US20050013702A1

US20050013702A1 - Screw compressor

Info

Publication number: US20050013702A1
Application number: US10/884,421
Authority: US
Inventors: Rolf Dieterich; Klaus Feller; Pascal Papadopoulos
Original assignee: Bitzer Kuehlmaschinenbau GmbH and Co KG
Current assignee: Bitzer Kuehlmaschinenbau GmbH and Co KG
Priority date: 2003-07-16
Filing date: 2004-07-02
Publication date: 2005-01-20
Also published as: DE10333400A1; EP1498611A1; CN1576588A

Abstract

In a screw compressor for gaseous media, in particular refrigerants, comprising a compressor housing, two screw rotors arranged in screw rotor bores in the compressor housing, which are rotatingly drivable and interact to compress the medium, and a control slide arranged adjacent the screw rotors and movable in a direction of displacement for controlling the compression of the screw compressor, in order to solve the problem that the compression of the screw compressor can be controlled, but not precisely regulated, it is proposed that a scannable element, which is scannable with a measuring sensor so as to recognize a position of the control slide in the direction of displacement, be coupled with the control slide.

Description

The present disclosure relates to the subject matter disclosed in German application No. 103 33 400.9 of Jul. 16, 2003, which is incorporated herein by reference in its entirety and for all purposes.

BACKGROUND OF THE INVENTION

The invention relates to a screw compressor for gaseous media, in particular refrigerants, comprising a compressor housing, two screw rotors arranged in screw rotor bores in the compressor housing, which are rotatingly drivable and interact to compress the medium, and a control slide arranged adjacent the screw rotors and movable in a direction of displacement for controlling the compression of the screw compressor.
With such screw compressors there is always the problem that the compression of the screw compressor can be controlled, but not precisely regulated.

SUMMARY OF THE INVENTION

This object is accomplished with a screw compressor of the kind described at the outset, in accordance with the invention, in that a scannable element, which is scannable with a measuring sensor so as to recognize a position of the control slide in the direction of displacement, is coupled with the control slide.
An element scannable in this way makes it possible to exactly detect the position of the control slide in the direction of displacement and hence to also exactly know and, if desired, regulate the set compression of the screw compressor.
For example, the scannable element could have an optically or magnetically scannable inner structure.
For reasons of simplicity, it has proven particularly expedient for the scannable element to have a scannable outer contour.
Such a scannable outer contour could, for example, be a tooth-like outer contour which is optically, inductively or mechanically scannable.
It is particularly simple when the scannable outer contour is a path with a scan area.
Such a path with a scan area could also be scanned in a non-contacting manner.
From a constructional point of view, a solution in which a path follower rests on the scan area of the path in mechanical contact therewith is particularly easy to carry out.
Such a scan area is particularly easy to scan when it extends at an incline to the direction of displacement of the control slide.
Furthermore, the scannability of the scan area is facilitated by the scan area extending substantially in a straight line, but at an incline to the direction of displacement of the control slide.
So far, the movability of the path follower has not been explained in further detail. In principle, it is conceivable for the path follower to be made to rotate about an axis by the effect of the path.
From a constructional point of view, however, a solution in which the path follower is movable in a direction extending transversely to the direction of displacement can be carried out in a particularly expedient way.
The path follower could be arranged on an arm and guided in a connecting member for movement on a curved path.
However, the path of the path follower can be detected in a particularly simple way when the path follower is movable in a straight line.
To enable the path which has to be detected by the path follower to be determined with as simple means as possible, it has proven expedient for the path to be designed such that the maximum distance to be traveled by the path follower in the transverse direction is less than the maximum distance to be traveled by the path in the direction of displacement. This solution has the particular advantage that conventional short-stroke position sensors can then be employed to detect the maximum distance traveled by the path follower, which makes a compact structural design of the screw compressor possible.
Further details of how the scannable element is arranged within the housing were not given in the above explanation of the individual solutions.
A particularly expedient solution makes provision for the scannable element to be arranged within the housing in the area of a bearing receptacle of the screw rotor. The scannable element can thus be accommodated in a particularly space-saving way.
The scannable element could, in principle, be arranged directly on the control slide itself, on a connection between the control slide and an adjusting device for the control slide or on the adjusting device for the control slide itself.
A solution which is particularly simple from a constructional point of view makes provision for the scannable element to be arranged on a carrier mounted on the control slide.
In order to make use of the space available in present screw compressors for the arrangement of the scannable element, provision is expediently made for the scannable element to extend in the direction of displacement of the control slide away from the control slide, in particular, in the direction opposite to an adjusting direction of the control slide.
It is particularly expedient for the carrier to be arranged at an end of a guide element of the control slide and to extend, for example, in the direction of a drive motor for the screw rotors.
So far, the arrangement of the carrier in relation to the overall configuration of the control slide has not been explained in further detail. A particularly expedient solution makes provision for the carrier to be arranged within a cross-sectional area of the control slide. This solution has the great advantage that the carrier can be pre-assembled on the control slide and hence inserted into the slide bore together with the slide, without insertion of the control slide into the slide bore being impeded by the carrier.
In particular, when the carrier is arranged on the guide element of the control slide, it is expedient for the carrier to be arranged within a cross-sectional area of the guide element of the control slide, so that, in this case, too, pre-assembly of the carrier on the guide element is possible, and this pre-assembled carrier does not obstruct insertion of the guide element into the part of the slide bore provided for the carrier.
Details of the design of the measuring sensor are not given in the above explanation of the individual claims. It is, for example, conceivable to design the measuring sensor such that it detects individual discrete positions.
It is, however, particularly simple for the measuring sensor to be a position sensor, so that positions directly following one another can be detected with it.
It is expedient for the measuring sensor to be designed so as to detect a displacement path of the path follower generated by the path transversely to the direction of displacement.
In order to have the possibility of exactly regulating the position of the control slide with the inventive solution, a control device is preferably provided for determining a position of the control slide by means of the measuring sensor and regulating the position of the control slide via actuation of an adjusting device for the control slide.
Further features and advantages of the invention are the subject of the appended claims and the drawings of an embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a longitudinal section through an embodiment of a screw compressor according to the invention; and
FIG. 2 an enlarged detail from FIG. 1 in the area of a compressor screw housing with control slide.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of a screw compressor according to the invention, as illustrated in FIG. 1, comprises a housing generally designated 10, which includes a section 12 on the motor side, a compressor section 14 and a section 16 on the pressure side.
An electric motor generally designated 20 is provided in the section 12 on the motor side. Its stator 22 is firmly seated in the section 12 of the housing 10 on the motor side and its rotor 24 is mounted for rotation about an axis 26 within the stator 22.
The rotor 24 drives a drive shaft 28 via which a pair of interacting screw rotors 30 is rotatingly drivable. The pair of screw rotors 30 is seated in screw rotor bores 32 of a compressor screw housing generally designated 34, which is arranged in the compressor section 14 of the housing 10.
On either side of the compressor screw housing 34 bearing receptacles 36 and 38 are provided in the outer housing 10. Shaft sections 40 and 42 extending from the screw rotors 30 are rotatably mounted by means of rotary bearings 44 and 46 in the bearing receptacles 36 and 38.
The bearing receptacles 36 and 38 and the compressor screw housing 34 are preferably integrally formed on the housing 10 in the area of the compressor section 14.
Also provided in the compressor screw housing 34 is a slide bore 48 in which a control slide 50 is movable in a direction of displacement 52 extending parallel to the axis 26. The control slide 50 is coupled via a coupling rod 54 with an adjusting device 56 comprising, for example, an adjusting cylinder 58 and an adjusting piston 60 which is displaceable by pressurized media within the adjusting cylinder 58, so that the control slide 50 coupled via the coupling rod 54 is likewise displaceable in accordance with the positions of the adjusting piston 60.
The control slide 50 has a control edge 64 facing an inlet side 62 of the compressor screw housing 34. The compression ratio can be reduced in a controlled manner by displacement of the control edge 64 in the direction of an outlet 66 of the compressor screw housing 34.
The compression ratio is at a maximum when the control edge 64 is displaced to a maximum extent in the direction of the inlet 62, whereas the compression ratio is at a minimum when the control edge 64 is displaced to a maximum extent in the direction of the outlet 66.
The adjusting device 56 is actuated via a control device generally designated 70 of the screw compressor, and exact regulation requires a position of the control slide 50 to be determinable.
For this reason, there is associated with the control slide 50 a path carrier 72 which, coupled with the control slide 50, is displaceable in the direction of the direction of displacement 52 and comprises a path 74 which can be scanned by a path follower 76.
The path 74 is preferably provided on the path carrier 72 in the form of a straight-lined scan area 78 which extends at an incline to the direction of displacement 52 preferably in such a manner that upon maximum displacement of the control slide 50 from the position corresponding to a maximum compression ratio to a position corresponding to a minimum compression ratio, it displaces the path follower 76 in its direction of movement 80 extending transversely, preferably approximately perpendicularly, to the direction of displacement 52, through a maximum path which is smaller than the maximum path of the control slide 50 with the path carrier 72 in the direction of displacement 52.
The path follower 76 is preferably formed by the head of a feeler pin 82 of a position sensor 84 which senses the path of the path follower 76 in the direction of movement 80 and transmits it to the control device 70. A definite position of the control slide 50 in the direction of displacement 52 is allocated to each individual position of the path follower 76 in the direction of movement 80, so that the respective position of the control slide 50 can be precisely detected with the position sensor 84.
In the illustrated embodiment, the path carrier 72 is preferably held on a guide element 86 of the control slide 50, which extends beyond the control edge 64 in the direction of displacement 52. More specifically, the path carrier 72 is held as a continuation of the guide element 86, but within a maximum cross section of the control slide 50, so that the path carrier 72, viewed in the direction of the axis 26, extends approximately in the area of the bearing receptacle 36 lying between the electric motor 20 and the compressor screw housing 34, more specifically, in an inner space 88 of the outer housing 10 surrounding the bearing receptacle 36. The inner space 88 extends around the bearing receptacle 36 as far as the inlet side 62 of the compressor screw housing 34 and also in the direction of the electric motor 20. Owing to the arrangement of the path carrier 72 within the maximum cross-sectional shape of the control slide 50 and, in particular, within a cross-sectional shape of the guide element 86, the control slide 50 with the path carrier 72 mounted thereon is insertable from the side of the outlet 66 into the slide bore 48 and slidable through this as far as the inner space 88.
The inner space 88 is preferably at the pressure of the inflow of refrigerant in the area of the inlet side 62.
The position sensor 84 is preferably seated on an outer side of the compressor section 14 of the housing 10 and with the feeler pin 82 passes through a bore 90 extending through the housing 10, so as to rest with the path follower 76 in a spring-biased manner on the path 74.
By exactly determining the position of the control slide 50 it is thus possible to precisely regulate the position of the control slide 50 by means of the control device 70, more specifically, by actuating the pressurization of the adjusting piston 60 in the adjusting cylinder 58 and monitoring the position reached by the control slide 50 via the position sensor 84.

