Patent Description:
In a heat pump type refrigerating appliance which is widely used in an electric appliance such as an air conditioner, a heater and a water heater, HCFC-based refrigerant is conventionally used as refrigerant. However, the HCFC-based refrigerant having large ozone depletion potential is subject to CFCs control. Therefore, R410A (R32: R125 = <NUM>: <NUM>) refrigerant which is HFC-based refrigerant having zero ozone depletion potential is generally used as alternative refrigerant of the HCFC-based refrigerant.

Under these circumstances, efforts are underway to arrest global warming on a world scale. Refrigerant makers, oil makers and air conditioner makers work toward further reduction and improvement of global warming potential (GWP), and work in research and development of new safe refrigerant and oil for new refrigerant.

Working toward such improvement, among the HFC-based refrigerants, R32 refrigerant is a next candidate refrigerant, and a compressor using the R32 refrigerant is proposed (see patent document <NUM> for example). The GWP of the R32 refrigerant is lower than that of R410A refrigerant, and COP (coefficient of performance) of the R32 refrigerant bears comparison with conventional refrigerants.

Moreover, Patent Document <NUM> forming the prior art from which the present invention starts, discloses, inter alia, a refrigerating apparatus. This known refrigerating apparatus comprises a sealed electric driving compressor whose sliding members are made of a material selected from iron type materials, composite materials of aluminum and carbon, iron type materials surface-treated with chromium nitride and ceramic materials.

Furthermore, Patent Document <NUM> discloses a variable capacity rotary compressor allowing oil to be smoothly supplied to compressing elements, regardless of a rotating direction of a rotating shaft. The variable capacity rotary compressor includes a rotating shaft which is rotated in a forward direction or a reverse direction to vary a compression capacity of the compressor. A shaft bearing supports the rotating shaft. An oil guide groove is spirally formed on at least one of the shaft bearing and the rotating shaft to supply oil. An oil storing chamber is defined at an upper portion of the shaft bearing to communicate with the oil guide groove, and stores a predetermined amount of oil therein.

Apart from that, Patent Documents <NUM> and <NUM> disclose, inter alia, a rotary compressor having a main bearing or a sub bearing provided with an oil groove. The depth of the oil groove is deeper than the radial length of an inner peripheral chamber of the main bearing or the sub bearing.

The R32 refrigerant has a feature that a GWP value thereof is low, but a boiling point of the R32 refrigerant is lower than that of the currently used R410A refrigerant. Hence, oil solubility degree of refrigerant is lowered. If the solubility degree is lowered, there is fear that refrigerant which is separated from oil is supplied to a compressor sliding portion when a compressor is operated, and there is fear that sliding-resistant characteristics are deteriorated due to gas-involvement and reliability of the compressor is deteriorated.

Here, one example of a conventional rotary compressor will be described. <FIG> is a vertical sectional view of the conventional rotary compressor described in patent document <NUM>, and <FIG> is a sectional view of a compression element of the conventional rotary compressor. An electric element <NUM> composed of stators <NUM> and a rotor <NUM>, and a compression element <NUM> which is driven by the electric element <NUM> are accommodated in a hermetic container <NUM>. Oil <NUM> is stored in a bottom of the hermetic container <NUM>. As shown in <FIG>, a shaft <NUM> includes an eccentric portion <NUM>.

A cylinder <NUM> forms a compression chamber concentrically with a rotation center of the shaft <NUM>. A main bearing <NUM> and an auxiliary bearing <NUM> hermetically close both side surfaces of the cylinder <NUM>. A piston <NUM> is mounted on an eccentric portion <NUM>, and rolls along an inner wall of the compression chamber. A vane (not shown) is in contact with the piston <NUM> and reciprocates. The compression chamber is partitioned by the vane into a high pressure chamber and a low pressure chamber. One end of a suction pipe <NUM> is press-fitted into the cylinder <NUM>, and opens into the low pressure chamber of the compression chamber, and the other end of the suction pipe <NUM> is connected to a low pressure side of a system (not shown) outside the hermetic container <NUM>. The main bearing <NUM> is provided with a discharge valve (not shown). A discharge muffler <NUM> having an opening is fitted into the main bearing <NUM>. One end of a discharge pipe <NUM> opens into a space in the hermetic container <NUM>, and the other end of the discharge pipe <NUM> is connected to a high pressure side of the system (not shown). An oil-feeding hole <NUM> is formed in the shaft <NUM> in its axial direction, and an oil panel <NUM> is accommodated in the oil-feeding hole <NUM>. The oil-feeding hole <NUM> is in communication, through a communication hole <NUM>, with a space formed by the eccentric portion <NUM> of the shaft <NUM> and the piston <NUM>.

