JP2002338945A - Sealing rubber composition, o ring and mechanical seal using sealing rubber composition, and coolant compressor using the o ring and the mechanical seal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mechanical seal having strength within a standard without generating a blister and a crack even if it is used for a sliding part of a coolant compressor using a carbon dioxide coolant. SOLUTION: The sealing rubber composition containing a hydrogenated nitrile rubber composition as a main component, the O ring 1 using it and the mechanical seal used in the coolant compressor 2 using the carbon dioxide coolant are provided. The coolant compressor 2 using the O ring and the mechanical seal is further provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for sealing and a rubber composition suitable for use as a sealing material for sliding parts and joint parts of a refrigerant compressor using carbon dioxide as a refrigerant. The present invention relates to an O-ring, a mechanical seal, and a refrigerant compressor using the same.

[0002]

2. Description of the Related Art Freon has conventionally been used as a refrigerant for a refrigerant compressor used in car air conditioners and the like. However, in recent years, replacement with carbon dioxide (CO ₂ ) has been promoted from the viewpoint of environmental problems such as depletion of the ozone layer due to the use of chlorofluorocarbon.

The sliding part of a refrigerant compressor such as an air conditioner is
A gap formed between a shaft of the compressor and a shaft hole of the housing is sealed with a mechanical seal so that the refrigerant does not leak out of the compressor. FIG. 7 shows a typical example of a conventional mechanical seal. That is, this type of mechanical seal is mounted on a mating ring 101 mounted on the housing 30 in a non-rotating state so as to be movable in the shaft direction via a case 103 and a packing 104 on the shaft 5 side, and is integrated with the shaft 5. Rotating seal ring 102
Is pressed by the urging force of the coil spring 105 to prevent the refrigerant and the refrigerating machine oil in the compressor internal space on the right side in the figure connected to the outer peripheral side of the sliding end surfaces of the two rings 101 and 102 from leaking to the atmosphere side space. It is what is being prevented.

In a conventional refrigerant compressor using chlorofluorocarbon as a refrigerant, a mechanical seal using an O-ring made of styrene-butadiene rubber or a fluorine-based rubber composition is used to maintain an appropriate sealing effect. Was.

FIG. 2 shows a graph of a refrigeration cycle of a refrigerant compressor of carbon dioxide refrigerant, and FIG. 3 shows a graph of a refrigeration cycle of a refrigerant compressor of Freon (R134a).
The pressure applied to Freon in the refrigeration cycle is about 0.2 MPa ~
3.0 MPa, and CFCs do not exceed the supercritical point. However, carbon dioxide is about 2.3 MPa to 13 MPa.
It is used under high pressures, and is used under conditions exceeding the supercritical point.

Under such conditions, carbon dioxide is
There is a characteristic that reactivity to rubber as a sealing material increases. Therefore, if styrene-butadiene rubber or fluorine-based rubber, which has been used as a fluorocarbon refrigerant, is used as a seal material for a mechanical seal, carbon dioxide permeates the rubber at high pressure, and as the pressure decreases, carbon dioxide becomes rubber. Swelling in the interior, causing the problem of tears and blisters. Such cracks and blisters degrade the mechanical seal and lose its sealing function, so that the conventional mechanical seal cannot be used in a refrigerant compressor using a carbon dioxide refrigerant.

Japanese Patent Application Laid-Open No. 11-293075 discloses a fluororubber composition in which graphite or mica is added to fluororubber having excellent resistance to carbon dioxide used as a refrigerant. However, a mechanical seal using a sealing material made of a fluororubber composition cannot avoid the occurrence of blisters and tears.

[0008]

SUMMARY OF THE INVENTION The present invention provides a rubber composition for sealing which does not generate blisters or cracks and has a small expansion (volume change rate) when carbon dioxide is used as a refrigerant under conditions exceeding the supercritical point. It is an object to provide an O-ring and a mechanical seal using a rubber composition and a refrigerant compressor using the same.

[0009]

In order to achieve the above object, the present invention provides a rubber composition for sealing used in a carbon dioxide atmosphere, comprising a hydrogenated nitrile rubber composition as a main component, and this seal. An O-ring characterized by including a rubber composition for sealing, and a mechanical seal characterized by using a sealing material including the rubber composition for sealing. Further, the present invention provides a refrigerant compressor for carbon dioxide refrigerant, wherein the O-ring and / or the mechanical seal described above is used for a required seal portion.

[0010]

Embodiments of the present invention will be described below in detail. Note that the embodiments described below do not limit the present invention.

