JP2616855B2 - Toothed belt - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toothed belt, and more particularly to a toothed belt having excellent heat resistance and chipping resistance by using rubber compositions having different properties.

[0002]

2. Description of the Related Art Toothed belts have the advantages of being able to reliably transmit without slip unlike flat belts and V-belts, and having the advantage that they do not require oiling as compared to the reliable transmission of gears and chains. In recent years, demand has increased rapidly. In particular, the advance is remarkable in the transmission drive of an overhead camshaft (OHC) of an automobile.

[0003] In recent years, however, due to social demands for energy saving and compactness, the ambient temperature around the engine room of an automobile has been increasing as compared with the conventional case. Accordingly, the operating environment temperature of the toothed belt has been increased.
Conventionally, chloroprene rubber has been mainly used for the toothed belt. However, in a high-temperature atmosphere, a problem has occurred in that cracks are generated at the root portion of the cured belt at an early stage.

[0004] With respect to such an early breakage phenomenon of the toothed belt, improvement in heat resistance of chloroprene rubber has been conventionally studied, and although some improvement has been made, there is a limit as long as chloroprene rubber is used. At present, it has not been able to achieve a sufficient effect. For this reason, the use of rubbers having excellent heat resistance, such as chlorosulfonated polyethylene rubber and hydrogenated nitrile rubber, has been studied. In particular, hydrogenated nitrile rubber has excellent heat resistance, and various studies have been conducted as a material suitable for a toothed belt. For example, Japanese Unexamined Patent Publication (Kokai) No. 62-159827 discloses the use of hydrogenated nitrile rubber. A toothed belt is disclosed.

[0005]

However, the heat resistance of the hydrogenated nitrile rubber is governed by the degree of hydrogenation of the polymer. In a system using a sulfur vulcanization system, the rubber hardness is required to obtain sufficient heat resistance. In addition, the tensile stress (modulus) becomes insufficient, and conversely, in order to obtain sufficient rubber hardness and tensile stress, there is a problem that the heat resistance is insufficient and the composition is easily cured.
Conventionally, the same hydrogenated nitrile rubber was used for the belt teeth, which have the back of the belt that repeats elongation and deformation when the belt meshes with the pulleys and the tooth root that receives the most stress concentration, so either one of the parts is sacrificed. Was receiving. For example, when a hydrogenated nitrile rubber that matches the characteristics of the belt teeth is used, the back of the belt does not have sufficient heat resistance and cracks occur from the back. Conversely, if a hydrogenated nitrile rubber that matches the characteristics of the back of the belt was used, the rubber hardness and tensile stress of the belt teeth were insufficient, and cracks occurred from the roots of the belt. An object of the present invention is to improve such a point and to provide a toothed belt having excellent heat resistance and tooth chipping resistance.

[0006]

That is, the feature of the present invention is that a plurality of teeth arranged along the longitudinal direction;
In a toothed belt having a back portion in which a core wire is embedded and a tooth cloth coated on a surface of the tooth portion, a sulfur vulcanization system having an iodine value (g / 100 g) of 5 or more and less than 15 is applied to the back surface rubber layer. Using the hydrogenated nitrile rubber composition used, the hydrogenated nitrile rubber composition using a sulfur vulcanized system having an iodine value (g / 100 g) of 15 or more in the tooth side rubber layer in contact with the hydrogenated nitrile rubber composition or the sulfur vulcanized system The point is to use the nitrile rubber composition using the above. The volume of the back surface rubber layer is four times or less than that of the tooth-side rubber layer.

FIG. 1 is a side view of a toothed belt according to the present invention. The toothed belt 1 has a plurality of teeth 2 along a longitudinal direction.
A back 4 in which a core wire 3 made of a glass fiber cord or an aramid fiber cord is embedded, and a tooth cloth 5 is adhered to the surface of the tooth portion 2. Then, different rubber compositions are used for the back surface rubber layer 6 and the tooth side rubber layer 7,
The back surface rubber layer 6 has a constant thickness. On the other hand, FIG.
In the toothed belt shown in (1), the back surface rubber layer 6 penetrates to the tooth portion 2 and becomes wavy in the longitudinal direction of the belt, and the tooth portion side rubber layer 7 also penetrates into the back portion 4.

Since the back 4 of the toothed belt is located outside the belt pitch line, it always receives a tensile force when the belt meshes with the pulley, and is always in contact with the tension pulley, so that a corresponding hardness is obtained. , Stress and heat resistance are required. Therefore, a hydrogenated nitrile rubber composition using a sulfur vulcanization system having an iodine value (g / 100 g) of 5 or more and less than 15 is used for the back surface rubber layer 6. The heat resistance and mechanical strength of this rubber composition are governed by the hydrogenation rate of the polymer, and the higher the hydrogenation rate,
That is, the lower the iodine value, the better the heat resistance, but the sulfur vulcanization system has a lower crosslink density. However, the iodine value (g / 10
If 0 g) is less than 5, vulcanization becomes difficult in a sulfur vulcanization system. If the iodine value (g / 100 g) exceeds 15, the sulfur vulcanization system is vulcanized easily and the hardness and stress are increased, but the heat resistance is inferior. Therefore, in order to have sufficient hardness, stress and sufficient heat resistance, it is necessary to use a hydrogenated nitrile rubber having an iodine value (g / 100 g) of 5 or more and less than 15.

