Abstract:
A pump has a pressure chamber and a control ring which is mounted to pivot about a pivoting axis and which undergoes a pivoting motion. The control ring can be pivoted about a deflection angle during its pivoting movement. An aperture is provided in the pressure chamber of the pump. The aperture opens or closes to varying degree based on the pivoting motion of the control ring. In a hydrodynamic retarder with such a pump, a lubricating and cooling medium is supplied at least to bearings of rotating components of the retarder. Differentiated lubrication and cooling, at least of the bearings, can be brought about during braking operation and during non-braking operation of the retarder.

Description:
[0001]    This application is a National Stage completion of PCT/EP2013/060006 filed May 15, 2013, which claims priority from German patent application serial no. 10 2012 208 244.1 filed May 16, 2012. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention concerns a pump and a hydrodynamic retarder, which is provided on a vehicle transmission. Preferably, the pump supplies at least bearings for rotating components of the retarder with a lubricating and cooling medium, and means are provided which bring about differentiated lubrication and cooling at least of the bearings when the retarder is operating with braking effect and without braking effect. 
       BACKGROUND OF THE INVENTION 
       [0003]    Besides the service brakes of a vehicle, which are usually in the form of friction brakes subject to wear, particularly in commercial vehicles additional, wear-free slowing-down devices such as retarders are used. Retarders include both additional hydrodynamic, hydrostatic or electrodynamic braking devices arranged on the transmission or on the engine, and systems which, in the form of a so-termed intarder, are arranged within the transmission housing. Furthermore a distinction is made between primary retarders, which work as a function of the engine speed, and secondary retarders which work as a function of the speed of the vehicle. In hydrodynamic retarders, to brake the vehicle the rotor is generally connected directly to a transmission shaft. In the case of primary retarders this shaft is the driveshaft or transmission input shaft, while in the case of secondary retarders it is the transmission output shaft. The stator of the retarder is as a rule arranged fixed to the housing, and the retarder is then usually not activated when a working space between the rotor and the stator is not filled with a fluid. 
         [0004]    To keep the dimensions of a hydrodynamic retarder small, the possibility exists of increasing the transmission ratio from the transmission shaft to the rotor of the retarder to ‘fast mode’ by means of a step-up stage. Since for reasons of cost, fitting space and safety no clutch is fitted between the retarder and a shaft that is driving the retarder, the mechanical components basically continue rotating even when the retarder is not operating with a braking effect and they therefore give rise to corresponding losses. This results in increased fuel consumption of the vehicle. Part of the retarder&#39;s overall loss is produced by the step-up stage, which is usually in the form of a spur gear pair that converts the retarder rotational speed to the fast range relative to the transmission output rotational speed. The losses consist essentially of splash and friction losses of the gearwheels. However, for reasons of space, the retarder shaft is often lower down in the transmission housing than the transmission output shaft, so that the gearwheel of the step-up stage arranged on the retarder shaft is immersed a certain distance under the oil level which varies dynamically during the operation of the transmission. During braking operation this is desirable and necessary, because the teeth of the step-up stage are very effectively lubricated and cooled thereby. Further losses take place in the rotary bearings of the shaft driving the retarder. Here too, during braking operation sufficient lubrication and cooling is unconditionally necessary, but during traction operation of the vehicle the components can get by with substantially less oil. 
         [0005]    In order to ensure the lubrication and cooling of the components of the retarder of a vehicle transmission in different operation conditions and thereby to reduce the aforesaid losses, in DE 10 2009 026 721 A1 a vehicle transmission with a hydrodynamic retarder is proposed, which has a device for driving and controlling the retarder, with bearings of the retarder and of the device for driving and controlling it and with means for lubricating and cooling the bearings and the device. In addition, means are provided for enabling differentiated lubrication and cooling of the bearings and the driving and control device with lubrication and cooling media during the braking operation of the retarder compared with when it is in a non-braking operating mode. These means for enabling differentiated lubrication and cooling are activated as a function of actuation signals of the retarder. For this a control valve is provided, which reacts to the actuation signal from an actuation sensor, for example on the brake pedal or on a brake lever, and which produces the retarder control pressure so that the lubricant and coolant is delivered as a function of the retarder control pressure. In the hydraulic retarder control system there is a control pressure whose value is zero during non-braking operation. During braking operation that control pressure is set by an electromagnetic valve in accordance with the braking torque required and the resulting pressure demand, to values between zero and the maximum control pressure. This results in a corresponding pump pressure. The control pressure and the braking torque are directly related. The higher the control pressure is, the larger the braking torque will be when the retarder is switched on. By relating the lubrication and cooling supply to the control pressure as a load-dependent quantity, a load-dependent lubricant and coolant volume flow is produced. The lubricant and coolant volume flow is produced by a pump, which is coupled to the rotor shaft of the retarder and which determines the lubricant and coolant volume flow via the control valve to the bearings that have to be lubricated and cooled. 
