JP2007522384A - Inexpensive gear fuel pump - Google Patents

Abstract

The present invention is directed to a gear pump having a housing 10 'with an internal pump chamber 200, an inlet 40' to it, and an outlet 42 'therefrom. The outlet is spaced from the inlet. A set of rotating gears 330, 332 are disposed in the chamber. The gear includes teeth that mesh during rotation. The gear is preferably a powder metal structure and is fixed to shafts 230, 232 having a rotation axis. A set of integral bearings 210, 212 is disposed within the chamber and bears one of the first and second ends of each shaft 320. The integral bearing provides precise alignment of the first and second ends of the shaft and keeps the shaft parallel.
[Selection] Figure 4

Description

This application claims priority from US Provisional Patent Application No. 60 / 554,582, filed February 13, 2004, and is hereby incorporated by reference.
The present invention relates generally to gear pumps. More particularly, the present invention relates to an improved bearing and gear assembly structure, and more particularly to what is used as a fuel pump and a method of manufacturing the same.

  A typical gear fuel pump is a fixed discharge pumping device. It receives fuel from a fuel tank, pressurizes the fuel, and delivers the fuel at high pressure to a fuel nozzle via an engine combustion fuel controller. A gear pump includes a housing, such as an aluminum housing, having an internal pump chamber generally formed by parallel intersecting cylindrical holes. Normally, first and second gears of similar shape are arranged in each hole, and the gears mesh with each other at the hole crossing region inside the housing. The first or drive gear has a splined drive shaft, and the first gear drives a second gear (commonly called a driven gear) as the shaft rotates. As the gear rotates in the housing, fluid is pumped from the pump inlet to the outlet. Gears are highly stressed at high pressures and loads. Spur or helical gears are used. Although spur gear is the most common. The gear is driven so that it does not mesh near the inlet and carries fluid around the hole to the area where the gear meshes. Gear engagement pushes fluid out of the pump chamber and fluid exits the pump housing from the outlet.

  During pump operation, the pressure of the fluid to be pushed out is higher at the outlet than at the inlet, so that the differential pressure creates a leakage flow from the outlet to the inlet across the boundaries of the various components. This leakage flow reduces the efficiency of the pump. In some cases, the leakage flow can vary considerably from one identical pump to another. Since the volume to be pushed out is a direct function of the volume discharged by the meshing gear, the variation in the depth of the meshing gear greatly affects the flow rate. It is therefore important to provide accurate gear alignment and meshing to improve pump efficiency.

  Typically, four separate bearings are placed in the holes to bearing or support a portion of the gear shaft. The bearing is typically in the form of a generally cylindrical outer surface with a flat surface that engages face-to-face along a portion of the circumference that aligns with the meshing area of the gear. The bearing is sized to fit into the pump chamber. In the usual case, the bearing is made with great care with respect to the design dimensions between the center of the plane and the diametrically opposite side of another cylindrical bearing. In order to minimize leakage paths, such bearings are made to form a tight fit within each hole in the pump and are not rare and good fits are always achieved due to tolerance variations. Not necessarily. Thus, during the assembly process, it was customary to scrape material from one or more bearing planes with the expectation that a precise fit would be achieved. Indeed, the bearings are designed to be trimmed to absorb tolerance variations while attempting to maintain a tight fit.

  However, in the cutting process, the parallelism of the flat surface with respect to the axial center line of the bearing may be lost, and a leakage path is generated. Instead, the flatness of the surface is lost during the cutting process and a leak path across the plane is generated again. The cutting process may lose the squareness or right angle accuracy of the flat surface with respect to the end of the bearing. It does not seal properly against the housing end wall and either prevents the bearing from moving properly in response to shaft deflection during operation or causes shaft misalignment. Cutting can also result in altered depths of meshing of the gears supported by the bearings, which change the pump flow rate.

  Another fundamental factor that produces different flow rates in other identical pumps is that each splined drive shaft and corresponding gear are conventionally made into a single bar driven gear, and its rod-like portion (ie, drive shaft) and gear Is formed as a single integrated unit. Thus, both ends of the drive shaft may be manufactured separately, resulting in different diameters at both ends that provide mating with the bearing.