FIG. 4 shows a refrigerant compressor using the mechanical seal of the present invention. In this compressor, when the shaft 5 operates, the rotation drives the orbiting scroll 9 via the orbiting drive mechanism. Due to the rotation of the scroll, the line contact portions of the two spiral projections 11, 18 gradually move toward the center of the spiral, and as a result, the closed space 21a,
21b (compression chamber) moves toward the center of the spiral while reducing the volume. Accordingly, the refrigerant that has flowed into the suction chamber 15 through the suction port (not shown) is taken into the closed space 21a from the outer terminal openings of the spiral projections 11 and 18, and is compressed while being compressed. From the center portion 21c of the fixed scroll 8 and then from the discharge port 38 to the radiator. in this way,
In the process of compressing the refrigerant, the refrigerant compressor has a cooling function through a cycle as shown in FIG.

Although the refrigerant normally operates on the above-described path, the shaft 5 is a sliding part,
Since a gap is formed between the shaft and the shaft insertion hole, there is a possibility that the refrigerant slightly leaks therefrom. In order to prevent these, a sealing material is used between the shaft 5 and the housing 30. Conventionally, a mechanical seal using a sealing material made of a fluorine-based rubber as a raw material, more specifically, a mechanical seal using an O-ring of a fluorine-based rubber has been adopted.
Problems such as blistering occur. Therefore, a metal seal is used for the fixed seal portion 3 where sliding is small. Since the metal seal lacks elasticity, there is a defect that the sealability is insufficient for use in a sliding portion. However, a metal seal having no permeation leakage is appropriately used for the non-sliding portion. The metal seal is preferably SUS
Is used, but is not limited to this.

The sliding portion is a portion of the shaft 5, and it is necessary to prevent the refrigerant from leaking through the O-ring 1 constituting the mechanical seal. Such a mechanical seal can be provided in the refrigerant compressor 2 of the present invention with the same structure as the conventional example shown in detail in FIG. The conditions required for the mechanical seal are the conditions of applying high pressure to carbon dioxide, more specifically, about 80 degrees, about 2.2 degrees where refrigerant is used.
Under the conditions of MPa to 10 MPa, swelling is small and blisters are not generated. Therefore, it is necessary that the carbon dioxide has low permeability. As a result of the study, attention was paid to the fact that a material containing a hydrogenated nitrile rubber composition as a main component, which is a substance having a high intermolecular cohesion force, as a substance satisfying such conditions, has a low carbon dioxide permeability.

The hydrogenated nitrile rubber has the following general formula:

Embedded image Which is a compound of a nitrile rubber obtained by copolymerizing butadiene and acrylonitrile, in which the double bond of butadiene is highly hydrogenated. Nitrile rubber has been used for O-rings, oil seals, belts and the like for automobiles. It is known that hydrogenated nitrile rubber obtained by hydrogenating this is further excellent in oil resistance, heat resistance and the like.

Further, in the refrigerant compressor, refrigeration oil is used for the purpose of maintaining the lubrication of the sliding portion. Under a high pressure, not only carbon dioxide but also a refrigerating machine oil component may permeate into a rubber composition used for a mechanical seal and cause swelling. Therefore, the sealing material of the present invention must be free from blisters and cracks even if oil is permeated at high temperature and high pressure, and must not lose the strength required for the sealing material.

Taking these conditions into consideration, it is preferable that the main component of the sealing material used for the mechanical seal of the sliding portion when the carbon dioxide refrigerant is used is a hydrogenated nitrile rubber composition. For example, C = of nitrile rubber (NBR)
Hydrogenated C double bond to reduce as much as possible.
Those based on saturated nitriles can be used. Preferably, the hardness of the hydrogenated nitrile rubber composition is from 80 to
95, and more preferably 88 to 92.

Such a composition can be produced by utilizing a known technique.

FIG. 1 shows an O-ring 1 which is one embodiment of the present invention and which constitutes a sealing material of a mechanical seal.
Such an O-ring can be manufactured by a known technique using a hydrogenated nitrile rubber composition. Further, the mechanical seal of the present invention is not limited to the O-ring, and a member having the same configuration as that of the conventional example shown in FIG. 7 can be manufactured using the hydrogenated nitrile rubber composition.

The mechanical seal using the O-ring made of the hydrogenated nitrile rubber composition of the present invention does not generate blisters and has a low rate of volume change even when used in the presence of a carbon dioxide refrigerant and refrigeration oil. Relatively low. This is a greatly improved characteristic as compared with a conventional mechanical seal.

When the mechanical seal of the present invention is used in a refrigerant compressor using a carbon dioxide refrigerant, the leakage of the refrigerant from the mechanical seal is 0.28 when the pressure is 9.7 mPa.
cm ³ / h, which was smaller than the target value of 0.54 cm ³ / h.

