engagement portion does not contact the female-side engagement portion in the rotational direction even if the second elastic body, which together with the turbine runner forms the dynamic damper, contracts when the lockup is being performed by the lockup clutch. Thus, vibration that is transmitted from the motor side to the input member by the dynamic damper formed by the turbine runner and the second elastic body can be more effectively damped when the lockup is being performed by the lockup clutch. 
     The hydraulic transmission apparatus according to a fifth aspect of the present invention may further include a frictional force generating mechanism placed between the input element of the damper mechanism and the turbine runner, and capable of applying to the input element a frictional force according to vibration that is transmitted from the input element to the turbine runner when the lockup is performed by the lockup clutch. That is, if vibration that is transmitted to the input member is damped by the dynamic damper when the lockup is performed by the lockup clutch and a rotational speed of the input member is included in a certain rotational speed range, resonance may occur in the input member and the input element of the damper mechanism when the rotational speed of the input member is included in another rotational speed range. Thus, the hydraulic transmission apparatus according to the fifth aspect includes the frictional force generating mechanism capable of applying to the input element the frictional force according to the vibration that is transmitted from the input element of the damper mechanism to the turbine runner when the lockup is performed by the lockup clutch. Accordingly, the rotational speed range of the input member in which the resonance occurs in association with the use of the dynamic damper is predetermined, and the frictional force according to the vibration that is transmitted from the input element of the damper mechanism to the turbine runner is applied from the frictional force generating mechanism to the input element when the rotational speed of the input member is included in this rotational speed range, whereby the resonance that occurs in association with the use of the dynamic damper can be satisfactorily damped, and transmission of the vibration to the downstream side of the input element can be satisfactorily suppressed. 
     According to a sixth aspect of the present invention, the frictional force generating mechanism may include a member that engages with one of the turbine runner and the input element of the damper mechanism with a clearance in the rotational direction, and may apply the frictional force to the input element when a twist angle of the dynamic damper that is formed by the turbine runner and the second elastic body becomes equal to or larger than the clearance. Thus, by determining the clearance according to the rotational speed range of the input member in which the resonance occurs in association with the use of the dynamic damper, the frictional force according to the vibration that is transmitted from the input element of the damper mechanism to the turbine runner can be more properly applied to the input element. 
     According to a seventh aspect of the present invention, the frictional force generating mechanism may be a multi-plate clutch mechanism that includes a first clutch plate that engages with one of the turbine runner and the input element of the damper mechanism with the clearance in the rotational direction, and a second clutch plate that engages with the other of the turbine runner and the input element of the damper mechanism. Thus, the frictional force according to the vibration that is transmitted from the input element of the damper mechanism to the turbine runner can be more properly applied to the input element when the rotational speed of the input member is included in the rotational speed range in which the resonance occurs in association with the use of the dynamic damper. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-sectional view showing a hydraulic transmission apparatus  1  according to an embodiment of the present invention; 
         FIG. 2  is an enlarged view showing a main part of the hydraulic transmission apparatus  1 ; 
         FIG. 3  is an enlarged view showing a main part of the hydraulic transmission apparatus  1 ; 
         FIG. 4  is an illustration illustrating operation of the hydraulic transmission apparatus  1 ; 
         FIG. 5  is an illustration illustrating operation of the hydraulic transmission apparatus  1 ; 
         FIG. 6  is an illustration showing the relation between the rotational speed of an engine as a motor and the vibration level in the hydraulic transmission apparatus  1 ; and 
         FIG. 7  is a partial cross-sectional view showing a hydraulic transmission apparatus  1 B according to a modification. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT 
     An embodiment of the present invention will be described below. 
       FIG. 1  is a partial cross-sectional view showing a hydraulic transmission apparatus  1  according to an embodiment of the present invention, and  FIG. 2  is an enlarged view showing a main part of the hydraulic transmission apparatus  1 . The hydraulic transmission apparatus  1  shown in these drawings is a torque converter that is mounted as a starting apparatus on a vehicle including an engine as a motor. The hydraulic transmission apparatus  1  includes: a front cover (an input member)  3  that is coupled to a crankshaft of the engine, not shown; a pump impeller (an input-side hydraulic transmission element)  4  fixed to the front cover  3 ; a turbine runner (an output-side hydraulic transmission element)  5  capable of rotating coaxially with the pump impeller  4 ; a stator  6  that straightens a flow of hydraulic oil (working fluid) from the turbine runner  5  to the pump impeller  4 ; a damper hub (an output member)  7  that is fixed to an input shaft of a transmission device as an automatic transmission (AT) or a continuously variable transmission (CVT), not shown; a damper mechanism  8  connected to the damper hub  7 ; and a single-plate friction type lockup clutch  9  capable of engaging (coupling) the front cover  3  with the damper mechanism  8  and of releasing the engagement (coupling) therebetween. 
