CN1145455A - Screw compressor with liquid lock preventing slide - Google Patents

Abstract

The invention concerns a single screw compressor having at least one capacity control slide, this slide being moved by thrust means, this slide being the only one to be, at start of the compressor, in a position insuring compression, wherein that elastic means are holding the slide in a position of part load when the compression is stopped and deform, during start-up, to let the slide reach the full load position as soon as the discharge pressure of the compressor reaches a set value.

Description

Screw compressor with the slide plate that prevents liquid lock

The present invention relates to a kind of positive discharge capacity rotary compressor with spiral and door rotor (gaterotor).

Being manufactured on the volume that the single-screw compressor that is provided with slide plate in the housing changes compressor everybody knows.

This structure all has announcement in many patents, as US4, and 261,691/4,579,513 or 5,087,182.

A serious problem of being run into by these compressors is to occur in when compressor is used for a refrigerator or air conditioner and starts under the situation that partially or completely is full of liquid refrigerant.In this phenomenon of industrial quarters is well-known, and can both take place under many situations: an injection valve that leaks, a compressor colder than vaporizer etc.

As compressor enough liquid is arranged wherein when starting, common result is that the performance of compressor reduces, the meaning that reduces is that the considerable pressure that is produced enters into the groove of spiral, they must compress a kind of incompressible fluid, liquid refrigerant, rather than compress compressible cooling gas; The phenomenon of well-known this compressed liquid is exactly " liquid lock " that common motor can not start compressor and break down.

When general used scheme is on the position of compressor volume minimum for adopting slide plate in the screw compressor, (being generally fully loaded about 15% to 20%) start compressor.

In the case, in case groove stops to be communicated with intakeport, it begins to align with exhaust port; In groove, just can not compress like this, and it can pumping liquid and liquid lock does not take place.

However, this scheme also has many defectives; At first, this requires to provide slide plate is controlled at least three positions usually: the sub load position of the initial position of 15% volume, 40% or 50% left and right sides volume and full load position (only having 15% volume position and fully loaded compressor may change between the two too much); Because slide plate by piston control, this means that the control of realization must provide three positions usually, this is much more more complex than the piston with simple two positions, and (then only needing during two positions) applies pressure or plus-pressure not to piston.Another kind of scheme be by in addition more complicated continuous control the piston with endless position is provided.

Second defective is that when 15% volume, compressor produces pressure in condenser very slow; Owing to make it cooling,, produce the danger that compressor is blocked when will not spray because of liquid like this in the liquid immigration compressor that compressor pressure is commonly used to be sprayed no matter this liquid is oil or liquid refrigerant.

In non-injected compressor (OIF compressor), in compressor, do not spray oil, only from the liquid refrigerant of condenser, it is mandatory starting compressor when the 50% volume left and right sides, so that produce pressure apace and begin liquid discharging nearly in 10 seconds.

In the single-screw compressor of a new generation, wherein two slide plates are operated separately, and one is uncharge when starting, and this means that another slide plate must start in the full load position; If liquid is arranged, when on the whole length at groove compression taking place, all consequences of liquid lock all will take place.

The object of the present invention is to provide a kind of single-screw compressor with at least one volume control slide plate, this slide plate is moved by thrust device and its characteristics are, in case elastic device moves to a part of load position with slide plate and is compressed fully and delivery pressure does not influence the position of slide plate when exceeding a setting value when compressor stops.

This value can fix between 1.2 to 2 times the suction pressure, and preferably fixes on about 1.5 times suction pressure.

Working condition of the present invention is as follows:

When starting, because the effect slide plate of elastic device is a sub load; Even there is liquid, liquid lock can not take place yet.

Still can in an enclosed slot, compress when it should be noted that the volume control position about 50%; 1 to 3 compression ratio is a convention, the groove and the volume of groove before exhaust port aligns be groove stop at volume when aliging with suction port about 1/3rd; When the groove full of liquid, liquid lock will take place like this.However, have been found that by (when starting, not loading fully for one having two slide plates, we will remember and make slide plate A, another has two positions: at full capacity and be approximately a halfload, to remember and make slide plate B) compressor test, if it is bottom at compressor that slide plate B is arranged to the compression of corresponding half compressor, it is possible starting compressor and do not have liquid lock under half load condition so.Liquid lock occurs in when slide plate starts under full load situation.If slide plate B is a sub load, compression produces too slowly so that can not begin liquid discharging before compressor breaks down.

