Patent Publication Number: US-2022219528-A1

Title: Fuel cell vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-002985 filed on Jan. 12, 2021, incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The technology disclosed herein relates to a fuel cell vehicle. 
     2. Description of Related Art 
     Japanese Unexamined Patent Application Publication No. 2019-98802 (JP 2019-98802 A) discloses a fuel cell vehicle. This fuel cell vehicle includes a vehicle body, a tank mounted on the vehicle body to store gas, a fuel cell unit that generates electricity by using the gas supplied from the tank, and a plurality of bands for fixing the tank to the vehicle body. 
     SUMMARY 
     In general, an automatic valve such as a solenoid valve is attached to a cap of the tank. The automatic valve generates operating noise such as clicking noise when the valve is opened and closed. The operating noise (vibration) of the automatic valve may be transmitted from the automatic valve to the tank, from the tank to the band, and from the band to the vehicle body and perceived by a user in the vehicle. The operating noise of the automatic valve is unnecessary for the user. The perception of such operating noise by the user may be a factor that reduces the commercial value of the fuel cell vehicle. 
     In view of the above, provided herein is a technology capable of suppressing the perception of the operating noise of the automatic valve provided in the tank by the user in the vehicle. 
     One aspect of the present disclosure provides a fuel cell vehicle. This fuel cell vehicle includes a vehicle body, a tank mounted on the vehicle body and configured to store gas, a fuel cell unit configured to generate electricity by using the gas supplied from the tank, and a first band configured to fix the tank to the vehicle body. The tank includes a valve-side end including a cap to which an automatic valve is attached, a base-side end opposite to the valve-side end, and a cylindrical tank side surface extending between the valve-side end and the base-side end. The first band extends in a circumferential direction along the tank side surface, and is located within a range of a first predetermined distance ±15 mm from the base-side end or within a range of a second predetermined distance ±15 mm from the valve-side end. The first predetermined distance and the second predetermined distance are values determined depending on a length of the tank. The following relational expressions are satisfied: Y 1 =0.24×L−41.5 mm, and Y 2 =0.17×L−12.5 mm, where Y 1  represents the first predetermined distance, Y 2  represents the second predetermined distance, and L represents the length of the tank. 
     According to research conducted by the inventors, it has been found that the operating noise (vibration) of the automatic valve has a common characteristic and the tank vibrates in a specific mode when the operating noise is transmitted to the tank. In this specific mode, a center point in a longitudinal direction of the tank vibrates with the largest amplitude as an antinode of vibration. In a section between the center point and the base-side end and in a section between the center point and the valve-side end, points having minimum amplitudes appear as nodes of vibration, respectively. It has been found that the positions of the nodes can be determined depending on the length of the tank, that is, can be determined based on the two relational expressions described above. Based on the findings described above, in the fuel cell vehicle, the first band configured to fix the tank to the vehicle body is provided at or near the position of the vibration node. As a result, it is possible to effectively suppress the transmission of the operating noise of the automatic valve provided in the tank to the vehicle body from the tank through the first band. That is, it is possible to suppress the perception of the operating noise by the user in the vehicle. 
     In the aspect described above, the fuel cell vehicle may further include a second band extending in the circumferential direction along the tank side surface and configured to fix the tank to the vehicle body. In this case, the first band may be located within the range of the first predetermined distance ±15 mm, and the second band may be located within the range of the second predetermined distance ±15 mm. According to this structure, the tank can firmly be fixed to the vehicle body by the two bands while suppressing the transmission of the operating noise of the automatic valve to the vehicle body. 
     In the aspect described above, the fuel cell vehicle may further include a neck mount configured to fix the valve-side end of the tank to the vehicle body. According to this structure, the valve-side end where the automatic valve is attached and its inertial force acts can be stabilized on the vehicle body. 
     In the aspect described above, the length of the tank may be 500 mm or more and 1800 mm or less. Further, the length of the tank may be 700 mm or more and 1600 mm or less. When these numerical conditions are satisfied, the two relational expressions related to the first predetermined distance and the second predetermined distance can accurately exert their functions. 
     In the aspect described above, a diameter of the tank may be 200 mm or more and 400 mm or less. Further, the diameter of the tank may be 250 mm or more and 350 mm or less. When these numerical conditions are satisfied, the two relational expressions related to the first predetermined distance and the second predetermined distance can accurately exert their functions. 
