JP2002283840A - Vapor-compression refrigeration cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the increase of the time needed for bringing close an after-evaporator temperature Te to a target after-evaporator temperature Teo, and to prevent the control of the after-evaporator temperature Te from diverging in the refrigeration cycle having a variable displacement compressor. SOLUTION: While the pressure in a swash plate chamber of a variable- displacement compressor is under PI(Proportional Integral) control, the value of the proportional control constant Kp and the integral control constant Ti<-1> of a PI control equation are made to increase as the absolute value of the difference between the target after-evaporator temperature Teo and the after- evaporator temperature Te increases. As a result, when heat load fluctuation is heavy, the after-evaporator temperature Te is made to reach promptly to the target after-evaporator temperature Teo to prevent the control of the after- evaporator temperature Te from diverging.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressor for sucking and compressing a refrigerant and a vapor compression refrigeration cycle having an evaporator for evaporating the decompressed and expanded refrigerant. It is effective to apply to machines.

[0002]

2. Description of the Related Art In a vapor compression refrigeration cycle, generally, the refrigerating capacity (heat absorption) of an evaporator is controlled by controlling the flow rate (mass flow rate) of a refrigerant circulating in the cycle. Therefore, in the invention described in Japanese Patent Publication No. 7-6503, the flow rate of the refrigerant circulating in the cycle is controlled by controlling the discharge capacity of the swash plate type variable displacement compressor.

By the way, the discharge capacity is a theoretical volume discharge amount discharged from the compressor when the shaft makes one rotation,
In the swash plate type variable displacement compressor, the discharge capacity is changed by controlling the pressure in the swash plate chamber to change the inclination angle of the swash plate, that is, the piston stroke.

[0004]

According to the invention described in the above publication, the flow rate of the refrigerant circulating in the cycle, that is, the discharge flow rate of the compressor, is controlled by an electromagnetic control valve that controls the pressure in the swash plate chamber. However, in a vapor compression refrigeration cycle employing a variable displacement compressor, the control current and control voltage and the refrigeration capacity exhibited by the evaporator do not always change linearly.

For this reason, when the invention is applied to the above-mentioned publication in a supercritical refrigeration cycle in which the discharge pressure of a compressor is equal to or higher than the critical pressure of the refrigerant, such as a vapor compression refrigeration cycle using carbon dioxide as a refrigerant, Problems become noticeable.

That is, in the invention described in the above publication, the pressure in the swash plate chamber is controlled by regulating the discharge pressure with an electromagnetic control valve and introducing the discharge pressure into the swash plate chamber. Because the discharge pressure of the machine is higher than the critical pressure,
Even if the opening degree of the electromagnetic control valve, that is, the control current or the control voltage slightly changes, the pressure in the swash plate chamber greatly changes.

[0007] Therefore, the discharge flow rate of the compressor greatly changes in response to a change in the control current, and the refrigerating capacity exerted by the evaporator does not linearly change in response to the control current.

For this reason, for example, when the refrigerating capacity actually exhibited by the evaporator (hereinafter, this refrigerating capacity is called the actual refrigerating capacity) is smaller than the control target refrigerating capacity, the actual refrigerating capacity is set to the control target refrigerating capacity. If the control current is changed so as to be closer, there is a high possibility that the actual refrigeration capacity greatly exceeds the control target refrigeration capacity.

Conversely, if the actual refrigerating capacity is larger than the control target refrigerating capacity and the control current is changed to bring the actual refrigerating capacity close to the control target refrigerating capacity, the actual refrigerating capacity will fall significantly below the control target refrigerating capacity. It is highly likely that Therefore, it is difficult to make the actual refrigerating capacity converge to the control target refrigerating capacity, and the control of the actual refrigerating capacity is likely to diverge.

[0010] In order to solve this problem, if the change in the control current is reduced when the control current is determined, the control of the actual refrigeration capacity can be prevented from diverging.
When the heat load in the evaporator greatly changes during rapid cooling or the like, a problem occurs that it takes time to bring the actual refrigeration capacity closer to the control target refrigeration capacity.

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to prevent the time required for approaching the actual refrigeration capacity from approaching the control target refrigeration capacity and to prevent the divergence of the actual refrigeration capacity control. I do.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an evaporator (4).
00), and a refrigerating capacity detecting means (7) for detecting a refrigerating capacity actually exhibited by the evaporator (400).
01), the target refrigerating capacity (Qeo) determined by the target refrigerating capacity determining means (700), and the refrigerating capacity detecting means (701)
Determines a control target value (V) based on the difference from the detected actual refrigeration capacity (Qe), and controls the discharge capacity of the compressor (100) according to the control target value (V).
00), and the value of the correction term (α) for correcting the control target value (V) is the absolute value (εa) of the difference (ε) between the target refrigerating capacity (Qeo) and the actual refrigerating capacity (Qe). It is characterized in that it is selected so as to become larger as becomes larger.

Thus, for example, when the present invention is applied to an air conditioner, the evaporator (400) for rapid cooling or the like is used.
When the heat load at the time has greatly changed, the absolute value (εa) of the difference (ε) between the target refrigeration capacity (Qeo) and the actual refrigeration capacity (Qe) increases, and the correction term (α) also increases.
Therefore, the actual refrigerating capacity (Qe) can be quickly increased, and the actual refrigerating capacity (Qe) can be quickly brought closer to the target refrigerating capacity (Qeo).

