JP2001090772A - Diaphragm for liquid sealed vibration control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a crack of a diaphragm end part by securing sufficient oil resistance, and reducing compression set in a diaphragm used as a flexible rubber film deformed by the negative pressure action of a negative pressure source in a switching control type liquid sealed vibration control device. SOLUTION: In a diaphragm 28 composed of a flexible rubber film deformed by the negative pressure action of a negative pressure source 50 by separating a space with an air chamber 24 connected to the negative pressure source 50 and an atmospheric pressure source 52 so as to be capable of being switched by a part of a wall of one liquid chamber 32 of plural liquid chambers 18, 32, 34 mutually communicated by orifice passages 20, 22, the diaphragm 28 is composed of a rubber composition mainly composed of nitrile rubber having a bonding acrylonitrile quantity not less than 35 wt.% and an iodine value not less than 17 g/100 g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm for a liquid filling type vibration damping device mainly used as an engine mount for an automobile.

[0002]

2. Description of the Related Art A liquid-filled type vibration damping device as a mount for supporting an automobile engine or the like so as not to transmit its vibration to a vehicle body includes a plurality of fluid communication devices connected to each other by an orifice passage. A chamber is provided, and the vibration isolation performance is obtained by the flow of the liquid sealed in these liquid chambers.

In recent years, in order to improve the performance of automobiles, it has been required for engine mounts for automobiles to have improved vibration damping performance both at the time of idling and at the time of running. As disclosed in JP-A-48188, a switching control type liquid filling type vibration damping device has been developed.

[0004] Such a switching control type liquid filled type vibration damping device is
In at least one of the plurality of liquid chambers communicated with each other by the orifice passage, a part of the wall is formed by a diaphragm as a flexible rubber film, and air sealed behind the diaphragm is formed. A negative pressure source and an atmospheric pressure source are switchably connected to the air chamber, and the diaphragm is deformed by the negative pressure action of the negative pressure source to switch the vibration isolation characteristics. It is configured.

In a device equipped with an internal combustion engine such as an automobile, the above-mentioned negative pressure source usually uses an intake system of the internal combustion engine, so that gasoline or oil flowing backward from the combustion chamber side of the internal combustion engine into the intake pipe is used. The oil vapor of the above flows into the air chamber. Therefore, in order to prevent such deterioration due to oil, the diaphragm used as the flexible rubber film is required to have oil resistance.

Therefore, a rubber composition containing nitrile rubber as a main component is used for the diaphragm of such a switch control type liquid-filled type vibration damping device, but a conventional diaphragm using nitrile rubber is not sufficient. Oil resistance is not secured. In addition, since the compression set is too large, liquid leakage from the seal portion may occur due to long-term use.

The present invention has been made in view of such a conventional problem, and a flexible rubber film which is deformed by the negative pressure of a negative pressure source in a switching control type liquid filled vibration isolator. It is an object of the present invention to secure sufficient oil resistance in a diaphragm used as a diaphragm, to reduce compression set, and to prevent liquid leakage from a seal portion.

[0008]

A diaphragm for a liquid filled type vibration damping device according to the present invention comprises a plurality of liquid chambers connected to each other by an orifice passage, and at least one of the liquid chamber walls has a negative pressure. A diaphragm made of a flexible rubber film deformed by the negative pressure action of the negative pressure source, separating the air chamber that is switchably connected to the source and the atmospheric pressure source; A diaphragm in a liquid filled type vibration damping device configured so that vibration damping characteristics can be switched by switching between a negative pressure source and an atmospheric pressure source, the nitrile rubber having a combined acrylonitrile amount of 35% by weight or more as a main component. It comprises a rubber composition.

By setting the amount of bound acrylonitrile to 35% by weight or more, sufficient oil resistance can be ensured as a diaphragm used in a switching control type vibration isolator. That is, the change in mass in the immersion test of the fuel oil C specified in JIS K6258 can be reduced, and deterioration due to oil components such as gasoline and oil from the negative pressure source can be reliably prevented. From such a viewpoint, the amount of bound acrylonitrile is more preferably 40% by weight or more.

[0010] In the diaphragm of the present invention, the nitrile rubber preferably has an iodine value (by the Wis method; the same applies hereinafter) of 17 g / 100 g or more. By setting the iodine value to 17 g / 100 g or more, it is possible to reduce the compression set and prevent liquid leakage from the seal portion due to long-term use. From such a viewpoint, the iodine value is more preferably 23 g / 100 g or more.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As a liquid filled type vibration damping device according to the present invention, specifically, the one shown in FIG. 1 can be mentioned.

A liquid-filled type vibration damping device 10 shown in FIG. 1 is an engine mount for an automobile, and has a first metal fitting 12 attached to an engine which is a vibration source and a first metal fitting 12 attached to a chassis or a frame. An anti-vibration base 16 made of a rubber elastic body is interposed between the two metal fittings 14.