If slide plate B holds the top of compressor, compressor even can start in the complete condition of full of liquid, and liquid lock can not take place.

By observe the provable liquid lock that do not exist of pressure in the groove with a Pressure probe and/or the intensity of circuit of passing the motor of Driven Compressor.

Under two kinds of above-mentioned situations, when liquid lock, pressure and intensity are the same when beginning usually, have spent a period of time, and pressure is the manyfold when beginning, and intensity is still high, show motor and no longer quicken and broken down.

Under those two kinds of situations (slide plate 9 is in a low level or a high position), compressor need be taken the part time of second for the liquid of turning.

After that, compressor begins to produce pressure immediately in condenser; Act on the pressure pressure elasticity device of slide plate end and take slide plate to position at full capacity.

Because opposite side is inoperative fully, compressor is in 50% load then and can produces pressure for liquid discharging apace in condenser.

Be full of half or fully the compressor of full of liquid is emptied between 0.15 to 0.3 second to carrying about 200cfm to show in the single-screw test of operation R22 under the 3600rpm; And be set at when head pressure reaches 1.5 times of suction pressure as the elastic device of spring and be compressed, slide plate returned to position at full capacity in 2 to 3 seconds.

So in fact do not postpone to reach jet pressure.

Simultaneously, under the situation of thrust device control sledge displacement, a piston only needs two positions, and can realize by apply or do not apply head pressure in the piston back.

By can more comprehensive understanding being arranged to the present invention to the description of a preferred embodiment of the present invention below in conjunction with accompanying drawing; Wherein:

Fig. 1 is the cross-sectional view along Fig. 2 center line I-I ';

Fig. 2 is the cross-sectional view along the line II-II ' among Fig. 1;

Fig. 3 shows along the cross-sectional view of figure center line III-III ';

Fig. 4 shows the another kind of structure of Fig. 3.

In Fig. 1, being installed in the spiral 1 of axle on 2 that supports rotationally by bearing 3 and 4 has screw thread 5 with tooth 6 engagements of the door rotor (gate-rotor) 7,8 of two symmetries.Spiral and door rotor all turn in shell 9.When being used for a refrigeration system, shell 9 is equipped with one or more slide plates 10 usually, and slide plate is preferably according to U. S. Patent the 4th, 571, makes for No. 166.Slide plate 10 is being by thrust device, be axially moveable as piston 12, again by driving as the oil pressure or the fluid power plant of discharging pressurized gas.

Shell 9 has a suction or low pressure port 13 to be communicated with suction pipe 14.The high voltage terminal 38 of exhaust port 41 and spiral 1 near the door rotor approaching.Sealed at the spiral 1 relative shell 9 at high voltage terminal 38 places by a high voltage terminal Sealing 15, its detailed content is at U. S. Patent 4,475, introduction arranged in 877.

According to U. S. Patent 5,087, No. 182, shell 9 comprise one with shell in the horizontal annular wall of main aperture 17 or encircle 16, and spiral 1 is positioned at wherein rotationally.Wall 16 has an exterior edge face 37, to be leaned on thereon by bolt 19 fixing end plates 18.Auxiliary bolt 20 stretches to end seal 15 by end plate 18 to be held end seals 15 and makes it be close to bearing 4 and come on the end plate 18 through a pad 21; Stay a gap 11 like this.

Can also see the groove 22 that wherein accommodates slide plate 10 and its fixed support 52, this groove 22 finishes in the axial positions that separates with gap 11.

According to prior art, the volume between spiral 1 and Sealing 15 is connected with suction pressure by the one or more holes 26 in the spiral.

Hereinafter described the present invention has two door rotors and two slide plates as shown in Figure 2, but also can be used for having the single-screw formula compressor of single door rotor and single slide plate.

In most of existing screw compressors, two slide plate 10a are different with 10b, and one has two positions promptly at full capacity and zero load, and another is full load and near halfload; The former is designated as slide plate A, and the latter is designated as slide plate B.

