EP3277957A1

EP3277957A1 - Hermetic compressor crankshaft with improved lubrication

Info

Publication number: EP3277957A1
Application number: EP15713484.2A
Authority: EP
Inventors: Bilgin Hacioglu; Serkan Kara
Original assignee: Arcelik AS
Current assignee: Arcelik AS
Priority date: 2015-03-31
Filing date: 2015-03-31
Publication date: 2018-02-07
Anticipated expiration: 2035-03-31
Also published as: EP3277957B1; WO2016155806A1; PL3277957T3

Abstract

The present invention relates to a crankshaft (1) for use in a hermetic compressor (2) comprising a bearing (3), a rotor (4) and a lubricant sump (5). The crankshaft (1) comprises a journal (7), an inner diameter surface (6a) for conveying the lubricant to the journal (7), a lubricant outlet (8) which is formed into the journal (7) and opens into the inner diameter surface (6a) of the crankshaft (1) and an outer diameter surface (6b) for the attachment to the rotor (4). In the crankshaft (1) of the present invention the shaft (6) comprises an axially extending slot (9) for conveying the lubricant from the sump (5) to the journal (7) upon rotation. The slot (9) fluidly connects, in the radial direction, the inner diameter surface (6a) to the outer diameter surface (6b) of the shaft (6). At least part of the slot (9) radially faces the innermost diameter surface (4a) of the rotor (4).

Description

HERMETIC COMPRESSOR CRANKSHAFT WITH IMPROVED LUBRICATION

The present invention relates to a crankshaft for use in a hermetically sealed reciprocating compressor of a refrigeration appliance with a variable refrigeration capacity.
Hermetically sealed reciprocating compressors are commonly known in the art. A hermetic compressor generally comprises a cylinder block which has a main bearing for supporting the crankshaft and a motor for rotating the crankshaft. In a commonly known configuration, the crankshaft comprises a vertical shaft which includes a journal for resting on the main bearing of the cylinder block. And the motor rotor has an inner diameter surface which can be attached onto the outer diameter surface of the crankshaft at a position below the main bearing. The lubrication of the moving parts is performed by the lubricant that is collected in the sump, i.e., the lower section of the hermetic casing. In particular, the journal must be intensively lubricated during the operation. Therefore, the vertical shaft is provided as a tubular structure in which the inner diameter surface conveys the lubricant from the sump to the journal under the action of centrifugal forces. The lubricant which ascends on the inner diameter surface of the shaft is distributed via a lubricant outlet towards the surface of the journal. In a commonly known configuration, the lubricant is conveyed from the sump to the inner diameter surface of the shaft through a lubricant pickup tube which is fixed to the lower end of the shaft and immersed into the lubricant sump. In a commonly known alternative configuration, the lower end of the shaft is directly immersed into the sump. This obviates the need for a pickup tube.
A problem with the prior art hermetic compressor is that when the refrigeration appliance is operated at a comparatively low refrigeration capacity, i.e., at a comparatively low rotational speed of the crankshaft, then the pumping effect weakens and thus the journal of the crankshaft receives less lubricant. The lubrication performance is of utmost importance. In case of insufficient lubrication, the surface of the journal and the surface of the main bearing wear rapidly and the life time of the compressor becomes shorter. Another problem with the prior art hermetic compressor is that the lubrication performance of the crankshaft puts a lower limit on the available refrigeration capacity.
An objective of the present invention is to provide a crankshaft for use in a hermetic compressor of a refrigeration appliance which solves the aforementioned problems of the prior art in a cost-effective way and which enables an improved lubrication performance at comparatively low refrigeration capacities and an energy-efficient operation.
This objective has been achieved by the crankshaft as defined in claim 1, the hermetic compressor as defined in claim 9 and the refrigeration appliance as defined in claim 11. Further achievements have been attained by the subject-matters respectively defined in the dependent claims.
In the crankshaft of the present invention, the shaft comprises an axially extending slot for conveying the lubricant from the sump to the journal upon rotation of the shaft. The slot fluidly connects, in the radial direction, the inner diameter surface of the shaft with the outer diameter surface of the shaft such that at least part of the slot radially faces the innermost diameter surface of the rotor.
A major advantageous effect of the present invention is that during the rotatory movement, the lubricant on the inner diameter surface of the shaft drifts outwardly into the axially extending slot where it revolves at a comparatively larger radial distance away from the axis of rotation and thus ascends under the influence of a comparatively larger centrifugal force along the innermost diameter surface of the rotor towards the journal. Thereby, the amount of lubricant which can be pumped towards the journal can be increased, and the lubrication performance of the crankshaft can be improved. Thereby, the wear can be reduced and life of the compressor can be prolonged. Another major advantageous effect of the present invention is that the vertical sidewalls of the axially extending slot function like a divider for the lubricant inside the slot and thus further improve the lubrication performance. Another major advantageous effect of the present invention is that the journal can be more effectively lubricated at comparatively lower rotational speeds, and thus the compressor can be operated at refrigeration capacities which are even lower than in the conventional compressors.
