EP1669606B1 - Screw compressor - Google Patents

Description

The invention relates to a screw compressor for compressing refrigerant in a refrigerant circuit, comprising a compressor housing, in which a screw rotor receptacle and an inlet channel and an outlet channel for the refrigerant to be compressed are provided, at least one arranged in the screw rotor receiving screw rotor, a drive for the at least one screw rotor and a lubricant supply which supplies lubricant from a pressurized lubricant reservoir via a line system to at least the at least one screw compressor during operation.

Such screw compressors are for example from the US 4,639,196 A or the US 3,905,729 A known, in these, however, there is the problem that when switching off the screw compressor is often the danger that lubricant continues to run in these and thus accumulates in the screw rotor receiving in the screw rotor and thus leads to problems when starting the screw rotor. For this reason, an external solenoid valve and an external flow switch are provided in the lubricant supply, which prevent excessive supply of lubricant, in particular when the screw compressor, standstill. However, these have the disadvantage that their reliability is not given reliable.

From the US 3,191,854 a check valve is known, which is acted upon on the one hand by a pressure in a lubricant reservoir and on the other hand acted upon by a lubricant pressure generated by an oil pump.

The US 4,336,001 discloses monitoring a screw compressor in a refrigeration cycle by acquiring absolute values for pressure.

The invention has for its object to improve a screw compressor of the generic type such that the operation and monitoring of the screw compressor made more reliable.

In a screw compressor of the type described above, the invention provides that it comprises a first differential pressure sensing element, which detects a pressure difference between the pressure in the outlet channel and a reference pressure influenced by a pressure in the refrigerant circuit reference pressure and that the screw compressor comprises a compressor control, which, if the pressure difference after a start-up phase of the drive is not in an established by compressing the refrigerant operating pressure range, the drive for the at least one screw rotor off.

The advantage of the solution according to the invention is to be seen in the fact that it is possible to monitor whether the screw compressor works in the sense of compressing the refrigerant and if this should not be the case, for example if the drive is running in the wrong direction, the drive off.

It is advantageous that no absolute detection of the pressure in the outlet channel takes place, but the pressure difference is determined to a reference pressure in the refrigerant circuit, so that thereby the dependence on the absolute pressure level in the outlet channel is not given, but the entire refrigerant circuit and thus also the screw compressor can work at different absolute pressure levels.

It is particularly advantageous if the reference pressure is influenced by a pressure in the high pressure section of the refrigerant circuit, so that thereby there is a reference pressure which is of the same order of magnitude as the pressure in the outlet channel, so that the differential pressure can be determined in a simple manner.

It is even better if the reference pressure is derived from, preferably proportional to, a pressure in the high-pressure section of the refrigerant circuit.

In principle, the reference pressure could be supplied to the differential pressure sensing element through a separate pressure line between the differential pressure sensing element and the respective section of the refrigerant circuit.

However, a particularly simple solution provides that the reference pressure is influenced by the pressure in the refrigerant circuit transmitted by the lubricant supply and acting on the lubricant reservoir.

In principle, it would be conceivable to design the first differential pressure sensing element completely independently of the valve in the lubricant supply.

However, a particularly favorable solution provides that the differential pressure sensing element comprises an actuating device for the valve in the lubricant supply and an actuating positions of the same detecting sensor.

Thus, the valve can be used directly to respond according to the differential pressure and then its positions can be used to detect the differential pressure.

For example, it would be conceivable to detect any elements of the valve in their different operating positions.

However, a particularly favorable solution provides that the sensor detects piston positions of the actuating device.

The detection of the piston positions can be done in various ways, for example, this inductive or magnetic field-responsive sensors can be used when the piston is provided with a magnet whose position is then detected by the sensor.

In connection with the previously described embodiment and the solution according to the invention, no further details were given as to how the start-up phase should be recorded and determined.

For example, it would be conceivable to set the startup phase of the drive by the number of revolutions occurring after the drive was switched on.

