Abstract:
A two-stage electro-magnetic valve maintains a pressing force applied onto a switch valve body from a press member after a lifting of an open-close valve body from a valve seat by an introduction of a pressure of a valve chamber. In such manner, the switch valve body need not be put in a pressure receiving state when the switch valve body is completely closed. In other words, it is not necessary for a pressure receiving diameter of the switch valve body to be smaller than a pressure receiving diameter of the open-close valve body. Such configuration increases design freedom of the pressure receiving diameter for the open-close valve body because it separates the diameter of the valve body from a diameter restriction of the switching valve body, which allows both valve bodies to have the same diameter, which maximizes the effect of a pressure cancel mechanism.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is based on and claims the benefit of priority of Japanese Patent Application No. 2014-25519, filed on Feb. 13, 2014, the disclosure of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present disclosure generally relates to an electro-magnetic valve. 
       BACKGROUND INFORMATION 
       [0003]    An electro-magnetic valve may be used as a tank sealing valve in an evaporated fuel processing apparatus. As shown in  FIG. 12  of a patent document 1 (i.e., Japanese Patent Laid-Open No. 2013-113401), such an electro-magnetic valve  100 A includes a valve chamber  103  to which a first passage  101  that is connected to a canister and a second passage  102  that is connected to a fuel tank are respectively connected. The electro-magnetic valve  100 A also includes a valve body  104  housed in the valve chamber  103  which opens and closes the first passage  101 , and an electro-magnetic actuator  105  which drives the valve body  104  toward a valve opening direction. 
         [0004]    The valve body  104  lifts from and seats on an annular valve seat  106  formed on an edge of an opening of the first passage  101 , for communication and dis-communication between the first passage  101  and the second passage  102  via the valve chamber  103 , that is, for opening and closing communications therebetween. 
         [0005]    The electro-magnetic valve  100 A of the patent document 1 has a pressure cancel mechanism. When a high pressure is applied on an opposite side, that is, an away-from-seat side, of the valve body  104  relative to the valve seat during a valve close time, a drive power for driving the valve body  104  must also be driven at a high power, which may deteriorate responsiveness of the driving operation of the valve body  104 . 
         [0006]    Thus, a pressure cancel mechanism for canceling differential pressure before and behind the valve body  104 , that is, a pressure difference between a valve seat side and an away-from-seat side, at the valve close time is provided as a pressure cancel chamber  108  that is formed behind (i.e., on the away-from-seat side of) the valve body  104  into which a pressure of the first passage  101  is introduced. 
         [0007]    For example, in the patent document 1, the pressure cancel chamber  108  is air-tightly defined against the valve chamber  103  by a pressure chamber defining member  109  (e.g., a diaphragm in this example) that is connected to a behind side of the valve body  104 . In such a structure, the valve body  104  receives a pressure receiving load Fb of the pressure cancel chamber  108 , i.e., on the away-from-seat side via the pressure chamber defining member  109 , and the valve body  104  also receives a pressure receiving load F 1  from the first passage  101  on the valve seat side. 
         [0008]    To make the most of the effect of this pressure cancel mechanism, it is desirable to equalize those two pressures, i.e., the pressure receiving load Fb and the pressure receiving load F 1 . That is, it is desirable that a pressure receiving diameter Dv of the valve body  104  is configured to be equal to an effective pressure receiving diameter Dc of the pressure chamber defining member  109 . In such case, the pressure receiving diameter Dv of the valve body  104  is a diameter of a surface that receives pressure from the first passage  101  at the valve close time of the valve body  104 . Further, the effective pressure receiving diameter Dc of the pressure chamber defining member  109  is a diameter computed from an area size (i.e., an effective pressure receiving area size) determined based on “a load (i.e., pressure) put on the pressure chamber defining member  109 .” 
         [0009]    Further referring to the other document, a patent document 2 (i.e., Japanese Patent Laid-Open No. 2005-291241) discloses an electro-magnetic valve  100 B which prevents a steep increase of an opening area size at the time of valve opening as shown in  FIG. 13  (in  FIG. 13 , the same numerals are assigned to the same configuration as the electro-magnetic valve  100 A of  FIG. 12 ). 
         [0010]    In the electro-magnetic valve  100 B, the first valve body  104 A, which lifts from and seats on a first valve seat  106   a  formed on an edge of an opening of the first passage  101 , has a communication hole  111  bored therein for communication between the first passage  101  and the valve chamber  103 , and the second the valve body  104 B provided as another valve body is used to opens and closes the communication hole  111 . The first valve body  104 A is designated as the switch valve body  104 A, because it switches an amount of the flow between the first passage  101  and valve chambers  103 . The second valve body  104 B is designated as the open-close valve body  104 B, because it opens and closes the first passage  101 . 
         [0011]    The open-close valve body  104 B is driven by the electro-magnetic actuator  105 , and the switch valve body  104 A is biased by a spring  112  in a valve lift direction, and is driven by a pressure difference before and behind the switch valve body  104 A. 
         [0012]    That is, when the open-close valve body  104 B lifts from the seat, the first passage  101  and the valve chamber  103  communicate with each other via communication hole  111  of the switch valve body  104 A. In other words, a fluid flows to the first passage  101  from the second passage  102 . The switch valve body  104 A is in a seated state under the pressure of the valve chamber  103  immediately after the lifting of the open-close valve body  104 B. Then, in a short time, as the pressure of the valve chamber  103  (i.e., the pressure of the second passage  102 ) falls, the switch valve body  104  lifts from the seat according to the biasing force of the spring  112 . 
         [0013]    Then, the pressure cancel mechanism is also provided in the electro-magnetic valve  100 B. In this electro-magnetic valve  100 B, a bellows is used instead of the diaphragm as the pressure chamber defining member  109 . In this case, too, to make the most of the effect of the pressure cancel mechanism, it is desirable that the pressure receiving diameter Dv 2  of the open-close valve body  104 B is equated to the effective pressure receiving diameter Dc of the pressure chamber defining member  109 , just like the above-mentioned example. 
         [0014]    In such case, for the two-stage type electro-magnetic valve  100 B having the two valve bodies, a mechanism for keeping a valve seated state is required with which the switch valve body  104 A is kept seated immediately after the lifting of the open-close valve body  104 B. 
         [0015]    Such a mechanism of the electro-magnetic valve  100 B is provided as a structure in which (i) the pressure receiving diameter Dv 1  of the switch valve body  104 A is longer than the pressure receiving diameter Dv 2  of the open-close valve body  104 B, and (ii) the pressure receiving load by the differential pressure between the valve chamber  103  and the first passage  101  starts to act on the switch valve body  104 A while the open-close valve body  104 B is still in the seated state. According to such mechanism, the switch valve body  104 A is kept in the seated state according to the pressure receiving load. 
         [0016]    In other words, the electro-magnetic valve  100 B has a restriction that the pressure receiving diameter Dv 2  of the open-close valve body  104 B must be smaller than the pressure receiving diameter Dv 1  of the switch valve body  104 A. 
         [0017]    When, on the other hand, the pressure receiving diameter of Dv 1  of the switch valve body  104 A is increased too much, a negative pressure in a fuel tank inducing a negative pressure in an inside of the valve chamber  103  causes the lifting of the switch valve body  104 A from the seat even when the open-close valve body  104 B is not in a driven state, which is a deficiency of the electro-magnetic valve to be serving as a tank sealing valve. That means, there is another restriction that the pressure receiving diameter Dv 1  cannot be increased too much. 
         [0018]    Therefore, in the conventional electro-magnetic valve  100 B, there are a couple of restrictions in terms of the diameter Dv 1  and the diameter Dv 2 , since the pressure receiving diameter of Dv 2  of the open-close valve body  104 B is determined, not freely, but by the relationship with the pressure receiving diameter of Dv 1  of the switch valve body  104 A. In other words, the effective pressure receiving diameter Dc has to be set in the middle of the pressure receiving diameter Dv 2  and the pressure receiving diameter of Dv 1 . 
         [0019]    In other words, in the conventional electro-magnetic valve  100 B, the pressure receiving diameter of Dv 2  of the open-close valve body  104 B cannot be equated to the effective pressure receiving diameter Dc of the pressure chamber defining member  109 , thereby making it impossible to maximize the effect of the pressure cancel mechanism. 
       SUMMARY 
       [0020]    It is an object of the present disclosure to maximize an effect of a pressure cancel mechanism of a two-stage electro-magnetic valve. 
