CONTROL DEVICE AND METHOD FOR OPERATING A REFRIGERANT COMPRESSOR

Abstract

Electronic control device for a refrigerant compressor, comprising at least one drive unit and a compression mechanism which is in operative connection with the drive unit and has at least one piston which, in an operating state of the refrigerant compressor, moves back and forth in a cylinder of a cylinder block of the refrigerant compressor for the operational compression of refrigerant and is driven by a crankshaft of the drive unit, wherein the electronic control device of the refrigerant compressor is at least designed to detect at least one physical process parameter, preferably the rotational speed (n) of the crankshaft or the power consumption of the refrigerant compressor, and to detect a switch-off signal directed at the refrigerant compressor, said switch-off signal terminating a refrigerant compressor operating phase in which the refrigerant compressor is operated as intended with a positive operating torque; and is also designed to regulate a torque applied by the drive unit to the crankshaft so as to adjust the rotational speed (n) of the crankshaft, wherein the electronic control device is further designed to apply a braking torque to the crankshaft immediately after detecting the switch-off signal, wherein the braking torque is applied in the opposite direction to the positive torque acting during the operating phase and the value of this braking torque is a function of the detected physical process parameter, preferably the rotational speed (n) of the crankshaft or the power consumption of the refrigerant compressor.

Claims

1. An electronic control device for a refrigerant compressor, which comprises at least a drive unit and a compression mechanism that is in operative connection with the drive unit and that has at least one piston that moves back-and-forth in a cylinder of a cylinder block of the refrigerant compressor in an operating state of the refrigerant compressor for compression of refrigerant as designed and is driven via a crankshaft of the drive unit where the electronic control device of the refrigerant compressor is configured at least to detect at least one physical process parameter of the refrigerant compressor, to detect a shutoff signal directed to the refrigerant compressor, which shutoff signal ends an operating phase of the refrigerant compressor, in which operating phase the refrigerant compressor is operated as designed with a positive operating torque, and to control a torque applied by the drive unit to the crankshaft in order to set its rotary speed (n), wherein the electronic control device is further configured to apply a braking torque to the crankshaft immediately after detection of the shutoff signal, where the braking torque is directed opposite to the positive torque that existed during the operating phase and the value of said braking torque is a function of the detected physical process parameter of the refrigerant compressor.

2. The electronic control device as in claim 1, wherein the physical process parameter is the rotary speed (n) of the crankshaft.

3. The electronic control device as in claim 1, wherein the value of the braking torque applied to the crankshaft immediately after detection of the shutoff signal is inversely proportional to the rotary speed (n) of the crankshaft that the crankshaft has at the moment of the detection of the shutoff signal.

4. The electronic control device as in claim 1, where the braking torque is maintained up to a complete stop of the crankshaft.

5. The electronic control device as in claim 1, wherein the braking torque applied to the crankshaft is realized as a braking profile, where a function defining the course of the braking profile is stored by the electronic control device.

6. The electronic control device as in claim 1, wherein the electronic control device is configured to compare the rotary speed (n) of the crankshaft with preset rotary speed values (n.sub., n.sub., . . . ) in a braking time extending between the detection of the shutoff signal and the complete stop of the crankshaft.

7. The electronic control device as in claim 6, wherein the course of the braking profile essentially follows a piecewise linear function, where a segment of the braking time is associated with each of the preset rotary speed values (n.sub., n.sub., . . . ), within which segment said piecewise linear function exhibits an essentially constant slope.

8. The electronic control device as in claim 5, wherein the value of the braking torque resulting from the course of the braking profile increases monotonously from the time of the detection of the shutoff signal to the time of the complete stop of the crankshaft.

9. A refrigerant compressor for use in a refrigeration unit where the refrigerant compressor comprises an electronic control device as in claim 1.

