WO2021081273A1

WO2021081273A1 - Coupling between a pump cam shaft and a gear

Info

Publication number: WO2021081273A1
Application number: PCT/US2020/056975
Authority: WO
Inventors: David M. Rix; Yogesh Vasantrao Birari; Animesh NANDY; Juan Pablo Acosta TREVINO
Original assignee: Cummins Inc
Current assignee: Cummins Inc
Priority date: 2019-10-23
Filing date: 2020-10-23
Publication date: 2021-04-29
Anticipated expiration: 2022-04-23

Abstract

A coupling is disclosed which is configured to interface with and deliver torque between a first and second member. The coupling may be part of a fuel pump system for a diesel engine and may transmit torque between a fuel pump cam shaft and a gear through compressive forces on the coupling. In the event that the coupling breaks, torque is still transmittable through the coupling. The cam shaft is configured to retain the coupling in place, as well as to break upon the delivery of a maximum torque. The disclosed torque delivery system provides increased strength to withstand engine overspeed events.

Description

COUPLING BETWEEN A PUMP CAM SHAFT AND A GEAR

FIELD OF THE DISCLOSURE

[0001] The present disclosure generally relates to couplings utilized to transfer torque, and more particularly to a coupling to transfer torque between a camshaft and a gear for a fuel pump system.

BACKGROUND OF THE DISCLOSURE

[0002] Many trucks on the road are powered by diesel engines, which utilize a fuel pump system where fuel is pumped from a low-pressure pump to a high-pressure pump before entering the common rail and ultimately the engine through fuel injectors. The high and low-pressure pumps are driven by a shared camshaft that directly drives the low-pressure pump. Engine braking is a common method used by vehicles with diesel engines to decelerate the vehicle when driving down a decline. However, this causes a sudden acceleration of the engine crankshaft, which also results in a sudden acceleration of the fuel pump camshaft. A similar phenomenon can occur in the event of a gear mis-shift i.e. shifting from a high gear to a low gear by skipping intermediate gears. Engine braking and gear mis- shifts are also known as engine overspeed events. The sudden acceleration from overspeed events often causes the coupling between the camshaft and the pinion gear in the low- pressure pump to break due to high torsional stress. The pieces of the broken coupling can then enter the fuel pump system, where they cause even more damage to the engine and surrounding parts of the vehicle. It is desirable to have a stronger coupling that can withstand the sudden accelerations caused by engine overspeed, while still maintaining the ability to quickly decouple the camshaft from the low-pressure pump if one of the pumps seizes. Furthermore, it is desirable to design a coupling that, upon failure, will not result in broken pieces that may enter the engine during operation.

SUMMARY OF THE INVENTION

[0003] According to one embodiment, the present disclosure provides a coupling between a pump cam shaft and a gear comprising an interior surface configured to interface with a first member; an exterior surface configured to interface with a second member; and a number of contact surfaces to transmit a torque from the first member to the second member, wherein the torque is transmittable through at least a compressive force on the coupling, and further wherein the torque is transmittable through the coupling if the coupling is broken.

[0004] According to another embodiment, the present disclosure provides a torque delivery system comprising a pump cam shaft; a drive end coupled to an end of the pump cam shaft; a coupling comprising a variable cross-sectional width, wherein an interior surface of the coupling is configured to couple with the drive end of the pump cam shaft; and a gear comprising a plurality of teeth, wherein an interior of the gear is configured to couple with an exterior surface of the coupling, such that a torque is transmittable between the pump cam shaft and the gear through the coupling.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0006] FIG. l is a front view of a coupling according to an embodiment of the present disclosure;

[0007] FIG. 2 is a partial front view of the coupling of FIG. 1;

[0008] FIG. 3 is a partial front view of another embodiment of the coupling of FIG. 1;

[0009] FIG. 4 is a perspective view of a pump cam shaft according to an embodiment of the present disclosure;

[0010] FIG. 5 is an enlarged partial, perspective view of the pump cam shaft of FIG.

3;

[0011] FIG. 6 is a perspective view of a gear according to an embodiment of the present disclosure;

[0012] FIG. 7 is a perspective view of the coupling, pump cam shaft, and gear of

FIGS 1, 2, and 4, respectively; [0013] FIG. 8 is a perspective view of a low pressure fuel pump according to an embodiment of the present disclosure;

[0014] FIG. 9 is a front view of the low pressure fuel pump of FIG. 7; and

[0015] FIG. 10 is a cross-sectional view of a fuel pump system according to an embodiment of the present disclosure.

