US20190010939A1

US20190010939A1 - Method for detecting a blocked valve of a coolant compressor and a control system for a coolant compressor

Info

Publication number: US20190010939A1
Application number: US16/069,233
Authority: US
Inventors: Ralf Karp; Hans WIGH
Original assignee: Nidec Global Appliance Germany GmbH
Current assignee: Secop GmbH
Priority date: 2016-01-18
Filing date: 2017-01-16
Publication date: 2019-01-10
Also published as: WO2017125334A1; CN108700051B; AT518199A1; CN108700051A; AT518199B1; EP3405673A1; EP3405673B1

Abstract

A method for detecting a blocked valve of a coolant compressor including a drive unit and a piston-cylinder unit for cyclical compression of a coolant, wherein the drive unit has an electric motor for driving the piston-cylinder unit, monitors the speed (ω) of the electric motor. A maximum speed (ωmax) of the electric motor is initially detected, and the following steps are carried out, as long as the speed (ω) of the electric motor substantially corresponds to the maximum speed (ωmax): determining a maximum value Xmax of a monitoring parameter (I, T) of the coolant compressor (1); determining a value Xt1 of the monitoring parameter (I, T) after a first time period (t1) after determining the maximum value Xmax; detecting a blocked valve if Xt1 is less than Xmax and (Xmax−Xt1)/Xmax≥ΔX applies, wherein ΔX is predetermined.

Description

FIELD OF THE INVENTION

The present invention relates to a method for detection of a blocked valve of a coolant compressor having a drive unit and a piston/cylinder unit for cyclical compression of a coolant, wherein the drive unit has an electric motor for drive of the piston/cylinder unit, wherein the speed of rotation of the electric motor is monitored.
Furthermore, the present invention relates to a control system for the coolant compressor, the coolant compressor comprising a drive unit and a piston/cylinder unit for cyclical compression of a coolant, wherein the drive unit has an electric motor for drive of the piston/cylinder unit, and wherein the control system has control electronics.

STATE OF THE ART

In the case of a coolant compressor having a drive unit and a piston/cylinder unit for cyclical compression of a coolant, wherein the drive unit has an electric motor for drive of the piston/cylinder unit, and wherein the speed of rotation of the electric motor is monitored, a possible error state exists if a valve is blocked. In this regard, this can particularly involve a blocked suction valve or pressure valve. In practice, however, a solenoid valve in the coolant circuit can also be defective, which solenoid valve does not necessarily have to be part of the coolant compressor.
In every case, the blocked valve has the result that coolant in the cooling circuit can no longer be transported to the extent required for cooling, or not at all, and cooling therefore can no longer take place. The usage apparatus that controls the coolant compressor, for example a refrigerator, determines that the temperature is not dropping, and then usually regulates the coolant compressor to maximal cooling power, so that the electric motor runs at the maximal speed of rotation—without success, however, since the coolant can no longer be transported in the cooling circuit.
Even if the cause of the blockage of the cooling circuit was originally not a blocked valve of the coolant compressor, blockage of the valve, in particular a pressure valve of the coolant compressor, comes about now, at the latest. This is because since due to continued operation of the compressor at the highest power level, the counter-pressure of the coolant in the pressure segment increases to such an extent that the pressure valve no longer opens, because the pressure built up by the coolant compressor is no longer sufficient for this purpose. In general, blockage of the pressure valve will always occur at least if the counter-pressure is high enough—independently of how this counter-pressure is achieved or produced.
In order to prevent the coolant compressor from permanently continuing to run at the highest speed of rotation due to the error state, it is known from the state of the art to define the increase in temperature of the compressor, for example above a certain limit temperature, as a termination condition. In other words, the temperature is continuously monitored, and if the limit temperature is exceeded and the electric motor preferably runs at the maximal speed of rotation when this happens, the electric motor is shut off.
It is a disadvantage of this known method that it does not work for all coolant compressors. Specifically, practice has shown that depending on the design or type of the coolant compressor, the temperature sometimes does not increase far enough so that a limit temperature can be established in practical manner.

TASK OF THE INVENTION

It is therefore a task of the present invention to make available a method that allows reliable detection of a blockage state or of a blocked valve of the compressor. Accordingly, it is a further task of the invention to make available a control system for a coolant compressor, which system allows reliable detection of a blockage state or a blocked valve of the compressor, so as to be able to take counter-measures.