On the other hand, when the actual refrigerating capacity (Qe) approaches the target refrigerating capacity (Qeo), the absolute value (εa) of the difference (ε) between the target refrigerating capacity (Qeo) and the actual refrigerating capacity (Qe) becomes smaller. , The correction term (α) becomes smaller, so that the amount of change in the control target value (V) becomes smaller. Therefore, since the actual refrigerating capacity (Qe) can be easily converged to the target refrigerating capacity (Qeo), the control of the actual refrigerating capacity (Qe) can be prevented from diverging.

As described above, according to the present invention, the control of the refrigeration capacity diverges while preventing the time required to bring the actual refrigeration capacity (Qe) closer to the target refrigeration capacity from increasing. Can be prevented.

The value of the correction term (α) for correcting the control target value (V) is, as in the second aspect of the invention, the difference between the target refrigerating capacity (Qeo) and the actual refrigerating capacity (Qe). The selection may be made so that the larger the absolute value (εa) of ε) becomes, the larger the value becomes.

Further, the value of the correction term (α) for correcting the control target value (V) is the difference between the target refrigerating capacity (Qeo) and the actual refrigerating capacity (Qe). The selection may be made so that the absolute value (εa) of ε) increases continuously as the absolute value (εa) increases.

Further, the value of the correction term (α) for correcting the control target value (V) may be selected based on the above equation (1).

Further, the correction term (α) may be a proportional control constant and an integral control constant of a function formula for proportional integral control, as in the fifth aspect of the present invention.

Further, the correction term (α) is a proportional control constant of a proportional integral control function,
It may be an integral control constant and a differential control constant.

According to the present invention, there is provided a vapor compression refrigeration cycle having a variable capacity compressor (100) for sucking and compressing a refrigerant and an evaporator (400) for evaporating the refrigerant decompressed and expanded. Means for determining a target value of the refrigerating capacity exerted by the evaporator (400), and a refrigerating capacity detecting means for detecting the refrigerating capacity actually exhibited by the evaporator (400) ( 701) and a flow rate control means (700) for determining a control target value (I) and controlling the discharge capacity of the compressor (100) according to the control target value (I). When at least the absolute value of the rate of change (dQe / dt) of the actual refrigerating capacity (Qe) detected by the refrigerating capacity detecting means (701) exceeds a predetermined rate of change, the previously determined control target value (I) To a predetermined amount (Δi Is varied, the actual refrigerating capacity (Qe)
When the absolute value of the rate of change (dQe / dt) is equal to or less than the predetermined rate of change, the difference between the target refrigerating capacity (Qeo) determined by the target refrigerating capacity determining means (700) and the actual refrigerating capacity (Qe) is determined. The control target value (I) is thus determined.

Thus, when the actual refrigerating capacity (Qe) changes significantly, the control target value (I) is forcibly changed to immediately change the discharge capacity of the compressor (100). The refrigerating capacity (Qe) is equal to the target refrigerating capacity (Qe).
o), the actual refrigeration capacity (Q
e) can quickly approach the target refrigeration capacity (Qeo).

According to the present invention, when the absolute value of the change rate (dQe / dt) of the actual refrigerating capacity (Qe) exceeds a predetermined change rate, the flow rate control means (700)
Is that the change rate (dQe / dt) of the actual refrigerating capacity (Qe) is positive and the actual refrigerating capacity (Qe) is equal to or greater than the target refrigerating capacity (Qeo) determined by the target refrigerating capacity determining means (700). Sometimes, the control target value (I) is changed so that the discharge capacity of the compressor (100) decreases, and the actual refrigeration capacity (Q
e) when the rate of change (dQe / dt) is negative and the actual refrigerating capacity (Qe) is less than or equal to the target refrigerating capacity (Qeo) determined by the target refrigerating capacity determining means (700). The control target value (I) is changed so that the discharge capacity of (1) increases.

Thus, even if the actual refrigerating capacity (Qe) changes excessively due to overshoot, the actual refrigerating capacity (Qe) can be quickly brought closer to the target refrigerating capacity (Qeo).

According to the ninth aspect of the present invention, when the absolute value of the rate of change (dQe / dt) of the actual refrigerating capacity (Qe) exceeds a predetermined rate of change, the flow rate control means (700)
When the absolute value of the rate of change (dQe / dt) of the actual refrigerating capacity (Qe) is equal to or more than a predetermined value, the amount of change in the control target value (I) is set to be equal to or more than a predetermined amount, and the change in the actual refrigerating capacity (Qe) is obtained. Rate (dQ
When the absolute value of (e / dt) is smaller than the predetermined value, the amount of change in the control target value (I) is set to be smaller than the predetermined value.

Thus, the actual refrigerating capacity (Qe) can be brought closer to the target refrigerating capacity (Qeo) more quickly.

According to the tenth aspect, when the absolute value of the change rate (dQe / dt) of the actual refrigerating capacity (Qe) exceeds a predetermined change rate, the flow rate control means (700)
Is characterized in that the change rate of the change amount of the control target value (I) with respect to the absolute value of the change rate (dQe / dt) of the actual refrigeration capacity (Qe) is always 0 or more.

