JPH04251158A - Operation control device for refrigerating device - Google Patents

Abstract

PURPOSE:To prevent thermal off-state produced during the lack of refrigerant circulation amt and frequently repeated restarting by changing an initial opening degree of a valve driven expansion valve. CONSTITUTION:When starting the operation of a freezing device, an initial opening degree of a motor-driven expansion valve 5 is set to a fixed value with an initial opening degree setting means 51. Then, the opening degree of the motor-driven expansion valve 5 is target-controlled with an opening degree control means 53 so that the discharge refrigerant temperature may be converged to a temperature capable of producing an optimum freezing effect. When the discharge refrigerant temperature exceeds a specified temperature, an operation control means 50 halts the operation of a compressor for a specified time and then restarts the operation while an opening degree increase means 52 increases the initial opening degree of the motor-driven valve 5 in restarting mode more than that in the previous starting time. This construction makes it possible to increase the circulation amount of refrigerant and thereby inhibit repeated thermal off-state and restarting.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control system for a refrigeration system, and more particularly to a reduction in the number of times a compressor starts and stops due to repeated thermo-off and restart operations.

0002

[Prior Art] Conventionally, for example, Japanese Patent Application Laid-Open No. 1850-1850
As disclosed in Publication No. 76, as an operation control device for a refrigeration system equipped with a refrigerant circuit in which a compressor, a heat source side heat exchanger, an electric expansion valve, and a user side heat exchanger are sequentially connected, Detects the degree of cooling and detects the degree of superheat during normal cooling operation.
During normal heating operation, the opening degree of the electric expansion valve is controlled to maintain the degree of subcooling at a predetermined value, while when starting operation of the refrigeration system, the opening degree of the electric expansion valve is adjusted in advance according to the operation mode. A known technique attempts to quickly converge to a target opening by controlling the opening to a predetermined opening.

0003

[Problems to be Solved by the Invention] By the way, in an operation control device for a refrigeration system in which the opening degree of an electric expansion valve is controlled using the optimum temperature of the discharged refrigerant that provides the optimum refrigeration effect as a control target value, In order to protect the compressor from an excessive rise in the discharge refrigerant temperature, when the discharge refrigerant temperature reaches a predetermined temperature or higher, the compressor is placed in a so-called thermo-off state in which the compressor is stopped for a predetermined period of time, and when a predetermined period of time has elapsed, the thermo-on is turned on. However, if the initial opening degree of the electric expansion valve is set to a constant value as in the conventional system for such a refrigeration system, the following will occur: There was a problem.

That is, as shown in FIG. 5, after the initial opening degree of the electric expansion valve is set to a constant value and operation is started, the amount of refrigerant circulation decreases due to the accumulation of refrigerant in the refrigerant circuit during operation. If there is a shortage, the discharge refrigerant temperature rises, and the opening degree of the electric expansion valve increases accordingly by target value control, but under conditions where the refrigerant circulation amount is insufficient, the rise in the discharge refrigerant temperature cannot be suppressed, and the discharge When the refrigerant temperature reaches a predetermined temperature or higher, the compressor turns off and stops (time x1 in the figure). Then, after a predetermined period of time has elapsed, when the electric expansion valve is restarted with the initial opening degree set to a constant value (time x1 in the figure), under conditions where the amount of refrigerant circulation is insufficient, the discharge refrigerant The temperature rises again and reaches the predetermined temperature, and the compressor stops thermo-off (time x2 in the figure). Then, after a certain period of time has passed, it switches to thermo-on and restarts (time x 3 in the diagram)
However, the discharge refrigerant temperature rises immediately and the thermostat turns off (
The process (time x4 in the figure) is repeated (below time x5 in the figure). Then, until the discharged refrigerant condition reaches a steady state, the compressor is repeatedly started and stopped due to thermo-on/thermo-off switching, which may lead to a decrease in operating efficiency and reliability. Ta.

The present invention was made in view of the fact that the above-mentioned repetition of thermo-on and thermo-off at the time of starting the compressor is caused by accumulation of refrigerant in one of the refrigerant circuits. Under conditions where refrigerant stagnation occurs, the objective is to reduce the number of times the compressor starts and stops by taking measures to ensure the amount of refrigerant circulating, thereby improving operational efficiency and reliability. .