         [0006]    This vehicle transmission disclosed in DE 10 2009 026 721 A1 takes into account the fact that during braking operation of the retarder, owing to operating forces higher power losses have to be dissipated in the bearings and teeth, and it satisfies the requirement for load-dependent cooling and lubrication during braking operation of the retarder by correspondingly reducing the power loss. During non-braking operation of the retarder, i.e. when the bearings are not under load, the necessary lubricant and coolant volume flow is indeed substantially smaller but it has to be matched to the maximum retarder rotational speed, even though at low rotational speeds far less cooling and lubrication would be required. Furthermore, for the control of the lubricant and coolant volume flow, a control valve is needed, which reacts to the actuation signals from the brake pedal or brake lever, which produces the retarder control pressure and which delivers the lubricant and coolant as a function of the retarder control pressure. 
         [0007]    In DE 10 2009 026 721 A1 the lubricant and coolant are delivered with the help of a pump. As an example of such a pump, DE 10 2006 061 326 A1 describes a pump having a pressure chamber and a control ring mounted to pivot about a pivoting axis, which undergoes a pivoting motion and which during the pivoting motion can pivot through a deflection angle. Such pumps, also known as reciprocating vacuum pumps or rotary vane pumps, are used in automotive applications as well. For example, they are also proposed as pumps in a hydrodynamic retarder described in DE 10 2008 000 901 A1. 
       SUMMARY OF THE INVENTION 
       [0008]    Against that background the purpose of the present invention is to propose a pump which can be controlled more simply and, by virtue of such a pump, to improve the lubricant and coolant supply to a hydrodynamic retarder equipped therewith and to minimize power losses in a vehicle transmission with such a retarder, 
         [0009]    These objectives are achieved by the characteristics specified in the description below. Advantageous further developments and design features of the invention are described below. 
         [0010]    The invention starts from the realization that the control of a pump with a pivoting control ring, in particular a reciprocating vacuum pump or rotary vane pump, takes place internally by virtue of the pivoting control ring, which is pivoted in such manner that the pump is adjusted to zero-delivery so that no power loss is caused by diverting the pump delivery volume through a pressure regulating valve. 
         [0011]    The pump according to the invention comprises a pressure chamber and a control ring mounted to pivot about a pivoting axis so that it undergoes pivoting motion, such that during its pivoting motion the control ring pivots through a specified deflection angle. 
         [0012]    A deflection angle is understood to mean the angle through which the control ring sweeps during its pivoting motion. A minimal deflection angle is reached in a position of the control ring when the compression spring is at maximum extension. A maximum deflection angle corresponds to a position of the control ring in which the compression spring is compressed to its maximum extent, 
         [0013]    This pivoting motion of the control ring can be used to adjust the medium delivered by the pump in accordance with requirements, in that the control ring is used to open an aperture in the pressure chamber of the pump to a greater or lesser extent, or to close it off completely, depending on the position and deflection angle of the control ring. 
         [0014]    In an advantageous version of the invention, the deflection angle of the pivoting motion of the control ring depends on the rotational speed of the pump and is in a characteristic ratio to the pump rotational speed. What this achieves is that as a function of the rotational speed and the concomitant loading of components to be supplied with lubricant or coolant, by virtue of the corresponding pivoting of the control ring the aperture is opened sufficiently for an appropriately large lubricant and coolant volume flow to be delivered to the components to be supplied. 
         [0015]    The control ring of the pump is acted upon by the spring force of a compression spring, and in an advantageous design the aperture in the pressure chamber when the deflection angle of the control ring about its pivoting axis is a minimum, is closed to its maximum extent (at low rotational speed). When the deflection angle of the control ring is at a maximum (at high rotational speed), the aperture in the pressure chamber is opened to the maximum extent against the spring force of the compression spring. 
