JP2839569B2 - Fluid compressor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a fluid compressor for compressing a medium to be compressed such as a refrigerant gas of a refrigeration cycle.

(Prior art) Compressors as fluid compressors used in refrigeration cycles, such as air conditioners and refrigerators, are generally reciprocating type using a reciprocating piston, and rotary type in which a disk-shaped piston is eccentrically rotated in a cylinder. Etc. are used.

However, fluid compressors of this type all have a drive unit such as a crankshaft that transmits rotational force to compression,
The structure of the compressor is complicated, and the number of parts is large.

Therefore, a fluid compressor called a helical blade type has recently been proposed. This constituted a compressor unit by combining a cylindrical cylinder having one end on the suction side and the other end on the discharge side, and a cylindrical piston provided with a helical blade on the outer peripheral surface. Things.

Specifically, it was a fluid compressor as shown in FIG. 1 to FIG. Here, the helical blade type fluid compressor will be described.

That is, 1 in FIG. 1 shows a hermetic compressor for a refrigerant gas as a fluid compressor used in a refrigeration cycle. The compressor 1 includes a closed case 2, an electric motor unit 3 and a compressor unit 4 disposed in the closed case 2.
And is configured. The electric motor unit 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. Both ends of the cylinder 7 are rotatably fitted into bearings 8 and 9 fixed to the inner surface of the end of the closed case 2. Thereby, both ends of the cylinder 7 are rotatably supported while being airtightly closed.

A cylindrical piston 11 (rotating body) having an outer diameter smaller than the inner diameter of the cylinder 7 is provided in the cylinder 7 along the axial direction of the cylinder 7. This piston
11 is arranged such that its central axis A is eccentric downward from the central axis B of the cylinder 7 by a distance e in FIG. 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.

At both ends in the axial direction of the piston 11, support shafts 12a and 12b are provided, respectively. And these support shafts 12
a and 12b are bearing holes 8c and 9c formed in the bearings 8 and 9, respectively.
The piston 11 is rotatably inserted into the cylinder 7
Can be turned.

A prism section 13 having a square cross section is formed on one support shaft section 12a of the piston 11. An Oldham ring having a rectangular long hole 14 as shown in FIG.
15 are provided. That is, the Oldham ring 15 is slidably fitted to the prism 13 along the longitudinal direction of the long hole 14. As shown in FIG. 2, one end of a pair of pins 16 is slidably provided on the outer peripheral surface of the Oldham ring 15 in a radial direction orthogonal to the longitudinal direction of the long hole 14. The other ends of these pins 16 are fitted and fixed in fitting holes 17 formed in the peripheral wall of the cylinder 7, and the piston 11 is connected to the cylinder 7 eccentrically in the radial direction of the cylinder 7. doing. When the electric motor section 3 is energized by this Oldham coupling and the cylinder 7 is driven to rotate integrally with the rotor 6, the rotational force of the cylinder 7 is increased by the piston through the Oldham ring 15.
11 to be transmitted. That is, the piston
Numeral 11 designates an adduction (rotation while rotating) with a part of the cylinder 7 in contact with the inner surface of the cylinder 7. The fitting hole 17 is hermetically closed by a lid member 18.

A spiral groove 19 is formed on the outer peripheral surface of the piston 11 along the axial direction of the piston 11, as shown in FIGS. The pitch of the groove 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 the groove 19 as shown in FIGS. The thickness of the blade 21 is substantially equal to the width of the spiral groove 19, and each part of the blade 21 is
It can freely move back and forth along the radial direction of. As a result, the outer peripheral surface of the blade 21 is
And slides on the inner peripheral surface of the cylinder 7 in close contact with the inner peripheral surface of the cylinder 7.

The blades 21 divide the space between the cylinder 7 and the inner peripheral surface and the outer peripheral surface of the piston 11 into a plurality of working chambers 22. That is, each working chamber 22 is a blade 21
Formed between two adjacent turns of The shape is substantially crescent extending from the contact portion between the piston 11 and the inner peripheral surface of the cylinder 7 along the blade 21 to the next contact portion. Due to the pitch of the blades 21, the volume of the working chamber 22 gradually decreases from the suction side to the discharge side of the cylinder 7.

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 the suction hole 23 opens inside the cylinder 7. The other end of the suction hole 23 is a suction pipe of a refrigeration cycle (not shown).
24 are connected. A discharge hole 25 is formed in the other bearing 9. One end of the discharge hole 25 communicates with the discharge end side in the cylinder 7. The other end of the discharge hole 25 is opened inside the closed case 2 so that the compressed gas is discharged into the closed case 2.

On the other hand, an oil introduction passage 26 is bored along the center axis A inside the piston 11 as shown in FIG. One end of the oil introduction passage 26 communicates with the bottom of the spiral groove 19 on the discharge side. The other end is a through hole formed in one bearing 8
An opening is formed in the oil reservoir 2a at the bottom of the sealed case 2 via the inlet tube 27 and the inlet tube 28. As a result, when the pressure in the sealed case 2 rises, the lubricating oil stored in the pool 2a
29 passes through the introduction pipe 28, the through hole 27 and the oil introduction passage 26, and the groove 19
Is introduced into a space between the bottom of the blade and the blade 21.

Reference numeral 31 denotes a suction groove, and 32 denotes a discharge pipe for discharging the compressed gas from the inside of the closed case 2 to the refrigeration cycle circuit.

In such a compressor, when the rotor 6 rotates by energization of the electric motor unit 3, the cylinder 7 also rotates integrally with the rotor 6. The piston 11 rotates while turning around the central axis B of the cylinder 7 with a part of the outer peripheral surface being in contact with the inner peripheral surface of the cylinder 7. The 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 that rotates together with the piston 11 rotates while the outer peripheral surface is in contact with the inner peripheral surface of the cylinder 7. Then, each part of the blade 21 is pushed into the groove 19 as it approaches the contact portion 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 portion. Thereby, the suction pipe 24 and the suction hole
As shown in FIGS. 5 to 9, the refrigerant gas sucked into the cylinder 7 through the cylinder 23 has a crescent-shaped working chamber 22.
In the state of being locked in, the piston 11 is sequentially transferred to the working chamber 22 on the discharge side as the piston 11 rotates, and is compressed. Then, the compressed refrigerant gas is discharged to the refrigeration cycle circuit through the discharge hole 25 formed in the bearing 9 on the discharge side, the inside of the sealed case 2, and the discharge pipe 32.

The blade 21 is constantly pressed toward the inner peripheral surface of the cylinder 7 by oil 29 introduced between the groove 19 and the blade 21, thereby preventing gas leakage in the working chamber 22.

(Problems to be solved by the problem) The blades 21 of the compressor have various performances required for refrigerant compression, such as a property that does not deteriorate even when exposed to the refrigerant, and a performance that can be easily fitted into the groove 19 (by elastic deformation). Required to screw into groove 19 (rigidity; low)
Is required.

Therefore, it has been considered to use a resin having properties such as a low coefficient of friction, refrigerant resistance, heat resistance, and low flexural modulus for the blade 21. Specifically, ethylene tetrafluoride (hereinafter referred to as PTFE) is considered.

Considering that blade 21 is made of this resin, PT
The FE forms the blade 21 by using a cutting process.

That is, according to the cutting direction, for example, as shown in FIG. 11, a cylindrical base material 33 is formed by compression molding and firing of a powder of ethylene tetrafluoride resin, and by cutting from the cylindrical base material 33, The blade 21a having the same pitch as shown in FIG. 1 is processed (in this case, “a” is added to the end of the blade 21 in order to clarify the PTFE blade).

Then, as shown in FIG. 13, the blade 21a is fitted into the spiral groove 19 having a variable pitch on the outer periphery of the piston 11. That is, the portion of the blade 21a corresponding to the portion having the large pitch is extended and fitted into the spiral groove 19.

By the way, the blade portion extended and fitted into the groove 19 is, as shown in FIG.
On the side that is in close contact with, is pressed into the groove 19 and is corrected.

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, and twisting occurs due to elastic recovery. When such a twist occurs, the surface contact between the outer peripheral surface of the blade 21a and the inner peripheral surface of the cylinder 7 is impaired.

For this reason, the inner peripheral surface of the cylinder 7 and the outer peripheral surface of the blade 21a may not completely adhere to each other, and the sealing performance may be deteriorated, and the compression performance may be reduced.

Further, the blade 21a made of PTFE has a disadvantage that productivity is not good because the blade 21 must be formed by cutting as described above.

