EP1072796B1 - Process for operating a screw-type compressor - Google Patents

Abstract

The cylinder chamber(44) of the compressor has a backflow orifice(58) and at least one intermediate backflow orifice(74,76) establishing a minimum position(Mi) and intermediate position(Z1,Z2) respectively. The control unit(66) in the mode for stepless control of the piston positions in a range between the intermediate position and minimum position activates the backflow orifice, and for stepless control of the piston positions outside the range between the intermediate position and minimum position activates the intermediate backflow orifice. An Independent claim is included for a control unit which activates feed flow in an established cycle.

Description

The invention relates to a method for operating a screw compressor comprising a housing having a rotor chamber, two in the rotor chamber arranged screw rotors, which in the housing about their respective Rotary axes are rotatably mounted and which meshing drivable together are to a medium to be compressed from a suction gas inlet of Encourage housing to a compressed gas outlet of the housing and to compress, one in the direction of the rotor axes movable and to the Rotor chamber adjoining slider for power control over the whoscious Length of the screw rotor, an adjusting device comprising a cylinder pressurized by a medium formed by a cylinder chamber and a piston coupled to the spool, one in the cylinder chamber provided and a minimum position defining reflux opening, at least one provided in the cylinder chamber and at least an intermediate position defining intermediate return flow, wherein according to the process in a stage control mode, either the reflux port is opened to the piston from any position between a maximum position and the minimum position to go back to minimum position and / or at least one intermediate return port is opened to push the piston up to proceed to this intermediate position, and / or open an inlet valve is to move the piston in the direction of a maximum position.

From the PATENT ABSTRACTS OF JAPAN vol. 018, no. 512 (M-1679), September 27, 1994 (1994-09-27) & JP 06 173872 A (HITACHI LTD), June 21, 1994 (1994-06-21) such a method is known. In this Procedures are in the control stage mode, the oil lines through valves switched while the supply is via a capillary. In stepless Control mode, more valves are switched and the supply takes place via further capillaries, while an oil reflux via another line he follows.

These solutions each see closure plates for the corresponding openings before, in the step control mode, the openings for the stepless Close the control mode and the openings in the stepless control mode for the stage control mode.

Furthermore, another embodiment shows a combination of the mode of operation, in which only by opening and closing valves Switching from a stepped control mode to the stepless control mode which can be done in the context of the tiered and the stepless control mode described lines and valves combined are.

So that the control device of such a screw compressor reliable However, it is necessary, the position of the piston of the controller to be able to recognize the screw compressor in the mixed To operate tax areas reliably.

For this reason, in a screw compressor known from the prior art a position detection for the piston and / or the slider required, which is expensive.

The invention is therefore based on the object, a method of the generic To improve the type so that this constructive as simple as possible Construction works reliably.

This object is according to the invention in a method of the type described above solved in that in a continuously variable control mode for infinitely variable control of the piston positions in a sub-control range between the intermediate position and the minimum position, the reflux opening is activated and for stepless control of piston positions outside of the sub-control range between the intermediate position and the minimum position the corresponding intermediate reflux opening is activated, and to hold a desired position of the piston, the inlet valve and the return flow and the Zwischenrückflußöffnung be closed.

The advantage of the solution according to the invention is thus to be seen in that the Possibility exists, the screw compressor in a structurally simple conception to operate and also by setting the reflux of the Piston actuating medium via the Zwischenrückflußöffnung the piston operate only in a desired sub-control area and thus a provide reliable information to the effect that unwanted Sub-control areas, for example, the sub-tax area between the Intermediate position and the minimum position, for stepless control of the Pistons can be excluded.

There is the possibility that a position monitoring of the piston and / or the slide, can be omitted and still is a controller with the required reliability possible, with the control states either directly by the type of control or by detecting the nature of the Control are recognizable.

In principle, the solution according to the invention is with a single intermediate reflux opening fully functional.

It is particularly favorable, however, if the method with several each working other sub-control areas defining intermediate reflux openings, and when the minimum allowable position of the piston in the respective Partial control range determined by the respective activated intermediate return flow is.

