ELECTRONIC CONTROL DEVICE FOR A REFRIGERANT COMPRESSOR

Abstract

The invention relates to an electronic control device (13) for a refrigerant compressor, comprising at least: a drive unit (18); and a compression mechanism (5) which is actively connected to the drive unit (18), with at least one piston (9) which is driven by a crankshaft (6) and moves back and forth between a lower and an upper dead point in a cylinder of a cylinder block (8), in which the electronic control device (13) is designed to detect, control and/or regulate the rotational speed () of the drive unit (18) and to at least approximately detect the piston position, and in which the electronic control device (13) is designed to drive the compression mechanism (5) by means of the drive unit (18) in such a way that at least one drive angle segment () and at least one transit angle segment () is provided for the duration of a regulating time interval (t) comprising more than one crankshaft rotation, for a plurality of crankshaft rotations, preferably for each crankshaft rotation of the regulating time interval (t), and the compression mechanism (5) is subject to a positive operating torque (Bm) during the at least one drive angle segment (), and to a smaller positive operating torque (Bmv) compared to the positive operating torque (Bm) or to no positive operating torque (Bm) during the at least one transit angle segment ().

Claims

1. An electronic control device for a refrigerant compressor, comprising at least a drive unit, a compression mechanism that is actively connected to the drive unit, with at least one piston that is driven by a crankshaft and moves back and forth between a lower and an upper dead point in a cylinder of a cylinder block, wherein the electronic control device is designed to detect and to control and/or regulate the rotational speed () of the drive unit, and to detect the piston position at least approximately, wherein the electronic control device as designed to drive the compression mechanism by means of the drive unit such that, for the duration of one regulating time interval (t) having more than one crankshaft rotation, for multiple crankshaft rotations, at least one drive angle segment () and at least one transit angle segment () are provided, and wherein the compression mechanism is exposed during the at least one drive angle segment () to a positive operating torque (Bm), and during the at least one transit angle segment () to a reduced positive operating torque (Bmv) relative to the positive operating torque (Bm), or to no positive operating torque (Bm).

2. The electronic control device of a refrigerant compressor according to claim 1, wherein the ratio between positive operating torque (Bm) and reduced positive operating torque (Bmv) is 1/0.2.

3. The electronic control device according to claim 1, wherein it is designed to provide multiple drive angle segments (.sub.n) and multiple transit angle segments (.sub.n) alternately during one crankshaft rotation.

4. The electronic control device according to claim 1, wherein it is designed to provide the drive angle segment or segments (, .sub.n) with positive operating torque (Bm) when the piston is located between a lower and an upper dead point in a compression phase.

5. The electronic control device according to claim 4, wherein it is designed to provide exactly one drive angle segment () and one transit angle segment () during one complete crankshaft rotation.

6. The electronic control device according to claim 1, wherein it is designed to provide the transit angle segment or segments (, .sub.n) with reduced positive operating torque (Bmv) or with no positive operating torque when the piston is located between an upper and a lower dead point in an intake phase.

7. The electronic control device according to claim 1, wherein it is designed to apply a braking torque to the compression mechanism during the transit angle segment or segments (, .sub.n).

8. The electronic control device according to claim 1, wherein it is designed to reduce or increase the rotational speed () of the drive unit during the regulating time interval (t).

9. The electronic control device according to claim 1, wherein it is designed to switch the drive unit to a powerless state at a switch-off time (AZ), so that this drive unit no longer generates positive operating torque (Bm), in order to let the compression mechanism run out to a standstill.

10. The electronic control device according to claim 9, wherein it is designed to provide the regulating time interval (t) immediately before the switch-off time (AZ).

11. The electronic control device according to claim 9, wherein it is designed to select the switch-off time (AZ) so that the kinetic energy of the compression mechanism at the switch-off time (AZ) is sufficient to enable the piston to overcome at least the next upper dead point following the switch-off time (AZ).

