JPH03337A - Pneumatic spring - Google Patents

Abstract

PURPOSE:To reduce hysteresis loss to increase anti-fatigue property and give excellent driving comfortableness by making a reinforcement layer of a complex cord in which nylon fiber is twined with aramid fiber, and covering the complex cord with a protection layer of flexible material. CONSTITUTION:The reinforcing layer 10 of the diaphragm body 5 of a pneumatic spring is made of a complex cord W in which nylon fiber N and aramid fiber A are twined, and the both surfaces of the cord W are coated with a protection layer of flexible material such as rubber, etc., to form the diaphragm body 5. Also, the diaphragm body 5 is constructed of two layers and a cord layer is positioned at some angle relative to an axis X-X. Since a hysteresis loss is produced by increasing and decreasing air pressure sealed in the diaphragm body 5, the aramid fiber A is twined integrally with the nylon N to reduce the hysteresis loss of the nylon remarkably. In the hybrid cord of aramid/ nylon, the nylon acts as a cushion material when the diaphragm body is bent to damp and absorb a stress due to bending, tension, and compression applied to the rigid aramid fiber.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an air spring used in a vehicle suspension system, and more specifically, to improve the hysteresis loss of conventional air springs and to withstand high load use. The present invention relates to a membrane body for air springs.

[Conventional technology]

The air spring device membrane 1 used for vehicle suspension systems, etc.
As shown in FIGS. 5 and 6, generally, a flexible material such as rubber with a reinforcing cord 2 embedded therein is molded and vulcanized into a substantially cylindrical or bellows shape, and air spring devices are attached to both ends of the flexible material such as rubber. The mounting portion 3 is attached to the vehicle, and compressed air is sealed inside the vehicle, which is used for purposes such as alleviating vibrations and shocks and adjusting vehicle height.

Figures 7 and 8 show examples of how the air spring device membrane 1 is used. In Figure 7, one end of the membrane 5 is fastened to the tip of the piston 4 of a vehicle suspension system through a ring 6a. At the same time, the other end side is tightened and fixed to the cap 7 via a tightening ring 6b.

In the case of FIG. 8, an intermediate ring 8 is fitted into the center of the membrane body 5 formed in a bellows shape, and face plates 9a and 9b are hermetically fitted to both ends of the membrane body 5. be.

Furthermore, as shown in FIGS. 5 and 6, the conventional membrane body 1 for an air spring device as described above usually has two reinforcing cord layers embedded inside and outside the membrane body, and the cords are embedded inside and outside the membrane body. are arranged so as to intersect with each other at an angle with respect to the axis X--X.

[Problems to be Solved by the Invention] However, since the reinforcing cord 2 used in the air spring is required to have extremely high bending fatigue resistance, two strands of nylon N as shown in Fig. 9 are used. Nylon N (6 nylon, 66 nylon, etc.) is usually used, but while nylon N has excellent bending fatigue resistance, it has large elongation and hysteresis loss, and therefore the rubber deformation between the cord layer and the bonded cord layer is also large. Become.

For this reason, the hysteresis loss of the nylon N and the hysteresis loss of the rubber between the layers overlap, resulting in the hysteresis loss of the air spring itself (friction as a suspension device).
increases, and a phase difference occurs in the strain relative to the stress applied to the membrane wall, which impedes absorption and mitigation of vibrations and shocks.

That is, vibrations and shocks are not absorbed, unrelaxed, or resonate, which adversely affects the ride comfort of the vehicle.

On the other hand, recent air springs, especially for vehicles, have been used in combination with conventional copper-iron springs, but in order to reduce weight and improve vehicle performance, there is a trend toward using only air springs, and it is inevitable that high-load air springs will be used. The need has arisen.

Therefore, it will be essential in the future to develop air springs that can reduce hysteresis loss and withstand high loads.

These improvement methods include increasing the modulus of rubber,
Although lower elongation has been considered, the bending rigidity of the membrane increases, and the reduction in hysteresis loss is not only ineffective, but also
It is not practical as it causes premature peeling and irritation between the eyebrows.

In addition, from a cord perspective, materials with low hysteresis loss, low elongation, high modulus, and high strength, such as aramid fiber, are being considered, but this type of fiber has extremely poor bending fatigue resistance compared to nylon. This shortens the life of the cord and causes damage to the air springs.

On the other hand, it is possible to make the nylon cord thicker to handle higher loads, but this increases the thickness of the membrane and further increases the hysteresis loss, which is not an effective means.

Therefore, there is a demand for a cord material with low hysteresis loss, high modulus, high strength, and excellent bending resistance.

[Purpose of the invention]

This invention was discovered as a result of intensive research by the inventors of the present invention in order to solve the above-mentioned problems.It reduces the hysteresis loss of conventional air springs and improves fatigue resistance, which is the biggest drawback of aramid fibers. This improves performance and provides extremely good ride comfort, especially in vehicle suspension systems, and also makes it possible to satisfy required performance without changing the thickness of the membrane wall of air springs used under high pressure and high load. The purpose is to provide an ideal air spring.

