High-pressure fuel pump

Information

  • Patent Grant
  • 6789459
  • Patent Number
    6,789,459
  • Date Filed
    Wednesday, October 16, 2002
    22 years ago
  • Date Issued
    Tuesday, September 14, 2004
    20 years ago
Abstract
A high pressure fuel pump includes a cylinder having a pressurizing chamber and a plunger inserted into the cylinder. The plunger is axially reciprocated by a lifter to pressurize fuel in the pressurizing chamber. A seal member encompasses a portion of the plunger that is projected from the cylinder. The seal member disconnects a cylinder side space surrounded by the seal member from a lifter side space outside the seal member. The seal member has an annular lip portion that contacts a peripheral surface of the plunger, and the annular lip portion has a pair of lips separated from each other in an axial direction of the plunger. An axial distance between the lips is greater than a stroke of the plunger. As a result, fuel does not enter the lifter side space, and lubricating oil does not enter the cylinder side space.
Description




BACKGROUND OF THE INVENTION




The present invention is related to a high pressure pump for pressurizing and supplying fluid, and more particularly, to a high pressure pump that is optimal for pressurizing and supplying fuel to a fuel injection valve of a vehicle engine.




Japanese Laid-Open Publication No. 8-68370 discloses a high pressure fuel pump used for a vehicle engine. The high pressure fuel pump has a cylinder, a plunger that is inserted into the cylinder, and a lifter that moves the plunger axially direction with respect to the cylinder. As the plunger reciprocates, the plunger pressurizes fuel in a pressurizing chamber, which is defined in the cylinder, and discharges the fuel from the pressurizing chamber.




The lifter contacts one end of the plunger that is projected from the cylinder. The lifter is slidably supported by a pump housing. A generally cylindrical seal member is attached to the cylinder so as to surround the portion of the plunger that is projected from the cylinder. The seal member has an annular lip portion defined at its distal end. The annular lip portion contacts an outer peripheral surface of the plunger. The seal member prevents fuel, which leaks from the pressurizing chamber through a clearance between the cylinder and the plunger from mixing with lubricating oil that lubricates the lifter.




FIGS.


4


(


a


) and


4


(


b


) are cross sectional views of a plunger


43


and a seal member


41


. Although not shown, a cylinder is positioned upward of FIGS.


4


(


a


) and


4


(


b


), and a lifter is positioned downward of FIGS.


4


(


a


) and


4


(


b


). The seal member


41


disconnects a cylinder side space (the space surrounded by the seal member


41


) from a lifter side space (the space outside the seal member


41


). The lip portion


42


of the seal member


41


has an upper lip


42




a


and a lower lip


42




b


that are spaced from each other in the axial direction of the plunger


43


. The upper lip


42




a


prevents fuel L


1


collected on the peripheral surface of the plunger


43


from entering the lifter side space. The lower lip


42




b


prevents that lubricating oil L


2


invades into the cylinder side space. Therefore, fuel and lubricating oil are prevented from mixing.




When the plunger


43


moves in a direction projecting out of the cylinder, that is, when the plunger


43


moves downward in FIG.


4


(


a


), the fuel L


1


collected on the peripheral surface of the plunger


43


is removed by the upper lip


42




a


. The removed fuel L


1


is stored in the cylinder side space and prevented from entering the lifter side space. On the other hand, when the plunger


43


moves in a direction entering the cylinder, that is, when the plunger


43


moves upward in FIG.


4


(


a


), the lubricating oil L


2


collected on the peripheral surface of the plunger


43


is removed by the lower lip


42




b


and prevented from entering the cylinder side space.




However, it is difficult to completely remove the fuel L


1


and the lubricating oil L


2


collected on the plunger


43


by the lip portion


42


. Therefore, in the high pressure fuel pump of the above publication, the mixing of the fuel and the lubricating oil is not sufficiently prevented. When the fuel leaks into the lifter side space and mixes with the lubricating oil, the lubricating oil is diluted and the lifter cannot be lubricated sufficiently.




When the plunger


43


moves from the highest position shown in FIG.


4


(


a


) to the lowest position shown in FIG.


4


(


b


), the fuel L


1


′ that is not removed by the upper lip


42




a


temporarily enters the space between the upper lip


42




a


and the lower lip


42




b


and then passes by the lower lip


42




b


to leak into the lifter side space.




When the plunger


43


moves from the lowest position shown in FIG.


4


(


b


) to the highest position shown in FIG.


4


(


a


), the lubricating oil that is not removed by the lower lip


42




b


temporarily enters the space between the upper lip


42




a


and the lower lip


42




b


and passes by the upper lip


42




a


to leak into the cylinder side space.




