EP2456979B1 - Method for controlling delivery quantity, and reciprocating compressor having delivery quantity control - Google Patents

Description

The invention relates to a method for flow control of a reciprocating compressor according to the preamble of claim 1. The invention further relates to a reciprocating compressor with flow control according to the preamble of claim 13.

State of the art

The pamphlets EP 0801227 A2 and EP 1400692 A1 disclose a method for influencing the pressure-dependent automatic, periodic opening movement of a closing member of a suction valve of a reciprocating compressor by means of a, if necessary, at least over part of the crank circuit acting on the closing member control device. Since the life of mostly suction and pressure side used, automatic compressor valves is primarily influenced by the impact stress at the alternate impact of the actual closing organ on seat or catcher, said document discloses a method in which the suction valve by means of a so-called lift-off gripper before reaching Pressure equilibrium is forcibly opened, in order to avoid a strong instantaneous acceleration of the closing member towards the catcher, which would occur during automatic opening. This allows to reduce the impact load of the compressor valve.

This method has the disadvantage that the suction and in particular the compressor valves used on the pressure side still have a high load, in particular when the compressor system is operated according to the method of a continuous backflow control. In the continuous flow control, the suction valve is kept open by means of Abhebegreifers during a partial angle range of the compression stroke and then closed, thereby affecting the flow rate.

A disadvantage of this known method is the fact that the closing member of the suction valve and the pressure valve is subject to relatively high wear, which requires a correspondingly high maintenance.

The publication WO2008 / 000698 A2 discloses another device for flow control of a reciprocating compressor. From this device has the disadvantage that the compressor side used compressor valve has a high stress.

Presentation of the invention

The object of the invention is to form a more advantageous method for controlling the flow rate of a reciprocating compressor. This object is achieved by a method comprising the features of claim 1. Dependent claims 2 to 12 relate to further advantageous method steps. The object is further achieved with a reciprocating compressor having the features of claim 13. The dependent claims 14 and 15 relate to further advantageous embodiments.

The object is achieved in particular with a method for regulating the flow rate of a reciprocating compressor by influencing the movement of a closing organ of an automatic suction valve by means of a screed driven by a control device during at least part of a cycle of the crank circuit,
wherein the method comprises a stepless backflow control, wherein the Abhebegreifer during a first portion of the cycle of the crank circuit against the closing member and prevents its closure, and wherein the Abhebegreifer is retracted during a second portion of the cycle of the crank circle and the closing member is closed,
and wherein the method further comprises an intermittent control in which the interceptor prevents the closing of the closing member during a whole cycle of the crank circuit,
wherein the flow rate is controlled at least by a combination of continuous backflow control and intermittent control, and wherein the closing member is influenced by the control device and the Abhebegreifer such that a closing member of an automatic pressure valve of the reciprocating compressor, at least during a predetermined minimum total opening angle when using the continuous backflow control a crank circuit is opened.

In the inventive method, the flow rate is controlled by the forced keeping open the suction valve. In this case, two different methods are used for control, namely a suspension control and the continuous backflow control. Both methods use a so-called lift-off gripper, which presses the closing member of the valve, for example a plate, ring or Poppetventil, in an open position, and preferably on the valve seat.

The reciprocating compressor has a compression chamber, which is supplied via a suction valve gas, and from which via an outlet valve, also referred to as a pressure valve, compressed gas is discharged. In the process of Aussetzregelung the closing member of the suction valve is kept open during an entire working cycle or a whole working cycle. As a result, during the compression phase, the pressure in the compression chamber does not rise above the pressure which is required to open the pressure valve, so that the aspirated gas is forced back into the suction line during the compression phase, thereby preventing compression and further transport into the pressure line Available. The pressure valve thus remains closed and this compression chamber thus promotes no gas via the pressure valve in the pressure line. If the intermittent control is deactivated, ie a normal operation is run, the compression chamber again conveys the entire gas flow via the pressure valve into the pressure line. If, for example, the reciprocating compressor has only one compression space, then the intermittent control can be operated in such a way that certain working cycles are operated with normal operation, and during certain operating cycles the intermittent control is activated. A disadvantage of the Aussetzregelung is thus that the amount of gas pumped by the reciprocating compressor can be regulated only gradually. Another disadvantage of the Aussetzregelung is that the unloaded compression chamber, that is, when not opening pressure valve, is not flowed through and thereby accumulate dirt in the compression chamber, which increases the wear of the valves and the packing rings and piston rings.