  Commonly assigned US Pat. No. 6,042,352 is directed to a type of gear pump in which an improved gear fuel pump has been developed. Other existing gear pump designs include U.S. Pat. Nos. 4,682,938, 4,193,745, 4,097,206, 3,003,426, No. 981,200 and No. 2,774,309 are known in the art.

  In view of the foregoing, it is apparent that there is a need for an improved gear pump that provides a solution to one or more of the disadvantages in the art. Improved gear pumps, such as fuel pumps, that provide a solution to each need that has been poorly addressed by the prior art, while providing a number of advantages to them that have not previously been realized, are notable in the art. It is still clearer to represent progress.

A new and improved gear fuel pump assembly is provided.
In particular, according to one embodiment of the present invention, the gear pump includes a housing that includes an internal pump chamber and an inlet and an outlet that are in communication with the chamber and are spaced apart. A set of rotating gears is disposed in the chamber, and each gear is fixed to each shaft having a rotating shaft. The gear teeth mesh and pressurize the fluid that is pushed out through the housing. A set of integral bearings are disposed at both ends of the gear within the chamber and bearing one of the first and second ends of each shaft. The integral bearing provides precise alignment of the first and second shafts and keeps the shafts parallel.

  Preferably, the gear is formed from powder metal and is fixed to a constant diameter shaft. Each gear is keyed to one of the shafts to rotate together, and if there is a slight misalignment, the dimensional tolerance between the shaft and the gear provides proper gear engagement.

  In accordance with another embodiment of the present invention, a method for assembling a gear pump is provided. The method includes providing first and second shafts having a substantially constant diameter along the longitudinal direction. Gears are advanced on each shaft and secured to each shaft. The integral bearing is then attached to the shaft. A bearing and geared shaft are mounted within the gear pump housing.

  According to one aspect of the invention, the integral bearing and gear are made from powdered metal. By using powder metal technology, integral bearings and gears can be formed without the need for extensive additional machining.

A major advantage of the present invention is the ability to provide a homogeneous integral bearing that has a high degree of accuracy in alignment compared to conventional bearings.
Another advantage of the present invention is the ability to provide a powder metal component for a gear pump that lasts longer than a component molded from conventional materials.

Yet another advantage resides in precision alignment associated with the use of integral bearings.
A further advantage is the considerable savings associated with powder metal components by reducing the extensive additional manufacturing steps associated with conventional bearings, gears, and shafts.

  Still further advantages and aspects of the present invention will become apparent from a reading and understanding of the following detailed description of the preferred embodiments.

  It should be understood that the description and drawings herein are merely exemplary, and that various modifications and changes may be made in the disclosed structure without departing from the spirit of the invention. Like numbers refer to like parts throughout the several views.

  Referring to FIG. 1, a conventional gear pump assembly GP is generally made of aluminum and typically includes a housing 10 having end flanges 12, 14 and an end plate or lid 16 for sealing the housing. Including. The end flange 12 includes a plurality of holes 18 and the lid 16 includes corresponding holes 20 that are dimensioned to receive conventional fasteners F that secure the lid to the housing. As shown in FIGS. 1 and 2, the end flange 12 and the lid 16 are substantially polygonal in cross section. However, it should be understood by those skilled in the art that end flange 12 and lid 16 may have other shapes based on the gear pump and / or the environment in which the pump is used. The housing further includes a recess 22 that receives the seal 24. The end flange 14 also includes a plurality of mounting holes 26 for mounting the gear pump GP to an optional rotational energy source (not shown).

