JP2002022299A - Cooling cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cooling cycle capable of attaining a sufficient cooling power either at the time of starting or at the time of abnormal rise of refrigerant pressure. SOLUTION: The refrigeration cycle comprises a compressor 1 for compressing a refrigerant containing carbon dioxide gas, a radiator 2 for cooling the refrigerant compressed by the compressor, a pressure control valve 3 for controlling pressure of the refrigerant cooled by the radiator and an evaporator 4 for cooling intake air by heat absorption of the refrigerant having the pressure controlled by the pressure control valve which are at least connected in series with piping 8. The refrigeration cycle is further provided with an intake air temperature detecting means 9 for detecting temperature of the intake air, a rotation speed detecting means 10 for directly or indirectly detecting the rotation speed of the compressor and a controlling means 11 for controlling the valve travel of the pressure control valve on the basis of temperature of the intake air detected by the intake air temperature detecting means and the rotation speed of the compressor detected by the rotation speed detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling cycle preferably used for an air conditioner for a vehicle, and more particularly to a cooling cycle using a carbon dioxide-containing refrigerant.

[0002]

2. Description of the Related Art In a cooling cycle of an air conditioner for vehicles, R
Fluorocarbon refrigerants such as -12 and R134a are used, but if these are released into the atmosphere, there is a concern about environmental problems such as global warming due to destruction of the ozone layer. For this reason, a cooling cycle using carbon dioxide, ethylene, ethane, nitric oxide or the like has been proposed as one of the measures against defluorocarbons (for example, see Japanese Patent Publication No. Hei 7-18602).

A cooling cycle using carbon dioxide gas such as carbon dioxide as a refrigerant is in principle the same as a conventional cooling cycle using chlorofluorocarbon. For example, the critical temperature of carbon dioxide is about 31 ° C. (For example, R-12 is 112 ° C.), the temperature of carbon dioxide on the radiator (gas cooler) side becomes higher than the critical temperature of carbon dioxide in summer or the like when the outside air temperature increases, and The difference is that carbon dioxide does not condense at the outlet of the vessel.

[0004] The state of the outlet of the radiator is determined by the discharge pressure of the compressor and the temperature of carbon dioxide at the outlet of the radiator. It is determined by the capacity and the outside air temperature. However, since the outside air temperature cannot be controlled, the temperature of carbon dioxide at the outlet of the radiator cannot be substantially controlled. However, since the state at the outlet of the radiator can be controlled by controlling the discharge pressure of the compressor (the refrigerant pressure at the outlet of the radiator), in summer when the outside air temperature is high, sufficient cooling capacity (enthalpy difference) can be obtained. In order to secure (1), the refrigerant pressure at the outlet of the radiator is increased.

That is, in a conventional cooling cycle using a chlorofluorocarbon refrigerant, the refrigerant pressure in the cycle is 0.2 to 1.6M.
In the cooling cycle using carbon dioxide or the like as a refrigerant, the refrigerant pressure in the cycle is 3.5 to 10 MPa.
Is significantly higher than that of the conventional fluorocarbons.

[0006]

Therefore, in a cooling cycle using carbon dioxide as a refrigerant, the amount of refrigerant discharged from the compressor at the start (startup) is unstable.
There is a problem that the cooling power of the intake air of the evaporator is weak.
When the difference between the set temperature and the cabin temperature is large in conventional in-vehicle air conditioners, maximize the rotation speed of the fan, open the air mix door fully, and supply the cool air that has passed through the evaporator to the room as it is. Is controlled, but as long as the cooling power of the cooling cycle itself is weak,
Sufficient cooling capacity cannot be demonstrated.

In the conventional cooling cycle, when the refrigerant pressure in the cooling cycle rises abnormally during operation, the electromagnetic clutch of the compressor is temporarily disengaged, and the cooling cycle is temporarily stopped, so that the compression cycle is stopped. This prevents leakage of refrigerant from the machine, seizure of lubricating oil in the cycle, and damage to piping components. After the cooling cycle is stopped, it is restarted after waiting for the refrigerant pressure in the cycle to drop to a predetermined equilibrium pressure. However, during such a cycle stoppage, sufficient cooling air cannot be supplied to the room because no cooling power is exhibited.

The present invention has been made in view of such problems of the prior art, and provides a cooling cycle capable of obtaining a sufficient cooling power both at startup and when the refrigerant pressure is abnormally increased. The purpose is to provide.

[0009]

According to the present invention, there is provided a compressor for compressing a carbon dioxide-containing refrigerant, and a radiator for cooling the refrigerant compressed by the compressor. And a pressure control valve for controlling the pressure of the refrigerant cooled by the radiator, and an evaporator for cooling the intake air by absorbing heat of the refrigerant, the pressure of which is controlled by the pressure control valve, and are connected by pipes at least in series. A cooling cycle, wherein intake air temperature detection means for detecting the temperature of the intake air, rotation speed detection means for directly or indirectly detecting the rotation speed of the compressor, the intake air temperature Control means for controlling the opening of the pressure control valve based on the temperature of the intake air detected by the detection means and the number of rotations of the compressor detected by the rotation number detection means. Is You.

[0010] In the cooling cycle of the present invention, the number of revolutions of the compressor (that is, the refrigerant discharge amount) that directly affects the cooling capacity of the evaporator, and the intake air that directly affects the required cooling amount. Based on the temperature, the opening of the pressure control valve, that is, the outlet pressure of the radiator is controlled.