In the above-described configuration, rotation of the rotor <NUM> is transmitted to the shaft <NUM>, and the piston <NUM> fitted into the eccentric portion <NUM> rolls in the compression chamber. The vane which abuts against the piston <NUM> partitions the compression chamber into the high pressure chamber and the low pressure chamber, thereby continuously compressing gas sucked by the suction pipe <NUM>. The compressed gas is discharged into the discharge muffler <NUM> from the discharge valve (not shown), opened into the space in the hermetic container <NUM> and discharged from the discharge pipe <NUM>.

Next, a flow of the oil <NUM> will be described. With rotation of the shaft <NUM>, the oil panel <NUM> accommodated in the oil-feeding hole <NUM> sucks the oil <NUM>. The sucked oil <NUM> is supplied to sliding portions of the eccentric portion <NUM> and an inner periphery of the piston <NUM> through the communication hole <NUM>. The oil <NUM> which lubricated the sliding portions stays in a space surrounded by the inner periphery of the piston <NUM> and a bearing end surface. Thereafter, the oil <NUM> which stays in the space is sucked into the cylinder <NUM> from an end surface of the piston <NUM>, supplied to the compression chamber, lubricates sliding portions of the piston <NUM> and a vane, and seals the compression chamber. Refrigerant filled in the system dissolves in the oil <NUM> which lubricates the compressor, and a solubility degree of refrigerant is lowered as its temperature is raised.

If the compressor which is in a halting state starts operating and a temperature of a compressing mechanism is raised, the oil <NUM> sucked into the compressing mechanism is heated, the solubility degree of refrigerant is lowered, refrigerant is deposited in its gaseous state and becomes air bubbles. Around the sliding portions and an oil groove where gas bubbles are less prone to be discharged, a flow of the oil <NUM> is blocked with the gas bubbles, there is a possibility that the oil <NUM> does not flow, and lubrication failure occurs, a bearing sliding portion seizes or wears. In the case of the R32 refrigerant, a boiling point is low and as a temperature thereof is raised, the solubility degree of refrigerant is largely lowered. Therefore, an amount of generated gas bubbles is larger as compared with the R410a refrigerant, and there is a serious problem that reliability of the bearing is deteriorated.

It is an object of the present invention to provide a rotary compressor capable of excellently supplying oil without being hindered by gas bubbles even if a boiling point of refrigerant is low, and capable of preventing a bearing sliding portion from seizing or wearing.

That is, the present invention provides a rotary compressor as defined in claim <NUM>, comprising, inter alia: a hermetic container storing oil and having a compression element, the compressor using refrigerant including R32, the compression element including: a shaft having an eccentric portion; a cylinder forming a compression chamber concentrically with a rotation center of the shaft; a bearing which hermetically closes both side surfaces of the cylinder and which pivotally supports the shaft; a piston which is mounted on the eccentric portion and which rolls along an inner wall of the cylinder by rotation of the shaft; and a vane which comes into contact with an outer periphery of the piston and which partitions the compression chamber into a high pressure chamber and a low pressure chamber, wherein a substantially spiral oil groove is provided in an inner peripheral surface of the bearing, one end of the oil groove opens at a bearing base portion which is on a side of the compression chamber, and another end of the oil groove opens at a bearing end which is on a side of a space in the hermetic container, and gas bubbles of the refrigerant are discharged into the hermetic container through the oil groove.

According to this configuration, oil existing in a gap between the shaft and an inner periphery of the bearing is discharged into the hermetic container by action of a viscosity pump generated by the substantially spiral oil groove. Therefore, gas bubbles generated in a sliding gap between the shaft and the bearing are forcibly discharged into the hermetic container together with the oil and thus, it is possible to prevent seizing and wearing caused by gas-involvement at the bearing sliding portion.

According to the rotary compressor of the present invention, gas bubbles generated in the sliding gap between the shaft and the bearing are forcibly discharged into the hermetic container, and it is possible to prevent seizing and wearing caused by gas-involvement at the bearing sliding portion. Therefore, even if refrigerant having a low boiling point and which is easily gasified when the refrigerant is dissolved in oil is used, it is possible to secure excellent reliability.

The invention provides a rotary compressor according to claim <NUM>.

According to the invention, oil existing in a gap between the shaft and an inner periphery of the bearing is discharged into the hermetic container by action of a viscosity pump generated by the substantially spiral oil groove. Therefore, gas bubbles generated in a sliding gap between the shaft and the bearing are forcibly discharged into the hermetic container together with the oil and thus, it is possible to prevent seizing and wearing caused by gas-involvement at the bearing sliding portion.

