JPH04344073A - Controlling method for drive of cooling circuit - Google Patents

Abstract

PURPOSE:To provide a method for controlling to drive, which can perform both an efficiency (room cooling) of power in a cooling circuit using a variable volume type compressor and stable room cooling. CONSTITUTION:A heat load in a condenser 4 is calculated by a control computer 17 based on detected information from an atmospheric temperature detector 20, a discharge temperature detector 21, a rotating speed detector 25 of a compressor 1 and a vehicle speed detector 26, and a heat load in an evaporator 7 is detected based on detected information from an input temperature detector 22, a blow-off temperature detector 23, a humidity detector 24 and air flow information from a blower 39. The state of a cooling circuit is decided by adding capacity and superheat degree of the variable volume type compressor 1 to the calculated load and the speed information from the detector 25, and the computer 17 so suitably selects the capacity and the superheat degree as to enhance a room cooling efficiency while obtaining stable room cooling.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a drive circuit in a cooling circuit composed of a condenser, an expansion valve, and an evaporator interposed on an external refrigerant circuit connecting the discharge side and suction side of a variable displacement compressor. This relates to a control method.

0002

2. Description of the Related Art In this type of cooling circuit, the flow rate of liquid refrigerant supplied to the evaporator is controlled by controlling the opening degree of an expansion valve provided upstream of the evaporator. As an expansion valve, JP-A-51-
A thermostatic automatic expansion valve as disclosed in Japanese Patent Application No. 86852 or an electric automatic expansion valve as disclosed in Japanese Patent Application Laid-open No. 137059/1986 is used. In a thermostatic automatic expansion valve, the opening degree of the expansion valve is controlled by gas pressure introduced from a temperature-sensitive cylinder installed on a refrigerant gas flow path between an evaporator and a compressor.

[0003] In an electric automatic expansion valve, the opening degree of the expansion valve is controlled based on temperature information before and after the evaporator, thereby achieving rapid cooling.

0004

[Problem to be solved by the invention] In a thermostatic automatic expansion valve, flow rate control is performed so that the degree of superheating of evaporated gas is constant, but the degree of superheating at which cooling efficiency is maximized varies depending on the refrigerant flow rate and heat load. However, it is not constant. Therefore, high cooling efficiency cannot always be maintained with liquid refrigerant flow rate control that keeps the degree of superheat constant, and power loss is unavoidable.

On the other hand, a similar problem exists in a conventional device using an electric automatic expansion valve capable of rapid cooling, and this conventional example also discloses an embodiment in which power loss is avoided by ON-OFF control of the compressor. However, it is difficult to obtain a stable cooling effect with ON-OFF control that only switches between the presence and absence of the cooling effect. An object of the present invention is to provide a drive control method in a cooling circuit that can improve cooling efficiency while obtaining a stable cooling effect.

[0006]

[Means for Solving the Problems] To this end, in the present invention,
A condenser, an expansion valve, and an evaporator are interposed on the external refrigerant circuit that connects the discharge side and suction side of the variable displacement compressor, and the capacity of the variable displacement compressor and the expansion valve are controlled by commands from outside the cooling circuit. Targeting cooling circuits that can be controlled by switching the flow rate, detects the thermal load and power in such a cooling circuit, selects the appropriate capacity of the variable displacement compressor based on the detected thermal load and detected power, and also determines the appropriate overheating. The variable displacement compressor is driven in the selected proper capacity state, and the flow rate in the expansion valve is controlled to bring about the selected proper superheat degree.

[0007]

[Operation] The state of the cooling circuit is determined by the refrigerant flow rate, the heat load on the condenser, and the heat load on the evaporator. There is a specific relationship between the cooling capacity per unit power (cooling efficiency) and the degree of superheat depending on the state of the cooling circuit. The compressor capacity and degree of superheat that provide a desirable relationship between the state of the cooling circuit and the set cooling temperature in consideration of the cooling efficiency are defined based on the specific relationship, and the state of the cooling circuit is detected and the set temperature is determined. By specifying the cooling temperature, the desired capacity and degree of superheat are selected. The variable displacement compressor is operated to provide this selected capacity and flow control at the expansion valve is effected to provide the selected degree of superheat.

