US20160319814A1

US20160319814A1 - Compressor

Info

Publication number: US20160319814A1
Application number: US15/102,351
Authority: US
Inventors: Dieter Mosemann; Ottomar Neuwirth; Dmytro Zaytsev
Original assignee: GEA Refrigeration Germany GmbH
Current assignee: GEA Refrigeration Germany GmbH
Priority date: 2013-12-12
Filing date: 2014-12-12
Publication date: 2016-11-03
Also published as: EP3080457B1; EP3080457A1; DK3080457T3; WO2015086159A1; CN105793572A; DE102013020534A1

Abstract

A screw compressor (10) with at least one screw rotor (20, 22) which is rotatably arranged about a rotational axis arranged in the axial direction. The at least one screw rotor (20, 22) is arranged in a compression area (24) which is fluid-tight against the surrounding area at least in some sections and opens into a high-pressure volume (26). The compressor (10) further has a Vi slide (28) for influencing an inner volume ratio of the compressor, the Vi slide (28) at least partly forming a section of the fluid-tight border of the compression area (24) and being arranged such that the position of the slide can be adjusted in the axial direction. The Vi slide (28) can be continuously displaced, and the compressor (10) has a device (32) for detecting the position of the slide.

Description

The present invention relates to a screw compressor according to the preamble of patent claim 1.
Such screw compressors are used in many applications since they are of robust design and can achieve high levels of efficiency. There are speed-regulated screw compressors, i.e. screw compressors which have two interengaging screw rotors for compressing a medium which is to be compressed, preferably refrigerant, of which the speed is regulated by closed-loop control, and also screw compressors which have a fixed speed.
A speed-regulated screw compressor having a slide for regulating a so-called internal volume ratio (also referred to as Vi) by closed-loop control is known from DE 199 16 983 A1. The internal volume ratio is the ratio of tooth-space volumes of the interengaging screw rotors at the beginning and end of the compression operation. The internal volume ratio of the compressor is influenced with the aid of the so-called Vi slide. Speed-regulated semi-hermetic compact screw compressors having a Vi slide for regulating the internal volume ratio in a stepped manner by closed-loop control are known from DE 10 2011 051 730 A1. In the case of the last-mentioned compressors, the Vi slide can be set in one of two possible positions, the internal volume ratio being greater in one of the positions than in the other.
Compressors according to DE 10 2011 051 730 A1, however, cannot be adapted in optimal fashion to any desired operating conditions. Compressor operation which is favorable in terms of energy is thus possible only to a limited extent. It is also possible for slide-movement errors to occur, and these can give rise to operation which is unfavorable in terms of energy and to increased susceptibility to malfunctioning.
Taking this as a starting point, it is an object of the present invention to specify a compressor which can be operated favorably in terms of energy as far as possible in all operating conditions, the intention being for susceptibility to malfunctioning to be kept to as low a level as possible.
This object is achieved by a compressor having the features of patent claim 1.
Accordingly, the object is achieved according to the invention by a screw compressor which has at least one screw rotor which is arranged such that it can be rotated about an axis of rotation arranged in the axial direction. The at least one screw rotor is arranged in a compression space, which is designed to be at least in sections fluid-tight in the direction of the surroundings and opens out into a high-pressure volume (26). The compressor also has a Vi slide for influencing a volume ratio of the compressor, wherein the Vi slide forms, at least in part, a portion of the fluid-tight boundary of the compression space and is arranged such that it can be displaced in position in the axial direction. The Vi slide can be displaced in a stepless manner and the compressor has a device for sensing the position of the Vi slide.
Since the Vi slide can be displaced in a stepless manner and the screw compressor has a device for sensing the position of the Vi slide, operation which is favorable in terms of energy is achieved along with a low level of susceptibility to malfunctioning.