In the method of backflow control, the suction valve is kept open by means of the lift-off gripper during a partial angle range of a complete compression stroke or a complete crank circuit and then closed, thereby affecting the flow rate. The suction valve is pressed only at the beginning of the compression phase by the Abhebegreifer. As a result, a part of the gas located in the compression chamber is pushed back into the suction line. As soon as the closing member of the suction valve closes completely, the remaining gas in the compression chamber is compressed and pressed via the pressure valve in the pressure line. During the backflow control, only a portion of the maximum possible gas flow from the compression chamber is thus conveyed via the pressure valve in the pressure line.

A disadvantage of the method of backflow control is the fact that the opening time of the automatic pressure valve is reduced accordingly for smaller flow rates, and that at flow rates less than 40% of the nominal flow, the opening time of the pressure valve is shortened such that the opening and closing speeds of the pressure valve can multiply. On the one hand, this leads to increased wear of the automatic pressure valve, and on the other hand, this reduces the range within which partial delivery quantities can be reliably conveyed. Another disadvantage of the backflow control is that the gas is heated more strongly before compression due to the longer residence time in the compression chamber and due to the heat transfer via the cylinder wall and due to a leakage flow through the piston. This has the consequence that the gas has an elevated temperature on the pressure side.

• Zum Fördern der maximalen Fördermenge wird das Saugventil nicht beeinflusst und öffnet und schliesst somit selbsttätig.
• Bei grossen Förderströmen, das heisst Fördermengen im Bereich zwischen etwa 100% und 80% der maximalen Fördermenge, wird eine stufenlose Rückstromregelung eingesetzt. Wobei es auch möglich ist, dass nicht jeder Zyklus des Kurbelkreises mit der Rückstromregelung geregelt wird, sondern das Saugventil auch beispielsweise einen oder zwei Zyklen selbsttätig und somit ohne Beeinflussung betrieben wird. Dieses Verfahren weist den Vorteil auf, dass der Abhebegreifer weniger beansprucht wird, sodass sich längere Standzeiten ergeben, und dass die Mengenregelung selbst weniger Energie verbraucht.

• Bei mittleren Förderströmen, das heisst bei Fördermengen im Bereich zwischen etwa 80% und 50% der maximalen Fördermenge, wird bei jedem Zyklus die stufenlose Rückstromregelung verwendet.
• Bei kleinen Förderströmen, das heisst bei Fördermengen im Bereich zwischen etwa 50% und 0% der maximalen Fördermenge, wird das Schliessorgan des Saugventils Mittels der Aussetzregelung während einer gewissen Anzahl Zyklen, beispielsweise einem oder zwei Zyklen, offen gehalten. Bei den anderen Zyklen kann entweder das Saugventil selbsttätig betrieben werden, oder zusätzlich, falls erforderlich, die Rückstromregelung eingesetzt werden.

The method according to the invention has the advantage that, by the combined use of backflow control and intermittent control, the amount delivered by the reciprocating compressor can be varied within a wide range, in particular without additional wear of the closing member of the suction valve and / or of the pressure valve. The reduction of the wear of the pressure valve is in particular the fact that the suction valve is kept open at low flow rates during certain cycles according to the Aussetzregelung and thus no gas is compressed, and that in the subsequent compression process a sufficiently large amount of gas is compressed, so that the closing member of the pressure valve during remains open a predetermined total opening angle, or so that the closing member of the pressure valve does not fall below a minimum opening angle. For the regulation of the delivery amount, there are essentially preferably three different methods available which can be used. In addition to a method with maximum delivery, in which the suction valve closes automatically, nor the already described method of backflow control and the already described method of Aussetzregelung. Depending on the amount of fluid to be delivered in each case, the control can take place, for example, as follows:

• To promote the maximum flow, the suction valve is not affected and thus opens and closes automatically.
• For large flow rates, ie flow rates in the range between about 100% and 80% of the maximum flow, a continuous backflow control is used. Whereby it is also possible that not every cycle of the crank circuit is regulated with the backflow control, but the suction valve is also operated, for example, one or two cycles automatically and thus without interference. This method has the advantage that the lift-off gripper is subjected to less stress, resulting in longer service lives, and that the volume control itself consumes less energy.

• At medium flow rates, ie at flow rates in the range between about 80% and 50% of the maximum flow rate, the continuous backflow control is used for each cycle.
• At low flow rates, ie at flow rates in the range between about 50% and 0% of the maximum flow rate, the closing member of the suction valve by means of Aussetzregelung during a certain number of cycles, such as one or two cycles, kept open. In the other cycles either the suction valve can be operated automatically, or in addition, if necessary, the backflow control can be used.

