Patent Publication Number: US-2013243571-A1

Title: Controllable coolant pump with a multi-part modular construction

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The following documents are incorporated herein by reference as if fully set forth: German Patent Application No. 102012204044.7, filed Mar. 15, 2012. 
     BACKGROUND 
     The invention relates to a controllable coolant pump for an internal combustion engine and also to a method for its assembly. 
     The coolant pump of a fluid-cooled internal combustion engine has the problem of effectively supporting the circulation of the coolant guided through cooling channels of the crankcase and the cylinder head. The coolant circuit can be expanded, for example, by a coolant loading of an air conditioning unit, a charge air cooler, fuel cooler, and/or lubricant cooler connected advantageously in series. Preferably, the coolant pump is driven directly by means of a belt drive. Through a direct coupling between the coolant pump and the crankshaft, a dependency of the pump rotational speed on the rotational speed of the internal combustion engine is set. From this it follows that, during a cold start of the internal combustion engine, the coolant circulates but a desired quick heating of the internal combustion engine and an optimum operating temperature associated with this is delayed. In the course of continuous optimization of internal combustion engines with respect to emissions and fuel consumption, there is the goal to bring the engine as quickly as possible to the operating temperature after a cold start. This reduces both the friction losses and also the emission values and also decreases fuel consumption. To achieve this effect, controllable coolant pumps are suitable whose displaced volume flow can be tuned to the cooling needs of the internal combustion engine. 
     From DE 199 01 123 A1 it is known as a measure to influence the displacement volume of a coolant pump to allocate an outer, overlapping slide to the impeller, wherein the effective vane width of the impeller can be changed by this slide and this slide is continuously adjustable in the axial direction. The adjustment of the slide is realized by the turning of a thread-like guide. DE 10 2005 004 315 A1 and DE 10 2005 062 200 A1 disclose controllable coolant pumps in which, for influencing the displacement amount within the pump housing, a valve slide is used that can move in the direction of the pump shaft axis. The annular valve slide forms an outer cylinder variably covering the outflow area of the impeller. According to DE 10 2005 004 315 A1, the valve slide also to be designated a guide plate is adjusted electromagnetically with a magnetic coil arranged in the pump housing. Alternatively, for adjusting the valve slide according to DE 10 2005 062 200 A1, an actuator is provided that is actuated pneumatically or hydraulically and includes push rods guided in the pump housing for adjusting the valve slide. These known coolant pumps have in common a one-part pump shaft. 
     SUMMARY 
     The objective of the present invention it to create a construction of a controllable coolant pump with which the function can be improved and the assembly of individual components of the coolant pump can be simplified. 
     This is achieved by a coolant pump and by a method for the assembly of the coolant pump according to one or more features of the invention. Preferred refinements of the invention are described below and in the claims. 
     The invention provides a construction and an arrangement to achieve a structural simplification of the controllable coolant pump For this purpose, an at least two-part pump shaft is provided, wherein the individual pump shaft sections form one module with the associated components. The individual modules are joined permanently by an interference fit via interfaces for forming a pump shaft before this can be inserted into the pump housing. The interfaces between the individual modules also to be called assemblies are here preferably provided in the wet area of the coolant pump. According to the invention, an actuation unit also to be called an actuator or actuating mechanism is provided whose displacement pump constructed, in particular, as an axial piston pump or radial piston pump is allocated directly to a section of the pump shaft, i.e., a module. Advantageously, the construction according to the invention offers the ability to design individual components of the modules under consideration of special requirements in the installation state or in the operating state of the coolant pump. Furthermore, for producing individual module components and for joining the modules, the optimal methods can be used. In addition, the concept according to the invention, the multiple parts of the pump shaft including the actuation unit, offers the ability for special components connected directly to the pump shaft to have different structural shapes. For example, individual sections of the pump shaft can have different diameters or can be shaped to simplify the assembly and the loading, durability, and function of the actuation unit or the pump shaft and consequently the coolant pump can be improved. Advantageously, the concept according to the invention for the multi-part pump shaft is neutral in terms of the installation space and can be integrated in an assembly-friendly way for the most extent without much adjustment to the installation space of conventional coolant pumps. Furthermore, the pump shaft according to the invention can be constructed economically from standardized components. 
     According to one refinement of the invention, a pump shaft comprising two modules is provided, wherein the modules are joined by an interface set between the displacement pump and the impeller. A first module includes a sub-shaft to which the water pump bearing, a slide ring seal, and also, of the actuation unit, a displacement pump and a pump outlet valve are allocated. This construction promotes the assembly of a displacement pump constructed especially as a radial piston pump due to good accessibility. The other module that can be preassembled is formed from an impeller shaft, the impeller, and also the guide plate device that includes of a guide plate, piston, and push rods and interacts with the actuation unit. The sub-pumps or pump shaft modules that can be preassembled can be joined in a simplified way to one overall assembly, the pump shaft. 
