Radial piston pump for high-pressure fuel delivery

Information

  • Patent Grant
  • 6406272
  • Patent Number
    6,406,272
  • Date Filed
    Monday, August 30, 1999
    25 years ago
  • Date Issued
    Tuesday, June 18, 2002
    22 years ago
Abstract
The invention relates to a radial piston pump for high-pressure fuel delivery in fuel injection systems of internal combustion engines, particularly in a common rail injection system. The pump includes a drive shaft that is supported in a pump housing and is embodied eccentrically or has a number of cam-like projections in the circumference direction. A number of pistons that are disposed radially with regard to the drive shaft are each disposed in a respective cylinder chamber and are set into a reciprocating motion in the radial direction in the cylinder chamber upon rotation of the drive shaft. Each respective cylinder chamber is sealed on the radial outside in relation to the drive shaft by a valve plate that has an intake side check valve and a high-pressure side check valve. In order to increase the efficiency of the pump, the intake side check valve has a tappet that passes through the valve plate and this tappet, on an end oriented toward the cylinder chamber has a valve disk that is placed in a sealed fashion against a sealing seat of the valve plate. On a side of the valve plate remote from the cylinder chamber, a device is provided, which pre-stresses the tappet in the closing direction.
Description




This application is a 35 USC 371 filing based upon PCT/DE98/01918 filed Jul. 09, 1998.




PRIOR ART




The invention relates to a radial piston pump for high-pressure fuel delivery in fuel injection systems of internal combustion engines, particularly in a common rail injection system, with a drive shaft that is supported in a pump housing and is embodied as eccentric or has a number of cam-like projections in the circumference direction. The pump includes a number of pistons that are disposed radially with regard to the drive shaft, each in a respective cylinder chamber, and can be set into a reciprocating motion in the radial direction in the cylinder chamber upon rotation of the drive shaft. Each respective cylinder chamber is sealed on the radial outside with regard to the drive shaft by a valve plate that has an intake side check valve and a high-pressure side check valve.




A radial piston pump of this kind has been disclosed by DE 44 01 074 A1. The check valve is provided on a side of the valve plate oriented toward the cylinder chamber, in a diametrically enlarged section of the cylinder chamber. A valve body that can be placed against a sealing seat of the valve plate or can be lifted up from the sealing seat is contained in a basket- or cup-shaped component which extends into the cylinder chamber toward the respective piston and is fastened to the valve plate.




The valve body is pressed toward the valve plate by way of a disk spring provided at the bottom of the cup-shaped component.




Based on this known radial piston pump, an object of the current invention is to improve its efficiency.




In a radial piston pump of the type mentioned above, this object is attained according to the invention by virtue of the fact that the intake side check valve has a tappet that passes through the valve plate and this tappet, on its end oriented toward the cylinder chamber, has a valve disk that can be placed in a sealed fashion against a sealing seat of the valve plate. On a side of the valve plate remote from the cylinder chamber, a device is provided which pre-stresses the tappet in the closing direction.




In this manner, the dead space that defines the piston stroke, i.e. the structural space of the intake side check valve, is significantly reduced. In the known radial piston pump, the stroke of the pump piston was defined by the outside of the cup-shaped component. Now, during the compression phase, the piston can extend at least almost to the outside of the valve disk of the check valve, i.e. even into the stroke region of the valve disk of the check valve. The dead volume is thus minimal and the efficiency of the radial piston pump is greater than in the previously known pump.




In a preferred embodiment of the radial piston pump according to the invention, the device that pre-stresses the tappet in the closing direction includes a spring, which is supported on one end against the side of the valve plate remote from the cylinder chamber and is supported on the other end against a counter support provided on the tappet.




The disposition of the device, which pre-stresses the tappet in the closing direction, on the side of the valve plate remote from the cylinder chamber brings with it the advantage that the device can be embodied in an intrinsically arbitrary manner so that it supplies a desired opening pressure for the check valve.




The counter support for the spring can be realized in an intrinsically arbitrary manner; for example, an axial stop can be provided on the tappet, e.g. by means of upsetting or notching. In a preferable manner and according to a variant of the invention, the counter support is constituted by a collared bushing element whose bushing section concentrically encompasses the tappet and whose collar section supports the spring. This opens up the possibility of sliding the counter support onto the tappet and fixing it in the desired location.




