EP3090177A1

EP3090177A1 - Crankshaft with facilitated counterweight adjustment and method of adjusting counterweights of the same

Info

Publication number: EP3090177A1
Application number: EP13818750.5A
Authority: EP
Inventors: Husnu Kerpicci; Kemal Sarioglu; Ahmet Refik Ozdemir; Serkan DORTKARDESLER
Original assignee: Arcelik AS
Current assignee: Arcelik AS
Priority date: 2013-12-23
Filing date: 2013-12-23
Publication date: 2016-11-09
Also published as: WO2015096848A1; TR201415645A2

Abstract

The present invention relates to a crankshaft (1) which is suitable for use in a reciprocating compressor (2) of a refrigeration appliance, wherein the reciprocating compressor (2) has a variable refrigeration capacity. The crankshaft (1) comprises a shaft (3) which has an overhang portion (4) and a pin (5) for pivotably attaching a connecting rod (6) which is coupled to a piston head (7). The pin (5) is formed on the overhang portion (4) eccentrically with respect to a rotation axis (Ax) of the shaft (3). The crankshaft (1) of the present invention further comprises a mounting seat (17) configured to hold through the action of magnetic force one or more than one additional counterweight (8) which has a mass and shape determined in accordance with a target refrigeration capacity of the reciprocating compressor (2).

