Orbital piston compressor with stepwise radial gap compensation function

Abstract

Orbital piston compressor (1) comprising a cylinder (3) defined by a cylinder inner wall (2), a movable orbital piston (4) arranged within the cylinder (3), and an eccentric shaft (15) driving the orbital piston (4), wherein a gap (6) between the outer surface (5) of the orbital piston (4) and the cylinder inner wall (2) is adjustable in discrete positions by means of an eccentric, wherein the eccentric has a compensating eccentric (9) with an outer part (10) within which an inner part (11) connected to the eccentric shaft (15) is arranged, wherein the outer part (10) has an inner coupling surface (12) designed as an internal toothing and the inner part (11) has an outer coupling surface (13) designed as an external toothing, so that the outer part (10) engages positively in the inner part (11) via the toothing (14), and wherein the rotational movement of the eccentric shaft (15) is transferred to the compensating eccentric (9).

Description

[0001] The invention relates to an orbital piston compressor with a cylinder defined by an inner cylinder wall, a movable orbital piston arranged inside the cylinder, and an eccentric shaft serving as a drive shaft.

[0002] Orbital piston compressors, also known as oscillating piston compressors, are a well-established technology. In their typical design, the aim is to maintain a defined, very minimal radial gap between the piston and the housing, ideally on the order of 0.005 to 0.05 mm, by using the tightest possible tolerances and short tolerance chains. This is particularly important to prevent contact between moving parts and to allow for a small, sealing oil gap. An excessively large gap reduces efficiency due to leakage losses of the refrigerant being compressed. However, maintaining and achieving these tolerances is technologically very complex.

[0003] DE 10 2008 025 186 A1 discloses a rotary piston engine with eccentrically adjustable cylinder segments.

[0004] The US 2007 / 0160 486 A1 reveals a rotary piston compressor.

[0005] DE 10 2020 101 311 A1 discloses a friction-optimized vacuum orbiter pump.

[0006] It is therefore the object of the present invention to eliminate or at least mitigate the disadvantages known from the prior art.

[0007] This problem is solved according to the invention by making a gap between the outer surface of the orbital piston and the inner wall of the cylinder adjustable in discrete positions by means of an eccentric, wherein the eccentric has a compensating eccentric with an outer part within which an inner part connected to the eccentric shaft is arranged, wherein the outer part has a coupling inner surface designed as internal teeth and the inner part has a coupling outer surface designed as external teeth, so that the outer part engages positively in the inner part via the teeth, and wherein the rotational movement of the eccentric shaft is transmitted to the compensating eccentric.

[0008] The basic idea is the use of a compensating eccentric. Depending on the angular position at which this component is mounted relative to the eccentric shaft, the radial gap changes. This is achieved through a very slight, yet still present, eccentricity between the outer diameter of the compensating eccentric and the inner diameter, and, for example, the toothed internal geometry. This incremental adjustability of the eccentricity, for example, via the number of teeth on the internal geometry, allows for the selection, during assembly, of the angular position of the compensating eccentric that exhibits the smallest, still functional gap. The advantage here is that component tolerances can be compensated for or widened, as the gap is adjustable. This results in a significant cost saving.Potentially unnecessary test series with varying radial gap dimensions can be avoided or carried out in a targeted manner to achieve easy adaptability. These advantages outweigh the disadvantages of an additional component. Furthermore, the possibility of out-of-roundness and coaxiality errors occurring with varying angles of rotation can be disregarded.

[0009] The basic design consists of a stationary housing comprising a cylindrical inner wall and an axially adjoining base / cover. This housing typically contains half-shells, some of which partially support the orbital piston. Rotary motion is initiated by a drive shaft / eccentric shaft, which is, for example, electrically driven. This rotary motion is transmitted via an eccentric with external teeth to a compensating eccentric with internal teeth. Decoupling between the rotating parts and the orbiting or oscillating orbital piston is achieved via a rolling bearing, such as a needle bearing, or alternatively, a plain bearing. If a predetermined point lies directly on another predetermined point, the maximum possible compensation, or the smallest possible gap / overlap, is selected. If the two points are opposite each other, i.e., offset by 180°, the largest possible gap is set.By moving the compensating eccentric tooth by tooth / step by step, the gap can be changed. This makes it possible, for example, to select the level of compensation where the system can just barely rotate without binding.

[0010] Friction is also minimized if a bearing is positioned between the outer part and the orbital piston. It has proven effective for the bearing to be designed as either a rolling or sliding bearing. Particularly with rolling bearing designs, the choice of a needle roller bearing has proven advantageous.

[0011] The invention is explained in more detail below with the aid of a drawing. The single figure, which is purely schematic and serves only to illustrate the invention, shows a cross-section through an orbital piston compressor 1 according to the invention with a stepwise radial gap compensation function. Only certain parts, and not all necessary parts, are shown. The orbital piston compressor 1 has a housing with a cylinder inner wall 2, which, together with a cover and a bottom, defines a cylinder 3. An orbital piston 4, which has an outer surface 5, is arranged inside the cylinder 3. Refrigerant can enter the cylinder 3 via an inlet 22 and exit via an outlet 23.

[0012] Between the inner cylinder wall 2 and the outer surface 5, there is an adjustable gap 6, which is only indicated. The gap 6 can be adjusted by means of a position-determining device designed as an eccentric. The eccentric has a compensating eccentric 9 with an outer part 10, inside of which an inner part 11 is arranged. An eccentric shaft 15, which serves as a drive shaft, is located within the inner part 11. The outer part 10 has an internally toothed coupling surface 12. The inner part 11 has an externally toothed coupling surface 13. The outer part 10 thus engages positively with the inner part 11 via the toothing 14, whereby the rotational movement of the eccentric shaft 15 is transmitted to the compensating eccentric 9.

[0013] There is also a bearing designed as a needle bearing 17. Furthermore, there is a sliding swivel joint 19, via which the orbital piston 4 is (additionally) supported.

[0014] Point 20 indicates a maximum dimension, and point 21 indicates an eccentric direction. When points 20 and 21 are aligned, the maximum possible eccentric position is achieved.

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