JPH0282064A - Overload control method for heat pump type air conditioner - Google Patents

Abstract

PURPOSE:To stabilize a rotation speed of a drive source and obtain a comfortable air conditioning performance by storing a rotation speed produced when a drive source enters a prohibited zone outside a preset zone due to overload, then setting controllably a rotation speed produced when the load is increased as a maximum rotation speed so that it may be lower than the stored rotation speed. CONSTITUTION:Overload operation forces a refrigerant pressure and a refrigerant temperature to plunge into a prohibited zone, exceeding the upper limit of a preset zone H-L at the point A, allowing the maximum rotation speed of an engine at this juncture to be stored. When the refrigerant pressure and the refrigerant temperature exceed the lower limit L of the preset zone H-L at the point B, the engine is adapted to return to the original high rotation operation once again. A maximum allowable rotation speed Nmo when it is returned, is controllably set to be lower by one step than the maximum rotation speed Nm stored when they entered the prohibited zone. It is, therefore, possible to operate the subsequent operation which is constantly stabilized with the maximum rotation speed Nmo on a substantial basis.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an overload control method for a heat pump type air conditioner, and more specifically, the present invention relates to a heat pump type air conditioner that stabilizes the rotational speed of a drive source and realizes comfortable air conditioning. This invention relates to an air conditioner overload control method.

[Prior art]

Heat pump type air conditioners include those whose refrigerant compressor is driven by an engine and those whose refrigerant compressor is driven by a motor. This heat pump type air conditioner reduces the pressure rise and temperature rise of the refrigerant that occurs when an overload is applied, such as when the temperature difference between indoors and outdoors becomes extremely large, regardless of whether it is for cooling or heating. , the rotational speed of the drive source, such as the engine or motor, is reduced to prevent abnormal stoppage.

That is, conventionally, as shown in FIG. 5, when the drive source is operated at the maximum rotation speed Nm, the refrigerant pressure or refrigerant temperature deviates from the upper limit H between the set range H-L at point A due to overload. Then, the rotation speed is stepped down so as to return it to the set band H-L again, and finally comes to a stop. By this step-down of the rotation speed, the pressure or temperature of the refrigerant gradually decreases, and when the lower limit is exceeded at point B, the drive source immediately rotates at the original maximum rotation speed Nm to increase the pressure and temperature of the refrigerant, I will try to repeat this from now on.

Therefore, according to the conventional control method, the driving source has to repeatedly increase and decrease its rotational speed, and the air conditioning capacity increases and decreases accordingly. Due to such vertical changes, there was a limit to the hope for comfortable and stable air conditioning.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an overload control method for a heat pump air conditioner that solves the conventional problems as described above, stabilizes the rotational speed of the drive source, and realizes comfortable air conditioning.

[Means to solve the problem]

To achieve the above object, the present invention drives a compressor by a drive source whose rotation speed is variable, and forcibly circulates the refrigerant compressed by the compressor to a refrigerant circulation circuit having an air conditioner, and the rotation speed of the drive source is When controlling and operating the drive source within a set band, the rotation speed when the drive source enters a prohibited band outside the set band due to overload is memorized, and the rotation speed when the drive source increases next time is determined from the stored speed. This is characterized in that the rotation speed is controlled to be lower than the rotation speed as the maximum rotation speed.

〔Example〕

The present invention will be explained below with reference to Examples.

FIG. 4 illustrates an engine-driven heat pump type temperature regulator that implements the overload control method of the present invention. The block surrounded by a chain line ■ is a power unit, ■ is an outdoor heat exchange unit, ■ is a branch unit, and ■ is an indoor heat exchange unit. The indoor heat exchange unit 1-IV is equipped with one or more branched temperature controllers depending on the temperature control capacity required for the room and the room units divided into multiple units. The branch unit) n [is connected to the outdoor heat exchange unit) fr.

The power unit (2) is provided with an engine (1) operated by gas fuel, and a pressure engine (2) connected to the engine (1) via a clutch (3). The compressor 2 compresses a refrigerant such as fluorocarbon into a high-temperature, high-pressure gas, and forcibly circulates this into a refrigerant circulation circuit equipped with a temperature regulator, which will be described later. Further, the engine 1 is configured to forcibly circulate engine cooling water to a hot water circulation circuit equipped with a temperature controller, which will be described later. The cooling water jacket of the engine 1 serves as a heat exchanger 4 in the hot water circulation circuit, and the exhaust pipe is also provided with a heat exchanger 5 that uses exhaust gas.

