Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
2000-05-31
2001-03-27
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C092S129000
Reexamination Certificate
active
06205980
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a delivery pump for high pressure pumps and in particular, to the drive of delivery pumps which work according to the reciprocating-plunger principle.
2. Discussion of Background
High-pressure delivery pumps have a plunger stroke which is relatively long in relation to the plunger diameter and are therefore suitable for producing high pressures. Such high-pressure delivery pumps are used, for example, for producing the injection pressure in fuel injection systems (e.g., common rail) for internal combustion engines. A high-pressure delivery pump of the generic type is disclosed in EP-A-881 380 A1 (hereinafter “EP '380”).
High-pressure delivery pumps of the generic type have a high-pressure cylinder or plunger cylinder and a cylindrical plunger movable therein in a reciprocating manner. The volume of the delivery space inside of the high-pressure cylinder is varied by the stroke movement of the plunger. During the filling stroke of the plunger, the delivery space can be connected to a supply space for a flow medium via a filling valve to fill the delivery space. The delivery space increases in swept volume with the flow medium. During a following delivery stroke with the filling valve closed, the pressure in the delivery space increases until a pressure valve opens and thereby connects the delivery space to a high-pressure space. The precise design of the high pressure pump is described in EP '380, the disclosure of which is hereby incorporated by reference so as to be expressly made the contents of the present application.
The plunger is driven by an eccentric drive. The eccentric drive includes an eccentric and said at least one relieved portion includes first and second relieved portions laterally defining said contact area, said first and second relieved portions each being provided at said outer circumference of said rolling ring. A disk-like widened portion is provided at a first end of the pre-loaded plunger. Because of the force ratios when passing through the top and bottom dead centers, the rolling ring rotates back and forth in the process and changes its direction of rotation twice during each revolution of the eccentric and eccentric shaft. This may lead to damage to the components of the eccentric drive at a high rotational speed of the eccentric shaft.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a high-pressure delivery pump which works in a trouble-free manner at a high rotational speed. This object is achieved with a high-pressure delivery pump which includes a high pressure cylinder. A plunger is displaceable in the high-pressure cylinder. An eccentric pin is arranged on a drive shaft and a rolling ring is rotatably mounted on the eccentric pin. Either the plunger or a part connected to the plunger, such as a widened portion, bears against the rolling ring via a contact area. The rolling ring has at least one recess or relieved portion.
According to the present invention, the at least one recess or relieved portion of the rolling ring allows a reduction of the moment of inertia of the rolling ring with respect to its axis of rotation. Due to the reduction in the moment of inertia, the acceleration moment of the rolling ring, during a change in the direction of rotation, is also reduced. As a result of the reduction of the acceleration moment, damage to the eccentric drive is prevented, especially in the region of the contact area between the rolling ring and the plunger.
Thus, it is possible to operate a high-pressure delivery pump of the generic type at higher rotational speeds than they previously were operated at, without the adverse effect of a sliding movement between the rolling ring and the plunger base occurring. Furthermore, the reduction in the moment of inertia and thus, in the total mass of the rolling ring as a whole, relieves the load on the eccentric-drive construction, since the bearings of the drive shaft are also subjected to lower loads.
Advantageous embodiments of the present invention includes as follows:
A first embodiment, wherein the recess or relieved portion may be formed at the outer circumference of the rolling ring. As a result, the stability of the rolling ring is not reduced, although at the same time, the moment of inertia can be reduced.
In another embodiment of the present invention, the rolling ring has a least one encircling recess at its outer circumference and axially outside of the region of the contact area. In this embodiment, the rolling ring is sunk symmetrically outside of the region of the contact area. As a result of the rolling ring being outside the contact area, the stability again is not reduced, but the moment of inertia is reduced. Thus, the acceleration moment, during changes in the direction of rotation, is also not reduced.
It is especially advantageous if the rolling ring has two encircling recesses, which laterally define the contact area and which are each provided at the outer margin of the rolling ring. This creates a symmetrical arrangement, which is optimized with regard to the reduction in the moment of inertia. In this embodiment, the requisite outside diameter of the rolling ring is present only in the region of the contact area. The rolling ring is reduced in mass outside the contact area.
REFERENCES:
patent: 2213994 (1940-09-01), Rankin
patent: 4548124 (1985-10-01), Ortelli
patent: 4739675 (1988-04-01), Connell
patent: 5947069 (1999-09-01), Koerner
patent: 6000368 (1999-12-01), Mikame
Moulis Thomas N.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
SIG - Schweizerische Industrie-Gesellschaft
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