Thus, the actual refrigerating capacity (Qe) can be brought closer to the target refrigerating capacity (Qeo) more quickly.

The change rate (dQ) of the actual refrigeration capacity (Qe)
When the absolute value of (e / dt) is equal to or less than a predetermined rate of change, the control target value (I) may be determined by the proportional integral control or the proportional integral derivative control as in the eleventh aspect of the present invention. desirable.

The flow rate control means (700) determines whether or not the absolute value of the rate of change (dQe / dt) of the actual refrigerating capacity (Qe) exceeds a predetermined rate of change, as in the twelfth aspect. Is desirably performed at intervals of 10 seconds or less.

Further, according to the invention of claim 13,
The compressor (100) may be applied to a vapor compression refrigeration cycle in which the refrigerant is compressed to a pressure higher than the critical pressure of the refrigerant.

Further, as in the invention according to claim 14, carbon dioxide may be used as a refrigerant.

Incidentally, the reference numerals in parentheses of the above means are examples showing the correspondence with the concrete means described in the embodiments described later.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment)
The vapor compression refrigeration cycle according to the present invention is applied to a vehicle air conditioner using a supercritical refrigeration cycle in which the refrigerant pressure on the high pressure side, that is, the discharge pressure of the compressor is equal to or higher than the critical pressure of the refrigerant, FIG. 1 is a schematic diagram of a supercritical refrigeration cycle.

In FIG. 1, a compressor 100 obtains power from a traveling engine to suck and compress a refrigerant. The compressor 100 has a swash plate as described in, for example, JP-A-2000-220557. This is a variable displacement compressor that changes the displacement by changing the angle of inclination. Incidentally, in the present embodiment, carbon dioxide is used as the refrigerant.

The tilt angle, that is, the angle between the swash plate and the direction perpendicular to the shaft is adjusted by adjusting the discharge pressure of the compressor 100 by the electromagnetic control valve 110 and then introduced into the swash plate chamber of the compressor 100. Alternatively, the pressure in the swash plate chamber is controlled by returning the refrigerant in the swash plate chamber to the suction side of the compressor.

Specifically, when the pressure in the swash plate chamber is reduced,
The inclination angle of the swash plate increases, the discharge capacity increases, and conversely,
When the pressure in the swash plate chamber is increased, the inclination angle of the swash plate is reduced, and the discharge capacity is reduced.

The radiator 200 is a high-pressure side heat exchanger for exchanging heat between outdoor air and a refrigerant.
Is a decompression means for decompressing and expanding the refrigerant flowing out of the radiator 200, and the evaporator 400 evaporates the liquid-phase refrigerant out of the refrigerant in the gas-liquid two-phase state by the decompressor 300 to generate a refrigerating ability. This is a low-pressure side heat exchanger that cools the air blown into the room.

The accumulator 500 separates the refrigerant into a gas-phase refrigerant and a liquid-phase refrigerant, and separates the gas-phase refrigerant from the compressor 1.
A gas-liquid separation means for flowing out toward the suction side of 00,
The internal heat exchanger 600 exchanges heat between the refrigerant flowing out of the accumulator 500 and the refrigerant flowing out of the radiator 200.

The first temperature sensor 701 detects the temperature of the air immediately after passing through the evaporator 400, thereby detecting the air temperature.
Reference numeral 00 denotes refrigeration capacity detection means for detecting the refrigeration capacity that is actually exerted. The detected temperature of the first temperature sensor 701 (hereinafter, referred to as the post-evaporation temperature Te) indicates the degree of opening of the electromagnetic control valve 110. Electronic Control Unit (ECU) 700 for Controlling
Has been entered.

The ECU 700 stores the temperature after evaporation Te
In addition to the above, a second temperature sensor 702 for detecting the air temperature inside the vehicle compartment, and a third temperature sensor 7 for detecting the air temperature outside the vehicle compartment
03, the detection value of an air-conditioning sensor such as a solar radiation sensor 704 for detecting the amount of solar radiation falling into the vehicle, and the vehicle interior temperature desired by the occupant by the occupant's manual operation (desired interior temperature)
Is set, and the set temperature Tset of the temperature setter 705 is input.

Next, the characteristic control operation of the compressor 100 in the air conditioner according to the present embodiment will be described.

The flow chart shown in FIG.
That is, the main procedure is executed at the same time as the start of the compressor 100. At the same time as the start of the air conditioner, the detected value of the air conditioning sensor and the set temperature Tset are read. The temperature of the blown air, that is, the target blow temperature TAO is calculated (S100).

[0044]

## EQU2 ## TAO = Kset × Tset−Kr × Tr−K
am × Tam-Ks × Ts-C1Kset, Kr, Ka
m, Ks: gain C1: constant Tr: indoor air temperature (detected temperature of second temperature sensor 702) Tam: outdoor air temperature (detected temperature of third temperature sensor 703) Ts: detected value of solar radiation sensor 704 Next, S100 The target value of the air temperature immediately after passing through the evaporator 400, that is, the target post-evaporator temperature Teo is determined based on the TAO calculated in (S110). Incidentally, as shown in FIG. 3, Teo is determined to be higher as TAO becomes higher, and a predetermined hysteresis is provided in the rising process and the falling process of TAO.

Here, Teo is a target value of the air temperature immediately after passing through the evaporator 400. Therefore, as Teo decreases, the target value Q of the refrigerating capacity exhibited by the evaporator 400 decreases.
eo (hereinafter, this target value is referred to as target refrigeration capacity Qeo)
Needs to be increased, and conversely, as Teo increases, the target refrigeration capacity Qeo needs to be reduced. That is, to determine Teo in this embodiment means to determine the target refrigeration capacity Qeo.

Similarly, as the post-evaporation temperature Te (hereinafter abbreviated as Te) decreases, the refrigeration capacity Qe actually exhibited by the evaporator 400 increases, and conversely, as the Te increases, the evaporator 400 increases. Since the actual refrigerating capacity Qe actually exerts a small value, detecting Te means, in the present embodiment, detecting the refrigerating capacity Qe actually exerted by the evaporator 400.

Then, the control voltage of the electromagnetic control valve 110, that is, the control target value V is proportionally integrated controlled (PI controlled) based on the following equation 3 so that Te becomes Teo.
The discharge capacity of the compressor 100, that is, the capacity of the evaporator 400 is controlled (S120). When the control voltage of the electromagnetic control valve 110 is changed, the current flowing through the electromagnetic control valve 110 changes. Therefore, controlling the control voltage of the electromagnetic control valve 110 means controlling the control current supplied to the electromagnetic control valve 110. Means to do.

[0048]

V = Kp × (ε + Ti ⁻¹ × ∫ε · dt) where ε = Teo−Te Kp: proportional control constant Ti ⁻¹ : integral control constant At this time, the proportional control constant Kp and the integral control constant Ti ⁻¹ Is not constant, and as shown in FIG. 4, is selected so that the absolute value εa (= | ε |) of the difference ε between Teo and Te increases stepwise.

Therefore, in this embodiment, Teo and Te
The greater the absolute value εa of the difference between the control voltage Vo and the control voltage Vo when the values of the proportional control constant Kp and the integral control constant Ti ⁻¹ are fixed values, as the absolute value εa (hereinafter, this value is referred to as a target residual εa) increases. Thus, the control voltage V is corrected so as to increase. Therefore, in the present embodiment, the proportional control constant Kp and the integral control constant Ti ⁻¹ are collectively referred to as a correction term α.

In FIG. 4, the proportional control constant Kp and the integral control constant Ti ^-1 are depicted as having the same value, but FIG. 4 shows the proportional control constant Kp and the integral control constant Ti-1.
^-1 (correction term α), and does not necessarily mean that the value of the proportional control constant Kp and the value of the integral control constant Ti ^-1 are the same.

Next, the operation and effect of this embodiment will be described.

According to the present embodiment, the correction term α is selected so as to increase as the target residual εa increases. For example, when the heat load in the evaporator 400 during rapid cooling changes greatly, the target The residual εa increases and the correction term α also increases. Therefore, the actual refrigerating capacity can be quickly increased, and the actual refrigerating capacity Qe can be quickly brought closer to the target refrigerating capacity Qeo.

On the other hand, the actual refrigerating capacity Qe is equal to the target refrigerating capacity Qe.
When the value approaches o, the target residual εa decreases and the correction term α decreases, so that the amount of change in the control voltage V decreases, so that the actual refrigerating capacity Qe can be easily converged to the target refrigerating capacity Qeo, Divergence of the actual control of the refrigeration capacity Qe can be prevented.

As described above, according to the present embodiment, the refrigeration capacity control, that is, the evaporative power control, that is, the time required for the actual refrigeration capacity Qe to approach the target refrigeration capacity Qeo is prevented. It is possible to prevent the post-temperature Te control from diverging.

As is clear from the above description,
This embodiment quickly changes the actual refrigerating capacity Qe to the target refrigerating capacity even when the heat load fluctuates due to a change in the amount of air passing through the evaporator 400 or a change in TAO due to a change in the set temperature Tset. The refrigeration capacity control, that is, the post-evaporation temperature Te control, can be prevented from diverging while approaching Qeo.

(Second Embodiment) In the first embodiment, the correction term α is changed stepwise with respect to the change of the target residual εa. In this embodiment, as shown in FIGS. Target residual ε
The correction term α is continuously changed with respect to the change in the target residual εa so that the correction term α is continuously increased as a becomes larger.

The value of the correction term α is expressed by the following equation (4). FIG. 5 is a characteristic diagram of the correction term α when n = 1, and FIG. 6 is a correction chart when n = 2. FIG. 7 is a characteristic diagram of a term α. Incidentally, if n is increased, the correction term α can be increased nonlinearly with respect to the target residual εa.

[0058]

Α = a × | ε | ⁿ + b where α: value of correction term (α) a, b: constant n: positive real number In FIGS. 5 and 6, the proportional control constant Kp and the integral control constant Ti ^Although the value of ^-1 is drawn as the same value, FIG.
Numeral 6 indicates the characteristics of the proportional control constant Kp and the integral control constant Ti ^-1 (correction term α).
This does not mean that the value of the integral control constant Ti- ¹ is the same as the value of the integral control constant Ti- ¹ . Therefore, the constants a and b may be different from the constants a and b for determining the proportional control constant Kp and the constants a and b for determining the integral control constant Ti ^-1 .

