Compressed Natural Gas Charging System

1. Field of the Invention

The present invention relates to a compressed natural gas charging system including a gas charging passageway whose one end is capable of being connected to a compressed natural gas supply means capable of supplying a compressed natural gas and whose other end opens into a gas vessel, and a one-way valve incorporated in the gas charging passageway to permit the compressed natural gas to flow from one end of the gas charging passageway toward the other end.

2. Description of the Related Art

Such a system is conventionally known from, for example, Japanese Patent Application Laid-open No. 301359/95 and corresponding U.S. Pat. No. 5,542,738.

In the known system, when the compressed natural gas supply means is connected to the one end of the gas charging passageway to charge the compressed natural gas into the gas vessel, because the flow area is constricted at the one-way valve, an adiabatic expansion of the compressed natural gas is produced across the one-way valve, whereby the temperature of the compressed natural gas is dropped due to the adiabatic expansion. For this reason, when the compressed natural gas is continuously charged, the temperature around the one-way valve is substantially dropped. In order to avoid such an excessive temperature drop, it is necessary to repeatedly conduct the operation of charging the compressed natural gas at intervals while waiting for the restoration of the temperature at every operation and hence, it is difficult to conduct a rapid charging of the compressed natural gas into the gas vessel. In order to carry out the rapid charging, despite the excessive temperature drop, it is necessary to use expensive materials resistant to a low temperature such as a rubber and a synthetic resin for forming a part or component constituting the one-way valve, and/or a part or component disposed downstream of the one-way valve, which increases the cost.

Accordingly, it is an object of the present invention to provide a compressed natural gas charging system, wherein an excessive temperature drop is prevented from occurring due to the adiabatic expansion of the compressed natural gas across the one-way valve, and the rapid charging is made possible and further, it is unnecessary to use the expensive material for parts or components constituting the one-way valve.

To achieve the above object, according to the present invention, there is provided a compressed natural gas charging system comprising a gas charging passageway whose one end is capable of being connected to a compressed natural gas supply means capable of supplying a compressed natural gas and whose other end opens into a gas vessel, and a one-way valve incorporated in the gas charging passageway to permit the compressed natural gas to flow from one end of the gas charging passageway toward the other end, wherein the system further includes a constriction provided in the gas charging passageway downstream of the one-way valve, the constriction having a constriction degree larger than that of the one-way valve. Thus, the excessive temperature drop due to the adiabatic expansion of the compressed natural gas is prevented from occurring across the one-way valve, and it is avoided that an expensive material is used for the parts of the one-way valve. Thus, it is possible to rapidly charge the compressed natural gas into the gas vessel.

According to another aspect and feature of the present invention, a plurality of gas vessels are provided as the gas vessel and the one-way valve is associated as a single, common one-way valve with the plurality of vessels, and the gas charging passageway comprises a main passage section in which the single one-way valve is provided, the main passage section being connected to one of the gas vessels, a connecting passage section connected to the main passage section at a location downstream of the one-way valve to connect the gas vessels to one another, and passage branches provided in the gas vessels, respectively, one end of each of the passage branches communicating with the connecting passage section and the other end of the passage branch opening into the gas vessel, each of the passage branches including a shut-off valve which is incorporated therein and has a constriction degree in an opened state thereof smaller than that of the one-way valve, and the constriction is provided in each of the passage branches at a location downstream of the shut-off valve. Thus, by using the single one-way valve common to the plurality of gas vessels, it is possible to provide a reduction in number of parts and to simplify the passage structure.

According to a further aspect and feature of the present invention, a cylindrical temperature diffusing member forming at least a portion of a downstream section of the gas charging passageway with respect to the one-way valve is mounted so as to extend into the gas vessel, and the constriction is provided at a tip end of the temperature diffusing member. Thus, a low temperature in the vicinity of the constriction is prevented to the utmost from being propagated to the one-way valve by the transfer of heat from the surrounding compressed natural gas to the temperature diffusing member.

According to a yet further aspect and feature of the present invention, the constriction is formed as a variable constriction whose constriction degree is variable. Thus, the adiabatic expansion can be controlled by the constriction.

The above and other objects, features and advantages of the invention will become apparent from the following detailed description of preferred embodiments taken in conjunction with the accompanying drawings.