However, it is particularly simple if the compressor control determines the start-up phase of the drive through a time window which defines a certain period of time after the drive has been switched on.

Preferably, the compressor control works in such a way that it checks whether the operating pressure range is reached during the start-up phase, that is to say that the compressor control must receive the signal indicating the operating pressure range at the latest at the end of the start-up phase.

In the simplest case, the operating pressure range is defined by the fact that the valve has left its closed position.

Alternatively or in addition to the exemplary embodiments described so far, a further advantageous embodiment provides that a second differential pressure sensing element is provided, which detects a pressure difference forming on the lubricant filter and that the compressor control switches off the drive when the pressure difference exceeds a threshold value.

The advantage of this solution is that it can be used to monitor whether the screw compressor is sufficiently supplied with lubricant, since the pressure difference is representative of the flow of the lubricant through the lubricant filter, resulting in a low pressure drop across the lubricant filter the pressure difference is reflected.

A particularly simple solution provides that the differential pressure sensing element detects the pressure of the lubricant in the line system in front of a filter body and after the filter body of the lubricant filter.

At best, the differential pressure sensing element is formed so that it comprises a piston which is acted on the one hand by lubricant before passing through the filter body and on the other hand by lubricant after passing through the filter body of the lubricant filter and thus adjusts the piston according to the pressure difference.

In order to be able to detect the individual positions of the piston, it is preferably provided that the differential pressure detection element comprises a sensor for detecting at least one position of the piston.

A particularly compact solution provides that the differential pressure sensing element is integrated into the compressor housing, that is, is mounted on this, that it forms part of an overall housing for the screw compressor.

The aforementioned object is also achieved in a screw compressor of the type described above in that a valve is provided in the line system of the lubricant supply, which is controllable by a pressure difference between the pressure in the outlet channel and influenced by a pressure in the refrigerant circuit reference pressure and refrigerant Compressive screw rotor opens, as well as closes at refrigerant non-compressing screw rotor.

The advantage of this solution is to be seen in the fact that there is the possibility to produce or interrupt the lubricant supply in direct correlation to the compression of the refrigerant by the screw rotor.

In addition, a significant advantage of the solution according to the invention is the fact that the valve does not operate on the basis of an absolute pressure, but rather establishes a pressure difference between the pressure in the outlet channel, that is to say the pressure of the compressed refrigerant, and a reference pressure resulting from a pressure in the refrigerant circuit is affected. This means that this makes it possible, regardless of the absolute pressure level at which the screw compressor and the refrigerant circuit work, to detect a proper function of the screw rotor.

Basically, the reference pressure can be influenced by any pressure in the refrigerant circuit.

A particularly simple solution provides that the reference pressure is influenced by a pressure in the high-pressure section of the refrigerant circuit, so that the reference pressure already has a pressure level which is not very different from the pressure level of the compressed refrigerant in the outlet channel. Thus, the control of the valve can be designed particularly simple.

It is particularly advantageous if the reference pressure is derived from a pressure in the high-pressure section of the refrigerant circuit, that is to say is preferably substantially proportional to the pressure in the high-pressure section of the refrigerant circuit.

In principle, it would be conceivable to provide a line via which the pressure in the high-pressure section of the refrigerant circuit is supplied to the valve for determining the pressure difference.

However, a particularly simple solution provides that the reference pressure is influenced by the pressure in the refrigerant circuit which is transmitted from the lubricant supply and acts on the lubricant reservoir.

The valve can be formed particularly easily if the valve can be controlled by a piston, on which, on the one hand, refrigerant under the pressure in the outlet channel and, on the other hand, the reference pressure act.

This can be realized in a particularly advantageous manner in that the piston of the valve can be acted upon by lubricant coming from the lubricant reservoir on the side intended for the action of the reference pressure and can be moved in the direction of its closed position.

