DESCRIPTION
Title of Invention
HERMETIC ROTARY COMPRESSOR
Technical Field
[0001]
The present invention relates to a hermetic rotary compressor intended for refrigeration cycles and that compresses refrigerant gas. Background Art [0002]
To allow a piston to be fitted onto an eccentric shaft in a process of assembling a compressor, a value obtained by subtracting the amount of eccentricity of the eccentric shaft with respect to the center of a main shaft or a countershaft from the radius of the eccentric shaft needs to be equal to or greater than the radius of the main shaft or the countershaft. Supposing that the value obtained by subtracting the amount of eccentricity from the radius of the eccentric shaft is smaller than the radius of the main shaft or the countershaft, if it is attempted to pass the main shaft or the countershaft through the piston and fit the piston onto the eccentric shaft, the outer periphery of the eccentric shaft and the inner periphery of the piston interfere with each other. Therefore, the piston cannot be fitted onto the eccentric shaft. [0003]
To increase the displacement volume of the compressor for increasing the capacity of the compressor, the outer diameter of the piston needs to be reduced, and the amount of eccentricity needs to be increased.
However, the above restriction imposed on the process of fitting the piston onto the eccentric shaft makes it impossible to increase the amount of eccentricity such that the value obtained by subtracting the amount of eccentricity from the radius of the eccentric shaft becomes smaller than the radius of the main shaft or the countershaft. [0004]

To solve the above problem, in a hermetic compressor according to a known technique, the diameter of the countershaft of the crankshaft is made smaller than the diameter of the main shaft, whereby the value obtained by subtracting the amount of eccentricity from the radius of the eccentric shaft is made to be equal to or greater than the radius of the countershaft (see Figs. 1 and 7 in Patent Literature 1, for example). Citation List Patent Literature [0005]
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2011-127430 Summary of Invention Technical Problem [0006]
The hermetic compressor disclosed by Patent Literature 1, however, has the following problems. Since the diameter of the countershaft is small, there is a high probability that the bearing unit may burn out. Furthermore, since the displacement volume is increased, that is, since the length of the eccentric shaft is increased, the eccentric shaft is likely to bend easily. If the length of the eccentric shaft is increased to increase the displacement volume, the eccentric shaft, which bears a gas load generated in the compression chamber, bends in microscopic order. If the eccentric shaft bends significantly, the countershaft is tilted in the counterbearing. Accordingly, the thickness of oil film in the bearing is reduced, and the smoothness of the bearing unit is deteriorated. Hence, the shaft and the bearing may burn out during the operation of the compressor. Consequently, the compressor may stop, being unable to restart. Regarding such problems, the relationship between the length of the counterbearing and the length of the eccentric shaft is not considered in the technique disclosed by Patent Literature 1. [0007]

The present invention is to solve the above problems and provides a hermetic rotary compressor that exhibits an increased displacement volume and an increased output without reducing the reliability so that a counterbearing does not burn out. Solution to Problem [0008]
A hermetic rotary compressor according to an embodiment of the present invention includes a sealed container that houses a motor provided in an upper part and a compression mechanism provided below the motor, the motor and the compression mechanism being connected to each other with a crankshaft. The compression mechanism includes the crankshaft including a main shaft that is fixed to the motor, a countershaft that is coaxial with the main shaft, and an eccentric shaft that is provided between the main shaft and the countershaft and is eccentric with respect to a center axis of the main shaft; a roiling piston fitted on the eccentric shaft; a cylinder having thereinside a cylindrical space in which the rolling piston is provided, the cylinder being fixed in the sealed container; a vane that sections a compression chamber into a suction-side compression chamber and a discharge-side compression chamber, the compression chamber being defined by an inner surface of the cylinder and an outer periphery of the rolling piston that orbits in the cylinder; a main bearing that closes an opening at an axial end of the cylinder from an upper side and bears rotation of the main shaft; and a counterbearing that closes an opening at another axial end of the cylinder from a lower side and bears rotation of the countershaft. Letting a length of the countershaft be L and a length of the eccentric shaft be I, 1/L is 0.75 or smaller.
Advantageous Effects of Invention [0009]
According to the above embodiment of the present invention, since the ratio of the length of the eccentric shaft to the length of the counterbearing is set appropriately, a hermetic rotary compressor that exhibits an increased displacement volume and an increased output without reducing the reliability so that the bearing does not burn out can be provided.