     The pump impeller  4  has a pump shell  40  firmly fixed to the front cover  3 , and a plurality of pump blades  41  arranged on the inner surface of the pump shell  40 . The turbine runner  5  has a turbine shell  50 , a plurality of turbine blades  51  arranged on the inner surface of the turbine shell  50 , and a turbine hub  52  that is fixed to the turbine shell  50  via a rivet, that is connected to the turbine shell  50  via the rivet, and that engages coaxially with the damper hub  7  via an engagement mechanism  10 . The pump impeller  4  and the turbine runner  5  face each other, and the stator  6  capable of rotating coaxially with the pump impeller  4  and the turbine runner  5  is placed between the pump impeller  4  and the turbine runner  5 . The stator  6  has a plurality of stator blades  60 , and the rotation direction of the stator  6  is set to only one direction by a one-way clutch  61 . The pump impeller  4 , the turbine runner  5 , and the stator  6  form a torus (an annular flow path) that circulates the hydraulic oil. 
     As shown in  FIG. 1 , the lockup clutch  9  is placed near an inner wall surface on the engine side of the front cover  3  so as to be substantially parallel to the inner wall surface. The lockup clutch  9  includes an annular lockup piston  90  slidably supported in an axial direction by the dumper hub  7 , and a friction member  91  bonded to a surface on the outer peripheral side of and on the front cover  3  side of the lockup piston  90 . The lockup piston  90  is placed near a portion of the front cover  3  extending in a radial direction, and a lockup chamber  95 , which is connected to a hydraulic control unit, not shown, via a hydraulic oil supply hole, not shown, and an oil passage formed in the input shaft, is defined between the back surface of the lockup piston  90  and the front cover  3 . 
     The damper mechanism  8  includes: an annular drive member (an input element)  81  that is coupled to a cylindrical outer peripheral portion  90   a  of the lockup piston  90  extending in the axial direction of the hydraulic transmission apparatus  1 , and that is placed substantially parallel to the lockup piston  90 ; a plurality of first coil springs (elastic bodies)  82  each having its one end fixed to the drive member  81 ; a plurality of second coil springs  83  each placed on the outer peripheral side of the hydraulic transmission apparatus  1 , each having its one end fixed to the drive member  81  like the first coil springs  82 , and each having higher rigidity than the first coil springs  82 ; and a driven member (an output element)  84  that is configured to be able to contact the respective other ends of the first coil springs  82  and the respective other ends of the second coil springs  83 , and that is coupled (fixed) to the damper hub  7  via a plurality of rivets (see  FIG. 1 ). 
     The driven member  84  is formed by two driven plates that face each other with the drive member  81  interposed therebetween, and that are coupled together via a plurality of rivets. The driven member  84  has a plurality of first spring accommodating portions each accommodating (supporting) the respective first coil spring  82  and each having a contact portion capable of contacting the other end (the end that is not fixed to the drive member  81 ) of the respective first coil spring  82 , and a plurality of second spring accommodating portions each accommodating (supporting) the respective second coil spring  83  and each having a contact portion capable of contacting the other end (the end that is not fixed to the drive member  81 ) of the respective second coil spring  83 . In the state where the damper mechanism  8  of the embodiment is attached, the contact portion of each first spring accommodating portion contacts the other end of the corresponding first coil spring  82 , and a small gap is formed between the contact portion of each second spring accommodating portion and the other end of the corresponding second coil spring  83 . 
     Thus, when the hydraulic oil in the lockup chamber  95  is discharged through the hydraulic oil supply hole, etc. by the hydraulic control unit, not shown, the lockup piston  90  moves toward the front cover  3 , and the friction member  91  bonded to the lockup piston  90  contacts the front cover  3  and frictionally engages with the front cover  3 , whereby the front cover  3  is engaged (coupled) with the damper hub  7  via the damper mechanism  8 . Accordingly, power from the engine is transmitted to the input shaft of the transmission device via the front cover  3 , the damper mechanism  8 , and the damper hub  7 . In this manner, in the case where torque that is transmitted from the lockup piston  90  to the drive member  81  of the damper mechanism  8  while the lockup is being performed is relatively small, and the amount of contraction of the first coil springs  82  is less than a predetermined amount, the second coil springs  83  do not contact the driven member  84 , and the torque transmitted to the drive member  81  is output to the transmission device via the first coil springs  82 , the driven member  84 , and the damper hub  7 . On the other hand, in the case where the torque that is transmitted from the lockup piston  90  to the drive member  81  of the damper mechanism  8  while the lockup is being performed is relatively large, and the amount of contraction of the first coil springs  82  is equal to or more than the predetermined amount, the gap between the second coil springs  83  and the driven member  84  is reduced, and the second coil springs  83  contact the driven member  84 , whereby the torque transmitted to the drive member  81  is output to the transmission device via the first coil springs  82  and the second coil springs  83 , the driven member  84 , and the damper hub  7 . As a result, if excessive torque is transmitted from the lockup piston  90  to the drive member  81  of the damper mechanism  8 , the excessive torque is absorbed by the second coil springs  83 . Note that in the lockup clutch  9  of the embodiment, the lockup is released when discharge of the hydraulic oil from the lockup chamber  95  is stopped. 
