Patent Grant
8459215
This application claims the benefit of German Patent Application No. 102011076137.3, filed May 19, 2011, which is incorporated herein by reference as if fully set forth.
The present invention relates to a coolant pump having a regulatable coolant flow, preferably provided for a cooling circuit of an internal combustion engine. In the pump housing of the coolant pump, a pump shaft fashioned as a hollow shaft with an associated impeller is rotatably mounted. A rotation of the impeller conveys a coolant via an intake connection into a spiral duct of the coolant pump, a displacement volume of the coolant pump is capable of being influenced by an axially displaceable guide disk that cooperates with an actuating mechanism or actuator system and is allocated to the impeller. For this purpose, the guide disk is connected in rotationally rigid fashion to a connecting rod guided in the hollow shaft of the impeller, and is capable of being displaced between two end positions, which are defined by a rear wall and a pump cover of the impeller.
In liquid-cooled, in particular water-cooled, internal combustion engines, the cooling water is pumped by a coolant pump in a closed circuit through cooling ducts of the engine block that supports the crankshaft and of the cylinder head, and the heated coolant is subsequently conducted into an air-water heat exchanger or cooler, where the water is cooled back down by vehicle airflow, or by a ventilator when the vehicle is stationary. The coolant pump that supports a circulation of the coolant is conventionally directly driven by a traction drive, in particular a belt drive, a traction mechanism connecting the belt pulleys of the crankshaft and of the coolant pump. An immediate coupling between the coolant pump and the crankshaft provides that the rotational speed of the pump is a function of the rotational speed of the internal combustion engine. It results from this that, when there is a cold start of the internal combustion engine, the coolant circulates, causing a delay in a desirable fast warming up of the internal combustion engine and in the reaching of an optimal operating temperature connected therewith.
In order to avoid this effect, regulatable coolant pumps are used whose displaced volume flow can be matched to a cooling requirement of the internal combustion engine. Using regulated coolant pumps, frictional losses can be minimized, because as the oil temperature increases the viscosity of the lubricant oil, and consequently the friction, is reduced, which has a favorable effect on the fuel consumption. At the same time, an improved exhaust gas emission is achieved, because the efficiency of the catalytic converter requires a minimum exhaust gas temperature, and a shorter span of time required to reach this temperature has an immediate positive effect on exhaust gas emissions. In the cold running phase of the internal combustion engine, automobile manufacturers desire a coolant flow of ≦0.5 l/h, also referred to as “zero leakage flow.” In the context of a new development of internal combustion engines for achieving energetically and thermo-mechanically improved operation, a savings in fuel of ≧2.5% was realizable under test conditions in connection with optimal thermal management.
As a measure for influencing the displacement volume of a coolant pump, from DE 199 01 123 A1 it is known to allocate to the open impeller a slider that overlaps the blades of the impeller and that modifies the effective blade width and that can be moved continuously in the axial direction and set at any position. The adjustment of the slider between an open position and closed position takes place by rotating a threaded-type guide. The regulatable coolant pump known from DE 100 57 098 A1 has a magnetic coil that works together with an armature disk and is displaceably situated in rotationally fixed, spring-loaded fashion on the drive shaft. Due to friction pads by which the impeller is connected to the armature disk, when the magnet is not energized the impeller is driven.
DE 10 2005 004 315 A1 and DE 10 2005 062 200 A1 show further regulatable coolant pumps in each of which a valve slide is attached that is displaceable in the direction of the axis of the pump shaft in order to influence the flow rate in the pump housing. The annular valve slide forms an outer cylinder that variably overlaps the outflow region of the impeller. According to DE 10 2005 004 315 A1, the valve slide, which can also be designated a guide disk, is electromagnetically displaced by a magnetic coil situated in the pump housing. Alternatively, according to DE 10 2005 062 200 A1 a pneumatically or hydraulically actuated actuator is provided for the displacement of the valve slide.
The object of the present invention is to create a regulatable coolant pump whose actuating mechanism can be housed within the axial packaging limits of conventional pumps.
According to the present invention, this object is achieved by the present invention, which provides an actuating mechanism, also referred to as an actuator system, containing a displacement pump integrated inside the coolant pump, an actuator, and a control valve. The overall actuating mechanism is thus integrated inside the regulated coolant pump. The actuator, fashioned as a piston-cylinder unit, has a pressure chamber that has a circular annular shape and agrees with an outer region of the guide disk and is positioned in the pump housing, and is intended to accommodate an axially displaceable piston that works together with the guide disk. Through the use of a control valve, the coolant flow of the displacement pump that charges the pressure chamber can be influenced, thus immediately influencing the position of the guide disk. With this actuating mechanism according to the present invention, using the actuator a precise positioning of the guide disk can take place in order to provide a volume flow matched to the particular cooling requirement of the internal combustion engine. In this way, in particular after a cold start a rapid heating of the internal combustion engine can be realized, connected with a reduction of frictional losses and of fuel consumption, and consequently of pollutant emissions. In addition, in long-term operation, by providing a precise displacement volume with the coolant pump, the engine temperature can be adjusted to the current load state of the internal combustion engine.
