JPH11236983A - Pulse pressure absorbing hose and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a pulse pressure absorbing hose and a method of manufacturing the same, which are capable of improving pulse pressure attenuation without lowering durability. SOLUTION: Between an inner rubber layer 1 and an outer rubber layer 5,
At least one reinforcing layer (2, 4) formed by braiding the reinforcing yarn (6) into a blade shape is embedded, and the major axis (L) and the minor axis (S) of the reinforcing layers (2, 4)
And the ratio (L / S) is set to 1.2 or more, and the braid angle θ ₁ in the short diameter portion S ′ is made smaller than the braid angle θ ₂ in the long diameter portion L ′.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse pressure absorbing hose used for a hydraulic pump, a power steering device, and the like, and a method for manufacturing the hose. More specifically, the present invention relates to a method for manufacturing a pulse pressure absorbing hose without reducing durability. The present invention relates to a pulse pressure absorbing hose that can be improved and a method of manufacturing the same.

[0002]

2. Description of the Related Art In general, a pressure fluid device such as a hydraulic pump or a power steering device is constituted by a pressure fluid supply source, an actuation device operated by the pressure fluid, and a pipe such as a hose connecting these devices. . However, since the pressure fluid supplied from the pressure fluid supply source generates a pulse pressure, the piping vibrates and generates noise, and in some cases, the operation of the actuator becomes unstable.

Therefore, various hoses have been proposed which absorb the above-mentioned pulse pressure. For example, the actual opening 63-1
The hose described in No. 12685 is provided with a foamed rubber layer inside a reinforcing layer, and the pulse pressure is absorbed by the foamed rubber layer. Further, the hose described in Japanese Utility Model Laid-Open No. 3-89291 has a buffer layer made of spun yarn having a large elongation on the outer peripheral side of the inner rubber layer, and this buffer layer increases the volume expansion to increase the pulse pressure. So that it absorbs. Further, the hose described in Japanese Patent Application Laid-Open No. 61-6494 absorbs a pulse pressure by inserting a muffler tube inside the hose.

However, as described above, the hose provided with the foamed rubber layer inside the reinforcing layer has a problem that the foaming agent promotes the aging of the rubber, so that the hose has poor aging resistance. Hose with a buffer layer has a problem that durability is reduced due to the use of spun yarn with high elongation in the buffer layer, and hoses with a muffler tube inside the hose require a muffler tube, so they are manufactured. There is a problem that the cost is increased, and in any case, there is a problem in improving the pulse pressure attenuation.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pulse pressure absorbing hose and a method of manufacturing the same, which are capable of improving pulse pressure attenuation without decreasing durability.

[0006]

According to the present invention, there is provided a pulse pressure absorbing hose according to the present invention, wherein at least one layer formed by braiding a reinforcing yarn into a braid between an inner rubber layer and an outer rubber layer. Wherein the ratio of the major axis to the minor axis of the reinforcing layer is 1.2 or more, and the braid angle of the reinforcing yarn with respect to the hose axis direction is smaller at the minor axis than at the major axis. It is assumed that.

As described above, the ratio of the major axis to the minor axis of the reinforcing layer is set to 1.
In addition to the above, the braid angle of the reinforcing yarn with respect to the hose axis direction is made smaller in the short diameter portion than in the long diameter portion, so that when a pulse pressure is applied, the reinforcing layer is deformed so that the cross-sectional shape approaches a circle. Therefore, the volume expansion of the hose can be increased while suppressing the elongation of the reinforcing yarn. Therefore, the pulse pressure damping property can be improved without lowering the durability.

Further, the method of manufacturing a pulse pressure absorbing hose according to the present invention is characterized in that a knitting machine for braiding reinforcing yarns at a constant rotational speed is provided with a rubber tube having a ratio of a major axis to a minor axis of 1.2 or more at a constant speed. And a reinforcing layer made of the reinforcing yarn is formed on the outer peripheral side of the rubber tube. By passing the rubber tube having the ratio of the major axis to the minor axis of 1.2 or more through the knitting machine in the usual manner, the braid angle of the reinforcing yarn with respect to the hose axial direction is smaller at the minor axis than at the major axis. Therefore, the pulse pressure absorbing hose of the present invention can be easily manufactured using the conventional manufacturing equipment.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. 1 to 3 illustrate a pulse pressure absorbing hose according to an embodiment of the present invention. In FIG. 1, between the inner rubber layer 1 and the outer rubber layer 5, two reinforcing layers 2 and 4 formed by braiding a plurality of reinforcing yarns in a blade shape so as to cross each other are inserted. An intermediate rubber layer 3 is interposed between the two reinforcing layers 2 and 4. The inner rubber layer 1, the reinforcing layer 2, the intermediate rubber layer 3, the reinforcing layer 4, and the outer rubber layer 5 are laminated and integrally formed into a hose. As the reinforcing yarn, nylon fiber,
In addition to long fiber yarns such as aramid fibers, polyester fibers, vinylon fibers and rayon fibers, steel wires and the like can be used.