(Third Embodiment) In the above embodiment, the control voltage V is determined by the proportional integral control, but in the present embodiment, the proportional integral derivative control (PI
D control), the control voltage V may be determined.

In this case, three of the proportional control constant Kp, the integral control constant Ti ⁻¹ and the differential control constant Td are the correction term α.

[0061]

V = Kp × (ε + Ti ⁻¹ × ∫ε · dt + Td ·
dε / dt) (Fourth Embodiment) In the first to third embodiments, the target residual εa
The correction term α is changed based on the absolute value (= | dTe) of the rate of change dTe / dt of Te (post-evaporation temperature), which is a parameter indicating the actual refrigerating capacity Qe.
/ Dt |) exceeds a predetermined rate of change, the control voltage V determined last time, that is, the control current value I is increased by a predetermined amount Δi
On the other hand, when the absolute value of the rate of change dTe / dt of Te is equal to or less than a predetermined rate of change, T is calculated by using the above equation 3 (proportional integral control) or equation 4 (proportional integral differential control).
The control voltage V, that is, the control current value I is determined based on the difference between eo (target evaporator post-evaporator temperature) and Te.

As described above, as Te decreases, the actual refrigerating capacity Qe increases, and conversely, as Te increases, the actual refrigerating capacity Qe decreases.
When t is positive, that is, when Te is on the rise,
When the rate of change dQe / dt of the actual refrigerating capacity Qe is negative, and conversely, when dTe / dt is negative, that is, when Te is on a downward trend, the rate of change dQe / dt of the actual refrigerating capacity Qe is positive.

In this embodiment, the correction term α
Is a constant, but the correction term α may be changed based on the target residual εa as in the first to third embodiments.

The characteristic control flow of this embodiment will be described below with reference to FIG.

The detected value of the air conditioning sensor and the set temperature Tset are read at the same time as the activation of the air conditioner, and the temperature of the air blown into the vehicle compartment, that is, the target blow temperature TAO is calculated based on the read values according to the above equation (2). (S200).

Next, based on the TAO calculated in S200, Teo is determined based on the map shown in FIG. 3 (S210), and the rate of change dTe / dt of Te is calculated (S220). Is increasing (dTe / dt>
0) or Te is on a downward trend (dTe / dt <0)
It is determined whether there is no change in Te (dTe / dt = 0) (S230).

When Te is on a downward trend,
It is determined whether or not the absolute value of the rate of change of Te is larger than a predetermined rate of change εod (S240). If the absolute value of the rate of change of Te is larger than the predetermined rate of change εod, Te is set to Te.
It is determined whether or not the value is larger than the set value determined based on o (S250).

In the present embodiment, a predetermined temperature range centered on Teo, that is, Teo + α or Teo−α is set as the set value determined based on Teo. Here, α is a real number of 0 or more.

If Te is equal to or smaller than the set value determined based on Teo, it is considered that the actual refrigerating capacity Qe exceeds the target refrigerating capacity Qeo, and the control current value determined last time is determined. the value obtained by subtracting the predetermined current value Δiad from I _n-1 and the present control current value I _n (S260).

On the other hand, if Te exceeds the set value determined based on Teo, it is considered that the actual refrigerating capacity is less than or equal to the target refrigerating capacity Qeo, and the control is performed. Without forcibly reducing the current value I, the control current value I is determined based on the difference between Teo and Te using Expression 3 or Expression 4 (S270). In this case, the control current value value I _n-1, which is previously determined may be present control current value I _n.

When Te is on the rise, T
It is determined whether or not the absolute value of the rate of change of e is greater than a predetermined rate of change εou (S280). If the absolute value of the rate of change of Te is greater than the predetermined rate of change εou, Te is equal to Teo.
It is determined whether or not the value is smaller than the set value determined based on (S290).

If Te exceeds the set value determined based on Teo, the actual refrigerating capacity is regarded as Qe being insufficient with respect to the target refrigerating capacity Qeo, and the control current determined previously. The predetermined current value Δia from the value value In _-1
The value obtained by adding the d and the present control current value I _n (S30
0).

On the other hand, if Te is equal to or less than the set value determined based on Teo, it is considered that the actual refrigerating capacity Qe exceeds or satisfies the target refrigerating capacity Qeo, and the control current value Without forcing I to increase,
The control current value I is determined based on the difference between Teo and Te using Equation 3 or Equation 4 (S270). In this case,
A control current value value I _n-1, which is previously determined may be present control current value I _n.

By the way, there is no change in Te (dTe / dt
= 0) in the case, the control current value value I _n-1, which is previously determined and the present control current value I _n (S310).

When it is determined in S240 that the absolute value of the rate of change of Te is equal to or smaller than the predetermined rate of change εod, or in S280, the absolute value of the rate of change of Te is equal to or smaller than the predetermined rate of change εod.
When it is determined that the current is less than ou, the control current value I is determined based on the difference between Teo and Te in Expression 3 or Expression 4 (S270).

Next, the control current value I determined in any of S260, S270, S300, and S310 is supplied to the electromagnetic control valve 110 to control the displacement of the compressor 100 (S320).

Here, the routine shown in S200 to S320 is defined as one cycle, and a predetermined time to (for example, 1
0 seconds), it is determined whether or not the timer time t based on the execution of S200 has exceeded a predetermined time to (S330), and the timer time t is set to the predetermined time t.
o, the process returns to S200 and again returns to S200.
Execute the following flow.

Therefore, the control current value I is equal to the predetermined time to
Together is updated every, the rate of change of Te is, in the present embodiment, the value obtained by dividing the difference between Te _n detected this time and Te _n-1 previously detected in a predetermined time-to, i.e. (Te _n -Te _{n- 1} )
/ To.

Next, the operation and effect of this embodiment will be described.

FIG. 8A shows changes in Te and the control current I in the air conditioner according to this embodiment.
(B) shows changes in Te and the control current I when the control current I is determined only by the proportional-integral control.

As is apparent from FIG. 8, when only the proportional integral control is performed, the control constants such as the proportional control constant and the integral control constant are small with respect to the change in Te, and at the time A when Te starts to decrease. , Te and Teo are relatively small, so that the rate of decrease of the control current I is small.

For this reason, the actual refrigerating capacity Qe is maintained at the target refrigerating capacity Qeo while the discharge capacity of the compressor 100 remains large even though the air flow is reduced and the heat load is rapidly reduced.
And Te drops sharply.

On the other hand, in this embodiment, when Te greatly changes, the control current I is forcibly reduced by Δiad.
As the actual refrigeration capacity Qe does not greatly exceed the target refrigeration capacity Qeo, the actual refrigeration capacity Qe does not greatly exceed the target refrigeration capacity Qeo.
eo can be quickly approached, that is, Te can be quickly approached to Teo.

Therefore, even if the air temperature Te immediately after passing through the evaporator 400 is detected by the actual refrigerating capacity Qe, a change in the heat load in the evaporator 400 can be immediately detected. Is less likely to occur. As a result, it is possible to improve the feeling of the blowing temperature, prevent the occurrence of frost in the evaporator 400, and improve the evaporator 4
Reheating due to excessive cooling at 00 becomes unnecessary.

In the above description, the case where the heat load suddenly decreases has been described as an example. However, when the heat load suddenly increases, the actual refrigerating capacity Qe is changed to the target refrigerating capacity Qeo similarly to the above description. Can be quickly approached.

The amount of change Δiau when increasing the control current I and the amount of change Δi when decreasing the control current I
Although iad may be the same value, the threshold value εou of the rate of change of Te when Te is in the process of rising and the threshold value εod of the rate of change of Te when Te is in the process of falling are the same. If Δiau and Δiad have the same value in the state described above, there is a high possibility that control will diverge, so εou and εod
Are equal to each other, one of Δiau and Δiad is made larger than the other, or when Δiau and Δiad are the same value, εou and εod
It is desirable to make one of them larger than the other.

When Te is in the process of rising and when Te is
In any case when is in the process of descending, Te
If the absolute value of the rate of change exceeds a predetermined value, the control current value I is forcibly controlled.
Even if e changes excessively, it is possible to quickly bring Te close to Teo.

In this embodiment, the control current value I is set to 1
Although updated every 0 seconds, the present embodiment is not limited to this, but the predetermined time to is preferably set to 10 seconds or less.

(Fifth Embodiment) In the fourth embodiment, Δia
Although u and Δiad are fixed values, in the present embodiment,
, That is, at least one of Δiau and Δiad is changed according to the absolute value of the change rate of the actual refrigeration capacity Qe.

Specifically, as shown in FIG. 9, in the control flow according to the fourth embodiment (see FIG. 7), S295 for determining Δiau according to the absolute value of the rate of change of Te, and the change in Te S for determining Δiad according to the absolute value of the rate
255 is added.

In determining Δiau and Δiad, as shown in FIG. 10A, when the absolute value of the rate of change of Te is large, Δiau and Δiad also become large, and the absolute value of the rate of change of Te is determined. Is small,
When the absolute value of the rate of change of Te is equal to or more than a predetermined value so that Δiau and Δiad also become small, Δiau and Δiaa
If d is greater than or equal to a predetermined amount and the absolute value of the rate of change of Te is less than a predetermined value, Δiau and Δiad are made less than a predetermined amount.

In FIG. 10A, Δiau and Δiad are changed in two steps with respect to the absolute value of the rate of change of Te. However, the present embodiment is not limited to this.
Δiau and ΔV with respect to the absolute value of the rate of change of Te as shown in FIG.
The rate of change of iad may be changed s such that it is always 0 or more. Further, the value of Δiau and the value of Δiad are not limited to the same value as described above.

Thus, the actual refrigerating capacity Qe can be quickly brought closer to the target refrigerating capacity Qeo.

(Sixth Embodiment) In the fifth embodiment, Te
Δiau and Δiad are changed in accordance with the absolute value of the rate of change of the control current value I.
_n−1 , that is, Δiau and Δiad are changed according to the current displacement of the compressor 100.

More specifically, as shown in FIG. 11, as the discharge capacity approaches the upper limit or the lower limit, Δiau and Δi
This is to reduce ad. Incidentally, FIG. 11A shows an example in which Δiau and Δiad are changed stepwise.
FIG. 11B shows an example in which Δiau and Δiad are changed steplessly. Further, the value of Δiau and the value of Δiad are not limited to the same value as described above.
Further, the change characteristics of Δiau and Δiad are not limited to the characteristics shown in FIG.