12. The electronic control device according to claim 9, wherein it is designed to select the switch-off time (AZ) so that the piston of the compression mechanism comes to a standstill after reaching the next upper dead point following the switch-off time (AZ) and before reaching the lower dead point immediately following this upper dead point.

13. The electronic control device according to claim 9, wherein it is designed to select the switch-off time (AZ) so that the piston of the compression mechanism comes to a standstill after the next upper dead point following the switch-off time (AZ) and before reaching a crank angle of 220 following this next upper dead point.

14. The electronic control device according to claim 1, wherein it is designed to form the positive operating torque (Bm) during the at least one drive angle segment () and/or the reduced positive operating torque (Bmv) during the at least one transit angle segment (), each with varying magnitude.

15. The electronic control device according to claim 14, wherein it is designed to form the common profile of the positive operating torque (Bm) and the reduced positive operating torque (Bmv) for each crankshaft rotation so that it corresponds to the load torque (Lm) acting on the compression mechanism during this crankshaft rotation.

16. A hermetically encapsulated refrigerant compressor with an electronic control device according to claim 1.

17. The hermetically encapsulated refrigerant compressor according to claim 16, wherein an acceleration sensor is provided on the drive unit and/or a pressure sensor is provided in the cylinder of the cylinder block.

18. A method for regulating a reciprocating piston refrigerant compressor, whose compression mechanism is driven with an operating torque by means of a drive unit, comprising the following steps during a regulating time interval (t) having more than one crankshaft rotation; for multiple crankshaft rotations of the regulating time interval (t), the following is performed each time; detect the position of the crankshaft or the piston of the reciprocating piston refrigerant compressor; compare the detected position to at least one prespecified reference position; starting from the at least one prespecified reference position, drive the compression mechanism with a positive operating torque (Bm) for the duration of at least one drive angle segment () of one crankshaft rotation; drive the compression mechanism with a reduced positive operating torque (Bmv) relative to the positive operating torque (Bm) or no positive operating torque for the duration of at least one transit angle segment ().

19. The method according to claim 18, wherein the ratio between positive operating torque (Bm) and reduced positive operating torque (Bmv) is 1/0.2.

20. The method according to claim 18, wherein multiple reference positions are provided during one crankshaft rotation.

21. The method according to claim 18, wherein exactly one drive angle segment () and one transit angle segment () are provided during one crankshaft rotation.

22. The method according to claim 18, wherein the at least one reference position is provided during a crank angle from 220 to 360.

23. The method according to claim 18, wherein the rotational speed of the reciprocating piston refrigerant compressor is reduced or increased during the regulating time interval (t).

24. The method according to claim 18, wherein the regulating time interval (t) is provided immediately before a switch-off time (AZ), after which the drive unit is switched to a powerless state.

25. The electronic control device of claim 1, wherein the multiple crankshaft rotations comprise each crankshaft rotation of the regulating time interval (t).

26. The electronic control device of claim 2, wherein the reduced operating torque is 1/0.1.

27. The electronic control device of claim 2, wherein the reduced operating torque is 1/0.03.

28. The electronic control device of claim 5, wherein the exactly one drive angle segment () is provided during a crank angle from 220 to 360.

29. The electronic control device of claim 5, wherein the exactly one drive angle segment () is provided during a crank angle from 270 to 360.

30. The electronic control device of claim 10, wherein the regulating time interval (t) is begun when a signal of the electronic control device of a refrigerator signals that a target temperature has been reached in a cooling compartment.

31. The method of claim 18, wherein the multiple crankshaft rotations comprise all crankshaft rotations.

32. The method of claim 19, wherein the reduced operating torque (Bmv) is 1/0.1.

33. The method of claim 19, wherein the reduced operating torque (Bmv) is 1/0.03.

34. The method of claim 22, wherein the crank angle comprises 270 to 360.

35. The method of claim 24, wherein the regulating time interval (t) begins when a signal of the electronic control device of a refrigerator signals that a target temperature has been reached in the cooling compartment.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0071] The invention will now be explained in more detail using one or more embodiments with reference to the following figures.