This means that the lubricant coming from the lubricant reservoir moves the piston into its closed position, provided that the pressure of the compressed refrigerant in the outlet channel is lower than the reference pressure.

In order to keep the valve closed in the closed position by the closed valve in the closed position, the valve is preferably formed so that it has a valve seat and a valve body comprising valve assembly which is formed so that when seated on the valve seat on the valve body the valve body acting pressure of the lubricant causes a force in the direction of the closed position of the valve body.

Furthermore, it is favorable if the valve body is acted upon by an elastic force store, for example a spring, which transfers the valve to its closed position during a pressure compensation on the piston and holds it in this position.

In order to install the screw compressor as possible as a unit in the respective refrigerant circuit, it is preferably provided that the valve is integrated in the compressor housing of the screw compressor.

This eliminates in particular costly installations in the lubricant line to the compressor.

Furthermore, a lubricant filter is preferably arranged in the line system for the lubricant for the preparation of the lubricant.

Also, the lubricant filter is preferably integrated in the compressor housing of the screw compressor to obtain a compact unit.

Further features and advantages of the invention are the subject of the following description and the drawings of an embodiment:

Fig. 1

eine schematische Darstellung eines erfindungsgemäßen Kältemittelkreislaufs mit mehreren Verdichtern;

Fig. 2

einen Längsschnitt durch ein Ausführungsbeispiel eines erfindungsgemäßen, in dem Kältemittelkreislauf gemäß Fig. 1 eingesetzten Verdichter;

Fig. 3

eine schematisierte Darstellung des Verdichters in Fig. 2 mit verschiedenen Komponenten desselben im Zusammenwirken mit einem Schmiermittelreservoir im Kältemittelkreislauf;

Fig. 4

eine ausschnittsweise Darstellung eines Teilbereichs eines Verdichtergehäuses mit einem Schnitt durch ein Schmiermittelfilter, ein Ventil in der Schmiermittelversorgung und einem ersten Differenzdruckerfassungselement und einem zweiten Differenzdruckerfassungselement, die alle in das Verdichtergehäuse integriert sind in einer geöffneten Stellung des Ventils, einer aus der Schließstellung heraus bewegten Stellung des ersten Differenzdruckerfassungselements und einer einen korrekten Schmiermittelfluss anzeigenden Stellung des zweiten Differenzdruckerfassungselements;

Fig. 5

einen Schnitt ähnlich Fig. 4 mit einer geschlossenen Stellung des Ventils bei einem in Schließstellung stehenden ersten Differenzdruckerfassungselement und einem unmittelbar nach Schließen des Ventils noch einen korrekten Schmiermittelfluss anzeigenden zweiten Differenzdruckerfassungselement;

Fig. 6

einen Schnitt ähnlich Fig. 4 mit einem in der geschlossenen Stellung stehendem Ventil, einem in Schließstellung stehenden ersten Differenzdruckerfassungselement und einem einen nicht korrekten Schmiermittelfluss anzeigenden zweiten Differenzdruckerfassungselements und

Fig. 7

einen Schnitt ähnlich Fig. 4 mit einem in der geöffneten Stellung stehenden Ventil, einem aus der geschlossenen Stellung herausbewegten ersten Differenzdruckerfassungselement und einem einen nicht korrekten Schmiermittelfluss anzeigenden Differenzdruckerfassungselement;

In the drawing show:

Fig. 1

a schematic representation of a refrigerant circuit according to the invention with a plurality of compressors;

Fig. 2

a longitudinal section through an embodiment of an inventive, in the refrigerant circuit according to Fig. 1 used compressor;

Fig. 3

a schematic representation of the compressor in Fig. 2 with various components thereof in cooperation with a lubricant reservoir in the refrigerant circuit;

Fig. 4

a partial view of a portion of a compressor housing with a section through a lubricant filter, a valve in the lubricant supply and a first differential pressure sensing element and a second differential pressure sensing element, which are all integrated into the compressor housing in an open position of the valve, a moved out of the closed position position of the first differential pressure sensing element and a correct lubricant flow indicating position of the second differential pressure sensing element;