For example, when the rotation speed of the compressor is low, the amount of refrigerant discharged is small, so that sufficient cooling power cannot be obtained in the evaporator. However, the outlet of the radiator (FIG. (Point G) increases, and a sufficient enthalpy difference can be secured, so that the cooling power of the evaporator can be increased.

When the temperature of the intake air is high, that is, when the outside air temperature is high, the radiator (points B to C in FIG. 15) is used.
Although the refrigerant temperature at the point) becomes higher than the critical temperature of the refrigerant and the refrigerant does not condense at the radiator outlet (the line segment BC does not intersect with the saturated liquid line), the opening degree of the pressure control valve is reduced. The pressure at the radiator outlet (point G in FIG. 15) increases,
Since a sufficient enthalpy difference can be secured, the cooling power of the evaporator can be increased.

(2) To achieve the above object,
According to the present invention, there is provided a discharge refrigerant pressure detection unit for detecting a discharge refrigerant pressure of the compressor, and the control unit is configured to control when the discharge refrigerant pressure detected by the discharge refrigerant pressure detection unit exceeds a predetermined pressure. A cooling cycle for increasing the opening of the pressure control valve is provided.

In the cooling cycle of the present invention, when the refrigerant pressure discharged from the compressor exceeds a predetermined pressure slightly lower than the limit pressure,
Although the opening degree of the pressure control valve is increased, the refrigerant pressure in the cooling cycle temporarily decreases, but does not stop the compressor, so that the refrigerant is continuously supplied to the evaporator, thereby cooling the evaporator. Power can be secured.

(3) To achieve the above object,
According to the present invention, a discharge refrigerant pressure detecting means for detecting a discharge refrigerant pressure of the compressor, and a discharge refrigerant pressure rise for calculating a rise amount per unit time of the discharge refrigerant pressure detected by the discharge refrigerant pressure detection means The discharge refrigerant pressure detected by the discharge refrigerant pressure rise degree calculation means when the discharge refrigerant pressure detected by the discharge refrigerant pressure detection means exceeds a predetermined pressure. A cooling cycle is provided for increasing the opening of the pressure control valve when the degree of rise of the pressure control valve exceeds a predetermined degree of rise.

In the cooling cycle of the present invention, when the refrigerant pressure discharged from the compressor exceeds a predetermined pressure slightly lower than the limit pressure,
When the degree of increase in the refrigerant pressure discharged from the compressor exceeds a predetermined degree of increase, the opening of the pressure control valve is increased. Therefore, although the refrigerant pressure in the cooling cycle temporarily decreases, it does not mean that the compressor is stopped, so that the refrigerant is continuously supplied to the evaporator, whereby the cooling power of the evaporator can be secured. In particular, the cooling cycle can be protected even when the refrigerant pressure suddenly rises to an abnormal level.

(4) In order to achieve the above object,
According to the present invention, it has a discharge refrigerant temperature detecting means for detecting a discharge refrigerant temperature of the compressor, and the control means, when the discharge refrigerant temperature detected by the discharge refrigerant temperature detection means exceeds a predetermined temperature A cooling cycle for increasing the opening of the pressure control valve is provided.

In the cooling cycle of the present invention, when the refrigerant discharged from the compressor exceeds a predetermined temperature slightly lower than the limit temperature, the opening of the pressure control valve is increased, so that the refrigerant pressure in the cooling cycle is temporarily reduced. However, since the compressor is not stopped, the refrigerant is continuously supplied to the evaporator, whereby the cooling power of the evaporator can be secured.

(5) In order to achieve the above object,
According to the present invention, a discharge refrigerant temperature detecting means for detecting a discharge refrigerant temperature of the compressor, and a discharge refrigerant temperature rise for calculating a rise amount per unit time of the discharge refrigerant temperature detected by the discharge refrigerant temperature detection means The discharge refrigerant detected by the discharge refrigerant temperature rise degree calculation means when the discharge refrigerant temperature detected by the discharge refrigerant temperature detection means exceeds a predetermined temperature. A cooling cycle is provided for increasing the opening of the pressure control valve when the temperature rise exceeds a predetermined rise.

In the cooling cycle of the present invention, when the temperature of the refrigerant discharged from the compressor exceeds a predetermined temperature when the temperature of the refrigerant discharged from the compressor exceeds a predetermined temperature slightly lower than the limit temperature, the pressure control is performed. Increase the opening of the valve. Therefore,
Although the refrigerant pressure in the cooling cycle temporarily decreases, it does not mean that the compressor is stopped, so that the refrigerant continues to be supplied to the evaporator, whereby the cooling power of the evaporator can be secured. In particular, the cooling cycle can be protected even when the temperature of the refrigerant suddenly rises to an abnormal level.

(6) In order to achieve the above object,
According to the present invention, there is provided a rotational speed increase degree calculating means for calculating an increase amount per unit time of the rotational speed of the compressor detected by the rotational speed detection means, and the control means includes the rotational speed increase degree calculation. A cooling cycle is provided for increasing the opening of the pressure control valve when the increase in the number of revolutions of the compressor detected by the means exceeds a predetermined increase.

In the cooling cycle of the present invention, when the increase in the rotational speed of the compressor exceeds a predetermined increase, the opening of the pressure control valve is increased, so that the refrigerant pressure in the cooling cycle temporarily decreases. However, since the compressor is not stopped, the refrigerant is continuously supplied to the evaporator, whereby the cooling power of the evaporator can be secured. Further, since the refrigerant pressure in the cooling cycle temporarily decreases, the load torque of the compressor also decreases, thereby improving the sense of acceleration of the vehicle.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the first cycle of the cooling cycle of the present invention.
FIG. 2 is a circuit diagram showing an embodiment, FIG. 2 is a control map used in the first embodiment of the present invention, FIG. 3 is a sectional view showing a pressure control valve used in a cooling cycle of the present invention, and FIG. FIG. 4 is a Mollier diagram for explaining a cycle.

