JPH06100395B2 - Refrigeration system operation controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an operation control device for a refrigeration system, and more particularly to preventing continuous operation of a high-voltage protection device during overload operation to allow continuous operation of the device. Related to improvements that made possible.

(Prior Art) Conventionally, in a so-called multi-type refrigeration system in which a plurality of indoor units are connected in parallel to one outdoor unit, when many indoor units operate, when the capacity is excessive (during overload operation) In addition, when the compressor operates at a high capacity, the high pressure in the refrigerant circulation system may abnormally rise, the high pressure protection device may operate, and the operation of the refrigeration system may be forcibly stopped. Therefore, when the high pressure rises abnormally, the capacity of the compressor is reduced in advance to suppress or eliminate the rise in the high pressure to prevent the operation of the high pressure protection device and to continuously operate the device. Is preferred.

Therefore, conventionally, for example, a compressor is provided with an unload mechanism,
The high voltage value at the time of operation of the unload mechanism is set lower than the high voltage value at the time of operation of the high voltage protection device, and when the high voltage rises, the unload mechanism is operated before the high voltage protection device operates. In some cases, the capacity of the compressor is reduced to enable continuous operation of the device.

Further, for example, in the one disclosed in JP-A-62-196542, an inverter for adjusting the capacity of the compressor is provided, and the capacity of the compressor is increased / decreased in a plurality of steps according to the number of operating indoor units, Considering that the capacity of the outdoor unit changes according to the outside air temperature, when the outdoor air temperature rises and the capacity of the outdoor unit increases during cooling operation in which many indoor units operate (that is, when the high pressure rises). In addition, the capacity of the compressor is reduced by an inverter to prevent the operation of the high-voltage protection device in advance, thus enabling continuous operation of the device.

(Problems to be Solved by the Invention) However, in the former case, since the capacity is reduced by the operation of the unload mechanism, the capacity is halved, the reduction range is large, and the freezing property is large. There is a drawback to decrease.

In the latter case, as shown in FIG. 10, the operating range of the high-pressure protection device is the operating range defined by the indoor wet-bulb temperature NWB (X axis) and the outdoor dry-bulb temperature GDB (Y axis). Is a region above the iso-high pressure line indicated by the solid line, but the region where the capacity of the compressor is reduced by one step is the region above the iso-temperature line indicated by the broken line in the figure, and since the slopes of the two lines are different, Although there is a region in which the capacity of the compressor is controlled to be further reduced by one step even though it is not the region where the protection device operates, the capacity control according to the load is not performed in that region, and there is a drawback that the refrigerating property is reduced as in the above. is there.

The present invention has been made in view of such points, and in particular,
When the capacity of the compressor is controlled to increase or decrease in multiple steps so as to keep the evaporation temperature of the refrigerant at the target value, when the evaporation temperature rises above the target value, the capacity of the compressor is also controlled to increase. In the high capacity state, as shown in FIG. 4 and FIG. 5, the condensation temperature Tc _O
At a constant outside air temperature, the evaporation temperature Te1 corresponding to is almost proportional to the capacity step of the compressor at that time,
Focusing on the fact that the evaporation temperature Te1 becomes lower as the capacity of the compressor increases, the purpose thereof is to provide an inverter in the compressor in a multi-type refrigeration system, and to make it possible to control the capacity in a plurality of steps. The capacity of the machine is controlled to increase or decrease so as to keep the evaporation temperature of the refrigerant at the target value as described above, and by setting the evaporation temperature Te1 of the refrigerant operating the high pressure protection device for each capacity step,
When the high pressure rises, the capacity of the compressor is reduced at the stage before the high pressure protection device does not operate, and it is possible to operate the equipment continuously while keeping the capacity as high as possible. The area where the capacity is reduced is made almost the same as the area that exceeds the iso-high voltage line shown by the solid line in Fig. 10 above, and the area where the capacity of the compressor is unnecessarily reduced is reduced to reduce the load as much as possible. It is intended to improve the refrigerating property by performing the capacity operation according to the above.

