JPH0261474A - Defrost operation control device for refrigeration equipment - Google Patents

Abstract

PURPOSE:To optimize the timing of effecting defrosting operation and improve integrated refrigerating capacity by a method wherein an operating time between the starting and the stopping of a compressor is detected with respect to respective cycles and the defrosting operation is effected when the ratio of the operating time at present to the operating time immediately after finishing the defrosting operation has become larger than a predetermined value. CONSTITUTION:A temperature in a refrigerator, which is detected by a thermostat (TH) in the refrigerator, is changed in accordance with the starting and stopping of a compressor 1, the operating time T1 of the initial operation of the compressor 1 after effecting defrosting operation by the compressor 1, next operating time T2 and the operating time T3 of third time are measured based on the signal of an initial time measuring means 20. The average value T of these operations is obtained as an initial operating time. Thereafter, the operating time in respective cycles between the starting and the stopping of the compressor 1 is measured by a present time measuring means 21 as the operating time Tn at present. When the ratio of the operating time Tn at present to the initial operating time T has become larger than a predetermined value alpha, the defrosting operation is effected by a control means 22.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a defrost operation control device for a refrigeration system,
In particular, it relates to measures to optimize the timing of defrost operation.

(Prior Art) Conventionally, as disclosed in, for example, Japanese Unexamined Patent Publication No. 59-197764, in a refrigeration system in which a compressor is started and stopped in response to a signal from a thermostat disposed in a part to be refrigerated, As a means of preventing frost from forming on the evaporator and reducing the refrigerating capacity, there is a system that controls the refrigeration equipment to perform defrost operation at fixed defrost intervals using a timer signal while the refrigeration equipment is in operation. This is known as a publicly known technique.

(Problems to be Solved by the Invention) However, for example, in the case of a container refrigerator, the time until frost formation may vary depending on the moisture content of the cargo inside the refrigerator, the shape of the evaporator, and the like. In that case, for example, when the temperature inside the refrigerator changes between a predetermined differential 61 corresponding to the start and stop of the compressor as shown in FIG. 9, the pull-down time (Fig. Looking at the operating time of the compressor (solid line), when the evaporator's refrigerating capacity is sufficiently large, the pull-down time is short (see ■ in the figure), but as the evaporator's refrigerating capacity decreases, the pull-down time becomes longer (Fig. ). Therefore, if the defrost operation is performed at a certain defrost interval, the defrost operation may be performed even though there is still sufficient refrigerating capacity, or conversely, the defrost operation may be performed even though there is insufficient refrigerating capacity due to frost formation. Defrost operation may not start immediately.

That is, since the timing of the defrost operation is not appropriate, the maximum refrigerating capacity, so-called integral refrigerating capacity, cannot be secured within a certain period of time. Furthermore, as a result, there is a problem in that power is wasted.

The present invention was developed based on the fact that when frost forms on the evaporator, the refrigerating capacity decreases and the pull-down time increases.The purpose of the present invention is to perform defrost operation based on changes in the pull-down time. By doing so, the purpose is to optimize the timing of defrosting operation and, in turn, to improve the integral refrigerating capacity.

(Means for solving the problem) To achieve the above object, the first means for solving the problem is to use a compressor that starts and stops based on the temperature difference between the temperature of the part to be refrigerated and the set temperature, as shown in Fig. 1. (1) A refrigeration system is assumed, in which a condenser (2), a pressure reduction mechanism (3), and an evaporator (4) are sequentially connected, and a refrigeration circuit (6) capable of defrost operation is provided.

And, as a defrost operation control device for the refrigeration equipment,
The above compressor (1
), an initial time measuring means (20) for measuring the initial operating time from starting to stopping of the compressor (11J), and a current time measuring means for measuring the current operating time from starting to stopping of the compressor (1) after the initial period has elapsed. (21) and the outputs of the initial time measuring means (20) and the current time measuring means (21), and when the ratio of the current operating time to the initial operating time becomes larger than a predetermined set value, Circuit (6
) is provided with a control means (22) for controlling the defrost operation.

