JPS59197756A - Controller for refrigeration cycle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a refrigeration cycle used in an air conditioner for an automobile or the like.

A refrigeration cycle mainly includes a compressor, a condenser, an expansion valve, and an evaporator. The principle is to evaporate the atomized refrigerant in the evaporator, and at the same time, remove heat of vaporization from the air around the evaporator to cool the air.

Conventionally, to control the cooling capacity in a refrigeration cycle that has a variable displacement compressor as a compressor, the evaporation pressure of the evaporator is detected and the capacity of the variable displacement compressor is adjusted to bring it closer to a predetermined set pressure. A method of control was adopted.

For example, when the cooling load increases and the cooling capacity no longer matches it, the refrigerant gas in the evaporator becomes hot and the evaporation pressure in the evaporator tends to rise.

In order to suppress this increase and maintain a predetermined evaporation pressure, the capacity of the compressor is feedback-controlled to a large capacity to maintain the evaporation pressure near a stable point. However, conventional refrigeration cycle control has the following drawbacks.

First, if refrigerant gas leaks from the refrigeration cycle and the evaporation pressure of the refrigerant gas in the evaporator decreases, the evaporation pressure in the evaporator will decrease, so to prevent this, the compressor is set to the small capacity side. controlled to. For this reason, the absolute amount of lubricating oil that quickly enters the compressor is reduced, and problems such as burning of the compressor are likely to occur.

Secondly, there are things related to the cooling load, such as humidity fluctuations in the intake air to be cooled by the evaporator fins, or fluctuations in the amount of intake air. l! The cooling capacity could not respond quickly to changes in the amount of air, and the temperature of the blown air fluctuated with changes in the cooling load, resulting in a poor cooling feeling. In other words, even if the cooling load fluctuates, it takes time for the fluctuation to appear as a fluctuation in the evaporation pressure of the refrigerant gas in the evaporator.
Or a situation such as insufficient cooling occurred.

An object of the present invention is to provide a refrigeration cycle control device that eliminates the above-mentioned drawbacks.

That is, the refrigeration cycle control device of the present invention includes a refrigeration cycle having a variable capacity compressor, an electromagnetic clutch that transmits driving force to the compressor, and a physical quantity related to the evaporation pressure of the evaporator of the refrigeration cycle. a first sensor that detects a physical quantity related to the cooling load; a second sensor that detects a physical quantity related to the cooling load; and a control device; the control device receives an electrical signal detected from the second sensor; a setting section for setting a physical quantity related to a first reference evaporation pressure of the evaporator; a capacity control unit that performs feedback control on the capacity of the capacity compressor; a measurement value detected from the first sensor;
and an electromagnetic clutch control section that puts the electromagnetic clutch in a disengaged state in accordance with a relationship with a set value corresponding to a physical quantity related to a reference evaporation pressure.

The variable displacement compressor may be any type as long as its discharge capacity can be varied. The discharge volume may change continuously, or may change discontinuously or stepwise.

Physical quantities related to the evaporation pressure of the evaporator include the evaporation pressure of the evaporator, the suction pressure on the suction side of the compressor, and the refrigerant temperature of the evaporator. Evaporation pressure and temperature have a certain relationship.

As the first sensor for detecting these physical quantities, for example, a pressure detection device as shown in FIG. 4 or other strain gauges can be used.

As the second sensor that detects a physical quantity related to the cooling load, for example, a temperature sensor that detects the degree of cooling of the air passing through the evaporator or the temperature of the air flowing into the evaporator;
Alternatively, a position detection sensor such as a variable resistor that detects the amount of air passing through the evaporator by a rotation speed switching signal of the blower, a potentiometer, or a potentiometer that detects the position of the air volume adjustment lever of the blower can be used. Also, outside the vehicle,
A temperature sensor that detects the temperature or humidity inside the vehicle, a humidity sensor, a solar radiation sensor that detects the amount of solar radiation, etc. can be used. One or more of these second sensors may be used simultaneously.