As the stroke of the plunger


43


lengthens to increase the discharged amount of the fuel, the leakage amount of the fuel and the lubricating oil increases.




BRIEF SUMMARY OF THE INVENTION




It is an object of the present invention to provide a high pressure pump for that guarantees prevention of fluid leakage from one of two spaces, which are disconnected by a seal member, into the other one of the two spaces.




To achieve the above object, a high pressure pump includes a cylinder having a pressurizing chamber. A plunger is inserted in the cylinder. The plunger is axially reciprocated with a predetermined stroke to pressurize fluid in the pressurizing chamber. The plunger has a projected portion projected from the cylinder. A drive member drives the projected portion to reciprocate the plunger. A seal member encompasses the projected portion. The seal member has an annular lip portion that contacts a peripheral surface of the projected portion. The annular lip portion has a pair of lips separated from each other in an axial direction of the plunger. An axial distance between the lips is greater than the stroke of the plunger.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a cross sectional view of a high pressure fuel pump according to an embodiment of the present invention.




FIGS.


2


(


a


) and


2


(


b


) are enlarged cross sectional views showing a lip portion of a seal member of FIG.


1


.





FIG. 3

is a graph showing the relationship of a leakage amount with respect to the difference between the distance between lips and a plunger stroke.




FIGS.


4


(


a


) and


4


(


b


) are cross sectional views showing a seal member of a prior art high pressure fuel pump.











DETAILED DESCRIPTION




A high pressure pump according to the present invention embodied in a high pressure fuel pump


11


that is applied to a vehicle engine will now be discussed with reference to

FIGS. 1

to


3


. Although not shown in the drawings, the high pressure fuel pump


11


of

FIG. 1

pressurizes fuel, which is sent from a fuel tank by a feed pump, to supply the fuel to a delivery pipe.




The high pressure fuel pump


11


has a housing


12


and a cylinder


13


, which is arranged in the housing


12


. The cylinder


13


has a pressurizing chamber


14


. A bracket


15


is fixed to the lower end of the housing


12


by a plurality of bolts


16


. The cylinder


13


is supported by the bracket


15


and the housing


12


. The cylinder


13


has a bore


13




a


that communicates with the pressurizing chamber


14


and extends axially. A plunger


17


is inserted in the bore


13




a


in an axially movable manner.




A guide cylinder


15




a


extends downward from the bottom surface of the bracket


15


. A lifter


18


, which is cylindrical and has a closed bottom, serves as a drive member is coupled and is fitted in the guide cylinder


15




a


in an axially movable manner. A basal end of the plunger


17


, which projects from the cylinder


13


, contacts an inner bottom surface of the lifter


18


. A camshaft


22


of an engine is arranged below the lifter


18


. A retainer


20


is engaged to a with the basal end of the plunger


17


. A spring


21


is arranged between the retainer


20


and the bracket


15


in a compressed state. The spring


21


presses the basal end of the plunger


17


toward the inner bottom surface of the lifter


18


and urges the lifter


18


toward the camshaft


22


.




The camshaft


22


has a cam (not shown) for driving a discharge valve of the engine and a drive cam


23


for driving the plunger


17


. The drive cam


23


has two cam noses


23




a


separated from each other by an angular interval of 180 degrees. The spring


21


presses and the lifter


18


against the cam surface of the drive cam


23


.




The cylinder


13


has a fuel supply passage


24


that communicates with the pressurizing chamber


14


. An electromagnetic spill valve


25


is arranged in the fuel supply passage


24


.




The electromagnetic spill valve


25


has an electromagnetic solenoid. When voltage is not applied to the electromagnetic solenoid, the electromagnetic spill valve


25


opens the fuel supply passage


24


to communicate the fuel supply passage


24


with the pressurizing chamber


14


. In this state, when the plunger


17


is lowered and projected from the cylinder


13


, low pressure fuel that is sent from a fuel tank (not shown) by the feed pump is drawn into the pressurizing chamber


14


via the fuel supply passage


24


. When voltage is applied to the electromagnetic solenoid, the electromagnetic spill valve


25


closes the fuel supply passage


24


and disconnects the fuel supply passage


24


from the pressurizing chamber


14


. In this state, when the plunger


17


is lifted and moved into the cylinder


13


, the volume of the pressurizing chamber


14


decreases, which in turn, pressurizes the fuel in the pressurizing chamber


14


.