Further, since gas generated from oil can reliably be discharged from the compression element portion into the hermetic container, it is possible to prevent gas from flowing toward the sliding portion of the compression element portion, and to provide a rotary compressor having enhanced reliability.

Optionally, the bearing comprises a main bearing which closes an upper surface side of the cylinder, and an auxiliary bearing which closes a lower surface side of the cylinder, and the oil groove is provided in at least one of the main bearing and the auxiliary bearing.

Accordingly, gas bubbles generated around at least one of sliding portions of both the bearings can forcibly be discharged into the hermetic container, and it is possible to reliably prevent gas-involvement at the bearing sliding portion.

Optionally, the rotary compressor further includes one more oil groove, the oil grooves are provided in both of the main bearing and the auxiliary bearing, respectively, and a width of the oil groove provided in the auxiliary bearing is wider than a width of the oil groove provided in the main bearing.

Accordingly, it becomes easy to discharge gas bubbles generated at the sliding portion of the auxiliary bearing which is located lower than the cylinder, and it is possible to efficiently suppress gas-involvement at the auxiliary bearing, and to secure higher reliability. That is, refrigerant gas has density which is lower than that of oil, and has low viscosity. Therefore, the refrigerant gas flows from the compression element portion upward in the vertical direction of a center axis of the shaft and thus, inconvenience such as gas-involvement is not easily generated at the main bearing. On the other hand, since the auxiliary bearing is soaked in the oil reservoir, gas generated from the compression element portion does not easily flow toward the hermetic container, and gas-involvement is prone to be generated. According to this configuration, it is possible to suppress gas-involvement at the auxiliary bearing where gas-involvement is easily generated, and it is possible to secure a flow of oil. Therefore, high reliability can be secured.

Optionally, a width of the oil groove provided in the bearing end is wider than a width of the oil groove provided in the bearing base portion.

Accordingly, it is possible to amplify a pump effect caused by oil viscosity on the outlet side of the bearing end where flow of oil is reduced with respect to flow of gas, and a flow path of oil can also be secured. Therefore, it is possible to restrain the oil flow from reducing, and to provide a rotary compressor having higher reliability.

The invention is not limited to the following embodiments.

<FIG> is a vertical sectional view of a rotary compressor according to a first embodiment, and <FIG> is a sectional view taken along a line A-A in <FIG>.

The rotary compressor shown in <FIG> and <FIG> uses R32 refrigerant or refrigerant substantially composed of R32. Here, the term "substantially" means a state where refrigerant mainly composed of R32 and refrigerant such as HFO-1234yf or HFO-1234ze are mixed.

As shown in <FIG>, according to the rotary compressor of the embodiment, an electric element <NUM> and a compression element <NUM> are accommodated in a hermetic container <NUM>, and oil is stored in an oil reservoir 3a formed in a bottom of the hermetic container <NUM>. The electric element <NUM> is composed of stators <NUM> and a rotor <NUM>, and the compression element <NUM> is driven by a shaft <NUM> connected to the rotor <NUM>.

The compression element <NUM> is composed of a cylinder <NUM>, a piston <NUM>, a vane <NUM>, a main bearing <NUM> and an auxiliary bearing <NUM>. The cylinder <NUM> is fixed to the hermetic container <NUM>. The piston <NUM> is rotatably fitted over an eccentric portion <NUM> of the shaft <NUM> which penetrates the cylinder <NUM>. The vane <NUM> is fitted into a vane groove <NUM>. The vane <NUM> follows the piston <NUM> which rolls along an inner wall surface of the cylinder <NUM> and reciprocates the vane groove <NUM>. The main bearing <NUM> and the auxiliary bearing <NUM> hermetically close an upper end surface <NUM> and a lower end surface <NUM> of the cylinder <NUM>, and support the shaft <NUM>.

The vane <NUM> is in contact with an outer peripheral surface of the piston <NUM>, and partitions a compression chamber <NUM> in the cylinder <NUM> into a high pressure chamber 16a and a low pressure chamber 16b. One end of a suction pipe <NUM> is press fitted into the cylinder <NUM> to open into the low pressure chamber 16b of the compression chamber <NUM>, and the other end of the suction pipe <NUM> is connected to a low pressure side of a system (not shown) at a location outside the hermetic container <NUM>. A discharge valve (not shown) opens and closes a discharge hole <NUM> which is in communication with the high pressure chamber 16a. The discharge valve is accommodated in a discharge muffler (not shown) which has an opening. One end of a discharge pipe <NUM> opens into the hermetic container <NUM>, and the other end thereof is connected to a high pressure side of the system (not shown).

