Oil lubricated common rail diesel pump

Abstract

An oil lubricated common rail diesel pump includes a pumping assembly and a drivetrain assembly. The pumping assembly includes a pump housing and a plunger mounted along a pumping axis. The drivetrain assembly includes a driveshaft and a cam mounted within a first chamber of a drivetrain housing. The plunger is arranged for reciprocating linear movement along the pumping axis within a second chamber of the housing upon rotation of the cam. The drivetrain assembly also includes a guide mounted within the housing between the cam and the plunger and being adapted to receive a cam follower. At least the housing is adapted to be substantially filled with oil in use and the guide includes at least one flow passage communicating between the first chamber and the second chamber.

Claims

1. An oil lubricated common rail diesel pump comprising: a pumping assembly; and a drivetrain assembly; the pumping assembly comprising: a pump housing; and a plunger mounted along a pumping axis; the drivetrain assembly comprising: a driveshaft; a drivetrain housing having a first chamber and a second chamber; a cam mounted within the first chamber, the plunger being arranged for reciprocating linear movement along the pumping axis within the second chamber upon rotation of the cam; and a guide mounted within the drivetrain housing between the cam and the plunger and being adapted to receive a cam follower; wherein at least the drivetrain housing is adapted to be substantially filled with oil in use and the guide comprises at least one flow passage communicating between the first chamber and the second chamber of the drivetrain housing, wherein the guide comprises a guide body comprising first and second ends and the at least one flow passage extends between the first and second ends and is open at both the first and second ends and the guide also comprises a substantially centrally located aperture extending between the first and second ends of the guide and open at both the first and second ends to provide guided sliding contact with the cam follower and wherein the drivetrain housing comprises an oil inlet adapted to deliver oil to the first chamber of the drivetrain housing in a region of the cam.

2. The oil lubricated common rail diesel pump according to claim 1, wherein each of the at least one flow passage is disposed within a peripheral portion of the guide body towards an outside wall or walls of the guide body.

3. The oil lubricated common rail diesel pump according to claim 1, wherein the guide comprises at least two flow passages approximately equally spaced from one another around the peripheral portion of the guide body.

4. The oil lubricated common rail diesel pump according to claim 1, wherein the centrally located aperture comprises an inner channel extending between the first and second ends.

5. The oil lubricated common rail diesel pump according to claim 4, wherein the aperture comprises at least one outer channel provided around a periphery of the inner channel and communicating with the inner channel between the first and second ends.

6. The oil lubricated common rail diesel pump according to claim 5, wherein each of the at least one flow passage and each of the at least one outer channel are approximately equally spaced around the periphery of the inner channel.

7. The oil lubricated common rail diesel pump according to claim 1, wherein the drivetrain housing comprises a first part comprising the first chamber and a second part comprising the second chamber, wherein the first chamber and the second chamber chambers are open to one another.

8. The oil lubricated common rail diesel pump according to claim 7, wherein the oil inlet is disposed so as to enter the first part of the housing towards a top of the first part of the drivetrain housing.

9. The oil lubricated common rail diesel pump according to claim 7, wherein an oil outlet is disposed in the second part of the drivetrain housing.

10. The oil lubricated common rail diesel pump according to claim 9 wherein the oil inlet and the oil outlet are disposed above the first chamber or at the top of the first chamber.

11. The oil lubricated common rail diesel pump according to claim 1, wherein cooling of one or more bearings of the oil lubricated common rail diesel pump comprises passive flow events or forced flow events.

12. A drivetrain assembly for an oil lubricated common rail diesel pump, the drivetrain assembly comprising: a driveshaft; a drivetrain housing having a first chamber and a second chamber, the second chamber adapted to receive a reciprocating plunger; a cam mounted within the first chamber; and a guide mounted within the drivetrain housing above the cam and being adapted to receive a cam follower wherein the guide comprises a substantially centrally located aperture extending between first and second ends of the guide and open at both the first and second ends to provide guided sliding contact with the cam follower in the same direction as the reciprocating plunger; wherein the drivetrain housing is adapted to be substantially filled with oil in use and the guide comprises at least one flow passage communicating between the first chamber and the second chamber of the drivetrain housing.

