Patent Publication Number: US-8978826-B2

Title: Compressor

Description:
TECHNICAL FIELD 
     The present invention relates to a compressor, and more particularly, to a compressor capable of sufficiently supplying oil to components where sliding occurs not only in a high speed driving mode but also in a low speed driving mode 
     BACKGROUND ART 
     Generally, a compressor is an apparatus for compressing fluid by converting mechanical energy into kinetic energy. This compressor may be largely categorized into a hermetic compressor and a semi-hermetic compressor. In the hermetic compressor, a driving motor and a compression unit for compressing fluid by being operated by the driving motor are installed at one hermetic container. On the other hand, in the semi-hermetic compressor, the driving motor and the compression unit are installed at different hermetic containers. 
     The compressor may be also categorized according to a compression mechanism to compress fluid. For instance, the compressor may be categorized into a rotary compressor, a reciprocating compressor, a scroll compressor, etc. according to a compression mechanism. The reciprocating compressor serves to compress a refrigerant under configurations that a crank shaft is coupled to a rotor of a driving motor, a connecting rod is coupled to the crank shaft, and a piston coupled to the connecting rod performs a linear reciprocation in a cylinder. 
       FIG. 1  is a sectional view showing an example of a reciprocating compressor. 
     As shown, the reciprocating compressor comprises a casing  1  having oil contained at a bottom thereof, a driving motor  10  installed in the casing  1 , a supporting unit  20  for elastically supporting the driving motor  10 , and a compression unit  30  disposed above the driving motor  10 . 
     The compression unit  30  includes a frame  31  elastically supported by the supporting unit  20 , a cylinder block  32  integrally provided at the frame  31 , a crank shaft  33  penetratingly-inserted into the frame  31  and forcibly-inserted into a rotor  12  of the driving motor  10 , a piston  34  inserted into the cylinder block  32 , a connecting rod  35  for converting a rotary motion of the crank shaft  33  into a linear reciprocation by connecting a cam portion of the crank shaft  33  to the piston  34 , a valve assembly  36  coupled to the cylinder block  32 , a discharge muffler  37  coupled to the cylinder block  32  so as to encompass the valve assembly  36 , and a suction muffler  38  installed at the valve assembly  36  so as to be connected to the valve assembly  36 . 
     Unexplained reference numeral  11  denotes a stator, F denotes an oil hole, and an SP denotes a suction pipe. 
     The operation of the reciprocating compressor will be explained as follows. 
     Once the driving motor  10  is operated, a rotation force of the driving motor  10  is transmitted to the crank shaft  33  to rotate the crank shaft  33 . Then, a rotation force of the crank shaft  33  is transmitted to the piston  34  via the cam portion and the connecting rod  35 . As a result, the piston  34  performs a linear reciprocation at an inner space of the cylinder block  32 . Here, the valve assembly  36  is together operated to suck gas to the inner space of the cylinder block  32  through the suction muffler  38 . The sucked gas is compressed, and then is discharged to outside of the casing  10  through the discharge muffler  37 . 
     The oil contained at the bottom surface of the casing  1  is sucked through the oil hole (F) formed in the crank shaft  33  by rotation of the crank shaft  33 . Then, the oil is supplied to components where sliding occurs to perform a lubrication operation, and then remains at the bottom surface of the casing  1 . 
     The compressor constitutes a part of a refrigerating cycle apparatus which generates cool air by using a phase change of a refrigerant, and the refrigerating cycle apparatus is installed at a refrigerator or an air conditioner, etc. The refrigerator or the air conditioner has a different driving state according to a load. More concretely, when a large load is applied to the refrigerator or the air conditioner, the compressor has a large gas compression capacity. On the other hand, when a small load is applied to the refrigerator or the air conditioner, the compressor has a small gas compression capacity. When the compressor has a large gas compression capacity, the driving motor  10  of the compressor is operated in a high speed driving mode to increase a gas compression capacity. On the other hand, when the compressor has a small gas compression capacity, the driving motor  10  of the compressor is operated in a low speed driving mode to decrease a gas compression capacity. If the driving motor  10  rotates in a low speed (less than 45 Hz) due to a small gas compression capacity, the amount of oil pumped up through the oil hole (F) of the crank shaft  33  is reduced by a rotation speed of the crank shaft  33 . This may cause oil to be supplied to components where sliding occurs with an insufficient amount. As a result, the components where sliding occurs are abraded, and thus are not smoothly operated. This may increase a frictional loss to lower the efficiency and to shorten a lifespan. To prevent this, an oil supply amount in a low speed driving mode may be increased through a structural change of the crank shaft. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     However, when the oil supply amount in a low speed driving mode is increased through a structural change of the crank shaft, an oil supply amount is drastically increased in a high speed driving mode. This may increase an input of the compressor, and increase a surface temperature, and increase a suction amount and a discharge amount. More concretely, when the compressor is in a low speed driving mode as shown in  FIG. 2 , an oil supply amount is low enough to be 60% or less than a proper oil supply amount. On the other hand, when the compressor is in a high speed driving mode, an oil supply amount is high enough to be 140% or more than a proper oil supply amount. 
