Patent Description:
Fluid pumps, and more particularly fuel pumps for pumping fuel, for example, from a fuel tank of a motor vehicle to an internal combustion engine of the motor vehicle, are known. A typical fuel pump includes a housing within which generally includes a pump section, a motor section, and an outlet section. The pump section includes an inlet plate, an outlet plate, and a pumping arrangement between the inlet plate and the outlet plate. The pumping arrangement is rotated by an electric motor located in the motor section, thereby causing fuel to be drawn into the housing through an inlet of the inlet plate and through an outlet passage of the outlet plate. The fuel then passes the electric motor and exits the housing through an outlet of the outlet section. The fuel pump may be an impeller type fuel pump where the pumping arrangement is an impeller or the fuel pump may be a gerotor-type fuel pump where the pumping arrangement is an inner gear rotor surrounded by an outer gear rotor, such as disclosed in <CIT>. Alternatively, the fuel pump may be a vane-type fuel pump, a gear-type fuel pump, or a roller vane-type fuel pump.

Electronic fuel pumps ("EFP's") used in vehicles were conventionally DC "brush" motor pumps. These DC pumps were driven by a constant voltage signal and were turned on and off in connection with the ignition switch of the vehicle, i.e. when the ignition switch was turned on, the DC pump was turned on, and when the ignition switch was turned off, the DC pump was turned off. As the demand for improved vehicle fuel economy has increased in the automotive industry, the need to regulate the flow and/or pressure provided by electronic fuel pumps has arisen. Such regulation requires a more robust pump design and sophisticated Fuel Pump Controllers ("FPC's"). Current fuel delivery modules ("FDM's") use electronic commutated ("EC") "brushless" pumps or DC pumps with special FPC's to feed fuel in "start-stop" and closed loop pressure control ("CLPC") fuel delivery systems designed to increase overall fuel system efficiency and pressure/flow control. One of the trade-offs of using an EFP with variable pressure/flow control is the increased wear and tear on the pump components, due to the increase in on-off and speed change cycles the EFP needs to withstand.

For example, the main considerations in designing the motor armature/rotor shaft to gear coupling interface to transmit both radial and axial loads in an EFP include strength, fatigue life, wear resistance, noise, and longevity (i.e., ability to maintain function without premature failure). As the required pressure levels and duty cycles for EFP's has increased, it has become more difficult to maintain a balance between cost, size, and function. One approach to transferring torque between the motor shaft and the rotating member of the pump section is a steel shaft engaged to a steel rotor interface. However, this type of interface is noisy and prone to fretting wear failures in low-lubricity fuel. The axial position of the motor shaft and resultant axial loads from the motorto the pump shaft may also be controlled by use of a collarorthrust pad. Inserting a plastic member between the shaft and pump section rotor can help alleviate the mechanical noise concerns, but use of a plastic member raises other mechanical issues not present in the metal-to-metal design. Specifically, this configuration uses a separate plastic molded component to couple the shaft to the inner gear. The plastic member reduces noise and the low-lubricity wear issues related to the metal-to-metal interfaces, but is not as strong and is more susceptible to fracturing or mechanical failure under high cyclic loading because of the weaker properties of the plastic material.

A need exists for a more robust drive shaft to gear coupling in an electronic fuel pump that alleviates one or more of these shortcomings.

An improved fluid pump for a vehicle fuel delivery module is provided. In specific embodiments, the fluid pump includes a housing and an inlet plate disposed within the housing. The inlet plate has an inlet which introduces fluid to the housing. An outlet plate is disposed within the housing. The outlet plate has an outlet passage. The fluid pump also includes an outlet which discharges fluid from the housing. The inlet, outlet passage, and outlet are in fluid communication with each other. An electric motor is disposed with the housing between the outlet plate and the outlet. The electric motor has a shaft that rotates about an axis. A pumping arrangement is rotationally coupled to the shaft such that rotation of the pumping arrangement by the shaft causes fluid to be pumped from the inlet to the outlet passage and through the outlet. The pumping arrangement is located axially between the inlet plate and the outlet plate, and the pumping arrangement includes a rotating element. The fluid pump further includes a thrust bearing driver including a disc-like plate having first and second faces, and two posts extending perpendicularly from the first face. The shaft has a terminal end including a pair of slots that cooperate with the posts of the thrust bearing driver. The rotating element has an inner surface including a pair of slots that cooperate with the posts of the thrust bearing driver. The posts of the thrust bearing driver are received in the slots of both the shaft and the rotating element, and the thrust bearing driver is sandwiched between the shaft, the inlet plate, and the rotating element.