Description

CRANKSHAFT WITH FACILITATED COUNTERWEIGHT ADJUSTMENT AND METHOD OF ADJUSTING COUNTERWEIGHTS OF THE SAME

The present invention relates to a crankshaft suitable for use in a reciprocating compressor of a refrigeration appliance, in particular a domestic refrigerator, which has a variable refrigeration capacity.
A refrigeration appliance such as a domestic refrigerator typically utilizes a reciprocating compressor to cyclically convey the refrigerant from an evaporator to a condenser. A conventional reciprocating compressor includes a cylinder block which has a compression chamber, a cylinder head which has an intake chamber and an exhaust chamber, a piston mechanism for compressing the refrigerant in the compression chamber and an electrical motor for driving the piston mechanism. In the conventional reciprocating compressor, a valve plate is interposed between the cylinder block and the cylinder head. By virtue of the valve plate, the compression chamber is selectively brought into fluid connection with the intake chamber and the exhaust chamber. The valve plate generally comprises an intake port and exhaust port. The intake port and exhaust port are typically configured by diaphragm reed valves which allow the refrigerant to flow only in a single direction. The intake chamber is located on a downstream side of the evaporator whereas the exhaust chamber is located on an upstream side of the condenser. In the conventional reciprocating compressor, the piston mechanism includes a piston head which is arranged to reciprocate within the compression chamber, a connecting rod and a crankshaft which are serially coupled to each other. The crankshaft is rotatably supported through a bearing formed into the cylinder block. In the conventional reciprocating compressor, the electrical motor includes a stator and a rotor which are typically configured as an asynchronous motor or a brushless direct current motor. The rotor is fixed to the crankshaft of the piston mechanism. As the piston moves outwards, the intake port fluidly connects the intake chamber with the compression chamber. Thereby, the refrigerant is sucked into the chamber. As the piston moves inwards, the exhaust port fluidly connects the compression chamber with the exhaust chamber. Thereby, the compressed refrigerant is discharged out of the compression chamber.
During the reciprocating movement of the piston, relatively high forces are generated which, in turn, act on the bearings especially when the refrigerant is being compressed by the piston mechanism. These forces set up vibrations in the compressor. Therefore, a counterweight is usually integrally formed with the crankshaft to reduce the forces on the bearings and to diminish the vibrations.
CN201433875 (Y) discloses a crankshaft for use in a reciprocating compressor of refrigeration appliance. This crankshaft has a counterweight which is integrally formed with the shaft. The size of the counterweight is adjusted through processing the crankshaft.
The forces acting on the bearings generally vary among compressors which have different refrigeration capacities. Thus, a drawback of the aforementioned conventional crankshaft is that its counterweight will not adequately balance the forces if it is installed in a reciprocating compressor which has a substantially different refrigeration capacity. Therefore, the aforementioned conventional crankshaft cannot be reliably used in reciprocating compressors with different refrigeration capacity.
An objective of the present invention is to provide a crankshaft which overcomes the aforementioned drawbacks of the prior art and which facilities adjustment of the counterweight in accordance with a target refrigeration capacity.
This objective has been achieved by the crankshaft according to the present invention as defined in claim 1, the counterweight assembly according to claim 10, and the method of adjusting a balance of the crankshaft according to claim 15. Further achievements have been attained by the subject-matters respectively defined in the dependent claims.
The crankshaft according to the present invention comprises a mounting seat configured to hold through the action of magnetic force one or more than one additional counterweight each having a mass and shape determined in accordance with a target refrigeration capacity of the reciprocating compressor. The mounting seat is made of a ferromagnetic material. In addition, at least one additional counterweight is a permanent magnet whereas each of the other additional counterweights is made of a permanent magnet or a ferromagnetic article.
By virtue of the mounting seat and the additional counterweights, namely the permanent magnets and the ferromagnetic articles, a balance of the crankshaft can be precisely adjusted in accordance with a target refrigeration capacity of the reciprocating compressor. A permanent magnet can be singly used or combined with one or more than one permanent magnet and/or one or more than one ferromagnetic article to obtain a cumulative counterweight that is designated for the target refrigeration capacity. As already mentioned above the mounting seat is made of a ferromagnetic material, however, in an embodiment, the mounting seat is permanently magnetized to improve the attraction between the additional counterweights and the mounting seat.
