JPH07190576A - Air conditioner - Google Patents

Abstract

PURPOSE:To provide an air conditioner in which a temperature of an item to be measured can be accurately obtained irrespective of any short circuited trouble of a temperature sensor and thereby a stable and proper operation of the air conditioner can be carried out. CONSTITUTION:Refirgerant temperatures Te1 and Te2 at the same measuring point are detected by temperature sensors 37a and 37b having the same characteristics from each other. If the temperature sensors 37a and 37b are of a negative characteristic thermistor, they select a lower sensing temperature of the detected temperatures Te1 and Te2 (the higher sensing temperature generated by a trouble in short circuit of the temperature sensor is ignored) and then the selected sensing temperature is inputted as a control information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-type air conditioner including an outdoor unit and a plurality of indoor units.

[0002]

2. Description of the Related Art Generally, an air conditioner has a heat pump type refrigeration cycle in which a compressor, a four-way valve, an outdoor heat exchanger, a flow rate adjusting valve, and an indoor heat exchanger are sequentially connected by piping to form an outdoor heat exchanger. The cooling operation is executed by causing the exchanger to function as a condenser and the indoor heat exchanger as an evaporator. During heating, the indoor heat exchanger functions as a condenser and the outdoor heat exchanger functions as an evaporator.

During operation, the capacity of the compressor is controlled according to the air conditioning load of the room in which the indoor heat exchanger is installed, and
The degree of superheat of the refrigerant in the evaporator is detected, and the flow rate of the refrigerant to the evaporator is controlled by adjusting the opening of the flow rate adjusting valve so that the degree of superheat falls within a predetermined constant value.

The degree of superheat corresponds to the difference between the temperature of the refrigerant flowing out of the evaporator and the temperature of the refrigerant flowing into the evaporator, and is detected from the temperature detected by the temperature sensor attached to the pipe. Appropriate control of this degree of superheat is desired in order to ensure stable operation of the refrigeration cycle and to prevent liquid back to the compressor. Therefore, accuracy is required for the temperature detected by the temperature sensor.

[0005]

Generally, a thermosensitive resistance element (for example, a negative characteristic thermistor) is used as a temperature sensor, but there is a concern of short-circuit failure or wire breakage failure in the thermosensitive resistance element.

Of these, the disconnection causes a sudden change from a state without failure to a state with failure, so that a large difference occurs in the detected temperature before and after the failure. Therefore, regarding the disconnection, the failure can be immediately detected from the change in the detected temperature.

However, a short circuit often progresses partially and the detected temperature gradually changes, so it is difficult to detect a failure. Therefore, the degree of superheat detection continues with a short circuit, which often adversely affects the operation and the life of the compressor.

The present invention takes the above circumstances into consideration,
It is an object of the present invention to provide an air conditioner capable of accurately capturing the temperature of a measurement target regardless of a short-circuit failure of a temperature sensor, thereby enabling stable and proper operation.

[0009]

An air conditioner according to a first aspect of the present invention includes a plurality of temperature sensors having the same characteristics, which are provided at the same measurement point of a refrigeration cycle circuit, and one of the detected temperatures of the temperature sensors, whichever is lower. Or means for selecting one of the higher ones according to the characteristics of each temperature sensor and fetching it as control information.

In the air conditioner of the second invention, a plurality of temperature sensors having the same characteristics are provided at the same measurement point of the refrigeration cycle circuit, a means for detecting a failure of these temperature sensors, and this failure is not detected. At this time, there is provided a means for selecting one of the detected temperature of each temperature sensor, whichever is lower or higher, according to the characteristic of each temperature sensor, and fetching it as control information.

In the air conditioner of the third aspect of the present invention, among the plurality of temperature sensors having the same characteristics and provided at a plurality of measurement points having a causal relationship with each other in the refrigeration cycle circuit, the temperature detected by these temperature sensors is the lowest. One of the higher side and the higher side is selected in consideration of the above-mentioned causal relationship and according to each temperature characteristic, and it is taken in as control information.