[0006]

[Means for Solving the Problems] In order to achieve the above object, the solution of the present invention is to increase the initial opening degree of the electric expansion valve at the time of restarting compared to the initial opening degree at the time of the previous startup.

Specifically, the means taken by the invention of claim 1, as shown in FIG. A refrigeration system is assumed to be equipped with a refrigerant circuit (9) formed by sequentially connecting heat exchangers (6).

[0008] As an operation control device for a refrigeration system,
initial opening degree setting means (51) for setting the initial opening degree of the electric expansion valve (5) to a constant value at the time of starting operation of the refrigeration system;
and a discharge temperature detection means (Th2) for detecting the discharge refrigerant temperature.
), and an opening control means (which receives the output of the discharge temperature detection means (Th2) and controls the opening degree of the electric expansion valve (5) using the optimum temperature of the discharged refrigerant that provides the optimum refrigeration effect as a control target value. 53), and an operation control means (Th2) which receives the output of the discharge temperature detection means (Th2) and stops the compressor (1) for a predetermined period of time and then restarts the compressor (1) when the discharge refrigerant temperature reaches a predetermined temperature or higher. 50) shall be provided.

Furthermore, the initial opening degree of the electric expansion valve (5) when the compressor (1) is restarted by the operation control means (50) is changed to be increased by a predetermined opening degree from the initial opening degree at the previous startup. The structure is such that an opening increasing means (52) is provided to increase the opening degree.

0010

[Operation] With the above configuration, in the present invention, when the refrigeration equipment starts operating, the initial opening degree setting means (51) sets the initial opening degree of the electric expansion valve (5) to a constant value, and then the opening degree is controlled. The means (53) controls the opening degree of the electric expansion valve (5) to a target value so that the temperature of the discharged refrigerant converges to the optimum temperature. At that time, if a shortage of refrigerant circulation to the compressor (1) occurs due to refrigerant accumulation in the refrigerant circuit (9) during operation of the refrigeration system, the discharge refrigerant temperature rises and the target value is increased accordingly. Although the opening degree of the controlled electric expansion valve (5) gradually increases,
Since the temperature of the discharged refrigerant increases rapidly, the opening degree control of the electric expansion valve (5) cannot sufficiently follow the rise, and the temperature of the discharged refrigerant exceeds a predetermined temperature. Then, when the compressor (1) is restarted after being stopped for a predetermined period of time by the operation control means (53), the discharge refrigerant temperature becomes the predetermined temperature or higher again, and the service
There is a risk that the operation of power-off, restart, thermo-off, etc. may be repeated, but in the present invention, the opening degree increasing means (52) allows the operation control means (53) to control the electric expansion valve (5) at the time of restart. Since the initial opening is changed to a predetermined opening greater than the initial opening at the previous startup, the startup starts with a large amount of refrigerant circulating, so the opening of the electric expansion valve (5) is reduced in response to a rise in the discharge refrigerant temperature. The followability of temperature control gradually improves, and thereafter, the rise in discharged refrigerant temperature is gradually suppressed and converges to a steady state. Therefore, frequent starting and stopping of the compressor (1) due to repetition of thermo-off, restart, etc. is prevented, deterioration of the air conditioning effect is avoided, and reliability is improved.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIG. 2 and subsequent drawings.

FIG. 2 shows the refrigerant piping system of an air conditioner to which the present invention is applied, where (1) is the compressor, and (2) is the pipe that is disconnected as shown by the solid line in the figure during cooling operation and as shown by the broken line in the figure during heating operation. (3) is an outdoor heat exchanger which is a heat source side heat exchanger that functions as a condenser during cooling operation and as an evaporator during heating operation, (4) is a receiver for storing liquid refrigerant. (5) is an electric expansion valve that has a refrigerant pressure reduction function and a refrigerant flow rate adjustment function; (6) is a user-side heat exchanger installed indoors that functions as an evaporator during cooling operation and as a condenser during heating operation. The indoor heat exchanger (7), which is an exchanger, is installed in the suction pipe of the compressor (1) and is an accumulator for removing liquid refrigerant from the suction refrigerant.