On the other hand, the tooth portion 2 of the toothed belt has a function of transmitting power by meshing with a pulley. In particular, the tooth root portion 8 receives a large shearing force with the core wire 3, and Since it receives a force in the direction away from the line 3, it is a region where cracks are particularly likely to occur, and higher hardness and stress than the back 4 are desired. Accordingly, in order to obtain higher hardness and stress, the tooth part side rubber layer 7 has an iodine value (g / 100).
g) A hydrogenated nitrile rubber composition or a nitrile rubber composition using a sulfur vulcanization system having 15 or more is used. When a hydrogenated nitrile rubber composition using a sulfur vulcanization system having an iodine value (g / 100 g) of 5 or more and less than 15 used for the back surface rubber layer 6 is used for the tooth side rubber layer 7, the hardness and stress are sufficient. Otherwise, a crack occurs at the root portion 8 early and the belt is damaged.

The volume ratio of the back surface rubber layer 6 to the tooth side rubber layer 7 is 4 or less, preferably 2 or less, with respect to 1 volume of the tooth side rubber layer 7. If it exceeds 4, the tooth portion 2 is largely occupied by the back surface rubber layer 6, so that it lacks mechanical strength and cracks occur in the tooth root portion 8 at an early stage. Further, the thickness of the back surface rubber layer 6 must be at least 0.1 mm or more. If the thickness is less than 0.1 mm, the effect of heat resistance cannot be sufficiently exhibited.

The tooth cloth 5 to be used is a plain woven fabric, a twill woven fabric, a satin woven fabric, etc. having elasticity in the weft direction (longitudinal direction of the belt). In order to further increase the stretchability, another plain polyester synthetic fiber yarn may be knitted on the plain-woven canvas, twill-woven canvas, or satin-woven canvas and coated as a knitted fabric. The above-mentioned tooth cloth 5 first has RFL on the surface of the weft and warp knitting the woven fabric.
It is covered with an adhesive layer made of a liquid, a cured product of an isocyanate solution or an epoxy solution, or a rubber paste.

The cord 3 is usually a glass fiber cord or an aramid fiber cord. As a typical example of the glass fiber cord configuration, three strands obtained by bundling a large number of alkali-free glass filaments having a diameter of 8 to 10 μ are collected, and the lower strands are twisted to a number of 5 to 25/10 cm to form a lasso, It is a cord obtained by collecting 0 to 13 cords and twisting them in the direction opposite to the twisting in the direction of twisting 3 to 13 times / 10 cm. Specifically, ECG150-3 / 6 to 3
/ 13. The aramid fiber cord is a raw yarn obtained by bundling 100 to 1000 filaments of 1 to 6 denier.

These codes are subjected to RFL treatment and overcoat treatment. The RFL solution is obtained by mixing a latex with an initial condensate of resorcinol and formalin. In this case, the molar ratio of resorcinol to formalin is 1:
It is preferable to set it to 0.5 to 3 in order to increase the adhesive strength. The initial condensate of resorcinol and formalin is mixed with latex such that the resin content is 2 to 100 parts by weight based on 100 parts by weight of the rubber content of the latex, and the total solid concentration is 5 to 40%. Adjusted to concentration.

[0014] The latex is styrene-butadiene.
Vinylpyridine terpolymer, chlorosulfonated polyethylene, hydrogenated nitrile rubber, epichlorohydrin,
Natural rubber, SBR, chloroprene rubber, olefin-vinyl ester copolymer, etc. In the present invention, a hydrogenated nitrile rubber composition or a nitrile rubber composition is used for the back surface rubber layer 6 and the tooth side rubber layer 7. For this purpose, styrene / butadiene / vinylpyridine terpolymer and hydrogenated nitrile rubber latex are preferred.

[0015]

In the toothed belt according to the present invention, the back portion 4 located outside the belt pitch line always receives a pulling force when the belt meshes with the pulley, or the back portion always contacts the tension pulley. Corresponding hardness, stress and sufficient heat resistance are required. On the other hand, the tooth portion 2 has a function of meshing with a pulley to transmit power, and in particular, a tooth root portion 8.
Is subjected to a large shearing force with the core wire 3 and also receives a force in a direction away from the core wire 3, so that it is in an area where cracks are likely to occur, so that a higher hardness and stress than the back part 4 Required. Therefore, these disadvantages are compensated for by using rubber compositions having different properties for the back portion 4 and the tooth portion 2.