  Referring to FIG. 2, the housing 10 includes a chamber 30 formed by two parallel intersecting cylindrical holes 32, 34. The housing 10 has an inlet 40 and an outlet 42. As shown in FIG. 1, the gear pump GP further includes a first gear 50 and a second gear 52 disposed in the holes 32 and 34 so as to substantially mesh with each other in a region indicated by a broken line 54 in FIG. 3. The first gear 50 is molded integrally with the hollow drive shaft or journal 60, while the second gear 52 is molded integrally with the hollow drive shaft or journal 62. Typically, shafts and gears are made from rods and machined to the desired shaft diameter and gear details. As will be appreciated, a substantial amount of bar is removed in this conventional manufacturing operation. Further, as described in the prior art, there are problems associated with the conventional structure.

  The driven shaft 62 includes a splined inner surface (not shown). The splined inner surface is engaged by the splined end of the rotating shaft S connected to a rotational energy source. The rotating shaft S passes through an opening (not shown) in the housing. An O-ring 68 and shaft seal 70 are provided around the opening to prevent external leakage of the gear pump. Seal 72 is normally connected to the drive shaft.

  Within the housing 10, both shafts 60, 62 have ends 76 that are supported or supported by each first bearing 80 and second bearing 82. The bearings 80, 82 are molded separately and are formed in a generally cylindrical shape about the axis of rotation of the shaft defined by the cylindrical openings 84, 86. Each bearing is provided with a respective plane 88, 90 at a portion directly adjacent to the point 54 where the gears 50, 52 mesh. Each plane 88 of the adjacent bearing 80 includes a hole or recess 92. The planes 88 face each other and are engaged with each other by pins 94 received in the holes. Similarly, each plane 90 of adjacent bearing 82 includes a hole or recess 96 that receives a pin 98. The planes 88, 90 are intended to be defined by a plane parallel to the center line of the openings 84, 86.

  Generally, the bearing is fixed longitudinally within the cylindrical holes 32, 34 of the housing 10. However, the bottom surface 100 of each bearing 82 includes a flange 102 having a plurality of openings (not shown) for receiving individual springs 104. In this way, the pressure bearing is longitudinally pressed or biased along the end 76 of the shaft 60, 62 within the cylindrical bore.

  The fuel is pushed out from the low pressure inlet side of the bearing 82 to the high pressure discharge side of the bearing 82. Gears 50, 52 received longitudinally between the bearings 80, 82 rotate about each parallel axis and mesh together. Fluid is moved from the inlet to the outlet around the outside of the gears 50, 52 to the outlet in a manner well known in the art.

  As shown in FIGS. 1 and 2, the cylindrical holes 32, 34 of the bearing structure and the housing 10 have an 8-shaped shape. In the manufacture of conventional bearings 80, 82, the controlled tolerance is the distance from the plane 88, 90 to the diametrically opposite point around the bearing. As described above, the planes 88, 90 are typically cut so that the bearings 80, 82 are fitted into the gear pump housing 10. In this way, controlled tolerances are lost to some extent during the cutting process. Since the bearing planes used in conventional gear pumps require cutting during assembly, the plane parallelism is lost to the bearing centerline, the planes associated with the respective top surfaces 110, 112 and bottom surfaces 114, 100 of the bearings 80, 82. A loss of flatness or squareness of 88, 90 occurs. As a result, the gear pump GP will leak or be less efficient than desired.

  As briefly described above, the gears 50, 52 are formed integrally with the shafts 60, 62. Each shaft and corresponding gear is manufactured from a single bar, in which case both ends 76 of the shaft and the gear are molded as a single unit. In this way, both ends of the shaft, which may result in different diameters at both ends, are molded separately. In order to correct this dimensional difference, the diameter of the large opposite end is usually polished to match the diameter of the other end. However, this polishing process may result in a loss of squareness or perpendicularity of the shafts 60,62 relative to the integral gears 50,52. This affects the meshing of the gears, and the volume being pushed out is a direct function of the volume discharged by the meshing gear, thus affecting the flow rate of the gear pump.

  Referring to FIG. 4, a gear pump according to the present invention is shown. Since many of the structures and functions are substantially identical, reference numbers with a single prime symbol (') refer to similar components (eg, housing 10 is referenced by reference number 10'); The new number displays the new component. Similarly, a description of components that remain unchanged is unnecessary.