         [0016]    Advantageously, the control ring can be provided with a control edge which, depending on the pivoted position of the control ring, closes the aperture to a greater or lesser extent, the aperture preferably being formed in a side face of the pump housing or in a housing cover thereof. 
         [0017]    For fine control of the lubricant and coolant volume flow the aperture can consist of a plurality of bores arranged in the movement direction of the pivoting motion of the control edge of the control ring, the bores having equal and/or different diameters, or else the aperture can also be in the form of an elongated slot that narrows in the closing direction, for example in a wedge shape. 
         [0018]    Furthermore, it can be provided that the at least one aperture is arranged approximately diametrically opposite the pivoting axis in the pump housing. 
         [0019]    The angular position of the aperture and the control edge of the control ring relative to the pivoting axis can be chosen such that there are specific opening and closing points in the swivel range of the control ring, by virtue of which a rotational speed limit for the opening and closing can be set, 
         [0020]    The invention also concerns a hydrodynamic retarder and a pump associated with the retarder, which supplies a lubricating and cooling medium at least to bearings of rotating components of the retarder, such that means are provided which bring about differentiated lubrication and cooling at least of the bearings when the retarder is in braking operation and in non-braking operation. 
         [0021]    According to the invention, for this it is provided that the pump is designed with a control ring mounted to be able to pivot about a pivoting axis, wherein the control ring communicates on one side with a pressure chamber and on the other side with a suction chamber, and wherein, in the pivoting movement range of the control ring, an aperture is located which is in communication by way of a lubricant and coolant line at least with the bearings in which the rotating components of the retarder are mounted. 
         [0022]    As mentioned, the invention starts from the realization that the control of a reciprocating vacuum pump or rotary vane pump takes place internally by means of the control ring mounted to pivot, which is pivoted in such manner that the pump is adjusted to zero delivery so that no power loss occurs due to diversion of the pump delivery volume through a pressure regulating valve. This pivoting motion of the control ring can be used in order to adjust the lubricant and coolant volume flow supplied at least to the bearings of the retarder in accordance with the mechanical loading and rotational speed, in that the control ring is used to open or close to a greater or lesser extent an aperture to the delivery chamber of the pump which communicates by way of a lubricant and coolant line at least with the bearings of the retarder, depending on the position of the control ring. 
         [0023]    Correspondingly, the aperture that communicates at least with the bearings of the retarder via the lubricant and coolant line is at least to a predominant extent or even completely closed when the control ring is at its maximum deflection, this being the case in particular at low rotational speeds and low loads when there is no great need for a large lubricant and coolant volume flow, but when the deflection of the control ring is at a minimum, i.e. as a rule at high rotational speeds and high loads, the aperture that communicates at least with the bearings of the retarder by way of the lubricant and coolant line is fully open and thus admits a large volume flow of lubricant and coolant to the bearings. 
         [0024]    To set a through-flow characteristic for the lubricant and coolant volume flow to the bearings, an outflow diaphragm aperture can advantageously be arranged in the area between the aperture and the bearings. 
         [0025]    Finally, the invention concerns a vehicle transmission with a hydrodynamic retarder and a pump associated with the retarder, which pump supplies a lubricant and coolant at least to bearings for rotating components of the retarder. The pump comprises a control ring mounted to pivot about a pivoting axis, which undergoes a pivoting motion. The control ring communicates on one side with a pressure chamber and on the other side with a suction chamber. By virtue of its pivoting movement the control ring opens or closes an aperture in the pressure chamber of the pump to varying extents, in order to provide differentiated lubrication and cooling of the bearings when the retarder is in braking operation and in non-braking operation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0026]    Below, the invention will be explained further with reference to an example embodiment illustrated in the drawings, which show: 
           [0027]      FIG. 1 : A schematic view of part of a vehicle transmission having a hydrodynamic retarder with an associated pump for lubricant and coolant, 
           [0028]      FIG. 2 : A schematic sectioned view through a rotary vane pump according to the invention, in a first delivery setting, 
           [0029]      FIG. 3 : A schematic sectioned view through the rotary vane pump of  FIG. 2 , in a second delivery setting, 
           [0030]      FIG. 4 : A schematic view of a second embodiment, showing an aperture in the rotary vane pump of  FIG. 1  connected by a lubricant and coolant line to the bearings, and 
           [0031]      FIG. 5 : A schematic view of a third embodiment, showing an aperture in the rotary vane pump of  FIG. 1  that communicates by way of a lubricant and coolant line with the bearings. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]      FIG. 1  shows schematically a transmission output shaft  4  of a vehicle transmission  2 , on which a first gearwheel  6  of a step-up stage  8  is fixed. A second gearwheel  10  of the step-up stage  8  meshes with the first gearwheel  6  by way of teeth  12 . The second gearwheel  10  is connected in a rotationally fixed manner to a rotor shaft  14  of a retarder  16 , whose rotor  18  is coupled rotationally fixed to the rotor shaft  14  by means of driving teeth  20 . The rotor shaft  14  is mounted by means of two bearings  22  to rotate in a housing  24 . By way of a pump coupling  26 , a pump shaft  28  of a pump  30  is connected to the rotor shaft  14 . The pump shaft  28  is mounted by means of two bearings  32  to rotate in the housing  24 . 
