JPH0570064B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a refrigeration cycle device that includes a variable rotation speed compressor and an inverter circuit that supplies driving power to the variable rotation speed compressor.

[Technical background of the invention]

Generally, refrigeration cycle devices used in air conditioners etc. are equipped with a variable rotation speed compressor and an inverter circuit that supplies driving power to the variable rotation speed compressor, and the output frequency of the inverter circuit is adjusted according to the air conditioning load. By controlling the on/off operation of the variable speed compressor, we can obtain the optimal refrigeration capacity to match the air conditioning load, improve comfort,
There are some that enable improved energy saving effects and precision control.

In other words, in such a refrigeration cycle device, for example, during cooling operation, when the indoor temperature To detected by the indoor temperature sensor becomes higher than the set temperature Ts (air conditioning load is large), the inverter circuit The output frequency (hereinafter referred to as operating frequency) F is increased and the rotation speed of the variable rotation speed compressor is increased to obtain a high refrigerating capacity. Further, when the indoor temperature To becomes lower than the set temperature Ts (air conditioning load is small), the operating frequency F is reduced, the rotation speed of the variable rotation speed compressor is reduced, and the refrigerating capacity is reduced. Then, in a situation where the indoor temperature To further decreases and the required operating frequency F becomes equal to or lower than the predetermined minimum operating frequency Fo, the operation of the variable rotation speed compressor is turned off.

[Problems with background technology]

However, in such refrigeration cycle equipment, if the air conditioning load is small and the variable speed compressor continues to rotate at low speed, and then the variable speed compressor is turned off, the lubricating oil of the variable speed compressor becomes likely to remain in the refrigeration cycle. However, if the variable rotation speed compressor is restarted with lubricating oil remaining in the refrigeration cycle, the variable rotation speed compressor may be damaged.

In addition, in the case of refrigeration cycles with long piping distances and a large amount of refrigeration, a liquid receiver is installed in the refrigeration cycle to prevent liquid from backing up to the compressor when the operation is stopped. In a situation where the variable speed compressor continues to rotate at a low speed and then the variable speed compressor is turned off, the refrigerant in the refrigeration cycle cannot be sufficiently recovered to the liquid receiver, resulting in a liquid backlog. When the variable rotation speed compressor is restarted, the variable rotation speed compressor is damaged. For this reason, there was an inconvenience that a long refrigerant recovery time had to be ensured before the operation of the variable rotation speed compressor was turned off.

[Purpose of the invention]

This invention was made in view of the above-mentioned circumstances, and its purpose is to prevent lubricating oil from remaining in the compressor during the refrigeration cycle when the variable rotation speed compressor is turned off; It is an object of the present invention to provide a refrigeration cycle device in which a sufficient amount of refrigerant in a refrigeration cycle can be collected in a liquid receiver, thereby preventing damage to a compressor.

[Summary of the invention]

The present invention includes a variable rotation speed compressor and an inverter circuit that supplies driving power to the variable rotation speed compressor, and controls the output frequency of the inverter circuit and controls the on/off operation of the compressor according to the load. The refrigeration cycle apparatus is provided with a control means for temporarily increasing the output frequency of the inverter circuit before the operation of the compressor is turned off.

[Embodiments of the invention]

A first embodiment of the present invention will be described below with reference to the drawings.

As shown in Fig. 3, a variable rotation speed compressor 1, a condenser (outdoor heat exchanger) 2, a pressure reducing device such as a capillary tube 3, and an evaporator (indoor heat exchanger) 4 are connected in sequence to achieve refrigeration. constitutes a cycle. That is, during cooling operation, the refrigerant is caused to flow in the direction of the solid arrow in the figure.

On the other hand, 10 is an AC power supply, and an inverter circuit 11 is connected to this power supply 10. This inverter circuit 11 once rectifies the output of the AC power supply 10, converts it into AC power of arbitrary frequency and voltage by a switching operation, and supplies the AC power to the variable rotation speed compressor 1 as driving power. supply.

