JP2017203115A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition having no abnormal noise in a liquid encapsulation type antivibration device even when a rubber-made movable sheet has vibration.SOLUTION: The rubber composition is a rubber composition of a rubber-made member which is used at a state contacting with encapsulated liquid in a liquid encapsulation type antivibration device and has a rubber composition consisting at least one kind of a synthetic rubber and a natural rubber, a vulcanization assistant containing saturated aliphatic acid with molecular weight of 200 or less and active zinc oxide, and a process assistant containing aliphatic acid ester and free of metallic soap.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rubber composition, and more particularly to a rubber composition for a rubber member used in a liquid-sealed vibration isolator in contact with the sealed liquid.

  Conventionally, as an anti-vibration device such as an engine mount that effectively absorbs and attenuates engine vibrations in a predetermined frequency range, a connecting bracket connected to the supported body side, a supporting bracket connected to the support body side, and both of these brackets A rubber elastic body that relatively displaces both the metal fittings by elastic deformation, a liquid chamber formed such that the volume changes in accordance with the deformation of the rubber elastic body, and the inside of the liquid chamber is a main liquid chamber. There is known a liquid-filled vibration isolator that includes a partition member that partitions into a sub-liquid chamber, and an orifice passage that communicates the main liquid chamber and the sub-liquid chamber. Patent Documents 1, 2).

  In this type of liquid-filled vibration isolator, not only an orifice passage that communicates the main liquid chamber and the sub liquid chamber, but also a plurality of anti-vibration actions can be obtained from a low frequency region to a high frequency region. A resonant system is often provided.

  For example, in Patent Document 1, a rubber movable plate housed in an orifice board (partition member) vibrates in synchronization with engine vibration having a relatively high frequency and a small amplitude, thereby causing the main liquid chamber hydraulic pressure to be Absorbing fluctuations is disclosed.

JP 2011-149448 A Japanese Patent Laying-Open No. 2015-4436

  However, when the liquid-filled vibration isolator is used for a long time, there is a problem that abnormal noise is generated from the liquid-filled vibration isolator. As a result of investigating this cause, when used for a long time, the thickness of the movable plate changes due to foreign matter adhering to the surface of the movable plate, and thus the phenomenon that abnormal noise occurs when the movable plate vibrates. It has become clear that it has occurred. This phenomenon was first discovered by the present inventors.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a rubber composition that does not generate abnormal noise even when a rubber movable plate vibrates in a liquid-filled vibration isolator. There is.

  The rubber composition of the present invention is a rubber composition that forms a rubber member used in contact with a liquid sealed in a liquid-sealed vibration isolator, and is a rubber component made of at least one of synthetic rubber and natural rubber And a vulcanization aid containing a saturated fatty acid having a molecular weight of 200 or less and activated zinc white, and a processing aid containing a fatty acid ester without containing metal soap.

Here, activated zinc white is zinc white having a large specific surface area compared to conventional zinc white (zinc oxide). Specifically, zinc obtained by conventional methods, such as an indirect method in which metal zinc is dissolved and evaporated and then oxidized, or a direct method in which zinc ore is reduced and roasted with coke to form metal zinc and then oxidized. While the specific surface area of the flower is generally less than 15 m ² / g, the specific surface area of the active zinc flower used in the present invention is as large as 20 m ² / g or more. This active zinc white can be obtained, for example, by a wet method in which a zinc sulfate or zinc oxide solution is reacted with a soda ash solution, and the reaction product is baked and pulverized.

  With such a configuration, it is possible to suppress the additive to the rubber composition from eluting from the inside of the rubber composition into the liquid and depositing on the surface of the rubber composition in contact with the liquid.

  Furthermore, it is preferable not to contain paraffin wax.

  Further, the rubber member may be immersed in the liquid.

  The saturated fatty acid is preferably 2-ethylhexanoic acid.

  2-ethylhexanoate zinc salt may be contained.

  Since the vulcanization aid and processing aid are specified substances, it is possible to suppress the phenomenon that foreign matter adheres to the surface of the rubber movable plate in the liquid-filled vibration isolator and causes abnormal noise. .

It is typical sectional drawing of a liquid enclosure type vibration isolator.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its application, or its use. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of brevity.

(Embodiment 1)
-Overall structure of liquid-filled vibration isolator-
FIG. 1 is a view showing a liquid-filled engine mount (liquid-filled vibration isolator) according to this embodiment. The liquid-filled engine mount 1 includes an engine bracket 3 formed with a through hole that is attached to a power plant in which an automobile engine and a transmission are combined, and a mount body 5 that is press-fitted into the through hole from below. An orifice plate 7 inserted into the through hole from above, a rubber diaphragm 9 press-fitted into the through hole so as to overlap the orifice plate 7, and the engine bracket 3 from the tangential direction of the through hole And a pair of stopper rubbers 11 attached to.

