Valve and solenoid valve operated by very small force

There are provided a valve which is opened by an improved two-step motion, a valve which operates positively without leakage of fluid even when the difference in pressure between inlet and outlet of the valve is very small, and an improvement of a solenoid valve using those valves. The present invention relates to small-sized opening/closing valve and solenoid valve capable of being operated by very small force and electric power using a dry cell or the like, and is suitable to a solenoid valve for automatic opening/closing control which is used in city gas appliances, etc.

FIELD OF ART 
The present invention relates to a valve and a solenoid valve for opening 
and closing the flow of fluid in a fluid pipe. Particularly, the present 
invention is concerned with small-sized opening/closing valve and solenoid 
valve capable of being operated by very small force and electric power, 
using a dry cell or the like. 
The present invention concerns an improved technique relating to a valve 
constructed so that a partial opening is made between a valve body and a 
valve seat in a closed state of the valve to eliminate a back pressure of 
fluid acting on the valve body and thereafter the valve is fully opened, a 
valve capable of operating positively without the leakage of fluid even 
when the back pressure is very low, and a solenoid valve using those 
valves. The present invention can contribute to the reduction in size of a 
valve driving electromagnet, power saving and the stabilization of 
operation. 
BACKGROUND ART 
Heretofore, as an automatic open/close controlling valve for gas appliances 
such as city gas appliances, there has been used a small-sized solenoid 
valve which is operated using a dry cell or the like. Calculation will now 
be made about the force required for opening and closing a 28 mm dia. in a 
city gas pipe for example used at an end user. For example, in a solenoid 
valve wherein fluid of gas pressure of 500 mm in terms of water column is 
opened and with a 28 mm dia. valve, a back pressure of about 300 g is 
exerted on the back of the valve in a closed state. An electromagnet for 
opening and closing such a valve requires a valve holding spring force of 
250 g, so it has heretofore been necessary to use a large-sized 
electromagnet having an initial pull-up force of 550 g and a stroke of 6 
mm or so. 
Thus, in the prior art, a large-sized electromagnet is required because of 
a great influence of the valve back pressure, so it is impossible to adopt 
a power source of a very small capacity such as a dry cell for example and 
the use of a commercial power source is unavoidable, thus resulting in 
increase of the equipment cost. 
There has been proposed a technique of attaching a small pilot valve for 
pressure equalizing to a valve, opening pilot valve prior to opening of 
the valve to eliminate the difference between upstream pressure and 
downstream pressure, thereby decreasing the force required for valve 
opening and closing to reduce the differential force of the valve. 
According to such technique, there have been known a construction wherein 
a pilot valve is disposed in a by-pass, and a construction wherein a valve 
element itself is formed with a pilot valve to provide a two-stage motion 
structure for a valve stem of a valve body between pilot valve open and 
valve body open. 
Such conventional technique of providing a by-pass and mounting a separate 
pilot valve therein and technique of incorporating a separate pilot valve 
in a valve body are disadvantageous in that both are complicated in 
structure and expensive. 
There also is a problem such that the lower limit value of electric power 
consumed for positively a solenoid valve using such valve varies greatly 
in each operation. For ensuring opening/closing operation even at a 
maximum variation, it is necessary to use a battery of a high voltage for 
example and set the power consumption rather high in each operation, 
counting a considerable safety factor. A further reduction of the power 
consumption has been desired. In an ordinary valve for gas, it is required 
that there be no leakage of fluid when the urging force of a spring for 
pressing a valve body against a valve seat is 80 g and the back pressure 
is 1,000 mm to 20 mmH.sub.2 O. In such a conventional valve as illustrated 
in FIG. 9, however, the back pressure is not always constant. In a 
solenoid valve for opening and closing a valve of D=28 mm, when the back 
pressure is 20 mmH.sub.2 O for example, it is almost the urging force of 
the spring alone that serves as a valve closing force, so there has been a 
likelihood of increased leakage of fluid between a valve seat 2 and a 
valve body 1. In this conventional example, leakage occurs at a back 
pressure below 150 mmH.sub.2 O. The numeral 3 denotes a valve stem and 
numeral 6 denotes a presser member for the valve body 1. 
