JPH08140305A - Thrust magnetic bearing of electric motor for turbo refrigerator or turbo heat pump - Google Patents

Abstract

PURPOSE: To obtain a thrust magnetic bearing which prevents a crack due to swelling, dissolution or a temperature change by a method wherein an aliphatic polyamine in parts by weight within a specific range is added to an epoxy resin in parts by weight at a specific value as a curing agent by a cold setting epoxy resin composition. CONSTITUTION: A bisphenol A type epoxy aliphatic polyamine is added as a curing agent so as to be hardened at room temperature. Addition amounts of an alyphatic polyamine with reference to 100 pts.wt. of a bisphenol A type epoxy are set respectively at 8 pts.wt., 10 pts.wt. and 12 pts.wt. A change in the weight of a molding resin is increased slightly to +1.7, +1.4 and +1.6%. However, their value is extremely small, it is not changed substantially, and the resistance to dissolution and swelling by Freon R-123 is very large. When the aliphatic polyamine in 8 to 12wt.% is added to the epoxy resin, the dissolution and the swelling of the molding resin due to Freon R-123 are suppressed remarkably. In addition, when a silica fine powder and a bulky rope are added, it is possible to prevent a crack from being generated due to a heat cycle test.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor for driving a turbo compressor of a turbo refrigerator or a turbo heat pump used in a refrigerator, an air conditioner or the like, and more particularly to a magnetic air gap of a thrust magnetic bearing of the electric motor. The present invention relates to a thrust magnetic bearing of an electric motor for a turbo refrigerator or a turbo heat pump, which is filled with an epoxy having a high resistance to Freon R-123 as a medium.

[0002]

BACKGROUND OF THE INVENTION Turbo chillers are used as cooling and heating sources in building or factory cooling, and turbo heat pumps are also used in building or factory cooling and heating. A turbo refrigerator and a turbo heat pump are composed of a turbo compressor, an evaporator, a condenser, and the like, in which the turbo compressor uses a circulating heat medium (hereinafter simply referred to as a refrigerant). It is compressed and transferred to a condenser, and is driven by an electric motor. Therefore, the electric motor that normally drives the turbo compressor is assembled integrally with the compressor, and the refrigerant is circulated in the electric motor to cool the heat generated in the coils of the electric motor. Has been done. In the past, mechanical bearings were used for the electric motor that drives this turbo compressor, but this mechanical bearing generates a large amount of vibration and noise during operation. An electric motor that uses a magnetic bearing that utilizes the repulsive force of the same magnetic pole) has been developed. In particular, the thrust magnetic bearing is composed of a coil, a yoke and a magnetic air gap between the magnetic poles S and N, as will be described later (see FIG. 3), and is directly exposed to the CFC refrigerant.

FIG. 2 is a partially cutaway vertical sectional view showing the structure of an electric unit installed in a turbo compressor. The turbo compressor 20 is fixed to the electric unit integrally with bolts and the like is used on the upper side of FIG. However, the description of the main body is omitted because it is not directly related to the technical content of the present invention. FIG. 3 is a cross-sectional view showing an enlarged detail of the portion A in FIG. The main structure of the electric motor 10 of the turbo compressor 20 will be described with reference to FIGS. 2 and 3. A stator 7 is arranged outside the rotor 6 having a rotating shaft 5 in a radial direction with a predetermined gap. There is. Radial magnetic bearings 4 are provided at the end of the rotary shaft 5 of the electric motor 10 connected to the turbo compressor 20 (upper side in FIG. 2) and the axially opposite side (lower side in FIG. 2). The thrust magnetic bearing 1 is provided at the lower axial end in FIG. The turbo compressor 20, a part of which is shown in FIG. 2, and both casings of the electric motor 10 are communicated with each other, and the refrigerant flowing in these spaces also enters the electric motor to be cooled. Therefore, the thrust magnetic bearing 1 serves as a refrigerant. Are exposed to CFCs.

