JPH0247666B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a refrigerator using a compressor with a variable rotation speed, and particularly relates to setting the rotation speed of the compressor.

(B) Prior Art In general, there is a control device for a conventional refrigerator, such as an air conditioner, which uses a compressor with a variable rotational speed, as described in Japanese Patent Laid-Open No. 55-96858. The control device described in this publication calculates the temperature difference between the set temperature of the conditioned room, outputs a rotation speed signal according to this temperature difference, changes the rotation speed (capacity) of the compressor, and changes the temperature of the conditioned room. The air conditioning was operated at a capacity commensurate with the size of the addition.

(C) Problems to be Solved by the Invention In such an air conditioner control device, when the temperature difference between the set temperature of the room to be conditioned is large, such as when the air conditioner starts operating, the compressor A signal indicating the maximum rotation speed was being output. This signal was maintained until the temperature difference between the set temperature and the room temperature became small to some extent.

Generally, the capacity of a heat exchanger, such as a condenser or an evaporator, in an air conditioner (refrigerator) is set smaller than the capacity of the compressor at its maximum capacity. This is because the operating time of the compressor at maximum capacity is small compared to the overall operating time of the air conditioner, so the capacity of the heat exchanger is set taking normal operating capacity into consideration, and the capacity of the heat exchanger is unnecessarily increased. This is to prevent the air conditioner from becoming larger as a result.

Therefore, for example, when the air conditioner starts operating, if the temperature difference between the set temperature and the room temperature is extremely large and the signal indicating the maximum rotation speed (maximum capacity) of the compressor is output for a long time, the capacity of the heat exchanger will be exceeded. of the output was supplied from the compressor, causing problems such as liquid returning to the compressor and lack of lubricating oil, which could lead to damage to the compressor.

In view of such problems, the present invention provides a control device that suppresses damage to the compressor as described above.

(d) Means for solving the problem The control device of the present invention includes a compressor whose rotation speed changes,
In a refrigerator in which a refrigeration cycle is configured by connecting a condenser, a pressure reducer, and an evaporator in a ring with refrigerant piping, a sub-control that controls the rotation speed of the compressor based on a rotation speed signal from the main control section. and a timer section for controlling the operation of the compressor at the maximum rotational speed for a predetermined time or less.

(e) Effect The refrigerator control device of the present invention can limit the time during which the compressor operates at the maximum rotation speed.

(F) Embodiment Below, an embodiment of the present invention applied to an air conditioner will be explained based on the drawings. First, FIG. This is a compressor whose rotational speed changes according to the frequency of the AC power source (the rotational speed is controlled by changing the frequency), and the condenser 2, pressure reducer 3, and evaporator 4 are connected in a ring with refrigerant piping. It constitutes a refrigeration cycle.

5 is a sub-control unit, which includes an inverter circuit 6 that connects six switching transistors in a three-phase bridge configuration and converts direct current to alternating current; and a signal generating circuit 7 which outputs a switching signal. This signal generation circuit 7 is supplied with alternating current from the inverter circuit 6 to the compressor 1 at a frequency corresponding to the frequency signal of the compressor 1 given from the main control section 8 . The frequency of this alternating current determines the rotation speed of the compressor. A rectifier circuit 9 converts the alternating current from the alternating current power supply 10 and supplies it to the inverter circuit 6.

The main control unit 8 includes a temperature setting device 11 that sets the temperature of the room to be conditioned, and a temperature sensor 12 that detects the temperature of the room to be conditioned. Although a variable resistor is used in the temperature setting device 11, the temperature setting device 11 is not limited to this, and the set temperature may be determined by a combination of a key switch and software.

Further, the main operations of the main control section 8 are performed based on the flowchart shown in FIG. First, when starting operation, set the flag to "0" and set " ₀ (frequency) =
30" signal to the sub-control unit 5. Next, input the set temperature T and room temperature t of the conditioned room, find the temperature difference between the set temperature T and the room temperature t, and calculate the set frequency from this temperature difference. This set frequency is “=F
(1T−t1)”, and this conversion is performed using the conversion diagram shown in FIG.