         [0021]    The electro-magnetic valve of the present disclosure is provided with a valve chamber, a first valve seat, a switch valve body, a first spring, a second valve seat, an open-close valve body, a return spring, an electro-magnetic actuator, and a pressure chamber defining member. The valve chamber is a space that has a first passage opening open to a first passage and a second passage opening open to a second passage. The first valve seat is annularly formed on an outside of the first passage opening in the valve chamber. The switch valve body is housed in the valve chamber, and has a communication hole that has a smaller diameter than the first passage opening, and switches a flow amount of a flow between the first passage and the valve chamber by lifting from and seating on the first valve seat. The first spring biases the switch valve body to lift away from the first valve seat. The second valve seat is annularly formed on an outside of an opening of the communication hole. 
         [0022]    The open-close valve body is another valve body that is positioned on an lift-off side (i.e., an away-from-seat side) of the switch valve body relative to the first valve seat, and open and closes the first passage to and from the valve chamber for communication and dis-communication between the first passage and the second passage by lifting from and seating on the second valve seat while the switch valve body is seating on the first valve seat. 
         [0023]    The return spring biases the open-close valve body toward the second valve seat. The electro-magnetic actuator, which is positioned on an lift-off side of the open-close valve body relative to the second valve seat, lifts the open-close valve body from the second valve seat against a biasing force of the return spring. 
         [0024]    The pressure chamber defining member defines a pressure cancel chamber that reduces a pressure difference between both sides, i.e., an upstream and a downstream, of the open-close valve body by applying the same pressure as a pressure in the first passage on the lift-off side of the open-close valve body, the lift-off side away from the second valve seat. 
         [0025]    The present the electro-magnetic valve is a so-designated the electro-magnetic valve of two-stage type, and, when the open-close valve body and the switch valve body operate one by one, an all-close state, an open-in-part state, and an all open state are realized. 
         [0026]    When the switch valve body is seated on the first valve seat and the open-close valve body is seated on the second valve seat, communication between the first passage and the second passage is closed/intercepted, which is an all-close state. 
         [0027]    When the open-close valve body is lifted from the second valve seat by the drive of the electro-magnetic actuator and the switch valve body is seated on the first valve seat by receiving a pressure of the valve chamber, communication between the first passage and the second passage via the communication hole and the valve chamber is partially opened, which is an open-in-part state. 
         [0028]    And, when, due to a pressure reduction of the valve chamber after the lifting of the open-close valve body, the switch valve body lifts from the first valve seat, communication between the first passage and the second passage is opened via the opening and the valve chamber, which is an all-open state. 
         [0029]    Further, the electro-magnetic valve of the present disclosure has, at a position in an inside of an abutting part that has an annular shape for seating on the second valve seat, a press member that presses the switch valve body toward the first valve seat with a biasing force greater than a force from the first spring during a period (a) between the all-close state and (b) a timing immediately after the lifting of the open-close valve body from the second valve seat. 
         [0030]    In other words, in the present disclosure, the press member is a structure that keeps the switch valve body in a seated state up until an immediately-after timing of the lifting of the open-close valve body, which forcefully presses the switch valve body against the valve seat up to such timing. In such case, since the pressure of the valve chamber is immediately applied to the switch valve body when the open-close valve body is lifted, the switch valve body is keep in a seated state by receiving such pressure applied thereon. 