First, the structure of the cooling cycle shown in FIG. 1 will be described. In the cooling cycle according to the present embodiment, the compressor 1, the radiator 2, the pressure control valve 3, the evaporator 4, and the accumulator 5 are arranged in this order. They are connected by a pipe 8 to form a closed circuit.

The compressor 1 obtains a driving force from the engine EG or the like, compresses the carbon dioxide refrigerant in a gaseous state, and discharges the refrigerant toward the radiator 2. The radiator 2 cools the carbon dioxide refrigerant compressed by the compressor 1 by exchanging heat with the outside air or the like. In order to promote the heat exchange or to allow the heat exchange even when the vehicle is stopped, the radiator 2 is cooled. A fan 6 is added. The radiator 2 is disposed, for example, on the front of a vehicle in order to maximize the difference between the temperature of the carbon dioxide refrigerant in the radiator 2 and the outside air temperature.

The pressure control valve 3 reduces the pressure of the high-pressure (about 10 MPa) carbon dioxide refrigerant flowing out of the radiator 2 by passing it through the pressure reducing holes 316, which will be described later. The pressure control valve 3 has a function of controlling the pressure on the outlet side of the radiator 2 as well as reducing the pressure of the carbon dioxide refrigerant. Evaporator (heat sink) 4
Flows into.

The evaporator 4 is for cooling the air blown into the vehicle interior. For example, the evaporator 4 is incorporated in the casing of an air-conditioning unit mounted on the vehicle. 4, the intake air is cooled, and is blown out to a desired position in the vehicle compartment through an outlet (not shown). That is, the carbon dioxide refrigerant in the gas-liquid two-phase state flowing down from the pressure control valve 3 cools it by removing latent heat of evaporation from the intake air when evaporating (vaporizing) in the evaporator 4.

The accumulator 5 separates the carbon dioxide refrigerant that has passed through the evaporator 4 into a gaseous state refrigerant and a liquid state refrigerant, and sends only the gaseous state refrigerant to the compressor 1 and the liquid phase refrigerant. The refrigerant in the state is temporarily stored.

Next, the pressure control valve 3 will be described. The pressure control valve 3 according to the present embodiment includes a pressure control valve body 31 for reducing the pressure of the high-pressure refrigerant from the radiator 2 and a pressure control hole 316 provided in the pressure control valve body 31 for controlling the opening degree. And an opening control device 34.

The pressure control valve body 31 includes a housing 311
Are assembled by screwing the housing 312 and the housing 313 into the housing.
Refrigerant inlet 314 through which high-pressure refrigerant flows from
The housing 311 has a refrigerant outlet 315 through which the decompressed refrigerant flows toward the evaporator 4.

In the housing 311 between the refrigerant inlet 314 and the refrigerant outlet 315, refrigerant passages 319 and 320 are formed, and a pressure reducing hole 316 forming a bottleneck between the refrigerant passages 319 and 320 is provided. I have. This decompression hole 3
16 is provided with a valve element 317 on the refrigerant flow path 319 side, and is connected to a piston 323 to be described later via a rod 321 to open and close the pressure reducing hole 316 at a predetermined opening. “318” shown in FIG. 3 is a coil spring that urges the valve body 317 in the closing direction of the pressure reducing hole 316.
The opening / closing operation of the pressure reducing hole 316 by the valve element 317 will be described later.

On the other hand, the housing 312 has a piston 3
A cylinder 322 into which the piston 23 is inserted is formed, and a control fluid inlet 326 is formed in an upper part of FIG. 3 (hereinafter, also referred to as a top surface side of the piston). A working fluid (in this embodiment, a carbon dioxide refrigerant circulating in the cooling cycle is used) is introduced into the top surface side space 325 of the piston 323. A coil spring 324 that biases the piston 323 downward is provided in the top surface side space 325, and the valve body 317 closes the pressure reducing hole 316 in a no-load state by balancing with the coil spring 318 described above. I do.

The back pressure acting on the top side space 325 is released from the piston 323 itself,
A back pressure release channel 37 is formed in order to improve the operation of. The back pressure release channel 37 of the present embodiment is
3 and a second back pressure release channel 371 formed in the shielding wall 36 described later. The control flowed into the top side space 325 of the piston 323. Fluid (carbon dioxide refrigerant) is used for these first and second fluids.
Through the back pressure relief flow paths 372 and 371 to reach the refrigerant flow path 320, whereby the piston 323 is connected to the cylinder 3
22 will slide smoothly.

In the present embodiment, the shielding wall 36 is fixed at a position of the housing 312 facing the refrigerant flow passage 320.
The shielding wall 36 substantially blocks the lower surface (hereinafter, also referred to as the rear surface) of the piston 323 from the refrigerant flow path 320. Except for the through-hole of the rod 321 and the above-mentioned second back pressure release flow path 371, the same. , Is shielded. This shielding wall 36
May be fixed to the housing 312 as a separate part,
Further, it may be formed integrally with the housing 312.

The opening control device 34 of this embodiment has a housing 341. A control fluid inlet 342 into which a control fluid flows into the housing 341 and a control fluid flows out toward the pressure control valve body 31. Control fluid outlet 344
Are formed. A valve port 347 as a bottleneck is formed between the control fluid inlet 342 and the outlet 344, and the needle valve 348 is opened and closed so as to open and close the valve port 347.
Is provided.

The needle valve 348 is connected to a plunger 350, and the plunger 350
The fine opening / closing of the valve port 347 by the needle valve 348 per unit time (duty ratio of opening and closing) is controlled by finely moving forward and backward by the magnetic field from FIG.

In this embodiment, the carbon dioxide refrigerant itself circulating in the cooling cycle is used as the control fluid.
Pipe 343 from the control fluid outlet 327 provided in
Through the control fluid outlet 344, and from the control fluid outlet 344 via the pipe 345 to the control fluid inlet 326 of the pressure control valve body 31.

Next, the operation of the cooling cycle of this embodiment will be described with reference to the Mollier diagram of FIG. First, a carbon dioxide refrigerant in a gaseous state is compressed by the compressor 1 (A-
B), the high-temperature and high-pressure gas-phase carbon dioxide refrigerant is cooled by the radiator 2 (B-C). Then, after the pressure is reduced by the pressure control valve 3 (CD), the carbon dioxide refrigerant in a gas-liquid two-phase state is evaporated by the evaporator 4 (DA), and the latent heat of evaporation is deprived from the intake air. And cool it. Thereby, the intake air introduced into the unit of the air conditioner is cooled, and is blown out into the vehicle interior to cool the vehicle interior.

The carbon dioxide refrigerant that has passed through the evaporator 4 is separated into gas and liquid by the accumulator 5, and only the refrigerant in the gaseous state is sucked into the compressor 1 again.

At the time of steady operation, C-
In the pressure reduction process of D, the following control is executed according to the heat load on the evaporator 4.

That is, when the heat load is high (when a large amount of cooling is required), such as in summer, the pressure control valve 3
It is necessary to increase the differential pressure between the refrigerant pressure at the inlet and the refrigerant pressure at the outlet, so that the opening of the valve element 317 is reduced.
The duty ratio of the needle valve 348 of the opening control device 34 is reduced (the opening time ratio is reduced). As a result, the amount of high-pressure refrigerant introduced from the control fluid outlet 327 into the space 325 on the top surface side of the piston 323 via the pipes 343 and 345 and the control fluid inlet 326 is reduced. Move upwards at
As a result, the valve element 317 also moves upward via the rod 321, and the opening of the pressure reducing hole 316 decreases. On the other hand, when the heat load is not so large, the pressure control valve 3
Since it is not necessary to make the pressure difference between the refrigerant pressure at the inlet and the refrigerant pressure at the outlet so large, the duty ratio of the needle valve 348 of the opening control device 34 is increased in order to increase the opening of the valve body 317. Thereby, the piston 32
Since the amount of high-pressure refrigerant introduced into the space 325 on the top surface side of the piston 3 increases, the piston 323 moves downward in FIG. 3, and as a result, the valve body 317 also moves downward via the rod 321 to reduce the pressure. The opening degree of the hole 316 increases.

When the piston 323 moves upward from the lower position, the space 325 on the top surface side of the piston 323 moves.
Is introduced into the refrigerant channel 320 via the first back pressure releasing channel 372 and the second back pressure releasing channel 371, so that the operation of the piston 323 is performed smoothly.

At this time, when the valve element 317 opens the pressure reducing hole 316, high-pressure refrigerant flows from the radiator 2 into the refrigerant flow paths 319 and 320 of the pressure control valve body 31, and the refrigerant pressure is applied to the back of the piston 323. However, in the present embodiment, the shielding wall 36 is provided here, so that the high-pressure refrigerant is prevented from directly acting on the back side of the piston 323. This can prevent dust such as iron powder contained in the refrigerant from adhering to the cylinder 322 and biting between the piston 323 and causing malfunction of the piston 323. In addition, the high-pressure refrigerant has the piston 323
Does not directly act on the back surface of the piston 323, thereby making it possible to avoid instability of the vertical movement of the piston 323.

The pressure control valve 3 of the present invention is not limited to the above-described embodiment, but can be variously modified and modified.

In the cooling cycle of the present embodiment, the following control method is employed in addition to the control during the steady operation described above. That is, a temperature sensor 9 for detecting the temperature of intake air is provided in the casing of the air conditioning unit and in front of the evaporator 4, and a rotation speed sensor 10 for detecting the rotation speed of the engine EG is provided. Is provided. The rotation speed sensor 10 detects the rotation speed of the engine output shaft, and is normally provided in a normal vehicle. However, in the present invention, it is sufficient if the rotation speed of the compressor 1 can be detected directly or indirectly. Therefore, the compressor 1 may be provided with a rotation speed sensor. In this example, the engine speed sensor 1 which is always provided
Since the value obtained by multiplying the pulley ratio by 0 is the rotation speed of the compressor 1, the engine rotation speed sensor 10 is shared.

The temperature sensor 9 and the rotation speed sensor 1
0 is sent to the controller 11, which determines the duty ratio of the pressure control valve 3 with reference to the control map shown in FIG.
To the opening degree control device 34.

The cooling cycle control using the temperature of the intake air by the temperature sensor 9 and the engine speed by the speed sensor 10 as control factors can be employed, for example, when the air conditioner is started.

For example, the refrigerant pressure is 10
In a carbon dioxide cooling cycle that is about twice as high, the refrigerant discharge amount of the compressor 1 becomes unstable from the start until the cycle becomes stable.
That is, the cooling capacity of the evaporator 4 cannot be expected until a certain discharge amount is obtained. In such a case, if the valve opening of the pressure control valve 3 is reduced (the opening duty ratio is reduced), the pressure at the radiator 2 outlet, that is, the point G in FIG. 15 increases, and a sufficient enthalpy difference can be secured. The cooling power of the evaporator 4 can be increased.