Each of the above-mentioned devices (1) to (7) has refrigerant piping (8
) are successively connected to form a refrigerant circuit (9) that causes heat transfer by circulating the refrigerant. Note that (13) is a supercooling capillary tube installed on the liquid pipe side of the outdoor heat exchanger (3).

[0014] Here, the compressor (1) of the refrigerant circuit (9)
) An oil recovery device (10) for recovering oil in the discharged refrigerant is interposed on the discharge side, and the oil recovery device (10) is connected between the compressor (1) and the accumulator (7). up to the suction pipe of
An oil return passage (11) for returning oil from the oil recovery device (10) to the suction side of the compressor (1) is provided via a flow control valve (12).

Furthermore, in the liquid pipe of the refrigerant circuit (9), the receiver (4) and the electric expansion valve (5) are arranged such that the electric expansion valve (5) is connected to the lower part of the receiver (4), that is, the liquid part. The common path (8a) is arranged in series so as to communicate with the common path (8a).
Between the point (P), which is the upper end of the receiver (4) in a), and the outdoor heat exchanger (3), the refrigerant flows from the outdoor heat exchanger (3) to the receiver (4). The indoor heat exchanger (6) is connected between the point (P) of the common path (8a) and the indoor heat exchanger (6) by the first inflow path (8b) via the first check valve (D1) that allows only the flow of A second inflow path (
8c), while the common path (8c)
The point (Q) which is the other end of the electric expansion valve (5) in a)
) and the point (S) between the first check valve (D1) and the outdoor heat exchanger (3).
3) A third check valve (D3) that allows only the flow of refrigerant to
between the point (Q) of the common path (8a) and the point (R) between the second check valve (D2) and the indoor heat exchanger (6) via the first outflow path (8d). are connected to each other by a second outflow path (8e) via a fourth check valve (D4) that allows only the flow of refrigerant from the electric expansion valve (5) to the indoor heat exchanger (6). Further, between a point (W) on the upstream side of the receiver in the common path (8a) and a point (U) on the upstream side of the fourth check valve (D4) in the second outflow path (8e), Liquid seal prevention bypass path (8f) with capillary tube (C) interposed
is provided to prevent liquid sealing when the compressor (1) is stopped.

[0016] In addition, the air conditioner is provided with sensors such as (Th2), a discharge pipe sensor (Thc) which is arranged in the discharge pipe of the compressor (1), and which detects the temperature of the discharge pipe.
is an external heat exchange sensor that is placed in the liquid pipe of the outdoor heat exchanger (3) and detects the condensation temperature of the refrigerant during cooling operation and the evaporation temperature of the refrigerant during heating operation; (Tha) is the outdoor heat exchanger (3)
The outside temperature sensor (The) is placed at the air inlet of the indoor heat exchanger (6) to detect the outside air temperature, and is placed in the liquid pipe of the indoor heat exchanger (6) to detect the evaporation temperature during cooling operation and the condensation temperature during heating operation. Heat exchange sensor, (Thr) is indoor heat exchanger (
6) A room temperature sensor located at the air intake port to detect the intake air temperature, (HPS) is a high pressure operating pressure switch that activates and stops abnormally when the high pressure side pressure reaches the upper limit, (LP
S) is a low-pressure operating pressure switch that activates and abnormally stops when the low-pressure side pressure reaches the lower limit, and each of the above sensors is connected to a controller (S) for controlling the operation of the air conditioner.
(not shown) so that signals can be input, and the controller controls the operation of each device according to the signals from the sensor.

In the refrigerant circuit (9), during cooling operation, the liquid refrigerant condensed and liquefied in the outdoor heat exchanger (3) flows from the first flow path (8b) to the common path (8a) and passes through the receiver ( 4) and after being depressurized by the electric expansion valve (5),
It is circulated through the second outlet path (8e), evaporated in the indoor heat exchanger (6), and returned to the compressor (1). Also, during heating operation, the liquid refrigerant condensed and liquefied in the indoor heat exchanger (6) is transferred to the second
It flows from the flow path (8c) to the common path (8a) and flows into the receiver (
4), and after being depressurized by the electric expansion valve (5), it passes through the first outflow path (8d), evaporates in the outdoor heat exchanger (3), and returns to the compressor (1), resulting in circulation.