Further, when the strength of a mechanical seal using such a new hydrogenated nitrile rubber sealing material (O-ring) was examined, the tensile strength, tensile stress, and tensile elongation were all the current values of R134a. The required values for the product were satisfied. Tensile strength, tensile stress, tensile elongation, rate of change in tensile strength, tensile elongation after immersing these mechanical seals in a refrigerant in which about 13% of a PAG-based oil is mixed with carbon dioxide refrigerant at 80 ° C. and 15 MPa for 100 hours. Both the rate change rates were within the required standard values.

As described above, the mechanical seal using the sealing material made of hydrogenated nitrile rubber roughly conforms to the standard value of R134a, and can be preferably used as the mechanical seal.

[0023]

The present invention will be described by way of examples. The examples are not given for the purpose of limiting the invention. In this embodiment, the resistance to carbon dioxide refrigerant was compared using O-rings made of different materials as the mechanical seal. [A immersion test] First, the state of the O-ring when the O-ring was immersed in a carbon dioxide refrigerant alone under the conditions of use of the refrigerant compressor was examined for the hydrogenated nitrile rubber O of the present invention.
The ring was compared with another rubber O-ring. The table below shows the O-rings used. Refrigerant, using the CO ₂ of Dainippon Aga gas. The specification is a liquefied gas of 99.9% purity.

[0024]

[Table 1]

The test includes a physical property test of the sealing material and
The tensile strength test was performed as follows. The test was based on a conventional sealing material evaluation test for CFC refrigerant R134a. This test corresponds to an acceleration test under the operating conditions of the refrigerant compressor using the O-ring of the present invention.

In the test procedure, first, the physical properties of each sample were measured. The sample was sealed in an autoclave device, and the inside of the device was evacuated for 15 minutes. Thereafter, a refrigerant was sealed in the device, the amount of the refrigerant was adjusted based on the total weight of the device, and allowed to cool at room temperature for 30 minutes. Next, the apparatus was put into a high-temperature oil bath and adjusted to 80 degrees over a few hours. Inside the device is 80 degrees, 15.0 MP
After confirming that it became a, it was immersed for 100 hours. After 100 hours, the mixture was allowed to cool at 25 ° C. and 5.0 MPa overnight. Thereafter, the refrigerant was quickly discharged within one minute, and the sample was taken out.

Table 2 shows the results of the change in volume and the presence or absence of blister immediately after the test and after 24 hours.

[0028]

[Table 2]

FIG. 5A shows an O-ring made of urethane rubber having blisters. The blister 40 is shown in FIG.
The expansion of the rubber resulting from the expansion of the gas in the O-ring as shown in FIG. FIG. 6 shows a fluororubber O-ring having a crack. Cracks are those in which the gas has expanded in the O-ring and the rubber has been torn. The O-ring made of hydrogenated nitrile rubber of the present invention did not cause a problem that the volume change rate was small and blisters and cracks were generated even when the O-ring was immersed in a refrigerant and a pressure difference was applied. On the other hand, it has been found that fluorine-based rubber, which has been conventionally used for a refrigerant, is liable to cause blisters and cracks when immersed in the refrigerant, and that the volume change rate is so large that the specifications are not satisfied. EPDM does not cause blisters or cracks, but doubles in volume due to swelling and is unsuitable for use as an O-ring. It was found that blisters were generated in other urethane-based rubbers and were not suitable for carbon dioxide refrigerant.

[B Immersion Test] An O-ring in an actual refrigerant compressor is used under conditions of being exposed to a mixture of carbon dioxide refrigerant and refrigerating machine oil at high temperature and high pressure. In the B immersion test, the following experiments were performed on two types of hydrogenated nitrile rubber O-rings that exhibited suitable properties as a sealing material in the A immersion test, and the strength was measured. The same refrigerant as used in the A immersion test was used as the refrigerant, and the refrigerating machine oil used was R134a's current refrigerating machine oil (for CAC) based on PAG oil.

In the test procedure, first, the normal physical properties and tensile strength of each specimen were measured. Next, two samples of one kind of sample were sealed in an autoclave device, and the inside of the device was filled with 15 samples.
Vacuum degassed for minutes. Thereafter, the refrigerating machine oil was sealed to such an extent that the sample was completely immersed, the refrigerant was sealed in the apparatus, the amount of the refrigerant was adjusted from the total weight of the apparatus, and the apparatus was allowed to cool at room temperature for 30 minutes.
Next, the apparatus was put into a high-temperature oil bath and adjusted to 80 degrees over a few hours. After confirming that the inside of the apparatus had reached 80 ° C. and 15.0 MPa, it was immersed for 100 hours. After 100 hours, 25
The mixture was allowed to cool at 5.0 MPa overnight. Thereafter, the refrigerant was quickly discharged within one minute, and the sample was taken out. Immediately after the test,
The normal physical properties after 24 hours and the tensile strength immediately after the test were measured.