  The gear pump GP ′ shown in FIGS. 4-6 includes a housing 10 ′ having a chamber 200 defining a single cylindrical hole 202. The housing 10 ′ receives a set of bearings 210, 212. Each bearing is an integral bearing formed from powder metal. That is, the bearing is a substantially homogeneous component that does not have a connecting line. They are continuous when compared to conventional two-body bearing assemblies. Each bearing preferably has a generally oval cross section. It will be appreciated that the circumference of each bearing mates with a similar measuring hole 202 in the housing 10 '. However, those skilled in the art will appreciate that the bearings and corresponding holes may have other contours that allow each bearing to be received in the chamber 200 of the housing 10 '.

  Referring to FIGS. 8-10, the integral bearing 210 fixed approximately longitudinally within the housing is concentric with the first or top surface 220, the second or bottom surface 222, and the axis of rotation of the shaft or journal 230,232. And a set of openings 224, 226 having a central axis. The bearing further includes first and second extension surfaces 236, 238. The first extension surface is substantially parallel to the second extension surface, and in a preferred structure, both extension surfaces are substantially planar. As described above, both ends 240 and 242 have an arc contour. However, the ends 240, 242 may have other shapes without departing from the scope and intent of the present invention.

  With continued reference to FIG. 7, the bottom surface 222 of the bearing 210 includes a dam 250, an inlet surface relief 252, and a discharge surface relief 254. In this way, the bearing dam 250 is positioned between the inlet face relief and the discharge face relief. The dam wall of the bearing forms a sealed dam region between the inlet side 256 and the outlet side 258, thus creating a low pressure region on the inlet side 40 'of the gear pump GP' and a high pressure region on its outlet side 42 '. The bearing further has an outflow hole 260 for draining the bearing lubrication. As shown in FIG. 10, the outflow hole 260 has a substantially constant diameter along its longitudinal direction and intersects the dam region 250 perpendicularly.

  Referring to FIGS. 11-14, the integral bearing 212 is concentric with the first or top surface 270, the second or bottom surface 272, the central axis of the openings 224 and 226 of the bearing 210 and the rotational axis of the shafts 230 and 232. A set of openings 274, 276 having axes. Similar to bearing 210, bearing 212 further includes first and second extended surfaces 280 and 282 that are substantially parallel and a set of arcuate ends 284, 286.

  Similar to the features of the bottom surface 222 of the bearing 210, the top surface 270 of the bearing 212 includes a dam 290, an inlet surface relief 292, and a discharge surface relief 294. The dam wall of the bearing forms a sealed dam between the inlet side 296 and the outlet side 298, thus creating a low pressure region on the inlet side 40 'of the gear pump GP' and a high pressure region on the outlet side 42 '. The bearing further includes a blind hole 300 for holding the biased spring 302.

As shown in FIG. 14, the bottom surface 272 of the bearing 212 includes a flange 310. A seal 312 is provided around the flange.
A set of gears 330, 332 are received longitudinally on shafts 230, 232 between bearings 210, 212 (FIG. 4). Referring to FIGS. 15-19, each shaft 230, 232 includes an axial recess 340 and first and second spaced circumferential grooves 342, 344 (FIG. 4). Circumferential grooves 342, 344 extend radially inward from the outer periphery 346 of each shaft for receiving a retaining ring or snap ring 350. The snap ring secures the gears 330, 332 to the shafts 230, 232 and prevents longitudinal movement of the gears with respect to each shaft.

  Each shaft 230, 232 is substantially hollow and has a substantially constant diameter along its length. As shown in FIG. 16, the shaft 232 also has a constant inner diameter. As shown in FIGS. 18 and 19, a spline is cut in a part 352 of the inner surface 350 of the drive shaft 230. The splined portion is engaged by the splined portion of the rotating shaft S ′ connected to the rotational energy source. The rotating shaft S ′ passes through an opening (not shown) in the housing.