[Structure of the invention]

In order to achieve the above object, this invention uses a hybrid (composite) cord made by twisting 6 nylon fibers and aramid fibers instead of the conventional cord made only of nylon fibers, and uses a hysteresis cord without changing the thickness of the membrane wall. The gist is a membrane body for air spring devices that reduces loss and provides high load resistance and fatigue resistance.

[Operation of the invention] This invention is constructed as described above, focuses on the hysteresis loss characteristics of aramid fibers, and twists and integrates aramid and nylon to significantly reduce the hysteresis loss of nylon. .

In the following description, the same components as those in the conventional example are denoted by the same drawings and the same reference numerals, and the description thereof will be omitted.

FIG. 1 shows a reinforcing layer 10 constituting a membrane body 5 of an air spring according to the present invention, and this reinforcing layer 10 is constructed into a composite cord W made by twisting nylon fibers N and aramid fibers A. .

Then, both surfaces of the composite cord W are coated with a protective layer made of a flexible material such as rubber to form the membrane body 5.

The membrane body 5 is constructed by stacking two layers as shown in FIGS. 5 and 6, and the cord layer is arranged at an angle with respect to the axis XX.

Then, the membrane body 5 constructed in this way is shown in FIGS. 7 and 8.
When used with an air spring device as shown in the figure,
Compressed air is sealed in the membrane body 5, and the air pressure sealed in the membrane body 5 increases or decreases in response to external stress.When the air pressure increases, the stress applied to the composite cord W increases, and vice versa. When the stress decreases, the stress becomes low, and in the process of repeating these steps, in the case of the conventional membrane body 5 using only nylon fibers N, fatigue (deterioration) phenomenon occurs in the rubber and cord. Moreover, this repetition causes a phase difference with respect to deformation in a material having viscoelastic properties such as rubber or cord, causing a phenomenon called hysteresis loss. As mentioned above, the occurrence of this hysteresis loss appears externally as unabsorbed or unrelaxed vibration or shock, or as a resonance phenomenon, and adversely affects the ride comfort of the vehicle.

Therefore, reducing these problems depends on how to reduce this hysteresis loss. However, conventional nylon fibers have large hysteresis loss,
Especially in the high temperature range (80-140"C), tan δ is 0.
It fluctuates greatly and increases from 0.02 to 0.08.

On the other hand, the hysteresis loss of aramid has extremely low temperature dependence, and the value of tan δ is stable in the entire temperature range of 0.01 to 0°02.

This invention focuses on the hysteresis loss characteristic of the aramid fiber A, and twists and integrates the aramid fiber A and nylon N to significantly reduce the hysteresis loss of nylon.

Here, nylon fibers include nylon 6, nylon 66, nylon 46, nylon 11, etc., and include fibers having an amide bond in the so-called aliphatic main chain.

Also, as aramid fiber, DuPont's Keular
", poly-paraphenylene terephthalamide represented by Akzo's "TWARON" and Teijin's "TE"
C) Polyparaphenylene-3 represented by "INORA"
, 4 diphenyl ether terephthalamide, and polymetaphenylene isophthalamide represented by DuPont's "NOMEX" and Teijin's "CONEX".

Next, we will discuss bending fatigue properties.

As is well known, nylon's bending fatigue resistance is among the best among fibers currently on the market, but the aramid/nylon hybrid cord mentioned above uses nylon to overcome the drawbacks of aramid fibers, which have poor bending fatigue resistance. It is a supplement.

In particular, air springs for vehicles are used under harsh conditions, so hybrid cords exhibit superior fatigue resistance than cords made only of aramid fibers.

In other words, in aramid/nylon hybrid cords, when the membrane body is bent (cord bending), the nylon is thought to act as a kind of buffer material, and the stress due to bending, stretching, and compression applied to the rigid aramid fibers is reduced. Relax and absorb.

Therefore, when considering the aramid/nylon ratio, the higher the nylon ratio, the better the fatigue resistance, but the above-mentioned hysteresis loss will increase.
This ratio is an important factor.

It is also possible to increase the number of twists in a single aramid cord to improve its fatigue properties, but increasing the number of twists is less effective and leads to a decrease in strength (so it is not a good idea).

The means to cope with higher loads on air springs is to increase the strength of the cord that bears the stress, but simply increasing the amount of fiber in the cord and increasing the diameter of the cord will not improve other properties, such as bending fatigue resistance, Hysteresis loss characteristics are impaired.

This invention was developed as a result of research into the high strength of the cord.
It has been found that the aramid/nylon hybrid yarn described above exhibits very high tenacity.

Normally, aramid fibers and nylon fibers have significantly different elongations at break, 3-5% for the former and 15-23% for the latter, so when they are twisted together, the aramid and nylon cut individually, resulting in the expected breaking strength. is often not obtained.

In this invention, based on this knowledge, the denier (positive fineness) of aramid fiber and nylon fiber is made as close as possible,
By using a plied structure, we succeeded in obtaining an extremely strong and efficient cord.