This means that with this solution it is possible to have several sub-control areas each with a minimum allowable position of the piston by activation set different intermediate reflux openings.

A particularly advantageous control mode provides that the piston thereby exclusively outside the sub-control area between the intermediate position and the minimum position lying sub-control areas is operated, that only the corresponding intermediate return is activated and not In addition, the reflux is activated, so that already by design the possibility exists, the undesirable part of the control area, for example the lying between the intermediate position and the minimum position Partial tax area, exclude.

In order to be able to carry out an exact stepless control, it is necessary that the position of the piston is recognizable. For this reason, it is preferable provided that the position of the piston, starting from the activated intermediate reflux corresponding intermediate position as Reference position is determined and the method is thus able, starting from this reference position, for example by integrating the Inflow times and reflux times, the position of the piston at least approximately with a precise re-reading of the position of the Piston is always possible when this again to the respective intermediate position has gone back to which then starting again the Position of the piston can be determined.

To the reflux port and the Zwischenrückflußöffnungen by the control device To be able to activate, for example, would be complex valves conceivable. A simple way is to provide each of the reflux ports and intermediate reflux ports are controlled by an associated controllable valve.

The valves could for example be designed so that with these as well a quantity control is possible. To the control however particularly simply to be able to design, it is preferably provided that each valve a only switchable between a flow position and a blocking position switchable valve is and thus has only two switching states.

With regard to the design of the adjusting device, in particular to achieve the minimum position, the different variants are conceivable. That's the way it would be For example, conceivable to apply the piston on two sides with a medium, wherein the one medium, the force for moving the piston of the Minimum position in the maximum position generated and the other medium the Restoring force for moving the piston back in the direction of the minimum position upon activation of the reflux ports or intermediate reflux ports generated.

However, it is particularly simple for the method according to the invention if the piston towards its minimum position by an elastic Power storage, for example, a spring is applied, which always for it ensures that the piston when activating at least one reflux or Zwischenrückflußöffnung moves in the direction of the minimum position, if this reflux or Zwischenrückflußöffnung still in between Piston and cylinder chamber enclosed cylinder volume opens.

With regard to the coupling between the piston and the slide it would be For example, still conceivable, a mechanical translation or a flexible coupling provided. It is particularly easy, however, if the slide over a Actuating rod is connected to the piston.

Preferably, the slide is rigidly connected to the piston. ,

According to the invention is by activation of the reflux or the Zwischenrückflußöffnung possible reflux of the piston acting on Medium always greater than the inflow through which the piston in the direction of Minimum position is movable.

It is particularly advantageous if in the stage control mode the inflow clocked activated, since in particular the running back of the piston Advantageously, since there are times available in which no Inflow of the piston acting on the medium takes place and thus the reflux and the return movement of the piston in the direction of the minimum position in can use advantageously. Thus, the response of the Power control improved.

It is particularly advantageous if the inflow in a definable clock is activated.

Furthermore, it is advantageous if the inflow in the fixed clock for a fixed Time duration is activated, with the fixable clock and the definable Duration not over the entire operating hours of the screw compressor must be set to the same values, but accordingly changing circumstances, such as changing operating temperature, new can be adjusted, for example, when applying oil as a medium the piston make an adjustment to the viscosity of the same.

Preferably, also in the stepless control mode, a clocking of the Inflow and in particular a clocking of the reflux.

Other features and advantages are the subject of the description below as well as the graphic representation of an embodiment.

FIG. 1 shows a schematic representation of a method according to the invention suitable screw compressor with a schematic longitudinal section through a Housing same.

An embodiment of a suitable for the inventive method screw compressor, shown in Fig. 1, includes a designated as a whole with 10 housing, which forms a rotor chamber 12, in which two parallel aligned and intermeshing screw rotors 14 about their respective axes of rotation 16 are rotatably mounted, wherein the bearing of the screw rotor 14 is preferably by both sides of the same arranged stub shaft 18 and 20 in provided in the housing 10 bearings 22 and 24, respectively.

