JPH0814434B2 - Compressor capacity control device for refrigeration equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a compressor capacity control device for a refrigeration system, and more particularly to an overcurrent trip prevention measure when the capacity of a compressor is controlled by an inverter.

(Prior Art) Conventionally, as a compressor capacity control device for a refrigeration system, as disclosed in, for example, Japanese Patent Laid-Open No. 59-56649, an air conditioner includes a compressor whose capacity is adjusted by an inverter. It is known that the capacity of the compressor is controlled to increase or decrease by an inverter according to a change in the air conditioning load in the room, and the air conditioning capacity is appropriately matched to the air conditioning load to provide comfortable air conditioning in the room.

(Problems to be solved by the invention) By the way, when controlling the capacity of the compressor to increase or decrease, if the number of stages of change in the capacity is set in multiple stages, the refrigerating capacity can be better responded to the refrigerating load and the refrigerating performance is improved. Can be achieved, which is preferable.

Therefore, for example, two compressors are provided, the capacity of one compressor is controlled by an inverter, and the capacity of the other compressor is controlled by an unload mechanism to control the total capacity of both compressors to a target capacity value. By doing so, it is possible to adjust the total capacity of the compressor in multiple stages at a relatively low price to improve the refrigeration performance.

Therefore, when the total capacity of the compressor is adjusted in multiple stages as described above, when the compressor on the unload mechanism side is started, the operating frequency suddenly rises to the commercial frequency as shown in FIG. At this time, there is a characteristic that a large starting current flows. On the other hand, at the time of starting the compressor on the inverter side, if the operating frequency is successively increased as shown in FIG. 8, the current gradually increases due to so-called soft start, and the sudden starting current as described above does not flow. . Therefore, when both compressors are started, as shown in FIG. 9, even if the inverter-side compressor is started first and the unload mechanism-side compressor is started later, the start-up current increases only on the unload mechanism side. The increase is not significant and is not a problem.

However, at the time of starting the compressor on the unload mechanism side, the input voltage drops at this time as shown in FIG. 6B due to the flow of the starting current having a large value as shown in FIG. 6A. Therefore, the output current value increases due to the lack of the input voltage of the inverter. As a result, when the output frequency of the inverter is high (the secondary current value is large), as indicated by the alternate long and short dash line in FIG. 5C, this instant corresponds to a trip due to the increase in the output current. There is a risk of exceeding the upper limit regulation value and causing the inverter to trip.

The present invention has been made in view of the above circumstances, and an object thereof is to perform unloading during operation of the inverter-side compressor when the capacity of the two compressors is controlled by the inverter and the unload mechanism as described above. When the compressor on the load mechanism side starts up, it is unavoidable to lower the input voltage at startup of the compressor on the unload mechanism side, and by limiting the secondary current value of the inverter to a low value beforehand, Even when the side compressor is started, the inverter's instantaneous trip is reliably prevented,
Therefore, in addition to improving reliability, the operation of the compressor on the inverter side is continued to expand the operation range.

(Means for Solving the Problem) In order to achieve the above object, a concrete solving means of the present invention is, as shown in FIG. 1, a first compressor (1) whose capacity is adjusted by an inverter (15). ) And the unload mechanism (2
The second compressor (2) whose capacity is adjusted by a), and the inverter (15) and the unload mechanism (2a) so as to control the total capacity of the two compressors (1) and (2) in multiple stages. A compressor capacity control device for a refrigeration system, which includes a capacity control means (51) for controlling the. When the second compressor (2) is started during the operation of the first compressor (1) by the operation control of the capacity control means (51), the capacity control means (5)
1), prioritizing the above-mentioned first compressor (1) to a low capacity, and immediately after starting the second compressor (2), the inverter (1
The inverter (15) is controlled so that the secondary current of 5) becomes a predetermined value or less, and then the second compressor (2) is started, and then the total of both compressors (1) and (2). A starting control means (52) for controlling the inverter (15) so that the capacity becomes a predetermined value and shifting to the control of the capacity control means (51) is provided.

(Operation) According to the present invention, according to the present invention, the capacity of the first compressor (1) is controlled by the capacity control means (51) by the inverter (15) and the second compressor (2) is operated during the refrigerating operation. ) Is capacity-controlled by the unloading mechanism (2a) by the capacity control means (51), so that the total capacity of both compressors (1), (2) is adjusted to substantially match the total target capacity corresponding to the load. .