[0072] FIG. 1, a schematic representation of a reciprocating piston refrigerant compressor in a refrigerant circuit,

[0073] FIG. 2, a schematic view of a compression mechanism,

[0074] FIG. 3, a diagram relating to the load torque profile and operating torque profile with respect to the crank angle in a reciprocating piston refrigerant compressor according to the prior art,

[0075] FIG. 4, a diagram relating to the angular acceleration of the crankshaft with respect to the crank angle in a reciprocating piston refrigerant compressor according to the prior art,

[0076] FIG. 5, a diagram relating to the load torque profile and operating torque profile with respect to the crank angle using an electronic control device according to the invention,

[0077] FIG. 6, a diagram relating to the angular acceleration of the crankshaft with respect to the crank angle using an electronic control device according to the invention,

[0078] FIG. 7, a diagram relating to the load torque profile and operating torque profile with respect to the crank angle with mirrored operating torque,

[0079] FIG. 8, a diagram relating ,h- angular acceleration of the crankshaft with respect to the crank angle with mirrored operating torque,

[0080] FIG. 9, a diagram relating to the load torque profile and operating torque profile with respect to the crank angle during a stopping process, and

[0081] FIG. 10, a diagram relating to the load torque profile and operating torque profile with respect to time during a stopping process.

[0082] FIG. 1 shows a schematic diagram of a reciprocating piston refrigerant compressor 1 connected to an electrical power supply 12 and regulated by means of an electronic control device 13 in a known coolant circuit with a condenser 2 of a throttle device 3 and an evaporator 4. The refrigerant removes heat from the cooling compartment in the evaporator 4, which cools the compartment. The evaporated refrigerant is compressed, by means of the compression mechanism 5 of the reciprocating piston refrigerant compressor 1, to a higher temperature, and consequently becomes a liquid again in the condenser 2, in order to be finally fed via the throttle device 3 back to the evaporator 4 of the cooling compartment.

[0083] In the present embodiment, the electronic control device 13 of the refrigerant compressor I communicates with an electronic control device 14 of a refrigerator 15. However, such a communications ability is not considered essential to the invention, because it is also conceivable that the electronic control device 13 communicates with a refrigerator 15 that itself does not have its own electronic control device, but instead only a thermostat.

[0084] FIG. 2 shows a schematic view of the compression mechanism 5 consisting of a crankshaft 6 driven by means of a drive unit 18, a connecting rod 7, and also a piston 9 that can move back and forth in a cylinder block 8. The compression mechanism 5 is supported by means of spring element 10 in a housing 11, wherein this spring element 10 is intended to absorb and compensate for oscillations occurring in the unit consisting of compression mechanism 5 and drive unit 18 due to the rotation of the crankshaft 6 and movements of the piston 9.

[0085] The drive unit 18 control led by the electronic control device 13 is a drive unit 18 with variable rotational speed, typically a brushless direct-current motor, whose rotational speed can be regulated by means of the electronic control device 13. The detection of the instantaneous rotational speed required for regulating the rotational speed is performed by detecting the countervoltage (induction countervoltage) induced in the motor winding, so that no other sensors are required, even though the electronic control device 13 according to the invention obviously can also interact with separate sensors for measuring the rotational speed, for example, Hall sensors.

[0086] During the operating period of a reciprocating piston refrigerant compressor with variable rotational speed, a distinction is to be made between basically 3 phases:

[0087] the starting phase

[0088] the normal regulated operating phase

[0089] the stopping process.

[0090] The basic condition is a cooling compartment temperature (=target temperature) of the refrigerator 15 that can be preselected by the user of a refrigerator 15 within limits. If a cooling compartment cooled to the target temperature is assumed and a load is placed in the refrigerator 15 or the refrigerator door is opened, warm air flows into the cooling compartment. The electronic control device 14 of the refrigerator 15 detects that the cooling compartment temperature is increased and sends a signal (usually a frequency signal) to the electronic control device 13 of the refrigerant compressor 1, with which this control device is informed that cooling power is needed, whereupon this control device controls and regulates the refrigerant compressor 1 in accordance with its programming, in order to supply (more or less) cooling power.

