Patent Publication Number: US-8539915-B2

Title: Cooling system for a motor vehicle

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims priority to German patent application DE 10 2009 007 695.6 filed on Feb. 5, 2009, which is hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a cooling system in a motor vehicle with a cooling circuit in which at least one internal combustion engine, one pump and one cooling device are arranged. 
     BACKGROUND 
     Owing to steadily rising energy prices and increasingly stricter emission values, vehicle manufacturers are increasingly trying to reduce the energy consumption of their motor vehicles, in particular the energy consumption which is not directly used to drive the motor vehicle. This includes in particular energy consumption while idling as well as the energy consumption of various electrical consumers within the motor vehicle. 
     The present invention is concerned with the problem of creating a cooling system in a motor vehicle, which has a much lower energy requirement compared to previously known cooling systems. 
     This problem is solved according to the invention by the subject matter of the independent claim  1 . Advantageous embodiments form the subject matter of the dependent claims. 
     The present invention is based on the general idea of, in a cooling system with a cooling circuit in which at least one consumer to be cooled, for example an internal combustion engine, one pump and one cooling device are arranged, connecting a pressure side and an intake side of the pump by means of a short circuit line, that is, by means of a bypass line, which is opened when cooling is not necessary and thereby conducts at least most of a coolant flow no longer through the internal combustion engine and the whole cooling circuit but diverts it into a short circuit with much less resistance. In order to divert or divide the coolant flow to the internal combustion engine or to the short circuit line which bypasses the pump, a valve device is used, which requires much reduced actuation forces owing to the short circuit line which is now present and thereby can be configured to be smaller and also more economical with regard to energy consumption. The valve device according to the invention is arranged in the region of the short circuit line, for example in the region of a branch of the short circuit line from the cooling circuit or in the region of a junction of the short circuit line into the cooling circuit. Furthermore, the valve device according to the invention can be switched between at least two positions, wherein in the first position at least most of the coolant flow flows through the short circuit line and in the second position at least most of the coolant flow flows through the internal combustion engine and not through the short circuit line. Any desired intermediate positions which allow any desired division of the coolant flow between the actual cooling circuit and the short circuit are of course also conceivable. If for example no cooling effect is needed in the internal combustion engine or another consumer to be cooled, the valve device can be moved into its first position and thereby the cooling medium can be pumped through the short circuit with comparatively low resistance. With the valve device according to the invention which is arranged in the region of the short circuit line, it is thus possible to control the cooling demand in the internal combustion engine and thus also the output of the coolant pump in a relatively flexible manner. If the internal combustion engine does not need cooling, the valve device is then simply moved into its first position so that at least most of the coolant flow flows through the short circuit line and no longer through the internal combustion engine or the cooling device. 
     SUMMARY 
     In an advantageous development of the solution according to the invention, the valve device is configured as a proportional valve. Compared to a valve device which can be switched to and from between only two positions, such a proportional valve has the great advantage that it can be switched into any desired intermediate positions, as a result of which a virtually freely selectable division of the coolant flow flowing through the internal combustion engine and the short circuit line is possible. This allows particularly precise control which prevents in particular the pressure peaks when switching between the two positions, which are typical for a valve which can be switched to and from between only two positions. Actuation of the valve device according to the invention can for example take place by means of an engine control unit which is present in any case and, in addition to the operating state of the internal combustion engine which occurs in each case, for example full load or partial load, also detects a temperature of the cooling medium. 
     Further important features and advantages of the invention can be found in the subclaims, the drawings and the associated description of the figures using the drawings. 
     It is self-evident that the features which are mentioned above and those which are still to be explained below can be used not only in the combination specified in each case, but also in other combinations or alone without departing from the framework of the present invention. 
     Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, with the same reference symbols referring to the same or similar or functionally identical components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       In the figures, 
         FIG. 1 to 5  schematically show different embodiments of a cooling system according to the invention, 
         FIG. 6  schematically shows a possible embodiment of a valve device, 
         FIG. 7  schematically shows a possible structure of a valve in the valve device, 
         FIG. 8  schematically shows a sleeve valve for the valve device, 
         FIG. 9  schematically shows a detail of the sleeve valve according to  FIG. 8 , 
         FIG. 10   a,b  schematically show the sleeve valve in two different switched positions. 
     