According to the invention, the suction valve is influenced by the control device and the lift-off gripper such that the closing member of the pressure valve of the reciprocating compressor is opened at least during a minimum predetermined opening angle range or a predetermined total opening angle of a crank circle. The opening angle range is at least 10 ° and preferably at least 20 ° to 30 °.

In a particularly advantageous embodiment of the inventive method of Abhebegreifer via a drive device, preferably an electromagnet, can be controlled very precisely, such that the speed of the closing closing member can be reduced prior to placement on the suction valve, so that the closing member at low speed on the suction valve hits and comes to rest, so that the closing organ thus "gentle" on the Suction valve touches down. In a particularly preferred method, the speed of the closing member during placement on the suction valve is less than 0.1 m / s. This advantageous method reduces the wear of the closing organ in addition.

In a further advantageous embodiment, the drive device comprises a controllable damping device in order to influence the speed of the Abhebegreifers and in particular the location of the reduced speed such that the closing member impinges when closing at low speed on the suction valve, so that the closing member thus "gently" on the Suction valve touches down and this closes. The damping device is particularly advantageously electrically controllable, and particularly advantageously comprises an electrorheological or magnetorheological fluid whose viscosity can be changed electrostatically or electromagnetically, so that the damping via electrical signals can be changed very quickly. However, the damping device can also be based on another principle and be configured for example as an electromagnet.

The invention will be described in detail below with the aid of exemplary embodiments.

Brief description of the drawings

Fig. 1

einen Längsschnitt durch ein ansteuerbares Ventil;

Fig. 2

ein Beispiel der Bewegung des Abhebegreifers, des Schliessorgans des Saugventils sowie der Geschwindigkeit des Abhebegreifers in Funktion des Kurbelwinkels;

Fig. 3

der Verlauf des Drucks im Verdichtungsraum des Hubkolbenkompressors bei unterschiedlichen Betriebsverfahren;

Fig. 4

der Verlauf des Ventilhubs des Saugventils und des Druckventils bei den in Figur 3 dargestellten Betriebsverfahren;

Fig. 5

ein Lastverlauf in einem PV-Diagramm bei unterschiedlichen Betriebsverfahren;

Fig. 6

charakteristische Grössen des Ventils in Funktion des Kurbelwinkels;

Fig. 7

schematisch ein Hubkolben-Kompressor.

Fig. 8

schematisch eine Steuereinrichtung zum Betätigen des auf das Saugventil wirkenden Greifers;

The drawings used to explain the embodiments show:

Fig. 1

a longitudinal section through a controllable valve;

Fig. 2

an example of the movement of the Abhebegreifers, the closing of the suction valve and the speed of the lift-off gripper as a function of the crank angle;

Fig. 3

the course of the pressure in the compression chamber of the reciprocating compressor with different operating methods;

Fig. 4

the course of the valve lift of the suction valve and the pressure valve at the in FIG. 3 illustrated operating procedures;

Fig. 5

a load curve in a PV diagram with different operating methods;

Fig. 6

characteristic values of the valve as a function of the crank angle;

Fig. 7

schematically a reciprocating compressor.

Fig. 8

schematically a control device for actuating the force acting on the suction valve gripper;

Basically, the same parts are given the same reference numerals in the drawings.

Ways to carry out the invention

Fig. 1 shows a longitudinal section through a controllable valve 1 comprising a compressor housing 4 with a suction valve 5 disposed therein, the position of which is influenced by a Abhebegreifer 6, wherein the Abhebegreifer 6 is actuated via a connecting rod designed as a connecting means 7 of a arranged outside the compressor housing 4 control device 2 ,

The compressor housing 4 comprises a lantern 4a, a gas space 4b, a compression chamber 4c and a lid 4d, wherein the compressor housing 4 also includes a not shown or not visible pressure valve 8, via which the compressed fluid can escape from the compression chamber 4c. The automatic intake valve 5 comprises a valve seat 5a, a closing member 5b movably mounted in a stroke direction B, also referred to below as a valve plate 5b, a valve catcher 5c and a return spring 5d. The lift-off gripper 6 comprises a plurality of gripper extensions 6a or fingers 6a, a guide 6b and a compression spring 6c. The lifting gripper 6, driven by the electromagnets 2a, slidably mounted in the stroke direction B, wherein the tip of the gripper extensions 6a can abut depending on the stroke in direction B on the valve plate 5b, and in particular can press the valve plate 5b against the valve catcher 5c, so that the Valve plate 5b is no longer movable, and the valve 5 thereby forcibly remains open. The control device 2 comprises as drive device an electromagnet 2 a with a magnet armature 2 b, a magnetic core 2 c and a magnetic coil 2 d. The control device 2 further comprises a housing 2m which is connected to the compressor housing 4 via the connecting part 2e. The control device 2 also comprises a drive device 2i or a control device 2i, electrical lines 2k, 21, wherein the electrical line 21 connects the drive device 2i with the solenoid 2a. The control device 2 comprises two guides 2f, 2g for slidably supporting the electromagnet 2a and the connecting rod 7 in the stroke direction B. In addition, a filter 3 may be provided. In an advantageous embodiment, the control device 2 also includes a sensor such as a displacement sensor 2h, which the hub or the position of the electromagnet 2a or the position of the lifting gripper 6 in the stroke direction B detected.

This in FIG. 1 shown controllable valve 1 can now be controlled in different ways over the cycles of the crank circuit. A cycle is understood to mean a rotation of the crankshaft of the reciprocating compressor through 360 °.

FIG. 2 shows the method of a continuous backflow control, wherein in FIG. 2 the lifting movement A of the Abhebegreifers 6, the stroke B of the valve plate 5b and the speed C of the Abhebegreifers 6 are shown in function of the crank angle, wherein a single revolution of the crankshaft is shown, that is FIG. 2 shows the course over an angle between 0 ° and 360 °. From the lifting movement B of the valve plate 5b it can be seen that the valve plate 5b automatically opens in the illustrated embodiment in the angular range between about 90 ° and 110 ° during suction, so that the valve plate 5b rests against the valve catch 5c. In the method of continuously variable backflow control, after opening the valve plate 5b, as shown by way of example by the curve A, the lifting gripper 6 is moved or moved until it bears against the valve plate 5b. Moreover, in FIG. 2 with the curve C nor the speed of the Abhebegreifers 6 shown. During automatic operation of the suction valve 5, the suction valve 5 would automatically close when reversing the direction of movement of the piston, in the example shown at 225 °. The method of stepless backflow control now causes the Abhebegreifer 6 rests during a first portion K1 of the cycle of the crank circle on the closing member 5b and prevents its closure, and that the Abhebegreifer 6 during a second portion K2 of the Cycle of the crank circle is moved back according to the course of the curve A2, wherein the closing member 5b, namely the valve plate 5b, due to the applied pressure conditions of the movement of the Abhebegreifers 6 follows or abhebegreifer 6 is applied, so that the valve plate 5b at some point, in the example shown approximately at 290 °, rests on the valve seat 5a and the valve 5 closes. In the further section K3, the lifting gripper 6 is moved even further, so that it is, for example, spaced from the valve plate 5b.

The movement of the closing member 5b is influenced via the drive device, in the illustrated embodiment via the solenoid 2a and the connecting rod 7 in the section K2 such that the Abhebegreifer 6 in function of the crank circle in FIG. 2 illustrated Hubverlauf A or the in FIG. 2 shown speed profile C, wherein the solenoid 2a is advantageously controlled such that the speed of the moving closing member 5a is reduced before placing on the suction valve 5, as in FIG. 2 is shown. In an advantageous embodiment, the Abhebegreifer 6 is then moved in a further section K3 still in an end position, advantageously as shown in the curve C with the "second hump" by again accelerated and then decelerated again, so that the Abhebegreifer 6, as in Stroke course A shown in the section K3, spaced, that is without direct contact with the closing member 5a, comes to a standstill. The electromagnet 2a is controlled in an advantageous method step such that the closing member 5b has a speed of less than 0.1 m / s during placement on the suction valve.

The valve 1 can also be operated with the method of Aussetzregelung. In the intermittent control of the Abhebegreifer 6 is moved such that it prevents the closing of the closing member 5b during a whole cycle of the crank circuit, preferably in that the Abhebegreifer 6 rests during the entire cycle on the closing member 5b, so that it remains open over the entire cycle.

FIG. 7 schematically shows a reciprocating compressor comprising a compressor housing 4 with a movably mounted, via a piston rod 4f driven piston 4e, which partially defines a compression chamber 4c. On the compressor housing 4, a suction valve 5 is also arranged, via which the fluid or gas to be conveyed is sucked. The reciprocating compressor also includes a gripper 6, which is driven by a control device 2 comprising a drive device. The control device 2, the suction valve 5 and the gripper 6 form a controllable valve 1. On the compressor housing 4, a pressure valve 8 is also arranged, via which the compressed gas leaves the compression chamber 4c. Of course, the reciprocating compressor may also comprise a plurality of compression spaces 4c, each compression space 4c comprising a separate piston 4e with piston rod 4f, and each compression space 4c comprising a separate, controllable valve 1.