[0008]

[Example] Hereinafter, an example embodying the present invention is shown in Figs.
This will be explained based on FIG. 15. On the refrigerant circuit 2 that connects the suction side and the discharge side of the variable displacement compressor 1, from the discharge side there are an oil separator 3, a condenser 4, a liquid receiver 5, an expansion valve 6, and an evaporator 7.
are interposed in order, and the refrigerant gas compressed by the variable displacement compressor 1 removes the lubricating oil mixed in a mist form to the oil separator 3.
After being separated in the condenser 4, it is cooled and becomes liquid, and is sent to the liquid receiver 5. The condensed refrigerant is sent to the evaporator 7 via the expansion valve 6, where it is evaporated. The refrigerant gas that has passed through the evaporator 7 is sucked into the variable capacity compressor 1. The air flow blown from the blower 39 to the evaporator 7 is cooled by the evaporation action in the evaporator 7, and this cooled air flow is introduced into the vehicle interior. The air blown from the blower 39 to the evaporator 7 is recirculated air from inside the vehicle. FIG. 2 shows an overall diagram of a variable displacement compressor. Suction chambers 31a,
32a and discharge chambers 31b, 32b are formed, and a control pressure chamber R1 is formed in the discharge chamber 32b on the rear housing 32 side.
is provided. A partition body 33 is fitted into the control pressure chamber R1 so as to be slidable in the direction of the rotating shaft 28. The control pressure chamber R1 is connected to the discharge pressure region and the suction pressure region via the electromagnetic switching valve 34, and the pressure in the control pressure chamber R1 is changed between the discharge pressure and the suction pressure by excitation and demagnetization of the electromagnetic switching valve 34. Switching is controlled to either one.

Swash plate chamber 3 in the suction pressure area that accommodates the swash plate 35
5a and the discharge chamber 32b can be switched to be disconnected from each other by a discharge valve forming plate 36 and a retainer 37 attached to the partition body 33, and when the discharge pressure is in the control pressure chamber R1, the partition body 33 is connected to the pressure spring 38. Control pressure chamber R1
The discharge valve forming plate 36 protrudes from the swash plate chamber 35a.
The communication between the discharge chamber 32b and the discharge chamber 32b is cut off. When the control pressure chamber R1 is at suction pressure, the partition body 33 is retracted into the control pressure chamber R1 by the pressure spring 38, and the discharge valve forming plate 36 and the retainer 37 are moved to the chain line position shown in FIG. In this transitional arrangement state, the swash plate chamber 35a and the discharge chamber 32b communicate with each other. When the communication between the swash plate chamber 35a and the discharge chamber 32b is cut off, suction and discharge in the cylinder bore 30a are substantially performed in the same way as on the cylinder bore 29a side (100% capacity), but the swash plate chamber 35a and the discharge chamber 32b are in communication with each other. In this state, there is no substantial inhalation or exhalation, and the capacity is reduced by half (50
% capacity).

The orifice 9 in the valve housing 8 of the expansion valve 6 is opened and closed by a ball valve body 10, and the ball valve body 10 is biased in the direction of closing the orifice 9 by the spring action of a pressing spring 12 via a support seat 11. has been done. A control pressure chamber R2 is defined in the upper part of the valve housing 8 via a diaphragm 13.
3 is connected to an action transmission rod 14. The action transmission rod 14 moves up and down in response to pressure fluctuations within the control pressure chamber R2, and the ball valve body 10 opens and closes the orifice 9 due to this up and down movement.

