MXPA99008467A - Hydraulic coupling having supplemental actuation - Google Patents

Abstract

A supplemental pressurized hydraulic supply (103) provides control of a hydraulic coupling (32a, 32b, 32c) that normally operates in response to differential rotation between a pair of rotary members (26, 28) to provide actuation of a clutch (68) that couples the pair of rotary members. A rotary seal assembly (104) of the supply (103) feeds pressurized hydraulic fluid to the coupling to provide supplemental actuation of the clutch (68) that is normally actuated by hydraulic fluid from a hydraulic pump (48) that operates in response to the differential rotation between the pair of rotary members. In one embodiment, the hydraulic coupling (32a) also includes a differential gear set (36). A further embodiment of the hydraulic coupling (32b) includes a clutch (68) having a pair of clutch packs (69) that can be individually actuated by the supplement pressurized hydraulic fluid supply (103). A further embodiment of the hydraulic coupling (32c) has a pair of rotary members embodied by an annular gear (26) and a rotary member (28) extending completely through the coupling.

Description

HYDRAULIC COUPLING WHICH HAS SUPPLEMENTARY ACTIVATION DESCRIPTION OF THE INVENTION This invention relates to a hydraulic coupling that is used with a vehicle transmission train within a housing thereof that contains hydraulic fluid to rotationally couple a pair of rotating members about the shaft. rotational. U.S. Patents 5,310,388 to Okcuoglu et al., 5,536,215 to Shaffer et al., And 5,595,214 to Shaffer et al., Describe hydraulic couplings wherein a pair of rotating members rotatably engage each other in response to rotation. differential between members. The coupling is done through the use of a hydraulic pump that is operated by the differential rotation of the torque of rotation member to be coupled. The pressurized fluid of the hydraulic pump causes the closing of a control valve whereby the pump couples the two rotation members. An object of the present invention is to provide an improved hydraulic coupling that can be operable to couple a pair of rotation members as there is differential rotation and which also has supplementary control to activate the engagement of the pair of rotation members with each other.

In carrying out the above object, a hydraulic coupling of the invention is used with a vehicle transmission train within a housing thereof containing hydraulic fluid to rotationally couple the pair of rotation members about the rotational axis. The hydraulic coupling includes a hollow construction cover that can rotate within a housing about the axis of rotation. A hydraulic coupling pump is located within the cover along the rotational axis and includes a toothed impeller rotatably connected to one of the rotating members and having external teeth. The hydraulic pump also includes an internal toothed ring mounted by the cover to rotate eccentrically with respect to the toothed driver and which includes internal teeth that exceed in one the teeth of the impeller and a network relationship with these to provide a pump action during the relative rotation between the cover and the toothed driver as the pair of -rotation members rotate relative to each other. An inlet port is provided through which the hydraulic fluid is pumped from the housing to the inner part of the cover by means of the hydraulic pump. A clutch of the coupling includes a piston chamber located within the cover and having an activation piston which is received within the piston chamber and which can be activated by pressurized hydraulic fluid to couple the clutch and engage the two rotation members each. The cover includes a transfer port through which the pressurized hydraulic fluid is pumped from the hydraulic pump to the piston chamber. The cover includes an outlet port through which pressurized hydraulic fluid flows from the piston chamber. A coupling control valve includes a valve element that can be moved between an open position spaced from the outlet port and a closed position that generally closes the exit port when the pumped fluid reaches a predetermined pressure to thereby increase the pressure of pressurized hydraulic fluid and activating the piston and coupling the clutch to thereby rotationally couple the pair of rotating members together. A supply of supplemental pressurized hydraulic fluid from the coupling provides the supply of pressurized hydraulic fluid within the inlet port of the cover to the pump independent of pumping activation of the pump. The supply of pressurized supplemental hydraulic fluid includes a rotary seal assembly that is fixedly mounted within the housing and has seals that seal inside the cover to define an entrance chamber that communicates with the entrance port. A first passage feeds the hydraulic fluid from the housing to the inlet chamber to flow through the inlet port during the pumping action of the hydraulic pump. The first passage has a check valve to prevent flow through it from the chamber. entrance to the accommodation. A second passage provides the supply of pressurized hydraulic fluid from a source to the inlet chamber. The second passage of supplemental pressurized hydraulic fluid supply as described above, has a junction with the first passage of this in a place towards the entrance chamber from the verification valve of the first passage. Different modalities of the hydraulic coupling are described. In a construction, the outlet port extends through the piston and the control valve is mounted on the piston. In another construction, the cover includes a wall separating the pump and the piston chamber, with the transfer port extending through that cover wall from a high pressure side of the pump to the piston chamber, and with the outlet port extending through that cover wall from the piston chamber to a low pressure side of the pump. One embodiment of the hydraulic coupling also includes a set of differential gears extending between the cover and the pair of rotation members. The hydraulic pump and the clutch of this embodiment are located within the cover adjacent to a rotation member on one side of the differential gear assembly. The other rotation member in this mode is located on the opposite side of the differential gear assembly from the hydraulic pump and the clutch. This embodiment with the set of gears that differentiate have particular utility to be used with a primary drive shaft of a vehicle transmission train. Another embodiment of the hydraulic coupling includes a second hydraulic pump generally constructed in the same manner as the hydraulic pump first mentioned and with the pair of hydraulic pumps respectively associated with the pair of rotating members extending along the axis of rotation. More specifically, the second hydraulic pump is located within the cover along the axis of rotation which includes a second impeller mounted rotatably toothed to the other rotation member and having external teeth. The second hydraulic pump also includes a second internal toothed ring mounted by the cover to rotate eccentrically with respect to the second toothed driver and which includes internal teeth exceeding in one the outer teeth of the second toothed driver in a network relationship with the latter. provide a pumping action during relative rotation between the cover and the second toothed driver. This embodiment of the hydraulic coupling also includes a second inlet port through which the hydraulic fluid is pumped