In an embodiment, the slot extends axially upwards until it joins the lubricant outlet on the journal. This embodiment is particularly advantageous as the pumping effect is enhanced when the length of the slot is increased. In this embodiment, during the rotary movement, the lubricant ascends on the inner diameter surface of the shaft as well as inside the slot and on the corresponding innermost diameter surface of the rotor up to the lubrication outlet. Thereby, an increased amount of lubricant can be distributed onto the surface of the journal and onto the surface of the main bearing.
In an alternative embodiment, the slot does not extend up to the lubricant outlet on the journal but terminates at a relatively lower level. This embodiment is particularly advantageous as the pumping effect can be precisely adjusted in accordance with the required refrigeration capacities. In a version of this embodiment, the slot axially extends up to a level which is located below the upper end of the innermost diameter surface of the rotor. During the rotary movement, the lubricant ascends on the inner diameter surface of the shaft as well as inside the slot and on the corresponding innermost diameter surface of the rotor. The lubricant inside the slot first ascends up to the end of the slot and therefrom continues to ascend on the inner diameter surface of the shaft to the lubrication outlet. Thereby, an increased amount of lubricant can be distributed onto the surface of the journal and onto the surface of the main bearing.
In another embodiment, the crankshaft is adapted for use with a lubricant pick up tube. This embodiment is particularly advantageous as the total length of the shaft can be reduced and the related costs can be saved. When the crankshaft is rotated by the electric motor, the pick-up tube sets the lubricant into whirling motion and the lubricant starts to ascend on the inner diameter surface of the pick-up tube into the slot and onto the corresponding innermost diameter surface of the rotor as well as onto the inner diameter surface of the shaft and therefrom via the lubricant outlet to the journal. In this embodiment, the slot extends from the lower end of the shaft axially upwards. In this embodiment, the pick up tube adjoins the lower end of the rotor so as to confine the ascending lubricant into the slot and onto the innermost diameter surface of the rotor and onto the inner diameter surface of the shaft. In a version of this embodiment, the lower end of the shaft can be inserted into the upper end of the lubricant pick-up tube. In an alternative version of this embodiment, the upper end the lubricant pick-up tube can be inserted into the lower end of the shaft.
In another embodiment, the lubricant pick up tube is attached to the shaft by press-fitting. Alternatively, the lubricant pick up tube can be attached to the shaft by heating and shrinking, or welding, or slip-fitting and applying an adhesive. Other methods known to those skilled in the art can be alternatively used.
In an alternative embodiment, the crankshaft is adapted for direct immersion in the sump, i.e., without using a lubricant picks up tube. This embodiment is particularly advantageous as the assembly costs can be reduced. In a version of this embodiment, the slot does not extends from the lower end of the shaft but from a relatively higher level which corresponds to at least the lower end of the rotor. In an alternative version of this embodiment, the slot extends from the lower end of the shaft upwards and is radially outwardly closed by a cover member such as a curved leaf up to the lower end of the rotor so as to confine the ascending lubricant into the slot.
In another embodiment, the shaft has one or more than one axially extending slots and associated lubricant outlets on the journal. In alternative versions of this embodiment, the slots are straight and/or curved. This embodiment is particularly advantageous as the pumping effect can be considerably more increased.
Additional advantageous effects of the crankshaft and the hermetically sealed compressor according to the present invention will become more apparent with the detailed description of the embodiments with reference to the accompanying drawings in which:
Figure 1 – is a schematic cutaway view of a hermetically sealed compressor which has a crankshaft according to an embodiment of the present invention;
Figure 2 – is a schematic side view of a crankshaft according to an embodiment of the present invention;
Figure 3 – is a schematic cutaway view of a hermetically sealed compressor which has a crankshaft according to another embodiment of the present invention;
Figure 4 – is a schematic side view of a crankshaft according to another embodiment of the present invention.
The reference signs appearing on the drawings relate to the following technical features.