A temperature sensing tube 15 is installed on the refrigerant gas pipe between the evaporator 7 and the compressor 1, so that the control gas pressure inside the temperature sensing tube 15 is introduced into the control pressure chamber R2. It has become. An electronic refrigeration element 16 is mounted on the temperature sensing tube 15. The electronic refrigeration element 16 is energized by a control computer 17 via a current control circuit 18 and a polarity switching circuit 19. By switching the polarity in the polarity switching circuit 19, that is, switching the direction of energization to the electronic refrigeration element 16, the joining surface side of the temperature sensitive cylinder 15 and the electronic refrigeration element 16 is switched between heating action and cooling action. Furthermore, the degree of heating or cooling on the joint surface side between the temperature sensing cylinder 15 and the electronic refrigeration element 16 is controlled by controlling the DC current value in the current control circuit 18. As a result, the control gas pressure within the temperature sensing cylinder 15 changes depending on the DC polarity and the DC current value, and this control gas pressure fluctuation spreads to the control pressure chamber R2.

When the control gas pressure inside the temperature sensing cylinder 15 increases due to heating of the temperature sensing cylinder 15, the diaphragm 13 moves downward, and the valve opening degree of the ball valve body 10 in the orifice 9 increases. That is, heating the temperature sensing cylinder 15 increases the flow rate of liquid refrigerant in the expansion valve 6, and the degree of superheat, which is the difference between the temperature at the outlet of the expansion valve 6 and the temperature at the outlet of the evaporator 7, decreases. . Conversely, when the control gas pressure inside the temperature sensing cylinder 15 decreases due to cooling of the temperature sensing cylinder 15, the diaphragm 13 moves upward, and the valve opening degree of the ball valve body 10 in the orifice 9 becomes smaller. That is, cooling the temperature sensing tube 15 reduces the flow rate of liquid refrigerant in the expansion valve 6, increasing the degree of superheating.

[0013] The control computer C has an outside air temperature detector 2.
0, discharge temperature detector 21, inlet temperature detector 22, outlet temperature detector 23, humidity detector 24, each detection information from the rotation speed detector 25 and vehicle speed detector 26 attached to the compressor 1, input setting device The energization of the electronic refrigeration element 16 is controlled based on the air volume S of the blower 39 and the set room temperature T0 inputted and set in advance by 27. Also, control computer C
switches and controls the electromagnetic switching valve 34 based on the detection information, the air volume S, and the set room temperature T0.

The flowcharts in FIGS. 7 to 15 represent an energization control program for the electronic refrigeration element 16 and a switching control program for the electromagnetic switching valve 34. The state of the cooling circuit is determined by the refrigerant flow rate (capacity x rotation speed n), the heat load on the condenser 4, and the heat load on the evaporator 7. There is a specific relationship between the cooling efficiency (value obtained by dividing the amount of heat exchange Q per unit time in the evaporator 7 by the power L) and the degree of superheating, depending on the state of the cooling circuit, and there is a relationship between the blowout temperature and the degree of superheating. There are also specific relationships depending on the state of the cooling circuit. Figures 3 to 6
is a map showing the relationship between the degree of superheating and the cooling efficiency and the relationship between the degree of superheating and the blowout temperature. Map M in Figure 3
1 (N1) is the case when the rotation speed n of the variable displacement compressor 1 is in the low rotation range N1 and the capacity is 100%, and the map M2 (N1) in FIG. 4 is the case when the rotation speed n of the variable displacement compressor 1 is This is a case where the engine is in the low rotation region N1 and the capacity is 50%. Figure 5
The map M1 (Nk) in FIG. 6 is for the case where the rotation speed n of the variable displacement compressor 1 is in the high rotation range Nk and the capacity is 100%, and the map M2 (Nk) in FIG. 6 is the rotation speed of the variable displacement compressor 1. This is a case where n is a high rotation region Nk and the capacity is 50%.

