Compressor

Abstract

 The invention relates to a compressor having a hermetically sealed housing (1) with direct suction. For this purpose a suction pipe (8) extends from the housing wall (1) to the motor-compressor unit (2). In order to improve the efficiency of the compressor an insulating jacket (19) surrounds the suction pipe and is spaced therefrom. The incoming gas in the suction pipe is then warmed to a minimal extent. The suction pipe is preferably a flexible coil spring element (15) or sleeve. The jacket (19) may be a plastics sleeve which is secured at one end. Figs. 1 and 2.

Description

[0001] The invention relates to a compressor comprising a hermetically sealed housing which accommodates a motor-compressor unit having an inlet opening with a connecting piece, the housing having a wall with an inlet opening which is provided with a connecting piece, said connecting pieces being interconnected by a suction pipe.

[0002] Such a compressor is known from DE-PS 26 50 937. For several decades compressors with hermetically sealed housings have been manufactured in which the suction pipe which extends from the evaporator terminates inside the housing. The motor-compressor unit draws the evaporated refrigerant from the space inside the housing. It is also known that an improved efficiency can be obtained by leading the suction pipe through the housing wall and connecting it directly to the inlet of the motor-compressor unit. This direct suction reduces the compression temperature, which reduces the likelihood of entrained oil being burnt. One of the requirements imposed on such a connection between the housing wall and the unit is that the pipe should "leak". Without this the pressure in the hermetically sealed housing may become lower (when refrigerant is absorbed in the oil) or higher than the pressure in the closed evaporator-compressor circuit. A higher pressure in the housing should be avoided, because this may result in additional noise being produced in the bearings.

[0003] The above-mentioned DE-PS proposes some constructions for direct suction. It employs, inter alia, sealing rings with a deliberately chosen leakage path. The disadvantage of sealing rings is that in the long run they may become swollen under the influence of the refrigerant and the oil, so that they become rigid. This results in additional noise being produced and in the connection being no longer "leaky". Other constructions proposed in said De-PS employ sliding and ball-type seals. These constructions are relatively rigid and are likely to transmit a substantial part of the vibrations to the housing, which again leads to additional noise. Moreover, such constructions are expensive.

[0004] A better solution is given in European Patent Application EP 0,073,469. For the direct suction it employs a flrxible suction pipe in the form of a closely coiled cylindrical coil spring element. Such an element does readily transmit contact noises and is "leaky" enough to provide pressure equalization but not so leaky that the relatively cold refrigerant can flow from the suction pipe to the warmer space inside the housing and back, in which case the gas which returns is relatively warm.

[0005] It is the object of the invention to provide a further improvement of the efficiency of such a direct- suction compressor.

[0006] To this end the invention is characterized in that the suction pipe is surrounded with an insulating jacket which is spaced from the suction pipe. The insulating jacket inhibits the exchange of gas in the suction pipe with gas in the space inside the housing, so that the incoming gas is warmed to a minimal extent. Moreover, the jacket damps gas pulsations in the gas flowing towards the space inside the compressor housing.

[0007] An embodiment of the compressor is characterized in that one end of the jacket is secured to one of the connecting pieces and the other end is directed downwards and is clear of the suction pipe and communicates with the space inside the compressor housing.

[0008] The jacket should surround the suction pipe at a distance therefrom such that the jacket cannot contact the suction pipe when the unit starts and stops. The jacket should be open at the bottom and in order to allow excess oil to drip back into the compressor housing.

[0009] Another embodiment of the compressor is characterized in that the jacket is made of a flexible porous material. An example of this is a braided metal 6r plastics sleeve.

[0010] An embodiment of the invention will now be described in more detail, by way of example, with reference to the accompanying drawing, in which

Fig. ₁ is a schematic sectional side elevation of a compressor, and

Fig. 2 shows a coil spring element forming the flexible suction pipe in the compressor shown in Fig. 1, with the surrounding jacket.

[0011] The compressor comprises a hermetically sealed housing 1 in which a motor-compressor unit 2 is suspended by means of springs 3. The unit comprises an electric motor 4 and a suction pump 5. The electric motor drives a piston 7 by means of a connecting rod 6. The evaporated refrigerant is drawn into the pump via a suction pipe 8 combined with mufflers in a connecting piece 14, is compressed by the pump and is pumped into the refrigerating system, not shown, via a pressure pipe 9. An oil bath ₁0 is situated in the lower part of the housing. The wall of the housing has a passage 1₁ provided with a connecting piece 12. The suction pump of the motor-compressor unit 2 has an inlet opening 13 with the connecting piece 14. The suction pipe 8 extends between the two connecting pieces 12, 14. The suction pipe is flexible, having the form of a cylindrical coil spring element ₁₅ with closely coiled turns 15. In one embodiment an insulating jacket 19 is rigidly connected to the connecting piece 14. The jacket is clear of the coil spring element 15. Preferably, the inner diameter of the jacket is 3 to 5 mm larger than the outer diameter of the coil spring element. Satisfactory results have been obtained with a coil spring element whose thickness is 0.8 - 1.0 mm, whose turns have a width of approximately 20 mm, whose length is approximately 50 mm and which has a pitch between the turns of 0.05 - 0.15 mm. Such a coil spring element allows movements of the motor-compressor unit relative to the housing and does not readily transmit acoustic vibrations, and, due to the narrow gaps between the turns, the suction pipe allows some leakage of gas and oil. The jacket provides a thermal insulation and damps gas pulsations in the gas towards the space indice the compressor housing.

[0012] The refrigerating system connected to the compressor always contains some oil carried from the compressor housing. In the coil spring element this oil settles between the turns and thus also provides some sealing for refrigerant vapour. An additional advantage of this is that when the unit is started and stopped oil is flung off by vibrations of the coil spring element, which may have a substantial amplitude. Thus, excess oil is discharged into the jacket and reaches the space inside the housing via the lower end of the jacket. Therefore, an oil separator is not needed. This construction also prevents oil splashes in the compressor housing from reaching the gaps between the turns of the coil spring element.

[0013] In order to allow for comparatively large displacements between the compressor unit and the housing it is favourable if the ends 17, 18 of the coil spring element or sleeve can be slid onto the connecting pieces 12, 14 over some distance. Preferably, the connecting pieces 12, 14 are made of a poor thermal conductor. This results in a further reduction of the heat transfer to the coil spring element and hence to the refrigerant.

[0014] Instead of the coil spring element a flexible sleeve, for example, a braided sleeve of a specific strength may be used for the suction pipe. The interstices in the braided sleeve should not be too large. Such a sleeve also meets the requirements and has the same advantages as a coil spring element.

[0015] The jacket may alternatively be a sleeve made of a flexible and porous material. This sleeve may surrounc the entire suction pipe with clearance, its ends being secured to the respective connecting pieces. A flexible sleeve follows the movements of the unit relative to the housing in the same way as the flexible suction pipe. However it is then required to give the interstices in the sleeve the correct dimensions.

Claims

1. A compressor comprising a hermetically sealed housing which accommodates a motor-compressor unit having an inlet opening with a connecting piece, the housing having a wall with an inlet opening which is provided with a connecting piece, said connecting pieces being interconnected by a suction pipe, characterized in that the suction pipe is surrounded with an insulating jacket which is spaced from the suction pipe.

2. A compressor as claimed in Claim 1, characterized in that one end of the jacket is secured to one of the connecting pieces and the other end is directed downwards and is clear of the suction pipe and communicates with the space inside the compressor housing.

3. A compressor as claimed in Claim ₁, characterized in that the jacket is made of a flexible and porour material.

Drawing