It is the object of the present invention to solve the above-mentioned 
problems of the prior art and provide an improved valve capable of being 
operated and closed with a very small force or a very small power source 
such as a battery without the need of using such a separate valve as has 
been referred to above, and also provide an improved technique relating to 
a solenoid valve using such improved valve. 
DISCLOSURE OR THE INVENTION 
The present invention adopts the following technical means for overcoming 
the above-mentioned problems. 
(1) Valve 
1 A valve operated by a very small force, comprising a valve seat, a valve 
body mounted on a valve stem and capable of moving into contact with and 
away from the valve seat, thereby assuming an open or closed state to 
control the flow of fluid, and an attraction releasing member for pushing 
up or pulling up a part of the valve body near the valve seat in 
accordance with the movement of the valve stem at the beginning of the 
valve opening motion to partially release the attracted state between the 
valve body and the valve seat. 
2 There may be used a valve body having flexibility in the valve 
opening/closing directions, and the attraction releasing member may be 
constituted by a push-up member for pushing up a part of the valve body 
positioned near the valve seat. 
3 As another embodiment, the valve stem may be mounted to the valve body 
through clearance in a lifting direction of the valve stem, and the 
attraction releasing member be constituted by a pull-up member for pulling 
up a part of the valve body positioned near the valve seat at the time of 
start-up of the valve opening motion of the valve stem. 
4 In this case, the valve may be constituted by a valve member having 
rigidity or flexibility. Also, the valve may be constructed in such a 
manner that the valve stem axis is in an offset position relative to the 
valve body axis. 
5 It is preferable that the valve comprise a valve seat and a valve body 
mounted to a valve stem and capable of moving into contact with and away 
from the valve seat, thereby assuming an open or closed state to control 
the flow of fluid, and that if the inside diameter of the valve seat is D 
mm and the diameter of a pressing portion for pressing the valve body 
directly is d mm, the following relationship be satisfied: 
EQU D.times.20%&gt;D-d&gt;1 mm 
(2) Solenoid Valve 
The present invention is also applied to a solenoid valve comprising a 
yoke; a fixed iron core fixed to the yoke; a movable iron core capable of 
moving into contact with and away from the fixed iron core; an electric 
winding wound round a magnetic path comprising the yoke, fixed iron core 
and movable iron core and which when electrified moves the movable iron 
core; a first spring interposed between the movable iron core and the 
fixed iron core and using the movable iron core away from the fixed iron 
core; a valve stem disposed in a valve stem disposing hole of the movable 
iron core; a valve seat; a valve body mounted to the valve stem and 
capable of moving into contact with and away from the valve seat, thereby 
assuming an open or closed state to control the flow of fluid; and a 
second spring interposed between the valve stem and the movable iron core 
so that the movable iron core is attracted to the fixed iron core against 
the urging force of the first spring while the valve body maintains its 
attracted state to the valve seat by the pressure of fluid in the initial 
electrified stage of the electric winding. The valve construction is as 
follows. 
a The solenoid valve is provided with an attraction releasing member for 
partially releasing the attracted state of the valve body to the valve 
seat by pushing up or pulling up a part of the valve body positioned near 
the valve seat through the motion of the valve stem in the initial stage 
mentioned above, the valve stem being disposed through a clearance with 
respect to a circumferential wall of the aforementioned valve stem 
disposing hole except a circumferential linear contact portion thereof 
with the circumferential wall. 
b Construction may be made so as to satisfy the following relationship 
wherein the inside diameter of the valve seat is D mm and the diameter of 
a pressing portion for pressing the valve body directly is d mm: 
EQU D.times.20%&gt;D-d&gt;1 mm 
c In the connection with the above b, the solenoid valve may be provided 
with an attraction releasing member which partially releases the attracted 
state between the valve body and the valve seat by pushing up or pulling 
up a part of the valve body positioned near the valve seat through the 
motion of the valve stem at the beginning of the valve opening motion. 
d In the above c, construction may be made so that the valve stem is 
disposed through a clearance with respect to the circumferential wall of 
the foregoing valve stem disposing hole except a circumferential linear 
contact portion thereof with the circumferential wall.