10. A refrigeration unit with a refrigerant compressor as in claim 9.

11. A method for operating a refrigerant compressor suitable for use in a refrigeration unit, which comprises a compression mechanism for compression of refrigerant and a drive unit, where the compression mechanism is driven by means of a crankshaft of the drive unit that is supplied with a torque, wherein the method comprises the following steps: detection of a shutoff signal ending an operating phase in which the refrigerant compressor is operated as designed with a positive operating torque; detection of a physical process parameter of the refrigerant compressor; a application of a braking torque to the crankshaft immediately after the detection of the shutoff signal, where the braking torque opposes the positive operating torque in its direction of action and the value of the braking torque is a function of the detected physical process parameter of the refrigerant compressor.

12. The method as in claim 11, wherein the physical process parameter is the rotary speed (n) of the crankshaft.

13. The method as in claim 11, wherein the value of the braking torque applied to the crankshaft immediately after detection of the shutoff signal is essentially inversely proportional to the rotary speed (n) of the crankshaft that the crankshaft has at the moment of the detection of the shutoff signal.

14. The method as in claim 11, wherein the braking torque is maintained at least in a segment within a braking time, where the braking time is the time between the detection of the shutoff signal and the complete stop of the crankshaft.

15. The method as in claim 14, wherein the braking torque is applied to the crankshaft in the form of a braking profile, where a function defining the course of the braking profile is stored by the electronic control device.

16. The method as in claim 15, wherein the value of the braking torque resulting from the course of the braking profile increases monotonously from the tune of the detection of the shutoff signal to the time of the complete stop of the crankshaft.

17. The method as in claim 14, wherein during the braking time the rotary speed (n) of the crankshaft is compared with preset rotary speed values (n.sub., n.sub., . . . ) and the braking time is divided at least partially, into process time segments (T.sub., T.sub., . . . ), where in each of said process time segments (T.sub., T.sub., . . . ) the rotary speed (n) of the crankshaft lies in a value range with which one of the preset speed values (n.sub., n.sub., . . . ) is associated.

18. The method as in claim 17, wherein the course of the braking profile essentially follows a piecewise linear function of the process time, where said function exhibits a segment with constant slope in each process time segment (T.sub., T.sub., . . . ).

19. The electronic control device of claim 1 wherein the at least one physical process parameter comprises one or more of: rotary speed (n) of the crankshaft, and power consumption of the refrigerant compressor.

20. The electronic control device as in claim 5, wherein the function defining the course of the braking profile comprises a linear dependency on the current rotary speed (n) of the crankshaft and/or the time elapsed since detection of the shutoff sign.

21. The electronic control device of claim 6, wherein the electronic control device is configured to compare the rotary speed (n) of the crankshaft a number of times with preset rotary speed values (n.sub., n.sub., . . . ) in a braking time extending between the detection of the shutoff signal and the complete stop of the crankshaft.

22. The electronic control device as in claim 21, wherein the electronic control device is configured to compare the rotary speed (n) of the crankshaft continuously with preset rotary speed values (n.sub., n.sub., . . . ) in a braking time extending between the detection of the shutoff signal and the complete stop of the crankshaft.

23. The refrigerant compressor as in claim 9, wherein the refrigeration unit comprises a refrigerator or freezer.

24. The method as in claim 11, wherein the physical process parameter comprises one or more of: rotary speed of the crankshaft, and power consumption.

25. The method as in claim 14, wherein the braking torque is maintained up to the complete stop of the crankshaft.

26. The method as in claim 15, wherein the function defining the course of the braking profile comprises a linear dependency on the current rotary speed (n) of the crankshaft and/or of the elapsed time since detection of the shutoff signal.

27. The method as in claim 17, wherein the rotary speed (n) of the crankshaft is compared a number of times with the preset rotary speed values (n.sub., n.sub., . . . ).

28. The method as in claim 26, wherein the number of times is continuously with the preset rotary speed values (n.sub., n.sub., . . . ).

29. The method as in claim 17, wherein the entire braking time is divided into process time segments (T.sub., T.sub., . . . ).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0073] The invention will now be explained in more detail by means of an embodiment example. The drawing is given as an example and is intended only to represent the ideas of the invention, but not to limit it any way or even to reproduce it conclusively.

[0074] Here:

[0075] FIG. 1 shows two mutually corresponding diagrams, which represent a stopping process regulated by means of a control device according to the invention.