The fixing of the counter support can take place in an intrinsically arbitrary manner. However, it has turned out to be advantageous if the counter support is attached to the tappet in a positively engaging manner, particularly by means of a crimping work cycle.




In order to preset the opening pressure of the check valve, a spring can be chosen that has particular dimensions or a particular spring constant. However, in order to be able to flexibly preset the opening pressure in the manufacture of radial piston pumps without having to resort to a multitude of various valve springs, which have to be kept on hand for this purpose, the proposal is made to fix the counter support in a position on the tappet such that the desired opening pressure of the check valve is produced. In particular, a counter support in the form of the above-mentioned collar bushing element has turned out to be advantageous for this purpose.




However, it can also turn out to be advantageous if the counter support is constituted by a disk- or plate-shaped component that rests against an axial stop on the tappet, for example a slit securing disk or the like that can be snapped onto the tappet. In such a case, axial stops can be provided at various axial positions on the tappet. However, it may turn out to be more advantageous to provide an axial stop, for example in the form of a circumferentially extending annular groove, and to keep securing disks of various thicknesses on hand and to use them depending on the opening pressure required. The thickness of a securing disk can be determined easily, and the selection during the assembly of the check valve is therefore easy.




In order to be able to optimally employ the structural space on the side of the valve plate remote from the cylinder chamber, it has turned out to be advantageous if at least one opening that is essentially radial to the longitudinal direction of the cylinder chamber is provided in the valve plate and communicates with a fuel supply opening in the housing. According to this concept of the invention, the fuel supply therefore does not occur from the radial outside with regard to the drive shaft, but rather fuel is supplied by way of an opening that extends in the plane of the valve plate. This radial opening then preferably feeds into the tappet through opening of the valve plate.




Other features, details, and advantages of the invention ensue from the graphic depiction and subsequent description of preferred embodiments of the invention.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a sectional view of a radial piston pump according to the invention;





FIG. 2

is a sectional view of plane II—II in

FIG. 1

;





FIG. 3

is a sectional view of a valve plate with a check valve, in an embodiment that is related to, but deviates slightly from the one in the radial piston pump according to

FIGS. 1 and 2

, and





FIG. 4

shows another embodiment of a valve plate with a intake side check valve.











DETAILED OF THE DRAWINGS





FIGS. 1 and 2

show a radial piston pump for high-pressure fuel delivery in fuel injection systems of internal combustion engines. The radial piston pump includes a component


2


, which constitutes a housing, in which a drive shaft


4


, which has an eccentric shaft section


6


, is rotatably supported by bearing components that can be seen in the drawing. A slide bushing


8


is provided, which encompasses the eccentric shaft section


6


, and the eccentric shaft section


6


rotates in this slide bushing


8


. On its circumference, the slide bushing


8


has 3 flattenings


10


that are offset from one another by 120°, against each of which a respective piston


12


rests with an intermediary pressure piece


16


that has a flat contact surface


14


.




Each respective piston


12


is supported so that it can carry out a reciprocating motion in a cylinder chamber


18


in the radial direction in relation to the drive shaft


4


. The cylinder chamber


18


is constituted by a bearing component


20


that is inserted into housing component


2


in the radial direction in relation to the drive shaft


4


, wherein this bearing component


20


has a through opening


22


for this purpose.




The end of the through opening


22


that is on the radial outside in relation to the drive shaft


4


is sealed by a valve plate


24


that is shown in detail in

FIG. 3

, which rests flat against the radially outer end of the bearing component


20


. An intake side check valve that is indicated as a whole with the reference numeral


26


and a high-pressure side check valve


28


are integrated into the valve plate


24


. The intake side check valve


26


includes a tappet


30


; which has a valve disk


32


on its end oriented toward the cylinder chamber


18


and extends through a through opening


34


in the valve plate


24


. The valve disk


32


can be pressed in a sealed fashion against a sealing seat


36


on the side of the valve plate


24


oriented toward the cylinder chamber


18


. On the opposite side of the valve plate


24


, a device is provided, which is labeled as a whole with the reference numeral


38


and is for pre-stressing the tappet


30


in the closing direction of the valve. The device


38


includes a valve spring


40


, which concentrically encompasses the tappet


30


and is supported on one end against a recess


42


in the valve plate


24


and is supported on the other end against a counter support


44


provided on the tappet


30


. The counter support


44


is constituted by a collar bushing element


46


whose bushing section


48


concentrically encompasses the tappet


30


and whose collar section supports the spring


40


.