     As shown in  FIG. 1 , the hydraulic transmission apparatus  1  of the embodiment includes a turbine coupling member  87  fixed to the turbine shell  50  of the turbine runner  5 , and a plurality of third coil springs  86  (second elastic bodies) arranged between the turbine coupling member  87  and the drive member  81  that forms the damper mechanism  8 , so that the third coil springs  86  contact both the turbine coupling member  87  and the drive member  81 . In the embodiment, one end of each third coil spring  86  contacts a contact portion formed in the turbine coupling member  87 , and the other end of each third coil spring  86  contacts a contact portion formed in an annular contact member  93  that is coupled via a rivet to an annular coupling portion  92  extended radially inward from a free end of the cylindrical outer peripheral portion  90   a  of the lockup piston  90 . Each third coil spring  86  is held by a plurality of spring support portions  88  each formed on the turbine coupling member  87  so as to extend in a circumferential direction, and a plurality of spring support portions  93   a  each formed on the contact member  93  so as to extend in the circumferential direction. Thus, since the turbine runner  5 , i.e., the turbine coupling member  87  fixed to the turbine runner  5 , engages with the drive member  81  of the damper mechanism  8  via the plurality of third coil springs  86 , the plurality of third coil springs  86  that are the elastic bodies form a dynamic damper, together with the turbine runner  5  and the turbine coupling member  87 . The turbine runner  5  and the turbine coupling member  87  serve as a mass that does not contribute to torque transmission between the front cover  3  (the input member) and the damper hub (the output member)  7  when the lockup is being performed in which the front cover  3  is engaged with the drive member  81  of the damper mechanism  8  by the lockup clutch  9 . 
     The hydraulic transmission apparatus  1  of the embodiment further includes a frictional force generating mechanism  89  placed between the drive member  81  of the damper mechanism  8  and the turbine runner  5 . The frictional force generating mechanism  89  is capable of applying to the drive member  81  a frictional force according to vibration that is transmitted from the drive member  81  to the turbine runner  5  when the front cover  3  is engaged with the drive member  81  of the damper mechanism  8  by the lockup clutch  9 , and the rotational speed of the engine as the motor is included in a predetermined resonance rotational speed range. 
     As shown in  FIG. 1 , the frictional force generating mechanism  89  of the embodiment is formed as a so-called multi-plate clutch mechanism, and is placed between the drive member  81  and the turbine coupling member  87  fixed to the turbine runner  5 . The frictional force generating mechanism  89  includes: a plurality of first clutch plates  891  that are formed in an annular shape, and that engage with the turbine coupling member  87  so as to be swingable about an axis of the hydraulic transmission apparatus  1 ; at least one second clutch plate  892  formed in an annular shape and placed between the first clutch plates  891 ; a base  894  that engages with the second clutch plate  892 , and that, in the embodiment, holds both an inner peripheral portion of an engagement member  893  capable of frictionally engaging with the rightmost first clutch plate  891  in the drawing, and an inner peripheral portion of the contact member  93  described above; and a biasing member  895  such as a disc spring or a wave washer, that is placed between the contact member  93  and the leftmost first clutch plate  891  in the drawing, and that presses the first and second clutch plates  891 ,  892  toward the engagement member  893 . A friction material  896  is bonded to substantially the entire front and rear surfaces of the first and clutch plates  891 ,  892 . In the embodiment, the base  894  is rotatably supported about the axis of the hydraulic transmission apparatus  1  by a support member  897  that is fixed to the turbine shell  50  (the turbine hub  52 ) via a rivet. Moreover, as shown in the drawing, the contact member  93  and the engagement member  893  are rotatable integrally with the base  894 , and movement of the contact member  93  and the engagement member  893  toward the damper mechanism  8  or toward the turbine runner  5  is restricted by snap rings fixed to the base  94 . 