     In the aspect described above, the tank may be made of a carbon fiber reinforced resin. According to this structure, the two relational expressions related to the first predetermined distance and the second predetermined distance can accurately exert their functions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein: 
         FIG. 1  is a left side view of a fuel cell vehicle of an embodiment; 
         FIG. 2  illustrates the electrical configuration of the fuel cell vehicle; 
         FIG. 3  illustrates a first tank fixed to a vehicle body; 
         FIG. 4  illustrates a second tank (or a third tank) fixed to the vehicle body; 
         FIG. 5  illustrates the internal structure of a solenoid unit of an automatic valve; 
         FIG. 6  schematically illustrates how the tank vibrates in a specific mode; 
         FIG. 7  illustrates simulation results regarding a position of a first node, in which the horizontal axis represents a length of the tank and the vertical axis represents a distance from a base-side end to the first node; 
         FIG. 8  illustrates simulation results regarding a position of a second node, in which the horizontal axis represents the length of the tank and the vertical axis represents a distance from a valve-side end to the second node; 
         FIG. 9  illustrates a frequency distribution of inertance measured in the vehicle of the embodiment, in which the horizontal axis represents a frequency and the vertical axis represents the inertance; and 
         FIG. 10  illustrates a frequency distribution of inertance measured in a related-art vehicle as a comparative example, in which the horizontal axis represents the frequency and the vertical axis represents the inertance. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     A fuel cell vehicle  10  of an embodiment (hereinafter referred to simply as “vehicle  10 ”) will be described with reference to the drawings. The vehicle  10  of this embodiment is one type of so-called automobile, and travels on roads. In the drawings, a direction FR indicates a front in a fore-and-aft direction (vehicle length direction) of the vehicle  10 , and a direction RR indicates a rear in the fore-and-aft direction of the vehicle  10 . A direction LH indicates a left in a lateral direction (vehicle width direction) of the vehicle  10 , and a direction RH indicates a right in the lateral direction of the vehicle  10 . A direction UP indicates an upper side in a vertical direction (vehicle height direction) of the vehicle  10 , and a direction DN indicates a lower side in the vertical direction of the vehicle  10 . The fore-and-aft direction, the lateral direction, and the vertical direction of the vehicle  10  may herein be referred to simply as “fore-and-aft direction”, “lateral direction”, and “vertical direction”, respectively. 
     As illustrated in  FIG. 1 , the vehicle  10  includes a vehicle body  12  and a plurality of wheels  14   f  and  14   r . The vehicle body  12  is mainly made of a metal material though the material is not particularly limited. The wheels  14   f  and  14   r  are rotatably attached to the vehicle body  12 . The wheels  14   f  and  14   r  include a pair of front wheels  14   f  and a pair of rear wheels  14   r . The number of wheels  14   f  and  14   r  is not limited to four. The vehicle body  12  can mainly be divided into a cabin  12   c  where a user rides, a front portion  12   f  located in front of the cabin  12   c , and a rear portion  12   r  located behind the cabin  12   c.    
     Referring also to  FIG. 2 , the vehicle  10  further includes a plurality of tanks  22  mounted on the vehicle body  12 , and a fuel cell unit  20  also mounted on the vehicle body  12 . The tanks  22  store gas to be supplied to the fuel cell unit  20 . Although not particularly limited, each tank  22  in this embodiment is a constant-volume high-pressure tank, and stores hydrogen gas to be supplied to a fuel electrode (anode) of the fuel cell unit  20 . The fuel cell unit  20  generates electricity by using the gas supplied from the tanks  22 . Since the specific structure of the fuel cell unit  20  is known, detailed description of the structure will be omitted herein. 
     For example, the tanks  22  in this embodiment include a first tank  22   a , a second tank  22   b , and a third tank  22   c . The first tank  22   a  is located below the cabin  12   c , and is arranged along the fore-and-aft direction. The second tank  22   b  and the third tank  22   c  are arranged in the rear portion  12   r  of the vehicle body  12  along the lateral direction. The number of tanks  22  in the vehicle  10  is not limited to three. The vehicle  10  may include at least one tank  22 . The length of the tank  22  may be 500 mm or more and 1800 mm or less. Further, the length of the tank  22  may be 700 mm or more and 1600 mm or less. The diameter of the tank  22  may be 200 mm or more and 400 mm or less. Further, the diameter of the tank  22  may be 250 mm or more and 350 mm or less. The tank  22  may be made of a carbon fiber reinforced resin. 
     The vehicle  10  further includes a traveling motor  16  and a battery pack  18 . Although not particularly limited, the traveling motor  16  is arranged in the rear portion  12   r . The traveling motor  16  is connected to the rear wheels  14   r  to drive the rear wheels  14   r . The vehicle  10  may include another traveling motor that drives the front wheels  14   f  in addition to or in place of the traveling motor  16  that drives the rear wheels  14   r . The vehicle  10  may include another prime mover such as an engine in addition to the traveling motor  16 . 