[0016] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the disclosure and such exemplifications are not to be construed as limiting the scope of the disclosure in any manner.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

[0017] Referring to FIGS. 1, 4, 6, and 10, in the illustrated embodiment, pump cam shaft 200 is part of a drive system for a high-pressure pump (HPP) 500, and gear 300 is part of a low pressure pump (LPP) 400 of a fuel injection system for a diesel engine (not shown). Pump cam shaft 200 receives torque from an upstream engine drive train and drives operation of the high-pressure pump 500 to pressurize low pressure fuel to a higher pressure before entering an accumulator (e.g., a common rail) for delivery to the engine cylinders by the fuel injectors. Coupling 100 couples pump cam shaft 200 to gear 300 so that pump cam shaft 200 can deliver a torque to gear 300. Gear 300 transfers torque from HPP 500 to LPP 400 to power operation of LPP 400. In combination, pump cam shaft 200, coupling 100, and gear 300 comprise a torque delivery system, or a torque assembly.

[0018] Referring now to FIGS. 1-2, an exemplary coupling 100 comprises an interior surface 105, an exterior surface 110, exterior contact members 120, and interior contact members 122. In the illustrated embodiment, coupling 100 comprises five exterior contact members 120, and five interior contact members 122. In other embodiments, coupling 100 may comprise any number of exterior contact members 120 and interior contact members 122. Coupling 100 of the illustrated embodiment is partially shaped from the intersection of two circles, Cl and C2 with respective diameters D1 and D2. In this way, the cross-sectional width of coupling 100 increases near ends of exterior contact members 120. Coupling 100 has a variable cross-sectional width between exterior contact members 120 and interior contact members 122, comprising a cross-sectional width W1 at a first location, and a shorter cross-sectional width W2 at a second location, where W1 and W2 are defined by the distance between the circumferences of circle Cl and circle C2, as shown in FIG. 2. Circles Cl and C2 are offset in such a way that the distance between their circumferences is variable, so the cross-sectional width of coupling 100 changes gradually with the curve of circles Cl and C2. Because coupling 100 has a larger cross-sectional width W1 near exterior contact members 120, coupling 100 can withstand higher compressive forces.

[0019] Coupling 100 also comprises a number of interior corners 132, exterior corners 134, interior edges 142, and exterior edges 144. Interior and exterior corners 132 and 134 may be positioned proximate interior contact members 122 and exterior contact members 120 respectively, or may generally refer to any corners on the respective interior or exterior of the coupling 100. Furthermore, interior and exterior edges 142 and 144 may refer to comer edges of the coupling 100 formed by the intersection of two faces of the coupling 100, or may also refer to the surfaces of faces themselves. Referring now to FIG. 3, interior comers 132, exterior comers 134, interior edges 142, and exterior edges 144 may be curved, beveled, chamfered, or otherwise rounded. Rounding edges and corners of the coupling 100 may reduce the magnitude of stress on the coupling 100 when in use.

[0020] In the illustrated embodiment, coupling 100 is composed of a polymer, such as polyether ether ketone, polycarbonate, polylactic acid, polyaryletherkeytone, acrylonitrile butadiene styrene, polyethylene, polyvinyl chloride, or other thermoplastics or thermosets. In other embodiments coupling 100 may be composed of metal or a polymer coated metal. The coupling 100 may be formed by molding, extrusion, additive manufacturing such as 3D printing, or any other manufacturing technique as is known in the art. In other embodiments, interior surface 105 and exterior surface 110 may be shaped differently to accommodate different torque delivery systems with different forces acting upon coupling 100, including shear forces and torsional forces. Furthermore, coupling 100 may be any thickness to accommodate the torque assembly which it is a part of. Increasing the thickness of coupling 100 may increase the force load that the coupling 100 may withstand when in use.

[0021] Referring now to FIG. 4, pump cam shaft 200 comprises a shaft body 205, lobes 201 coupled to shaft body 205, drive end 210, and shaft bore 214. Pump cam shaft 200 is configured to rotate about a central, longitudinal axis Al. In the illustrated embodiment, pump cam shaft 200 is a cam shaft within a fuel pump system for a diesel engine (not shown). In other embodiments, pump cam shaft 200 can be any rotatable shaft configured to deliver or receive a torque within any system, not limited to engines. For example, pump cam shaft 200 may be a crankshaft, drive shaft, jackshaft, or another shaft part of any torque delivery system. In the illustrated embodiment, pump cam shaft 200 is composed of metal, but in other embodiments pump cam shaft 200 may be composed of polymer coated metal, polymers or other suitable material.