[0018] Here, the control contents during cooling operation by the above controller will be explained based on the flowchart of FIG. When the air conditioner starts operating, first, in step ST1, the thermo-off number Up is set to the initial value "0".
In step ST2, the electric expansion valve (5) (50
The initial opening degree Po (fully opened at 0 pulses) is expressed by the formula Po
Set based on =250+Up x50 (pulse). In other words, immediately after the air conditioner starts operating, Po = 2
It becomes 50 (pulse). Next, steps ST3 and ST4
, ST5, an outdoor fan (not shown), a four-way switching valve (2
) and compressor (1) are turned on sequentially, and step ST6
Then, the discharge refrigerant temperature T2 detected by the discharge pipe sensor (Th2) is input, and the electric expansion valve (5) is input in step ST7.
) is controlled to a target value. That is, the evaporation temperature Te of the refrigerant detected by the internal heat exchange sensor (The),
From the refrigerant condensation temperature Tc detected by the external heat exchanger sensor (Thc), the formula Tk = 4-1.13Te +
1.72Tc, the optimum temperature Tk that provides the optimum refrigerating effect of the device is calculated, and the opening degree P of the electric expansion valve (5) is controlled so that the discharge refrigerant temperature T2 converges to this optimum temperature Tk.

Then, while the electric expansion valve (5) opening degree P is being controlled to the target value, the discharge refrigerant temperature T2 rises, and it is determined in step ST8 that the discharge refrigerant temperature T2 has reached the thermo-off setting value. If the temperature exceeds 135°C for 100 seconds, step ST9 is performed to protect the compressor (1).
Proceed to step 1 and calculate the number of thermo-off cycles U after the air conditioner starts operating.
p is integrated by 1, and in step ST10, the compressor (
After stopping the thermo-off of 1), in step ST11,
After waiting for 3 minutes after the thermostat is turned off, the control returns to step ST2.

[0020] In the above flow, steps ST10,
The operation control means (50) of the present invention is configured by controlling steps ST11 to ST3, ST4, and ST5, and the initial opening degree setting means (50) is configured by controlling steps ST1 and ST2.
1) is configured. Also, steps ST9 and ST
The control in step ST7 constitutes the opening degree increasing means (52), and the control in step ST7 constitutes the opening degree control means (53).

Therefore, in the above embodiment, when the air conditioner starts operating, the initial opening degree setting means (51) sets the initial opening degree Po of the electric expansion valve (5) to a constant value (205 pulses), and then , by the opening control means (53),
The opening degree P of the electric expansion valve (5) is controlled to a target value so that the discharge refrigerant temperature T2 converges to the optimum temperature Tk. At that time, as shown in FIG. 4, if a shortage of refrigerant circulation to the compressor (1) occurs due to refrigerant accumulation in the refrigerant circuit (9) during operation of the air conditioner, the discharge refrigerant temperature T2 rises,
The opening degree P of the electric expansion valve (5), which is controlled by the target value, gradually increases accordingly, but since the discharge refrigerant temperature T2 rises rapidly, controlling the opening degree P of the electric expansion valve (5) is not enough. Sometimes. After that, the opening degree P of the electric expansion valve (5)
When the temperature reaches the maximum allowable value (for example, the opening degree of about 480 pulses), the rise in the discharge refrigerant temperature T2 cannot be suppressed, and the temperature exceeds the predetermined temperature (thermo-off set value 135°C) (in the figure). time to ). Then, the operation control means (53) maintains the compressor (1) in a so-called thermo-off state in which it is stopped for a predetermined period of time (3 minutes), and then is controlled to restart the compressor (1). However, under conditions where the amount of refrigerant circulating is insufficient, the compressor (
After the restart in step 1), even if the initial opening degree Po of the electric expansion valve (5) is set to a constant value and operation is continued, the discharge refrigerant temperature T2
exceeds the thermo-off set value (135°C) again, and the thermo-off, restart, thermo-off, etc. are repeated, which not only impairs the air conditioning effect, but also damages the compressor (1).
There is a risk that reliability may be impaired due to frequent starting and stopping. especially,
As in the above embodiment, a constant displacement compressor (1) is used, and the electric expansion valve (5) is used with the discharge refrigerant temperature T2 as a control index.
) has the advantage of providing a high air conditioning effect due to its simple configuration, but on the other hand, the capacity of the compressor (1) is fixed, making it impossible to suppress an excessive rise in the discharge refrigerant temperature T2. There is a risk.