A high pressure fuel passage


26


extends from the pressurizing chamber


14


through the cylinder


13


and the housing


12


. A check valve


27


is arranged in the high pressure fuel passage


26


. When the fuel pressure in the pressurizing chamber


14


exceeds a predetermined value, the check valve


27


is opened, and the high pressure fuel is supplied from the pressurizing chamber


14


to a delivery pipe (not shown) via the high pressure fuel passage


26


. The high pressure fuel is further distributed from the delivery pipe to each fuel injection valve of the engine.




When the engine is driven, the drive cam


23


is rotated integrally with the camshaft


22


and the lifter


18


is reciprocated axially with respect to the guide cylinder


15




a


in accordance with the profile of the drive cam


23


. The plunger


17


is reciprocated axially in cooperation with the lifter


18


. As shown by the double-dashed line in

FIG. 1

, when the drive cam


23


is positioned at rotation position R


1


, the lifter


18


is moved to the lowest position where the lifter


18


is closest to the camshaft


22


. In this state, the distal end


17




a


of the plunger


17


is moved to the lowest position where the distal end


17




a


is farthest from the pressurizing chamber


14


and the volume of the pressurizing chamber


14


is maximized.




When the drive cam


23


is rotated in the counterclockwise direction in

FIG. 1

from rotation position R


1


to rotation position R


2


, one of the cam noses


23




a


lifts the lifter


18


. This projects the distal end


17




a


of the plunger


17


into the pressurizing chamber


14


and gradually decreases the volume of the pressurizing chamber


14


. When the drive cam


23


is further rotated from rotation position R


2


to rotation position R


3


, one of the cam noses


23




a


moves the lifter


18


to the highest position. In this state, the distal end


17




a


of the plunger


17


moves to the highest position where the volume of the pressurizing chamber


14


is minimized. In this manner, a fuel pressurizing stroke is performed when the drive cam


23


lifts the plunger


17


.




In the pressurizing stroke, unless voltage is applied to the electromagnetic solenoid of the electromagnetic spill valve


25


, the fuel in the pressurizing chamber


14


is not discharged to the delivery pipe and spilled into the fuel tank via the fuel supply passage


24


. If voltage is applied to the electromagnetic solenoid at a proper timing during the pressurizing stroke, the electromagnetic spill valve


25


closes the fuel supply passage


24


. Therefore, the fuel in the pressurizing chamber


14


is pressurized as the plunger


17


moves upward. The pressurized fuel pushes and opens the check valve


27


to be discharged into the delivery pipe. The fuel discharge amount is adjusted by changing the closing timing of the electromagnetic spill valve


25


during the pressurizing stroke. The electromagnetic spill valve


25


is controlled by an electronic control unit (not shown) arranged in the engine in accordance with running condition of the engine.




When the drive cam


23


is further rotated in the counterclockwise direction in

FIG. 1

from rotation position R


3


, the urging force of the spring


21


gradually lowers the lifter


18


and the plunger


17


from the highest position. When the drive cam


23


is rotated to rotation position R


1


, the lifter


18


and the plunger


17


reaches the lowest position again. In this manner, when the drive cam


23


allows the plunger


17


to be lowered, a fuel intake stroke is performed.




When the lifter


18


and the plunger


17


reaches the highest position, the electronic control unit stops applying voltage to the electromagnetic solenoid of the electromagnetic spill valve


25


. Therefore, the electromagnetic spill valve


25


remains opened during the intake stroke. The fuel sent from the fuel tank by the feed pump is drawn into the pressurizing chamber


14


via the fuel supply passage


24


.




Afterward, the above-described pressurizing stroke and intake stroke are executed repeatedly and a proper amount of high pressure fuel is discharged from the high pressure fuel passage


26


to the delivery pipe.




As shown in

FIG. 1

, a coupling cylinder


13




b


extends downward from the lower end of the cylinder


13


and through the bracket


15


. The coupling cylinder


13




b


forms part of the bore


13




a


. A generally cylindrical seal member


28


is fitted to and around the coupling cylinder


13




b


. The seal member


28


encompasses the portion of the plunger


17


projected from the plunger


17


. The seal member


28


disconnects an inner space, or cylinder side space A


1


, which is encompassed by the seal member


28


from an outer space, or a lifter side space A


2


, which is defined outside the seal member


28


. A slight amount of the fuel in the pressurizing chamber


14


leaks into the cylinder side space A


1


through a clearance between the wall of the bore


13




a


and the peripheral surface of the plunger


17


. Lubricating oil for lubricating the lifter


18


exists in the lifter side space A


2


. The seal member


28


prevents the fuel in the cylinder side space A


1


from mixing with the lubricating oil in the lifter side space A


2


.




