JPH01107056A - Air conditioner - Google Patents

Abstract

PURPOSE: To prevent possible oil shortage in a compressor and wet vapor suction to the compressor by providing a control part to accomplish a gradual raise in the operation frequency of the compressor at the start of operation or after the end of the defrosting operation while restricting the rise until the temperature of a condenser reaches a specified value. CONSTITUTION: At the start of a compressor, the temperature of a room heat exchanger working as condenser is detected by a sensor 23. In the unstable operation in which the temperature fails to reach a set value, a start braking means 35 in a control section 20 continues to output an operation frequency command higher than the commercial power source frequency but lower than the maximum operation frequency to suppress the rise in the frequency operation frequency of the compressor. Then, in the stable operation in which the temperature of a room heat exchanger, the start braking means 35 ceases the outputting of the operation frequency command and instead, an operation frequency command of an operation frequency determining means 31 is supplied to an inverter drive circuit 36. As a result, the operating frequency of the compressor is raised to the maximum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an air conditioner equipped with an inverter circuit that supplies driving power to a compressor.

(Prior art) Air conditioners are equipped with an inverter circuit that supplies driving power to the compressor, and by controlling the output frequency of the inverter circuit according to the air conditioning load, it is possible to achieve the optimal capacity to handle the air conditioning load. There are some that aim to improve the benefits, comfort, and energy saving effects.

In such an air conditioner, at the start of operation or after the end of defrosting operation, the output frequency of the inverter circuit (hereinafter referred to as compressor operating frequency F) is increased to a target frequency corresponding to the air conditioning load. However, if the temperature increases all at once, it will adversely affect the life of the refrigeration cycle equipment.

Therefore, conventionally, as shown in FIG. 7, the operating frequency F is increased in stages at regular intervals after the start of operation or after the end of defrosting operation.

That is, for the first minute, the operating frequency F is set to a value F7 lower than the commercial power frequency, and for the next minute, the operating frequency F is set to a value F7 higher than the commercial power frequency.
Set the operating frequency F to a value F9 lower than max, and then set the operating frequency F to the maximum operating frequency F1l, which is the target frequency.
It has led to laX.

Note that the target frequency is the highest operating frequency Fwax, but this is because the load is high at the start of operation and after the defrosting operation is completed.

However, such control in which the operating frequency F is simply increased at regular intervals may cause the following problems.

For example, if the operation is stopped for a long time or the outside temperature is extremely low, so-called refrigerant stagnation occurs in the compressor, and even if the compressor is started in this state and the operating frequency F continues to increase, The input is used to separate the stale refrigerant in the compressor, making it difficult to create a pressure difference between the high-pressure side and the low-pressure side of the refrigeration cycle. thus,
If the operating frequency F continues to rise without any pressure difference,
The lubricating oil in the compressor is discharged together with the stagnant refrigerant, making it impossible to recover it and causing a so-called oil level shortage. Moreover, liquid refrigerant accumulated in the refrigeration cycle is sucked into the compressor as it is, resulting in so-called liquid back. This liquid backlog is particularly noticeable when heating is resumed after the defrosting operation is completed.

That is, the lack of oil level causes insufficient lubrication of the main bearing of the compressor, which adversely affects the life of the compressor. Also,
Of course, liquid backlog has a negative impact on the life of the compressor.
It may even cause damage to the compressor.

This invention was made in view of the above circumstances,
The purpose of this is to prevent the oil level in the compressor from running out and liquid back-up to the compressor, thereby extending the life of the compressor and providing an air conditioner that enables efficient operation. It's about doing.

[Structure of the Invention] (Means for Solving the Problems) A means for increasing the operating frequency of the compressor in stages at the start of operation or after the end of defrosting operation, and a means for increasing the operating frequency by increasing the operating frequency by adjusting the temperature of the condenser. Alternatively, means for suppressing the rate of change to a predetermined value until it reaches a set value is provided.

(Function) In unstable operation where the condenser temperature or its rate of change has not yet reached the set value, the increase in operating frequency is suppressed to a predetermined value.
In stable operation where the temperature of the condenser or its rate of change reaches the set value, an increase in the operating frequency is allowed.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

In Fig. 1, 1 is a variable capacity compressor;
A four-way valve 2, an outdoor heat exchanger 3, a pressure reducer such as an expansion valve 4
, an indoor heat exchanger 5, etc. are successively connected to form a heat pump type refrigeration cycle. That is, during cooling operation, the refrigerant flows in the direction of the solid arrow in the figure, and the outdoor heat exchanger 3 acts as a condenser and the indoor heat exchanger 5 acts as an evaporator. During heating operation, the refrigerant flows in the direction of the dashed arrow in the figure by switching the four-way valve 2, and the indoor heat exchanger 5 becomes a condenser and the outdoor heat exchanger 3 becomes a condenser.
acts as an evaporator.

An outdoor fan 6 is provided near the outdoor heat exchanger 3, and an indoor fan 7 is provided near the indoor heat exchanger 5.

