Patent Application
20190368481
The present invention relates to a lubricant receptacle according to the preamble of Claim 1.
The invention also relates to a refrigerant compressor according to the preamble of Claim 7.
Ensuring sufficient lubrication of all moving parts is especially important for refrigerant compressors. For this purpose, it can be provided that lubricant that collects in a lubricant sump covering the bottom area of the compressor housing is conveyed via the crankshaft in the direction of the cylinder.
To this end, a sleeve-like lubricant receptacle is often provided, which is rotationally fixedly connected to the crankshaft and arranged coaxially therewith and protrudes at one end into the lubricant sump. Lubricant that has penetrated through an inlet opening from the lubricant sump into a receiving portion of the lubricant receptacle is forced by the rotation of the lubricant receptacle—which is produced by rotation of the crankshaft—into a paraboloid shape, the paraboloid extending along the inner wall of the lubricant receptacle and the inner wall of the crankshaft.
A maximum level to which the lubricant present in the receiving portion of the lubricant receptacle can be lifted in this manner is naturally achieved in the region of the clear internal diameter of the crankshaft and depends on the square of rotational speed of the lubricant receptacle and the square of the clear internal radius of the crankshaft or the lubricant receptacle.
With an appropriate selection of the production parameters (for example, clear internal radius of the crankshaft, height of the outlet bores) and process parameters (for example, rotational speed of the crankshaft, viscosity of the lubricant), it is possible to convey the lubricant from the bottom of the compressor housing by means of the lubricant receptacle via the crankshaft of the compressor to the supporting points of the main bearing for the crankshaft, to the crank pin, and to connecting rod of the refrigerant compressor.
A compressor having a lubricant receptacle of this kind is known from WO 2009/092147 A1, for example.
When such devices are used, however, there is typically a formation of gas bubbles within the lubricant receptacle and/or in the region of the inlet opening and/or within the entire lubricant conveying system (i.e. in the region between the lubricant sump and the components to be lubricated in which lubricant is present), which gas bubbles are responsible for temporary cut-outs of the lubrication system. In addition, these bubbles can lead to fluctuations of the vertical position of the lower apex of the paraboloid. If this apex moves down into the region of the inlet opening, this can cause an interruption of the lubricant conveying system and thus the collapse of the paraboloid shape of the lubricant inside the lubricant receptacle and/or the crankshaft.
The disruption of the lubricant conveying system can result in fluctuations of the oil delivery from the crank pin. In extreme case, which can be considered a cessation of the oil delivery, all moving parts run without lubrication, whereby the compressor fails within a very short time.
An object of the present invention is therefore that of providing a lubricant receptacle—and consequently also a lubricant compressor having a lubricant receptacle according to the invention—wherein a lasting closure of the inlet opening due to formation of gas bubbles in the region of the lubricant receptacle or the inlet opening can be prevented.
It should additionally be ensured that gas bubbles, once they have arisen, break up within a very short time and thus do not lead to any longer-term closure of the lubricant receptacle.
In addition, the lubricant receptacle according to the invention should be particularly cost-effective to produce and easy to install.
In a lubricant receptacle according to the invention for vertical conveyance of lubricant by means of a crankshaft of a refrigerant compressor, the lubricant receptacle comprising: at least one rotationally symmetrical sleeve-like receiving portion for receiving lubricant, wherein the longitudinal axis of the receiving portion can be arranged coaxially with a longitudinal axis of the crankshaft of the refrigerant compressor; a fastening portion adjoining the receiving portion, in order to fasten the lubricant receptacle on the crankshaft; and at least one end region adjoining the receiving portion, which end region closes off the receiving portion, apart from an inlet opening, wherein the inlet opening enables entry of lubricant from a lubricant sump into the lubricant receptacle, which protrudes at least partially into the lubricant sump, wherein the inlet opening is arranged surrounding the longitudinal axis in the end region, this object is achieved in that the inlet opening, viewed in the direction of the longitudinal axis, either has a circular peripheral shape and a center point of the inlet opening is offset from the longitudinal axis, or in that the inlet opening has a non-circular shape viewed in the direction of the longitudinal axis.
In concrete terms, a projection, specifically an orthogonal projection of the end region along the longitudinal axis of the receiving portion, is to be formed asymmetrically with respect to rotation about the intersection point of the longitudinal axis of the receiving portion and the end portion, because an asymmetric design of this kind can avoid lasting closure of the inlet opening by the formation of gas bubbles in the region of lubricant receptacle or the inlet opening. Although it is possible in principle that the inlet opening of the lubricant receptacle may be closed off for a brief time by a gas bubble, the lubricant receptacle according to the invention has the effect that, due to an inhomogeneous distribution of the centripetal forces acting on any gas bubbles that may have exited from the lubricant receptacle and are closing the inlet opening, the bubbles are unstable and immediately detach from the inlet opening. In such a case, the inlet opening is again released after a very short time, a maximum of roughly 2 seconds, so that a lasting closure can be prevented.