13. A guide of a drivetrain assembly for an oil lubricated common rail diesel pump, the guide being adapted to be mounted within a drivetrain housing above a cam and being adapted to receive a cam follower, wherein the guide comprises at least one flow passage therethrough between a first and second end thereof and also comprises a substantially centrally located aperture extending between first and second ends of the guide and open at both the first and second ends to provide guided sliding contact with the cam follower.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a better understanding of the invention, and to show how exemplary embodiments may be carried into effect, reference will now be made to the accompanying drawings in which:

(2) FIG. 1 is a schematic cross-sectional view of a common rail diesel pump comprising a drivetrain assembly according to an exemplary embodiment of the invention;

(3) FIG. 2 is a perspective view of a guide of the drivetrain assembly for the common rail diesel pump of FIG. 1 or 4;

(4) FIG. 3 is a schematic cross-sectional view of the drivetrain assembly of FIG. 1; and

(5) FIG. 4 is a schematic cross-sectional view of a common rail diesel pump comprising a drivetrain assembly according to an alternative embodiment of the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

(6) According to an exemplary embodiment of the invention, FIG. 1 shows an oil lubricated common rail diesel pump 1 comprising a pumping assembly 10 and a drivetrain assembly 20, the pumping assembly 10 comprising a pump housing 12 and a plunger 14 mounted along a pumping axis A-A, the drivetrain assembly 20 comprising a driveshaft 24 and a cam 26 mounted within a first chamber 28 of a drivetrain housing 22, the plunger 14 being arranged for reciprocating linear movement along the pumping axis A-A within a second chamber 30 of the drivetrain housing 22 upon rotation of the cam 26, the drivetrain assembly 20 further comprising a guide 40 mounted within the drivetrain housing 22 between the cam 26 and the plunger 14 and being adapted to receive a cam follower 16a, 16b, wherein at least the drivetrain housing 22 is adapted to be substantially filled with oil in use and the guide 40 comprises at least one flow passage 48 communicating between the first chamber 28 and the second chamber 30 of the drivetrain housing 22.

(7) FIG. 2 shows an exemplary version of the guide 40. The guide 40 comprises a body 41, which in this case is substantially cylindrical in shape in order to fit directly (preferably press-fit) within a cylindrical aperture within the chamber 30 of the drivetrain housing 22. It is, however, to be appreciated that the body 41 of the guide 40 may be of any suitable external shape to correspond with either the internal shape of a chamber, or an adapter which may sit inside such a chamber.

(8) The guide 40 comprises first and second ends 42, 43, respectively.

(9) The guide 40 comprises a substantially centrally located aperture 44 between the two ends 42, 43. The aperture 44 is adapted to provide guided sliding contact with a cam follower shoe 16a of the cam follower 16.

(10) The aperture 44 comprises an inner channel 45 extending between the first and second ends 42, 43 and defining a shape that substantially corresponds with the external shape of the cam follower shoe 16a. The shape of the inner channel 45 is generally defined by a plurality of disconnected internal walls 45a-d, which in this case comprise substantially straight walls 45a-d in order to define a substantially rectangular-shaped inner channel 45 (as indicated by the dotted lines). The inner channel 45 shown is configured to provide guided sliding contact with a generally rectangular-shaped cam follower shoe 16a. However, it is to be appreciated that a plurality of walls 45a-d may be shaped and contoured to define a substantially circular, or other shaped channel 45 to fit with an alternatively shaped cam follower shoe 16a.

(11) In the exemplary embodiment shown, the aperture 44 further comprises a plurality of outer channels 46a-d extending between first and second ends 42, 43. Each of the outer channels 46a-d is peripheral to the inner channel 45 and communicates with the inner channel 45 along their full length between the first and second ends 42, 43. In this case, there are four outer channels 46a-d, one provided at each corner of the substantially rectangular-shaped inner channel 45, although it is to be appreciated that one, two, three or more outer channels 46 could be provided as long as the integrity and the shape of the inner channel 45 was neither compromised nor caused to be unsuitably shaped with respect to the cam follower shoe 16a. A further consideration is given to the spacing of the outer channels 46, which is approximately equal, in order to retain balanced proportions to the body 41.

