Scroll fluid machine having a dust seal fitted within annular groove and having ends overlapped in the wider portion of the annular groove

In a scroll fluid machine, an orbiting scroll engages with a stationary scroll to form a sealed chamber in which fluid can be compressed toward a center with revolution of the orbiting scroll with respect to the stationary scroll. An annular groove is formed near the outer circumference of the stationary scroll. A dust seal fits in the annular groove of the stationary scroll. The annular groove has almost the same width, but has a wider portion having the twice the width as the other. In the wider portion of the annular groove, the ends of the dust seal are overlapped. The overlapped surfaces are rough to engage with each other.

BACKGROUND OF THE INVENTION

The present invention relates to a scroll fluid machine such as a scroll compressor, a scroll vacuum pump, a scroll expander or a scroll blower.

Such a scroll fluid machine comprises an orbiting scroll supported on an eccentric shaft portion of a drive shaft to turn, and a stationary wrap comprising a stationary end plate having a stationary wrap. An orbiting wrap on an orbiting end plate of the orbiting scroll engages with the stationary wrap to form a sealed chamber between the stationary and orbiting wraps. The scroll fluid machine has a self-rotation preventing device for preventing the orbiting scroll from rotating on its own axis.

By the eccentric shaft portion of the drive shaft and the self-rotation preventing device, the orbiting scroll is eccentrically revolved so that the volume in the sealed chamber gradually decreases toward the center for compression or increases away from the center for depressurizing to discharge from the outer circumference.

The ends of the orbiting and stationary wraps have engagement grooves in which tip seals fit in sliding contact with the opposing end plates sealingly.

In the scroll fluid machine, U.S. Pat. No. 6,695,597 discloses a dust seal on the outer circumference of engagement area of orbiting and stationary wraps. The dust seal comprises a circle; a partially-separated circle the ends of which are contacted or made close; a partially-separated circle the ends of which are engaged with an outer side face of an outermost tip seal; the same as part of a tip seal; and a seal member on the outermost wrap contacting the other sliding surface, as known from the US Patent and other references.

However there are disadvantages in the dust seal of the known scroll fluid machine as below.

The circular dust seal fitted in an annular groove requires quite high accuracy in size and a lot of works and technique. Furthermore, heat and sideward pressure generated with operation stretches or the annular groove is deformed to cause unsuitable fitting. Deviation of the dust seal in the annular groove causes failure in sealing.

(b) partially separated circle the ends of which contacts or become close

To absorb thermal expansion of the dust seal, a little gap has to be formed between the ends in advance. But it is impossible to prevent dust from coming in through the gap completely. To prevent this, the ends of the dust seal are tilted or overlapped, but such working is troublesome to increase cost. The dust seal is likely to move in the annular groove circumferentially.

(c) partially separated circle the ends of which contacts the outer side surface of the outermost tip seal

The annular groove must be formed noncircular, which is not so easy for working. During operation, a gap is formed between the end of the dust seal and the outer side surface of the tip seal, so that dust is introduced through the gap.

(d) partially the same as the tip seal

The annular groove must communicate with an engagement groove for the tip seal, which requires a lot of work and technique to increase cost. The dust seal is integrally formed with the tip seal or the end is partially contacted with the outer side surface of the tip seal, which causes the disadvantages as above.

(e) A seal member of the outermost wrap on the opposite sliding surface

A groove in which the seal member engages becomes complicate in shape to make working troublesome and increase cost. The tip seal wears to cause failure in dust sealing.

SUMMARY OF THE INVENTION

In view of the disadvantages in the prior art, it is an object of the invention to provide a scroll fluid machine in which a dust seal is fitted in an annular groove by merely overlapping the ends of the dust seal without special machining of the dust seal.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1shows a scroll compressor according to the present invention. The present invention may be applied to a scroll fluid machine such as a scroll expander as well.

The scroll compressor inFIG. 1is known and will be described simply. The left and right sides are front and rear respectively inFIG. 1.

A stationary scroll1at the front or left side ofFIG. 1comprises a circular stationary end plate4having an inlet2at the outer circumference and an outlet3at the center. A spiral stationary wrap5is provided on the rear surface of the stationary end plate4and a plurality of corrugate cooling fins6are provided at regular intervals on the front surface.

An orbiting scroll7behind the stationary scroll1comprises an orbiting end plate8which has a spiral orbiting wrap9on the front surface facing the stationary scroll1and a plurality of corrugated cooling fins10at regular intervals on the rear surface.

Behind the orbiting scroll7, a bearing plate11is disposed. At the center of the rear surface of the orbiting scroll7, there is a tubular boss15which supports an eccentric shaft portion13of a drive shaft12which rotates therein. At three points of the outer circumference of the orbiting scroll7, there is a known crank-pin-type self-rotation preventing device16so that the orbiting scroll7eccentrically revolves around the drive shaft12with respect to the stationary scroll1fixed to a housing17in which the orbiting scroll7is contained.

A cover plate18is provided on the front surface of the stationary scroll1and fixed by a screw19. The orbiting scroll7is fixed to the bearing plate11by a screw20. A portion21of the stationary scroll1is put on the front surface of the housing17and fixed by a bolt22and a nut23.

At the end of the stationary wrap5and the orbiting wrap9, there are formed grooves5aand9ain which tip seals “S” fits in sliding contact with the orbiting end plate8of the orbiting scroll7and the stationary end plate4of the stationary scroll1.

FIG. 2shows a portion21of the stationary scroll1seen from the rear. An annular groove31is formed on the outer circumference of the portion21of the stationary scroll1to surround the stationary wrap5. The annular groove31has almost the same width but a wider portion30that is twice the width of the other partially.

A dust seal32fits in the annular groove31. The ends of the dust seal32are overlapped in the wider portion30and contact or become close to the circumferential end faces30a,30bof the wider portion30.

As shown inFIG. 3, on the bottom of an annular groove31, a backup tube33is fitted to apply elastic force to the dust seal32.

FIGS. 4 and 5show different shapes of a wider portion30of an annular groove31. InFIG. 4, an outer circumferential surface30cof the wider portion30is tilted to become closer toward an inner circumferential surface30d,and inFIG. 5, inner and outer circumferential surfaces30c,30dof the wider portion30are inclined in approximate parallel with each other.

FIG. 6shows a dust seal32which has a plurality of grooves34on overlapping surfaces of the ends.

FIG. 7shows a dust seal32which has rough surfaces35on overlapping surfaces of the ends.

The foregoing merely relates to embodiments of the invention. Various changes and modifications may be made by a person skilled in the art without departing from the scope of claims wherein: