Piping for compressed fuel in motorcar

In a motorcar having a compressed fuel cylinder charged with a compressed fuel disposed in a compartment, pipes connected to the fuel cylinder within the compartment are connected to a joint unit penetrating a partition wall partitioning the compartment from an outside and the joint unit is connected to pipes connected to an internal combustion engine and the like out of the compartment. A fuel charge passage, a fuel supply passage and a relief passage in a cylinder cap of the fuel cylinder and a fuel charge passage, a fuel supply passage and a relief passage in an interior side of the joint unit are connected with each other through an interior charge pipe, and interior supply pipe and an interior fuel relief pipe, respectively. A fuel charge pipe, a fuel supply pipe and a relief pipe out of the compartment are connected to a fuel charge passage, a fuel supply passage and a relief passage in an exterior side of the joint unit. The interior fuel charge pipe, the interior fuel supply pipe and the interior fuel relief pipe are covered by a seal cover airtightly. A fuel leakage inspection is conducted by comparing gas pressures at two different times after fuel charging in the piping outside the compartment.

BACKGROUND OF THE INVENTION 
The present invention relates to a motorcar having a compressed fuel tank 
charged with a compressed fuel such as natural gas or liquefied petroleum 
gas disposed in a compartment such as a trunk room, particularly to a 
structure of a piping for the compressed fuel in the motorcar and a method 
for inspecting leakage of the piping. 
Japanese Laid-Open Patent Publication No. Sho 52-93024 (1977) discloses a 
motorcar having a compressed fuel tank charged with liquefied petroleum 
gas (LPG) disposed in a trunk room in which a circumference of the 
compressed fuel tank, a supporting member of the tank and a pipe 
connection part of the tank is closed up tightly by a fuel cylinder case 
and a fuel cylinder case cover so that a fuel gas leaking out from the 
connection part between the compressed fuel tank and a pipe does not flow 
into the trunk room. 
In the motorcar described in the above Japanese Publication, the fuel 
cylinder case and the fuel cylinder case cover have to cover the 
supporting member of the compressed fuel tank as well as the whole of the 
tank, so that the case and the case cover becomes broad, and also, a 
length of a edge of the case to be joined to the car body becomes long to 
necessitate a careful attention for the tight closing up thereof. 
Moreover, the working time is prolonged necessarily and a high cost is 
inevitable. 
Japanese Laid-Open Patent Publication No. Hei 7-195948 (1995) discloses a 
structure for sealing a compressed fuel tank piping of a motorcar. In this 
structure, as shown in FIG. 11, a compressed fuel supply auxiliary unit 02 
housing devices necessary for charging a fuel into a compressed fuel tanks 
01 and for supplying the fuel from the tanks 01 to an internal combustion 
engine is covered with a seal case 03 which is supported by a supporting 
member 06 standing from a floor 05 within a trunk room 04. Pipes 08 
extending free from the auxiliary unit 02 are exposed at openings 07 of 
the seal case 03. Four pipes 08 are connected with valves 09 attached to 
the compressed fuel tanks 01, and other two pipes 08 are connected with a 
gas charging pipe 010 and a fuel supply pipe 011 on the outside of the car 
room, respectively. The fuel supply pipe 011 is connected to an internal 
combustion engine not shown. So as to cover these pipes 08, both ends of 
two tubular covers 014 are tightly attached to openings 07 of the seal 
case 03 and tubular end plates 012 attached to the valves 09 and both ends 
of another tubular cover 014 are tightly attached to another opening 07 of 
the seal case 03 and a tubular opening 013 standing from the floor 05. 
According to the prior art of the Japanese Publication No. Hei 7-195948, 
since only parts having a chance of gas leak occurring is covered by the 
tubular covers 014, a small sealing member can be used and it is not 
necessary to cover-up to a supporting member of the tank so that the 
sealing structure is simplified. However, since all connection of the 
pipes 08 must be carried out within the narrow trunk room, it is difficult 
to perform the pipe connection work in a short time, efficiently and 
surely. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided an improved piping 
structure for compressed fuel in a motorcar which comprises a compressed 
fuel tank disposed in a compartment of the motorcar; a joint unit 
supporting plate detachably fitted to an opening of a partition wall 
partitioning the compartment from an outside; and a joint unit integrally 
attached to and penetrating the joint unit supporting plate, the joint 
unit having an interior joint positioned inside of the compartment to be 
connected with an interior pipe arranged inside of the compartment and an 
exterior joint positioned outside of the compartment to be connected with 
an exterior pipe arranged outside of the compartment. 