     Therefore, it is an object of the present invention to provide a compressor capable of sufficiently supplying oil to components where sliding occurs not only in a high speed driving mode but also in a low speed driving mode, by increasing an oil supply amount in a low speed driving mode, and by restricting an oil supply amount in a constant or high speed driving mode by making the oil supply amount to be in a saturated state when the compressor has reached a predetermined speed. 
     Solution to Problem 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a compressor, comprising: a casing having oil contained at an inner space thereof; a driving motor installed at the inner space of the casing, and configured to generate a rotation force; a compression unit installed at the inner space of the casing, and configured to compress a refrigerant by receiving a rotation force of the driving motor; and an oil supply unit configured to pump up the oil of the casing to the compression unit by using a centrifugal force generated by the rotation force of the driving motor, wherein in an assumption that a ratio between an oil supply amount and a rotation speed of the driving motor is a gradient, a gradient when the rotation speed of the driving motor is less than a predetermined speed is referred to as a ‘first gradient’, a gradient when the rotation speed of the driving motor is more than a predetermined speed is referred to as a ‘second gradient’ and the second gradient is smaller than the first gradient. 
     According to another aspect of the present invention, there is provided a compressor, comprising: a casing having oil contained at an inner space thereof; a driving motor installed at the inner space of the casing, and configured to generate a rotation force; a compression unit installed at the inner space of the casing, and configured to compress a refrigerant by receiving a rotation force of the driving motor; a crank shaft having an oil hole therein, and configured to transmit the rotation force of the driving motor to the compression unit; and an oil feeder installed so as to be communicated with the oil hole of the crank shaft, and configured to pump up the oil of the casing, wherein an oil supply amount is saturated at a rotation speed corresponding to 70˜80% of a rotation speed of the driving motor or more than. 
     Advantageous Effects of Invention 
     The compressor of the present invention may have the following advantages. 
     Firstly, an oil supply amount in a low speed driving mode may be increased by controlling a shape of an oil passage and the oil feeder, and an oil supply amount in a constant or high speed driving mode may be restricted by making the oil supply amount to be in a saturated state when the compressor has reached a predetermined speed. 
     Secondly, the compressor may have an enhanced performance by supplying a sufficient amount of oil to components where sliding occurs not only in a high speed driving mode but also in a low speed driving mode. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view of a reciprocating compressor in accordance with the conventional art; 
         FIG. 2  is a graph showing a change of an oil supply amount according to a change of a driving speed in the reciprocating compressor of  FIG. 1 ; 
         FIG. 3  is a sectional view of a reciprocating compressor according to the present invention; 
         FIG. 4  is a longitudinal sectional view showing an assembled state of an oil feeder to a crank shaft in the reciprocating compressor according to the present invention; 
         FIG. 5  is a frontal view of the crank shaft and the oil feeder of  FIG. 4 ; 
         FIG. 6  is a sectional view taken along line I-I in  FIG. 5 , which is for explaining the number of turns of an external groove; and 
         FIG. 7  is a graph comparing a gradient change between an oil supply amount and a driving speed with respect to the external groove and the oil feeder according to the present invention, with that of the conventional art. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     Hereinafter, a compressor according to the present invention will be explained in more detail. 
       FIG. 3  is a sectional view of a reciprocating compressor according to the present invention. 
     As shown, the reciprocating compressor comprises a casing  1  having oil contained at a bottom thereof, a driving motor  10  installed in the casing  1  and configured to generate a driving force, a supporting unit  20  configured to elastically support the driving motor  10 , and a compression unit  100  disposed above the driving motor  10 . 
     The compression unit  100  includes a frame  110  disposed above the driving motor  10 , a cylinder block  120  integrally provided at the frame  110 , a crank shaft  130  penetratingly-inserted into the frame  110  and forcibly-inserted into a rotor  12  of the driving motor  10 , a piston  140  inserted into the cylinder block  120 , a connecting rod  150  configured to convert a rotary motion of the crank shaft  130  into a linear reciprocation by connecting a cam portion  133  of the crank shaft  130  to the piston  140 , a valve assembly  160  coupled to the cylinder block  120 , a discharge muffler  170  coupled to the cylinder block  120  so as to encompass the valve assembly  160 , and a suction muffler  180  installed at the valve assembly  160  so as to be connected to the valve assembly  160 . 