BEST FORM FOR PRACTICING THE INVENTION 
The valve and solenoid valve of the present invention will be described in 
detail hereinunder. 
(1) Valve 
First Embodiment 
A first embodiment of the present invention will be described below with 
reference to the explanatory views of FIGS. 1(a) and 1(b). 
The valve of this embodiment comprises a valve seat 2; a valve body 1 
mounted on a valve stem 3 and capable of moving into contact with and away 
from the valve seat 2, thereby assuming an open state or a closed state to 
control the flow of fluid, a valve body 1 having flexibility in the valve 
opening/closing directions; and an attraction releasing member which 
partially releases an attracted state between the valve body 1 and the 
valve seat 2 by pushing up a part of the valve body 1 positioned near the 
valve seat at the beginning of a valve opening motion of the valve stem 3. 
The valve stem 3 is located such that its central axis is positioned 
within the inner diameter of the valve seat 2. When the valve is closed, 
the valve body 1 is pushed against the valve seat 2 so that the valve seat 
2 is pushed with an equal force over the entire rim portion of the valve 
seat 2. In this embodiment, as the attraction releasing member, the valve 
stem 3 is provided with a push-up member 4 having a convex portion 5 for 
pushing up a part of the valve body 1 positioned near the valve seat 2 
upon abutment with the valve body. In this embodiment, moreover, a 
metallic piece 7 is fixed to the valve stem 3 through a seal 8, and the 
valve body 1 and the push-up member 4 are attached to the metallic piece 
7. Further, a valve body presser member 6 is mounted on the valve body 1. 
In the explanatory view of FIG. 1(a), the valve seat 2 and the valve body 1 
are in a closed state. The valve body 1 is mounted to the valve stem 3, 
and as shown in FIG. 1(b), it has flexibility in operating directions of 
the valve stem 3, that is, in the opening/closing directions of the valve 
body 1. 
FIG. 1(b) is an explanatory view showing the state of various portions just 
after the start of movement of the valve stem 3 in the valve opening 
direction. The pulling-up force of the valve stem 3 is concentrated on the 
convex portion 5 positioned near the valve seat 2 to partially release the 
attracted state between the valve body 1 and the valve seat 2. Upon such 
partial release of the attracted state, fluid flows through this portion 
to equalize the pressure between the upstream side and the downstream side 
of the valve, so that there is no longer any back pressure based on 
pressure difference and then the valve stem 3 can open the valve easily 
with a very small force. According to an experiment, it turned out that 
the foregoing fluid back pressure of about 300 g could be decreased to 
half. 
Second Embodiment 
A second embodiment of the present invention will be described below with 
reference to FIGS. 2(a) and 2(b). FIGS. 3(a) and 3(b) are explanatory 
views of a plate member. 
In the valve of this embodiment, a valve stem 3 is mounted to a flexible 
valve body 1 through a clearance in a lifting direction of the valve stem, 
and it is constructed so as to pull up a part of the valve body 1 
positioned near a valve seat 2 at the beginning of a valve opening motion 
started by pulling up the valve stem. More specifically, a plate member 22 
is mounted to the valve stem 3 and is accommodated in a floating state 
within a cavity of the valve body, and a pull-up member 23, which is a 
projection, is formed in an offset position on the plate member 22. As 
shown in FIG. 3, the plate member 22 is fixed to the lower end of the 
valve stem 3 with a bolt 21 and is provided with the projection 23 formed 
on a part thereof. This projection or the pull-up member 23 pulls up a 
part of an upper flange 24 of the valve body 1 at the beginning of the 
valve opening motion of the valve stem 3. 