[0091] In the example concerning an object, the electronic control device 13 of the refrigerant compressor 1 starts this compressor order to compress the refrigerant and remove heat from the cooling compartment and in order to restore the target temperature. This startup initiates the starting phase. Here, the refrigerant compressor 1, more specifically its drive unit 18, is accelerated to a certain rotational speed prespecified by the electronic control device 13 of the refrigerant compressor 1. Reaching this rotational speed ends the starting phase. At this time, the target temperature has usually not yet been reached.

[0092] The refrigerant compressor then transitions into the normal regulated operating phase. This continues as long as the refrigerant compressor 1 is switched on or, expressed somewhat more technically, as long as energy is supplied to the refrigerant via the compression mechanism 5 and the drive unit 18 of the refrigerant compressor 1 generates an operating torque. The compression mechanism 5 can rotate during this normal regulated operating phase at a different rotational speed, according to whether more or less heat is to be removed from the cooling compartment. For example, if someone opens the doors of the refrigerator 15 during such a normal regulated operating phase, due to the incoming warm air, the electronic control device 14 of the refrigerator 15 demands more cooling power from the refrigerant compressor 1, so that the electronic control device 13 of the refrigerant compressor 1 increases the rotational speed of the drive unit 18, and thus of the compression mechanism 5, in order to be able to dissipate the heat flowing into the cooling compartment.

[0093] Increasing the rotational speed is associated with increased energy demands on the refrigerant compressor 1. If the electronic control device 14 of the refrigerator 15 detects that the current cooling compartment temperature is approaching the target temperature, the electronic control device 14 of the refrigerator 15 will send a corresponding signal to the electronic control device 13 of the refrigerant compressor 1, in order to request less cooling power and to not shoot past the target temperature and to approach this target temperature slowly. The electronic control device 13 of the refrigerant compressor 1 will, in turn, reduce the rotational speed of the drive unit 18 of the compression mechanism 5 due to this request.

[0094] If the electronic control device 14 of the refrigerator 15 detects that, in the meantime, the cooling compartment temperature has increased again, because, for example, new loads were placed in the cooling compartment, then the electronic control device H of the refrigerator 15 will again request more cooling power from the electronic control device 13 of the refrigerant compressor 1, so that this will again increase the rotational speed of the drive unit 18 of the compression mechanism 5.

[0095] If, after an appropriate duration of the normal regulated operating phase, the target temperature is reached, the electronic control device 14 of the refrigerator 15 sends a signal to the electronic control device 13 of the refrigerant compressor 1, with which this control device is informed that the target temperature has been reached. Then the electronic control device 13 of the refrigerant compressor 1 switches off the drive unit 18 (switch-off time AZ). Switching off the drive unit 18 has the result that the compression mechanism 5 is located together with the drive unit 18 in a driveless state, and continues to rotate only due to mass inertia until the rotational speed is 0. Colloquially, it could also be said that the refrigerant compressor runs out.

[0096] During the operation of the compression mechanism, shocks can be generated that are exerted by the load torque during the compression phase on the compression mechanism 5 and that repeat with each crankshaft rotation and can coincide at low rotational speeds with the natural frequency of the oscillation system formed by the spring element 10, whereby the deflection of this spring element increases such that it can lead to contact between the unit consisting of compression mechanism 5 and drive unit 18 with the housing 11, whereby undesired noise emissions are generated.

[0097] In addition, during the stopping process, when the drive unit 18 no longer generates operating torque, a reversal of the direction of rotation of the compression mechanism 5 can occur, whereby an additional shock is exerted on the compression mechanism that likewise results in an undesirably strong deflection of the spring element 11 [sic; 10], with the consequence that this reversal of the direction of rotation also produces the risk that the unit consisting of the compression mechanism 5 and drive unit 18 come into contact with the housing 11 and produce sound emissions.