     The first clutch plate  891  has a plurality of radial protrusions  891   a  that are arranged at regular intervals in an inner peripheral portion of the first clutch plate  891 , and that extend radially inward. The turbine coupling member  87  fixed to the turbine runner  5  has a plurality of (the same number as the radial protrusions  891   a ) axial protrusions  87   a  extending in the axial direction toward the front cover  3  (toward the engine) so as to be able to engage with the radial protrusions  891   a  of the first clutch plate  891 . Each axial protrusion  87   a  of the turbine coupling member  87  has a shorter circumferential length than the interval between adjacent ones of the radial protrusions  891   a  of the first clutch plate  891 , and as shown in  FIG. 2 , is located between adjacent ones of the radial protrusions  891   a  of the first clutch plate  891 . Thus, the first clutch plate  891  engages with the turbine coupling member  87  (the turbine runner  5 ) with a clearance (a backlash) in a rotational direction. 
     The number of axial protrusions  87   a  and radial protrusions  891   a,  the interval between adjacent ones of the axial protrusions  87   a,  and the interval between adjacent ones of the radial protrusions  891   a  are determined so that each axial protrusion  87   a  of the turbine coupling member  87  does not contact any of the radial protrusions  891   a  located on both sides of the axial protrusion  87   a,  and the contact member  93 , the engagement member  893 , and the base  894  rotate integrally by the frictional force of the friction material  896 , when the front cover  3  is not engaged with the drive member  81  of the damper mechanism  8  by the lockup clutch  9  during traveling of a vehicle, or when the rotational speed of the front cover  3  is not included in the above resonance rotational speed range even if the front cover  3  is engaged with the drive member  81  of the damper mechanism  8  by the lockup clutch  9  during traveling of the vehicle. In the embodiment, the number of axial protrusions  87   a  and radial protrusions  891   a,  the interval between adjacent ones of the axial protrusions  87   a,  and the interval between adjacent ones of the radial protrusions  891   a  are determined so that the clearance (the backlash) between the axial protrusion  87   a  of the turbine coupling member  87  and the radial protrusion  891   a  of the first clutch plate  891  is reduced (a twist angle of the dynamic damper becomes equal to or larger than the clearance) by vibration of the turbine runner  5 , and the axial protrusion  87   a  contacts the radial protrusion  891   a , even if the frequency of the vibration of the turbine runner  5  that engages with the drive member  81  via the plurality of third coil springs  86  is the smallest when the front cover  3  is engaged with the drive member  81  of the damper mechanism  8  by the lockup clutch  9  and the rotational speed of the engine as the motor, that is, the front cover  3 , is included in the above resonance rotational speed range. 
     As shown in  FIGS. 1 and 2 , the engagement mechanism  10  engaging the damper hub  7 , which is coupled to the driven member  84  as the output element of the above damper mechanism  8 , with the turbine hub  52  is formed by a plurality of (four about the axis in the embodiment) protruding damper-side engagement portions (male-side engagement portions)  7   a  formed in the outer periphery on the right side in the drawing (on the side of the turbine runner  5 ) of the damper hub  7 , and a plurality of recessed turbine-side engagement portions (female-side engagement portions)  52   a  formed in the inner periphery of the turbine hub  52  so as to engage with the damper-side engagement portions with a clearance (a backlash) in the rotational direction (the circumferential direction), respectively. As shown in  FIGS. 2 and 3 , a columnar surface formed between adjacent ones of the turbine-side engagement portions  52   a  is in slide contact with a columnar surface formed between adjacent ones of the damper-side engagement portions  7   a,  whereby the turbine runner  5  is swingably supported about the axis of the hydraulic transmission apparatus  1  with respect to the damper hub  7 . In the embodiment, as shown in  FIG. 3 , an angle θ is determined so that the damper-side engagement portion  7   a  does not contact the turbine-side engagement portion  52   a  even if the third coil springs  86 , which together with the turbine runner  5  and the turbine coupling member  87  forms the dynamic damper, contracts when the lockup is being performed by the lockup clutch  9 , where “θ” represents an angle that defines the clearance in the rotational direction (the direction shown by an arrow in the drawing) between the damper-side engagement portion  7   a  and the turbine-side engagement portion  52   a  (between a side surface on the downstream side in the rotational direction of the damper-side engagement portion  7   a  and a side surface on the downstream side in the rotational direction of the turbine-side engagement portion  52   a ) when the centerline of the damper-side engagement portion  7   a  matches the centerline of the turbine-side engagement portion  52   a  corresponding to this damper-side engagement portion  7   a.    
     That is, the angle θ is determined as a relative rotation angle between the damper hub  7  and the turbine runner  5  (the turbine hub  52 ), which allows the third coil springs  86  to contract sufficiently when the lockup is being performed. 