In general, reinforcement cords for air spring membranes have a structure in which two fibers of the same denier are twisted together (for example, 2
10d/2), by twisting aramid fibers with a denier similar to that of nylon fibers with nylon fibers, not only can a cord with high strength be obtained, but also an excellent cord can be obtained without increasing the cord diameter.

This means that it is possible to provide a high-load air spring without increasing the thickness of the membrane, which has great technical value.

The effects will be explained in detail in Examples below.

[Example 1] A hybrid cord having the following specifications was prepared by twisting Kevlar type 964200 denier manufactured by DuPont and 66 nylon 210d manufactured by Asahi Kasei Corporation.

The cord was first immersed in an epoxy aqueous solution and then heated to 235°C.
Heat set for 60 seconds with
formalin-latex) and heated at 230°C for 6 hours.
A 0-second heat set was performed to obtain an adhesive-treated cord.

Tensile strength and elongation were measured using an Autograph manufactured by Futtsu Seisakusho Co., Ltd., and the stress-strain curve shown in FIG. 4 was obtained. At the same time, Kevlar cord (200d/2, 50 twists/
10 cm, first twist 50 times/10cm); 2 types of 66 nylon cord (210d/2, both first twist and first twist 50 times 710
cm; 210d/3 first twist 50 times/l0CII
, 41 twists/IQcm) were similarly measured.

As shown in FIG. 2, the behavior of the Kevlar/66 nylon hybrid cord was similar to that of Kevlar, and the breaking strength was almost the same as that of the nylon cord 2 L Od/3.

Incidentally, the cord gauge was as follows.

In this way, the hybrid cord has a small cord diameter (possible,
Moreover, high breaking strength can be obtained.

[Example 2] 130 cords from Example 1 were arranged at equal intervals of 5 cm, a sheet of chloroprene rubber compound with a thickness of 0.16 plates was made from this, and both sides of the cord layer were sandwiched in a sandwich shape. Two corded rubber sheets were prepared, molded using a membrane molding machine, and then vulcanized at 150° C. for 30 minutes to produce membrane bodies for air springs as shown in FIGS. 5 and 6.

Thereafter, the hysteresis loss characteristics of the membrane were measured, and the curve shown in FIG. 3 was obtained.

Both 210d/2 and 210d/3 membranes using nylon cord as a reinforcing material have large hysteresis loss, and 210d/3, which has a larger cord diameter, has a larger loss. This means that the loss increases as the cord diameter becomes thicker, and it can be seen that the cord diameter is greatly involved in the hysteresis loss. On the other hand, membranes with hybrid cord as a reinforcing layer show better results with much smaller loss than those with nylon cords.

[Example 3] The membrane of Example 2 was subjected to a durability test under the following conditions, and then the cord was taken out and the remaining strength of the cord was measured.
The results shown in Figure 4 were obtained.

Bending cycle: 3.0 Hz Stroke: ±50M Internal pressure: 7.5 kgf/cnl temperature
Degree: Room temperature durability number = 2 million times As shown in the graph, the hybrid cord has slightly lower bending fatigue resistance than the nylon cord, but it has about twice the strength retention rate of the Kevlar cord, and is significantly stronger than the Kevlar alone. It has been improved.

〔Effect of the invention〕

This invention provides a reinforcing layer for an air spring membrane body in which a reinforcing cord is embedded parallel to a flexible material such as rubber as described above, in which the reinforcing layer is a composite cord made by twisting nylon fibers and aramid fibers. Since this composite cord is constructed by covering it with a protective layer made of a flexible material, the following excellent effects can be achieved.

(1) Hysteresis loss characteristics are improved.

(2) A high-load air spring can be obtained without increasing the cord diameter (core layer).

(3) An air spring having both bending fatigue resistance and high strength can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a composite cord made by twisting nylon fibers and aramid fibers constituting a reinforcing layer according to the present invention, and Fig. 2 is an explanatory diagram of stress strain curves in an embodiment of the present invention. , FIG. 3 is an explanatory diagram showing the hysteresis characteristics in the embodiment of this invention, FIG. 4 is a graph explanatory diagram of the cord strength retention rate after the durability test in the embodiment of this invention, and FIGS. FIG. 6 is an explanatory diagram of an air spring, FIGS. 7 and 8 are explanatory diagrams showing examples of the use of air springs, and FIG. 9 is an explanatory diagram of a conventional nylon reinforcing cord. l...Air spring device membrane body, 2...Reinforcement cord, 3.
... Mounting part, 5... Membrane body, 10... Reinforcement layer, Work 1.
... Cord layer, N... Nylon fiber, A... Aramid fiber, W... Composite cord.

Claims (1)

[Claims] In a reinforcing layer of an air spring membrane body in which a reinforcing cord is covered with a flexible material such as rubber, the reinforcing layer is a composite cord made of twisted nylon fibers and aramid fibers, and flexible material is applied to both sides of the composite cord. An air spring characterized by being constructed by laminating protective layers made of flexible materials.