(12) The outer channels 46a-d are generally smoothly contoured in order to minimise stress in the guide body 41 when a side load from the cam follower shoe 16a is applied during rotation of the drivetrain assembly 20. In this case, the outer channels 46a-d comprise a plurality of short internal walls arranged to provide a generally curved internal shape. In addition, at junctions where the outer channels 46a-d meet with the walls 45a-d defining the inner channel 45, the outer channels 46a-d comprise short outwardly-angled walls in order to avoid a sharp edge/corner. The general shape of the outer channels 46a-d are chosen to maximise their volume given the shape of the body 41 and the inner channel 45, whilst limiting stress levels. In this case, given the cylindrical shape of the body 41 and the rectangular-shaped channel 45, the outer channels 46a-d adopt a substantially isosceles trapezoid prism shape (with curved corners).

(13) As shown in FIG. 2, the body 41 comprises two flow passages 48a-b extending between first and second ends 42, 43 of the guide 40. The two passages 48a-b are located approximately diametrically opposite one another on the body 41 and on either side of the aperture 44. In order to maximise their volume, the flow passages 48a-b are provided between pairs of outer channels 46b-c and 46a-d respectively. However, it is to be appreciated that further passages 48 may be disposed between other pairs of outer channels 46, or where outer channels 46a-d are not provided, further passages 48 may be equally spaced around the periphery of the inner channel 45, which in that case would simply comprise the aperture 44.

(14) The passages 48a-b are generally smoothly contoured in order to minimise sharp edges and corners which may cause stress. In this case, the passages 48a-b are shown to comprise a plurality of short internal walls arranged to provide a substantially curved internal shape. The general shape of the passages 48a-b are chosen to maximise their volume given the shape of the body 41 and the aperture 44. In this case, given the cylindrical shape of the body 41, the passages 48a-b adopt a substantially isosceles trapezoid prism shape (with curved corners).

(15) The drivetrain housing 22 comprises a first part 22a enclosing the first chamber 28 and a second part 22b enclosing the second chamber 30. The second part 22b is substantially open-ended in order to receive and mount a lower part 12a of the pump housing 12 therein. An upper part 12b of the pump housing 12 sits atop the second part 22b of the drivetrain housing 22. Accordingly, the first and second chambers 28, 30 are substantially closed once assembled with the pump housing 12.

(16) The closed chambers 28, 30 allow for the majority of the drivetrain housing 22 to be substantially filled with oil around the various components of the drivetrain assembly 20 and accommodated components of the pump assembly 10.

(17) The first chamber 28 of the drivetrain housing 22 comprises a substantially cylindrical compartment of varying diameter across its length in order to contain the driveshaft 24 and the cam 26 therein.

(18) As shown in FIG. 3, the driveshaft 24 comprises a substantially elongate cylindrical body comprising a front bearing journal 24c with a front bearing 24e mounted thereon, and a rear bearing journal 24d with a rear bearing 24f mounted thereon.

(19) The driveshaft 24 is attached at a first end 24a to a drive means (not shown), which dictates the rotational axis B-B of the driveshaft 24 and therefore, the rotational path of the cam 26 fitted thereon.

(20) At a second end 24b, the housing 22 provides a rear chamber space 28b. The rear bearing 24f is mounted (press-fit) into the housing 22 to support the rear journal 24d at one end of the chamber 28 in order to maintain the stability of the rotational axis B-B of the driveshaft 24.

(21) At the first end 24a, the housing 22 provides a front chamber space 28c adjacent the front bearing 24e. The front bearing 24e is also mounted (press-fit) into the housing 22 to support the front journal 24c at an opposite end of the chamber 28.

(22) The second chamber 30 of the drivetrain housing 22 comprises a substantially cylindrical compartment of substantially equal diameter. The second chamber 30 is disposed perpendicularly to the first chamber 28 so as to be generally upstanding above the cam 26. Accordingly, the pumping axis A-A and the driveshaft rotational axis B-B are disposed substantially perpendicularly to one another.

(23) The chambers 28, 30 are generally open to one another, e.g. flow of fluid is permissible between the chambers 28, 30 around the drive assembly 20 components.

(24) Accordingly, with the driveshaft 24 and the cam 26 in situ in the first chamber 28, the first chamber 28 provides a number of spaces 28a, 28b, 28c around the driveshaft 24, bearings 24e, 24f and cam 26, which allow for oil flow/reservoirs for lubrication purposes.

