MXPA00006146A - Oil pump for a hermetic compressor - Google Patents

Abstract

Hermetic refrigeration compressor for household and similar refrigeration appliances, comprising a sealed casing (12), whose bottom (10) forms a sump for the lubricating oil (14), in which there are housed both the actual compressor and the related driving motor (16) which share a hollow crankshaft (20) rotating about a vertical axis, pumping means (34, 36) for the lubricating oil being connected to the lower end portion of said crankshaft. Said pumping means comprise a sleeve (34), which is rigidly fixed at the lower end portion of the crankshaft (20), and a piston member (36) which is elastically connected to the stator (22) of the motor (16) and floats freely inside said sleeve.

Description

OIL PUMPS FOR A HERMETIC COMPRESSOR DESCRIPTION The present invention relates to a hermetic refrigeration motor compressor unit, in particular for use in refrigerators of the domestic appliance type. It is generally known that the current refrigeration compressor (which is usually of the reciprocating or rotating type) and the related electric drive motor has a common shaft that joins in a sealed housing. Due to the resulting impossibility of carrying out any type of maintenance subsequently, it is imperative that a reliable, continuous and effective lubrication of the mobile parts of said hermetically sealed unit be ensured to be assured throughout its operative life, which may reach be more than 15 years old, of the refrigeration appliance in which the unit is mounted. For this purpose, the hermetic motor compressor unit comprises means which are adapted to ensure, during periods of operation thereof, an adequate flow of the oil that is filled in an appropriate amount in the sealed cover at the end of the compressor manufacturing cycle. , in such a way that not only the lubrication of the moving parts is allowed, but also that it prevents its overheating. It is a generally known practice for the aforementioned means to be provided in the form of a downward extension of the shaft, this is longitudinally perforated and formed to be able to suck the oil from the bottom of the sealed cover and diffuse it, substantially by an effect centrifuge, inside the parts to be lubricated. Such construction is usually effective in the case of traditional hermetic motor compressor units that are equipped with a single phase bipolar induction motor operating from 2700 to 3000 rpm. However, hermetic engine compressor units are still being used for a few years now, which are equipped with brushless motors with direct electric current that are capable of operating at adjustable speeds that vary from a maximum it can reach as much as 4000 rpm up to a minimum which on the contrary can be as low as 1000 rpm or even less, for the purpose of optimizing the performance of the related refrigeration apparatus, particularly from an energy use point of view. Also known are hermetic motor compressor units that are equipped with a four-pole induction motor that operates at a speed of only 1500 rpm. So, for a same capacity or cooling results, a greater displacement of the compressor is needed. In both cases mentioned above, traditional cooling and lubrication means such as those mentioned above are largely unsuitable due to the fact that the low rotation speeds of the shaft do not ensure a proper flow rate and supply head of the oil sucked from the bottom of the shaft. the cover closed, or a complete diffusion of the same oil to all the parts that need to be ubiquitous. In a hermetic motor compressor unit in which the electric drive motor is accommodated below the compressor, it has been proposed that a worm member be inserted with a slight radial space in the hollow shaft starting from the lower end thereof ( see WO 96/29516). The relative movement between the e e and the worm member, which extends along the entire electric drive motor and which is retained by a support that is fixed to the stator of the motor, secures the desired oil flow. This solution, however, has the disadvantage that the helical insert is completely contained within the handle and is affected by the heat transmitted by the motor. As a result, the mutual expansions tend to be carried out during the operation of the engine compressor unit, which causes the radial space between the insert and the shaft to be altered, with corresponding variations in the lubrication performance. It has also been proposed that a pumping chamber with an endless screw member protrudingly attached to the lower end portion of the shaft and a static sleeve associated therewith. (see WO 93/22557 and EP-A-0 728 946) are provided in the engine compressor unit. This type of solution causes an additional radial space to be created between the static sleeve and the inner surface of the rotating shaft, so that inevitable leaks are made due to the infilton of oil through the space, resulting in a speed of Reduced flow of the oil that is being pumped. In addition, such a solution seems quite difficult and expensive to implement, since care must be taken to ensure, between the two components of the pumping chamber, not only the aforementioned circumferential space, but also the space in the plane horizontal between the sleeve and the lower end portion of the shaft to prevent these parts from suffering a wear effect due to friction during opeon. Abstracts of Japanese Patents vol 009, No. 275 (M-426) November 2, 1985 (1985-11-02) & JP 60 119389 A (Toshiba KK), June 26, 1985 (1985-06-26) describe a lubrication system which is also comprised of a helically grooved element (fluted), which can also be considered as being elastically connected to the stator However, in said documents a sepa rotating sleeve is not provided entirely outside the motor, but a rotating hollow motor shaft is used as part of the oil suction means. Therefore, the oil suction means are not completely outside the rotor axis, because the fixed element is inserted inside the rotor shaft. This solution is affected by several heat transfer problems. Therefore, it is a main purpose of the present invention to provide, through the use of simple and reliable low cost means, an improved hermetic compressor unit that is capable of ensuring an effective oil flow at speeds of opeon that can be as low as approximately 800 rpm. On the basis of this, it will be better explained below, these and other objects are achieved in an hermetic motor compressor unit provided with an oil suction arrangement with the characteristics mentioned in the api annexes. In any case, said characteristics, together with the advantages of the present invention, will be better understood from the description given below by means of the non-limiting example with reference to the attached drawings, in which: Figure 1 is a cross-sectional view along the vertical plane of the lower portion of the hermetic motor compressor unit comprising the oil suction arrangement according to the present invention, in a first embodiment thereof; Figure 2 is a similar view as illustd in Figure 1, but showing only the oil suction arrangement in a second embodiment thereof; Figure 3 is a schematic view of the component parts of the oil suction arrangement shown in Figure 2. Referring to Figure 1, it can be noted that the articles and details of the hermetic engine compressor unit that are used do not they have relevance for the purposes of the present invention, starting from the current compressor, they are not shown as they are considered as widely known by all those skilled in the art. A sealed metal cover 10 has a lower portion 12 forming the manifold in which the oil 14 is collected, which is filled during the manufacture of the compressor, ensures the lubrication of the moving parts of an electric drive motor 16 and a compressor located above it that can, for example, be of the alternative type.

In this particular embodiment, the motor 16 is of the brushless direct current type with a rotor 18 of permanent magnet fixed to a vertical hollow shaft (which is common in the compressors located above it) and a similar stator 22. The lower portion of the stator comprises a rod 24 that supports (with the aid of a pair of slots not shown in the Figure for reasons of simplicity) end portions 26 and 28 of a clamp 30 that are substantially made of a spring steel rod. As can be seen, this clamp 30 is substantially U-shaped with a central zone 32 with mu scan. Fixed to the lower end portion of the hollow shaft 20 is a sleeve 34 that extends beyond vertically within the manifold 14 to be able to sink into and withdraw from the lubrication oil collected therein. The sleeve 34 is adapted to rotate together with the hollow shaft 20. Inserted inside the sleeve 34 is an oil suction member 36 which is provided, on its outer surface, with a helical groove advantageously extending therethrough, ie covering the entire length of the same member. This groove will cooperate with the inner wall of the sleeve 34, forming a channel that ensures the passage of the oil from the manifold 10 into the interior of the shaft 20. The sleeve 34 and the grooved member 36 are preferably made of plastic material, i.e. material with a lower heat conductivity than that of the metal material used to be the hollow shaft 20 itself. This solution is clearly simpler and less expensive in terms of both the construction itself and the assembly concerned. It also allows the problems associated with the mutual thermal expansion of the sleeve and the fluted member to be largely eliminated. By conclusion, the performance and reliability characteristics of the entire compressor unit of the hermetic motor are improved, in accordance with the present purpose of the present invention. The splined member 36 is supported by the elastic clamp 30, whose central zone 32 is freely inserted into a depression provided in the lower head portion of the member 36. This type of elastic assembly allows the member 36 to float, but does not rotate, within of the sleeve 34 during the operation of the engine compressor unit, with this possibly allowing to occur from the axle 20 axles and to compensate the oil suction arrangement. A second embodiment of the present invention, which is based on the same principle of operation and which ensures practically the same level of effectiveness as the aforementioned embodiment, is illustrated in Figures 2 and 3, in which the same reference numbers they are used to indicate articles and details corresponding to those illustrated in Figure 1. As a result, to the lower end portion of the shaft 20, once again a sleeve 34 is fixed, in this case, however, by means of a extension 40 of the same axis. In the sleeve 34 a floating piston member 36 is inserted which is supported by the elastic clamp 30 whose end portions 26 and 28 are connected to the motor cover 16, as shown in Figure 1. The difference related to the construction is found in the fact that the floating member 36 (FIG. 2) is provided on its outer surface with two opposed axial and opposite grooves 42 which cooperate with the corresponding openings 44 and 54 which are provided at different respective levels and In addition, a profiled spring washer 46 is mounted between the member 36 of the sleeve 34. This profiled cam washer 46 is fixed to the sleeve 34, preferably by joining, and adapts to the sleeve wall 34. to act against a crossed extension 56 that is provided in the lower end portion of the member 36. This extension 56 in turn is provided with a depression. n open downwards, in which the elastic bracket 30 holding the oil suction arrangement is able to insert 1 i b r ave heavily. The attachment of the extension 40 to the axis 20 (see Figure 2) is achieved by simply snapping the two parts together, thanks to the ability of the upper end portion of the extension 40 to deform due to the presence of a depression 48, as well as a button 50 that engages a notch 52. Button 50 and notch 52 are provided on the outer surface of the extension 40 and the inner surface of the shaft 20., respectively.