Fig. 5

similar to a cut Fig. 4 with a closed position of the valve at a first differential pressure detecting element in the closed position and a second differential pressure sensing element still indicating a correct lubricant flow immediately after closing the valve;

Fig. 6

similar to a cut Fig. 4 with a standing in the closed position valve, a standing in the closed position first differential pressure sensing element and an incorrect lubricant flow indicating second differential pressure sensing element and

Fig. 7

similar to a cut Fig. 4 a valve in the open position, a first differential pressure sensing element moved out of the closed position, and a differential pressure sensing element indicating improper lubricant flow;

An embodiment of a refrigerant circuit according to the invention, in Fig. 1 denoted as 10, comprises a plurality of parallel connected compressors 12a to 12c, the high pressure ports 14a to 14c are connected to a high pressure line system 16, which leads into a designated as a whole by 18 lubricant, in which separated from the high pressure and compressed refrigerant lubricant becomes.

From the lubricant separator 18, a high-pressure line 20 passes through a heat exchanger 22, which cools the compressed refrigerant, and then to an expansion valve 24, which serves to lower its temperature by releasing the refrigerant, so that the expanded refrigerant in a heat exchanger 26 has the possibility to give up heat again.

The expanded refrigerant is passed through a low pressure line 28 to low pressure ports 30a to c of the compressor 12a to c.

The compressors 12a, 12b and 12c are arranged in parallel in the refrigerant circuit 10, but can be individually switched on or off, depending on the requested cooling capacity.

Furthermore, a supply of the parallel-connected compressors 12a, 12b and 12c with lubricant takes place from a lubricant reservoir 32 forming in the lubricant separator 18 and an external line system 34 originating from the lubricant reservoir 32 leading to a lubricant supply connection 36a, 36b and 36c of the respective compressor 12a to 12c leads.

An example of such a compressor 12 is shown in FIG Fig. 2 and comprises a compressor housing 40, in which a screw rotor receptacle 42, for example in the form of two screw rotor bores, which serves to receive two cooperating screw rotors 44, 46 is provided.

The screw rotors 44, 46 engage in each other for compressing the refrigerant, wherein one of the screw rotors, for example the screw rotors 46, is driven by a drive motor 48 as a whole, which is likewise arranged in the compressor housing 40.

The drive motor 48 drives a drive shaft 50 on which the screw rotor 46 and a rotor 52 of the drive motor are seated and which is rotatably mounted in the compressor housing 40 about a rotor axis 54.

The rotor 52 of the drive motor 48 is driven by the interaction with a stator 56 likewise arranged in the compressor housing 42.

Preferably, the screw compressor is constructed from the basic principle, as in the European patent application WO 02/053917 is described, to which reference is made in full.

The compressor housing 40 comprises on a side opposite to the drive motor 48 side, a bearing housing 58, in which bearing units 60 and 62 for the storage of screw rotors 44, 46 are arranged.

Such a screw compressor is again schematized in Fig. 3 represented, for the sake of simplicity, the drive motor 48 and only one screw rotor, namely the screw rotor 46 are shown in its schematic arrangement in the likewise schematically drawn compressor housing.

Furthermore, as in Fig. 2 and 3 to the screw rotors 44 and 46 an inlet channel 70 and also, as in Fig. 3 in the compressor housing 40, an outlet channel 72 is provided, which leads the compressed refrigerant to the high-pressure port 14, on which a non-return valve 74 is arranged, through which the compressed refrigerant enters the high-pressure line system 16 and is then guided to the lubricant separator 18.

In the compressor housing 40 itself, an internal lubricant line system 80 is provided, which, starting from the lubricant supply port 36 through a lubricant filter 82 filtered lubricant on the one hand to the bearing units 60, 62 for the screw rotors and on the other hand, the screw rotors 44, 46 to lubricate this while running. In addition, it can be used to supply the device for power control of the screw compressor with pressurized lubricant.