An operation of the rotary compressor having the above-described configuration will be described below.

First, rotation of the rotor <NUM> is transmitted to the shaft <NUM>. With rotation of the shaft <NUM>, the piston <NUM> fitted over the eccentric portion <NUM> rolls in the compression chamber <NUM>. Since the vane <NUM> which abuts against the piston <NUM> partitions the compression chamber <NUM> into the high pressure chamber 16a and the low pressure chamber 16b, gas sucked by the suction pipe <NUM> is continuously compressed. The compressed gas is released into an internal space of the hermetic container <NUM> through the discharge hole <NUM>, and is discharged from the discharge pipe <NUM> into the system (not shown).

Next, the flow of oil will be described. <FIG> is a sectional view of the auxiliary bearing <NUM> (and main bearing <NUM>) in this embodiment. A substantially spiral oil groove <NUM> is formed in an inner peripheral wall of a hole of each of both the bearings <NUM> and <NUM>, and the shaft <NUM> penetrates the hole. Both ends of each of the bearings <NUM> and <NUM> open at a bearing base portion <NUM> and a bearing end <NUM>.

Oil is stored in the oil reservoir 3a formed in the bottom of the hermetic container <NUM>. With rotation of the shaft <NUM>, oil is sucked from a oil-feeding hole <NUM> formed in a bottom of the shaft <NUM>, and the oil is supplied to the eccentric portion <NUM> under an effect of a centrifugal pump by an oil panel (not shown) provided in the shaft <NUM>. Oil is supplied to a space formed by the eccentric portion <NUM> and the piston <NUM> through a communication hole <NUM> provided in the eccentric portion <NUM>. Oil is supplied to various sliding portions from a clearance between the eccentric portion <NUM> and the piston <NUM> and from a clearance between the piston <NUM> and each of the bearings <NUM> and <NUM>, thereby lubricating the various sliding portions. Oil supplied to the space between the piston <NUM> and the eccentric portion <NUM> is sucked into the oil groove <NUM> of the auxiliary bearing <NUM> under the effect of the viscosity pump caused by the flow generated by rotation of the shaft <NUM>, a flow from the bearing base portion <NUM> toward the bearing end <NUM> is generated and the oil is discharged. While the oil moves in the oil groove <NUM>, the oil reaches a clearance between the shaft <NUM> and the auxiliary bearing <NUM> to lubricate the auxiliary bearing <NUM>.

Concerning the main bearing <NUM> also, oil is sent upward from the bearing base portion <NUM> through the oil groove <NUM> provided in the main bearing <NUM>, and the oil is discharged from the bearing end <NUM>. While the oil moves through the oil groove <NUM>, the shaft <NUM> and the main bearing <NUM> are lubricated with oil.

As described above, oil forcibly flows around the bearings <NUM> and <NUM> in the rotary compressor of this embodiment. Hence, even under refrigerant environment in which refrigerant such as R32 refrigerant is easily gasified when it is dissolved in oil, gasified gas bubbles are forcibly discharged into the hermetic container <NUM>, gas-involvement does not occur at the bearing sliding portion, and it is possible to prevent seizing and galling from generating at the bearings <NUM> and <NUM>.

A width of an oil groove 23b of the auxiliary bearing <NUM> is wider than that of an oil groove 23a of the main bearing <NUM>. Therefore, following effects can be expected.

That is, since density of refrigerant gas is lower than that of oil, an upward force in the vertical direction acts on gas bubbles of refrigerant gas in oil by buoyancy. In the oil groove 23a of the main bearing <NUM>, an upward flow in the vertical direction is generated as a discharging flow of oil from the compression element <NUM> into the hermetic container <NUM>. Hence, since a direction of buoyancy acting on refrigerant gas and a direction of the discharging flow of oil match with each other, gas bubbles of refrigerant gas in the oil groove 23a of the main bearing <NUM> are easily discharged from the compression element <NUM> into the hermetic container <NUM>.

The auxiliary bearing <NUM> is soaked in the oil reservoir 3a, a direction of the discharging flow of oil is downward in the vertical direction, and this direction is opposite from the direction of buoyancy which acts on gas bubbles of refrigerant gas. Therefore, it becomes difficult to discharge the gas bubbles of refrigerant gas from the compression element <NUM> into the hermetic container <NUM>. Hence, it is possible to sufficiently secure the amount of oil supplied under the effect of the viscosity pump by increasing the width of the oil groove 23b of the auxiliary bearing <NUM>, and it is possible to secure high reliability at the auxiliary bearing <NUM> where gas-involvement is prone to be generated by increasing the oil flow more than the main bearing <NUM>.