In order to assemble the intake side check valve


26


, the tappet


30


is inserted from the side of the valve plate


24


closest to the cylinder chamber, through the opening


34


until the valve disk


32


rests in a sealed fashion against the valve seat


36


. Then the spring


40


is slid onto the tappet


30


from the opposite end. Finally, the collar bushing element


48


is slid onto the tappet


30


inside the spring


40


until the restoring force of the spring


40


produces a desired resistance that defines the opening pressure of the check valve. The collar bushing element


48


is fastened in this position on the tappet


30


, e.g. by means of a crimping work cycle, wherein the bushing section


48


of the collar bushing element


46


is deformed into a radial circumferential groove


52


of the tappet


30


.




As can be further inferred from

FIG. 3

, in contrast to the depiction of

FIGS. 1 and 2

, in

FIG. 3

, an opening


54


that extends in the plane of the plate is provided for the supply of fuel. The opening


54


feeds into the tappet through opening


34


of the valve plate


24


. With the intake stroke of the piston


12


, the tappet


30


or the valve disk


32


is lifted up from the sealing seat


36


counter to the initial stress of the spring


40


so that fuel is conveyed past the valve disk


32


and can be aspirated into the cylinder chamber


18


by way of the supply opening


54


. With the subsequent compression stroke, the intake side check valve


26


closes and the piston


12


can extend with its piston face until it almost reaches the valve disk


32


of the intake side check valve


26


. The high-pressure fuel then travels by way of a recess


56


to the high-pressure side check valve


28


and from there, to a high-pressure outlet fitting


58


of the radial piston pump.





FIG. 4

shows another embodiment of an intake side check valve


60


that differs from the embodiment described above essentially by virtue of the fact that the counter support


62


is constituted by a slit securing disk


64


that can be clipped onto the tappet


66


in the region of an annular groove


68


that extends in the circumference direction. Since the annular groove


68


and the axial stop are provided on the tappet


66


, the desired opening pressure of the check valve is adjusted through the selection of a securing disk


64


of a particular thickness d.




From

FIG. 4

it is also clear that a large part of the stroke H of the tappet


66


or the valve disk


70


can be utilized for the compression stroke of the pump piston.




In the instance depicted, the fuel delivery does not occur by means of an opening in the plane of the valve plate


72


, but (in accordance with

FIGS. 1 and 2

) from the side of the valve plate


62


remote from the cylinder chamber


74


, as indicated by the arrows


76


.




The foregoing relates to a preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.



