JPH0388993A - Compressor - Google Patents

Abstract

PURPOSE:To enhance the sealing performance and durability by making a blade of a compressor from a copolymeric resin of ethylene tetrafluoride and perfluoroalcoxyethylene having a specific melt flow index through an injection molding process so as to give a certain value of mean surface roughness. CONSTITUTION:A blade 21 of a compressor with helical blade is made from a copolymeric resin of ethylene tetrafluoride and perfluoroalcoxyethylene having a melt flow index over 20g/10min in the form of a molding obtained through an injection molding process so as to give a mean surface roughness below 20mum. To mold this blade 21 a die is used in such a specified shape that the gate position is located at the discharge end to which the pitch reduces, wherein the cylinder temp. is approx. 380 deg.C, die temp. approx. 270 deg.C, and injection pressure approx. 1000kg/cm<2>. This provide a blade equipped with a high dimensional accuracy, a surface roughness with high flatness, which should give the compressor a good satisfactory sealing performance and durability.

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a compressor that compresses a medium to be compressed, such as refrigerant gas in a refrigeration cycle. (Prior art) Compressors used in refrigeration cycles, such as air conditioners and refrigerators, generally use a reciprocating type that uses a reciprocating piston, or a rotary type that rotates a disk-shaped piston eccentrically within a cylinder. There is. However, all of these types of compressors have the disadvantage that the structure of the drive section, such as the crankshaft that transmits rotational force to the compressor, and the compressor section are complex, and the number of parts is large. Therefore, recently, a compressor called a helical blade type has been proposed. The compressor section is constructed by combining a cylindrical cylinder with one end on the suction side and the other end on the discharge side, and a cylindrical piston with a spiral blade on its outer circumferential surface. It is something. Specifically, the compressor was as shown in FIGS. 1 to 10. Here, we will explain this helical blade type compressor. That is, 1 in FIG. 1 indicates a hermetic compressor for refrigerant gas used in a refrigeration cycle. The compressor 1 includes a closed case 2, and a motor section 3 and a compressor section 4 disposed within the closed case 2. The electric motor section 3 includes a substantially annular stator 5 fixed to the inner surface of the sealed case 2 and an annular rotor 6 provided inside the stator 5. The compressor section 4 has a cylindrical cylinder 7. The rotor 6 is coaxially fixed to the outer peripheral surface of the cylinder 7. Further, both ends of the cylinder 7 are rotatably fitted into bearings 8 and 9 fixed to the inner surface of the end portion of the closed case 2. Thereby, both ends of the cylinder 7 are hermetically closed and rotatably supported. A cylindrical piston 11 having an outer diameter smaller than the inner diameter of the cylinder 7 is disposed inside the cylinder 7 along the axial direction of the cylinder 7 . This piston 11 is arranged such that its central axis A is eccentrically downward in FIG. 1 by a distance e with respect to the central axis B of the cylinder 7. With this arrangement, a part of the outer peripheral surface of the piston 11 is brought into contact with the inner peripheral surface of the cylinder 7. Furthermore, support shaft portions 12a and 12b are provided at both axial ends of the piston 11, respectively. These support shaft portions 12a and 12b are rotatably inserted and supported in bearing holes 8c and 9c formed in the bearings 8 and 9, respectively, allowing the piston 11 to pivot relative to the cylinder 7. A prismatic portion 13 having a square cross section is formed on one support shaft portion 12 a of the piston 11 . This prismatic portion 13 is provided with an Oldham ring 15 in which a rectangular long hole 14 is bored as shown in FIG. That is, the prismatic portion 13
An Oldham ring 15 is fitted into the elongated hole 14 so as to be slidable along the longitudinal direction thereof. Further, on the outer circumferential surface of the Oldham ring 15, as shown in FIG.
One end of each is implanted so that it can slide freely. The other ends of these bins 16 are fitted and fixed into fitting holes 17 formed in the peripheral wall of the cylinder 7, and the piston 11 is connected to the cylinder 7 so as to be eccentric with respect to the radial direction of the cylinder 7. are doing. By this Oldham coupling, when the electric motor section 3 is energized and the cylinder 7 is rotated together with the rotor 6, the rotational force of the cylinder 7 is transmitted to the piston 11 via the Oldham ring 15. That is, the piston 11 is connected to the cylinder 7
Inside, a part of the cylinder 7 is in contact with the inner surface of the cylinder 7 and rotates internally (swivels while rotating on its own axis). Note that the fitting hole 17 is hermetically closed by a cover member 18. Further, the outer peripheral surface of the piston 11 has a spiral groove 1 along the axial direction of the piston 11, as shown in FIGS. 1 to 3.
is formed. The pitch of the grooves 19 is gradually reduced from the right side to the left side in these drawings, that is, from the suction side to the discharge side of the cylinder 7. A spiral blade 21 is fitted into this groove 19 as shown in FIGS. 2 and 3. The thickness dimension of this blade 21 almost matches the width dimension of the spiral groove 19, and each part of the blade 21 can freely move forward and backward with respect to the groove 19 along the radial direction of the piston 11. ing. Thereby, the blade 21 slides on the inner circumferential surface of the cylinder 7 with the outer circumferential surface in close contact with the inner circumferential surface of the cylinder 7. The blade 21 partitions the space between the inner circumferential surface of the cylinder 7 and the outer circumferential surface of the piston 11 into a plurality of working chambers 22 . That is, each working chamber 22 is formed between two adjacent windings of the blade 21. In addition,
Its shape is approximately crescent-shaped, extending along the blade 21 from one contact point between the piston 11 and the inner peripheral surface of the cylinder 7 to the next contact point. And this blade 2
With a pitch of 1, the volume of the working chamber 22 is equal to that of the cylinder 7.
It gradually becomes smaller from the suction side to the discharge side. On the other hand, a suction hole 23 penetrates in the axial direction inside the bearing 8 located on the suction side of the cylinder 7. One end of this suction hole 23 opens into the inside of the cylinder 7. A suction pipe 24 of a refrigeration cycle (not shown) is connected to the other end of the suction hole 23. Further, the other bearing 9 is provided with a discharge hole 25 . This discharge hole 2
One end of 5 communicates with the discharge end side inside the cylinder 7. Further, the other end of the discharge hole 25 opens into the inside of the sealed case 2, so that the compressed gas is discharged into the sealed case 2. On the other hand, an oil introduction passage 26 is bored inside the piston 11 along its central axis A, as shown in FIG. One end of this oil introduction path 26 communicates with the bottom of the spiral groove 19 on the discharge side. The other end opens into an oil reservoir 2a at the bottom of the sealed case 2 via a through hole 27 formed in one of the bearings 8 and an introduction pipe 28. As a result, when the pressure inside the sealed case 2 increases, the two lubricating oils stored in the oil reservoir 2a pass through the introduction pipe 28, the through hole 27, and the oil introduction path 26, and connect the bottom of the groove 19 and the blade 21. It is now being introduced into the space between. Note that 31 is a suction groove, and 32 is a discharge pipe for discharging compressed gas from inside the sealed case 2 to the refrigeration cycle circuit. In such a compressor, when the rotor 6 rotates due to energization of the electric motor section 3, the cylinder 7 also rotates together with the rotor 6. The piston 11 rotates while turning around the central axis B of the cylinder 7, with a part of its outer circumferential surface contacting the inner circumferential surface of the cylinder 7. Note that such relative rotational movement between the piston 11 and the cylinder 7 is ensured by the Oldham ring 15. On the other hand, the blade 21 rotating together with the piston 11 rotates with its outer circumferential surface in contact with the inner circumferential surface of the cylinder 7. Then, each part of the blade 21 is pushed into the groove 19 as it approaches the contact area between the outer peripheral surface of the piston 11 and the inner peripheral surface of the cylinder 7, and exits from the groove 19 as it moves away from the contact area. As a result, the suction pipe 24
The refrigerant gas sucked into the cylinder 7 through the suction hole 23 is trapped in the crescent-shaped working chamber 22 as shown in FIGS.