Here, in the above embodiment, the opening degree increasing means (
52), the initial opening degree Po of the electric expansion valve (5) at the time of restart by the operation control means (53) is changed to be larger than the initial opening degree at the previous startup by a predetermined opening degree (50 pulses). That is, as shown in Fig. 4, after restarting by increasing the initial opening degree Po to 300 pulses at time t1, the discharge refrigerant temperature T2 rises again and exceeds the thermo-off set value (135°C) (Fig. time t2),
When the thermostat is turned off, at the next restart (time t in the diagram)
3), the initial opening degree Po of the electric expansion valve (5) is 35
Set to 0 pulse. Therefore, by increasing the initial opening Po of the electric expansion valve (5), the operation is started with a certain amount of refrigerant circulation secured, so that the electric expansion valve ( The followability of the opening degree control in 5) improves each time the engine is restarted, and thereafter, the rise in the discharge refrigerant temperature T2 is gradually suppressed and converges to a steady state. Therefore, thermo off, restart,...
Frequent starting and stopping of the compressor (1) due to repetition of the above can be prevented, and deterioration of the air conditioning effect can be avoided, and reliability can be improved.

[0023] In the above embodiment, the cooling operation was explained, but it goes without saying that the present invention can be applied not only to the cooling operation but also to the heating operation.

[0024]

As explained above, according to the operation control device for a refrigeration system of the present invention, the initial opening degree of the electric expansion valve is set to a constant value at the start of operation of the refrigeration system, and then the discharge refrigerant temperature is optimized. The opening degree of the electric expansion valve is controlled to a target value so that the temperature converges, and when the discharge refrigerant temperature exceeds a predetermined temperature while the refrigeration equipment is operating, the compressor is thermo-off stopped for a predetermined time and then restarted. At the same time, the initial opening degree of the electric expansion valve upon restart is increased by a predetermined degree from the initial opening degree at the previous startup, so that the discharge refrigerant temperature rises due to insufficient refrigerant circulation and the compressor is unable to reach full support. -Even if the thermo-off is stopped, the process of restarting and thermo-off can be prevented from being repeated many times, and by reducing the number of times the compressor starts and stops, the air conditioning effectiveness and reliability can be improved. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the invention.

FIG. 2 is a refrigerant piping system diagram of the air conditioner according to the embodiment.

FIG. 3 is a flowchart showing the control contents of the controller.

FIG. 4 is a diagram of changes in discharge refrigerant temperature and electric expansion valve opening degree over time in the example.

FIG. 5 is a diagram of changes in discharge refrigerant temperature and electric expansion valve opening degree over time in a conventional example.

[Explanation of symbols]

1 Compressor 3 Outdoor heat exchanger (heat source side heat exchanger) 5
Electric expansion valve 6 Indoor heat exchanger (user side heat exchanger) 9
Refrigerant circuit 50 Operation control means 51 Initial opening setting means 52 Opening increasing means 53 Opening controlling means

Claims (1)

[Claims] [Claim 1] Compressor (1), heat source side heat exchanger (3)
, a refrigeration system equipped with a refrigerant circuit (9) formed by sequentially connecting an electric expansion valve (5) and a user-side heat exchanger (6),
initial opening degree setting means (51) for setting the initial opening degree of the electric expansion valve (5) to a constant value at the time of starting operation of the refrigeration system;
and a discharge temperature detection means (Th2) for detecting the discharge refrigerant temperature.
), and an opening control means (which receives the output of the discharge temperature detection means (Th2) and controls the opening degree of the electric expansion valve (5) using the optimum temperature of the discharged refrigerant that provides the optimum refrigeration effect as a control target value. 53), and upon receiving the output of the discharge temperature detection means (Th2), when the discharge refrigerant temperature reaches a predetermined temperature or higher, the compressor (1) is stopped with thermo-off for a predetermined time and then restarted. and an operation control means (50) for controlling the initial opening degree of the electric expansion valve (5) when the compressor (1) is restarted by the operation control means (50) from the initial opening degree at the previous startup. 1. An operation control device for a refrigeration system, comprising an opening increasing means (52) for increasing the opening by a predetermined amount.