In that case, the first compressor (1) on the side of the impactor (15)
When the second compressor (2) on the side of the unloading mechanism (2a) is started during the operation of, the starting control means (52)
Prior to starting the second compressor (2), the capacity of the first compressor (1) on the inverter (15) side is low, for example, once the capacity control means (51) is activated. The operation is controlled to the minimum capacity, and the secondary current value of the inverter (15) originally becomes a small value. After that, when the compressor (2) on the unload mechanism (2a) side starts in this state, the input voltage drops and the secondary current value of the inverter (15) also increases, but the upper limit regulation value corresponding to the trip is reached. The operation of the compressor (1) on the inverter (15) side is still continued. Therefore, the reliability of the inverter (15) can be improved and the operating range 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).
Are five indoor units with the same internal configuration. Inside the outdoor unit (A), a first compressor (1) and a second compressor (2) connected in parallel with each other, a four-way switching valve (3), and an outdoor blower fan (4a). ) And an expansion valve (5), and each of the devices (1) to (5) is connected to a refrigerant pipe (6) so that the refrigerant can flow therethrough. . In addition, each indoor unit (B)
To (F) each include an indoor heat exchanger (10) having an indoor blower fan (10a) and an expansion valve (11), and the expansion valve (11) is electrically increased or decreased in its valve opening degree. Each of the devices (10) and (11) is connected through a refrigerant pipe (12) so that the refrigerant can flow therethrough.

The five indoor units (B) to (F) are
Refrigerant circulation systems (14) are formed by being connected in parallel to each other by refrigerant pipes (13) and being circulated to the outdoor unit (A) so that a refrigerant circulation system (14) is formed. 3) is switched as indicated by the broken line in the figure and the refrigerant is circulated as indicated by the dashed arrow in the figure, so that each indoor heat exchanger (1
The heat quantity absorbed from the room in 0) is repeatedly radiated to the outside air in the outdoor heat exchanger (4) to cool each room, while
During the heating operation, the four-way switching valve (3) is switched as shown by the solid line in the figure to circulate the refrigerant as shown by the solid line arrow in the figure, so that the exchange of heat is reversed and the room is heated. There is.

In addition, the first compressor (1) has an inverter (15).
Is connected, and 30% to 100% of the inverter (15)
The operating frequency of the compressor (1) is adjusted in 8 steps by the output of the frequency setting signal in 10% steps up to%, and its capacity is increased or decreased in multiple steps (9 steps including stop). Has been done.

The second compressor (2) has a suction port (2c) and a discharge port (2) in a closed casing (2b), as shown in detail in FIG.
d) is formed, and a piston (2g) driven by a motor (2e) via a drive shaft (2f) is arranged in the closed casing (2b), and is pumped by the piston (2g). Gas (discharge gas) is discharged from the discharge gas passage (2h) to the discharge gas passage (2b) through a discharge gas pipe (2i),
It is designed to lead to the discharge port (2d). And, in the middle of the discharge gas passage (2h), the unloading mechanism (2
a) is arranged, and the unload mechanism (2a) includes a valve body (21) for opening and closing an opening (2k) provided in the partition wall (2j) of the discharge gas passage (2h), and the valve body (21). A spring (2m) that urges in the valve opening direction and a pressure chamber (2n) are provided behind the valve body (21). The valve body (21) is acted upon by high pressure (discharging gas pressure) when the pilot solenoid valve (17) provided in the pilot pressure introducing passage (16) communicating with the pressure chamber (2n) is closed. The opening (2k) is closed by the valve body (21) and the entire amount of discharge gas is guided to the discharge port (2d) to make the capacity of the second compressor (2) full load (100%), while the pilot solenoid valve When the low pressure is applied when (17) is opened, the valve (21) is urged to the right in the figure by the urging force of the spring (2m) to open the opening (2k), and a part of the discharge gas is discharged. Opening (2k)
Bypass to the lower part inside the closed casing (2b) via
It unloads the capacity of the second compressor (2) to 50%.

Further, in FIG. 2, (20) is a pressure equalizing hot gas bypass circuit that connects the refrigerant pipes (6), (6) (the discharge pipe and the suction pipe) before and after the four-way switching valve (3), The bypass circuit (20) is provided with a hot gas solenoid valve (21) which is opened during a low load in a cooling operation state, a defrosting operation of the outdoor heat exchanger (4), and the like.

