EP1710435A1 - Refrigerant compressor - Google Patents

Abstract

The compressor has a cylinder unit with a piston that moves in an oscillating manner in a cylinder housing, and a cylinder head with an inlet chamber. A switching valve interrupts an inlet flow of the cylinder unit. A control (130) activates the switching valve for operating the compressor in a lower part-load range. The control operates the valve in successive switching intervals which are shorter than a shortest time period after which a temperature of an evaporator (32) in an operating refrigerating system has risen during an interruption of the inlet flow.

Description

The invention relates to a refrigerant compressor for refrigeration systems comprising at least one cylinder unit, which has a cylinder housing and a piston oscillatingly movable in the cylinder housing, a cylinder head, with an inlet chamber through which an inlet flow of the at least one cylinder unit passes and with one of an outlet flow of the at least one cylinder unit Outlet chamber, and a switching valve for interrupting the inlet flow.

Such refrigerant compressors are known from the prior art, in these consists with the switching valve, the ability to permanently disable one or more cylinder units or permanently switch on.

With this solution, a control of the mass flow rate is only possible in accordance with the ratio of the stroke volume of the deactivated cylinder units and the stroke volume of the working cylinder units.

The invention is therefore based on the object to improve a refrigerant compressor of the generic type such that it can be operated in any part load ranges.

This object is achieved in a refrigerant compressor of the type described above according to the invention that a control is provided for driving the switching valve, which operates the switching valve in consecutive, each an opening interval and a closing interval of the switching valve comprehensive switching intervals for operation of the refrigerant compressor in a lower part load range, which are shorter than a shortest period of time after which a temperature of an evaporator in the working refrigeration system has increased by about 10% at an interruption of the intake flow.

The advantage of the solution according to the invention is the fact that this opens up the possibility to operate a refrigerant compressor, in particular a reciprocating compressor in a lower part load range at any part load, as by the ratio of the opening intervals and the closing intervals within each switching interval of the mass flow to be compressed continuously and is arbitrarily adjustable.

In this case, time periods are selected for the switching intervals, which are sufficiently short, so that due to the inertia of the reaction of the refrigeration system according to the invention to the switching intervals only insignificant temperature fluctuations in the evaporator of the refrigerators arise that do not affect a precise control of the temperature.

Alternatively to the solution described above, in a further embodiment of a refrigerant compressor of the type described above, a controller for driving the switching valve is provided, which for the operation of the refrigerant compressor in a lower part-load range Operating the switching valve in successive, one opening interval and a closing interval of the switching valve comprehensive switching intervals that are shorter than about 10 seconds.

By such a limitation of the duration of the switching intervals, the possibility is created in accordance with the invention to operate the refrigerant compressor in the lower part load range at any adjustable partial load, without the pressure fluctuations in the refrigeration system occur, affecting the quality of the control of the same.

It is even more advantageous if the switching intervals are shorter than about 2 seconds.

In order to be able to operate the switching valves effectively, it is preferably provided that the switching intervals are longer than approximately 0.02 seconds.

It is even more advantageous if the switching intervals are longer than 0.05 seconds, and it is particularly favorable if the switching intervals are longer than 0.1 seconds.

It is particularly advantageous for a switching of the switching valve, when the switching intervals correspond to a switching frequency which is smaller than a natural frequency of the switching valve.

It is even better if the switching intervals correspond to a switching frequency which is smaller by more than a factor of 5 than a natural frequency of the switching valve.

In principle, it would be conceivable to switch off a part of the cylinder units with the control according to the invention in the lower part-load range and to operate only a part of the cylinder units in the switching intervals.

However, a particularly expedient solution provides that the controller operates in the lower part-load range all cylinder units of the refrigerant compressor in the switching intervals.

It is also conceivable to switch off only a part of the cylinder units in the upper part-load range and to operate another part of cylinder units in the switching intervals.

It is particularly favorable, however, if the controller operates all cylinder units in the switching intervals in the entire partial load range.