In particular embodiments, the posts of the thrust bearing driver have a polygonal or a circular cross-sectional shape.

In specific embodiments, the slots of the shaft and the rotating element have a shape that complements the cross-sectional shape of the posts of the thrust bearing driver.

In particular embodiments, the posts of the thrust bearing driver have an outer portion that includes a rounded surface and an inner portion that includes a flat surface.

In specific embodiments, the slots of the shaft have a shape that complements the flat surface of the posts of the thrust bearing driver, and the slots of the rotating element have a shape that complements the rounded surface of the posts of the thrust bearing driver.

In particular embodiments, the posts of the thrust bearing driver are symmetrically arranged on the first face of the plate.

In particular embodiments, the posts of the thrust bearing driver are arranged proximate an outer edge of the plate.

In particular embodiments, the terminal end of the shaft engages the first face of the plate.

In particular embodiments, the second face of the plate engages a surface of the inlet plate.

In particular embodiments, the posts of the thrust bearing driver mate with the slots of the shaft and the slots of the rotating element to couple the shaft to the rotating element.

In particular embodiments, the thrust bearing driver is sandwiched between the shaft and the inlet plate in an axial direction, and the thrust bearing driver is sandwiched between the shaft and the rotating element in a radial direction.

In specific embodiments, the rotating element is an inner gear rotor that together with an outer gear rotor form the pumping arrangement.

Various advantages and aspects of this disclosure may be understood in view of the following detailed description when considered in connection with the accompanying drawings, wherein:.

A fluid pump is provided. Referring to <FIG>, wherein like numerals indicate corresponding parts throughout the several views, the fluid pump is illustrated and generally designated as a fuel pump <NUM> for pumping liquid fuel, by way of non-limiting example only gasoline or diesel fuel, from a fuel tank (not shown) to an internal combustion engine (not shown). While the fluid pump is illustrated as fuel pump <NUM>, it should be understood that the invention is not to be limited to a fuel pump, but could also be applied to fluid pumps for pumping fluids other than fuel. The fuel pump <NUM> includes a thrust bearing driver that provides for one or more of improved durability, reduced noise, torque transfer between the motor drive shaft and the pump gears, and angular and radial self-alignment of the drive shaft, pump inner gear, and pump inlet plate. Certain features of the fuel pump <NUM> are functional, but can be implemented in different aesthetic configurations.

With reference to <FIG>, fuel pump <NUM> generally includes a pump section <NUM> at one end, a motor section <NUM> adjacent to pump section <NUM>, and an outlet section <NUM> adjacent to motor section <NUM> at the end of fuel pump <NUM> opposite pump section <NUM>. A housing <NUM> of fuel pump <NUM> retains pump section <NUM>, motor section <NUM> and outlet section <NUM> together. Fuel enters fuel pump <NUM> at pump section <NUM>, a portion of which is rotated by motor section <NUM> as will be described in more detail below, and is pumped past motor section <NUM> to outlet section <NUM> where the fuel exits fuel pump <NUM> through an outlet <NUM> of outlet section <NUM>.

Motor section <NUM> includes an electric motor <NUM> which is disposed within housing <NUM>. Electric motor <NUM> includes a shaft <NUM> extending therefrom into pump section <NUM>. Shaft <NUM> rotates about a first axis <NUM> when an electric current is applied to electric motor <NUM>. Electric motors and their operation are well known, consequently, electric motor <NUM> will not be discussed further herein.

With continued reference to <FIG> and now with additional reference to <FIG>, pump section <NUM> includes an inlet plate <NUM>, a pumping arrangement, and an outlet plate <NUM>. The pumping arrangement includes a rotating element that is illustrated as an inner gear rotor <NUM>. The pumping arrangement is also illustrated as including an outer gear rotor <NUM>. Collectively, inner gear rotor <NUM> and outer gear rotor <NUM> will be referred to herein as pumping arrangement <NUM>, <NUM>. Inlet plate <NUM> is disposed at the end of pump section <NUM> that is distal from motor section <NUM> while outlet plate <NUM> is disposed at the end of pump section <NUM> that is proximal to motor section <NUM>. Pumping arrangement <NUM>, <NUM> is rotatably disposed within a gear rotor bore <NUM> which extends into outlet plate <NUM> from the face of outlet plate <NUM> that abuts inlet plate <NUM>. Gear rotor bore <NUM> is centered about a second axis <NUM> (best shown in <FIG>) which is parallel and laterally offset relative to first axis <NUM>. In this way, pumping arrangement <NUM>, <NUM> is located axially between inlet plate <NUM> and outlet plate <NUM> such that inlet plate <NUM> interfaces with pumping arrangement <NUM>, <NUM> in an inlet sealing surface interface <NUM> and such that outlet plate <NUM> interfaces with pumping arrangement <NUM>, <NUM> in an outlet sealing surface interface <NUM>. Gear rotor bore <NUM> is diametrically sized to allow outer gear rotor <NUM> to rotate freely therein while substantially preventing radial movement of outer gear rotor <NUM>. Gear rotor bore <NUM> is axially sized, i.e. in the direction of second axis <NUM>, to be slightly larger than the thickness of pumping arrangement <NUM>, <NUM> in order to allow inner gear rotor <NUM> and outer gear rotor <NUM> to rotate freely therein while keeping the clearance at inlet sealing surface interface <NUM> and outlet sealing surface interface <NUM> sufficiently small to allow the fluid to be pressurized by rotation of pumping arrangement <NUM>, <NUM>. By way of non-limiting example only, the axial clearance at each of inlet sealing surface interface <NUM> and outlet sealing surface interface <NUM> may be <NUM>, for a total of <NUM> axial clearance provided for pumping arrangement <NUM>, <NUM> within gear rotor bore <NUM>. Inlet plate <NUM> includes an inlet <NUM> which extends therethrough to provide fluid communication from the outside of fuel pump <NUM> to gear rotor bore <NUM> while outlet plate <NUM> includes an outlet plate outlet passage <NUM> which extends therethrough to provide fluid communication from gear rotor bore <NUM> to outlet section <NUM>.

Inner gear rotor <NUM> includes a plurality of external teeth <NUM> on the outer perimeter thereof which engage complementary internal tooth recesses <NUM> of outer gear rotor <NUM>, thereby defining a plurality of variable volume pumping chambers <NUM> between inner gear rotor <NUM> and outer gear rotor <NUM>. It should be noted that only representative external teeth <NUM>, internal tooth recesses <NUM> and pumping chambers <NUM> have been labeled in the drawings. As shown, inner gear rotor <NUM> has eight external teeth <NUM> while outer gear rotor <NUM> has nine internal tooth recesses <NUM>; however, it should be understood that inner gear rotor <NUM> may have any number n external teeth <NUM> while outer gear rotor <NUM> has n+<NUM> internal tooth recesses <NUM>. Inlet <NUM> of inlet plate <NUM> is aligned with a portion of gear rotor bore <NUM> within which the geometry between external teeth <NUM> and internal tooth recesses <NUM> create pumping chambers <NUM> of relative large size while outlet plate outlet passage <NUM> of outlet plate <NUM> is aligned with a portion of gear rotor bore <NUM> within which the geometry between external teeth <NUM> and internal tooth recesses <NUM> create pumping chambers <NUM> of relatively small size. A sleeve <NUM> is disposed in an outlet plate bore 32a of outlet plate <NUM>. Shaft <NUM> extends the sleeve <NUM> such that sleeve <NUM> and shaft <NUM> form a bearing interface which allows shaft <NUM> to rotate freely about first axis <NUM> while preventing movement of shaft <NUM> in a lateral direction relative to first axis <NUM>. Inner gear rotor <NUM> may also include a notch <NUM> in which an end of sleeve <NUM> is disposed. In alternative embodiments not shown, shaft <NUM> may extend through the outlet plate bore 32a of outlet plate <NUM> such that outlet plate bore 32a and shaft <NUM> form the bearing interface, i.e. the sleeve <NUM> may not be present. Inner gear rotor <NUM> is rotationally coupled to shaft <NUM> as described in more detail below, and consequently, when electric motor <NUM> is rotated by application of an electric current, inner gear rotor <NUM> rotates about first axis <NUM>. By virtue of external teeth <NUM> engaging internal tooth recesses <NUM>, rotation of inner gear rotor <NUM> causes outer gear rotor <NUM> to rotate about second axis <NUM>. In this way, the volume of pumping chambers <NUM> decreases as each pumping chamber <NUM> rotates from being in communication with inlet <NUM> to being in communication with outlet plate outlet passage <NUM>, thereby causing fuel to be pressurized and pumped from inlet <NUM> to outlet plate outlet passage <NUM>. The fuel is then communicated past the electric motor <NUM> to outlet <NUM>.