The invention provides that the inlet opening is arranged surrounding the longitudinal axis in the end region. The necessary asymmetry of the orthogonal projection of the end region in relation to rotations about the intersection point between the longitudinal axis of the receiving portion and the end region is achieved by non-circular formation of the peripheral shape of the inlet opening, or by correspondingly offsetting a center of a circular inlet opening from the longitudinal axis.
The end region of the lubricant receptacle can either be flat, in which case the periphery of the inlet opening is located in a plane; or the end region of the lubricant receptacle is formed as a curved surface, so that the periphery of the inlet opening arranged in the end region describes a three-dimensional curve. In the latter case, the inlet opening has a circular or non-circular peripheral shape as viewed in the direction of the longitudinal axis.
There are advantages in terms of production if the inlet opening has its origin in the rotational center of the end region of the lubricant receptacle. The necessary shape of an inlet opening of his kind enclosing the intersection point between the longitudinal axis of the receiving portion and the end region, which shape leads to the required asymmetry of said projection of the end region, can be provided in this case in a simple manner by further machining. Proceeding from a circular, centrally arranged bore, this can create an inlet opening having a peripheral shape that is capable of satisfying the required asymmetry condition.
In addition, an inlet opening arranged surrounding the longitudinal axis leads to an even faster detachment of a gas bubble closing the inlet opening. Differently from lubricant receptacles having inlet openings that are arranged radially outwardly—i.e. not enclosing the longitudinal axis—gas bubbles that have formed within the lubricant receptacle according to the invention can reach the inlet opening faster. This is explained by the fact that lubricant that has penetrated through the inlet opening from the lubricant sump into the receiving portion of the lubricant receptacle is initially forced by the rotation of the lubricant receptacle—which is produced by rotation of the crankshaft—into a paraboloid shape, the paraboloid extending along the inner wall of the lubricant receptacle. During the rotation of the lubricant receptacle in an operating state of the compressor, to the crankshaft of which the lubricant receptacle is attached, an outgassing effect within the lubricant receptacle leads to a change in the geometry of the paraboloid. This has the effect that an apex of the paraboloid, which apex is formed in the region of the longitudinal axis of the receiving portion, descends further and further in the direction of the end region of the lubricant receptacle. Only when the apex of the paraboloid reaches the inlet opening can a part of the paraboloid—namely the gas bubble—escape from the lubricant receptacle. Due to the arrangement and shape of the inlet opening according to the invention, the gas bubble detaches from the inlet opening after a very short time—usually after a few tenths of a second. However, if the inlet opening is not formed surrounding the longitudinal axis, but rather in a radially outward peripheral region of the end region, a gas bubble can escape from the lubricant receptacle—if it all—only much later. In such a case, there can be a collapse of the paraboloid within the lubricant receptacle or a critical reduction in the delivery of lubricant.
In principle, inlet openings of the orthogonal projection of the end region that are shaped and arranged in a wide variety of manners can provide the required asymmetry in relation to rotation about the intersection point of the longitudinal axis of the receiving portion with the end region of the lubricant receptacle, i.e. the center of the projection. For example, the aforementioned asymmetry can be achieved by an elliptical or circular inlet opening, wherein the center of a circular inlet opening does not coincide with the intersection point of the longitudinal axis of the receiving portion with the end region of the lubricant receptacle.
A preferred embodiment of the invention therefore provides that the inlet opening has an elliptical peripheral shape as viewed in the direction of the longitudinal axis.
Inlet openings with a substantially elliptical peripheral shape that does not describe a mathematically perfect ellipse, but nevertheless has a similar appearance, can also be advantageous.
In a preferred embodiment of the lubricant receptacle, the required asymmetry of the inlet opening can be achieved in a particularly simple and cost-saving manner in that the inlet opening has the shape of an elongated hole. The center of the elongated hole can either coincide with the intersection point of the longitudinal axis of the receiving portion with the end region of the lubricant receptacle, or can be offset therefrom. In both cases, the required asymmetry is achieved because the projection of the end region along the longitudinal axis of the receiving portion with respect to rotation about the intersection point of the longitudinal axis of the receiving portion with the end region is asymmetrical due to the elongated hole.
It has been found that the implementation of the inlet opening according to the invention as an elongated hole is particularly advantageous with respect to the entry of lubricant from the lubricant sump into the receiving portion, or with respect to the avoidance of lasting closures of the inlet opening due to gas bubbles.
