Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Reexamination Certificate
1997-08-29
2001-04-03
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
C123S506000, C137S543230, C137S539000
Reexamination Certificate
active
06209527
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to pressure regulating valve.
Pressure regulating valves operate in a fuel injection system of internal combustion engines with fuel pumps preferably arranged in a fuel tank for regulation of a system pressure.
A known pressure regulating valve of this type in a fuel supply system for internal combustion engine is disclosed in the German patent document DE 42 31 731 A1. In this pressure regulating valve, the valve closing spring is supported between the valve member and an adjusting screw which is screwed at the end side in the control chamber, so that the spring force of the valve closing spring and thereby the fuel pressure regulated by the pressure regulating valve in a discharge can be adjusted. When the fuel pressure applied in the valve chamber of the fuel pump reaches an opening pressure provided by the spring force F of the valve closing spring and the cross-section A of the valve opening, the valve member is lifted from the valve seat and controls so much overflow quantity Q that the regulating pressure p
r
=F/A is adjusted. The regulating pressure p
r
depends from the throughflow quantity Q, since with increasing through flow quantity Q the stroke of the valve member is increased and thereby the spring force F is increased due to the spring strength of the valve closing spring. The characteristic line p
r
(Q) of the pressure regulating valve which exhibits the operational dependency of the regulating pressure p
r
from the discharge quantity, has thereby an increase. In other words, the regulating pressure increases with the throughflow quantity.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a pressure regulating valve which avoids the disadvantages of the prior art.
In keeping with these features and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated in a pressure regulating valve, in which downstream of the valve opening a throttle surface is arranged so that between the valve member and the inner wall of the control chamber, a pressure at the valve member which counteracts the spring pressure is provided.
When the pressure regulating valve is designed in accordance with the present invention, a throughflow-dependent intermediate pressure is produced at the throttle surface, which compensates the spring force increase, so that the characteristic line increase at least in the working region of the pressure regulating valve is substantially equal to zero.
By corresponding design of the valve opening, spring force of the valve closing spring, and its spring rigidity as well as the valve member diameter and the size of the throttle surface, both the regulating pressure and the steepness of the characteristic line of p
r
(Q) is determined within predetermined limits.
If the steepness of the characteristic line is made approximately zero, then the pressure regulated by the pressure regulating valve is completely independent from the throughflow quantity and is exclusively dependent from the adjusted spring force of the valve closing spring.
It is to be understood that due to corresponding design also the characteristic line can be obtained with a negative pitch, so that, as desired in specific application, with the increasing throughflow quantity the pressure regulated by the pressure regulating valve is reduced.
In accordance with a preferable embodiment of the invention, for forming the throttle surface, a guiding gap is provided between the valve member and the chamber wall of the control chamber. The throttle surface is then provided by a ring gap surface formed because of the guiding gap between the valve member and the chamber wall. Due to the required size of the throttle surface, a guiding gap can be obtained which can result in a poor guidance of the valve member on a chamber wall of the control chamber. This is avoided when in accordance with a preferable embodiment of the present invention, the chamber wall of the control chamber is provided with radially projecting axial ribs which are spaced from one another and form axial guides for the valve member so as to simultaneously provide an exact measurement for the required throttle surface. In this case, the throttle surface is determined by the sum of the intermediate space cross-section between the axial ribs.
If the valve member is guided on the chamber wall of the control chamber and the guiding gap dimensioned exclusively with consideration of the operational safety of the pressure regulating valve, then in accordance with an advantageous embodiment of the present invention, a throttle opening is provided in the chamber wall of the control chamber and opens inside the control chamber in the region between the valve seat and a guiding surface formed on the valve member. A throttle surface is represented by the opening cross-section, while additionally because of the guiding gap between the valve member and the chamber wall, the ring gap surface must be provided.
Since in the inventive pressure regulating valve, the valve stroke and thereby the spring force with the conventionally used helical pressure spring and valve closing spring increase linearly with the throughflow quantity Q, which increases by the intermediate pressure produced by the throttle surface squarely with the throughflow quantity, a characteristic line increase can be provided near zero only within a predetermined quantity region for the throughflow quantity. By the above mentioned design of the different sizes, such as valve opening, valve member diameter, spring force and spring rigidity of the valve closing spring and the throttle surface, it is however possible to select this quantity range so that it corresponds to the working region of the regulating valve. A characteristic line increase which is exactly zero is provided when in accordance with a preferable embodiment of the invention a valve closing spring is used with a progressive spring characteristic line or alternatively the throttle surface is changed in dependence on the stroke of the valve member.
In accordance with a preferable embodiment of the present invention, the valve member is connected with a vibration damper for avoiding vibrations of the valve member. Such a vibration damper can be realized in a simple manner when in accordance with a further embodiment of the present invention a damping piston is arranged in a dead space communicating with a valve chamber and having a defined gap distance to a dead space wall, and fixedly connected to a connecting rod with the valve member. During the stroke of the valve member and thereby a connected stroke of the damping piston, the displaced liquid quantity must be pressed through a ring gap between the damping piston and the dead space wall so that a greater damping action is obtained with a faster stroke movement of the damping piston. For slower movement, the damping force is quasi zero so that the type of damping does not influence the hysteresis of the regulation negatively. For the selection of the piston diameter and the ring gap between the damping piston and the dead chamber wall, the damping action of the vibration damper can be adjusted to the conditions provided by the vibration conditions of the valve member.
In accordance with a preferable embodiment of the present invention, the valve chamber is formed as a diameter-reducing opening portion of a stepped opening which is provided in the valve body and ends blindly. The supply and withdrawal portions are realized by two radial openings extending radially to the opening axis. In the diameter-increasing opening portion, a control chamber is provided with a closing cap, in which a cap bottom of the valve closing with a valve seat is formed. The dead chamber for receiving the damping piston is formed as a non-round depression at the opening bottom of the stepped opening.
The connecting rod which is fixedly connected either with the valve member or with the damping piston carries an outer threaded portio
Bueser Wolfgang
Eiler Erich
Niederkofler Michael
Rose Jochen
Strohl Willi
Miller Carl S.
Robert & Bosch GmbH
Striker Michael J.
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