Further, as shown in FIG. 1, the second solution is based on a refrigeration system similar to the first solution, and the compressor (1
) is used to measure the initial number of repetitions of operation (
23), current number measuring means (24) for measuring the number of current operation repetitions of the compressor (1) in a fixed period having the same time as the initial period, and the initial number measuring means (24);
3) and the current number of times measuring means (24), when the ratio of the number of current operation repetitions to the initial number of operation repetitions becomes lower than a predetermined set value, the refrigeration circuit (6
) is provided with a control means (22) for controlling the defrost operation.

(Function) With the above configuration, in the invention of claim (1), the pressure operation time measuring means (20) measures the initial operation time in the initial period immediately after the end of the defrost operation of the compressor (1), and the current time The measuring means (21) measures the current operating time of the compressor (1) after the initial period has elapsed;
The control means (22) performs the defrost operation when the ratio of the current operating time to the initial operating time becomes larger than a predetermined value.

In that case, under the predetermined load conditions, the operating time of the compressor (1) immediately after the defrost operation is completed is used as a reference, and the subsequent change in operating time is compared using the initial operating time as a reference. ), the rate of decrease in the operating time of the compressor (1) due to the decrease in the refrigeration capacity due to frost formation is detected, and the refrigeration capacity is lower than the predetermined required value. The exact point in time will be detected. Therefore, the defrost operation is performed at appropriate timing, and the fractional refrigeration capacity and power usage efficiency are improved.

Further, in the invention of claim ('2J), the initial number measuring means (
23), the number of repetitions of operation of the compressor (1) in the initial period immediately after the end of the defrost operation is totaled A1. Then, the current number of times detection means (24) measures the current number of repetitions of operation in a period of the same length as the initial period, and further, the control means (22) determines that the number of repetitions of current operation is equal to the number of repetitions of the initial operation. When the ratio becomes lower than a predetermined value ', defrost operation is performed.

Therefore, similarly to the invention of claim (1) above, the evaporator (4
) An increase in pull-down time, or a decrease in the number of repeated operations, due to a decrease in refrigeration capacity due to frost was detected.
The rate of decline in refrigerating capacity is accurately ascertained, and defrost operation can be performed at the appropriate timing.

(Example) Hereinafter, examples of the present invention will be described based on the drawings from FIG. 3 to FIG. 8 and the following drawings.

FIG. 3 shows a first embodiment in which the invention of claim (1) is applied to a marine container refrigerator, in which (1) is a compressor, and (2) is a compressor that condenses the refrigerant discharged from the compressor (1). useless condenser,
(3) is an expansion valve as a pressure reducing mechanism that reduces the pressure of the refrigerant condensed in the condenser (2), and (4) is located inside the refrigerator (A) and is used to reduce the pressure of the refrigerant that has been reduced in pressure by the expansion valve (3). This is an evaporator for evaporation. The above-mentioned devices (1) to (4) are connected to each other through refrigerant piping (5) so that the refrigerant can flow, and the cold heat imparted by the condenser (2) is released into the air inside the refrigerator by the evaporator (4). A refrigeration circuit (6) is configured.

In addition, a three-way valve (7) is connected to the discharge pipe (5b) of the compressor (1).
) is interposed, and the - side connection port of the three-way valve (7) is provided with a hot gas bypass path (8) that connects the discharge pipe (5b) and the liquid pipe (5a) so that the refrigerant can be bypassed. The ends of are connected. That is, during operation of the device, the three-way valve (7) is connected to the hot guy bypass path (8) as necessary.
By switching to the side, defrost operation is performed.

In addition, an internal thermostat (TH) is installed inside the refrigerator (A) to detect the temperature difference between the internal temperature and the set temperature, and the signal from the internal thermostat (TH) is transmitted throughout the device. It is connected for input to a controller (9) that controls the operation of the controller.

The controller (9) controls starting and stopping of the compressor (1), connection switching of the three-way valve (7), etc. based on the temperature difference between the internal temperature and the set temperature.