Further, even when the temperature of the intake air is high, that is, when the outside air temperature is high irrespective of the rotation speed of the compressor 1, the valve opening of the pressure control valve 3 is reduced (the opening duty ratio is reduced). 15), the outlet of the radiator 2, that is, FIG.
, The pressure at point G increases, and a sufficient enthalpy difference can be secured, so that the cooling power of the evaporator 4 can be increased.

As described above, in this embodiment, the number of revolutions of the compressor 1 which directly affects the cooling capacity of the evaporator 4, that is, the refrigerant discharge amount, and the intake air which directly affects the required cooling amount The opening degree of the pressure control valve 3, that is, the outlet pressure of the radiator 2 is controlled based on the temperature of the radiator 2, so that a sufficient cooling capacity can be exerted even at the time of startup in which the refrigerant discharge amount is unstable.

The above is the basic configuration of the cooling cycle of the present invention, and the control shown in FIGS. 4 to 14 can be added to this.

FIG. 4 is a circuit diagram showing another embodiment of the cooling cycle according to the present invention. In the configuration shown in FIG. 1, a pressure sensor 12 for detecting the refrigerant pressure discharged from the compressor 1 and a pressure increase degree An arithmetic circuit 13, a temperature sensor 14 for detecting the temperature of the refrigerant discharged from the compressor 1, a temperature increase calculating circuit 15, and a rotation speed increase calculating circuit 16 are added. In the following embodiments, the cooling cycle is basically controlled using this configuration.

First, FIG. 5 is a flowchart showing a control procedure according to the second embodiment of the present invention, and FIG. 6 is a time chart showing the control state. In this example, the pressure sensor 12 shown in FIG. 4 is used, and by detecting the refrigerant pressure discharged from the compressor 1, control is performed so as to exert a sufficient cooling capacity even if the refrigerant pressure in the cooling cycle abnormally rises. .

That is, the discharge refrigerant pressure detected by the pressure sensor 12 in step 2 of FIG. 5 exceeds a predetermined value P3 (for example, 15.5 MPa) slightly lower than the upper limit value P1 (for example, 16.5 MPa) shown in FIG. In step 3, a flag indicating that aperture correction is being performed is set, and in step 4, aperture correction is added. The pressure sensor 12
Is 2 msec. The throttle correction here refers to correction control for forcibly increasing the valve opening of the pressure control valve 3, and in this example, the duty ratio is 2
% Increase.

When the aperture correction is started, in steps 5 and 6, a standby time timer and an aperture correction standby time elapsed flag are initialized. Here, the standby time is the minimum unit time for executing the aperture correction, and is 200 msec in this example.
It has been.

Next, at step 7, it is determined whether or not the refrigerant pressure detected by the pressure sensor 12 has dropped below the lower limit predetermined value P4 (for example, 15 MPa) shown in FIG. Steps 8 and 9
Initializes the throttle-in-progress flag and stops the aperture correction to return to the original valve opening.

On the other hand, the refrigerant pressure is set to the lower limit predetermined value P4
If not, steps 8 and 9
And return to step 1. In step 1, since there is the aperture correction flag set in step 3, the process proceeds to step 10, and since the aperture correction standby time elapsed flag is not set, the process proceeds to step 11. Step 11
Then, it is determined whether or not the aperture correction standby time of 200 msec has elapsed. When the time of 200 msec has elapsed, the process proceeds to step 12, and the aperture correction standby time elapsed flag is set.

At step 13, it is determined again whether the refrigerant pressure has exceeded the predetermined value P3. If the refrigerant pressure has exceeded the predetermined value P3, at step 14, a 2% increase in the duty ratio is further performed in the throttle correction. At steps 15 and 16, the standby time timer and the aperture correction standby time elapsed flag are initialized.

FIG. 6 shows the above control state. In this embodiment, when the discharge refrigerant pressure of the compressor 1 detected by the pressure sensor 12 exceeds the predetermined value P3, the valve opening of the pressure control valve 3 is forcibly opened, and the compressor 1 is stopped without stopping. Reduce refrigerant pressure. This forcible correction of the valve opening is executed until the refrigerant pressure in the cycle falls to or below the lower limit predetermined value P4. If the value exceeds P3, the pressure control valve 3
The valve opening is forcibly opened.

In the cooling cycle of this embodiment, although the refrigerant pressure in the cooling cycle temporarily decreases, the refrigerant is not supplied to the evaporator 4 because the compressor 1 is not stopped.
Even at the time of abnormality, the cooling power of the evaporator 4 can be secured.

Next, another embodiment will be described with reference to FIGS. FIG. 7 is a flowchart showing a control procedure according to the third embodiment of the present invention, and FIG. 8 is a time chart showing the control state. In this example, the pressure sensor 12 shown in FIG.
And a pressure rise degree calculation circuit 13 is used to detect the rise degree of the discharge refrigerant pressure of the compressor 1 so as to exert sufficient cooling capacity even if the refrigerant pressure in the cooling cycle rises abnormally. .

Here, the degree of pressure increase refers to the amount of increase in the refrigerant pressure per unit time. In this example, the amount of increase in the refrigerant pressure in the past one second is calculated, and the refrigerant pressure has increased to a predetermined value P5 or more. When the degree of increase in the case becomes 2 MPa / sec or more, the aperture correction is forcibly executed.