As it rotates, it is sequentially transferred to the working chamber 22 on the discharge side and compressed. Then, this compressed refrigerant gas is
A discharge hole 25 formed in the bearing 9 on the discharge side, and a sealed case 2
Among them, the water is discharged to the refrigeration cycle circuit through the discharge pipe 32. Note that the blades 21 are constantly pressed toward the inner peripheral surface of the cylinder 7 by oil 29 introduced between the grooves 19 and the blades 21, and the blades 21 of such a compressor are exposed to the refrigerant in the working chamber. Various performances necessary for refrigerant compression, such as properties not deteriorating even when the refrigerant is deformed, and performance that allows easy fitting into the groove 19 (performance (rigidity; low) necessary for screwing into the groove 19 while being elastically deformed) are required. Therefore, it has been considered to use a resin having properties such as a small coefficient of friction, resistance to coolant, low heat resistance, and low flexural modulus for the blade 21. Specifically, tetrafluoroethylene (hereinafter referred to as PTFE) is considered. Considering that the blade 21 is made of this resin, P
The blade 21 is formed by cutting the TFE. That is, according to the cutting method, for example, as shown in FIG. 11, a cylindrical base material 33 is formed by compression molding and firing of powder of polytetrafluoroethylene resin, and a cylindrical base material 33 is formed by cutting from this cylindrical base material 33. Machining blades 21a with equal pitch as shown in Fig. 12 (here, PT
In order to clarify that the blade is made of FE, raJ is added to the end of the word blade 21). Then, as shown in FIG. 13, this blade 21a
into the spiral groove 19 of variable pitch on the outer periphery of the piston 11. That is, the portion of the blade 21a corresponding to the larger pitch portion is stretched and fitted into the spiral groove 19. By the way, the blade portion that has been stretched and fitted into the groove 19 is pushed into the groove 19 and corrected on the side where the cylinder 7 and piston 11 come into close contact, as shown in FIG. However, on the side of the working chamber 22 where the cylinder 7 and the piston 11 are separated, the blade portion protrudes from the groove 19 and is opened, causing twisting due to elastic recovery. When such twisting occurs, the surface contact between the outer circumferential surface of the blade 21a and the inner circumferential surface of the cylinder 7 is impaired. For this reason, the inner circumferential surface of the cylinder 7 and the outer circumferential surface of the blade 21a may not be in complete contact with each other, resulting in poor sealing performance and a risk of deterioration of compression performance. Furthermore, since the blade 21a made of PTFE must be constructed by cutting as described above, it has a drawback that productivity is not good. Considering these points, it is conceivable to construct the blade 21 by injection molding instead of cutting. Specifically, the material of the injection molded blade 21 includes:
A melt-moldable tetrafluoroethylene/perfluoroalkoxyethylene copolymer resin (hereinafter referred to as PFA) can be considered as a material that satisfies the above conditions. For example, as shown in FIG. 15, a blade forming chamber 34a having the same pitch as one spiral groove is formed in a pair of molds 34
PFA is injected into this mold 34 to form the blade 2.
1b (in order to clarify that the blade is made of PFA, rbJ is added to the end of the word blade 21). Note that 35 indicates the gate position of the blade forming chamber 34a. Then, this blade 21b is fitted into the spiral groove 19. According to the blade 21b formed by such injection molding, the entire blade has a shape that follows the spiral groove 19, so unlike the blade 21b made from PTFE, the blade 21b follows the groove 19.
Even when the blade 21b jumps out, the outer circumferential surface of the blade 21b is in complete contact with the inner circumferential surface of the cylinder 7. This type of injection molding is based on the melt flow index (a measure of the fluidity of thermoplastic resin when it is melted: MI; AS).