into the cover by the second hydraulic pump. The clutch of this embodiment includes a second piston chamber located within the cover and having a second activation piston which is received within the second piston chamber and which can be activated by the pressurized hydraulic fluid to couple the clutch and engage the two members rotate with each other. The cover includes a second transfer port through which the pressurized hydraulic fluid is pumped from the second hydraulic pump into the second piston chamber, and the cover also includes a second outlet port through which the pressurized hydraulic fluid flows from the second piston chamber. A second control valve includes a second valve member that can be moved between an open position spaced apart from the second outlet port and a closed position that generally closes the second outlet port when the pumped fluid reaches a predetermined pressure to thereby further increase pressurized hydraulic fluid pressure and activate the second piston and engage the clutch to thereby rotationally couple the pair of rotating members together. The supply of pressurized hydraulic fluid supplementary to this embodiment of the hydraulic coupling can operate to feed the hydraulic fluid into the second inlet port of the cover to the second pump independent of the pumping action of the second pump. In the double pump mode of the hydraulic couplingThe clutch includes first and second clutch packs each of which includes a pair of sets of clutch plates alternating with each other. A clutch plate assembly of each clutch pack is fixed rotatably to the cover. The other clutch plate assembly of the first clutch pack is rotatably fixed to one rotation member, while the other clutch plate assembly of the second clutch pack is rotatably fixed to the other rotation member. The clutch is located between the first mentioned piston and the second piston. An additional embodiment of the hydraulic coupling has a rotation member provided with an elongated shape extending along the rotational axis. The other rotating member of this embodiment of the hydraulic coupling has an annular shape and is mounted on the cover extending around the axis of rotation. The objects, features and advantages of the present invention will be more apparent from the following detailed description of the best modes for carrying out the invention when taken together with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic plan view of a vehicle transmission train which includes a pair of hydraulic couplings constructed in accordance with the present invention and respectively located on a rear primary transmission shaft and on a shaft of auxiliary front transmission. Figure la is a sectional view taken along the line direction la-la of Figure 1 to illustrate one embodiment of the hydraulic coupling on the rear primary transmission shaft. Figure Ib is a sectional view taken along the direction of the line lb-lb of Figure 1 through the other embodiment of the hydraulic coupling on the front auxiliary transmission shaft. The Figure is a view similar to Figures la and Ib of another embodiment of the hydraulic coupling. Figure 2 is a sectional view taken through a pump of the hydraulic coupling mode shown in Figure la along the direction of its line 2-2 and describes the pump as having an impeller with six teeth engaged with an internal toothed ring having seven teeth to provide a pumping action that allows the pump to have a relatively constant pump pressure that facilitates the activation of an associated clutch without the pulsation of fluid pressure. Figure 3 is a view similar to Figure 2 illustrating that the pump may also have its driver provided with five teeth and its internal gear ring provided with six teeth when a greater pumping capacity is desired. Figure 4 is a view similar to Figures 2 and 3, but illustrates the impeller having seven teeth and the internal gear ring having eight teeth when it is desired that the fluid pressure has greater constancy. Figure 5 is a schematic perspective view illustrating the construction of the inlet valves for the inlet ports through which the hydraulic fluid is pumped into a coupling cover. Figure 6 is a sectional view taken along the direction of line 6-6 in Figure 5 to illustrate the open and closed operation of the inlet valve. Figure 7 is a partial sectional view illustrating the construction of a control valve of the hydraulic coupling, with a valve member of the control valve shown in an open position indicated by a continuous line with respect to an outlet port, and with the valve element shown in imaginary lines indicating the closed position with respect to the outlet port. Figure 8 is a perspective view further illustrating the construction of the outlet port and the control valve. Figure 9 is an enlarged sectional view illustrating a transfer port and associated check valve through which the hydraulic fluid is pumped to a clutch activation piston. Figure 10 is a partial perspective view further illustrating the check valve of the transfer port in its closed position. Figure 11 is a partial perspective view similar to Figure 10, but with the transfer port check valve shown in its open position. Figure 12 is an axial view of a construction of the clutch activation piston. Figure 13 is a sectional view of the activation piston taken along the line 13-13 direction in Figure 12. Figure 14 is a perspective view illustrating the control valve outlet port which it includes a main passage and a purge passage and which is mounted within a recess. Figure 15 is a sectional view taken through the control valve generally in the direction of line 15-15 in Figure 14 which also illustrates the valve element that controls the flow of fluid through the port illustrated. Figure 16 is a partial view illustrating a valve transfer port of a supercharged circuit provided by the embodiment in Figure 1 of the hydraulic coupling. Figure 17 is a view illustrating the control valve for the output port of the supercharged circuit. Figure 18 is a schematic view illustrating the fluid flow of the supercharged circuit. Figure 19 is a sectional view similar to Figure 7 of a modified construction of the control valve. Figure 20 is a perspective view similar to Figure 8 but with the modified construction of the control valve. Figure 21 is a partial view illustrating the distal end of the valve member which defines a purge passage of the outlet port.

Figure 22 is an exploded sectional view taken in the same direction as Figure 19 through another embodiment of the control valve wherein the valve member is flat and has an elongated straight shape and wherein the valve body it has a recess whose port end is deeper than the location in which the valve element is mounted. Figure 23 is an exploded perspective view further illustrating the embodiment of Figure 22, which is assembled for use as illustrated in both of these views by an adhesive that is provided in a film. Figure 24 is a sectional view of a further modification of the control valve taken in the same direction as Figure 22 and having the same construction except for the assembly thereof which is provided by the illustrated mechanical fasteners being injection molded with the body of the valve. Figure 25 is a view similar to Figure 18 illustrating a further version of the supercharged circuit wherein the control valve of this invention is constructed to control a pair of ports. Figure 26 is an exploded perspective view of the control valve of Figure 25.