         [0031]    Therefore, according to the present disclosure, unlike the conventional technique, the switch valve body needs not to receive the pressure while the open-close valve body is seated, which makes it unnecessary to shrink a pressure receiving diameter of the open-close valve body to be smaller than a pressure receiving diameter of the switch valve body. In other words, the pressure receiving diameter of the open-close valve body is freely designed from a restriction of the pressure receiving diameter of the switch valve body, which increases its design flexibility. Therefore, for making the most of an effect of a pressure cancel mechanism, it becomes possible to have the diameter of the open-close valve body configured to be equal to the effective pressure receiving diameter of the pressure chamber defining member. In other words, the pressure cancel mechanism is utilized to the full in a maximized manner. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    Objects, features, and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings, in which: 
           [0033]      FIG. 1  is a sectional view of an electro-magnetic valve in a first embodiment of the present disclosure; 
           [0034]      FIG. 2  is a sectional view of an important part of the electro-magnetic valve in an all-close state in the first embodiment; 
           [0035]      FIG. 3  is a partial view of  FIG. 2  in a larger scale in the first embodiment; 
           [0036]      FIG. 4  is a sectional view of the electro-magnetic valve immediately after a lifting of an open-close valve in the first embodiment; 
           [0037]      FIG. 5  is a partial view of  FIG. 4  in a larger scale in the first embodiment; 
           [0038]      FIG. 6  is a sectional view of an important part of the electro-magnetic valve in an open-in-part state in the first embodiment; 
           [0039]      FIG. 7  is a partial view of  FIG. 6  in a larger scale in the first embodiment; 
           [0040]      FIG. 8  is a sectional view of an important part of the electro-magnetic valve in the open-in-part state in the first embodiment; 
           [0041]      FIG. 9  is a partial view of  FIG. 8  in a larger scale in the first embodiment; 
           [0042]      FIG. 10  is a sectional view of an important part of the electro-magnetic valve in a second embodiment; 
           [0043]      FIG. 11  is a sectional view of an important part of the electro-magnetic valve in a third embodiment; 
           [0044]      FIG. 12  is a sectional view of an important part of the electro-magnetic valve in a conventional example; and 
           [0045]      FIG. 13  is a sectional view of an important part of the electro-magnetic valve in the conventional example. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]    The following embodiments describe details about the embodiments of the present disclosure. 
       First Embodiment 
       [0047]    The first embodiment is described with reference to  FIGS. 1-9 . 
         [0048]    The electro-magnetic valve of this example is a tank sealing valve  1  of an evaporated fuel transpiration prevention apparatus, for example. 
         [0049]    The evaporated fuel transpiration prevention apparatus prevents a transpiration of the evaporated fuel to the atmosphere by re-directing a fluid, i.e., the evaporated fuel in the fuel tank, to an intake pipe of an internal-combustion engine via a canister. 
         [0050]    The tank sealing valve  1 , which is connected in the middle of piping between a fuel tank and a canister, opens and closes the communication between the fuel tank and the canister. 
         [0051]    The tank sealing valve  1  is a normally-closed type, and opens a passage between the fuel tank and the canister according to a valve open command from an ECU. For example, at a fuel refill time, according to the valve open command from the ECU or the like, the tank sealing valve  1  opens a passage between the fuel tank and the canister, lowering the pressure of the fuel tank for preventing the release of the evaporated fuel to the open air. 
         [0052]    The tank sealing valve  1  is provided with a housing  3  which forms a valve chamber  2 , a first valve seat  4 , a switch valve body  5 , a first spring  6 , a second valve seat  7 , an open-close valve body  8 , a return spring  9 , an electro-magnetic actuator  10 , and a pressure chamber defining member  11 . 
         [0053]    The housing  3  includes (i) a flow passage formation part  3   a  which provides a first passage  15  connected to the canister, a second passage  16  connected to the fuel tank, and the valve chamber  2  that has an opening  15   a  of the first passage  15  and an opening  16   a  of the second passage  16 , and (ii) a drive chamber formation part  3   b  which houses the electro-magnetic actuator  10 . 
         [0054]    The second passage  16  always communicates with the valve chamber  2 , and the pressure of the valve chamber  2  is equalized with the pressure of the second passage  16  (i.e., the fuel tank). Since the pressure on the fuel tank side is usually high and the fluid flows from the fuel tank to the canister, the second passage  16  is an upstream side in such flow and the first passage  15  is a downstream side therein. 
         [0055]    In the valve chamber  2 , the first valve seat  4  is annularly formed on the outside of the opening  15   a  of the first passage  15 . 
         [0056]    The flow passage formation part  3   a  has a cylindrical piping  20  which serves as the first passage  15 , and, on one axial end of this piping  20 , a first annular plane  20   a  and a second annular plane  20   b  are provided, the first annular plane  20   a  extending from an inner periphery of an opening toward an outer circumference and the second annular plane  20   b  disposed on an outside of the plane  20   a  with a step interposed therebetween in a connecting manner to shift the position of the plane  20   b  toward a farther axial end. This first plane  20   a  serves as the first valve seat  4 . 
         [0057]    The switch valve body  5  is a valve body housed in the valve chamber  2 , which is seatable on and liftable from the first valve seat  4 . In the present embodiment, the switch valve body  5  has a disk shape. 