In a particularly preferred embodiment variant of the lubricant receptacle according to the invention, a fluid-dynamically optimal scooping up of lubricant from the lubricant sump into the receiving portion of the lubricant receptacle can be achieved if the longitudinal hole is delimited by semicircles at both ends and the long side of the elongated hole is greater than the radius of the semicircular delimitations.
In order to facilitate the production of a longitudinal hole of this kind, a particularly preferred embodiment variant of the lubricant receptacle according to the invention provides that the length of the long side of the elongated hole is between the value of the radius of the semicircular delimitations and twice said value.
Long sides refer in this regard to those sides of the slotted hole that are straight and parallel to one another. The total length of the elongated hole is composed of the length of the long side plus the two radii of the semicircular delimitations.
Because the size and shape of the inlet opening has an influence on the paraboloid forming in the receiving portion of the lubricant receptacle in rotation, these parameters must be selected carefully. It has proved to be particularly advantageous in another particularly preferred embodiment variant of the lubricant receptacle according to the invention if the size of the inlet opening is between 5 and 30 percent, preferably 10 and 25 percent and especially preferably between 15 and 20 percent of the clear cross-sectional area of the receiving portion. Thereby a particularly advantageous paraboloid shape can be formed within the receiving portion.
In order to convey the lubricant present in the receiving portion of the lubricant receptacle in the direction of the cylinder through the interior of the crankshaft by utilizing the rotation thereof, the rotational paraboloid being formed must not be disturbed on the inner lateral surfaces of the lubricant receptacle and the crankshaft if possible.
To achieve a transition between the receiving portion of the lubricant receptacle and the crankshaft that is as free of interruptions as possible, it is provided that the lubricant receptacle has a fastening portion (16) adjoining the receiving portion, in order to mount the lubricant receptacle on the crankshaft. Alternatively or additionally, fastening of the lubricant receptacle to the rotor rotationally fixedly connected to the crankshaft can be achieved by means of this fastening portion.
In a preferred embodiment of the invention, the lubricant receptacle contains at least one lubricant driver for lubricant in order to favor the formation of the lubricant paraboloid within the lubricant receptacle.
The lubricant driver can be formed by a rigid structure such as a twisted sheet metal element arranged in the receiving portion.
In a refrigerant compressor comprising: a hermetically sealable compressor housing; an electric drive unit arranged in the housing interior of the compressor housing and comprising a rotor and a stator; a crankshaft rotationally fixedly connected to the rotor; and a piston-cylinder unit arranged in the housing interior and comprising a piston movably mounted in a cylinder of the piston-cylinder unit and drivable by the crankshaft to compress refrigerant, an additional object of the invention is achieved in that the refrigerant compressor has a lubricant receptacle according to the invention in order to convey lubricant from a lubricant sump arranged in a bottom region of the compressor housing to the piston-cylinder unit via the crankshaft, wherein the lubricant receptacle is fixedly connected to the crankshaft.
By using a lubricant receptacle according to the invention in a hermetically sealable refrigerant compressor—particularly due to the asymmetric formation of the end region of the lubricant receptacle in relation to rotations of the projection of the end region about the center point between the longitudinal axis of the receiving portion and the end region—it is possible to ensure a lubrication of all components of the refrigerant compressor requiring lubrication that is improved in comparison to conventional, i.e. symmetrical lubricant receptacles, since the lasting closure of the inlet opening by formation of gas bubbles in the region of the lubricant receptacle or the inlet opening can be avoided and the influence of fluctuations of the lower apex of the paraboloid on the overall lubricant conveying system can be reduced.
Due to the continuous lubricant flow from the receiving portion into the crankshaft and from the crankshaft via exit openings to the components of the refrigerant compressor requiring lubrication during operational usage of the lubricant receptacle, it is necessary to ensure a continuous resupply of lubricant into the receiving portion of the lubricant receptacle.
In a particularly preferred embodiment of the refrigerant compressor according to the invention, it is provided for this purpose that the end region of the lubricant receptacle protrudes at least in certain portions into the lubricant sump so that the inlet opening is arranged within the lubricant sump in order to enable entry of lubricant from the lubricant sump into the receiving portion of the lubricant receptacle.
In order to favor the formation of the paraboloid shape of the lubricant in the receiving portion, another particularly preferred embodiment of the refrigerant compressor according to the invention provides that the lubricant receptacle is fastened by means of the fastening portion to an end portion of the crankshaft remote from the piston cylinder unit and/or to the rotor.