Figure 27 is a sectional view taken along the curved line 27-27 of Figure 25 in an exploded manner to further illustrate the construction of the control valve whose valve body is illustrated being secured by an adhesive on a movie. Figure 28 is a sectional view of a further embodiment of the control valve taken in the same direction as Figure 27 and having the same construction except for the assembly thereof, which is provided by illustrated mechanical fasteners being injection molded with the valve body. With reference to Figure 1 of the drawings, a vehicle transmission train schematically indicated by 10 includes a motor 11 which activates a transmission 12 whose output is connected to a transfer cover 13. A rear transmission shaft 14 has a front end rotationally activated by the transfer cover 13 through a universal joint and has a rear end that activates a universal joint to rotationally activate the rear axle 16 which functions as the primary activation axis of the vehicle as illustrated. A front transmission shaft 18 has a rear end rotatably activated by the transfer cover 13 through a universal joint and has a front end that activates a universal joint for rotationally activating the front axle 20 which functions as an auxiliary drive shaft. to provide traction on the four wheels of the vehicle when necessary. The rear axle includes a differential 22a for transmitting a torque while the front axle includes a shaft unit 22b for transmitting a torque as will be described hereinafter. With reference to the Figure of the drawings, the differential 22a of the rear axle 16 is rotationally activated by a rotation activating member 24. The differential 22a operates to activate a pair of semiaxes 26 and 28 of the rear axle 16 in such a way that these axes respectively exemplify a pair of rotating members which rotate about a common axis of rotation A. The differential 22a includes a housing 30 for containing the hydraulic fluid and for having suitable seals not shown through which the rotating members. 24, 26 and 28 are projected. Within the housing 30, the differential 22a includes a hydraulic coupling 32a which operates to rotationally couple the axle shafts 26 and 28 activated by the rotation activation member 24 as will be described here in more detail. Continuing with reference to Figure la, the hydraulic coupling 32a includes a cover 34 of a hollow construction that rotates within the housing about the axis of rotation A and is connected to the semiaxis-type rotation members 26 and 28 by a planetary gear assembly. which is shown as a set of bevel gear type differential gears 36 as will be described here in more detail. The cover 34 as illustrated, includes a capped member 38 and a cap member 40 which each have peripheral flanges secured together by circumferentially spaced screws 42 which also secure a serrated ring 44 of the beveled type which is rotatably activated by a beveled activation portion 46 of the rotation activation member 24. With combined reference to Figures la and 2, the hydraulic coupling 32a also includes a hydraulic pump 48 located within the cover 34 along the rotary axis A and includes a component of pumping exemplified by a toothed impeller 50 having external teeth 52. The hydraulic pump also includes an internal toothed ring 54 mounted by the cover 34 to rotate eccentrically with respect to the toothed driver 50 and including internal teeth 56 in a number exceeding in one to the teeth of the impeller and which are in a gear ratio co n the teeth of the impeller to provide a pumping action during relative rotation between the cover and the toothed impeller. As will be described later here, the impeller 50 more preferably has six teeth 52 and the internal gear ring 54 has seven teeth 56 which is a ratio that provides sufficient pumping capacity for the hydraulic pump to act effectively as a seal while still having pumping pressure relative constant without pulsation of fluid that would adversely affect the hydraulic coupling provided between the rotation members. As shown in Figure 3, it is also possible that the hydraulic pump 48 'has its impeller 50' provided with five external teeth 52 'and that the toothed ring 54' has six teeth 56 'meshing with the teeth of the impeller, which it is a construction-- that will provide some greater pumping capacity, but less consistency in fluid pressure, although not inconsistent to interfere with the effective hydraulic coupling between the rotation members. Similarly, as illustrated in Figure 4, it is also possible for the hydraulic pump 48 '' to have its impeller 50 '' provided with seven external teeth 52 '' and for its internal toothed ring 54 '' to have eight internal teeth 56 '' when a more consistent fluid pressure is desired although there is an accompanying decrease in the amount of fluid pumped. In this way, the impeller preferably has between five and seven external teeth, six being most preferable while the internal gear ring has one more tooth compared to the number of teeth of the impeller used. With combined reference to Figures 5, 6 and 6, the cover 34 has an inlet 58 through which the hydraulic fluid is pumped into the cover by the hydraulic pump 48. As illustrated in Figure 1, there are actually two inlets 58 in such a way that the pumping is carried out in both directions of the relative rotation between the rotation members exemplified by the half-shafts 26 and by the half-shafts 28 as well as the cover 34. In this connection, each of the inlets 58 includes an associated check valve 60 for opening and closing the input ports 62 of varying sizes along the direction of rotation. Each check valve 60 as shown in Figures 5 and 6 has a thin valve member 64 that is mounted by guides in such a manner that the threaded screws 66 shown by the solid line for movement between the open position of Figure 6 and the imaginary lines indicate the closed position. During a direction of relative rotation between the impeller 50 and the cover 34 shown in Figure 2, one of the check valves 60 is opened to allow the hydraulic fluid to be pumped from the housing 30 into the cover 34 while the another check valve 60 is then closed so that the hydraulic fluid is not pumped out of the cover through the inlet port. During the opposite direction of the relative rotation between the impeller 50 and the cover 34, the open and closed positions of the input ports 58 are reversed. As illustrated in Figure la, a clutch 68 is received within the cupped member 38 of the cover 34 adjacent to the joint thereof with the cover member 40 of the cover. Within the cover cap member 40, a pump housing insert 70 of the cover is mounted and received by the hydraulic pump 48 interferes with the clutch 68. This insert 70 has an annular piston chamber 71 that receives an activation piston. clutch 72 engaging the clutch 68 as will be described here in more detail for coupling the cover 34 with the left half axle 26 as will also be described here in more detail. The insert 70 also has a wall 70 'which separates the hydraulic pump 48 from the piston chamber and defines at least two transfer ports 74 through which the hydraulic fluid is "pumped from one side at high pressure of the hydraulic pump 48 to a clutch activation piston 72 within the piston chamber 71. This flow through the transfer ports 74 is through one of the transfer ports towards a relative rotation direction between the impeller 52 and the toothed ring 54 and through the other transfer port 74 during the other direction of the relative rotation between the impeller and the toothed ring. Each of the transfer ports 74 has an associated check valve 76 of a construction which will be described here in more detail in conjunction with Figures la to 11. These check valves 76 ensure that the hydraulic fluid pumped from the high pressure side of the pump through any of the transfer ports to the clutch activation piston 72 is not pumped back to the low pressure side of the hydraulic pump 48 through the other transfer port. As best illustrated in Figures 7 and 9, an outlet port 78 is also provided and in the coupling mode of the Figure is located on the clutch activation piston 72. A control valve 80 of the coupling controls the flow of fluid through the outlet port 78. More specifically, the pumped hydraulic fluid increases in pressure in response to the increased relative rotation between the pump impeller and the toothed ring and thus corresponds to the relative rotation between the left and right half axles 26 and 28. As the fluid Hydraulic pumped reaches the predetermined pressure, the valve 80 closes as will be described here in more detail to close the outlet port 78 and thus prevent the hydraulic fluid from being pumped from the hydraulic pump 48. This valve closure further increases the pressure of the hydraulic fluid pumped due to a torque transfer between the semiaxes 26 and 28. The fluid pressure causes the The hydraulic pump 48 acts as a detent coupling the impeller 52 with the internal toothed ring 54 and also causes the piston 72 to activate the clutch 68 in such a way that the left and right half shafts engage each other through the cover 34 a as the clutch blocks any differential action of the differential gear assembly 36. As best illustrated in Figures 7 and 8, the valve 80 includes an elongated metal band valve element 82 having a portion or end 84 that is assembled. in a separate relationship to the outlet port 78 in any suitable manner as by means of head screws 86 illustrated. The valve element 82 also has a distal end 88 that can be moved between the open position indicated by the solid line, spaced from the outlet port 78 as shown in Figure 7 and the closed position - indicated by the line imaginary that closes the exit port. This valve element 82 is of the bimetallic type and thus includes two metals 90 and 92 having different coefficients of thermal expansion such as to cause the valve element to move as its temperature rises or falls. More