FIG. 1 is a perspective schematic view of a system for supplying a fuel to an engine in a vehicle according to a first embodiment of the present invention;

FIG. 2 is a vertical sectional view of the arrangement of an essential portion of the fuel supplying system;

FIG. 3 is a partial vertical sectional view of a gas vessel;

FIG. 4 is an enlarged view of an essential portion in FIG. 3;

FIGS. 5A and 5B are graphs illustrating the gas charging characteristic according to the present invention;

FIGS. 6A and 6B are graphs illustrating the gas charging characteristic in the prior art;

FIG. 7 is a sectional view similar to FIG. 3, but illustrating a fuel supplying system according to a second embodiment of the present invention;

FIG. 8 is a vertical sectional side view of the arrangement of an essential portion of a fuel supplying system according to a third embodiment of the present invention;

FIG. 9 is a partial vertical sectional view of a gas vessel of the third embodiment;

FIG. 10 is an enlarged vertical sectional view of a one-way valve of the third embodiment;

FIG. 11 is a sectional view similar to FIG. 3, but illustrating a fuel supplying system according to a fourth embodiment of the present invention; and

FIG. 12 is a sectional view similar to FIG. 3, but illustrating a fuel supplying system according to a fifth embodiment of the present invention.

The present invention will now be described by way of preferred embodiments with reference to the accompanying drawings.

Referring first to FIGS. 1 and 2, a gas vessel 15 filled with a compressed natural gas is mounted at a rear portion of a vehicle body of a vehicle V. The compressed natural gas from the gas vessel 15 is supplied via a gas fuel supply passageway 16 and a regulator 17 to an engine E which is mounted at a front portion of the vehicle body. The gas fuel supply passageway 16 includes a first supply line 18 connected at its one end to the gas vessel 15, a supply passage section 19 provided in a sensor block 21 and connected at one end to the other end of the first supply line 18, and a second supply line 20 which interconnects the other end of the supply passage section 19 and the regulator 17. The sensor block 21 is fixedly disposed at the rear portion of the vehicle body in front of the gas vessel 15, and a manual on-off valve 22 is incorporated in the second supply line 20. Mounted to the sensor block 21 are a temperature sensor 23 for detecting the temperature of the compressed natural gas flowing through the supply passage section 19, and a pressure sensor 24 for detecting the pressure of the compressed natural gas flowing through the supply passage section 19.

Referring to FIG. 3, a plug 25.sub.1 is threadedly mounted at one end of the gas vessel 15. A relief valve (not shown) is incorporated in the plug 25.sub.1 and adapted to be opened at a predetermined temperature or higher. As shown in FIG. 2, a first relief line 26 connected to the relief valve is connected to one end of a relief passage 27 provided in the sensor block 21, and a second relief line 28 is connected at its one end to the other end of the relief passage 27. The other end of the second relief line 28 opens to the outside in the vicinity of a side of the rear portion of the vehicle body.

The compressed natural gas is charged into the gas vessel 15 by connecting a gas charging passageway 31.sub.1 to a compressed natural gas supply means 30 (see FIG. 2) such as a gas tank which is placed in a gasoline station or the like. The gas charging passageway 31.sub.1 is provided at its one end with a connecting means 32 which is capable of being connected to the compressed natural gas charging means 30. The other end of the gas charging passageway 31.sub.1 opens into the gas vessel 15.

The gas charging passageway 31.sub.1 includes a first charging line 33 having, at its one end, the connecting means 32 disposed to face a side of the vehicle body, a first charging passage section 34 provided in the sensor block 21 and connected at its one end to the other end of the first charging line 33, a second charging line 35 connected at its one end to the other end of the charging passage section 34 and at the other end of the second charging line 35 to the plug 25.sub.1 of the gas vessel 15, a second charging passage section 36 provided in the plug 25.sub.1 and connected at its one end to the second charging line 35, a one-way valve 37.sub.1 disposed in the gas vessel 15 and connected to the other end of the second charging passage section 36, and a third charging passage section 38 connected at its one end to the second charging passage section 36 through the one-way valve 37.sub.1 and extending rectilinearly within the gas vessel 15. A constriction 39.sub.1 is provided at the other end of the gas charging passageway 31.sub.1, i.e., at the other end of the third passage section 38, and opens into the gas vessel 15.

The second charging passage section 36 is provided in the plug 25.sub.1 to assume a substantially L shape with one end opening into an outer surface of the plug 25.sub.1 and with other end opening into an inner end face of the plug 25.sub.1 within the gas vessel 15.

The one-way valve 37.sub.1 has a valve housing 40 which is formed into a substantially cylindrical shape and threadedly fitted into the plug 25.sub.1. A valve bore 41 and a slide bore 42 having a larger diameter than that of the valve bore 41 are coaxially provided in the valve housing 40. The valve bore 41 is coaxially connected to the other end of the second charging passage section 36. An annular valve seat 43 is formed in a stepped fashion between the valve bore 41 and the slide bore 42. A valve member 45 is slidably received in the slide bore 42 and has an annular sealing portion 44 which is capable of being seated on the valve seat 43.

A cylindrical temperature diffusing member 46.sub.1 defining the third charging passage section 38 therein is coaxially coupled to the valve housing 40 through a cylindrical heat insulating material 47. A valve spring 48 is compressed between the temperature diffusing member 46.sub.1 and the valve member 45 for exhibiting a spring force in a direction to cause the sealing portion 44 to seat on the valve seat 43. Moreover, a passage 49 is provided in the valve member 45 and adapted to interconnect the second charging passage section 36 and the third charging passage section 38, when the valve member 45 is moved in such a direction that the sealing portion 44 leaves the valve seat 43.

When a gas pressure applied to the valve member 45 from the side of the second charging passage section 36 and the valve bore 41 is larger, by a predetermined value, than a pressure applied to the valve member 45 from the side of the third charging passage section 38 by the valve spring 48, the one-way valve 37.sub.1 is opened to permit the flowing of the compressed natural gas from the side of the second charging passage section 36 to the side of the third charging passage section 38, but to inhibit the flowing of the compressed natural gas from the side of the third charging passage section 38 back to the side of the second charging passage section 36. Moreover, because the one-way valve 37.sub.1 is disposed in the gas vessel 15, damaging of the one-way valve 37.sub.1 is avoided to the utmost, even when the vehicle is involved in a collision accident.

The heat insulating material 47 is formed from, for example, a synthetic resin, so that it is integrally coupled to one end of the temperature diffusing member 46.sub.1 by molding. The heat insulating material 47 is threadedly mounted to the valve housing 40, whereby the one end of the temperature diffusing member 46.sub.1 is coaxially coupled to the valve housing through the heat insulating material 47.

The constriction 39.sub.1 is a stationary constriction which is set at the given constriction degree larger than a constriction degree provided when the one-way valve 37.sub.1 is opened. The constriction 39.sub.1 is provided at the other end of the temperature diffusing member 46.sub.1. Thus, the other end of the third charging passage section 38 defined in the temperature diffusing material 46.sub.1, i.e., the other end of the gas charging passageway 31.sub.1, is opened into the gas vessel 15 through the constriction 39.sub.1.

The plug 25.sub.1 is provided with a recess 51 which opens into an outer end face of the plug 25.sub.1. A cylindrical guide member 53 is threadedly fitted into the open end of the recess 51 to define an outlet chamber 52 between the cylindrical guide member 53 and the plug 25.sub.1. The second supply line 20 constituting a portion of the gas fuel supply passageway 16 is connected to the outlet chamber 52.

A threaded member 54 with its outer end directed outwardly is coaxially and threadedly fitted into the guide member 53 for advancing and retreating movements. The threaded member 54 is provided at its one end with an engage hole 55 of a substantially hexagonal shape in section, into which a tool is engaged for rotating the threaded member 54.

The plug 25.sub.1 is provided with an outlet passage 56 coaxial with the outlet chamber 52, and a valve seat 57, into a central portion of which the outlet passage 56 opens, and which faces an inner end of the outlet chamber 52. A valve member 59 is integrally and coaxially connected to an inner end of the threaded member 54 and has a sealing portion 58 which is capable of being seated on the valve seat 57. Thus, the outlet passage 56 can be switchably put into and out of communication with the outlet chamber 52 by advancing and retreating the threaded member 54 from outside.

Referring also to FIG. 4, a shut-off valve 61.sub.1 is mounted between the outlet passage 56 and the inside of the gas vessel 15. The shut-off valve 61.sub.1 includes a valve housing 63.sub.1 which is formed between a valve chamber 62 leading to the inside of the gas vessel 15 and plug 25.sub.1 and threadedly mounted at one end to the plug 25.sub.1, a stationary core 64.sub.1 fixedly mounted at the other end of the valve housing 63.sub.1, a plunger 65.sub.1 which is axially movably inserted into the valve housing 63.sub.1 with one end facing the valve chamber 62 and with other end being in proximity to and opposed to the stationary core 64.sub.1, and a valve seat 66 which is provided on the plug 25.sub.1 to face the valve chamber 62. The other end of the outlet passage 56 opens into a central portion of the valve seat 66. The shut-off valve 61.sub.1 further includes a valve member 68 connected to the other end of the plunger 65.sub.1 and having an annular sealing portion 67 which is capable of being seated on the valve seat 66, a coil 69 disposed in the valve housing 63.sub.1 and capable of exhibiting an electromagnetic force in a direction to move the plunger toward the stationary core 64.sub.1, and a return spring 70 which is compressed between the stationary core 64.sub.1 and the plunger 65.sub.1 to exhibit a spring force for moving the plunger 65.sub.1 away from the stationary core 64.sub.1.