Brief Description of Drawings [0010]
[Fig. 1] Fig, 1 is a vertical sectional view of a hermetic rotary compressor according to Embodiment 1.
[Fig. 2] Fig. 2 is a schematic diagram illustrating a piston and a vane-type compression chamber according to Embodiment 1.
[Fig. 3] Fig. 3 is a diagram illustrating a crankshaft of the hermetic rotary compressor according to Embodiment 1.
[Fig. 4] Fig. 4 is a table that summarizes the relationship between a ratio l/L and the occurrence of surface roughness of a countershaft in the hermetic rotary compressor according to Embodiment 1.
[Fig. 5] Fig. 5 is a schematic diagram illustrating an orbit-type compression chamber.
Description of Embodiment [0011]
Embodiment 1
Fig. 1 is a vertical sectional view of a hermetic rotary compressor 100 according to Embodiment.
The hermetic rotary compressor 100 includes a sealed container 1 in which a high-pressure atmosphere is contained. The sealed container 1 includes an upper container 1a and a lower container 1b. A motor 2 including a stator 2a and a rotor 2b, and a compression mechanism unit 3 that is driven by the motor 2 are housed in the sealed container 1. [0012]
A rotational force generated by the motor 2 is transmitted through a crankshaft 4 to the compression mechanism unit 3. [0013]
The crankshaft 4 includes a main shaft 4a fixed to the rotor 2b of the motor 2, a countershaft 4b provided across the compression mechanism unit 3 from the main shaft 4a, and an eccentric shaft 4c provided between the main shaft 4a and the

countershaft 4b. The countershaft 4b is coaxial with the main shaft 4a. The reiative outer diameters of the main shaft 4a, the countershaft 4b, and the eccentric shaft 4c are set such that a value obtained by subtracting the amount of eccentricity of the eccentric shaft with respect to the center of the main shaft and the countershaft from the radius of the eccentric shaft 4c becomes equal to or greater than the radius of the main shaft. The crankshaft 4 has an oil-feeding hole thereinside.
A main bearing 5 is fitted on the main shaft 4a of the crankshaft 4 with a clearance for sliding interposed therebetween and supports the main shaft 4a such that the main shaft 4a is rotatable. Acounterbearing 6 is fitted on the countershaft 4b of the crankshaft 4 with a clearance for sliding interposed therebetween and supports the countershaft 4b such that the countershaft 4b is rotatable. The length of the main bearing 5 in the axial direction is set so as to be as long as possible in a space between the compression mechanism unit 3 and the motor 2. The counterbearing 6 is designed as long as possible in accordance with the axial length of the countershaft 4b in a space below the compression mechanism unit 3. [0014]
Two axial ends of an internal space of a cylinder 7 in which a rolling piston 8 siidably fitted on the eccentric shaft 4c of the crankshaft 4 and a vane 13 are housed are closed with the main bearing 5 provided on the upper side in Fig. 1 and with the counterbearing 6 provided on the lower side in Fig. 1, whereby a compression chamber 9 is provided. [0015]
Fig. 2 is a schematic diagram illustrating the piston and the vane-type compression chamber according to Embodiment.
The compression mechanism unit 3 includes the cylinder 7 and the vane 13. The cylinder 7 is fixed to the inner periphery of the sealed container 1. The cylinder 7 has the internal space, which has a cylindrical shape. The rolling piston 8 rotatably fitted on the eccentric shaft 4c of the crankshaft 4 is positioned in the internal space. The vane 13 moves along a groove provided in the cylinder 7. The vane 13 moves by following the movement of the rolling piston 8 that orbits in the cylinder 7. Thus,

the vane 13 sections the compression chamber 9 defined by the inner wall of the
cylinder 7 and the rolling piston 8 into a suction-side compression chamber 9a and a
discharge-side compression chamber 9b.
[0016]
An accumulator 12 is provided adjacent to the sealed container 1. A suction
connecting pipe 10 connects the cylinder 7 and the accumulator 12 to each other.
[0017]
The rolling piston 8 is fitted on the eccentric shaft 4c of the crankshaft 4 that
eccentrically rotates in the cylinder 7 with the rotation of the crankshaft 4.
Refrigerant gas compressed by the rolling piston 8 and the vane 13 is discharged into
the sealed container 1 and is delivered through a discharge pipe 11 to a refrigeration
cycle such as a refrigerating and air-conditioning apparatus.
[0018]
Fig. 3 is a diagram illustrating the crankshaft of the hermetic rotary compressor
100 according to Embodiment.
In the crankshaft 4, the main shaft 4a and the countershaft 4b are coaxial with each other, and the center axis of the eccentric shaft 4c is shifted from the center axis of the main shaft 4a and the countershaft 4b. As illustrated in Fig. 3, letting the length of the eccentric shaft 4c of the crankshaft 4 be I and the length of the countershaft 4b be L, l/L is set to 0.75 or smaller. [0019]
The hermetic rotary compressor 100 is configured as described above. Therefore, for example, if the length of the eccentric shaft 4c is increased to increase the displacement volume of the compressor 100 for increasing the capacity of the compressor, the eccentric shaft 4c that bears a gas load generated in the compression chamber 9 bends in microscopic order. If the eccentric shaft 4c bends significantly, the countershaft 4b supported by the inner periphery of the counterbearing 6 is tilted. Accordingly, the thickness of oil film provided at the contact part between the counterbearing 6 and the countershaft 4b is reduced in some part, triggering deterioration in the smoothness of the counterbearing 6. In