The internal lubricant line system 80 can also be guided to other bearings of the screw rotors 44, 46 and the drive motor 48.

The lubricant filter 82 becomes, as in Fig. 2 . 3 and 4 shown, formed by a filter housing 84 integrated in the filter housing 84, in the interior 86 a filter body 88 is inserted, which filters in the interior 86 entering lubricant and a filtered by the filter body 88 space 90 the filtered lubricant to a designated as a whole by 92 Lubricant stop valve leads, soft in a cover body 94 of the filter housing 84 and thus also in the compressor housing 40 is integrated.

The lid body 94 comprises an opening 96 for the lubricant which is open toward the space 90 and is adjoined by a receiving space 100 leading to a valve seat 98 for a valve body 102 of the lubricant stop valve 92.

On a side opposite the receiving chamber 100 side of the valve seat 98, a discharge channel 104 is provided for the filtered and the valve seat 98 by flowing lubricant, starting from the outflow chamber 104, the further internal lubricant line system 80 continues.

The outflow space 104 also passes through a valve body 102 carrying the valve stem 106 which leads from the valve body 102 to a valve piston 108 which separates two arranged in a cylinder housing 110 cylinder chambers 112 and 114 from each other, wherein the cylinder housing 110 also in the lid body 94 of the valve housing 84 is integrated.

The cylinder chamber 112 lies on a side facing the valve body 102 and is connected via a branch passage 116 to the outflow channel 104 of the internal lubricant line system 80, so that the valve piston 108 can be acted upon by lubricant present in the cylinder chamber 112 at a pressure P1.

The cylinder chamber 114 is connected via a guided in the compressor housing 40 channel 118 to the outlet channel 72 of the screw compressor 12, so that the valve piston 108 on the other hand is pressurized by the pressure P2 in the outlet channel 72 refrigerant.

In addition, in the cylinder housing 110 still a valve piston 108 acting spring 120 is provided, which acts on the valve piston 108 in the direction of a closed position, in which the Venilkolben 108 ensures that the valve body 102 sealingly rests on the valve seat 98 and in particular at pressure equalization on Valve piston 108 keeps the valve closed.

The opening and closing of the lubricant stop valve 92 thus takes place by moving the valve piston 108 in accordance with the pressure difference between the pressure P1 in the cylinder chamber 112 and the pressure P2 in the cylinder chamber 114.

If the pressure P2 in the cylinder chamber 114 is higher than the pressure P1 in the cylinder chamber 112, the lubricant stop valve 92 opens in that the valve piston 108 moves into the open position against the force of the spring 120 and thus causes the valve body 102 from the valve seat 98th lift off, so that lubricant from the space 90 in the discharge channel 104 and from this in the secondary internal lubricant line system 80 can occur.

This condition is reached when the screw compressor is operating, that is, the two screw rotors 44 and 46 compress the refrigerant such that refrigerant compressed in the outlet passage 72 is at high pressure P2 so that the pressure P2 in the cylinder chamber 114 compresses to high pressure Corresponds to refrigerant.

Since the effective and the cylinder chamber 114 limiting cross-sectional area of the valve piston 108 is greater than the effective cross-sectional area of sitting on the valve seat 98 valve body 102 on which in the closed position of the pressure P3, the lubricant acts in the space 90, which results in refrigerant compression in the outlet channel 72 High pressure P2 causes the valve piston 108 lifts the valve body 92 of the valve seat 98 and thus in his, in Fig. 4 illustrated open position passes.

Thus, a supply of lubricant to the screw compressor via the internal lubricant line system 80 with the in the space 90 of the filter body 88 accumulating and under the pressure P3 lubricant, which is approximately proportional to a pressure in the high pressure line system 16 and thus to the pressure in the lubricant separator 18.

