Valve device

A valve device including a housing formed with a passage, valve elements for opening and closing the passage, a spring for urging the valve elements, and a controller for displacing the valve elements against the spring force. The spring has at least two deflection modes, one of which shows a larger spring constant than the other deflection mode and appears in one of two valve positions. The controller outputs a relatively large force for displacing the valve elements to the valve position at which the spring is deflected at the larger spring constant.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a valve device provided, for example, in 
an antiskid control system of a vehicle. More particularly, it relates to 
a valve device for opening and closing a passage connecting a master 
cylinder and a wheel cylinder. 
2. Description of the Related Art 
In a conventional antiskid control system, a construction in which a 
three-port-three-position valve is provided for increasing, holding, or 
decreasing a pressure in a wheel cylinder is known. Such a 
three-port-three-position valve has two valve elements for opening and 
closing two ports which communicate with the master cylinder and a 
reservoir for the brake oil. In a valve device described in Japanese 
Examined Utility Model Publication No. 58-17169, such a 
three-port-three-position valve has a construction in which a movable 
member supporting the two valve elements is moved according to an amount 
of electric current applied to a solenoid, a main spring being provided 
between the movable member and a casing, and a subspring being provided 
between one of the valve elements and the movable member. Thus, when an 
electric current is not applied to the solenoid, the movable member is at 
a first position in which one of the valve elements closes the 
corresponding port. Conversely, when a small electric current is applied 
to the solenoid, the movable member is at a second position against the 
main spring in which both valve elements close each corresponding port 
through the force of the subspring. Further, when a large electric current 
is applied to the solenoid, the movable member is at a third position 
against the main spring in which one of the above valve elements opens the 
corresponding port and the other valve element closes the corresponding 
port, by compressing the subspring. 
As described above, in the conventional valve device, two kind of springs 
are needed, i.e., the main spring and the subspring, and the subspring 
must be provided between the two valve elements in the movable member. 
Therefore, the construction of the valve device is complicated. Further, 
in a construction wherein the two valve elements can take three positions, 
the spring constants of the main spring and the subspring, and the loads 
preset to the springs, must correspond precisely to the electromagnetic 
force of the solenoid. 
SUMMARY OF THE INVENTION 
Therefore, an object of the present invention is to provide a valve device 
having a simplified construction in which only one spring can be used, and 
in which a force for displacing a valve element need not be precisely set. 
According to the present invention, there is provided a valve device 
comprising a housing having first and second passages, a valve means for 
opening and closing the first and second passages, a spring for urging the 
valve means with a force according to the amount of deflection of the 
spring, and a control means for displacing the valve means to one of the 
valve positions which the valve means can assume. The valve means open the 
first passage and close the second passage in a first valve position, 
close the first and second passages in a second valve position, and close 
the first passage and open the second passage in a third valve position. 
The spring has first and second deflection modes, and the spring constant 
of the second deflection mode is larger than that of the first deflection 
mode. The spring enters the second deflection mode at one of the valve 
positions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will now be described below with reference to the 
attached drawings. 
FIG. 1 shows a first embodiment of the present invention. In this drawing, 
an inlet port 1, first outlet ports 2, and a second outlet port 3 are 
connected to a master cylinder (not shown), a wheel cylinder (not shown), 
and reservoir (not shown), respectively. The inlet port 1 is opened and 
closed by a first valve element 4, and the second outlet port 3 is opened 
and closed by a second valve element 5. As described later, when a movable 
member 6 is at a first valve position shown in the drawing, the first 
valve element 4 opens the inlet port 1 and the second valve element 5 
closes the second outlet port 3. When the movable member 6 is at a second 
valve position, the first and second valve elements 4 and 5 close the 
ports 1 and 3. When the movable member 6 is at a third valve position, the 
first valve element 4 closes the inlet port 1 and the second valve element 
5 opens the second outlet port 3. 