In order to achieve the targeted adjustment of the coolant flow or of the volume flow, the guide disk or guide plate is advantageously displaced axially relative to the impeller by an actuating mechanism that is as neutral as possible with regard to the available space in the axial direction, and that therefore does not require adaptation to the surrounding construction, for example the drive of the coolant pump. The actuating mechanism according to the present invention is therefore capable of being integrated within the axial packaging boundaries of conventionally constructed coolant pumps made up of a belt drive, bearing, sliding ring seal, and impeller. The actuating mechanism design according to the present invention moreover enables an integrated assembly of all components, together with a compact construction form that is simple and robust from the point of view of manufacturing and assembly and that can be economically designed so as to be standardizable for different sizes of coolant pumps. The integrated displacement pump can be made smaller due to the pressure piston-guide disk, preferably forming an assembly, because this constructive design has a relatively large piston surface. In addition, the actuating mechanism that is maximally integrable into the existing constructive space of the coolant pump for the active influencing of the coolant flow rate is distinguished by high operational safety and reliability, and by a high degree of volumetric efficiency. The actuating mechanism is advantageously realizable with a low manufacturing and assembly expense. Moreover, a conventional coolant pump can be immediately exchanged for a coolant pump having an actuating mechanism according to the present invention. In contrast to previous solutions that provide an electromagnetic or electromechanical actuation of the guide disk, the present invention has an actuation based on hydraulic pressure, such that the displacement pump integrated in the coolant pump compresses the cooling medium in order to produce the hydraulic pressure. In contrast to a known solution in which an oil hydraulic system of the internal combustion engine displaces the guide disk, the coolant used for actuation according to the present invention brings about a self-sufficiently produced hydraulic pressure. This less critical actuation energy does not require any additional hydraulic connections, for example between the internal combustion engine and the pump housing, and also does not require an increased sealing expense in order to effectively prevent oil from entering the coolant of the internal combustion engine.
Further features and advantages of the present invention result from the claims, from the drawings, and from the associated description of the Figures.
According to a preferred embodiment of the present invention, it is provided to use as displacement pump a geared pump whose driving gear is advantageously connected in rotationally rigid fashion to the pump shaft and whose driven gear is at least indirectly rotatably mounted in the pump housing. The two gears running in opposite directions of the displacement pump, which form a gear pump having an intake connection and a pressure connection, engage one another at the intake side of the pump. The hydraulic fluid enters into open tooth gaps of the gears, and due to the rotation the hydraulic fluid is conveyed to the pressure connection via the region enclosed by the pump housing. Due to the engagement of the two gears that takes place, the hydraulic fluid is pressed out of the tooth gaps into the pressure connection of the pump. Instead of a geared pump, other displacement or delivery pumps may also be used that are capable of being integrated into the coolant pump in order to displace the guide disk. As a measure for simplifying assembly, the present invention includes a displacement pump that can be placed axially into the pump housing of the coolant pump as a pre-assembled unit. Advantageously, the displacement pump, realized in particular as a pre-manufactured geared pump containing all components, can be assembled in automated fashion so as to optimize costs.
A preferred actuator design includes a pressure chamber formed as a circular ring, in particular manufactured without machining, forming a formed sheet metal part having a U-shaped cross-sectional profile, pressed into a wet region of the pump housing. Alternatively, according to the present invention a pressure chamber made of a suitable plastic may be used. The pressure chamber, set into a corresponding opening of the pump housing, is connected to the control valve and/or to the displacement pump via at least one hydraulic or pressure connection. In the pressure chamber, open at one side, a piston that works together with the outer contour of the guide disk can be placed so as to be linearly displaceable and sealed. Here a recommended option is for the guide disk to be connected in one piece to the piston, such that this unit is advantageously manufactured without machining. The piston guided in the pressure chamber preferably forms a 180° flange at the end side having a U-shaped cross-sectional profile. This piston shape is connected immediately to the cylindrical part, the outer diameter of the guide disk, resulting in an optimal pressure applied to the piston surface and thus to the actuator for adjusting the guide disk. Depending on the quality of the displacement of the displacement pump, a seal is provided between the movable piston and the stationary pressure chamber. Sufficient displacement pressure permits leakage of the coolant into the pressure chamber. If leakage is to be prevented, a recommended solution is to fully exploit the pressure energy of the displacement pump and to minimize the leakage by using suitable seals.
In addition, the control valve is allocated to a pressure line that connects a pressure side of the displacement pump to the pressure chamber in the pump housing. A bore or a separate line made inside the coolant pump in the pump housing can be provided as pressure line or pressure medium connection. Preferably, the control valve that works together with the actuator is positioned as an assembly inside the coolant pump, via which valve the coolant flow, or its pressure potential, is forwarded to the actuator and thus to the piston of the guide disk depending on the positioning requirement. Alternatively, the present invention includes a control valve situated outside or separate from the coolant pump. Independent of the position of installation, control valves may be used that can be actuated electrically, magnetically, pneumatically, or hydraulically, via which the hydraulically acting actuator can be activated. In the operating state, the control valve is preferably controlled by a control unit or by an engine management system of the internal combustion engine.
In order to ensure cooling of the internal combustion engine even given failure of the actuating mechanism, the actuator includes a failsafe device or failsafe coupling. This device or coupling has a device connected to the actuator, preferably including a spring device. In the event of a failure or drop in pressure of the displacement pump, the spring device causes the piston, including its associated guide disk, to automatically be displaced into a position that corresponds to a maximum opening of the impeller and thus the largest flow rate of the coolant pump. A preferred design provides that the spring device is situated in the pressure chamber of the actuator between a stationary fixed point and the piston. Alternatively, the spring device can be placed between the connecting rod and the pump housing.
Further features of the present invention result from the following description of drawings in which a preferred exemplary embodiment is presented.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 076 137 | May 2011 | DE | national |
| Number | Date | Country |
|---|---|---|
| 19901123 | Jul 2000 | DE |
| 10057098 | Mar 2002 | DE |
| 102005062200 | Feb 2007 | DE |
| 102005004315 | Apr 2007 | DE |
| Number | Date | Country | |
|---|---|---|---|
| 20120291723 A1 | Nov 2012 | US |