     Operation of the above hydraulic transmission apparatus  1  will be described below with reference to  FIGS. 4 to 6 , etc. In the hydraulic transmission apparatus  1 , when the lockup is released in which the front cover  3  is not engaged with the drive member  81  by the lockup clutch  9 , the power from the engine as the motor is transmitted via a path formed by the front cover  3 , the pump impeller  4 , and the turbine runner  5 . Thus, the turbine runner  5  (the turbine hub  52 ) rotates relative to the damper hub  7 , and the clearance in the rotational direction between the damper-side engagement portion  7   a  and the turbine-side engagement portion  52   a  that form the engagement mechanism  10  is reduced, whereby the turbine runner  5  (the turbine hub  52 ) is engaged with the turbine hub  7 . As a result, the turbine hub  52  is engaged by the engagement mechanism  10  with the damper hub  7  coupled to the driven member (the output element)  84  of the damper mechanism  8 , and the turbine runner  5  and the damper hub  7  rotate integrally. Thus, when the lockup is released, as shown by solid lines in  FIG. 4 , the power from the engine as the motor is transmitted to the input shaft of the transmission device via a path formed by the front cover  3 , the pump impeller  4 , the turbine runner  5 , the turbine hub  52 , the engagement mechanism  10 , and the damper hub  7 . In this manner, when the lockup is released, the turbine runner  5  is directly coupled to the damper hub  7 , that is, the driven member  84  as the output element of the damper mechanism  8 . This can suppress damping of the torque transmitted from the pump impeller  4  to the turbine runner  5  by the first coil springs  82  and the second coil springs  83  of the damper mechanism  8 . 
     On the other hand, when the lockup is performed in which the front cover  3  is engaged with the drive member  81  of the damper mechanism  8  by the lockup clutch  9 , as shown by solid lines in  FIG. 5 , the power from the engine as the motor is transmitted to the input shaft of the transmission device via a path formed by the front cover  3 , the lockup clutch  9 , the drive member  81 , the plurality of first and second coil springs  82 ,  83 , the driven member  84 , and the damper hub  7 . At this time, variation in torque that is input to the front cover  3  is absorbed mainly by the first and second coil springs  82 ,  83  of the damper mechanism  8 . 
     The clearance (the angle θ) in the rotational direction between the damper-side engagement portion  7   a  and the turbine-side engagement portion  52   a  that form the engagement mechanism  10  is determined so that the damper-side engagement portion  7   a  does not contact the turbine-side engagement portion  52   a  even if the third coil springs  86  contract when the lockup is being performed. That is, when the lockup is being performed, the turbine runner  5  (the turbine hub  52 ) and the damper hub  7  rotate relative to each other rather than rotate integrally, and the third coil springs  86  are allowed to contract sufficiently. In the hydraulic transmission apparatus  1  of the embodiment, the turbine runner  5 , that is, the turbine coupling member  87  fixed to the turbine runner  5 , is engaged with the drive member  81  of the damper mechanism  8  via the plurality of third coil springs  86 . Thus, when the lockup is being performed by the lockup clutch  9 , the plurality of third coil springs  86  that are the elastic bodies form the dynamic damper, together with the turbine runner  5  and the turbine coupling member  87 . The turbine runner  5  and the turbine coupling member  87  serve as the mass that does not contribute to torque transmission between the front cover  3  (the input member) and the damper hub (the output member)  7  when the lockup is being performed. Vibration that is transmitted from the motor side to the front cover  3  can be more effectively damped by such a dynamic damper. 
     That is, in the hydraulic transmission apparatus  1  of the embodiment, the turbine coupling member  87  fixed to the turbine runner  5  engages via the plurality of third coil springs  86  (the elastic bodies) with the drive member  81 . Among the plurality of elements that form the damper mechanism  8 , the drive member  81  has higher vibrational energy than the driven member  84  especially when the lockup is performed and the rotational speed of the front cover  3  (the engine speed) is relatively low. Vibration is absorbed by the dynamic damper, which is formed by the plurality of third coil springs  86 , and the turbine runner  5  and the turbine coupling member  87  serving as the mass, on a more upstream side in a power transmission path to the transmission device to which the power from the front cover  3  is to be transmitted. Thus, when the lockup is performed, vibration that is transmitted from the engine side to the hydraulic transmission apparatus  1 , that is, the front cover  3 , is effectively absorbed (damped) by the dynamic damper before being damped by the elements located on the downstream side of the drive member  81  of the damper mechanism  8 , whereby transmission of the vibration to the downstream side of the drive member  81  can be satisfactorily suppressed. 
