Abstract:
A variable coolant pump for a cooling circuit of an internal combustion engine. The variable coolant pump includes a pump head having an inlet, an annular channel and an outlet; a pump housing rotatably supporting a pump shaft having an axial end; a pump blade wheel mounted on the axial end of the pump shaft and disposed in the pump head; and a plurality of adjustable guide blades arranged concentrically about the pump blade wheel between the annular channel and the pump blade wheel. Each adjustable guide blade has two longitudinal sides and outer edge and includes a first pivot, a second pivot and a third pivot. The first and second pivots extend at right angles to a respective one of the two longitudinal sides in a vicinity of the outer edge. The first and second pivots define an axis of rotation and rotatably support the respective guideblade in the pump head about the axis of rotation. The third pivot is disposed in parallel with the first and second pivots in an area in the adjustable guide blade remote from the axis of rotation and protrude into an oblong recess in an adjustment ring rotatably arranged in the pump head. The oblong recess has a radial and a tangential component.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     Priority is claimed to German Patent Application No. DE 10 2008 027 157.8, filed Jun. 6, 2008. The entire disclosure of said application is incorporated by reference herein. 
     FIELD 
     The present invention is directed to a variable coolant pump for the cooling circuit of an internal combustion engine, comprising a pump housing in which a mechanically or electrically driven pump shaft is rotatably supported and on whose axial end a pump blade wheel is mounted that is arranged in a pump head having an inlet, an annular channel and an outlet, a plurality of adjustable guide blades being arranged concentrically about the blade wheel between the annular channel and the blade wheel in the pump head. 
     BACKGROUND 
     To save fuel and to reduce the carbon dioxide emissions of an internal combustion engine, various measures have been proposed over the last years to provide a coolant conveyance in the coolant circuit of an internal combustion engine that is adapted to actual needs. In this context, one has to differentiate between electrically driven pumps where the coolant flow is changed by adjusting the rotational speed of the electric motor, and mechanically driven pumps, operated via a belt or chain drive, where the coolant flow is varied either via hysteresis clutches or changes in the inflow or outflow geometries in the area of the pump blade wheel. Compared to electric pumps or pumps with a hysteresis clutch, a control through a change in the inflow or outflow geometry is often clearly more economically realized. 
     Variable coolant pumps have thus been recently developed where the outlet cross section can be closed by means of a substantially pot-shaped valve element that is arranged for axial displacement in the pump housing. Mostly, the pot-shaped valve element is displaced using a solenoid acting on the pot-shaped valve element against a spring force so that, when the magnet is energized, the outlet cross section of the pump blade wheel is closed. Such coolant pumps are described, for example, in DE 10 2005 004 315 A1 or DE 10 2004 054 637 A1. 
     Drawbacks of these prior art embodiments are the rather high control effort of the solenoid and the rather large space required for accommodating a solenoid of enough strength to displace and support the pot-shaped valve element. 
     Coolant pumps are described in WO 2004/059142 A1 and WO 2007/025375 A2, wherein guide blades are arranged at the inlet in front of the blade wheel of the pump in order to control the incident flow to the blade wheel and thus the volume of coolant conveyed. To this end, the guide blades are swiveled approximately around their central axes via a turnable ring. These prior art embodiments are disadvantageous in that either the incident flow to the pump head has to be radial because the pump is driven on the suction side, or additional axial installation space is required for the accommodation of the guide blades. When the installation space is limited, the actuator has to apply a rather high torque in order to adjust the guide blades. 
     A centrifugal pump with adjustable guide vanes is described in DE 736 266, which are arranged in the vicinity of the pump&#39;s diffuser behind the blade wheel. These guide blades are also turned approximately about their central axes in order to avoid the occurrence of wobbling. Again, great actuating forces and high torques have to be applied by the actuator. 
     SUMMARY 
     An aspect of the present invention to provide a variable coolant pump that requires as little installation space as possible, and wherein the actuator required for the adjustment of the guide blades can be realized as small as possible. 