     According to one alternative, two-part construction of the pump shaft according to the invention, the first module is formed from the sub-shaft, the roller bearings, and the slide ring seal. The additional module includes both the actuation unit and also the guide plate device. The displacement pump of the actuation unit is inserted according to this pump shaft construction in an end-side section of the impeller shaft, wherein advantageously an extended radial guidance of the displacement pump is set. This installation position of the displacement pump also causes a changed position of the interface between the sub-shaft and the impeller shaft on the slide ring seal side of the displacement pump. The interface is formed by a diameter-reduced shaft projection of the impeller shaft that is pressed with a non-positive fit into a recess of the sub-shaft. This two-part pump shaft arrangement advantageously allows a larger structural shape clearance in the design of the actuation unit. In addition to a radial guide length improving the displacement pump constructed as a radial piston pump, a shortened axial overall length of the pump shaft is also set, due to a radial position overlap between the slide ring seal and the shaft sections that are pressed together in the area of the interface. Furthermore, the concept according to the invention offers the ability to use an impeller shaft with an increased outer diameter, wherein consequently a correspondingly larger piston diameter of the guide plate device can be realized advantageously. 
     The invention further comprises another divided pump shaft that includes three modules assembled via two interfaces. The first module is here formed by the sub-shaft with the associated roller bearings and the slide ring seal. A second module comprises an intermediate shaft to which a radial piston pump and the pump outlet valve of the actuation unit are allocated. Due to the increased diameter of the intermediate shaft relative to the sub-shaft, an advantageously larger guide length for the radial piston pump is set in the radial direction. The third module includes the impeller shaft with associated impeller and the guide plate device consisting of the guide plate, piston, and push rods and interacting with the actuation unit. The following module arrangement provides an alternative pump shaft construction including three modules. The first module comprises the sub-shaft in which an axial piston pump of the actuation unit is integrated in an installation space-optimized manner. The water pump bearing and the slide ring seal are also allocated to the sub-shaft. The other second module includes the intermediate shaft and the pump outlet valve of the actuation unit. A third module is formed by the impeller shaft, the impeller, and the guide plate device of the actuation unit that consists of the guide plate, the piston, and the push rods. 
     Preferably, the modules or their shafts, the sub-shaft, the impeller shaft, and/or the intermediate shaft are joined permanently in the area of the interfaces by an interference fit with non-positive and positive fit connection. As an alternative or addition to the non-positive fit interference connection, a material fit connection can be provided by bonding or welding in the area of the interfaces. It is further provided according to the invention to introduce into the impeller shaft, at the end side, a central, pocket hole-like recess forming a cylinder that is designed for holding a piston interacting with the actuation unit. In the area of the interface, the impeller shaft is connected to the intermediate shaft or the sub-shaft by an interference fit. For this purpose, the impeller shaft encloses an end-side section of the associated shaft. For constructing the interface between the drive shaft and the intermediate shaft, the intermediate shaft forms a receptacle or a central projection extending in the axial direction. For the non-positive fit coupling, the associated sub-shaft can be pressed with one end section into the intermediate shaft receptacle. As an alternative, a projection of the intermediate shaft can be fit as an interface with a non-positive connection into a corresponding opening in the sub-shaft. 
     A preferred construction of the invention further provides that the diameter of the piston of the guide plate device corresponds to or exceeds the diameter of the sub-shaft or the intermediate shaft. For example, this structural principle has the effect, for a two-part pump shaft, of increasing the piston diameter corresponding to two wall thicknesses of the impeller shaft, which corresponds, in surface area, to an increase by a factor of 1.5-2.0. An increased piston diameter reduces the load on the upstream displacement pump that thus can be advantageously dimensioned more economically and smaller and consequently requires less installation space. Advantageously, in this way the actuation or adjustment force for the guide plate adjustment is increased or if necessary the reaction force is reduced on the actuation unit of the displacement pump. In a pump shaft including three modules in which an end area of the intermediate shaft is enclosed by the impeller shaft, a piston surface can be realized that is increased by a factor of 3-4 relative to a one-part pump shaft. Alternatively, a pump shaft with three modules is provided in which, within the sub-shaft, a displacement actuation pump constructed as an axial piston pump is integrated. In this construction, due to an increased distance to the slide ring seal, the intermediate shaft can be connected to the sub-shaft via an outer interference connection. This measure also allows the diameter to be adapted to the impeller shaft, in order to increase the piston diameter and thus the piston surface area. 