WAYS TO IMPLEMENT THE INVENTION

[0076] FIG. 1 shows two mutually corresponding diagrams, which represent the rotary speed n of a crankshaft of a refrigerant compressor and the torque M applied to the crankshaft during an operating phase II, in which the refrigerant compressor is operated as designed, and also during a stopping process III in the said operating phase, in each case as a function of the process time t.

[0077] At time t.sub.0, which coincides with the origin of the abscissa, an electronic control device according to the invention detects a start signal directed to the refrigerant compressor. In reaction to the start signal a drive unit of the refrigerant compressor sets the crankshaft of the refrigerant compressor into motion. After the crankshaft has been initially put into a preset position in the course of a corresponding starting operation I of the refrigerant compressor, the crankshaft is accelerated from said position to a preset rotary speed n.sub.Start. As soon as the rotary speed of the crankshaft has reached the value n.sub.Start, the starting operation I is over, and the refrigerant compressor is ready for use in order to make available on demand cooling output needed by a refrigeration unit in which the refrigerant compressor is used. As long as such a demand does nor exist or has not been communicated to the electronic control device according to the invention of the refrigerant compressor from another control device of the refrigeration unit in which the refrigerant compressor is used, the crankshaft maintains the rotary speed n.sub.Start. Reaching and holding the stalling speed n.sub.Start can be managed according to the invention by means of an open control circuit.

[0078] As soon as a specific demand for cooling output has been communicated to the electronic control device according to the invention, which cooling output can be automatically set by the other control electronics of the refrigeration unit or can be manually set by a user of the refrigeration unit and which cooling output corresponds to a specific desired temperature in the refrigeration unit, the rotary speed n of the crankshaft is regulated by means of a closed control circuit from the starting speed n.sub.Start to a rotary speed set point n.sub.Soll in a range between about 700 revolutions per minute (hereinafter abbreviated as rpm) and 4000 rpm, which corresponds to the preset demand for cooling output. For this, a specific positive drive torque M is applied to the crankshaft, which is varied in correspondence with a measured value of the current rotary speed n of the crankshaft until the rotary speed set point n.sub.Soll is reached. Said rotary speed set point n.sub.Soll will be maintained until the required cooling output has been made available to the refrigeration unit and as a result the desired temperature has been reached in the refrigeration unit or a region of the refrigeration unit, for example the freezer compartment of a refrigerator.

[0079] After the desired temperature has been reached, this is communicated to the electronic control device in the form of a shutoff signal directed to the refrigerant compressor. The stopping process III that is initiated following the detection of said shutoff signal, at the end of which the crankshaft is at a complete stop, develops according to the invention as follows:

[0080] Immediately after detection of the shutoff signal, the electronic control device applies a torque directed opposite to the torque present in the operating phase II (according to its direction) to the crankshaft and thus initiates the braking process at the same time. The stopping process III thus does not have any of the time preceding the braking process that is known from the prior art, in which the crankshaft runs uncontrolled in order to reduce the rotary speed of the crankshaft below a specific sufficiently low value before applying the braking torque. This significantly shortens the stopping process overall, which shortens the time in which the refrigerant compressor runs through a rotary speed range that is critical for noise generation, thus the range between about 700 rpm and 0 rpm.

[0081] Since, however, the braking torque that would be necessary to completely stop a crankshaft having a high rotary speed n.sub.Soll at the time of the detection of the shutoff signal, thus to bring it to a stop, would be much too high, both from the standpoint of energy efficiency and for reasons of noise technology, and moreover there would also be the danger that components of the control device and or the refrigerant compressor would suffer damage during this harsh braking, it is provided according to the invention that the braking torque applied to the crankshaft immediately after the detection of the shutoff signal is a function of the rotary speed that the crankshaft has at the time of the detection of the shutoff signal.