During the operation of the unit, when the shaft 20 rotates together with the extension 40 and the sleeve 34, the profiled cam washer 46 acts against the extension 56 and pushes the piston-like member 36 downwardly against the action of the elastic clamp 30 which tends to deflect, that is, push member 36 upwards. As a result, thanks to the combined effect of the curvature of the washer 46 and the elasticity of the clamp 30, the rotation of the shaft 20 is able to achieve a rotational movement of the member 36 in a vertical direction. The lubricating oil is removed from the oil sump within the notches 42 of the piston-like member 36 when the sleeve 34 is rotated in the position in which it allows the notches 42 to communicate with the lower openings 44. This occurs during the downward movement of the member 36. When the sleeve 34 then rotates through an angle of approximately 90 ° with respect to the aforementioned position, the oil is able to flow from the notches 42 through the upper openings 54 within. of the hollow handle 20. This occurs during the upward movement of my emb 36.

The solution described therefore constitutes a positive displacement piston pump without movable valves.

Claims (5)

1. A hermetic motor compressor unit for domestic use and similar cooling apparatus, comprises a sealed cover, the bottom of which forms a manifold for the lubrication oil, in which the current compressor and the related motor are housed which share a Common hollow crankshaft rotating about a vertical axis, the lubrication oil suction means are provided in the lower end portion of the crankshaft, characterized in that the oil suction means comprise a sleeve, which is rigidly fixed to the portion at the lower end of the crankshaft and in which a fluted member is inserted, which is elastically connected to the stator of the engine, the oil suction means extend downwards completely out of the hollow crankshaft, the sleeve and the fluted member are made of a material having a thermal conductivity lower than the material of which the hollow shaft is made. The hermetic motor compressor unit according to claim 1 or 2, characterized in that the fluted member is supported by a substantially U-shaped clamp formed by a metal band or wire, the intermediate zone of which engages the portion of lower end of the fluted member, and whose lateral arms are anchored to the stator of the electric motor. The hermetic motor compressor unit according to any of claims 1 to 3, characterized in that the fluted member is a member that is provided on its outer surface with a helical groove that forms the channel through which the oil passes. lubrication of the c omp resor. The hermetic motor compressor unit according to any of claims 1 to 3, characterized in that the fluted element is a piston-like member that is provided on its outer surface with mutually opposed axial notches that are adapted to cooperate with the corresponding radial openings p arranged at different respective levels and passing through the wall of the sleeve. The hermetic motor compressor unit according to claim 4, characterized in that in the lower end portion of the sleeve there is a profiled spring cam washer which cooperates with a cross extension of the piston member.