During operation of the refrigeration system, the refrigerant discharged from the compressor (1) is condensed in the condenser (2), then reduced to a predetermined low pressure state in the expansion valve (3), and evaporated in the evaporator (4). compressor (
Return to 1). Then, as shown in FIG. 5, the above refrigeration cycle is repeated, and the cold heat provided by the condenser (2) is applied to the air in the refrigerator (A) by the evaporator (4).
), the refrigerator interior (A) is cooled from thermo-on to thermo-off within a predetermined differential ΔT (for example, a value of about 2 degrees Celsius), and the temperature inside the refrigerator approaches the set temperature (solid line in the figure). When the internal temperature detected by the internal thermostat (TH) reaches the set temperature (when the thermostat is off), the compressor (
1) is stopped and the stopped state is maintained until the temperature inside the refrigerator rises to the set temperature again (the broken line portion in the figure). In addition, as described below, if frost forms on the evaporator (4) during operation of the device and the refrigerating capacity decreases, the three-way valve (7) switches to the hot gas bypass path (8). , compressor (1)
The high-temperature, high-pressure gas discharged from the evaporator (4
) to defrost the evaporator (4).

Next, the control content of the controller (9) will be explained based on the flowchart of FIG. 4 and FIG. 5. When the defrost top operation is completed in step S1 (Ih in the figure),
The compressor (1) is started in step S2, and the compressor (1) is started in step S3.
Pull down the refrigerator interior (A) in step S4, and pull down the refrigerator interior (A) in step S4.
When A) reaches the set temperature, the compressor (1) is stopped. Then, during the initial period immediately after the defrost operation is completed, that is, while the compressor (1) is repeatedly started and stopped three times, in step S5, the compressor (1) in each cycle of starting and stopping is performed.
The operating times Tt + T2 and T3 in 1) are calculated in total by n1 based on the humidity change of the internal thermostat (TH), respectively. In other words, as shown in FIG.
Measure rl l T2 + T3. Then, in step S6, the average value T is calculated using the formula T= (TI +72 +
T3)/3, and the value T is taken as the initial operating time. Thereafter, during operation of the device, the current operating time Tn in each cycle of starting and stopping the compressor (1) is measured in step S7, and in step S8, the initial operating time Tn of the current operating time Tn is measured. ratio to (Tn
/T) is larger than a predetermined constant α.

If the determination is YES, that is, Tn/T>α, it is determined that frost has formed on the evaporator (4), and the process moves to step S9, where the refrigeration circuit (6) The connection of the three-way valve (7) is switched to the hot gas bypass path (8) side, and a defrost operation is started in which the discharged gas is directly introduced into the evaporator (4) (D2 in the figure).

In the above control flow, steps S5 and S6 cause the compressor (
Initial time measuring means (20) is configured to measure the initial operating time from start to stop of step 1), and in step S7, the current time measuring means (20) is configured to measure the current operating time of the compressor (1) after the initial period has elapsed. Means (21) are constructed. Further, in step S9, when the outputs of the initial time measuring means (20) and the current time measuring means (21) are received, and the ratio of the current operating time to the initial operating time becomes larger than a predetermined set value, the above-mentioned Refrigeration circuit (6)
A control means (22) is configured to control the defrost operation at the time of the defrost operation.

Therefore, in the above embodiment, the internal thermostat) (
If the internal temperature detected by the compressor (TH) changes as shown in Fig. 5 in response to the start and stop of the compressor (1), the first compressor after the compressor (1) performs defrost operation. (1
), the next driving time T2, and the third driving time T3 are measured based on the signal from the driving time measuring means (20), and their average value T is determined as the initial driving time. After that, the current time measuring means (21)
As a result, the operating time in each cycle of starting and stopping the compressor (1) is measured as the current operating time Tn, and the control means (22) sets the ratio of the current operating time Tn to the initial operating time T to a predetermined value α. Defrost operation is performed when the temperature exceeds .