     Thus, in the hydraulic transmission apparatus  1  of the embodiment, the resonance frequency of the dynamic damper that is formed by the plurality of third coil springs  86  and the turbine runner  5  and the turbine coupling member  87  serving as the mass, that is, the rigidity (the spring constant) of the third coil springs  86  and the weight (inertia) of the turbine runner  5 , the turbine coupling member  87 , and the like are adjusted based on the number of cylinders of the engine as the motor, and the engine speed when the lockup is performed. Accordingly, as shown by a solid line in  FIG. 6 , vibration that is transmitted from the engine as the motor to the hydraulic transmission apparatus  1 , that is, the front cover  3 , when the engine speed is relatively low can be effectively absorbed (damped) by the dynamic damper, and transmission of the vibration to the downstream side of the drive member  81  can be satisfactorily suppressed, as compared to, for example, the case where the dynamic damper is coupled to the driven member  84  of the damper mechanism  8  (see a dashed line in  FIG. 6 ). As a result, in the hydraulic transmission apparatus  1  of the embodiment, power transmission efficiency can be improved by performing the lockup when the engine speed reaches a relatively low lockup rotational speed Nlup of about 1,000 rpm, for example, and vibration that tends to be produced between the front cover  3  and the drive member  81  when the rotational speed of the front cover  3  (the engine speed) is relatively low at the time of and after engagement of the lockup clutch  9 , can be satisfactorily damped. 
     If the vibration that is transmitted to the front cover  3  is damped by the dynamic damper and the vibration level is reduced when the front cover  34  is engaged with the drive member  81  of the damper mechanism  8  by the lockup clutch  9  and the rotational speed of the front cover  3  (the engine speed) is included in a low rotational speed range including the lockup rotational speed Nlup, resonance may occur in the front cover  3  and the drive member  81  when the rotational speed of the front cover  3  (the engine speed) increases thereafter, as shown by two-dot chain line in  FIG. 6 . Thus, in the embodiment, the rotational speed range of the front cover  3  (the engine) in which the resonance occurs in association with the use of the dynamic damper is predetermined as the resonance rotational speed range described above, and the frictional force according to the vibration that is transmitted from the drive member  81  to the turbine runner  5  via the third coil springs  86  and the turbine coupling member  87  is applied from the frictional force generating mechanism  89  to the drive member  81  when the rotational speed of the front cover  3  (the engine) is included in the resonance rotational speed range. 
     That is, when the clearance (the backlash) between the axial protrusion  87   a  of the turbine coupling member  87  and the radial protrusion  891   a  of the first clutch plate  891  that forms the frictional force generating mechanism  89  is reduced and the axial protrusion  87   a  contacts the radial protrusion  891   a  due to the vibration of the turbine runner  5  that engages with the drive member  81  (the contact member  93 ) of the damper mechanism  8  via the third coil springs  86 , the turbine coupling member  87 , the contact member  93 , and the coupling portion  92  of the lockup piston  90 , the first clutch plate  891  is moved (rotated) with respect to the drive member  81  by the turbine runner  5 . Thus, the frictional force according to the vibration of the turbine runner  5  can be applied to the drive member  81  via the first and second clutch plates  891 ,  892 , the friction material  896 , the engagement member  893 , the base  894 , the contact portion  93 , and the coupling portion  92  of the lockup piston  90 . In this manner, as shown in  FIG. 6 , the resonance that occurs in association with the use of the dynamic damper can be satisfactorily damped, and transmission of the vibration to the downstream side of the drive member  81  can be satisfactorily suppressed. 
     As described above, when the lockup is being released by the lockup clutch  9  in the hydraulic transmission apparatus  1  of the embodiment, the turbine runner  5  is engaged with the damper hub  7  coupled to the driven member  84  as the output element of the damper mechanism  8  by the engagement mechanism  10 , and the turbine runner  5  and the damper hub  7  rotate integrally. Thus, when the lockup is being released by the lockup clutch  9 , the turbine runner  5  is directly coupled to the damper hub  7  (the driven member  84  of the damper mechanism  8 ). This can suppress damping of the torque transmitted from the pump impeller  4  to the turbine runner  5  by the first coil springs  82  and the second coil springs  83  of the damper mechanism  8 . When the lockup is being performed by the lockup clutch  9 , the turbine runner  5  is not engaged with the damper hub  7  (the driven member  84  of the damper mechanism  8 ) by the engagement mechanism  10 , and the turbine runner  5  and the damper hub  7  do not rotate integrally. Thus, when the lockup is being performed by the lockup clutch  9 , the turbine runner  5  is capable of swinging with respect to the damper hub  7  (the output element) of the damper mechanism  8 , and forms the dynamic damper together with the third coil springs  86 , whereby vibration can be satisfactorily damped by the dynamic damper. Accordingly, the torque transmission capability obtained when the lockup is being released and the damping capability obtained when the lockup is being performed can be improved in the hydraulic transmission apparatus  1  of the embodiment. 
