Abstract:
Pump, for example for pumping lubricating oil in an internal combustion engine, more particularly a multi-stroke vane cell pump, with a rotor and vanes which can slide at least radially in rotor slots and have vane heads that slide along a stroke contour, the stroke contour having a radial outlet that can be closed by a valve device.

Description:
BACKGROUND 
     The present invention relates to a pump, for example, for pumping lubricating oil of an internal combustion engine, in particular a multistroke vane-cell pump, having a rotor and vanes which are at least radially displaceable in rotor slots, whose vane heads slide along a stroke contour, the stroke contour having, among other things, a radial outlet opening, which is closeable by a valve device. 
     Such pumps are known. Thus, for example, a multistroke vane-cell pump whose stroke contour is made of sheet metal is known. In this pump, the switchable second pumping stage is directly connected to the intake area of the first pumping stage via a radial groove in the sheet metal contour in the event of low temperature of the lubricating oil, so that at a low temperature only the first stage of the double-stroke vane-cell pump pumps. When the temperature increases, the switching stage, i.e., stage 2 of the vane-cell pump, is closed by an element which is adjustable as a function of the temperature, in such a way that the second stage of the double-stroke vane-cell pump also pumps the lubricating oil under pressure into the lubricating oil channels of the engine. The temperature-dependent switching also closes this radial groove and the volume flow is supplied to the system pressure area via a check valve. The valve, which is adjustable as a function of the temperature, is opened and closed with the aid of a conical seat. The disadvantage of this approach is the small flow cross sections that may be achieved, resulting in an excessive pressure drop; in addition, the flow around the valve seat results, for part of the volume flow, in a flow directed against the actual intake volume flow. These flows result in losses which cause an early onset of cavitation in the intake area. Furthermore, the manufacture of the seat valve is very complicated and is therefore expensive. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to develop an adjustable valve which performs the adjustment function in a cost-effective manner and offers the lowest possible flow resistance and an outlet flow directed toward the intake flow. 
     This object is achieved by a pump, for example, for pumping lubricating oil of an internal combustion engine, in particular a multistroke vane-cell pump, having a rotor and vanes which are at least radially displaceable in rotor slots, whose vane heads slide along a stroke contour, the stroke contour having, among other things, a radial outlet opening, which is closeable by a valve device, the valve device having, according to the present invention, an elastically deformable valve tongue which is mounted on the stroke contour tangentially on the outside in such a way that in the open position in the direction of flow the valve tongue makes an outlet flow in the direction of the intake flow possible by the valve tongue essentially representing a flow guide surface parallel to the outlet flow. According to the present invention, in the closed state the valve tongue essentially assumes the contour shape on the outside of the stroke contour in the area of the outlet opening. Furthermore, a pump is preferable in which the pump tongue is opened by the spring force of the elastic tongue material. It has the advantage that the open valve represents minimum flow resistance and therefore the hydraulic efficiency and the mechanical efficiency of the pump may be substantially improved. 
     A pump according to the present invention is characterized in that the valve tongue is pressed in the closed position from the outside against the stroke contour by an actuator that is adjustable as a function of the temperature and/or an additional spring. The actuator that is adjustable as a function of the temperature and the additional spring are preferably connected in series with regard to the adjustment path and adjustment forces generated by these two elements. Furthermore, the actuator that is adjustable as a function of the temperature is to close the valve device when the temperature increases. 
     In addition, a pump is preferred in which the additional spring is able to hold the pump device closed until a certain pressure is attained. This has the advantage that, in addition to the valve device that is adjustable as a function of the temperature, a pressure limiting function may also be implemented. Furthermore, a pump is preferred in which the spring force of the valve tongue acts against the spring force of the additional spring. In addition, a pump is preferred in which the actuator that is adjustable as a function of the temperature influences the spring pre-tension force of the additional spring. This has the advantage that, depending on the design of the actuator and the additional spring, different pressure limiting levels may be set. Furthermore, a pump is preferred in which the valve device may perform both the function of a valve that is adjustable as a function of the temperature and the function of a pressure limiting valve. This has the advantages that the second stage may be switched on when the temperature increases, while the second stage may be switched off again when a maximum pressure is exceeded. 
     Another pump according to the present invention is characterized in that the valve tongue is attached to the side of the radial outlet opening of the stroke contour through which the vanes pass first. This has the advantage that when the valve tongue is opened, it represents a flow guide surface in the direction of flow in a hydraulically advantageous manner, allowing a low-loss flow pattern to be produced. 
     Furthermore, a pump is preferred in which both the stroke contour and the valve tongue are made of sheet metal, preferably a thin spring steel, and are preferably attached to one another by laser welding, discharge welding, or soldering. 