         [0058]    At a center of the disk of the switch valve body  5 , a communication hole  21  penetrating in a board-thickness direction is provided. The communication hole  21  has an opening that has a smaller diameter than the opening  15   a , and makes the first passage  15  and the valve chamber  2  freely communicable. 
         [0059]    Therefore, in a seated state of the switch valve body  5  seated on the first valve seat  4 , the first passage  15  and the valve chamber  2  are communicable via the communication hole  21  having a smaller diameter than the opening  15   a , and, in a lifted state of the switch valve body  5  lifted from the first valve seat  4 , the first passage  15  and the valve chamber  2  are flowably-connected via the opening  15   a . In other words, the passage area size between the first passage  15  and the valve chamber  2  is switched by the lifting and the seating of the switch valve body  5 . 
         [0060]    The first spring  6  biases the switch valve body  5  towards a lift direction which lifts the valve body  5  from the first valve seat  4 . 
         [0061]    In the present embodiment, a supporter part  20   c  is formed on an inside of the piping  20  at a position on the other axial end side of the first plane  20   a , and the first spring  6  is positioned between the switch valve body  5  and the supporter part  20   c.    
         [0062]    The second valve seat  7  is annularly formed on the outside of the opening of the communication hole  21 . In other words, the second valve seat  7  is formed on a housing  3  that provides the first valve seat  4 , and the second valve seat  7  is positioned on an outside of the first valve seat  4 . 
         [0063]    In the present embodiment, the second plane  20   b  serves as the second valve seat  7 . 
         [0064]    The open-close valve body  8  is another valve body positioned on a lift-off side of the switch valve body  5 , which is a side away from the first valve seat  4 . 
         [0065]    The open-close valve body  8  opens and closes the first passage  15  to the valve chamber  2  by the lifting from and the seating on the second valve seat  7  when the switch valve body  5  is seated, for opening and closing the communication between the first passage  15  and the second passage  16 . 
         [0066]    The open-close valve body  8  has a closed-end cylindrical shape which opens to the second valve seat side, and has an abutting part  25  which lifts from and seats on the second valve seat  7  on its open end. The abutting part  25  is formed in an annular shape with a sealer that is made of the rubber material. 
         [0067]    The open-close valve body  8  has, on a bottom of the cylinder, a hole, and a cylindrical shaft  27  is inserted into such hole so that the shaft  27  protrudes from a lift-off side of the bottom which is away from the second valve seat  7 . 
         [0068]    The return spring  9  biases the open-close valve body  8  in a seating direction seating the valve on the second valve seat  7 . 
         [0069]    The electro-magnetic actuator  10  is positioned on a lift-off side (i.e., away from the second valve seat  7 ) of the open-close valve body  8 , and drives the open-close valve body  8  to the lifting side (i.e., the lift-off side away from the second valve seat  7 ) in a resisting manner resisting to the biasing force of the return spring  9 . 
         [0070]    The electro-magnetic actuator  10  has a coil  30  which generates magnetism by receiving a power supply, a moving body  31  which moves in one body with the open-close valve body  8 , and a stator  32  which houses the moving body  31  in a slidable manner as well as attracting the moving body  31  with the magnetism generated by the coil  30 . 
         [0071]    The moving body  31  has a tube shape, and a part of the shaft  27  protruding from the open-close valve body  8  is fixed onto an inside of the tube (of the moving body  31 ). Thereby, the moving body  31  is fixed to the open-close valve body  8  via the shaft  27 . Further, an in-cylinder part of the open-close valve body  8  and an inside of the moving body  31  are connected via an inside of a cylinder of the shaft  27 , which allows communication of a fluid passing therethrough. 
         [0072]    The pressure chamber defining member  11  is a member for forming a pressure cancel chamber  35  that is air-tightly separated from the valve chamber  2  on an lift-off side of the open-close valve body  8  (i.e., the lift-off side away from the second valve seat  7 ) when the open-close valve body  8  is seated. 
         [0073]    The pressure cancel chamber  35  puts the same load that is equal to the pressure of the first passage  15  on lift-off side of the open-close valve body  8  when the open-close valve body  8  is seated. Thereby, the differential pressure between the upstream and the downstream of the open-close valve body  8  (i.e., pressure difference between the second valve seat side and the lift-off side away from the second valve seat) is reduced. 