TM standard, D-3307) is larger, the workability is better. By the way, the blade 21b used in a helical blade type compressor needs to have high dimensional accuracy and low surface roughness (good surface smoothness) in order to ensure sealing performance and durability. However, there is a conflicting relationship between dimensional accuracy and surface roughness. That is, when using PFA with a small critical shear rate,
From the viewpoint of dimensional accuracy, it is sufficient to perform molding at a high speed closest to the critical shear speed, but on the other hand, the surface roughness deteriorates. Conversely, from the point of view of surface roughness, it is sufficient to perform molding at a speed lower than the critical shear rate, but dimensional accuracy deteriorates. That is, when molding is performed at high speed using PFA with a small critical speed, roughness occurs on the surface of the molded product, and the smoothness is significantly impaired. Furthermore, when molding is performed at a speed lower than the critical shear rate, sufficient injection pressure cannot be applied because the melt viscosity of PFA is high (because the molten PFA that flows into the mold 35.35 is easily cooled during the flow process). As a result, the transferability of the mold shape is significantly impaired. Note that there is a relationship that the higher the value of the melt flow index, the higher the critical shear rate. For this reason, it has been difficult for the PFA blade 21b to obtain the required performance due to the conflicting relationship between dimensional accuracy and surface roughness (surface smoothness). This invention was made with attention to these circumstances,
The purpose is to provide a compressor with excellent blade sealing properties and durability. In order to achieve the above object, the compressor of the present invention has blades with a melt flow index of 20 fr/
A molded article 'C' is formed by injection molding a tetrafluoroethylene/perfluoroalkoxyethylene copolymer resin of 10 m1n or more to an average surface roughness of 20 μm or less. (Function) The compressor of the present invention achieves both the high dimensional accuracy and high smoothness of the surface roughness required of a helical blade type compressor by constructing the blades through the extrusion process described above. You can get a blade with performance. Therefore, the sealing performance and durability of a helical blade compressor can be improved by using a blade made of fluorinated ethylene◆perfluoroal]oxyethylene copolymer resin. Moreover, since the melt flow index value is large,
Blade productivity is high, and compressor costs can be reduced accordingly. (Embodiment) The present invention will be described below with reference to the embodiment shown in FIG. 16. Here, the configuration of each component of the helical blade compressor is the same as in Figures 1 to 10, so the explanation of that part is omitted.

[7. In this section, the main part, the blade 21, will be explained. In this embodiment, the blades 21 of the helical blade type compressor described in the "Prior Art" section are made of tetrafluoroethylene/perfluoroalkoxyethylene copolymer resin with a melt flow index of 20./1'0 LIin or more. (hereinafter referred to as PFA) has an average surface roughness of 2
It is constructed from a molded body molded by injection molding to a size of 0 μm or less. To explain the blade 21, the blade 21 according to the first embodiment uses two types of blades 21b. That is, for the blade 21b, molds 34, 34 having the shape shown in FIG. 15 and having a gate position 5 on the discharge end side where the pitch is small are used, and a mold clamping pressure of 150 tons is applied.
The melt flow index (A S
A molded article obtained by injection molding TM standard D-3307, 372° C., 5 kg) to have an average surface roughness (smoothness) of “20 μm” is used. Then, two types of PFA blades 2] and b were constructed by changing the molding conditions. Specifically, the molding conditions during the above injection molding process are cylinder temperature of 380°C, mold temperature of 270°C, and injection pressure of 1.0°C.
00 kg/c-, two types of molded products were constructed with two different injection times: 3 seconds and 5 seconds. As a result of applying these blades 21 to the helical blade type compressor shown in Fig. 1, it was found from experiments that a PF with a melt flow index of 20 g/10 cin or more was obtained.
