Patent Publication Number: US-2019193560-A1

Title: Auxiliary power take-off assembly

Description:
This application is a National Stage completion of PCT/EP2017/065399 filed Jun. 22, 2017, which claims priority from German patent application serial no. 10 2016 212 209.6 filed Jul. 5, 2016. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to an auxiliary power take-off assembly with a motor-dependent auxiliary power take-off for a vehicle transmission having a torque converter. 
     BACKGROUND OF THE INVENTION 
     Vehicle transmissions in utility vehicles often have an auxiliary power take-off assembly by means of which additional attached assemblies of various types in the vehicle can be driven. This applies just as well to transmissions with a friction disk clutch as to transmissions fitted with a torque converter. 
     Auxiliary power take-offs are used particularly in buses, trucks, building machines, agricultural machines or special-purpose vehicles. 
     Auxiliary power take-offs are available in drive-dependent, clutch-dependent or motor-dependent designs. For example, drive-dependent auxiliary power take-offs supply the hydraulic system of dual-circuit steering systems with working pressure, whereby rolling vehicles still remain steerable when the primary system has failed due to an engine failure. Clutch-dependent auxiliary power take-offs are suitable for short-term or long-term operation during driving or at rest. Motor-dependent auxiliary power take-offs differ from clutch-dependent auxiliary power take-offs in that with motor-dependent auxiliary power take-offs there is a direct connection to the crankshaft of the drive motor of the vehicle, bypassing the vehicle clutch or the torque converter, so that such auxiliary power take-offs are permanently mechanically connected to the crankshaft of the drive motor. They are designed for high, constant power delivery in long-term operation and can be loaded with the maximum motor torque. They can be operated while the vehicle is driving or at rest, and can be engaged or disengaged under load. Typical fields of use are additional attached aggregates such as high-pressure pumps for fire engines, shuttle high-pressure flushing and suction vehicles, earth drilling equipment, concrete mixers and concrete pumps. 
     From DE 26 56 669 C2 a motor-dependent auxiliary power take-off on a vehicle transmission with a torque converter has become known, in which a drive engine of the vehicle is connected permanently by way of the pump shaft of the torque converter to a drive input shaft of an auxiliary power take-off assembly. The drive input shaft acts upon a transmission chain that consists of at least one drive input element in the form of a gearwheel and a drive output element, wherein the drive output element of the transmission chain is connected to an additional assembly which is to be driven. At the same time the drive input element of the transmission chain also drives a pressure medium pump of the transmission. The drive output element comprises a shifting element by which the additional assembly can be coupled to the auxiliary power take-off assembly. 
     In such an arrangement the whole of the transmission chain always runs together with the auxiliary power take-off assembly. The tooth engagements of the drive input element rotate constantly, since the shifting element of the auxiliary power take-off assembly is first arranged in the drive output element and thus only the downstream components can be decoupled. Accordingly, even at low loads there is always some rolling loss and in particular a lot of noise from the gear teeth. In addition the shifting clutch along with its associated actuating equipment take up a lot of space in the drive output element and make the auxiliary power take-off assembly a large and heavy attachment. 
     SUMMARY OF THE INVENTION 
     The purpose of the present invention is to improve an auxiliary power take-off assembly and in particular to have a positive effect on noise emission and the fitting space required, and also to reduce losses. 
     This objective is achieved by an auxiliary power take-off assembly having the characteristics specified in the independent claims. Its design features are the object of subordinate claims. 
     In a vehicle having a transmission with a torque converter, an auxiliary power take-off assembly is provided. The pump shaft of the torque converter is connected permanently to a drive motor of the vehicle and, for its part, is in torque-transmitting connection with a drive input shaft of the auxiliary power take-off assembly. The auxiliary power take-off assembly comprises a transmission chain that enables torque to be transmitted between the driveshaft and an additional assembly to be driven. The said additional assembly can be any of the components described earlier in the surroundings of the utility vehicle. The transmission chain consists at least of a drive input element designed to take up torque from the driveshaft, and a drive output element designed to deliver torque to the additional assembly. In the auxiliary power take-off assembly a shifting element is provided, which according to the invention is functionally arranged between driveshaft and the drive input element of the transmission chain and serves to enable optional connection of the driveshaft to the drive input element. This makes it possible for the auxiliary power take-off assembly already directly behind the driveshaft connected to the pump shaft of the torque converter, to be completely decoupled from the rest of the transmission chain and the additional assembly so that when not needed those elements do not have to be entrained into rotation and therefore do not produce any losses and any noise. This increases the efficiency of the auxiliary power take-off assembly, which can also be made more compact due to the omission of the shifting clutch in the drive output element. 
     Advantageously, the drive input element in the transmission chain and the driveshaft have the same rotational axis, which is the case when the rotational axes of the torque converter and the transmission as a whole coincide. The shifting element then also has the same rotational axis. If the shifting element is arranged between the driveshaft and the drive input element, then without any negative effect on the fitting space available there it can have a diameter large enough to ensure a large effective surface area for torque transmission or for the production of friction. 