In particular, it can be provided that an internal diameter of the receiving portion of the lubricant receptacle coincides with a clear internal diameter of the crankshaft, and that the fastening portion of the lubricant receptacle is pressed from the outside onto the end portion of the crankshaft, so that a continuous transition between the receiving portion of the lubricant receptacle and the crankshaft is ensured.
The invention will now be explained in detail with reference to embodiments. The drawings are for the sake of example and are intended to present the inventive concept, but not to restrict it, much less reproduce it exhaustively
Therein:
The lubricant receptacle 1 comprises a fastening portion 16 for fastening the lubricant receptacle 1 to a crankshaft 2 or a rotor 11 of a lubricant compressor 3 (see
This receiving portion 4 itself has a cylindrical lateral surface and is closed off by an end region 5 of the lubricant receptacle 1 at the lower side, i.e. at a side remote from the fastening portion 16.
The above yields a sleeve-like structure of the lubricant receptacle 1, which is open toward the top and closed off by the end region 5 toward the bottom, apart from an inlet opening 6 for lubricant. Both the fastening portion 16 and the receiving portion 4 are rotationally symmetrical relative to rotation about a longitudinal axis 8 of the receiving portion 4.
In the operating state of the lubricant receptacle 1, in which the lubricant receptacle 1 is arranged coaxially with crankshaft 2 and rotationally fixedly connected to the crankshaft 2, the inlet opening 6 establishes a fluidic connection between a housing interior of the refrigerant compressor 3 and the receiving portion 4.
The shape of the inlet opening 6, which is formed as an elongated hole in this specific embodiment, has the effect that a projection 18 of the end region 5 along the longitudinal axis 8 is no longer symmetrical under rotation about an intersection point 19 of the longitudinal axis 8 with the end region 5. Only the rotation of the projection 18 about the intersection point 19 by an angle of 360° images the projection 18 of the end region 5 back on itself, and therefore the condition for rotational symmetry, according to which two-dimensional objects are rotationally symmetrical if a rotation about a point by every arbitrary angle images the object onto itself, is specifically not fulfilled.
Precisely this asymmetry of the end region 5 of the lubricant receptacle 1 caused by the inlet opening 6 has the effect that, in the operating state of the lubricant receptacle 1—in which operating state the lubricant receptacle 1 is rotationally fixedly connected to the crankshaft 2 of the refrigerant compressor 3 and arranged coaxially with the crankshaft 2 such that at least the end region 5 protrudes in portions into a lubricant sump 7 of the refrigerant compressor 3 (see
In the illustrated embodiment variant, the crankshaft 2 is rotationally fixedly connected to the rotor 11 surrounding a stator 12 of the drive unit 10 for the refrigerant compressor 3 according to the invention, and is set into rotation by the drive unit 10. This rotational movement of the crankshaft 2 firstly causes a piston 14 of the piston cylinder unit 13 to be moved periodically back and forth between two dead center points of a cylinder 15 in order to draw in refrigerant from the housing interior, compress it and then discharge it; secondly, the rotating crankshaft 2 also sets the lubricant receptacle 1 into a rotational motion which has the effect that the lubricant having reached the receiving portion 4 through the inlet opening 6 assumes the shape of a paraboloid 20.
With an appropriate selection of the production parameters for the lubricant receptacle 1 (in particular the internal diameter of the receiving portion 4) and of the process parameters for the operating state of the refrigerant compressor 3 according to the invention (in particular the rotational speed of the crankshaft 2), the lubricant in the receiving portion 4 reaches a level due to the shape of the paraboloid 20 that enables a passage of lubricant from the lubricant receptacle 1 into the crankshaft 2.
For further conveyance of the lubricant, the crankshaft 2 can be produced at least in portions as a hollow cylinder, in which case lubricant can escape from the crankshaft 2 via openings in the lateral surface of the hollow cylinder and reach the components of the refrigerant compressor 3 provided for lubrication; in such a case, the maximum level must reach at least up to a first opening in the lateral surface. The crankshaft 2 can also be implemented as a solid cylinder, however, and be furnished with an eccentric bore 21, generally running upward at an incline, by means of which bore 21 the further conveyance of the lubricant is achieved. In the case of an inclined bore 21, a lower maximum level of the lubricant may sometimes be sufficient, because it need merely enable a passage of lubricant into the bore 21 and not cover the entire distance up to the first opening. Within the inclined bore 21 of the crankshaft 2, the lubricant is pressed against a wall of the bore 21 and thereby conveyed up to the first opening in the lateral surface of the crankshaft 2.
| Number | Date | Country | Kind |
|---|---|---|---|
| GM 50271/2016 | Dec 2016 | AT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/084445 | 12/22/2017 | WO | 00 |