Table 3 shows the results of the normal physical property test of the O-ring specimen immediately after the B immersion test and after 24 hours. From this result, it can be seen that the volume change rate immediately after the immersion test is larger than when the carbon dioxide refrigerant is used alone. Also, after 24 hours, when the carbon dioxide refrigerant alone was used, gas was released, and the volume was restored to the same volume as a new product, but when the refrigerating machine oil was used in combination, the oil remained in the sample. The volume did not return.

[0033]

[Table 3]

Next, the results of measuring the strength of the sample before the test and the sample after the B immersion test are shown in Tables 4 and 5.
Shown in

[0035]

[Table 4]

[0036]

[Table 5]

From these results, it was found that all the specimens after the test maintained the strength within the standard. This B
From the results of the immersion test, the hydrogenated nitrile rubber O-ring has a large volume change rate when the carbon dioxide refrigerant and the refrigerating machine oil are used together, but does not generate blisters or cracks and has the necessary specifications in terms of strength. It turned out to be full. Therefore, it was found that the hydrogenated nitrile rubber O-ring of the present invention can be suitably used for a refrigerant compressor using a carbon dioxide refrigerant.

In the above-described embodiment, an example in which the present invention is applied to an O-ring as a seal material of a mechanical seal has been described. However, as shown in FIG. The same applies to the O-ring 1a interposed in the sliding portion between the back pressure block 8a provided on the fixed scroll 8 and the housing 30a.

[0039]

The sealing rubber composition containing the hydrogenated nitrile rubber composition of the present invention as a main component, the O-ring and the mechanical seal using the same can be used even if a carbon dioxide refrigerant is used under high pressure. The rate is low and the quality deterioration due to the occurrence of blisters and tears is small. In addition, the refrigerant compressor for carbon dioxide refrigerant using the O-ring and / or the mechanical seal of the present invention has less refrigerant leakage, and the durability of the O-ring and the mechanical seal is improved as compared with the conventional one. I understood that.

[Brief description of the drawings]

FIG. 1 is a diagram showing an O-ring used for one embodiment of the present invention and a mechanical seal.

FIG. 2 is a diagram showing a refrigeration cycle when carbon dioxide is used as a refrigerant.

FIG. 3 is a diagram showing a refrigeration cycle when chlorofluorocarbon (R134a) is used as a refrigerant.

FIG. 4 is a diagram showing a cross section of a refrigerant compressor for carbon dioxide refrigerant using the O-ring and the mechanical seal of the present invention.

FIG. 5 is a view showing a blister resulting from a refrigerant immersion experiment of a mechanical seal.

FIG. 6 is a diagram showing cracks generated as a result of a refrigerant immersion experiment of a mechanical seal.

FIG. 7 is a view showing a conventional mechanical seal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 O-ring 1a O-ring 2 Refrigerant compressor 3 Fixed seal part 5 Shaft 8 Fixed scroll 8a Back pressure block 9 Orbiting scroll 11 Spiral projection 15 Suction chamber 18 Spiral projection 21a Sealed space (compression chamber) 21b Sealed space (compression chamber) 21c closed space (compression chamber) 30 housing 30a housing 34 discharge port 38 discharge port 40 blister 41 crack 101 mating ring 102 seal ring 103 case 104 packing 105 coil spring

Continued on the front page (72) Inventor Takayuki Hagita 1 Nagoya Laboratory, Iwazuka-cho, Nakamura-ku, Nagoya-shi, Aichi Prefecture Inside of Nagoya Research Laboratory, Mitsubishi Heavy Industries, Ltd. Address: Mitsubishi Heavy Industries, Ltd. Cooling Business Division (72) Inventor Kiyohito Matsukawa 60 Kutsubo, Iwazuka-cho, Nakamura-ku, Nagoya-shi, Aichi F-1 term in Churyo Engineering Co., Ltd. 3H003 AA05 AB06 AC03 AD03 BC01 3J040 AA01 AA13 BA02 FA06 4H017 AA03 AC01 AC11 AC14 AD03 AE05

Claims (4)

[Claims] 1. A sealing rubber composition used under a carbon dioxide atmosphere, comprising a hydrogenated nitrile rubber composition as a main component. 2. An O-ring comprising the rubber composition for sealing according to claim 1. 3. A mechanical seal using a sealing material comprising the rubber composition for sealing according to claim 1. 4. A refrigerant compressor for carbon dioxide refrigerant, wherein the O-ring according to claim 2, the mechanical seal according to claim 3, or both of them are used for a required seal portion.