     The battery pack  18  is arranged in the rear portion  12   r  of the vehicle body  12 . The position of the battery pack  18  is not particularly limited. The battery pack  18  is electrically connected to the traveling motor  16  and the fuel cell unit  20 . As described above, the fuel cell unit  20  generates electricity by using the gas supplied from the tanks  22 . Electric power P 1  generated by the fuel cell unit  20  is supplied to and consumed by the traveling motor  16 . The electric power P 1  generated by the fuel cell unit  20  is also supplied to and stored in the battery pack  18 . For example, when the electric power P 1  generated by the fuel cell unit  20  is insufficient, electric power P 2  stored in the battery pack  18  is supplied to the traveling motor  16 . When the traveling motor  16  generates regenerative electric power P 3 , the regenerative electric power P 3  is supplied to and stored in the battery pack  18 . 
     Next, the tanks  22  and structures for fixing the tanks  22  to the vehicle body  12  will be described with reference to  FIGS. 3 and 4 . As illustrated in  FIGS. 3 and 4 , each tank  22  includes a valve-side end  26 , a base-side end  24  opposite to the valve-side end  26 , and a cylindrical tank side surface  25  extending between the valve-side end  26  and the base-side end  24 . A cap  28  is provided at the valve-side end  26 . An automatic valve  30  is attached to the cap  28 . Although not particularly limited, the automatic valve  30  in this embodiment is a solenoid valve, and includes a valve mechanism  32  and a solenoid unit  34  for driving the valve mechanism  32 . The automatic valve  30  is controlled by a control unit (not illustrated). The automatic valve  30  is generally opened when the vehicle  10  is activated and closed when the vehicle  10  is stopped. 
     As illustrated in  FIG. 5 , the solenoid unit  34  includes a case  50  and a plunger  52 , a stopper  54 , a coil  56 , a spring  58 , and a body  60  arranged in the case  50 . The plunger  52  is arranged between the stopper  54  and the body  60 . The spring  58  is located between the plunger  52  and the stopper  54 , and urges the plunger  52  toward the body  60 . The plunger  52  is connected to the valve mechanism  32 , and moves between the stopper  54  and the body  60  to open or close the valve mechanism  32 . 
     That is, when the automatic valve  30  opens the valve mechanism  32 , the plunger  52  is magnetized by energizing the coil  56 . As a result, the plunger  52  moves toward the stopper  54 . When one end  52   a  of the plunger  52  strikes the stopper  54 , operating noise such as clicking noise is generated. When the automatic valve  30  is closed, the plunger  52  is demagnetized by stopping the energization of the coil  56 . As a result, the plunger  52  moves toward the body  60  by an elastic force of the spring  58 . When the other end  52   b  of the plunger  52  strikes the body  60 , operating noise such as clicking noise is also generated. 
     Referring back to  FIG. 3 , the first tank  22   a  is fixed to the vehicle body  12  by using a first band  40 . The first band  40  extends in a circumferential direction along the tank side surface  25 , and both ends of the first band  40  are fixed to the vehicle body  12 . For example, the width of the first band  40  may be 30 mm or more and 40 mm or less. The length of the first tank  22   a  is approximately 1530 mm, and the diameter of the first tank  22   a  is approximately 300 mm. A distance D 1  from the base-side end  24  to the first band  40  is approximately 300 mm. These numerical values will be described in detail later. The first tank  22   a  is further fixed to the vehicle body  12  by using a neck mount  36 . The neck mount  36  fixes the valve-side end  26  of the first tank  22   a  to the vehicle body  12 . 
     As illustrated in  FIG. 4 , each of the second tank  22   b  and the third tank  22   c  is fixed to the vehicle body  12  by using not only the first band  40  but also a second band  42 . The second band  42  also extends in the circumferential direction along the tank side surface  25 , and both ends of the second band  42  are fixed to the vehicle body  12 . For example, the width of the second band  42  may be 30 mm or more and 40 mm or less. Although not particularly limited, the second tank  22   b  and the third tank  22   c  have the same size as that of the first tank  22   a . That is, the lengths of the second tank  22   b  and the third tank  22   c  are approximately 1530 mm. The diameters of the second tank  22   b  and the third tank  22   c  are approximately 300 mm. The distance D 1  from the base-side end  24  to the first band  40  is also approximately 300 mm. A distance D 2  from the valve-side end  26  to the second band  42  is approximately 270 mm. The numerical value related to the distance D 2  will also be described in detail later. Similarly to the first tank  22   a , each of the second tank  22   b  and the third tank  22   c  is further fixed to the vehicle body  12  by using the neck mount  36 . 