If the drive motor 48 and thus also the screw rotors 44 and 46 come to a standstill, the pressure of the compressed refrigerant in the outlet channel 72 collapses and thus the pressure P2 in the cylinder chamber 114 also drops. This results in that the pressure P1 in the cylinder chamber 112 moves the valve piston 108 in the direction of its closed position, which in Fig. 5 is shown.

In this closed position then breaks the pressure P1 in the cylinder chamber 112 together, but on the other hand causes the pressure P3 in the space 90, which acts on the valve body 102 that the valve body 102 remains in its seated on the valve seat 98 position and thus the supply of further internal lubricant line system 80 and with lubricant from the space 90 interrupts, so that is prevented by the fact that constantly lubricant from the lubricant reservoir 32 trailing and thus accumulates in the screw compressor, for example, the screw rotor receptacle 42 thereof.

However, the lubricant stop valve 92 has not only the task, when switching off the drive motor 48 and thus the movement of the screw rotors 44 and 46 to interrupt the lubricant flow from the space 90 of the lubricant filter 82 in the other internal lubricant line 80, but is also part of a first pressure difference detection element 130th , which additionally comprises a position sensor 132 for the positions of the valve piston 108.

The position sensor 132 is formed for example by a so-called reed relay 134 and the reed relay 134 triggering magnetic body 136, which in turn is moved with the valve piston 108 in the cylinder housing 110.

As soon as the magnet body 136 is at the level of the reed relay 134, it triggers a contact, so that the position sensor 132, for example, with an appropriate arrangement close to the closed position of the valve piston 108, is able to detect the valve piston 108 in this closed position.

In addition, it is also possible to detect whether the valve piston 108 has left the closed position and thus the valve body 102 has lifted from the valve seat 98 and the supply of lubricant to the other internal lubricant line system 80 releases, as in Fig. 4 is shown.

The signal of the position sensor 132 is forwarded to a compressor controller 140, with which also the drive motor 48 is controllable.

The differential pressure sensing element 130 now provides not only the ability for the compressor controller 140 to detect whether the lubricant stop valve 92 has opened, but also the ability to detect whether the screw rotors 44, 46 are driven by the drive motor 48 in the correct direction of rotation and thus the intended Build up pressure P2 in outlet channel 72. In the wrong direction of rotation of the screw rotor 44, 46 no pressure is built up in the outlet channel.

This pressure in the outlet channel, which corresponds to the pressure P2 in the cylinder chamber 112, according to the invention is not absolutely detected, but in relation to the reference pressures P1 and P3, by the pressure in the high pressure section 16, 20 of the refrigerant circuit 10, in particular the pressure in the lubricant separator 18th influenced, preferably proportional to this pressure. Thus, with the first differential pressure sensing element 130, it is possible to determine whether the pressure P2 in the outlet passage 72 is greater than the pressures P1 and P3 and to determine whether the pressure P2 is so high that refrigerant compressed to high pressure through the check valve 74 into the High-pressure line system 16 is promoted.

In this case, it is considered that the screw rotors 44 and 46 rotate in the correct direction, and thus damage due to wrong rotational direction of the screw rotors 44, 46 can be prevented.

The compressor controller 140 is preferably designed so that it observes the position sensor 132 within a time window after switching on the drive motor 48 and checks whether the valve piston 108 has left the closed position.

For example, the time window is set to last a maximum of one second. The time window can also be made even shorter, for example, half a second.

If, within the time window, it is detected by the compressor controller 140 that the valve spool 108 has not left the closed position, the compressor controller 140 assumes that the screw rotors 44, 46 either rotate in the wrong direction or are otherwise damaged, causing the drive motor to shut off 48 leads.

In addition to the first differential pressure sensing element 130, which primarily detects the proper operation of the screw rotors 44, 46 after the drive motor 48 has started, a second differential pressure sensing element 150 is provided which, as in FIGS Fig. 4 to 7 1, a cylinder housing 152 is provided, in which a piston 154 is provided, which separates a first cylinder chamber 156 from a second cylinder chamber 158, which are arranged on opposite sides of the piston 154.