specifically, as the hydraulic fluid is heated as during continuous use, the valve member end 88 moves toward the outlet port 78 obtaining as a net result that the less viscous fluid closes the valve 80 at the same pressure as the pumped fluid corresponding to the same amount of relative rotation between the semiaxes. In addition, upon cooling of the hydraulic fluid such as after allowing it to rest for a certain period of time, the end of the valve element 88 moves away from the outlet port 78 in such a manner that the valve closes at the same pressure as the pump. more viscous hydraulic fluid. In this way, the bimetallic valve element 82 is compensated in temperature as it is compensated by changes in viscosity as the hydraulic fluid is heated and cooled to ensure that the coupling between the two rotation members exemplified by the two half shafts it is carried out at the same relative rotation speed. More specifically, the closing of the valve as discussed above causes the hydraulic pump 28 to then function as the detent limiting the relative rotation between the two rotation members exemplified by the two half shafts and also causes activation of the clutch 68 to further engage the two semiaxes to each other. As further illustrated in Figures 7 and 8, the outlet port 78 preferably includes a main passage 94 which is closed by the valve member 82 as its end 88 moves from the open position to the closed position as shown in FIG. described previously. The outlet port 78 also includes a purge passage 96 which remains open even when the valve member 82 is closed with respect to the main passage 94 in order to provide a hydraulic fluid purge flow which cools the clutch 68 and also ensures that the Hydraulic fluid pressure inside the valve 48 does not increase excessively at an uncontrolled speed. When the valve element 82 opens, the flow of fluid through both passages of the outlet port 78 provides for purging the purge passage 96 to remove any small particles that may block the smaller cross-sectional flow area of the purge passage. The control valve 80 then cleans itself during normal use. Also, the purge passage 96 allows the pressurized fluid to flow from the piston chamber 71 when the hydraulic pumping stops as the pair of rotating members stop rotating relative to one another and the clutch 68 is decoupled as that the pressure in the piston chamber decreases as will be described here in more detail. In this construction of the control valve 80, the purge passage 96 is defined by the valve body provided by the piston 72 (Figure 7) on which the valve member 82 is mounted. As shown in Figures 7 and 8, the coupling includes an elongated mounting recess 98 having a portion or end 100 in which one end 84 of the valve member 82 is assembled and has another end 102 in which the main passage 94 and the purge passage 96 of the output body 78 is located. This recess together with the bimetallic valve element 82 provides a continuously variable change in the cross-sectional flow area of the flow to the outlet port 78 from the other side of the valve element such that movement at the end of the element Valve 88 in response to temperature changes provides accurate control of the pressure at which the valve element closes to initiate operation of the hydraulic pump such as a detent and clutch activation. For any given predetermined open position of the valve element 82, there is a certain pressure at which the hydraulic fluid of a certain speed will cause the closure of the valve element. This results from the flow of hydraulic fluid between the valve member end 88 and the adjacent end of the recess 102 to the outlet port 78. This flow causes a low pressure in the fluid during the passage beyond the end of the valve member 88. so that there is less force acting on the outlet side of the end of the valve element 88 than on the hydraulic pump side which respectively are the lower and upper sides as illustrated in Figure 7. The movement of the valve member 8- 2 to change the position of its end 88 in response to changes in temperature varies the cross-sectional area of flow between this end of valve element and the end of recess 102 to thereby exactly compensate for changes in temperature and ensure that the closing of the valve 80 corresponds to the same speed of relative rotation between the rotation members exemplified by the semiaxes 26 and 28 shown in Fig. ura la. Referring to Figure la, the hydraulic coupling 32a includes a supply of supplemental pressurized hydraulic fluid 103 for feeding the pressurized hydraulic fluid within the inlet port 58 in the cover 34 to the pump 48 independent of the pumping action of the pump. More specifically, the supply of supplemental pressurized hydraulic fluid 103 includes a rotary seal assembly 104. which includes a member 105 having schematically illustrated fixed connections 105a to the cover to define an inlet chamber 105b having a generally annular shape extending around the adjacent rotation member 26. The rotation seal assembly 104 also includes rotation seals 106 having annular shapes and sealing between the member 105 and the cover 34 on its lid member 40 as described above. These seals 106 can be attached to either member 105 to slide relative to the cover cap member 40 or can be attached to the cover cap member 40 to slide relative to the seal assembly member 105. Still referring to Figure, a suitable conduit member provides a first passage 107 having a lower portion 107a for feeding the hydraulic fluid from a lowermost portion of the lubricant manifold of the differential housing 30 to the intake chamber 105b to allow flow through the port inlet 58 during the pumping action of the hydraulic pump 48. This first passage 107 also has a check valve 107b to prevent flow therethrough from the inlet chamber 105b to the differential housing 30. A second passage 108 it is also provided for feeding the pressurized hydraulic fluid to the inlet chamber 105b. The supplemental hydraulic fluid supply 1Q3 also includes a source 109 of pressurized hydraulic fluid that will ordinarily be exemplified by an electric pump, which is selectively operated to provide pressurized hydraulic fluid through the second passage 108 to the inlet chamber. It should also be appreciated that the pumping source 109 can also be activated by starting the engine of the associated vehicle or an accessory activated by the engine or by movement of the vehicle. A passage 109a feeds the hydraulic fluid from the lowermost portion of the lubricant manifold of the differential housing 30 to the pump source 109 to allow flow through the second passage 108 to the inlet chamber 105b. This second passage 108 has a junction 110 with the first passage 108 at a location towards the entrance chamber 105b from the check valve 107b of the first passage 107 such that the hydraulic fluid pressurized from the pump source 109 does not flow back within the lowermost portion of the lubricant manifold of the differential housing 30 after being pressurized but instead flows into the inlet chamber 105b to allow flow to the hydraulic pump 48 through the inlet port 58. A control 111 which will be described here in more detail, has a suitable connection to the pump source 109 to control its operation and the consequent flow of the pressurized flow to the hydraulic pump 48 independent of its pumping operation. Before continuing with a more detailed description of the supplementary pressurized hydraulic fluid supply operation 103, an additional structure of the hydraulic coupling will first be established to facilitate an understanding of the operation that provides the coupling between the pair of rotation members 26 and 28 Referring to Figure la, the hydraulic coupling 32a has the clutch 78 extending between the left half shaft 26 and the cover 34. This clutch 68 includes alternating sets of clutch plates 112 and 114 with a clutch plate assembly 112 having peripheries outer with slot connections 116 to the cover 34, and with the other set of clutch plates 114 having a central opening with slot connections 118 to the left half shaft 26 which also has slot connections 120 towards the pump driver 50 in the opposite side of the insert 79 from the clutch. The pumped hydraulic fluid acting on the clutch piston 72 as described above compresses the clutch plate assemblies 112 and 114 to provide engagement between the cover 34 and the rotation member exemplified by the semiaxis 26. Hydraulic fluid pumped which flows through the activation piston 72 through the purging passage of the previously described outlet port then flows along the semiaxes 26 and 28 to exit the passage of the cover 34. As mentioned previously, the hydraulic coupling 32a illustrated in Figure 1 has the planetary gear set exemplified by the bevel type differential gear set 36 connecting the cover 34 and the exemplified rotation members by the left and right half axles 26 and 28. The differential gear assembly 36 is positioned on the opposite side of the clutch 68 from the hydraulic pump 48 -e and includes a pair of beveled side gears 124 and 126 which have respective slot connections 128 and 130 to the rotation members exemplified by the semiaxes 26 and 28. The planetary gears 132 of the differential gear assembly 36 each mesh with the pair of side gears 124 and 126 and are rotatably supported by a cross pin 134 which extends through the axis of rotation A between the opposite sides of the cover 34. The differential gear assembly 36 provides a differential action between the rotation members modified by the semiaxes 26 and 28 until the closing of the valve 80 causes that the hydraulic pump 48 functions as a detent and also activates the clutch 68 as previously described whereby the semiaxis 26 engages through the 128 slot connections, the side gear 124, the planetary gears 132 supported by the cross piece 134 and with this the cover 34, the side gear 126 and the groove connections 130 with the other half shaft 28.