[0098] In summary, it can be stated that low rotational speeds, independent of whether the refrigerant compressor is in the starting phase, the normal regulated operating phase, or the stopping process, always produce the risk that the oscillation system formed by the spring element 10 will be excited in the range of its natural frequency and will therefore produce the described contacts that produce noise between the unit consisting of the compression mechanism 5 and drive unit 18 and housing 11.

[0099] FIG. 3 shows a diagram of the profile of the load torque Lm with respect to the crank angle during a normal regulated operating phase of a reciprocating piston refrigerant compressor known from the prior art, whose drive unit 18 drives the compression mechanism 5 with an operating torque Bm. Here, it was assumed that the crankshaft rotates in the clockwise direction. The direction of rotation thus goes from 0 (upper dead point) to 360 (upper dead point).

[0100] As shown from the diagram, the load torque Lm is greatest shortly before the piston 9 reaches the upper dead point in the compression phase, that is, at approx. 330, and is negative at the beginning of the intake phase, that is, in the present case, at approx. 10, i.e., the load Lm in this section of the intake phase (re-expansion phase) supports the rotation of the compression mechanism 5.

[0101] FIG. 4 shows a diagram in which the angular acceleration {acute over ()} of the crankshaft 6 with respect to the crank angle is plotted as a result of the ratio between the load torque Lm and operating torque Bm as shown in FIG. 3.

[0102] It can be seen that the maximum negative angular acceleration {acute over ()} of the crankshaft 6 occurs at the time of the maximum load torque Lm, while the angular acceleration {acute over ()} is positive during the intake phase and at the beginning of the compression phase up to approx. 250, so that the rotational speed of the crankshaft 6 is increased in this crank angle range.

[0103] The angular acceleration {acute over ()} here varies in the present embodiment between the values of approx. 3400 rad/s.sup.2 and approx. +1000 rad/s.sup.2. This circumstance has the result that, despite the applied operating torque Bm with respect to one crankshaft rotation, the rotation of the compression mechanism 5, especially the crankshaft 6, is very uneven, and in the range of a crank angle of approx. 330 the load torque Lm exerts a shock on the compression mechanism 5, wherein this shock repeats for every crankshaft rotation and the oscillations already described in detail above are generated, with the similarly already described negative effects, wherein the load torque Lm increases with decreasing rotational speed .

[0104] In practice, reciprocating piston refrigerant compressors are therefore not operated at rotational speeds that are in the range of the natural frequencies of the oscillation system.

[0105] To nevertheless enable operation even at low rotational speeds without the risk of disruptive noise emissions, it is provided according to the invention that the electronic control device 13 is designed so that it actively varies the operating torque Bin during a regulating time interval t at least once per crankshaft rotation as a function of the crank angle, by increasing the voltage supply of the drive unit 18 during a drive angle segment relative to the rest of the crankshaft rotation.

[0106] FIG. 5 shows the profile of the load torque Lm known from FIG. 3 during one crankshaft rotation, but with schematically shown operating torque Bm that is applied according to the invention by the electronic control device 13 and is regulated so that exactly one drive angle segment is provided, during which the drive unit 18 drives the compression mechanism 5 with a positive operating torque Bm, and exactly one transit angle segment , during which the drive unit 18 drives the compression mechanism 5 with a reduced positive operating torque Bmv relative to the positive operating torque or, alternatively, does not drive at all (see dashed line of Bmv), wherein the transitions between the positive operating torque Bm and the reduced operating torque Bmv are indeed drawn, but are not provided with an extra reference symbol, but instead are allocated to the positive operating torque Bm for the sake of simplicity.

[0107] The ratio between the positive operating torque Bm and reduced positive operating torque Bmv is preferably 1/0.03 in this embodiment. Typical pressure ratios in reciprocating piston refrigerant compressors, however, also permit ratios from 1/0.1 or 1/0.2 without deviating from the concept of the invention.