The first cylinder chamber 156 is acted upon by the pressure P1, which also corresponds approximately to the pressure in the first cylinder chamber 112, while the second cylinder chamber 158 is acted upon by a pressure P4, the pressure of the lubricant in the interior space 86 of the filter housing 84 before passing through the Filter body 88 corresponds.

The piston 154 now moves according to the difference of the pressures P1 and P4, the piston 154 in addition in the direction of his in the Fig. 4 and 5 That is, the sum of the forces exerted on the piston 154 by the spring 160 and the pressure P1 is greater than the force exerted on the piston 154 by the pressure P4.

This correct lubricant flow indicating position of the piston 154 is taken when the valve body 102 is lifted from the valve seat 98 and thus the pressure P1 acts on the piston 154, but on the other hand, the pressure P4 before the filter body 88 is not substantially greater than the pressure P1 , which is the case when the filter body 88 for the lubricant is not added by dirt ( Fig. 4 ).

The correct lubricant flow indicating position of the piston 154 is thus dependent on a proper function of the filter body 88 and also dependent on the fact that the lubricant stop valve 92 is opened at all.

When the lubricant stop valve 92 is closed, the piston 154 remains in its correct lubricant flow indicating position as long as the pressure P1 has not collapsed (FIG. Fig. 5 ) and, when the pressure P4 is greater than the pressure P1, goes to the incorrect lubricant flow indicating position (FIG. Fig. 6 ).

On the other hand, when the lubricant stop valve 92 is opened, as in Fig. 7 shown, and yet the piston 154 not in its correct lubricant flow indicating position but an opposite position, this means that the filter body 88 is clogged and thus arises at this too high a pressure drop.

Thus, with the second differential pressure sensing element 150, it is possible to check and monitor the correct lubricant flow partially redundantly to the lubricant stop valve 92.

This is done by means of a second position sensor 162 which is also designed as a reed contact 164 and detects the position of a magnet 166 entrained by the piston 154 when the piston 154 is in its correct oil flow position.

Also, the position sensor 162 is connected to the compressor controller 140 so as to be able to check the correct flow of lubricant through the second differential pressure sensing element 150 and, if necessary, shut off the drive motor in the event of improper lubricant flow, damage due to insufficient lubrication of the screw rotors 44 , 46 or the bearings 60, 62 to avoid.

Claims (21)