     In an advantageous embodiment of the invention, as the drive input element of the transmission chain a gearwheel of a gearwheel chain consisting of a mutually engaging sequence of gearwheels is provided. In auxiliary power take-off assemblies gearwheels form a tried and tested way to transmit torque, which can also be used if necessary to adapt the rotational direction of the drive output element and thus of the additional assembly. 
     An alternative way to transmit torque to the additional assembly is provided by a wrap-around drive, for example in the form of a metallic link chain or an elastic toothed belt or drive belt. In this case it is advantageous to provide a wheel of the wrap-around drive as the drive input element, which depending on the application carries external teeth or a corresponding groove for a V-belt. 
     Preferably, the shifting element is actuated pneumatically, hydraulically, by an electric motor or electromagnetically. The manner of actuation can be adapted to the respective circumstances of the vehicle. If the vehicle is a large utility vehicle whose brakes are actuated pneumatically, then a supply of compressed air is already present in the vehicle. In such cases the transmission of the vehicle is often also actuated pneumatically and by means of appropriate supply lines compressed air can also be delivered to the area of the shifting element in the transmission. In vehicles with hydraulic transmission actuation, in particular hydraulically shifted automatic transmissions having a gearset structure that consists of a series of planetary gearsets, the clutches and brakes within the transmission are actuated by a hydraulic control system whose delivery lines are inside or even outside the transmission and carry hydraulic fluid from the control unit to the said clutches and brakes. The lines are provided within the transmission both in the fixed transmission housing walls and also in rotating components such as the transmission shafts. Thus it can be advantageous in the case of hydraulic actuation to supply the hydraulic fluid through the driveshaft to the shifting element. For this, an appropriate seal on the driveshaft must be provided, which however, in such transmissions, is an often present measure since in numerous applications hydraulic fluid is conveyed by rotating shafts. The shifting element can be provided sitting directly on the driveshaft. In an advantageous design, for the hydraulic actuation the shifting element can be connected hydraulically to the control unit of the transmission. In that way an additional control unit for actuating the auxiliary power take-off assembly can be omitted and the shifting element is actuated directly from the transmission control system. Functional dependencies of the auxiliary power take-off control on the transmission controls can be adjusted to one another simply and quickly in the same control system. If necessary it is also possible to use components already present in the standard transmission control system, such as valves etc., conjointly for actuating the shifting element of the auxiliary power take-off assembly. Any pressure lines present in the transmission housing can if necessary also be used in the same way. 
     In the case of electromagnetic or electric motor actuation of the shifting element, the electric connection leads are laid out in the transmission housing or can be fixed on the inner or even the outer surface of the transmission housing between the shifting element and the associated control unit, so that the control unit can in this case too be incorporated in an electric part of a hydraulic control unit. Electric control can be realized regardless of the type of vehicle, since even in smaller utility vehicles there is bound to be an electric supply system. Electric motor and electromagnetic shifting elements are generally known to those with knowledge of transmissions. When electrical energy is supplied, a mechanical connection is formed between components that would rotate independently of one another in the absence of energy input. By virtue of the mechanical connection torque can be transmitted from the driveshaft to the drive input element in the auxiliary power take-off assembly. 
     Embodiments of the shifting element can advantageously provide that the shifting element is in the form of a claw shifting element, a cone synchronizer or a frictional shifting element. Claw shifting elements are preferably used for shifts at rest, since otherwise it is necessary for the parts of the claw shifting element which are to be joined to rotate at the same speed, and this must be brought about or established. With cone synchronizers the rotational speed equalization can be produced by means of the conical friction surfaces. When rotational speed equalization has been achieved, clutch gearing on the conical synchronizer can engage and transmit the torque. Like a frictional shifting element, a cone synchronizer can be engaged while the vehicle is driving. In a frictional shifting element a plurality of friction disks are provided, which in the non-actuated condition of the frictional shifting element can rotate relative to one another while in the actuated condition they are pressed against one another in order to transmit torque. As paired materials for friction disks adjacent to one another, steel/steel and lining/steel are suitable. Suitable linings for friction disks are generally known. 
     In an embodiment of a claw shifting element the shifting element is provided with claws on its end faces, which when actuated axially by suitable actuation means engage in one another axially. Such claw shifting elements are axially compact. 
     A further type of claw shifting element is advantageously designed in such manner that the claw shifting element is arranged in a shifting sleeve. In this case the individual claws again engage axially in one another but on the components involved the claws are arranged in the radial direction. As a rule such claw shifting elements are axially wider, but have greater stability. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described in greater detail with reference to drawings, which show: 
         FIG. 1 : A schematic representation of a vehicle 
         FIG. 2 : A transmission of a vehicle with an auxiliary power take-off assembly 
         FIG. 3 : A first schematic representation of a shifting element 
         FIG. 4 : A second schematic representation of a shifting element 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a schematic vehicle representation of a motor vehicle  2  comprising a drive motor  4 , a transmission  6  and a torque converter  8  arranged between the drive motor  4  and the transmission  6 . The transmission  6  is connected by way of a drive output shaft  10  and a differential  12  to the two rear wheels  14 . 