         [0033]    The pump  30  is a controlled reciprocating vacuum pump or rotary vane pump whose basic structure is known from DE 10 2010 010 799 A1. The mode of operation of a reciprocating vacuum pump is described in detail in DE 195 32 703 C1, in particular as regards its control. The content of those two documents is here included completely in the object of the present disclosure. 
         [0034]      FIG. 2  shows the reciprocating vacuum pump  30  according to  FIG. 1 , which comprises in a pump housing  34 , a control ring  38  mounted to pivot about a pivoting axis  40 . This control ring  38  is mounted and sealed in the pump housing  34  in such manner that it can be acted upon by the pressure in a pressure chamber  42  and can thereby be pivoted against the force of a spring  44  accommodated in a suction chamber  48 . Inside the control ring  38 , in a known manner a rotor  36  can be driven in rotation by means of the pump shaft  28 . The pump shaft  28  is mounted to rotate in the pump housing  34  by means of the bearing  32  shown in  FIG. 1 . 
         [0035]    In the control ring  38  is mounted to rotate an outer rotor  58  which is connected in a rotationally fixed manner to the rotor  36  by means of pendulum drive elements  46  fitted into the outer rotor  58 . When the control ring  38  pivots about its pivoting axis  40  the pump  30  can be adjusted between a position shown in  FIG. 2  which gives a minimum delivery volume flow and a position shown in  FIG. 3  which given a maximum delivery volume flow, This takes place automatically since when the pump  30  is operating a pressure builds up in the pressure chamber  42 , which is as a rule the pump pressure. If the pressure increases toward the nominal pump pressure, the pressure in the pressure chamber  42  causes the control ring  38  to pivot in opposition to the force of the spring  44 . 
         [0036]    In the actuation position shown in  FIG. 2  the control ring  38  and the outer rotor  58  arranged therein have only a slight eccentricity relative to the rotor  36 , whereby the pump  30  is set to its minimum delivery capacity. In this position a control edge  54  radially on the outside of the control ring  38  allows passage through an aperture  50  in the pump housing  34 , which aperture communicates by way of a lubricant and coolant line ( FIG. 1 ) at least with the bearings  22  of the rotor shaft  14  of the retarder  16 . Preferably, the bearings  32  of the pump shaft  28  and the teeth  12  of the step-up stage  8  are also supplied with lubricant and coolant by way of the lubricant and coolant line  52 . In the actuation position of the pump  30  shown in  FIG. 2 , the largest possible lubricant and coolant volume flow is supplied to the bearings  22  and  32  and to the step-up stage  8 . As a rule this position corresponds to non-braking operation of the retarder  16  at high rotational speeds of the transmission output shaft  4 , during which an abundant supply of lubricant and coolant to the step-up stage  8  and to the bearings  22  and  32  is required. 