The thrust magnetic bearing 1 will be described with reference to FIG. 3. The thrust magnetic bearing 1 includes a pair of coils 3a and 3b facing each other in the axial direction, and outer yokes 8a and 8b.
Inner yokes 9a, 9b and annular magnetic gaps 2a, 2
As shown in the drawing, the two magnetic poles, which are formed by b and the magnetic poles facing each other in the axial direction, are oriented so that the magnetic poles having the same signs face each other. The flange F that rotates in conjunction with the rotating shaft 5 (see FIG. 2) is arranged with a predetermined gap between the opposing magnetic poles, and is supported by the magnetic field in the thrust direction. Since the refrigerant enters the electric motor 10, the refrigerant that has entered the magnetic gaps 2a and 2b is prevented from coming into contact with the coils 3a and 3b and causing a short circuit. Are molded to prevent the refrigerant from coming into contact with the coil. Conventionally, trichloromonofluoromethane called R-11 has been used as a refrigerant for turbo chillers and turbo heat pumps, but this R-11 destroys the ozone layer in the stratosphere, thus preserving the global environment. For the purpose of 1995
It is decided to be abolished in the year. Dichlorotrifluoroethane (hereinafter referred to as R-123), which has a very small ozone depletion coefficient and is called R-123, is used as a candidate material for a refrigerant to be replaced with R-11 in this type of equipment. Almost all have been decided. However, this R-123 has a greater reactivity to organic substances such as a resin than the conventional R-11 and has a strong swelling action and a dissolving action.
A mold resin that does not swell and dissolve with -123 is needed.

An example of using R-123 in a turbo refrigerator or a turbo heat pump is disclosed in Japanese Patent Application Laid-Open No. 4-237. In this publication, a stator coil of an electric motor is formed by an epoxy resin using an imidazole compound as a curing agent. It describes a resin that is less likely to be dissolved or swelled by the insulating treatment. As the mold resin used in the electric motor, when it is dissolved or swollen by R-123, the CFC refrigerant (R-123) reaches the coil inside the mold resin, invades the insulation of the coil, and causes short circuit between wires. It causes a malfunction and causes the coil to burn out. In addition, the mold resin may crack during the operation of the turbo heat pump, or due to the temperature change caused by the operation or stop of the turbo heat pump.However, even if the refrigerant penetrates into the crack and reaches the coil, May cause burnout. For this reason, the material of the molding resin used for the thrust magnetic bearing must not be one that is invaded or cracked by the Freon refrigerant.

[0006]

However, the mold resin for the thrust magnetic bearing of the electric motor for the turbo heat pump according to the prior art using R-11 as the refrigerant is the epoxy resin or the aromatic polyamine containing the acid anhydride as the curing agent. A mixture of an epoxy resin used as a curing agent and silica powder as an inorganic filler has been used, but these epoxy resin mixtures are strongly swelled and dissolved by the refrigerant R-123 which is a CFC substitute. Therefore, the refrigerant R-12
No. 3 penetrates into the coil and causes a short circuit between the coils, which causes burnout and cannot be used as a material for the mold resin of the thrust magnetic bearing portion. The present invention provides a molded resin for thrust magnetic bearing which can be used by protecting the thrust magnetic bearing without being swelled or dissolved even when it is used in contact with R-123, and without causing cracking due to thermal cycle. The challenge is to provide.

[0007]

The present invention has been made to solve the above-mentioned problems, and is for a thrust magnetic bearing of an electric motor of a turbo refrigerator or a turbo compressor of a turbo heat pump using R-123 as a refrigerant. As a mold resin, an aliphatic polyamine is used as a curing agent for a room temperature curable epoxy resin composition, silica is contained as an inorganic filler to improve crack resistance, and a glass-based rope or cloth is used as an aggregate. The above problems can be solved by putting it in, hardening it at room temperature and using it.