Curve E111 in map M1 (N1)
represents the relationship between the blowout temperature and the degree of superheat when the heat load in the cooling circuit is in a low load region, and curve E211
represents the relationship between the outlet temperature and the degree of superheat when the heat load is in the medium load range. Curve E311 represents the relationship between the blowout temperature and the degree of superheat when the heat load is in the high load region,
Curve E411 represents the relationship between the blowout temperature and the degree of superheat when the heat load is in the ultra-high load region.

Similarly, the curve E in the map M1 (N1)
11k represents the relationship between the outlet temperature and the degree of superheat when the heat load in the cooling circuit is in the low load region, and curve E2
1k, E31k, and E41k represent the relationship between the blowout temperature and the degree of superheating when the heat load is in a medium load area, a high load area, and an extremely high load area, respectively. Map M1 (N1)
Curve F111 represents the relationship between cooling efficiency and degree of superheating when the heat load in the cooling circuit is in the low load region, and curve F211 represents the relationship between cooling efficiency and degree of superheating when the heat load is in the medium load region. Represents a relationship. Curve F311 represents the relationship between cooling efficiency and degree of superheating when the heat load is in a high load area, and curve F411 represents the relationship between cooling efficiency and degree of superheating when the heat load is in an extremely high load area. .

Similarly, the curve F in map M1 (N1)
11k represents the relationship between the cooling efficiency and the degree of superheat when the heat load in the cooling circuit is in the low load region, and the curve F21k
, F31k, and F41k represent the relationship between the cooling efficiency and the degree of superheating when the heat load is in a medium load area, a high load area, and an extremely high load area, respectively. The rotation range Ni (i=1 to k) of the variable capacity compressor 1 is divided and set from a low rotation range N1 to a high rotation range Nk, and maps M1 (Ni), M2 ( Ni) functions E11i, E21i, E31i, E41i
, F11i , F21i , F31i , F41i
is obtained in advance for each rotation region Ni.

The control computer 17 detects the outside air temperature T1, the discharge temperature T2, and the inlet temperature T3 which is the vehicle room temperature.
, the blowout temperature T4 cooled by the evaporator 7,
The humidity W in the vehicle interior, the rotation speed n of the variable capacity compressor 1, and the vehicle speed V are sampled at regular time intervals. The control computer 17 grasps the rotation speed range Ni of the detected rotation speed n, and creates a map M1 (N
i), M2(Ni).

Next, the control computer 17 calculates the heat load Qx in the condenser 4 based on the detected outside air temperature T1, the detected discharge temperature T2, and the detected vehicle speed V, and also calculates the detected inlet temperature T3, the detected air outlet temperature T4, the detected humidity W, and the detected vehicle speed V. The heat load Qy on the evaporator 7 is calculated based on the air volume S of the blower 39, and the load state on the cooling circuit is grasped. When the rotation speed n is in the low rotation speed region N1 and the heat load is in the low load region, the control computer 17 uses the map M
Function E11 in 1(N1), M2(N1)
1, F111, E121, F121.

Difference between cabin temperature T3 and set temperature T0 (
T3 - T0) is larger than the tolerance ΔT0, the control computer 17 selects 100% capacity control, and also sets the set temperature T0 and the functions E111 and F111.
The optimal superheat degree θ111 is selected from The electromagnetic switching valve 34 is subjected to switching control to provide a selected 100% capacity, and the variable displacement compressor 1 is switched to 100% capacity.
Operated at capacity. At the same time, the polarity switching circuit 19 receives DC polarity switching control in the direction that brings about the selected degree of superheat θ111, and the current control circuit 18 receives control to increase or decrease the DC current value that brings about the selected degree of superheat θ111. 6 is controlled to the valve opening degree that brings about the superheat degree θ111.

[0021] The difference between the cabin temperature T3 and the set temperature T0 (
If T3 - T0 ) is within the tolerance ΔT0, the control computer 17 selects 50% capacity control, and
The optimum superheat degree Θ121 is selected from the set temperature T0 and the functions E121 and F121. The electromagnetic switching valve 34 is subjected to switching control to provide the selected 50% capacity, and the variable displacement compressor 1 is operated at 50% capacity. At the same time, the polarity switching circuit 19 receives DC polarity switching control in the direction that brings about the selected degree of superheat Θ121, and the current control circuit 18 receives control to increase or decrease the DC current value that brings about the selected degree of superheat Θ121. 6 is controlled to the valve opening degree that brings about the superheat degree Θ121.

[0022] The difference between the cabin temperature T3 and the set temperature T0 (
If T3 - T0 ) is smaller than the tolerance -ΔT0, the control computer 17 selects 50% capacity control, and also sets the set temperature T0 and functions E121 and F121.
The optimal superheat degree θ121 is selected from The electromagnetic switching valve 34 is subjected to switching control to provide the selected 50% capacity, and the variable displacement compressor 1 is operated at 50% capacity. At the same time, the polarity switching circuit 19 receives DC polarity switching control in the direction that brings about the selected degree of superheat θ121, and the current control circuit 18 receives control to increase or decrease the DC current value that brings about the selected degree of superheat θ121. 6 is controlled to the valve opening degree that brings about the superheat degree θ121.

Maps M1 (N1), M in FIGS. 3 and 4
2 (N1), in the low rotation range N1, the blowout temperature T4 is 50% lower in 100% capacity operation.
Although the temperature is lower than that of capacity operation, the cooling efficiency is 50% lower than that of capacity operation.
% capacity operation is better than 100% capacity operation. Therefore, when only cooling efficiency is considered, variable capacity compressor 1
It is better to operate the vehicle at 50% capacity, but if the vehicle interior temperature T3 is higher than (T0 + ΔT0), it is desirable to place more emphasis on rapid cooling of the vehicle interior than on cooling efficiency. Therefore, the variable displacement compressor 1 is operated at 100% capacity, and the cooling efficiency Q/L is as low as represented by the curve F111, but the interior of the vehicle is quickly cooled. The degree of superheating θ111 is the set temperature T0 and the function E111
, F111, it is set appropriately considering both cooling efficiency and rapid cooling.

[0024]T0 +ΔT0 ≧T3 ≧T0 −ΔT
When the desired cooling state of 0 has been achieved, it is desirable to place emphasis on cooling efficiency. Therefore, the variable capacity compressor 1 is operated at 50% capacity, and the cooling efficiency Q/L is as high as represented by the curve F121. The superheat degree Θ111 is the set temperature T0 and the functions E121 and F1
21, it is set appropriately considering both cooling efficiency and rapid cooling.

In the overcooling state where T3 < T0 - ΔT0, it is desirable to place emphasis on cooling efficiency and to return the cabin temperature T3 to a desired temperature range. Therefore, the variable displacement compressor 1 is operated at 50% capacity, and the cooling efficiency is Q/L.
The efficiency is as high as that shown by the curve F121. The superheat degree θ121 is the set temperature T0 and the function E121, F
121, it is set appropriately considering the release of supercooling.

When the rotational speed n is in the low rotational speed region N1 and the thermal load is in the medium load region, the control computer 17 uses the function E in the maps M1(N1) and M2(N1).
211, F211, E221, F221. Difference between cabin temperature T3 and set temperature T0 (T3
-T0 ) is larger than the tolerance ΔT0, the control computer 17 selects 100% capacity control, and selects the optimum superheat degree θ211 from the set temperature T0 and the functions E211 and F211. If the difference between the vehicle interior temperature T3 and the set temperature T0 (T3 - T0) is within the tolerance ΔT0, the control computer 17
In addition to selecting 0% capacity control, the superheat degree Θ is optimally set from the set temperature T0 and the functions E221 and F221.
Select 221. Vehicle interior temperature T3 and set temperature T0
If the difference (T3 - T0) is smaller than the tolerance -ΔT0, the control computer 17 selects 50% capacity control, and also sets the set temperature T0 and the function E221,
The optimum superheat degree θ221 is selected from F221.