         [0074]    In the present embodiment, the pressure chamber defining member  11  is a diaphragm, and has a thin film ring shape with the rubber material, and has, on its inner periphery end, an inner circumference fixed part  11   a  fixed to the open-close valve body  8 , and has, on its peripheral edge, an outer circumference fixed part  11   b  fixed to the housing  3 . 
         [0075]    The inner circumference fixed part  11   a  is fixed to a back end of the open-close valve body  8 . The outer circumference fixed part  11   b  is pinched between the flow passage formation part  3   a  and the drive chamber formation part  3   b , which are provided respectively as two separate parts of the housing  3 . 
         [0076]    Thereby, the lift-off side of the pressure chamber defining member  11  (i.e., the diaphragm) away from the second valve seat  7  serves as the pressure cancel chamber  35  separated from the valve chamber  2 . In other words, the space in which the electro-magnetic actuator  10  is housed also serves as the pressure cancel chamber  35 . 
         [0077]    Further, the pressure of the first passage  15  is introduced into the pressure cancel chamber  35  via the inside of the open-close valve body  8 , the inside of the shaft  27 , the inside of the moving body  31 , the inside of the moving body  31 , and a sliding gap between the moving body  31  and stator  32  when the open-close valve body  8  is seated. 
       Feature of the Present Embodiment 
       [0078]    The tank sealing valve  1  has, at a position in an inside of an abutting part  25  that has an annular shape for seating on the second valve seat  7 , a press member  40  that presses the switch valve body  5  toward the first valve seat  4  with a (biasing) force greater than a force from the first spring  6  during a period (a) between an all-close state and (b) a timing immediately after the lifting of the open-close valve body  8  from the second valve seat  7 . 
         [0079]    Here, the all-close state is a state in which the switch valve body  5  is seated on the first valve seat  4  and the open-close valve body  8  is seated on the second valve seat  7 . In other words, it is a state in which the electro-magnetic actuator  10  is not receiving a power supply, and the passage between the first passage  15  and the second passage  16  is closed. 
         [0080]    The press member  40  applies a force for pressing the switch valve body  5  from the all-close state up until a timing that is immediately after the lifting of the open-close valve body  8  so that the seated state of the switch valve body  5  is kept unchanged, and releases the force thereafter. 
         [0081]    One exemplary configuration of the press member  40  adopted in the present embodiment is described below. 
         [0082]    In the following description, the driving direction of the open-close valve body  8  is designated as an axial direction, with the second valve seat side designated as a forward side and the opposite side designated as a backward side. In other words, a right-hand side in the drawing is a forward side, and a left-hand side in the drawing is a backward side. 
         [0083]    The press member  40  is provided with a column piece  41 , a stopper  42 , and a second spring  43  which are respectively described in the following. 
         [0084]    The column piece  41  is disposed to be movable in an axial direction relative to the open-close valve body  8  in an inside of the abutting part  25 . 
         [0085]    For example, the column piece  41  has a column shape and is loosely inserted in an inside of the cylinder of the open-close valve body  8 . Further, a forward face of the column piece  41  abuts on and separates from the switch valve body  5 , and a backward end of the column piece  41  has a flange  41   a  formed thereon. 
         [0086]    The stopper  42  regulates the movement of the column piece  41  toward the forward side of the axial direction while being fixed to the open-close valve body  8 . 
         [0087]    For example, the stopper  42  is fixed as an inner brim that protrudes from an inner circumference surface of the cylinder of the open-close valve body  8 , and regulates the movement of the column piece  41  toward the forward side of the axial direction by engagingly stopping the flange  41   a.    
         [0088]    The second spring  43  is positioned on the backward side of the column piece  41 , and biases the column piece  41  toward the stopper  42 . Namely, the column piece  41  is biased to the forward side in the axial direction, i.e., in the direction which presses the switch valve body  5 . The spring load of the second spring  43  is greater than the first spring  6 . 
         [0089]    The position and the dimension of both of the column piece  41  and the stopper  42  are, in the all-close state in which the column piece  41  abuts on the switch valve body  5 , set to provide a gap space  44  between the stopper  42  and the column piece  41  along the axial direction (refer to  FIG. 3 ). 
         [0090]    In such manner, when the open-close valve body  8  in the all-close state moves toward the backward side and lifts from the seat, the stopper  42  abuts on the flange  41   a  after the move by the open-close valve body  8  by an amount of the gap space  44 , and thereafter lifts and brings/separates the column piece  41  away from the switch valve body  5  toward the backward side in the move with the open-close valve body  8  and the column piece  41 . 