contrast, according to Embodiment, since the ratio l/L of the length I of the eccentric shaft to the length L of the countershaft 4b of the crankshaft 4 is set to 0.75 or smaller, the crankshaft 4 that bears the gas load can exhibit high rigidity. Hence, the tilting of the countershaft 4b within the inner periphery of the counterbearing 6 can be suppressed. [0020]
Fig. 4 is a table that summarizes the relationship between the ratio l/L and the occurrence of surface roughness of the countershaft in the hermetic rotary compressor 100 according to Embodiment. The circular marks in the table each indicate that no roughness was observed in the surface of the countershaft 4b that is in contact with the counterbearing. The cross marks in the table each indicate that roughness was observed in the surface of the countershaft that is in contact with the counterbearing. In an experiment conducted by using a hermetic rotary compressor 100 that was actually in use, while the ratio l/L of the length of the eccentric shaft 4c to the length of the countershaft 4b was varied, whether or not burnout occurred was checked. As a result, when l/L was greater than 0.75, surface roughness due to abrasion of the sliding surface, which is a sign of burnout, was observed. When l/L was 0.75 or smaller, some abrasion was observed but the abraded surface was smooth, which was not considered to be a sign of burnout. [0021]
The material of the crankshaft 4 included in the hermetic rotary compressor 100 according to Embodiment that exhibited the results summarized in Fig. 4 had a modulus of longitudinal elasticity of 150000 to 220000 N/mm2. Furthermore, the smaller the ratio l/L, the higher the rigidity of the crankshaft 4, which is advantageous in suppressing the burnout of the bearing. In a typical hermetic rotary compressor 100, the practical lower limit of l/L is about 0.5. [0022]
The elements of the crankshaft 4 according to Embodiment have the following dimensions.

The countershaft 4b has a length I of 10 mm to 100 mm. The countershaft 4b has a diameter of 10 mm to 50 mm. The countershaft 4b and the counterbearing 6 each have a length that influences the level of the pressure generated by the load borne by the bearing unit. That isJ the shorter the length, the greater the pressure and the higher the probability of burnout. The countershaft 4b and the counterbearing 6 each have a diameter that influences the relative speeds at the respective contact surfaces of the countershaft 4b and the counterbearing 6. The faster the relative speeds, the higher the probability that the bearing unit may burn out. The smaller the diameters of the countershaft 4b and the counterbearing 6, the higher the relative speeds.
The eccentric shaft 4c has a diameter of 20 mm to 80 mm. The diameter of the eccentric shaft 4c influences the displacement volume. The greater the diameter, the greater the displacement volume and the greater the load borne by the eccentric shaft 4c. The greater the load, the higher the probability that the bearing unit may burn out.
The countershaft 4b has an outer diameter that is smaller than the outer diameter of the main shaft 4a by about 0 to 5 mm. Since the countershaft 4b is thinner than the main shaft 4a, the amount of eccentricity of the eccentric shaft 4c can be made greater than in a case where the main shaft 4a and the countershaft 4b have the same diameter. Thus, the displacement volume can be increased. Here, the value obtained by subtracting the amount of eccentricity of the eccentric shaft 4c with respect to the center of the countershaft 4b from the radius of the eccentric shaft 4c needs to be equal to or greater than the radius of the countershaft 4b but may be smaller than the radius of the main shaft 4a. If such conditions are satisfied, the rolling piston 8 can be fitted from the side of the countershaft 4b.
Operating conditions (the rotation speed, the refrigerant to be used, and the lubricant) for the hermetic rotary compressor 100 are the same as those for a hermetic rotary compressor 100 intended for typical refrigerators and other like apparatuses. [0023]