When the rotational speed n is in the low rotational speed region N1 and the thermal load is in the high load region, the control computer 17 uses the function E in the maps M1(N1) and M2(N1).
Select 311, F311, E321, F321. Difference between cabin temperature T3 and set temperature T0 (T3
-T0 ) is larger than the tolerance ΔT0, the control computer 17 selects 100% capacity control, and selects the optimum superheat degree θ311 from the set temperature T0 and the functions E311 and F311. If the difference between the vehicle interior temperature T3 and the set temperature T0 (T3 - T0) is within the tolerance ΔT0, the control computer 17
In addition to selecting 0% capacity control, the superheat degree Θ is optimally set from the set temperature T0 and functions E321 and F321.
Select 321. Vehicle interior temperature T3 and set temperature T0
If the difference (T3 - T0) is smaller than the tolerance -ΔT0, the control computer 17 selects 50% capacity control, and also sets the set temperature T0 and the function E321,
Select the optimum superheat degree θ321 from F321.

When the rotational speed n is in the low rotational speed region N1 and the thermal load is in the extremely high load region, the control computer 17 selects the functions E411, F411, E421, F421 in the maps M1(N1) and M2(N1). do. Difference between cabin temperature T3 and set temperature T0 (T3
-T0) is larger than the tolerance ΔT0, the control computer 17 selects 100% capacity control and selects the optimum superheat degree θ411 from the set temperature T0 and the functions E411 and F411. If the difference (T3 - T0) between the vehicle interior temperature T3 and the set temperature T0 is within the tolerance ΔT0, the control computer 17 selects 50% capacity control and optimally sets the set temperature T0 and the functions E421 and F421. Select the superheat degree Θ421. Vehicle interior temperature T3 and set temperature T0
If the difference (T3 - T0) is smaller than the tolerance -ΔT0, the control computer 17 selects 50% capacity control, and also sets the set temperature T0 and function E421.
, F421, the optimally set superheat degree θ421 is selected.

[0029] The rotation speed n of the compressor 1 is in the low rotation speed region N1.
The blowout temperature T4 is greatly affected by the degree of superheating in the low load region and medium load region, and as the degree of superheating is increased, the blowout temperature T4 increases. Therefore, if you want to quickly lower the detected cabin temperature T3,
This can be addressed by reducing the degree of superheating under % capacity operating conditions. 5 if you want to quickly release the supercooling state where the cabin temperature T3 has fallen below the set temperature T0.
This can be dealt with by increasing the degree of superheating under 0% capacity operating conditions.

When the cabin temperature T3 is within a desired temperature range, it is possible to increase the cooling efficiency by operating at 50% capacity. The cooling efficiency Q/L is greatly affected by the degree of superheating in the high load region and the ultra-high load region, and the cooling efficiency increases as the degree of superheating is reduced. Therefore, if the cabin temperature T3 is in the desired temperature range,
Further improvement in cooling efficiency can be achieved by reducing the degree of superheating under a 0% operating state.

When the rotational speed n is in the high rotational speed region Nk and the thermal load is in the low load region, the control computer 17 uses the function E in the maps M1(Nk) and M2(Nk).
Select 11k, F11k, E12k, F12k. In the case of (T3 - T0)>ΔT0, the control computer 17 selects 100% capacity control, and
The optimum superheat degree θ11k is selected from the set temperature T0 and the functions E11k and F11k. T0 +Δ
In the case of T0 ≧T3 ≧T0 - ΔT0, the control computer 17 selects 50% capacity control and also selects the optimum superheat degree Θ12k from the set temperature T0 and the functions E12k and F12k. (T3 −T0
)<-ΔT0, the control computer 17
% capacity control is selected, and the superheat degree θ1 is optimally set from the set temperature T0 and the functions E12k and F12k.
Select 2k.