That is, the predetermined value P3 of the above-described embodiment is used.
A threshold value of a slightly lower predetermined value P5 (for example, 15 MPa) and a lower limit predetermined value P6 (for example, 13 MPa) are set, and if the refrigerant pressure detected by the pressure sensor 12 in step 21 exceeds the predetermined value P5. Proceed to step 22. In step 22, the degree of increase of the refrigerant pressure in the past one second calculated by the pressure increase degree calculation circuit 13 is 2 MPa / s.
If it exceeds ec, throttle correction is executed in step 23, and the valve opening of the pressure control valve 3 is set to a duty ratio of 20% / 4 ms.
Forcibly open at the speed of ec. In addition, you may fully open immediately.

This throttle opening control is continued until the refrigerant pressure becomes equal to or lower than the lower limit predetermined value P6.
When it becomes 6 or less, the valve opening is returned to the original valve opening in steps 24 and 25.

FIG. 8 shows the above control state. In this example, if the discharge refrigerant pressure detected by the pressure sensor 12 exceeds the predetermined value P5 and the rise degree of the discharge refrigerant pressure calculated by the pressure rise degree calculation circuit 13 exceeds the predetermined value (2 MPa / sec) , The valve opening of the pressure control valve 3 is forcibly fully opened, and the compressor 1
The refrigerant pressure in the cycle is reduced without stopping.
This forcible full-opening correction of the valve opening is executed until the refrigerant pressure in the cycle falls below the lower limit predetermined value P6.

In the cooling cycle of this example, although the refrigerant pressure in the cooling cycle temporarily decreases, the refrigerant is not supplied to the evaporator 4 because the compressor 1 is not stopped.
Even at the time of abnormality, the cooling power of the evaporator 4 can be secured. In particular, the cooling cycle can be protected even when the refrigerant pressure suddenly rises to an abnormal level.

Next, another embodiment will be described with reference to FIGS. FIG. 9 is a flowchart showing a control procedure according to the fourth embodiment of the present invention, and FIG. 10 is a time chart showing the control state. In this example, the temperature sensor 14 shown in FIG. 4 is used, and by controlling the temperature of the refrigerant discharged from the compressor 1, control is performed so as to exert a sufficient cooling capacity even if the refrigerant temperature in the cooling cycle abnormally rises. .

That is, the temperature of the discharged refrigerant detected by the temperature sensor 14 in step 32 of FIG.
Exceeds a predetermined value T3 (for example, 175 ° C.) slightly lower than the upper limit T1 (for example, 180 ° C.) shown in FIG.
At step 4, an aperture correction is added. Note that the sample interval of the temperature sensor 14 is set to 2 msec. The throttle correction here refers to correction control for forcibly increasing the valve opening of the pressure control valve 3, and in this example, the duty ratio is increased by 2%.

When the aperture correction is started, in steps 35 and 36, a standby time timer and an aperture correction standby time elapsed flag are initialized. Here, the standby time is a minimum unit time for executing the aperture correction, and is 10 sec in this example.
It has been.

Next, at step 37, the lower limit predetermined value T4 of the refrigerant temperature detected by the temperature sensor 14 shown in FIG.
(For example, 165 ° C.) or less, and if the temperature falls below the lower limit predetermined value T4, the aperture correction in-progress flag is initialized in steps 38 and 39, and the aperture correction is stopped to return to the original valve opening. return.

On the other hand, when the refrigerant temperature is lower than the lower limit predetermined value T4
If not, the program jumps steps 38 and 39 and returns to step 31. Step 31
Then, the process proceeds to step 40 because the aperture correction in-progress flag is set in step 33, and the process proceeds to step 41 because the aperture correction standby time elapsed flag is not set. In step 41, it is determined whether or not the aperture correction standby time of 10 seconds has elapsed. When the time of 10 seconds has elapsed, the process proceeds to step 42, and the aperture correction standby time elapsed flag is set.

In step 43, it is determined again whether the refrigerant temperature has exceeded the predetermined value T3, and if it has exceeded the predetermined value T3, in step 44, a 2% increase in the throttle ratio is further performed at the duty ratio. In steps 45 and 46, a standby time timer and an aperture correction standby time elapsed flag are initialized.

FIG. 10 shows the above control state. In this example, when the temperature of the refrigerant discharged from the compressor 1 detected by the temperature sensor 14 exceeds a predetermined value T3, the valve opening of the pressure control valve 3 is forcibly opened, and the cycle within the cycle is stopped without stopping the compressor 1. Reduce refrigerant pressure. This forced correction of the valve opening is performed until the refrigerant temperature in the cycle falls to or below the lower limit predetermined value T4. When the value exceeds the value T3, the valve opening of the pressure control valve 3 is further forcibly opened.

In the cooling cycle of this embodiment, although the refrigerant pressure in the cooling cycle temporarily decreases, the refrigerant is not supplied to the evaporator 4 because the compressor 1 is not stopped.
Even at the time of abnormality, the cooling power of the evaporator 4 can be secured.

Another embodiment will be described with reference to FIGS. 11 and 12. FIG. 11 is a flowchart showing a control procedure according to the fifth embodiment of the present invention, and FIG. 12 is a time chart showing the control state. In this example, a temperature sensor 14 and a temperature rise degree calculation circuit 15 shown in FIG.
By detecting the degree of increase in the temperature of the refrigerant discharged from the compressor 1, control is performed so that a sufficient cooling capacity is exhibited even if the temperature of the refrigerant in the cooling cycle abnormally increases.

Here, the degree of temperature rise refers to the amount of increase in the refrigerant temperature per unit time. In this example, the amount of increase in the refrigerant temperature in the past one second is calculated, and the refrigerant temperature has risen to a predetermined value T5 or more. When the degree of rise in the case becomes 10 ° C./sec or more, the aperture correction is forcibly executed.

That is, the predetermined value T3 of the above-described embodiment is used.
A threshold value of a slightly lower predetermined value T5 (for example, 160 ° C.) and a lower limit predetermined value T6 (for example, 150 ° C.) are set, and the refrigerant temperature detected by the temperature sensor 14 in Step 51 is reduced to the predetermined value T5. If it exceeds, go to step 52.
In step 52, when the degree of rise in the refrigerant temperature in the past one second calculated by the temperature rise degree calculation circuit 15 exceeds 10 ° C./sec, throttle correction is executed in step 53, and the valve opening degree of the pressure control valve 3 is set. Are forcibly opened at a duty ratio of 20% / 4 msec. In addition, you may fully open immediately.

The throttle opening control is continued until the refrigerant temperature falls below the lower limit predetermined value T6.
When it becomes 6 or less, the valve is returned to the original valve opening in steps 54 and 55.

FIG. 12 shows the above control state. In this example, the temperature of the discharged refrigerant detected by the temperature sensor 14 is a predetermined value T.
When the temperature exceeds 5 and the degree of rise of the discharge refrigerant temperature calculated by the temperature rise degree calculation circuit 15 exceeds a predetermined value (10 ° C./sec), the valve opening of the pressure control valve 3 is forcibly fully opened, The refrigerant pressure in the cycle is reduced without stopping the compressor 1. This forced full opening correction of the valve opening is executed until the refrigerant temperature in the cycle falls to or below the lower limit predetermined value T6.

In the cooling cycle of the present embodiment, although the refrigerant pressure in the cooling cycle temporarily decreases, the refrigerant is not supplied to the evaporator 4 because the compressor 1 is not stopped.
Even at the time of abnormality, the cooling power of the evaporator 4 can be secured. In particular, the cooling cycle can be protected even when the temperature of the refrigerant suddenly rises to an abnormal level.

Another embodiment will be described with reference to FIGS. 13 and 14. FIG. 13 is a flowchart showing a control procedure according to the sixth embodiment of the present invention, and FIG. 14 is a time chart showing the control state. In this example, the rotation speed sensor 10 and the rotation speed increase calculation circuit 16 shown in FIG. 4 are used, and by detecting the increase in the rotation speed of the compressor 1, even if the rotation speed in the cooling cycle abnormally increases. Control is performed so that sufficient cooling capacity is exhibited and the feeling of acceleration of the vehicle is improved.

The increase in the number of revolutions referred to herein means the amount of increase in the number of revolutions per unit time. In this example, the amount of increase in the number of revolutions in the past one second is calculated, and the increase is 1000 rpm in terms of engine speed. When the speed becomes / sec or more, the aperture correction is forcibly executed.

That is, when the rotational speed detected by the rotational speed sensor 10 is larger than the previously sampled rotational speed in step 61, the process proceeds to step 62. In step 62, the increase in the number of revolutions in the past one second calculated by the revolution number increase calculation circuit 16 is 1 in terms of engine speed.
If it exceeds 000 rpm / sec, throttle correction is executed in step 63, and the valve opening of the pressure control valve 3 is forcibly opened at a duty ratio of 2% / 10 msec. In addition, you may fully open immediately.

This aperture opening control is performed in step 6
At 1, the rotation speed is continued until the current rotation speed becomes lower than the rotation speed sampled at the previous time.

FIG. 14 shows the above control state. In this example, when the increase in the rotation speed calculated by the rotation speed increase calculation circuit 16 exceeds a predetermined value (1000 rpm / sec), the valve opening of the pressure control valve 3 is forcibly fully opened, and the compressor 1 The refrigerant pressure in the cycle is reduced without stopping. The forcible valve opening is fully corrected until the engine speed decreases.

In the cooling cycle of the present embodiment, although the refrigerant pressure in the cooling cycle temporarily decreases, the refrigerant is not supplied to the evaporator 4 because the compressor 1 is not stopped.
Even at the time of abnormality, the cooling power of the evaporator 4 can be secured. Further, since the refrigerant pressure in the cooling cycle temporarily decreases, the load torque of the compressor 1 also decreases, thereby improving the sense of acceleration of the vehicle.

By the way, in any of the above-described embodiments, the refrigerant pressure, the refrigerant temperature, or the number of revolutions is set to the upper limit values P1, T
When the pressure exceeds 1, R1, the compressor 1 is stopped. At this time, the valve opening of the pressure control valve 3 is fully opened. Then, when returning the cooling cycle from this state, the compressor 1 is restarted. At this time, it is desirable to execute control to gradually or stepwise close the valve opening of the pressure control valve 3. This is because if the valve opening is rapidly reduced, the refrigerant pressure and the refrigerant temperature will rise rapidly, and the engine will stop when idling. In addition, when the engine speed drops to, for example, 600 rpm or less in the process of gradually or stepwise controlling the valve opening to be small, the valve opening is temporarily stopped from being reduced, and the valve opening is maintained. It is desirable to control it.

The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[0089]

As described above, according to the present invention, the opening degree of the pressure control valve is controlled based on the rotational speed of the compressor and the temperature of the intake air. , The sufficient enthalpy difference can be secured, and the cooling power of the evaporator can be increased. In particular, this is a control method effective at the time of starting where the refrigerant discharge amount is unstable.