[0108] In FIG. 5, the beginning of the compression phase KP is also marked with the reference symbol 16 and the beginning of the intake phase is marked with the reference symbol 17. As can also be seen from FIG. 5, the electronic control device 13 of the refrigerant compressor 1 regulates the drive unit 18 so that the drive angle segment is completely or for the most part within the compression phase. Depending on the (average) magnitude of the positive operating torque Bm and thus on the output capability of the drive unit 18, the drive angle segment can be greater or less than shown in the embodiment.

[0109] As can be seen from FIG. 6, which shows a diagram relating to the angular acceleration {acute over ()} of the crankshaft 6 with respect to the crank angle for the use of an electronic control device 13 according to the invention with an operating torque profile according to FIG. 5, this driving of the compression mechanism 5, both applied over a defined crank angle and also controlled with respect to magnitude during one crankshaft rotation with two different operating torques Bm and Bmv, leads to the result that the angular acceleration {acute over ()} of the crankshaft 6 with respect to the crank angle (and thus also the rotational frequency with respect to the crank angle) has a significantly more even profile than is the case for conventional reciprocating piston refrigerant compressors according to the prior art and shown in FIG. 4. In the present embodiment, the rotational frequency in the crank angle range between 30 and 210 is approximately constant, so the crankshaft experiences no acceleration. In the range of the crank angle between 210 and 360, the crankshaft is initially accelerated and then braked again, so that the evenness of the rotational frequency of the crankshaft is influenced only insignificantly and thus also the shocks acting on the compression mechanism are significantly lower than was previously the case.

[0110] In another variant of the invention, it can be provided that the profile of the positive operating torque Bm and the reduced positive operating torque Bmv together, with which the compression mechanism 5 is driven, corresponds practically to the profile of the load torque Lm, to which the compression mechanism 5 is exposed, but with the opposite sign and possibly with larger or smaller magnitudes in some sections, according to whether the rotational speed of the compression mechanism should be kept constant, increased, or reduced.

[0111] FIG. 7 shows a matched combination of positive operating torque Bm and reduced positive operating torque Bmv. As can be seen from the diagram, the positive operating torque Bm varies both in the drive angle segment and also in the transit angle segment , so that the profile of the load torque Lm is reproduced, but with the opposite sign.

[0112] FIG. 8 shows that, in this case, the angular acceleration {acute over ()} of the crankshaft 6 is constant, whereby a constant rotational frequency is produced with respect to the crank angle and thus a constant rotational speed is also produced.

[0113] Another advantage of the electronic control device 13 according to the invention is the ability to optimize the stopping process of a reciprocating piston refrigerant compressor 1, in that this compressor

[0114] can be either actively run down until a full standstill, without having to actively brake the compression mechanism 5 and without causing a rotation of the compression mechanism 5 in the opposite direction or

[0115] can be actively run down until just before standstill, but in any even until rotational frequencies are below 450 rpm, preferably below 250 rpm, where the drive unit 18 can be itched off without a problem, because at these low rotational frequencies, the piston striking backward, if it does so at all, no longer has any negative noise-related effects.

[0116] Here, the profile of the positive operating torque Bm and the reduced positive operating torque Bmv is not matched to the profile of the load torque Lm such that the first profile is practically equivalent to a mirrored load torque Lm (see FIGS. 7 and 8), because this would lead to a constant rotational frequency and constant rotational speed overall.

[0117] During the stopping process, however, the rotational speed should be slowed independent of the fluctuation of the rotational frequency with respect to the crank angle , so that the electronic control device 13 exerts the operating torque lam and the reduced positive operating torque Bmv so that the shocks occurring from the load torque Lm during the compression phase on the compression mechanism are dissipated for the most part, but the rotational speed overall decreases.

[0118] Simultaneously, the positive operating torque Bm can be selected so that, in any event, in the compression phase, there is always sufficient drive to prevent the piston 9 from striking backward.

[0119] Here it can also be provided, in contrast to the shown embodiments, that the drive angle segment begins in the intake phase of the piston 9, so that the piston 9 is already provided with sufficient momentum before entry in the compression phase, in order to overcome the subsequent upper dead point, without causing backward striking by the load torque Lm.