     As a safety measure in the case of an emergency, the invention includes a fail-safe device for the actuation unit. For this purpose, in the cylinder of the impeller shaft there is a compression spring that loads the piston in the direction of the pump outlet valve. For example, after a loss of the hydraulic circuit of the actuation unit, the activated fail-safe device has the effect that the compression spring returns the piston to its original position. At the same time, the guide plate connected to the piston via the push rod is moved into a position in which the largest possible impeller cross section is set, guaranteeing a maximum volume flow of the coolant pump. 
     For the assembly or completion of the coolant pump, a method including the following steps is provided. First the pump housing of the coolant pump is positioned or aligned. Then the individual modules of the pump shaft are preassembled, wherein each module comprises a shaft section or an intermediate shaft and also other components allocated to the pump shaft. Advantageously, here the displacement pump constructed as a radial piston pump in the actuation unit is held together during assembly by means of a tensioning band. Then force is applied to two or three modules by means of a pressing tool to form one pump shaft. Finally, the pump shaft is inserted, aligned, and fixed in a final position of the pump housing, before the belt pulley is fixed on the sub-shaft and an impeller cover is fixed on the opposite side of the coolant pump. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       The invention is explained below using preferred embodiments with reference to the accompanying figures. Shown are: 
         FIG. 1  is a schematic diagram of a controlled coolant pump with a single-part pump shaft, 
         FIG. 2  is a view of a controlled coolant pump according to  FIG. 1  with a first embodiment of a two-part pump shaft according to the invention, 
         FIG. 3  is a view of a second embodiment of a controlled coolant pump according to the invention with a two-part pump shaft as an alternative to  FIG. 2 , 
         FIG. 4  is a view of a controlled coolant pump according to  FIG. 1  with a third embodiment of a three-part pump shaft according to the invention, and 
         FIG. 5  is a view of a fourth embodiment of a controlled coolant pump according to the invention with a three-part pump shaft as an alternative to  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     In  FIG. 1 , all of the components of a controlled coolant pump  1  are shown in a schematic diagram, wherein this coolant pump is designed, in particular, for cooling an internal combustion engine and is driven by means of a traction mechanism drive of which a belt wheel  3  connected to a pump shaft  2  is shown. The pump shaft  2  is supported by a roller bearing  4  so that it can rotate in a pump housing  5  and is sealed by a slide ring seal  6 . A guide plate  13  that can move in the axial direction is allocated to a rotationally locked impeller  10  connected to the pump shaft  2 . A volume flow supplied by the coolant pump  1  is adjustable with this guide plate. For adjusting the guide plate  13 , an actuation unit  15  is provided with associated displacement pump  17  and a pump outlet valve  18  that interacts with a guide plate device  20  including the guide plate  13 , a push rod  23 , a piston  24 , and a compression spring  21 . For generating pressure, a cam rotating with the pump shaft  2  applies a force on a not-shown piston that oscillates in a pressure space in the displacement pump  17  constructed as a radial piston pump that is fixed in position in the pump housing  5 . Between the pressure space of the displacement pump  17  and a cylindrical high-pressure space  22  formed in the pump shaft  2  there is a pressurized medium connection not shown in  FIG. 1 . A guide plate adjustment is performed as soon as a flow of pressurized medium generated by the displacement pump  17  loads the high-pressure space  22  of the pump shaft  2  formed as a cylinder  12  via the opened pump outlet valve  18 . In this way, the piston  24  inserted therein is moved in the direction of the arrow that is connected to the guide plate  13  via the push rod  23 . Starting from the shown neutral or starting position of the guide plate  13  in which the impeller  10  supplies the maximum volume flow, the guide plate  13  can be adjusted up to an end position in which the impeller is completely covered on the outside. In the high-pressure space  22  of the pump shaft  2  there is also a compression spring  21  forming a fail-safe device  25  and applying a force on the piston  24  in the direction opposite the arrow. In an emergency, for example, for a loss of the actuation unit  15 , the compression spring  21  automatically moves the piston  24  in the direction opposite the arrow and at the same time moves the guide plate  13  into the position shown in  FIG. 1 . 
       FIGS. 2 to 4  show the coolant pump  1  with multi-part pump shafts  7 ,  7 ′,  7 ″ as an alternative to a one-part pump shaft. Here, the components matching those of  FIG. 1  are provided with the same reference symbols and are not described comprehensively below. 
       FIG. 2  shows a first embodiment of a multi-part pump shaft  7  according to the invention that is assembled from modules  30 ,  31  including all of the associated components. Here, the module  30  is formed from a sub-shaft  27  together with the belt pulley  3 , the roller bearings  4 , the slide ring seal  6 , the displacement pump  17 , and the pump outlet valve  18  of the actuation unit  15 . The additional module  31  is formed from the impeller shaft  28  and the guide plate device  20  including the compression spring  21 . The modules  30 ,  31  are connected by an interface  35  in which the sub-shaft  27  is pressed with one end section into the impeller shaft  28  and simultaneously borders the high-pressure space  22  formed as cylinder  12  in the impeller shaft  28 . 