A first port member 8 is fitted in one opening of a cylindrical casing 7 
and a cylinder member 13 is fitted in the other opening of the casing 7. A 
central portion 34 of the first port member 8 extends through the casing 7 
to reach one opening of the cylinder member 13; the other opening of the 
cylinder member 13 holds a second port member 9. An annular retainer 18 is 
provided between an outer surface of the central portion 34 and an inner 
surface of the corresponding opening of the cylinder member 13. The 
central portion 34 is formed with a hole 35 extending in the axis of the 
central portion 34, and the end of the central portion 34 facing the 
cylinder member 13 is fitted a pipe member 10, i.e., the inlet port 1 is 
formed by the hole 35 and the pipe member 10. The outer end of the first 
port member 8 is provided with a filter 11 through which the inlet port 1 
communicates with the master cylinder (not shown). The second port member 
9 is formed with a hole 36 extending in the axial direction thereof, and 
the end of the second port member 9 facing the cylinder member 13 is 
fitted with a pipe member 12, i.e., the second outlet port 3 is formed by 
the hole 36 and the pipe member 12. The first outlet ports 2 are formed in 
the second port member 9 around the second outlet port 3, the first outlet 
ports 2 being located around the second outlet port 3 at constant 
intervals in such a manner that the number of first outlet ports 2 is 
four. The cylinder member 13 is formed with passages 29 for communicating 
the inlet port 1 to the first outlet ports 2, the passages 29 being 
located circumferentially in the cylinder member 13. 
The first valve element 4 is a ball valve located adjacent to an opening of 
the pipe member 10 to open and close the inlet port 1. The first valve 
element 4 is fixed in a spherical recess formed in a support member 14 
which is connected to free ends of flat springs 15 by a nut 16. As shown 
in FIG. 2, the flat springs 15 extend in a radial direction about the 
first valve element 4 and are connected to each other by an annular plate 
17 at the outer portion of the flat springs 15. The annular plate 17 is 
fixed between the annular retainer 18 and the cylinder member 13. Thus, 
the flat springs 15 are deflected with the fixed ends thereof held by the 
annular plate 17, so that the first valve 4 element is maintained in close 
contact with the opening of the pipe member 10 to close the inlet port 1. 
A coil spring 22 is provided between a spring seat 23 formed around the 
pipe member 10 and the support member 14 to urge the support member 14 in 
a direction along which the first valve 4 will separate from the pipe 
member 10. 
Similarly, the second valve element 5 is fixed to a support member 21 by a 
nut 19, the support member 21 being provided in the free ends of flat 
springs 20, so that the second valve element 5 located adjacent to the 
opening of the pipe member 12 opens and closes the second outlet port 3. 
The flat springs 20 have the same construction as the flat springs 15, 
i.e., the flat springs 20 extend in a radial direction and are connected 
to each other by an annular plate, similar to the annular plate 17, which 
is fixed between the cylinder member 13 and the second port member 9, so 
that the flat springs 20 are deflected with the fixed ends thereof held by 
the annular plate. 
The flat springs 15 and 20 are deflected by the movable member 6 which is 
engageble with the springs 15 and 20. The movable member 6 has a 
cylindrical shape, and is slidably fitted in an inner hole 24 of the 
cylinder member 13. A front portion of the movable member 6 is formed with 
radial grooves 25 for receiving the flat springs 15, and a part of this 
portion of the movable member 6 is formed into an angular shape so that 
the peak of the angle is in contact with the flat springs 15, thus forming 
pressing portions 26 as shown in FIG. 1. On the other hand, rear portions 
of the movable member 6 are formed with radial holes 27 through which the 
flat springs 20 extend, rear walls of the holes 27 being formed with a 
semi-circular section so that pressing portions 28 engageble with the flat 
springs 20 are formed. The movable member 6 is urged against and engages 
with a stopper 32 provided on an inner surface of the second port member 9 
by the flat springs 15, at the position shown in FIG. 1. 
The movable member 6 is made of a magnetic material, so that, when the 
solenoid 3a is energized, the movable member 6 is drawn to the left in 
FIG. 1. The solenoid 30 is provided between the casing 7 and the first 
port member 8, and is fixed there by a retainer 18 made of a non-magnetic 
material. The solenoid 30 is connected to an electric source (not shown) 
through a lead line 31. 
In this embodiment, the solenoid 30 is operated in three states, i.e., a 
state in which no electric current is applied, a state in which a 
relatively small electric current is applied, and a state in which a 
relatively large electric current is applied, and thus the movable member 
6 can be set in three positions. 
A first passage is constructed by the inlet port 1, the spaces 38 (FIG. 2) 
of the flat springs 15, the passages 29, the spaces of the flat springs 
20, and the first outlet ports 2. A second passage is constructed by the 
first outlet ports 2, the radial holes 27 of the movable member 6, and the 
second outlet port 3. 
Operation of the movable member 6 is described with reference to FIGS. 3a, 
3b, and 3c. 