A mounting bore 71 is provided in the plug 25.sub.1 to open into the inner end of the plug 25.sub.1. The mounting bore 71 has a diameter larger than that of the outlet passage 56 and is coaxial with the outlet passage 56, and one end of the cylindrical valve housing 63.sub.1 is threadedly fitted into the mounting bore 71. The valve chamber 62 is defined between the plug 25.sub.1 and the one end of the valve housing 63.sub.1, and an annular passage 72 is defined between the plunger 65.sub.1 as well as the valve member 68 and the valve housing 63.sub.1 and leads to the valve chamber 62. The valve housing 63.sub.1 is provided with a plurality of communication holes 73 which permit the passage 72 to communicate with the inside of the gas vessel 15.

A cylindrical portion 68a is integrally and coaxially connected to the valve member 68 and inserted into the valve housing 63.sub.1 to define the passage 72 between the cylindrical portion 68a and the valve housing 63.sub.1. A shaft portion 65a is integrally and coaxially connected to one end of the plunger 65.sub.1 and loosely inserted into the cylindrical portion 68a. The valve member 68 is provided with a pilot valve bore 74 which has a diameter far smaller than that of the outlet passage 56 and coaxially leads at one end to the outlet passage 56. A sealing portion 76 is provided at one end face of the shaft portion 65a and is capable of being seated on a valve seat 75 which is provided on the valve member 68. The other end of the pilot valve bore 74 opens into a central portion of the valve seat 75. A pair of elongated holes 77, 77 are provided in the cylindrical portion 68a to extend axially on one diametrical line of the cylindrical portion 68a, and a pin 78 is inserted at its opposite ends into the elongated holes 77, 77 and passed through a hole in an intermediate portion of the shaft portion 65a.

In such shut-off valve 61.sub.1, in a condition in which the coil 69 has been deenergized to locate the plunger 65.sub.1 at a position spaced apart from the stationary core 64.sub.1, the valve member 68 is in a position in which the sealing portion 67 thereof has been seated on the valve seat 66 to close the outlet passage 56, and the shaft portion 65a integral with the plunger 65.sub.1 is in a position in which the sealing portion 76 thereof has been seated on the valve seat 75 to close the valve bore 74. In this case, the pressure in the valve chamber 62, i.e., the pressure in the gas vessel 15 is applied to the valve member 68 in a direction to force the sealing portion 67 to be seated on the valve seat 66. Therefore, the valve member 68 is maintained at a closed position under the action of a relatively large force. In such a condition, it is difficult to exhibit, by the coil 69, an electromagnetic force for immediately operating the valve member 68 in an opening direction. A force obtained by multiplying, by the pressure in the gas vessel 15, a value resulting from subtraction of the sealing area of the sealing portion 76 seated on the valve seat 75 from the maximum cross-sectional area of the plunger 65.sub.1 is applied to the plunger 65.sub.1 and the shaft portion 65a in a direction to force the sealing portion 76 to be seat on the valve seat 75. It is not possible to exhibit an electromagnetic force by the coil 69 for overcoming such gas pressure force. Therefore, when the coil 69 is energized in the closed state of the shut-off valve 61.sub.1, the plunger 65.sub.1 is first moved toward the stationary core 64.sub.1, so that the sealing portion 76 of the shaft portion 65a integral with the plunger 65.sub.1 is moved away from the valve seat 75 to open the pilot valve bore 74. During this time, the opposite ends of the pin 78 moved along with the shaft portion 65a remain inserted in the elongated holes 77, 77 and hence, the axial relative movement of the shaft portion 65a relative to the valve member 68 is permitted. Thus, the difference in pressure between the valve chamber 62 and the outlet passage 56 is decreased in response to the opening of the pilot valve bore 74, thereby providing a condition in which the valve member 68 can be moved in an opening direction by a relatively small force. When the opposite ends of the pin 78 are brought into engagement with ends of the elongated holes 77, 77 adjacent the plunger 65.sub.1, the valve member 78 is moved in the opening direction along with the plunger 65.sub.1 operated by the electromagnetic force of the coil 69, thereby completely opening the outlet passage 56.