FIG. 3 shows now the course of the pressure in a compression chamber 4c of a reciprocating compressor in function of the crank angle for different operating methods. In the illustrated embodiment, the bottom dead center U _{TP is} at 90 °, that is, in this position, the compression chamber 4c reaches the maximum Volume. The top dead center O _TP is in this example at 270 °, that is, at this position, the compression chamber 4c reaches the minimum volume. In the first section D, the movement of the closing member 5b of the suction valve 5 is carried out automatically, so that over a crank angle of 360 ° the pressure curve shown results. The movement of the closing member of the pressure valve 8 takes place in FIG. 3 always automatically. In the illustrated embodiment, the pressure-side pressure, for example, about 3.1 bar, wherein the pressure valve 8 opens in the illustrated embodiment, including bias by the valve springs at a pressure of about 3.2 bar. The pressure valve 8 opens approximately at a crank angle of 190 °. The automatic pressure valve 8 is fully opened in the illustrated embodiment during an angular range Kw of about 50 °, because the pressure valve 8 in this maximum open angle range K _{W has} the maximum valve lift before the pressure valve 8 closes again. The total opening angle Kv, during which the valve is open, that is, the closing member is lifted from the valve seat, or the entire opening time of the pressure valve 8 is about 80 °. In the second section E a skip control is shown, in which, as described above, the closing member 5b is kept open over the entire crank angle of 360 ° from Abhebegreifer 6, so that results in the compression chamber 4c of the pressure profile shown. The pressure in the compression chamber 4c is constantly below 3.2 bar, so that the pressure valve 8 does not open automatically. In the third section F, a continuous backflow control is shown, in which, as in FIG. 2 described, the closing member 5b is kept open during part of the crank angle of 360 ° from Abhebegreifer 6, so that the pressure build-up in the compression chamber 4c based on the crank angle takes place later, and the pressure curve shown results. The pressure valve 8 opens approximately at a Crank angle of 210 °. The automatic pressure valve 8 remains fully open in the illustrated embodiment during a Maximaloffenwinkelbereich Kw of about 30 ° before the valve lift, as in FIG. 4 shown reduced, and the valve 8 completely closes again after the total opening angle Kv. The total opening angle Kv, during which the valve 8 is open, or the total opening time of the valve is about 60 °.

In the Aussetzregelung thus the suction valve 5 is kept open during a whole working cycle. As a result, the sucked gas is pushed back into the suction line during the compression phase and thus is the compression and further transport into the pressure line is not available. The compression chamber does not deliver gas. If the skip control deactivated, the compression chamber again promotes the full fluid flow.

In contrast, in the continuously variable backflow control, the closing element 5b of the suction valve 5 is pressed on only at the beginning of the compression phase. As a result, a portion of the gas is forced back into the suction line. Closes the suction valve 5, the remaining gas can be compressed in the compression chamber and pressed by the pressure valve in the pressure line. The compression chamber promotes only part of the maximum possible gas flow.

Both methods use the lift-off gripper 6 to push the sealing element 5b of the valve 5, for example a plate, ring or poppet valve, against the valve catcher 5c and thus into the open position. Since in the continuous backflow control of the lift gripper 6 in a work cycle of the closed in the open position and must be moved back again, and there in the suspension control for the same sequence of movements a longer time available
stands, the power consumption, the required forces, the travel speeds and the stress of the components used in the continuous backflow control are higher.

The flow rate of a reciprocating compressor can now, as in FIG. 3 indicated, are controlled by a combination of continuous backflow control F and Aussetzregelung E in a wide range, in addition also the section D can be used for flow control, during which the closing member 5b moves automatically. These three types of operation D, E, F of operating the valve 5 can now be combined with each other, so that, for example, during successive cycles initially only the type of operation D, E or F takes place, and later, for example, a combination of at least two of the three types of operation D, E and F.
The valve could for example be controlled such that different flow rates are controlled so that the suction valve 5 is automatically operated at high flow rates during certain cycles, and is operated during certain cycles according to the continuous backflow control,
that the suction valve 5 is operated at medium flow rates during each cycle according to the continuous backflow control, and that the suction valve 5 is constantly kept open at low flow rates during certain cycles, and is operated during certain cycles according to the stepless backflow control.

FIG. 4 shows the lifting movement 8c of the pressure valve 8 in function of the crankshaft angle. In addition, the lifting movement 5e of the closing member 5b of the suction valve 5 is shown as a function of the crankshaft angle. The movement of the pressure valve 8 takes place automatically, whereas the movement of the closing member 5b of the suction valve 5 as described above in the Aussetzregelung E and the backflow control F is determined by the gripper 6. Well recognizable in FIG. 4 the maximum open angle range Kw, within which the valve 8 has a maximum valve lift, that is, is open to the maximum. In addition, the total opening angle Kv can be seen, during which the valve 8 is opened.