       FIG. 2  shows an automatic transmission  6  with a torque converter  8 , designed according to the prior art. In a transmission housing  16 , a bridging clutch  20  is provided between the output shaft  18  of the drive motor  4  and the torque converter  8  and can connect the output shaft  18  to the transmission input shaft  22  in order to bridge across the torque converter  8 . The output shaft  18  is connected via the pump wheel P of the torque converter  8  to the pump shaft  24 . The turbine wheel T of the torque converter  8  is permanently connected to the transmission input shaft  22 . The guide wheel L of the torque converter  8  is attached to the housing  16  by way of a freewheel  26 . Projecting out of the transmission  6  is the output shaft  28 , which is connected to the drive output shaft  10  ( FIG. 1 ). 
     Connected to the pump shaft  24  is the drive input shaft  30  of the auxiliary power take-off assembly  32 . In  FIG. 2  the drive element  34  of the auxiliary power take-off assembly  32  is connected directly to the drive input shaft  30 . The drive input element  34  serves on the one hand to drive a lubricant pump  36  via the gearwheel  38 . On the other hand, via the drive input element  34  the intermediate wheel  40  of the auxiliary power take-off assembly  32  is turned, which in turn drives the drive output element  42  of the auxiliary power take-off assembly  32 . Connected to the drive output element  42  is a shifting element  44  which optionally connects the drive output element  42  to the drive output shaft  46 . In this arrangement the components always rotate along with the output shaft  18  of the drive motor  4  as far as the drive output element  42 . 
       FIG. 3  shows a first embodiment of the invention, represented schematically. The same components as in  FIG. 2  are given the same indexes. In the transmission housing  16  the pump shaft  24  is connected to the drive motor via a torsion damper  48 . Connected to the pump shaft  24  is the driveshaft  30 , on which the drive input element  34  of the auxiliary power take-off assembly  32  is mounted to rotate, for example in a needle bearing  50 . The drive input element  34  has a friction disk carrier  52  on which at least one inner friction disk  54  is provided. The at least one friction disk  54  can be brought into torque-transmitting contact with at least one outer friction disk  56  on the driveshaft  30 , in that the piston  58  presses the friction disk  54  against the friction disk  56 . The rotational speed difference relative to the transmission housing  16  is compensated for by means of an axial bearing. The piston  58  is actuated by a hydraulically or pneumatically applied pressure, represented by the arrow  60 , which pressure is built up in the piston chamber  62 . The pressure is admitted from the inside of the transmission  6  through the transmission housing  16 . 
     The essential elements of the shifting element  64  consist of the friction disk carrier  52 , the friction disks  54  and  56  and the actuating piston  58 . The intermediate wheel  40  in the auxiliary power take-off assembly  32  meshes with the drive input element  34 , which wheel  40  in turn meshes with the drive output element  42 . The additional assembly  66  to be driven is connected directly to the drive output element  42 . 
     By means of the shifting element  64 , the drive input element  34  can be decoupled from the driveshaft  30 . Then, in the decoupled condition the components of the auxiliary power take-off assembly  32  and the additional assembly  66  are no longer driven and no longer rotate with the driveshaft  30 . Noise and losses of the otherwise driven and rotating elements no longer occur. 
     The shifting element  64  and the driveshaft  30  rotate about the same rotational axis  72 . 
       FIG. 4  shows a second embodiment of the invention, in which a modified shifting element  68  is provided. The other components correspond essentially to the components described in  FIG. 3 . In this case too a friction disk carrier  52  is built onto the drive input element  34 , which carrier has at least one inner friction disk  54 . Here, two outer friction disks  56  are provided, arranged on either side of the inner friction disk  54 . When actuated the piston  58  presses the friction disks  54  and  56  together and thereby transmits torque between the driveshaft  30  and the drive input element  34 . For the actuation of the piston  58  in this case pneumatic or hydraulic actuating media is delivered through the driveshaft  30  into the piston chamber  62 , as indicated by the arrow  70 . 
     INDEXES 
     
         
           2  Motor vehicle 
           4  Drive motor 
           6  Transmission 
           8  Torque converter 
           10  Drive output shaft 
           12  Differential 
           14  Rear wheel 
           16  Transmission housing 
           18  Output shaft 
           20  Bridging clutch 
           22  Transmission input shaft 
           24  Pump shaft 
           26  Freewheel 
           28  Output shaft 
           30  Driveshaft 
           32  Auxiliary power take-off assembly 
           34  Drive input element 
           36  Lubricant pump 
           38  Gearwheel 
           40  Intermediate wheel 
           42  Drive output element 
           44  Shifting element 
           46  Drive output shaft 
           48  Torsion damper 
           50  Needle bearing 
           52  Friction disk carrier 
           54  Friction disk 
           56  Friction disk 
           58  Piston 
           60  Arrow 
           62  Piston chamber 
           64  Shifting element 
           66  Additional assembly 
           68  Shifting element 
           70  Arrow 
           72  Rotational axis 
         P Pump wheel 
         T Turbine wheel 
         L Guide wheel