     As described above, in the vehicle  10  of this embodiment, the tanks  22  are mounted on the vehicle body  12 , and the automatic valve  30  is attached to the cap  28  of each tank  22 . As described above, the automatic valve  30  is, for example, a solenoid valve, and generates the operating noise such as clicking noise when the valve is opened or closed. The operating noise (vibration) of the automatic valve  30  may be transmitted from the automatic valve  30  to the tank  22 , from the tank  22  to the bands  40  and  42 , and from the bands  40  and  42  to the vehicle body  12  and perceived by the user in the vehicle (that is, in the cabin  12   c ). 
     In this regard, the operating noise (vibration) of the automatic valve  30  has a common characteristic (for example, a similar frequency distribution). As a result of simulating the behavior of the tank  22  by a computer in consideration of the characteristic of the operating noise, it has been found that the tank vibrates in a specific mode when the operating noise of the automatic valve  30  is transmitted to the tank  22 . As illustrated in  FIG. 6 , in this specific mode, a center point CN in a longitudinal direction of the tank  22  vibrates with the largest amplitude as an antinode of vibration. In a section between the center point CN and the base-side end  24  and in a section between the center point CN and the valve-side end  26 , points N 1  and N 2  having minimum amplitudes appear as nodes of vibration, respectively. It has been found that the positions of the nodes N 1  and N 2  vary depending on the length of the tank. 
       FIG. 7  illustrates results of the above simulation for the first node N 1  appearing in the section between the center point CN and the base-side end  24 . As illustrated in  FIG. 7 , when a length L of the tank  22  is approximately 1530 mm, a distance Y 1  from the base-side end  24  to the first node N 1  is approximately 300 mm. When the length L of the tank  22  is approximately 1270 mm, the distance Y 1  from the base-side end  24  to the first node N 1  is approximately 280 mm. When the length L of the tank  22  is approximately 750 mm, the distance Y 1  from the base-side end  24  to the first node N 1  is approximately 125 mm. These results demonstrate that there is a relationship of Y 1 =0.24×L−41.5 mm between the distance Y 1  from the base-side end  24  to the first node N 1  and the length L of the tank  22 , and a variation of ±15 mm may actually occur with respect to the relational expression. 
       FIG. 8  illustrates results of the simulation for the second node N 2  appearing in the section between the center point CN and the valve-side end  26 . As illustrated in  FIG. 8 , when the length L of the tank  22  is approximately 1530 mm, a distance Y 2  from the valve-side end  26  to the second node N 2  is approximately 270 mm. When the length L of the tank  22  is approximately 1270 mm, the distance Y 2  from the valve-side end  26  to the second node N 2  is approximately 170 mm. When the length L of the tank  22  is approximately 750 mm, the distance Y 2  from the valve-side end  26  to the second node N 2  is approximately 130 mm. These results demonstrate that there is a relationship of Y 2 =0.17×L−12.5 mm between the distance Y 2  from the valve-side end  26  to the second node N 2  and the length L of the tank  22 , and a variation of ±15 mm may actually occur with respect to the relational expression. 
     Based on the findings described above, the positions of the vibration nodes N 1  and N 2  on the tank  22  can be determined in advance from the length L of the tank  22 . The bands  40  and  42  for fixing the tank  22  to the vehicle body  12  can be provided at or near the positions of the vibration nodes N 1  and N 2 , respectively. Specifically, when the distance Y 1  calculated for the first node N 1  is defined as a first predetermined distance, it is appropriate that the first band  40  be arranged within a range of the first predetermined distance ±15 mm (that is, Y 1 ±15 mm) from the base-side end  24 . When the distance Y 2  calculated for the second node N 2  is defined as a second predetermined distance, it is appropriate that the second band  42  be arranged within a range of the second predetermined distance ±15 mm (that is, Y 2 ±15 mm) from the valve-side end  26 . The vehicle  10  in this embodiment is designed so that the distances D 1  and D 2  (see  FIGS. 3 and 4 ) satisfy these relationships. 
       FIG. 9  illustrates inertance measured in the vehicle  10  of this embodiment.  FIG. 10  illustrates inertance measured in a related-art vehicle as a comparative example. As indicated by an arrow A in  FIG. 10 , in the vehicle  10  of this embodiment, transmission of vibration caused by the operating noise of the automatic valve  30  is significantly suppressed as compared with the related-art vehicle. As a result, it is possible to avoid or suppress the perception of the operating noise by the user in the vehicle. The related-art vehicle herein means that the positions of the first band  40  and the second band  42  in the vehicle  10  of this embodiment are determined based on a design concept of the related art. 
     Although the embodiment is described above in detail, the embodiment is only illustrative and is not intended to limit the claims. The technologies described in the claims encompass various modifications and changes to the specific examples described above. The technical elements described herein or illustrated in the drawings exert technical utility solely or in various combinations, and are not limited to the combination described in the claims as filed. The technologies described herein or illustrated in the drawings may simultaneously achieve a plurality of objects, and exert technical utility by achieving one of the objects.