  The shafts 230, 232 are formed by conventional metal manufacturing. On the other hand, each gear 330, 332 (FIGS. 20-21) is made of powder metal and includes an opening 360 suitable for receiving one of the shafts 230,232. The dimensional tolerance between the outer diameter of the shaft and the diameter of the gear opening 360 provides some automatic alignment of the gear teeth 362 when the gear meshes when the gear / shaft is not correctly aligned. Each gear is fixed substantially perpendicular to each shaft. Each gear further includes an axial groove 364. The shaft axial recess 340 and the gear axial groove 364 are sized to receive pins 370 that secure or key the gear to the shaft.

  In general, a first snap ring 350 is secured to one of the first and second grooves 342, 344 of the shafts 230, 232 to assemble the gear pump GP '. The snap ring prevents axial movement of the gear on the shaft. Pin 370 is placed in axial recess 340. Gears 330, 332 are advanced over each shaft so that the axial grooves are aligned with the pins and axial recesses. In this way, the axial recesses and grooves together form a pin housing, which prevents rotation of the gear on each shaft. A second snap ring 350 is secured in the other groove, thereby securing the gear to each shaft in the longitudinal or axial direction. An integral continuous bearing 212 is mounted in the chamber 202 of the housing 10 '. The assembled shaft (ie, the shaft with the gear mounted thereon) is attached to the bearing. Shaft portion 320 is received in housing openings 274, 276. The integral bearing 210 is then attached to the assembled shaft, and the shaft portion 320 is received in the housing openings 224, 226. In this way, the integral bearing provides precise alignment of the shaft and keeps the shaft parallel within the housing. A lid 16 'is secured to the housing via a conventional fastener F'.

  Accordingly, the present invention provides a gear pump having a powder metal component with distinct advantages over conventional components. In addition to the specificity of using powder metal technology to make the bearings 210, 212, the continuous shape of the bearings provides a high degree of accuracy in alignment by avoiding the conventional connected individual bearings 80,82. In this way, the central axis of the bearing opening can be accurately aligned.

  Furthermore, the integral bearings 210, 212 in the preferred embodiment are linear designs, i.e., designs that traverse the top and bottom surfaces of the bearings, while conventional bearings 80, 82 have an eight-shaped design when connected. By incorporating a linear design, a more accurate and easy alignment of the bearings 210, 212 to the chamber 200 of the housing 10 'can be achieved compared to a conventional 8-shaped design.

  The integral bearings 210, 212 allow greater control of the aperture in centerline to centerline positioning when the control is on the order of 1 / 100th of a millimeter. However, the two-part shape of the figure-eight design generally requires machining that is leveled to achieve its accuracy, which is very time consuming. In addition, since separate bearings 80, 82 are connected, separation of the two-part bearing occurs, thereby not allowing functional operation. On the other hand, since the bearings 210, 212 have a unified design, they cannot be separated during operation of the gear pump GP '.

  The advantages over the above-described conventional design approach compared to the low cost powder metal design approach of the present application are shown in Tables 1 and 2 below as an example.

It should be understood that the percentage (%) and dollar ($) figures are merely estimates, and that the values may differ from those quoted on a means-of-measure basis.
Thus, the use of powdered metal to manufacture the gear pump GP 'component results in an improved manufacturing cost structure for gear pump manufacturing and assembly. This is true because gears, bearings and shafts make up the majority of the fuel pump components.

  Exemplary embodiments have been described with reference to the preferred embodiments. Obviously, modifications and changes may occur to others upon reading and understanding the above detailed description. The exemplary embodiments are intended to be configured to include all of those modifications and variations as long as they fall within the scope of the appended claims or their equivalents.

  The present invention may take physical forms in particular components and component structures. These preferred embodiments are described in detail herein and illustrated in the accompanying drawings that form a part of the present invention.