         [0091]    By providing the gap space  44 , the column piece  41  separates from the switch valve body  5  after the lifting of the open-close valve body  8  from the seat, instead of causing the separation of the column piece  41  from the switch valve body  5  at the same time of the lifting of the open-close valve body  8 . This gap space  44  is set to have a small dimension so that the column piece  41  separates from the switch valve body  5  immediately after the lifting of the open-close valve body  8  from the seat. 
         [0092]    The column piece  41  abuts on the switch valve body  5 , allowing a flow of fluid from the communication hole  21  to an inside of the cylinder of the open-close valve body  8 . In other words, the abutment of the column piece  41  (on the open-close valve body  8 ) is not an air-tightly made on an opening edge of the communication hole  21 . 
         [0093]    Further, the column piece  41  may have a tube shape, and may have a configuration in which the inside of the cylinder of the column piece  41  communicates with the inside of the cylinder of the communication hole  21  and the open-close valve body  8 . 
       Operational Effect of the Present Embodiment 
       [0094]    The operational effect of the present embodiment is described with the operation of the tank sealing valve  1 . 
         [0095]    The tank sealing valve  1  is in the all-close state, as shown in  FIGS. 2 and 3  when no power supply is provided thereto. 
         [0096]    At such time, the column piece  41  presses the switch valve body  5  toward the first valve seat  4  and the switch valve body  5  is in the seated state, since the spring load of the second spring  43  is greater than the first spring  6 . Further, when the column piece  41  is in an abutting state onto the switch valve body  5 , the gap space  44  is formed between the stopper  42  and the column piece  41 . 
         [0097]    When the electro-magnetic actuator  10  receives a power supply according to the valve open command from the ECU, the moving body  31  moves toward the backward side, elastically deforming the pressure chamber defining member  11  (i.e., the diaphragm), and the open-close valve body  8  lifts from the second valve seat  7 . 
         [0098]    As shown in  FIGS. 4 and 5 , immediately after the lifting of the valve body  8 ), the column piece  41  is kept in a press state in which it applies a pressure to the switch valve body  5 . 
         [0099]    In addition, the pressure of the valve chamber  2  acts on the switch valve body  5  immediately after the lifting of the open-close valve body  8 . Since the pressure of the valve chamber  2  at a time of having the valve open command is usually a positive pressure, which is higher than the pressure of the first passage  15 , a pressure receiving load according to the differential pressure between the valve chamber  2  and the first passage  15  is applied onto the lift-off side of the switch valve body  5  away from the first valve seat  4 . 
         [0100]    Therefore, the switch valve body  5  is kept in the seated state seating on the first valve seat  4 , by the pressure receiving load and the force from the column piece  41  (at a time) immediately after the lifting of the open-close valve body  8 . 
         [0101]    When the open-close valve body  8  lifts further, i.e., by an amount equal to or exceeding the gap space  44 , the column piece  41  is regulated/constrained by the stopper  42 , thereby lifting the column piece  41  together with the open-close valve body  8  (refer to  FIGS. 6 and 7 ). 
         [0102]    In other words, even though the pressing force from the column piece  41  is released (at such a timing), the pressure receiving load is already put onto the switch valve body  5 . Therefore, when the pressure of the valve chamber  2  is high, the switch valve body  5  does not follow the lifting of the open-close valve body  8 . That is, the switch valve body  5  does not lift from the seat. 
         [0103]    Then, the fluid flows from the second passage  16  into the first passage  15  via the communication hole  21  and the valve chamber  2 , by the lifting of the open-close valve body  8 . 
         [0104]    This state, i.e., when the open-close valve body  8  is lifted and the switch valve body  5  is seated, is designated an open-in-part state (refer to  FIGS. 4 to 7 ). 
         [0105]    Thereby, the pressure of the second passage  16  and the valve chamber  2  falls. In other words, the pressure receiving load of the switch valve body  5  also falls. 
         [0106]    When this pressure receiving load lowers than the biasing force of the first spring  6 , as shown in  FIGS. 8 and 9 , the switch valve body  5  lifts from the first valve seat  4 . In other words, an all-open state in which the fluid flows from the second passage  16  into the first passage  15  via the opening  15   a  and the valve chamber  2  is realized. 