In that case, even if the load conditions of the refrigeration equipment differ depending on a certain period of use, for example, the type of product in the cargo in the refrigerator or the temperature set in the refrigerator changes, under the load conditions, the Since the operating time of the compressor (1) is used as a reference and the subsequent changes in operating time are compared using the initial operating time as a reference, pull-down due to a decrease in refrigerating capacity is detected regardless of changes in the internal condition of the refrigerator. A decrease in the time, that is, the operating time Tn of the compressor (1) is detected, and the rate of decrease in the refrigerating capacity can be accurately grasped.

Therefore, it is possible to detect the exact point in time when the refrigerating capacity drops below a predetermined required value, and by performing defrost operation at the appropriate timing, it is possible to improve the integral refrigerating capacity, that is, the power usage efficiency. It is.

In the above-mentioned first embodiment, in order to improve reliability, the average value of the three operation times was calculated as the initial operation time immediately after the defrost operation was completed, but the initial operation time value of only one time was calculated. may be used.

Next, a second embodiment according to the invention of claim (a) will be described. In the second embodiment as well, the configuration of the refrigeration system is the same as that of the third embodiment.
This is exactly the same as the first embodiment shown in the figure.

Next, the control contents of the controller (9) will be explained based on FIGS. 6 to 8.

FIG. 6 is a flowchart showing the control contents, and in steps 5IO-3I2, the same control as steps 81 to S3 of the control flow in the first embodiment is performed (the fourth
(see figure). Next, in response to the temperature change inside the refrigerator shown in Fig. 7, the thermo-off points at which the compressor (1) switches to thermo-off, at which it stops, are determined in order from immediately after the defrost operation ends (a), (
b), (C) (d), (e), ...,
In step SI4, the compressor (1
) start and stop repetition count (initial operation repetition count)
Measure Na. Next, in step SI5, each subsequent thermo-off time point (b), (c), (d).

(e),... for a certain period of time T, which is the same as the initial period Te above.
Number of operation repetitions Nn (n-b, c.

d, e, ...) in total flFJ. That is, as shown in FIG. 8, for example, the number of times is Nb and Nb, respectively.
c, Nd, Ne,... And step 81
6, each time the ratio Nn with the initial number of operation repetitions Na
/Na() Mari, Nb /Na, Nc /Na
, Nd/Na, Ne/Na, -=) and compares it with a predetermined value α' to determine the current number of operation repetitions N.
The defrost operation is performed when the ratio Nn/Na of n and the initial number of operation repetitions Na becomes Nn /Na <α'. For example, as shown in FIG. 8, if the number of times the operation is repeated during a certain period of time Tc immediately after the end of the defrost operation is 5, the defrost operation will be performed when Nn15<α'.

In the above control flow, in step SI4, the compressor (
An initial number hand+1111 means (23) is configured to measure the number of initial operation repetitions in step SI5, and in step SI5, the current number of operation repetitions of the compressor (1) is measured in a predetermined period having the same time as the initial period. A current count hand 71111 means (24) is configured. Also,
By step S+7, the above-mentioned initial number measuring means (23)
and receives the output of the current number of times measuring means (24), and when the ratio of the number of current operation repetitions to the initial number of operation repetitions becomes lower than a predetermined set value, defrost operation is performed in the refrigeration circuit (6). Control means to control (
22) is configured.

Therefore, in the invention of claim (2), the initial number measuring means (23) measures the number of times the compressor (1) is operated and stopped during the initial period Tc immediately after the end of the defrosting operation, that is, the number of repeated operations. .

Then, the current number of operation repetition times Nn is measured by the current number of times detection means (24) in the period Tc having the same length as the initial period Te, and furthermore, the value of the current number of operation repetitions Nn is measured by the control means (22). Number of repetitions of operation N
When the ratio Nn/Na to a becomes lower than a predetermined value α', the defrost operation is performed.

Therefore, similarly to the invention of claim (1) above, a decrease in the number of repeated operations due to an increase in pull-down time due to a decrease in refrigerating capacity is detected, the rate of decrease in refrigerating capacity is accurately grasped, and appropriate timing is detected. This allows you to perform defrost operation.

In addition, in each of the above embodiments, the internal thermostat (TH)
The operating time or number of repetitions of operation of the compressor (1) is detected from the temperature change detected by the controller (9). Needless to say, it's a good thing.

