Patent Publication Number: US-2012037828-A1

Title: Valve for controlling a flow

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a valve for controlling a flow of a medium in a heating system and/or cooling system of a motor vehicle. 
     A cooling system and/or heating system of a motor vehicle generally includes a heat source which is to be cooled, for example a vehicle engine, which is to be cooled by means of a cooling medium through free or forced convection. The heating performance or cooling performance is dependent here on the size of the flow of coolant. 
     The heat conducted away from the heat source by the coolant can simultaneously be used to heat a passenger compartment. For this purpose, heating circuits and cooling circuits of modern motor vehicles generally have different sub-circuits, for example a radiator branch, a bypass branch and/or a heating heat-exchanger branch. The distribution of the stream of coolant among the different branches of the cooling circuit and heating circuit is controlled here by means of at least one valve. Such a valve is known, for example, from DE 10 2006 053 307 A1. In the valve described in said document, application of pressure on one side causes hydraulic forces to bring about an axial displacement of the valve body in the direction of a transmission cover, as a result of which a frictional torque is increased. This leads to a situation in which a movement of the valve body is made more difficult. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to make available an improved valve for controlling a flow of a medium in a heating system and/or cooling system of a motor vehicle. 
     A valve according to the invention for controlling a flow of a medium in a heating system and/or cooling system of a motor vehicle comprises a valve housing which has at least a first duct, and a regulating disk which is provided for opening and closing the first duct. In this context, the regulating disk is arranged at a first end of a rotatably mounted drive shaft which extends from the regulating disk through an axial opening in the valve housing into a spring space which is arranged in the valve housing. In this context, a second end of the drive shaft which is arranged in the spring space has a spur gear. Furthermore, a spring whose first end is supported on the valve housing and whose second end is supported on the spur gear is arranged in the spring space. 
     A spring with a relatively flat spring characteristic curve can advantageously be used here. As a result, the sealing function of the valve can be ensured even when there are relatively large tolerances of the installed components. Furthermore, an advantageous relatively constant frictional torque is achieved between the regulating disk and the duct independently of an application of pressure on both sides of the regulating disk and independently of a direction of flow through the valve. 
     The spring is advantageously embodied as a helical spring, wherein the drive shaft runs through the spring. As a result, a spring force is advantageously applied symmetrically to the drive shaft. 
     The spring preferably has a spring constant between 5 N/mm and 25 N/mm. Such a relatively low spring constant advantageously gives rise to a relatively constant frictional torque between the regulating disk and a seal of the first duct. 
     According to one development of the valve, an end side of the spur gear has a circumferential groove in which an annular run-up disk is arranged. In this context, the second end of the spring is supported on the run-up disk. This advantageously reduces a friction force occurring between the spring and the spur gear. 
     According to an additional development of the valve, a first sealing bushing is arranged at an end, facing the regulating disk, of the first duct, which sealing bushing is supported against the valve housing via a first sealing ring. In this context, the regulating disk is pressed against the first sealing bushing by the spring. This advantageously makes possible a cost-effective and reliable seal of the first duct. 
     The first sealing ring preferably has a cross-shaped cross section. The sealing ring then advantageously seals both when pressure is applied to the valve from the regulating disk side and when pressure is applied from the duct side. The valve is therefore suitable for both flow directions. 
     The spring expediently generates a pressure per unit surface area between 0.1 N/mm 2  and 0.5 N/mm 2  between the regulating disk and the first sealing bushing. From experience, this has advantageously been found to be a favorable compromise between a reliable seal of the first duct and freely moving rotatability of the regulating disk. 
     In one development of the valve, a bearing bushing is arranged in the axial opening and the drive shaft is led through the bearing bushing. 
     The valve housing can preferably be connected to an external housing in such a way that a transportation path which can be closed off by the regulating disk is produced for the medium between the first duct and the external housing. The valve can then advantageously be connected either to an external housing which has a further duct or directly to a housing of the heat source which is to be cooled, for example the vehicle engine. 
     In one preferred embodiment of the valve, the valve housing has a second duct, wherein the regulating disk is provided for opening and closing the first and/or the second duct. The valve can then advantageously be used to distribute the medium among different branches of the heating system and/or cooling system. 
     A second sealing bushing is expediently arranged at an end of the second duct facing the regulating disk, said sealing bushing being supported against the valve housing by means of a second sealing ring. In this context, the regulating disk is pressed against the second sealing bushing by the spring. Furthermore, the first and the second sealing rings are composed of the same material and have essentially the same height. This advantageously provides a uniform seal both of the first and of the second duct. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be explained in more detail with reference to the appended figures, in which: 
         FIG. 1  is a schematic view of a valve  100 , and 
         FIG. 2  is a schematic view of a regulating disk. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic view of a section through a valve  100 . The valve  100  can serve to control a flow of a medium in a heating system and/or cooling system of a motor vehicle. The medium is expediently a liquid with a high thermal capacity, for example water. The heating system and/or cooling system can serve to cool a heat source of the motor vehicle, for example a vehicle engine, and/or to heat a passenger compartment of the motor vehicle. 
     The valve  100  comprises a valve housing  110  which has a first duct  140  and a second duct  150 . The first duct  140  and the second duct  150  serve to connect lines of the heating system and/or cooling system in which the medium circulates. One of the two ducts  140 ,  150  can also be dispensed with. 
     The valve housing  110  also has a coupling connection  130  which has the shape of an annular flange in the illustrated example. The valve housing  110  can be connected, for example bonded or screwed, in a seal-forming fashion to an external housing by means of the coupling connection  130 . The external housing can be a housing cover which fits the valve housing  110  and has a further coolant duct. The external housing can, however, also be a housing of the heat source to be cooled, for example a housing of the vehicle engine. The medium can flow from the external housing into the first duct  140  and/or the second duct  150  or from the first duct  140  and/or the second duct  150  into the external housing. 
