Patent Document

This claims the benefit of German Patent Application DE 10 2013 208 158.8, filed May 3, 2013 and hereby incorporated by reference herein. 
     The invention relates to a friction clutch comprising an input side and an output side, which are arranged to rotate about an axis of rotation, an fluid chamber fillable with a cooling liquid, the fluid chamber comprising a first friction partner that is axially displaceable and in a torque-locking engagement with the input side, at least one second friction partner that is axially displaceable and in a torque-locking engagement with the output side, at least one inner disc carrier coupled to one of the two friction partners radially on the outside, and a compression device having a pressure chamber fillable with a pressure fluid to provide axial compression of the friction partners to generate a torque-locking engagement between the input side and the output side 
     BACKGROUND 
     EP 1 610 018 B1, for example, discloses a friction clutch embodied as a wet-running start-up clutch. The friction clutch comprises an input side and an output side, which are arranged for rotation, as well as an fluid chamber. To transmit a torque between the input side and the output side in a frictional way, first friction discs are provided that are in a torque-locking engagement with the input side and are axially displaceable. Furthermore, second friction discs are provided, which are likewise axially displaceable and are connected to the output side in a torque-locking way. The actuating piston is displaced in an axial direction by a pressure chamber into which a pressure fluid is introduced and compresses the friction discs to establish a torque-locking engagement between the input side and the output side. 
     Moreover, DE 10 2008 060 577 discloses a torque converter including a friction clutch. 
     In both cases, the friction clutches are cooled by a cooling liquid provided in a housing of the friction clutch. The cooling liquid absorbs the heat that is generated as the clutch is being engaged to prevent the clutch, in particular the friction discs of the friction clutch, from over-heating. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a clutch with improved cooling, i.e. an improved heat removal from the friction discs. 
     In accordance with the invention, an improved friction clutch comprises an input side and an output side, which are arranged for rotation about an axis of rotation, and an fluid chamber that is fillable with a cooling liquid, wherein a first friction partner that is displaceable in an axial direction and in torque-locking engagement with the input side and at least one second friction partner that is displaceable in an axial direction and in torque-locking engagement with the output side are provided in the fluid chamber. In addition, at least one inner disc carrier coupled radially on the outside to one of the two friction partners and a compression device including a pressure chamber fillable with a pressure fluid are provided in the fluid chamber to achieve axial compression of the friction partners to create a torque-locking engagement between the input side and the output side. Moreover, a deflection device is provided in the fluid chamber, the deflection device in particular arranged axially adjacent to the inner disc carrier. The inner disc carrier includes at least one first passage for the cooling liquid to pass through the inner disc carrier. The deflection device is designed to feed back at least a first portion of the cooling liquid flowing in a radially outward direction between the friction partners in a radially inward direction to the first passage of the inner disc carrier. 
     In this way, direct circulation of the cooling liquid is provided at the friction partners, reliably ensuring improved cooling of the friction partners. In addition, after-cooling is achieved while the clutch is in an engaged condition so that the friction partners have already been sufficiently cooled for a reengagement. Thus the total thermal stress on the friction partners in the friction clutch may reliably be maintained on a low level and the friction clutch may absorb higher start-up torques. Thus the friction clutch on the whole may transmit a higher torque even though its weight and installation space remain the same. 
     In accordance with a further embodiment of the invention, the inner disc carrier has a toothed section arranged in an axial direction and an attachment section arranged in a radial direction. The passage is arranged in the toothed section. The toothed section is designed to provide a form-locking or positive connection between the first and second friction partners. Furthermore, the toothed section is located radially outward and is connected to the attachment section on the side of the toothed section that is opposite the deflection device. In addition, internal circulation is not hampered or even blocked by the attachment region of the inner disc carrier. Moreover, it is no longer necessary to provide recesses in the attachment section of the inner disc carrier to ensure an internal circulatory volume flow. 
     In accordance with a further embodiment, a feed channel is provided in the axial direction between the compression device and the inner disc carrier. The feed channel is designed to guide the cooling liquid from the inside in a radially outward direction to the first and/or second friction partner. In this way, additional cooled-down cooling liquid may be directly fed to the friction partners to improve cooling. In addition, the cooling oil fed into the clutch housing from outside the clutch housing replaces the heated oil already present in the housing, causing the oil in the clutch to be continuously exchanged or to be exchanged as required as portion of an external coolant circuit. The aforementioned option of being able to avoid recesses in the attachment section allows the formation of an essentially fluid-tight feed channel between the attachment region of the inner disc carrier and the clutch piston, providing a targeted and effective way of supplying external cooling liquid, in particular cooling oil, to a disc package formed by the friction partners. Thus even in a condition in which the internal circulation largely comes to a halt due to identical rotary speeds on the drive side and on the power take-off side (e.g. when the clutch is engaged), after-cooling of the disc arrangement is ensured. 