Further, (22) is a heating overload bypass circuit connected to the refrigerant pipe (6) serving as a discharge pipe during the heating operation, and the bypass circuit (22) includes an auxiliary capacitor (23).
Further, a high pressure control valve (24) which is opened when the pressure of the refrigerant is high is provided so that the refrigerant from the compressors (1) and (2) is exchanged with the indoor heat through the bypass circuit (22) when the heating is overloaded. Bowl (1
0) are bypassed, and each indoor heat exchanger (10) is bypassed to the refrigerant pipe (6) on the downstream side.

In addition, (25) is the bypass circuit (2
A liquid injection bypass circuit for connecting the downstream side of the auxiliary condenser (23) of 2) to the refrigerant pipe (6) (intake pipe) on the downstream side of the four-way switching valve (3), the liquid injection bypass circuit (25). An electromagnetic valve (26) for injection, which opens and closes in conjunction with the operation of the compressors (1) and (2), and an expansion valve (27) are interposed in the engine.

Also, (30) is the receiver, (31) is the accumulator,
(32) is a supercooling coil, (33) is an oil separator, and the lubricating oil separated by the oil separator (33) passes through an oil passage (34) to both compressors (1), (2 ).

Furthermore, in each indoor unit (B)-(F),
(TH1) is the temperature of the corresponding indoor air (suction air temperature)
Room temperature sensors (TH2) and (TH3) for detecting the temperature of the indoor heat exchanger (10), which function as an evaporator during the cooling operation, are temperature sensors for detecting the temperature of the refrigerant. In the outdoor unit (A), (TH4) is a temperature sensor that detects the refrigerant discharge temperature of the first and second compressors (1) and (2),
(TH5) is an evaporation temperature sensor that detects the evaporation temperature of the refrigerant in the outdoor heat exchanger (4) during heating operation, and (TH6) is the intake gas temperature of the first and second compressors (1) and (2). It is a suction gas temperature sensor. Further, (P1) is a pressure sensor that detects the discharge gas pressure during heating operation, and the suction gas pressure during cooling operation, and (HPS) is a high-pressure pressure switch for protecting the compressor.

Next, the control of the first and second compressors (1) and (2) will be described based on the control flow of FIG. 4 by taking the cooling operation as an example. Note that this capacity control is performed by an outdoor control unit (not shown) provided in the outdoor unit (A).

In FIG. 4, after starting, the refrigerant temperature T ₂ obtained by converting the intake air amount gas pressure detected by the pressure sensor (P ₁ ) in step S ₁ into the equivalent saturation temperature, that is, the evaporation temperature (the refrigerant during heating operation, After the condensation temperature of the compressor is detected, PI control (proportional-integral control) is performed as feedback control of the total capacity of the compressors (1) and (2).
S ₂ in the compressor (1), a target total volume L ₁ (2), the deviation of the evaporator temperature T ₂ and the target value _{T. 2O,} current and previous values e (t), e (t- Based on Δt), the following equation L ₁ = L _O + Kc [e (t) −e (t−Δt) + {Δt / 2Ti} {e (t) so that the evaporation temperature T ₂ becomes the target value T _2O. + E (t−Δt)}] L _O ; Current total capacity Kc; Gain (constant) Ti: Integration constant Δt; Sampling time.

Thereafter, in step S ₃ based on the total volume map of the first table below the compressor corresponding to the total target volume L ₁ (1), to grasp the total amount of (2), corresponding to the total volume The capacity of the first compressor (1) is controlled by the inverter (15) based on the actual capacity maps of the compressors (1) and (2) in Table 2 below, and the second compressor is also used. Adjust the capacity of (2) with the unload mechanism (2a). Then, in step S ₄ , after waiting for the elapse of the sampling time Δt, the process returns to step S ₁ and the above operation is repeated.

Here, the total capacity map in Table 1 above shows that the total capacity of the compressors (1) and (2) to be controlled is zero.
Multi-step (1% gradually increasing from 30% value to 200%)
In addition to being divided into 9 stages), the range of the total target capacity L ₁ is distinguished when the capacity is increasing and when it is decreasing.