In another embodiment, the mounting seat itself functions a main counterweight. Thus, a center of mass of the mounting seat is radially offset from the rotation axis of the crankshaft and also radially opposed to the pin. In this embodiment, the mounting seat is configured by a surface of a main counterweight formed on the crankshaft. In an alternative embodiment, the mounting seat does not function as a counterweight, i.e., its center of mass is located on the rotation axis.
In another embodiment, an upper surface of the main counterweight is parallel to an axial direction. Thus, the counterweights can be stacked onto the upper surface to obtain the necessary cumulative counterweight.
In another embodiment, the pin has an extended portion which defines a gap in an axial direction so as to secure a passage for the additional counterweights underneath the connecting rod and the piston head. The gap is predetermined in accordance with a maximum height of the additional counterweights that need to be piled up to achieve balance at a highest target refrigeration capacity.
In the present invention, the additional counterweights are attached solely by using magnetic forces. By virtue of the magnetic forces, the additional counterweights can be quickly and firmly assembled with the crankshaft. Thereby, the use of any auxiliary fixing means like screws, rivets and the like become superfluous. Such auxiliary means are generally vulnerable to break down because of the relatively high forces which are generated during a rotation of the crankshaft. In principle, such auxiliary fixing means can be reinforced as a counter measure. However, this incurs additional costs and prolongs the manufacturing process. In the present invention, the additional counterweights save time and cost.
Additional advantages of the crankshaft according to the present invention will become apparent with the detailed description of the embodiments with reference to the accompanying drawings in which:
Figure 1 – is a schematic view of a crankshaft according to an embodiment of the present invention;
Figure 2 – is a schematic view of the crankshaft with an additional counterweight according to another embodiment of the present invention;
Figure 3 – is a schematic view of the crankshaft with two additional counterweights according to another embodiment of the present invention;
Figure 4 – is a schematic view of the crankshaft with three additional counterweights according to another embodiment of the present invention;
Figure 5 – is a schematic partial view of a reciprocating compressor which includes a crankshaft with three additional counterweights according to an embodiment of the present invention;
Figure 6 – is a schematic exploded partial view of the reciprocating compressor shown in Fig. 5;
Figure 7 – is a schematic view of a reciprocating compressor according to an embodiment of the present invention.
The reference signs appearing on the drawings relate to the following technical features.
1. Crankshaft
2. Reciprocating compressor
3. Shank
4. Overhang portion
5. Pin
5a. Upper portion
5b. Lower portion
6. Connecting rod
7. Piston head
8. Additional counterweight
8a. Permanent magnet
8b. Ferromagnetic article
9. Main counterweight
10. Surface
11. Gap
12. Electrical motor
12a. Stator
12b. Rotor
13. Cylinder block
14. Casing
15. Lubricant
16. Spring
17. Mounting seat
The crankshaft (1) is suitable for use in a reciprocating compressor (2) of a refrigeration appliance (not shown). The reciprocating compressor (2) has a variable refrigeration capacity. The crankshaft (1) comprises a shank (3) which has an overhang portion (4) and a pin (5) for pivotably attaching a connecting rod (6) which is to be coupled to a piston head (7). The pin (5) is formed eccentrically with respect to a rotation axis (Ax) of the shank (3) on the overhang portion (4) (Figs. 1 to 7).
The crankshaft (1) according to the present invention further comprises a mounting seat (17) configured to hold through the action of magnetic force one or more than one additional counterweight (8) which has a mass and shape determined in accordance with a target refrigeration capacity of the reciprocating compressor (2). The mounting seat (17) is made of a ferromagnetic material. At least one additional counterweight is a permanent magnet (8a). Each of the other additional counterweights (8) is made of a permanent magnet (8a) or a ferromagnetic article (8b) (Figs. 1 to 7).
In an embodiment, the mounting seat (17) is configured by a main counterweight (9) which is formed by the overhang portion (4). A center of mass of the main counterweight (9) is radially opposed to the pin (5) and radially offset from the rotation axis (Ax). The mounting seat (17) is configured by a surface (10) of the main counterweight (9) (Figs. 1 to 7). In this embodiment, one or more than additional counterweight (8) is placed on the main counterweight (9) to attain the proper amount of counterweight (8) necessary for the target refrigeration capacity of the reciprocating compressor (2).
In another embodiment, a normal of the upper surface (10) of the main counterweight (9) is parallel to an axial direction (Ax) (Figs. 1 to 7). In this embodiment, one or more than one additional counterweights (8) are stacked upon each other on the surface (10) of the main counterweight (9).