(Means for Solving Problems) In order to achieve the above object, the solving means of the present invention is
As shown in the figure, for an outdoor unit (A) containing a compressor (1) that is adjusted to a plurality of capacity steps by an inverter (2a), a plurality of indoor heat exchangers (12) are installed. A refrigerant circulation system (Z) formed by connecting indoor units (B) to (F) in parallel is provided, and the refrigerant circulation system (Z) is provided.
It is premised on a multi-type refrigeration system in which the capacity of the compressor (1) is controlled so as to keep the evaporation temperature of the refrigerant at the target value. Then, an evaporation temperature detecting means (50) for detecting the evaporation temperature of the refrigerant in the refrigerant circulation system (Z) is provided, and the evaporation temperature of the refrigerant corresponding to the condensation temperature of the refrigerant immediately before the high pressure protection device operates is set to a high pressure. As the upper limit evaporation temperature for protection, the upper limit evaporation temperature setting means (51) set for each capacity step of the compressor (1) and the output of the evaporation temperature detection means (50) are received, and the evaporation temperature of the refrigerant at that time is received. When the upper limit evaporation temperature of the upper limit evaporation temperature setting means (51) corresponding to the capacity step of the compressor (1) is exceeded, the inverter (2a) is controlled to forcibly decrease the capacity step of the compressor (1). And a capacity reducing means (52) for controlling the capacity.

(Operation) According to the present invention, according to the present invention, the capacity of the compressor (1) is adjusted by the inverter (2a) when the evaporation temperature of the refrigerant in the refrigerant circulation system (Z) exceeds the target value during the refrigerating operation. When the evaporation temperature of the refrigerant is lower than the target value due to the high control, the evaporation temperature of the refrigerant is conversely controlled to be low, and the evaporation temperature is reduced to the target value. As it elevates toward, the evaporation temperature converges to the target value.

Thus, as described above, when the evaporation temperature of the refrigerant exceeds the target value, in particular, many indoor units (B) to (F) are operated and the capacity of the indoor heat exchanger (12) approaches the maximum capacity. Then, the high pressure of the refrigerant circulation system (Z) greatly rises and approaches the pressure value at which the high pressure protection device operates, but at this time,
When the evaporation temperature of the refrigerant becomes equal to or higher than the upper limit evaporation temperature of the upper limit evaporation temperature setting means (51) corresponding to the capacity step of the compressor (1) at that time, the capacity step of the compressor (1) is changed to the capacity reduction means ( Since it is forcibly lowered by 52), the rise in high voltage is suppressed or eliminated, and the operation of the high voltage protection device is prevented in advance, so that the device continues to operate.

In that case, the evaporation temperature corresponding to the condensation temperature of the refrigerant at the time of operation of the high pressure protection device differs depending on the capacity step of the compressor (1) being taken at that time. Since the evaporation temperature of the refrigerant immediately before the operation of is set by the upper limit evaporation temperature setting means (51),
It is possible to continuously operate the device while securing the capacity as high as possible as compared with the conventional one in which the capacity is uniformly halved by operating the unload mechanism.

Moreover, the constant line of the upper limit evaporation temperature of the evaporation temperature set by the upper limit evaporation temperature setting means (51) is different from the conventional high voltage line shown by the broken line for each capacity step as shown in FIG. (See FIG. 10), it has a slope closer to that of FIG. 10 and can narrow the area in which the capacity of the compressor is unnecessarily lowered by one step, so that the area for carrying out capacity control according to the load can be expanded.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings starting from FIG.

FIG. 2 shows an embodiment in which the present invention is applied to a multi-type air conditioner, (A) is an outdoor unit, and (B) to (F).
Is an indoor unit connected in parallel to the outdoor unit (A). The outdoor unit (A) includes a compressor (1)
And an oil separator (4) for separating the oil in the gas discharged from the compressor (1), and a four-way switching that switches as shown by the solid line in the drawing during heating operation and as shown by the broken line in the drawing during cooling operation. A valve (5), an outdoor heat exchanger (6) that serves as a condenser during cooling operation and an evaporator during heating operation, and its fan (6a)
A supercooling coil (7), an outdoor electric expansion valve (8) that adjusts the refrigerant flow rate during cooling operation, and performs a refrigerant throttling operation during heating operation, a receiver (9) that stores liquefied refrigerant, and an accumulator. (10) is built in as a main device, and each of the devices (1) to (10) is connected through a refrigerant communication pipe (11) so that the refrigerant can flow.