    
    
     DETAILED DESCRIPTION 
     According to  FIG. 1 to 5 , a cooling system  1  according to the invention, which can be arranged for example in a motor vehicle, has a cooling circuit in which at least one internal combustion engine  2 , one pump  3  and one cooling device  4  are arranged. According to the invention, a short circuit line  5  which bypasses the pump  3  is now provided, which connects a pressure side of the pump  3  with an intake side of the same. Furthermore, a valve device  6  which can be switched between at least two positions is provided in the region of the short circuit line  5 , that is more precisely in the region of the branch of the same from the cooling circuit or in the region of the junction of the same into the cooling circuit or into a bypass line. The valve device  6  can be configured as what is known as a multiway valve, in particular as a 3-2-way valve, and in the first position as shown in  FIGS. 1 and 4  can conduct at least most of the coolant flow, preferably the entire coolant flow, through the short circuit line  5 , whereas in the second position as shown in  FIGS. 2 and 3  it conducts at least most of the coolant flow, preferably the entire coolant flow, through the internal combustion engine  2  and not through the short circuit line  5 . According to  FIG. 1 to 5 , the respective coolant flow is shown by corresponding flow arrows. 
     In general a bypass line  7  which bypasses the cooling device  4  can preferably be provided in the cooling system  1  according to the invention, with it being conceivable for the short circuit line  5  as shown in  FIG. 1  also to open into the bypass line  7 . With the valve device  6  according to the invention it is possible to switch over the same in particular in the event that the internal combustion engine  2  needs no or only a little cooling, as a result of which the coolant flow must be pumped exclusively or at least partially through the short circuit with much lower resistance, as shown in  FIG. 1 , so that in this case the pump  3  can be operated at a much lower output. The state shown in  FIG. 1  is for example conceivable in the event of a cold start of the internal combustion engine  2 , in which the latter does not have to be cooled, and should not be cooled as cooling of the same would be advantageous neither for driving comfort nor for emission of pollutants. Owing to the short circuit line  5  which is provided according to the invention, the valve device  6  needs much reduced actuation forces and can thereby be configured to be smaller and also more economical with regard to energy consumption. Without the presence of the short circuit line  5 , much greater actuation forces would be necessary to switch the valve device  6 , which means a higher energy demand. At the same time the valve device  6  itself would also have to be designed to be larger and therefore heavier, which likewise means an increased energy demand. 
     According to FIGS.  1  and  3 - 5 , the valve device  6  according to the invention is arranged in the cooling circuit downstream of the pump  3 , whereas it is arranged in the cooling circuit upstream of the same according to  FIG. 2 . The valve device  6  can for example be configured as a throttle device and/or be actuated pneumatically, electrically or hydraulically. An engine control unit  8  can in particular be used for actuation, which unit for example detects an operating state of the internal combustion engine  2 , in particular a full load or partial load state, and/or a temperature of the cooling medium. For the sake of clarity this is only shown in  FIG. 1 , but can likewise also be present in the cooling systems  1  according to  FIGS. 2 and 3 . To this end, a thermostat  9  can be provided for example in the junction region of the bypass line  7  into the cooling circuit. Of course it is also conceivable for the valve device  6  to be configured as a poppet valve or as an annular slide valve, with the valve device  6  always being configured on the basis of a “fail-safe” principle in such a manner that it remains in its second position when in the inactive, that is, non-actuated state and thereby ensures sufficient cooling of the internal combustion engine  2  in every case. It is of course also conceivable for the valve device  6  according to the invention to be configured as a proportional valve, as a result of which any desired division of the coolant flow through the internal combustion engine  2  and the short circuit line  5  can be effected. 
     According to  FIG. 4 , the valve device  6  is arranged in the junction region of the short circuit line  5  into the bypass line  7 , wherein in this case too at least most of the coolant flow flows through the short circuit line  5  when the valve device  6  is moved into its first position, as the said short circuit line has a much lower flow resistance compared to the cooling circuit which leads through the internal combustion engine  2  and the cooling device  4 . The bypass line  7  is of course purely optional, so that this can also be omitted, as shown in  FIG. 5 . 
     In general the valve device  6  according to the invention allows the regulation of a volumetric flow in the cooling circuit through the internal combustion engine  2  with the possibility of reducing this volumetric flow to zero if necessary. If the valve device  6  is activated, the pump  3  conveys the cooling medium in the low-resistance short circuit and not through further consumers to be cooled such as the internal combustion engine  2 . If in contrast a little cooling is needed in the internal combustion engine  2 , the thermostat  9  or a valve device  10  coupled thereto can suppress a coolant flow through the cooling device  4  and conduct it through the bypass line  7  (cf.  FIG. 3 ). If, on the other hand, the cooling effect of the cooling device  4  is needed, which can be determined for example by a correspondingly increased coolant temperature at the thermostat  9 , the valve device  10  which is coupled to the thermostat  9  can be switched in such a manner that the coolant flow no longer flows through the bypass line  7  but rather through the cooling device  4  (cf.  FIG. 2 ). The valve device  10  which is coupled to the thermostat  9  can be configured in the same manner as the valve device  6 . 
     In general, at least three different cooling levels, namely no cooling ( FIG. 1 ), low cooling ( FIG. 3 ) and higher cooling ( FIG. 2 ) can be set with the two valve devices  6  and  10 . The configuration of the valve devices  6  and  10  as proportional valves means furthermore that any desired intermediate cooling levels can be set. A low activation force at least of the valve device  6  is possible thanks to the respective connection of the short circuit line  5  from the pressure side to the intake side of the pump  3 . An intervention in the main coolant flow of the internal combustion engine  2  is likewise not necessary. In addition there is also the possibility of limiting the pressure of the coolant circuit within the valve device  6 . 
     The cooling system  1  according to the invention has in principle the following advantages:
         reduction in the risk of cavitation in the pump  3  when intervening in the coolant flow,   low switching force at least of the valve device  6 ,   fast response,   integrated parallel overpressure function,   “fail safe” function   integration into a cooling circuit at any point,   low energy demand,   rapid engine heating thanks to a corresponding switch of the valve device  6  into its second position.       