In the explanatory view of FIG. 2(a), the valve seat 2 and the valve body 1 
are in a closed state. 
FIG. 2(b) is an explanatory view showing the state just after the start of 
movement of the valve stem 3 in the valve opening direction. The 
pulling-up force of the valve stem 3 is concentrated on the projection 
(pull-up member) 23 to open a part of the seal between the valve body 1 
and the valve seat 2, so that the foregoing back pressure of about 300 g 
acting on the valve can be decreased to half. The projection 23 may be 
provided on the valve body 1 side, not the plate member 22 side. 
Third Embodiment 
A third embodiment will now be described with reference to FIG. 4 in which 
the axis of a valve stem 3 is eccentric with respect to the axis of a 
valve body 1. The valve body 1 is put on a valve seat 2, and the eccentric 
valve stem 3 is engaged with the valve body 1 through a clearance in a 
lifting direction of the valve stem. Although the central line of the 
valve stem 3 is displaced with respect to the central point of the valve 
seat 2, the central line of the valve stem 3 is placed within the inner 
diameter of the valve seat 2. A flat plate-like presser plate 32 is 
mounted to the lower end of the valve stem 3, and a push-up member 33 is 
formed on the upper surface of the presser plate 32. When the valve stem 3 
is pulled up, the pull-up member 33 comes into abutment with a part of the 
upper flange 34 of the valve body and pulls up the valve body in the 
eccentric position. 
First, the valve body is tilted and pulled up with a very small force to 
equalize the fluid pressure between the upper and lower surfaces of the 
valve body, then the whole of the valve body is pulled up. Thus, the 
opening of the valve can be attained with a very weak force. 
Although in the above second and third embodiments a flexible valve body 
was used as the valve body 1, a rigid valve body may be used. By pulling 
up the rigid valve body 1 in the eccentric portion, the valve body can be 
tilted with a very weak force and so it is possible to greatly reduce the 
valve opening force. In the case of the flexible valve body 1, the valve 
body 1 is made flexible to the extent that it is slightly deformed when 
pulled up partially and the seal between the valve body and the valve seat 
is opened partially. For example, if the valve body is formed using a hard 
rubber, there can be attained the above flexibility easily. The shape of 
the valve body is designed so that the lower surface of the valve body 
serves as a close contact surface with the valve seat and the valve body 
is connected to the valve stem through a clearance in the lifting 
direction of the valve stem. The flexible body may be formed by integral 
molding. In this case, the valve body is deformed at a time of assembly of 
the valve stem and the plate member is pushed into the cavity of the valve 
body. Also, a plurality of members may be assembled into an integral body 
by bonding or using a physical mounting means or the like. 
Fourth Embodiment 
A valve according to this embodiment will now be described with reference 
to FIG. 5. 
FIGS., 5(a) and (b) illustrate the valve in its opened state and its closed 
state, respectively. In this embodiment, a ring 40 having a diameter of d 
mm, which is an example of the pressing portion referred to herein, is 
inserted between the valve body 1 and the presser member 6 in the 
conventional valve illustrated in FIG. 9. The valve of this embodiment is 
constructed so as to satisfy the following relationship wherein the inside 
diameter of the valve seat 2 is D mm: 
EQU D.times.20%&gt;D-d&gt;1 mm 
In this construction, when the valve stem 3 is pressed by a spring, the 
valve body 1 deflects downwards at the contact portion thereof with the 
valve seat 2, thus permitting a satisfactory sealing effect to be 
exhibited with a small urging force. If the D-d value is too large, the 
deflection will become large, and if it is too small, there will be no 
deflection. Under both conditions, a leakage of fluid may easily occur. It 
is desirable that the D-d value be within the above range. 