It is a disassembled perspective view of the conventional gear pump assembly. FIG. 2 is a partially cutaway top view of a cover plate and a housing of the conventional gear pump assembly shown in FIG. 1. It is sectional drawing seen roughly along the 3-3 line of FIG. 1 is an exploded perspective view of a gear pump assembly according to the present invention. FIG. FIG. 5 is a partially cutaway top view of the cover plate and the housing of the gear pump assembly shown in FIG. 4. FIG. 6 is a cross-sectional view schematically seen along line 6-6 in FIG. FIG. 5 is a bottom view of the integral first bearing of the gear pump assembly shown in FIG. 4. It is sectional drawing seen roughly along the 8-8 line of FIG. 7 which shows a 1st bearing. FIG. 5 is a top view of a first bearing of the gear pump assembly of FIG. 4. FIG. 10 is a cross-sectional view schematically seen along line 10-10 in FIG. 9; FIG. 5 is a top view of an integral second bearing of the gear pump assembly shown in FIG. 4. FIG. 12 is a cross-sectional view schematically showing the second bearing taken along line 12-12 of FIG. 11. It is a bottom view of the 2nd bearing of the gear pump assembly shown in FIG. FIG. 14 is a cross-sectional view schematically viewed along line 14-14 in FIG. 13. FIG. 5 is a plan view of a first shaft of the gear pump assembly of FIG. 4. FIG. 16 is a cross-sectional view schematically seen along line 16-16 in FIG. 15; It is a top view of the 2nd shaft of the gear pump assembly shown in FIG. It is a side view of the 2nd shaft of FIG. FIG. 19 is a cross-sectional view schematically seen along line 19-19 in FIG. FIG. 5 is a top view of the gear pump assembly of FIG. 4. It is sectional drawing seen roughly along the 21-21 line of FIG.

Claims (17)

A housing containing an internal pump chamber;
An entrance to the chamber;
Spaced from the inlet and outlet from the chamber;
A set of rotating gears in the chamber, the gears including teeth meshing during rotation, each gear being fixed to a shaft having a rotating shaft, and disposed in the chamber; A set of integral bearings bearing one of the first and second ends of each shaft, providing a precise alignment of the first and second ends of the shaft and maintaining the shaft in parallel Integrated bearing,
Gear pump with   The gear pump of claim 1, wherein the integral bearing is made from powdered metal.   The gear pump of claim 1, wherein each integral bearing has a generally oval cross section.   Each integral bearing includes a top surface, a bottom surface, a pair of openings having a central axis concentric with the rotational axis of the shaft, and first and second extension surfaces, and both ends of the first surface are a pair. The gear pump of claim 1, wherein the gear pump is coupled to corresponding ends of the second surface by arcuate ends.   The gear pump according to claim 4, wherein the first extension surface is parallel to the second extension surface.   The gear pump of claim 4, wherein the first and second extension surfaces are substantially flat.   The gear pump of claim 1, wherein each gear is made from powder metal.   The gear pump of claim 7, wherein each gear includes an opening that receives the shaft, thereby allowing automatic alignment of gear teeth when the gear is engaged.   The gear pump of claim 1, wherein each shaft includes an axial recess and each gear includes an axial groove dimensioned to receive a pin that prevents rotation of the gear on each shaft.   The gear pump of claim 1, wherein each shaft includes first and second grooves extending radially around each shaft to receive an associated snap ring.   The gear pump according to claim 1, wherein each gear is fixed vertically to each shaft. Providing first and second shafts having a substantially constant diameter along a longitudinal direction;
Advancing the gears on each shaft;
Fixing the gear to each shaft;
Mounting a bearing on the shaft; and mounting the bearing and the shaft on which the gear is mounted in a housing of a gear pump;
Assembly method of a gear pump comprising:   The method of claim 12, further comprising preventing rotation of the gear with respect to each shaft.   The method of claim 12, further comprising providing an integral continuous bearing at each end of the shaft.   The method of claim 14, further comprising bearing each shaft within the integral bearing, wherein the integral bearing provides accurate alignment of the shaft.   The method of claim 12, further comprising molding each gear from powder metal, whereby each gear has a substantially uniform composition throughout.   The method of claim 12, further comprising forming the bearing from powder metal, whereby the at least one bearing is homogeneous.

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