Controllable Cooling System for a Motor Vehicle, Coolant Pump Therefor, Impeller for Use in the Coolant Pump, and Method for Controlling a Coolant Flow in Such a Cooling System

Abstract

The present invention relates to a controllable cooling system ( 1 ) for a motor vehicle, comprising a coolant circuit which routes coolant to and out of an internal combustion engine, and to a mechanically operated, controllable main coolant pump ( 3 ) and an electrically operated, controllable secondary coolant pump ( 5 ). The cooling system further comprises a control device which controls the main coolant pump ( 3 ) and the secondary coolant pump ( 5 ) in dependence on operating conditions of the internal combustion engine. The invention furthermore provides an electrically operated, controllable secondary coolant pump ( 5 ) for such a cooling system ( 1 ), an impeller ( 25 ) for use in this secondary coolant pump ( 5 ), and a method for controlling the coolant flow in such a cooling system ( 1 ).

1 . A controllable cooling system for a motor vehicle, comprising:
 a coolant circuit for supplying and discharging coolant to and from an internal combustion engine of the vehicle;   a mechanically operated, controllable main coolant pump comprising an inlet for supplying the coolant into the main coolant pump and an outlet for discharging the coolant to the internal combustion engine, and   an electrically operated, controllable secondary coolant pump comprising an inlet for supplying the coolant into the secondary coolant pump and an outlet for discharging a coolant, conveyed as a bypass coolant flow, towards the main coolant pump,   wherein the secondary coolant pump is arranged upstream of the main coolant pump in the direction of flow, forking off from a coolant line leading to the main coolant pump in the direction of coolant flow,   the coolant conveyed by means of the secondary coolant pump is supplied, downstream of the main coolant pump and without flowing through the main coolant pump, into the outlet leading to the internal combustion engine,   the secondary coolant pump comprises a pump casing with a pump chamber formed therein, wherein on a section of the pump casing an electric motor is arranged which provides driving power for the secondary coolant pump by means of a drive shaft extending into the pump chamber,   the secondary coolant pump in the pump chamber comprises an impeller serving as a conveyor member which is coaxially arranged on the drive shaft and drivably connected thereto, and   the secondary coolant pump comprises a control slide valve formed on the impeller which can be moved at least to open and closed positions, for controlling the bypass coolant flow conveyed by the secondary coolant pump, particularly for preventing back-flow of the coolant in a direction opposite to the conveying direction of the secondary coolant pump.   
     
     
         2 . The system according to  claim 1 , wherein the main coolant pump comprises a pump casing with a pump chamber formed therein, wherein an impeller serving as a conveyor member is arranged in the pump chamber and is driven via a shaft extending into the pump chamber which is preferably driven by a belt drive. 
     
     
         3 . The system according to  claim 1 , wherein the main coolant pump further comprises a control slide valve formed on the impeller and arranged coaxially thereto which can be moved at least to open and closed positions, preferably along the impeller mounted in the pump chamber, for controlling the coolant flow conveyed by the main coolant pump. 
     
     
         4 . The system according to  claim 1 , wherein the electric motor of the secondary coolant pump is designed as a dry rotor or wet rotor. 
     
     
         5 . The system according to  claim 1 , further comprising a control device which controls the main coolant pump and/or the secondary coolant pump in dependence on assigned operating conditions of the internal combustion engine. 
     
     
         6 . An electric coolant pump for use in a cooling system according to  claim 1 , wherein the electric coolant pump is designed as a radial flow pump and comprises:
 a pump casing;   a preferably flange-like inlet and a preferably flange-like outlet;   a pump chamber formed in the pump casing, wherein a pump wheel is arranged on a pump shaft in the pump chamber, the pump wheel being drivable by an electric motor through the intermediary of the pump shaft, and   a slide valve that is displaceable at least to open and closed positions, for controlling a bypass coolant flow conveyed by the coolant pump, particularly for preventing back-flow of the coolant in a direction opposite to the conveying direction of the secondary coolant pump,   wherein the coolant to be conveyed, diverted from a coolant line, can be introduced into the pump chamber formed in the pump casing through the substantially conically extending inlet, and the coolant introduced into the pump chamber can be discharged from the pump chamber through the outlet arranged substantially at a right angle radially to the inlet line;   wherein the impeller arranged in the pump chamber and designed as a radial flow pump impeller sucks the coolant in through rotational movement in an axial direction and conveys it into the outlet in a radial direction;   the slide valve is designed as a control slide valve arranged coaxially to the pump shaft on the impeller; and   the electric motor is preferably arranged on a section of the pump casing facing away from the inlet;   wherein the electric motor comprises a drive shaft protruding into the pump chamber,   the impeller and the control slide valve are coaxially arranged on the drive shaft and are retained on the drive shaft in a positive fit manner, preferably by means of retaining members, and   the control slide valve is cylindrically designed, enclosing the impeller, and is displaceable in an axial direction of the impeller to open and closed positions.   
     