Further optional features of the invention are specified in the dependent claims and in the following description of the figures. The features described in each case can be realized individually or in any desired combinations. Accordingly, the invention will be described hereinbelow by way of exemplary embodiments and with reference to the accompanying drawings, in which:

FIG. 1 shows a view of an exemplary embodiment of a compressor according to the invention; and

FIG. 2 shows an enlarged illustration of part of FIG. 1.

FIG. 1 illustrates a possible embodiment of a compressor according to the invention, more specifically of a screw compressor 10 according to the invention, which will also be referred to hereinbelow as compressor 10 for short. The compressor 10 has a housing 12 and an electric motor 14, which is arranged in the housing 12. The compressor 10 also has a driveshaft 16 and a compression device 18 with a first and a second screw rotor 20 and 22, the screw rotors engaging one inside the other. The screw rotors 20, 22 are driven in rotation via the driveshaft 16 directly (in alternative embodiments indirectly, for example via a transmission arrangement). In alternative embodiments, it is also possible for a compressor according to the invention to have just one screw rotor or even three or more screw rotors.
The first screw rotor 20 is arranged such that it can be rotated about a first axis of rotation arranged in the axial direction. The second screw rotor 22 is arranged such that it can be rotated about a second axis of rotation, which extends parallel to the first axis of rotation. Both the first and the second screw rotors 20, 22 are arranged in a compression space 24, which is designed to be at least in sections fluid-tight in the direction of the surroundings and opens out into a high-pressure volume 26.
The compressor 10 also has a Vi slide 28, which forms by boundary surfaces 30, at least in part, a portion of the fluid-tight boundary of the compression space 24. The Vi slide 28 is arranged such that it can be displaced in position in the axial direction. It is also possible for the Vi slide 28 to be displaced in a stepless manner. In addition, the compressor 10 has a device 32 for sensing the position of the Vi slide, in particular the axial position of the Vi slide 28.
As can be seen, in particular, from FIG. 2, the device 32 for sensing the position of the Vi slide has a rod-like contact element or a rod 34 which engages, at a first end 36, in a recess, in the form of a groove 38, formed on the Vi slide 28. The groove 38 has an increasing depth in the axial direction so that the axial position of the Vi slide 28 can clearly be identified. At a second end 40, the spring-loaded rod 34 is in operative engagement with a position sensor 41, and it is therefore possible for the position of the Vi slide 28 to be determined. In order to ensure that the rod 34 is in contact with the base of the groove 38 in each case, it is subjected to prestressing in the direction of the groove 38, or subjected to loading in the appropriate direction, by an elastic element in the form of a spring (compression spring) 40.
The compressor 10 also has an adjustment device 42 for adjusting the position of the Vi slide 28. In the embodiment described here, the Vi slide 28 is adjusted in position hydraulically. For this purpose, the compressor 10 has a cylindrical recess or chamber 44, in which a piston 46, which is connected to the Vi slide 28, is arranged in an axially displaceable manner. The piston 46 is sealed in the direction of a chamber wall 47 by means of a seal 48 and subdivides the chamber 44 into two sub-volumes, that is to say a first sub-volume 50 and a second sub-volume 52, these being separated from one another in a fluid-tight manner by the piston 46 provided with the seal 48.
In order for the piston 46, and thus also the Vi slide connected thereto, to be displaced in the axial direction, it is possible for example to increase the pressure in the first sub-volume 50 and/or to decrease the pressure in the second sub-volume 52. In order to bring about movement in the opposite direction, the pressure in the first sub-volume 50 is reduced and/or that in the second sub-volume 52 is increased. Provided for this purpose are a first valve 54 and a second valve 56, by means of which the first sub-volume 50 and the second sub-volume 52 can be subjected to pressure by way of hydraulic fluid or else can also be correspondingly relieved of loading. In the embodiment described here, the two valves 54, 56 are designed in the form of magnetic valves, whereas for example also electrically or electromechanically actuated valves would be conceivable in alternative embodiments. In the embodiment described, the compressor 10 has a closed-loop controller (not illustrated in the figures), by means of which that position of the Vi slide 28 which is optimum for the prevailing operating condition is adjusted in each case.
It should be pointed out here that, in alternative embodiments, it is also possible to provide an open-loop controller instead of a closed-loop controller. In further alternative embodiments, the Vi slide 28 is actuated via a pneumatic device or a mechanical device, for example with or counter to the prestressing of an elastic element.
To summarize: in order to make possible the optimum internal volume ratio Vi, and thus compressor operation which is favorable in terms of energy, under any desired operating conditions within the operating limits of the compressor 10, the compressor 10 is designed with stepless Vi regulation by closed-loop control, wherein the Vi slide 28 can be adjusted in a stepless manner and is equipped with a slide-position sensor. FIG. 2 shows an exemplary embodiment of a compressor 10 according to the invention. In this example, an oblique groove 38 is arranged in the Vi slide 28. A spring-loaded rod 34 pushes into the groove 28 by way of a first end. A second end of the rod 34 is connected to a slide-position sensor 41. The Vi slide 28 may be adjusted, for example, hydraulically. For this purpose, magnetic valves 54, 56, for increasing Vi and reducing Vi, are arranged on the compressor 10. In order for the optimum position of the Vi slide 28 calculated by a closed-loop controller or open-loop controller to be reached, the respective valve 54, 56 is activated by the open-loop controller or closed-loop controller (for example by a pulse/pause signal) until the necessary position of the Vi slide 28 has been communicated by the slide-position sensor 41 to the open-loop controller or closed-loop controller.
Although the invention is described with reference to embodiments having fixed combinations of features, it also covers the other advantageous combinations conceivable, as are specified in particular, but not exhaustively, by the dependent claims. All the features disclosed in the application documents are claimed as being essential to the invention, in so far as they are novel, individually or in combination, over the prior art.