1. Screw compressor (12) for compressing refrigerant in a refrigerant circuit (10), comprising a compressor housing (40) in which a screw rotor receiving means (42) and an inlet channel (70) as well as an outlet channel (72) for the refrigerant to be compressed are provided, at least one screw rotor (44, 46) arranged in the screw rotor receiving means, a drive (48) for the at least one screw rotor (44, 46) and
   a lubricant supply which conveys lubricant from a lubricant reservoir (32) acted upon by pressure via a line system (34, 80) at least to the at least one screw rotor (44, 46) during operation,
   characterized in that this comprises a first differential pressure detection element (130) which detects a difference in pressure between the pressure (P2) in the outlet channel (72) and a reference pressure (P1, P3) influenced by a pressure in the refrigerant circuit (10), and in that the screw compressor (12) comprises a compressor control (140) which switches off the drive (48) for the at least one screw rotor (44, 46) when the difference in pressure following a starting phase of the drive (48) is not in an operating pressure range determined by compression of the refrigerant.
2. Screw compressor in accordance with claim 1, characterized in that the reference pressure (P1, P3) is influenced by a pressure in the high pressure section (16, 20) of the refrigerant circuit (10).
3. Screw compressor in accordance with claim 1 or 2, characterized in that the reference pressure (P1, P3) is influenced by the pressure in the refrigerant circuit (10) transferred by the lubricant supply (34, 80) and acting on the lubricant reservoir (32).
4. Screw compressor in accordance with any one of the preceding claims, characterized in that the first differential pressure detection element (130) comprises an actuating device (110, 108) for the valve (92) in the lubricant supply as well as a sensor (132) detecting actuating positions thereof.
5. Screw compressor in accordance with claim 4, characterized in that the sensor (132) detects piston positions of the actuating device (110, 108).
6. Screw compressor in accordance with any one of claims 1 to 5, characterized in that the compressor control (140) determines the starting phase of the drive (48) by means of a time frame.
7. Screw compressor in accordance with claim 6, characterized in that the compressor control (140) checks whether the operating pressure range is reached during the starting phase.
8. Screw compressor in accordance with any one of the preceding claims, characterized in that a second differential pressure detection element (150) is provided, which detects a difference in pressure forming at the lubricant filter (82), and in that the compressor control (140) switches off the drive (48) when the difference in pressure exceeds a threshold value.
9. Screw compressor in accordance with claim 8, characterized in that the second differential pressure detection element (150) detects the pressure of the lubricant in the line system (34, 80) in front of a filter member (88) of the lubricant filter (82) and behind the filter member (88) of the lubricant filter (82).
10. Screw compressor in accordance with claim 9, characterized in that the differential pressure detection element (150) comprises a piston (154), which is acted upon, on the one hand, by lubricant prior to passing through the filter member (88) and, on the other hand, by lubricant after passing through the filter member (88).
11. Screw compressor in accordance with claim 9 or 10, characterized in that the differential pressure detection element comprises a sensor (162) for detecting at least one position of the piston (154).
12. Screw compressor in accordance with any one of claims 8 to 11, characterized in that the differential pressure detection element (150) is integrated in the compressor housing (140).
13. Screw compressor in accordance with any one of the preceding claims, characterized in that a valve (92), which is controllable by way of a difference in pressure between the pressure (P2) in the outlet channel (72) and a reference pressure (P1, P3) influenced by a pressure in the refrigerant circuit (10) and which opens when the screw rotor (44, 46) is compressing refrigerant and closes when the screw rotor (44, 46) is not compressing refrigerant, is provided in the line system (34, 80) of the lubricant supply.
14. Screw compressor in accordance with claim 1, characterized in that the reference pressure (P1, P3) is influenced by the pressure in the refrigerant circuit (10) acting on the lubricant reservoir (32) and transferred by the lubricant supply.
15. Screw compressor in accordance with claim 13 or 14, characterized in that the valve (92) is controllable by a valve piston (108) on which refrigerant subject to the pressure (P2) in the outlet channel (72), on the one hand, and the reference pressure (P1, P3), on the other hand, act.
16. Screw compressor in accordance with claim 15, characterized in that the valve piston (108) of the valve (92) can be acted upon on the side provided for the action of the reference pressure (P1, P3) by lubricant coming from the lubricant reservoir (32) and is movable in the direction of its closing position.
17. Screw compressor in accordance with any one of claims 13 to 16, characterized in that the valve (92) has a valve assembly which comprises a valve seat (98) and a valve member (102) and is constructed such that the pressure (P3) of the lubricant acting on the valve member (102) when the valve member (102) is seated on the valve seat (98) results in a force in the direction of the closed position of the valve member (102).
18. Screw compressor in accordance with any one of claims 13 to 17, characterized in that the valve (92) is integrated in the compressor housing (40) of the screw compressor (12).
19. Screw compressor in accordance with any one of claims 13 to 18, characterized in that a lubricant filter (82) is arranged in the line system (34, 80) for the lubricant.
20. Screw compressor in accordance with claim 19, characterized in that the lubricant filter (82) is integrated in the compressor housing (40) of the screw compressor (12).
21. Screw compressor in accordance with claim 19 or 20, characterized in that the valve (92) is integrated in a cover member (94) of a lubricant filter housing (84).

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