     
         7 . The coolant pump according to  claim 6 , wherein the control slide valve is connected to the impeller such that blades of the impeller penetrate the control slide valve. 
     
     
         8 . The coolant pump according to  claim 6 , wherein the electric motor is designed as a dry rotor and is sealed from the pump chamber by means of a shaft seal arranged on the drive shaft. 
     
     
         9 . The coolant pump according to  claim 6 , wherein the electric motor ( 7 ) is designed as a wet rotor and is cooled by the coolant conveyed by the coolant pump. 
     
     
         10 . The coolant pump according to  claim 6 , wherein the control slide valve is displaceable along the drive shaft by means of at least one actuator arranged in the coolant pump, wherein the actuator is designed as a pneumatically, magnetically and/or hydraulically actuated slide valve or as an electric servomotor. 
     
     
         11 . The coolant pump according to  claim 6 , wherein the control slide valve comprises a section enclosing the drive shaft and facing towards the inlet, with a threaded section formed on its inner circumference. 
     
     
         12 . The coolant pump according to  claim 11 , wherein a threaded section complementary to the threaded section of the control slide valve is formed on a section of the drive shaft facing away from the electric motor, and the control slide valve is displaceable along the drive shaft by mutual engagement of the threaded sections. 
     
     
         13 . The coolant pump according to  claim 6 , wherein the control slide valve is designed to follow the contour of the front side of the impeller and has arranged at its outer end a radially continuous closure member, wherein a first sealing member, arranged radially outside the control slide valve, is disposed at an end of the closure member facing away from the electric motor. 
     
     
         14 . The coolant pump according to  claim 13 , wherein a receptacle into which the closure member of the control slide valve can be introduced in the open position thereof is formed in the pump chamber. 
     
     
         15 . The coolant pump according to  claim 13 , wherein a second sealing member, arranged radially inside the control slide valve, is disposed at a radially outer end of the impeller facing towards the electric motor. 
     
     
         16 . The coolant pump according to  claim 15 , wherein the diameter of the first sealing member is larger than the diameter of the second sealing member. 
     
     
         17 . The coolant pump according to  claim 15 , wherein the outlet can be tightly closed, via the closure member, the first sealing member and the second sealing member, by the control slide valve in the closed position thereof. 
     
     
         18 . The coolant pump according to  claim 6 , wherein a braking member is further provided, by means of which the impeller can be secured to an inner wall of the pump casing. 
     
     
         19 . The coolant pump according to  claim 18 , wherein the braking member is formed on the impeller and preferably consists of a pretensioned braking spring or plate-like brake disc which preferably comprises at its radially outer ends, in a radially inward direction, substantially wedge-tapered thickenings, wherein the braking member can be brought into frictional engagement with the inner wall of the pump casing adjoining the electric motor, preferably by means of the thickenings, to secure the impeller to the pump casing. 
     
     
         20 . The coolant pump according to  claim 18 , wherein the braking member, including in particular, the thickenings thereof, is designed to disconnect from the inner wall of the pump casing as the speed of rotation of the impeller caused by the drive shaft of the electric motor increases, so as to disengage the impeller. 
     
     
         21 . An impeller for use in a coolant pump according to  claim 6  for a cooling system according to  claim 1 , said impeller comprising:
 a plurality of blades that are preferably typical of radial flow pumps and formed on the impeller surface facing towards a coolant inlet; 
 a recess for receiving a drive shaft; 
 a control slide valve connected to the impeller; and 
 a braking member arranged on the impeller. 
 
     
     
         22 . The impeller according to  claim 21 , wherein the control slide valve comprises at its front end a first sealing member arranged radially outside thereof and the impeller comprises at its radially outer end a second sealing member arranged radially inside the control slide valve. 
     
     
         23 . The impeller according to  claim 21 , wherein the control slide valve is integrally formed with the impeller such that the blades of the impeller penetrate the control slide valve in an axial direction. 
     