PRESENTATION OF THE INVENTION

Extensive test series with different types of coolant compressors, which each have a drive unit and a piston/cylinder unit for cyclical compression of a coolant, wherein the drive unit has an electric motor for drive of the piston/cylinder unit, and wherein the speed of rotation of the electric motor is monitored, have shown that the drastically reduced or actually completely stopped mass flow that occurs in a blockage state or in the case of a blocked valve can lead to the result that although certain monitoring parameters increase in value at first and reach a maximal value, they then decrease again within a certain, preferably predeterminable time span, while the electric motor continues to run at maximal speed of rotation.
Here and in the following, “maximal speed of rotation” should always be understood to be the maximal speed of rotation that the coolant compressor or the electric motor actually reaches in the present cooling circuit. For various reasons, this maximal speed of rotation can deviate from a theoretically technically possible maximal speed of rotation of the electric motor, for example because for noise reasons, the usage apparatus does not make use of or demand the theoretically technically possible maximal speed of rotation of 4000 min⁻¹, for example, but rather sets a lower speed of rotation of 3600 min⁻¹, for example, as a “reference maximal speed of rotation.” Furthermore, the most varied external circumstances, such as an overly low supply voltage, for example, can lead to the result that the reference maximal speed of rotation (and, of course, also the theoretically technically possible maximal speed of rotation of the electric motor) is not achieved, so that the maximal speed of rotation is actually lower than the reference maximal speed of rotation (and, of course, also the theoretically technically possible maximal speed of rotation of the electric motor).
A typical monitoring parameter would be the current consumption of the electric motor, which, after having risen to a maximum, which amounts to 0.85 A, for example, drops back to a certain value—for example to 0.425 A—within a certain time span, while the electric motor is constantly running at the maximal speed of rotation.
It can therefore be used as a decisive criterion for the existence of a blocked valve that the decrease of the monitoring parameter within the certain period of time is “great enough,” wherein this value depends on the respective type of the coolant compressor and can be established and then correspondingly predetermined by means of a laboratory experiment.
Accordingly, it is provided, according to the invention, in the case of a method for detection of a blocked valve of a coolant compressor having a drive unit and a piston/cylinder unit for cyclical compression of a coolant, wherein the drive unit has an electric motor for drive of the piston/cylinder unit, wherein the speed of rotation of the electric motor is monitored, that first, a maximal speed of rotation of the electric motor is detected, and that the following steps are carried out, as long as the speed of rotation of the electric motor essentially corresponds to the maximal speed of rotation:

- determination of a maximal value X_maxof a monitoring parameter of the coolant compressor;
- determination of a value X_t1of the monitoring parameter after a first time span after the determination of the maximal value X_max;