Further, concerning the substantially spiral oil grooves 23a and 23b of the bearings <NUM> and <NUM>, widths of the oil grooves 23a and 23b provided in the bearing base portion <NUM> are narrower than widths of the oil grooves 23a and 23b provided in the bearing end <NUM>. According to this configuration, an area of the oil groove <NUM> is gradually increased from the bearing base portion <NUM> toward the bearing end <NUM>. According to this, it is possible to continuously amplify the pump effect caused by viscosity toward the bearing end <NUM> with respect to the flow of gas, a flow path can also be secured and therefore, a pressure loss caused by insufficient flow path is not generated. Hence, it is possible to provide a rotary compressor having higher reliability.

<FIG> shows a locus of an axis of the eccentric portion when the eccentric portion receives a varied load and rotates. The upward direction in <FIG> is a direction in which the vane <NUM> is mounted. It can be found in <FIG> that a region (portion other than axis locus A) where a load is not applied exists on the side of the bearings <NUM> and <NUM>. By a load generated by compressing gas in the rotary compressor, the shaft <NUM> rotates eccentrically in a load direction as shown by the axis locus A with respect to centers of the bearings <NUM> and <NUM>. If the oil groove <NUM> is provided in a place having a large load, since areas of the bearings <NUM> and <NUM> which receive the load are reduced, a surface pressure is extremely increased, and there is fear that seizing and galling of the bearings <NUM> and <NUM> are generated. Hence, if the oil groove <NUM> is provided in a place having a small load, it is possible to sufficiently secure a bearing area of a portion to which a load is applied, and excellent lubricating state can be obtained.

<FIG> is a vertical sectional view showing essential portions of a rotary compressor of a second embodiment. The same symbols are allocated to the same functional members as those of the first embodiment, and description thereof will be omitted.

The rotary compressor of the second embodiment includes a plurality of, e.g., two cylinders <NUM>. The oil groove <NUM> described in the first embodiment is employed in the rotary compressor having the plurality of cylinders <NUM>, and the same effect can be obtained.

Kinds of oil are not limited in the above embodiments.

Although the embodiments have been described based on a case where R32 refrigerant or refrigerant which is substantially composed of R32 is used, mixture refrigerant of R32 and other refrigerant may be used. For example, it is possible to use mixture refrigerant of R32 refrigerant and hydrofluoroolefin (e.g., 1234yf) having carbon-carbon double bond. The mixture refrigerant including R32 may include two or more kinds of refrigerants other than R32.

Claim 1:
A rotary compressor which uses refrigerant including R32, and which stores oil and a compression element (<NUM>) in a hermetic container (<NUM>), wherein the compression element (<NUM>) comprises:
a shaft (<NUM>) having an eccentric portion (<NUM>);
a cylinder (<NUM>) forming a compression chamber (<NUM>) concentrically with a rotation center of the shaft (<NUM>);
a bearing (<NUM>, <NUM>) which hermetically closes both side surfaces of the cylinder (<NUM>) and which pivotally supports the shaft (<NUM>);
a piston (<NUM>) which is mounted on the eccentric portion (<NUM>) and which rolls along an inner wall of the cylinder (<NUM>) by rotation of the shaft (<NUM>);
a vane (<NUM>) which is fitted into a vane groove (<NUM>) and which partitions the compression chamber (<NUM>) into a high pressure chamber (16a) and a low pressure chamber (16b), wherein
the vane (<NUM>) contacts the outer periphery of the piston (<NUM>) and follows the piston (<NUM>) which rolls along an inner wall surface of the cylinder (<NUM>) and reciprocates the vane (<NUM>) in the vane groove (<NUM>),
a spiral oil groove (<NUM>) is provided in an inner peripheral surface of the bearing (<NUM>, <NUM>), and
one end of the oil groove (<NUM>) opens at a bearing base portion (<NUM>) which is on a side of the compression chamber (<NUM>), and another end of the oil groove (<NUM>) opens at a bearing end (<NUM>) which is on a side of a space in the hermetic container (<NUM>),
characterized in that
in the spiral oil groove (<NUM>), an opening of the bearing end (<NUM>) is located along the inner peripheral surface of the bearing (<NUM>,<NUM>) in a rotation direction of the shaft (<NUM>) ahead of an opening of the bearing base portion (<NUM>);
and in that
the oil groove (<NUM>) is provided in an angular region not containing an axial locus (A) of the eccentric portion (<NUM>), the angular region being one where no load is applied to the bearing (<NUM>, <NUM>) when the eccentric portion (<NUM>) rotates under a varying load.