     In accordance with a further embodiment, the friction clutch includes a housing that separates the fluid chamber from an environment. The fluid chamber further includes an outer disc carrier that has at least one second passage and is coupled radially on the inside to the other one of the two friction partners. A collection channel designed to collect the cooling liquid that flows between the friction partners and passes through the outer disc carrier via the second passage in a radially outward direction is provided between the outer disc carrier and the housing. In this way, a complete radial flow through the entirety of the friction partners is ensured. 
     The flow through the disc package formed by the friction discs is especially increased by providing the friction discs that are fixed for co-rotation to the drive side with fluid-enhancing structures such as grooves or recesses that are suitable for accelerating the cooling liquid flowing into the clutch package in a circumferential direction to achieve a pumping effect of the cooling oil over the friction surfaces of the clutch due to centrifugal forces. 
     In accordance with a further embodiment, the collection channel is arranged to circumferentially run around the outer disc carrier and aligned to be essentially parallel to the axis of rotation. In this way, a reliable axial flow of the cooling liquid in the direction of the deflection device is ensured. 
     In accordance with a particularly advantageous embodiment, the deflection device may comprise a guide portion designed to divide the cooling liquid flowing out of the collection channel into a first portion and a second portion of cooling liquid. 
     In accordance with a further embodiment, the guide portion of the deflection device and the first and/or second friction partner facing the guide portion define a first feed-back channel, which connects the first passage of the inner disc carrier to the collection channel to guide the first portion of the cooling liquid directly from the collection channel to the first passage of the inner disc carrier. 
     In accordance with a further embodiment, the deflection device and the housing define a second feed-back channel in the axial direction, the second feed-back channel extending in a radially inward direction further outwards and connected to the collection channel. The second feed-back channel guides the second portion of the cooling liquid in a radially inward direction. In this way, reliable cooling and lubrication of components located further radially inward and for example integrated into the deflection device, for example, such as a centrifugal pendulum-type absorber, a spring damper, or a double-spring damper, may be achieved by the second portion of the cooling liquid. 
     In accordance with a particularly advantageous embodiment, the deflection device may be connected for co-rotation to the power take-off side of the clutch and during the engagement of the clutch the deflection device may have a rotary speed difference relative to the discs that are fixed for co-rotation with the drive side (engine) and are equipped with fluid-enhancing structures, the speed difference generating a cooling oil circulation in the clutch housing that encompasses the largest possible portion of the clutch housing. 
     As a result of this cooling liquid circulation, thermal energy is discharged from the disc package and transferred to the other components of the clutch (clutch housing, potentially torsional vibration damper etc.) and most notably stored in the volume of cooling liquid. 
     In this process, both an amount of cooling liquid included in the clutch housing by the cooling liquid circulation internal to the clutch housing and the components encompassed by the cooling liquid circulation may be used as buffers for the thermal loss caused by the engagement of the clutch, reducing the friction surface temperatures in the disc package to a considerable extent in the case of clutch engagement processes, in particular successive clutch engagement processes that occur multiple times within a short period of time. 
     In accordance with a further embodiment, on an end face facing the friction partners, the compression device includes a further deflection device that is at least partially arranged radially inward relative to the friction partner facing the compression device and is designed to deflect the cooling liquid flowing out of the feed channel towards the first or second friction partner and to feed it directly to the first or second friction partner. 
     In accordance with a further embodiment, the deflection device comprises at least one centrifugal pendulum-type absorber in connection with a spring damper or a double-spring damper or, alternatively a spring damper or a double-spring damper. In this way, a particularly compact friction clutch may be provided, allowing the spring damper, the dual spring damper and/or the centrifugal pendulum-type absorber to be simultaneously cooled and lubricated by the second portion of the cooling liquid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in more detail below based on a drawing. 