As shown in

FIGS. 1

,


2


(


a


), and


2


(


b


), the seal member


28


has a metal support cylinder


29


and a rubber seal


30


, which is arranged along the inner surface of the support cylinder


29


. An annular lip portion


31


defined at the lower end of the rubber seal


30


contacts the peripheral surface of the plunger


17


. The lip portion


31


has an upper lip


31




a


and a lower lip


31




b


, which are separated from each other in the axial direction of the plunger


17


. The edge of the upper lip


31




a


and the edge of the lower lip


31




b


are pressed against the peripheral surface of the plunger


17


.




In this embodiment, the lip portion


31


is designed and formed so that an axial distance S


1


between the upper lip


31




a


and the lower lip


31




b


is greater than stroke S


2


of the plunger


17


. More specifically, the distance S


1


is the axial distance between the portion of the upper lip


31




a


contacting the peripheral surface of the plunger


17


and the portion of the lower lip


31




b


contacting the peripheral surface of the plunger


17


.




When the plunger


17


is not moving, the upper lip


31




a


prevents the fuel L


1


collected on the peripheral surface of the plunger


17


from entering the lifter side space A


2


, as shown in FIG.


2


(


a


). The lower lip


31




b


prevents the lubricating oil L


2


collected on the peripheral surface of the plunger


17


from entering the cylinder side space A


1


. Therefore, the fuel and the lubricating oil are prevented from mixing.




In the intake stroke, that is, when the plunger


17


is moves downward as viewed in FIG.


2


(


a


), the fuel L


1


collected on the peripheral surface of the plunger


17


is removed by the upper lip


31




a


. The removed fuel L


1


is held in the cylinder side space A


1


and prevented from entering the lifter side space A


2


. On the other hand, in the discharge stroke, that is, when the plunger


17


is moved upward as viewed in FIG.


2


(


a


), the lubricating oil L


2


collected on the peripheral surface of the plunger


17


is removed by the lower lip


31




b


and prevented from entering the cylinder side space A


1


.




When the plunger


17


is moved downward in the intake stroke, the fuel L


1


that is not removed by the upper lip


31




a


remains on the peripheral surface of the plunger


17


, as shown in FIG.


2


(


b


). However, as described above, in this embodiment, the axial distance S


1


between the upper lip


31




a


and the lower lip


31




b


is larger than the stroke S


2


of the plunger


17


. Therefore, when the plunger


17


moves from the highest position shown in FIG.


2


(


a


) to the lowest position shown in FIG.


2


(


b


), the residual fuel L


1


′ does not pass by the lower lip


31




b


to enter the lifter side space A


2


. The residual fuel L


1


′ only enters the space between the upper lip


31




a


and the lower lip


31




b.






Although not shown in the drawings, when the plunger


17


moves upward in the discharge stroke, the lubricating oil that is not removed by the lower lip


31




b


remains on the peripheral surface of the plunger


17


. However, in the same manner as described above, when the plunger


17


moves from the lowest position shown in FIG.


2


(


b


) to the highest position shown in FIG.


2


(


a


), the residual lubricating oil does not pass by the upper lip


31




a


to enter the cylinder side space A


1


. The residual lubricating oil only enters the space between the upper lip


31




a


and the lower lip


31




b.






As described above, in this embodiment, the fuel L


1


′ that is not removed by the upper lip


31




a


does not enter the lifter side space A


2


. Further, the lubricating oil that is not removed by the lower lip


31




b


does not enter the cylinder side space A


1


. This prevents fuel and lubricating oil from being mixed. Accordingly, dilution of the lubricating oil with the fuel is prevented, and satisfactory lubrication of the lifter


18


is maintained.





FIG. 3

is a graph showing the relationship between the leakage amount of the fuel and the lubricating oil with respect to the difference between the distance S


1


and the plunger stroke S


2


(S


1


−S


2


). The result shown by the graph was obtained through experiments. As apparent from the graph, when the difference (S


1


−S


2


) is greater than a predetermined positive value, that is, when the distance S


1


is greater than or equal to the plunger stroke S


2


by a predetermined value, the leakage amount of the fuel and the lubricating oil is significantly decreased.




The seal member


28


has the metal support cylinder


29


and the rubber seal


30


, which is arranged on the inner surface of the support cylinder


29


. The support cylinder


29


faces the lifter side space A


2


and is not exposed to the fuel in the cylinder side space A


1


. Therefore, even if low grade fuel that contains moisture exists in the cylinder side space A


1


, the metal support cylinder


29


does not rust.




The present invention may be embodied as follows.




