EP1537370A1

EP1537370A1 - Refrigerating device with ventilator and control method therefor

Info

Publication number: EP1537370A1
Application number: EP03784035A
Authority: EP
Inventors: Athanasious Athanasiou
Original assignee: BSH Bosch und Siemens Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2002-08-05
Filing date: 2003-07-21
Publication date: 2005-06-08
Also published as: WO2004015342A1; CN1675511A; CN100430673C; DE10235783A1; DE10235783B4

Abstract

The invention relates to a refrigerating device comprising a compressor (8), a condenser (9) and an evaporator (6) which are connected in a refrigerating circuit, at least one ventilator (7, 10) which is arranged on the condenser (9) and/or evaporator (6) and one control circuit (11) for controlling the switching on or turning off of the compressor (8) and the ventilator (7, 10). According to the invention, the ventilator (7, 10) can be adjusted according to different rotational speeds (n1, n2). Said rotational speeds are fixed according to the relative duration of actuation of the compressor (8).

Description

Refrigerator with fan and control method therefor

The present invention relates to a refrigeration device with a refrigerant circuit, in which a compressor, a condenser and an evaporator are connected to one another, and in which a fan on the condenser and / or the evaporator for intensifying the heat exchange between the condenser and the environment of the refrigeration device or is arranged between the evaporator and a refrigerator of the refrigerator.

Attaching a fan to a heat exchanger such as a condenser or evaporator of a refrigeration device has the advantage that the heat exchanger surface required to achieve the required heat exchange capacity is reduced, so that compact, inexpensive heat exchangers can be used. On the other hand, the addition of a fan complicates the construction of a refrigerator and thus increases the risk of malfunctions. The operating noise of a refrigerator is also increased by adding a fan.

The object of the present invention is to provide a refrigeration device with heat exchange reinforced by a fan, which is energy-saving and has a low noise level.

The object is achieved by a refrigeration device with the feature of claim 1. While in conventional refrigeration devices the fan is switched on and off coupled to the operation of the compressor at a fixed speed, different speeds of the fan can be realized in the refrigeration device according to the invention. In the simplest case, a switch can be provided on which a user can set the speed of the fan; the setting can be made, for example, on the basis of the expected average ambient temperature of the refrigerator. In the case of a high ambient temperature, for example in a tropical environment, a high heat exchange capacity is required. In this case, a high speed is expediently set in accordance with a nominal power specified for the type of fan. When used in a cooler environment, for example in a normally heated living room with a moderate climate, and even more when used in an unheated room, for example in a basement, the fan can be set by setting a lower speed Power consumption is reduced, its service life is extended and noise is reduced.

However, the speed of the fan is preferably set automatically by a control circuit which also serves to switch the compressor and the fan on and off.

In the simplest case, this control circuit is set up to operate the fan either with one of two discrete speed levels, a full or a reduced speed.

According to a first embodiment, the control circuit is connected to a temperature sensor, which is used to record the temperature in the vicinity of the fan, and determines the speed of the fan based on the temperature recorded by this sensor. This configuration is particularly expedient if the fan is intended for forced circulation of the air in the interior of the refrigerator, since a temperature sensor for detecting the interior temperature in the vicinity of the evaporator is provided in each refrigerator and can also be used to control the fan speed without additional costs.

According to another embodiment, the control circuit is configured to detect the relative duty cycle of the compressor and to determine the speed of the fan based on this relative duty cycle. This option is practical both for a fan attached to the evaporator of the refrigerator and for a fan attached to the condenser; in the case of a condenser fan, however, it has the particular advantage that it enables speed control without the need for an additional sensor. There are several ways to measure the compressor's duty cycle. A simple possibility is the calculation of a moving average, wherein a time constant of the average calculation is expediently greater than a typical duration of the operating cycle of the compressor, so that the moving average does not grow above a threshold value each time during an operating phase of the compressor the control circuit operates the fan at high speed. Another way of calculating the duty cycle is to measure the compressor on and off times in each compressor operating cycle and to calculate the ratio at the end of a cycle.

Further features, advantages and special features of the present invention result from the following description of exemplary embodiments with reference to the attached figures. Show it:

1 shows a schematic section through a refrigerator according to the invention;

2 shows a flowchart of a control method for the refrigeration device according to a first embodiment;

3 shows time diagrams of operating parameters of a refrigeration device controlled by the method from FIG. 2;

Fig. 4 is a timing diagram of the fan speed according to a modified

Embodiment of the method from FIG. 2; and

5 shows a flowchart of a control method according to a second embodiment of the invention.