The operation of the first embodiment will be described below. If the compressed natural gas supply means 30 is connected to one end of the gas charging passageway 31.sub.1 when charging a compressed natural gas into the gas vessel 15, the compressed natural gas is charged into the gas vessel 15 through the one-way valve 37.sub.1 and the constriction 39.sub.1 included in the compressed gas supply passageway 31.sub.1. At that time, the opening degree of the one-way valve 37.sub.1 is varied as shown in FIG. 5A in accordance with a variation in pressure in the gas vessel 15. Since the constriction 39.sub.1 having the constriction degree larger than that of the one-way valve 37.sub.1 is provided at a downstream end of the gas charging passageway 31.sub.1, a temperature drop as shown in FIG. 5B occurs in the vicinity of the constriction 39.sub.1 due to an adiabatic expansion produced when the compressed natural gas flows through the constriction 39.sub.1. However, the compressed natural gas produces a loss in pressure when it flows through the one-way valve 37.sub.1 and hence, the pressure differential across the constriction is relatively reduced. Therefore, the extent of the adiabatic expansion at the constriction 39.sub.1 is suppressed, and the temperature drop in the vicinity of the constriction 39.sub.1 also becomes relatively small. Further, the pressure differential across the one-way valve 37.sub.1 is smaller than the pressure differential across the constriction 39.sub.1 and hence, the temperature drop in the vicinity of the one-way valve 37.sub.1 is less severe, as shown in FIG. 5B, and thus, the temperature is prevented from being steeply dropped in the vicinity of the one-way valve 37.sub.1. As a result, it is unnecessary to use an expensive material such as a rubber and a synthetic resin resistant to a low temperature for forming the one-way valve 37.sub.1, and it is unnecessary to wait for the restoration of the normal temperature. Therefore, it is possible to rapidly charge the compressed natural gas.

In contrast, in the prior art compressed natural gas charging system in which the constriction 39.sub.1 is not provided downstream of the one-way valve 37.sub.1, the charging characteristic is as shown in FIGS. 6A and 6B. More specifically, a steep temperature drop as shown in FIG. 6B occurs in the vicinity of the one-way valve 37.sub.1 due to an adiabatic expansion produced when the compressed natural gas flows through the one-way valve 37.sub.1. For this reason, as shown in FIG. 6A, the gas charging operation must be discontinued to for wait the restoration of the normal temperature, and it is impossible to rapidly charge the compressed natural gas into the gas vessel 15.

In addition, a temperature drop of the compressed natural gas occurs at the constriction 39.sub.1. However, because the cylindrical diffusing member 46.sub.1 forming at least a portion of the downstream section of the gas charging passageway 31.sub.1 from the one-way valve 37.sub.1 is mounted to extend into the gas vessel 15, and the constriction 39.sub.1 is provided at the tip end of the temperature diffusing member 46.sub.1, a low temperature in the vicinity of the constriction 39.sub.1 is prevented to the utmost from being propagated to the one-way valve 37.sub.1 by the transfer of heat from the surrounding compressed natural gas to the temperature diffusing member 46.sub.1. Further, by the fact that the heat insulating material 47 is interposed between the temperature diffusing member 46.sub.1 and the one-way valve 37.sub.1, the low temperature in the vicinity of the constriction 39.sub.1 is reliably prevented from being propagated to the one-way valve 37.sub.1.

Further, because the gas charging passageway 31.sub.1 and the gas supply passageway 16 are independent from each other, it is possible to provide a difference between the characteristic of charging of the compressed natural gas into the gas vessel 15 and the characteristic of supplying of the compressed natural gas from the gas vessel 15.

FIG. 7 illustrates a second embodiment of the present invention. In the second embodiment, an electric heater 80 is mounted in an outer surface of the temperature diffusing member 46.sub.1. Thus, the low temperature in the vicinity of the constriction 39.sub.1 is reliably prevented from being propagated to the one-way valve 37.sub.1 by heating by the electric heater 80, and it is unnecessary to use an expensive material such as a rubber and a synthetic resin resistant to a low temperature for forming the one-way valve 37.sub.1. In addition, it is possible to rapidly charge the compressed natural gas.

FIGS. 8 to 10 illustrate a third embodiment of the present invention. FIG. 8 is a vertical sectional side view of the arrangement of an essential portion of a fuel supplying system; FIG. 9 is a partially vertical sectional view of a gas vessel; and FIG. 10 is an enlarged vertical sectional view of a one-way valve.

Referring first to FIG. 8, a plurality of, e.g., three first, second and third gas vessels 15.sub.1, 15.sub.2 and 15.sub.3 filled with a compressed natural gas are mounted in the vehicle V (see FIG. 1). A plug 25.sub.2 is threadedly mounted at one end of each of the gas vessels 15.sub.1, 15.sub.2 and 15.sub.3, and a relief valve (not shown) is mounted in the plug 25.sub.2 and adapted to be opened at a predetermined temperature or higher. A first relief line 26 commonly connected to these relief valves is connected to one end of a relief passage 27 provided in the sensor block 21, and a second relief line 28 is connected at its one end to the other end of the relief passage 27.