Claims

1. Screw compressor for gaseous media, in particular refrigerants, comprising a compressor housing, two screw rotors arranged in screw rotor bores in the compressor housing, which are rotatingly drivable and interact to compress the medium, a control slide arranged adjacent the screw rotors and movable in a direction of displacement for controlling the compression of the screw compressor, and a scannable element which is scannable with a measuring sensor so as to recognize a position of the control slide in the direction of displacement and is coupled with the control slide.

2. Screw compressor in accordance with claim 1, wherein the scannable element has a scannable outer contour.

3. Screw compressor in accordance with claim 2, wherein the scannable outer contour is a path with a scan area.

4. Screw compressor in accordance with claim 3, wherein a path follower rests on the scan area of the path in mechanical contact therewith.

5. Screw compressor in accordance with claim 4, wherein the scan area extends at an incline to the direction of displacement of the control slide.

6. Screw compressor in accordance with claim 5, wherein the scan area extends substantially in a straight line.

7. Screw compressor in accordance with claim 4, wherein the path follower is movable in a transverse direction extending transversely to the direction of displacement.

8. Screw compressor in accordance with claim 7, wherein the path follower is movable in a straight line.

9. Screw compressor in accordance with claim 3, wherein the path is designed such that the maximum distance to be traveled by the path follower in the transverse direction is less than the maximum distance to be traveled by the path in the direction of displacement.

10. Screw compressor in accordance with claim 1, wherein the scannable element is arranged within the housing in the area of a bearing receptacle of the screw rotors.

11. Screw compressor in accordance with claim 1, wherein the scannable element is arranged on a carrier mounted on the control slide.

12. Screw compressor in accordance with claim 11, wherein the scannable element extends in the direction of displacement of the control slide away from the control slide.

13. Screw compressor in accordance with claim 12, wherein the carrier is arranged at the end of a guide element of the control slide.

14. Screw compressor in accordance with claim 11, wherein the carrier is arranged within a cross-sectional area of the control slide.

15. Screw compressor in accordance with claim 11, wherein the carrier is arranged within a cross-sectional area of the guide element.

16. Screw compressor in accordance with claim 1, wherein the measuring sensor is a position sensor.

17. Screw compressor in accordance with claim 16, wherein the measuring sensor detects a displacement path of the path follower generated by the path transversely to the direction of displacement.

18. Screw compressor in accordance with claim 1, wherein a control device is provided, which determines a position of the control slide by means of the measuring sensor and regulates a position of the control slide via actuation of an adjusting device for the control slide.