In another embodiment, the pin (5) includes an upper portion (5a) and a lower portion (5b). The upper portion (5a) is suitable for pivotably attaching the connecting rod (6). The lower portion (5b) is arranged below the upper portion (5a). The upper portion (5b) spans a gap (11) in the axial direction (Ax) to secure an unimpeded passage of the one or more than one additional counterweight (8) being stacked on each other on the mounting seat (17) underneath the connecting rod (6) and the piston head (7) (Fig. 1 to 7). As the shank (3) rotates, the stack of additional counterweights (8) is conveyed underneath the connecting rod (6) and the piston head (7) without interfering with them.
In another embodiment, a height of the lower portion (5b) is slightly larger than a maximum total height of the additional counterweights (8) which can be stacked onto one another on the mounting seat (17) (Figs. 1 to 7). Thereby, the crankshaft (1) can be modified in accordance with a plurality of different target refrigeration capacities.
In another embodiment, the mounting seat (17) is configured to form-fittingly contact the additional counterweight (8) (Figs. 1 to 7). Thereby, the additional counterweights (8) are firmly attracted to the mounting seat (17) and prevented from being dislocated under the influence of centripetal forces during rotation of the crankshaft (1).
In another embodiment, the mounting seat (17) is flat (Figs. 1 to 7). In this embodiment, counterweights (8) have accordingly flat surfaces.
In another embodiment, the mounting seat (17) has an outer contour which matches the outer contour of the additional counterweight (8) (Figs. 1 to 7).
In another embodiment, the outer contour of the mounting seat (17) is semicircular shaped (Figs. 1 to 7).
The present invention also provides a counterweight assembly for use with the crankshaft (1). The counterweight assembly comprises one or more than one additional counterweight (8) for separate or combined use with the crankshaft (1) to adjust a balance thereof in accordance with the target refrigeration capacity. Each of the counterweight (8) has a shape and mass respectively predetermined in accordance with the variable refrigeration capacity. At least one additional counterweight (8) is made of a permanent magnet (8a) and each of the other additional counterweights (8) is made of a permanent magnet (8a) or a ferromagnetic article (8b) (Fig. 1 to 7).
In another embodiment, the permanent magnet (8a) is one of a rare earth magnet, a ferrite magnet, an al-ni-co magnet. The ferromagnetic article (8b) is an iron alloy. Each additional counterweight (8) is provided in form of a thin plate (Figs. 1 to 7).
In another embodiment, the outer contour of each additional counterweight (8) is semicircular shaped (Figs. 1 to 7).
The present invention also provides a reciprocating compressor (2) which comprises a crankshaft (1) of the present invention. The reciprocating compressor (2) further comprises an electrical motor (12) which includes a stator (12a) and a rotor (12b). The rotor (12b) is fixed onto the shank (3). The reciprocating compressor (2) further comprises a cylinder block (13) which has a compression chamber and a cylinder head which has an exhaust chamber and an intake chamber. The reciprocating compressor (2) further comprises a casing (14). The cylinder block (13) is arranged on springs (15) and mounted on a bottom of the casing (14). The bottom of the casing (14) functions as a sump of oil (15) for lubricating the crankshaft (1) and the other moving parts such as the connecting rod (6) and the piston (7) (Figs. 1 to 7).
In another embodiment, the reciprocating compressor (2) comprises one or more than one additional counterweight (8) stacked on the mounting seat (17). At least one additional counterweight (8) is a permanent magnet (8a). Each of the other additional counterweights (8) is made of a permanent magnet (8a) or a ferromagnetic article (8b). In different version of this embodiment, the reciprocating compressor (2) respectively comprises 1 to 3 additional counterweights (8), wherein each configuration corresponds to a different refrigeration capacity (Figs. 2 to 4).
In another embodiment, the reciprocating compressor (2) comprises no additional counterweight (Fig. 1).
In another embodiment, the refrigeration appliance (not shown) is a domestic refrigerator which comprises the reciprocating compressor (2) and a control unit (not shown) which is configured to operate the electrical motor (12) of the reciprocating compressor (2) in accordance with the target refrigeration capacity.
The present invention also provides a method of adjusting a balance of the crankshaft (1). The method comprises:
- a step of determining a mass and shape of one or more than one an additional counterweight (8) in accordance with a target refrigeration capacity of the reciprocating compressor (2). The method further comprises:
- a step of using magnetic force to respectively mount the one or more than one additional counterweight (8) onto a mounting seat (17) of the crankshaft (1).
The mounting seat (17) is made of a ferromagnetic material. At least one additional counterweight is a permanent magnet (8a). Each of the other additional counterweights is made of a permanent magnet (8a) or a ferromagnetic article (9b).
In the present invention, the required amount of additional counterweights (8) can be firmly and quickly assembled with the crankshaft (1) by using magnetic forces. Thereby, the same crankshaft (1) of the present invention can be reliably and efficiently installed into a reciprocating compressor (2) which has a desired refrigeration capacity.