         [0037]      FIG. 3  shows a position of the control ring  38  in which the pump  30  is set to its maximum delivery position. In this position the aperture  50  in the pump housing  34  is at least mostly or even completely closed, so that only a very small volume flow of lubricant and coolant passes to the step-up stage  8  and to the bearings  22  and  32 . As a rule this operating position of the pump  30  corresponds to a low rotational speed of the transmission output shaft  4  and to non-braking operation of the retarder  16 , when the size of the lubricant and coolant volume flow required is small. Intermediate positions of the control ring  38  result in partial opening of the aperture  50  in the pump housing  34  by the control edge  54  of the control ring  38 , with corresponding adjustment of the size of the lubricant and coolant volume flow, 
         [0038]    As can be seen in  FIG. 4 , the aperture  50  in the pump housing  34  can be subdivided into a plurality of bores  50   a,    50   b,    50   c  a distance apart in the pivoting direction  60  of the control ring  38 , the bores having different diameters, whereby depending on the pivoted position of the control ring  38 , the lubricant and coolant volume flow can be controlled stepwise by the control edge  54 . 
         [0039]    Continuous control of the lubricant and coolant volume flow is enabled by an aperture  50   d  as shown in  FIG. 5 , in that the aperture  50   d  is for example in the form of a wedge-shaped slot with a tapering cross-section. 
         [0040]    The angular position of the aperture  50 , the bores  50   a,    50   b,    50   c  or of the slot  50   d  and the control edge  54  of the control ring  38  relative to the pivoting axis  40  can be chosen such that there are predetermined opening and closing points which can differ from the maximum positions shown in  FIGS. 2 and 3 , by which means lower and upper rotational speed limits can be set. 
         [0041]    In the lubricant and coolant line  52  at least one outflow diaphragm aperture  56  can be arranged, which enables the setting of a through-flow characteristic to the bearings  22  and/or  32  and to the teeth  12  ( FIG. 1 ). As shown in  FIGS. 2 and 3  the aperture  50 , the bores  50   a,    50   b,    50   c  or the slot  50   d  can be located in a side face of the pump housing  34  or in a housing cover of the pump  30 . Likewise, as shown it is possible to position the aperture  50 , the bores  50   a,    50   b,    50   c  or the slot  50   d  in a sealing surface of the pump housing  34  approximately diametrically opposite the pivoting axis  40 . 
         [0042]    By virtue of the action of pressure on the control ring  38  on the pressure chamber side  42  in opposition to the force of the spring  44 , a constant pump pressure is produced. By virtue of the adjustment movement of the control ring  38 , the pump pressure can be kept constant over the entire rotational speed range. The adjustment path or deflection angle of the control ring  38  is accordingly in a characteristic ratio to the rotational speed, so that as the rotational speed increases the deflection angle of the control ring  38  becomes larger and the lubricant and coolant flow volume therefore also becomes larger. Thus, the control ring  38  can be regarded as a gate that operates in a rotational speed dependent manner. By way of the aperture  50 , the bores  50   a,    50   b,    50   c  or the slot  50   d,  over the adjustment range of the control ring  38  lubricant and coolant can be drawn off and supplied to the bearings  22  and  32  and to the teeth  12 . In this case, at low rotational speeds the aperture  50 , the bores  50   a,    50   b,    50   c  or the slot  50   d  are mostly or fully closed. At the maximum rotational speed the outflow cross-section is largest and the volume flow of lubricant and coolant is as large as possible. 
         [0043]    LIST OF INDEXES 
         [0044]      1  Vehicle transmission 
         [0045]      4  Transmission output shaft 
         [0046]      6  First gearwheel 
         [0047]      8  Step-up stage 
         [0048]      10  Second gearwheel 
         [0049]      12  Teeth 
         [0050]      14  Rotor shaft 
         [0051]      16  Retarder 
         [0052]      18  Rotor 
         [0053]      20  Driving teeth 
         [0054]      22  Rotor shaft bearing 
         [0055]      24  Housing 
         [0056]      26  Pump clutch 
         [0057]      28  Pump shaft 
         [0058]      30  Pump 
         [0059]      32  Pump shaft bearing 
         [0060]      34  Pump housing 
         [0061]      36  Rotor 
         [0062]      38  Control ring 
         [0063]      40  Pivoting axis 
         [0064]      42  Pressure chamber 
         [0065]      44  Spring 
         [0066]      46  Pendulum drive element 
         [0067]      48  Suction chamber 
         [0068]      50  Aperture 
         [0069]      50   a  Bore 
         [0070]      50   b  Bore 
         [0071]      50   c  Bore 
         [0072]      50   d  Slot 
         [0073]      52  Lubricant and coolant line 
         [0074]      54  Control edge 
         [0075]      56  Outflow diaphragm aperture 
         [0076]      58  Outer rotor 
         [0077]      60  Pivoting direction of the control ring