When slide plate A is in as shown in Figure 2 compressor when bottom, because pressing the direction of arrow 50, spiral rotates, this is just in the compressor for compressing bottom.At this moment, compressor can start under the situation of half full of liquid, and liquid lock does not take place, but still liquid lock can take place when it is full of fully.

When slide plate A is in the bottom and slide plate B when being in the top, compressor can start under the situation of full of liquid and liquid lock not take place so.

If why can start compressor with the present invention and slide plate be under the full-load conditions can not reason unclear; No matter be at full capacity or sub load, groove all must full of liquid and compression to incompressible liquid should be taken place in both cases.Probably when the first helical rotation process has just begun, groove is full, but after compressor starts operation little by little, in liquid and/or pressure drop, have enough motions with produce flash gasoline and thereafter by liquid volume that arbitrary groove was sucked less than groove was reached before discharging minimum volume; And may be the problem of degree, promptly when slide plate at full capacity the time this phenomenon be not enough to stop liquid lock, but a half that only compresses its length when groove is enough, and when groove be not that (slide plate B is on top) is especially true during in the bottom but on top.

Fig. 3 shows the slide plate B among Fig. 2.

Slide plate is promoted by the thrust device such as piston 12 and bar 51.Pressure, for example oil pressure introduced by a pump, or discharge gas pressure be by a pipe 60 be placed on after the piston slide plate is moved to the sub load position; When pressure from manage shed 60 after, the pressure at 54 places, slide plate end pushes back piston and make line 53 to contact with line 56, and guarantees that slide plate is at full capacity.

According to F.P. 2,562,167 make (other structure also can, only however change the present invention) standing part of slide plate is depicted as 52, moving element is 10.

On Fig. 3, shown moving element 10 is partly to be opened by spring assembly 24a on the position when starting.

Extend between the moving element 10 online 53 and 54; Gapped 56 between the edge 55 of the edge 53 of moving element and standing part, can overflow and turn back to suction port by its liquid or gas; Like this in a well-known mode, compression process begins during regional beyond groove is in edge 53 fully.

Should be noted that slide plate 10 is when starting and not exclusively open; When the needs sub load, head pressure or oil pressure are applied to face after the piston 12, promote slide plate and reach line 57 places until edge 54 (pressure is preferably at the high voltage terminal of standing part 52; See Fig. 1).

The displacement that one bolt, 58 restraining spring 24a cause makes it reach one with the width 56 that will open of control is enough to the degree that allows liquid overflow when starting, and it is in groove, do not produce an excess pressure, but little as enough to make compressor have maximum volume also in condenser, to produce pressure as soon as possible.Fig. 4 shows a kind of different structure, and the bar 51b that promotes slide plate 10 and be arranged in pipe 59 is arranged, and a spring 24b is arranged in the pipe.

In Fig. 4, when shown slide plate 10 is a few second that is in after the startup; The end of the pressure pushing and pressing moving slide 10 that produces at the compressor exhaust end, and the edge is begun shared position 54 when spring 24b stretches and move on to position 54b; In this position, moving element 10 is crushed on the standing part 52, and slide plate is in position at full capacity.

For this reason, no matter be at Fig. 3, in 4 still in other scheme that is equal to, the calculating of spring should be that spring can be compressed fully between head pressure reaches 1.2 to 2 times suction pressure, generally during the setting value about 1.5 times.

In case should be noted that to reach this pressure, no matter be Fig. 3 or the situation of Fig. 4, do not take up position if there is the springing device that slide plate just may take place, compressor transmits same air-flow and does not exist as these devices.

The present invention shown in should also be noted that has the piston of a promotion slide plate, spurs but the present invention may easily be made piston be positioned at the slide plate opposite side by change; Perhaps make those elastic devices rather than compression, for example be hinged with the high pressure side of moving element 10 by traction control.

Claims (2)

1. single-screw compressor, has at least one volume control slide plate (10), this slide plate (10) is moved by thrust device (12), this slide plate is unique one will be in the locational parts that guarantee compression when compressor start, it is characterized in that, elastic device (24) remains on slide plate on the position of sub load when compressor stops and distortion, in case just make slide plate reach position at full capacity when the head pressure of compressor reaches setting value in start-up course.

2. compressor as claimed in claim 1 is characterized in that, when head pressure reached 1.5 times that are roughly suction pressure, described elastic device made slide plate reach position at full capacity.

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