On the other hand, 10 is a commercial AC power supply, and an inverter circuit 11 is connected to the power supply 10. This inverter circuit 11
This rectifies the AC voltage of the power supply 10, converts it into an AC voltage of a predetermined frequency by switching, and supplies the AC voltage to the drive motor of the compressor 1 as driving power.

Further, 20 is a control unit that performs overall control of the air conditioner, and external parts include a four-way valve 2, an outdoor fan 6, and an indoor fan 7.
, an inverter circuit 11, an operation section 21, an indoor temperature sensor 22, and a heat exchanger temperature sensor 23 are connected. The heat exchanger temperature sensor 23 is attached to the indoor heat exchanger 5.

Here, the main parts of the control section 20 are shown in FIG.

Reference numeral 31 denotes an operating frequency determining means, which determines a target operating frequency according to the difference (air conditioning load) between the moisture level Ta set by the indoor temperature setting device 21a in the operating unit 21 and the detected moisture level TS of the indoor temperature sensor 22; An operating frequency command corresponding to the determined content is supplied to the command switching means 32.

33 is a condenser temperature setting device for setting the condenser temperature, and the set value T1 and the detected temperature TO of the heat exchanger temperature sensor 23 are set.
are compared by a comparator 34. The comparator 34 emits a coincidence signal when the detected temperature TC reaches a set value T1, and the coincidence signal is supplied to the activation control means 35.

The startup control means 35 sequentially issues different operating frequency commands A and B at regular intervals in response to the starting signal or the defrosting end signal, and for the operating frequency command B, a matching signal is supplied from the comparator 34. It is designed to continue outputting until the

After the command switching means 32 is supplied with the starting signal or the defrosting end signal, the command switching means 32 gives the operating frequency command supplied from the starting control means 35 to the inverter drive circuit 36; When the supply runs out, the operating frequency command supplied from the operating frequency determining means 31 is then given to the inverter circuit 36.

The inverter circuit 36 switches and drives the inverter circuit 11 in accordance with the operating frequency command from the command switching circuit 32.

Next, the operation of the above configuration will be explained with reference to FIGS. 3, 4, and 5.

The heating operation is set using the operation control unit 21, a desired indoor temperature Ta is set, and an operation start operation is performed.

Then, the control section 20 switches the four-way valve 2.

Furthermore, in the control section 20, a start signal is input to the start control means 35, and the start control means 35 issues an operating frequency command A. This operating frequency command A corresponds to an operating frequency F7 lower than the commercial power supply frequency, and is supplied to the inverter drive circuit 36 via the command switching means 32.

Thus, the compressor 1 is first started at the operating frequency F7.

When the compressor 1 starts, the four-way valve 2 is in switching operation, so a heating cycle is formed, and the indoor heat exchanger 5 becomes the condenser,
Outdoor heat exchanger 3 acts as an evaporator.

The activation control means 35 starts a time count t at the same time as the operating frequency command A is generated, and when the time count t reaches a certain value ti (for example, one minute), it issues an operating frequency command B. This operating frequency command B is higher than the commercial power supply frequency and has a maximum operating frequency F n+a
It corresponds to an operating frequency Fs lower than x, and is supplied to the inverter drive circuit 36 via the command switching means 32.

In this way, after a certain period of time, for example, 1 minute, the compressor 1
The operating frequency F increases stepwise from F7 to FB.

On the other hand, the temperature of the indoor heat exchanger 5 acting as a condenser is detected by the heat exchanger temperature sensor 23, and if the detected temperature TC does not reach the set value T1, the activation control means 3
5 continuously generates the operating frequency command B, and the operating frequency F
Note that it is desirable that the operating frequency F9 is equal to or lower than the average value of the commercial power supply frequency and the maximum operating frequency Fmax.

When the detected temperature TC reaches the set value T1, the activation control means 3
5 no longer issues the operating frequency command B, and instead, the operating frequency command of the operating frequency determining means 31 is supplied to the inverter drive circuit 36.

The operating frequency command issued from the operating frequency determining means 31 corresponds to the air conditioning load, and since the load is generally high at the start of operation, it corresponds to the maximum operating frequency Fm-ax.

In this way, the operating frequency F of the compressor 1 increases from FB to the maximum operating frequency F max.

At this time, the control unit 20 turns on the indoor fan 7 at the same time as the operating frequency F increases.

In this way, at the start of operation, in unstable operation where the condenser humidity TC has not yet reached the set value T1 due to refrigerant stagnation, the increase in the operating frequency F is suppressed to a predetermined value lower than the maximum operating frequency FIIla×, and the condensation During stable operation in which the chamber temperature TO reaches the set value T1, that is, in a state where a pressure difference of 10-minutes occurs between the high-pressure side and the low-pressure side of the refrigeration cycle, the operating frequency F
By allowing the increase in the maximum operating frequency F max to the maximum operating frequency F max, the amount of lubricating oil discharged from the compressor 1 can be reduced, and therefore heating operation can be started without running out of oil level. Furthermore, liquid backflow to the compressor 1 can be prevented.

Therefore, the life of the compressor 1 can be extended.

In particular, since there is no oil level shortage or liquid back up, the compressor 1 can be started efficiently, resulting in a good start-up of the heating capacity. Moreover, since the operation of the indoor fan 7 is turned off while the increase in the operating frequency F is suppressed, the pressure on the high pressure side increases quickly, and the time required to reach stable operation can be shortened. It can greatly contribute to improving the characteristics.