The set frequency determined in this way is “=
180", it is determined whether the timer is up or not. If the time is up and the flag is "0", the timer is reset and started at the same time. At the same time, the flag is set to "1".Next. “＝
180”, the signal output to the sub-control unit 5 is set to “ _0”.
= 180", and thereafter maintains the output of the signal " ₀ = 180". After this, the timer starts the timer.
When UP, the signal output to the sub-control unit 5 is set to “ ₀ =
160” and maintain the output of “ ₀ = 160” thereafter.

After maintaining this kind of operation, the temperature difference between the set temperature T and the room temperature t becomes smaller and the set frequency becomes “
≦160'', a set frequency corresponding to this temperature difference is output from the main control section 8 to the sub control section 5.

Incidentally, the timer time of the timer may be set according to the capacity of the compressor 1 and the capacities of the condenser 2 and evaporator 4 so that liquid return does not occur. Moreover, the frequency signal output to the sub-control unit 5 is “ ₀ =30~ ₀ =
It is assumed that the timer time is longer than the time it takes to reach 180”.

The operation of the air conditioner configured as described _above will be explained based on FIG. = 180", but in reality the output signal to the sub-control unit 5 increases from " ₀ = 30" and increases to " ₀ = 180".
It is something that becomes. If this " ₀ = 180" signal operation (compressor 1 operation with 180Hz AC) is maintained for a predetermined time (time P ₀ to P ₂ ), even if the set frequency is "= 180", the secondary The signal to the control unit 5 becomes " ₀ =160", and operation based on the signal " ₀ =160" (operation of the compressor 1 with 160 Hz alternating current) is performed.

After maintaining such “ ₀ = 160” operation,
When the temperature difference between the set temperature T and the room temperature t becomes 5 or less at time P ₃ , the frequency signal ₀ also becomes small and at time P ₄
Balance with the load size when . After this, when there is a sudden increase in the load at time _P5 , the frequency signal ₀ also increases and becomes " ₀ = 180", and the frequency signal ₀ changes according to the magnitude of the load.

As mentioned above, in this control device the maximum frequency signal
Since the maximum time during which ₀ is output is limited by the timer, it is possible to limit the time during which the condenser 2 and the evaporator 4 are supplied with capacity exceeding their capacity.

In the above embodiment, since an induction motor was used for the compressor 1, the number of revolutions was controlled by frequency, but when a DC motor is used, the applied voltage may be changed.

(g) Effects of the invention The control device of the present invention includes a compressor whose rotation speed changes,
In a refrigerator in which a refrigeration cycle is configured by connecting a condenser, a pressure reducer, and an evaporator in a ring with refrigerant piping, a sub-control that controls the rotation speed of the compressor based on a rotation speed signal from the main control section. Since it is equipped with a timer section that keeps the compressor operating at the maximum rotation speed for a predetermined time or less, even if a compressor with a capacity greater than the capacity of the condenser or evaporator is used, the operation at the maximum rotation speed can be avoided for a long time. This prevents liquid from returning to the compressor. Furthermore, a small-capacity heat exchanger can be used, and the refrigerator can be made smaller.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an air conditioner using a device showing an embodiment of the present invention, Fig. 2 is a flowchart showing the operation of the main parts of the main control section shown in Fig. 1, and Fig. 3 is a 2 is a conversion diagram showing the relationship between the conversion formulas shown in FIG. 2, and FIG. 4 is an explanatory diagram showing the operation based on the flowchart shown in FIG. 2. 1...Compressor, 2...Condenser, 3...Compressor,
4... Evaporator, 5... Sub control section, 8... Main control section.

Claims (1)

[Claims] 1. In a refrigerator in which a refrigeration cycle is constructed by connecting a compressor whose rotation speed changes, a condenser, a pressure reducer, and an evaporator in a ring with refrigerant piping, compression is controlled based on a rotation speed signal from the main control unit. 1. A control device for a refrigerator, comprising: a sub-control unit that controls the rotation speed of the refrigerator; and a timer unit that controls the operation of the compressor at the maximum rotation speed for a predetermined time or less.