Fig. 1 shows a schematic section through a refrigerator according to the present invention. An interior 3 is enclosed by a heat-insulating body 1 and a door 2 attached to it. A chamber 5, in which an evaporator 6 is accommodated, is separated from the interior 3 by a partition 4. The chamber 5 is connected to the interior 3 by two passages. A fan 7 is arranged in one of these passages, the operation of which causes a forced exchange of air between the chamber 5 and the interior 3.

A refrigerant circuit of the refrigeration device comprises the evaporator 6, a compressor 8, and a condenser 9. The condenser 9 mounted on the rear wall of the body 1 is assigned a second fan 10 for generating an air flow along the surface of the condenser 9. The fans 7, 10 and the compressor 8 are by a Electronic control circuit 11 controlled, which is connected to a temperature sensor 1 2 installed in the interior 3. The control circuit 11 switches the compressor 8 in and out in accordance with the detection result of the temperature sensor 12 in order to keep the temperature in the interior 3 within a predetermined interval. Coupled to the operation of the compressor 8, it also switches the fans 7, 10 on and off. In the simplest case, the fans 7, 10 can be operated simultaneously with a compressor, or can be switched on and off a little later in order to take into account the fact that at the beginning of a compressor operating phase, the condenser 9 and the evaporator 6 deal with them Environment are still substantially in thermal equilibrium and no increased heat exchange can be achieved by operating the fan 7 or 10, while immediately after the compressor is switched off, the condenser 9 is still warmer for a while and the evaporator 6 is colder than its surroundings.

A first embodiment of an operating method for the control circuit 11 from FIG. 1 is described with reference to FIG. 2. When the refrigerator is switched on, the control circuit 11 initializes a measured value RED for the relative duty cycle, i.e. for the ratio of the running time of the compressor 8 to the total running of the refrigerator, to an arbitrarily definable value. In the example considered here, initialization is carried out to a threshold value A, the function of which will be explained in more detail later; any other initial value would also be possible.

At regular intervals, each time a timer has expired, the control circuit 11 checks whether the compressor is switched on (S3). If so, the value of the relative duty cycle RED is incremented by 1 in step S4 and then (S5) multiplied by a factor (1-ε) which is slightly less than 1. If it is determined in step S3 that the compressor 8 is switched off, the method immediately proceeds to step S5. It is then determined in step S6 whether conditions for an operation of the fan 7 or 10 are met. In the simplest case, this condition is equivalent to the question of whether the compressor is switched on or not; the fan runs when the compressor is switched on, and the fan is switched off when the compressor is switched off. Alternatively, it can be provided that the fan is only switched on after a predetermined first time period after the compressor has been switched on and in each case after a second time period after the switch-off the compressor is switched off. The two periods can be different from each other; in particular, the second time period can be determined depending on the RED value. The larger the value of RED, the larger the second time span.

If step S6 reveals that the conditions for turning on the fan are not met, the process returns to step S2 with the fan remaining off.

On the other hand, if it is determined that the conditions for switching on the fan 7 or 10 are met, the relative switch-on duration RED is compared with the threshold value A in step S7. If the threshold value A is exceeded, the high-speed fan is started up (S8) if the threshold value falls below the low-speed threshold (S9), and the method returns to step S2. The fan remains in operation until a repeat of step S6 determines that the conditions for its operation are no longer met. The limit value A can be the same or different for the fans 7, 10.

FIG. 3 shows an example of the development over time of operating parameters of the refrigeration device controlled by the method according to FIG. 2. Graph A shows the state, switched on or off, of the compressor over the course of three compressor operating cycles. A cycle begins when the compressor 8 is switched on at time t0, t4 or tδ, when the control circuit 11 determines that the temperature in the interior 3 has exceeded an upper limit value. If this temperature falls below a lower limit, at times t2, t6, t10, the compressor 8 is switched off again. The fans 7 and 10 are switched on and off at times t1, t5, t9 and t3, .7, t11, as shown in graph B. The process of FIG. 2 is repeated in each cycle [tO, t4], [t4, t8], [t8, t12]; graph C shows the development that the mean value of the relative duty cycle RED takes.