In the hermetic rotary compressor 100 configured as described above, since the ratio i/L of the length ! of the eccentric shaft to the length L of the countershaft 4b of the crankshaft 4 is set to 0.75 or smaller, the bending of the eccentric shaft 4c of the crankshaft 4 under the gas load borne by the eccentric shaft 4c can be suppressed. Accordingly, the roughening of the counterbearing that supports the rotating crankshaft 4 and the burnout of the bearing can be prevented. Thus, the hermetic rotary compressor 100 can exhibit high reliability in spite of an increased displacement volume thereof. [0024]
While Embodiment concerns a case where the rolling piston 8 and the vane 13 are separate members, the hermetic rotary compressor 100 may employ an orbit-type piston in which the rolling piston 8 and the vane 13 are combined together to form an integral body. In such a case also, a highly reliable hermetic rotary compressor 100 as to be described below can be obtained.
Fig. 5 is a schematic diagram illustrating an orbit-type compression chamber 9. Portions of the compression mechanism unit 3, which has been described above, corresponding to the roiling piston 8 and the vane 13, respectively, are combined together to form an integral body, thereby forming an orbit-type rolling piston 8a. The cylinder 7 is configured in such a manner as to fit the orbit-type rolling piston 8a. [0025]
In a norma! operation, the refrigerant to be taken into the hermetic rotary compressor 100 and to be compressed therein is gas as a compressible fluid. In some situations such as at the start of the hermetic rotary compressor 100 and in an operation at a iow ambient temperature, liquid refrigerant as a non-compressible fluid may be taken into the hermetic rotary compressor 100 from the refrigeration cycle. If liquid refrigerant as a non-compressible fluid is taken into and compressed in the hermetic rotary compressor 100, the pressure in the compression chamber 9 suddenly rises. Accordingly, an excessive load is applied to the main bearing 5 and the counterbearing 6 that bear the compression load. [0026]

In the hermetic rotary compressor 100 including the roiling piston 8 and the vane 13 that are separate members, if the pressure in the compression chamber 9 suddenly rises, the vane 13 also receives the pressure. Then, an outward force acts on the vane 13 in the compression chamber 9, and the vane 13 moves away from the rolling piston 8, causing the high-pressure side (the discharge-side compression chamber 9b) and the low-pressure side (the suction-side compression chamber 9a) of the compression chamber 9 to communicate with each other. Hence, the rise of the pressure is prevented. Thus, the bearing load applied to the main bearing 5 and the counterbearing 6 is eased, and the bearing unit is prevented from being damaged. [0027]
In contrast, in the hermetic rotary compressor 100 including the rolling piston 8 and the vane 13 that are combined together to form an integral body, the above-described sudden rise of the pressure in the compression chamber 9 cannot be prevented. Consequently, an excessive load may be applied to the bearing unit, increasing the probability that the bearing unit may be damaged. However, the above-described ratio l/L of the length I of the eccentric shaft 4c to the length L of the crankshaft 4 is set to 0.75 or smaller. Therefore, even in the case where liquid refrigerant as a non-compressible fluid is compressed, the bearing unit is prevented from burning out and from being damaged, whereby an advantageous effect of increasing the reliability of the hermetic rotary compressor 100 can be produced. Reference Signs List [0028]
1 sealed container 1a sealed container 1b sealed container 2 motor 2a stator 2b rotor 3 compression mechanism unit 4 crankshaft 4a main shaft 4b countershaft 4c eccentric shaft 5 main bearing 6 counterbearing 7 cylinder 8 rolling piston 8a (orbit-type) rolling piston 9 compression chamber 9a suction-side compression chamber 9b discharge-side compression chamber 10 suction connecting pipe 11 discharge pipe 12 accumulator 13 vane 100 hermetic rotary compressor L length of countershaft I length of eccentric shaft

CLAIMS [Claim 1]
A hermetic rotary compressor comprising:
a sealed container housing a motor provided in an upper part and a compression mechanism provided below the motor, the motor and the compression mechanism being connected to each other with a crankshaft,
the compression mechanism including
the crankshaft including a main shaft fixed to the motor, a countershaft coaxial with the main shaft, and an eccentric shaft provided between the main shaft and the countershaft and being eccentric with respect to a center axis of the main shaft;
a rolling piston fitted on the eccentric shaft;
a cylinder having thereinside a cylindrical space in which the rolling piston is provided, the cylinder being fixed in the sealed container;
a vane configured to section a compression chamber into a suction-side compression chamber and a discharge-side compression chamber, the compression chamber being defined by an inner surface of the cylinder and an outer periphery of the rolling piston configured to orbit in the cylinder;
a main bearing configured to close an opening at an axial end of the cylinder from an upper side and bears rotation of the main shaft; and
a counterbearing configured to close an opening at another axial end of the cylinder from a lower side and bears rotation of the countershaft,
wherein l/L is 0.75 or smaller where a length of the countershaft is L and a length of the eccentric shaft is I. [Claim 2]
The hermetic rotary compressor of claim 1,
wherein an outer diameter of the countershaft is smaller than or equal to an outer diameter of the main shaft. [Claim 3]

The hermetic rotary compressor of claim 1 or 2, wherein the rolling piston and
the vane are combined together to form an integral body.
[Claim 4]
The hermetic rotary compressor of any one of claims 1 to 3,
wherein the crankshaft is made of a material having a modulus of longitudinal
elasticity of 150000 to 220000 N/mm2.