In the housing 10, a suction side of the screw rotor 14 is further arranged Suction gas inlet 26 arranged and a pressure side of the same lying Compressed gas outlet 28, wherein the screw rotor 14 to be compacted Promote medium from the suction inlet 26 to the compressed gas outlet 28 and thereby compacted.

To adjust the compressor power, a slider 30 is provided, which in the housing 10 in a direction 32 parallel to the axis of rotation 16 of Screw rotor 14 is slidably mounted and starting from the compressed gas outlet 28 extends in the direction of the suction gas inlet 26, while with his Slider top 34 adjacent to the screw rotor 14 and with a front slide edge 36 determines the location from which a compression of the to be compacted medium through the two intermeshing screw rotor 14 takes place.

The slider 30 is fixedly connected to an actuating rod 38, with which via a designated as a whole with 40 actuator of the slide 30 is adjustable in the direction 32.

The adjusting device 40 comprises a cylinder housing 42, which is a cylinder chamber 44 encloses, in which a piston 46 is movable, fixed to the Actuating rod 38 is connected, wherein the actuating rod 38 preferably a piston rod of the piston 46 forms.

In this case, the piston 46 is also parallel to the direction 32 in the cylinder chamber 44 movable and that of a minimum position Mi, for example a power of the order of 25% of the maximum power of the Compressor corresponds, up to a maximum position Ma, which of the Maximum output of the compressor corresponds, and intermediate positions Z1 and Z2, which are described in detail below be explained.

The minimum position Mi of the piston corresponds to one minimal enclosed between cylinder chamber 44 and piston 46 Cylinder volume and the position Ma a maximum enclosed between the piston 46 and the cylinder chamber 44 Cylinder volume, while the intermediate positions Z1 and Z2 correspond to cylinder volumes between the minimum cylinder volume and the maximum cylinder volume lie.

The adjusting device 40 is for adjusting the piston 46 with acted upon by pressurized oil, which, for example by an oil pressure pump 50 or a final pressure of the condensing medium pressurized reservoir on a for the application of the piston required pressure maintained becomes. From the oil pressure pump 50, the oil flows through a Supply line 52 via a throttle 54, for example, formed as a capillary to a supply line 56, which with a reflux opening 58 in the cylinder chamber 44 opens. The supply line 56 is further provided with a Return line 60 connected to the suction gas inlet 26 of the Housing 10 leads.

For controlling individual positions of the piston 46 in the Cylinder chamber 44 is in the supply line 52 an inlet valve 62 provided and in the return line 60, a return valve 64, both preferably electromagnetic via a controller 66, designated as a whole are controllable.

To move the piston 46 from the minimum position Mi to another Position between the minimum position Mi and the maximum position Ma will be Inlet valve 62 opened by the controller 66, wherein the oil pressure pump 50th Oil via the supply line 52, the supply line 56 and the return flow 58 pumped into the cylinder chamber 44 and thus under magnification the cylinder volume, the piston 46 is applied, until the desired position of the piston 46 is reached. Then, the inflow valve 62 closed. Thus, the slider 30 is preferably in a position in which the compressor power between the minimum value and the maximum value, wherein the minimum position Mi of the piston 46 preferably the position of minimum power of the slider 30 is assigned and the Maximum position Ma of the piston 46, the position of maximum power of Slider 30.

To move the piston 46 from a position between the minimum position Mi and the maximum position Ma in the direction of the minimum position Mi will the return valve 64 is opened by the controller 66, so that oil from the of the cylinder chamber 44 and the piston 46 enclosed cylinder volume can flow off via the return line 60 and preferably to Suction gas inlet 26 flows, so that the piston 46 so long in the direction of Minimum position shifts as long as the return valve 64 from the controller 66 is kept open.

After closing the return valve 64, the piston 46 remains in the achieved Standing position.

Preferably, to all positions between the minimum position Set Mi and the maximum position Ma can, the return port 58 facing a piston head 68 in a cylinder housing bottom 70 of the cylinder housing 42 arranged.