In this embodiment, the leakage of fluid did not occur even at a back 
pressure of 20 mmH.sub.2 O under the conditions of D=28 mm, D-d=1 to 5 mm 
and ring thickness=0.2 mm. As the valve body 1 there was used a rubber 
having a hardness of 50.degree. to 80.degree.. 
Although the ring 40 is used as an example of the pressing portion in this 
embodiment, this constitutes no limitation. For example, the ring 40 and 
the presser member 6 may be formed integrally. 
(2) Solenoid Valve 
Solenoid valves according to embodiments of the present invention will be 
described below. 
FIG. 6 is a vertical sectional view of a solenoid valve embodying the 
present invention. This solenoid valve, indicated at 10, includes a yoke 
13, a fixed iron core 11 fixed to the yoke 13, and a movable iron core 12 
capable of moving into contact with and away from the fixed iron core 11. 
The movable iron core 12 is urged downwards in FIG. 5 by means of a first 
spring 16. Further, a permanent magnet 18 is disposed near the fixed iron 
core 11, and an electric winding 17 is disposed in a magnetic path 
constituted by the yoke 13, fixed iron core 11 and movable iron core 12. 
When the electric winding 17 is electrified, the movable iron core 12 is 
attracted to the fixed iron core 11, coupled with the effect of a magnetic 
flux of the permanent magnet 18, and moves upward in FIG. 6. A valve stem 
3 is disposed within a valve stem disposing hole 20 of the movable iron 
core 12. The shape and the state of arrangement of the valve stem 3 will 
be described later. To a lower portion of the valve stem 3 projecting from 
the valve stem disposing hole 20 is mounted the valve of the present 
invention shown in FIG. 1. 
When the electric winding 17 is not electrified and the movable iron core 
12 occupies its lower position in FIG. 5 under the biasing force of the 
first spring 16, the valve body 1 is attracted to the valve seat 2, 
whereby the fluid flow path is held in a valve closed state, while when 
the electric winding 17 is electrified, the movable iron core 12 is 
attracted to the fixed iron core 11, the valve body 11 moves away from the 
valve seat 2, and the fluid flow path assumes a valve-open state. 
This embodiment resides in an improvement of a solenoid valve using any of 
the valves illustrated in FIGS. 1, 2, 4, 5 and operated by a very small 
force, and a characteristic feature thereof resides in a mounting 
structure for the movable iron core and the valve stem. The construction 
of this embodiment will be described below in detail with reference to 
FIGS. 6 and 7. FIG. 7 is a vertical sectional view showing on a larger 
scale the valve stem and the vicinity thereof illustrated in FIG. 6. to 
clearly indicate a state in which the valve stem 3 is contacted in linear 
form with the valve stem disposing hole 20. 
The valve stem 3 is disposed within the valve stem disposing hole 20 except 
a part of its lower portion. In the circumferential direction (transverse 
direction in FIG. 7) of the valve stem 3 there is formed a gap between the 
valve stem and an inner wall 12a of the movable iron core 12 which defines 
the valve stem disposing hole 20, provided the valve stem 3 is formed with 
a linear contact portion 3a for restricting the position of the valve stem 
in the hole 20. The linear contact portion 3a is in linear contact with 
the inner wall 12a of the movable iron core 12 in the circumferential 
direction thereof. 
In this embodiment, the metallic piece 7 is in contact with the lower 
portion of the movable iron core 12 through inclined surfaces to cause the 
central axis of the valve stem 3 to coincide with the central axis of the 
valve stem disposing hole 20 together with said contact part 3a when the 
valve is closed, resulting in a friction between the valve stem 3 and the 
inner wall of the valve stem disposing hole 20 which is restricted to a 
minimum friction. In such construction of this embodiment, at the time of 
a valve opening operation which will be described later, only the linear 
contact portion 3a of the valve stem 3 slides with respect to the movable 
iron core 12 and hence the frictional resistance between the valve stem 
and the movable iron core is kept to a minimum, whereby the reduction of 
power consumption can be attained and variations in power consumption can 
be suppressed. 
