JP2001280424A - Belt for high temperature oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power transmission belt having an extended operating life used in an internal combustion engine. SOLUTION: A nitrile rubber with hydrogen additives in which a hydrogen additives rate is not less than 95% and an amount of acrylonitrile is 15% to 23% is used as a raw material rubber for power transmission belt. By reducing the amount of oil resistant acrylonitrile in the raw material rubber, the rubber becomes apt to absorb an oil ingredient. The raw material rubber of the power transmission belt 14 absorbs the lubricating oil 12 stored in the interior of the internal combustion engine 11, swells and becomes soft, and then the degradation of the power transmission belt because of hardening of the rubber is retarded to extend the operating life of the belt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission belt provided in an internal combustion engine for transmitting rotation of a crankshaft to a drive camshaft for opening and closing an intake / exhaust valve.

[0002]

2. Description of the Related Art A power transmission belt used in an internal combustion engine hardens and deteriorates with the lapse of time due to oxidation of a rubber material. When the rubber reaches a certain hardness, cracks occur on the belt surface, and the belt may be broken thereafter. In order to extend the life of the power transmission belt, it is conventionally known to lower the initial hardness of rubber to delay the time until the power transmission belt breaks.

Usually, the power transmission belt is provided outside the engine. In recent years, it has been proposed that the power transmission belt be formed inside the engine in order to reduce the weight of the internal combustion engine. The power transmission belt provided inside the internal combustion engine is always in contact with the lubricating oil inside the engine, and is used under an environment different from a normal power transmission belt.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to improve the durability of a power transmission belt used inside an internal combustion engine.

[0005]

The power transmission belt according to the present invention has a hydrogenation rate of 95% in order to maintain heat resistance and the like.
As described above, a hydrogenated nitrile rubber (hereinafter, referred to as H-NBR) in which the amount of acrylonitrile is suppressed to 15 to 23% to facilitate oil absorption is molded as a raw material rubber.

[0006] Dimethacrylic zinc is blended in the raw material rubber of the power transmission belt in order to suppress heat generation and heat generation due to internal friction. The compounding amount is preferably 13.5 parts by weight of zinc dimethacrylate per 100 parts by weight of H-NBR or a mixture of H-NBR and ethylene propylene copolymer (hereinafter referred to as EPM).

For example, in order to set the swelling of the raw rubber by oil to an appropriate level, H
-20 parts by weight or less of EPM is mixed with 100 parts by weight of NBR.

[0008] H-contained in the raw material rubber of the power transmission belt
A peroxide-based vulcanizing agent is used for vulcanization of a mixture of NBR or H-NBR and EPM. This increases the elasticity and increases the strength of the belt against chipping.

For example, the above-mentioned raw rubber is used only for the back rubber portion, only the tooth rubber portion, or both the back rubber portion and the tooth rubber portion of the power transmission belt.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an internal combustion engine to which a power transmission belt 14 according to one embodiment of the present invention is applied. The power transmission belt 14 is mounted on the crankshaft pulley 15 and the camshaft pulley 13, and transmits the rotational movement of the crankshaft pulley 15 that rotates clockwise to the camshaft pulley 13 that drives the intake and exhaust valves. A lubricating oil 12 is stored inside the internal combustion engine 11, and an impeller 16 that rotates in the direction of the arrow in conjunction with the rotational movement of the crankshaft pulley 15 moves the lubricating oil 1 along an oil guide plate 17.
Jump up 2. The splashed lubricating oil 12 causes the crankshaft pulley 15 and the power transmission belt 14 to receive oil.

FIG. 2 is a perspective view in which a part of the power transmission belt 14 is cut. A circular tooth portion 19 is formed on one surface of the power transmission belt 14, and the surface thereof is
Covered by 0. At the boundary between the belt main body 18 (belt back rubber portion) and the tooth portion 19, the core wire 2 extends in the longitudinal direction of the belt.
1 is buried. Belt body 18 of power transmission belt 14
H-NBR with a hydrogenation rate of 95% or more
(Polymer) is used as a raw rubber.

The amount of acrylonitrile used as the raw material rubber of the power transmission belt 14 is smaller than that of H-NBR used as the raw material rubber of the conventional power transmission belt. The amount of acrylonitrile having oil resistance which is blended with H-NBR generally used as a raw material rubber of the power transmission belt 14 is about 25% or more, whereas H-NBR of the present embodiment has 15 to 23%. % Only. For this reason, the power transmission belt 14 of the present embodiment is more likely to absorb oil than a normal power transmission belt. The power transmission belt 14 that has absorbed the oil swells and softens.