The setting unit changes the set value of a physical quantity related to the evaporation pressure in the evaporator so as to control the evaporation pressure of the evaporator to a constant target value in feedback control that varies the cooling capacity according to fluctuations in the cooling load. Has a function.

The capacity control section has a function of causing the evaporation pressure to follow the set value and then changing the discharge capacity of the compressor so as to change the cooling capacity.

The electromagnetic clutch control unit is configured to prevent refrigerant gas from leaking from the refrigeration cycle, causing the evaporator pressure to drop below a predetermined value.
Alternatively, if the temperature of the evaporator rises abnormally, or if the refrigerant temperature in the evaporator does not drop much even after a certain amount of 1 t;'i ml has passed after the operation of the refrigeration cycle, the electric 1a clutch is disengaged and the compressor is turned off. It has a function that prevents burnout due to lack of lubricant. In this case, the pressure setting value that does not cause seizure of the compressor is, for example, 0.5 kg.
/cm2 ・GN degree.

The refrigeration cycle control device of the present invention configured as described above prevents seizure caused by lack of lubricating oil in the compressor even if gas leaks during refrigeration cycle operation. Since the refrigeration cycle can be operated with a high cooling capacity, the cooling feeling is good and there is little energy loss.Furthermore, seizure due to refrigerant gas leakage can be prevented to a certain extent without disengaging the electromagnetic clutch.

For example, if refrigerant gas leaks and the amount of refrigerant circulated within the refrigeration pile decreases, thereby reducing the cooling capacity of the refrigeration cycle, the temperature of air blown from the evaporator increases. The second sensor detects this, and as a result, the compressor is controlled to the larger capacity side, so seizures due to lack of lubricating oil in the compressor can be prevented to some extent.

The present invention will be explained in detail below.

FIG. 1 is an overall configuration diagram of an automobile air conditioner having a refrigeration cycle control device according to an embodiment of the present invention. As shown in FIG. 1, the refrigeration cycle control device of this embodiment includes a refrigeration cycle consisting of a variable capacity compressor 1fill, a condenser 12, a receiver 13, an expansion valve 14, and an evaporator 15, and detects the pressure inside the evaporator 15. It consists of a pressure detection device 40, a thermistor 30 that detects the temperature of the air from the evaporator 15, and a control device @50. The compressor 11 is equipped with an electromagnetic valve 513 for air conditioning control, and the compressor 11 is driven by an automobile engine (not shown) via an electromagnetic clutch 514.

FIG. 2 is an electrical circuit diagram of the control device 50. As shown in FIG. 2, the control device 50 inputs the potential Va determined by the pressure P of the evaporator 15, the resistance value R30 of the thermistor 30, etc. to the inverting input terminal of the comparator 504, and outputs the output of the oscillator 503 which outputs a sawtooth wave. is input to the non-inverting input terminal of comparator 504. The output of the comparison Mu 504 is the transistor 508
connected to the base terminal of the The collector of transistor 508 is connected to relay 511. relay, 511
controls the operation of the electromagnetic valve 513 that operates the variable capacity mechanism of the variable capacity compressor. On the other hand, the potential Vp determined by the pressure of the evaporator 15 is input to the inverting input terminal of the comparator 505, and the potential Vd determined by the resistance division between the resistors 507 and 506 is input to the non-inverting input terminal of the comparator 505. .

The output of comparator 505 controls opening and closing of relay 512 via transistor 509 and transistor 510. Relay 512 controls on/off of electromagnetic clutch 514 of compressor 11 .

FIG. 3 J3 and FIG. 4 are diagrams showing the configuration of the pressure detection device used in this embodiment. As shown in FIG. 4, the pressure detection device 40 receives pressure through a pressure receiving surface 44. As shown in FIG. The position of the pressure receiving surface 44 is determined by the balance between the pressure and the spring 45. A slide contact 42 is connected to the pressure receiving surface 44, and the slide contact 42 contacts the resistor 41.
1 Slide up. That is, a change in the pressure sensed by the pressure receiving surface can be expressed as a change in the resistance 41. The pressure receiving surface is directed into the evaporator outlet pipe 16 as shown in FIG.