detection of a blocked valve, if X_t1is less than X_maxand (X_max−X_t1)/X_max≥Δ_Xholds true, wherein Δ_Xis predetermined.
In this regard, the blocked valve can particularly be a blocked suction valve or pressure valve. In practice, however, the blockage state can also be triggered by a different defective element in the cooling circuit, such as a solenoid valve, for example, which element does not necessarily have to be part of the coolant compressor. As has already been described above, however, this blockage state generally results in a blocked valve of the coolant compressor, in particular a blocked pressure valve of the coolant compressor, wherein the blocked valve blocks the mass flow of the coolant for the most part, preferably completely.
In the usage case, continued running of the electric motor at the maximal speed of rotation is caused by a usage apparatus that controls the coolant compressor, for example by a refrigerator, since the usage apparatus determines that the desired cooling is not taking place and therefore demands continued maximal cooling capacity. A typical value for the maximal speed of rotation would be 3000 min⁻¹to 4000 min⁻¹. In this regard, it should be noted that clearly, a coolant compressor having a variable speed of rotation is involved, since otherwise, only a single speed of rotation in the operation of the coolant compressor would be provided, which would then simultaneously also represent the maximal speed of rotation.
Certain minimal variations in the speed of rotation are unavoidable in practice. For this reason, it is practical to assume a certain tolerance range around the maximal speed of rotation, typically maximally ±2%. If the speed of rotation changes in such a manner that it deviates more greatly from the maximal speed of rotation, in particular if it is more than 2% lower than the maximal speed of rotation, the method is interrupted. In the case of an increasing speed of rotation, the actual maximal speed of rotation had not yet been reached, wherein the method is usually restarted when the actual maximal speed of rotation has been reached. In the case of a decreasing speed of rotation, it can typically be assumed that the blockage situation or the blocked valve was no longer present, that therefore the desired cooling was able to occur, and the usage apparatus demanded a lower cooling capacity. The method is therefore interrupted and only restarted when the maximal speed of rotation is reached once again.
As has already been stated, it is dependent on the respective type of the coolant compressor how greatly the monitoring parameter decreases over time. In this regard, it is provided, in the case of a preferred embodiment of the method according to the invention, that Δ_Xis 0.2, preferably Δ_Xis ≥0.4, particularly preferably Δ_Xis ≥0.5. In other words, the percentage decrease in the value of the monitoring parameter must amount to at least 20%, preferably at least 40%, particularly preferably at least 50%.
As has already been stated, the current consumption of the electric motor can be used as a monitoring parameter, which shows the behavior over time as described, in the blockage state. Analogously, a motor winding temperature and a temperature of control electronics of the electric motor or of the coolant compressor also demonstrate the same temperature behavior, and for this reason these temperatures are also suitable as monitoring parameters. In a preferred embodiment of the method according to the invention, it is therefore provided that the monitoring parameter is a current consumption by the electric motor or a temperature of control electronics of the coolant compressor, particularly of the electric motor, or of a motor winding of the electric motor. Clearly, these temperatures must always be indicated relative to the ambient temperature of the coolant compressor. If the ambient temperature is 20° C. (room temperature), for example, and if 90° C. is measured as the maximal value, then X_maxmust be indicated as being 70° C.
As was determined in extensive experiments, it is recommended not to carry out the determination of the maximal value X_maximmediately after detection of the maximal speed of rotation of the electric motor, but rather to wait a certain, predeterminable time to do so. This allows a certain equilibrium of the pressure conditions to occur, for which the monitoring parameter can first assume its maximal value X_max. Otherwise, the danger exists that the value of the monitoring parameter will increase even further until the equilibrium of the pressure conditions has been reached. For this reason, it is provided, according to a preferred embodiment of the method according to the invention, that the determination of the maximal value X_maxtakes place only after an initiation time span after detection of the maximal speed of rotation of the electric motor. In other words, detection of the maximal speed of rotation defines a starting time or a starting point in time for the method. In the aforementioned preferred embodiment, the initiation time span is allowed to elapse immediately after the starting time or the starting point in time, before determination of the maximal value X_maxof the monitoring parameter is carried out.
The optimal initiation time span can be determined in experiments for different coolant compressor types, and then be predetermined accordingly, wherein the initiation time span typically amounts to several minutes. For this reason, it is provided, in a preferred embodiment of the method according to the invention, that the initiation time span amounts to at least 5 min, preferably at least 10 min, particularly preferably at least 15 min.
In order to have the greatest possible reliability that the conditions for the blockage state or for a blocked valve are actually fulfilled, verification can take place, in that the monitoring parameter is determined once again shortly after its last determination, and compared with the maximal value X_max. If this comparison also indicates the blockage state, it can be assumed, with very great reliability, that the blockage state or a blocked valve actually exists. For this reason, it is provided, in a preferred embodiment of the method according to the invention, that after a verification time span after detection of the blocked valve, a value X_t2of the monitoring parameter is determined, and detection of the blocked valve is verified if X_t2is less than X_maxand (X_max−X_t2)/X_max≥Δ_Xholds true. In this regard, waiting for the verification time span is supposed to take possible fluctuations of the monitoring parameter into account, i.e. if the value of the monitoring parameter is correspondingly low even after the verification time span, it can be assumed, with great likelihood, that this lowering is not attributable to a random variation.