When the pressure of the refrigerant discharged from the compressor, the temperature of the discharged refrigerant or their rise exceeds a predetermined value, the opening of the pressure control valve is increased, so that the refrigerant pressure in the cooling cycle is temporarily reduced. Although it does decrease, it does not mean that the compressor is stopped, so that the refrigerant is continuously supplied to the evaporator, whereby the cooling power of the evaporator can be secured.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a cooling cycle according to the present invention.

FIG. 2 is a control map used in the first embodiment of the present invention.

FIG. 3 is a sectional view showing a pressure control valve used in the cooling cycle of the present invention.

FIG. 4 is a circuit diagram showing a second embodiment of the cooling cycle of the present invention.

FIG. 5 is a flowchart illustrating a control procedure according to a second embodiment of the present invention.

FIG. 6 is a time chart showing a control state according to a second embodiment of the present invention.

FIG. 7 is a flowchart illustrating a control procedure according to a third embodiment of the present invention.

FIG. 8 is a time chart showing a control state according to a third embodiment of the present invention.

FIG. 9 is a flowchart illustrating a control procedure according to a fourth embodiment of the present invention.

FIG. 10 is a time chart showing a control state according to a fourth embodiment of the present invention.

FIG. 11 is a flowchart illustrating a control procedure according to a fifth embodiment of the present invention.

FIG. 12 is a time chart showing a control state according to a fifth embodiment of the present invention.

FIG. 13 is a flowchart illustrating a control procedure according to a sixth embodiment of the present invention.

FIG. 14 is a time chart showing a control state according to a sixth embodiment of the present invention.

FIG. 15 is a Mollier chart for explaining a cooling cycle of carbon dioxide refrigerant.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor 2 ... Radiator 3 ... Pressure control valve 4 ... Evaporator 5 ... Accumulator 6, 7 ... Fan 8 ... Refrigerant piping 9 ... Temperature sensor (intake air temperature detection means) 10 ... Rotation speed sensor (rotation speed detection) 11) Controller (control means) 12 ... Pressure sensor (discharge refrigerant pressure detection means) 13 ... Pressure rise calculation circuit (discharge refrigerant pressure rise calculation means) 14 ... Temperature sensor (discharge refrigerant temperature detection means) 15 ... Temperature Rise degree calculation circuit (discharge refrigerant temperature rise degree calculation means) 16 ... Rotation number rise degree calculation circuit (rotation number rise degree calculation means)

Claims (7)

[Claims] 1. A compressor for compressing a carbon dioxide-containing refrigerant, a radiator for cooling the refrigerant compressed by the compressor,
A pressure control valve for controlling the pressure of the refrigerant cooled by the radiator, and an evaporator for cooling the intake air by an endothermic effect of the refrigerant, the pressure of which is controlled by the pressure control valve, are piped at least in series. In a cooling cycle, intake air temperature detection means for detecting the temperature of the intake air, rotation speed detection means for directly or indirectly detecting the rotation speed of the compressor, the intake air temperature detection means And a control means for controlling the opening of the pressure control valve based on the temperature of the intake air detected by the control means and the rotational speed of the compressor detected by the rotational speed detection means. 2. The control means includes a control map in which the relationship between the temperature of the intake air, the number of revolutions of the compressor, and the degree of opening of a pressure control valve is determined, and the pressure control is performed based on the control map. 2. The cooling cycle according to claim 1, wherein the opening of the valve is controlled. 3. A discharge refrigerant pressure detecting means for detecting a discharge refrigerant pressure of the compressor, wherein the control means is configured to detect the discharge refrigerant pressure when the discharge refrigerant pressure detected by the discharge refrigerant pressure detection means exceeds a predetermined pressure. 3. The cooling cycle according to claim 1, wherein the opening degree of the pressure control valve is increased. 4. A discharge refrigerant pressure detecting means for detecting a discharge refrigerant pressure of the compressor, and a discharge refrigerant pressure increase degree for calculating a rise amount per unit time of the discharge refrigerant pressure detected by the discharge refrigerant pressure detection means. Computing means, the control means, when the discharged refrigerant pressure detected by the discharged refrigerant pressure detecting means exceeds a predetermined pressure, the discharge refrigerant pressure detected by the discharged refrigerant pressure rise degree calculating means, 3. The cooling cycle according to claim 1, wherein the opening degree of the pressure control valve is increased when the rising degree exceeds a predetermined rising degree. 5. A discharge refrigerant temperature detecting means for detecting a discharge refrigerant temperature of said compressor, wherein said control means is adapted to detect when the discharge refrigerant temperature detected by said discharge refrigerant temperature detection means exceeds a predetermined temperature. 3. The cooling cycle according to claim 1, wherein the opening degree of the pressure control valve is increased. 6. A discharge refrigerant temperature detecting means for detecting a discharge refrigerant temperature of the compressor, and a discharge refrigerant temperature rise degree for calculating a rise amount per unit time of the discharge refrigerant temperature detected by the discharge refrigerant temperature detection means. Computing means, wherein the control means, when the discharged refrigerant temperature detected by the discharged refrigerant temperature detecting means exceeds a predetermined temperature, the discharged refrigerant temperature detected by the discharged refrigerant temperature rise degree calculating means 3. The cooling cycle according to claim 1, wherein the opening degree of the pressure control valve is increased when a rising degree of the pressure exceeds a predetermined rising degree. 7. A rotation speed increase degree calculating means for calculating an increase amount per unit time of the rotation number of the compressor detected by the rotation number detection means, wherein the control means calculates the rotation number increase degree. 3. The cooling cycle according to claim 1, wherein the opening degree of the pressure control valve is increased when an increase in the number of revolutions of the compressor detected by the means exceeds a predetermined increase.