         [0107]    In the present embodiment, the conventional structure in which a pressure receiving diameter of the open-close valve body  8  is different from a pressure receiving diameter of the switch valve body  5  for applying the pressure onto the switch valve body in the all-close state is not required. 
         [0108]    That is, in the conventional structure, for keeping the seated state of the switch valve body  5  immediately after the lifting of the open-close valve body  8 , the pressure is already applied in the all-close state onto the switch valve body by providing a difference between (i) a pressure receiving diameter of the open-close valve body  8  and (ii) a pressure receiving diameter of the switch valve body  5 . 
         [0109]    However, in the present embodiment, the structure for keeping the seated state of the switch valve body  5  immediately after the lifting of the open-close valve body  8  is realized as the one in which the press member  40  presses the switch valve body  5  up until the immediately-after timing of the lifting of the open-close valve body  8 , i.e., by the time when the pressure of the valve chamber  2  is introduced into the switch valve body  5 . 
         [0110]    According to such a structure, it is not necessary for the switch valve body  5  to receive the pressure in the all-close state. In other words, it is not necessary for the pressure receiving diameter of the open-close valve body  8  to be smaller than the pressure receiving diameter of the switch valve body  5 . Therefore, the pressure receiving diameter of the open-close valve body  8  may be designed without regard to the pressure receiving diameter of the switch valve body  5 , which increases a degree of freedom of how those diameters are designed. Therefore, for making the most of the effect of the pressure cancel mechanism, the pressure receiving diameter Dv 2  of the open-close valve body  8  may be equated to the effective pressure receiving diameter Dc of the pressure chamber defining member  11  (i.e., the diaphragm). That is, the effect of the pressure cancel mechanism is maximized. 
       Second Embodiment 
       [0111]    The second embodiment is described with reference to  FIG. 10 , in which the difference from the first embodiment is mainly described. 
         [0112]    In the present embodiment, the same numerals of the first embodiment are assigned to the same parts for the reference to the preceding description and for the brevity thereof. 
         [0113]    In the present embodiment, the second valve seat  7  is formed on the lift-off side of the switch valve body  5 , which is a side away from the first valve seat  4 . 
         [0114]    According to such configuration, the pressure receiving diameter of Dv 1  of the switch valve body  5  is equated to the pressure receiving diameter of Dv 2  of the open-close valve body  8 . 
         [0115]    In addition, a portion  5   a  which seats on the first valve seat  4  of the switch valve body  5  has a lip shape to form an elastic-resin seal member that is made of a rubber material or the like. 
         [0116]    According to such configuration, by absorbing an impact of the seating of the switch valve body  5  and the open-close valve body  8  with the seal member, an impact noise is reduced. 
       Third Embodiment 
       [0117]    The third embodiment is described with reference to  FIG. 11 , in which the difference from the first embodiment is mainly described. 
         [0118]    In the present embodiment, the same numerals of the first embodiment are assigned to the same parts for the reference to the preceding description and for the brevity thereof. 
         [0119]    In the present embodiment, the second valve seat  7  is formed on the lift-off side of the switch valve body  5 , which is a side away from the first valve seat  4 , just like the second embodiment. 
         [0120]    According to such configuration, the pressure receiving diameter of Dv 1  of the switch valve body  5  is equated to the pressure receiving diameter of Dv 2  of the open-close valve body  8 . 
         [0121]    Further, the switch valve body  5  is configured in the following manner. That is, both of the portion  5   a  which seats on the switch valve body  5  and a portion  5   b  that serves as the second valve seat  7  (i.e., a portion on which and from which the abutting part  25  of the open-close valve body  8  abuts and separates) are formed as the elastic-resin seal member that is made of the rubber material or the like. In other words, an annular sealer is fixed onto the both sides of the switch valve body  5 . 
         [0122]    According to such configuration, by absorbing an impact of the seating of the switch valve body  5  and the open-close valve body  8  with the seal member, an impact noise is reduced. 
         [0123]    (Modification) 
         [0124]    In the first to third embodiments, the diaphragm is used as the pressure chamber defining member  11 . However, a bellows may be used instead, as the electro-magnetic valve disclosed in the patent document 2. 
         [0125]    Although the present disclosure has been fully described in connection with preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art, and such changes, modifications, and summarized scheme are to be understood as being within the scope of the present disclosure as defined by appended claims.