[0012]

In the air conditioner of the first aspect of the invention, the temperature at the same measurement point of the refrigeration cycle circuit is detected by a plurality of temperature sensors having the same characteristics, and the lower or higher one of the detected temperatures is detected. Select according to the characteristics of each temperature sensor,
Take it in as control information.

In the air conditioner of the second invention, the temperature at the same measurement point of the refrigeration cycle circuit is detected by a plurality of temperature sensors having the same characteristics, and a failure of each temperature sensor is detected, and this failure is detected. Only when this is not done, the lower or higher detected temperature among the detected temperatures of each temperature sensor is selected according to the characteristics of each temperature sensor, and that is taken in as control information.

In the air conditioner of the third aspect of the invention, the temperatures at a plurality of measurement points in the refrigeration cycle circuit, which have a causal relationship with each other, are detected by a plurality of temperature sensors having the same characteristics, and the temperature detected by these temperature sensors is the lowest. The higher or higher one is selected in consideration of the above-mentioned causal relationship and according to the characteristics of each temperature sensor, and that is selected as control information.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 4, a plurality of indoor units B are connected to the outdoor unit A by piping. The outdoor unit A is
The compressors 1 and 2 housed in a common closed case are provided. The compressor 1 is an inverter-driven variable capacity compressor. The compressor 2 is a commercial power source driven fixed capacity compressor.

The high pressure side pipe 4a is connected to the discharge port of the compressor 1. Connect the high pressure side pipe 4b to the discharge port of the compressor 2,
The check valve 3 is provided in the high pressure side pipe 4b. The high pressure side pipe 4 a and the high pressure side pipe 4 b are connected to the high pressure side pipe 4. The low-pressure side pipe 5 is connected to the suction ports of the compressors 1 and 2.

An outdoor heat exchanger 8 is connected to the high pressure side pipe 4 via an oil separator 6 and a four-way valve 7. A dryer 11 is connected to the outdoor heat exchanger 8 via a check valve 9 and a liquid tank 10. Check valve 9 and heating expansion valve 1
Connect 2 in parallel. An outdoor fan 13 is provided near the outdoor heat exchanger 8.

A strainer 15 is connected to the low pressure side pipe 5 via an accumulator 14 and a four-way valve 7.

The oil separator 6 is composed of compressors 1 and 2.
Lubricating oil contained in the refrigerant discharged from is extracted. A pipe 16 for returning oil is connected from the oil separator 6 to the low-pressure side pipe 5.

One end of the cooling bypass 17 is connected to the liquid side pipe between the check valve 9 and the liquid tank 10.
The other end of the cooling bypass 17 is connected to the low pressure side pipe between the four-way valve 7 and the accumulator 14. Then, the cooling bypass 17 is provided with the flow rate adjusting valve 18.

By such pipe connections, the outdoor unit A and each indoor unit B constitute a heat pump type refrigeration cycle circuit. During cooling, the four-way valve 7 is set to a neutral state, whereby the refrigerant discharged from the compressors 1 and 2 is caused to flow in the direction of the solid line arrow in the drawing to form a cooling cycle, and the outdoor heat exchanger 8 is connected to the condenser, Each indoor heat exchanger 33 functions as an evaporator. Four-way valve 7 when heating
By this, the refrigerant discharged from the compressors 1 and 2 is caused to flow in the direction of the broken line arrow to form a heating cycle, and each indoor heat exchanger 33 functions as a condenser and the outdoor heat exchanger 8 functions as an evaporator. Let

The flow rate adjusting valve 18 and each flow rate adjusting valve 3
Reference numeral 2 is a pulse motor valve whose opening continuously changes according to the number of input drive pulses. Hereinafter, the flow rate adjusting valve is abbreviated as PMV.

The high pressure switch 21 and the temperature sensor 25 are attached to the high pressure side pipe 4a. The high pressure switch 22 and the temperature sensor 26 are attached to the high pressure side pipe 4b. The high pressure switches 21 and 22 are activated when the pressure of the refrigerant rises abnormally and reaches a predetermined value.