A thrust bearing driver <NUM> couples shaft <NUM> to inner gear rotor <NUM>. Thrust bearing driver <NUM> includes a disc-like plate <NUM> having a first face <NUM> and a second face <NUM>. Two projections in the form of pins, prongs, or posts <NUM> extend generally perpendicularly from first face <NUM>. Posts <NUM> are generally elongated and have a length in an axial direction (direction of first axis <NUM>) that is much larger than the thickness of plate <NUM> in the axial direction. As shown in <FIG>, posts <NUM> are also generally cuboid/prismoid/prismatic in shape (such as a generally rectangular prism) with a generally parallelogram cross-section (e.g., square, rectangular), although the posts are not limited to this shape and may be, for example, cylindrical in shape or have any of various polygonal shapes. For example, as shown in <FIG>, the posts <NUM> of a thrust bearing driver <NUM> may be cylindrical and have a circular cross-sectional shape. Alternatively, as shown in <FIG>, the posts <NUM> of a thrust bearing driver <NUM> may have a "half-rounded" shape in which the outer half of the post <NUM> is cylindrical (with a semi-circular cross-section) and has a rounded/curved surface, while the inner half of the post <NUM> is polygonal (square, rectangle, etc.) and has generally flat surfaces (with a square or rectangular cross-sectional shape). Additionally, while the posts <NUM> may have a generally square or rectangular cross-section, the corners/edges of the post may be beveled or rounded, and is within the scope of the embodiments disclosed herein.

The posts <NUM> are symmetrically disposed on the first face <NUM> such that the posts <NUM> are an equal distance from the center of face <NUM>. The posts <NUM> are also disposed proximate an outer edge <NUM> of the plate <NUM>. Shaft <NUM> has a terminal end <NUM> opposite motor <NUM> that includes a pair of slots <NUM> radially disposed on the side surface <NUM> of the shaft <NUM>, the slots <NUM> being formed as depressions in the side surface <NUM>. Slots <NUM> are arranged <NUM> degrees from each other in a radial direction around surface <NUM>, extend axially from terminal end <NUM> towards motor <NUM>, and are in the form of an elongated curved groove. The slots <NUM> of shaft <NUM> have a shape that complement (are sized and shaped) to receive and mate with the posts <NUM> of thrust bearing driver <NUM>. For example, as shown best in <FIG>, the slots <NUM> have flat sides and a generally rectangular shape to receive the posts <NUM> of the thrust bearing driver <NUM>. Alternatively, as shown in <FIG>, in embodiments in which the cylindrical shaped posts <NUM> having a circular (or semi-circular) cross-section, the slots <NUM> of the shaft <NUM> have a semicircular cross-section and are generally rounded to receive the cylindrical shaped posts <NUM>. The terminal end <NUM> of shaft <NUM> is disposed between the two posts <NUM>, and when posts <NUM> are received in slots <NUM>, the terminal end <NUM> contacts and engages first face <NUM> of thrust bearing driver <NUM>. Similarly, inner gear rotor <NUM> has an inner circular/cylindrical surface <NUM> that includes a pair of slots <NUM> radially disposed on surface <NUM> of the inner gear. The inner surface <NUM> of inner gear rotor <NUM> defines a void space in the center of the inner gear rotor <NUM> through which the shaft <NUM> is disposed. Slots <NUM> are arranged <NUM> degrees from each other in a radial direction around surface <NUM>, extend axially from a side <NUM> of inner gear rotor <NUM>, and are in the form of an elongated curved groove. The slots <NUM> also may not extend all the way from side <NUM> of the inner gear rotor <NUM> to the opposite side <NUM>. The slots <NUM> of innergear rotor28 have a shape that complements (is sized and shaped) to receive and mate with the posts <NUM> of thrust bearing driver <NUM>. Particularly, when the posts <NUM> of thrust bearing driver <NUM> are received in slots <NUM>, the shaft <NUM> is coupled to the inner gear rotor <NUM>, the side <NUM> of the inner gear rotor <NUM> faces an inner surface <NUM> of inlet plate <NUM>, and the second face <NUM> of the thrust bearing driver <NUM> engages the inner surface <NUM>. In this arrangement, thrust bearing driver <NUM> is sandwiched between shaft <NUM> and inlet plate <NUM> in an axial direction (in the direction of first axis <NUM>), and is sandwiched between shaft <NUM> and inner gear rotor <NUM> in a radial direction (in a direction extending outwardly from and perpendicular to the first axis <NUM>). In the alternative embodiments of the thrust bearing driver <NUM> shown in <FIG>, the thrust bearing driver <NUM> has a polygonal inner half having flat sides that mate with a shaft having slots with flat sides, while the thrust bearing driver <NUM> has a rounded outer half that mates with rounded slots on the inner gear rotor <NUM>.

