Valves and valve actuation – With material guide or restrictor
Reexamination Certificate
2001-05-24
2002-10-15
Morris, Lesley D. (Department: 3754)
Valves and valve actuation
With material guide or restrictor
C239S569000, C239S601000, C251S359000, C251S333000
Reexamination Certificate
active
06464201
ABSTRACT:
BACKGROUND OF THE INVENTION
When utilizing air springs in passenger cars, a largest possible air volume is to be used to obtain optimal suspension comfort. Mostly, there is insufficient space at the wheel because of chassis components such as a longitudinal control arm, brake and drive shaft. For this reason, this large air volume is subdivided into an air spring volume and an ancillary volume (see
FIG. 1
a
). The ancillary volume can then be accommodated at a location in the vicinity such as in the engine compartment, in the longitudinal support, in the trunk, et cetera. Both volumes are then connected by a line having a cross section which is of such a dimension that an air exchange can take place very rapidly and without significant pressure loss. If the vehicle travels on cobblestones, for example, then the air spring contracts and expands in correspondence to the road speed at a high frequency. Each spring contraction operation and each spring expansion operation is associated with an air exchange which may not be hindered because the suspension comfort would otherwise be reduced.
A high suspension comfort means a reduced spring stiffness. In accordance with the above, this is achieved with a large air spring volume. It is, however, a disadvantage that the steering becomes loose. Likewise, for a low spring stiffness, the driving performance changes when braking, when accelerating, and in travel through a curve as well as with rapid avoidance maneuvers. This change in driving performance is in the direction of instability which is unwanted because driving safety is thereby affected.
In order to resolve this conflict between comfortable air spring design and stability of the driving performance, the above-described line is provided with a valve, which can be blocked (see
FIG. 1
b
). During normal driving conditions, the valve is open and is open in such a manner that the valve presents no significant hindrance for the air exchange between the air spring and the ancillary volume. If the vehicle is now braked, accelerated or driven in a curve or is compelled to execute a rapid defensive maneuver, then the valve is abruptly closed by a control apparatus which can detect the driving state by means of sensors. Thus, the air spring and the ancillary volumes are separated from each other with the consequence that only the air spring volume is available for the suspension operation. The spring stiffness is therefore higher and the vehicle has a more stable driving performance.
The valve is again opened as soon as the control apparatus detects that none of the above-described driving conditions is present any longer. This opening operation has to be carried out in such a manner that a pressure difference between the air spring volume and the ancillary volume, which has possibly formed in the meantime, can be slowly compensated so that there is therefore no sudden drop or upward bucking of the vehicle. only when the pressure compensation is complete can the valve again be completely opened.
Valves for this purpose are known. They are mostly realized as precontrol valves in truck design wherein a small electromagnetic valve switches a large pneumatically actuated valve (see FIG.
2
). The alternative is an electromagnetic actuation of the valve. In the design of passenger cars, there is, however, no corresponding compressed air source of sufficient power present in order to switch the pneumatically actuated valve. For this reason, only the electromagnetic actuation remains (see
FIG. 3
a
).
Independently of the nature of the actuation (magnetic valve or pneumatically actuated valve), a large valve stroke is needed as a consequence of the large line cross section in order to clear or enable the cross section completely (
FIG. 3
b
). If the cross-sectional area of the line is defined as A
L
=D
L
2
·n/4, then the open cross section is characterized by A
VR
=L
UR
·H
R
=D
R
·H·H
R
for a circular valve seat. This results from the peripheral length L
UR
and the stroke H
R
. In order that there be no constriction, both cross-sectional areas A
L
and A
VR
have to be of the same size so that: H
R
=D
R
/4. In practice, this means a stroke H
R
of approximately 5 mm for D
L
=20 mm.
Two disadvantages are associated with the large stroke. First, the actuating force of an electromagnet drops disproportionately with distance becoming ever greater. Accordingly, for valve actuation, an electromagnet is required which has a larger number of turns having low resistance and therefore also having a large valve mass and introducing a high cost. Secondly, armature and sealing body of the valve are accelerated by its spring in the direction toward the valve seat when switching off the actuating current. As a consequence of the large stroke, high speeds and large decelerations become effective when landing on the valve seat; that is, the sealing body generates a noise when striking the valve seat, which can be similar to the blow of a hammer.
In truck air spring systems, valves exist for rapid closing and slow opening on the basis of a pneumatic actuation.
Magnetic valves are known in passenger car air springs and have been adapted to the larger line cross section. Additionally, a pressure relief has been provided in order to reduce the acting forces. However, all of these solutions are associated with friction and do not permit a trouble-free adjustment or control. In the manufacture of trucks, the valves are pneumatically actuated because the pneumatic has a higher energy density. The high energy consumption (compressed air escapes) is of no essential significance. Likewise, the switching noise is also of no great consequence.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a valve for a motor vehicle air spring.
The valve of the invention is for a motor vehicle air spring system including an air spring volume and an ancillary volume. The valve is mounted between the air spring volume and the ancillary volume and the valve includes: an inlet having a cross section (A
L
) and an outlet having a cross section (A
L
); a star nozzle defining a valve seat and being disposed between the inlet and the outlet; a valve body movable between a first position wherein the valve body is in contact engagement with the valve seat to close a flow path between the air spring volume and the ancillary volume and a second position wherein the flow path is at least partially open; the star nozzle including a nozzle body having a plurality of mutually intersecting slots (n
s
) formed concentrically therein; each of the slots having a length (D
s
) and a width (S
S
); the star nozzle having a peripheral length (L
US
) increased with respect to the peripheral length (L
UR
) of a round nozzle with the valve having a valve cross section (A
VS
) given by A
VS
=L
US
*H
S
wherein H
S
is star nozzle stroke and the star nozzle stroke is given by H
s
=A
VS
/L
US
wherein the peripheral length (L
US
) is given by L
US
=D
s
*S
s
*n
s
; the star nozzle having a pass-through cross section (A
DS
) corresponding to the valve cross section (A
VS
) and being so large that the pass-through cross section (A
DS
) corresponds at least to the cross section (A
L
) Of the inlet and the outlet; and, the nozzle body having a valley-like recess formed between each two mutually adjacent ones of the slots.
The valve of the invention has the following characteristics, namely:
a) small mass;
b) low consumption of electrical energy;
c) full cross section without throttling;
d) very short reaction time;
e) stable performance in the presence of flow forces;
f) tight blocking of the line;
g) finely metered continuous opening;
h) no disturbing noise; and,
i) cost effective.
According to the invention, a star nozzle is used in lieu of a circular valve seat. This star nozzle (
FIG. 5
) is characterized in that a desired number of slots n
S
having the length D
S
and the width s
S
are concentrically arranged and mutually intersect. As a special case, a nozzle with n
S
=1 is con
Bastianelli John
Continental Aktiengesellschaft
Morris Lesley D.
Ottesen Walter
LandOfFree
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