Reciprocating pump

Details Reciprocating pump Reciprocating pump

1998-04-23

1999-08-17

Nguyen, Hoang

Expansible chamber devices

Abutment connection between working member and power...

417273, 417470, F16J 110, F04B 104

Patent

active

059377348

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a piston pump, in particular a high pressure pump for a fuel injection device of an internal combustion engine.


PRIOR ART

In a known piston pump of this kind (DE 44 19 927 A1), three pistons disposed in the shape of a star are driven by means of an eccentric pin which is provided on a free end of a drive shaft that is provided in a cantilevered fashion in the pump housing. A cup-shaped part is supported so that it can rotate on the eccentric pin by means of a roller bearing which is lubricated through a lubrication line provided in the drive shaft. In lieu of the roller bearing, a slide bearing can also be used, which can also be embodied as a dry bearing with a suitable pairing of materials.
The transfer of force from the eccentric pin to the pistons is carried out by means of flexible transfer elements that are fastened to the pistons and to the cup-shaped part, which is supported on the drive shaft and does not rotate, so that no sliding friction occurs between the pistons and their actuating element, i.e. the cup-shaped part, or the transfer elements. Theoretical and Applied Hydraulics! W. Gotz, 1983, Robert Bosch GmbH, Stuttgart, has disclosed a radial piston pump with external piston support in which during the operation of the pump, a cylinder star is rotated by a drive shaft via a coupling. The cylinder star has a number of cylinders in which pistons are disposed so they can be moved radially. The cylinder star with the pistons is circumferentially enclosed by an essentially non-rotating stroke ring and the pistons are supported with their radial outer ends via slide shoes against the inner circumferential surface of this stroke ring and this surface is used as a slide bearing surface.
In order to achieve a hydrostatic bearing relief of the slide bearings constituted by the stroke ring and the slide shoes, in the middle of its sliding surface, each slide shoe has a recess which communicates with the respective cylinder chamber. In the direction of the sliding motion in addition to the recess, grooves are also provided in the sliding surfaces of the slide shoes and these grooves extend crosswise to the movement direction.
When this known pump operates, the slide shoes continuously move in one direction along the inner circumference surface of the stroke ring.
In a known radial piston pump (DE 42 41 827 A1) with internal piston support, an eccentric part is non-rotatably disposed on a drive shaft and the outer circumference surface of this eccentric part acts as a slide bearing surface for the pistons supported on it. In this known pump, the relative movement between the sliding surface on the piston and the slide bearing surface on the eccentric part also continuously occurs in the same direction.


ADVANTAGES OF THE INVENTION

The piston pump has the advantage over the prior art that high lateral forces on the piston, which would have to be absorbed by the piston guide, are prevented. In particular, lateral forces that act on one side, like the ones that occur in conventional radial piston pumps, are prevented without having to provide costly actuating elements between the stroke ring and the piston.
A particular advantage of the invention is comprised in that the medium to be delivered by the pump travels into all regions between the slide bearing surface on the stroke ring and the slide shoe, although the stroke ring only executes an oscillating sliding motion in relation to the slide shoe and the movement length of this oscillating motion is less than the length of the sliding surface on the slide shoe in the movement direction.
It is particularly advantageous to use a stroke ring made of plastic, in particular polyimide or PEEK, since this produces particularly low-friction support surfaces, so that additional bearing elements between the stroke ring and the crank element as well as friction improving measures on the sliding surface disposed on the piston are no longer necessary.
The use of coatings, in particular carbon coatings on the sliding surface disposed on th

REFERENCES:
patent: 4068982 (1978-01-01), Quarve
patent: 5178524 (1993-01-01), Nicol
patent: 5364234 (1994-11-01), Eickmann
patent: 5564908 (1996-10-01), Phillips et al.
patent: 5775203 (1998-07-01), Osborn et al.
patent: 5839349 (1998-11-01), Volz

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