  The mount body 5 has an inner plate 25 made of aluminum alloy connected to the vehicle body side, an outer pipe 15 made of aluminum alloy, and a rubber elastic body 35 vulcanized and bonded so as to connect them. The outer pipe 15 is attached to the engine bracket 3 by press-fitting the outer pipe 15 into the through hole. Thus, the liquid-filled engine mount 1 of the present embodiment is such that the cylinder axis direction of the outer pipe 15 faces the up-down direction, the pair of stopper rubbers 11 face each other in the vehicle front-rear direction, and The pair of stopper rubbers 11 are attached to the power plant and the vehicle body such that the insertion direction of the pair of stopper rubbers 11 faces the vehicle width direction.

  In the liquid-filled engine mount 1, a buffer solution (liquid) (not shown) is placed in a cavity defined by the inner peripheral surface of the engine bracket 3, the mount body 5 (specifically, the rubber elastic body 35), and the diaphragm 9. The cavity, which is sealed, forms a liquid chamber 31 for absorbing and mitigating vibrations of the power plant that is input to the rubber elastic body 35. Thus, the interior of the liquid chamber 31 is divided up and down by the orifice plate 7, and the lower side thereof is a pressure receiving chamber 31 a whose volume is enlarged or reduced as the rubber elastic body 35 is deformed. The upper side of the chamber 31 is an equilibrium chamber 31b that absorbs fluctuations in the volume in the pressure receiving chamber 31a by expanding or contracting the volume by deformation of the diaphragm 9.

  As the buffer (liquid), glycol compounds such as ethylene glycol and diethylene glycol, water, and the like can be used.

  As a result, in the liquid-filled engine mount 1, for example, when the automobile is stopped and the engine is in an idle operation state, low-frequency idle vibration caused by torque fluctuation or the like is absorbed by the rubber elastic body 35, and is transmitted to the vehicle body. Vibration transmission is suppressed.

-Orifice plate structure-
The orifice plate 7 includes a storage chamber formed by an upper lid portion 19a and a lower lid portion 19b made of resin and a movable plate 41 stored in the storage chamber.

  A plurality of communication holes 21a, 21a,... Are formed in the upper lid portion 19a so that the accommodation chamber communicates with the equilibrium chamber 31b. On the other hand, the lower lid portion 19b has the accommodation chamber in the pressure receiving chamber 31a. A plurality of communication holes 21b, 21b,... Are formed so as to communicate with each other. The movable plate 41 accommodated in the accommodation chamber is made of rubber. When engine vibration having a relatively high frequency and a small amplitude is input, the movable plate 41 vibrates in synchronism with the vibration to change the hydraulic pressure in the pressure receiving chamber 31a. To absorb.

-Rubber member-
In the present embodiment, rubber members used in contact with the sealed liquid are the rubber elastic body 35, the diaphragm 9, and the movable plate 41. The rubber elastic body 35 and the diaphragm 9 are in a state where only one surface is in contact with the liquid, but the outer surface of the movable plate 41 is in contact with the liquid. That is, the movable plate 41 is immersed in the sealed liquid.

  These rubber members add a saturated fatty acid having a molecular weight of 200 or less (for example, 2-ethylhexanoic acid) and activated zinc white as a vulcanization aid to a rubber component composed of at least one of synthetic rubber and natural rubber, The rubber composition is composed of a fatty acid ester added as a processing aid and no paraffin wax, which is usually added as an antioxidant. The anti-aging agent is for preventing the rubber from being deteriorated by ozone. However, when the whole is immersed in a liquid like the movable plate 41, oxidation due to ozone is difficult to occur, and therefore rubber aging hardly occurs even if an anti-aging agent is not included.

  A rubber composition constituting a conventional rubber member uses stearic acid and ordinary zinc oxide as a vulcanization aid, metal soap as a processing aid (metal component is zinc), and paraffin wax as an anti-aging agent. It was. The vulcanization aid is mostly zinc stearate in rubber members. By using such a material, when the rubber member comes into contact with the liquid, paraffin wax bleeds out on the surface of the rubber member, and zinc stearate and metal soap are eluted into the liquid, and the surface of the rubber member A large amount of paraffin wax was deposited. The paraffin wax played a role of holding powdered zinc stearate and metal soap on the surface of the rubber member.

  In particular, since the temperature in the engine room has decreased to the vicinity of the melting point of paraffin wax due to the improvement in fuel efficiency in automobiles in recent years, the solid amount of paraffin wax on the surface of the rubber member is increased, and the foreign matter thickness on the surface of the movable plate 41 is There was a tendency to increase. For this reason, the clearance gap between a storage chamber and the movable plate 41 became small, and when the movable plate 41 vibrated, it collided with the storage chamber and an abnormal noise came to arise.

  In the rubber member of the present embodiment, a combination of saturated fatty acid having a molecular weight of 200 or less and activated zinc white is used as a vulcanization aid in place of the combination of conventional stearic acid (molecular weight 284.5) and normal zinc oxide. ing. Zinc stearate, which is a metal soap, is produced from a conventional vulcanization aid, and this is powdered and deposited on the surface of the rubber member. Since this zinc stearate has a large particle size of the zinc oxide from which it is derived and stearic acid also has a large molecular weight, it has been deposited as a powder occupying a large volume on the surface of the rubber member as a powder having a large particle size. On the other hand, since the vulcanization aid of this embodiment has a smaller acid portion and smaller zinc portion than the conventional one, the volume of the precipitated powder is much smaller than the conventional one. Furthermore, since the active zinc white can provide the same effect as the vulcanization aid even if the amount added to the rubber is smaller than that of the conventional zinc oxide, the amount of the powdery substance can also be reduced in this respect.

  Various saturated fatty acids having a molecular weight of 200 or less are conceivable. For example, 2-ethylhexanoic acid (molecular weight 144.2) is excellent in performance as a vulcanization aid because of its large molecular weight. Moreover, since 2-ethylhexanoic acid is a branched saturated fatty acid, the molecular shape becomes small, and when it becomes 2-ethylhexanoate zinc salt together with active zinc white, it becomes a powder having a small diameter, and precipitation occurs. However, it occupies only a small volume as a whole, and is a preferable saturated fatty acid in light of the object of this embodiment. In this case, 2-ethylhexanoate zinc salt is also present inside the rubber member.

  Moreover, in the rubber member of this embodiment, since a fatty acid ester is used as a processing aid in place of the conventional metal soap, if it is metal soap, it will be deposited in the form of a powder on the surface of the rubber member. On the other hand, such precipitation does not occur.

  With these vulcanization aids and processing aids, the powdery substance deposited on the surface of the rubber member of this embodiment is orders of magnitude larger than when using conventional vulcanization aids and processing aids. The amount decreases. Therefore, in this embodiment, even if the liquid-filled vibration isolator is used for a long time, the amount of powdery material adhering to the surface of the movable plate 41 is very small, and abnormal noise is generated even when the movable plate 41 vibrates. There is no.

  Furthermore, in this embodiment, paraffin wax is not added to the rubber composition constituting the rubber member. The paraffin wax bleeds out to the surface of the rubber member that is in contact with the liquid and attaches a powdery substance such as zinc stearate to increase the thickness of the deposit on the surface of the rubber member. Since the conventional rubber member contains paraffin wax, abnormal noise is generated by the vibration of the movable plate 41 even when the liquid-sealed vibration isolator is used for a relatively short time. In this embodiment, since there is no paraffin wax that promotes the adhesion of the powdery substance to the surface of the movable plate 41, no abnormal noise is generated due to the vibration of the movable plate 41 even when the liquid-filled vibration isolator is used for a long time.

(Other embodiments)
The above-described embodiment is an exemplification of the present invention, and the present invention is not limited to these examples, and these examples may be combined or partially replaced with known techniques, common techniques, and known techniques. Also, modified inventions easily conceived by those skilled in the art are included in the present invention.

  The rubber constituting the rubber member may be any material such as natural rubber, isoprene, EPDM, NBR and BR, and a plurality of types of rubbers may be mixed.

  The saturated fatty acid contained in the vulcanization aid preferably has a molecular weight of 200 or less, more preferably 150 or less. The saturated fatty acid is preferably branched.

  To the vulcanization aid and processing aid, another type of vulcanization aid or processing aid that does not impair the effects of the present application may be added. Alternatively, a saturated fatty acid having a molecular weight of 200 or less and a saturated fatty acid zinc salt, which is a reaction product of activated zinc white, may be added as a vulcanization aid, and in this case, 2-ethylhexanoate zinc salt is preferable. .

Claims (5)

A rubber composition for a rubber member used in a state of being in contact with a liquid sealed in a liquid-sealed vibration isolator,
A rubber component comprising at least one of synthetic rubber and natural rubber;
A vulcanization aid containing a saturated fatty acid having a molecular weight of 200 or less and activated zinc white;
A rubber composition comprising: a processing aid that does not contain metal soap and contains a fatty acid ester.   The rubber composition according to claim 1, which does not contain paraffin wax.   The rubber composition according to claim 1, wherein the rubber member is immersed in the liquid.   The rubber composition according to any one of claims 1 to 3, wherein the saturated fatty acid is 2-ethylhexanoic acid.   The rubber composition according to any one of claims 1 to 4, wherein a 2-ethylhexanoate zinc salt is contained.

Images