Of course, particularly preferred embodiment variants are also conceivable, in which the condition (X_max−X_t2)/X_max≥Δ_X′ is checked, wherein Δ_X′≠Δ_X, preferably Δ_X′>Δ_Xholds true. In other words, for verification, it is checked whether the monitoring parameter of the coolant compressor continues to develop, in terms of time, in the manner that model calculations and/or laboratory experiments make it likely to expect, wherein this development over time will typically be a further reduction.
The optimal verification time span can be determined in experiments for different coolant compressor types and then be established accordingly, wherein the verification time span typically amounts at most to a few minutes. For this reason, it is provided, in a preferred embodiment of the method according to the invention, that the verification time span amounts to 15 s to 5 min, preferably 30 s to 3 min, particularly preferably 45 s to 1 min 30 s.
The first time span can also depend on the type of the coolant compressor and can be predetermined accordingly—in particular on the basis of conducted experiments. In this regard, it is provided, in a preferred embodiment of the method according to the invention, that the first time span amounts to at least 3 h, preferably at least 5 h, particularly preferably at least 6 h.
In a preferred embodiment of the method according to the invention, it is provided that after detection of the blocked valve, a corresponding error message is written into a readable memory provided for this purpose. Analogously, it is provided, in a preferred embodiment of the method according to the invention, that after verification of the detection of the blocked valve, a corresponding error message is written into a readable memory provided for this purpose. The respective writing into the readable memory makes it possible to make this information available to different control systems—for example a control system of the usage apparatus—for further processing. Furthermore, particularly if a non-volatile memory such as a so-called FLASH, EPROM or NVRAM memory is involved, the information can also be read out at a later point in time for diagnosis purposes.
In practice, detection or verification of the blockage state or of the blocked valve can be used to turn the compressor off, since it is clear that the desired cooling cannot be achieved in this state. Continued running of the electric motor at the maximal speed of rotation would therefore mean unnecessary stress on the compressor as well as unnecessary energy consumption. Accordingly, an operating method for operation of a coolant compressor is provided according to the invention, the operating method comprising the method according to the invention, wherein after detection of the blocked valve, the electric motor is stopped. Analogously, an operating method for operation of a coolant compressor is provided, according to the invention, the operating method comprising the method according to the invention, wherein after verification of the detection of the blocked valve, the electric motor is stopped. Preferably, the electric motor does not consume any current in the stopped state, so that no unnecessary energy consumption takes place.
Experiments have shown that the cause for the blockage situation is sometimes no longer present after a restart of the coolant compressor. For example, it can happen that a solenoid valve triggered the blockage situation, because it had not opened and thereby blocked the coolant circuit, and that this solenoid valve now opens as provided after all. For this reason, it is provided, in a preferred embodiment of the operating method according to the invention, that the electric motor is restarted after a second time span. Waiting for the second time span can serve, in this regard, to bring about a certain relaxation of the pressure conditions, and this can contribute to release of a blocked valve. Furthermore, a temperature of the compressor can also relax or decrease during the second time span, and this can also contribute to release of a blocked valve.
Particularly if the blocking valve demonstrates erratic behavior and correspondingly is blocked in some runs of the coolant compressor and not blocked in other runs, the second time span can be kept relatively short, in particular in the second range. For this reason, it is provided, in a preferred embodiment of the operating method according to the invention, that the second time span amounts to at least 3 s, preferably at least 6 s, particularly preferably at least 15 s. In general, however, it must be noted that the values for the second time span can vary greatly, depending on the application.
In practice, it is practical not to allow the second time span to become arbitrarily long, since, of course, error states can also occur in which a blocked valve is no longer released. For this reason, it is provided, in a particularly preferred embodiment of the operating method according to the invention, that the second time span amounts to maximally 60 min. In other words, it is assumed that the clocking valve must release within this maximal duration of the second time span, and otherwise an error state is assumed, in which the blocking valve is no longer released.
Analogous to what has been said above, it is provided, according to the invention, in a control system for a coolant compressor, the coolant compressor comprising a drive unit and a piston/cylinder unit for cyclical compression of a coolant, wherein the drive unit has an electric motor for drive of the piston/cylinder unit and wherein the control system has control electronics, that the control electronics are set up for carrying out a method according to the invention and/or for carrying out an operating method according to the invention.
Finally, in order to make available a coolant compressor that can reliably determine a blockage state or a blocked valve and react to it, it is provided, according to the invention, in a coolant compressor having a drive unit and a piston/cylinder unit for cyclical compression of a coolant, wherein the drive unit has an electric motor for drive of the piston/cylinder unit, that the coolant compressor has a control system according to the invention.
It should be noted that in all the above explanations, the coolant compressor can be, in particular, a coolant compressor having a hermetically sealed housing, wherein the drive unit and the piston/cylinder unit are disposed in the housing.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be explained in greater detail using an exemplary embodiment. The drawings are used as examples and are supposed to present the idea of the invention, but not to restrict it in any way or to reproduce it conclusively.