[0022] Referring now to FIG. 5, drive end 210 comprises driving members 222, and collar 215. Drive end 210 is configured to interface with interior surface 105 of coupling 100. More specifically, driving members 222 are configured to interface with interior contact members 122 of coupling 100, such that when drive end 210 rotates about axis Al, driving members 222 will engage interior contact members 122 to rotate coupling 100 about axis Al. Drive end 210 is coupled to shaft body 205 through a connecting member 220. Connecting member 220 contains a drilling 230 which connects the exterior of pump cam shaft 200 to shaft bore 214. Drilling 230 is provided to allow fluid, such as oil, to travel between the exterior of pump cam shaft 200 and the interior of shaft bore 214. Drilling 230 also creates a weak point in connecting member 220, to allow connecting member 220 to break upon the application of a maximum torque to pump cam shaft 200. In this way, in the event that LPP 400 or HPP 500 locks up or malfunctions, connecting member 220 can undergo a controlled break at connecting member 220 to prevent greater damage to the engine. The diameter of connecting member 220 can be altered based on the targeted torsional strength for the pump cam shaft 200. In other embodiments, drive end 210 and driving members 222 may differ in shape and quantity to accommodate different embodiments of coupling 100 as described previously.

[0023] Referring now to FIG. 6, gear 300 comprises teeth 310, grooves 312, a drive cavity 319 with a drive surface 322 forming drive recesses 320, and central opening 330. Teeth 310 and grooves 312 are configured to mesh with another gear as is known in the art.

In the illustrated embodiment, gear 300 is a pinion gear and is configured to mesh with exterior gear 413 (see FIG. 7). Gear 300 is configured to interface with the exterior surface 110 of coupling 100. Exterior contact members 120 are configured to interface with drive recesses 320 such that when coupling 100 rotates about axis Al, exterior contact members 120 will engage drive recesses 320 to rotate gear 300 about axis Al. In the illustrated embodiment, gear 300 is composed of metal, but in other embodiments gear 300 may be composed of polymers, polymer coated metal or other suitable materials. In other embodiments, drive recesses 320 and drive surface 322 may differ in shape or quantity to accommodate different embodiments of coupling 100 as described previously.

[0024] Referring now to FIG. 7, pump cam shaft 200, coupling 100, and gear 300 are shown as configured to be coupled to one another. Coupling 100 can be inserted into drive cavity 319 of gear 300 such that exterior contact members 120 interface with drive surface 322 to provide a stop for the insertion of coupling 100. After coupling 100 is inserted into gear 300, portions of drive cavity 319 are not covered by coupling 100 (see FIG. 8). Also, small clearances are provided between exterior contact members 120 and drive recesses 320 such that coupling 100 has a small distance to move within gear 300 to accommodate axial and angular misalignment of the torque assembly. Drive end 210 of pump cam shaft 200 can then be inserted into the interior surface 105 of coupling 100. Similarly, a small clearance is provided between interior contact members 122 and the driving members 222 such that drive end 210 has a small distance to move within coupling 100 to accommodate axial and angular misalignment of the torque delivery system. Drive end 210 interfaces with the portions of drive cavity 319 (specifically, drive surface 322) not covered by coupling 100 to prevent drive end 210 from entering central opening 330 of gear 300. When coupled together as described above, pump cam shaft 200 is driven to rotate about axis A1 by an engine (not shown), which causes driving members 222 to engage interior contact members 122, thereby causing coupling 100 to rotate about axis Al. Rotation of coupling 100 then causes exterior contact members 120 to engage drive recesses 320, thereby causing gear 300 to rotate about axis Al. Accordingly, a torque is transferred from pump cam shaft 200 to gear 300.

[0025] In other embodiments, coupling 100 may interface with two pump cam shafts instead of a pump cam shaft and a gear. In such embodiments, a first pump cam shaft may be configured to interface with interior surface 105 of coupling 100, and a second pump cam shaft may be configured to interface with exterior surface 110 of coupling 100. Furthermore, in still other embodiments, coupling 100 may interface with two gears. In such embodiments, a first gear may be configured to interface with interior surface 105 of coupling 100, and a second gear may be configured to interface with exterior surface 110 of coupling 100.

