GB2188376A - Electric driven compressor - Google Patents

Abstract

An electric motor compressor unit for a refrigerator or air conditioning apparatus has a compressor unit within a sealed container and an electric motor located outside of the container in driving relation with the compressor unit. The motor is a linear induction motor. As shown, the compressor unit 110 is formed of housing 112 and lid 114 and comprises a piston 128 driven by a crank 124. A disc 36 is located on the crankshaft within the unit and is driven from outside by faceplate induction motor 38. <IMAGE>

Description

SPECIFICATION Electric motor-compressor units This invention relates to electric motor-compressor units for example, for those used in refrigeration apparatus.

Domestic refrigerators usually employ a motor com pressor unit which com prises a sea led container in which a compressor and an electric drive motor for the compressor are located. The compressor has a cylinder with a piston reciprocatable within the piston by way of a crank on a drive shaft connected to the electric motor. Refrigerant vapour, for example dichlorodifluoromethane, is contained within the sealed container, compressed by the compressor and passed through a condensor where it is cooled bysurroundingairand is liquified.The liquified gas next passes through an expansion valve or capilliary tube and becomes a cold vapour before circulating in an evaporator where heat is extracted from the food compartment of the refrigerator to warm the cold vapour in the evaporator. The container of the motor-compressor unit is sealed to prevent any egress of the refrigerant vapour to the atmosphere.

Since the electric motor is almost always of the induction type and since it is located within the sealed container, any electrical faultwhich occurs in the motor creates the need for a major operation in order to repairthe motor. The entire motor-compressor unit has to be disconnected from the refrigerant circulation pipes and then removed from the refrigerator. The seal of the container must be broken in order to gain access to and repair or replace the electric motor, after which the container is re-sealed, the unit is replaced and the lost gas replenished.

An object of the present invention is to provide an electric motor-compressor unit in which the maintenance on the motor is simplified.

According to the present invention a motorcompressor unit comprises a sealed container, a com pressor u nit within the container and a drive motor in driving relation with the compressor and wherein the drive motor is an electric face plate induction motor mounted externally of the container.

With this construction anyfaulton the linearinduction motor can be readily overcome either by repairing the motor or replacing it without the necessity of opening the sealed container.

In orderthatthe invention may be more readily understood it will now be described, by way of example only, with reference to the accompanying drawings in which: Figure lisa sectional view th rough the lower part of a domestic refrigerator showing diagrammatically the location and construction of atypical motorcompressor unit of the prior art; Figure2isasimilarviewbutshowingthelocation and construction of a motor-compressor unit according to the present invention; and Figure 3 is a plan view of a typical linear induction faceplate motor.

As shown in Figure 1 a domestic refrigerator 2 has a door 4 and an insulated casing 6 recessed at 8 to receive a motor-compressor unit 10. The unit comprises a housing 12 and a lid 14sealed together at flanged portions 16 to form a container. Within the container there is an electric drive motor 18 which hasa rotorshaft20 rotatablymounted in bearings 22 and carrying a crank 24. This crank is connected to the connecting rod 26 of a piston 28 which forms part of a piston-cylinder device forming a compressor 30.

An oil thrower 32 assists in lubricating the bearings ofthe rotor and ofthe crank. The container is resiliently mounted at 34 to part of the casing 6.

With the arrangement shown in Figure 1, if there is an electrical fault in the motor 18 it is necessary to disconnect the motor-compressor unit 10 from the refrigeration system of the refrigerator, and open the container in orderto gain accesstothemotor.

Referring to Figure 2, the domestic refrigerator 2 has a compressor unit 110 with a housing 112anda lid 1 14 sealed together at 1 16 to form a container.

Within the container there is a shaft 120 rotatable in bearings 122 and carrying a crank 124. The crank is connected to a connecting rod 126ofa piston 128 which is part a compressor 130. An oil thrower 132 is provided and the compressor unit is resiliently mounted at 134to partofthecasing 6.

The shaft 120 carries a disc36 located within the container close to the underside of the lid 114. An electric linear induction motor, known as a faceplate, motor 38 is removably secured to the outside of the lid 1 so asto be close to the disc36. The face ofthe motor 38 is arranged parallel to the plane ofthe disc 36. The lid 1 14is of a non-magnetic material, e.g.

stainless steel.The disc36 is mainlyof copperor aluminium with iron inserts.

Excitation ofthe faceplate motor sets up a rotating magneticfield which connects with the disc36, causing the disco rotate and thus actuate the compressor 130 by way of the crank and piston rod.

If, and when, an electrical fault in the motor needs attention, the removal ofthe linearfaceplate motor 38 from the outside of the lid is a simple taskwhich does not mean that the unit has to be removed from the refrigerator nor does it mean that the container 110 has to be unsealed.

Afurther advantage to be gained from the invention is readily seen from comparison of Figures 1 and 2 of the drawings. The space occupied by the unit of Figure 2 is considerably less than that of the unit of Figure 1, in fact in the case of an average domestic refrigerator, the increase in useful space available for food storage is found to be a little over 1 cubicfoot in a nominal 5 cubic foot refrigerator.

Yet another advantage is found in the fact that heat generated by the motor is not dissipated within the container 110 as is the case of the prior art motorcompressor unit where the generated heat preheats the refrigerant vapour before it enters the compressor 30.

The unit 110 may, if desired, be mounted at 90"two the position shown in Figure 2, with the linearfaceplate motor being towards the rear of the refrigerator.

The saving in useful space is approximately the same but the motor is even more accessible for maintenance purposes. In this alternative arrangementthe oil thrower 132 would be dispensed with and lubricating oil which lies in the lower part of the housing 112 is thrown up to lubricate the bearings by indentations which would be formed in the surfaces of the disc 36.

Although the invention has been shown and illust- rated with reference to a domestic refrigerator, it can of course be applied with equal advantage to any refrigeration unit such as industrial refrigeration systems, or air conditioners.

Claims (5)

1. An electric motor compressor unitfor use in cooling apparatus comprising a compressor unit within a container which is sealed except for refrigerant inlet and outlet pipes for the compressor unit and an electric motor mounted externally of the container and in driving relation with the compressor unit.

2. An electric motor compressor unit as claimed in claim 1, in which the electric motor is a linear induction motor and it is in driving relation with a rotatable disc forming part ofthe compressor unit.

3. An electric motor compressor unit as claimed in claim 2, in which the compressor unit comprises a piston reciprocatable within a cylinder, a crank shaft for reciprocating the piston and with said rotatable disc mounted onthecrankshaft.

4. An electric motor compressor unit as claimed in claim 3, in which the linear induction motoris mounted on the container.

5. An electric motor compressor unitsubstantially as hereinbefore described with reference to Fig ures 2 and 3 ofthe accompanying drawing.