Thus, it is possible to prevent the displacement of the compressor 100 from excessively changing.

(Other Embodiments) The characteristics (FIGS. 4 to 6) of the proportional control constant Kp and the integral control constant Ti ^-1 (correction term α) shown in the above embodiment are examples of the present invention. The invention is not limited to this. Therefore, Te
The value of the correction term α may be different when the difference ε (Teo−Te) between o and Te is a positive number and when it is a negative number.

In the above-described embodiment, the present invention is applied to the supercritical refrigeration cycle using carbon dioxide as a refrigerant.
The present invention is not limited to this, and can be applied to a vapor compression refrigeration cycle using another fluid such as Freon or nitrogen as a refrigerant.

In the above-described embodiment, Teo and Te
The correction term α is determined based on the absolute value εa of the difference from
The air temperature immediately after passing through the evaporator 400 is
0, and the pressure of the refrigerant in the evaporator 400 can be uniquely obtained from the temperature in the evaporator 400. Therefore, the absolute value εa of the difference between Teo and Te is used instead of the target value εa. The correction term α may be determined based on the absolute value of the refrigerant pressure inside the evaporator, that is, the difference between the target refrigeration capacity Qeo and the actual pressure inside the evaporator 400.

In the above embodiment, the control voltage V is determined by the proportional integral control or the proportional control differential control. However, the present invention is not limited to this, and other feedback control methods may be used.

In the above embodiment, the proportional control constant K
Although p, the integral control constant Ti ⁻¹ and the differential control constant Td are used as correction terms, a correction term α different from the proportional control constant Kp, the integral control constant Ti ⁻¹ and the differential control constant Td may be provided.

Further, in the above-described embodiment, the vapor compression refrigeration cycle according to the present invention is applied to an air conditioner for a vehicle for cooling. However, the application of the present invention is not limited to this. It can be applied to other heat pump type air conditioners and the like.

Further, at least two of the above embodiments are described.
You may combine two or more.

Further, as an example in which the heat load fluctuates, in the above-described embodiment, the case where the amount of air blown to the evaporator 400 is changed has been described as an example. However, the fluctuation factor of the heat load is not limited to this. The heat load of the radiator 200, which is the high-pressure side heat exchanger, the suction temperature of the evaporator 400, the compressor 100
The present invention can respond quickly to these changes.

In the fourth to sixth embodiments, S200 to S200
Although the routine shown in S320 is executed as one cycle at every predetermined time to, the fourth to sixth embodiments are not limited to this. For example, whether or not the control current value I is forcibly changed is determined. May be performed during the predetermined time to, and the other control may be performed for a time sufficiently shorter than the predetermined time to, that is, always.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a vapor compression refrigeration cycle according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a control flow of the compressor in the vapor compression refrigeration cycle according to the first embodiment of the present invention.

FIG. 3 is a graph showing a relationship between Teo and Te in the vapor compression refrigeration cycle according to the embodiment of the present invention.

FIG. 4 is a graph showing the relationship between the difference between Teo and Te and the value of a correction term in the vapor compression refrigeration cycle according to the first embodiment of the present invention.

FIG. 5 is a graph showing a relationship between a difference between Teo and Te and a value of a correction term in a vapor compression refrigeration cycle according to a second embodiment of the present invention.

FIG. 6 is a graph showing a relationship between a difference between Teo and Te and a value of a correction term in a vapor compression refrigeration cycle according to a second embodiment of the present invention.

FIG. 7 is a flowchart showing a control flow of a compressor in a vapor compression refrigeration cycle according to a fourth embodiment of the present invention.

FIG. 8 is an explanatory diagram for explaining an effect of a vapor compression refrigeration cycle according to a fourth embodiment of the present invention.

FIG. 9 is a flowchart showing a control flow of a compressor in a vapor compression refrigeration cycle according to a fifth embodiment of the present invention.

FIG. 10 is a characteristic diagram of Δiau and Δiad in a vapor compression refrigeration cycle according to a fifth embodiment of the present invention.

FIG. 11 is a characteristic diagram of Δiau and Δiad in a vapor compression refrigeration cycle according to a sixth embodiment of the present invention.

[Explanation of symbols]

100: compressor, 200: radiator, 300: decompressor, 4
00: evaporator, 500: accumulator, 600: internal heat exchanger.

Claims (14)