With regard to the duration of the switching intervals, a wide variety of possible solutions are conceivable. For example, a variant which is particularly favorable for reasons of simplicity provides that the control operates with time-constant switching intervals.

Another advantageous solution provides that the controller varies the switching intervals according to a drive speed of the refrigerant compressor.

With regard to the design of the switching valve so far no details have been made.

Thus, it would be conceivable to design the switching valve so that it acts directly, for example magnetically controlled, on the inlet flow.

For reasons of the required high valve forces, it has proved to be advantageous if the switching valve is a servo valve.

In particular, it is advantageous if the servo valve comprises a valve body which can be actuated by a pressure associated with the pressure in the outlet chamber.

In order to ensure that the valve body does not automatically assume the end position brought about by the pressure in the outlet chamber, it is preferably provided that the valve body is acted upon by an elastic force store acting in the opposite direction to the action of the pressure on the valve body.

With regard to the actuation of the valve body by the pressure in the outlet chamber a variety of constructive solutions are conceivable. For example, solutions with membranes acted upon by the pressure in the outlet chamber or the like would be conceivable.

A particularly expedient solution provides that the valve body is coupled to a pressure which is acted upon by the pressure in the outlet chamber and is guided in a switching cylinder housing, which then actuates the valve body.

With regard to the application of the switching piston, it has proven to be advantageous if the switching piston and the switching cylinder housing enclose a switching cylinder chamber and when the pressure in the switching cylinder chamber is controllable.

Furthermore, it is favorable for structural reasons, when the valve body and the switching piston form a unit which is guided in the switching cylinder housing.

Furthermore, it is advantageous in such a servo valve, if this comprises a controllable by the control valve control.

Such a control valve is formed, for example, as a fast-reacting, electrically actuated solenoid valve or similarly constructed valve.

To operate the servo valve is provided in an advantageous embodiment, that the control valve opens or closes a connection channel between the control cylinder chamber and the outlet, so that in a simple way there is the possibility to pressurize the control piston with under pressure in the outlet chamber medium.

In order to achieve the highest possible natural frequency and thus short switching time in such a servo valve, it is preferably provided that the natural frequency of the unit consisting of switching piston, valve body and elastic energy storage at least equal to the natural frequency of the switching valve.

Such a high natural frequency of the switching valve can be achieved in particular when the switching piston is made of a lightweight construction material.

Such a lightweight material may for example be a light metal or a plastic, for example, a fiber-reinforced plastic.

A further advantageous embodiment of the control piston provides that this is designed as a hollow body, so that also by a high natural frequency of the unit of control piston, valve body and elastic energy storage device can be achieved.

Further features and advantages of the invention are the subject of the following description and the drawings of some embodiments.

Fig. 1

eine schematische Darstellung einer erfindungsgemäßen Kälteanlage;

Fig. 2

einen Querschnitt längs Linie 2-2 durch ein Kältemittelverdichter der erfindungsgemäßen Kälteanlage;

Fig. 3

einen Schnitt durch ein Schaltventil integriert in einen Zylinderkopf in der geöffneten Stellung eines Ventilkörpers des Schaltventils;

Fig. 4

einen Schnitt ähnlich Fig. 3 in einer geschlossenen Stellung des Ventilkörpers des Schaltventils;

Fig. 5

eine schematische Darstellung eines Schaltintervalls umfassend ein Öffnungsintervall und ein Schließintervall;

Fig. 6

eine schematische Darstellung eines Verhaltens der Temperatur des Verdampfers in der Kälteanlage bei Unterbrechung der Verdichtung von Kältemittel;

Fig. 7

einen Schnitt ähnlich Fig. 3 durch ein zweites Ausführungsbeispiel eines erfindungsgemäßen Kältemittelverdichters und

Fig. 8

einen Schnitt ähnlich Fig. 4 durch das zweite Ausführungsbeispiel eines erfindungsgemäßen Kältemittelverdichters.