[0026] The configuration of the gear 300, coupling 100, and drive end 210 when assembled as described above results in compressive forces acting on coupling 100. In such a configuration, coupling 100 can withstand higher torques than if it were designed to withstand shear or torsional forces in the process of transferring torque. Coupling 100 also acts as a barrier between surfaces of drive end 210 and gear 300 to prevent wear over time.

[0027] In other embodiments, coupling 100, drive end 210, and gear 300 may all be configured such that coupling 100 may be inserted into drive end 210, and gear 300 may be inserted into coupling 100. In such an embodiment, drive end 210 would be configured to interface instead with exterior surface 110 of coupling 100, and gear 300 would be configured to interface with interior surface 105 of coupling 100. Furthermore, in other embodiments gear 300 may deliver torque to pump cam shaft 200 through coupling 100. In yet further embodiments, drive recesses 320 within the gear 300 may be driving members, protrusions, or other members configured to interact or interface with the coupling 100. Furthermore, driving members 222 of the pump cam shaft 200 may be recesses, or other members configured to interact or interface with the coupling 100.

[0028] Referring now to FIG. 8, low-pressure pump 400 comprises a LPP housing

405, an LPP face 410, LPP gasket 415, and plate fasteners 411. LPP housing 405 contains gear 300 which rotates about axis Al, parallel with the central axis of LPP shaft 420. Exterior gear 413 is configured to mesh with teeth 310 of gear 300 as is known in the art. The rotation of gear 300 initiates rotation in exterior gear 413. Gear 300 and exterior gear 413 are separated by divider 417 to maintain relative positions of gear 300 and exterior gear 413.

[0029] Referring now to FIG. 9, the torque delivery system is shown looking down axis Al towards low-pressure pump 400 (pump cam shaft 200 is not shown). Coupling 100 is inserted within gear 300 and configured to receive pump cam shaft 200. Furthermore, low- pressure pump 400 comprises a pressure regulator 430 within LPP shaft 420 to prevent pressure buildup in the torque assembly. In the illustrated embodiment, LPP shaft 420 is filled with a liquid, such as a lubricant, and pressure regulator 430 maintains the pressure of the liquid at a desired level to avoid the mixing of the liquid in LPP shaft 420 with liquid in HPP 500.

[0030] Referring now to FIG. 10, high-pressure pump 500 is coupled to low-pressure pump 400 through face plate 475. HPP face 510 is coupled to LPP face 410 through face plate 475 which is secured with plate fasteners 411. In the illustrated embodiment, plate fasteners 411 are screws, but in other embodiments may be bolts, clips, rivets, or other coupling means. HPP 500 and LPP 400 each further comprise HPP gasket 515 and LPP gasket 415 respectively to improve the seal between each of HPP face 510 and LPP face 410 to face plate 475. As mentioned previously, LPP shaft 420 can be filled with a liquid, which then can fill shaft bore 214. Drilling 230 in pump cam shaft 200 fluidly couples shaft bore 214 to cavity 445 surrounding drive end 210 of pump cam shaft 200. The torque delivery system will therefore be lubricated to minimize wear over time. HPP 500 further comprises a seal 530 to prevent the liquid in cavity 445 from entering HPP 500 and mixing with the liquid (lubricant) in HPP 500.

[0031] When pump cam shaft 200 is coupled to gear 300 through coupling 100, collar

215 does not touch coupling 100 or gear 300 and leaves a small gap 440 between collar 215 and gear 300. Gap 440 allows for axial or angular misalignment of pump cam shaft 200 and gear 300. In the event that coupling 100 breaks during use, collar 215 retains any pieces of coupling 100 within the torque assembly and prevents pieces of coupling 100 from entering HPP 500 or LPP 400 and causing further damage. Furthermore, since coupling 100 is retained in place, pump cam shaft 200 is still capable of delivering torque to gear 300 through coupling 100 if coupling 100 breaks.

[0032] Deceleration of a vehicle using engine braking or a gear mis-shift often results in a torque on pump cam shaft 200 reaching up to ~110 Nm. The torque delivery system of the present disclosure is capable of withstanding torques of at least -140 Nm. At torques above -140 Nm, connecting member 220 of pump cam shaft 200 acts as a fuse and breaks in order to maintain the condition of LPP 400 and HPP 500. Due to the high compressive strength of coupling 100, connecting member 220 breaks before coupling 100. With higher torsional strength, the torque delivery system can withstand sudden acceleration of the engine camshaft experienced during an engine overspeed event.