     A regulating disk  170 , which preferably has a circular cross section and serves to open and close a connection between the external housing and the first duct  140  and the second duct  150 , is arranged inside the coupling connection  130 .  FIG. 2  is a schematic view of the regulating disk  170 . The regulating disk  170  has a plurality of regulating openings  171 . Depending on the axial rotational angle of the regulating disk  170 , one of the regulating openings  171  is arranged between the external housing and the first duct  140  or the external housing and the second duct  150 . By turning the regulating disk  171  it is therefore possible to open and close connections between the external housing and the first duct  140  and/or the second duct  150 . Furthermore, the respective opening cross section can be varied by turning the regulating disk  170 . The flow of medium can be controlled by changing the opening cross section. 
     The valve housing  110  also has an axial opening  160  which extends from the regulating disk  170  through the valve housing  110  as far as an outer side of the valve housing  110  which is arranged between the first duct  140  and the second duct  150 . In a part of the axial opening  160  which faces the regulating disk  170  a cylindrical-casing-shaped bearing bushing  210  is arranged. A part of the axial opening  160  which faces away from the regulating disk  170  is widened to form a spring space  230 . The axial opening  160  which forms the spring space  230  is closed off with a transmission cover  220  on the outer side of the valve housing  110  arranged between the first duct  140  and the second duct  150 . 
     An essentially cylindrical drive shaft  180  extends from the regulating disk  170  through the bearing bushing  210  into the spring space  230 . The end of the drive shaft  180  facing the regulating disk  170  penetrates the regulating disk  170  perpendicularly in a center of the regulating disk  170  and is rigidly connected to the regulating disk  170 . Rotation of the drive shaft  180  about its longitudinal axis therefore brings about a rotation of the regulating disk  170  about its central axis. 
     At its end arranged in the spring space  230 , the drive shaft  180  has a spur gear  190 . The spur gear  190  is in engagement with a worm  200  which is arranged in the valve housing  110  and which is connected to a drive mechanism, for example a motor. The drive shaft  180  can be turned about its longitudinal axis by means of the worm  200  and the spur gear  190 . 
     An end side, facing the bearing bushing  210 , of the spur gear  190  has an annular groove  260  which runs around the drive shaft  180 . An annular run-up disk  270  is arranged in the groove  260 . Furthermore, a spring  240 , which is preferably embodied as a helical spring, is arranged in the spring space  230 . The drive shaft  180  runs axially through the spring  240 . A first end of the spring  240  is supported against a section, surrounding the bearing bushing  210 , of the valve housing  110 . A second end of the spring  240  is supported against the spur gear  190  by means of the run-up disk  270 . The spring  240  applies a force, acting in the direction of the transmission cover  220 , to the drive shaft  180 , by means of which force the regulating disk  170  is pressed in the direction of the first duct  140  and of the second duct  150 . The run-up disk  270  serves to reduce friction between the spring  240  and the spur gear  190 , said friction occurring in the case of a rotation of a drive shaft  180  around its longitudinal axis. The run-up disk  270  and the groove  260  can also be dispensed with. In this case, the second end of the spring  240  is supported directly on the spur gear  190 . 
     An end, facing the regulating disk  170 , of the second duct  150  has a cylindrical-casing-shaped sealing bushing  280  which is supported by means of an annular sealing ring  290  against a section, forming the second duct  150 , of the valve housing  110 . The force which is applied to the drive shaft  180  by the spring  240  presses the regulating disk  170  against the sealing bushing  280 , said sealing bushing  280  being supported against the valve housing  110  by means of the sealing ring  290 . The sealing bushing  280  and the sealing ring  290  bring about a seal of the junction region between the second duct  150  and the regulating disk  170 . The end, facing the regulating disk  170 , of the first duct  140  also has a sealing bushing  280  which is supported by means of a sealing ring  290  and by which the junction region between the first duct  140  and the regulating disk  170  is sealed. In order to ensure a uniform seal of the junction regions between the regulating disk  170  and the first duct  140  or the second duct  150 , the sealing rings  290  and the sealing bushings  280  of the first duct  140  and of the second duct  150  each have the same height in the axial direction. The two sealing bushings  280  and the two sealing rings  290  are preferably each composed of the same material and have the same hardness. The two sealing bushings  280  and the two sealing rings  290  are particularly preferably each manufactured by means of the same tool. 
     The spring  240  preferably has a relatively flat spring characteristic curve with a spring constant between 5 N/mm and 25 N/mm. This has the advantage that the force with which the regulating disk  170  is pressed against the sealing bushing  280  fluctuates only to a slight degree due to the tolerances of the components which determine the axial installation space of the spring  240 . This in turn results in a relatively constant necessary rotational torque of the regulating disk  170  against the sealing bushings  280  and therefore also in a relatively constant driving torque of the motor. 
     The spring preferably generates a pressure per unit surface area between 0.1 N/mm 2  and 0.5 N/mm 2  between the regulating disk  170  and the sealing bushings  280 . 
     The sealing rings  290  are expediently embodied in such a way that they support both internal pressure and external pressure in order to permit use of the valve  100  for both flow directions. The sealing rings  290  then bring about a reliable seal of the junction regions between the first duct  140  and the regulating disk  170  and respectively between the second duct  150  and the regulating disk  170 , both for the case in which a higher pressure is applied to the first duct  140  and to the second duct  150  than to the side of the regulating disk  170  facing the external housing and for the case in which a lower pressure is applied to the first duct  140  and to the second duct  150  than to the side of the regulating disk  170  facing the external housing. This can be achieved, for example, by using sealing rings  290  with a cross-shaped cross section.