The raw rubber of the power transmission belt 14 oxidizes with time, and its hardness increases. If the hardness of the raw material rubber 14 of the power transmission belt reaches a certain level, cracks may occur at the back of the belt, which may cause breakage thereafter. The power transmission belt 14 swells due to rubber oil absorption,
Utilizing softening, the time until the raw rubber reaches a certain hardness is prolonged, and the occurrence of cracks is delayed. This can extend the life of the belt.

It is preferable that zinc dimethacrylate is blended in the raw material rubber of the power transmission belt 14 in order to improve heat resistance and the like. For example, when 100 parts by weight of H-NBR or a mixture of H-NBR and EPM used for the raw material rubber of the power transmission belt 14 is 100 parts by weight, 13.5 parts by weight of zinc dimethacrylate is added.

As the raw material rubber of the power transmission belt 14, H
A mixture of 20 parts by weight or less of EPM with respect to 100 parts by weight of NBR may be used. That is, H-NBR,
By using a mixture of the polymer EPM having a high swelling property at a predetermined ratio as a raw material rubber of the power transmission belt 14, the swelling of the power transmission belt 14 with oil can be set to an appropriate level. As a result, the time until the raw rubber reaches a certain hardness can be delayed to extend the life of the belt.

If the raw material rubber of the power transmission belt absorbs too much oil, the swelling of the power transmission belt becomes excessive, resulting in poor meshing between the belt teeth 19 and the pulley. If the volume of the power transmission belt increases by 15% or more from the volume before swelling, the belt teeth 19 become incompletely meshed with the pulley. Therefore, EP
The compounding amount of M is desirably 20 parts by weight or less based on 100 parts by weight of H-NBR.

The rubber material of the power transmission belt 14 is HN
It is obtained by subjecting BR or a mixture of H-NBR and EPM to vulcanization with a peroxide. Vulcanization with peroxide has the effect of suppressing plastic deformation of the raw rubber, increasing the elasticity, and increasing the strength of the power transmission belt 14 against chipping. H-NB contained in raw rubber
When R is 100 parts by weight or a mixture of H-NBR and EPM, it is preferable to perform vulcanization using 6 parts by weight of a peroxide-based vulcanizing agent.

In this embodiment, the surface of the tooth portion 19 is covered with the canvas 20, but the canvas 20 may be omitted according to the purpose. Tooth portion 19 provided on power transmission belt 14
Are formed as circular teeth, but the shape of the teeth is not limited to a circle.

In this embodiment, the teeth 19 and the belt back 1
8, H-NBR or a mixture of H-NBR and EPM is used as the raw material rubber, but H-NBR or H-NBR and E-EBR are used in only one of the tooth rubber portion or the back rubber portion.
What mix | blended PM may be used as raw material rubber.
The material of the cord 20 is not particularly limited, but high-strength glass fiber is preferably used.

[0021]

EXAMPLES Hereinafter, the present invention will be described with reference to Examples along with Comparative Examples, but the present invention is not limited to these Examples.

Column A in the table shown in FIG.
7 shows polymer blending of raw rubber used for the power transmission belts of Comparative Examples 1 and 2. The first column of column A is H-
The hydrogenation rate of NBR, the second column in column A is the amount of acrylonitrile contained in H-NBR, and the third column in column A is H-NB
The parts by weight of the EPM compounded with respect to 100 parts by weight of R are shown. Although not shown in the table, the raw rubbers of Examples 1 to 7 and Comparative Examples 1 and 2 include H-NBR or H-NBR and E
10 parts by weight of zinc oxide, 13.5 parts by weight of zinc dimethacrylate, 20 parts by weight of carbon black, trimellitate isonolyl 8
Parts by weight, 1.5 parts by weight of substituted diphenylamine, 1.5 parts by weight of zinc benzimidazole, and 6 parts by weight of a peroxide-based vulcanizing agent.

