JPH1038196A - Aluminum or aluminum alloy-made air tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight aluminum or aluminum alloy-made air tank easily manufactured and having low cost. SOLUTION: A first air tank main body 1 is constituted of a first body part 31a and first end plates 32a, 32b formed on both ends of the first body part 31a. The first body part 31a and the first end plates 32a, 32b are integrally provided by hydraulically bulging an aluminum alloy-made extruded material, and the first end plates 32a, 32b are molded by being drawn by spinning after hydraulic bulging. Connecting nozzles (bosses) 7, 8a, 8b are formed on the center parts of the first end plates 32a, 32b and the side surface of the first body part 31a. The connecting nozzles are provided by projecting work when the first air tank main body 1 is hydraulically bulged. Therefore, it is unnecessary to provide after-processing such as boring work and welding work to the air tank main body 1 in order to form the connecting nozzles, and also it is unnecessary to provide a thick part in order to process the connecting nozzles. Therefore, the air tank has high precision, and the manufacturing cost is extremely low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum or aluminum alloy air tank used for an air brake system of a truck or the like. In the present specification, pure aluminum and aluminum alloy are collectively referred to as aluminum.

[0002]

2. Description of the Related Art Conventionally, steel tanks have been used as air tanks for use in air brake systems for trucks and the like. In recent years, there has been a demand for further reducing the weight of trucks in order to further increase the load capacity of the trucks and to prevent environmental destruction. In recent years, the number of vehicles equipped with an anti-lock brake system has been increasing, and such trucks require more air tanks than conventional ones. For these reasons, an air tank made of aluminum has been proposed in order to further reduce the weight of the air tank.

FIG. 6 is a sectional view showing an air tank of the first prior art (Japanese Utility Model Laid-Open No. 6-74549). As shown in FIG. 6, the air tank 51 includes a main tank 52 and sub tanks 53, 5 provided at both ends of the main tank 52.
And 4. The main tank 52 includes a first constituent member 55 and a second constituent member 56,
The constituent member 55 and the second constituent member 56 have the same shape.
The first component member 55 has a bottomed cylindrical shape, and includes a first bottom portion 63 protruding outward in the axial direction and a first cylindrical portion 59 connected to the first bottom portion 63. First
The cylindrical portion 59 is obtained by pressing.
The first bottom portion 63 is obtained by spatula drawing. Similarly, the second component member 56 includes a second bottom portion 64 and a second cylindrical portion 60 that are convex toward the outside in the axial direction. An opening edge 68 of the second cylindrical portion 60 is coaxially butted against an opening edge 67 of the first cylindrical portion 59,
The butted portion is welded from the outside to form a welded portion 52a.

A third bottom 63 of the first component member 55 has a third
The constituent member 57 is connected. The third component 57 has the same shape as the first component 55, and the third bottom 65 and the third
And a cylindrical portion 61. The open end 69 of the third cylindrical portion 61 is coaxial with the first component 55.
Is connected to the peripheral portion 63a of the first bottom portion 63, and this connection portion is welded from the outside to form a welded portion 52b. On the other hand, a fourth component 58 is connected to the second bottom 64 of the second component 56. The fourth component 58 has the same shape as the second component 56, and includes a fourth bottom 66 and a fourth cylindrical portion 62. Second component member 56
The opening end 70 of the fourth cylindrical portion 62 is coaxial with
Is connected to the peripheral portion 64a of the second bottom portion 64, and this connection portion is welded from the outside to form a welded portion 52c. The main tank 52 and the sub tanks 53, 5
The air tank 4 is provided with a connection nozzle (not shown) for inflow or outflow of compressed air. The air tank thus configured is made of aluminum, so that it is lightweight and has welds 52a, 52b. And 52c, which are advantageous in that manufacture is easy.