The outdoor heat exchange unit ■ has a discharge pipe 6 from the compressor 2.
A four-way switching valve 8 is provided between these two pipes, and two pipes 9, 1 are connected to the four-way switching valve 8.
0 constitutes a refrigerant circulation circuit. Additionally, a bypass valve 45 is provided between the discharge pipe 6 and the suction pipe 7.
A bypass pipe having a bypass valve 45 is provided so that the load can be reduced by opening the bypass valve 45. Further, the discharge pipe 6 and the suction pipe 7 are provided with a temperature sensor 40.44 and a pressure sensor 41.43, respectively.

This refrigerant circulation circuit can be used for either heating or cooling operation by switching the refrigerant circulation direction, but this figure shows heating operation, and the refrigerant is routed through the pipes 9 as shown by the arrow.
The liquid is discharged from the pipe 10 and returned to the pipe 10.

In this heating circulation, the pipe 9 is connected to the branch unit ■
A plurality of branch pipes 11.・Branched to -111,
It is connected to the pipes 12, -, 12 in the indoor heat exchange unit IV. Indoor heat exchangers 13 that function as refrigerant condensers are connected to the pipes 12, respectively, and radiate condensed heat indoors. The pipe 12 on the discharge side is again connected to the branch pipe 14 of the branch unit 7) I[[, and then converged into one pipe 15 in the outdoor heat exchange unit (2). Next, the pipe 15 is connected to the receiver 16,
From here, it is connected via a pipe 18 to an outdoor heat exchanger 19 that functions as an evaporator, and then returns to the pipe 10 described above. The pipe 18 includes an expansion valve 17 that adiabatically expands the refrigerant.
is provided.

The above is a case of heating operation, but in cooling operation, the refrigerant may be circulated in the opposite direction to the direction of the arrow by switching the four-way switching valve 8.

In this cooling operation, contrary to the above heating operation, the indoor heat exchanger 13 acts as an evaporator and removes evaporation heat from the room, and the outdoor heat exchanger 19 acts as a condenser.

On the other hand, in the hot water circulation circuit for circulating engine cooling water, the hot water is forced to circulate by a cooling water pump 20 provided in the outdoor heat exchange unit II. Exhaust heat from the engine is absorbed into engine cooling water by a heat exchanger 4.5, and a pipe 21 exiting from the heat exchanger 4.5 is connected to a pipe 22 in the outdoor heat exchange unit 2, and then branched into two pipes 23 and 24. this house,
One pipe 23 is connected to a radiator 26 via a control valve 25 that is automatically controlled to open and close, and is connected to an air separator 27. After passing through the cooling water pump 2o, the engine exhaust heat is returned to the heat exchanger 4.5.
It is designed to circulate.

The other pipe 24 has a plurality of branch pipes 28. -..., 28, which are connected to the pipes 29, 29 in the indoor heat exchange unit 1-rV, respectively, and allow hot water to pass through the floor heating panels 30, -, 30 provided as temperature controllers. There is. The piping 29 on the discharge side passes through the branch pipes 31, -, 31 of the branch unit (2) again, is converged to the piping 32 of the outdoor heat exchange unit H, and joins the same air separator 27 as described above.

The engine 1 that serves as the driving source in the temperature control device described above is
The temperature sensor of the refrigerant circulation circuit whose rotation speed is 40.4
4 and the detection signals of the pressure sensors 41 and 43, the control unit 50 performs control as shown in the graph shown in FIG.

That is, as shown in FIG. 1, when the refrigerant pressure and refrigerant temperature exceed the upper limit H of the set range H at point A and enter the prohibited range due to overload operation, the engine speed increases, for example, to 200 r, p, m, and at the same time, the maximum engine speed Nm when entering the prohibited band is stored. Then, when the refrigerant pressure and refrigerant temperature exceed the lower limit of the set band H-L at point B due to the step-down of the engine speed, the engine is restarted to its original high speed again, and the For example, set the allowable maximum rotation speed Nmo by one step (20
The rotational speed is controlled to be lower by 0r, p, m,).

In this way, by controlling the allowable maximum rotational speed Nmo at the time of recovery by setting it lower, for example, by one step, than the maximum rotational speed Nm at the time of entry into the forbidden zone, subsequent operation can be controlled to a maximum rotational speed Nmo. It can provide constant and stable operation. In other words, the engine speed is not repeatedly lowered as in the conventional case, and the air conditioning capacity is kept stable without increasing or decreasing, making it possible to achieve extremely comfortable air conditioning.

In the present invention, the engine speed is stepped down when the engine speed enters the forbidden zone due to overload until the engine is stopped at -a as shown in FIG.

However, when the safe rotational speed Ns is lower than the required rotational speed Pid from the load on the engine, the engine may be rotated at a low speed that does not cause the engine to stop.