A pressure sensor 23 is attached to the high pressure side pipe 4. The pressure sensor 24 and the temperature sensor 2 are attached to the low-pressure side pipe 5.
Install 7. The temperature sensor 28 is attached to the outdoor heat exchanger 8. An outdoor air temperature sensor 29 is installed at a predetermined location of the outdoor unit A.
Install.

Between the dryer 11 and the strainer 15,
Strainer 31 and flow rate adjustment valve 32 of indoor unit B
The indoor heat exchanger 33 is connected via. Indoor heat exchanger 3
An indoor fan 34 is provided in the vicinity of 3. And PMV3
2 and the indoor heat exchanger 33, the pressure sensor 3 is provided on the liquid side pipe.
5 and the temperature sensor 37 are attached. Indoor heat exchanger 33
A pressure sensor 36 and a temperature sensor 38 are attached to the gas side pipe connected to the. An indoor temperature sensor 39 is provided in the passage of the intake air of the indoor fan 34. The other indoor units B have the same configuration and the same connection.

The temperature sensors 37 and 38 are used for the indoor heat exchanger 3.
Indoor heat exchanger 3 during cooling when 3 functions as an evaporator
In order to detect the degree of superheat of the refrigerant in No. 3, a temperature sensitive resistance element such as a negative characteristic thermistor is used.

Further, although only one temperature sensor 37 is shown in FIG. 1, it is actually 2 as shown in FIGS.
Two temperature sensors 37a and 37b are prepared.

That is, a pair of thermo insertion pipes 41, 41 are attached to the pipe 40 connected to the indoor heat exchanger 33,
Two temperature sensors 3 are provided on the thermo insertion pipes 41, 41.
7a and 37b are inserted respectively. At the time of this insertion, the spring-shaped fixing members 42, 42 are inserted together, and the elasticity of the fixing members 42, 42 causes the temperature sensor 37a,
37b is pressed against the inner peripheral surfaces (pipe 40 side) of the thermo insertion pipes 41, 41, respectively.

Although not shown, the temperature sensor 38 is actually provided with two temperature sensors 38a and 38b like the temperature sensors 37a and 37b.

The control circuit is shown in FIG.

The outdoor unit A has an outdoor controller 50. The indoor control unit 60 of each indoor unit B is wire-connected to the outdoor control unit 50.

The outdoor controller 50 comprises a microcomputer and its peripheral circuits. In this outdoor control unit 50,
Four-way valve 7, outdoor fan motor 13M, PMV 18, high pressure switches 21 and 22, pressure sensors 23 and 24, temperature sensors 25, 26 and 27, heat exchanger temperature sensor 28, outside air temperature sensor 29, commercial AC power supply 51, and inverter. Switch 52 and switch 53 are connected.

The inverter 52 rectifies the voltage of the AC power supply line in the outdoor control unit 50, converts it into a voltage of a predetermined frequency by switching according to a command from the outdoor control unit 50, and outputs it. This output becomes the drive power for the compressor motor 1M.

The switch 53 is, for example, a contact of an electromagnetic contactor. The compressor motor 2M is connected to the AC power supply line in the outdoor control unit 50 via the switch 53.

The indoor control unit 60 comprises a microcomputer and its peripheral circuits. In this indoor control unit 60,
PMV 32, indoor fan motor 34M, pressure sensor 3
5, 36, temperature sensors 37a, 37b, 38a, 38
b, the room temperature sensor 39, and a remote control type operation device (hereinafter, abbreviated as remote controller) 61 are connected.

The indoor control unit 60 and the temperature sensor 37
The temperature detection circuit shown in FIG. 6 is interposed between the connection with a and 37b.

That is, the DC voltage V is applied to the series circuit of the temperature sensor 37a and the resistor Ra, and the voltage Va generated at the resistor Ra based on the change in the resistance value of the temperature sensor 37a (hereinafter referred to as the output voltage of the temperature sensor 37a). ) Is input to the outdoor control unit 60 as the detected temperature information. Temperature sensor 3
The DC voltage V is applied to the series circuit of the resistor 7b and the resistor Rb, and the voltage Vb (hereinafter referred to as the output voltage of the temperature sensor 37b) generated in the resistor Rb based on the change in the resistance value of the temperature sensor 37b is used as the detected temperature information. Input to the outdoor control unit 60.