It should also be noted in conjunction with Figure 1, that the differential gear assembly 36 upon transferring the torque between the rotation members exemplified by the semiaxes 26 and 28 causes a separating action that moves a bevelled side gear 124 toward the clutch 68 for compressing the clutch plates 112 and 114 thereof in the same manner as the piston 72 compresses the clutch to thereby provide activation of the clutch which also engages the axle shafts relative to each other. With reference to Figure Ib, the axis unit 22b of the front axle includes another embodiment of the hydraulic coupling 32b having a construction similar to the previously described embodiment, except that it will be noticed and thus have similar reference numbers applied to the components similar to it in such a way that much of the above description is applicable and does not need to be repeated. This embodiment of the hydraulic coupling 32b provides a coupling without any differential gear assembly between the rotation members specified by the front half shafts 26 and 28. Each front half shaft 26 and 28 has an associated hydraulic pump 48 and the clutch 68 has first and second clutch packs 69, each of which includes a pair of sets of clutch plates 112 and 114 alternating with each other. A set of clutch plates 112 of each clutch pack 69 is rotatably fixed to the cover 34 by the slot connections 116. The other clutch plate assembly 114 of the first clutch pack 69 shown to the left is rotatably fixed by the slot connections 118 to a rotation member exemplified by the left-26 half-axis. Another set of clutch plates 114 of the second clutch pack 69 shown to the right is rotatably fixed by the slot connections 118 to the other rotation member exemplified by the right half shaft 28. Continuing with the reference of Figure Ib, the hydraulic coupling 32b includes a pair of inserts 71 with one of the inserts being supported by the cover cap member 40 at one end of the coupling adjacent to the rotating member exemplified by the left half shaft 26 and with the other end supported by the capped member 38 of the cover adjacent to the other rotation member exemplified by the right half shaft 28. Each insert 71 supports the associated hydraulic pump 48 whose toothed driver 50 is secured by the slot connection 120 to the associated axle shaft 26, 28. Each insert 70 also defines the camera of associated piston 71 and receives an associated piston 72 such that there are first and second pistons in this loc mode alizados on opposite sides of the clutch 68. The insert defines the transfer valve 74 through which the pressurized fluid from the high pressure side to the pump 48 is pumped into the associated piston chamber 71 as will be described here in more detail. The cover cap member 40 defines an inlet port 58 with the associated valve 60 while the coupled member 38 of the cover defines a second inlet port 58 with an associated valve 60. - Each piston 72 of this embodiment has a port output 78 and supports an associated control valve 80 of a previously described construction. These control valves have valve elements that can be moved between an open position spaced from the associated outlet port and a position that generally closes the associated outlet port when the pumped fluid reaches a predetermined pressure to thereby further increase the fluid pressure Hydraulic pressurized and activate the associated piston to engage the clutch. Such a clutch coupling rotatably couples the pair of rotating members exemplified by the left and right half axes 26 and 28 to each other. The supply of supplemental pressurized hydraulic fluid 103 of this embodiment has the same construction as the previously described embodiment illustrated in Figure 1., but includes another seal assembly 104 associated with the right end of the coupling in addition to the seal assembly 104 associated with the left end of the coupling. Thus, in this embodiment, the pressurized hydraulic fluid of the pumping source 109 feeds the pressurized hydraulic fluid through the second passage 108 to the first and second inlet chambers defined by the members 105 and their associated seals 106 so that both hydraulic pumps 48 are powered by the pressurized hydraulic fluid under the operation of the control 111. This selective supplemental supply of the pressurized hydraulic fluid to the pumps 48 is additional to the hydraulic fluid pumped through the lower portion 107a of the first passage 107 associated with each assembly of seal 104 in response to the differential rotation between the rotation members exemplified by the semiaxes 26 and 28. With the embodiments of Figures la and Ib, the outlet port 78 and each associated control valve 80 is located on the piston 72 As such, the flow of a hydraulic fluid through the purge passage of the outlet port 78 cools the embryo. Figure 68. The following description of the insert 70 defining the transfer port 74 and the piston 72 through which the outlet port 78 extends under the control of the associated control valve 80 will be established together with Figures 9-15 . With reference to Figures 9 to 11, each transfer port 74 extends through the wall 70 'of the insert 70 from the pump side to the piston side and has the associated check valve 76 mounted on the piston side wherein the piston is sealed between the annular inner and outer flange 142 and 144 by seals suitable as O-rings 146 and 148 shown. On the pump side, the transfer port 74 has an enlarged shallow pickup portion 150 which allows the pumped hydraulic fluid to be received from different circumferential locations around the rotational axis for eventual flow through the transfer port and check valve 76 on the piston side to be able to provide piston activation as previously described. As best illustrated in Figures 10 and 11, each check valve 76 includes a metal band valve element 152 having one end 154 mounted to the metal insert by suitable fasteners 156 as shown head screws and has another distal end 158 which normally inclines towards the closed position of Figure 10 by the elastic force of a spring of the valve member. However, the pressurized fluid to be pumped acts against the inclination of the spring to provide the opening of the valve distal end 158 as shown in Figure 11 to allow the flow of fluid that moves the piston and to activate the clutch as described. previously.

It should be noted that the cross-sectional flow area through the transfer port 74 shown in Figure 9 and the cross-sectional flow area through the outlet port of the open control valve 80 shown in Figures 7 and 8 are usually tuned to be approximately equal to each other. Tuning of the coupling can also be done by making the transfer sectional area of the transfer port 74 smaller than the flow area in the cross section of the open control valve 80 to delay the closing of the control valve and the consequential activation of the clutch 68. In addition, a faster control valve closure and consequent clutch activation can be achieved by making the transverse flow area of the transfer port 74 larger than the cross-sectional flow area of the open control valve 80. In addition, it may also be possible to tune the operation by controlling the tilt of the closing spring of the transfer port valve element 152. With reference to Figures 12 and 13, another embodiment of the piston 72 of the hydraulic coupling is illustrated having the control valve 80 mounted on it as previously described and also It is also shown having a coating 160 of an elastomeric rubber type material, such as an ethylene acrylic resin, on one side which is facing the hydraulic pump in the assembled condition. This liner 160 also defines annular inner and outer seals 162 and 163 for sealing with the adjacent outer and inner annular walls of the mating insert 70 to provide a slidably sealed relationship. This coating 160 is injection molded to a stamped steel plate 164 of the piston 72 and also has positioning lugs 166 spaced circumferentially around its periphery to protect the seals 162 and 163 when the piston moves in its full extension to the left inside the coupling cover. With further reference to Figures 14 and 15, the liner 160 is injection molded to define the outlet port 78 with its main passage 94 and purge passage 96 previously described as well as to define the mounting recess 98 in which the valve element 82 of the control valve 80 is mounted as specifically shown in Figure 15. The injection molding of the liner facilitates the ratio of the outlet port 78 to its main passage 94 and purge passage 96. In addition, it shall be Note that the liner 160 may have an annular portion 168 that extends through a hole in the piston plate 164 to easily define the required cross-sectional flow area of the main passage 94 of the outlet port 78 to thereby also facilitate Tuning the coupling as described above. Referring to Figure 1, a coupling unit 22c includes another embodiment of the hydraulic coupling-32c and includes components that are identical to the previously described modes, except that it should be noted that similar reference numbers apply to these and many of the same. the previous descriptions are applicable and do not need to be repeated. However, the hydraulic coupling 32c has the rotation member 26 provided with a fixed screw connection 138 to the cover 34. This rotation member 26 has a ring shape through which the axis of rotation A extends, and the other rotation member 28 has an elongated shape extending through the cover 34 and through the ring shape of the rotation member 26. The hydraulic pump 48 and the clutch 68 are located within the cover 34 and operate from the same manner as previously described together with the embodiment of Figure la, except for the fact that there is no associated differential gear assembly. During use, the rotation member 26 can provide a takeoff for the activation of the auxiliary axis, while the other rotation member 28 provides activation between the vehicle engine and the primary activation axis. However, when there is a difference in the rotation speed between the axes, the operation of the hydraulic coupling 32c then couples the axes together by means of the pump and clutch operation in the same manner as previously described. In addition, the supply of supplemental pressurized hydraulic fluid 103 has the same construction and components as the embodiment of Figure 1 in such a way that the previous description is applicable and does not need to be repeated. It should be noted that the coupling 32c illustrated in the Figure differs from the couplings 32a and 32b respectively illustrated in Figures la and Ib in that the wall 70 'of the cover insert 70 separates the hydraulic pump 48 from the clutch 68 has both the transfer port 74 as the outlet port 78 extending through it unlike the other two embodiments where the outlet port extends through the activation piston associated with the clutch. This construction provides a supercharged circuit as will be described later. More specifically as illustrated in the Figures 16 to 18, two sets of transfer and output ports 74- and 78 with the associated check valves 76 and the control valves 80 are provided with each set _ located within an associated pick-up portion 150 on the side of the Pump the wall of the insert through which the ports extend. During a direction of relative rotation between the rotation members 26 and 28 (Figure 1), the pumped hydraulic fluid flows from the hydraulic pump through the left transfer ports and output ports 74 and 78 shown in Figure 18 to the piston chamber so that there is a flow to the right output port 78 back to the low pressure side of the pump as illustrated by the arrows with solid lines 170 and 172. During the other direction of relative rotation between the pair of members In the case of rotation, the hydraulic fluid flows from the pump through the right and the output ports 76 and 78 into the piston chamber so that there is a flow to the left output port 78 as shown by the arrow with imaginary lines 174 and 176. As such, there is a continuous pumping during the relative rotation between the pair of rotating members from the hydraulic pump to the piston chamber 71 for to provide activation of the clutch 68 while the hydraulic fluid is then pumped back to the low pressure side of the hydraulic pump for additional pressurization. With the embodiment of Figure l of the hydraulic coupling 32d, there is no flow of hydraulic fluid to the clutch plates 112 and 114. As such, it is desirable to have a lubrication passage 178 as shown to provide lubrication to the clutch plates. This lubrication passage 178 includes passage portions 180 through the rotation members 28 toward the clutch plates 112 and 114 toward the adjacent slot connections 118 of the clutch plates 114 to the rotation member 28. The flow through of these passage portions 178 and 189 of the lubrication passage 178 from a pump source suitable in this way provides lubrication that functions as a cooler for the clutch plates 112 and 114 on the clutch side of the piston 72. With reference to the Figures 19-21, another version of the control valve 80d is illustrated and has the same construction as the control valves previously described, except that as will be noted, similar reference numbers apply to similar components thereof and the description above therefore it is also applicable and will not be repeated. However, in this construction of the construction valve 80d, the distal end 88 of the elongate bimetallic band valve element 82 defines the bleed passage 96d of the outlet port 78 while the valve port provided by the piston 72 defines the Main passage 94 of port 78. Thus, in the closed position illustrated by the representation in imaginary lines in Figure 19, the purge passage 96d allows the pressurized hydraulic fluid to be purged through port 78 as in the previous mode described and, upon opening the valve element 82 as illustrated by the representation of solid lines, the purge passage 96d is cleaned of any accumulation by the fluid flow in the same manner as previously described. The operation of both valve constructions is thus similar. Each of the control valve embodiments described above has a control valve element 82 provided with the distal end 88 thereof extending in an inclined relationship with respect to its mounting portion or end 84 in the open position of the valve . This inclined relationship is provided by a bend in the control valve element adjacent its mounting end 84. Upon moving to the closed position, the control valve member 82 assumes a generally flat shape. With reference to Figures 22-28, additional modes of the control valve 80e, 80e ', 80f and 80f' are illustrated and most of their construction is similar as the previously described control valves except as will be noted. As such, similar reference numbers apply to similar components thereof and most of the description in this way is also applicable and will not be repeated.