         FIG. 1  is a diagrammatic longitudinal sectional view of a friction clutch. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a diagrammatic longitudinal sectional view of a friction clutch  10 . The friction clutch  10  comprises an input side  15  and an output side  20 , which are arranged for rotation about an axis of rotation  25 . The friction clutch  10  further comprises a housing  30 , connected at the input side to a drive train  35  on the left-hand side of  FIG. 1 . The drive train  35  may be a combustion engine, a hybrid drive, or an electric motor. On the inside, the housing  30  includes a fluid chamber  40  sealed against the environment of the friction clutch  10  by the housing  30 . Thus a cooling liquid  45  present in the fluid chamber  40  remains in the housing  30 . The housing  30  is arranged for co-rotation with an outer disc carrier  50 . A plurality of first friction discs  55  is arranged radially inward on the outer disc carrier  50 . The first friction discs  55  have an outer toothing  56 . The outer disc carrier  50  has an interior toothing  60  meshing with the outer toothing  56  of the first friction disc  55 . As first friction partners, the first friction discs  55  are thus axially displaceable and arranged for co-rotation with the outer disc carrier  50  in a form-locking way via the interior toothing  60  of the outer disc carrier  50 . The outer disc carrier  50  further comprises a stop  65 . The stop  65  is arranged axially adjacent to the first friction discs  55 . In this way, the first friction discs  55  are connected to the input side  15  in a torque-locking way. 
     An inner disc carrier  70  is provided radially inward relative to the outer disc carrier  50 . The inner disc carrier  70  includes an attachment region  75  and a toothing region  80 . The attachment region  75  is radially outwardly connected to the toothing region  80 . The toothing region  80  comprises an outer toothing  85 . Multiple second friction discs  90  are arranged radially to the outside on the inner disc carrier  70 . Radially to the inside, each of the second frictions discs  90  has an interior toothing  95  that meshes with the outer toothing  85  of the inner disc carrier  70  so that as second friction partners, the second friction discs  70  are connected to co-rotate with the inner disc carrier  70 , yet are axially displaceable in the axial direction on the outer toothing  85  of the inner disc carrier  70 . In the toothing region  80 , the inner disc carrier includes a plurality of first passages  100 . In a similar way, the outer disc carrier  50  includes a plurality of second passages  105  in the region of the inner toothing  60 . The second passages  105  are provided in the region of the inner toothing  50 . Radially to the inside, the attachment region  75  of the inner disc carrier  70  is connected to the output side  20  via a hub  106 . 
     A compression device  110  is provided to the left of the inner disc carrier  70 . The compression device  110  comprises a piston  115  that delimits a pressure chamber  120  together with the housing  30 . A protrusion  125  is provided on the piston  115  on a radial level of the first friction disc  55 . When the pressure chamber  120  is actuated and filled with a pressure fluid  130 , the piston protrusion  125  acts to contact the front face of the first friction disc  55  and to apply a pressure F to the friction disc  55 . 
     A feed channel  135  extending radially outward from the inside is provided between the inner disc carrier  70 , i.e. its attachment region  75 , and the piston  115 . In the axial direction, the feed channel  135  is delimited by the said piston  115  and by the attachment region  75  of the inner disc carrier  70 . Radially to the outside of the outer disc carrier  50 , a collection channel  140  is provided. The collection channel  140  is delimited by the outer disc carrier  50  and the housing  30 . The collection channel  140  circumferentially runs around the outer disc carrier  50  and is aligned to be essentially parallel to the axis of rotation  25 . A deflection device  145  is provided axially adjacent to the outer disc carrier  50  and to the inner disc carrier  70 , respectively. The deflection device  145  comprises a guide section  150  arranged radially outwardly on the deflection device  145 . Together with the friction discs  55 ,  90 , in the axial direction the guide section  150  defines a first feed-back channel  155 . To the right of the first feed-back channel  155 , the deflection device  145  or rather the guide section  150  and the housing  30  define a second feed-back channel  160 . The second feed-back channel  160  extends radially inward from outside. The first and second feed-back channels  155 ,  160  are connected to the collection channel  140 . 
     As an alternative to the embodiment shown in  FIG. 1 , in a manner analogous to the inner toothing  60 , the housing  30  might be provided with an inner toothing on its inner wall in its outer circumferential region. Thus in addition to its function as a container for the oil, the housing  30  might be embodied as an outer disc carrier. In this case, the collection channel would be defined radially to the outside by the outer disc carrier formed on the housing  30  and radially to the inside by the outer diameter of the second friction discs  90  meshing with the inner disc carrier  70 . The cooling liquid  45  might then be guided to the deflection device  145  in the axial direction via left-out teeth of the first friction discs  55 . 