     In an embodiment, the present invention provides for a variable coolant pump for a cooling circuit of an internal combustion engine. The variable coolant pump includes a pump head having an inlet, an annular channel and an outlet; a pump housing rotatably supporting a pump shaft having an axial end; a pump blade wheel mounted on the axial end of the pump shaft and disposed in the pump head; and a plurality of adjustable guide blades arranged concentrically about the pump blade wheel between the annular channel and the pump blade wheel. Each adjustable guide blade has two longitudinal sides and outer edge and includes a first pivot, a second pivot and a third pivot. The first and second pivots extend at right angles to a respective one of the two longitudinal sides in a vicinity of the outer edge. The first and second pivots define an axis of rotation and rotatably support the respective guideblade in the pump head about the axis of rotation. The third pivot is disposed in parallel with the first and second pivots in an area in the adjustable guide blade remote from the axis of rotation and protrude into an oblong recess in an adjustment ring rotatably arranged in the pump head. The oblong recess has a radial and a tangential component. Such an arrangement of the pivots and such a design of the oblong recesses in the adjustment ring allow a significant reduction of the torque to be applied by the actuator for a rotation of the adjustment ring as compared with known embodiments. In addition, the installation space required for the accommodation of the guide blades is reduced to a minimum, since the guide blades can be mounted in the vicinity of the pump head&#39;s diffuser. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described in greater detail below on the basis of embodiments and of the drawings in which: 
         FIG. 1  is a schematic top plan view of a coolant pump of the present invention with the lid opened. 
         FIG. 2  is a side elevational view of the top half of the coolant pump illustrated in  FIG. 1 , shown in schematic section. 
         FIG. 3  is a view of the coolant pump, corresponding to  FIG. 1 , however, with the guide blades in a closed position. 
         FIG. 4  is a side elevational view of the top half of the coolant pump illustrated in  FIG. 3 , shown in schematic section. 
         FIG. 5  is a side elevational view of a guide blade for a coolant pump according to the present invention. 
         FIG. 6  is a top plan view on a guide blade as shown in  FIG. 5 . 
         FIG. 7  is a side elevational view of a guide blade shown as an alternative embodiment to the one in  FIG. 5 . 
         FIG. 8  is a top plan view on an adjustment ring according to the present invention, wherein one guide blade is illustrated in a closed position and another is shown in an opened position. 
     
    
    
     DETAILED DESCRIPTION 
     For a further reduction of the torque to be applied, the radial component is smaller over the entire adjustment angle than the tangential component. 
     The groove or the oblong hole is, for example, contoured so that the proportion of the radial component as compared to the tangential component increases as the adjustment angle increases from the closed guide blade position. Such a design of the grooves or oblong holes allows for a more precise control of the coolant volume conveyed, since a rotation of the adjustment ring from the closed position causes a lesser turning of the guide blades in a first region than in the following region. When the angle of rotation of the guide blades is the same, however, the difference in the coolant volume conveyed is larger than in the second portion. A precise control of the coolant volume thereby becomes possible, especially when little coolant is conveyed. 
     At the inner circumference of the adjustment ring, tangentially extending recesses can be formed for the passage of the first pivots, the length of which corresponds to the maximum angle of rotation of the adjustment ring, the first pivots being supported in the pump head. Such a structure minimizes the number of elements to be used. At the same time, the recesses serve as abutments for defining the maximum angle of rotation so that no tension or pressure forces can be caused between the two axes of the guide blade by the adjustment. 
     For the centring and the support of the adjustment ring and for the extension of the durability of the pivots, spacer rings are provided on the first pivots at the level of the recesses of the adjustment ring, wherein the outer diameter of the spacer rings substantially correspond to the width of the recesses and are received by the recesses in the adjustment ring so that these spacer rings serve as abutments and as guides and supports for the adjustment ring and thereby define the angle of rotation. 
     In an embodiment of the present invention, the guide blades are made from sheet metal and have a length corresponding to the distance from one axis of rotation to the adjacent axis of rotation. Such a structure is economic to manufacture. 
     In an embodiment of the present invention, the guide blades are profiled and are longer than the distance from one axis of rotation to the adjacent axis of rotation so that the end of each guide blade, averted from the axis of rotation, abuts in the vicinity of the rotational axis of the adjacent guide blade. This structure is suited to increase the efficiency of the pump by optimizing the flow discharge. In addition, great tightness can be achieved in the closed state of the guide blades. 
     A coolant pump can thereby be provided that is adapted to be controlled mechanically, while requiring only little adjustment forces. At the same time, the effort in components and installation space is minimized. 
     The coolant pump of the present invention, shown in part in  FIGS. 1 to 4 , is formed by a pump housing (not illustrated in the Figures) in which a driven pump shaft  1  is rotatably supported. The pump shaft  1  may be driven either mechanically by the crankshaft via a V-belt or a chain drive so that the pump shaft  1  is driven at a fixed rotational speed ratio with respect to the crankshaft, or the shaft may be driven at a constant rotational speed by means of an electric motor. 