In the drawing show:

Fig. 1

a schematic representation of a refrigeration system according to the invention;

Fig. 2

a cross section along line 2-2 through a refrigerant compressor of the refrigeration system according to the invention;

Fig. 3

a section through a switching valve integrated in a cylinder head in the open position of a valve body of the switching valve;

Fig. 4

a section similar to Figure 3 in a closed position of the valve body of the switching valve.

Fig. 5

a schematic representation of a switching interval comprising an opening interval and a closing interval;

Fig. 6

a schematic representation of a behavior of the temperature of the evaporator in the refrigeration system in the interruption of the compression of refrigerant;

Fig. 7

a section similar to FIG. 3 by a second embodiment of a refrigerant compressor according to the invention and

Fig. 8

a section similar to FIG. 4 by the second embodiment of a refrigerant compressor according to the invention.

An exemplary embodiment of a refrigeration system according to the invention, designated as a whole by 10, comprises a refrigerant compressor 12, from whose high-pressure connection 14 a line 16 leads to a condenser designated as a whole by 18, in which the compressed refrigerant condenses due to heat dissipation.

From the condenser 18 liquid refrigerant flows in a line 20 to a collector 22, in which the liquid refrigerant collects and from which this then flows via a line 28 to an expansion valve 30 for an evaporator 32.

After flowing through the evaporator 32, the vaporized refrigerant flows via a line 34 to a low pressure port 36 of the refrigerant compressor 12th

As shown in FIG. 2, the refrigerant compressor 12 according to the invention is designed as a reciprocating compressor and comprises a compressor housing 40, in which two cylinder banks 42a and 42b arranged in a V-shape are provided, each of which comprises at least one, in particular two or more cylinder units 44.

Each of these cylinder units 44 is formed from a cylinder housing 46, in which a piston 48 is oscillated by the fact that the piston 48 is driven by a connecting rod 50, which in turn sits on an eccentric 52 of an eccentric shaft 54 which is driven for example by an electric motor 55 is.

The cylinder housing 46 of each of the cylinder units 44 is closed by a valve plate 56 on which a cylinder head 58 is disposed.

Preferably, the valve plate 56 covers not only a cylinder housing 46 of a cylinder bank 42, but all cylinder housing 46 of the respective cylinder bank 42 and in the same way, the cylinder head 58 also engages over all the cylinder housing 46 of the respective cylinder bank 42nd

The compressor housing 40 further comprises an inlet channel 60 communicating with the low-pressure connection 36, which is integrated, for example, in the compressor housing 40.

As shown enlarged in FIG. 3, each cylinder bank 42 is associated with a switching valve 70, designated as a whole, which serves to convey an inlet flow 74 that passes from the inlet channel 60 into the respective cylinder head 58 and into an inlet chamber 72 thereof through the valve plate 56 of refrigerant to break.

When the switching valve 70 is opened, the inlet flow 74 has the possibility, via an inlet opening 76 provided in the valve plate 56 and an inlet valve 78 provided on the valve plate 56, into a cylinder chamber bounded by the respective piston 48 and the respective cylinder housing 46 and the valve plate 56 80 to be compressed therein by the oscillating movement of the piston 48, so that via an outlet opening 82 and an outlet valve 84, an outlet stream 86 exits the cylinder chamber 80 and enters an outlet chamber 88 of the cylinder head 58.

The switching valve 70 is formed as a servo valve, which is integrated in the cylinder head 58 and has a valve body 90, with which an opening provided in the valve plate 56 Eihströmöffnung 92 of the inlet chamber 72 is closed.

The valve body 90 is further arranged on a switching piston 94, which is guided in a switching cylinder housing 96, so that the switching piston 94 is movable in the direction of the valve plate 56 by pressure present in a switching cylinder chamber 98 to close the inflow opening 92 in the same.

A switching cylinder unit 100 formed from the switching cylinder housing 96, the switching piston 94 and the switching cylinder chamber 98, which is integrated in the cylinder head 58, is controllable via a control valve 110 which comprises an electromagnetically movable control piston 112, with which a control valve seat 114 is closable, the control piston 112 and the control valve seat 114 are provided for interrupting or releasing a connection between a pressure channel 116 leading to the outlet chamber 88 and a pressure supply channel 118 leading to the switching cylinder chamber 98.

When the connection between the high-pressure passage 116 and the pressure supply passage 118 is released, the switching cylinder chamber 98 is under the high pressure prevailing in the discharge chamber 88 and consequently the switching piston 94 moves in the direction of the valve plate 56 and presses the valve body 90 against the latter, around the inlet opening 92 in the valve plate 56 to close.

In this case, the force acting on the switching piston 94 by the high pressure in the switching cylinder chamber 98 counteracts the force of an elastic force accumulator 120 which is supported on the switching cylinder housing 96 on the one hand and on the other hand acts on the switching piston 94 such that it moves away from the valve plate 56 and thus moves the valve body 90 into a position releasing the inlet opening 92.

In particular, the switching piston 94 is provided with a pressure relief passage 122 which leads from an opening facing the switching cylinder chamber 98 to an outlet opening 124 shown in FIG. 4, which closes the valve body 90 and the closing position 92 in the inlet opening 92 Switching piston 94 opens into the inlet chamber 72. The pressure relief passage 124 thereby causes the pressure in the switching cylinder chamber 98 to rapidly collapse when the connection between the high-pressure passage 116 and the pressure feed passage 118 is interrupted, thus releasing the switching piston 94, together with the valve body 90, into the inlet opening 92 under the action of the elastic force accumulator 120 , move in Fig. 3 shown position.

The switching valve 70 can be controlled by a controller 130 shown in FIG. 1 such that it closes and opens the switching valve 70 in continuously successive switching intervals SI, wherein each of the switching intervals SI has an opening interval O, in which the valve body 90 is in its releasing position Passage of the inlet stream 74 through the inlet opening 92 allows, and a closing interval S, in which the valve body 90, as shown in Fig. 4, in its closing position, the flow of the inlet stream 74 through the inlet opening 92 blocked.

Within the duration of the respective switching interval SI, the duration of the opening interval O and the closing interval S relative to each other can now be set variably in all partial load ranges, so that either the opening interval O is greater than the closing interval or vice versa.

In the extreme case, the opening interval O may substantially extend over the entire duration of the switching interval SI, while the closing interval S is arbitrarily small, or vice versa, the closing interval S may extend substantially over the entire duration of the switching interval SI, so that the opening interval O becomes arbitrarily small.

Since in the refrigeration system 10 according to the invention via the expansion valve 30 is generally carried out an evaporation of liquid refrigerant, an interruption of the compression of refrigerant through the refrigerant compressor 12 leads to an increase in the temperature T in the evaporator 32nd

However, the system is provided with a reaction inertia, so that when the extraction of refrigerant from the evaporator 32 is interrupted, the temperature T of the evaporator 32 does not rise immediately but, as shown in FIG. 6, requires a time Z to increase by one value D to rise.

As long as the value D is less than 10% of an outlet temperature T _{A of} the evaporator, these fluctuations are irrelevant to the function of the refrigeration system according to the invention.

For this reason, the switching interval SI is set to be shorter than the time Z that elapses until the temperature T of the evaporator 32 rises from a temperature T _{A of} the evaporator 32 by a value D of about 10% better about 5%, when there is a sudden interruption in the extraction of refrigerant from the evaporator 32 and the supply of high pressure medium at the high pressure port 14.

This ensures that the opening intervals O and the closing intervals S within the respective switching interval SI have an insignificant effect on the function of the refrigeration system and only lead to slight temperature fluctuations of the evaporator 32 of the refrigeration system according to the invention.

Usually, the durations of the switching intervals SI are shorter than about 10 seconds, more preferably less than about 2 seconds.

On the other hand, to ensure sufficient opening intervals O, the switching intervals are longer than about 0.02 second, more preferably longer than 0.05 second, and preferably longer than 0.1 second.