FIGS. 7A and 7B are views showing an air tank according to a second prior art, in which FIG. 7A is a front view, FIG. 7B is a cross-sectional view showing an enlarged nozzle portion, and FIG. FIG. 3 is a cross-sectional view (JP-A-6-300192). As shown in FIG. 7A, the main body 80 of the air tank is a cylindrical extruded material, and is made of an aluminum alloy specified in JIS 6063 or the like. End plates 75 made of aluminum are joined to both ends of the body 80 by welding. Each end plate 75 has a convex shape toward the outside in the axial direction. Two disk-shaped partitioning end plates 76 are arranged in the body 80 so that their axes are coaxial with the body 80. End plate 76 for each partition
Is made of aluminum, has a concave shape toward the end of the body 80, and has a peripheral edge welded to the inner wall of the body 80. As described above, the inside of the body 80 is reduced to 3 by the two end plates 75 and the two partition end plates 76.
It is divided into a main tank 80a surrounded by a partition head plate 76 and sub tanks 80b and 80c surrounded by a partition head plate 76 and a head plate 75.

A protruding pedestal 81 having a constant width is formed on the outer surface of the main body 80 over the entire length in the longitudinal direction. The protruding pedestal portion 81 is obtained by being formed integrally with the body portion 80 during extrusion molding. Further, since the protruding pedestal portion 81 is for providing a connection nozzle described later, a plurality of protruding pedestal portions 81 are provided in accordance with the required number of nozzles and the nozzle forming portion. Further, as shown in FIG. 7B, the pedestal outer surface 81a of the protruding pedestal portion 81 is a plane perpendicular to the radial direction of the body portion 80 in order to easily connect a connection nozzle described later. . In the protruding base 81,
A communication hole 81b is provided, and a connection nozzle 82 is welded to the pedestal outer surface 81a so as to be coaxial with the communication hole 81b. A female screw 82a is provided on the inner surface of the connection nozzle 82.
Are formed, and the pipe 83 is screwed. The connection nozzle 82 is provided at the center of the end plate 75 in addition to the protruding base 81.

In the second prior art, a projecting portion 85 may be formed on the body 80 of the main body as shown in FIG. The protruding portion 85 extends in the longitudinal direction of the body portion 80, similarly to the protruding pedestal portion 81,
It is obtained by being molded integrally with the body 80 during extrusion molding. However, the thickness of the protruding portion 85 in the radial direction of the body portion 80 is thicker than that of the protruding pedestal portion 81. The outer surface 85a of the protruding portion 85 is
Similarly to the above, a plane perpendicular to the radial direction of the body 80 is formed. A connection hole 85a is formed in the protruding portion 85, and a female screw 85b is formed on the inner surface of the connection hole 85a.
Thereby, the pipe 83 is screwed into the connection hole 85a, similarly to the protruding pedestal portion 81 shown in FIG. 7B.

The air tank thus configured has the advantage of being lightweight because it is made of aluminum. In addition, in the case where the protruding pedestal portion 81 shown in FIG. 7B is provided, there is an advantage that the connection nozzle 82 is easily welded to the outer surface 81a because the pedestal outer surface 81a is flat. Further, in the case where the protruding portion 85 shown in FIG. 7C is provided, since the connection hole 85a is obtained at the time of molding, there is an advantage that it is not necessary to weld the connection nozzle 82.

[0009]

However, the above-mentioned prior art has the following problems. First, in the first prior art shown in FIG. 6, it is necessary to provide a plurality of connection nozzles (bosses) on the outer surfaces of the main tank 52 and the sub tanks 53 and 54 in the post-process as necessary in the post-process. There is a problem. That is, each component 55 to 55
58 is formed by extrusion, and the bottoms 63 to 66 are formed.
In addition to the necessity of drawing and forming the connection nozzle, it is necessary to provide a through hole in the main tank 52 and the sub tanks 53 and 53 and then weld the connection nozzle to the outer surface of each tank so as to be coaxial with the through hole. is there. As described above, since the number of manufacturing steps is large and the work is troublesome, there is a disadvantage that the cost of the obtained air tank is high. In particular, since the outer surface of each tank is a curved surface, welding of the connection nozzle is extremely complicated.

On the other hand, in the second prior art shown in FIG. 7B, a protruding pedestal 81 is provided on the main body 80, and the outer surface 82 of the protruding pedestal 81 is flat.
There is an advantage that the connection nozzle 82 can be easily welded to the outer surface 82. Further, in the second conventional technique shown in FIG. 7C, since the connection hole 85a is provided at the time of extrusion molding, there is an advantage that a welding step is not required. However, in the air tank shown in FIG.
1 extends in the longitudinal direction of the body 80, and FIG.
In the air tank shown in FIG. 5, since the protruding portion 85 extends in the longitudinal direction of the body portion 80, a protruding pedestal portion or a protruding portion is formed even in a portion where there is no connection nozzle or the like, and the weight of the air tank increases. . For this reason, the weight of the air tank of the second prior art is substantially the same as that of the steel air tank, and there is a problem that a lightweight air tank cannot be obtained. Particularly, in the air tank shown in FIG. 7B, the weight of the protruding portion 85 is further increased because the thickness of the protruding portion 85 is large.