Indoor control unit 60 and temperature sensors 38a, 38
A similar temperature detection circuit is also interposed between the connection with b.

The indoor control unit 60 mainly includes the following functional means.

[1] Means for sending the operation mode command, the operation start command, and the operation stop command to the outdoor unit A based on the operation of the remote controller 61.

[2] A means for obtaining the difference (air conditioning load) between the temperature detected by the indoor temperature sensor 39 (intake air temperature) and the temperature set by the remote controller 61 and notifying the outdoor unit A of the required capacity corresponding to the temperature difference. .

[3] Means for controlling the opening of the PMV 32 according to the required capacity of the indoor unit.

[4] During cooling, the lower one of the temperature sensors 38a, 38b on the outlet side of the indoor heat exchanger 33 is taken in as control information (detection temperature Te ₂ ) and the temperature sensor on the inlet side of the indoor heat exchanger 33 is taken in. A means for taking in the lower one of 37a and 37b as control information (detection temperature Te ₁ ) and detecting the difference (= Te ₂ −Te ₁ ) between the two detection temperatures taken in as the degree of superheat of the refrigerant in the indoor heat exchanger 33. .

[5] Temperature sensor 37a (and 38a)
Output voltage Va is zero, the temperature sensor 37a (and 3
If the output voltage Vb of the temperature sensor 37b (and 38b) is zero, it is determined that the temperature sensor 37b
(And 38b) is a means for determining a disconnection failure.

[6] Temperature sensor 37a (and 38a)
When it is determined that the disconnection failure of the temperature sensor 37b (and 38b) is used for the above-mentioned superheat detection, the temperature sensor 37b
A means for using the temperature sensor 37a (and 38a) for detecting the degree of superheat when the disconnection failure of (and 38b) is determined.

[8] A means for correcting the opening of the PMV 32 so that the detected degree of superheat falls within a predetermined constant value.

The outdoor control unit 50 mainly includes the following functional means.

[1] The operating capacity of the compressors 1 and 2 (the number of operating compressors 1 and 2 and the operating frequency F of the compressor 1)
A means for controlling according to the total required capacity of each indoor unit B.

[2] The four-way valve 7 is set to the neutral state, and the refrigerant discharged from the compressors 1 and 2 is transferred to the four-way valve 7, the outdoor heat exchanger 8, each flow rate adjusting valve 32, each indoor heat exchanger 33, and the four-way valve. 7
Means for returning to the compressors 1 and 2 through the air conditioner to execute the cooling operation.

[3] The four-way valve 7 is switched, and the refrigerant discharged from the compressors 1 and 2 is passed through the four-way valve 7, each indoor heat exchanger 33, each flow rate adjusting valve 32, the outdoor heat exchanger 8, and the four-way valve 7. Compressor 1,
A means for returning to 2 and performing heating operation.

Next, the operation of the above configuration will be described.

With the remote controller 61 of any indoor unit B,
It is assumed that a desired operation mode and a room temperature (hereinafter, referred to as a set temperature) are set and an operation for starting operation is performed.

Then, at least the compressor 1 of the compressors 1 and 2 is started and the operation is started. In the cooling operation mode, the four-way valve 7 is set in the neutral state, the refrigerant flows in the direction of the solid arrow in FIG. 1, and the cooling cycle is formed. Thereby, the outdoor heat exchanger 8 functions as a condenser, and the indoor heat exchanger 33 functions as an evaporator.

The indoor unit B obtains the difference between the temperature detected by the indoor temperature sensor 39 (intake air temperature) and the temperature set by the remote controller 61, and informs the outdoor unit A of the required capacity corresponding to the temperature difference. Further, the opening degree of the PMV 32 is set to an opening degree according to the required capacity of the unit.

The outdoor unit A operates the operating capacities of the compressors 1 and 2 (the operating number of the compressors 1 and 2 and the operating frequency F of the compressor 1) in accordance with the total required capacity from each indoor unit B. Set to capacity.