FIG. 3a shows a state is which an electric current is not applied to the 
solenoid 30. In this state, the movable member 6 is at a first valve 
position, so that the front portion 26 is in contact with the flat springs 
15 and the rear portion 28 is not in contact with the flat spring 20. That 
is, the movable member 6 is urged to the right in the drawing by the force 
of the flat springs 15, and thus the first valve element 4 opens the inlet 
port 1. Accordingly, the second outlet port 3 is closed by the second 
valve element 5 through the force of the flat springs 20. Therefore, brake 
oil flows into the inlet port 1 and flows to the first outlet port 2 
through the spaces 38 of the springs 15, the passages 29, and spaces 
between the flat springs 20, and is supplied to the wheel cylinder (not 
shown). As a result, pressure in the wheel cylinder (not shown) is 
increased. 
FIG. 3b shows a state in which a relatively small electric current is 
supplied to the solenoid 30. In this state, the movable member 6 is moved 
by the solenoid 30 to a second valve position which is slightly to the 
left of the first valve position. When the movable member 6 is in this 
second valve position the flat springs 15 are deflected by the portion 26, 
so that the first valve element 4 is in close contact with the opening of 
the inlet port 1, to close the inlet port 1. At this position, the rear 
portion 28 is not in contact with the flat springs 20, so that the second 
valve element 5 is urged by the flat springs 20 to close the second outlet 
port 3. Therefore, both of the ports 1 and 3 are closed and pressure in 
the wheel cylinder (not shown) is kept at a constant value. 
FIG. 3c shows a state in which a relatively large electric current is 
applied to the solenoid 30. The movable member 6 is moved further to the 
left in comparison with the second valve position by the solenoid 30, to a 
third valve position. When the movable member 6 is in position, the flat 
springs 15 are more strongly urged by the portion 26, so that the inlet 
port 1 is closed by the first valve element 4 and the flat springs 20 are 
urged by the rear portion 28 to separate the second valve element 5 from 
and open the second outlet port 3. Thus, the first valve element 4 closes 
the inlet port 1 and the second valve element 5 opens the second outlet 
port 3, so that brake oil in the wheel cylinder (not shown) flows into the 
valve device through the first outlet port 2 and returns to the reservoir 
(not shown) through the second outlet port 3, and as a result, pressure in 
the wheel cylinder (not shown) is reduced. 
As shown in FIG. 3b; a deflection curve of the flat springs 15 when the 
movable member 6 is at the second valve position is essentially different 
from a deflection curve of the flat springs 15 when the movable member 6 
is at the third valve position shown in FIG. 3c. That is, the deflection 
curve in FIG. 3b does not have inflection points while the deflection 
curve in FIG. 3c has such inflection points. In other words, the flat 
springs 15 deflect in a first deflection mode at the second valve 
position, and in a second deflection mode at the third valve position. 
Thus, the spring constant K.sub.3 of the flat springs 15 when the movable 
member 6 is in the third valve position is larger than the spring constant 
K.sub.2 of the flat springs 15 when the movable member 6 is in the second 
valve position. Therefore, to shift the movable member 6 from the second 
valve position to the third valve position, the movable member 6 must be 
urged by a relatively large force. 
FIG. 4 shows a relationship between a displacement and a force applied to 
the movable member 6, namely, a relationship between displacements of the 
flat springs 15 and 20 and the spring forces thereof. In FIG. 4, points 
P.sub.1, P.sub.2, and P.sub.3 show the first, second, and third valve 
positions of the movable member 6, respectively. When the movable member 6 
is located near the second valve position, a force necessary for 
displacement of the movable member 6 is such that the flat springs 15 are 
deflected in the first deflection mode shown in FIG. 3b, and varies along 
the straight line I in proportion to the displacement. Then, if the 
movable member 6 displaces over the point P in FIG. 4, the flat springs 15 
are deflected in the second deflection mode as shown in FIG. 3c, and the 
flat springs 20 are also deflected. In this condition, a force necessary 
for deflecting only the flat springs 15 varies, as shown by the straight 
chained line J. However, since a force necessary for deflecting the flat 
springs 20 varies as shown by the straight chained line K, a force 
necessary for displacing the movable member 6 is obtained by superimposing 
the force applied to the flat springs 15 and the force applied to the flat 
springs 20 so that a variation of the force for the movable member 6 is as 
shown by the solid line L. Therefore, a force F.sub.3 necessary for 
displacing the movable member 6 to the third valve position must be double 
a force F.sub.2 necessary for displacing the movable member 6 to the 
second valve position. In short, past the point P.sub.4 in the FIG. 4, the 
force for displacing the movable member 6 becomes suddenly large, so that 
the movable member 6 is not displaced to the third valve position by a 
force only slightly larger than the force F.sub.2. 