The present invention has been made in view of the above problems, and has as its object to provide a lightweight aluminum or aluminum alloy air tank which is easy to manufacture and low in cost.

[0012]

An aluminum or aluminum alloy air tank according to the present invention comprises a first body,
A first air tank body in which the first end plates at both ends of the first body are integrally formed by hydraulic bulging, and one or more first connections obtained by extending the first air tank body during bulging; And a nozzle.

In this case, a second air tank main body in which the second body and a second end plate at one end of the second body are integrally formed by hydraulic bulging, and an overhang during bulging of the second air tank main body. It has one or a plurality of second connection nozzles obtained by processing, and the first end plate of the first air tank main body is fitted into the other end of the second air tank main body and is airtightly fixed. Good.

Further, a second air tank body in which the second body and a second end plate at one end of the second body are integrally formed by hydraulic bulging, a third body, and a third body. One or more third air tank bodies formed integrally with a third end plate at one end by hydraulic bulging, and one or more second connection nozzles obtained by extending the second air tank body at the time of bulging. And one or a plurality of third airbags obtained by extending the third body during bulging of the third air tank body.
A connection nozzle, and the other end of the second air tank main body is fitted in one of the third end plates of the third air tank main body to be air-tightly fixed, and the first end plate of the first air tank main body is It may be fitted in one of the other ends of the third air tank body and fixed in an airtight manner.

In the air tank made of aluminum or aluminum alloy according to the present invention, the first air tank main body is obtained by being integrally formed by hydraulic bulging. That is, the first body is obtained by molding by hydraulic bulging, and the first head plate is obtained by squeezing during the hydraulic bulging. The first connection nozzle is obtained by bulging during hydraulic bulging. As described above, in the hydraulic bulging process, the first end plate and the first connection nozzle are formed, so that there is no need to form the air tank by joining the first end plate to the first body in a later step. Further, it is not necessary to join the first connection nozzle to the obtained hole by welding or the like after the first body portion and the first end plate are perforated. Therefore, the manufacturing process is simplified, and the manufacturing cost is reduced. Further, since it is not necessary to provide the first connection nozzle in a subsequent step, it is not necessary to provide a pedestal or the like for connecting the first connection nozzle on the first body, and the first connection nozzle is not required.
The body becomes thin over the entire area. Thereby, the aluminum or aluminum alloy air tank according to the present invention is extremely lightweight.

When the aluminum or aluminum alloy air tank is composed of two air tank bodies, the second air tank body may be fixed to the first air tank body. In this case, the second body of the second air tank body is obtained by being formed by hydraulic bulging, and the second end plate at one end of the second body is squeezed during hydraulic bulging. It shall be assumed. In addition to the high roundness of the second body, the first end plate of the first air tank body is airtight at the other end of the second air tank body because the first end plate has a predetermined curved shape. And is fixed. For example, when welding is performed as the fixing means, air does not leak from the welded portion, and the welded portion is extremely good.

Further, an air tank made of aluminum alloy is
When it is constituted by more than one air tank body, one or more third air tank bodies are prepared. It is assumed that the third body of each third air tank is obtained by molding by hydraulic bulging, and the third end plate at one end of the third body is obtained by squeezing at the time of hydraulic bulging. . For example,
When the number of the air tank main bodies is three, the number of the third air tank main bodies is one, and the other end of the second air tank main body is fitted in the third end plate of the third air tank main body to be air-tightly fixed. The first end plate of the first air tank main body is fitted and fixed to the other end of the third air tank main body. When the number of the air tank bodies is four, the third air tank body is two, and the other end of the second air tank body is connected to one of the third air tank bodies.
The third end plate of the air tank main body is fitted and fixed in an airtight manner, and the third end plate of the other third air tank main body is connected to one third end plate.
The first end plate of the first air tank main body is fitted and fixed to the other end of the other air tank main body. When the number of air tank bodies is five or more, three or more third air tank bodies may be prepared and each air tank may be fixed as described above. Since all the air tank bodies are obtained by hydraulic bulging, the airtightness between the tank bodies is good, and the leakage of the internal air can be prevented.

