The present invention relates to a seal in a scroll fluid machine and particularly to a seal which is fitted in an engagement groove of an end plate, an orbiting wrap and/or a fixed wrap in a scroll compressor or a scroll vacuum pump.
In this specification, “upper” and “lower” mean an entrance and the bottom of an engagement groove respectively in which a seal is fitted.
A scroll fluid machine such as a scroll compressor or a vacuum pump is well-known among persons skilled in the art and comprises an orbiting scroll rotatably mounted on an eccentric end portion of a drive shaft and a fixed scroll. The orbiting scroll comprises an orbiting end plate having an orbiting wrap, and the fixed scroll comprises a fixed end plate having a fixed wrap. The orbiting wrap engages with the fixed wrap to allow a sealed chamber to be formed between the fixed and orbiting wraps. The scroll fluid machine also comprises a plurality of self-rotation preventing devices for preventing the orbiting scroll from rotating on its own axis. Such a scroll fluid machine is disclosed in JP6-207588A and JP3248618B.
With the axial end portion of the drive shaft and the self-rotation preventing devices, the orbiting scroll is eccentrically revolved to decrease the volume of the sealed chamber towards the center or to increase it away from the center thereby compressing a gas sucked from the outer circumference towards the center or decompressing a gas sucked from the center away from the center.
The orbiting and fixed wraps comprise an involute curve increasing a diameter gradually in a direction of rotation around the center; a curve comprising very short curves combined in a circumferential direction; or the combination of the curves above. A gap between the orbiting and fixed wraps is exactly determined not to excessively contact the wraps to each other and not to become too wide.
An engagement groove is formed in the end plate or tip ends of the orbiting and fixed wraps, and a dust seal or a tip seal is fitted in the engagement groove to slide hermetically with the opposing end plate.
The dust seal or tip seal comprises a backup material on the bottom of the engagement groove to improve gas-tightness with the counter end plate and a sealing material made of resin on the upper surface of the backup material.
The backup material comprises a porous material softer than the sealing material in
The backup materials in the tip seal in the prior art involve the following disadvantages.
The elastic material 10 as backup material in JP6-207588A is made of heat-resistant porous elastic material such as sponge rubber having a rectangular cross-section to allow axial or sideward deformation of the scroll 2 to become smaller.
Depending on the width of the tooth grooves 5 of the teeth 3 in the elastic material 10 and scroll 3, the elastic material 10 excessively engages in the tooth grooves 5 to solidify the elastic material 10 thereby failing to exhibit sufficient elasticity. On the contrary, the elastic material 10 loosely engages in the tooth grooves 5 to reduce gas-tightness around it or not to exhibit sufficient pressing force onto the tip seal 9.
The tip seal 9 in JP3248618B is integrally formed with the porous rectangular cross-sectioned backup material 41 made of softer material than the self-lubricating sealing material 92 such as polytetrafluoroethylene resin. Under high temperature or radioactivity, an adhesive is deteriorated to lose adherence or makes the sealing material 92 peeling off the backup material 91 involving poor sealing capability.
The backup material 5 in JP2-145686U is made of band-like fluorine rubber to make it difficult for the ends to be bound to form a circle. Gas-tightness in the bound ends becomes poor making it impossible to keep gas-tightness from the one side to the other side of the sealing groove 1a. Thus, the backup material 5 employed in a scroll fluid machine such as a vacuum pump causes its performance to become worse to make its use impossible.
In view of the disadvantages, it is an object of the invention to provide a seal in a scroll fluid machine in which a backup material and a sealing material are fitted in an engagement groove at the end of an orbiting wrap or a fixed wrap without an adhesive which is likely to deteriorate or to powder, thereby positioning the backup material in the engagement groove properly and applying suitable repulsive force to the sealing material to improve the performance of the scroll fluid machine.
The features and advantages of the invention will become more apparent from the following description with respect to embodiments as shown in accompanying drawings wherein:
A seal 5 according to the present invention is also fitted in an engagement groove 4 of the tip end of a spiral orbiting wrap 3 standing on the orbiting end plate 2 as tip seal. A seal is fitted in an engagement groove of the tip end of a fixed wrap standing on the fixed end plate of the fixed scroll.
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The backup material 6 is annular when it is used as a dust seal in a vacuum pump to prevent dust from invading into a pump chamber, while it is band-like to reduce a compressed gas from leaking through the end of a wrap when it is used as a tip seal.
The foregoing merely relate to embodiments of this invention. Various changes and modifications may be made by a person skilled in the art without departing from the scope of claims wherein:
Number | Date | Country | Kind |
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2005-282439 | Sep 2005 | JP | national |