As shown in FIG. 2, the inner rubber layer 1, the intermediate rubber layer 3 and the outer rubber layer 5 have respective flattened cross-sectional shapes.
(L / S) is 1.2 or more. This major axis L
If the ratio of the diameter S to the minor diameter S is 1.2 or more, the effect of expanding the volume of the hose is obtained. However, in consideration of the operation of extracting the mandrel and the operation of coating the rubber tube, the upper limit is preferably set to 3. The cross-sectional shape of the reinforcing layers 2 and 4 is not particularly limited as long as the ratio of the major axis L to the minor axis S is 1.2 or more, and may be hexagonal or octagonal. However, considering the use of a mandrel, it is preferable to make the shape elliptical. In addition, by making the inner peripheral cross-sectional shape and the outer peripheral cross-sectional shape circular with respect to the flattened reinforcing layers 2 and 4, a perfect circular metal fitting can be used as a fastener for connecting the hose. You may make it become.

FIG. 3 is a view in which the reinforcing layer of the hose is cut open in the axial direction of the hose and developed. As shown in FIG. 3, the braid angle θ ₁ of the reinforcing yarn 6 in the short diameter portion S ′ with respect to the hose axis direction is smaller than the braid angle θ ₂ of the reinforcing yarn 6 in the long diameter portion L ′ with respect to the hose axis direction. . Braid angle theta ₁ of the short diameter portion S 'is preferably set in a range of 25 ° to 60 °. On the other hand, it is preferable that the braid angle θ ₂ of the major diameter portion L ′ is set in the range of 30 ° to 65 °. The difference (θ ₂ −θ ₁ ) between the minimum value of the braid angle θ _{1 and} the maximum value of the braid angle θ ₂ is preferably set to 4.7 ° or more.

As described above, the ratio (L / S) of the major axis L to the minor axis S (L / S) of the reinforcing layers 2 and 4 is set to 1.2 or more, and the braid angle θ ₁ of the minor section S ′ is changed to the major axis L ′. Is smaller than the braid angle θ _2, the tension distribution in the circumferential direction of the hose becomes non-uniform so that the tension in the short diameter portion S ′ becomes low, and the cross section of the reinforcing layers 2 and 4 when pulse pressure is applied Since the shape is deformed so as to approach a circle, the volume expansion amount of the hose can be increased while the elongation of the reinforcing yarn 6 is suppressed.
Therefore, for example, although the durability is superior to the case where the modulus of the reinforcing yarn is lowered to increase the elongation, the pulse pressure damping property can be improved by increasing the volume expansion amount. Further, since the above-mentioned hose does not require the use of a foamed rubber layer or a silencer tube, there is no problem associated with them.

The pulse pressure absorbing hose described above can be easily manufactured by the following manufacturing method. First, as shown in FIG. 4, a rubber tube T having a ratio of a major axis to a minor axis of 1.2 or more is extruded. It is preferable to insert a flat mandrel M inside the rubber tube T so as to satisfy the ratio of the major axis / minor axis. The cross-sectional shape of the rubber tube T is not particularly limited as long as the ratio of the major axis to the minor axis is 1.2 or more, but is preferably elliptical in consideration of the mandrel extraction operation. Next, as shown in FIG. 5, the flattened rubber tube T is passed at a constant speed through a knitting machine B for braiding the reinforcing yarn A at a constant rotation speed, and the reinforcing yarn A is formed on the outer peripheral side of the rubber tube T. The reinforcing layer R is formed. The rubber tube T corresponds to the inner rubber layer 1 and the intermediate rubber layer 3, and the reinforcing layer R corresponds to the reinforcing layer 2 and the reinforcing layer 4.

As described above, when the rubber tube T having the ratio of the major axis to the minor axis of 1.2 or more is passed through the knitting machine B by a usual method, as a result, the ratio of the major axis to the minor axis of the reinforcing layer R is reduced. 1.
At the same time, the braid angle of the reinforcing yarn A constituting the reinforcing layer R with respect to the axial direction of the hose becomes smaller in the short diameter portion than in the long diameter portion, and the tension in the short diameter portion decreases. Therefore, according to the above manufacturing method, the pulse pressure absorbing hose shown in FIGS. 1 to 3 can be easily manufactured by using the conventional manufacturing equipment.