     In this embodiment, the deflection device  145  comprises a spring damper  165  symbolically indicated in  FIG. 1 . Alternatively, it is conceivable for the spring damper  165  to be embodied as a double-spring damper (symbolically indicated by the dashed line). Furthermore the guide section  150  of the deflection device  145  may, for example, be embodied as a centrifugal pendulum-type absorber. Furthermore, instead of the arrangement perpendicular to the axis of rotation  25  as shown in  FIG. 1 , the guide section  150  may have a contour or may be inclined relative to the axis of rotation  25 . 
     When the pressure chamber  120  is filled with a pressure fluid  130  under pressure, the piston  115  is displaced in the direction of the deflection device  145 , causing the friction discs  55 ,  90  to be pressed against each other. The displacement path of the friction discs  55 ,  90  is limited by the stop  65 , so that an axial compression of the friction discs  55 ,  90  occurs. This is done to establish a torque-locking connection between the friction discs  55 ,  90 , connecting the input side  15  to the output side  20  in a torque-locking way. When they are being engaged, friction occurs between the friction discs  55 ,  90 , causing the friction discs  55 ,  90  to be warmed up due to the frictional heat. To discharge this heat, the cooling liquid  45  is provided in the fluid chamber. The cooling liquid  45  flows radially outward from the inside via the feed channel  135 . This is achieved due to the fact that the outer disc carrier  50  and the piston  115  are connected to the input side  15  and thus continuously rotate at the input rotary speed when the combustion engine is in operation. This causes the cooling liquid to be accelerated in the radial direction and to be subjected to centrifugal forces that urge the cooling liquid  45  in the feed channel  135  in a radially outward direction. Despite the change in the cross-section of the feed channel  135  when the piston  115  is actuated, the attachment region  75  is spaced a portion from the piston  115  in such a way that even in the actuated condition of the piston  115 , the cross-section of the feed channel  135  is large enough to ensure a sufficient flow of cooling liquid  45  through the feed channel  135  to the friction discs  55 ,  90 . The protrusion  125  of the piston forms a further deflection device  170  that axially deflects the cooling liquid  45 , which flows in an outward direction, in order directly to supply cooling liquid  45  to the friction discs  55 ,  90 . The cooling liquid  45  directly flows between the first and second friction discs  55 ,  90 . Then the cooling liquid  45  flows further radially outward and passes through the second passages  105  in the outer disc carrier  50 . The cooling liquid  45  is collected by the collection channel  140  radially on the outside of the outer disc carrier  50  and is guided away from the outer disc carrier  50  in an axial direction in the direction of the deflection device. Radially on the outside of the deflection device  145  the housing  30  deflects the cooling liquid  45  radially inward in the direction of the guide section  150 . The guide section  150  divides the flow of cooling liquid coming from the outer disc carrier  50  into a first portion  175  and a second portion  180 . The first portion  175  of the cooling liquid  45  flows to the left and into the first feed-back channel  155  in a radially inward direction. The first feed-back channel  155  ends radially on the inside at the level of the inner disc carrier  70 . Radially to the inside of the toothed region  80 , the cooling liquid is attracted by a suction effect created by the cooling liquid  45  that flows away between the friction discs  55 ,  90 . The cooling liquid  45  that is located radially inward of the toothed region  80  passes through the first passages  100  in the toothed region  80  again to flow in a radially outward direction between the friction discs  55 ,  90 . The newly entered cooling liquid  45  leaves the region of the friction discs  55 ,  90  radially to the outside via the second passages  105  of the outer disc carrier  50 , completing the circuit for the first portion  175  of the cooling liquid  45 . The second portion  180  of the cooling liquid flows to the right between the deflection device  145  and the housing  30  in a radially inward direction via the second feed-back channel. The second portion  180  of the cooling liquid  45  cools the spring damper  165 . Depending on the design of the spring damper  165 , a portion  185  of the second portion  180  of cooling liquid  45  passes into the first feed-back channel  155  via the spring damper  165  an follows the first portion  175  in the circuit of cooling liquid  45  described above. The remaining portion of the second portion  180  of cooling liquid  45  continues through the second feed-back channel  160  or, in an alternative embodiment, flows in a radially inward direction on both sides of the deflection device  145 . Having reached the radial inside, the remaining portion of the second portion  180  of cooling liquid  45  flows axially along the hub  106  to the feed channel  135  via an optional first external cooling device arranged outside the friction clutch  10  and an optional external fluid pump to complete the cooling liquid circuit. 