The compressor (1) is provided with an inverter (2a) that variably adjusts the operating frequency (that is, capacity step) of the compressor (1) to a plurality of stages (for example, five stages), and a pilot. An unload mechanism (2) that adjusts the capacity of the compressor (1) according to the level of pressure in two stages: 100% capacity full load state and 50% capacity unload state.
b) and the pilot pressure to the pilot pipe (not shown) of the unload mechanism (2b) are supplied to the discharge pipe (11) of the compressor (1).
The solenoid valve (2c) for switching to the n) side (high pressure side) or the suction pipe (11q) side (low pressure side) is attached.
When c) is switched to the high pressure side, the operating capacity of the compressor (1) is switched to the full load state of 100%, while when the solenoid valve (2c) is switched to the low pressure side, the operation of the compressor (1) It is configured so that it can be switched to the unload state where the capacity is 50%.

Further, the indoor units (B) to (F) have the same configuration, and inside thereof, an indoor heat exchanger (12), which serves as an evaporator during cooling operation and a condenser during heating operation, and its blower fan ( , And an indoor electric expansion valve (13), which is provided in the liquid refrigerant branch pipes (11a), adjusts the refrigerant flow rate, and performs a refrigerant throttling action during the cooling operation.
2) and (13) are connecting pipes (11) equipped with a manual shutoff valve (17).
A refrigerant circulation system (Z) that is connected to the outdoor unit (A) via b) and circulates the refrigerant to the outdoor unit (A) and a plurality of (five) indoor units (B) to (F). Has been done.

In addition, in each indoor unit (B) ~ (F), (TH
1) ... are room temperature sensors that detect the room temperature, and (TH2) ... and (TH3) ... are temperature sensors that detect the temperature of the liquid side and gas side piping of the indoor heat exchangers (12). Further, in the outdoor unit (A), (TH4) is a temperature sensor that detects the temperature of the discharge pipe of the compressor (1), and (TH5)
Is an evaporation temperature sensor that detects the evaporation temperature in the outdoor heat exchanger (6) during heating operation, (TH6) is an intake gas temperature sensor that detects the intake gas temperature of the compressor (1), and (P1) is discharge during heating operation. It is a pressure sensor that detects the pressure of gas and the pressure of suction gas during cooling operation.

In addition, in FIG. 2, various auxiliary devices are provided in addition to the above main devices. (1h) is a capillary tube that is provided in an oil return pipe (11u) that returns lubricating oil from the oil separator (4) to the compressor (1), and controls the amount of returned oil.
Reference numeral (21) is a hot gas solenoid valve that is provided in a pressure equalizing hot gas bypass circuit (11d) that connects the discharge pipe and the suction pipe and that opens when defrosting or the like. Reference numeral (11e) is a heating overload control bypass circuit, and the bypass circuit (11e) includes an auxiliary capacitor (22) and a first check valve (2).
3), the high-pressure control valve (24) and the second check valve (25), which open when the indoor heat exchanger (12) (condenser) is under a low load during heating operation, are sequentially connected in series, A liquid seal prevention bypass circuit (11f) and (11f ') for preventing liquid seal at the time of stop of operation is provided in a part thereof through a third check valve (27) and a capillary tube (CP3). .
Furthermore, (11g) is the above heating overload bypass circuit (11e)
Connect between the liquid refrigerant side pipe and the main gas intake gas pipe,
A liquid injection bypass circuit for adjusting the degree of superheat of intake gas during air-conditioning operation, wherein the liquid injection bypass circuit (11g) opens and closes in conjunction with turning on and off of the compressor (1). (29) and an automatic expansion valve (30) whose opening is adjusted according to the degree of superheat of the intake gas detected by the temperature sensing tube (TP1).

Further, in FIG. 2, (F1) to (F6) are liquid purification filters provided in the refrigerant circuit or the oil return pipe, (HPS) is a high pressure switch for protecting the compressor, and (SP) is It is a service port.

Next, the control of the operating capacity of the compressor (1) will be described by taking the cooling operation as an example. The capacity control is performed by the outdoor control device (15) connected to the outdoor unit (A).

That is, as the evaporation temperature detecting means (50) for detecting the refrigerant temperature Te obtained by converting the intake gas pressure detected by the pressure sensor (P1) into the equivalent saturation temperature, that is, the evaporation temperature of the refrigerant in the refrigerant circulation system (Z). After functioning, PI control (proportional-integral control) is performed as feedback control of the operating capacity of the compressor (1) so as to maintain this evaporation temperature Te at the target value _T2O , and the target of the compressor (1) is determined. Capacity L ₁ ,
Based on the current and previous values e (t) and e (t-Δt) of the deviation between the evaporation temperature Te and its target value T _2O , the following equation L is set so that the evaporation temperature Te reaches its target value T _{2O. 1} = L _O + Kc {e (t) -e (t-Δt) + (Δt / 2Ti) (e (t) + e (t-Δt)} L _O ; Current operating capacity Kc; Gain (constant) Ti; Integral time Δt; calculated by sampling time, when the evaporation temperature Te of the refrigerant exceeds the target value Te _O , the capacity step of the compressor (1) is increased, while conversely, when the evaporation temperature Te is less than the target value Te _O , The capacity step of the compressor (1) is lowered.

After that, the operating capacity of the compressor (1) corresponding to the target capacity L ₁ is grasped based on a preset capacity map, and the actual operating capacity of the compressor (1) is adjusted so as to become this operating capacity. It is controlled by the inverter (2a) and the unload mechanism (2b). Then, after the elapse of the sampling time Δt, the above operation is repeated, and the capacity of the compressor (1) is controlled so that the evaporation temperature Te of the refrigerant in the refrigerant circulation system (Z) is maintained at the target value Te _O. There is.

Thus, the outdoor control device (15) has a compressor (1) in order to suppress or eliminate an abnormal increase in high pressure during cooling overload.
The capacity control is performed as follows.

That is, as shown in FIG. 3, the operating frequency of the compressor (1), that is, the capacity step Fmax is Fmax = 0,40,50,60,70H.
Condensation temperature of the refrigerant in the refrigerant circulation system (Z) immediately before the operation of the high pressure protection device at each capacity step under the 5 stages of z
Evaporation temperature corresponding to Tc (hereinafter, referred to as the upper limit evaporation temperature) as the value of a predetermined differential, the following formula _{Tel = Te S -C 1 (F} T -40) -C 2 (Tair-T O) Te2 = Te L -C ₁ (Fmax−40) −C ₂ − (Tair−T _O ) Calculate and set.

Here, Te1 is the upper limit of the differential of the upper limit evaporation temperature, Te2 is the lower limit of the differential of the upper limit evaporation temperature, F2
_T is the operating frequency of the compressor (1), Tair is the outside air temperature, Te _S is the upper limit evaporation temperature when the operating frequency of the compressor (1) is the reference frequency (40 Hz), and Te _L is the above upper limit evaporation temperature. the upper limit evaporation temperature with a predetermined deviation with respect to _{Te S (Te S> Te L} ), Fmax
Is the upper limit frequency of the regulated compressor (1), T _O is the reference temperature, C ₁ is a proportional constant with respect to the operating frequency, and C ₂ is a proportional constant with respect to the outside air temperature.

As described above, the upper limit evaporation temperatures Te1 and Te2 at the outside air temperature Tair
The correction value is set so that if the capacity of the compressor (1) is constant, the condensation temperature Tc of the refrigerant is almost proportional to the outside air temperature Tair, as shown in FIG. Ta
This is because the slope of the constant line of the upper limit evaporation temperature Te1 shown in FIG.

Then, as shown in FIG. 3, when the thermostat is turned on, Fm
The capacity corresponding to Fmax = 40Hz in the figure is set from the stopped state of ax = 0, and thereafter the evaporation temperature Te is changed with respect to the differential lower limit value Te2 of the upper limit evaporation temperature according to the upper limit of the operating frequency (capacity step) at that time. However, if Te <Te2, the process sequentially shifts to in the figure to increase the upper limit of the operating frequency (capacity step) by one step, and finally reach the maximum step (Fmax = 70 Hz). On the other hand, in each of the above capacity steps, when the evaporating temperature Te has a relation of Te> Te1 with respect to the differential upper limit value Te1 of the upper limit evaporating temperature, there is a situation in which the high pressure protection device may be activated when the high pressure abnormally rises. Judgment, capacity step (Fmax =
40Hz) and move from here to the capacity step that satisfies the relationship of Te <Te2.