In order to restore the engine rotation to the maximum allowable rotation speed Nlll0 when the engine is stepped down to stop as in the former case, it is necessary to directly restore the engine rotation speed from 0 to the maximum rotation speed Nmo, as shown in Figure 1. Bye. However, when the engine is restarted from the safe engine speed Ns in the unstopped state to the allowable maximum engine speed Nmo as in the latter case, the engine is not directly restored as in the former case. At this time, for example, the maximum allowable rotation speed Nm is increased while increasing the rotation by one step (200r, p, m,) every 40 seconds.

to reach. At this time, for the engine, the state in which the engine is idling with the bypass valve 45 of the refrigerant circulation circuit open, and the state in which the bypass valve 45 is closed is also considered as one step. .

Also, in the above control, the maximum allowable rotation speed Nm.

After the system has been restored, this restriction condition can be canceled when the following conditions are met. In other words,■
When the thermostat is turned off, ■ When the operation continues for 30 minutes after restarting, ■ When the number of indoor temperature controllers in use changes (change in load), ■ Safe rotation speed Ns ≧ Requested rotation speed from the engine load For example, when Pid.

The above-mentioned control of the engine speed is carried out by a third control unit 50 having a system configuration as shown in the block diagram in FIG.
It can be implemented according to a flowchart as shown in the figure.

The control section 50 has a calculation section 51 in the center as shown in FIG. 2, and the above-mentioned temperature sensors 40, 41,
A sensor part 52 is connected, including pressure sensors 42, 43 and the like. Further, the calculation unit 51 includes a read-only storage device 53 storing a program for the above-mentioned control;
A read/write storage device 54 is connected which stores the engine rotational speed Nm and the allowable maximum rotational speed Nmo when entering the prohibited band, and an output section 55 is further connected to instruct the engine 1 to output the calculation results. There is.

The flow diagram in FIG. 3 shows that the flow from S (start) to RTS (return to start) is repeated. Step 56 in this flow calculates the engine rotational speed Nm −1 step = new maximum allowable rotational speed Nmo at the time of entry into the forbidden zone, and stores it in the storage device 54.
In addition, step 57 means performing the determination and processing of the above-mentioned (1) to (2), which are the conditions for canceling the maximum allowable rotational speed Nmo.

In the above-described embodiments, an engine-driven heat pump is illustrated, but the present invention can also be applied to a motor-driven heat pump.

〔Effect of the invention〕

As described above, in the control method according to the present invention, a compressor is driven by a drive source having a variable rotation speed, and the refrigerant compressed by the compressor is forcedly circulated through a refrigerant circulation circuit having an air conditioner, and the rotation speed of the drive source is changed. In order to control and operate the drive source within the set band, the rotation speed when the drive source enters the prohibited zone 4 degrees outside the set band due to overload is memorized, and the rotation speed when the drive source increases next time is stored as described above. Since the engine speed is controlled to be a maximum engine speed that is lower than the stored engine speed, the engine speed at the time of restarting can be kept constant and stable.

That is, unlike conventional control methods, the engine speed does not repeatedly rise and fall, and as a result, the air conditioning capacity remains stable without any rises or falls, making it possible to achieve extremely comfortable air conditioning.

[Brief explanation of the drawing]

Figure 1 shows the refrigerant pressure when implementing the present invention. A graph showing changes in temperature over time in comparison with engine speed, FIG. 2 is a block diagram of a control unit implementing the present invention,
Fig. 3 is a flowchart of the same, Fig. 4 is a schematic diagram of an air conditioner implementing the present invention, and Fig. 5 is a graph showing changes in refrigerant pressure and temperature over time using the conventional control method in comparison with engine rotation speed. It is. 1... Engine, 2... Compressor, 8... Four-way valve,
13... Indoor heat exchanger, 17... Expansion valve, 19...
・Outdoor heat exchanger, 40.41...Temperature sensor 42
゜43...Pressure sensor, 50...Control unit, 51.
. . . Arithmetic unit, 52 . . . Sensor part, 53 . . . Read-only storage device, 54 . . . Read/write storage device, 55
...Output section.

Claims (1)

[Claims] A compressor is driven by a drive source with a variable rotation speed, the refrigerant compressed by the compressor is forced to circulate through a refrigerant circulation circuit having an air conditioner, and the rotation speed of the drive source is controlled within a set band for operation. , the rotation speed when the drive source enters the prohibited band outside the set band due to overload is stored, and the rotation speed when the drive source increases next time is set to a rotation speed lower than the stored rotation speed as the maximum rotation speed. An overload control method for a heat pump type air conditioner, characterized in that the overload control method is performed as follows.