In the piping structure of the present invention, the piping work can be 
performed as follows. Firstly, the interior pipe to be arranged inside of 
the compartment is previously connected to the interior joint of the joint 
unit and the compressed fuel tank, at the outside of the compartment, and 
the joint unit and the tank thus connected by the interior pipe are 
brought in the compartment together, then the tank is set and the joint 
unit supporting plate integral with the joint unit is fitted to the 
opening or the partition wall. And after that, the exterior pipe arranged 
outside of the compartment is connected to the exterior joint of the joint 
unit exposed to the outside of the partition wall. 
In this way, according to the present invention, the connecting work of the 
compressed fuel piping can be performed in a broad space outside of the 
compartment instead of in a narrow space in the compartment so that the 
connecting work can be done easily, surely and efficiently. 
The above-mentioned piping structure of the present invention may comprise 
a fuel charge passage formed in the joint unit; a fuel supply passage 
formed in the joint unit in parallel with the fuel charge passage; an 
interior fuel charge pipe having an end connected to the compressed fuel 
tank and another end connected to an interior joint of the fuel charge 
passage; an interior fuel supply pipe having an end connected to the 
compressed fuel tank and another end connected to an interior joint of the 
fuel supply passage; an exterior fuel charge pipe having an end connected 
to a fuel charging mouth and another end connected to an exterior joint of 
the fuel charge passage; and an exterior fuel supply pipe having an end 
connected to an internal combustion engine and another end connected to an 
exterior joint of the fuel supply passage. 
According to the constitution, the internal combustion engine and the fuel 
charging mouth on the outside of the compartment can be connected to the 
compressed fuel tank in the compartment through the exterior pipes, the 
joint unit and the interior pipes. 
The piping structure of the present invention may comprise a relief passage 
formed in the joint unit in parallel with the fuel charge passage and the 
fuel supply passage; an interior relief pipe having an end connected to a 
relief valve attached to the compressed fuel tank and another end 
connected to an interior joint of the relief passage; and an exterior 
relief pipe having an opening end and another end connected to an exterior 
side of the relief passage. 
According to this constitution, a relief valve piping for discharging a 
fuel within the compressed fuel tank when the pressure in the tank exceeds 
a predetermined pressure can be arranged in addition to the fuel supply 
pipe to the internal combustion engine and the fuel charge pipe to the 
compressed fuel tank. 
The fuel supply passage in the joint unit may be provided with a pressure 
sensor and a temperature sensor for detecting pressure and temperature in 
the fuel supply passage. 
The joint unit may be provided with a connecting passage connecting the 
fuel charge passage with the fuel supplying passage, and a hand-operated 
valve capable of opening and shutting the connecting passage. 
The interior fuel charge pipe and the interior fuel supply pipe may 
communicate with an interior of the compressed fuel tank through 
communicating passages in a pipe attachment member attached to the 
compressed fuel tank, and the pipe attachment member may be provided with 
hand-operated valves capable of opening and shutting the communicating 
passages respectively. According to this constitution, communication 
between the fuel charge pipe and the fuel tank or between the fuel supply 
pipe and the fuel tank can be established or cut off at will. 
Further, according to the present invention, there is provided a method for 
inspecting leakage of the aforementioned piping structure for a compressed 
fuel in a motorcar, comprising steps of: closing the both hand-operated 
valves of the pipe attachment member of the compressed fuel tank, and 
opening the hand-operated valve of the joint unit; closing the exterior 
joint of the fuel supply passage in the joint unit with a plug, or 
connecting the exterior supply passage to the exterior joint of the relief 
passage with a pipe or a hose; connecting a compressed gas charging means 
to the exterior joint of the fuel charge passage in the joint unit; 
charging a compressed gas from the compressed gas charging means; 
detecting gas pressures in the piping immediately after and after a 
predetermined time elapses; and judging whether there is a difference 
between the both detected gas pressures or not to inspect leakage of the 
piping inside of the compartment. 
Inspection of leakage of the piping outside of the compartment can be 
performed by that after completion of the above-mentioned inspection, the 
exterior joints of the fuel supply passage and the fuel charge passage in 
the joint unit are connected to the fuel supply pipe leading to the 
internal combustion engine and the fuel charge pipe leading to the fuel 
charging mouth on a car body respectively, a compressed gas is charged 
from the fuel charging mouth, gas pressures in the piping immediately 
after charging and after a predetermined time elapses are detected, and 
then whether there is a difference between the both detected pressures or 
not is judged.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Hereinafter, a preferred embodiment of the present invention will be 
described with reference to FIGS. 1 to 10. 