The figures show:

FIG. 1 a schematic axonometric view of a coolant compressor according to the invention, with the top housing half removed,

FIG. 2 a diagrammatic illustration of the method according to the invention.

WAYS FOR IMPLEMENTATION OF THE INVENTION

FIG. 1 shows a coolant compressor 1 according to the invention, wherein a hermetically sealed housing 2 of the coolant compressor 1 is shown only in part, i.e. a top half of the housing 2 has been removed in order to allow a view into the housing 2. In the interior of the housing 2, a cylinder housing 3 of a piston/cylinder unit can be seen. The cylinder housing 3 is mounted on a drive unit 4, which comprises an electric motor for drive of the piston/cylinder unit. In this regard, the electric motor drives a piston of the piston/cylinder unit in a cylinder, which cylinder is disposed in the cylinder unit 3, by way of a crankshaft 10 and a piston rod. As a result, a cyclical movement of the piston in the cylinder, along a cylinder axis, is implemented in order to compress coolant.
In this regard, the coolant is drawn into the cylinder by way of a suction muffler 9 and a suction valve disposed in the valve plate 6, compressed, and conducted into a pressure pipe 8 that leads outward, by way of a pressure valve disposed in the valve plate 6. The coolant is subsequently conducted to a condenser (not shown) in a coolant circuit of a usage apparatus, such as a refrigerator, for example, into which coolant circuit the coolant compressor 1 is integrated.
The valve plate 6 is mounted on the cylinder in the region of a cylinder head, wherein a cylinder cover 5 can be seen in FIG. 1, which is screwed onto the cylinder by means of screws 7. In this regard, the valve plate 6 is disposed between the cylinder cover 5 and the cylinder.
The coolant compressor 1 is operated at a variable speed of rotation ω, i.e. the speed of rotation ω is dependent on the cooling power that is demanded by the usage apparatus. At maximal cooling power, the electric motor runs at a maximal speed of rotation ω_max, which typically amounts to 3000 min⁻¹to 4000 min⁻¹.
In a blockage state, the mass flow of the coolant in the cooling circuit is greatly reduced or stops entirely. The blockage state can be caused by a blocked valve of the coolant compressor 1 or leads to a blocked valve of the coolant compressor 1, since the valve, particularly the pressure valve, can no longer open properly due to the pressure conditions that are building up. The latter means that the pressure built up by the piston/cylinder unit is not great enough to overcome the counter-pressure that has built up due to the blockage state.
In order to be able to reliably determine the blockage state or a blocked valve, it is provided, according to the invention, that aside from the speed of rotation w, monitoring parameters of the coolant compressor 1 are constantly monitored so as to determine their progression over time. In particular, a current consumption I of the electric motor as well as a temperature T of control electronics of the coolant compressor 1 or of the electric motor or of a motor winding of the electric motor are possible as monitoring parameters. Clearly, these temperatures must always be indicated relative to the ambient temperature (typically room temperature or 20° C.) of the coolant compressor.
According to the invention, after detection of the maximal speed of rotation ω_max, the following steps are carried out, as long as the speed of rotation ω of the electric motor essentially corresponds to the maximal speed of rotation ω_max:

- determination of a maximal value X_maxof the monitoring parameter of the coolant compressor 1;
- determination of a value X_t1of the monitoring parameter after a first time span t1 after the determination of the maximal value X_max;
- detection of a blocked valve, if X_t1is less than X_maxand (X_max−X_t1) /X_max≥Δ_Xholds true, wherein Δ_Xis predetermined.

