Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-05-15
2001-09-04
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S506000, C137S493300
Reexamination Certificate
active
06283094
ABSTRACT:
PRIOR ART
The invention is based on a pressure valve for a fuel injection pump. One such pressure valve, known from an earlier German Patent Application, DE 197 10 891.1, is inserted into a feed line between a pump work chamber of a fuel injection pump and an injection site of the internal combustion engine to be supplied by the pressure valve. This known pressure valve, acting as an equal-pressure valve, has a valve body inserted into a tubular stub forming a valve housing. The valve body has an axial through conduit and, with its end face remote from the pump work chamber, it forms a first valve seat. A pressure valve closing member that opens in the direction of the injection site is guided in the axial through conduit of the valve body and is held with a sealing face on the first valve seat by the force of a first valve spring. An axial through bore is disposed in the pressure valve closing member; this through bore can be closed by a reverse-flow valve that opens in the direction of the pump work chamber. In the known pressure valve, this reverse-flow valve is embodied as a ball valve, to which end the movable valve member is embodied as a valve ball. This valve ball can be brought into contact, by a restoring spring forming a second valve spring, with a valve seat face of the pressure valve closing member that opens in the direction of the injection site, and a spring plate as provided between the restoring spring and the valve ball. This spring plate has a spherical surface guiding the valve ball and a bearing face, remote from this spherical guide face, for the restoring spring.
The known pressure valve has the disadvantage that when the reverse-flow valve, embodied as a ball valve, opens, a backup pressure is built up at the edge toward the spring plate. Consequently a backup cushion develops over time between the valve ball and the spherical surface of the spring plate; although this does allow the spring plate to execute a relatively long stroke, the valve ball cannot follow this opening stroke motion. Thus an overly small outflow cross section is opened at the ball valve, and thus the flow rate at the reverse flow valve of the known pressure valve is insufficient or fluctuates, and the equal-pressure valve thus functions incorrectly. Furthermore, because of the backup pressure cushion between the valve ball and the spring plate and its irregular collapse, in conjunction with vibration in the outflowing fuel in the feed line, the result is that the valve ball alternatingly lifts up from and hammers onto the guide face of the spring plate, which causes increased wear of the contact faces of the spring plate and the valve ball. Furthermore, because of the higher spring stress, breakage of the restoring spring occurs more often, so that the reliability and service life of the ball valve inside the pressure valve is restricted considerably.
ADVANTAGES OF THE INVENTION
The pressure valve according to the invention has the advantage over the prior art that by the provision of interruptions in the closed ball guide face on the spring plate, the buildup of a backup pressure can be averted. The valve ball during the opening stroke motion of the ball valve thus follows in the opening stroke direction without any restriction in the deflection motion of the spring plate, thus uncovering an adequate opening cross section of the valve seat face, which makes a uniform fuel transfer at the ball valve possible. Lifting of the spring plate from the valve ball can also be averted, so that the spring plate does not execute a separate, longer stroke, and thus puts less stress on the restoring spring. An alternating lifting up and hammering down of the valve ball on the spring plate can also be averted, which considerably reduces the mechanical wear of these components.
The interruptions of the spherical surface, guiding the valve ball, on the spring plate are preferably embodied as obliquely extending recesses, by which on the one hand a sharp stream deflection point of the outflowing fuel and thus a backup pressure point can be avoided, and furthermore a connection of the spherical guide face with the rear spring chamber can be made. A lesser fuel pressure prevails in this rear spring chamber, so that because of the pressure drop to the outflowing fuel, no backup pressure can build up. The recesses or interruptions in the closed spherical guide face of the spring plate can alternatively be embodied as bores, slits or indentations instead; what is essential is that there be an interruption in the closed contact face between the valve ball and the spherical surface. Another advantage is attained by chamfering the transitional face between the radial circumferential wall face of the cylindrical spring plate and the end face of the spring plate toward the valve ball. This chamfering of the end face of the spring plate, in addition to the polished sections on the spring plate, enables an improved flow past the spring plate. Inclination angles of the chamfer of approximately 30° to 45° to the longitudinal axis of the spring plate are especially advantageous. It is also especially advantageous for the angles of inclination of the oblique polished face at the spherical surface and the chamfer on the face end of the spring plate to have the same angle from the longitudinal axis, preferably 300. To further improve the fuel transfer at the spring plate, axial polished faces, preferably three of them, are also provided on its cylindrical circumferential wall surface. The guidance of the spring plate in the axial direction is effected in a structurally simple way via the remaining cylindrical wall web regions, which are guided slidingly displaceably along the wall of the valve body. To guarantee a secure contact of the restoring spring, which urges the valve ball in the closing direction, with the spring plate, the bearing face of the restoring spring on the spring plate is embodied as an annular end face, which is adjoined radially inward by a remaining tanglike region, which is surrounded by the restoring spring.
The embodiment of the spring plate of the ball valve according to the invention is described here taking as an example a pressure valve for installation in a feed line between a fuel injection pump and an injection site of the internal combustion engine to be supplied, but it can also be used in all other ball valves, such as simple check valves.
Further advantages and advantageous refinements of the subject of the invention can be learned from the drawing, description and claims.
REFERENCES:
patent: 1999967 (1935-04-01), Miller et al.
patent: 4577606 (1986-03-01), Bohringer et al.
patent: 4651779 (1987-03-01), Filippi et al.
patent: 5293897 (1994-03-01), Warga et al.
patent: 5295469 (1994-03-01), Kariya et al.
patent: 196 49 541 A1 (1998-06-01), None
patent: 197 10 891 A1 (1998-09-01), None
Gimie Mahmoud
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
Yuen Henry C.
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