As shown in FIG. 1, on a side of a rear body 2 of a motorcar 1 is formed a 
door opening for a rear door. A fuel cylinder 6, namely a compressed fuel 
tank, is brought in the rear body 2 through the door opening 3 in a state 
that a seat back 5 of a rear seat 4 capable of rising and falling back and 
forth is fallen in front. The fuel cylinder 6 is placed on a cylinder 
supporting frame 9 installed on a floor panel 8 within a trunk room 7 in 
rear of the rear seat 4 and attached to the cylinder supporting frame 9 
with a fixing belt 10 firmly. 
The floor panel 8 is formed with an opening 11 (FIG. 3) at a position 
directly under a front end part of a place where the fuel cylinder 6 is 
installed and a joint unit supporting plate 12 is fitted in the opening 11 
detachably. A joint unit 13 is fitted to the joint unit supporting plate 
12 integrally penetrating the plate 12. 
As shown in FIG. 4, the fuel cylinder 6 is provided with a cylinder cap 14 
which is a pipe attachment member and has a fuel charge passage 15, a fuel 
supply passage 16 and a relief passage 17. The passages 15, 16, 17 are 
formed in parallel with each other and opened into the fuel cylinder 6 
respectively. The fuel charge passage 15 is provided with a hand-operated 
charge valve 18 and a check valve 19 allowing the fuel to flow only toward 
the fuel cylinder 6. The fuel supply passage 16 is provided with a 
electromagnetic supply valve 20, a hand-operated supply valve 21 and a 
check valve 22 allowing the fuel to flow only out of the fuel cylinder 6. 
The relief passage 17 is provided with a relief valve 23 opening only when 
the pressure within the fuel cylinder 6 exceeds a predetermined pressure. 
At outer ends of the passages 15, 16, 17 are provided pipe joints 24, 25, 
26 respectively. 
As shown in FIG. 5, in the joint unit 13 are formed a fuel charge passage 
27 and a fuel supply passage 28 in parallel, which passages are bent two 
times in respective planes to form U-shapes. The passage 27, 28 
communicates with each other through a U-shaped communicating passage 
having a hand-operated valve 31 interposed. Further, a relief passage 29 
having two rectangular bent portions is formed in parallel with the fuel 
charge passage 27 and the fuel supply passage 28. 
As shown in FIGS. 8 and 9, the hand-operated valve 31 is composed of a 
valve main body 70 and an attachment member 74. The valve main body 70 has 
a male screw 71 formed on a periphery of an outer end part, a hexagonal 
hole formed within the outer end part and abutting seal part 73 at an 
inner end. The attachment member 74 has a female screw 75 and a male screw 
76. The male screw 71 of the valve main body 70 is engaged with the female 
screw 75 of the attachment member 74 with O-ring 79 interposed between the 
valve main body 70 and the attachment member 74. The male screw 76 of the 
attachment member 74 with an O-ring 80 fitted to the base portion of the 
screw is engaged with a female screw 78 of the joint unit 13 to attach the 
hand operated valve 31 to the joint unit 13. 
To open and close the hand-operated valve 31, a tool, not shown, is 
inserted into the hexagonal hole 72 of the valve main body 70 and turned 
in either direction so that the abutting seal part 73 is separated from or 
contact with the valve seat 77. 
As shown in FIGS. 4 and 5, a pressure sensor 34 and a temperature sensor 35 
are provided to communicating passage 32, 33 communicating with the fuel 
supply passage 28 for detection of pressure and temperature in the fuel 
supply passage 28. 
The interior side 13a of the joint unit 13 is provided with interior pipe 
joints 36, 37, 38 connected to respective ends of the fuel charge passage 
27, the fuel supply passage 28 and the relief passage 29, and the exterior 
side 13b of the joint unit 13 is provided with exterior pipe joints 39, 
40, 41 connected to respective other ends of the passages 27, 28, 29. 
The pipe joints 24, 25, 26 of the cylinder cap 14 are connected to the 
interior pipe joints 36, 37, 38 of the joint unit 13 by an interior fuel 
charge pipe 42, an interior fuel supply pipe 43 and an interior fuel 
relief pipe 44, respectively. These pipe joints and the pipes are covered 
by a rubber seal cover 45 in the lump. Both ends of the seal cover 45 are 
fitted around the cylinder cap 14 joint unit interior side 13a of the 
joint unit 13 and tightened airtightly by clamps 46, respectively. 
The exterior pipe joint 39 at the exterior side 13b of the joint unit 13 is 
connected to an end of a fuel charge pipe 47 which has the other end 
connected to a fuel charging mouth 49 at a fuel charging lid 48 provided 
on a side of the rear body 2 of the car. 