Maps M1 (Nk), M in FIGS. 5 and 6
2 (Nk), in the high rotation range Nk, the blowout temperature T4 is 50% lower in 100% capacity operation.
Although the temperature is lower than that of capacity operation, the cooling efficiency is 50% lower than that of capacity operation.
% capacity operation is better than 100% capacity operation. Therefore, when only cooling efficiency is considered, variable capacity compressor 1
It would be better to operate at 50% capacity, but T3
>(T0 +ΔT0), it is desirable to place more importance on rapid cooling of the vehicle interior than on cooling efficiency. Therefore,
The variable capacity compressor 1 is operated at 100% capacity, and the cooling efficiency Q/L is as low as represented by the curve F11k, but the interior of the vehicle is quickly cooled. Superheat degree θ11k
is appropriately set based on the set temperature T0 and the functions E11k and F11k, taking both cooling efficiency and rapid cooling into consideration.

[0033]T0 +ΔT0 ≧T3 ≧T0 −ΔT
When the desired cooling state of 0 has been achieved, it is desirable to place emphasis on cooling efficiency. Therefore, the variable displacement compressor 1 is operated at 50% capacity, and the cooling efficiency Q/L is as high as represented by the curve F12k. The superheat degree Θ11k is the set temperature T0 and the functions E12k, F1
From 2k onwards, it is set appropriately considering both cooling efficiency and rapid cooling.

In the overcooling state where T3 < T0 - ΔT0, it is desirable to place emphasis on cooling efficiency and to return the cabin temperature T3 to a desired temperature range. Therefore, the variable displacement compressor 1 is operated at 50% capacity, and the cooling efficiency is Q/L.
The efficiency is as high as that shown by the curve F12k. The superheat degree θ12k is the set temperature T0 and the function E12k, F
From 12K onwards, it is set appropriately considering the cancellation of supercooling.

When the rotational speed n is in the high rotational speed region Nk, the control computer 17 uses maps M1(Nk), M
2(Nk) functions E21k, F21k,
E22k and F22k are selected, and capacity control selection and superheat degree (θ11k, θ12k, Θ12k , θ21k
, θ22k , θ22k , θ31k , θ32k
, Θ32k , θ41k , θ42k , Θ42k )
Make a selection.

[0036] The rotation speed n of the compressor 1 is in the high rotation speed region Nk.
As in the case of the low rotational speed region N1, the blowout temperature T4 is greatly influenced by the degree of superheating in the low load region and the medium load region, and as the degree of superheating decreases, the blowout temperature T4 decreases. Therefore, in order to quickly lower the cabin temperature T3 in a low load state and a medium load state,
As in the case of the low rotational speed region N1, this can be dealt with by reducing the degree of superheating under 100% capacity operation. If the supercooling state where the vehicle interior temperature T3 is lower than the set temperature T0 needs to be quickly released, this can be done by increasing the degree of superheating under the 50% capacity operating state.

When the cabin temperature T3 is within a desired temperature range, it is possible to increase the cooling efficiency by performing 50% capacity operation. The cooling efficiency Q/L in the case of 50% capacity operation increases by increasing the degree of superheating. Therefore, when the vehicle interior temperature T3 is within a desired temperature range, the cooling efficiency can be further improved by increasing the degree of superheating under the 50% operating condition.

[0038] The rotational speed n is in a rotational speed range Ni (
i≠1,k), the control computer 17 also creates maps M1(Ni), corresponding to the rotational speed region Ni.
Functions E21i and F21i in M2(Ni)
, E22i, F22i, and select capacity control and superheat degree (θ11i, θ12i, Θ12i
, θ21i , θ22i , θ22i , θ31i
, θ32i , θ32i , θ41i , θ42i ,
Θ42i) is selected.