Therefore, considering these points, instead of cutting,
It is conceivable to configure the blade 21 by injection molding.

Specifically, the material of the blade 21 by injection molding includes:
A melt-moldable tetrafluoroethylene / perfluoroalkoxyethylene copolymer resin (hereinafter referred to as PFA) may be considered as satisfying the above conditions.

For example, as shown in FIG. 15, a blade forming chamber 34a having the same pitch as the spiral groove 19 is constituted by a pair of molds 34, and PFA is injected into the molds 34 to form the blade 21b ( Here, "b" is added to the end of the blade 21 to clarify the blade made of PFA). Reference numeral 35 denotes a gate position of the blade forming chamber 34a.

Then, the 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 along the spiral groove 19. Therefore, unlike the case made of PTFE, even when the blade 21b protrudes from the groove 19, the cylinder 7 The outer peripheral surface of the blade 21b completely adheres to the inner peripheral surface of the blade 21b.

In such injection molding, the larger the melt flow index (a measure of the fluidity of the thermoplastic resin at the time of melting: MI; ASTM standard, D-3307), the better the processability.

By the way, the blade 21b used in the helical blade type compressor needs to have high dimensional accuracy and small surface roughness (smoothness of the surface; good) in order to ensure sealing performance and durability.

However, there is a conflicting relationship between dimensional accuracy and surface roughness.

That is, when using a small critical shear rate PEA,
From the point of dimensional accuracy, molding may be performed at a high speed closest to the critical shear rate, but on the other hand, the surface roughness deteriorates. Conversely, in terms of surface roughness, molding may be performed at a lower speed than the critical shear rate, but the dimensional accuracy deteriorates.

That is, when molding is performed at a high speed using PFA having a low critical speed, the surface of the molded article becomes rough, and the smoothness is significantly impaired. Also, when molding is performed at a speed lower than the critical shear rate, the melt viscosity of PFA (because the molten PFA that has flowed into the dies 35, 35 is easily cooled during the flow)
, The injection pressure is not sufficiently applied, and the transferability of the mold shape is significantly impaired.

In addition, as the value of the melt flow index becomes higher,
The critical shear rate is related to increase.

For this reason, the PFA blade 21b is difficult to obtain the required performance because the conflicting dimensional accuracy and surface roughness (surface smoothness) relationship hinders.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fluid compressor excellent in blade sealability and durability.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, a fluid compressor of the present invention comprises a blade having a melt flow index of 20 g / 10 min.
The above-mentioned tetrafluoroethylene / perfluoroalkoxyethylene copolymer is constituted by a molded article formed by injection molding having an average surface roughness of 20 μm or less.

(Operation) The fluid compressor of the present invention has a surface roughness of high dimensional accuracy and high smoothness required for a helical blade type fluid compressor by forming a blade from the above-described molding process. It is possible to obtain a blade having both performances.

Therefore, the sealability and durability of the helical blade type fluid compressor can be improved by the blade made of the fluorinated ethylene / perfluoroalkoxyethylene copolymer.

In addition, since the value of the melt flow index is large, the productivity of the blade is high, and the cost of the compressor can be reduced accordingly.

(Example) Hereinafter, the present invention will be described based on an example shown in FIG.

Here, since the configuration of each component of the helical blade type compressor as the fluid compressor is the same as in FIGS. 1 to 10, the description of the components is omitted, and in this section, the blade 21 as a main part will be described. I will do it.

In this embodiment, the blade 21 of the helical blade type compressor described in the section of the "prior art" was used to form a resin having a melt flow index of 20 g / 10 min or more. PF
A) (corresponding to an ethylene tetrafluoride / perfluoroalkoxyethylene copolymer) formed by injection molding with an average surface roughness of 20 µm or less.

Describing the blade 21, two types of blades 21b are used for the blade 21 according to the first embodiment.

That is, for the blade 21b, a mold 34, 34 having a shape in which the gate position 35 is defined on the discharge end side where the pitch shown in FIG. 15 is small is used, and the melt flow index is determined by an injection molding machine with a mold clamping pressure of 150 tons. (ASTM standard, D-3307, 372 ° C, 5k
A molded article obtained by injection-molding g) so as to have an average surface roughness (smoothness) of “20 μm” is used. By changing the molding conditions, two types of PFA blades 21b are formed. More specifically, the molding conditions for the above injection molding process are cylinder temperature 380 ° C, mold temperature 270 ° C, and injection pressure 1,000k.
g / cm ² and the difference between the two injection times of 3 seconds and 5 seconds,
It comprises two types of molded products.