FIG. 2 illustrates these method steps using the diagrammatic representation of the progression of I and T as a function of time t. Directly under this diagram, the time progression of the speed of rotation ω of the electric motor is shown. In this regard, in the embodiment of the method according to the invention that is shown, after first-time detection of the maximal speed of rotation ω_max, a predeterminable initiation time span t0 is allowed to elapse first, so that a certain equilibrium of the pressure conditions can occur, before X_maxis determined. Typically, t0 amounts to at least 5 min, preferably at least 10 min, particularly preferably at least 15 min.
In a typical usage case analogous to FIG. 2, the current I, for example, has increased to a value of X_max−0.85 A after the initiation time span to. Analogously, in such a typical usage case, the temperature T has increased, after the initiation time span t0, to a value that results in Xmax=70° C., for example (corresponds to measured 90° C. at 20° C. ambient temperature).
The determination of X_t1takes place after expiration of the first time span t1 after the determination of X_max, wherein t1 typically amounts to at least 3 h, preferably at least 5 h, particularly preferably at least 6 h. In other words, the time that has elapsed between the first-time detection of the maximal speed of rotation ω_maxand the determination of X_t1amounts to t0 +t1. In a typical usage case analogous to FIG. 2, the current I has decreased to a value of X_t1=0.425 A after the first time span t1, or, for example, to a value that is equal to a relative reduction of 20% to 50%. Analogously, in such a typical usage case, the temperature T has dropped to a value that results in X_t1=50° C. (corresponds to measured 70° C. at 20° C. ambient temperature), for example, after the first time span t1.
Depending on the type of the coolant compressor 1, a specific value can be predetermined for Δ_X, wherein typically, Δ_X≥0.2, preferably Δ_X≥0.4, particularly preferably Δ_X≥0.5 holds true. The value that matches the respective type can preferably be determined in a laboratory experiment. In the exemplary embodiment shown in FIG. 2, (X_max−X_t1)/X_max≈0.56. When Δ_X=0.5 is set, a blocked valve or the blockage state is therefore detected.
In the exemplary embodiment of FIG. 2, verification of the detection of the blocked valve takes place for security, in that after the determination of X_t1, a relative short verification time span t2 is allowed to elapse, and then a present value X_t2of the monitoring parameter is determined, and the condition (X_max−X_t2)/X_max≥Δ_Xis checked. Typically, the verification time span t2 amounts to 15 s to 5 min, preferably 30 s to 3 min, particularly preferably 45 s to 1 min 30 s.
In a typical usage case analogous to FIG. 2, the current I has decreased to a value of X_t2=0.23 A, for example, after the verification time span t2. Analogously, in such a typical usage case, the temperature T has dropped to a value that results in X_t2=18.9° C. (corresponds to measured 38.9° C. at 20° C. ambient temperature), for example, after the verification time span t2.
In the exemplary embodiment of FIG. 2 that is shown, (X_max−X_t2)/X_max≈0.73. In other words, when Δ_X=0.5 is set, the previously performed detection of the blocked valve is confirmed or verified.
To carry out the method described, the coolant compressor 1 has a control system having control electronics, which control electronics are set up for carrying out the said method. Preferably, these control electronics also form the aforementioned control electronics of the electric motor.
In the exemplary embodiment of FIG. 2, the control electronics are furthermore set up to carry out an operating method according to the invention, according to which the electric motor is stopped after verification of the blocked valve or the blockage state. Accordingly, in the lower diagram of FIG. 2, the speed of rotation ω drops from the maximal speed of rotation w_maxto 0.
After being stopped, the electric motor no longer consumes any current I, while the temperature T of the control electronics or of the motor winding slowly decreases further (down to the ambient temperature), and for this reason, in FIG. 2 the progression of T in the region after t2 is indicated with a broken line.
Since the cause for the blockage situation is sometimes no longer present after a restart of the coolant compressor 1, the control electronics can be set up for restarting the electric motor after a relative short second time span t3. Typically, the second time span t3 amounts to only a few seconds, for example at least 3 s, preferably at least 6 s, particularly preferably at least 15 s. In practice, the second time span t3 is typically limited to maximally up to 60 min.
In the lower diagram of FIG. 2, different situations after the electric motor is turned on again are shown with dotted lines. One of these situations would be that the electric motor is running at the maximal speed of rotation ω_maxagain; this will particularly be the case if the blockage situation continues to exist. In such a case, the method according to the invention, for detection of a blocked valve, would be started immediately once again, by means of detection of the maximal speed of rotation ω_max.
However, in particular if the blockage situation no longer exists, situations can also occur in which the speed of rotation ω of the electric motor lies below the maximal speed of rotation ωmax. In such a case, the method according to the invention, as described, for detection of a blocked valve, would not be started, but rather would only be started as soon as the maximal speed of rotation ω_maxis detected subsequently.
It should be noted that the control system can have a memory into which a corresponding error message is written after detection or verification of the blockage state, which error message can then be read out of the memory again, in particular for diagnosis purposes. Furthermore, the memory can serve for storing values to be called up during the method or operating method according to the invention, in particular for storing the values for Δ_X, t0, t1, t2, and t3, for the specifically present coolant compressor 1.