The opening duration of the automatic pressure valve 8 is determined by the angular range during which the pressure in the compression chamber 4c is above the opening pressure of the pressure valve 8, according to the exemplary embodiment FIG. 3 above a pressure of 3.2 bar. From the in FIGS. 3 and 4 shown with F continuous backflow control can be seen that the angular range of the open pressure valve 8 is reduced, the later the closing member 5b is closed. This has the consequence, in particular for small flow rates, that the pressure valve 8 would only be opened during a very short total opening angle Kv if the backflow control were used continuously. In order to increase the total opening angle Kv of the pressure valve 8 at low flow rates, the reciprocating compressor is operated such that the Aussetzregelung E is used during one or more crank cycles to promote in the subsequent backflow control F a large enough amount of gas, so that the pressure valve 8 over a total opening angle Kv of at least 10 ° and preferably over a total opening angle Kv of at least between 20 ° and 30 ° remains open. This has the consequence that the pressure valve 8 is opened long enough to avoid excessive shocks or excessive opening or closing speeds. This considerably extends the life of the pressure valve 8. FIG. 5 shows a load curve in a PV diagram in different operating methods, namely as already in FIG. 3 shown, at full load D with automatic suction valve 5, in the Aussetzregelung E and in the continuous flow control F.

A compressor may be configured such that it as in FIG. 7 represented per cylinder only one compression space 4c, wherein such a compression space 4c is also referred to below as the upper compression space. The compressor may also be designed such that it has a second compression chamber in the same cylinder, which is separated from the first compression chamber by the piston 4e, so that during the movement of the piston 4e the fluid is compressed in one compression chamber and drawn in the other compression chamber. The second compression space is also referred to below as the lower compression space. In a particularly advantageous method, the flow rate control takes place as in FIG. 3 indicated such that the pressure valve 8 of the reciprocating compressor at least during a predetermined angular range Δ of 20 ° to 30 ° before reaching the top dead center O _TP (the upper compression space) respectively bottom dead center U _TP (at the lower compression space, if the cylinder two compression spaces includes) of the crank circuit opens. An advantage of this method is that only the opening time must be determined because the closing time is reasonably well known and an idealized valve in Dead center of the upper or, if present, lower compression space is.

The opening time of the pressure valve 8 can be determined, for example, by measuring the pressure in the compression chamber and comparing it with the final pressure, or by knowing the operating cases of the compressor via a previous, respectively simultaneous calculation of the maximum opening time of the suction valve over the reversal point of the movement of the piston. so that the minimum opening time or the minimum opening angle of the pressure valve is not exceeded.

The FIG. 6 shows characteristic variables of the controllable valve 1 as a function of the crank angle or the angle of rotation to the in FIG. 6 in the path diagram shown movement curve B of the valve plate 5b and the course of motion A of the lift-off gripper 6 to obtain. In addition, in the curve C, the speed profile of the lift-off gripper 6 is shown. In addition, in the curve G, the force caused by the electromagnet 2a and shown in the curve H, the current required to drive the solenoid 2a current. In the FIG. 6 Processes shown are particularly important to the in FIG. 2 shown, "gentle landing" of the valve plate 5b on the valve catch 5c to effect.

FIG. 8 schematically shows a further embodiment of a control device 2 for actuating and driving the force acting on the suction valve 5 gripper 6. The control device 2 comprises a drive device 2n, which via the linearly movably mounted connecting rod 7 with the in FIG. 7 schematically illustrated gripper 6 is connected. The drive device 2n shown in this embodiment comprises a linear drive 2w and a electrically controllable damping device 2o, wherein the damping device 2o has the function of the electrically driven to dampen the movement generated by the linear drive 2w so that the gripper 6 and the valve plate 5b of the suction valve 5 such as in FIG. 2 shown moves. The linear drive 2w has a linearly movable connecting rod 2t, which is operatively connected to the connecting rod 7. In the illustrated embodiment, the damping device 2o is disposed between the linear drive 2w and the gripper 6. However, the damping device 2o could also be arranged at a different location, in the illustrated view of the control device 2, for example, above the linear drive 2w. The damping device 2o can be configured in a variety of ways to effect a damping of the movement of the linear drive 2w. In order to bring about the invention "soft landing" of the valve plate 5b on the valve catcher 5c is the in FIG. 8 schematically illustrated damping device 2o particularly advantageous. The damping device 2o comprises a cylinder 2p and in its interior a linearly displaceable piston 2r which divides the interior of the cylinder 2p into a first inner space 2q and a second inner space 2s. The two inner spaces 2q, 2s are connected to each other via a fluid-conducting connection 2u, so that a fluid is exchangeable between the two inner spaces 2q, 2s. In an advantageous embodiment, the two inner spaces 2q, 2s are conductively connected to each other via an electrically controllable damping or throttle 2v fluid. A drive and control device 2i is electrically connected via electrical lines 2k, 21 signal to the linear drive 2w and the controllable damping 2v, so that both the linear drive 2w and the damping properties of the damping device 2o are controllable in order to control the position or the speed of the valve plate 5b such that as in FIG. 2 exemplified a "gentle landing" of the valve plate 5b is effected. In the FIG. 8 Control device 2 shown also includes a device for determining the stroke and / or the speed of the gripper or the valve plate 5b. This device is in FIG. 8 not shown.