For example, when the total required capacity is small, the output frequency F of the inverter 52 is controlled to control the compressor 1
The single variable capacity operation of is executed. When the total required capacity increases, the output frequency F of the inverter 52 is controlled, the switch 53 is turned on, and the variable capacity operation of the compressor 1 and the fixed capacity operation of the compressor 2 are executed.

On the other hand, as shown in the flow chart of FIG. 7, it is confirmed whether the output voltage Va of the temperature sensor 37a is zero and whether the output voltage Vb of the temperature sensor 37b is zero. If both the output voltages Va and Vb are not zero, the refrigerant temperatures Ta and Tb based on the output voltages Va and Vb are detected under the judgment that the temperature sensors 37a and 37b are not broken.

Since the temperature sensors 37a and 37b are negative characteristic thermistors, when the refrigerant temperatures Ta and Tb increase, the resistance values of the temperature sensors 37a and 37b decrease and the resistance R increases.
The voltages Va and Vb generated at a and Rb become high. When the refrigerant temperatures Ta and Tb decrease, the resistance values of the temperature sensors 37a and 37b increase and the voltage V generated in the resistors Ra and Rb.
a and Vb are lowered.

When the refrigerant temperatures Ta and Tb are detected, the lower detected temperature is selected and the detected temperature is selected as the indoor heat exchanger 3.
It is taken as the temperature Te ₁ of the refrigerant flowing into _No. 3 and as control information.

Here, the reason why the lower detected temperature is taken in is
For the following reasons. That is, the temperature sensors 37a and 37b
When a partial short circuit failure occurs in either of the above, an error occurs in the detected temperatures Ta and Tb. The direction of this error is high because it is a negative characteristic thermistor. Therefore, by incorporating the lower sensed temperature, the sensed temperature of the temperature sensor in which the short circuit failure has occurred is ignored, and the temperature can be sensed without error. what if,
Even if both of the temperature sensors 37a and 37b are partially short-circuited, the lower detected temperature has the smaller error.

If the temperature sensors 37a and 37b are positive temperature coefficient thermistors, the higher one of the detected temperatures Ta and Tb may be selected.

Detected temperature T of the temperature sensors 38a and 38b
The same selection is made for a and Tb, and the selected detected temperature is taken in as the temperature Te ₂ of the refrigerant flowing out from the indoor heat exchanger 33 and as control information.

When the intake of the temperatures Te ₁ and Te ₂ is completed in this way, the difference between the two temperatures (= Te ₂ -Te ₁ ) is detected as the degree of superheat of the refrigerant in the indoor heat exchanger 33. Then, the opening degree of the PMV 32 is corrected so that the detected degree of superheat falls within a predetermined constant value.

Therefore, regardless of the short-circuit failure of the temperature sensor, the temperature of the refrigerant can be accurately captured and the superheat degree can be controlled with high accuracy, and stable and proper operation can be performed.

By the way, when a disconnection failure occurs in the temperature sensor 37a, the output voltage Va of the temperature sensor 37a becomes zero. At this time, the temperature sensor 37a determines that there is a disconnection failure,
The degree of superheat is detected using the temperature Tb detected by the temperature sensor 37b. When the disconnection failure of the temperature sensor 37b occurs, the detected temperature Ta of the temperature sensor 37a is used.

In the case of this disconnection failure, it is not possible to select the one with the lower detection temperature, so there is a concern that the accuracy of the superheat detection may be reduced, but the advantage of being able to continue operation is greater than that.

In the above embodiment, only the disconnection failure was judged, but as shown in FIG.
(And 38a, 38b) detected temperature Ta, Tb difference Δ
If the temperature difference ΔT exceeds the predetermined value ΔTs, the temperature sensor with the higher detection temperature is determined to be a short circuit failure, assuming that the short circuit failure has progressed to an unacceptable state. However, it may be configured such that it is notified by a display or the like.