It was confirmed that the blade 21 injection-molded using A with an average surface roughness of 20 μm or less had high sealing performance and durability. Here, to explain the contents of the experiment, "Freon 12" was used as the refrigerant gas in the compressor, and when the electric motor section 3 was energized, the cylinder 7 and piston 11 were heated to r3.6.
The refrigerant gas pressure on the suction side was set to 5 kg/cjJ by rotating at a speed of 00 rpmJ, and the discharge refrigerant gas pressure at that time was measured. In this experimental example, the performance of a compressor to which the blade 21 described above is applied is measured. The measurement time was 10 hours. Under the same conditions, we also measured the performance of the compressor using different blades. In this comparative example, two types of blades 21C were injection molded using PFA with a melt flow index of 10 g/10 m1n under the same molding conditions as in Example 1 (to clarify Comparative Example 1). , with rcJ added to the end of the word), and as comparative example 2, density 2.15sr/c
The blade 21a was formed by cutting at an equal pitch using polytetrafluoroethylene resin (PTFE). In addition, in Example 2, two types of blades 21b made by injection molding under the same molding conditions as in Example 1 were also used using PFA with a melt flow index of 10 g/10 m1n. Then, Example 1 was processed by injection molding. In order to compare the dimensional accuracy and smoothness of the blades 21b, 21c of Comparative Example 1 and Comparative Example 1, the molded blades 21b, 21
Measure the difference in the width direction, the difference in the height direction, and the amount of depression due to thinning on the side of the blade between the gate position 35 and the end portion on the opposite side of the blade 2.
1b. The average roughness of the surface of the gate position 35 of 21c was measured. The measurement results are shown in "Table 1" attached. In addition, only the above-mentioned discharge side refrigerant gas pressure was measured for the blade 21a that was machined and was different from the injection molded blades 21b and 21c. As a result of conducting the above experiment, the following was found as shown in FIG. In other words, from FIG. 16, when looking at the characteristics obtained with the blade 21c made by injection molding using PFA with a melt flow index of 10 g/1011 inches in Comparative Example 1, the one with an injection time of 3 seconds shows that the discharge side Refrigerant gas pressure is 5
It can be seen that it only goes up to kg/c-. Furthermore, the refrigerant gas pressure decreased to 1 kg/C- or less in 5 to 10 hours. In addition, it was observed that the refrigerant gas pressure of the blade 21c for which the same injection time was 5 seconds did not increase and compression was not performed. Considering this point, it can be seen from Table 1 that the blade 21c of Comparative Example 1 with an injection time of 5 seconds has considerably poor dimensional accuracy;
It can be seen that this is why compression is no longer possible. In addition, the blade 21c with an injection time of 3 seconds has a previous injection time of 5 seconds.
Although it is recognized that the refrigerant gas pressure has increased because the dimensional accuracy is slightly improved compared to the second example, it is recognized that the refrigerant gas pressure has decreased because the surface roughness is large. On the other hand, the density of Comparative Example 2 is 2.15 g/an? The blade 21a is made of tetrafluoroethylene resin by cutting.
Looking at the characteristics obtained in Comparative Example 1, the decrease in refrigerant gas pressure was not observed, but the refrigerant gas pressure was 6 kg.
/ cj, indicating that the sealing performance was poor due to poor adhesion as described in the section of "Prior art J." On the other hand, the melt flow index of Example 1 was 20 g/1.