(25) With the plunger 14, upper end of the cam follower 16 and guide 40 in the second chamber 30, the second chamber 30 provides spaces around the plunger 14, follower 16 and guide 40 etc., which allow for oil flow/reservoirs for lubrication purposes.

(26) In order to effect oil delivery to the chambers 28, 30 and to top-up the level of oil therein, the first part 22a of the drivetrain housing 22 comprises an oil inlet 27, which is connected to a supply of pressurised oil from an engine oil pump (not shown). The oil inlet 27 connects with a flow orifice 29 which delivers the oil to the first chamber 28 in the region of the cam 26. The chamber 28 provides a circumferential space 28a around the cam 26 and follower 16 to receive a volume of the oil.

(27) Onward distribution of the oil to the other spaces within the first chamber 28 and to the second chamber 30 is effected by natural flow between the components in addition to a number of drillings or flow conduits.

(28) In an exemplary embodiment, the first part 22a of the housing 22 comprises a rear bearing drilling 31 between the circumferential chamber space 28a and the rear chamber space 28b in order to adequately circulate a cooling flow of oil to the mounting (interface) of the rear journal 24d within the rear bearing 24f. The first part 22a of the housing 22 also comprises a front bearing drilling 32 between the front chamber space 28c and the circumferential space 28a in order to adequately circulate a cooling flow of oil to the mounting (interface) of the front journal 24c within the front bearing 24e.

(29) The communication between the circumferential space 28a of the first chamber 28 and the second chamber 30 provides a flow of oil upwardly into the second chamber 30. This upward flow of oil is facilitated primarily by the flow passages 48 and the outer channels 46 of the guide 40 around the cam follower 16.

(30) In the exemplary embodiment shown, the oil inlet 27 is disposed so as to enter the first part 22a of the housing 22 towards a top of the first part 22a of the first chamber 28. Distribution of the oil throughout the chambers 28, 30 can then use natural fluid hydrodynamics to flow into the various unoccupied spaces 28b, 28c, 30 and fill up the housing 22. This, however, is not essential and the oil inlet 27 may be provided at another location, but always with the aim of retaining oil within at least the first chamber 28 of a stationary pump.

(31) In the embodiment shown, an oil outlet 33 is disposed so as to exit the second part 22b of the housing 22 towards a top of the second part 22b, but below the housing 12 of the pump 10, in order to provide a natural overflow out of the second chamber 30, whilst retaining a substantially oil-filled condition to the housing 22. Upon first-filling, flow and top-up events, distribution of the oil from the inlet 27 and throughout the chambers 28, 30 will fill the housing 22 until the oil level reaches the outlet 33, at which point any excess oil is provided with an escape route.

(32) In the embodiment of FIG. 1, surfaces of the front bearing 24e and the rear bearing 24f are cooled by passive cooling events. However, a passive cooling flow is not always sufficient to provide the necessary temperature reduction to the bearings.

(33) FIG. 4 shows an alternative embodiment of the present invention using forced flow events to cool the surfaces of the bearings, for situations where passive flows through the bearings are not sufficient to keep the bearings sufficiently cool, To effect forced cooling flow across the bearings, an additional conduit 27a is employed between the inlet 27 and the rear chamber space 28b. This facilitates forced flow of oil between the rear bearing 24f and the respective journal 24d. Furthermore, a channel 35 through the axis of the driveshaft 24 onwardly delivers oil from the rear chamber space 28b to a lubrication channel 36 through the front journal 24c providing forced flow of oil to the front bearing 24e and the front journal 24c. In this case the drilling 32 between the front chamber space 28c and the circumferential chamber space 28a of the cambox functions to relieve the 4 bar flow pressure from acting on the seal. However, the passive approach is preferred since flow variation will increase demands on engine oil pump if forced flow is utilised.

(34) In the embodiment of FIG. 4, the outlet 33 is in a similar position to that shown in respect of the embodiment of FIG. 1.

(35) In the embodiments of FIGS. 1 and 4, the oil inlet 27 receives oil, which has been pressurised by the engine oil pump, though a feed pipe (not shown) from a cleaned source of oil, e.g. from the clean side of an oil filter within the engine. The oil outlet 33 returns oil though a feed pipe (not shown) to a low-pressure uncleaned source of oil, e.g. to a crankcase of the engine (not shown).