     On one axial end  2  of the pump shaft  1 , a pump blade wheel  3  is arranged that rotates together with the pump shaft  1 . The pump blade wheel  3  is surrounded by a pump head  4  that is formed with a central inlet  5 , an annular channel  6  as well as a tangential outlet, the outlet not being illustrated in the schematic illustration in the Figures. 
     Accordingly, when the pump blade wheel  3  rotates, the coolant is drawn through the axial inlet  5  into the pump blade wheel  3  and, at the radial outlet of the pump blade wheel, it is conveyed towards the annular channel  6 , from where it flows to the tangential outlet of the pump head  4 . 
     Between the radial outlet of the pump blade wheel  3  and the annular channel  6 , the pump head  4  is formed with a diffuser  7  in which, according to the present invention, guide blades  8  are arranged along a circular line. The guide blades  8  comprise three pivots  9 ,  10 ,  11 , as shown in  FIGS. 5 to 7 . The pivots  9 ,  10 ,  11  can be perpendicular to the longitudinal axis  12  of each guide blade  8 . The first and the second pivots  9 ,  10  can be arranged near an outer edge  13  of each guide blade  8 . The pivot pins  9  and  10  serve as the axis of rotation of the guide blades  8 . The third pivot  11  can be arranged in the area  14  of the guide blades  8  remote from the axis of rotation and can be slightly shorter than the first and second pivots  9 ,  10 . 
     As shown in  FIGS. 2 and 4 , the first and second pivots  9 ,  10  can be supported in the pump head  4  of the coolant pump. For this purpose, the bipartite pump head  4  can be provided with two blind bores  15 ,  16  of which the first blind bore  15  can be formed in a rear wall  17  of the pump head  4 , whereas the second blind bore  16  can be formed in a lid  18  of the pump head  4 . In the assembled state of the pump head  4 , the ends of the first and second pivots  9 ,  10 , protruding beyond the third pivot  11 , can be arranged in the blind bores  15 ,  16 . 
     In the area adjacent to the guide blades  8 , the first and second pivots  9 ,  10  can each be surrounded by spacer rings  19 ,  20  whose height is about equal to the height of the third pivot  11 . According to the present invention, the spacer rings  19  and thus the first pivots  9  and the third pivots  11  cooperate with corresponding recesses  21  and grooves or oblong holes  22  of an adjustment ring  23  that is rotatably arranged in a space  25  of the rear wall  17  of the pump head  4  such that an inner wall  26  of the rear wall  17 , leading to the annular channel  6 , can be substantially linearly extended. The number of oblong holes  22  and recesses  21  corresponds to the number of guide blades  8 . In the lid  18  of the pump head  4 , a corresponding recess  32  can be formed in which another ring  33  can be arranged that, in the present embodiment, can be stationary in the housing and also can have recesses for receiving the second pivot  10 . 
     The recesses  21  of the adjustment ring  23  extend tangentially on the inner circumference  24  of the adjustment ring  23  and have a tangential length corresponding to a maximum adjustment angle α of the adjustment ring  23 . In these recesses  21 , the first pivots  9  can be arranged together with their spacer rings  19 . Seen in the circumferential direction of the adjustment ring  23 , the oblong holes  22  can each be provided between the recesses  21  and have a width corresponding to the diameter of the third pivots  11 . In the assembled state, the third pivots  11  each protrude into the oblong holes  22  that are inclined, i.e. have a radial component r and a tangential component t. The tangential component t can be larger over the whole adjustment angle α than the radial component r, wherein, in the present embodiment, the oblong holes  22  can be of linear shape. 
     The outer circumference of the adjustment ring  23  can be formed with a flange-shaped projection  27  having a through-hole  28  through which a pin  29  extends which is provided at the end of a lifting rod  30  of an actuator  31 . In an embodiment, this actuator  31  is only schematically illustrated. It may be operated pneumatically, hydraulically, electrically or even magnetically. Generally, the lifting rod  30  is controlled in dependence on the thermal data of the internal combustion engine. The actuator  31  can, for example, also be arranged in the space  25  in the rear wall  17  of the pump head  4 . Because of the special arrangement of the oblong holes  22  as well as the axis of rotation of the guide blades  8  with respect to the oblong holes  22 , only low actuating forces occur so that the actuator  31  can be made compact in size. 