Further, 20 is an indoor temperature sensor, and the detection result of this indoor temperature sensor 20 is supplied to an arithmetic circuit 21. This arithmetic circuit 21 calculates the difference between the detection result of the indoor temperature sensor 21, that is, the indoor temperature To and the set temperature Ts, determines the rotation speed of the compressor 1 according to the calculated temperature difference, and A rotation speed setting command corresponding to the rotation speed is supplied to the control circuit 22. This control circuit 22
The switching element of the inverter circuit 11 is turned on and off at a timing corresponding to a rotation speed setting command from the arithmetic circuit 21, and the inverter circuit 11 outputs AC power of a predetermined frequency and voltage.

Next, the operation of the above configuration will be explained with reference to FIGS. 1 and 2.

Now, check the indoor temperature using the operation control unit (not shown).
Set Ts and perform operation start operation. Then, the arithmetic circuit 21 outputs a rotation speed setting command corresponding to the difference between the indoor temperature To and the set temperature Ts. In this way, the inverter circuit 11 operates at a predetermined frequency (hereinafter referred to as
AC power of F (referred to as the operating frequency) is output, and the compressor 1 is thereby turned on. In other words, cooling operation starts.

During this cooling operation, if the indoor temperature To is much higher than the set temperature Ts, the compressor 1 rotates at high speed at the maximum operating frequency _F1 and exhibits the maximum refrigerating capacity. Then, as the indoor temperature To decreases, the operating frequency F gradually decreases accordingly.
In this way, the indoor temperature To approaches the set temperature Ts,
When the temperature eventually falls below the set temperature Ts, the compressor 1 begins to rotate at a low speed at the lowest operating frequency _F2 .

However, when reaching the lowest operating frequency _F2 region,
The arithmetic circuit 21 increases the operating frequency F by a certain period of time t according to the rotation speed setting command. When the operating frequency F increases, the rotation speed of the compressor 1 increases, and the refrigerating capacity increases. Then, after a certain period of time t has elapsed, the arithmetic circuit 21 sets the operating frequency F to "0" according to the rotation speed setting command, and turns off the operation of the compressor 1. In other words, the cooling operation is interrupted.

Due to the interruption of cooling operation, the indoor temperature To rises,
When the temperature exceeds the set temperature Ts, the arithmetic circuit 21 again sets the operating frequency F corresponding to the difference between the indoor temperature To and the set temperature Ts, and restarts the compressor 1. In other words, cooling operation is restarted.

In this way, when the compressor 1 is turned off, the operating frequency is increased once before the operation is turned off, and the rotational speed of the compressor 1 is increased to increase the refrigerating capacity. The lubricating oil contained therein can be returned to the compressor 1. Therefore, when the compressor 1 is restarted, the compressor 1 is not damaged.

Next, a second embodiment of the present invention will be described with reference to FIG. However, in FIG. 4, the same parts as in FIG. 3 are given the same reference numerals, and detailed explanation thereof will be omitted.

As shown in FIG. 4, a variable rotation speed compressor 1, a condenser 2, a liquid receiver 5, an electromagnetic on-off valve 6, a pressure reducing device such as an expansion valve 7, an evaporator 4, a gas-liquid separator 8, etc. are connected in sequence. This constitutes a refrigeration cycle.
In this case, considering that the piping distance is long and the amount of refrigerant sealed is large, the liquid receiver 5 and the gas-liquid separator 8 are
is provided to prevent liquid from backing up to the compressor 1 when the operation is stopped. Thus, the excitation coil 6c of the electromagnetic on-off valve 6 is connected to the control circuit 22. In this case, the control circuit 22 has a drive control function not only for the inverter circuit 11 but also for the electromagnetic on-off valve 6, and turns on (opens) the electromagnetic on-off valve 6 during normal operation. There is.