The fluid-conducting connection 2u and the electrically controllable damping 2v could also be arranged on the damping device 2o or within the damping device 2o, in particular also on the piston 2r in that the piston 2r has, for example, a fluid-conducting connection between the first and second internal spaces 2q, 2s ,

In a particularly advantageous embodiment, the fluid of the damping device 2o at least partially consists of an electrorheological or magnetorheological fluid. Such liquids have the property that their viscosity is electrically controllable, so that with such liquids, an electrically controllable throttle section can be configured. Such a throttle section has the advantage that the viscosity can be varied within a wide range, and that the viscosity can be changed very quickly with the aid of the electrical signal. The damping properties of such a damping device 2o are characterized very quickly changed, so that the movement of the piston 2r and thus the movement of the connecting rod 7, the gripper 6 and ultimately the valve plate 5b can be so damped or is controlled and controlled, the valve plate 5b with respect to the path traveled and speed a "gentle landing" is carried out.

Damping devices comprising an electrorheological or magnetorheological fluid are known, for example, from the document WO2008 / 141787A1 or from the publication EP 1034383B1 known.

The linear drive 2w can be designed, for example, as a hydraulic or pneumatic drive, as an electromagnetic drive, as a linear motor or as an electric motor with a translation.

In an advantageous embodiment, the control device 2 comprises an adaptive pilot control, with which the stroke A and the speed C of the lift-off gripper 6 are regulated.

In an advantageous embodiment, the control device 2i comprises an adaptive pilot control device in order to generate control signals for the electromagnet 2a from the control variables of the stroke A and the speed C of the lift-off gripper 6.

Claims (15)