By the way, as the heating operation progresses, frost gradually forms on the surface of the outdoor heat exchanger 3, which acts as an evaporator, and if left as it is, the heating capacity will decrease.

Thus, the control unit 20 periodically or as needed returns the four-way valve 2 and switches the heating cycle to the defrosting cycle (same as the cooling cycle).

That is, the outdoor heat exchanger 3 is defrosted using the heat of the high-temperature refrigerant.

During this snow removal operation, the control unit 20 sets the operating frequency F to the defrosting operating frequency F def. Furthermore, during the defrosting operation, the operation of the indoor fan 7 is turned off to prevent cold air from being blown into the room.

Thereafter, the control unit 20 switches the four-way valve 2, ends the defrosting operation, and returns to the heating operation. At this time, the operating frequency F is first set to F7 in the same way as at the start of operation described above,
After one minute, it is set to Fe, and this state is continued until the condenser temperature TC reaches the set value T1. And the condenser temperature T
When C reaches the set value T1, the operating frequency F increases from Fe to the highest operating frequency F laX.

At this time, the control unit 20 turns on the indoor fan 7 at the same time as the operating frequency F increases.

In this way, even when returning to heating after defrosting operation,
In unstable operation where the condenser temperature Tc has not yet reached the set value T1, increase the operating frequency F to the maximum operating frequency F1lla
Keep the condenser temperature TO at a predetermined value lower than X, and keep the condenser temperature TO at the set value T.
The increase in operating frequency F during stable operation reaching 1 is the highest operating frequency F I! By allowing up to 100 mL of liquid, liquid backflow to the compressor 1 can be prevented, and the life of the compressor 1 can be extended.

In particular, since no liquid back up occurs, the compressor 1 can be operated efficiently, and the heating capacity can be started up easily. Moreover, since the operation of the indoor fan 7 is turned off while the increase in the operating frequency F is suppressed, the pressure on the high pressure side increases quickly, and the time required to reach stable operation can be shortened. It can greatly contribute to improving the characteristics.

In the above embodiment, whether or not the refrigeration cycle is in a stable operating state is determined by comparing the condenser temperature TC and the set value T1, but the determination may be made based on the rate of change in the condenser temperature Tc.

In this case, as shown in FIG. 6, a change rate calculating means 37 for calculating the rate of change of the condenser temperature TC is provided, a change rate setting device 38 is provided in place of the condenser temperature setting device 33, and a change rate setting device 38 is provided instead of the condenser temperature setting device 33. A timer 39 is provided.

That is, at the start of the operation or after the end of the defrosting operation, the rate of change of the condenser temperature TC and the corresponding set value are compared by the comparator 34 for a certain period of time based on the time measured by the timer 39. The increase in operating frequency F is suppressed to Fe until the rate of change reaches the set value, and when the rate of change reaches the set value, the operating frequency F changes from Fe to the highest operating frequency F! l
It rises to 1aX.

In this way, by using the rate of change in the condenser temperature TC, it is possible to accurately judge whether the refrigeration cycle is in a stable operating state, and there is an advantage that the reliability of liquid bag protection is greatly improved.

Further, in the above embodiment, only the heating operation has been described, but the same control is performed at the start of the cooling operation.

In addition, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without changing the gist.

[Effects of the Invention] As described above, according to the present invention, there is provided a means for increasing the operating frequency of the compressor in stages at the start of operation or after the end of defrosting operation, and a means for increasing the operating frequency of the condenser. Since a means is provided to keep the temperature or its rate of change at a predetermined value until it reaches the set value, it is possible to prevent the oil level in the compressor from running out and liquid back into the compressor, thereby extending the life of the compressor. At the same time, it is possible to provide an air conditioner that enables efficient operation.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a refrigeration cycle and a control circuit in one embodiment of the present invention, FIG. 2 is a diagram showing the configuration of the main part of the control section in the same embodiment, and FIG. 3 is a diagram showing the operation of the same embodiment. FIGS. 4 and 5 are flowcharts for explaining the operation of the same embodiment, FIG. 6 is a diagram showing the configuration of a modification of the control section in the same embodiment, and FIG. is a diagram for explaining the operation of a conventional air conditioner. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Four-way valve, 3... Outdoor heat exchanger, 4... Expansion valve (pressure reducer), 5... Indoor heat exchanger, 11... Inverter circuit, 20...control unit. Applicant's Representative Patent Attorney Takehiko Suzue Figure 4 Time (Mysterious) - Figure 5

Claims (1)

[Claims] In an air conditioner that is equipped with a refrigeration cycle in which a compressor, a condenser, a pressure reducer, an evaporator, etc. are connected in sequence, and that controls the operating frequency of the compressor according to the air conditioning load, at the start of operation or at the end of defrosting operation. and means for increasing the operating frequency of the compressor in stages; and means for suppressing the increase in the operating frequency to a predetermined value until the temperature of the condenser or the rate of change thereof reaches a set value. Characteristic air conditioner.