Furthermore, in a cylinder housing jacket 72 intermediate return openings 74 and 76 at different distances from the Minimum position Mi of the piston 46 arranged with Intermediate return lines 78 and 80 are connected, which in turn in the return line 60 between the return valve 64 and the suction gas inlet 26 open. Each of the intermediate return lines 78 and 80 is with an intermediate return valve 82 and 84 provided, with which the respective Intermediate return line 78 and 80 is closed.

Due to the position of the intermediate return openings 74 and 76 in Distance from the minimum position Mi of the piston 46 is the Location of these associated intermediate positions Z1 and Z2 set of the piston 46, wherein at a stepless Control mode, the intermediate positions Z1 and Z2 are such that the standing in this piston 46 before the intermediate return openings 74 and 76, respectively.

By controlling the intermediate return valves 82 and 84 by means of the control device 66, it is now possible via the intermediate return ports 74 or 76 oil from the Cylinder chamber 44 to flow out, provided that the respective cylinder volume up to the intermediate return openings 74 and 76 or extends beyond.

Preferably, the intermediate positions Z1 and Z2 are such that the intermediate position Z1 corresponds to a position of the slide 30, wherein the Screw compressor in a medium power range, that is, for example on the order of 50%. Furthermore, the intermediate position Z2, for example, defined so that it corresponds to a position of the slider 30, in which the screw compressor with a power of the order of magnitude from 70% to 80% works.

But there are also in accordance with the invention other definitions of Intermediate positions Z1 and Z2 possible. Furthermore, it is also according to the invention possible to provide even more than two intermediate positions Z1 and Z2.

In addition, the piston 46 or the slider 30 is preferably still with an elastic energy storage, that is, for example, a spring 90, such beaufschlagt that both the piston 46 and the slider 30 the Tendency to reduce the cylinder volume, that is without oil pressure the cylinder volume between piston 46 and cylinder chamber 44 in the minimum position Mi of the piston 46 and thus the position minimum power of the screw compressor.

The screw compressor according to the invention can now be as follows in the operate stepless control mode:

When starting the screw compressor is due to the elastic Force accumulator 90 of the piston 46 and an optionally preceding Opening the return valve 64 and thus also the slider 30 in the minimum position, the means the screw compressor runs with minimal power at. Should now the screw compressor with a higher Power are operated, so the inlet valve 62 in the Inlet line 52 is opened and consequently the oil pump 50 is delivering Oil via the supply line 52 in the supply line 56 and thus via the reflux opening 58 in the piston 46th and the cylinder chamber 44 limited cylinder volume, thereby this is increased and the piston 46 from the minimum position We moved in the direction of the maximum position.

This can increase the performance of the screw compressor to any possible position of the piston 46 respectively.

If this is a position of the piston 46 between the minimum position Mi and the intermediate position Z1 reached, so can by locking the inlet valve 62 this position obtained or by opening the return valve 64 this Position again in the direction of the minimum position Mi changed be, with the minimum position Mi at closed Inlet valve 62 can be approached quickly and at open inlet valve 62 can be approached slowly, if more oil flows through the return valve 64 than through the inlet valve 62 flows.

Usually, however, there is a desire, screw compressor in an upper performance range, that is in one Power range above a minimum value of the order of magnitude of 50%.

For this reason, usually by opening the inlet valve 62 in the supply line 52 of the piston 46 so far moves that he reaches the intermediate position Z1 or himself beyond this, moving towards the maximum position Ma.

To now the screw compressor according to the invention in the operate at the upper power range and at the same time be sure can that without monitoring the position of the piston 46th and / or the slider 30 can be prevented that this be moved back so far that they again the lower Power range between the intermediate position Z1 and the Reach minimum position, the controller 66 operates in the upper power range, that they to the process of the piston 46 in the direction of the maximum position Ma the inlet valve 62 opens and thus via the supply line 52 and the Supply line 54 oil in the piston 46 and the Cylinder chamber 44 enter enclosed cylinder volume to let.

