METHOD FOR DETECTING A BLOCKED VALVE OF A COOLANT COMPRESSOR AND A CONTROL SYSTEM FOR A COOLANT COMPRESSOR

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 () of the electric motor. A maximum speed (.sub.max) of the electric motor is initially detected, and the following steps are carried out, as long as the speed () of the electric motor substantially corresponds to the maximum speed (.sub.max): determining a maximum value X.sub.max of a monitoring parameter (I, T) of the coolant compressor (1); determining a value X.sub.t1 of the monitoring parameter (I, T) after a first time period (t1) after determining the maximum value X.sub.max; detecting a blocked valve if X.sub.t1 is less than X.sub.max and (X.sub.maxX.sub.t1)/X.sub.max.sub.X applies, wherein .sub.X is predetermined.

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 () of the electric motor is monitored, wherein first, a maximal speed of rotation (.sub.max) 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 (.sub.max): determination of a maximal value X.sub.max of a monitoring parameter (I, T) of the coolant compressor (1); determination of a value X.sub.1 of the monitoring parameter (I, T) after a first time span (t1) after the determination of the maximal value X.sub.max; detection of a blocked valve, if X.sub.t1 is less than X.sub.max and (X.sub.maxX.sub.t1)/X.sub.max.sub.X holds true, wherein .sub.X is predetermined.

2. The method according to claim 1, wherein .sub.X is 0.2, preferably .sub.x is z 0.4, particularly preferably .sub.X is 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.sub.max takes place only after an initiation time span (t0) after detection of the maximal speed of rotation (.sub.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.sub.t2 of the monitoring parameter (I, T) is determined, and detection of the blocked valve is verified if X.sub.t2 is less than X.sub.max and (X.sub.maxX.sub.t2)/X.sub.max.sub.X holds 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.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0036] 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.

[0037] The figures show:

[0038] FIG. 1 a schematic axonometric view of a coolant compressor according to the invention, with the top housing half removed,

[0039] FIG. 2 a diagrammatic illustration of the method according to the invention.

WAYS FOR IMPLEMENTATION OF THE INVENTION

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The coolant compressor 1 is operated at a variable speed of rotation , i.e. the speed of rotation 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 .sub.max, which typically amounts to 3000 min.sup.1 to 4000 min.sup.1.

[0044] 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.

[0045] 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.

[0046] According to the invention, after detection of the maximal speed of rotation .sub.max, 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 .sub.max: [0047] determination of a maximal value X.sub.max of the monitoring parameter of the coolant compressor 1; [0048] determination of a value X.sub.t1 of the monitoring parameter after a first time span t1 after the determination of the maximal value X.sub.max; [0049] detection of a blocked valve, if X.sub.t1 is less than X.sub.max and (X.sub.maxX.sub.t1) /X.sub.max.sub.X holds true, wherein .sub.X is predetermined.

[0050] 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 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 .sub.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.sub.max is determined. Typically, t0 amounts to at least 5 min, preferably at least 10 min, particularly preferably at least 15 min.

[0051] In a typical usage case analogous to FIG. 2, the current I, for example, has increased to a value of X.sub.max0.85 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).

[0052] The determination of X.sub.t1 takes place after expiration of the first time span t1 after the determination of X.sub.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 .sub.max and the determination of X.sub.t1 amounts to t0 +t1. In a typical usage case analogous to FIG. 2, the current I has decreased to a value of X.sub.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.sub.t1=50 C. (corresponds to measured 70 C. at 20 C. ambient temperature), for example, after the first time span t1.

[0053] Depending on the type of the coolant compressor 1, a specific value can be predetermined for .sub.X, wherein typically, .sub.X0.2, preferably .sub.X0.4, particularly preferably .sub.X0.5 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.sub.maxX.sub.t1)/X.sub.max0.56. When .sub.X=0.5 is set, a blocked valve or the blockage state is therefore detected.

[0054] 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.sub.t1, a relative short verification time span t2 is allowed to elapse, and then a present value X.sub.t2 of the monitoring parameter is determined, and the condition (X.sub.maxX.sub.t2)/X.sub.max.sub.X is 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.

[0055] In a typical usage case analogous to FIG. 2, the current I has decreased to a value of X.sub.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.sub.t2=18.9 C. (corresponds to measured 38.9 C. at 20 C. ambient temperature), for example, after the verification time span t2.

[0056] In the exemplary embodiment of FIG. 2 that is shown, (X.sub.maxX.sub.t2)/X.sub.max0.73. In other words, when .sub.X=0.5 is set, the previously performed detection of the blocked valve is confirmed or verified.

[0057] 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.

[0058] 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 drops from the maximal speed of rotation w.sub.max to 0.

[0059] 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.

[0060] 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.

[0061] 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 .sub.max again; 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 .sub.max.

[0062] However, in particular if the blockage situation no longer exists, situations can also occur in which the speed of rotation of the electric motor lies below the maximal speed of rotation max. 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 .sub.max is detected subsequently.

[0063] 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 .sub.X, t0, t1, t2, and t3, for the specifically present coolant compressor 1.

REFERENCE SYMBOL LIST

[0064] 1 coolant compressor [0065] 2 housing of the coolant compressor [0066] 3 cylinder housing [0067] 4 drive unit [0068] 5 cylinder cover [0069] 6 valve plate [0070] 7 screw [0071] 8 pressure pipe that leads outward [0072] 9 suction muffler [0073] 10 crankshaft [0074] I current consumption of the electric motor [0075] T temperature of control electronics of the electric motor or of a motor winding of the electric motor [0076] t time [0077] t0 initiation time span [0078] t1 first time span [0079] t2 verification time span [0080] t3 second time span [0081] speed of rotation of the electric motor [0082] .sub.max maximum speed of rotation of the electric motor