     The frame  110  includes a body portion  111  having a flat shape in a horizontal direction, a boss portion  112  extendingly-formed at one side of a bottom surface of the body portion  111  in a vertical direction, and a shaft insertion hole  113  penetratingly-formed at the boss portion  112  and configured to insertion-support the crank shaft  130  therein. 
     As shown in  FIG. 4 , the crank shaft  130  includes a shaft portion  131  having a predetermined length and inserted into the shaft insertion hole  113  of the frame  110 , a balance weight portion  132  extendingly-formed at the end of the shaft portion  131 , a cam portion  133  extendingly-formed at one side of the balance weight portion  132  in a predetermined length so as to be eccentric with the shaft portion  111 , and configured to couple the connecting rod  150  thereto, and an oil hole  134  penetrating the crank shaft  130  in an axial direction. 
     The oil hole  134  of the crank shaft  130  includes a first oil hole  134   a  having a predetermined inner diameter corresponding to a predetermined depth in a length direction from a lower end of the shaft portion  131 , a second oil hole  134   b  consecutive with the first oil hole  134   a  and formed to have an inner diameter smaller than that of the first oil hole  134   a , and a third oil hole  134   c  consecutive with the second oil hole  134   b , inclined from a center line of the second oil hole  134   b  and penetrating the end of the balance weight portion  132 . 
     On an outer circumferential surface of the shaft portion  131  of the crank shaft  130 , formed is an external groove  135   a  communicated with the oil hole  134 . On an inner wall of the first oil hole  134   a  of the shaft portion  131 , formed is an internal groove  135   b  communicated with the external groove  135   a . On an outer circumferential or inner circumferential surface of the shaft portion  131 , formed is a connection groove  135   c  formed in a ring shape and configured to connect the external groove  135   a  and the internal groove  135   b  with each other. At the connection groove  135   b , formed is a first communication hole  136   a  configured to communicate the connection groove  135   b  and the external groove  135   a  with each other. Between the external groove  135   a  and the third oil hole  134   c , formed is a second communication hole  136   b  configured to communicate the external groove  135   a  and the third oil hole  134   c  with each other. 
     The external groove  135   a  is formed on the outer circumferential surface of the shaft portion  131  in a spiral shape, and the external groove  135   a  has a predetermined width and depth. Once the crank shaft  130  has been inserted into the shaft insertion hole  113  of the frame  110 , a region of the shaft portion  131  where the external groove  135   a  is positioned is implemented on an inner wall of the shaft insertion hole  113 . Accordingly, the shaft portion  131  contacts the inner wall of the shaft insertion hole  113  of the frame  110  thus to be supported thereby. 
     The internal groove  135   b  is implemented in the form of one or more curved lines. The curved line of the internal groove  135   b  is formed in the same direction as a rotation direction of the crank shaft  130 , i.e., in an opposite direction to a winding direction of the external groove. Although not shown, when the internal groove  135   b  is formed in plurality in number, the internal grooves  135   b  may be formed in the same direction. In this case, the internal grooves  135   b  may be formed in different directions. 
     An oil feeder  190  configured to pump up the oil contained at the bottom of the casing  1  is coupled to a lower end of the shaft portion  131 . 
     The same reference numerals were given to the same components as those of the conventional art. 
     The operation of the compressor according to the present invention will be explained as follows. 
     As aforementioned, once the driving motor  10  is operated, a rotation force of the driving motor  10  is transmitted to the crank shaft  130  to rotate the crank shaft  130 . Then, a rotation force of the crank shaft  130  is transmitted to the piston  140  via the cam portion  133  and the connecting rod  150 . As a result, the piston  140  performs a linear reciprocation at an inner space of the cylinder block  120 . Here, the valve assembly  160  is together operated to suck gas to the inner space of the cylinder block  120  through the suction muffler  180 . The sucked gas is compressed, and then is discharged to outside of the casing  1  through the discharge muffler  170 . 
     The oil contained at the bottom surface of the casing  1  is pumped up by the oil feeder  190  coupled to a lower end of the crank shaft  130  by rotation of the crank shaft  130 . This oil is sucked through the oil hole  134  formed in the crank shaft  130 , and then is dispersed out to be supplied to components where sliding occurs. 