Therefore, as shown in FIGS. 5 and 6, during cooling operation, when the indoor temperature To falls below the set temperature Ts and the compressor 1 begins to rotate at a low speed at the minimum operating frequency _F2 , the calculation The circuit 21 outputs a rotation speed setting command to increase the operating frequency F by a certain time t. Then, the control circuit 22
First, the electromagnetic on-off valve 6 is turned off (closed), and in this state, the operating frequency F is increased for a certain period of time t. Operating frequency F when the electromagnetic on-off valve 6 is off
When the number of rotations increases, a large amount of refrigerant in the refrigeration cycle flows into the liquid receiver 5 due to the increase in refrigeration capacity accompanying the increase in the rotational speed of the compressor 1. Then, after a certain period of time t has elapsed, the arithmetic circuit 21 sets the operating frequency F to "0" according to the rotation speed setting command, and turns off the operation of the compressor 1. In other words, the cooling operation is interrupted.

That is, compressor 1 with the lowest operating frequency Fo
At low speed rotation, the refrigerant in the refrigeration cycle is transferred to the liquid receiver 5.
This solution deals with the problem that refrigerant cannot be recovered sufficiently when the compressor 1 is restarted.As mentioned above, the refrigerant is forcibly and reliably recovered before the compressor 1 is turned off, thereby preventing liquid back up when the compressor 1 is restarted. This is to prevent damage to the equipment.

In this second embodiment, the operation of the control circuit 22 based on the rotation speed setting command of the arithmetic circuit 21 turns off the electromagnetic on-off valve 6 and increases the operating frequency F. As shown in the figure, an indoor temperature thermostat 30 is provided that operates when the indoor temperature To reaches a predetermined value below the set temperature Ts, and when this indoor temperature thermostat 30 operates, the electromagnetic on-off valve 6 is turned off and controlled by its operating signal. The operating frequency F may be increased by the circuit 22.

Furthermore, although the operating frequency F was increased for a certain period of time t, as shown in FIG.
A pressure switch 40 that operates when the refrigerant pressure falls below a certain value is provided in the refrigerant suction side piping, and the operation frequency F continues to increase until the pressure switch 40 operates, and immediately after that, the operation of the compressor 1 is turned off. You can also do this.

Further, in each of the above embodiments, the application to an air conditioner has been described, but the present invention can be similarly applied to other equipment as long as the refrigerating capacity is controlled variablely using a variable rotation speed compressor.

〔Effect of the invention〕

As described above, according to the present invention, when the compressor is turned off, the control means for temporarily increasing the output frequency of the inverter circuit before the operation is turned off is provided, so that when the variable rotation speed compressor is turned off, Refrigeration that prevents compressor lubricating oil from accumulating during the refrigeration cycle, or allows sufficient refrigerant to be collected in the receiver, thereby preventing damage to the compressor. We can provide cycle equipment.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining changes in operating frequency in the first embodiment of the present invention, Fig. 2 is a flowchart for explaining the operation of the same embodiment, and Fig. 3 is a refrigeration diagram in the same embodiment. A block diagram of a cycle and a control circuit, FIG. 4 is a block diagram of a refrigeration cycle and a control circuit in a second embodiment of the present invention,
FIG. 5 is a flowchart for explaining the operation in the same embodiment, FIG. 6 is a diagram for explaining the change in operating frequency and the operation of the electromagnetic on-off valve in the same embodiment, and FIGS. 7 and 8 are FIG. 9 is a block diagram of a refrigeration cycle and a control circuit each showing a modification of the same embodiment, and is a flowchart for explaining the operation of the conventional refrigeration cycle device. 1... Variable rotation speed compressor, 2... Condenser, 4...
... Evaporator, 11 ... Inverter circuit, 20 ... Indoor temperature sensor, 21 ... Arithmetic circuit, 22 ... Control circuit.

Claims (1)

[Claims] 1. Equipped with a variable rotation speed compressor and an inverter circuit that supplies driving power to the variable rotation speed compressor,
In a refrigeration cycle device that controls the output frequency of the inverter circuit and controls the on/off operation of the compressor according to the load, when the compressor is turned off, the output frequency of the inverter circuit is temporarily adjusted before turning off the compressor. A refrigeration cycle device characterized by being provided with a control means for increasing the temperature.