Also, in each of the above capacity steps, when the thermostat is turned off, the state shifts to the stopped state of Fmax = 0.

Therefore, with the above configuration, the upper limit evaporation temperature Te1, Te2 (refrigerant evaporation temperature corresponding to the condensation temperature of the refrigerant immediately before the high pressure protection device is activated) as the upper limit evaporation temperature for high pressure protection, based on the above formula, The upper limit evaporation temperature setting means (51) is configured so as to be set for each capacity step of the compressor (1). Further, according to the state transition diagram of FIG. 3, the upper limit evaporation temperature (51) of the upper limit evaporation temperature setting means (51), which receives the output of the above evaporation temperature detection means (50) and the evaporation temperature Te of the refrigerant corresponds to the capacity step at that time ( When the differential upper limit value Te1) of the upper limit evaporation temperature is exceeded, after returning the capacity step of the compressor (1) to the lowest capacity step, the evaporation temperature Te is forced to the capacity step ~ which satisfies the relation of Te <Te2. Inverter (2
A capacity reducing means (52) for controlling a) is constructed.

Therefore, in the above embodiment, basically, the capacity of the compressor (1) is adjusted to be increased or decreased by the inverter (2a), and the evaporation temperature Te of the refrigerant is controlled to be maintained at the target value Te _O. When the temperature Te exceeds the target value Te _O , the capacity of the compressor (1) shifts to a higher step to reduce the evaporation temperature Te and try to converge to the target value Te _O.

In that case, in particular, when many of the indoor units (B) to (F) are operated to enter the cooling overload state, the high pressure of the refrigerant circulation system (Z) abnormally rises, and the operation of the high pressure protection device is stopped. However, the evaporation temperature of the refrigerant before the operation
When Te exceeds the differential upper limit Te1 of the upper limit evaporation temperature set by the upper limit evaporation temperature setting means (51),
Since the capacity step of the compressor (1) is forcibly reduced by the capacity reducing means (52), the operation of the device can be favorably continued without causing the operation of the high pressure protection device.

At that time, the differential upper limit value Te1 of the upper limit evaporation temperature in the upper limit evaporation temperature setting means (51) is determined by the compressor (1).
The capacity is set for each capacity step, and as shown in FIG. 7, for example, when the compressor (1) is at 100% capacity, it is low at Te1 (100).
Then, as the capacity of the compressor (1) gradually decreases to 90%, 80%, etc., it gradually increases (Te1 (90) <Te1 (80)
…) So, for example, the evaporation temperature Te is 100% at 100% capacity
When the differential upper limit value Te1 (100) of the upper limit evaporation temperature corresponding to the capacity is exceeded, the capacity step of the compressor (1) is reduced by the capacity reducing means (52) to the differential lower limit value Te2 of the upper limit evaporation temperature. On the other hand, since the capacity step (for example, Fmax = 60Hz (at 90% capacity)) satisfies the relationship of Te <Te2, the capacity is uniformly halved by the operation of the unload mechanism (2b) as in the past. The continuous operation of the device can be performed while ensuring the operating capacity of the compressor (1) as high as possible.

Further, since the constant line of the differential upper limit value Te1 of the upper limit evaporation temperature approaches the slope of the iso-high pressure line at which the high pressure protection device operates, as shown in FIG. 9, compared with the conventional one shown in FIG. The region in which the capacity step of the compressor (1) is unnecessarily reduced and controlled can be narrowed, and the region in which the capacity control of the compressor (1) is controlled according to the load can be expanded accordingly. Moreover, in the present embodiment, the upper limit evaporation temperatures Te1 and Te2 can be corrected according to the outside air temperature Tair, and the slope of the constant line can be made substantially equal to the slope of the iso-high pressure line. The capacity control area of (1) can be maximized.

Further, since the upper limit evaporation temperature is provided with a differential, the evaporation temperature Te exceeds the differential upper limit value Te1 (100) at 100% capacity and the capacity of the compressor (1) becomes 90% capacity as shown in FIG. Even when it decreases, the capacity increase control is performed for the first time when it becomes less than the lower limit differential value Te2 (90), and hunting does not occur.

