Scroll fluid machine having a fixed scroll with a heat-releasing projection

In a scroll fluid machine, a fixed scroll has a fixed wrap, and an orbiting scroll has an orbiting wrap which engages with the fixed wrap to form a compressing chamber between the orbiting and fixed wraps. The orbiting scroll is rotatably mounted around an eccentric axial portion of a driving shaft and revolved by the driving shaft. A gas introduced from the outer circumference of the fixed scroll is compressed in the compressing chamber as it flows towards the center. Parts near the center is heated by a compressed gas. On the other surface of the fixed scroll to the surface having the fixed wrap, a plurality of cooling fins are provided. Air is introduced between the cooling fins to cool the machine. Between the cooling fins, a heat-releasing projection is provided to improve cooling efficiency.

BACKGROUND OF THE INVENTION

The present invention relates to a scroll fluid machine and especially to a scroll fluid machine such as a scroll compressor or a scroll vacuum pump in which a fixed wrap of a fixed scroll engages with an orbiting wrap of an orbiting scroll mounted around an eccentric axial portion of a driving shaft, the orbiting scroll being eccentrically revolved by the driving shaft so that a gas sucked from the outer circumference of the fixed scroll can be compressed towards the center and discharged.

In a scroll fluid machine, a long-time operation increases temperature of an eccentric axial portion of a driving shaft, and bearings and packing that support the driving shaft to cause the bearings and packing to be damaged.

To prevent such situation, US2004/0241030A1 discloses a scroll fluid machine having a number of cooling fins on the surface of a fixed scroll to increase cooling efficiency.

However, in the scroll fluid machine, the cooling fins are radially provided on the surface of a fixed scroll to limit a cooling area and cooling performance. To increase the cooling area, increased number of the radial cooling fins makes gaps between the cooling fins denser to make cooling wind more unlikely to pass through to decrease cooling efficiency. Particularly, in the radial cooling fins, the gap between the cooling fins becomes narrower towards the center to make it more difficult for cooling wind to pass through towards the center having relatively higher temperature than in the outer circumference.

SUMMARY OF THE INVENTION

In view of the disadvantage in the prior art, it is an object of the invention to provide a scroll fluid machine improving cooling efficiency by increasing a cooling area along which air flows on the surface of a fixed scroll.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

InFIG. 1, a cylindrical housing1comprises a rear casing3and a front cover4. The housing1has an inlet1afor sucking external air in the housing1and an outlet1bfor discharging a compressed gas compressed in the housing1to the outside.

The casing3and the cover4comprises approximately circular fixed end plates31,41facing each other and having fixed wraps32and42spirally formed as an involute curve to constitute fixed scrolls33,43.

On the rear surface of the fixed scroll33and on the front surface of the fixed scroll43, there are provided a plurality of cooling fins10radially extending from the center of the fixed scrolls33,43to the outer circumference and a plurality of short heat-releasing projections11,11each of which is disposed between the adjacent cooling fins10and10.

The heat-releasing projection11is provided close to the outer circumference of each of the fixed scrolls33,43or at a wider gap between the adjacent cooling fins10and10. The projection11is lower in height than the fin10.

A number of radial cooling fins10and small heat-releasing projections11are provided on the surfaces of the fixed scrolls33,43of the housing1thereby increasing cooling area without making denser between the cooling fins10and10through which external air passes. Furthermore, when cooling fans8,9described later rotates, turbulence occurs in air current thereby preventing bearings14,15and packing from being damaged by heat.

In the radially-extending cooling fins10, the gap between the adjacent cooling fins10and10becomes wider from the center toward the outer circumference. Thus, during operation, a finger of an operator is likely to put in the gap between the cooling fins10and10to cause hindrance in the operation. In this embodiment, the heat-releasing projection11is provided to prevent the operator's finger from putting in the gap thereby improving security.

The heat-releasing projection11extends radially straight or inclined as shown as11ainFIGS. 1 and 2. The projection11may be forked at the radially inner end inFIG. 4, mounted to the side of the cooling fin10inFIG. 5, corrugated or bent, thereby increasing turbulence.

In a sealed chamber2between the fixed scrolls33and43, an orbiting scroll5is rotatably supported around an eccentric axial portion61of a driving shaft6rotatably fitted in the center of the housing1. The driving shaft6is connected at the rear end to a motor(not shown) and rotatably supported in axial holes31a,41aalong the center of the fixed end plates31,41via bearings14,15.

The orbiting scroll5has on the front and rear surfaces orbiting wraps51,51engaging with the fixed wraps32,42respectively and is connected to the fixed end plate31with three known pin-crank-type self-rotation preventing devices7.

The driving shaft6rotates by the motor, so that the orbiting scroll5is eccentrically revolved thereby gradually reducing the volume of the compressing chambers21,21towards the center. A external gas in the compressing chambers21,21from the inlet1ais gradually compressed and finally discharged to the outside from the outlet1b. External air sucked from the inlet1ais compressed and its temperature rises as it flows towards the center.

To the driving shaft6which projects from the fixed end plates41,31, the front and rear cooling fans8,9are mounted. The front cooling fan8rotates to produce external air current going forwards, while the rear cooling fan9rotates to produce air current going rearwards.

Cover plates12,12are fixed to the front surface of the cover4and the rear surface of the casing3. In the cover4, a cover protection13is mounted on the front surface of the cover plate12to cover the cooling fan8.

The rear surfaces of the cover plates12,12contact the cooling fins10,10but does not contact the heat-releasing projections11,11. Thus, the front and rear cooling fans8,9rotate to allow external air to pass towards the center between the cooling fins10. The rear surfaces of the cover plates12,12may be placed close to the cooling fins10,10without contacting them.

In the front side of the housing1, rotation of the front cooling fan8allows external air A to be sucked between the cooling fins10and10on the outer circumference of the cover4.

Sucked air A goes towards the center along the side of the cooling fin10with turbulence by the heat-releasing projection11thereby increasing cooling effect. Air goes to the center without hindrance between the cooling fins10and10to effectively cool the center which is likely to become high temperature.

Air A sucked in the center is transferred forwards through an opening121and discharged from an opening131of the protecting cover13.

In the rear part of the housing1, the rear cooling fan9rotates to allow external air B to be sucked between the cooling fins10and10on the outer circumference of the casing3. Sucked air B goes towards the center as well as air A and discharged through an opening121of the cover plate12rearwards to cool the motor disposed behind.

The embodiments relate to a both-side scroll fluid machine in which a both-side orbiting scroll is disposed between two fixed scrolls. The present invention may also apply to a one-side scroll fluid machine in which a one-side fixed scroll engages with a one-side orbiting scroll. With rotation of the cooling fans8,9, external air current flows towards the center, but may flow towards the outer circumference.

The foregoing merely relate 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: