US20060070398A1

US20060070398A1 - Compressor intended to compress coolant fluid for a refrigeration or air conditioning installation

Info

Publication number: US20060070398A1
Application number: US11/236,763
Authority: US
Inventors: Jean De Bernardi; Yves Rosson
Original assignee: Danfoss Commercial Compressors SA
Current assignee: Danfoss Commercial Compressors SA
Priority date: 2004-10-05
Filing date: 2005-09-28
Publication date: 2006-04-06
Also published as: FR2876165A1; ITTO20050697A1; FR2876165B1; CN100485188C; CN1760547A

Abstract

A compressor intended to compress coolant fluid for a refrigeration or air conditioning installation, comprising a substantially vertical body consisting of a casing intended to receive in particular a lubricating liquid in its bottom portion forming a reservoir, and means of heating the lubricating liquid. The means of heating the lubricating liquid and means of acoustic insulation and thermal insulation situated below the heating means are placed close to the bottom wall of the casing.

Description

The present invention relates to a compressor intended to compress the coolant fluid for a refrigeration or air conditioning installation.

BACKGROUND OF THE INVENTION

In a known manner, the phenomena of migration of the coolant fluid within a refrigeration or air conditioning circuit appear when the latter is not in service.
Specifically, when the compressor is at a lower temperature than that of the heat exchangers, the coolant fluid migrates, under the temperature gradient effect, from the heat exchangers to the compressor.
This phenomenon occurs particularly in the morning, when the installation is situated outdoors, the heat exchangers being heated by the sun and rising in temperature more rapidly than the solid parts of the compressor which have a greater thermal inertia.
This phenomenon occurs in the reverse direction after the sun goes down, the coolant fluid migrating from the compressor to the heat exchangers, which cool down more quickly than the compressor.
During these migrations in the cooling circuit, the cooling fluid, by moving in the different portions of the cooling circuit, may cause the mechanical parts to be washed by condensation, carrying away the fluid lubricating the walls of these parts.
Furthermore, in the casing of the compressor toward which the coolant fluid migrates, the coolant fluid and the lubricant mix together, these two fluids in liquid form being miscible, the mixture having the effect of reducing the viscosity of the lubricant.
Consequently, when the circuit is returned to service, the lubrication is insufficient, due to the washing of the mechanical parts and the reduction in viscosity of the lubricant, which may cause premature wear or even a breakage of the mechanical parts of the installation.
The known solutions for resolving this problem consist first in having non-return valves at the outlet of the compressor, on the discharge side, and secondly in heating the compressor casing, and thus the lubricant contained in this casing.
This heating prevents the appearance of the temperature gradient described hereinabove and hence the appearance of the migration phenomenon.
The two solutions are ideally employed in parallel for greater security.

DESCRIPTION OF THE PRIOR ART

In existing compressors, as described in document U.S. Pat. No. 5,252,036, the heating device is situated on the side wall of the compressor. A seal surrounds the heating device in order to prevent an excessive heat loss toward the outside.
However, this arrangement is not very advantageous because it cannot be used to heat all the oil by making use of the convection currents in the casing to heat the lubricant uniformly. On the other hand, placement on the side wall is disadvantageous because it allows major heat loss by forced convection due to the wind.
Document U.S. Pat. No. 4,208,883, which describes a device for thermally regulating the temperature of the lubricant, suggests positioning the heating device beneath the compressor. In this document, the heating means are regulated by a device making it possible to control the temperature of the lubricant.
However, no measure is taken to reduce the heat loss through radiation.
In the known types of device, the criterion used to ensure that the migration does not occur is to maintain a temperature difference between the lubricant contained in the casing and the outside temperature of the order of 10 K by heating.
Consequently, powers of the order of 75 to 150 W are needed to power the heating devices. This power may have to be adjusted to suit the size of the compressor.
In addition to the migration phenomena, a second important technical problem relating to the compressors of the prior art concerns their acoustic emissions.
To reduce the noise emitted by these compressors, a first solution used in the prior art is to cover the compressor with an absorbent jacket which can be used to achieve an attenuation of the order of 7 dB, particularly effective for high frequencies, above 800 Hz.
However, the jackets are not effective in reducing the emitted low frequency noise, and they also constitute devices of complex structure combining several materials whose cost is high compared with the cost of the compressor.
A second solution is described in document JP 53 099504, the compressor body being mounted on springs in a compartment, this compartment itself being mounted on springs passing through a layer of acoustically insulating material, in the form of solid or liquid foam situated in a housing integral with the compressor attachment support.
This document consequently describes a complex device, in which the compressor is completely contained in a compartment, this disposition making access to the latter difficult and involving the installation of an intermediate platform supporting the compartment, which increases the overall space requirement of the compressor.
Other documents, such as document JP 2002 243211, also describe devices in which a compartment completely contains the compressor, in order to reduce the emitted noise.
These devices also have disadvantages of space requirement and complex structure and cost.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a compressor which, in a restricted space requirement and a simple construction, can be used to achieve heating requiring a reduced energy consumption, and to emit a reduced acoustic power, particularly in the low frequencies.
Accordingly, the subject of the present invention is a compressor intended to compress coolant fluid for a refrigeration or air conditioning installation, comprising a substantially vertical body consisting of a casing intended to receive in particular a lubricating liquid in its bottom portion forming a reservoir, and means of heating the lubricating liquid, wherein the means of heating the lubricating liquid and means of acoustic insulation and thermal insulation situated below the heating means are placed close to the bottom wall of the casing.
Such a disposition can be used to reduce significantly the power consumed to heat the lubricating liquid, because the heat insulation means reflect the energy toward the compressor and the dissipations due to the wind are diminished.
This disposition can also be used to reduce to a surprising degree the emitted acoustic power, particularly in the field of the low frequencies, because it appears that the low frequency waves are emitted to a greater degree at the bottom wall of the casing.
This disposition is also used, with the abovementioned advantages, to cause a minimal space requirement.
Advantageously, the acoustic insulation and thermal insulation means are at a distance from the support to which the compressor is attached.
According to one embodiment, the acoustic insulation and thermal insulation means comprise at least one layer of insulating material.
Advantageously, at least one layer of insulating material comprises a cellular material.
According to one embodiment, at least one layer of insulating material comprises felt.
Advantageously, at least one layer of insulating material comprises a fibrous material.
Advantageously, the acoustic insulation and thermal insulation means also comprise a rigid support plate.
According to one embodiment, the acoustic insulation and thermal insulation means also comprise a film for protecting and retaining the insulating material.
Advantageously, the thermal and acoustic insulation means have a top surface whose shape at least in part substantially complements that of the bottom wall of the casing.
According to one embodiment, the heating means comprise at least one electric resistance attached to the bottom wall of the casing, outside the latter.
Advantageously, at least one electric resistance is attached to the bottom wall of the casing by adhesive means.
According to one embodiment, the thermal insulation and acoustic insulation means are kept in position relative to the compressor body by attachment means.
Advantageously, the attachment means comprise at least one elastic clip kept in position by gripping a projecting portion of the compressor and a substantially horizontal lug, the thermal and acoustic insulation means pressing on the lugs of the attachment means.
According to one embodiment, the attachment means are at least two in number.
Advantageously, the thermal and acoustic insulation means allow the attachment feet of the compressor to pass through.
According to one embodiment, the compressor comprises an acoustic insulation jacket covering the body of the compressor.
The present invention also relates to a thermodynamic machine using at least one compressor as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

In any case, the invention will be clearly understood with the aid of the following description, with reference to the appended schematic drawing, representing, as a nonlimiting example, an embodiment of a compressor according to the invention.
FIG. 1 is a general view in perspective.
FIG. 2 is a view in section on a larger scale along II-II of FIG. 1.
FIG. 3 represents a partial exploded view in perspective of the compressor of FIG. 1.
FIG. 4 represents schematically an acoustic emission spectrum of a compressor according to the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A compressor 2 intended to compress coolant fluid for a refrigeration or air conditioning installation according to the invention is represented in FIGS. 1 to 3. This compressor comprises a substantially vertical body 3 comprising a casing 4 intended to receive in particular a lubricating liquid 5 in its bottom portion forming a reservoir.
In this embodiment, the compressor casing comprises a side wall 11 and a base plate 6 having a dish-shaped central portion 7, intended to form the bottom wall of the casing, bordered by a peripheral rim 8, also comprising attachment orifices 9 for first means of attachment 10 to a support 12, situated outside the peripheral rim 8, and a return 13 made on the edge of the plate 6 and directed downward.
The side wall 11 and the base plate 6 are attached at the rim 8, the lower edge of the side wall 11 resting on the outside of the rim 8 forming an abutment.
The first attachment means 10 consist, in a known manner, of a stud made of elastic material 14 of the rubber type forming a supporting foot for the compressor and having a longitudinal opening in which can be housed a bolt 15 intended to be housed also in an opening 16 of the support 12.
According to an essential feature of the invention, the compressor 2 comprises means 17 of heating the lubricating liquid 5, placed close to the bottom wall 7 of the casing, and acoustic insulation and thermal insulation means 18 placed beneath the heating means 17.
The heating means consist of an electric resistance 17 attached to the bottom wall 7 of the casing, outside the latter, attached to the bottom wall of the casing by adhesive means 19, and intended to be connected to an external source of electric power by two connecting conductor wires 20.
The acoustic insulation and thermal insulation means 18 consist of a member having a top surface whose shape substantially complements that of the bottom wall of the casing 7, comprising the following elements, superposed from the bottom up:

- a flat rigid support plate 22,
- a layer of cellular insulating material 23, whose shape substantially complements that of the bottom wall 7 of the casing,
- a film 24 made of plastic material, protecting and keeping the cellular material in position, the film being bonded or heat sealed to the flat plate 22 on the periphery of the latter.