     The direct circulation of the cooling liquid  45  from the collection channel  140  via the first feed-back channel  155  towards the passages  100  in the disc carrier  70  results in a particularly efficient cooling of the friction discs  55 ,  90 . Especially if there is a rotary speed difference between the input side  15  and the output side  20 , for example when the vehicle starts to move, a particularly strong flow of cooling liquid through the friction discs  55 ,  90  may be generated. The flow of cooling liquid  45  at the friction discs  55 ,  90  may additionally be improved by providing inclined or radial grooves on the friction discs  55 ,  90 . In accordance with a particularly advantageous aspect, the aforementioned grooves may be provided in the friction discs that are connected to the input side  15  of the friction clutch  10  (in the illustrated embodiment the first friction discs  55 ). In this way, in particular at the maximum rotary speed difference, i.e. when the input side  15  rotates at motor speed and the power take-off side is at a standstill, a particularly strong flow of cooling liquid passes between the friction discs  55 ,  90 . Moreover, the targeted supply of fresh cooling liquid  45  via the feed channel  135  and the first feed-back channel  155  ensures reliable after-cooling, so that in the engaged condition, the friction discs  55 ,  90  continue to be cooled to attain a particularly low starting temperature at the friction discs  55 ,  90  for the next engagement cycle. 
     The circulation of the cooling liquid  45  in the cooling circuit is interrupted as little as possible if the attachment region  75  is arranged on the side of the toothed region  80  opposite the deflection device  145 . The resultant cup shape of the inner disc carrier  70  is open to the cooling liquid  45  coming from the first feed-back channel  155 . Alternatively, it is conceivable for the attachment region  75  to be arranged on the toothed region  80  to be parallel and adjacent to the deflection device  145 . To allow circulation of the cooling liquid in the way described above, the attachment region  75  has numerous passages through which the first cooling liquid  45  coming from the first feed-back channel  155  may flow to the toothed region  80  and to the first passages  100 , respectively. 
     An advantage of the design described above is that no further components such as nonreturn valves are necessary for the circulation of the cooling liquid  45 . Moreover, there is no influence on the forces, in particular in the axial direction, of the piston  115  or a centrifugal-oil cover that may usually be arranged between the attachment region  75  and the piston  115 . In addition, although the installation space of the assembly is the same, more space is available for the spring damper  165 , which may be more complex as a result. 
     In the illustrated embodiment, the inner disc carrier  70  has an L-shaped cross section. It is to be understood that other cross-sectional shapes are possible. For example, the attachment region  75  might be arranged in the toothed region  80 , resulting in a T-shaped cross section of the inner disc carrier  70 . It is also conceivable for the attachment region  75  to be inclined relative to the axis of rotation  25  instead of perpendicular to the axis of rotation  25 . 
     In the embodiment of  FIG. 1 , the outer disc carrier  50  is connected to the input side  15  and the inner disc carrier  70  is connected to the output side  20 . Alternatively, it is conceivable for the inner disc carrier  70  to be connected to the input side  15  (engine) and for the outer disc carrier  50  to be connected to the output side  20 . 
     In accordance with a further embodiment, the inner disc carrier  70 , together with the housing  30 , might be connected for co-rotation to the input side  15  or coupled via a torsional vibration damper and on the output side, the outer disc carrier  50  might be coupled to the transmission input shaft of a transmission that follows in the drive train of the friction clutch  10 . In a further alternative embodiment, the outer disc carrier  50  might be connected to the transmission input shaft by means of the deflection device. 
     LIST OF REFERENCE NUMERALS 
     
         
           10  friction clutch 
           15  input side 
           20  output side 
           25  axis of rotation 
           30  housing 
           35  drive train 
           40  fluid chamber 
           45  cooling liquid 
           50  outer disc carrier 
           55  first friction disc 
           56  outer toothing 
           60  inner toothing 
           65  stop 
           70  inner disc carrier 
           75  attachment region 
           80  toothed region 
           85  outer toothing 
           90  second friction disc 
           95  inner toothing 
           100  first passage 
           105  second passage 
           106  hub 
           110  compression device 
           115  piston 
           120  pressure chamber 
           125  protrusion of the piston 
           130  pressure fluid 
           135  feed channel 
           140  collection channel 
           145  deflection device 
           150  guide section 
           155  first feed-back channel 
           160  second feed-back channel 
           165  spring damper 
           170  further deflection device 
           175  first cooling liquid portion 
           180  second cooling liquid portion 
           185  further cooling liquid portion

Technology Category: 2