REFERENCE SYMBOL LIST

1 coolant compressor
2 housing of the coolant compressor
3 cylinder housing
4 drive unit
5 cylinder cover
6 valve plate
7 screw
8 pressure pipe that leads outward
9 suction muffler
10 crankshaft
I current consumption of the electric motor
T temperature of control electronics of the electric motor or of a motor winding of the electric motor
t time
t0 initiation time span
t1 first time span
t2 verification time span
t3 second time span
ω speed of rotation of the electric motor
ω_maxmaximum speed of rotation of the electric motor

Claims

1. A method for detection of a blocked valve of a coolant compressor (1) having a drive unit (4) and a piston/cylinder unit for cyclical compression of a coolant, wherein the drive unit (4) has an electric motor for drive of the piston/cylinder unit, wherein the speed of rotation (ω) of the electric motor is monitored, wherein first, a maximal speed of rotation (ω_max) of the electric motor is detected and that the following steps are carried out, as long as the speed of rotation (ω) of the electric motor essentially corresponds to the maximal speed of rotation (ω_max):

determination of a maximal value X_maxof a monitoring parameter (I, T) of the coolant compressor (1);

determination of a value X₁of the monitoring parameter (I, T) after a first time span (t1) after the determination of the maximal value X_max;

detection of a blocked valve, if X_t1is less than X_maxand (X_max−X_t1)/X_max≥Δ_Xholds true, wherein Δ_Xis predetermined.

2. The method according to claim 1, wherein Δ_Xis ≥0.2, preferably Δ_xis z 0.4, particularly preferably Δ_Xis z 0.5.

3. Method The method according to claims 1 to , c claim 1, wherein the monitoring parameter is a current (I) consumption by the electric motor or a temperature (T) of control electronics of the coolant compressor (1), particularly of the electric motor, or of a motor winding of the electric motor.

4. Method The method according to claim 1, wherein the determination of the maximal value X_maxtakes place only after an initiation time span (t0) after detection of the maximal speed of rotation (ω_max) of the electric motor.

5. Method The method according to claim 4, wherein the initiation time span (t0) amounts to at least 5 min, preferably at least 10 min, particularly preferably at least 15 min.

6. The method according to claim 1, wherein after a verification time span (t2) after detection of the blocked valve, a value X_t2of the monitoring parameter (I, T) is determined, and detection of the blocked valve is verified if X_t2is less than X_maxand (X_max−X_t2)/X_max≥Δ_Xholds true.

7. The method according to claim 6, wherein the verification time span (t2) amounts to 15 s to 5 min, preferably 30 s to 3 min, particularly preferably 45 s to 1 min 30 s.

8. The method according to claim 1, wherein the first time span (t1) amounts to at least 3 h, preferably at least 5 h, particularly preferably at least 6 h.

9. The method according to claim 1, wherein after detection of the blocked valve, a corresponding error message is written into a readable memory provided for this purpose.

10. The method according to claim 6, wherein, wherein after verification of the detection of the blocked valve, a corresponding error message is written into a readable memory provided for this purpose.

11. An operating method for operating a coolant compressor (1), the operating method comprising the method according to claim 1, wherein the electric motor is stopped after detection of the blocked valve.

12. The operating method for operating a coolant compressor (1), the operating method comprising the method according to claim 6, wherein the electric motor is stopped after verification of the detection of the blocked valve.

13. The operating method according to at claim 11, wherein the electric motor is restarted after a second time span (t3).

14. The operating method according to claim 13, wherein the second time span (t3) amounts to at least 3 s, preferably at least 6 s, particularly preferably at least 15 s.

15. The operating method according to claim 13, wherein the second time span (t3) amounts to maximally 60 min.

16. A control system for a coolant compressor (1), the coolant compressor (1) comprising a drive unit (4) and a piston/cylinder unit for cyclical compression of a coolant, wherein the drive unit (4) has an electric motor for drive of the piston/cylinder unit, and wherein the control system has control electronics, characterized in that wherein the control electronics are set up for carrying out the method according to claim 1 and/or for carrying out an operating method.

17. A coolant compressor (1) having a drive unit (4) and a piston/cylinder unit for cyclical compression of a coolant, wherein the drive unit (4) has an electric motor for drive of the piston/cylinder unit, wherein the coolant compressor has the control system according to claim 16.