During the first cycle [tO, t4], the ambient temperature of the refrigeration device is low and a short operating period [tO, t2] of the compressor 8 is sufficient to cool the interior 3 sufficiently. During this period, the value of RED increases asymptotically against a limit value, which is dependent on the parameter ε and the frequency with which the process steps of FIG. 2 are repeated. While the compressor 8 is switched off, in the time intervals [t2, t4], [t6, tδ], ... RED converges asymptotically to 0.

The graph D shows the speed of the fan 7 or 10 as a function of time based on the dash-dotted line labeled A on the graph C as the threshold value A of the method. In the first cycle, the relative duty cycle RED remains shorter than A during the entire operating time [t1, t3] of the fan. The control circuit 11 therefore operates the fan 7 or 10 at a low speed n1.

At a higher ambient temperature during the operating cycles [t4, tδ] and [tδ, t12], the operating phase of the compressor δ is extended, so that the threshold value A is exceeded in the course of the operating phase [t4, t6] of the compressor. This is detected by the control method of FIG. 2 in step S7, whereupon the control circuit increases the speed of the fan 7, 10 to a value n2, which corresponds to full load operation of the fan.

At time tδ, at the beginning of the third cycle shown, the relative duty cycle RED is longer than at time t4, so that the fan speed is increased to n2 shortly after the fan is switched on.

In the course of a few operating cycles at the elevated ambient temperature, a stationary regime is established, the longer the operating phases of the compressor δ, the shorter the length of time at the beginning of each operating phase of the fan in which the fan is operated with a low operating number n1 are, and can also become zero.

While with reference to Fig. 2 described expensive processes, even during the course of an operating phase of the compressor, whether the relative duty cycle has exceeded the threshold value A, different methods are also possible, in which such a check is carried out only once in each operating cycle, preferably at the beginning of the operating cycle when switching on of the compressor. Fig. 4 shows a time course of the fan speed, the results if such a modified method is carried out on the basis of the compressor running times according to FIG. 3A and the RED values according to FIG. 3C. Instead of the threshold value A, a changed, lower threshold value A 'is used as a basis. At the beginning of the first and second operating cycle, at times t0, t4, the RED value is less than A ', so that the fan runs at the low speed n1 during the entire switch-on time [t1, t3] or [t5, t7] , Only at the beginning of the third phase did the extended compressor runtime have such an effect in the second phase that the RED value is above A '. As a result, the fan operates at high speed n2 from t9 to t11.

A second embodiment of a control method, which also realizes the behavior shown in FIG. 4, is shown in the flow chart of FIG. 5. When the refrigerator is switched on, the relative duty cycle RED is initialized to an arbitrarily selectable value in step S1 1; in other words, it is determined whether the fan 7 or 10 should run at low speed n1 or at high speed n2 during the first operating cycle of the refrigeration device. Then, in steps S12, two registers, designated BZ or VZ, are set to zero for the total operating time of the refrigeration device or the operating time of the compressor of the refrigeration device. The fan 7 or 10 can be switched on simultaneously with that of the compressor δ or at any later point in time. The operating time counter BZ is incremented in regular time intervals controlled by the expiry of a timer (S13) (S14). If a check (S15) shows that the compressor δ is switched on, the compressor operating time counter VZ is also incremented (S16). In step S17 it is checked whether the current operating phase of the compressor has ended. This is the case when the control circuit 11 puts the compressor back into operation after a previous switch-off phase. As long as this is not the case, the method returns to step S13. In this way, steps S13 to S17 are repeated cyclically in the course of an operating phase, the control circuit being able to switch the fan 7 or 10 on and off at any appropriate point in time in the course of such an operating phase.

If it turns out that the operating phase has ended, the control circuit determines the relative duty cycle RED for this operating phase by dividing the count values VZ and BZ. Depending on whether the relative duty cycle received is above or below of the limit value A (S19), the high speed n2 (S20) or the low speed n1 is determined for the subsequent operating phase (S21). Then the process returns to S12.