The seal member


28


may not be attached to the housing


12


or the bracket


15


instead of the cylinder


13


.




The support cylinder


29


may be embedded in the rubber seal


30


. Alternatively, contrary to an arrangement shown in

FIG. 1

, the rubber seal


30


may be arranged around the support cylinder


29


.




The application of the present invention is not limited to the high pressure fuel pump shown in FIG.


1


and but may be applied to a variety of high pressure fuel pumps. For example, in the pump of

FIG. 1

, the closing timing of the electromagnetic spill valve


25


during the pressurizing stroke is changed to adjust the fuel discharge amount. However, the present invention may be embodied in a high pressure fuel pump that adjusts the fuel discharge amount by changing the opening timing of the electromagnetic valve during the intake stroke.




The present invention may be also be embodied in a high pressure pump that pressurizes fluid other than fuel.



Claims
  • 1. A high pressure pump comprising:a cylinder having a pressurizing chamber; a plunger inserted in the cylinder, wherein the plunger is axially reciprocated with a predetermined stroke to pressurize fluid in the pressurizing chamber, the plunger having a projected portion projected from the cylinder; a drive member for driving the projected portion to reciprocate the plunger; and a seal member encompassing the projected portion, wherein the seal member has an annular lip portion that contacts a peripheral surface of the projected portion, the annular lip portion having a pair of lips separated from each other in an axial direction of the plunger, wherein the seal member disconnects an inner side space surrounded by the seal member from an outer side space outside the seal member, fluid that leaks from the pressurizing chamber exists in the inner side space, and lubricating oil that lubricates the drive member exists in the outer side space, and wherein each lip has a contact portion that contacts the peripheral surface of the projected portion, and an axial distance between the contact portions of the two lips is greater than the stroke of the plunger by a predetermined value so that a section of the peripheral surface of the projected portion that contacts one of the lips does not contact the other one of the lips when the plunger reciprocates.
  • 2. The high pressure pump according to claim 1 wherein the seal member has a metal support cylinder and a rubber seal arranged on an inner surface of the support cylinder, and the annular lip portion is arranged on one end of the rubber seal.
  • 3. The high pressure pump according to claim 1, wherein the cylinder has a coupling cylinder, the plunger projects out of the cylinder from the coupling cylinder, and the seal member is fitted to the coupling cylinder so as to surround the coupling cylinder.
  • 4. A high pressure pump comprising:a cylinder having a pressurizing chamber; a plunger inserted in the cylinder, wherein the plunger is axially reciprocated with a predetermined stroke to pressurize fluid in the pressurizing chamber, the plunger having a projected portion projected from the cylinder; a drive member for driving the projected portion to reciprocate the plunger; and a seal member encompassing the projected portion, wherein the seal member has an annular lip portion that contacts a peripheral surface of the projected portion, the annular lip portion having a pair of lips separated from each other in an axial direction of the plunger, wherein the seal member disconnects an inner side space surrounded by the seal member from an outer side space outside the seal member, fluid that leaks from the pressurizing chamber exists in the inner side space, and lubricating oil that lubricates the drive member exists in the outer side space, and wherein each lip has a contact portion that contacts the peripheral surface of the projected portion, and an axial distance between the contact portions of the two lips is greater than the stroke of the plunger by a predetermined value so that a section of the peripheral surface of the projected portion that contacts one of the lips does not overlap a section of the peripheral surface of the projected portion that contacts the other one of the lips when the plunger reciprocates.
  • 5. The high pressure pump according to claim 4, wherein the seal member has a metal support cylinder and a rubber seal arranged on an inner surface of the support cylinder, and the annular lip portion is arranged on one end of the rubber seal.
  • 6. The high pressure pump according to claim 4, wherein the cylinder has a coupling cylinder, the plunger projects out of the cylinder from the coupling cylinder, and the seal member is fitted to the coupling cylinder so as to surround the coupling cylinder.
Priority Claims (1)
Number Date Country Kind
2000-116422 Apr 2000 JP
PCT Information
Filing Document Filing Date Country Kind
PCT/JP01/03261 WO 00
Publishing Document Publishing Date Country Kind
WO01/79698 10/21/2001 WO A
US Referenced Citations (2)
Number Name Date Kind
5567134 Inoue Oct 1996 A
5752430 Kawajiri et al. May 1998 A
Foreign Referenced Citations (6)
Number Date Country
04-353262 Dec 1992 JP
11-082238 Mar 1999 JP
11-153069 Jun 1999 JP
2001-050174 Feb 2001 JP
2001-055963 Feb 2001 JP
WO0047888 Aug 2000 WO