The exterior pipe joint 40 at the exterior side 13b of the joint unit 13 is 
connected to an end of a fuel supply pipe 50 which is connected to an 
internal combustion engine 52 installed in an engine room 51 at a front 
part of the motorcar 1 with a hand-operated valve 55, a strainer 56, a 
pressure regulating unit 54 and an injector 53 inserted in order. 
The hand-operated valve 55 and the strainer 56 are provided with pipe 
joints 57, 58. These pipe joints 57, 58 and the above-mentioned pipe 
joints 24, 25, 26, 37, 38, 39, 40, 41 are constituted as shown in FIG. 10. 
The pipe joint comprises a joint main body 60 to be detachably screwed in 
the joint unit 13 or the cylinder cap 14, a sleeve 61 fitted on the pipe 
and engaged with an enlarged end of the pipe, a cap nut 62 screwed on the 
joint main body engaging with the sleeve 61, and an O-ring 63 inserted 
between an outer end face of the joint main body 60 and the enlarged end 
of the pipe. In case of the pipe joint 57, 58, the joint main body 60 may 
be the valve main body of the hand-operated valve 55 or the main body of 
the strainer 56. When the joint main body 60 is screwed in the joint unit 
13 or the cylinder cap 14, a O-ring 65 is fitted on a base portion of a 
male screw part 64 of the joint main body 60 beforehand. 
ECU 66 receives detection signals from the pressure sensor 34 and the 
temperature sensor 35 in the joint unit 13, detection signals from certain 
pressure and temperature sensors (not shown) of the pressure regulating 
unit 54, and other data necessary for operation of the internal combustion 
engine. On the basis of these signals and data, ECU 66 performs on-off 
control of the electromagnetic supply valve 20 of the fuel cylinder 6 and 
fuel supply timing control of the injector 53 through an injector driver 
59. 
All of the fuel cylinder 6, the interior fuel charge pipe 42, the interior 
fuel supply pipe 43, the fuel relief pipe 44, the joint unit 13, the seal 
cover 45 and the cylinder supporting frame 9 are assembled together at the 
outside of the car previously to form a modular tank assembly with the 
fuel cylinder fixed to the cylinder supporting frame 9 by the fixing belt 
10. The modular tank assembly is brought in the trunk room 7 through the 
door opening 3 of the rear car-body 2 and the upper part of the seat back 
5 fallen down. Then, the cylinder supporting frame 9 is fixed to the floor 
panel 8, the joint unit 13 is fitted in the opening 11 of the floor panel 
8, and the joint unit supporting plate 12 integral with the joint unit 13 
is fixed to the floor panel 8, aid this is the only work to be done in the 
trunk room 7. 
After that, at the outside of the car, to the exterior joints 39, 40, 41 of 
the joint unit 13 are connected the fuel charge pipe 47, the fuel supply 
pipe 50 and the relief pipe 67 respectively to complete connecting work of 
the exterior piping. 
As described above, connecting works of interior pipes as well as exterior 
pipes are carried out on the outside of the car so that the connecting 
works can be performed easily, surely and efficiently. 
In the course of assembling the modular tank assembly, a leakage inspection 
of the interior piping is carried out as follows. Before both ends of the 
seal cover 45 is fixed to the joint unit 13 and the cylinder cap 14, the 
hand-operated charge valve 18 and the hand-operated supply valve 21 of the 
cylinder cap 14 are closed, the hand-operated valve 31 of the joint unit 
13 is opened, and the exterior pipe joint 40 and the exterior pipe joint 
41 are connected with each other by a pipe or hose. Then a compressed gas 
is charged from the exterior pipe joint 39 of the joint unit 13 and gas 
pressure in the fuel charge passage 27 and the fuel supply passage 28 is 
detected by the pressure sensor 34. It the pressure does not vary until a 
predetermined time elapses, it is judged that there is no leak in the 
interior piping and if the pressure varies, it is judged that there is a 
leak. 
A leakage inspection of the exterior piping is carried out after the 
connecting works of the exterior pipes are completed, as follows. A 
compressed gas is charged from the fuel charging mouth 49, and pressure in 
the fuel supply passage 28 is detected immediately and after a 
predetermined time elapses by the pressure sensor 34. If no difference is 
found between the detected values of the pressure, it is judged that there 
is no leak in the exterior piping and if a difference is found, it is 
judged that there is a leak. 
In such a manner, according to the present embodiment, leakage inspection 
of the fuel supply system can be performed very easily and surely. 
Moreover, as the interior piping is sealed by the seal cover 45 in the 
lump, sealing structure is simple and sealing work can be done very 
efficiently and surely.