[0120] Through appropriate magnitude matching of the positive operating torque Bm and the reduced positive operating torque Bmv to each other, the compression mechanism 5 can slow its rotational movement overall up to full standstill or up to a time at which a possible backward striking of the piston 9 would no longer have any negative noise-related effects.

[0121] Here, it is essential that the electronic control device 13 can also, in the course of reducing the rotational speed for the purpose of preparing the switching off of the drive unit 18, provide at least one such drive angle segment and at least one such transit angle segment at least during a regulating time interval t lasting multiple crankshaft rotations.

[0122] FIG. 9 shows a diagram relating to the profile of the load torque Lm, the positive operating torque Bm, the reduced positive operating torque Bmv, the rotational speed , and the angular acceleration {acute over ()} of the compression mechanism 5 beyond multiple crankshaft rotations and over a regulating time interval t, wherein the rotational speed is continuously reduced until the drive is switched off at the switch-off time AZ at a rotational speed below 450 rpm, preferably below 250 rpm. The switching off is here performed preferably during the compression phase.

[0123] According to the invention it is provided that the electronic control device 13 continuously drives the compression mechanism with a positive operating torque Bm during a drive angle segment and a reduced positive operating torque Bmv during a transit angle segment , instead of switching off the drive unit 18 realized in the prior art at relatively high rotational speeds and subsequently letting it run out, with the optional additional application of a braking torque, wherein the positive operating torque Bm preferably remains constant, optionally slightly increases, in terms of magnitude for each crankshaft rotation up to the switch-off time AZ, in order to compensate for the loss of speed and thus the reduction in the kinetic energy.

[0124] Preferably, the positive operating torque Bm remains constant, but is applied, in any event, with decreasing rotational speed over a longer time span, thus, also during an increasing crank angle.

[0125] In this way, the compression mechanism is always compressed somewhat more or somewhat longer or both, in order to be able to overcome the load torque and to compensate for the lost kinetic energy of the unit consisting of the compression mechanism 5 and drive unit 18. Switching off the drive unit 18 takes place only at a very low rotational speed below 450 rpm, preferably below 250 rpm.

[0126] The regulating time interval t ends in the present embodiment at the switch-off time AZ or, in other words, the regulating time interval t immediately precedes the switch-off time AZ.

[0127] As can be seen from FIG. 9, after the switch-off time AZ, the piston 9 strikes backward, because the compression mechanism 5 is no longer exposed to operating torque during the stopping process and the piston 9 can no longer overcome the load torque Lm in the compression phase. Consequently, a pendulum motion of the crankshaft 6 about the lower dead point is realized, wherein the occurring load torques Lm are small in terms of magnitude such that these no longer cause the spring element 10 to deflect, which leads to contact between the unit consisting of the compression mechanism 5 and drive unit 18 on one hand and the housing 11 on the other hand.

[0128] FIG. 10 corresponds to FIG. 9, but with the difference that the abscissa is not the crank angle , but instead the time t. It can be seen that with increasing rotational speed , the time period over which the positive operating torque Bm is applied, increases.

[0129] The rotational speed reaches an inflection point at approx. t=0.78, which corresponds to the backward striking of the piston 9. The pendulum motion visible from FIG. 9 about the lower dead point and the associated continuous changing of the rotational speed to between a positive value and a negative value is no longer seen in FIG. 10.

LIST OF REFERENCE SYMBOLS

[0130] 1 Reciprocating piston refrigerant compressor

[0131] 2 Condenser

[0132] 3 Throttle device

[0133] 4 Evaporator

[0134] 5 Compression mechanism

[0135] 6 Crankshaft

[0136] 7 Connecting rod

[0137] 8 Cylinder block

[0138] 9 Piston

[0139] 10 Spring element

[0140] 11 Housing

[0141] 12 Power supply

[0142] 13 Electronic control device of the refrigerant compressor

[0143] 14 Electronic control device of the cooling chamber

[0144] 15 Cooling chamber

[0145] 16 Start of the compression phase

[0146] 17 Start of the intake phase

[0147] 18 Drive unit