The vibration isolating base 16 has a substantially umbrella shape, and a first metal fitting 12 is vulcanized and bonded at the upper center thereof, and an upper opening of a substantially cylindrical second metal fitting 14 is formed at a lower peripheral portion. Are vulcanized and adhered.

The second metal fitting 14 below the vibration isolating base 16
Inside the main liquid chamber 18 in which the vibration-proof base 16 forms a part of the chamber wall, first and second two orifices 20 and 22 communicating with the main liquid chamber 18, first and second orifices. Having first and second diaphragms 28, 30 communicating with the orifices 20, 22 and separating the air chambers 24, 26 from each other.
And second sub liquid chambers 32 and 34 are provided.

The first orifice 20 and the second orifice 22 have different liquid passage resistances, and the first sub-liquid chamber 32 has a liquid passage resistance in the first orifice 20 having a small liquid passage resistance (large sectional area). The second sub-liquid chambers 34 are connected to the second orifices 22 having a large resistance (small cross-sectional area).

The main liquid chamber 18 is formed between the partition plate 36 and the vibration-isolating substrate 16 by a disk-shaped partition plate 36 disposed opposite to the lower surface of the vibration-isolating substrate 16. The orifice 20 is formed on the outer periphery of the partition plate 36.

The first sub liquid chamber 32 is formed below the partition plate 36 between the first diaphragm 28 and the lower side.
The first diaphragm 28 made of a flexible rubber film is provided with a ring-shaped metal member 38 at a peripheral portion thereof.
Is attached to the upper surface of a partition member 40 which is fitted to the inner surface of the second metal fitting 14 in a liquid-tight manner via a seal rubber. The air chamber 24 is formed between the first diaphragm 28 and the recess at the center of the upper surface of the partition member 40. An orifice 22 is formed on the outer periphery of the partition member 40.

The second auxiliary liquid chamber 34 is formed below the partition member 40 between the second diaphragm 30 and the second sub-liquid chamber 34. The lower surface of the partition member 40 is supported by a ring-shaped metal member 42. The ring-shaped metal member 42 is provided with a ring-shaped metal member 44 disposed on a peripheral portion of the second diaphragm 30 made of a flexible rubber film. The lower part 14a of the second metal part 14 is fixed by caulking together with the bowl-shaped metal part 46 constituting the air chamber 26 below the two diaphragms 30. The bowl-shaped fitting 46 may be omitted and the air chamber 26 may not be provided.

The air chamber 24 separated by the first diaphragm 28 is connected to a switching means 54 such as a valve through a communication path 48 that passes through the inside of the partition member 40 and from the side surface to the outside of the second fitting 14. ing. The switching means 54 is configured to switchably connect the air chamber 24 to an intake pipe of the internal combustion engine, which is the negative pressure source 50, and to open to the atmosphere, which is the atmospheric pressure source 52, such as a command signal from the control unit 56. By the operation described above, either the negative pressure or the atmospheric pressure can be introduced into the air chamber 24.

As a result, the first diaphragm 28 can be switched between a movable state and a non-movable state in accordance with the vibration state. That is, when the first orifice 20 having a small liquid passage resistance is operated, the air chamber 24 is connected to the atmospheric pressure source 52 to make the first diaphragm 28 movable, and the second orifice 22 having the large liquid passage resistance functions. At this time, the air chamber 24 is connected to the negative pressure source 50 to stop the movement of the first diaphragm 28 so that the first orifice 20 having a large sectional area does not function.
With 0 and 22, a sufficient damping effect can be exerted on vibrations in different frequency bands.

In the liquid filling type vibration damping device 10 having the above structure, the first diaphragm 28 forming a part of the chamber wall of the first sub liquid chamber 32 can be switched between a negative pressure source 50 and an atmospheric pressure source 52. Since the air chamber 24 is separated from the air chamber 24, the air chamber 24 is exposed to oil vapor such as gasoline or oil of the internal combustion engine flowing backward from the negative pressure source 50 to the air chamber 24. Therefore, the first diaphragm 28 is required to have oil resistance.

Therefore, as the first diaphragm 28, a flexible rubber film made of a rubber composition containing nitrile rubber as a main component having a bound acrylonitrile amount of 35% by weight or more, preferably 40% by weight or more is used. Although the upper limit of the amount of bound acrylonitrile is not particularly limited, it is usually 50% by weight.
The following is preferred.

As the nitrile rubber, hydrogenated nitrile rubber is preferred. Hydrogenated nitrile rubber is obtained by adding a hydrogen atom to the double bond in the nitrile rubber molecule,
As a result, a double bond is substantially eliminated. More specifically, those having a hydrogenation rate of 80% or more are preferable.

The nitrile rubber preferably has an iodine value of 17 g / 100 g or more, more preferably 23 g, in order to reduce the compression set and prevent the liquid from leaking from the seal portion due to long-term use. / 100g
Above, particularly preferably 26 g / 100 g or more. Although the upper limit of the iodine value is not particularly limited, it is usually 60 g / 10
0 g or less is preferable.