Then, as a result of applying these blades 21 to the helical blade type compressor shown in FIG. 1, it was found from experiments that the blades 21 injection-molded with a PFA having a melt flow index of 20 g / 10 min or more and an average surface roughness of 20 μm or less were high. It was confirmed that sealability and durability were obtained.

Here, to explain the contents of the experiment, "Freon 12" is used as the refrigerant gas for the compressor, and "3,600 rp" is applied to the cylinder 7 and the piston 11 when the electric motor unit 3 is energized.
m '', and the suction side refrigerant gas pressure `` 0.5 kg / c
m ² ”, and the refrigerant gas pressure discharged at that time was measured.

Then, in this experimental example, the performance of the compressor to which the blade 21 is applied is measured. The measurement time was 10 hours. Under the same conditions, the performance of the compressor when different blades were applied was measured.

In this comparative example, as Comparative Example 1, two types of blades 21c (comparative example 1) injection-molded under the same molding conditions as in Example 1 above using PFA having a melt flow index of 10 g / 10min.
And "c" was added to the suffix to make it clearer), and as Comparative Example 2, a tetrafluoroethylene resin P having a density of 2.15 g / cm ³
A blade 21a formed by equal pitch cutting using TFE) was used.

In addition, in Example 2, two types of blades 21b formed by injection molding using PFA having a melt flow index of 10 g / 10min under the same molding conditions as in Example 1 were also used.

Then, in order to compare the dimensional accuracy and the smoothness of the blades 21b and 21c of the injection molded examples 1 and 2 and the comparative example 1, the gate positions 3 of the molded blades 21b and 21c are compared.
Measure the dimensional difference in the width direction, the dimensional difference in the height direction, and the dent amount due to the sinking of the blade side surface between the portion 5 and the end portion on the opposite side, and the portion of the gate position 35 of the blades 21b and 21c. The average roughness of the surface was measured. The results of this measurement are shown in the attached “Table-1”.

Note that only the measurement of the discharge-side refrigerant gas pressure was performed on the cutting blade 21a different from the injection-molded blades 21b and 21c.

As a result of performing the above experiment, it was found that the results are as shown in FIG.

That is, from FIG. 16, the characteristics obtained with the blade 21c made by injection molding using PFA having a melt flow index of 10 g / 10min in Comparative Example 1 show that the injection time is 3 times.
It can be seen that in the case of seconds, the refrigerant gas pressure on the discharge side rises only up to 5 kg / cm ² . Moreover, 1kg / cm ^{2 for} 5 to 10 hours
The following shows the characteristic that the refrigerant gas pressure decreases.

It was also found that the blade 21c having the same injection time of 5 seconds did not increase the refrigerant gas pressure and was not compressed.

Considering this point, it can be seen from Table 1 that the blade 21c having an injection time of 5 seconds in Comparative Example 1 has considerably poor dimensional accuracy.
It can be seen that compression is no longer performed due to this. In addition, the blade 21c having an injection time of 3 seconds has a slightly higher dimensional accuracy than the previous injection time of 5 seconds, and although a rise in the refrigerant gas pressure is recognized, the surface roughness is large. It is recognized that the refrigerant gas pressure has decreased.

On the other hand, when the characteristics obtained with the blade 21a formed by cutting with the tetrafluoroethylene resin having a density of 2.15 g / cm ³ in Comparative Example 2 were observed, a decrease in the refrigerant gas pressure was observed as in Comparative Example 1. Although not found, the refrigerant gas pressure was only about 6 kg / cm ² , indicating that the sealing property was poor due to poor adhesion as described in the section of “Prior Art”.

On the other hand, the melt flow index of Example 1 was 20 g / 10 mi.
Looking at the characteristics obtained with the blade 21b made by injection molding with PFA n, those with an injection time of 3 seconds have a slight refrigerant gas pressure in 5 to 10 hours because the surface roughness is 20 μm. However, it was confirmed that a high refrigerant gas pressure was output. This is considered to be due to the high dimensional accuracy and the surface roughness of 20 μm.