     An alternative two-part pump shaft  7  is shown in  FIG. 3  in which the module  30  is made from the components, the sub-shaft  27 , the roller bearings  4 , and the slide ring seal  6 . The additional module  31  includes the actuation unit  15  and comprises, among other things, the displacement pump  17  and the guide plate device  20 . The displacement pump  17  is inserted in an end-side section of the impeller shaft  28 , wherein an extended radial guide of the displacement pump  17  is set. This displacement pump position has the result that the interface  35  set between the sub-shaft  27  and the impeller shaft  28  is displaced toward the side of the displacement pump  17  directed toward the slide ring seal  6 . The impeller shaft  28  consequently forms a diameter-reduced shaft projection  14  pressed into a recess  19  of the sub-shaft  27  with a non-positive fit. Through a radial overlap of the position between the slide ring seal  6  and the shaft sections that are pressed together and form the interface  35 , a compact pump shaft  6  with a shortened axial structural length is set. 
       FIG. 4  shows a three-part pump shaft  7 ′ comprising the modules  30 ′,  31 ′,  32 ′. The sub-shaft  27 ′ together with the belt pulley  3 , the roller bearings  4 , and the slide ring seal  6  form the module  30 ′. The additional module  31 ′ comprises, comparable to  FIG. 2 , the impeller shaft  28 ′ and the guide plate device  20  including the compression spring  21 . In the high-pressure space  22 ′ with larger dimensions in the cylinder  12 ′ of the impeller shaft  28 ′, a piston  24 ′ with a diameter D 2  is guided that exceeds the diameter D 1  of the sub-shaft  27 ′. The modules  30 ′,  31 ′ bound the module  32 ′ that includes an intermediate shaft  29 ′ and the displacement pump  17 ′ and the pump outlet valve  18  of the actuation unit  15 ′. The modules  31 ′ and  32 ′ are connected via the interface  35 ′ in that the intermediate shaft  29 ′ is pressed with one end section into the high-pressure space  22 ′ of the impeller shaft  28 ′. The interface  37 ′ of the modules  30 ′ and  32 ′ is formed by a projection  39  that extends in the axial direction and is fit into a central opening  41  of the sub-shaft  27 ′ with non-positive and positive fit connections. 
     In  FIG. 5 , an alternative pump shaft  7 ″ including three modules  30 ″,  31 ″,  32 ″ is shown. Here, the module  30 ″ is made from the sub-shaft  27 ″, the belt pulley  3 , the roller bearings  4 , and the slide ring seal  6 , wherein a displacement pump  17 ″ constructed as an axial piston pump in the actuation unit  15 ″ is integrated in the sub-shaft  27 ″. The module  31 ″ is built matching the module  31 ′ according to  FIG. 3 . The module  32 ″ arranged between the modules  30 ″ and  31 ″ includes the intermediate shaft  29 ″ and the pump outlet valve  18 . The modules  31 ″ and  32 ′ are pressed in the area of the interface  35 ″ with a non-positive fit, comparable to the interface  35 ′ according to FIG.  3 ″. The other interface  37 ″ between the modules  30 ″ and  32 ″ comprises a receptacle  43  of the intermediate shaft  29 ″ in which an end section of the sub-shaft  27 ′ is pressed. 
     LIST OF REFERENCE NUMBERS 
     
         
         
           
               1  Coolant pump 
               2  Pump shaft 
               3  Belt wheel 
               4  Roller bearing 
               5  Pump housing 
               6  Sliding ring seal 
               7 ,  7 ′,  7 ″ Pump shaft 
               10  Impeller 
               12 ,  12 ′,  12 ″ Cylinder 
               13  Guide plate 
               14  Shaft projection 
               15 ,  15 ′,  15 ″ Actuation unit 
               17 ,  17 ′,  17 ″ Displacement pump 
               18  Pump outlet valve 
               19  Recess 
               20  Guide plate device 
               21  Compression spring 
               22 ,  22 ′,  22 ″ High-pressure chamber 
               23  Push rod 
               24 ,  24 ′,  24 ″ Piston 
               25  Fail-safe device 
               27 ,  27 ′,  27 ″ Sub-shaft 
               28 ,  28 ′Impeller shaft 
               29 ′,  29 ″ Intermediate shaft 
               30 ,  30 ′,  30 ″ Module 
               31 ,  31 ′,  31 ″ Module 
               32 ′,  32 ″ Module 
               35 ,  35 ′,  35 ″ Interface 
               37 ′,  37 ″ Interface 
               39  Projection 
               41  Depression 
               43  Receptacle