Looking at the characteristics obtained with the blade 21b made by injection molding with 0 mIn PFA, the one with an injection time of 3 seconds has a surface roughness of 20 μm, so refrigerant gas is slightly lost in 5 to 10 hours. Although a decrease in pressure was observed, it was confirmed that high refrigerant gas pressure was being output. This is considered to be due to the high dimensional accuracy and surface roughness of 20μ4. In addition, it was observed that with the blade 21b having an injection time of 5 seconds, there was no decrease in refrigerant gas pressure even after 10 hours of operation, and a compression of 9 kg/cd was obtained. This is considered to be due to the surface roughness of the 13μ layer. In addition, the melt flow index of Example 2 was 35 g/10
Blade 2 made by injection molding with m1n PFA
Looking at the characteristics obtained in No. 1, for both injection times of 3 seconds and 5 seconds, there was no decrease in refrigerant gas pressure even after 10 hours of operation, and a high refrigerant gas pressure of about 10 kg/cd was observed. This is considered to be because the blade 21b of Example 2 has better sealing performance than the blade 21b of Example 1 in terms of both dimensional accuracy and surface roughness. In summary, the PTFE blade 21a constructed by cutting cannot be used in a compressor because its sealing performance is significantly reduced. Also, the melt flow index is 20g/l. The blade 21b made by injection molding with PFA of less than iin has poor dimensional accuracy. Moreover, even if the molding conditions are changed to improve dimensional accuracy, the critical shear rate is small, so roughness occurs on the surface that significantly impairs sealing performance, making it difficult to use in compressors. According to experiments, especially the melt flow index r20
g/10txIn or more” and surface roughness “
Blade 2 formed by injection molding of 20 μm or less
1b is in a condition that does not interfere with normal driving,
It was capable of operating a compressor. This means that the blade 21b has achieved both the required performance of high dimensional accuracy and surface roughness due to the above-mentioned requirements, and has become suitable for a helical blade type compressor. Therefore, it is possible to improve the sealing performance and durability of the helical blade compressor. Moreover, since the melt flow index value is large,
The productivity of the blade 21b is also high, which has the advantage of reducing the cost of the compressor. [Effects of the Invention] As explained above, according to the present invention, a blade can be obtained that has both high dimensional accuracy and high smoothness and surface roughness required for a helical blade type compressor. Therefore, it is possible to provide a helical blade compressor with excellent sealing performance and durability. Furthermore, as the value of the melt flow index increases, the productivity of the blade increases, so it is possible to reduce the cost of the compressor.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a helical blade compressor,'! Figure A2 is an exploded view showing the compressor section, Figure 3 is a perspective view showing the piston, Figure 4 is a sectional view showing the connection between the piston and cylinder by an Oldham ring, and Figures 5 to 9 are refrigerant gas. Fig. 10 is a side view of the compressor section, Fig. 11 is a perspective view showing a cylindrical base material of tetrafluoroethylene resin, and Fig. 12 is a diagram showing the cylindrical base material. A side view showing a blade made by cutting, tA13 is a cross-sectional view showing the compressor section into which the blade made by cutting is installed, and Fig. 14 is a compressor into which the blade made by injection molding is installed. Cross-sectional view showing the machine part, 1st
Figure 5 is a sectional view showing a mold for injection molding the blade, and Figure 16 is a blade of one embodiment of the present invention, a cutting blade made of tetrafluoroethylene resin, and a material made of a material with a small melt flow index. FIG. 3 is a diagram showing a comparison between the refrigerant gas pressure on the discharge side and that of the injection molding blade. 7...Cylinder 8.9...Bearing, 11...Piston, 15...Oldham ring, one...Spiral groove, 21b...Blade.

Claims (1)

[Claims] A cylindrical cylinder with one end on the suction side and the other end on the discharge side, and a cylindrical piston inserted into the cylinder eccentrically so that a part of the outer circumferential surface touches the inner circumferential surface of the cylinder. , a spiral groove formed on the outer peripheral surface of the piston with a pitch that decreases from the suction side to the discharge side; a spiral blade inserted therein; and support means for supporting the end portions of the piston and cylinder, one of which supports the end portions of the piston and the cylinder so as to be rotatable about the axis, and the other end of the piston and the cylinder so as to be rotatable relative thereto;
In the compressor, the blade has a melt flow index of 20 g/10, and a means for rotating the axis support side and rotating the rotating support side relative to the axis in accordance with the rotation.
1. A compressor comprising a molded article formed by injection molding a tetrafluoroethylene/perfluoroalkoxyethylene copolymer resin with an average surface roughness of 20 μm or less.