Further, in the above embodiment, the two temperature sensors are attached to the same measurement point, but the two temperature sensors are provided at a plurality of measurement points having a causal relationship with each other, and among the detected temperatures of these temperature sensors, A configuration may be adopted in which either the lower one or the higher one is selected in consideration of the causal relationship and according to each temperature characteristic, and that is selected as control information. This is effective when it is difficult to attach two temperature sensors to the same measurement point due to restrictions on the location where the temperature sensors are attached.

[0070]

As described above, the air conditioner of the first invention detects the temperature at the same measurement point of the refrigeration cycle circuit by a plurality of temperature sensors having the same characteristics, and the detected temperature is the lowest. The higher or higher detection temperature is selected according to the characteristics of each temperature sensor, and it is taken in as control information, so the temperature of the measurement target can be accurately captured regardless of short-circuit failure of the temperature sensor. As a result, stable and proper operation is possible.

The air conditioner of the second invention detects the temperature at the same measurement point of the refrigeration cycle circuit by a plurality of temperature sensors having the same characteristics, and detects an abnormality in each temperature sensor.
Only when this abnormality is not detected, the lower or higher detection temperature among the detection temperatures of each temperature sensor is selected according to the characteristics of each temperature sensor, and it is configured to capture it as control information. It is possible to accurately capture the temperature of the measurement target regardless of the short circuit failure of the sensor, which enables stable and proper operation.

In the air conditioner of the third aspect of the invention, the temperatures at a plurality of measurement points in the refrigeration cycle circuit, which have a causal relationship with each other, are detected by a plurality of temperature sensors having the same characteristics, and the temperature detected by these temperature sensors is the lowest. Whichever is higher or higher is selected according to the characteristics of each temperature sensor in consideration of the above causal relationship and is taken in as control information. The temperature of the object to be measured can be accurately captured without being restricted by the mounting location, etc., and thus stable and proper operation can be performed.

[Brief description of drawings]

FIG. 1 is an exploded perspective view for explaining attachment of a temperature sensor according to an embodiment of the present invention.

FIG. 2 is a view showing a mounting state of a temperature sensor in the embodiment.

FIG. 3 is a view of FIG. 2 viewed from the side.

FIG. 4 is a configuration diagram of a refrigeration cycle of the same embodiment.

FIG. 5 is a block diagram of a control circuit of the embodiment.

FIG. 6 is a wiring diagram of a temperature detection circuit in the embodiment.

FIG. 7 is a flowchart for explaining the operation of the embodiment.

FIG. 8 is a flowchart for explaining an operation of a modified example of the same embodiment.

[Explanation of symbols]

A ... Outdoor unit, B ... Indoor unit, 1 ... Variable capacity compressor, 2 ... Fixed capacity compressor, 8 ... Outdoor heat exchanger, 32 ...
PMV (flow rate control valve), 33 ... Indoor heat exchanger, 37a,
37b, 38a, 38b ... Temperature sensor, 50 ... Outdoor control unit, 60 ... Indoor control unit.

Claims (3)

[Claims] 1. In a multi-type air conditioner comprising an outdoor unit and a plurality of indoor units, a plurality of temperature sensors having the same characteristics, which are provided at the same measurement point of a refrigeration cycle circuit, and a temperature detected by these temperature sensors. Select either the lower one or the higher one according to the characteristics of each temperature sensor,
An air conditioner characterized by comprising means for taking it in as control information. 2. In a multi-type air conditioner comprising an outdoor unit and a plurality of indoor units, a plurality of temperature sensors having the same characteristics are provided at the same measurement point of a refrigeration cycle circuit, and a failure of these temperature sensors is detected. Means for selecting one of the detected temperature of each temperature sensor, whichever is lower or higher, according to the characteristics of each temperature sensor, and fetching it as control information. An air conditioner characterized by being equipped with. 3. A multi-type air conditioner comprising an outdoor unit and a plurality of indoor units, and a plurality of temperature sensors having the same characteristics, which are provided at a plurality of measurement points having a causal relationship with each other in a refrigeration cycle circuit. Of the detected temperatures of the temperature sensor, either low or high temperature is selected in consideration of the above-mentioned causal relationship and according to each temperature characteristic, and means for fetching it as control information is provided. An air conditioner characterized by.