The operation of this embodiment will now be described. In the valve closed 
state (before the supply of electric power to the electric winding 17) as 
shown in FIGS. 1(a) and 6, upon start of electrifying of the winding 17, 
the movable iron plate 12 is slightly attracted to the fixed iron core 11 
against the urging force of the first spring 16 which is not so strong 
yet, whereby the valve stem 3 is slightly lifted upward through a second 
spring 15. This state is as illustrated in FIG. 1(b). The pulling-up force 
of the valve stem 3 is concentrated on the convex portion 5 positioned 
closed to the valve seat 2, whereby the attracted stat between the valve 
body 1 and the valve seat 2 is partially released. Consequently, as has 
been explained in connection with FIG. 1, fluid flows through this portion 
and the fluid back pressure acting on the valve is reduced, so that the 
movable iron core 12 and the valve stem 3 are attracted to the fixed iron 
core 11 against the biasing force of the first spring 16 and the valve 
assumes an open state. Thus, by performing the valve opening operation in 
a two-step portion, there can be constituted a solenoid valve capable of 
performing a valve opening/closing operation using a very small electric 
power. 
Further, since the valve stem 3 slides only at its linear contact portion 
3a with respect to the inner wall 12a of the movable iron core 12, the 
electric power consumed for the valve opening/closing operation is further 
decreased and at the same time it is possible to suppress variations in 
such power consumption. According to an experiment conducted by the 
present inventors, in the case of a valve stem not specially taking into 
the account the decrease of the sliding resistance with respect to the 
movable iron core 12, under the conditions of a gas fluid pressure 1,000 
mmH.sub.2 O and a coil resistance 5 .OMEGA. of the electric winding 17, a 
minimum voltage to be applied to the winding 17 necessary for performing 
the valve opening operation is 2.0 V to 2.4 V and it varies in this range 
at every valve opening operation, but by minimizing the sliding resistance 
of the valve stem 3 as described above, the valve was operated stably at a 
lower voltage of 1.6 V.+-.0.1 V and with few variations. As a result, by 
incorporating a lithium battery for example in the solenoid valve 10, it 
is made possible to operate the valve several ten thousand times in terms 
of the number of opening/closing motions and about ten years in terms of 
the operation period. 
Referring now to FIG. 8, there is illustrated an embodiment different from 
that shown in FIG. 7. As to reference numerals, dashes are affixed to the 
same numerals as in FIG. 7, and explanation will be omitted except 
portions peculiar to this embodiment. 
In this embodiment, the lower portion of movable iron core 12' has a valve 
stem supporting portion 12a' which comes into linear contact with a valve 
stem 3' along the circumference of the valve stem 
The upper portion of the valve stem ' is formed in a conical shape, and a 
vertex 3b' of the cone is in abutment with a conical concave 12b' formed 
in the movable iron core 12'. The position of the valve stem 3' in the 
valve stem disposing hole 20 is determined by the linear contact thereof 
with the valve stem supporting portion 12a' and also by the fitting of the 
vertex 3b' and the concave 12b', whereby the reduction of the sliding 
resistance in the valve opening motion is attained. 
As to the valve stem supporting means used in the present invention, no 
limitation is made to the above two embodiments of solenoid valves. 
Various other constructions may be adopted if only the valve stem slides 
in linear contact with the movable iron core in the circumferential 
direction of the valve stem. 
Although the solenoid valves of the above embodiments employ the valve 
illustrated in FIG. 1, there may be used any of the valves illustrated in 
FIGS. 2, 4 and 5. 
In the case of a solenoid valve using the valve shown in FIG. 5, it may be 
constructed so that the valve is opened in a two-step motion, using the 
push-up member 4 shown in FIG. 1.