In addition, the capacity maps of the compressors (1) and (2) in Table 2 above show that when the total capacity is in the range of 30% to 100%, the capacity of the first compressor (1) is in steps of 10%. In the first map where the capacity of the second compressor (2) increases and the capacity of the second compressor (0) keeps 0% (stop), and the total capacity of the first compressor (1) is 80% to 150%. Capacity is the same as above
In the second map where the capacity of the second compressor (2) keeps 50% and increases in 10% increments, and the total capacity ranges from 130% to 200%, the first compressor (1) The capacity of the second compressor (2) increases by 10%, and the capacity of the second compressor (2) holds 100%. Then, when the total capacity increases or decreases in the first map and the total capacity increases to 110% in the state where the capacity of the first compressor (1) is the maximum value (100%), the process moves to the second map. , The capacity of the second compressor (2) is adjusted to be increased from 0% to 50% by the unload mechanism (2a), and the capacity of the first compressor (1) is adjusted by the inverter (15) to 10%.
It is adjusted to decrease from 0% to 60%, and then each capacity value of this second map is taken according to the increase and decrease of the total capacity,
When the total capacity decreases from 80% to 70% when the capacity value of the compressor (1) is 30% of the minimum value, the second compressor (2) is moved to the first map. Is adjusted to 0% and the capacity of the first compressor (1) is adjusted to 70% by the inverter (15).

Similarly, if the total capacity increases or decreases on the second map and the total capacity increases from 150% to 160% with the capacity of the first compressor (1) at the maximum value (100%), the third map will appear. After the transition, the capacity of the second compressor (2) becomes the unload mechanism (2a).
The capacity of the first compressor (1) is adjusted to be reduced from 100% to 60% by the inverter (15) while being adjusted to be increased from 50% to 100%. After that, each capacity value of this third map is taken according to the increase or decrease in the total capacity, and the total capacity is 130% when the capacity value of the first compressor (1) is 30% of the minimum value.
When the first compressor (1) is reduced from 120% to 120%, the second map is moved to adjust the capacity of the second compressor (2) from 100% to 50%. ) Capacity is adjusted to 70% by the inverter (15).

Therefore, according to the control flow of FIG. 4, the total capacity of both compressors (1) and (2) is adjusted in multiple stages (19 stages) to the total volume corresponding to the total target volume L _{1 as shown} in Table 2 above. Inverter (15) and unload mechanism (2a)
The capacity control means (51) is configured to control the.

Therefore, in the control flow of FIG.
In S _3, at the time of starting the unloading mechanism (2a) of the compressor (2), the control at startup flow of FIG. 5 is carried out. That is, in the startup control flow of FIG. 5, to grasp the change of the total target capacity L ₁ in step S _S1, the total target capacity L ₁ 100
Only when YES from 110% to 110%, it is determined that the compressor (2) on the unloading mechanism (2a) side has been started, and the process proceeds to step S _S2 .

And, the compressor (2) on the side of the unload mechanism (2a)
At the time of starting up, first, in step S _S2 , the inverter (15) is operated and controlled so that the capacity of the first compressor (1) on the inverter (15) side is reduced to 30% of the lowest stage (minimum capacity),
After that, in step S _S3 , the second unloading mechanism (2a) side
This second compressor is started by starting the compressor (2) and controlling the opening of the pilot solenoid valve (17) of FIG. 3 in step S _S4 to operate the unload mechanism (2a). Control the capacity of (2) to 50%. Then, in step S _S5 , the first compressor (1) is controlled by the inverter (15) to have a capacity of 60% as shown in Table 2, and the process returns.

Therefore, when the total target capacity L ₁ is increased from 100% to 110% according to the startup control flow of FIG. 5, that is, the operation control of the capacity control means (51) controls the first compressor (1). When the second compressor (2) is started during the operation of 100% capacity, the first compressor (1) is preliminarily operated at the lowest stage of 30% capacity in preference to the capacity control means (51). After controlling the inverter (15) so that the second compressor (2) is started, the inverter (15) is controlled so that the total capacity of both compressors (1) and (2) becomes a predetermined value. The start-up control means (52) is configured to control the capacity and shift to the control of the capacity control means (51).

Therefore, in the above embodiment, when the indoor units (B) to (F) are in the cooling operation, the total target capacity L _{1 of} the compressors (1) and (2) is calculated based on the evaporation temperature T _2. The capacity of the first compressor (1) is controlled by the capacity control means (51) by the inverter (15) so that the capacity stage corresponds to the target total capacity L ₁ , and the second compressor is also controlled. The capacity of (2) is controlled by the capacity control means (51) by the unload mechanism (2a), and the total capacity of the compressors (1) and (2) is accurately adjusted to the total target capacity L _1. . As a result, the evaporation temperature T _{2 of the} refrigerant converges favorably to the target value T _2O , and each room is cooled and air-conditioned well.