     A part of the oil sucked to the first oil hole  134   a  of the oil hole  134  is sucked through the external groove  134   a , thereby being supplied to a space between the shaft portion  131  of the crank shaft  130  and the shaft insertion hole  113  of the frame  110 . This oil flows through the third oil hole  134   c  to be supplied to a space between the cam portion  133  of the crank shaft  130  and the connecting rod  150 . Then, this oil is dispersed to inside of the casing  1 . Here, if the internal groove  135   b  is formed at the oil hole  134 , a sufficient amount of oil may be smoothly sucked to be transmitted to the external groove  135   a.    
     The amount of oil sucked through the crank shaft is related to a driving capacity of the compressor, i.e., a rotation speed of the driving motor. 
     For instance, when the compressor is operated in a large capacity mode, i.e., when the driving motor  10  rotates with a high speed (more than 60 Hz), the oil feeder  190  generates a large pumping force while rotating with a high speed by the rotation force of the crank shaft  130 . The oil feeder  190  pumps up the oil contained at the bottom surface of the casing  1  with a large amount. This oil is sucked through the oil hole  134 , the internal groove  135   b  and the external groove  135   a  of the crank shaft  130 . Then, this oil is dispersed to inside of the casing  1  to be supplied to components where sliding occurs. 
     On the other hand, when the compressor is operated in a small capacity mode, i.e., when the driving motor  10  rotates with a low speed (less than 45 Hz), the oil feeder  190  rotates with a low speed due to a small rotation force of the crank shaft  130 . This may cause a relatively small pumping force. Accordingly, the oil contained at the bottom surface of the casing  1  is not smoothly sucked along a flow passage of the crank shaft  130 . As a result, a sufficient amount oil may not be supplied to components where sliding occurs. 
     The oil feeder  190  and an oil passage  134  have to be formed so that a larger amount of oil can be pumped up in a condition that the driving motor has the same rotation speed, with considering that the driving motor  10  rotates with a low speed. However, when the oil passage  134  and the oil feeder  190  are designed to be profitable for oil supply, a larger amount of oil than an optimum amount can be supplied in a constant speed driving mode (e.g., 50 Hz or 60 Hz) as well as a high speed driving mode. This may cause the aforementioned problems, e.g., increment of an input of the compressor, increment of a surface temperature, and increment of a suction amount and a discharge amount. Accordingly, it is preferable to design the oil passage  134  and the oil feeder  190  so that an oil pumping amount can be decreased in a constant speed driving mode as well as a high speed driving mode, whereas an oil pumping amount can be increased in a low speed driving mode. 
     For this, the oil passage  134  and the oil feeder  190  have to be designed so that an oil supply amount can be saturated when the driving motor  10  has a predetermined driving speed, e.g., 40 Hz corresponding to about 70% of a rotation speed of a constant speed type driving motor (or constant speed type compressor), or so that a gradient of an oil supply amount with respect to a rotation speed of the driving motor  10  can be less than 1.0 (more preferably less than 0.5). A ratio of an oil supply amount with respect to a rotation speed of the driving motor  10  (hereinafter, will be referred to as a gradient of an oil supply amount) may be defined as an oil supply ratio difference with respect to a rotation speed ratio difference from a point where an oil supply amount is lowered by a degree more than a predetermined level to a maximum rotation speed (e.g., 140% of a constant speed). The oil passage  134  and the oil feeder  190  have to be designed so that the gradient of an oil supply amount with respect to a rotation speed of the driving motor  10  can be less than 1.0 (more preferably less than 0.5). This means that the oil passage  134  and the oil feeder  190  have to be designed so that a second gradient can be smaller than a first gradient as shown in  FIG. 7 . Here, the first gradient is defined as a gradient of an oil supply amount before a rotation speed of the driving motor  10  reaches a specific speed, and the second gradient is defined as a gradient of an oil supply amount after the rotation speed of the driving motor  10  reaches the specific speed. 
     Here, the gradient of an oil supply amount may be calculated by dividing an oil supply ratio difference by a rotation speed ratio difference. The rotation speed ratio may be calculated by dividing a rotation speed by a constant speed (50 or 60 Hz). And, the oil supply ratio may be calculated by dividing an oil supply amount according to a rotation speed by an oil supply amount in a constant speed driving mode. 
     In order for the oil supply amount to be saturated or to have a gradient less than 1.0 (preferably less than 0.5) at a region corresponding to 70% of a rotation speed of the driving motor  10  (constant speed type driving motor) or more than, the number of turns of the external groove  135   a  disposed on the outer circumferential surface of the crank shaft  130  is properly controlled, and the shape of the oil feeder  190  is properly changed. 