(36) The oil inlet 27 and associated pressurised feed pipe (not shown) is generally of smaller diameter than the unpressurised oil outlet 33. An unrestricted flow of oil out of the housing 22 is enabled, which is expected to be at, or less than atmospheric pressure.

(37) In an alternative embodiment, the oil inlet 27 comprises a further oil filter before oil enters the housing 22.

(38) In the exemplary embodiments, the cam follower 16 comprises a substantially rectangular shoe 16a, sized to fit snugly within the guide 40 (the guide 40 is shown most clearly in FIG. 2), within the inner channel 45 as defined by the inner channel walls 45a-d. The corners of the shoe 16a are not bounded by walls as they move within the open volume of the outer channels 46a-d without any substantial contact with walls of the outer channels 46a-d. The inner channel walls 45a-d are sufficient to retain a sliding engagement of the shoe 16a within the inner channel 45 and along the pumping axis A-A without any significant lateral movement or twisting.

(39) The use of a rectangular shoe 16a enables a stable sliding engagement with the guide 40, whilst providing a smaller footprint than a traditional round tappet. This smaller footprint of the shoe 16a provides a lesser degree of fluid (oil) displacement within the chambers 28, 30 of the drivetrain housing 22 as it moves up and down the pumping axis A-A.

(40) The shoe 16a provides an internal cylindrical cavity 16c accessed via an underside of the shoe 16a. The cavity 16c accommodates an upper portion of a roller 16b, which roller 16b sits atop the cam 26 and eases the translation (by reducing friction) of the rotational movement of the cam 26 to the linear reciprocating movement of the shoe 16a and therefore, the plunger 14. As the cam 26 rotates, the roller 16b rides along the surface of the cam 26 by spinning within the cavity 16c of the shoe 16a.

(41) When the engine in which the pump 1 of either embodiment of the present invention is installed is switched off, the pump 1 will tend partially to drain of oil. The oil in the pump 1 will drain down to whichever is the lowest of the inlet and outlet connectors. Accordingly, both the inlet 27 and outlet 33 must be located sufficiently high up in the pump 1 to ensure that the drivetrain housing 22 does not drain completely of oil when the engine is switched off. Specifically, the inlet 27 and outlet 33 must be located to ensure that oil is largely maintained within the first chamber 28, and therefore around the region of the roller 16c, for when the engine re-starts.

(42) Therefore, in the described embodiments, the inlet 27 and outlet 33 are located in the drivetrain housing 22, above the roller 16c.

(43) However, in alternative embodiments, for example if the pump 1 is to be installed in an engine in a different orientation to that shown in the Figures, the inlet 27 and outlet 33 would be relocated, to ensure oil is maintained around the region of the roller 16c as above.

(44) The drivetrain housing 22 is generally shaped to minimise the space taken up by the pump 1 within an engine. As such, the housing 22 generally resembles a bisecting cylinder arrangement to reduce the volume of the housing 22 within an engine.

(45) In use, the shoe 16a sits snugly within the inner channel 45 of the guide 40. As the cam 26 rotates (driven by rotation of the driveshaft 24), the roller 16b rides along the cam 26 to provide a low-friction, reciprocating linear movement along axis A-A to the shoe 16a in which the roller 16b is partially housed, and thereon to the plunger 14.

(46) As the cam 26 rotates, oil is naturally displaced within the cavity 28.

(47) Further oil displacement is caused by the linear movement of the roller 16b/shoe 16a as oil is forced upwardly within the second chamber 30 by the solid body of the shoe 16a. Any resultant pressure pulses are minimised since flow passages 48 provided within the guide 40 reduce the impact of the oil displacement by allowing for oil to backflow relative to the shoe 16 direction as opposed to being forced in one direction. Further control of the oil displacement is provided by the rectangular configuration of the shoe 16a, which allows for a smaller shoe 16a with sufficient surface area and load capacity to withstand the pumping events, thereby providing a smaller surface area and volume to effect oil displacement. Pressure fluctuations are therefore, kept to a minimum.

(48) In the present invention, the oil-filled drivetrain housing 22 ensures immediate lubrication is available following a stationary event, as opposed to waiting for oil pressure rises at a starting event. In addition, there are a variety of mounting angles available to the vehicle manufacturer and vehicle tilt is not limited due to the oil-filled housing 22.

(49) Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.