1. Method for delivery quantity control of a reciprocating compressor, in which the movement of a closing body (5b) of a self-acting intake valve (5) is influenced during at least part of a cycle of crank rotation by an unloader (6) driven by a control device (2), wherein the method comprises a continuously variable backflow regulation, in which the unloader (6) lies against the closing body (5b) during a first section (K1) of the cycle of crank rotation and prevents its closure, and in which the unloader (6) is driven back during a second section (K2) of the cycle of crank rotation and the closing body (5b) is closed, characterized in that the method further comprises a skip regulation, in which the unloader (6) prevents closure of the closing body (5b) during a whole cycle of crank rotation,
   that the delivery quantity is regulated by at least a combination of continuously variable backflow regulation and skip regulation, and that during use of the continuously variable backflow regulation the closing body (5b) is influenced by the control device (2) and the unloader (6) in such a way that a closing body of a self-acting pressure valve (8) of the reciprocating compressor is opened during at least a predetermined minimal total opening angle (Kv) of a crank rotation.
2. Method according to claim 1, characterised in that for small delivery quantities, the intake valve (5) is held open under skip regulation during certain cycles, whereby the closing body of the pressure valve (8) does not fall below a minimal opening angle.
3. Method according to claim 2, characterised in that, the predetermined total opening angle (Kv) is at least 10°, and preferably lies at least in the range between 20° and 30°.
4. Method according to claim 3, characterised in that, the intake valve (5) is influenced by the control device (2) and the unloader (6) in such a way that the closing body of the pressure valve (8) of the reciprocating compressor is opened at least during a predetermined angular range (Δ) of a crank rotation before the upper, respectively lower dead centre (O_TP, U_TP).
5. Method according to claim 4, characterised in that the predetermined angular range (Δ) is at least 10°, and preferably lies at least in the range between 20° and 30°.
6. Method according to one of the preceding claims, characterised in that, the progression of pressure (P) in the compression space of the reciprocating compressor is measured and/or calculated, and that the control device (2) steers the unloader (6) in dependence on the progression of pressure (P), on each occasion during at least a cycle of crank rotation, under constantly variable backflow regulation or skip regulation in such a way that the progression of pressure (P) has a pressure (P) at least during a predetermined total opening angle (Kv) of a crank rotation which lies above the opening pressure of the pressure valve (8), such that the pressure valve (8) is automatically opened during the total opening angle (Kv).
7. Method according to one of the preceding claims, characterised in that, during a plurality of cycles of crank rotation, the delivery quantity is regulated only by constantly variable backflow regulation or only by skip regulation, and/or that, for large delivery quantities, the intake valve (5) is driven automatically during a plurality of successive cycles.
8. Method according to one of the preceding claims, characterised in that, various delivery quantities are regulated in such a way, that, for large delivery streams, the intake valve (5) is automatically driven during certain cycles and is driven with constantly variable backflow regulation during certain cycles; that, that, for middle-sized delivery quantities, the intake valve (5) is driven during every cycle with constantly variable backflow regulation; and that, for small delivery quantities, the intake valve (5) is constantly held open during certain cycles under skip regulation, and driven with constantly variable backflow regulation during certain cycles.
9. Method according to one of the preceding claims, characterised in that, the backflow regulation occurs in such a way that the control device (2) comprises an electromagnet (2a) which drives the unloader (6), and that the electromagnet (2a) is steered in such a way that the unloader (6) lies against the closing body (5b) during a first section (K1) of the crank rotation and prevents its shutting, and that the unloader (6) influences the movement of the closing body (5b) during shutting during a second section (K2) of the crank rotation in such a way that the speed of the moving closing body (5b) is reduced prior to seating on the intake valve (5).
10. Method according to one of claims 1 to 8, characterised in that, the backflow regulation occurs in such a way that the control device (2) comprises a drive mechanism (2n), which drives the unloader (6), and that the drive mechanism (2n) comprises a steerable damping mechanism (2o) which damps the movement of the unloader (6), wherein the drive mechanism (2n) is steered in such a way that the unloader (6) lies against the closing body (5b) during a first section (K1) for the crank rotation and prevents its shutting, and that the unloader (6) influences the movement of the closing body (5b) during shutting during a second section (K2) of the crank rotation in such a way that the speed of the moving closing body (5b) is reduced prior to seating on the intake valve (5).
11. Method according to claim 9 or 10, characterised in that, during seating on the intake valve (5), the speed of the closing body (5b) is less than 0.1 m/ s.
12. Method according to one of claims 9 to 11, characterised in that, after the seating of the closing body (5b), during a third section (k3) of the crank rotation, the control device (2) once again accelerates the unloader (6) and then brings it to rest, in order to distance the unloader (6) from the closing body (5b) and to bring the unloader (6) to an end position.
13. Reciprocating compressor with constantly variable delivery quantity regulation, with an unloader (6) arranged on at least one self-acting intake valve (5) of the compressor, with a control device (2) for driving the unloader (6), as well as with a closing body (5b) of the intake valve (5), and with a self-acting pressure valve (8), wherein the unloader (6) during operation acts on the closing body (5b) in such a way that the intake valve (5) is opened over a controllable part of the working stroke of the compressor, wherein the control device (2) comprises a drive mechanism (2n) which acts via a connection means (7) on the unloader (6), and wherein the control device (2) comprises a constantly variable backflow regulation, in which during operation the unloader (6) lies against the closing body (5b) during a first section (K1) of the cycle of crank rotation and prevents its shutting, and in which the unloader (6) returns during a second section (K2) of the cycle of crank rotation such that the closing body (5b) shuts, characterised in that the control device (2) in addition comprises a skip regulation, in which during operation the unloader (6) prevents the shutting of the closing body (5b) during a complete cycle of crank rotation, and that unloader may be controlled by the control device (2) by two different methods, the constantly variable backflow regulation and the skip regulation, and that during use of the continuously variable backflow regulation the closing body (5b) is influenced by the control device (2) and the unloader (6) in such a way, that a closing body of the pressure valve (8) is opened during a predetermined minimal total opening angle (Kv) of a crank rotation.
14. Compressor according to claim 13, characterised in that, the drive mechanism (2n) is in the form of an electromagnet (2a), and/or n that, the drive mechanism (2n) comprises a drive (2w) and a steerable damping mechanism (2o), wherein the damping mechanism (2o) is adapted and arranged such that it damps the movement of the drive (2w).
15. Compressor according to one of claims 13 to 14, characterised in that, the control device (2) comprises a mechanism for measuring and/or calculating the pressure progression (P) in the compression space of the reciprocating compressor, and that the control device (2) is such that it drives the closing body (5b) via the unloader (6) in free-running mode or with backflow regulation or with skip regulation, in order to open the pressure valve (8) automatically during a total opening angle (Kv).

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