Pressure control valve

A pressure control valve has a substantially closed housing, an armature provided with an integrated valve body, a valve seat with which the valve body cooperates, a spring acting on the valve body so that the valve body cooperates with the valve seat, an electromagnet arranged to adjust a control pressure. The magnet armature is somewhat bucket-shaped. A projection extends in an interior of the housing and operates for guiding a magnetic flux. The magnet armature surrounds the projection and is mounted on the valve body in a friction-transmitting manner. A second spring acts on the valve body so as to counteract an action of the first mentioned spring.

BACKGROUND OF THE INVENTION 
The present invention relates to pressure control valves. More particularly 
it relates to pressure control valves having a substantially closed 
housing, an armature arranged in the housing and having an integrated 
valve body which cooperates with the valve seat under the action of a 
spring. 
Pressure control valves of the above mentioned general type are known in 
the art. In such valves the control pressure can be adjusted by a 
proportional magnet which acts as an actuating an adjusting device. The 
control curve of such a pressure control valve is dependent on the 
manufacturing and mounting tolerances to a high degree and especially on 
axial distance of magnet armature from the valve housing with the given 
distance of the valve body from the valve seat. Occurring deviations 
change the characteristic curve of each individual valve considerably so 
that often expensive adjusting steps must be taken. Moreover, such 
pressure control valves are long and have a tendency to be unstable in the 
control region, especially in the sense of deviation over the control 
point. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a pressure 
control valve which avoids the disadvantages of the prior art. 
More particularly, it is an object of the present invention to provide a 
pressure control valve which can be very short and which dampens the 
movements of the valve member and armature with the oil-filled armature 
space and therefore prevent deviations beyond the adjusting or regulating 
value. 
In keeping with these objects and with others which will become apparent 
hereinafter, one feature of the present invention resides, briefly stated, 
in a pressure control valve of the above mentioned type in which the 
magnet armature is substantially bucket-shaped and partially surround a 
projection which extends in the interior of the housing and serves for 
magnetoc flux guidance, the magnet armature is frictionally mounted on the 
valve body, and another spring in addition to the first spring is arranged 
on the valve body and counteracts the action of the first spring which 
biases the valve body toward the valve seat. 
When the pressure control valve is designed in accordance with the present 
invention it eliminates the disadvantages of the prior art and provides 
for the above mentioned advantageous results. It can made very short and 
it dampens the movements of the valve member and the armature with the oil 
filter armature space to prevent deviations over the adjusting and control 
valve. Also, due to the special construction of the valve a very accurate 
adjustment of the distance between the valve seat and the magnet armature 
is possible, so that the manufacturing and mounting tolerances can be 
compensated. 
In accordance with another feature of the present invention, the valve body 
is supported in the housing on two bearing points provided in the housing. 
Still another feature of the present invention is that the valve seat is 
formed as a flat seat, while the valve body is provided with a 
correspondingly designed flat end side. 
Finally, the adjustment of the first mentioned spring can be changed by an 
adjusting screw. 
The novel features which are considered as characteristic for the invention 
are set forth in particular in the appended claims. The invention itself, 
however, both as to its construction and its method of operation, together 
with additional objects and advantages thereof, will be best understood 
from the following description of specific embodiments when read in 
connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A pressure control valve has a housing 10 composed of a valve housing 11 
and a bucket-shaped magnet housing 12. The magnet housing 12 is closed by 
a cover 13 which is provided with a cylindrical projection 14 extending 
into the interior of the housing. The projection 14 forms a through-going 
stepped longitudinal opening 15A, 15B. Its opening portion 15B extending 
from the outer side of the cover 13 has a smaller diameter and is closed 
by an adjusting screw 16. A magnet coil 18 is arranged in the interior of 
the magnet housing. Its inner diameter is greater than the outer diameter 
of the projection 14. 
The magnet housing has a bottom 20. An axially extending three-step opening 
21 extends from the bottom 20 through the valve housing 11. The individual 
opening portions, starting from the bottom 20 of the magnet housing, are 
identified as 21A, 21B, 21C and 21D. The flat shoulder formed between the 
opening portions 21D and 21C serves as a valve seat 22 which cooperates 
with a flat end side of the cylindrical valve body 23. The outer diameter 
of the valve body 23 at its end which faces the valve seat 22 is smaller 
than the diameter of the opening portion 21C. The opposite end of the 
valve body extends in the opening portion 15A of the projection 14 and 
there is supported in a sliding ring 25 which is inserted in an annular 
groove 24. A further sliding ring 26 is fixedly inserted in the opening 
portion 21B and serves as a support of the valve body 23. The valve seat 
22 is connected through an opening portion 21D with the not shown pressure 
medium source. Its connection is identified with reference A. The pressure 
medium discharge is performed through a transverse opening 28 which 
extends through the valve housing in the region of the opening portion 
21C. The transverse opening 28 is connected with a not shown container 
whose connection is identified as O. 