Capacity control and superheat degree control that can achieve both stable cooling action and high cooling efficiency are not limited to the above embodiments; for example, if the cabin temperature T3 has not reached the desired temperature range, If you get very close,
It is also possible to switch from 100% capacity operation to 50% capacity operation. When the detected rotational speed is low and the thermal load is low or medium load, map M1 (N
It is also possible to perform control such that map 1) is selected and map M2 (N1) in FIG. 4 is selected when the heat load is high or extremely high.

When the detected rotational speed is high and the thermal load is low or medium load, map M2 (Nk
) is also possible. Further, in the present invention, the heat load area is further subdivided, and an electromagnetic clutch is interposed between the variable displacement compressor and the vehicle engine, and 0% capacity operation is performed by turning off the electromagnetic clutch. By employing such a control method, it is possible to obtain a more stable cooling effect and achieve high cooling efficiency.

Furthermore, the present invention is applicable to a cooling circuit using a variable capacity swash plate compressor other than a swash plate compressor.

[0042]

As described in detail above, the present invention selects the appropriate capacity of a variable displacement compressor based on the detected heat load and the detected power, selects the appropriate degree of superheat, and maintains the selected appropriate capacity state. In addition to driving the variable displacement compressor, the expansion valve controls the flow rate to bring about the selected appropriate degree of superheat, so cooling efficiency takes into account the relationship between the actual cooling temperature and the desired cooling temperature. It has the excellent effect of being able to selectively control and achieve high cooling efficiency while providing a stable cooling effect.

[Brief explanation of the drawing]

FIG. 1 is a combination diagram of a cooling circuit and a side sectional view of an expansion valve showing an embodiment embodying the present invention.

FIG. 2 is a longitudinal sectional view of a variable displacement compressor.

FIG. 3 is a graph showing the relationship between the blowout temperature and cooling efficiency in a low rotational speed region and the degree of superheating.

FIG. 4 is a graph showing the relationship between the blowout temperature and cooling efficiency in a medium rotation speed region and the degree of superheating.

FIG. 5 is a graph showing the relationship between the blowout temperature and cooling efficiency in a high rotational speed region and the degree of superheating.

FIG. 6 is a graph showing the relationship between the blowing temperature and cooling efficiency and the degree of superheating in an ultra-high rotational speed region.

FIG. 7 is a flowchart representing a capacity control program and a superheat degree control program.

FIG. 8 is a flowchart representing a capacity control program and a superheat degree control program.

FIG. 9 is a flowchart representing a capacity control program and a superheat degree control program.

FIG. 10 is a flowchart representing a capacity control program and a superheat degree control program.

FIG. 11 is a flowchart representing a capacity control program and a superheat degree control program.

FIG. 12 is a flowchart representing a capacity control program and a superheat degree control program.

FIG. 13 is a flowchart representing a capacity control program and a superheat degree control program.

FIG. 14 is a flowchart representing a capacity control program and a superheat degree control program.

FIG. 15 is a flowchart representing a capacity control program and a superheat degree control program.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Variable displacement compressor, 6... Expansion valve, 16... Electronic refrigeration element for controlling the flow rate in the expansion valve, 17... Control computer 17 for controlling capacity and degree of superheat.

Claims (1)

[Claims] Claim 1: A condenser, an expansion valve, and an evaporator are interposed on an external refrigerant circuit that connects the discharge side and the suction side of a variable displacement compressor, and the variable displacement compressor is controlled by a command from outside the cooling circuit. In a cooling circuit that can switch and control the capacity and flow rate in the expansion valve, thermal load and power are detected, and based on the detected thermal load and detected power, the appropriate capacity of the variable displacement compressor is selected, and the appropriate degree of superheat is selected. A drive control method in a cooling circuit that drives a variable capacity compressor in a selected proper capacity state and controls the flow rate in an expansion valve to bring about a selected degree of superheat.