[0008]

As a mold resin for a thrust magnetic bearing of an electric motor for driving a turbo compressor of a turbo refrigerator or a turbo heat pump which uses R-123 having a high reactivity as a refrigerant, glass fiber is used as an aggregate and aliphatic polyamine is used as a mold resin. By molding the epoxy resin composition used as a curing agent into a magnetic gap, the coil of the thrust magnetic bearing is isolated from the refrigerant without causing swelling and dissolution by R-123 and cracking due to temperature change. We were able to.

[0009]

EXAMPLES Comparative Examples and Examples obtained by respectively curing an epoxy resin composition conventionally used as a mold resin and an epoxy resin composition improved to solve the above problems are used as a refrigerant. The results of examining the weight change before and after immersion in R-123 are shown below. Table 1
Is the weight obtained by immersing the respective mold resins of three examples according to the present invention, two comparative examples and two conventional examples after curing treatment in R-123 heated to 105 ° C. for two weeks. It shows the change.

[0010]

[Table 1]

The above Examples 1 to 3 and Comparative Examples 1 and 2
Is obtained by adding an aliphatic polyamine as a curing agent to bisphenol A type epoxy and curing at room temperature. The amount of the aliphatic polyamine added to 100 parts by weight of bisphenol A type epoxy is 8, 10, 12 respectively in Examples 1 to 3.
Parts by weight, and Comparative Examples 1 and 2 are 7, 13 parts by weight, respectively. In Conventional Examples 1 and 2, 115 parts by weight of an acid anhydride was added as a curing agent to bisphenol A type epoxy as a molding resin according to the prior art, and the mixture was heated and cured, and 60 parts by weight of an aromatic polyamine was cured. What was added as an agent and cured at room temperature was used. The weight changes of the mold resins of Comparative Examples 1 and 2 are + 2.6%,
+ 2.4% shows a slight swelling tendency. The weight changes of the mold resins of Conventional Examples 1 and 2 are + 16.3% and-, respectively.
At 5.3%, the former was significantly swollen and the latter was dissolved, and the weight was decreased by 5.3% by immersion, and the tendency of dissolution was large.
Compared with these, the weight changes of the mold resins of Examples 1 to 3 were +1.7, +1.4 and + 1.6%, respectively.
However, the values were very small and substantially unchanged, and it was found that the resistance to dissolution and swelling by R-123 was very large. Next, the results of investigations on the crack resistance of the mold resin against temperature changes will be shown. FIG. 1 is a half-body sectional view showing a test jig used in a heat cycle test. In this test jig, two rings 12a and 12b are concentrically fixed to a disk 11 by a plurality of bolts 13.
A ring-shaped groove is formed between the outer peripheral surface of 2a and the inner peripheral surface of the ring 12b located radially outward, with a gap 12c having a predetermined size. Table 2 shows a comparison of the number of cracks generated in the mold resin by filling the gap 12c with various epoxy resin compositions, molding the test pieces, and subjecting the test jigs to a heat cycle test.

[0012]

[Table 2]

In both Example 4 and Comparative Example 3 of the table, 150 parts by weight of silica fine powder as an inorganic filler was added to 100 parts by weight of the epoxy resin in addition to Example 2 described above. Only used bulky rope as aggregate. Further, the conventional examples 3 and 4 are respectively the above-mentioned conventional example 1
In both Nos. 2 and 2, silica fine powder was added as an inorganic filler to 100 parts by weight of the epoxy resin, and neither aggregate was used. The heat cycle is applied to each mold resin by a method in which the test jig is molded for 2 hours in a heating furnace at 80 ° C. and taken out for 2 hours at room temperature, and the heat treatment is alternately performed. 50 cycles were performed, and after the test, the number of cracks in the mold resin was examined. As a result of this test, the mold resins of Conventional Examples 3 and 4 had 3 and 2 cracks, respectively, and the mold resin of Comparative Example 3 had 8 cracks. Was not cracked. From this result, Example 4 using bulky rope as the aggregate
It was found that since the mold resin of No. 2 has a great resistance to cracking due to thermal cycles, R-123 can be prevented from penetrating and coming into contact with the coil.