       FIG. 4  is a longitudinal sectional view showing an assembled state of the oil feeder to the crank shaft in the reciprocating compressor according to the present invention,  FIG. 5  is a frontal view of the crank shaft and the oil feeder of  FIG. 4 , and  FIG. 6  is a sectional view taken along line I-I in  FIG. 5 , which is for explaining the number of turns of the external groove. 
     As shown in  FIGS. 4 to 6 , the number of turns of the external groove  135   a  is preferably in the range of about 1˜2 so that a flow resistance against oil can be generated from the external groove  135   a  when the rotation speed of the driving motor  10  reaches about 40 Hz, i.e, so that a winding angle (α) from the first communication hole  136   a  to the second communication hole  136   b  can be about 360˜720° When the number of turns of the external groove  135   a , i.e., the number of turns of the external groove  135   a  from the first communication hole  136   a  to the second communication hole  136   b  is less than 1, a big difference occurs between an oil supply amount in a high speed driving mode and an oil supply amount in a low speed driving mode like in the conventional art. On the other hand, when the number of turns of the external groove  135   a  is more than 1.75, a saturated oil supply amount does not occur if the driving motor rotates with a low speed less than a specific speed. Accordingly, the number of turns of the external groove  135   a  is preferably in the range of 1˜1.75. 
     As shown in  FIGS. 4 and 5 , the oil feeder  190  includes a guide member  191  fixed to a lower end of the crank shaft  130  and configured to guide flow of oil by being communicated with the oil hole  134 , and a pumping member  192  inserted into the guide member  191  and configured to pump up oil. 
     The guide member  191  consists of a cylindrical portion  191   a  having the same inner diameter and coupled to a lower end of the first oil hole  134   a  of the crank shaft  130 , and a conical portion  191   b  integrally extending from a lower end of the cylindrical portion  191   a  and having an inner diameter gradually decreased towards a lower side. Here, the conical portion  191   b  is formed to have a length longer than that of the cylindrical portion  191   a , so as to smoothly pump up oil. 
     A depth of the guide member  191  soaked in oil may be in the range of 10˜30% of a height of a starting end of the external groove  135   a , preferably 15˜25%. For instance, in an assumption that the compressor is kept at an ordinary temperature, the height of the starting end of the external groove  135   a  is in the range of about 65˜68 mm, and the depth of the guide member  191  soaked in oil is in the range of 10˜16 mm. 
     In the reciprocating compressor according to the present invention, an oil supply amount through the oil hole  134  of the crank shaft  130  is increased in a low speed driving mode, but is decreased in a constant speed driving mode as well as a high speed driving mode. 
       FIG. 7  is a graph comparing a gradient change between an oil supply amount and a driving speed with respect to the external groove and the oil feeder according to the present invention, with that of the conventional art. 
     As shown, in the conventional art, when the driving motor rotates with a low speed driving mode (about 50% of a constant speed), an oil supply amount is less than 20% of that in a constant speed driving mode. Furthermore in the conventional art, an oil pumping amount is increased to a gradient of about 1.45 as the rotation speed of the driving motor is increased. However, in the reciprocating compressor having the oil passage  134  and the oil feeder  190  of the present invention, an oil supply amount is increased when the rotation speed of the driving motor  10  is low. And, in the present invention, a saturation phenomenon occurs, i.e., an oil supply amount is not significantly increased when the rotation speed of the driving motor  10  is constant or high. That is, in the present invention, an oil supply amount in a low speed driving mode is increased by 20% of an oil supply amount in a constant speed driving mode or more than. On the other hand, an oil supply amount is decreased as a gradient of a motor rotation ratio with respect to an oil supply amount is drastically decreased, from a region of about 35˜40 Hz corresponding to 75% of that in a constant speed driving mode. 
     In the present invention, the shape of the oil passage and the oil feeder are properly controlled, thereby increasing an oil supply amount in a low speed driving mode of the driving motor, but decreasing an oil supply amount in a constant speed driving mode or a high speed driving mode by implementing a saturation state. Under these configurations, the compressor of the present invention may have an enhanced performance by sufficiently supplying oil to components where sliding occurs not only in a low speed driving mode but also in a high speed driving mode. 
     The compressor of the present invention was applied to a reciprocating compressor. However, the compressor of the present invention may be also applied to a rotation type of motor, and a compressor capable of pumping up oil when the rotation type of motor rotates. 
     It will also be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.