Claims
  • 1. A radial piston pump for high-pressure fuel delivery in fuel injection systems of internal combustion engines comprising a common rail injection system, said pump comprises a drive shaft (4) that is supported in a pump housing (2) and includes an eccentric shaft section (6) in the circumference direction, a number of pistons (12) that are disposed radially with regard to the eccentric shaft section (6) of the drive shaft (4), each piston in a respective cylinder chamber (18, 74), each piston is set into a reciprocating motion in a radial direction in the cylinder chamber (18, 74) due to the eccentric shaft section (6) upon rotation of the drive shaft (4), wherein each respective cylinder chamber (18, 74) is sealed on the radial outside in relation to the eccentric shaft section (6) of the drive shaft (4) by a one piece valve plate (24, 72) that has an intake side first check valve (26, 60) and a high-pressure side second check valve (28), the intake side first check valve (26, 60) has a tappet (30, 66) that passes through the valve plate (24, 72) and this tappet, on an end oriented toward the cylinder chamber (18, 74), has a valve disk (32, 70) that is placed in a sealed fashion against a sealing seat (36) of the valve plate (24, 72), and that on a side of the valve plate (24, 72) remote from the cylinder chamber (18, 74), a device (38) is provided, which pre-stresses the tappet (30, 66) in a closing direction, wherein the device (38) that pre-stresses the tappet (30, 66) in the closing direction includes a spring (40) that is supported on one end against a side of the valve plate (24, 72) remote from the cylinder chamber (18, 74) and is supported on another end against a counter support (44, 62) provided on the tappet (30, 66), and the counter support (44, 62) is attached to the tappet (30, 66) in a positively engaging manner, by means of crimping.
  • 2. The radial piston pump according to claim 1, in which the counter support (44) is constituted by a collar bushing element (46) whose bushing section (48) concentrically encompasses the tappet (30) and whose collar section (50) supports the spring (40).
  • 3. The radial piston pump according to claim 1, in which the counter support (44) is fixed in a position on the tappet (30) such that a pre-selected opening pressure of the check valve (26) is produced.
  • 4. The radial piston pump according to claim 2, in which the counter support (44) is fixed in a position on the tappet (30) such that a pre-selected opening pressure of the first check valve (26) is produced.
  • 5. The radial piston pump according to claim 1, in which at least one opening (54) is provided in the valve plate (24) and this opening is aligned essentially radial to a longitudinal direction of the cylinder chamber (18) and communicates with a fuel supply opening.
  • 6. The radial piston pump according to claim 2, in which at least one opening (54) is provided in the valve plate (24) and this opening is aligned essentially radial to a longitudinal direction of the cylinder chamber (18) and communicates with a fuel supply opening.
  • 7. The radial piston pump according to claim 5, in which the radial opening (54) feeds into the tappet through a second opening (34) of the valve plate (24).
  • 8. A radial piston pump for high-pressure fuel delivery in fuel injection systems of internal combustion engines comprising a common rail injection system, said pump comprises a drive shaft (4) that is supported in a pump housing (2) and includes an eccentric shaft section (6) in the circumference direction, a number of pistons (12) that are disposed radially with regard to the eccentric shaft section (6) of the drive shaft (4), each piston in a respective cylinder chamber (18, 74), each piston is set into a reciprocating motion in a radial direction in the cylinder chamber (18, 74) due to the eccentric shaft section (6) upon rotation of the drive shaft (4), wherein each respective cylinder chamber (18, 74) is sealed on the radial outside in relation to the eccentric shaft section (6) of the drive shaft (4) by a one piece valve plate (24, 72) that has an intake side first check valve (26, 60) and a high-pressure side second check valve (28), the intake side first check valve (26, 60) has a tappet (30, 66) that passes through the valve plate (24, 72) and this tappet, on an end oriented toward the cylinder chamber (18, 74), has a valve disk (32, 70) that is placed in a sealed fashion against a sealing seat (36) of the valve plate (24, 72), and that on a side of the valve plate (24, 72) remote from the cylinder chamber (18, 74), a device (38) is provided, which pre-stresses the tappet (30, 66) in a closing direction, wherein the device (38) that pre-stresses the tappet (30, 66) in the closing direction includes a spring (40) that is supported on one end against a side of the valve plate (24, 72) remote from the cylinder chamber (18, 74) and is supported on another end against a counter support (44, 62) provided on the tappet (30, 66), and the counter support (62) is constituted by a slit disk (64) that rests against an axial stop (68) which is part of the tappet (66).
  • 9. The radial piston pump according to claim 8, in which at least one opening (54) is provided in the valve plate (24) and this opening is aligned essentially radial to a longitudinal direction of the cylinder chamber (18) and communicates with a fuel supply opening.
  • 10. The radial piston pump according to claim 9, in which the radial opening (54) feeds into the tappet through opening (34) of the valve plate (24).
  • 11. The radial piston pump according to claim 8 in which the counter support (44) is fixed in a position on the tappet (30) such that a pre-selected opening pressure of the check valve (26) is produced.
Priority Claims (1)
Number Date Country Kind
197 29 790 Jul 1997 DE
PCT Information
Filing Document Filing Date Country Kind
PCT/DE98/01918 WO 00
Publishing Document Publishing Date Country Kind
WO99/02861 1/21/1999 WO A
US Referenced Citations (7)
Number Name Date Kind
302978 Brislin Aug 1884 A
317963 Ballantine May 1885 A
319446 Boyle Jun 1885 A
507901 Grist Oct 1893 A
4758135 Woodward et al. Jul 1988 A
4813452 Smith Mar 1989 A
5382140 Eisenbacher et al. Jan 1995 A