As described above, when the aliphatic polyamine is added in the range of 8 to 12 parts by weight with respect to 100 parts by weight of the epoxy resin, the dissolution and swelling of the mold resin by R-123 are remarkably suppressed, and further silica is further added. The addition of fine powder and bulky rope prevented the occurrence of cracks in the heat cycle test. Although the amount of the fine silica powder added was 150 parts by weight with respect to 100 parts by weight of the epoxy resin in the examples of the present invention, generally, if the amount added is too small, the strength of the mold resin is insufficient and cracking occurs. On the other hand, if the amount of addition is too large, the viscosity of the epoxy resin composition will become too high.
100 to 200 parts by weight is preferred. Further, silica is suitable as the inorganic filler because it has a small specific gravity and a low dielectric constant, but it may be an insulating fine powder such as alumina that can be used at low cost. As the epoxy resin according to each of the embodiments of the present invention, bisphenol A type and bisphenol F type epoxy resins as the epoxy component, for example, Epicoat 828, 827, 807 (all are trade names: Yuka Shell Co., Ltd.) are suitable. Can be used. In the examples, bulky rope was mentioned as the aggregate, but bulky cloth, chop strands, filament mats and the like can also be used with similar effects.

[0015]

According to the present invention, a glass fiber bulky rope is used as an aggregate as a mold resin for a thrust magnetic bearing exposed to the refrigerant of an electric motor for driving a turbo compressor used in a turbo refrigerator or a turbo heat pump. By using an epoxy resin composition containing silica powder as a filler and a curing agent for an aliphatic polyamine, R-
Even when 123 is used as a refrigerant, swelling of the resin by the refrigerant,
It has a remarkable effect of preventing the occurrence of cracking due to melting and thermal cycles, and also preventing a short circuit between lines caused by contact of the refrigerant with the coil.

[Brief description of drawings]

FIG. 1 is a half-body sectional view showing a test jig used for a heat cycle test.

FIG. 2 is a partially cutaway vertical sectional view showing the structure of an electric unit installed in a turbo compressor.

FIG. 3 is an enlarged sectional view showing details of a portion A in FIG.

[Explanation of symbols]

 1 Thrust Magnetic Bearing 2a, 2b Magnetic Air Gap 3a, 3b Coil 4 Radial Magnetic Bearing 5 Rotating Shaft 6 Rotor 7 Stator 10 Electric Motor 20 Turbo Compressor

Claims (4)

[Claims] 1. A turbo compressor driven by an electric motor, a condenser, an evaporator, pipes connecting the respective devices, and a control device for controlling the respective devices. In a turbo refrigerator or a turbo heat pump that performs refrigeration or heating / cooling with dichlorotrifluoroethane as a heat medium that circulates inside through the pipe:
The thrust bearing of the electric motor is a magnetic bearing, and the room temperature curing type epoxy resin composition in which 8 to 12 parts by weight of aliphatic polyamine is added as a curing agent to 100 parts by weight of the epoxy resin in the molding resin filled in the magnetic gap. A thrust magnetic bearing for a motor for a turbo refrigerator or a turbo heat pump, characterized in that 2. The epoxy resin of the room temperature curable epoxy resin composition is a bisphenol A type resin or a bisphenol F type resin, and 100 to 200 parts by weight of an inorganic filler such as silica based on 100 parts by weight of the epoxy resin. The thrust magnetic bearing of the electric motor for a turbo refrigerator or a turbo heat pump according to claim 1, which is added. 3. The crack resistance is improved by mixing at least one selected from the group consisting of glass bulky rope, bulky cloth, chop strand and filament mat as an aggregate of the room temperature curable epoxy resin composition. A thrust magnetic bearing for an electric motor for a turbo refrigerator or a turbo heat pump according to claim 1 or 2. 4. A thrust magnetic bearing for an electric motor for a turbo refrigerator or a turbo heat pump according to claim 1, wherein a curing accelerator is added to the room temperature curable epoxy resin composition.