Note that where the flat springs 20 are not provided, the second valve 
element 5 is connected to the movable member 6 through a connecting 
member. 
FIG. 5a, 5b and 5c shown a second embodiment of the present invention. In 
this second embodiment, the valve device is provided with a spool valve. 
A casing 40 is formed with an inlet port 1 and first and second outlet 
ports 2 and 3. A spool valve 42 is slidably housed in a bore 41 formed in 
the casing 40. The spool valve 42 has a passage 43 for allowing brake oil 
to flow from the inlet port 1 to the first outlet port 2 and for brake oil 
to flow from the first outlet port 2 to the second outlet port 3. A 
solenoid 44 is mounted between the casing 40 and a core 45 fitted in the 
casing 40, and fixed by a non-magnetic annular seal 46 fitted on an end 
portion of the core 45. A flat spring 47 is inserted between an end 
portion of the core 45 and an end portion of the spool valve 42, the outer 
periphery of the flat spring 47 being fixed to an inner wall of the casing 
40. A coil spring 48 is provided around a projection 49 formed on the end 
face of the core 45 to press against the flat spring 47 so that the flat 
spring 47 is always in contact with the spool valve 42. 
The position of the spool valve 42 is varied according to the amount of 
electric current applied to the solenoid 44. FIG. 5a shows a state in 
which an electric current is not applied to the solenoid 44. In this 
state, the spool valve 42 is located at the left in the drawing, namely, a 
first valve position, by the flat spring 47 and the coil spring 48, so 
that the inlet port 1 communicates with the first outlet port 2. As a 
result, brake oil discharged from a master cylinder (not shown) is 
supplied to a wheel cylinder (not shown) through the inlet port 1, the 
spool valve 42, and the first outlet port 2, and thus pressure in the 
wheel cylinder (not shown) is increased. 
FIG. 5b shows a state in which a relatively small electric current is 
applied to the solenoid 44. In this state, the spool valve 42 is moved to 
the second valve position by the solenoid 44. That is, the spool valve 42 
presses against the coil spring 48 and the flat spring 47 to flatten the 
flat spring 47 and bring it into contact with the projection 49, so that 
the inlet port 1 and the second outlet port 3 are closed and thus the 
passages among the ports 1, 2, and 3 are shut. As a result, the wheel 
cylinder (not shown) is closed-off from the master cylinder (not shown) 
and a reservoir (not shown), and thus pressure in the wheel cylinder (not 
shown) is kept at a constant value. 
FIG. 5c shows a state in which a relatively large electric current is 
applied to the solenoid 44. In this state, the spool valve 44 is strongly 
moved by the solenoid 44 to the third valve position. That is, the spool 
valve 42 is located at the right in the drawing and the flat spring 47 
deflected into a wave shape so that a circular portion around the center 
of the flat spring 47 is deflected away from, i.e., convexly, the core 45 
and the portions either side of center portion of the flat spring 47 are 
deflected away from, i.e., convexly, the spool valve 42. Thus, the spool 
valve 42 connects the first outlet port 2 to the second outlet port 3. As 
a result, brake oil in the wheel cylinder (not shown) is returned to the 
reservoir (not shown) and thus pressure in the wheel cylinder (not shown) 
is reduced. 
In this second embodiment, although the spool valve 42 comprises an 
armature which is moved by electromagnetic force generated by the solenoid 
44, an armature may be provided independent of the spool valve 42. Also, 
it is not necessary for the casing 40 to form a part of an electromagnetic 
circuit with the spool valve 42 and the core 45. Further, in the second 
embodiment, substantially the same function can be shown by a construction 
without the coil spring 48. 
Note, although each of the above embodiments is constructed in such a 
manner that the movable member 6 and the spool valve 42 can take the 
first, second, and third valve positions, in another embodiment the 
construction may be such that the movable member 6 and the spool valve 42 
take any two valve positions among the above three valve positions, and 
the flat springs 15 and 47 deflect in the second deflection mode in one of 
the two valve positions. 
Further, the means for displacing the valves need not be operated by an 
electromagnetic force from the solenoid, but can be operated by a 
hydraulic force such as oil pressure. 
Although embodiments of the present invention have been described with 
reference to the attached drawings, many modifications and changes may be 
made by those skilled in this art without departing from the scope of the 
invention.