A preferred operating range provides switching intervals SI whose duration is between 0.1 and 10 seconds.

In order to ensure such short switching intervals SI, it is preferably provided that the switching pistons 94 together with the valve body 90 and the elastic force accumulators 120 have a natural frequency higher than the frequency corresponding to the maximum switching intervals SI, so that the switching pistons 94 are able to realize the opening intervals O and the closing intervals S substantially instantaneously within the switching intervals SI.

Preferably, the natural frequencies of the systems of switching piston 94, valve body 90 and elastic energy storage device 120 by a factor of at least 5 or even better at least 10 higher than the switching intervals SI corresponding frequencies.

To realize this, it is expediently provided that the switching pistons 94 are made of a lightweight construction material, for example light metal or plastic, in order to move small masses.

In a second embodiment of a refrigerant compressor according to the invention, shown in FIGS. 7 and 8, the switching pistons 94 'are designed as hollow bodies in order to achieve the lowest possible mass and thus the highest possible natural frequency.

The solution according to the invention provides, for example, such a switching valve 70 per cylinder bank, so that there is the possibility of correspondingly switching off the inlet flow for all cylinder units 44 of a cylinder bank 42.

However, it is also conceivable to arrange such a switching valve 70 so that it controls the inlet flow 74 to all cylinder units 44 of the entire refrigerant compressor.

In an advantageous solution, the controller 130 controls all cylinder units 44 at the same switching intervals, at least in a lower part-load range, that is, in a range between about 1% and about 30% of the maximum mass flow.

But even in higher partial load ranges, for example, in an upper part load range between about 30% and 100% of the maximum mass flow, it is advantageous to operate all cylinder units 44 with the same switching intervals to avoid balancing problems of the reciprocating compressor, resulting in a complete shutdown of cylinder units 44.

The controller 130 is now able to control the switching valve 70 in an operation of the refrigerant compressor 12 in the full load range such that the valve body 90 is constantly in the inlet opening 92 releasing position, so that the inlet flow 74 to all cylinder units 44 of the respective cylinder bank 42nd can flow.

In this case, the maximum mass flow of refrigerant is compressed to high pressure H.

It is also possible in a zero-load range to control the switching valve 70 such that the valve body 90 is constantly in its position closing the inflow opening 92. In this case, essentially no mass flow of refrigerant is compressed. Only the mass flow flowing through the pressure channel 116 and the pressure supply channel 118 and the pressure relief channel 122 is compressed.

In the partial load range, the controller 130 is capable of continuously adjusting any partial load by variably setting the duration of the opening interval O and the duration of the closing interval S which add to the period of the switching interval SI in the desired ratio.

In this case, the switching interval SI can be the same in all partial load ranges.

However, it is also conceivable to vary the switching interval SI either proportionally or in individual steps depending on the rotational speed of the eccentric shaft 54 and thus of the electric motor 55.

For example, the variation of the switching interval SI occurs so that at low speed of the electric motor, the switching intervals SI are long and at high speed of the electric motor, the switching intervals are shorter.

The advantage of the solution according to the invention is the fact that in the reciprocating compressor, the power consumption is proportional to the mass flow and thus with a reduction of the mass flow through successive opening intervals O and closing intervals S in the partial load range, the possibility to reduce the power consumption of the reciprocating compressor.

In addition, the solution according to the invention makes it possible to configure the start-up process of the refrigerant compressor 12 by controlling the mass flow rate in such a way that the risks from boiling-out refrigerant are minimized.