[0018]

Next, an embodiment of the present invention will be described.
This will be specifically described with reference to the accompanying drawings. FIG. 1 is a diagram showing an aluminum or aluminum alloy air tank according to a first embodiment of the present invention, wherein (a) is a front view,
(B) is a sectional view showing the connection nozzle in an enlarged manner, and (c) is a side view. As shown in FIG. 1A, the first air tank body 1 includes a first body 31a and first end plates 32a and 32b formed at both ends of the first body 31a. The first body 31a of the first air tank body 1 and the first
The head plates 32a and 32b are obtained by integrally molding an extruded material made of an aluminum alloy by hydraulic bulging.
After the above-described hydraulic bulging, the first end plates 32a and 32b are formed into a round shape by narrowing both ends of the cylinder by spinning. Therefore, the first body portion 31a and the first end plate 32
There is no seam at the connection with the a and 32b, and the connection is made smoothly. The first end plates 32a and 32b are
A connection nozzle (boss) for air inflow and outflow is formed in the center of the first end plates 32a and 32b so as to be coaxial with the first body 31a along the axial direction of 1a. 7
Are formed. Similarly, connection nozzles 8a and 8b are formed on the side surface of the first body 31a.

As shown in FIG. 1B, the connection nozzle 7
Are obtained by bulging during hydraulic bulging of the first air tank body 1 and are smoothly connected to the first air tank body 1. The same applies to the connection nozzles 8a and 8b. These connection nozzles 8a and 8b can be formed by processing the first body 31a by bulging so as to protrude from the first body 31a, and then threading the protrusion. Further, as shown in FIG. 1C, two connection nozzles 8a and 8b are provided along the circumferential direction of the cylindrical portion 31. The first air tank body 1
Is formed from an aluminum alloy such as JIS 6000 series.

In the air tank made of aluminum or aluminum alloy thus configured, the first body 31a and the first end plates 32a, 32b are simultaneously formed integrally by hydraulic bulging, so that the first body is formed. There is no need to form the first air tank body 1 by joining the 31a and the first end plates 32a and 32b by welding or the like. In addition, when the tank is formed by the hydraulic bulging process, the connection nozzles 7, 8a, and 8b are simultaneously formed by performing drawing and overhanging processing on the first air tank body 1, so that the first air tank body 1 is formed with holes. There is no need to form a connection nozzle by providing a post-process such as welding. Therefore, unlike the related art, there is no need to provide an extra thick portion in the longitudinal direction of the trunk portion, so that the weight can be reduced, the manufacturing process of the air tank is simplified, and the manufacturing cost is extremely low. Further, since the first air tank main body 1 is obtained by hydraulic bulging, the dimensional tolerance of the diameter of the first body 31a is small and the roundness is high. Similarly, the first end plate 32
Since a and 32b are obtained by hydraulic bulging, they have a desired shape such as a spherical surface with high accuracy.

Note that, unlike the embodiment described later, since there is no welded portion, the air tank in this embodiment can withstand high pressure.

FIGS. 2A and 2B are views showing an air tank made of aluminum or an aluminum alloy according to a second embodiment of the present invention, wherein FIG. 2A is a front view, FIG. (C) is a side view. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and the detailed description thereof will be omitted.
As shown in FIG. 2, the air tank includes a first air tank main body 1 and a second air tank main body 2,
The air tank body 1 is substantially the same as that of the first embodiment. However, the connection nozzle 7 is not formed on the first end plate 32b. The second air tank main body 2 includes a second body 31b and a second end plate 32c formed at one end of the second body 31b. Second trunk portion 31b and second end plate 32
c is obtained by being integrally formed by hydraulic bulging, and the second end plate 32c is formed by squeezing by spinning after hydraulic bulging. Second
A connection nozzle (boss) 7 is formed at the center of the end plate 32c so as to be coaxial with the second body 31b. The second body 31b has the same diameter as the first body 31a,
Connection nozzles 8c and 8d are formed on the peripheral surface of 1b.
The other end of the second body 31b is an open end, and the end plate 32b of the first air tank main body 1 is airtightly fitted into the open end. As shown in FIG. 2 (b), the other end of the second body 31b is in contact with the boundary between the first body 31a and the end plate 32b, and the abutting portion is subjected to butt welding to perform welding. A part 15 is formed. The connection nozzles 8a and 8c are located on the same plane passing through the axis of the air tank, and as shown in FIG. 8d is present.