[Claims] 1. A vapor compression refrigeration cycle having a variable capacity compressor (100) for sucking and compressing a refrigerant and an evaporator (400) for evaporating the refrigerant decompressed and expanded, wherein the evaporator (400) ), A refrigeration capacity determination means (700) for determining a target value of the refrigeration capacity exerted by the evaporator (400), a refrigeration capacity detection means (701) for detecting a refrigeration capacity actually exhibited by the evaporator (400), A control target value (V) is determined based on a difference between the target refrigerating capacity (Qeo) determined by the target refrigerating capacity determining means (700) and the actual refrigerating capacity (Qe) detected by the refrigerating capacity detecting means (701). And a flow control means (700) for controlling the discharge capacity of the compressor (100) according to the control target value (V). The value of the correction term (α) for correcting the control target value (V) is ,
The target refrigerating capacity (Qeo) and the actual refrigerating capacity (Qe)
And the absolute value (εa) of the difference (ε) from the above is selected so as to increase. 2. The value of a correction term (α) for correcting the control target value (V) is determined by an absolute value (εa) of a difference (ε) between the target refrigerating capacity (Qeo) and the actual refrigerating capacity (Qe). 2. The vapor compression refrigeration cycle according to claim 1, wherein the size is selected so as to increase stepwise as the value of ()) increases. 3. The value of the correction term (α) for correcting the control target value (V) is an absolute value (εa) of a difference (ε) between the target refrigeration capacity (Qeo) and the actual refrigeration capacity (Qe). The vapor compression refrigeration cycle according to claim 1, wherein the vapor compression refrigeration cycle according to claim 1 is selected so that the larger the value is, the larger the value is. 4. The method according to claim 3, wherein α = a × | ε | ⁿ + b α: the value of the correction term (α) a, b: a constant n: a positive real number The control target value (V) is The value of the correction term (α) to be corrected is
A vapor compression refrigeration cycle, which is selected based on the above formula (1). 5. The vapor compression system according to claim 1, wherein the correction term (α) is a proportional control constant and an integral control constant of a function formula for proportional integral control. Refrigeration cycle. 6. The method according to claim 1, wherein the correction term (α) is a proportional control constant, an integral control constant, and a differential control constant of a function formula for proportional integral control. Vapor compression refrigeration cycle. 7. A vapor compression refrigeration cycle having a variable capacity compressor (100) for sucking and compressing a refrigerant and an evaporator (400) for evaporating the refrigerant decompressed and expanded, wherein the evaporator (400) ), A target refrigeration capacity determination means (700) for determining a target value of the refrigeration capacity exerted by the evaporator (400), and a refrigeration capacity detection means (701) for detecting the refrigeration capacity actually exhibited by the evaporator (400). A flow control means (700) for determining a target value (I) and controlling a discharge capacity of the compressor (100) according to the control target value (I); When the absolute value of the rate of change (dQe / dt) of the actual refrigerating capacity (Qe) detected by the refrigerating capacity detecting means (701) exceeds a predetermined rate of change, the previously determined control target value (I) Predetermined amount (Δ ) Is changed, the when the absolute value of the rate of change of the actual refrigerating capacity (Qe) (DQE / dt) is below a predetermined change rate, the target refrigerating capacity target cooling capacity determining means (700) is determined (Qe
o) and the control target value (I) is determined based on the difference between the actual refrigeration capacity (Qe) and the vapor compression refrigeration cycle. 8. The rate of change (dQ) of the actual refrigeration capacity (Qe)
When the absolute value of (e / dt) exceeds a predetermined change rate, the flow rate control means (700) determines that the change rate (dQe / dt) of the actual refrigeration capacity (Qe) is positive and The actual refrigerating capacity (Qe) is the target refrigerating capacity (Q) determined by the target refrigerating capacity determining means (700).
eo) or more, the control target value (I) is changed so that the discharge capacity of the compressor (100) decreases, and the change rate (dQe / dt) of the actual refrigeration capacity (Qe) is negative. And the actual refrigerating capacity (Qe) is determined by the target refrigerating capacity (Qe) determined by the target refrigerating capacity determining means (700).
eo) In the following cases, the control target value (I) is changed so that the discharge capacity of the compressor (100) increases. 9. The change rate (dQ) of the actual refrigeration capacity (Qe)
When the absolute value of (e / dt) exceeds a predetermined change rate, the flow rate control means (700) determines that the absolute value of the change rate (dQe / dt) of the actual refrigeration capacity (Qe) is equal to or greater than a predetermined value. When the change amount of the control target value (I) is equal to or more than a predetermined amount, when the absolute value of the change rate (dQe / dt) of the actual refrigerating capacity (Qe) is less than a predetermined value, the control target value (I) 9. The vapor compression refrigeration cycle according to claim 7, wherein the amount of change in I) is less than a predetermined amount. 10. The rate of change (d) of the actual refrigeration capacity (Qe)
When the absolute value of (Qe / dt) exceeds a predetermined rate of change, the flow control means (700) sets the control target value with respect to the absolute value of the rate of change (dQe / dt) of the actual refrigeration capacity (Qe). 10. The vapor compression refrigeration cycle according to claim 7, wherein the rate of change of the amount of change in (I) is always 0 or more. 11. The rate of change (d) of the actual refrigeration capacity (Qe)
When the absolute value of (Qe / dt) is equal to or less than a predetermined change rate, the flow rate control means (700) determines the control target value (I) by proportional integral control or proportional integral differential control. Any one of claims 7 to 10
A vapor compression refrigeration cycle according to any one of the first to third aspects. 12. The flow control means (700) determines whether or not the absolute value of the rate of change (dQe / dt) of the actual refrigerating capacity (Qe) exceeds a predetermined rate of change by an interval of 10 seconds or less. The vapor compression refrigeration cycle according to any one of claims 7 to 11, wherein the refrigeration cycle is performed. 13. The compressor according to claim 1, wherein the compressor compresses the refrigerant to a pressure higher than a critical pressure of the refrigerant.
13. The vapor compression refrigeration cycle according to any one of claims 12 to 12. 14. The vapor compression refrigeration cycle according to claim 1, wherein carbon dioxide is used as a refrigerant.