Also, with the blade 21b having an injection time of 5 seconds, it was found that the refrigerant gas pressure did not decrease even after 10 hours of operation, and compression of 9 kg / cm ² was obtained. This is considered because the surface roughness is 13 μm.

The melt flow index of Example 2 was 35 g / 10 min.
Looking at the characteristics obtained with the blade 21 made by injection molding with the PFA, both the injection time of 3 seconds and 5 seconds, there was no decrease in the refrigerant gas pressure after 10 hours operation, about 10 kg / cm ² And high refrigerant gas pressure was observed. This is considered to be because the blade 21b of the second embodiment is superior to the blade 21b of the first embodiment in terms of both the dimensional accuracy and the surface roughness, and thus has excellent sealing properties.

In summary, the PTFE blade 21a formed by cutting cannot be used for a compressor because the sealing property is significantly reduced.

The blade 21b made by injection molding with a PFA having a melt flow index of less than 20 g / 10min has poor dimensional accuracy. In addition, even if the molding conditions are changed to improve the dimensional accuracy, the surface is so rough that the sealing performance is greatly impaired because the critical shear rate is low, and it is difficult to use the compressor.

According to experiments, especially the melt flow index "20kg
The blade 21b formed by injection molding with a PFA of / 10 min or more and a surface roughness of 20 μm or less can operate the compressor without hindering normal operation. there were. This means that the blade 21b has been required to have the required high dimensional accuracy and high surface roughness, and has become suitable for a helical blade type compressor.

Therefore, the sealing performance and durability of the helical blade type compressor can be improved.

In addition, since the value of the melt flow index is large, the productivity of the blade 21b is high, and the cost of the compressor can be reduced accordingly.

[Effects of the Invention] As described above, according to the present invention, a blade having both high dimensional accuracy and high surface roughness with high smoothness required for a helical blade type fluid compressor can be obtained.

Therefore, it is possible to provide a helical blade type fluid compressor excellent in sealing performance and durability.

In addition, as the value of the melt flow index increases, the productivity of the blade increases, so that the cost of the fluid compressor can be reduced.

[Brief description of the drawings]

1 is a sectional view showing a helical blade type fluid compressor, FIG. 2 is an exploded view showing a compressor section, FIG. 3 is a perspective view showing a piston, and FIG. 4 is an Oldham ring of a piston and a cylinder. FIG. 5 to FIG. 9 are cross-sectional views showing the connecting portion, and FIG.
Figure is a side view of the compressor section, FIG. 11 is a perspective view showing a cylindrical preform of tetrafluoroethylene resin, FIG. 12 is a side view showing a blade manufactured by cutting the cylindrical preform, FIG. 13 is a cross-sectional view showing a compressor section in which a blade made by cutting is incorporated, FIG. 14 is a cross-sectional view showing a compressor section in which a blade made by injection molding is incorporated, and FIG. FIG. 16 is a cross-sectional view showing a mold for injection-molding a blade. FIG. 16 shows a blade according to an embodiment of the present invention, a cutting blade made of ethylene tetrafluoride resin, and an injection-molded blade made of a material having a low melt flow index. FIG. 4 is a diagram showing the discharge side refrigerant gas pressure in comparison with FIG. 7 ... Cylinder, 8,9 ... Bearing, 11 ... Piston, 15
... Oldham ring, 19 ... spiral groove, 21b ... blade.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F04C 18/30-18/352 F04C 2/30-2/352 C08L 27/18

Claims (1)

(57) [Claims] 1. A cylinder having a cylindrical shape which is disposed eccentrically in the cylinder along the axial direction of the cylinder, and a part of which is rotatable relative to the cylinder while a part thereof is in contact with an inner peripheral surface of the cylinder. And a helical groove provided on the outer periphery of the rotator and formed at a pitch that gradually decreases from the suction side to the discharge side of the cylinder. A spiral blade that has an outer peripheral surface that is in close contact with the inner peripheral surface and that partitions a space between the inner peripheral surface of the cylinder and the outer peripheral surface of the rotating body into a plurality of working chambers; A flow characterized by comprising a molded article formed by injection molding of a tetrafluoroethylene / perfluoroalkoxyethylene copolymer having a melt flow index of 20 g / min or more and an average surface roughness of 20 μm or less. Compressor.