Referring also to FIG. 9, the compressed natural gas is charged into each of the gas vessels 15.sub.1, 15.sub.2 and 15.sub.3 by connecting a gas charging passageway 31.sub.2 to the compressed natural gas supply means 30. The gas charging passageway 31.sub.2 includes: a main passage section 81 which has a single one-way valve 37.sub.2 common to the gas vessels 15.sub.1, 15.sub.2 and 15.sub.3 and which is connected to one of the gas vessels 15.sub.1, 15.sub.2 and 15.sub.3, e.g., the first gas vessel 15.sub.1 ; a connecting passage section 82 connected to the main passage section 81 downstream of the one-way valve 37.sub.2 for connecting the gas vessels 15.sub.1, 15.sub.2 and 15.sub.3 to one another; and passage branches 83.sub.1 provided in the gas vessels 15.sub.1, 15.sub.2 and 15.sub.3. One end of each of the passage branches 83.sub.1 communicates with the connection passage section 82, and the other end opens into the gas vessels 15.sub.1, 15.sub.2 and 15.sub.3, respectively.

The main passage section 81 includes a first charging line 33 having, at its one end, a connecting means 32 which is capable of being connected to the compressed natural gas supply means 30, a first charging passage 34 provided in the sensor block 21 and having one end communicated with the other end of the first charging line 33, a second charging line 35 having one end connected to the other end of the first charging passage 34, and a one-way valve 37.sub.2 interposed between the plug 25.sub.2 of the first gas vessel 15.sub.1 and the second charging line 35.

Referring to FIG. 10, a valve housing 84 of the one-way valve 37.sub.2 includes a first housing half 85 air-tightly connected to the second charging line 35, and a second housing half 86 which is threadedly fitted into the plug 25.sub.2 of the first gas vessel 15.sub.1 and also threadedly fitted to the first housing half 85. A valve chamber 87 is defined within the valve housing 84.

A valve bore 88 is provided in the first housing half 85 and coaxially connected to the second charging line 35. An annular valve seat 89 is also provided in the first housing half 85, and an end of the valve bore 88 opens into the valve chamber 87 at a central portion of the valve seat 89. A valve member 91 is accommodated in the valve chamber 87 and has an annular sealing portion 90 which is capable of being seated on the valve seat 89. The valve member 91 is formed into a shape which permits the compressed natural gas to flow toward the plug 25.sub.2 when the sealing portion 90 is moved away from the valve seat 89. Moreover, a valve spring 92 is compressed between the valve member 91 and the second housing half 86 for biasing the valve member 91 in a direction to force the sealing portion 90 to be seated on the valve seat 89.

The connecting passage section 82 includes: outlet chambers 52 provided in the plugs 25.sub.2, respectively; communication passages 93 which are provided in the plugs 25.sub.2 to traverse the outlet chambers 52, respectively; a communication line 94.sub.1 which permits the communication passages 93 in the first and second gas vessels 15.sub.1 and 15.sub.2 to communicate with each other; and a communication line 94.sub.2 which permits the communication passages 93 in the second and third gas vessels 15.sub.2 and 15.sub.3 to communicate with each other. A communication bore 95 (see FIG. 10) is provided in the second housing half 86 to lead to the valve chamber 87 in the one-way valve 37.sub.2, and is in communication with the communication passage 93 in the first gas vessel 15.sub.1. A first supply line 18 of a gas fuel supply passageway 16 (see FIG. 8) is in communication with the communication passage 93 in the third gas vessel 15.sub.3.

Referring particularly to FIG. 9, the passage branch 83.sub.1 includes: an outlet passage 56 provided in the plug 25.sub.2 such that its end opening into the outlet chamber 52 can be closed by the sealing portion 58 of the valve member 59; a passage 96 provided in the plug 25.sub.2 such that it can be switchably put into and out of communication with the outlet passage 56 by a shut-off valve 61.sub.2 mounted at an inner end of the plug 25.sub.2 ; a passage 97 which is defined in a cylindrical temperature diffusing member 46.sub.2 attached at its base end to the inner end of the plug 25.sub.2 substantially in parallel to the shut-off valve 61.sub.2, with one end of the passage 97 communicating with the passage 96; and a constriction 39.sub.1 provided at a tip end of the temperature diffusing member 46.sub.2 and leading to the other end of the passage 97. The shut-off valve 61.sub.2 is formed so that the constriction degree in its closed state is smaller than that of the one-way valve 37.sub.2.