That is, a sulfur vulcanization system having an iodine value (g / 100 g) of 5 or more and less than 15 is used for the back surface rubber layer 6 of the back portion 4 so as to have sufficient hardness and stress and sufficient heat resistance. Hydrogenated nitrile rubber composition is used, and a sulfur vulcanization system having an iodine value (g / 100 g) of 15 or more is used for the tooth side rubber layer 7 in order to obtain a higher hardness and stress than the back part 4 in particular. By using a nitrile rubber composition or a nitrile rubber composition, a toothed belt having excellent heat resistance and tooth chipping resistance can be obtained.

[0017]

The present invention will be described in more detail with reference to the following examples. Example 1 Three ECG150s were aligned as glass core wires, and resorcinol 1% by weight, 37% formalin 1% by weight, vinyl
Pyridine-SBR latex 18% by weight, deionized water 8
After immersion in an RFL treatment solution consisting of 0% by weight, drying and baking, the number of twists of 16 times / 10 cm was reduced to 13%.
This was fully aligned, and the number of twists was 8 times / 10 cm, then immersed in rubber paste, and heat-treated to obtain a glass fiber cord having a configuration of ECG150-3 / 13.

On the other hand, the tooth cloth is a twill fabric having a thickness of 0.20 mm on a belt cross section using 6.6 nylon wooly processed yarn for the weft and industrial 6.6 nylon for the warp, and hydrogenated nitrile rubber. What was processed by was used. And
For the back surface rubber layer and the tooth side rubber layer, a rubber composition containing hydrogenated nitrile rubber as a main raw material shown in Table 1 was used. Table 2 shows the vulcanization properties of the rubber composition in Table 1.

[0019]

[Table 1]

[0020]

[Table 2]

A sheet having a predetermined thickness of a rubber composition corresponding to the back surface rubber layer and the tooth side rubber layer is doubled, and the toothed belt shown in FIG. 2 is manufactured by using a conventional press-fitting method using these materials. did. The obtained belt is a STPD having a tooth pitch of 8.0 mm, a number of teeth of 105 and a predetermined width.
The obtained belt was tooth-shaped, and the time until cracks were generated was measured by a heat resistant running test and a high load running test. Table 3 shows the results.

In the heat resistant running test, a toothed belt having a width of 19.1 mm is engaged with a driving pulley (21 teeth) and a driven pulley (42 teeth), and a tension pulley (52 mm in diameter) is engaged between both pulleys. Let it. The running conditions were an ambient temperature of 120 ° C., a driving pulley rotation speed of 7200 rpm,
The load is 5 horsepower and the initial tension is 15 kgf. In a high-load running test, a toothed belt having a width of 12.7 mm was engaged with a driving pulley (21 teeth) and a driven pulley (42 teeth).
A tension pulley (52 mm in diameter) is engaged between both pulleys. The running conditions include an ambient temperature of 120 ° C., a rotational speed of the driving pulley of 7,200 rpm, a load of 8 hp, and an initial tension of 15 rpm.
kgf.

[0023]

[Table 3]

As a result, it is understood that the toothed belt of the embodiment is excellent in heat resistance and tooth chipping resistance.

[0025]

As described above, in the toothed belt of the present invention, the back surface rubber layer has an iodine value (g / 100 g) of 5 or more having sufficient hardness, stress and sufficient heat resistance.
A hydrogenated nitrile rubber composition using a sulfur vulcanization system having a sulfur iodine value (g / 100 g) of 15 or more is used in order to obtain higher hardness and stress on the tooth side rubber layer. By using a hydrogenated nitrile rubber composition or a nitrile rubber composition using, a toothed belt having excellent heat resistance and tooth chipping resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view of a toothed belt according to the present invention.

FIG. 2 is a side view of another toothed belt according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Toothed belt 2 Tooth part 3 Core wire 4 Back part 5 Tooth cloth 6 Back surface rubber layer 7 Tooth side rubber layer 8 Tooth base

Claims (2)

(57) [Claims] 1. A toothed belt having a plurality of tooth portions arranged along a longitudinal direction and a back portion in which a core wire is buried, wherein a surface of the tooth portion is covered with a tooth cloth. A hydrogenated nitrile rubber composition using a sulfur vulcanization system having an iodine value (g / 100 g) of 5 or more and less than 15 is used, and an iodine value (g / 100 g) is 15
A toothed belt using the hydrogenated nitrile rubber composition using the above sulfur vulcanization system or the nitrile rubber composition using the sulfur vulcanization system. 2. The toothed belt according to claim 1, wherein the volume of the back surface rubber layer is four times or less than the volume of the tooth side rubber layer, and the thickness of the back surface rubber layer is at least 0.1 mm or more.