     A pump is also preferred in which the actuator that is adjustable as a function of the temperature is connected to the valve tongue on one side and is supported by the additional compression spring on the other side. Furthermore, with the actuator that is adjustable as a function of the temperature in the retracted position, the additional compression spring is to hold the valve device closed using minimum pre-tension (minimum pressure limitation). This has the advantage that, at low temperatures, a minimum pressure, for example, of 2 bar, may be maintained for low-loss lubrication and, when the pressure is exceeded, the second stage may be switched to pressureless recirculation to save power. 
     Furthermore, a pump is preferred in which the additional spring maintains the valve device closed using maximum pre-tension with the actuator that is adjustable as a function of the temperature extended (maximum pressure limitation). This has the advantage that, for example, at high temperature, a lubricating oil pressure of 5 bar, for example, may be attained before the second pressure stage is switched to recirculation pressure for power saving. 
     The pump according to the present invention is characterized in that the valve tongue may be pressed against the stroke contour by the actuator that is adjustable as a function of the temperature using a molded element, possibly having an articulation or hinge device. This has the advantage that an absolutely form-fitting sealing of the valve tongue is ensured by the shape of the element. Therefore, a pump is preferred in particular in which the contact surface of the molded element corresponds to the outside contour of the stroke contour. 
     Furthermore, a pump is preferred in which the valve tongue is made from a thermostatic bimetal. This has the advantage that via precise tuning with the actuator switching point, a large force becomes available for opening the second stage and a small force acts against the actuator during closing. 
     Furthermore, a pump is preferred in which the valve tongue is made from a sheet metal strip in the form of an over-dead-center spring having a snap effect. This has the advantage that the counterpressure in pressureless recirculation of the second stage may be substantially reduced again, which results in improved hydraulic mechanical efficiency. The actuator applies the force for closing the valve device, while the static and dynamic pressure of the second stage generates the force for opening. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is now described with reference to the figures. 
         FIG. 1  shows a pump according to the present invention in cross section. 
         FIG. 2  shows an enlarged detail X of  FIG. 1 . 
         FIG. 3  shows an enlarged detail Y, the top view onto the actuator, and the valve tongue. 
         FIG. 4  shows an actuator having a fixedly integrated molded element. 
         FIG. 5  shows an actuator having a movable molded element. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a two-stroke vane-cell pump in cross section. A stroke contour  3  in the form of a sheet metal ring is shown in a pump housing  1 . Stroke contour  3  contains a first pressure outlet  5  and a second pressure outlet  7 , a spring tongue valve  8  being situated at second pressure outlet  7 . In the area of second pressure outlet  7 , stroke contour  3  is interrupted by a radial outlet opening  11 . This outlet opening  11  is closed by valve tongue  9  when actuator  13  that is adjustable as a function of the temperature is extended and valve tongue  9  is pressed against stroke contour ring  3 . Valve tongue  9  is attached to stroke contour ring  3  in area  15 , so that in the open state of the tongue valve illustrated here, unimpeded flow through outlet opening  11  in flow area  17  of the pump may take place. The outflow from area  17 , with valve tongue  9  functioning as a flow guide wall here, is again supplied to the actual rotation unit of the double-stroke vane-cell pump in area  19  of flow channel  23 , which surrounds contour ring  3 , through a radial intake opening  21  in contour ring  3 . The other elements of a double-stroke vane-cell pump such as the rotor and the vanes are not depicted here, but are known from the related art and are not further elucidated here for the sake of simplicity. It is essential for the present invention that, for reducing the flow resistance and optimizing the flow direction in area  17  of flow channel  23 , valve tongue  9  made of a thin spring metal sheet is attached to sheet metal stroke contour ring  3  in area  15  by laser welding, for example. This valve tongue is therefore attached to the side of outlet opening  11  and of outlet area  7  of stroke contour  3  which the vanes pass by first in the direction of rotation. The flow is thus directed into intake channel  23  when the tongue valve is open. The complete channel cross section is thus available for the flow in area  17  when the tongue valve is open. This results in minimum flow resistance. 