According to a variant, the layer of insulating material comprises felt.
According to another variant, the layer of insulating material comprises a fibrous material, such as glass fiber or rock wool.
The thermal insulation and acoustic insulation means 18 are held in position relative to the compressor body by second attachment means 25 each comprising an elastic clip 26 held in position by gripping the return 13 of the compressor base plate 6 and a substantially horizontal lug 27, the flat and rigid plate 22 supporting the thermal and acoustic insulation means resting on the lugs 27 of the second attachment means 25.
These second attachment means 25 are four in number and preferably at least two in number depending on the variants.
These second attachment means are used to make it easier to install and remove the thermal and acoustic insulation means 18 on/from the compressor body 2.
The thin insulation means 18 are thus held in position beneath the compressor, without contact with the support 12, and delimit a housing for the heating means with the thin bottom wall of the casing.
This disposition is particularly helpful in protecting the heating means 17 from the effects of the wind, which cannot cause a major heat loss. In addition, the heating means are placed beneath the casing, thus making it possible to cause in the latter a uniform temperature mix of the lubricating liquid by convection currents.
Furthermore, the thermal and acoustic insulation means 18 are separated from the support, which assists with this insulation.
It is therefore possible to maintain a temperature with an electric power of the order of 50 to 60 W, hence much less than that of the devices of the prior art, thus allowing a smaller dimensioning of the heating means power supply circuit.
The thermal and acoustic insulation means 18 have a horizontal cross section allowing the compressor attachment feet 14 to pass through.
In a known manner, the acoustic emission spectrum of a compressor according to the prior art has a curve as shown in FIG. 4, the power P being represented on the y axis and the frequency F on the x axis.
It appears on this curve that the compressor has a considerable emitted power in a frequency band situated around 600 Hz.
The dispositions according to the invention make it possible to obtain a reduction in the emitted power in this band, the attenuation being of the order of −5 dBa.
This result is important, because the insulation jackets covering the whole compressor body do not make it possible to obtain a significant attenuation in this frequency band.
According to a variant, the compressor also comprises an acoustic insulation jacket 28 shown in dot-and-dash lines covering the compressor body 2.
The addition of this jacket makes it possible to obtain an attenuation of the order of −7 dBa, in a frequency band situated above 900 Hz.
The addition of this jacket on the compressor according to the invention makes it possible to obtain an overall attenuation of the order of −14 dBa across the whole spectrum.
This unexpected result is obtained thanks to the action of the insulation means on one frequency band, and to the action of the jacket on a different frequency band.
As it goes without saying, the invention is not restricted to the preferred embodiment described hereinabove, as a nonlimiting example; on the contrary it embraces all the variant embodiments thereof in the context of the following claims.
Thus, it is possible to use several different layers of insulating materials.
Also, the measurements taken for one embodiment of the invention are cited as an example; these measurements may be different for other embodiments.

Claims

1. A compressor for compressing coolant fluid for an air conditioning installation, comprising a substantially vertical body comprising a casing for receiving a lubricating liquid in its bottom portion forming a reservoir, and means of heating the lubricating liquid, wherein the means of heating the lubricating liquid and means of acoustic insulation and thermal insulation situated below the heating means are placed close to the bottom wall of the casing.

2. The compressor as claimed in claim 1, wherein the acoustic insulation and thermal insulation means are at a distance from the support to which the compressor is attached.

3. The compressor as claimed in claim 1, wherein the acoustic insulation and thermal insulation means comprise at least one layer of insulating material.

4. The compressor as claimed in claim 3, wherein at least one layer of insulating material comprises a cellular material.

5. The compressor as claimed in claim 3, wherein at least one layer of insulating material comprises felt.

6. The compressor as claimed in claim 3, wherein at least one layer of insulating material comprises a fibrous material.

7. The compressor as claimed in claim 3, wherein the acoustic insulation and thermal insulation means also comprise a rigid support plate.

8. The compressor as claimed in claim 3, wherein the acoustic insulation and thermal insulation means also comprise a film for protecting and retaining the insulating material.

9. The compressor as claimed in claim 1, wherein the thermal and acoustic insulation means have a top surface whose shape at least in part substantially complements that of the bottom wall of the casing.

10. The compressor as claimed in claim 1, wherein the heating means comprise at least one electric resistance attached to the bottom wall of the casing, outside the latter.

11. The compressor as claimed in claim 10, wherein at least one electric resistance is attached to the bottom wall of the casing by adhesive means.

12. The compressor as claimed in claim 1, wherein the thermal insulation and acoustic insulation means are kept in position relative to the body of the compressor by attachment means.

13. The compressor as claimed in claim 12, wherein the attachment means comprise at least one elastic clip kept in position by clipping a protruding portion of the compressor and a substantially horizontal lug, the thermal and acoustic insulation means pressing on the lugs of the attachment means.

14. The compressor as claimed in claim 13, wherein the attachment means are at least two in number.

15. The compressor as claimed in claim 1, wherein the thermal and acoustic insulation means allow the attachment feet of the compressor to pass through.

16. The compressor as claimed in claim 1, which comprises an acoustic insulation jacket covering the body of the compressor.

17. A thermodynamic machine including at least one compressor as claimed in claim 1.