The above rubber composition contains the above nitrile rubber as a main component and various compounding agents usually used therein, for example, a vulcanizing agent such as a peroxide, a vulcanization accelerator, a vulcanization aid, an antiaging agent. It is prepared by appropriately blending and kneading agents, carbon black, zinc white, process oil and the like. Then, the rubber composition is vulcanized and molded according to a conventional method, whereby the diaphragm made of a flexible rubber film is molded.

[0026]

EXAMPLE Six types of hydrogenated nitrile rubbers (hydrogenation rate = 95%) having different bound acrylonitrile amounts in the range of 20 to 50% by weight were used as the nitrile rubber. Rubber compositions 1 to 6 were prepared.

[0027]

[Table 1] A test piece was prepared from each of the obtained rubber compositions, and JIS
An immersion test of fuel oil C specified in K6258 was performed, and the rate of change in mass was measured. The oil resistance was evaluated as follows.
The case of exceeding 0% was evaluated as “x”, the case of 35% to 40% was evaluated as “○”, and the case of less than 35% was evaluated as “◎”. Table 2 shows the results
Shown in

[0028]

[Table 2] As shown in Table 2, when the acrylonitrile content of the nitrile rubber is less than 35% by weight, the mass change is too large, and sufficient oil resistance is obtained as a diaphragm used in a switching control type vibration isolator such as the present invention. I couldn't. In contrast,
When the content was 35% by weight or more, sufficient oil resistance was obtained.

Next, the nitrile rubber has an iodine value of 7
Using six kinds of hydrogenated nitrile rubbers (bonded acrylonitrile amount = 45% by weight, hydrogenation rate = 95%) different in the range of 30 g / 100 g to No. 3 according to the composition shown in Table 1 above. Rubber compositions 7 to 12 were prepared.

A test piece was prepared from each of the obtained rubber compositions, and a compression set test was performed at 100 ° C. for 250 hours at a compression ratio of 25% according to JIS K6262, and the compression set was measured. did. The evaluation was “x” when the compression set exceeded 30%, “○” when it was 30% to 25%, and “◎” when it was less than 25%. Table 3 shows the results
Shown in

[0031]

[Table 3] As shown in Table 3, the iodine value of the nitrile rubber was 15 g /
In the case of 100 g or less, the compression set was too large. However, in the case of 17 g / 100 g or more, the compression set could be suppressed low.

The above No. 9 and no. Using the respective rubber compositions of No. 11, a first diaphragm 28 of the liquid-filled anti-vibration mount 10 shown in FIG. 1 described above was prepared, and the anti-vibration mount 10 was mounted on a passenger car as an engine mount,
A one-year running test was conducted. After the running test, it was confirmed whether or not liquid leakage occurred from the seal portion of the diaphragm 28. In the case of No. 9, liquid leakage occurred, whereas in the case of No. 9, In the case of No. 11, no liquid leakage was observed.

[0033]

As described above, according to the present invention, by setting the amount of acrylonitrile bonded to nitrile rubber to 35% by weight or more, the negative pressure effect of the negative pressure source in the switching control type liquid-filled vibration isolator can be obtained. In the diaphragm deformed by the above, sufficient oil resistance can be secured, and deterioration due to oil such as gasoline and oil from the negative pressure source can be reliably prevented.

The nitrile rubber has an iodine value of 17 g /
By setting it to 100 g or more, it is possible to reduce the compression set and prevent liquid leakage from the seal portion due to long-term use.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a liquid filled type vibration damping device using a diaphragm of the present invention.

[Explanation of symbols]

 10 liquid-filled vibration damping device 18 main liquid chamber 20 first orifice 22 second orifice 24 air chamber 28 first diaphragm 32 first sub-liquid chamber 34 2 sub liquid chamber 48 communication path 50 negative pressure source 52 atmospheric pressure source 54 switching means

Claims (5)

[Claims] A plurality of liquid chambers connected to each other by an orifice passage;
It is formed of a diaphragm made of a flexible rubber film which is separated from a negative pressure source and an air chamber which is switchably connected to an atmospheric pressure source and is deformed by the negative pressure action of the negative pressure source. A diaphragm in a liquid-filled type vibration damping device configured to switch vibration damping characteristics by switching between the negative pressure source and the atmospheric pressure source, wherein a nitrile rubber having a combined acrylonitrile amount of 35% by weight or more is mainly used. A diaphragm for a liquid filling type vibration isolator, comprising a rubber composition as a component. 2. The method according to claim 1, wherein the amount of the bound acrylonitrile is 40% by weight.
The diaphragm according to claim 1, wherein: 3. The nitrile rubber has an iodine value of 17 g / 1.
2. The diaphragm according to claim 1, wherein the weight is not less than 00 g. 4. The nitrile rubber has an iodine value of 23 g / 1.
2. The diaphragm according to claim 1, wherein the weight is not less than 00 g. 5. The diaphragm according to claim 1, wherein said nitrile rubber is a hydrogenated nitrile rubber.