Claims (23)

Comprising refrigerant compressor for refrigeration systems
at least one cylinder unit (44) having a cylinder housing (46) and a piston (48) oscillating in the cylinder housing (46), a cylinder head (58) with one of an inlet stream (74) of the at least one cylinder unit (44) throughflowed inlet chamber (72) and with an outlet chamber (88) penetrated by an outlet flow (86) of the at least one cylinder unit (44)
and a switching valve (70) for interrupting the inlet flow (74), characterized in that a control (130) is provided for driving the switching valve (70), which for operating the refrigerant compressor (12) in a lower part-load range, the switching valve (70) operating in successive switching intervals (SI), each comprising an opening interval (O) and a closing interval (S) of the switching valve (70), which are shorter than a shortest time (Z), after which a temperature (T) of an evaporator (32) in the working refrigeration system (10) has increased by approximately 10% when the inlet flow (74) is interrupted. Refrigerant compressor according to the preamble of claim 1 or claim 1, characterized in that a control (130) for driving the switching valve (70) is provided, which for operating the refrigerant compressor (12) in a lower part-load range, the switching valve (70) in successive Switching intervals (SI) that are shorter than about 10 seconds. Refrigeration compressor according to claim 2, characterized in that the switching intervals are shorter than about 2 seconds. Refrigeration compressor according to one of the preceding claims, characterized in that the switching intervals (SI) are longer than about 0.02 seconds. Refrigerant compressor according to claim 4, characterized in that the switching intervals (SI) are longer than about 0.05 seconds. Refrigeration compressor according to claim 5, characterized in that the switching intervals (SI) are longer than about 0.1 seconds. Refrigerant compressor according to one of the preceding claims, characterized in that the switching intervals (SI) correspond to a switching frequency which is smaller than a natural frequency of the switching valve (70). Refrigerant compressor according to claim 7, characterized in that the switching intervals (SI) correspond to a switching frequency which is smaller than a natural frequency of the switching valve (70) by more than a factor of 5. Refrigeration compressor according to one of the preceding claims, characterized in that the controller (130) in the lower part load range all cylinder units (44) in the switching intervals (SI) operates. Refrigerant compressor according to claim 9, characterized in that the controller (130) in the entire partial load range, all cylinder units (44) in the switching intervals (SI) operates. Refrigerant compressor according to one of the preceding claims, characterized in that the controller (130) operates with time-constant switching intervals (SI). Refrigerant compressor according to one of the preceding claims, characterized in that the controller (130) varies the switching intervals (SI) in accordance with a drive speed of the refrigerant compressor (12). Refrigerant compressor according to one of the preceding claims, characterized in that the switching valve (70) is a servo valve. A refrigerant compressor according to claim 13, characterized in that the servo-valve (70) comprises a valve body (90) operable by a pressure related to the pressure in the discharge chamber (88). Refrigerant compressor according to claim 14, characterized in that the valve body (90) is acted upon by an opposite to the action of the pressure on the valve body (90) acting elastic force accumulator (120). Refrigerant compressor according to one of claims 14 or 15, characterized in that the valve body (90) is coupled to a pressure associated with the pressure in the outlet chamber (88) pressure and in a switching cylinder housing (96) guided switching piston (94) is coupled. Refrigerant compressor according to one of claims 14 to 16, characterized in that the switching piston (94) and the switching cylinder housing (96) enclose a switching cylinder chamber (98) and that the pressure in the switching cylinder chamber is controllable. Refrigerant compressor according to one of claims 14 to 17, characterized in that the valve body (90) and the switching piston form a unit which is guided in the switching cylinder housing (96). Refrigerant compressor according to one of claims 13 to 18, characterized in that the servo valve (70) comprises a controllable by the controller (130) control valve (110). Refrigeration compressor according to claim 19, characterized in that the control valve (110) opens or closes a connection channel (116, 118) between the switching cylinder chamber (98) and the outlet chamber (88). Refrigerant compressor according to one of claims 15 to 20, characterized in that the natural frequency of the unit of switching piston (94), valve body (90) and elastic energy accumulator (120) at least equal to the natural frequency of the switching valve (70). Refrigerant compressor according to one of claims 14 to 21, characterized in that the switching piston is made of a lightweight material. Refrigerant compressor according to one of claims 14 to 22, characterized in that the switching piston (94 ') is designed as a hollow body.

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