Variable flow water pump

[0001] This application claims the benefit of Provisional Application Nos. 60/197,069, filed Apr. 13, 2000 and 60/242,619, filed Oct. 23, 2000.

[0002] The subject invention relates to a variable capacity water pump with an impeller for use in automotive engines and the like.

[0003] The cooling mechanism for an internal combustion engine used in an automobile normally comprises a coolant pump, commonly referred to as a water pump, of a centrifugal-type. The most common arrangement utilizes the engine rotation to drive a shaft via a belt connection between a driving pulley (connected to the crankshaft) and a driven pulley. The example shown in FIG. 1 shows a typical water pump P with an impeller 20 fastened to a rotating shaft 30 and drivable by the pulley 40, which is attached to the engine crankshaft (not shown). The impeller 20 includes a flange 22 having several integral blades or vanes 24 projecting axially therefrom toward the inlet path 26. When the pulley 40 rotates, the drive shaft 30 rotates, and thus, the vanes 24 similarly rotate with the impeller 20. Coolant enters the passageway 50 and is thrown outward by centrifugal force to an outlet port (not shown) via the outlet path 28.

[0004] Although this system is simple, it has the disadvantage of supplying a fixed capacity of coolant that is often unnecessarily large. This over-capacity arises because the pump output is sized to deliver a minimum flow amount of coolant at low engine speeds. At higher engine speeds, such as those experienced under normal highway driving conditions, the flow amount becomes excessive because it is directly proportional to engine speed. This leads to poor cooling efficiencies and increased power losses.

[0005] An alternative arrangement uses an electric motor instead of the engine to drive the impeller. For instance, U.S. Pat. No. 3,840,309 discloses a variable capacity centrifugal pump with vanes that move via a pivoting linkage mechanism between a threaded nut and a cross-mount that is attached to a propeller shaft rotated by an electric motor. However, this type of design adds weight and cost because extra components are required. Also, the capacity of the battery and generator needs to be increased in order to supply the extra power needed by the motor.

[0006] Still further, U.S. Pat. Nos. 4,752,183 and 5,169,286 disclose two similar variations of a variable output centrifugal pump utilizing a shroud with recesses through which the vanes protrude. The shroud is axially moved over the vanes to vary the exposed area and, therefore, the quantity of coolant that flows through the water pump. This design fails to properly control fluid flow into the volute and allows coolant to pass beneath the impeller. Furthermore, it does not allow for varying the pump capacity with the engine rotational speed.

[0007] The present invention provides a water pump having variable capacity in accordance with a relatively simple mechanical means that obviates the need for expensive electric motors or shrouds that can cause turbulent flow.

[0008] According to the present invention, a variable capacity coolant pump includes a pump body for directing the flow of fluid through the pump between an inlet and an outlet and a shaft rotatably connected to the pump body. An impeller is coupled to the pump body for pumping fluid through the pump body from the inlet to the outlet. The impeller includes a shroud and at least one vane pivotally coupled to the shroud for pivotal movement between a plurality of pitch angles relative to the shaft. A pitch plate is operatively coupled to the vane for controlling the pitch angle of the vane. A spring is coupled to the pitch plate for biasing the vane to a maximum pitch angle wherein the vane varies in pitch in response to a force of fluid pressure from the inlet and automatically reduces the pitch angle of the vane upon an increase in the fluid pressure from the inlet to reduce the flow of fluid to the-outlet. In an alternative embodiment, the pitch angle is also controlled externally via an actuator.

[0025] Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, FIG. 2 shows a first preferred embodiment of a variable capacity coolant pump, or water pump P comprised of a housing 4 including an impeller I. The impeller I is fastened to a rotatable shaft 10 drivable by a pulley (not shown) that is belt driven from the engine crankshaft in a well-known manner.

[0026] The impeller I includes a lower flange or shroud 5 having a plurality of pivotal vanes 2 projecting axially toward the inlet path of the pump. Each vane 2 is connected to an upper flange or shroud 1 via rivets 11 and guided within arcuate shaped slots 3a, 3b between the shrouds 1, 5. Directly underneath the lower shroud 5, and rigidly connected to the rotatable shaft 10, is a pitch plate 6 having slots 13 to accommodate the pitch control tabs 12 projecting from the bottom of each of the plurality of vanes 2, as best shown in FIGS. 3 and 4.

[0027] Further, a torsional pitch spring 7 is disposed around the rotatable shaft 10, and extends to the edge of the lower shroud 5, such that the torsional spring 7 normally biases the impeller I to its most forward position, where the vanes 2 are held in their highest pitch position. The slots 13 in the pitch plate 6 restrict the movement of the vanes so that they are set to an optimal position, or pitch, for low pump rotational speeds.