     In the embodiment, the turbine runner  5  is coupled to the drive member  81  as the input element of the damper mechanism  8  via the third coil springs  86  that engage with both the turbine runner  5  and the drive member  81 . Thus, vibration is absorbed by the dynamic damper, which is formed by the turbine runner  5 , the turbine coupling member  87 , and the third coil springs  86 , on the more upstream side in the power transmission path to the transmission device to which the power from the front cover  3  is to be transmitted. Accordingly, vibration that is transmitted from the motor side to the hydraulic transmission apparatus, that is, the front cover  3 , can be effectively absorbed (damped) by the dynamic damper before being damped by the elements located on the downstream side of the drive member  81  (the input element) of the damper mechanism  8 , whereby transmission of the vibration to the downstream side of the drive member  81  (the input element) can be satisfactorily suppressed. Note that in the case where the drive member  81  (the input element) of the damper mechanism  8  is formed by a plurality of members, the dynamic damper need only be configured so as to absorb vibration from any one of the plurality of members that form the drive member  81  (the input element). It should be noted that the third coil springs  86  and the frictional force generating mechanism  89  may be omitted from the above hydraulic transmission apparatus  1 . In this case, when the lockup is being performed by the lockup clutch  9 , the turbine runner  5  is capable of swinging with respect to the damper hub  7  (the driven member  84  of the damper mechanism  8 ), and forms a so-called turbine damper. Thus, vibration can also be satisfactorily damped by such a turbine damper. 
     Moreover, the engagement mechanism  10  of the embodiment includes the plurality of damper-side engagement portions  7   a  (the male-side engagement portions) provided on the driven member  84  side of the damper mechanism  8 , that is, provided in the damper hub  7 , and the plurality of turbine-side engagement portions  52   a  (the female-side engagement portions) provided in the turbine runner  5  and capable of engaging with the damper-side engagement portions  7   a  (the male-side engagement portions), respectively. The damper-side engagement portion  7   a  engages with the turbine-side engagement portion  52   a  with the clearance θ in the rotational direction based on the angle θ determined so that the damper-side engagement portion  7   a  contacts the turbine-side engagement portion  52   a  in the rotational direction when the lockup is being released by the lockup clutch  9 , and that the damper-side engagement portion  7   a  does not contact the turbine-side engagement portion  52   a  in the rotational direction when the lockup is being performed by the lockup clutch  9 . The angle θ that defines the clearance is determined so that the damper-side engagement portion  7   a  does not contact the turbine-side engagement portion  52   a  in the rotational direction even if the third coil springs  86 , which form the dynamic damper together with the turbine runner  5 , contract when the lockup is being performed by the lockup clutch  9 . Thus, the turbine runner  5  and the damper hub  7  (the driven member  84 ) of the damper mechanism  8  are made to rotate integrally when the lockup is being released by the lockup clutch  9 , and the turbine runner  5  and the damper hub  7  (the driven member  84 ) of the damper mechanism  8  are made not to rotate integrally when the lockup is being performed by the lockup clutch  9 , whereby the vibration that is transmitted from the engine to the front cover  3  can be more efficiently damped by the dynamic damper. Note that although the damper-side engagement portions  7   a  are protruding (male) engagement portions, and the turbine-side engagement portions  52   a  are recessed (female) engagement portions in the above embodiment, the damper-side engagement portions  7   a  may be recessed (female) engagement portions, and the turbine-side engagement portions  52   a  may be protruding (male) engagement portions. 
     The hydraulic transmission apparatus  1  is placed between the drive member  81  of the damper mechanism  8  and the turbine runner  5 , and includes the frictional force generating mechanism  89  capable of applying to the drive member  81  the frictional force according to the vibration that is transmitted from the drive member  81  to the turbine runner  5  when the lockup is performed by the lockup clutch  9  and the rotational speed of the front cover  3  is included in the predetermined rotational speed range. That is, if the vibration that is transmitted to the front cover  3  is damped by the dynamic damper when the lockup is performed by the lockup clutch  9  and the rotational speed of the front cover  3  is included in a certain rotational speed range, resonance may occur in the front cover  3  and the drive member  81  of the damper mechanism  8  when the rotational speed of the front cover  3  is included in another rotational speed range. Thus, in the hydraulic transmission apparatus  1  of the embodiment, the rotational speed range of the front cover  3  in which the resonance occurs in association with the use of the dynamic damper is predetermined, and the frictional force according to the vibration that is transmitted from the drive member  81  of the damper mechanism  8  to the turbine runner  5  is applied from the frictional force generating mechanism  89  to the drive member  81  when the rotational speed of the front cover  3  is included in this rotational speed range. 
     In this manner, the resonance that occurs in association with the use of the dynamic damper can be satisfactorily damped, and transmission of the vibration to the downstream side of the drive member  81  can be satisfactorily suppressed. 
