JP5453144B2 - Air spring - Google Patents

Description

  The present invention relates to an air spring used for truck automobiles, railway vehicles, and the like. More specifically, the present invention relates to a cylindrical rubber film, a large-diameter plate-like member hermetically joined to one end portion in the axial direction thereof, and a cylindrical rubber. A peripheral surface capable of rolling and guiding an inverted tube portion formed by folding the other end side with elastic deformation of the cylindrical rubber film. The present invention relates to an air spring formed on a piston.

  As this type of air spring, those disclosed in Patent Document 1 and Patent Document 2 are known. That is, as shown in FIG. 6, the air spring B includes a vertical cylindrical diaphragm (an example of a cylindrical rubber film) 1 that forms a wall portion of the first internal space S <b> 1 that is a gas chamber, and a vertical axis thereof. A disk-shaped upper plate (an example of a large-diameter plate member) 2 that is caulked and fixed to a large-diameter bead portion (an example of one end portion) 1A formed at the upper end of a diaphragm 1 having a center P, and a lower end of the diaphragm 1 And a piston 3 tightly fitted to a small-diameter bead portion (an example of the other end portion) 1B.

  The upper plate 2 includes an attachment flange 4 for attaching and fixing the upper plate 2 to the vehicle body frame F (see FIG. 3), and an air supply / exhaust hole 5 into the diaphragm 1. The air supply / discharge hole 5 is constituted by a metal pipe 12 or the like that is welded to the upper plate 2 and is hermetically fixed. The piston 3 is covered with a fitting cylinder portion 8 having a short vertical length for the small-diameter bead portion 1B of the diaphragm 1 to be dropped and externally fitted, and an inverted cylinder portion 1C which is a portion where the lower side of the diaphragm 1 is folded inward. It consists of a straight cylinder-shaped main tube portion 7 and the like, and is configured to have a common axis P with the diaphragm 1. A bottom plate 9 is attached to the lower end of the main cylinder portion 7, and a mounting bolt 10 for fixing to the axle side member is provided on the bottom plate 9.

  Thus, the diaphragm 1 is pushed so as to cover the piston 3, and the outer peripheral surface 3A of the main cylinder portion 7 is configured to be able to roll and guide the inverted cylinder portion 1C. A circular hole 11 is formed in the upper surface of the fitting cylinder portion 8, and the second internal space S <b> 2 inside the piston 3 and the first space S <b> 1 are communicated with each other through the circular hole 11. A stopper rubber 6 is bolted to the upper surface of the piston 3 via a bead holding disc 13. Reference numeral 2B denotes an inner plate for sandwiching the upper bead portion 1A by this and the main plate 2A.

  Now, in a bus which is an example of a vehicle equipped with an air spring, as shown in FIG. 4 of Patent Document 3, an axle (24) which is an axle side member and a frame (F) which is passed under the vehicle body. In general, an air spring (A) is interposed between the upper and lower sides. However, in a low floor vehicle such as a non-step bus that has become barrier-free in recent years, the space between the bottom of the vehicle body and the axle is so narrow that an air spring cannot be arranged. Therefore, in such a case, as shown in FIG. 3, air springs A (B) are arranged between the lower surface 21 a of the tire house portion 21 of the vehicle body 20 and the leg member 23 erected from the axle 22. Such a configuration will be adopted.

  However, in the structure shown in FIG. 3, the height difference between the rolling center X provided on the axle 22 side and the air spring A increases, and the piston 3 attached to the axle 22 side in accordance with the rolling by the radius R moves in the vertical direction. Not only will it be displaced in the horizontal direction as well. As a result, as shown in FIG. 4, the upper plate 2 is displaced in the direction in which it sinks into the axle 22 (the state indicated by the phantom line in FIG. 4) or is displaced in the floating direction (the state indicated by the one-dot broken line in FIG. 4). ), The piston 3 is displaced laterally with respect to the upper plate 2 and the curvature of the folded portion 1D of the diaphragm 1 is clearly reduced. In the dimension specifications of each part shown in FIG. 4, the curvature of the folded part 1 </ b> D at the outer part of the vehicle body is the smallest when the upper plate 2 is indicated by a one-dot broken line rolled upward.