As illustrated in Figures 22 and 23, another embodiment of the control valve 80e includes a valve body 190 that is preferably injection molded from a suitable plastic and has a portion or end 100 in which the portion or end 84 of the elongated valve element 82 is mounted by fastening screws 86 and has an end 102 in which the main passage 94 of the body 78 extends through the valve body. The valve element 82 is generally planar between its portion 84 and its distal end 88. The recess 98 of the valve body 190 has a greater depth at the end 102 thereof than in the portion provided at its end 100 and is inclined therebetween. . As such, the control valve 80e is open with the flat valve element 82 mounted within the recess 98 and is closed by moving the distal end 88 of the valve member toward port 78 in the same manner as it was previously described along with the purge flow through the purge passage 96. Continuing with reference to Figure 22, a connector 192 of the control valve 80e is provided to secure the valve body 190 for use such as the piston 72 as illustrated with a port portion 78 'aligned with port 78 of the valve body. This connector 192 as illustrated is exemplified by a suitable plastic film 194 with a suitable adhesive on each side thereof for securing the valve body 190 within a depressed hole 196 of the piston 72. The film 194 can be die-cut. obtaining the required shape which, as shown in Figure 23, includes a port opening 78". The best results are obtained with the control valve 80e when the recess 98 has a curved surface 198 providing the inclination between its portion 100 and its end 102. In this way, the elongated control valve element 82 moves in, and out coupling with the curved surface 198 by a line continuously in motion as it moves between the open and closed positions with respect to port 78. Referring to Figure 24, another embodiment of the control valve 80e 'has the same construction that the embodiment of Figures 22 and 23 except for the fact that its connector 192, instead of being a piece of film with adhesive on both sides, is provided with at least one mechanical fastener 200,202. As illustrated, there is a fastener 200 through which the port 98 extends and which has a headed end 204 to provide a snap connection to the piston 72 through the piston port 78 '. In addition, the other illustrated fastener 202 is located adjacent to the depressed mounting portion 100 which extends through a hole 205 and has a snap connector end 206 to provide the securing of the valve body 190 in position. It should be appreciated that each of the embodiments illustrated in Figures 19-24 while being illustrated for use on the piston 72 can also be mounted on the wall of the cover 70 for use in the supercharged circuit as illustrated in Figure 18. In addition, each of the elongated valve elements previously described 82 has its elongated configuration provided by a straight shape although this elongated configuration can also be provided by a curved shape as with the valve 76 shown in Figure 18 and as hereinafter further on it will be described in detail along with the modalities of Figures 25-28. With reference to Figure 25, another embodiment of the control valve 80f is constructed to operate in the supercharged circuit as previously described in conjunction with Figure 19, but which provides control of both ports 78 through the cover wall so that the flow returns to the side, lowers the pressure of the hydraulic pump. More specifically, also as shown in Figures 26 and 27, the valve body 190 of this embodiment in the control valve 80f has an elongated mounting recess 98 with a curved shape including opposite ends 102 and a curved intermediate portion 100 extending between its ends. Valve member 82 is generally planar as the embodiments of Figures 22-24 and has a pair of opposed distal ends 88 as well as a curved intermediate portion 84 extending between its ends. This curved intermediate portion 84 of the control valve element 82 is mounted within the recess 98 in the curved intermediate portion 100 thereof by means of threaded fastening screws 86. Both ports 78 have the same construction with a main passage 94 and a purge passage 96 which functions as previously described adjacent the associated ends 102 of the recess 98. This recess 98 has a greater depth at each end 102 thereof than in the intermediate portion 100 and is inclined at each end thereof to its intermediate portion as illustrated in Figure 27. This inclination is preferably provided by a pair of curved surfaces 198 such that each distal end 88 of the flat valve member 82 is moved by a continuously moving line in and out of engagement with the associated curved surface during the movement between the open and closed positions with respect to the associated port 78. As illustrated in Figure 27, the control valve 80f has a connector 192 which is exemplified by an adhesive plastic film on both sides 194 as the previously described embodiment of Figures 22 and 23. Similarly, since the valve body 198 it is preferably a plastic injection mold made of a suitable plastic or a die-casting made of steel or aluminum, other ways of manufacturing the valve body are possible. As illustrated in Figure 28, another embodiment of the control valve 80f has the same construction as the control valve 80g of Figures 25-27, but has its connector 192 exemplified by a pair of mechanical fasteners-200 as the element As such, these mechanical fasteners 200 extend through suitable port portions 78 'in the coupling wall 70 such that the control valve provides flow control back to the pump in the manner previously described together with Figure 19. It will be appreciated that each of the embodiments of Figures 22-28 as illustrated with the valve body 190 as an injection molding, can also be constructed as part of the piston or coupling wall that provides part of the piston housing in the broader aspect of the invention. However, particular advantages are achieved by the injection molding of the valve body as specifically described. It should also be appreciated that each of the embodiments wherein the purge passage 96 is illustrated as being part of a valve body may also have the purge passage constructed as part of the distal end 88 of the associated valve member 82 as the embodiment of Figures 19-21. The supply in the supplemented pressurized hydraulic fluid 103 of each embodiment of the hydraulic coupling can operate in different ways. First, the control 111 can be adjusted so that the pump source 109 does not supply any pressurized hydraulic fluid to the hydraulic coupling in such a way that the coupling of the pair of rotation members 26 and 28 is only carried out during the activation of the clutch in response to a differential rotation between the members and the closing of the control valve. Second and at another end the control 111 can be adjusted in such a way that the pump source 109 provides sufficient pressurized hydraulic fluid to the hydraulic coupling to continuously activate the clutch and thereby continuously couple the pair of rotation members 26 and 28 when necessary for the operation of the particular vehicle when desired. further, the control 111 can operate the pump source 109 to provide pressurized hydraulic fluid intermediate the coupling in such a way that the valve closure and clutch activation is carried out at a lower speed of the differential rotation between the torque of rotation members 26 and 28 compared to the case where there is no supplementary activation. To the point at which the pump source 109 pressurizes, the hydraulic fluid may vary to be able to control the amount of differential rotation between the pair of rotation members 26 and 28 to which the control valve closes to activate the clutch and provide the coupling between these members. The control 111 that operates the supplementary pressurized hydraulic fluid supply for the coupling can operate in different ways. In its most basic operation, a mounted vehicle activation control such as a switch or a valve can provide manual control which is the most preferable variable to control to the point at which the fluid will be pressurized to provide supplemental clutch activation. It is also possible for the vehicle computer to operate control 111 in response to other vehicle or environment variables such as engine speed, vehicle speed, vehicle inclination, vehicle acceleration, ambient temperature, speed differences. of the rim and axle, operation of the automatic braking system, and operation of the vehicle traction control system, etc. Such control can be done through a dedicated electronic circuit that operates independently or in synchronization with other electronic systems of the vehicle.