At that time, when the compressor (2) on the side of the unload mechanism (2a) is started, that is, when the total target capacity L ₁ is increased from 100% to 110%, the startup control means (52) is the capacity control means (52). In preference to 51), the capacity of the first compressor (1) on the side of the inverter (15) is controlled to be reduced to the lowest 30% capacity value,
The secondary current value of the inverter (15) greatly decreases from the value corresponding to 100% to the value corresponding to 30% as shown by the solid line in FIG. As a result, the second compressor (2) on the side of the unload mechanism (2a) is subsequently started, and its starting current suddenly increases as shown in FIG. Even if this instantaneous drop occurs as shown in (b), the inverter (1
Although secondary current value of 5) increases in accordance with its, does not lead to the upper limit current value I _T trip regulations. Therefore, as indicated by the alternate long and short dash line in FIG.
As in the case of starting the compressor (2), the secondary current value without causing a trip of the inverter (15) beyond the upper limit current value I _T, the improvement of reliability is achieved, first The operation range of the compressor (1) can be expanded by continuing the operation of the compressor (1).

Incidentally, in the above embodiment, the second unit on the unload mechanism (2a) side is
Of the inverter (15) side when the compressor (2) of the
The capacity of the compressor (1) was controlled to the lowest value of 30%.
Other may be set to a smaller volume side, such as 40% or 50%, that is, as long as the secondary current of the inverter (15) is set to a low volume that does not exceed the upper limit current value I _T.

In the above embodiment, the capacity of the first compressor (1) is controlled by the inverter (15) in eight steps, and the capacity of the second compressor (2) is controlled by the unload mechanism (2a) in two steps. The total capacity is controlled in 19 steps, but the number of capacity control steps may be other steps.

Further, in the above-described embodiment, the description has been given by taking the cooling operation as an example, but it is needless to say that the same can be applied to the heating operation, and the invention is not limited to the multi-type air conditioner, and other one outdoor unit. However, it goes without saying that the present invention can be similarly applied to a normal air conditioner to which one indoor unit corresponds, and other refrigerating apparatuses such as those in which indoor and outdoor units are integrated.

(Effects of the Invention) As described above, according to the present invention, the first and second
When the capacity of each compressor is controlled by the inverter and the unload mechanism, the capacity of the compressor on the inverter side should be set to a low capacity in advance when the compressor on the unload mechanism side starts while the compressor on the inverter side is operating. Since the second compressor is started after the control, even if the secondary current of the inverter is increased due to the decrease of the input voltage when the compressor on the unload mechanism side is started, The secondary current value can be suppressed to a small value to prevent an instantaneous trip of the inverter, and reliability can be improved and the operating range can be expanded.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of the present invention. 2 to 6 show an embodiment of the present invention, FIG. 2 is a refrigerant piping system diagram applied to a multi-type air conditioner, and FIG. 3 is a specific internal configuration of the second compressor. FIG. 4, FIG. 4 is a flow chart showing the capacity control of the compressor, FIG. 5 is a flow chart showing the control at startup of the compressor on the unload mechanism side, and FIG. 6 is an operation explanatory view. 7 and 8 are diagrams showing the operating frequency and starting current waveform of the compressor on the unload mechanism side and the compressor on the inverter side, respectively.
The figure is a diagram showing a total current waveform when both compressors are sequentially started. (1) ... first compressor, (2) ... second compressor,
(2a) …… Unload mechanism, (21) …… Valve disc, (2n)…
… Pressure chamber, (14) …… Refrigerant piping system, (15) …… Inverter, (17) …… Pilot solenoid valve, (51) …… Capacity control means, (52) …… Startup control means.

Claims (1)

[Claims] 1. A first compressor (1) whose capacity is adjusted by an inverter (15), a second compressor (2) which is quantitatively adjusted by an unloading mechanism (2a), and both compressors (1). The inverter (15) and the unload mechanism (2a) so as to control the total capacity of 1) and 2) in multiple stages.
When the second compressor (2) is started during the operation of the first compressor (1) by the operation control of the capacity control means (51), The first compressor (1) has priority over the capacity control means (51).
Is set to a low capacity to control the inverter (15) so that the secondary current of the inverter (15) immediately after the second compressor (2) is started becomes a predetermined value or less, and then the second compressor (2) After starting 2), the start-up control for controlling the inverter (15) so that the total capacity of both compressors (1), (2) becomes a predetermined value and shifting to the control of the capacity control means (51). A compressor capacity control device for a refrigeration system, comprising a means (52).