     Moreover, the frictional force generating mechanism  89  of the embodiment is formed as the multi-plate clutch mechanism including the first clutch plates  891  that engage with the turbine coupling member  87  (the turbine runner  5 ) with the clearance in the rotational direction, and the second clutch plate  892  that engages with the base  894  coupled to the drive member  81  of the damper mechanism  8  via the contact member  93 , etc. Thus, the frictional force according to the vibration that is transmitted from the drive member  81  of the damper mechanism  8  to the turbine runner  5  can be more properly applied to the drive member  81  when the rotational speed of the front cover  3  is included in the rotational speed range in which the resonance occurs in association with the use of the dynamic damper. Note that in the frictional force generating mechanism  89 , the first clutch plates  891  may be engaged with the turbine coupling member  87 , and the second clutch plate  892  may be engaged with the base  894  with a clearance (a backlash) in the rotational direction. 
       FIG. 7  is a partial cross-sectional view showing a hydraulic transmission apparatus  1 B according to a modification. An engagement mechanism  10 B of the hydraulic transmission apparatus  1 B shown in the drawing is formed by an annular member  7   b  that is fixed (coupled) to the damper hub  7  via a rivet and that has a plurality of holes (female-side engagement portions) as the damper-side engagement portions, and a turbine-side engagement portion  87   b  that is extended from the turbine coupling member  87  and that engages with the holes of the annular member  7   b  with a clearance in the rotational direction. Such an engagement mechanism  10 B can also engage the turbine runner  5  with the damper hub  7  (the driven member  84  of the damper mechanism  8 ) so that the turbine runner  5  and the damper hub  7  rotate integrally, when the lockup is being released by the lockup clutch  9 , and can cause the turbine runner  5  and the damper hub  7  not to rotate integrally when the lockup is being performed by the lockup clutch  9 . Note that as shown in the drawing, the frictional force generating mechanism  89  of the hydraulic transmission apparatus  1 B of  FIG. 7  includes the first clutch plate  891  that engages with a support portion  87   c  extended from the turbine coupling member  87 , with a clearance (a backlash) in the rotational direction, the second clutch plate  892  that engages with a contact member  93 B that contacts the third coil springs  86 , and the engagement member  893  that is held by the support portion  87   c  of the turbine coupling member  87 . The contact member  93 B is fixed via a rivet to a coupling member  92 B that engages with the cylindrical outer peripheral portion  90   a  of the lockup piston  90 , and that is supported in the radial direction by the annular member  7   b.  Thus, the base  894  of the hydraulic transmission apparatus  1  can be omitted in the hydraulic transmission apparatus  1 B. 
     The correspondence between main elements of the embodiment and main elements of the invention described in the section “SUMMARY OF THE INVENTION” will be described below. In the above embodiment, the hydraulic transmission apparatus  1 , which includes: the pump impeller  4  connected to the front cover  3  as the input member coupled to the engine as the motor; the turbine runner  5  capable of rotating together with the pump impeller  4 ; the damper mechanism  8  having the drive member (the input element)  81  that is coupled to the turbine runner  5 , the first and second coil springs  82 ,  83  that are the elastic bodies and engage with the drive member  81 , and the driven member (the output element)  84  that is coupled via the damper hub  7  to the component to which the power from the engine is to be transmitted; and the lockup clutch  9  capable of performing the lockup in which the front cover  3  is engaged with the drive member  81  of the damper mechanism  8 , and capable of releasing the lockup, corresponds to the “hydraulic transmission apparatus.” The engagement mechanism  10  that engages the turbine runner  5  with the damper hub  7  (the driven member  84 ) so that the turbine runner  5  and the damper hub  7  (the driven member  84 ) rotate integrally when the lockup is being released by the lockup clutch  9  and that does not engage the turbine runner  5  with the damper hub  7  (the driven member  84 ) so that the turbine runner  5  and the damper hub  7  (the driven member  84 ) do not rotate integrally when the lockup is being performed by the lockup clutch  9  corresponds to the “engagement mechanism.” The third coil springs  86  that engage with both the turbine runner  5  and the drive member  81  of the damper mechanism  8  correspond to the “second elastic body.” 
     It should be noted that the correspondence between the main elements of the embodiment and the main elements of the invention described in the section “SUMMARY OF THE INVENTION” is shown by way of example only in order to specifically describe the invention described in the section “SUMMARY OF THE INVENTION,” and thus does not limit the elements of the invention described in the section “SUMMARY OF THE INVENTION.” That is, the embodiment is merely a specific example of the invention described in the section “SUMMARY OF THE INVENTION,” and the invention described in the section “SUMMARY OF THE INVENTION” should be construed based on the description in that section. 
     It should be noted that although the embodiment of the invention is described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the subject of the present invention. 
     The present invention can be used in the field of manufacturing hydraulic transmission apparatuses, etc.