Furthermore, in each of the above embodiments, a hot gas bypass method is applied as the defrosting operation method;
The defrosting operation method according to the present invention is not limited to the above-mentioned method, and similar effects can be obtained by, for example, a method in which a cycle switching mechanism is arranged to perform defrosting operation in a reverse cycle.

(Effects of the Invention) As explained above, according to the invention of claim (1), in a refrigeration system equipped with a compressor that starts and stops with thermo-on and thermo-off, the operating time between starting and stopping the compressor is Since each cycle is detected and the defrost operation is performed when the ratio of the current operation time to the operation time immediately after the end of the defrost operation becomes larger than a predetermined value, the rate of decline in refrigerating capacity under a predetermined load condition can be calculated. It is possible to accurately grasp the temperature and perform defrost operation at an appropriate timing, thereby improving the integral refrigerating capacity, that is, the power usage efficiency.

According to the invention of claim ('2J), in a refrigeration system similar to the invention of claim (1), the ratio of the current number of repeated operations of the compressor to the number of repeated operations of the compressor immediately after the end of the defrosting operation is less than or equal to a predetermined value. Since the defrost operation is performed when the temperature becomes 1, the same effect as the invention of claim (1) can be obtained.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 represent claims (1) and (2), respectively.
FIG. 2 is a block diagram showing the configuration of the second invention. Figures 3 to 8
The figures show an embodiment, Fig. 3 is a refrigerant system diagram showing the configuration of the refrigeration system, Fig. 4 is a flowchart showing the control contents of the first embodiment, and Fig. 5 is the operation in the invention of claim (1). Figure 6 is a temperature change characteristic diagram explaining the time detection method.
A flowchart showing the control contents of the embodiment, and FIGS. 7 and 8 show a method for detecting the number of repeated operations in the second embodiment, with FIG. 7 being the initial period and FIG. 8 being based on each thermo-off point. It is a figure which shows the detection method in each period, respectively. FIG. 9 is a diagram showing a conventional method of setting the defrost operation start timing using a constant defrost interval. (1)...Compressor, (2)...Condenser, (3)...
・Expansion valve (pressure reduction mechanism), (4)...Evaporator, (20)
... initial time measuring means, (21) ... current time measuring means, (22) ... control means, (23) ... initial number measuring means, (24) ... current number measuring means. Patent Applicant Daikin Industries, Ltd. Agent Patent Attorney 1) Hiroshi (and 2 others) Figure 3 Figure Figure

Claims (2)

[Claims] (1) A compressor (1), a condenser (2), a pressure reducing mechanism (
3) and an evaporator (4) connected in sequence, and a refrigeration system equipped with a refrigeration circuit (6) capable of defrost operation,
The above compressor (1
); an initial time measuring means (20) for measuring the initial operating time from starting to stopping of the compressor (1); and a current time measuring means (20) for measuring the current operating time from starting to stopping of the compressor (1) after the initial period has elapsed. 21), and upon receiving the outputs of the initial time measuring means (20) and the current time measuring means (21), when the ratio of the current operating time to the initial operating time becomes larger than a predetermined set value, the refrigeration circuit Control means (2) for controlling the defrost operation in (6)
2) A defrost operation control device for a refrigeration system, comprising: (2) A compressor (1), a condenser (2), a pressure reducing mechanism (
3) and an evaporator (4) connected in sequence, and a refrigeration system equipped with a refrigeration circuit (6) capable of defrost operation,
an initial number measuring means (23) for measuring the number of initial operation repetitions of the compressor (1) in a predetermined initial period immediately after the end of the defrosting operation; The current number of times measuring means (24) for measuring the number of current repeated times of operation, the initial number of times measuring means (23) and the current number of times measuring means (24) are received, and the ratio of the current number of repeated times of operation to the initial number of repeated times of operation is determined as a predetermined value. A defrost operation control device for a refrigeration system, comprising: a control means (22) for controlling the refrigeration circuit (6) to perform a defrost operation when the value becomes lower than a set value.