The shut-off valve 61.sub.2 includes: a valve housing 63.sub.2 threadedly mounted at its one end to the plug 25.sub.2 to define a valve chamber 62 between the valve housing 63.sub.2 and the plug 25.sub.2 ; a stationary core 64.sub.2 fixedly mounted at the other end of the valve housing 63.sub.2 ; a plunger 65.sub.1 which is axially movably inserted into the valve housing 63.sub.2 with one end facing the valve chamber 62 and with the other end being in proximity to and opposed to the stationary core 64.sub.2 ; a valve member 68 connected to the other end of the plunger 65.sub.1 and capable of closing the other end of the outlet passage 56; a coil 69 disposed in the valve housing 63.sub.2 and capable of exhibiting an electromagnetic force in a direction to urge the plunger 65.sub.1 toward the stationary core 64.sub.2 ; and a return spring 70 compressed between the stationary core 64.sub.2 and the plunger 65.sub.1 to exhibit a spring force for urging the plunger 65.sub.1 away from the stationary core 64.sub.2. The structure of the connection of the plunger 65.sub.1 and the valve member 68 is identical to those in the first and second embodiments.

The passage 96 is provided in the plug 25.sub.2 with one end thereof communicating with the valve chamber 62, and the temperature diffusing member 46.sub.2 is threadedly attached to the inner end of the plug 25.sub.2, such that the passage 97 provided therein communicates with the other end of the passage 96.

In the third embodiment, the connecting passage section 82 of the gas charging passageway 31.sub.2 also functions as a passage for supplying the compressed natural gas from each of the gas vessels 15.sub.1, 15.sub.2 and 15.sub.3, and the one-way valve 37.sub.2 is mounted as a single part common to the gas vessels 15.sub.1, 15.sub.2 and 15.sub.3. Thus, it is possible to provide a reduction in the number of parts and simplify the passage structure.

Moreover, the constriction 39.sub.1 is disposed downstream of the shut-off valve 61.sub.2 and has the constriction degree larger than that of the one-way valve 37.sub.1 and that of the shut-off valve 61.sub.2 (when it is opened) disposed downstream of the one-way valve 37.sub.2. Therefore, as in the previously described embodiments, it is avoided that excessive adiabatic expansion of the compressed natural gas is produced across the one-way valve 37.sub.2, and it is unnecessary to use an expensive material such as a rubber and a synthetic resin resistant to a low temperature for forming the one-way valve 37.sub.1. Therefore, it is possible to rapidly charge the compressed natural gas.

Additionally, the cylindrical temperature diffusing member 46.sub.2 forming at least a portion of the downstream section of the gas charging passageway 31.sub.2 from the shut-off valve 61.sub.2 is mounted to extend into the gas vessel 15.sub.1, and the constriction 39.sub.1 is provided at the tip end of the temperature diffusing member 46.sub.2. Therefore, the low temperature in the vicinity of the constriction 39.sub.1 is prevented to the utmost from being propagated to the shut-off valve 61.sub.2 and the one-way valve 37.sub.2 by the transfer of heat from the surrounding compressed natural gas to the temperature diffusing member 46.sub.2.

In the third embodiment, a heat insulting material may be interposed between the temperature diffusing member 46.sub.2 and the plug 25.sub.2, and an electric heater 80 (see FIG. 7) may be mounted in the temperature diffusing member 46.sub.2.

FIG. 11 illustrates a fourth embodiment of the present invention, wherein portions or components corresponding to those in the third embodiment are designated by like reference characters.

The fourth embodiment is substantially similar to the third embodiment, but is different from third embodiment in that the constriction degree of a constriction 39.sub.2 provided at the tip end of the temperature diffusing member 46.sub.2 is variable such that it is increased with a reduction in surrounding temperature.

This constriction 39.sub.2 includes a tapered surface 101 which is provided on an inner surface of a tip end of the temperature diffusing member 46.sub.2 and into a central portion of which a through-hole 100 coaxially provided in the tip end of the temperature diffusing member 46.sub.2 opens, a shaft 103 inserted into the through-hole 100 and having at one end a valve portion 102 opposed to the tapered surface 101, and an actuator 104 connected to the shaft 103.

The actuator 104 is movable axially, as the volume of a wax 105 is varied by a variation in temperature. The actuator 104 has a housing 106 which is fixedly connected at its base end to the temperature diffusing member 46.sub.2 to define a lead-out chamber 107 leading to the through-hole 100 between the housing 106 and the tip end of the temperature diffusing member 46.sub.2. A plurality of radial communication bores 108 are provided in the housing 106 for permitting the lead-out chamber 107 to communicate with the inside of the gas vessel 15.sub.1.

