1. Field of the Invention
The present invention relates to a brake hose constituting a part of a brake system for an automobile, or the like.
2. Description of the Related Art
Conventionally, a brake hose constituting a part of a brake system for a passenger car, a bus, a truck, a train, or the like has been used as a hydraulic transmission hose connecting a chassis and a wheel caliper as an important safety part related to braking of an automobile, or the like.
Since such a brake hose is, in general, exposed to a severe mechanical stress such as bending or rolling by a repeated steering wheel operation, swaying of a wheel, or the like, the excellent fatigue resistance is required. Furthermore, in order to ensure a sharp movement of the brake system, the excellent expansion resistance is also required.
As a conventional brake hose with these characteristics required, those with a multi-layer structure having a first reinforcing fiber layer, an intermediate rubber, a second reinforcing fiber layer, and an external layer rubber successively disposed on the outer circumference of a tube-like internal layer rubber directly in contact with a brake fluid have been used widely.
Here, as the first and second reinforcing fiber layers, those provided by weaving a reinforcing fiber material such as a polyvinyl alcohol fiber and a rayon fiber have been used commonly for ensuring the fatigue resistance and the expansion resistance required for a brake hose.
In contrast, as a rubber material constituting the internal layer rubber, the intermediate rubber, and the external layer rubber, in general, a natural rubber (NR), a chloroprene rubber (CR), a styrene butadiene rubber (SBR), an ethylene propylene diene rubber (EPDM), isobutylene rubber (IIR), or the like are used. These rubber materials are used according to the characteristics required for each part.
The polyvinyl alcohol fiber and the rayon fiber for providing the first and second reinforcing fiber layers have a problem in that they can easily be deteriorated by a certain kind of a brake fluid and they have a poor durability. Therefore, recently, as the reinforcing fiber material constituting the first and second reinforcing fiber layers, use of a polyethylene terephthalate fiber, which has the excellent corrosion resistance, is discussed.
However, although the polyethylene terephthalate fiber has the dramatically superior corrosion resistance compared with the polyvinyl alcohol fiber and the rayon fiber, since it has a small elastic modulus as a fiber, it is disadvantageous in terms of the expansion resistance (volume expansion amount), which is one of the important characteristics of a brake hose.
In the case the polyethylene terephthalate fiber is used in the first and second reinforcing fiber layers, although the corrosion resistance and the fatigue resistance can be improved dramatically compared with the conventional brake hoses, in contrast, since the volume expansion amount of the hose is made larger at the time of pressurizing, the braking response or the brake feeling becomes dull, and thus there is a risk of having the state of the xe2x80x9cpoor braking performancexe2x80x9d.
Accordingly, in order to solve the above-mentioned problems effectively, the present invention has been achieved, and an object thereof is to provide a novel brake hose capable of sufficiently satisfying the fatigue resistance and the corrosion resistance, with the excellent expansion resistance.
In order to solve the above-mentioned problems, a first invention is a brake hose comprising a reinforcing fiber layer made of a polyethylene-2,6-naphthalate fiber on the outer circumference of an internal layer rubber for filling a brake fluid as shown in a first aspect. A second invention is a brake hose comprising a reinforcing fiber layer on the outer circumference of an internal layer rubber for filling a brake fluid as well as an external layer rubber on the outer circumference of the reinforcing fiber layer, wherein the reinforcing fiber layer is made of a polyethylene-2,6-naphthalate fiber as shown in a second aspect.
Moreover, a third invention is a brake hose comprising a first reinforcing fiber layer, an intermediate rubber, a second reinforcing fiber layer, and an external layer rubber provided successively on the outer circumference of an internal layer rubber for filling a brake fluid, wherein the first reinforcing fiber layer is made of a polyethylene-2,6-naphthalate fiber as shown in a third aspect. A fourth invention is a brake hose comprising a first reinforcing fiber layer, an intermediate rubber, a second reinforcing fiber layer, and an external layer rubber provided successively on the outer circumference of an internal layer rubber for filling a brake fluid, wherein the first and second reinforcing fiber layers are made of a polyethylene-2,6-naphthalate fiber as shown in a fourth aspect.
Furthermore, a fifth invention is a brake hose comprising a first reinforcing fiber layer, an intermediate rubber, a second reinforcing fiber layer, and an external layer rubber provided successively on the outer circumference of an internal layer rubber for filling a brake fluid, wherein the first reinforcing fiber layer is made of a polyethylene-2,6-naphthalate fiber as well as the second reinforcing fiber layer is made of any one selected from the group consisting of a polyethylene terephthalate fiber, a polyvinyl alcohol fiber, and a rayon fiber.
That is, in the present invention, a polyethylene-2,6-naphthatlate fiber is adopted instead of the conventionally used reinforcing fiber materials, such as a polyvinyl alcohol fiber, a rayon fiber, and a polyethylene terephthalate fiber as the innermost side fiber reinforcing layer to be provided on the outer circumference of the internal layer rubber for filling the brake fluid.
As later described, the polyethylene-2,6-naphthalate fiber can provide the excellent fatigue resistance as well as it does not have a disadvantage of deterioration with respect to a certain kind of a brake fluid found in the conventional polyvinyl alcohol fiber, rayon fiber, or the like, nor a disadvantage of a poor expansion resistance found in the polyethylene terephthatlate fiber, or the like as described later.
Therefore, by using the polyethylene-2,6-naphthalate fiber provided with these excellent characteristics as the reinforcing fiber material for a fiber reinforcing layer, the corrosion resistance and the expansion resistance can both be provided at a high level, which has been difficult for the conventional reinforcing fiber materials.
Specifically, since one having a 0.5 to 8.5% dry heat shrinkage at 150xc2x0 C., a 6.5 g or more tensile strength per a unit denier, and a 5% or less elongation at 4.5 g per a unit denier load is used as the polyethylene-2,6-naphthalate fiber as shown in a sixth aspect, the above-mentioned effects can be achieved further certainly.
Furthermore, since the internal layer rubber, the intermediate rubber, and the external layer rubber are made of any rubber material selected from the group consisting of a natural rubber (NR), a chloroprene rubber (CR), a styrene butadiene rubber (SBR), an ethylene propylene diene rubber (EPDM), isobutylene rubber (IIR), and a chlorosulfonated polyethylene (CSM) as shown in a seventh aspect, a brake hose with a low expansion property and the excellent corrosion resistance and fatigue resistance can be obtained easily.