The connection nozzles 7, 8a, 8b, 8c,
8d is obtained by extending the first air tank main body 1 and the second air tank main body 2 when performing hydraulic bulging.

Since the air tank made of aluminum or aluminum alloy thus configured is obtained by molding by bulging, the first body portion 31a and the second body portion 31b have extremely high roundness. Similarly, since the first end plate 32b is obtained by molding by bulging, the curved shape of the first end plate 32b is desired. For this reason, in the present embodiment, in addition to achieving the same effects as the first embodiment shown in FIG. 1, the other end of the second body 31b is connected to the boundary between the first body 31a and the first end plate 32b. Since it is in close contact with the portion, the welding state of the welded portion 15 is extremely good.

FIG. 3 is a front view showing an air tank made of aluminum or aluminum alloy according to a third embodiment of the present invention. 3, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 3, the air tank includes a first air tank main body 1, a second air tank main body 2, and a third air tank main body 3, and the first air tank main body 1 and the second air tank main body 2
Are the same as those of the second embodiment. The third air tank body 3 includes a third body 31c and a third end plate 32d formed at one end of the third body 31c. The third trunk portion 31c and the third end plate 32d are obtained by being integrally formed by hydraulic bulging, and the third end plate 32d is formed by being squeezed by spinning after being subjected to hydraulic bulging. . Third air tank body 3
Has the same diameter as the air tank bodies 1 and 2, and the third body 3
Connection nozzles 8e and 8f are formed on the side surface of 1c.
The end plate 32b of the first air tank main body 1 is airtightly fitted to the other end of the third trunk portion 31c. On the other hand, the third trunk 31
The third end plate 32c of c is fitted into the other end of the second body 31b. As in the second embodiment shown in FIG. 2, a welded portion 15 is formed at the joint of each tank body.

The aluminum or aluminum alloy air tank thus configured is obtained by molding each tank by bulging.
a to 31c have extremely high roundness and the end plates 31a to 31c
The curved surface shape of 31d is very close to the desired shape. This provides the same effect as that of the second embodiment shown in FIG. 2, and has the effect that the number of tanks is large and can be used for various purposes. Play. In this embodiment, the number of the tank bodies is set to three, but may be larger.

Next, an installation mode of the air tank made of aluminum or aluminum alloy of this embodiment will be described.
FIG. 4 is a diagram showing a first installation mode of an aluminum or aluminum alloy air tank, where (a) is a side view,
(B) is a front view. 4, the same components as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 4, in this installation mode, two air tanks shown in FIG. 3 are bundled and fixed to the support member 41. FIG. 4 (a)
As shown in FIG. 3, the support member 41 includes a bottom plate 42 and a side plate 43.
And a swash plate 44. At one end of the bottom plate 42,
The lower end of the side plate 43 is connected to be perpendicular to the bottom plate 42, and the side plate 43 is fixed to a truck or the like,
A recess 45 is formed. The swash plate 44 is connected so that both ends are connected to the other end of the bottom plate 42 and the upper end of the side plate 43, respectively.
Is arranged. In the upper half and lower half of the swash plate 44,
Each has a concave portion 49 extending in the horizontal direction,
The curvature of each concave portion 49 is the same as the curvature of the air tank 40 in the circumferential direction. The air tank 40 is disposed on each concave portion 49. Reinforcing members 46 are disposed between the substantially central portion of the swash plate 44 and the bottom plate 42 and between the substantially central portion of the swash plate 44 and the side plate 43. Upper end of swash plate 44, air tank 4
An air tank fixing tape 47 is stretched over the upper portion of the swash plate 44 and the lower end of the swash plate 44. One end of the fixing tape 47 is fixed to the upper end of the swash plate 44 by bolts 48 a and the other end of the tape 47. Is a bolt 48 at the lower end of the swash plate 44
b.

