Abstract:
A back-gap controlling apparatus for compressor is proposed to reduce an initial torque for the motor of a compressor. A high pressure between the two scroll units of the compressor can temporarily separate the two scroll units. The casing pro se or a sealing buffer can be used to limit a displacement amount of the scroll unit The excessive displacement of scroll unit can be prevented to enhance lifetime of motor.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a back-gap controlling apparatus for a compressor, and more particularly to back-gap controlling apparatus for a compressor to temporarily separate two scroll units of the compressor, thus reducing initial torque to operate the motor and limiting a displacement amount of scroll unit.  
         [0002]     The scroll compressor generally comprises two scroll units in spiral shape, wherein one scroll unit is fixed and referred to as fixed scroll, and another scroll unit has rotational movement with respect to the fixed scroll and is referred to as orbital scroll. The two scroll units are engaged each other and have 180-degree phase difference.  
         [0003]     The orbital scroll has rotation around the fixed scroll, thus forming closed space therebetween. A working fluid is shrunk, within the closed space, from peripheral to center, and then ejected out of the two scroll units. In this way, the compression stroke is provided.  
         [0004]     In above-mentioned operation, the orbital scroll is driven by a driving member. It is well known that a static friction coefficient is larger than a dynamic friction coefficient for moving a body. Therefore, a larger force is required to move the orbital scroll. The driving member requires large torque to overcome a static friction between the orbital scroll and the static scroll. The driving member has risk of damage and the lifetime of the driving member is reduced.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention provides a back-gap controlling apparatus for compressor to prevent an excessive displacement amount of the orbital scroll and the fixed scroll of the compressor and to prevent fluid leakage.  
         [0006]     Accordingly, the present invention provides a back-gap controlling apparatus for compressor. The back-gap controlling apparatus comprises a casing comprising an accommodation space therein; an orbital scroll arranged in the accommodation space; and a fixed scroll arranged in the accommodation space and engaged with the orbital scroll. A compressed fluid pressure due to an operation between the orbital scroll and the fixed scroll will push the fixed scroll away from the orbital scroll. An abutting section to limit a displacement amount of the fixed scroll is provided between the casing and the fixed scroll. 
     
    
     BRIEF DESCRIPTION OF DRAWING  
       [0007]     The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself however may be best understood by reference to the following detailed description of the invention, which describes certain exemplary embodiments of the invention, taken in conjunction with the accompanying drawings in which:  
         [0008]      FIG. 1  shows a sectional view of the first preferred embodiment of the present invention.  
         [0009]      FIG. 2  shows the first preferred embodiment of the present invention before balance.  
         [0010]      FIG. 3  shows the first preferred embodiment of the present invention after balance.  
         [0011]      FIG. 4  shows a sectional view of the second preferred embodiment of the present invention.  
         [0012]      FIG. 5  shows a sectional view of the third preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]      FIG. 1  shows a sectional view of the first preferred embodiment of the present invention. The present invention provides a back-gap controlling apparatus for compressor. The compressor comprises a casing  10  composed of a first shell  101  and a second shell  102  below the first shell  101 . The inner diameter of the first shell  101  is equivalent to the inner diameter of the second shell  102  to define an accommodation space for accommodating other elements in the compress. An orbital scroll  20  is placed in the casing and connected to a driving member  40 . A fixed scroll  30  is arranged in the casing  10  and engaged with the orbital scroll  20 . A floating oil seal  70  is provided atop the fixed scroll  30 . When the orbital scroll  20  and the fixed scroll  30  begin to operate, a fluid pressure generated by compression will push the fixed scroll  30  away from the orbital scroll  20 . Moreover, an abutting section  50  is provided between the orbital scroll  20  and the fixed scroll  30  to limit the displacement amount of the fixed scroll  30 , thus providing the back-gap controlling apparatus according to the present invention. In one preferred embodiment of the present invention, the abutting section  50  is a baffle plate placed within the first shell  101  and atop the fixed scroll  30  and the oil seal  70 , thus limiting the axial displacement amount of the fixed scroll  30 .  
         [0014]      FIGS. 2 and 3  show the first preferred embodiment of the present invention before and after balance, respectively. The oil seal  70  can be pushed upward when the driving member  40  is rotated. At this time, a back pressure chamber  80  is defined by the oil seal  70  and the fixed scroll  30 . Moreover, the oil seal  70  and a baffle plate screwed to the casing  10  will separate a high pressure chamber  90  and a low pressure chamber  91 . When the fixed scroll  30  is pushed away from the orbital scroll  20 , the contact area between the orbital scroll  20  and the fixed scroll  30  can be reduced. Therefore, the static friction is reduced. As already mentioned, to move a body in rest state needs larger force in comparison to move a body in moving state. Therefore, less rotational force is required to keep an already-moving body in moving status. The body will achieve rotational balance within shorter time. Because the fluid pressure will push the fixed scroll  30  away from the orbital scroll  20 , the driving member  40  will fast achieve rotational balance by less torque.  
         [0015]     Moreover, the fixed scroll  30  is pushed away from the orbital scroll  20  until the fixed scroll  30  is in contact with the baffle plate when the compressor begins to operate. This can prevent excessive displacement of the fixed scroll  30  and pressure leakage. Afterward, when the driving member  40  achieves rotational balance, the high-pressure fluid in the back pressure chamber  80  will provide force to push downward the fixed scroll  30 . Therefore, the fixed scroll  30  has downward movement until the fixed scroll  30  is again engaged with the orbital scroll  20 , as shown in  FIG. 3 . In this situation, friction is still present between the orbital scroll  20  and the fixed scroll  30 . However, the friction is far smaller than the static friction accounting for rest body because the driving member  40  is in rotational balance.  
         [0016]      FIG. 4  shows a sectional view of the second preferred embodiment of the present invention. The second preferred embodiment is different to the first preferred embodiment in that the inner diameter of the first shell  101  is smaller than the inner diameter of the second shell  102 . An abutting section  50 ′ of another type is directly formed on a bottom peripheral of the first shell  101 . Therefore, the abutting section  50 ′ will limit the displacement of the fixed scroll  30  when the fixed scroll  30  is pushed away from the orbital scroll  20 .  
         [0017]      FIG. 5  shows a sectional view of the third preferred embodiment of the present invention. The third preferred embodiment is different to previous preferred embodiments in that a sealing buffer  60  is provided between the first shell  101  and the second shell  102 . The sealing buffer  60  is of annulus shape and has inner diameter the same as the inner diameter of either the first shell  101  or the second shell  102 . Moreover, the inner diameter of the sealing buffer  60  can be set between the inner diameter of either the first shell  101  and the second shell  102 . The sealing buffer  60  can buffer a contact between the fixed scroll  30  and the first shell  101 , therefore the operation noise and component abrasion can be prevented.  
         [0018]     The back-gap controlling apparatus according to the present invention has following advantages. There is higher pressure between the orbital scroll and the fixed scroll when the compressor begins to operate. The pressure will temporarily separate the orbital scroll and the fixed scroll to reduce contact area between the orbital scroll and the fixed scroll. Therefore, friction between the orbital scroll and the fixed scroll can also be advantageously reduced. The initial torque for operating the compressor can also be reduced and the driving member can fast achieve rotational balance. The lifetime of the compressor can be enhanced. The compressed fluid pressure due to operation between the orbital scroll and the fixed scroll will push the fixed scroll away from the orbital scroll and the fixed scroll has axial contact with the casing. The initial torque for operating the motor can be reduced and the liquid leakage due to excessive displacement can be prevented. The lifetime of motor can be enhanced and the excessive displacement of scroll unit can be prevented.  
         [0019]     Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.