     It should be noted that the adjustment ring  23  should be supported in the pump head  4  in a manner that allows for an adjustment with as little friction as possible. Of course, it would be possible to also design the adjustment ring  23  as an adjustment ring with corresponding oblong holes into which fourth pivots would extend that would have to be arranged opposite the third pivots  11 , whereby a guiding would be achieved on both sides, wherein a corresponding support would have to be provided for this ring as well and a coupling with the actuator  31  would be necessary. 
     In the event of a cold start of the internal combustion engine, the lifting rod  30  of the actuator  31  is in its extended position, as shown in  FIGS. 3 and 4 . Here, the adjustment ring  23  is rotated counter-clockwise by the lifting arm  30 , whereby the third pivots  11  in the oblong holes  22  and the first pivots  9  in the recesses  21  abut against the first abutment on the adjustment ring  23 . Since the beginning of the oblong holes  22  is spaced by the same radial distance from the centre of rotation of the adjustment ring as the oblong holes  15 ,  16 , the guide blades  8 , in this state, lie on a common circular line for their entire length. The length of the guide blades  8  is chosen such that the respective ends of the guide blades contact each other in this state so that the ring formed by the guide blades  8  is perfectly closed. This means that no coolant is conveyed in this state. 
     After the cold start phase has ended and the coolant has been heated up in the area of the cylinders, the actuator  31  is operated so that the lifting rod  30  is retracted at least in part, whereby the adjustment ring  23  rotates clockwise. This rotation causes the third pivots  11  to slide radially outward in the oblong holes  22 , whereby the guide blades  8  are also rotated clockwise about their pivot axis. Thus, the coolant can now be conveyed by the pump blade wheel  3  into the annular channel  6  and thus toward the outlet. Here, the guide blades  8  assume a position by which the conveyance of the coolant in the coolant pump is further improved, since they serve as an outlet guide blade means. Depending on the position of the guide blades  8 , respectively different coolant volumes can be conveyed at the same rotational speed of the pump so that a control is achieved that is effective over the entire range. The maximum discharge volume can be obtained in the fully open position of the guide blades  8  shown in  FIGS. 1 and 2 , in which the first pivots  9  and the second pivots  11  abut on the opposite abutments of the oblong holes  22  and the recesses  21 , respectively. 
     The guide blades  8  shown in  FIGS. 5 and 7  have different shapes, with the guide blade  8  shown in  FIG. 5  being made, for example, of sheet metal and having a constant thickness, whereas the guide blade  8  shown in  FIG. 7  is usually made, for example, from plastics and has a contoured shape especially suited for a further minimization of the pressure loss in the flow, while the sheet metal blade is extremely economic to manufacture. 
       FIG. 8  shows the present adjustment ring  23  with two guide blades  8 , of which a first one is in the open position, whereas a second one is in the closed position. In addition, the position of the spacer ring  19  of a guide blade  8  is illustrated in both end positions so that the maximum angle of rotation is visible. Compared to the embodiment shown in  FIGS. 1 and 3 , the guide blades  8  are longer in the present embodiment so that, in the closed position, the respective end of a guide blade  8  rests on the next guide blade  8  in the vicinity of the axis of rotation thereof. This additionally improves the tightness, however, with such a design, care should be taken that the shape of the guide blades is selected such that unwanted flow resistances and turbulences are avoided. 
     The coolant pump of the present invention is suited for a continuous regulation of the coolant volume in an internal combustion engine without having to use controlled shaft drives. The installation space required is extremely small. The actuation forces or the torque to be applied for adjusting the guide blades are extremely low because of the inclined arrangement of the oblong holes so that a smaller actuator can be used than in known embodiments. 
     An additional advantage is also obtained by a corresponding contouring of the oblong holes  22 , while omitting the linearity, whereby, by the maximum possible adjustment angle, an adjustment angle of the guide blades  8 , can be set that differs from the respective adjustment angle of the adjustment ring  23 . Further modifications and structural changes can of course be made so that the scope of protection is not restricted to the embodiments described herein. For example, a second adjustment ring can also be provided on the opposite side of the pump head  4 , cooperating with a corresponding fourth pin. Further, on this side, the support can be done immediately in the housing without interposition of another ring. 
     Although the present invention has been described and illustrated with reference to specific embodiments thereof, it is not intended that the present invention be limited to those illustrative embodiments. Those skilled in that art will recognize that variations and modifications can be made without departing from the true scope of the present invention as defined by the claims that follow. It is therefore intended to include within the present invention all such variations and modifications as fall within the scope of the appended claims and equivalents thereof.