Although the embodiment of the Figure the hydraulic coupling that has the set of differential gears has been illustrated to be used in the rear axle that functions as the primary activation axis, it is also possible to use this modality with the set of differential gears in the front axle as part of a trans-axle vehicle traction system. Similarly, the hydraulic coupling mode illustrated in Figure Ib can also be used as the auxiliary activation on the rear axle as well as on the front axle as previously described. In the same way, the modality of the Figure can be used as part of a vehicle transfer case or another component of the vehicle transmission train which is also the case with the other modalities. In addition, the different coupling constructions as shown in Figures la, Ib, and may have the outlet port 78 and the associated control valve 80 provided in the piston 72 or in the wall of the cover 70 '. Since the best modes for carrying out the invention have been described in detail, those familiar with the technique to which this invention relates will recognize various alternatives, designs and modalities for practicing the present invention as defined by the following claims.

Claims (10)

1. CLAIMS 1. A hydraulic coupling that is used with a vehicle transmission train inside a housing thereof containing hydraulic fluid to rotationally couple a pair of rotating members about an axis of rotation, the hydraulic coupling is characterized in that it comprises: a cover of a hollow construction that can rotate within the housing about the axis of rotation; a hydraulic pump located within the cover along the axis of rotation and including a toothed driver rotatably connected to one of the rotation members and having external teeth; The hydraulic pump also includes an internal toothed ring mounted by the cover to rotate eccentrically with respect to the toothed driver and which includes internal teeth in a number exceeding in one the teeth of the impeller and a gear ratio with this to provide an action pumping during relative rotation between the cover and the serrated driver as the pair of rotating members rotate relative to each other; an inlet port through which the hydraulic fluid is pumped from the housing within the cover by a hydraulic pump; a clutch including a piston chamber located within the cover and having an activation piston which is received within the piston chamber and which acts by means of the pressurized hydraulic fluid to couple the clutch and couple the two rotation members together; the cover includes a transfer port through which the pressurized hydraulic fluid is pumped from the hydraulic pump to the piston chamber; the cover also includes an outlet port through which the pressurized hydraulic fluid flows from the piston chamber; a control valve that includes a valve element that moves between an open position separated from the outlet port and a closed position that generally closes the outlet port when the pumped fluid reaches a predetermined pressure to thereby further increase the fluid pressure pressurized hydraulic and activate the piston and engage the clutch to thereby rotationally couple the pair of rotating members together; and a supply of supplemental pressurized hydraulic fluid that feeds the pressurized hydraulic fluid into the inlet port of the cover to the pump independent of the pumping action of the pump. The hydraulic coupling according to claim 1, characterized in that the supply of supplementary pressurized hydraulic fluid includes a rotary seal assembly that is fixedly mounted within the housing and has seals that seal with the cover to define an inlet chamber that is communicates with the port of entry; a first passage for feeding the hydraulic fluid from the housing to the inlet chamber to allow flow through the inlet body during the pumping action of the hydraulic pump; the first passage has a check valve to prevent flow through it from the inlet chamber to the housing; a second passage to feed the pressurized hydraulic fluid to the inlet chamber; and a source of pressurized hydraulic fluid to selectively provide pressurized hydraulic fluid through the second passage to the inlet chamber. The hydraulic coupling according to claim 2, characterized in that the second passage of the supplementary pressurized hydraulic fluid supply has a junction with the first passage thereof to a location towards the inlet chamber from the check valve of the first passage. 4. The hydraulic coupling according to claim 1, characterized in that the outlet port extends through the piston and the control valve is mounted on the piston. 5. The hydraulic coupling according to claim 1, characterized in that the cover includes a wall separating the pump and the piston chamber, the transfer port extends through its wall from one side at high pressure of the pump to the piston chamber, the outlet port extends through the wall from the piston chamber to allow a low pressure side of the pump. The hydraulic coupling according to claim 1, characterized in that the coupling further comprises a set of differential gears extending between the cover and the pair of rotating members. The hydraulic coupling according to claim 6, characterized in that the hydraulic pump and the clutch are located within the cover adjacent to a rotation member on one side of the differential gear assembly, and the other rotation member is located on the opposite side of the differential gear set of the hydraulic pump and the clutch. The hydraulic coupling according to claim 1, characterized in that it includes a second hydraulic pump located within the cover along the axis of rotation and including a second toothed driver rotatably connected to the other rotation member and having external teeth; the second hydraulic pump also includes a second internal toothed ring mounted by the cover to rotate eccentrically with respect to the second toothed driver which includes internal teeth in a number exceeding in one the teeth of the second toothed driver and which is in a ratio of gearing therewith to provide a pumping action during relative rotation between the cover and the second toothed driver; a second inlet port through which the hydraulic fluid is pumped into the cover by the second hydraulic pump; the clutch includes a second piston chamber located within the cover and having a second activation piston which is received within the second piston chamber and which is activatable by the pressurized hydraulic fluid to couple the clutch and engage the two members of the piston. rotation among themselves; the cover includes a second transfer port through which the pressurized hydraulic fluid is pumped from the second hydraulic pump into the second piston chamber; the cover also includes a second outlet port through which the pressurized hydraulic fluid flows from the second piston chamber; a second control valve includes a second valve element movable between an open position separated from the second outlet port and a closed position that generally closes the second outlet port when the pumped fluid reaches a certain pressure to thereby increase the pressure of the hydraulic fluid and activating the second piston and coupling the clutch to thereby rotationally couple the pair of rotating members together; and the supply of supplemental pressurized hydraulic fluid operates to feed the pressurized hydraulic fluid within the second inlet port of the cover to the second pump independent of the pumping action of the second pump. The hydraulic coupling according to claim 6, characterized in that the clutch includes first and second clutch packs, each of which includes a pair of sets of clutch plates alternating with each other; A set of clutch plates of each clutch pack is rotatably fixed to the cover; the other clutch plate assembly of the first clutch pack is rotatably fixed to a rotation member; the other clutch plate assemblies of the second clutch pack are rotatably fixed to the other rotation member; and the clutch is located between the first mentioned piston and the second piston. The hydraulic coupling according to claim 1, characterized in that the rotating member has an elongated shape extending along the axis of rotation, and the other rotating member has an annular shape and is mounted on the cover which extends around the axis of rotation.