In operation, electricity is applied to electric motor <NUM> which causes pumping arrangement <NUM>, <NUM> to rotate via rotating of shaft <NUM>, thereby drawing fuel in through inlet <NUM> to pumping chambers <NUM> at an initial pressure which may be by way of non-limiting example only, <NUM> kPa. Rotation of pumping arrangement <NUM>, <NUM> further causes the volume of pumping chambers <NUM> to decrease as each pumping chamber <NUM> rotates from being in communication with inlet <NUM> to being in communication with outlet plate outlet passage <NUM>, thereby causing fuel to be pressurized to a final pressure which may be by way of non-limiting example only, on the order of <NUM> kPa, and pumped from inlet <NUM> to outlet plate outlet passage <NUM> to high pressure chamber # located downstream of outlet plate outlet passage <NUM> within housing <NUM>. The fuel is communicated past electric motor <NUM> to outlet <NUM>. The thrust bearing driver <NUM> transfers torque from the shaft <NUM> to the pumping arrangement <NUM>, <NUM>, and balances the load prevent against radial side loading to keep the inner gear rotor <NUM> centered. The thrust bearing driver <NUM> also provides a bearing surface between the shaft <NUM> and the inlet plate <NUM> to reduce or eliminate noise and wear that typically exists with direct shaft to inlet plate surface arrangements. Further, the thrust bearing driver <NUM> provides angular and radial alignment of the shaft <NUM>, the inner gear rotor <NUM>, and the inlet plate inner surface <NUM> to prevent against misalignment of the shaft <NUM> to the inlet plate <NUM> and to ensure contact of the thrust bearing driver <NUM> with the inlet plate surface <NUM>. Moreover, the thrust bearing driver <NUM> provides a dual pin/key engagement of the shaft <NUM> and inner gear rotor <NUM> that adds durability to the drive of the fuel pump <NUM>.

Claim 1:
A fluid pump (<NUM>) comprising:
a housing (<NUM>);
an inlet plate (<NUM>) disposed within the housing (<NUM>), the inlet plate (<NUM>) having an inlet (<NUM>) which introduces fluid to the housing (<NUM>);
an outlet plate (<NUM>) disposed within the housing (<NUM>), the outlet plate (<NUM>) having an outlet passage (<NUM>);
an outlet (<NUM>) which discharges fluid from the housing (<NUM>);
the inlet (<NUM>), outlet passage (<NUM>), and outlet (<NUM>) being in fluid communication with each other;
an electric motor (<NUM>) disposed with the housing (<NUM>) between the outlet plate (<NUM>) and the outlet (<NUM>), the electric motor (<NUM>) having a shaft (<NUM>) that rotates about an axis (<NUM>);
a pumping arrangement (<NUM>, <NUM>) rotationally coupled to the shaft (<NUM>) such that rotation of the pumping arrangement by the shaft causes fluid to be pumped from the inlet (<NUM>) to the outlet passage (<NUM>) and through the outlet (<NUM>), the pumping arrangement being located axially between the inlet plate (<NUM>) and the outlet plate (<NUM>), and the pumping arrangement including a rotating element (<NUM>); and characterised by further comprising:
a thrust bearing driver (<NUM>) including a disc-like plate (<NUM>) having first (<NUM>) and second (<NUM>) faces, and two posts (<NUM>) extending perpendicularly from the first face (<NUM>);
the shaft (<NUM>) having a terminal end (<NUM>) including a pair of slots (<NUM>) that cooperate with the posts (<NUM>) of the thrust bearing driver (<NUM>);
the rotating element (<NUM>) having an inner surface (<NUM>) including a pair of slots (<NUM>) that cooperate with the posts (<NUM>) of the thrust bearing driver (<NUM>);
wherein the posts (<NUM>) of the thrust bearing driver (<NUM>) are received in the slots (<NUM>, <NUM>) of both the shaft (<NUM>) and the rotating element (<NUM>), and the thrust bearing driver (<NUM>) is sandwiched between the shaft (<NUM>), the inlet plate (<NUM>), and the rotating element (<NUM>).