  As described above, the curvature of the folded portion 1D may become extremely small, and if this phenomenon continues, there is a disadvantage that the diaphragm 3 is relatively early in the air due to breakage such as cracking or tearing. May occur.

JP 2005-36860 A JP 2007-51745 A JP 2007-51745 A

  In view of the above circumstances, the object of the present invention is that the folded portion of the diaphragm is easily damaged at an early stage even if it is used in a location that is clearly displaced not only in the vertical direction but also in the horizontal direction due to structural improvements. The object is to provide an improved air spring which has a tendency to be suppressed or eliminated and to have practical durability.

The invention according to claim 1 includes a cylindrical rubber film 1, a large-diameter plate-like member 2 hermetically joined to one end in the axial center P direction of the cylindrical rubber film 1, and the axial center P direction of the cylindrical rubber film 1. A peripheral surface 3A having a piston 3 hermetically bonded to the end portion and capable of rolling and guiding a reverse cylinder portion 1C formed by folding the other end side with elastic deformation of the cylindrical rubber film 1; In the air spring formed on the piston 3,
The piston 3 is a joint side end 3a on the side where the cylindrical rubber film 1 is hermetically joined in the direction of the axis P in this, and a downwardly expanding tapered cylinder continuing below the joint side end 3a. Comprising a portion 3b and a large-diameter cylindrical portion 7 continuing below the tapered cylindrical portion 3b, the joining side end portion 3a being formed of a stepped cylindrical member whose diameter is reduced ,
The length L in the direction of the axis P of the joining side end 3a is such that the cylindrical rubber film 1 has a minimum curvature at the folded portion 1D of the cylindrical rubber film 1 to the piston 3. It is determined to be more than the covering depth,
The ratio of the diameter of the end portion on the large-diameter plate-like member 2 side in the joint-side end portion 3a to the end portion on the large-diameter plate-like member 2 side in the large-diameter cylindrical portion 7 is set to 92 to 97%. it is characterized in that there.

  According to the invention of claim 1, the details will be described in the section of the embodiment, but since the piston is formed of a stepped cylindrical member having a reduced diameter on the joining side end portion, the large-diameter plate-like member is used. In the case where the piston is relatively laterally displaced while being separated in the axial direction, the curvature of the folded portion of the cylindrical rubber film can be efficiently increased. As a result, it is possible to avoid damages such as early cracks and tears due to the small curvature of the folded portion and inconvenience of air leakage caused thereby. As a result, the tendency of the folded portion of the cylindrical rubber film to be easily damaged early is suppressed or eliminated even if it is used in places that are clearly displaced not only vertically but also horizontally due to structural improvements. Thus, an improved air spring having practical durability can be provided.

According to the invention of claim 1, the curvature of the folded portion in the cylindrical rubber film is maintained while maintaining the spring constant associated with the cushion in which the large-diameter plate member and the piston approach each other in the axial direction as much as possible. Since the diameter can be increased, it is possible to provide an air spring that can improve durability while maintaining good suspension characteristics.

Sectional view showing structure of air spring (Example 1) Plan view of FIG. Schematic diagram of the main part showing an example of the structure adopted for a non-step bus Operational diagram showing the state near the turn-up part during rolling Schematic diagram of the main part showing the situation where the tightest curvature of the folded part is improved Sectional view showing a conventional air spring

  Embodiments of an air spring according to the present invention will be described below with reference to the drawings. In the air spring A of the embodiment, portions having the same functions as those of the air spring B of the conventional example shown in FIG. Contains.