Crankshaft
Compressor
Main bearing

3a. Surface
3b. End
4. Rotor
4a. Surface
4b. End
4c. Surface
4d. End
5. Sump
6. Shaft
6a. Surface
6b. Surface
6c. End
7. Journal
8. Outlet
9. Slot
10. Tube
10a. Surface
10b. Surface
10c. End
11. Outlet
The crankshaft (1) is suitable for use in a hermetic compressor (2) The hermetic compressor (2) comprises a main bearing (3) (or cylinder block) for supporting the crankshaft (1), a rotor (4) which has an innermost diameter surface (4a) for attachment onto the crankshaft (1) below the main bearing (3) and a lubricant sump (5) (Fig. 1 to 4).
The crankshaft (1) comprises: a vertical shaft (6) which comprises a journal (7) for resting on the main bearing (3), an inner diameter surface (6a) for conveying the lubricant from the sump (5) to the journal (7) upon rotation of the shaft (6), a lubricant outlet (8) on the journal (7), wherein the lubricant outlet (8) opens into the inner diameter surface (6a) of the shaft (6) and an outer diameter surface (6b) for attachment to the rotor (4) (Fig. 1 to 4).
In the crankshaft (1) of the present invention, the shaft (6) comprises an axially extending slot (9) for conveying the lubricant from the sump (5) to the journal (7) upon rotation of the shaft (6). The slot (9) fluidly connects, in the radial direction, the inner diameter surface (6a) of the shaft (6) to the outer diameter surface (6b) of the shaft (6). At least part of the slot (9) radially faces the innermost diameter surface (4a) of the rotor (4) (Fig. 1 to 4).
The hermetic compressor (2) of the present invention comprises the crankshaft (1). The crankshaft (1) is journalled into the main bearing (3). And the rotor (4) is attached onto the shaft (6) below the main bearing (3) (Fig. 1 to 4).
The refrigeration appliance (not shown) of the present invention comprises the hermetic compressor (2) (Fig. 1 to 4).
In an embodiment, the slot (9) axially extends from the lower end (6c) of the shaft (6) and terminates at a level (L) below the outlet (8) on the journal (7). In this embodiment, the shaft (6) is adapted for use with a lubricant pick up tube (10) whose upper end (10c) is adapted to adjoin the lower end (4d) of the rotor (4). In this embodiment, the outer diameter surface (6b) at the lower end (6c) of the shaft (6) is adapted for attachment onto the inner diameter surface (10a) at the upper end (10c) of the lubricant pick up tube (10). In a version of this embodiment, said level (L) is below the upper end (4b) of the innermost diameter surface (4a) of the rotor (4) (Fig. 1 to 2).
In another embodiment, the slot (9) axially extends from the lower end (6c) of the shaft (6) and terminates at the outlet (8) on the journal (7). In this embodiment, at least part of the slot (9) radially faces the inner diameter surface (3a) of the main bearing (3). In this embodiment, the shaft (6) is adapted for use with a lubricant pick up tube (10) whose upper end (10c) is adapted to adjoin the lower end (4d) of the rotor (4). In this embodiment, the outer diameter surface (6b) at the lower end (6c) of the shaft (6) is adapted for attachment onto the inner diameter surface (10a) at the upper end (10c) of the lubricant pick up tube (10) (Fig. 3 to 4).
In another embodiment, the outer diameter surface (6b) at the lower end (6c) of the shaft (6) is attached into the inner diameter surface (10a) of the lubricant pick up tube (10) by press-fitting. Alternatively, the shaft (6) can be attached the lubricant pick up tube (10) by heating and shrinking, or welding, or slip-fitting and applying an adhesive. Other methods known to those skilled in the art can be alternatively used. In this embodiment, the upper end (10c) of the lubricant pick up tube (10) is adapted to adjoin the lower end (4d) of the rotor (4) (Fig. 1 to 4).
In another embodiment, the crankshaft (1) further comprises an additional lubricant outlet (11) on the journal (7). The additional lubricant outlet (11) opens into the inner diameter surface (6a) of the shaft (6) (Fig. 1 to 4).
In another embodiment, the rotor (4) has a large inner diameter surface (4c) above its innermost diameter surface (4a). In this embodiment, the lower end (3b) of the main bearing (3) radially faces the large inner diameter surface (4c) of the rotor (4) (Fig. 1 to 4).
In another embodiment, the rotor (4) is attached onto the crankshaft (1) for instance by press-fitting. Alternatively the rotor (4) can be attached onto the crankshaft (1) for instance by heating and shrinking, or welding, or slip-fitting and applying an adhesive. Other methods known to those skilled in the art can be alternatively used (Fig. 1 to 4).
A major advantageous effect of the present invention is that during the rotatory movement, the lubricant on the inner diameter surface (6a) of the shaft (6) drifts outwardly into the axially extending slot (9) where it revolves at a comparatively larger radial distance away from the axis of rotation, and thus ascends under the influence of a comparatively larger centrifugal force along the innermost diameter surface (4a) of the rotor (4) towards the journal (7). Thereby, the amount of lubricant which is pumped towards the journal (7) increases. Consequently, the lubrication performance of the crankshaft (1) improves. In particular, the wear can be reduced and the life of the compressor (2) can be prolonged. Another major advantageous effect of the present invention is that the vertical sidewalls of the axially extending slot (9) function like a divider that increases the speed of the lubricant inside the slot (9), and thus further improve the pumping effect. Another major advantageous effect of the present invention is that the journal (7) can be more effectively lubricated at comparatively lower rotational speeds, and thus the compressor (2) can be operated at refrigeration capacities which are even lower than the conventional refrigeration capacities. Other additional advantageous effects of the present invention can be taken from the aforementioned embodiments.