     
         24 . The impeller according to  claim 21 , wherein the braking member is formed on a back side surface of the impeller. 
     
     
         25 . The impeller according to  claim 21 , wherein the braking member consists of a pretensioned braking spring or plate-like brake disc capable of being brought into frictional engagement with a surface opposite the back side surface of the impeller, to secure the impeller to this surface. 
     
     
         26 . The impeller according to  claim 21 , wherein the braking member is designed such that its braking effect decreases as the speed of rotation of the impeller increases, whereby it approaches the back side surface of the impeller to disengage the impeller. 
     
     
         27 . The impeller according to  claim 21 , wherein the control slide valve is designed to follow the contour of the impeller and comprises at its outer end a radially continuous closure member. 
     
     
         28 . The impeller according to  claims 21 , wherein the control slide valve comprises in its frontal area a hollow, compartment-like section with a threaded section formed on the inner circumferential wall thereof. 
     
     
         29 . A method for controlling a coolant flow in a cooling system of a motor vehicle according to  claim 1 , wherein the cooling system comprises a controllable main coolant pump mechanically operated by the driving force of an internal combustion engine arranged in the vehicle and a controllable secondary coolant pump electrically operated by a separately arranged electric motor, said method comprising the steps of:
 detecting a current operating condition of an internal combustion engine of the vehicle;   detecting a coolant temperature of a coolant circulating in a coolant circuit of the vehicle;   reading out control parameters from a cooling circuit map;   controlling the main coolant pump and the secondary coolant pump based upon the control parameters read out from the cooling circuit map; and   controlling the coolant flow by selectively switching the main coolant pump and/or the secondary coolant pump.   
     
     
         30 . The method according to  claim 29 , wherein the current operating condition of the internal combustion engine includes a start-stop condition, a warm-up condition, a low-load condition, a normal-load condition, an eco condition, a high-rpm condition, and a residual heat storing condition. 
     
     
         31 . The method according to  claim 29 , wherein the control parameters in the cooling circuit map include at least a desired coolant temperature, and/or a desired motor temperature and/or a desired coolant flow rate, and/or the like. 
     
     
         32 . The method according to  claim 30 , wherein, when the current operating condition of the internal combustion engine is the warm-up condition, the secondary coolant pump is switched to an OFF-mode condition and a coolant flow through the main coolant pump is interrupted by means of a control slide valve arranged in the main coolant pump, such that circulation of the coolant is interrupted. 
     
     
         33 . The method according to  claim 30 , wherein, the current operating condition of the internal combustion engine is the start-stop condition in which the main coolant pump is temporarily unpowered during a stop phase of the internal combustion engine, the secondary coolant pump is switched to an ON-mode condition, by means of which the coolant is circulated through the secondary coolant pump. 
     
     
         34 . The method according to  claim 30 , wherein, when the current operating condition of the internal combustion engine is the low-load condition, a coolant flow through the main coolant pump is interrupted by means of a control slide valve arranged in the main coolant pump and the secondary coolant pump is switched to an ON-mode condition, by means of which the coolant is circulated through the secondary coolant pump. 
     
     
         35 . The method according to  claim 30 , wherein, when the current operating condition of the internal combustion engine is the normal-load condition, the secondary coolant pump is switched to an OFF-mode condition and the control slide valve thereof is closed, by means of which the coolant in the coolant circuit is circulated through the main coolant pump. 
     
     
         36 . The method according to  claim 30 , wherein, when the current operating condition of the internal combustion engine is the eco condition, operation of the main coolant pump is selectively interrupted by means of an overrunning clutch provided on the belt drive system of the main coolant pump, or a control slide valve arranged in the main coolant pump is controlled such that the coolant flow in the main coolant pump is interrupted and the coolant is circulated through the secondary coolant pump in order for a desired elevated motor temperature to be obtained. 
     
     
         37 . The method according to  claim 30 , wherein, when the current operating condition of the internal combustion engine is the high-rpm condition, the coolant flow of the main coolant pump is routed, at least in part, in the bypass mode via the secondary coolant pump to the intake side of the main coolant pump. 
     
     
         38 . The method according to  claim 30 , wherein, when the current operating state of the internal combustion engine is the residual heat storing condition with the internal combustion engine at a standstill, both the control slide valve of the main coolant pump and the control slide valve of the secondary coolant pump are closed in order to prevent circulation of the coolant in the cooling circuit.