[Example 1]
As shown in FIGS. 1, 2, and 3, the air spring A according to the first embodiment includes a diaphragm (an example of a cylindrical rubber film) 1 having a longitudinal axis P and an upper end (direction of the axis P). An upper plate (an example of a large-diameter plate-like member) 2 that is air-tightly joined to one end of the piston 2 and a piston 3 that is air-tightly joined to the lower end of the diaphragm 1 (an example of the other end in the axis P direction). The piston 3 is formed with a circumferential surface 3 </ b> A capable of rolling and guiding the inverted tube portion 1 </ b> C formed by folding back the lower end side with the elastic deformation of the diaphragm 1.

  The upper plate 2 attached to the lower surface 21a of the tire house portion 21 of the vehicle body 20 via the frame F includes a substantially downward plate-shaped main plate 2A that covers the upper bead portion 1A of the diaphragm 1 from above, and an inner side of the upper bead portion 1A. And an inner plate 2 </ b> B that fits together, and is integrated by a plurality of bolts and nuts 14. A boss 5 for supplying and discharging air into the diaphragm 1 is fixed in a state of penetrating the plates 2A and 2B, and mounting flanges 4 are fixed at two positions on the outer periphery of the main plate 2A.

  As shown in FIG. 1, the piston 3 attached to the leg member 23 on the axle 22 has a fitting cylinder portion 8 at the upper end where the lower bead portion 1 </ b> B of the diaphragm 1 is externally fitted, and below the fitting cylinder portion 8. The following small-diameter cylindrical part (an example of the joining side end) 3a, a downwardly expanding tapered cylindrical part 3b that continues below the small-diameter cylindrical part 3a, and a large-diameter cylindrical part that continues below the tapered cylindrical part 3b (of other parts) An example) is formed of a stepped cylindrical member provided with 7. That is, the piston 3 is formed of a stepped cylindrical member whose upper end (joining side end), which is the side where the diaphragm 1 is hermetically joined in the direction of the axis P, is reduced in diameter. A bottom plate 9 having fixing bolts 10 to be caulked (clamped) fixed is fixed to the lower side of the piston 3, and a stopper rubber 6 is attached to the upper surface via a bead holding disc 13.

  The stopper rubber 6 is for elastically supporting the upper plate 2 when the diaphragm 1 is in an airless state such as when the air is vented or punctured. The air spring A shown in FIG. 1 shows a state in which the folded portion 1D is about to reach the large-diameter cylindrical portion 7, and the axis Y of the upper plate 2 and the axis P of the male piston 3 are in a straight line. Match. The large-diameter cylindrical portion 7 includes a lower cylindrical portion 7A having a constant diameter (or substantially constant) rising from the bottom plate 9, and an upper cylindrical portion 7B that continues to the tapered cylindrical portion 3b in a state of slightly expanding to the tapered cylindrical portion 3b. have.

  Now, in the example of mounting on the low floor bus shown in FIG. 3, only the main part of the changing behavior when the vehicle body 20 rolls around the rolling axis X directly below the floor wall 20A is shown in FIG. . FIG. 4 has been studied using a conventional air spring B, and the change of the air spring B accompanying the rolling with respect to the rolling axis X of the vehicle body 20 is expressed as the movement of the piston 3 with respect to the upper plate 2 fixed in position. It is drawn. As for the diaphragm 1 and the piston 3, a solid line indicates a standard state (free state), a one-dot broken line indicates a cushion state (state where the vehicle body sinks), and a virtual line indicates a rebound state (state where the vehicle body is lifted).

  Even in the standard state, the air spring B is in a positional relationship in which the shaft center P of the upper plate 2 and the shaft center P of the piston 3 are not collinear and are twisted in an angled manner. In the cushion state where the piston 3 is lowered with respect to the upper plate 2, the shaft centers P and Y are further separated from each other to the left and right and become more twisted. In the rebound state in which the piston 3 moves up with respect to the upper plate 2, the shaft centers P and Y approach each other in the left-right direction, but pass through and the piston shaft center P is slightly displaced to the inside of the upper plate shaft center Y, and The positional relationship is slightly twisted in the opposite direction to the aforementioned twist.