In the hose manufacturing method of the present invention, the flattened rubber tube T is passed at a constant speed through a knitting machine B for knitting the reinforcing yarn A at a constant rotational speed, so that the braid angle is automatically set in the hose circumferential direction. To change it. Therefore, it is necessary to keep the rotation speed of the knitting machine B and the passing speed of the rubber tube T constant as in the ordinary braiding process. However, the rotation speed of the knitting machine B and the passing speed of the rubber tube T are not limited to specific speeds, but can be set arbitrarily according to the braid angle, manufacturing conditions, and the like.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In manufacturing a hose having a laminated structure shown in FIG. 1, a rubber tube to be passed through a knitting machine is flattened so that the ratio of the major axis to the minor axis of the reinforcing layer is made different, and
Pulse pressure absorbing hoses of Comparative Examples 1 to 4 and Examples 1 to 3 were manufactured by changing the set braid angle of the knitting machine in various ways. The set braid angle of the knitting machine is a braid angle of the reinforcing layer formed on the outer peripheral side of the rubber tube having a circular cross section based on the rotation speed of the knitting machine and the passing speed of the rubber tube. Therefore, if the rubber tube passing through a knitting machine has been flattened, the actual braid angle theta ₂ is larger than the set braid angle, the actual braid angle theta ₁ is set braid angle with the shorter diameter portion in the major axis portion Smaller than.

An internal pressure of 6 MPa is applied to each of the pulse pressure absorbing hoses obtained as described above, and the volume expansion amount (ml /
m) was measured. In addition, each pulse pressure absorption hose is
mm and an internal pressure of 4.9 MPa, while circulating the oil, an input value (dB) and an output value (dB) were measured when a pulse pressure of 130 Hz was applied, and the pulse pressure transmission rate was obtained. Further, each pulse pressure absorbing hose was set to a length of 300 mm, an impulse test for giving a trapezoidal wave impulse was performed under the condition that an oil at a temperature of 140 ° C. was circulated at an internal pressure of 11.8 MPa, and the number of impulses until breakage was measured. . These measurement results are shown in Table 1 using an index with the conventional hose of Comparative Example 1 being 100.

[0018]

[Table 1]

As apparent from Table 1, Examples 1 to
The hoses of No. 3 each had a large volume expansion and a small pulse pressure transmissibility, and thus had excellent pulse pressure attenuating properties. Further, the durability in the impulse test was not substantially lower than that of Comparative Example 1. On the other hand, the hoses of Comparative Examples 2 and 3 each have a braid angle reduced while the reinforcing layer has a circular cross section, so that although the pulse pressure damping property is improved, the durability in the impulse test is higher than that of Comparative Example 1. Had dropped significantly.
In the hose of Comparative Example 4, the ratio of the major axis / minor axis of the reinforcing layer was too small, and the effect of improving the pulse pressure attenuation was insufficient.

[0020]

As described above, according to the pulse pressure absorbing hose of the present invention, at least one reinforcing layer formed by braiding reinforcing yarn into a braid is provided between the inner rubber layer and the outer rubber layer. By embedding, the ratio of the major axis to the minor axis of the reinforcing layer is set to 1.2 or more, and the braid angle of the reinforcing yarn with respect to the hose axis direction is smaller in the minor axis part than in the major axis part, so that the elongation of the reinforcing thread is The volume expansion of the hose can be increased while suppressing the pressure, and the pulse pressure attenuation can be improved without lowering the durability.

Further, according to the method for producing a pulse pressure absorbing hose of the present invention, a knitting machine for braiding reinforcing yarns at a constant rotational speed is provided.
The above-described pulse pressure absorbing hose is manufactured by a conventional method in which a rubber tube having a ratio of the major axis to the minor axis of 1.2 or more is passed at a constant speed and a reinforcing layer made of a reinforcing thread is formed on the outer peripheral side of the rubber tube. It can be easily manufactured using equipment.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing a pulse pressure absorbing hose according to an embodiment of the present invention.

FIG. 2 is a sectional view of the pulse pressure absorbing hose of FIG.

FIG. 3 is a developed view in which a reinforcing layer of the pulse pressure absorbing hose of FIG. 1 is cut open in a hose axial direction.

FIG. 4 is a cross-sectional view showing a rubber tube in the method for manufacturing a pulse pressure absorbing hose according to the embodiment of the present invention.

FIG. 5 is a side view showing a braiding step in the method for manufacturing a pulse pressure absorbing hose according to the embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inner rubber layer 2 inner reinforcing layer 3 intermediate rubber layer 4 outer reinforcing layer 5 outer rubber layer L major axis L 'major axis part S minor axis S' minor axis part

Claims (2)

[Claims] At least one reinforcing layer formed by braiding reinforcing threads into a braid is embedded between an inner rubber layer and an outer rubber layer, and the ratio of the major axis to the minor axis of the reinforcing layer is set to 1. 2. A pulse pressure absorbing hose in which the braid angle of the reinforcing yarn with respect to the hose axial direction is made smaller at a shorter diameter portion than at a longer diameter portion. 2. A rubber tube having a ratio of a major axis to a minor axis of 1.2 or more is passed at a constant speed through a knitting machine for braiding a reinforcing yarn at a constant rotational speed, and the reinforcing tube is placed on the outer peripheral side of the rubber tube. A method for manufacturing a pulse pressure absorbing hose forming a reinforcing layer made of yarn.