In the method described above, the relative duty cycle RED used to control the fan speed during an operating cycle of the refrigerator is obtained exclusively from the ratio of the compressor operating time to the total operating time during the immediately preceding operating cycle. Alternatively, it can also be provided that the relative duty cycle is obtained in step S1δ by a moving averaging taking into account the relative duty cycles measured in more recent operating cycles. For this purpose, the relative duty cycle RED (n) for an nth operating cycle is calculated in step S1δ using the following formula

RED (n) = -RED (n - l) + (-) ^ - a a BZ

In a second embodiment of the refrigeration device according to the invention, in addition to the components already described above with reference to FIG. 1, a second temperature sensor 13 is provided, which is connected to the control circuit 11 and is arranged on the outside of the refrigeration device for detecting its ambient temperature. This sensor, shown in dashed lines in FIG. 1, enables the control circuit 11 to detect a temperature difference between the interior 3 of the refrigeration device and the surroundings and, on the basis thereof, to estimate the cooling capacity required. In this embodiment, a measurement of the relative duty cycle RED can be dispensed with, since an estimate of an expected relative duty cycle is possible on the basis of the difference in the temperatures measured by the sensors 12, 13. This embodiment has the advantage in particular over the embodiments described with reference to FIGS. 4 and 5 that they enable a reaction to a changed cooling capacity requirement already in the operating cycle of the compressor in which the change occurs, and not only in a subsequent one. The control circuit 11 decides on the rotational speeds at which the fan 7 and / or 10 is operated, and on their operating times on the basis of the outside temperature measured by the temperature sensor 13. Typical values for relative The operating times of the compressor δ and the corresponding operating times of the fans 7 and 10 are shown in Table 1 as a function of the room temperature:

As can be seen, at low ambient temperatures the relative duty cycle of a fan, in particular fan 7, can be shorter than that of the compressor. This can be achieved by choosing a longer delay period between switching on the compressor and the fan than between switching off the fan and the fan.

Claims

claims

1. refrigeration device with a compressor (8) connected in a refrigerant circuit,

Condenser (9) and evaporator (6), at least one fan (7, 10) arranged on the condenser (9) and / or evaporator (6) and one

Control circuit (11) for controlling the switching on and off of the compressor (8) and the fan (7, 10), characterized in that different speeds (n1, n2) can be set on the fan (7, 10).

2. Refrigerating appliance according to claim 1, characterized in that the speed (n1, n2) of the fan is adjustable by the control circuit (11).

3. Refrigerating appliance according to claim 2, characterized in that the control circuit (11) is set up to operate the fan (7, 10) at a full (n2) or a reduced (n1) speed.

4. Refrigerating appliance according to claim 2 or 3, characterized in that the control circuit (11) is connected to a temperature sensor (13) for detecting the temperature in the vicinity of the fan and the speed (n1, n2) of the fan (7, 10) on the basis of those detected by the sensor (13)

Temperature.

5. Refrigerating appliance according to claim 2 or 3, characterized in that the control circuit (11) is set up to detect the relative duty cycle (RED) of the compressor (8) and the speed (n1, n2) of the fan (7, 10) on the basis this relative duty cycle (RED).

6. Refrigerating appliance according to claim 5, characterized in that the control circuit (1 1) determines the relative duty cycle (RED) by a moving averaging (S2 - S6).

7. Refrigerating appliance according to claim 3 and claim 5 or 6, characterized in that when the fan (7, 10) is operated at full speed (n2), its relative duty cycle is at least as large as that (RED) of the compressor (8) is.

8. Refrigerating appliance according to claim 5 or 6, characterized in that the relative duty cycle of the fan (7, 10) at least as large as that (RED) of

Compressor (8) is.

9. Refrigerating appliance according to one of claims 5 to 7, characterized in that the control circuit (11) detects the average relative duty cycle (RED) of the compressor (8) with a time constant which is longer than a typical operating cycle [tO, t4], the Compressor (δ).

10. Method for operating a fan (7, 10) arranged on an evaporator (6) or condenser (9) of a refrigeration device, in which the speed (n1, n2) of the fan (7, 10) corresponds to one on the evaporator (6 ) or

Condenser (9) required heat exchange capacity is set.

11. The method according to claim 10, characterized in that the speed (n1, n2) between a full (n2) and a reduced speed (n1) is selected.

12. The method according to claim 10 or 11, characterized in that the speed (n1, n2) is determined based on a relative duty cycle (RED) of a compressor (8) of the refrigerator.

13. The method according to claim 12, characterized in that the relative duty cycle (RED) is calculated by moving averaging (S2 - S6).

14. The method according to claim 13, characterized in that the relative duty cycle (RED) is recalculated at regular time intervals.

5. The method according to claim 12 or 13, characterized in that the relative duty cycle is calculated once per on / off cycle of the compressor (S1δ).