[0028] In operation, when the engine is first started, the torsional pitch spring 7 holds the impeller in its most forward position. The vanes 2 rotate about their rivets 11 and are held in their highest pitch position, as shown in FIG. 5a. The highest pitch position may be further defined by the vanes 2 extending generally transverse or approaching perpendicular to the center axis of the shroud 1. As the pump speed increases, the drag torque on the impeller I increases, causing the impeller I to rotate in a reverse direction relative to the pitch plate 6. This movement of the impeller I relative to the pitch plate 6 causes the vanes 2 to rotate about their rivets 11 to a lower pitch position, as shown in FIG. 5b. The lower pitch position may be further defined by the vanes arranged generally parallel with the circumferential outer edge of the shroud 1. A force balance is realized between the torsional pitch spring 7, which biases the impeller I to its forward most position (and vanes 2 in the highest pitch position), and the fluid drag torque, which biases the impeller I to its rearward position (and vanes 2 in the lowest pitch position).

[0029] Therefore, as the pump speed increases in response to increasing engine speed, the vanes 2 rotate about their rivets 11 from their highest pitch position, illustrated in FIG. 5a, toward their lowest pitch position, illustrated in FIG. 5b. The guiding slots 13 that are cut into the pitch plate 6 limit the maximum position, or range of movement, of the vanes 2 to a predetermined limit, dependent on engine cooling requirements.

[0030] Referring now to FIGS. 6-9, another embodiment of the impeller arrangement is illustrated. The essential elements are arranged in a similar fashion as before, except that the pitch plate 106 is axially fixed to the rotational shaft 10, but is rotationally free thereon and is affected by the torsion pitch spring 107, which no longer contacts the lower shroud 105. Further, the pitch control tabs 112 are now located on the outer edges of the vanes 102, and the rivets 111 are located on the opposite edge, as shown in FIGS. 6 and 8.

[0031] At low rotational speeds, the torsion pitch spring 107 holds the vanes 102 in their outer most, or highest pitch, position, shown in FIG. 9a. The torsional pitch spring 107 reacts against the rotational shaft 110 and rotates the pitch plate 106 against the pitch control tabs 112 on the bottom of the vanes 102. As the pump rotational speed increases, the fluid pressure on the vanes 102 causes the vanes 102 to rotate about their rivets 111 against the pressure being applied to the pitch control tabs 112 by the pitch plate 106. A balance of forces is once again achieved, where the force exerted by the torsional pitch spring 107 onto the vanes 102 is opposed by the back pressure of the fluid flowing across the forward face of the vanes 102. At high rotational speeds, the vanes 102 are rotated to their lowest pitch positions, illustrated in FIG. 9b.

[0032] FIG. 10 discloses an alternate embodiment whereby the torsional pitch spring is replaced by a compression pitch spring 113, a sliding shell 114, a helically motivated rotating shell 115 and a C-clip 116. The sliding shell 114 is rotationally fixed onto the main rotational shaft 110 by the spline 117, and the rotating shell 115 is axially fixed by the C-clip 116. Tabs 119 on the sliding shell 114 consequently impart a rotating torque onto the rotating shell 115 by applying an axial force to a helical slot 120 in the rotating shell 115. The combination of compression pitch spring 113, sliding shell 114, rotating shell 115 and the straight spline 117 applies the same outward force to the vanes 102 by imparting a rotating force onto the pitch plate 106. This applies an outward force to the pitch control tab 112 located on the bottom of the vane 102. The rotating force is generated when the compression pitch spring 113 axially pushes the sliding shell 114 against the rotating shell 115. The outward force on the vanes 102, derived from the compression spring 113, is again balanced by the fluid pressure acting on the vanes.

[0033] Finally, FIGS. 11-13 illustrate yet another alternate embodiment of the invention whereby the vane pitch is controlled by an external actuator 256. In operation, the actuator 256 moves the rod 255 axially. An arm 254 connects the rod 255 to a bearing 253. The subsequent motion of the rod 255 and arm 254 combination causes the bearing 253 to move axially. The bearing 253 then drives the control rod 259 axially. The internal shaft is rigidly attached to pin 260, which acts on the helical grooves 262 in the rotation shell 252, illustrated more clearly in FIG. 13, to cause it to rotate. The direction of rotation, clockwise or counterclockwise, depends on the direction that the control rod 259 moves in. The rotation shell 252 acts on or otherwise engages the lower shroud 205, and, indirectly, the entire impeller sub-assembly, causing the sub-assembly to rotate. The pitch plate 206, which is rigidly attached to the rotating shaft 210, acts on the pitch control tabs 212 of the vanes 202 to change the pitch of the vanes 202. In operation, an external electronic controller can be used to determine the vane 202 pitch angle for a given pump speed and engine temperature.

[0034] Having now fully described the invention, any changes can be made by one of ordinary skill in the art without departing from the scope of the invention as set forth herein. For example, the pitch plate or vanes can also be driven by an electronic or hydraulic actuator. Further, the pitch plate could be replaced by a set of linkages.

[0035] The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described.