The columns B and C in FIG. 3 show the results of the oil immersion test in which the raw rubber used in the power transmission belts of Examples 1 to 7 and Comparative Examples 1 and 2 was immersed in oil. The results are shown. In the oil immersion test, a change in volume and a change in hardness of the raw rubber were measured. Column B shows the volume change and hardness change of each raw rubber after immersing the raw rubbers of Examples 1 to 7 and Comparative Examples 1 and 2 in oil at 150 ° C. for 168 hours. The first column in column B shows the percentage change in volume when the volume before immersing the raw rubber in oil is 100. B
In the second row of the column, the hardness before immersing the raw rubber in oil is 100.
The hardness change at the time of is expressed as a percentage, and the hardness was measured in accordance with the DURO-A standard. Column C shows the volume change and hardness change of each raw rubber after immersing the raw rubbers of Examples 1 to 7 and Comparative Examples 1 and 2 in oil at 150 ° C. for 672 hours. The first and second columns in column C correspond to the first and second columns in column B. The first column in column C shows the volume change, and the second column shows the hardness change in numerical values.

Column D shows the results of running tests in oil on the power transmission belts of Examples 1 to 7 and Comparative Examples 1 and 2. The running test in oil was performed in the running test device 22 in oil shown in FIG. The shape of each power transmission belt 23 of Examples 1 to 7 and Comparative Examples 1 and 2 was HU tooth shape,
6. 35mm pitch, 84 teeth, belt width 7m
m. Each power transmission belt 23 is hung on a 19 tooth drive pulley 24 and a 38 tooth driven pulley 25 to
The vehicle was rotated at pm. At this time, the in-oil running test device 22
The ambient temperature was set to 140 ° C., and a part of the belt was immersed in oil 27 heated by a heater 26.
Each numerical value is a value obtained by measuring a time required for the power transmission belt to reach a hardness of 95 as a guide to breakage. However, the time shown in Example 7 indicates the time until the belt breaks because the power transmission belt was broken due to poor meshing between the belt teeth and the pulley before the raw rubber reached the hardness of 95. I have.

[Raw Rubber of Examples and Comparative Examples]
A few raw rubbers use H-NBR having a hydrogenation rate of 95% and an acrylonitrile amount of 23% or less, and no EPM. The raw rubbers of Comparative Examples 1 and 2 are H-NBR having an acrylonitrile content of 25% or more.
It is generally used as a raw material rubber for a power transmission belt. In Examples 4, 5, and 7, the same H-NBR as in Example 3 in which the degree of hydrogenation was 95% and the amount of acrylonitrile was 23%.
The raw material rubber was prepared by mixing EPM with EPM. The amounts of EPM are 20 parts by weight, Example 5 is 10 parts by weight, and Example 7 is 30 parts by weight when the amount of EPM is 100 parts by weight of H-NBR. The raw rubber of Example 6 was H-NB having a hydrogenation rate of 95% and an acrylonitrile amount of 17%.
R and the same amount of EPM as in Example 5 were used.

[Oil immersion test and running test in oil] Example 1
3 and Comparative Examples 1 and 2. 15 raw rubber
In column B of Table 1 showing the results of an oil immersion test in which the oil was immersed in oil at 0 ° C. for 168 hours, the volume of the raw rubber in Comparative Examples 1 and 2 was increased by less than 5.0% as compared to before the oil immersion. In contrast, in Examples 1-3, 6.8-12.4%
Increased. That is, for raw rubbers having the same hydrogenation rate, the smaller the amount of acrylonitrile, the greater the swelling by oil and the greater the increase in volume. On the other hand, the hardness changes of Examples 1 to 3 showed negative values. That is, all of Examples 1 to 3 are softer than before oil immersion. On the other hand, the changes in hardness in Comparative Examples 1 and 2 were both +2, indicating that they were harder than before oil immersion.

In column C showing the results after the oil immersion test in which the raw rubber was immersed in oil at 150 ° C. for 672 hours,
3 increased to 7.4 to 13.3%, and the volumes of Comparative Examples 1 and 2 increased to 4.7 to 6.2%. In any case, the volume has not been increased by 15%, which is a measure for causing poor engagement with the pulley. The hardness changes are +1, +3, and +4 in Examples 1, 2, and 3, respectively, and +11 and +7 in Comparative Examples 1 and 2, respectively. That is, similar to the result in column B,
It is shown that, in an oily environment, the smaller the amount of acrylonitrile, the larger the volume increase due to swelling but the smaller the degree of hardening.

According to column D showing the results of running tests in oil of belts using these as raw rubber, Examples 1 to 3 showed a hardness of 9
The time to 5 exceeded 950 hours in all cases, whereas Comparative Examples 1 and 2 were less than 800 hours. From the above, under the environment in oil, the amount of acrylonitrile is small and H-
The power transmission belt using NBR as a raw rubber increases in volume due to oil swelling, but its hardness decreases. In other words, it can be seen that the time until the raw rubber reaches a certain hardness is prolonged, so that the time until the belt breaks is delayed, and the life of the belt in oil is prolonged.