However, to return the piston 46 in the direction the minimum position not the return valve 64 is open, but the intermediate return valve 82 in the intermediate return line 78. This has the consequence that thus the piston 46th can only move so far towards the minimum position, until it reaches the intermediate position Z1, in which the Piston 46 is in front of the intermediate return opening 74 and thus on further moving in the direction of the minimum position the Intermediate return opening 74 automatically blocked and thus also the return of oil from the cylinder volume in the Intermediate return line 78 prevents.

The method of the piston 46 to the intermediate position Z1 can at solely opening the intermediate return valve 82 fast and with additional opening of the inlet valve 62 carried out slowly, provided by the intermediate return valve 82 more oil flows out than flows through the inlet valve 62.

This is inevitably ensured that the piston 46 in Direction of minimum position not on the intermediate position Z1 is moved out. This is also for the controller 66 without monitoring the position of the piston 46 and / or the Slider 30 can be seen that the piston 46 in one position which is at least one power of the compressor in of the order of 50%, but by no means below this value. Thus, only by the fact that the Control device 66 only the inlet valve 62 and the Intermediate return valve 82 is actuated, a control or regulation area specified for the piston, the desired value of not less than 50%, but between the intermediate position Z1 and the maximum position Ma lies.

If the control and regulation range for the piston 46 is still on Higher values are limited, so after adjustment of the piston 46 to at least to the intermediate position Z2 the control device 66 only an actuation of the Inlet valve 62 and the intermediate return line 80 associated Intermediate return valve 84, so that the piston 46 at his movement toward the minimum position only the Intermediate position Z2 can reach, for example, in the Magnitude between 70% and 80% of the capacity of the compressor lies, and this intermediate Z2 will - in same as in connection with the intermediate position Z1 described - in such an operation of the Intermediate return valve 84 and holding the return valve 64 and the intermediate return valve 82 in the closed Position due to the constructive arrangement of the intermediate return opening 76 not below, without here one Monitoring the position of the piston 46 is required.

The control device 66 may in the inventive Screw compressors, however, not only in the described stepless control mode work, in which ultimately one Stepless positioning of the piston between the minimum position Wed and the maximum position Ma is possible.

Alternatively, the control device according to the invention also work in a staged control mode, in which only the intermediate position Z1, the intermediate position Z2 and the maximum position Ma next to the minimum position Mi are approachable.

For this purpose, the inlet valve 62 according to the invention in a fixed clock for a fixed time interval opened so that the pressurized oil in the through the Piston 46 and the cylinder chamber 44 enclosed cylinder volume entry. Are both the return valve 64 and the intermediate return valves 82 and 84 are closed, then thereby the piston 46 at each supply of the under pressure standing oil moves in the direction of maximum position Ma, so that after one by the time intervals for feeding the Oil's total interval set the maximum position Ma is reached.

If, on the other hand, only the intermediate position Z1 is to be reached, then this becomes Intermediate return valve 82 is opened, which results in that when the Piston in the intermediate position Z1 is, a slight advancing of the Piston 46 beyond the intermediate position Z1 addition causes the piston 46th the intermediate return opening 74 releases and thus the over the supply opening 48 the cylinder volume supplied oil in turn via the intermediate return opening 74 and the intermediate line 78 flows off, so that the piston 46 always slightly around the intermediate position Z1 moves around and thus in this can be defined.

In the same way, there is the possibility of the piston 46 also in the Intermediate position Z2 by opening the intermediate return valve 84 and Keep closed the return valve 64 and the intermediate return valve 82nd hold.

Finally, there is also the possibility of the minimum position Mi thereby to achieve that the return valve 64 is opened and thus more oil the cylinder volume can flow, as via the inlet valve 62 and the Throttle 54 flows.

Preferably, the return valve is also when switching off and before switching 64 open.

The functioning of the screw compressor according to the invention in the Staged or stepped control mode assumes that always at least as much oil through the respective return valves 64, 82 and 84 drain can flow as via the inlet valve 62. Preferably, the inflowing Oil quantity should be adjusted so that it is always less than via the return valves 64, 82 and 84 when activated same amount of oil returning.