The end of the valve body which extends into the opening portion 15A has an 
axially extending blind hole 29 which starts from the end side. A pressure 
spring 30 abuts against the bottom of the blind hole, while its opposite 
end abuts against an adjusting screw 16. Under the action of the spring 
30, the valve body 23 is pressed against the valve seat 22. A 
substantially bucket-shaped magnet armature 31 is mounted in a 
friction-transmission manner on the valve body 23 in the region of the 
inner space of the magnet coil 18, so that its bottom 32 faces toward the 
valve housing 11. The bottom is provided with a longitudinal opening 23 
for the friction-transmitting mounting. The outer diameter of the magnet 
armature 31 is somewhat smaller than the inner diameter of the coil 18, 
and its inner diameter is somewhat greater than the outer diameter of the 
projection 14, which extends in the interior of the magnet armature. 
A projection 34 is provided at the lower side of the bottom 32 of the 
magnet armature 31. It extends in the opening portion 21A, and its 
diameter is smaller than the diameter of this opening portion. A second 
pressure spring 35 is supported on the projection 34, while its opposite 
end abuts against the shoulder 36 between the opening portions 21B and 
21A. 
Due to the second spring 35 the action of the first spring 30 can be made 
weaker or compensated so that the characteristic of the valve can be 
adjusted in any desirable manner. 
When the magnet is not supplied with current and the connection A does not 
have pressure, with the respectively adjusted spring the pressure control 
valve is closed. In other words, the valve body 23 abuts against the valve 
seat 22. Therefore, the opening portion 21D which is connected with the 
pressure medium source is closed at one end. When the pressure built up in 
the opening portion 21D exceeds the force at the end surface of the valve 
body 23, by a value which is greater than the difference between the force 
of the spring 30 and the counteracting spring 35, the valve body 23 is 
lifted from its seat. Thereby, the pressure medium connections A and O are 
connected through the opening portions 21D and 21C as well as the 
transverse opening 28 so that the pressure medium is discharged. Thereby a 
pressure regulation or pressure reduction is obtained of the pressure 
medium stream which flows to A for actuation of a consumer. 
Simultaneously, the pressure medium passes through the bearing gap between 
the sliding ring 26 and the valve body 23 and reaches the interior of the 
magnet housing 12, so that it is filled with the pressure medium. Through 
the bearing gap between the sliding ring 25 and the valve body 23 the 
pressure medium reaches the opening portion 15A. 
If the pressure control valve is used for example in a transmission of a 
motor vehicle, the pressure control valve can be filled with the pressure 
medium during the mounting and built in under the oil level. The magnet 
housing is then filled with the pressure medium before the building-in and 
actuation. 
By the respective control of the proportional magnets, the pressure can be 
increased, as required for opening of the valve. 
Due to pressure medium filling of the magnet housing 12 and also the 
pressure medium filled long gaps between the magnet armature 31 and magnet 
coil 18 as well as between the magnet armature 31 and the projection 14, a 
hydraulic damping is obtained which reduces the instabilities of the 
control conditions. A further damping effect is produced due to the volume 
change of the pressure medium accommodated in the valve housing during the 
movement of the magnet armature and the valve body. For this purpose, the 
pressure medium must pass through the small bearing gaps between the 
sliding rings 25, 26 and the valve body 23. The thusly adjusted further 
damping effect increases with a reducing bearing gap. 
Due to the shaping of the magnet armature which partially surrounds the 
projection 14 serving for the magnetic flux, the pressure control valve 
can be made especially short. 
Due to the friction-transmitting mounting of the armature on the valve 
body, the axial air gap between the magnet armature 31 and the bottom 20 
of the magnet housing during the mounting of the pressure control valve 
can be adjusted with respect to the valve seat 22, for example by an 
adjusting disc. Therefore, this value can be maintained independent of the 
manufacturing and mounting tolerances connected with the tool and 
therefore maintained approximately constant. 
Due to the remote location of the bearing points of the valve body from one 
another and therefore of the magnet armature, the eccentricity can be 
maintained very low. Therefore, the magnetic transfer forces and the 
hysteresis of the control curve of the valve is also maintained very 
small. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
pressure control valve, it is not intended to be limited to the details 
shown, since various modifications and structural changes may be made 
without departing in any way from the spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.