Claims

A crankshaft (1) for use in a hermetic compressor (2) comprising a main bearing (3) for supporting the crankshaft (1), a rotor (4) which has an innermost diameter surface (4a) for attachment onto the crankshaft (1) below the main bearing (3) and a lubricant sump (5), the crankshaft (1) comprising a vertical shaft (6) which has a journal (7) for resting on the main bearing (3), an inner diameter surface (6a) for conveying the lubricant from the sump (5) to the journal (7) upon rotation of the shaft (6), a lubricant outlet (8) on the journal (7), wherein the lubricant outlet (8) opens into the inner diameter surface (6a) of the shaft (6), an outer diameter surface (6b) adapted for attachment to the rotor (4), the crankshaft (1) being characterized in that

the shaft (6) comprising an axially extending slot (9) for conveying the lubricant from the sump (5) to the journal (7) upon rotation of the shaft (6), wherein the slot (9) fluidly connects, in the radial direction, the inner diameter surface (6a) of the shaft (6) with the outer diameter surface (6b) of the shaft (6) and wherein at least part of the slot (9) radially faces the innermost diameter surface (4a) of the rotor (4).
The crankshaft (1) according to claim 1, characterized in that the slot (9) axially extends from the lower end (6c) of the shaft (6) and terminates at a level (L) below the outlet (8) on the journal (7), wherein the shaft (6) is adapted for use with a lubricant pick up tube (10) whose upper end (10c) is adapted to adjoin the lower end (4d) of the rotor (4) and wherein the outer diameter surface (6b) at the lower end (6c) of the shaft (6) is adapted for attachment onto the inner diameter surface (10a) at the upper end (10c) of the lubricant pick up tube (10), or the inner diameter surface (6a) at the lower end (6c) of the shaft (6) is adapted for attachment onto the outer diameter surface (10b) at the upper end (10c) of the lubricant pick up tube (10).
The crankshaft (1) according to claim 2, characterized in that said level (L) is below the upper end (4b) of the innermost diameter surface (4a) of the rotor (4).
The crankshaft (1) according to claim 2, characterized in that said level (L) is above the lower end (3b) of the inner diameter surface (3a) of the main bearing (3), wherein at least part of the axially extending slot (9) radially faces the inner diameter surface (3a) of the main bearing (3).
The crankshaft (1) according to claim 1, characterized in that the slot (9) axially extends from the lower end (6c) of the shaft (6) and terminates at the outlet (8) on the journal (7), wherein at least part of the axially extending slot (9) radially faces the inner diameter surface (3a) of the main bearing (3), wherein the shaft (6) is adapted for use with a lubricant pick up tube (10) whose upper end (10c) is adapted to adjoin the lower end (4d) of the rotor (4) and wherein the outer diameter surface (6b) at the lower end (6c) of the shaft (6) is adapted for attachment onto the inner diameter surface (10a) at the upper end (10c) of the lubricant pick up tube (10), or the inner diameter surface (6a) at the lower end (6c) of the shaft (6) is adapted for attachment onto the outer diameter surface (10b) at the upper end (10c) of the lubricant pick up tube (10).
The crankshaft (1) according to any one of claims 2 to 5, characterized in that a lubricant pick up tube (10) for conveying the lubricant from the sump (5) to the inner diameter surface (6a) of the shaft (6) upon rotation, wherein the outer diameter surface (6b) at the lower end (6c) of the shaft (6) is attached onto the inner diameter surface (10a) at the upper end (10c) of the lubricant pick up tube (10) and wherein the upper end (10c) of the lubricant pick up tube (10) is adapted to adjoin the lower end (4d) of the rotor (4).
The crankshaft (1) according to any one of claims 2 to 5, characterized in that a lubricant pick up tube (10) for conveying the lubricant from the sump (5) to the inner diameter surface (6a) of the shaft (6) upon rotation, wherein the inner diameter surface (6a) at the lower end (6c) of the shaft (6) is attached onto the outer diameter surface (10b) at the upper end (10c) of the lubricant pick up tube (10) and wherein the upper end (10c) of the lubricant pick up tube (10) is adapted to adjoin the lower end (4d) of the rotor (4).
The crankshaft (1) according to claim 1, characterized in that an additional lubricant outlet (11) on the journal (7), wherein the additional lubricant outlet (11) opens into the inner diameter surface (6a) of the shaft (6).
A hermetic compressor (2) characterized in that the crankshaft (1) as defined in any one of claims 1 to 8, a main bearing (3) which supports the crankshaft (1), a rotor (4) which has an innermost diameter surface (4a) for attachment onto the outer diameter surface (6b) of the shaft (6) below the main bearing (3) and a lubricant sump (5) for supplying the lubricant to the journal (7) of the shaft (6).
The hermetic compressor (2) according to claim 9, characterized in that the rotor (4) has a large inner diameter surface (4c) above its innermost diameter surface (4a), wherein the lower end (3b) of the main bearing (3) radially faces the large inner diameter surface (4c) of the rotor (4).
A refrigeration appliance characterized in that the hermetic compressor (2) as defined in claim 9 or 10.