[0033] While this invention has been described as having exemplary designs, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

[0034] Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements. The scope is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.”

[0035] Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B or C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C.

[0036] Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic with the benefit of this disclosure in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments.

[0037] Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. § 112(f), unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Claims

CLAIMS:

1. A torque delivery system comprising: a coupling comprising an interior surface, an exterior surface, and a number of contact surfaces; a first member configured to interface with the interior surface of the coupling; a second member configured to interface with the exterior surface of the coupling, wherein the number of contact surfaces are configured to transmit a torque from the first member to the second member, the torque transmittable through at least a compressive force on the coupling; and a collar on at least one of the first member and the second member, wherein the collar retains the coupling in a position to transmit torque even when the coupling is broken.

2. The torque delivery system of claim 1, wherein the coupling is composed of a polymer and has a variable cross-sectional width.

3. The torque delivery system of claim 1, wherein the first member is a pump cam shaft and the second member is a gear.

4. The torque delivery system of claim 3, wherein a drive end is coupled to the pump cam shaft through a connecting member and the interior surface of the coupling is configured to interface with the drive end, wherein the connecting member is configured to break at a maximum torque.

5. The torque delivery system of claim 4, wherein the connecting member comprises a drilling, which creates a weak point in the connecting member and fluidly couples a shaft bore within the pump cam shaft to an exterior of the pump cam shaft.

6. The torque delivery system of claim 4, wherein the drive end comprises a number of driving members configured to transmit torque to a number of interior driving members of the coupling.

7. The torque delivery system of claim 1, wherein a first gap is formed between the coupling and the first member, and a second gap is formed between the coupling and the second member to accommodate axial or angular misalignment of the coupling with at least one of the first member and the second member.

8. The torque delivery system of claim 1, wherein the coupling is positioned to prevent direct contact between a portion of the first member and a portion of the second member.

9. The torque delivery system of claim 1, wherein the first member comprises a number of driving members and the second member comprises a number of driving recessions, wherein the coupling is positioned between the number of driving members and the number of driving recessions.

10. A torque delivery system comprising: a pump cam shaft having a drive end and a connecting member, wherein the connecting member couples the drive end to the pump cam shaft and is configured to break upon receiving a maximum torque; a coupling having a variable cross-sectional width, wherein an interior surface of the coupling is configured to couple with the drive end of the pump cam shaft; and a gear comprising a plurality of teeth, wherein an interior of the gear is configured to couple with an exterior surface of the coupling, such that a torque is transmittable between the pump cam shaft and the gear through the coupling.

11. The torque delivery system of claim 10, wherein the pump cam shaft is driven by an upstream engine drive train, and the gear is located within a low-pressure fuel pump.

12. The torque delivery system of claim 11, wherein the low-pressure fuel pump comprises a pressure regulator within a low-pressure pump tube.

13. The torque delivery system of claim 10, wherein the pump cam shaft comprises a collar, wherein the collar is configured to retain the coupling in the torque transmitting system in the event of a coupling break.

14. The torque delivery system of claim 10, wherein the connecting member comprises a drilling, the drilling configured to be a weak point within the connecting member.

15. The torque delivery system of claim 14, wherein the drilling is further configured to fluidly couple an exterior of the pump cam shaft with a bore within the pump cam shaft.

16. A coupling between a first member and a second member comprising: an interior surface configured to interface with the first member; an exterior surface configured to interface with the second member, wherein the coupling has a cross-sectional width between the interior surface and the exterior surface, the cross-sectional width at least partially defined by the intersection of two non-concentric circles such that the width is variable; and a number of contact members configured to transmit a torque between the first member and the second member through compressive force on the contact members, wherein the cross-sectional width is largest at the contact members.

17. The coupling of claim 16, wherein the coupling is composed of a thermoplastic polymer and prevents direct contact of the first member with the second member.

18. The coupling of claim 17, wherein the coupling comprises rounded edges and comers.

19. The coupling of claim 16, wherein the first member is a gear and the second member is a shaft.

20. The coupling of claim 19, wherein the gear, the shaft, and the coupling are part of a fuel pump system for a diesel engine.