     According to  FIG. 6 , a possible prototype of the valve device  6  is shown with a solenoid  11 , which moves a valve tappet  12  by creating a magnetic field which is spatially as constant as possible. The valve device shown has two inlets  13 ,  13 ′ and an outlet  14 , as a result of which it is possible to mix the input flows as desired to form a common output flow. 
     According to  FIG. 7 , the valve device  6  has two valve discs  15 ,  15 ′ which are arranged on the valve tappet  12 , with the valve disc  15  preferably being configured in one piece with the valve tappet  12 . In the example shown the valve disc  15 ′ is produced as a separate component and secured in the axial direction  17  on the valve tappet  12  by means of a securing element  16 . A spring  19  is provided between the valve disc  15 ′ and a valve seat ring  18 , which spring preloads the valve disc  15  against the valve seat ring  18  and thus into its closed position. Such a configuration of the valve device  6  is suitable in particular for flow rates of &lt;120 l/min, with only very low leakage flows being likely thanks to the good sealing effect. 
     According to  FIGS. 8 and 9 , a further possible embodiment of the interior of the valve device  6  is shown. In this case a combined valve disc  15 ″ and two springs  19 ′ and  19 ″ are provided. The spring  19 ′ is configured as a safety spring, while an overpressure function can be ensured with the spring  19 ″. The combined valve disc  15 ″ has two valve plates  20  and  20 ′ which bear closely against associated valve seats  21  and  21 ′ depending on the switched position.  FIGS. 10   a  and  10   b  show the two extreme switched positions of the valve device  6 , with the bypass line  7  being closed in  FIG. 10   a  and the bypass line  7  being open in  FIG. 10   b , as in for example a cold start. The individual parts of the valve device  6 , in particular the valve discs  15 ,  15 ″, can be formed from metal or plastic.