Further, at the time of starting the apparatus, the evaporation temperature Te of the refrigerant is extremely high when the pressure is equalized, and the relationship of Te <Te2 in each capacity step ~ in Fig. 3 is not satisfied, and the compressor (1) is Initially, it operates at the lowest step Fmax = 40Hz, but if the evaporation temperature Te decreases due to this operation, it will become Fmax = 50Hz operation when the relationship of Te <Te2 (40) is satisfied, and then 60Hz operation in the same manner. , 70Hz operation, so the start-up of operation will be performed relatively quickly. Moreover, since the compressor (1) starts to rotate at the maximum capacity at the time of starting in order to lower the evaporation temperature, the risk of high pressure cut due to overshoot can be avoided.

In the above embodiment, the operating frequency of the compressor (1) is controlled by the inverter (2a) in five stages including the stop time. However, the number of capacity control stages is not limited to this, but may be controlled in multiple stages. Good. The compressor may be of a reciprocating type, a rotating type, a centrifugal type, or the like, and the unloading mechanism may be a suction type, an open type, a hot gas bypass type, or the like.

(Effects of the Invention) As described above, according to the present invention, in the multi-type refrigeration system, the upper limit evaporation temperature (of the high pressure protection device) is increased for each capacity step of the compressor whose capacity is adjusted to a plurality of steps by the inverter. The evaporation temperature of the refrigerant, which corresponds to the condensation temperature of the refrigerant just before the operation, was set, and when the upper limit evaporation temperature was exceeded, the capacity of the compressor was forcibly reduced and controlled. The increase in high pressure at the time of overload is suppressed or eliminated in the stage before the high pressure protection device is activated while the high capacity step of the compressor is secured, so that the continuous operation of the device can be performed while maintaining high refrigeration capacity. In addition to being possible, it is possible to expand the region for controlling the capacity of the compressor corresponding to the load and improve the refrigerating property.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 to 9 show an embodiment of the present invention, FIG. 2 is a refrigerant piping system diagram applied to an air conditioner, FIG. 3 is a state transition diagram,
FIG. 4 is a diagram showing the change characteristic of the upper limit evaporation temperature with respect to the change of the capacity of the compressor, FIG. 5 is a diagram showing the relationship between the upper limit evaporation temperature and the capacity of the compressor, and FIG. FIG. 7 is a diagram showing a change characteristic of the condensing temperature, FIGS. 7 and 8 are operation explanatory diagrams, and FIG. 9 is a diagram showing that an area where the capacity reduction control of the compressor is unnecessarily reduced. FIG. 10 is a view corresponding to FIG. 9 showing a conventional example. (A) …… Outdoor unit, (B) to (F) …… Indoor unit, (1) …… Compressor, (2a) …… Inverter, (P
1) …… Pressure sensor, (12) …… Indoor heat exchanger, (Z)
…… Refrigerant circulation system, (50) …… Evaporation temperature detection means, (5
1) …… Upper limit evaporation temperature setting means, (52) …… Volume reduction means.

Claims (1)

[Claims] 1. A plurality of indoor units having an indoor heat exchanger (12) for an outdoor unit (A) having a compressor (1) having a plurality of capacity steps adjusted by an inverter (2a). A refrigerant circulation system (Z) in which units (B) to (F) are connected in parallel is provided, and the compressor (1) has a capacity so that the evaporation temperature of the refrigerant in the refrigerant circulation system (Z) is maintained at a target value. A multi-type refrigeration system controlled, wherein an evaporation temperature detecting means (50) for detecting an evaporation temperature of the refrigerant in the refrigerant circulation system (Z) and a condensation temperature of the refrigerant immediately before the high pressure protection device operates. The evaporation temperature of the refrigerant corresponding to the above is set as the upper limit evaporation temperature for high pressure protection by the upper limit evaporation temperature setting means (51) and the evaporation temperature detecting means (50) which are set for each capacity step of the compressor (1). Received output, evaporation temperature of refrigerant Is the upper limit evaporation temperature setting means (51) corresponding to the capacity step of the compressor (1) at that time.
Control means for controlling the inverter (2a) so as to forcibly reduce the capacity step of the compressor (1) when the upper limit evaporation temperature is exceeded. apparatus.