Expansible chamber devices – Abutment connection between working member and power...
Reexamination Certificate
1999-03-11
2001-04-17
Look, Edward K. (Department: 3745)
Expansible chamber devices
Abutment connection between working member and power...
C417S470000, C184S006800, C123S090350
Reexamination Certificate
active
06216583
ABSTRACT:
The invention relates to a piston pump, in particular a radial piston pump of the roller tappet type for high-pressure fuel delivery in fuel injection systems of internal combustion engines, particularly in a common rail injection system. A drive shaft that has a number of cam-like projections in the circumference direction and with at least one tappet that is disposed radially with regard to the drive shaft. In its radially inner end region, this tappet has a rotatable roller, which is reliably supported against the drive shaft in the region of its projections so that this roller can roll in the circumference direction.
It goes without saying that with a piston pump of this kind, preferably a number of radially disposed tappets is provided, which on their end remote from the drive shaft, either rest against a piston that defines a high-pressure side or define the high-pressure side themselves and thus directly perform a displacement or compression function.
Particularly in the above-mentioned common rail applications, the piston pump is not used for direct injection into the motor cylinder, but is instead used for delivery into a high-pressure reservoir. For functional and cost-related reasons, the aim is to reduce the number of separate supply units in comparison to conventional injection systems (e.g. series pump, plug-in pump) by virtue of the fact that—as already mentioned at the beginning—the drive shaft of the piston pump has a number of projections in the circumference direction, which consecutively produce a stroke motion in a radial piston or radial tappet during a rotation of the drive shaft (multiple cam system).
However, this leads to an increased load on the drive components, in particular of the tappet and the rotatably supported roller. In comparison to single-cam systems, the delivery times of the radial piston or radial tappet are increased while the relief times between the delivery phases are shortened. As a result of this, there is less time available for the formation of a lubricating film or a regeneration of the lubricating film in the region of the bearing of the roller. In piston pumps of the type mentioned above, this leads to increased wear as a result of insufficient lubrication in the region of the bearing of the roller. Because of the long delivery times, the lubricating oil is pressed out of the bearing gap and cannot penetrate back into the bearing location in sufficient quantity during the relatively short relief times.
The object of the current invention, therefore, is to reduce the wear in piston pumps of this generic type, without having to reduce the tappet load (piston force, piston or tappet stroke, relative speed of the roller in relation to its bearing).
This object is attained by means of a piston pump of the type mentioned above, which is characterized according to the invention by means of a lubricant supply opening that leads from the circumference of the tappet and feeds into the radially inner tappet end region supporting the roller and at least during a part of the stroke, communicates with a lubricant supply line of the housing, which line feeds into the cylinder chamber.
The proposal is therefore made according to the invention to produce a lubrication of the bearing location of the roller by means of the lubricant supply opening embodied in the tappet. According to the invention, the lubricant supply opening, which preferably communicates with a lubricating oil circuit of the motor, feeds either directly into the region of the slide surfaces or into the so-called roller chamber, which is defined by the roller axle and by the end region of the tappet that contains the roller.
Since lubricant is introduced by way of the lubricant supply opening either directly into the boss or into the roller chamber of the tappet, there is a sufficient quantity of lubricant available. In the first instance, the lubricant is introduced directly into the region of the surfaces sliding against each other and in the second instance, there is always so much lubricant available in the roller chamber that the lubricant can nevertheless penetrate in a sufficient quantity into the bearing location during the relatively short relief times mentioned at the beginning.
The piston pump can be embodied in a particularly simple manner from a technical manufacturing standpoint so that each tappet has a roller with rigidly attached bearing pins, with which the roller is rotatably supported in the end region of the tappet.
The roller, however, can also be rotated in relation to a bolt that extends parallel to the rotation axis of the drive shaft and can be supported by this bolt in the end region of the tappet.
As already indicated above, it turns out to be particularly advantageous if the lubricant supply opening in the end region of the tappet feeds into at least one tappet boss that is for supporting the bearing pins or the bearing bolt of the roller. It would also be conceivable for the bearing pins or the bolt to be embodied with an annular groove in the boss region, which groove coincides with the lubricant supply opening.
It has also turned out to be advantageous if the bolt is fixed in relation to the tappet and has a lubricant conducting device that communicates with or coincides with the lubricant supply opening and leads to the surfaces of the bolt/roller pairing that slide against each other. With a fixed bolt, these slide surfaces are disposed on the inside between the roller and bolt. The lubricant conducting device is thus used to transport the lubricant, which is supplied into the boss or into the roller by way of the lubricant supply opening, to the surfaces of the bolt/roller pairing that slide against each other. If the lubricant supply opening feeds into the boss region, then according to one variant of the invention, the proposal is made that the lubricant conducting device be constituted by a lateral bore in the bolt and another bore in the bolt that extends obliquely in relation to the longitudinal direction of the bolt and feeds into the region of the slide surfaces. The lubricant thus travels via the lubricant supply opening into the lateral bore that extends essentially in the radial direction, into the interior of the bolt, and from there, into the region of the slide surfaces by way of the other bore that extends obliquely to the longitudinal direction of the bolt.
The lubricant conducting device, however, in a manner that is simple and therefore advantageous from a technical manufacturing standpoint, could also be constituted by a surface groove that runs in the longitudinal direction of the bolt and extends into the region of the slide surfaces.
The surface groove can have an intrinsically arbitrary cross sectional shape; it has turned out to be advantageous if it is embodied as convexly rounded in terms of the cross section in the longitudinal direction of the bolt. Moreover, it has turned out to be advantageous if the surface groove is closed in the longitudinal direction of the bolt, i.e. if it does not feed to the end faces of the bolt, in order to prevent the lubricant from escaping in this undesired direction.
The lubricant conducting device could furthermore be constituted by a flattening on the bolt circumference extending in the longitudinal direction of the bolt, which is particularly easy to produce from a technical manufacturing standpoint.
It also turns out to be advantageous if a groove extending in the stroke direction is provided in the circumference surface of the tappet and/or in the inner surface of the cylinder. In the reciprocating motion of the tappet, the groove assures that in each stroke position, the lubricant supply opening of the tappet communicates with the lubricant supply line of the housing, which line feeds into the inner surface of the cylinder.
In order to be able to control the lubricant flow rate in the system, the proposal is made to provide a throttle device in the lubricant supply line of the housing, i.e. upstream of the tappet in the supply direction. This achieves freedom with regard to th
Goettel Thomas
Klinger Horst
Kuhn Uwe
Loesch Gerd
Rosenau Bernd
Greigg Edwin E.
Greigg Ronald E.
Look Edward K.
Robert & Bosch GmbH
Rodriguez Hermes
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