Next, Examples 3, 4, 5, and 7 will be compared. Comparing the results in columns B and C of Examples 3, 4, 5, and 7, the greater the blending amount of EPM, the greater the swelling of the raw rubber by oil and the greater the volume, while the more the curing was suppressed. However, in Example 7, the increase in volume had already exceeded 15% in the 168-hour oil immersion test in Column B. Also, in the running test of the belt in column D in oil, before the hardness reached 95, the belt was broken in 800 hours due to poor meshing with the pulley. Therefore, it is considered that Example 7 in which 30 parts by weight of EPM is blended with respect to 100 parts by weight of H-NBR, the swelling due to oil is too large. On the other hand, if the EPM compounding amount is H-NBR10
Examples 3 and 4, which are 20 parts by weight or less based on 0 parts by weight,
5 shows that as a result of the oil immersion test, the raw rubber swells moderately and the hardening of the rubber is suppressed, and the result of the belt running test in oil is 90.
0 hours or more. Therefore, from the comparison of Examples 3, 4, 5, and 7, the proportion of EPM to H-NBR was H-NBR.
It is considered that an EPM of 20 parts by weight or less is an appropriate amount based on 100 parts by weight of BR.

Next, by comparing Examples 5 and 6, H-NBR
The effect of the amount of acrylonitrile on a belt made of a rubber blended with EPM and EPM is considered. Column B and C
As a result of the oil immersion test with the raw rubber in the column, the raw rubbers of Examples 5 and 6 have the same amount of EPM, but the H-NBR
It can be seen that Example 6 having a smaller amount of acrylonitrile had a larger volume due to more oil absorption and less rubber curing. In the running test in oil using the belt shown in column D, the hardening of the raw rubber was suppressed.
Has a longer time to reach a hardness of 95. As described above, even when the raw material rubber of the power transmission belt is a mixture of H-NBR and EPM, similar to the case where H-NBR is used as the raw material rubber,
It can be seen that the smaller the amount of acrylonitrile in H-NBR, the lower the rubber curing and the longer the time until the belt breaks.

[0031]

According to the present invention, the time until the belt breaks is extended by utilizing the fact that the rubber absorbs the oil in the oily environment and suppresses the hardening without lowering the initial hardness of the rubber. The running life can be extended.

[Brief description of the drawings]

FIG. 1 is a sectional view of an internal combustion engine provided with a power transmission belt according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view of a part of the power transmission belt shown in FIG.

FIG. 3 shows compounding of polymers of raw rubbers of Examples 1 to 7 and Comparative Examples 1 and 2, results of an oil immersion test, and results of Examples 1 to 7 and Comparative Examples 1 and 2 of a running test in oil. It is a table.

FIG. 4 is a cross-sectional view of a power transmission belt in-oil traveling test device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Internal combustion engine 12 Lubricating oil 13 Camshaft pulley 14 Power transmission belt 15 Crankshaft pulley 16 Impeller 17 Oil guide plate 18 Belt body (belt back part) 19 Tooth part 20 Canvas 21 Core wire 22 In-oil running test device 23 Power transmission belt 24 Drive Pulley 25 Driven Pulley 26 Heater 27 Oil

Claims (7)

[Claims] 1. A power transmission belt formed by using a hydrogenated nitrile rubber which is a polymer having a hydrogenation rate of 95% or more and an acrylonitrile amount of 15 to 23% as a raw material rubber. 2. The power transmission belt according to claim 1, wherein zinc dimethacrylate is blended with the hydrogenated nitrile rubber. 3. The power transmission belt according to claim 1, wherein a material obtained by blending 20 parts by weight or less of an ethylene propylene copolymer with 100 parts by weight of the hydrogenated nitrile rubber is molded as a raw material rubber. 4. The power transmission belt according to claim 1, wherein a peroxide-based vulcanizing agent is used for vulcanizing the hydrogenated nitrile rubber. 5. The power transmission belt according to claim 1, wherein the hydrogenated nitrile rubber is used as a raw material rubber only in a belt back rubber portion. 6. The power transmission belt according to claim 1, wherein the hydrogenated nitrile rubber is used as a raw material rubber only in a belt tooth rubber portion. 7. The power transmission belt according to claim 1, wherein the hydrogenated nitrile rubber is used as a raw material rubber for both a belt back rubber portion and a tooth rubber portion.