LIST OF REFERENCE SIGNS

10 Compressor
12 Housing
14 Electric motor
16 Driveshaft
18 Compression device
20 First screw rotor
22 Second screw rotor
24 Compression space
26 High-pressure volume
28 Slide or Vi slide
30 Boundary surfaces
32 Device for sensing the position of the Vi slide
34 Rod
36 First end of the rod 34
38 Groove
40 Second end of the rod 34
41 Position sensor
42 Adjustment device
44 Recess or chamber
46 Piston
47 Chamber wall
48 Seal
50 First sub-volume of the chamber 44
52 Second sub-volume of the chamber 44
54 First valve
56 Second valve

Claims

1. A screw compressor having at least one screw rotor which is arranged such that it can be rotated about an axis of rotation arranged in the axial direction, wherein the at least one screw rotor is arranged in a compression space, which is designed to be at least in sections fluid-tight in the direction of the surroundings and opens out into a high-pressure volume, wherein the compressor also has a Vi slide for influencing an internal volume ratio of the compressor, wherein the Vi slide forms, at least in part, a portion of the fluid-tight boundary of the compression space and is arranged such that it can be displaced in position in the axial direction,

wherein

the Vi slide can be displaced in a stepless manner and the compressor has a device for sensing the slide position.

2. The compressor as claimed in claim 1, wherein

the Vi slide has a slide-position sensor or a position transducer.

3. The compressor as claimed in claim 1, wherein

the Vi slide has an axially arranged recess, in particular groove, of which the depth increases in the axial direction.

4. The compressor as claimed in claim 3, wherein

the compressor has a rod with two ends, wherein one end of the rod engages in the recess, and wherein the rod is in operative engagement with a position sensor.

5. The compressor as claimed in claim 4, wherein

the rod is in operative engagement with an elastic element, in particular a spring.

6. The compressor as claimed in claim 1, wherein

the compressor has an adjustment device for adjusting the position of the Vi slide.

7. The compressor as claimed in claim 6, wherein

the adjustment device has a hydraulic device, a pneumatic device or a device for transmitting mechanical force.

8. The compressor as claimed in claim 1, wherein

the compressor has an open-loop or closed-loop controller for controlling or regulating the position of the Vi slide.