Furthermore, the clocked operation of the inlet valve 62 creates still the possibility by changing the clock frequency or each open period of the inlet valve 62 the to vary supplied amount of oil, for example, in itself changing oil temperature or changing other Conditions that affect the flow behavior of the oil, especially when flowing through the throttle 54 impact.

Claims (11)

1. Method of operating a screw compressor comprising a housing with a rotor chamber (12), two screw rotors (14) arranged in the rotor chamber, said screw rotors being mounted in the housing (10) for rotation about their respective axes of rotation (16) and being intermeshingly drivable in order to convey a medium to be compressed from a suction gas inlet (26) of the housing (10) to a pressure gas outlet (28) of the housing (10) and thereby compress the medium to be compressed, a slide (30) movable in the direction of the rotor axes (16) and adjoining the rotor chamber (12) for controlling the capacity via the effective length of the screw rotors (14), an adjusting device (40), comprising a cylinder to which pressure is applied by a medium, said cylinder being formed by a cylinder chamber (44) and a piston (46) coupled with the slide (30), a return flow opening (58) provided in the cylinder chamber (44) and defining a minimum position (Mi), and at least one intermediate return flow opening (74, 76) provided in the cylinder chamber (44) and defining at least one intermediate position (Z1, Z2), wherein, in accordance with the method, in a stepwise control mode, either the return flow opening (58) is opened in order to return the piston (46) from any position between a maximum position (Ma) and the minimum position (Mi) to the minimum position (Mi), and/or at least one intermediate return flow opening (74, 76) is opened in order to displace the piston (46) as far as this intermediate position (Z1, Z2), and/or a feed valve (62) is opened in order to displace the piston (46) in the direction of a maximum position (Ma),
   characterized in that t in a continuous control mode the return flow opening (58) is activated for the continuous control of the piston positions in a partial control range between the intermediate position (Z1, Z2) and the minimum position (Mi), and in that the corresponding intermediate return flow opening (74, 76) is activated for the continuous control of piston positions outside of the partial control range between the intermediate position (Z1, Z2) and the minimum position (Mi), and in that the feed valve (62) and the return flow opening (58) as well as the intermediate return flow opening (74, 76) are closed for holding a desired position of the piston (46).
2. Method as defined in claim 1, characterized in that the minimum permissible position of the piston (46) in the respective partial control range is defined by the respectively activated intermediate return flow opening (74, 76) of several intermediate return flow openings (74, 76).
3. Method as defined in claim 1 or 2, characterized in that the piston (46) is exclusively operated in partial control ranges lying outside of the partial control range between the intermediate position (Z1, Z2) and the minimum position (Mi) by only the corresponding intermediate return flow opening (74, 76) for the control being activated.
4. Method as defined in any one of the preceding claims, characterized in that the position of the piston (46) is determined on the basis of the intermediate position corresponding to the activated intermediate return flow opening (74, 76) as reference position.
5. Method as defined in any one of the preceding claims, characterized in that each of the return flow openings and intermediate return flow openings (58, 74, 76) is controlled by an associated controllable valve (64, 82, 84).
6. Method as defined in claim 5, characterized in that the valve (64, 82, 84) is only switched between a flow-through position and a shut-off position.
7. Method as defined in any one of the preceding claims, characterized in that the piston (46) is acted upon by an elastic energy storing device (90) in the direction of its minimum position (Mi).
8. Method as defined in any one of the preceding claims, characterized in that in the stepwise control mode with an inflow which, when averaged over time, is approximately constant, only the return flow opening (58) or one of the intermediate return flow openings (74, 76) is activated.
9. Method as defined in claim 8, characterized in that the inflow is activated in cycles in the stepwise control mode.
10. Method as defined in claim 9, characterized in that the inflow is activated in a fixable cycle.
11. Method as defined in claim 9 or 10, characterized in that the inflow is activated in the fixable cycle for a fixable length of time.

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