[0082] Specifically, it is provided and is clearly evident from FIG. 1 that the braking torque applied to the crankshaft immediately after the detection of the shutoff signal is lower in the case of a high setpoint value of the rotary speed n.sub.Soll of the crankshaft at the time of the detection of the shutoff signal than in the case of a low setpoint value of the rotary speed n.sub.Soll of the crankshaft at the time of the detection of the shutoff signal. The value of the braking torque applied to the crankshaft immediately after detection of the shutoff signal is thus inversely proportional to the rotary speed n.sub.Soll that the crankshaft has at the time of the detection of the shutoff signal. Alternatively, it can also be provided that in establishing the value of the braking torque immediately after the detection of the shutoff signal, a different detected physical process parameter, for example the power consumption of the refrigerant compressor, is used in place of the rotary speed of the crankshaftthe braking torque thus is a function of a different process parameter.

[0083] Thus, if the crankshaft at the time of the detection of the shutoff signal has a high rotary speed n.sub.Soll, the braking torque applied at the beginning of the stopping process will initially lead to a comparably weak braking of the crankshaft, whereas the braking effect is comparably high when the crankshaft has a low rotary speed n.sub.Soll at the time of the detection of the shutoff signal.

[0084] Because of the braking process that has already been initiated at the same time as the beginning of the stopping process, the rotary speed of the crankshaft decreases faster than in refrigerant compressors according to the prior art, in which the crankshaft initially runs uncontrolled for purposes of reducing the speed before the braking torque is applied to the crankshaft, which is ultimately intended to cause the complete stopping of the crankshaft and to prevent a reversal of the direction of rotation in the last moment of the stopping process.

[0085] In order to achieve a continuously greater braking effect with progressive process time t since the detection of the shutoff signal, the braking torque applied to the crankshaft forms a braking profile extending over an entire braking period extending between the detection of the shutoff signal and the complete stopping of the crankshaft. This means that the crankshaft is subjected to a braking torque during the entire braking time. The value of said braking torque, which arises from the course of the braking profile, increases monotonically from the time of the detection of the shutoff signal up to complete stopping of the crankshaft. The course of the braking profile can itself in turn involve a function of the current rotary speed of the crankshaft in each case and/or the process time t (for example, the time that has elapsed since the beginning of the stopping process), where a function defining said course is stored by the control device according to the invention.

[0086] In the embodiment examples shown the braking time iswithout a loss of generalitydivided into four (scenario 1) or into two (scenario 2) process time segments (T.sub.1, T.sub.2, T.sub.3, T.sub.4, or T.sub.11, T.sub.22). Within each one of these process segments the relevant rotary speed of the crankshaft, which is monitored by the electronic control device at a high frequency, for example at a frequency higher than 10 Hz, and is compared with preset values (n.sub.1, n.sub.2, n.sub.3, n.sub.0, or n.sub.3, n.sub.0) of the rotary speed, in each case lies in a region which is associated in each case with a preset value of the rotary speed. The braking profile, which extends over the entire braking time and thus over all of the process time segments (T.sub.1, T.sub.2, T.sub.3, T.sub.4, or T.sub.11, T.sub.22), can thus be formed so that it follows the course of a piecewise linear function of the process time t, where the slope of said function has a different constant value in each individual process segment (T.sub.1, T.sub.2, T.sub.3, T.sub.4, or T.sub.11, T.sub.22).

[0087] Below the last non-vanishing, preset value of the rotary speed (in both scenarios this is the rotary speed n.sub.3) the said slope of the said piecewise linear function of the process time t takes the value zerothe braking profile applied to the crankshaft, more precisely its value, is therefore constant in the last process time segment (T.sub.4 in scenario 1, T.sub.22 in scenario 2) of the braking time. Thus, the braking behavior produced by the electronic control device according to the invention during the final process time segment, which immediately precedes the complete stopping of the crankshaft, differs from that of the other process time segments, in which the value of the braking torque each time grows, or increases, monotonically.

REFERENCE NUMBER LIST

[0088] M torque

[0089] n rotary speed of crankshaft

[0090] n.sub., n.sub., . . . preset rotary speed values

[0091] n.sub.Start preset rotary speed

[0092] n.sub.Soll set value of rotary speed

[0093] t process time

[0094] t.sub.0 time point of the detection of a start signal

[0095] T.sub.i, T.sub.ii process time segments of the braking time (i=1, 2, . . . , 11, 22, . . . )