  When the vehicle body 20 rolls at the rolling axis X from the state in which the air spring A is in the reference posture as shown by the solid line in FIG. 4, the upper plate 2 sinks with respect to the piston 3 as shown by the phantom line. The curvature of the folded portion 1D at the inner side of the vehicle body and the folded portion 1D at the outer side of the vehicle body when the upper plate 2 is lifted with respect to the piston 3 as shown by a one-dot broken line are clearly reduced. That is, the shaft center P of the diaphragm 1 and the shaft center Y of the upper plate 2 are laterally misaligned and twisted with each other. In this case, the curvature of the folded portion 1D becomes the smallest in the folded portion 1D at the outer portion of the vehicle body when the upper plate 2 is lifted with respect to the piston 3, as shown by the one-dot broken line in FIG. is there.

  FIG. 5 is an enlarged view of the main part in the cushion state showing the improvement of the curvature of the folded portion when the air spring A according to the present invention is used, and the conventional very small curvature of the folded portion 1D (the portion indicated by a one-dot broken line) is shown. It can be seen that there is a clear and significant improvement. In the air spring A of the first embodiment, the diameter dimension ratio (D / R) of the diameter D of the small diameter cylindrical portion 3a to the diameter R of the large diameter cylindrical portion 7 is set to 92 to 97% (3 to 8% decrease). Yes. As an example, when a durability test was performed with a rolling test device (not shown) using a piston having a configuration in which the diameter of the small diameter cylindrical portion 3a was reduced by 5% of that of the large diameter cylindrical portion 7, a conventional air spring B ( As compared with the durability test in the case of using FIG. 6), durability improvement of 2 to 3 times was confirmed. As a result, the folded portion 1D is improved so that it does not (or is unlikely) to cause inconveniences such as cracks and tears occurring relatively early and leading to air leakage.

  By the way, the length L in the direction of the axis P of the small-diameter cylindrical portion 3a is appropriately determined depending on the depth of coverage of the diaphragm 1 on the piston 3 when the curvature of the folded portion 1D is the smallest. In this case, in order to maintain the spring constant in a predetermined range, it is desirable to set the length L in the axis P direction of the small diameter cylindrical portion 3a to the minimum necessary.

[Another Example]
As the shape of the small-diameter cylindrical portion 3a, as shown in the first embodiment, in addition to a straight cylindrical shape or a substantially straight cylindrical shape, a curved cylindrical shape having a tapered cylindrical shape, a constricted shape, or a barrel shape whose diameter gradually changes. But it ’s okay.

1 Cylindrical rubber membrane 1C Reversed cylinder part
1D Folded part 2 Large-diameter plate-like member 3 Piston 3a Joining side end
3b Taper tube
7 Large diameter tube
L Length of joint side end in axial direction P

Claims (1)

A cylindrical rubber film, a large-diameter plate-like member that is airtightly joined to one end portion in the axial direction of the cylindrical rubber film, and a piston that is airtightly joined to the other end portion in the axial direction of the cylindrical rubber film, An air spring formed on the piston with a circumferential surface capable of rolling and guiding an inverted tube portion formed by folding the other end side with elastic deformation of the cylindrical rubber film,
The piston has a joint-side end that is the side on which the cylindrical rubber film is hermetically joined in the axial direction of the piston, a downwardly-expanding tapered tubular portion that continues below the joint-side end, and the taper A large-diameter cylindrical portion that continues below the cylindrical portion, and is formed of a stepped cylindrical member in which the joint-side end portion is reduced in diameter ,
The length in the axial direction of the joining side end portion is equal to or greater than the depth of covering of the cylindrical rubber film to the piston when the curvature of the folded portion of the cylindrical rubber film is the smallest. Stipulated in
An air spring in which a ratio of a diameter of an end portion on the large-diameter plate-like member side in the joining-side end portion to an end portion on the large-diameter plate-like member side in the large-diameter cylindrical portion is set to 92 to 97% .

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