The other end of the shaft 103 is passed through the lead-out chamber 107 and slidably fitted in the housing 106. One end of a sealing member 109 slidably fitted in the housing 106 abuts against the other end of the shaft 103. A limiting flange 103a is integrally provided at an intermediate portion of the shaft 103 in the lead-out chamber 107 to protrude radially outwardly. The limiting flange 103a functions to limit the movement of the shaft 103 toward an axially other end, i.e., the movement of the shaft 103 in a direction to increase the constriction degree with movement of the valve portion 102 toward the tapered surface 101, by the abutment against the housing 106.

A peripheral edge of a diaphragm 110 is clamped at a tip end of the housing 106, and a dish-like cap 111 is secured to the tip end of the housing 106 for charging a wax 105 between the cap 111 and the diaphragm 110. An oil 112 is filled between the diaphragm 110 and the housing 106, and the other end of the sealing member 39.sub.2 faces the oil 112.

Such constriction 39.sub.2 ensures that if the temperature of the compressed natural gas in the gas vessel 15.sub.1 is dropped, the shaft 103 is moved in a direction to increase the constriction degree due to a reduction in volume of the wax, and if the temperature is increased, the shaft 103 is moved in a direction to decrease the constriction degree due to an increase in volume of the wax 105. Therefore, at a low temperature, the amount of compressed natural gas being charged can be suppressed to limit the adiabatic expansion, and at a higher temperature, the charging speed can be increased sufficiently.

FIG. 12 illustrates a fifth embodiment of the present invention, wherein portions or components corresponding to those of each of the previously described embodiments are designated by like reference characters.

Each of the passage branches 83.sub.2 constitutes a gas charging passageway 31.sub.3 together with a main passage section 81 having a one-way valve 37.sub.2 and a connecting passage section 82 connected to the main passage section 81 downstream of the one-way valve 37.sub.2. The passage branch 83.sub.2 includes: an outlet passage 56 which is provided in a plug 25.sub.3 such that its end opening into the outlet chamber 52 can be closed by the sealing portion 58 of the valve member 59; a passage 113 which is provided in a plunger 65.sub.2 of a shut-off valve 61.sub.3 mounted to an inner end of the plug 25.sub.3, such that the passage 113 can be switchably put into and out of communication with the outlet passage 56 by the shut-off valve 61.sub.3 ; a passage 114 provided in a stationary core 64.sub.3 of the shut-off valve 61.sub.3 and leading to the passage 113; and a constriction 39.sub.1 which is provided in the stationary core 64.sub.3 and coaxially connected to the passage 114 and which opens into the gas vessel 15.sub.1.

The shut-off valve 61.sub.3 includes: a valve housing 63.sub.2 which is threadedly attached at its one end to the plug 25.sub.3 to define a valve chamber 62 between the valve housing 63.sub.2 and the plug 25.sub.3 ; a stationary core 64.sub.3 fixedly mounted at the other end of the valve housing 63.sub.2 ; a plunger 65.sub.2 which is axially movably inserted into the valve housing 63.sub.2 with one end of the plunger 65.sub.2 facing the valve chamber 62 and the other end being in proximity to and opposed to the stationary core 64.sub.3 ; a valve member 68 connected to the other end of the plunger 65.sub.2 and capable of closing the other end of the outlet passage 56; a coil 69 disposed in the valve housing 63.sub.2 and capable of exhibiting an electromagnetic force in a direction to urge the plunger 65.sub.2 toward the stationary core 64.sub.3 ; and a return spring 70 compressed between the stationary core 64.sub.3 and the plunger 65.sub.2 to exhibit a spring force for urging the plunger 65.sub.2 away from the stationary core 64.sub.3. The structure of the connection of the plunger 65.sub.2 and the valve member 68 is identical to that in each of the previously described embodiments.

The passage 113 is coaxially provided in the plunger 65.sub.2 with its one end communicating with the valve chamber 62, and the passage 114 is provided in the stationary core 64.sub.3, so that it is coaxially connected to the passage 113.

In the fifth embodiment, in addition to the prevention of the generation of an excessive adiabatic expansion across the one-way valve 37.sub.2, the passage structure can be simplified by formation of the passage branch 83.sub.2 in the shut-off valve 61.sub.3.

Although the embodiments of the present invention have been described in detail, it will be understood that the present invention is not limited to the above-described embodiments, and various modifications in design may be made without departing from the spirit and scope of the invention defined in the claims.