Since the air tank of this embodiment is lightweight,
Even when two air tanks are installed on a truck or the like via the support member 41, the weight burden does not increase. The number of air tanks installed on the support member 41 is not limited to two, and three or more air tanks may be installed as shown in FIG.

[0029]

As described above, according to the present invention,
Since the air tank body and the connection portion are obtained by molding by hydraulic bulging, it is possible to obtain a lightweight and rigid aluminum or aluminum alloy air tank which is high in dimensional accuracy, low in cost, easy to assemble, and lightweight. Can be. Also, there is no need to provide a thick portion for the connection portion.

[Brief description of the drawings]

FIG. 1 is a view showing an aluminum or aluminum alloy air tank according to a first embodiment of the present invention, wherein (a)
Is a front view, (b) is a cross-sectional view showing an enlarged connection nozzle,
(C) is a side view.

FIG. 2 is a view showing an aluminum or aluminum alloy air tank according to a second embodiment of the present invention, wherein (a)
Is a front view, (b) is a sectional view showing an enlarged welded portion,
(C) is a side view.

FIG. 3 is a front view showing an aluminum or aluminum alloy air tank according to a third embodiment of the present invention.

4A and 4B are views showing an installation form of an aluminum or aluminum alloy air tank, wherein FIG. 4A is a side view and FIG.
Is a front view.

FIG. 5 is a side view showing another embodiment of an aluminum or aluminum alloy air tank.

FIG. 6 is a cross-sectional view showing an air tank of the first prior art.

FIGS. 7A and 7B are views showing an air tank according to a second conventional technique, wherein FIG. 7A is a front view, FIG. 7B is a cross-sectional view showing an enlarged nozzle portion, and FIG. It is sectional drawing.

[Explanation of symbols]

 1; first air tank main body 2; second air tank main body 3; third air tank main body 7, 8a, 8b, 8c, 8d, 8e, 8f; connection nozzles 31a, 31b, 31c; Endplates 40, 51; Air tank 41; Support member 42; Bottom plate 43; Side plate 44; Swash plate 45; Depression 46; Reinforcement member 47; Air tank fixing tapes 48a, 48b; Bolt 49; 52b, 52c; welded parts 53, 54, 80b, 80c; sub tank 55; first constituent member 56; second constituent member 57; third constituent member 58; fourth constituent member 59; first cylindrical part 60; Part 61; third cylindrical part 62; fourth cylindrical part 63; first bottom parts 63a, 64a; peripheral part 64; second bottom part 65; third bottom part 66; fourth bottom part 67. 68, 69, 70; opening edge 75; end plate 76; partitioning end plate 80; main body body 81; protruding pedestal portion 81a; pedestal outer surface 81b; communication hole 82; connection nozzle 82a, 85b; Part 85a; connection hole

Claims (3)

[Claims] 1. A first body and first ends of both ends of the first body.
Aluminum having a first air tank main body formed integrally with a head plate by hydraulic bulging and one or a plurality of first connection nozzles obtained by extending the bulge processing of the first air tank main body. Or an aluminum alloy air tank. 2. A second body and a second body at one end of the second body.
A second air tank main body formed integrally with a head plate by hydraulic bulging, and one or more second connection nozzles obtained by extending the second air tank main body at the time of bulging; The aluminum or aluminum alloy air tank according to claim 1, wherein the first end plate of the first air tank main body is fitted into the other end of the main body and is air-tightly fixed. 3. A second body, and a second body at one end of the second body.
A second air tank main body in which a head plate is integrally formed by hydraulic bulging, a third body, and one or a plurality of third heads in which one end of the third body is integrally formed by hydraulic bulging. 3 air tank body, one or a plurality of second connection nozzles obtained by bulging at the time of bulging the second air tank body, and bulging the third body at the time of bulging the third air tank body. One or a plurality of third connection nozzles, and the other end of the second air tank main body is fitted in any one of the third end plates of the third air tank main body, and is air-tightly fixed. 2. The air tank made of aluminum or aluminum alloy according to claim 1, wherein the first end plate of the air tank main body is fitted into one of the other ends of the third air tank main body and air-tightly fixed. 3.