Claims

A crankshaft (1) suitable for use in a reciprocating compressor (2) of a refrigeration appliance, wherein the reciprocating compressor (2) has a variable refrigeration capacity, the crankshaft (1) comprising a shank (3) which has an overhang portion (4) and a pin (5) for pivotally attaching a connecting rod (6) which is coupled to a piston head (7), wherein the pin (5) is formed on the overhang portion (4) eccentrically with respect to a rotation axis (Ax) of the shank (3), characterized in that a mounting seat (17) configured to hold through the action of magnetic force one or more than one additional counterweight (8) each having a mass and shape determined in accordance with a target refrigeration capacity of the reciprocating compressor (2), wherein the mounting seat (17) is made of a ferromagnetic material and wherein at least one additional counterweight is a permanent magnet (8a) and each of the other additional counterweights (8) is made of a permanent magnet (8a) or a ferromagnetic article (8b).
The crankshaft (1) according to claim 1, characterized in that the mounting seat (17) is configured by a surface (10) of a main counterweight (9) which is formed by the overhang portion (4), wherein a center of mass of the main counterweight (9) is radially opposed to the pin (5) and radially offset from the rotation axis (Ax).
The crankshaft (1) according to claim 2, characterized in that a normal of the surface (10) of the main counterweight (9) is parallel to an axial direction (Ax).
The crankshaft (1) according to claim 2 or 3, characterized in that the pin (5) includes upper portion (5a) for pivotably attaching the connecting rod (6) and a lower portion (5b) arranged below the upper portion (5a), wherein the lower portion (5b) spans a gap (11) in the axial direction (Ax) to secure a unimpeded passage of the one or more than one additional counterweight (8) stacked on each other on the mounting seat (17) underneath the connecting rod (6) and the piston head (7).
The crankshaft (1) according to claim 4, characterized in that a height of the lower portion (5b) is slightly larger than a total height of the one or more than one additional counterweight (8) stacked onto one another on the mounting seat (17).
The crankshaft (1) according to any one of claims 1 to 5, characterized in that the mounting seat (17) is configured to form-fittingly contact the additional counterweight (8).
The crankshaft (1) according to claim 6, characterized in that the mounting seat (17) is flat.
The crankshaft (1) according to any one of claims 1 to 7, characterized in that the mounting seat (17) has an outer contour which matches the outer contour of the additional counterweight (8).
The crankshaft (1) according to claim 8, characterized in that the outer contour of the mounting seat (17) is semicircular shaped.
A counterweight assembly comprising one or more than one additional counterweight (8) for separate or combined use with the crankshaft (1) according to any one of claims 1 to 9 to adjust a balance thereof in accordance with the target refrigeration capacity, wherein each of the counterweight (8) has a shape and mass respectively predetermined in accordance with the variable refrigeration capacity, and wherein at least one additional counterweight (8) is made of a permanent magnet (8a) and each of the other additional counterweights (8) is made of a permanent magnet (8a) or a ferromagnetic article (8b).
The counterweight assembly according to claim 10, characterized in that the permanent magnet (8a) is one of a rare earth magnet, a ferrite magnet, an al-ni-co magnet, and the ferromagnetic article (8b) is an iron alloy and each additional counterweight (8) is provided in form of a thin plate.
The counterweight assembly according to claim 10 or 11, characterized in that the outer contour of each additional counterweight (8) surface is semicircular shaped.
A reciprocating compressor (2) comprising a crankshaft (1) according to any one of claims 1 to 9 and one or more than one additional counterweight (8) stacked on the mounting seat (17), wherein at least one additional counterweight (8) is a permanent magnet (8a), and each of the other additional counterweights (8) is made of a permanent magnet (8a) or a ferromagnetic article (8b).
A refrigeration appliance, in particular a domestic refrigerator comprising the reciprocating compressor (2) according to claim 13 and a control unit configured to operate an electrical motor (12) of the reciprocating compressor (2) in accordance with the target refrigeration capacity.
Method of adjusting a balance of a crankshaft (1) suitable for use in a reciprocating compressor (2) of a refrigeration appliance, in particular a domestic refrigerator, wherein the reciprocating compressor (2) has a variable refrigeration capacity, said method comprising:

- a step of determining a mass and shape of one or more than one an additional counterweight (8) in accordance with a target refrigeration capacity of the reciprocating compressor (2) and

- a step of using magnetic force to respectively mount the one or more than one additional counterweight (8) onto a mounting seat (17) of the crankshaft (1), wherein the mounting seat (17) is made of a ferromagnetic material, and at least one additional counterweight is a permanent magnet (8a), and each of the other additional counterweights is made of a permanent magnet (8a) or a ferromagnetic article (9b).