     To close outlet opening  11 , actuator  13  that is adjustable as a function of the temperature is provided, which here in  FIG. 1  is directly connected to valve tongue  9 . On its other side, actuator  13  is supported by an additional spring  25 . Spring  25  is selected in such a way that when actuator  13  is retracted, there is a minimum pre-stress by the valve in the closed state, which is not depicted here in  FIG. 1  this time. This means that the actuator is retracted, but additional spring  25 , together with the actuator, presses spring tongue  9  against outlet opening  11 . The minimum pre-stress may correspond, for example, to an outlet pressure of 2 bar, and as soon as this outlet pressure is exceeded in the pump, the pressure is able to press the spring tongue valve into the open position depicted in  FIG. 1  and thus press actuator  13  into the position depicted here against the pre-stress force of spring  25 . The setpoint of the minimum pressure limitation is thus exceeded in  FIG. 1 . The equilibrium of forces acting on the valve device in  FIG. 1  is made up of the pre-stress of compression spring  25  less the restoring effect by the spring force of valve tongue  9 . The pressure force of the hydraulic medium in outlet area  7  and possibly the forces applied by the flow act supportively in the opening direction. If actuator  13  is extended due to the increase in the lubricating oil temperature, spring tongue  9  of the tongue valve is pressed against stroke ring  3  on one side, but also the pre-stress force of spring  25  increases due to extending actuator  13 , and outlet opening  11  of the switchable pump stage is closed. Because the pre-stress of spring  25  has now been increased, the corresponding pumping pressure is unable to press spring tongue  9 , together with extended actuator  13 , against the force of spring  25  again in the direction of opening and thus to perform the function of maximum pressure limitation until a pressure of 5 bar, for example, is reached. Therefore, according to the present invention, a superimposition of functions of two different pressure limiting stages is combined with a temperature adjustability by closing outlet opening  11  when the temperature increases. The maximum pressure limitation of 5 bar, for example, is implemented by actuator  13  via the overstroke effect because the actuator extends further as the temperature continues to rise, and thus the pre-stress of additional spring  25  further increases until this spring force pre-stress corresponds to the maximum pressure of 5 bar, for example. The exact temperature adjustment and pressure points may, of course, be varied according to the present invention for the different requirements in the motor vehicles. One advantage of this valve device according to the present invention compared to the related art is that a restoring spring present in the latter may be omitted. Furthermore, spring  25 , which in this case assumes the function of the overstroke spring, may have a more compact design because this system allows the valve device to be opened at lower pressures. 
     When an engine is stopped after it has properly warmed up (both pressure stages of the double-stroke vane-cell pump have pumped), the reduction in temperature causes actuator  13  to retract. The restoring forces needed therefore are applied by compression spring  25 , which initially compresses actuator  13 . Because the pre-stress of spring  25  decreases with the retraction of actuator  13 , an intermediate position caused by hysteresis may result. This is, however, beneficial for the next cold start of the pump because the higher pre-stress results in a start using both pump stages. As soon as the second pump stage has built up pressure, the actuator hysteresis is overcome and the actuator retracts entirely. 
     Actuator  13  is positioned in relation to spring tongue  9  as a function of a diagram of forces. It may be convenient to place actuator  13  in such a way that it braces spring tongue  9  against stroke ring  3 . To do so, a bearing device must be provided between actuator  13  and spring tongue  9 , as depicted in  FIG. 2 . It is thus possible to produce this form-fitting bearing device via a sphere  27  on actuator  13 , for example, and a corresponding receptacle on spring tongue  9 .  FIG. 3  shows a bearing device between actuator  13  and spring tongue  9  in top view. 
     In another variant according to the present invention, spring tongue  9  is pressed onto stroke ring  3  with the aid of an additional molded element  29  ( FIGS. 4   a  and  4   b ). This molded element  29  may be manufactured from different materials, preferably from plastic, and its contact surface for spring tongue  9  corresponds to the outer contour of stroke ring  3 . Spring tongue  9  is then bent by molded element  29  and pressed onto contour ring  3 . Molded element  29  is rigidly connected to actuator  13 . 
       FIG. 5  shows an embodiment which may be necessary for reasons of installation space. Molded element  31  is mounted movably with respect to actuator  13  and may thus be rotated away from stroke contour ring  3 . This results in a fully open flow cross section in discharge area  17  of the valve device. In both specific embodiments in  FIGS. 4 and 5 , a power-saving discharge in intake area  23  of the double-stroke vane-cell pump is ensured by spring tongue  9 , which represents a tangential flow guide plate for the discharge flow. 
     Another alternative according to the present invention lets molded element  29  or  31  close or open outlet opening  7  directly, without a spring tongue  9  installed in-between. To achieve an appropriate sealing effect, molded element  29  or  31  may be made of an elastomer for this purpose. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  pump housing 
           3  stroke contour 
           5  first pressure outlet 
           7  second pressure outlet 
           8  spring tongue valve 
           9  valve tongue 
           11  radial outlet opening 
           13  actuator that is adjustable as a function of the temperature 
           15  valve tongue attachment area 
           17  flow area around the stroke contour 
           19  flow channel intake area 
           21  radial intake opening 
           23  flow channel 
           25  additional spring 
           27  spherical bearing device on actuator 
           29  additional molded element on actuator 
           31  movably mounted molded element