Control by the refrigeration cycle control device of this embodiment is performed as follows.

As shown in FIGS. 2, 3, and 4, the pressure P of the evaporator is detected by a pressure detection device 40 as a potential Vp.

This potential Vp is input to the inverting input terminal of the comparator 504 as a potential Va determined by resistance division between the setting resistor 502, thermistor 30, and resistor 501. This potential va
is compared with the sawtooth potential Vc input from the oscillator 503, and if the sawtooth potential VC exceeds the potential Va, the comparator 504 outputs a high level output. As a result, transistor 508 becomes conductive, relay 511 operates, and electromagnetic valve 513 is energized.

Consider a case where the temperature of the air blown from the evaporator 15 is constant and the resistance value R30 of the thermistor 30 does not change.

In such a case, if the evaporation pressure P in the evaporator 15 tries to decrease by a minute amount for some reason, the potential Vp, which was initially V side, decreases by a minute amount and becomes Vk-, + as shown in FIG. leading to. As a result, the potential va decreases. Therefore, as a result of the decrease in the potential Va, the output of the comparator 504, which is output by comparing the sawtooth potential Vc, is
), the high-level output takes a long time, that is, the duty ratio becomes too large. As a result, the opening time of the electromagnetic valve 513 becomes longer (as the pressure of the intermediate pressure air decreases, the spool valve for controlling the capacity of the compressor 11 moves, the capacity of the compressor 11 decreases, and the evaporator 15 The pressure of the evaporator 15 rises, and the pressure that once tried to drop slightly is returned to the set value.By feedback-controlling the evaporation pressure to a constant set value in this way, the pressure at 70 of the evaporator 15
strikes are prevented.

Next, consider a case where the pressure P inside the evaporator 15 is constant and the temperature of the air blown from the evaporator 15 changes. The temperature of the air blown from the evaporator 15 increases and the resistance value of the mister 3o decreases.

As a result, the value of the potential Va with respect to the same potential Vp increases, and as shown in FIG. 6(b), the output from the comparator 504 becomes an output with a short high level time, that is, a small duty ratio. . As a result, the opening time of the electromagnetic valve 513 becomes shorter, and the pressure in the intermediate pressure chamber increases, causing the spool valve to move in the opposite direction and the compressor capacity to increase. As a result, the evaporating pressure saw of the evaporator is lowered, and the refrigerant temperature is lowered. Therefore, the cooling capacity is improved, and the temperature of the air blown from the evaporator 15 decreases, approaching the original temperature of the blown air. In this way, the compressor capacity is always corrected to a value suitable for the cooling load, so it is possible to reduce the compression drive power. The variable capacity compressor 11 used in this embodiment controls the pressure in the intermediate pressure chamber by intermittently controlling the solenoid valve 513 depending on the duty ratio, and thereby changes the compressor capacity by changing the position of the spool valve. It is something. The spool valve controls the opening/closing and position of a bypass hole for returning refrigerant to the suction side during the compression stroke, and such a mechanism may be of a known type.

Next, consider the case where refrigerant gas leaks from the frozen cycle, resulting in a drop in evaporation pressure. The evaporation pressure of the evaporator 15 is detected as a potential Vp by the pressure detection device 4o, and the increased potential Vp is input to the inverting input terminal of the comparator 505. On the other hand, a potential Vd determined by resistance division between a resistor 507 and a resistor 506 is input to a non-inverting input terminal of the comparator 505. When the pressure inside the evaporator 15 abnormally decreases due to gas leakage and the value of the potential Vp decreases, and the value of the potential Vp becomes lower than the potential Vd, the output of the comparator 505 becomes high level. As a result, transistor 509 is turned on and transistor 510 is turned off. As a result, relay 512 opens, power to electromagnetic clutch 514 is cut off, and electromagnetic clutch 514 is placed in a disconnected state. The compressor then stops.

As described above, according to the refrigeration one-day control system of the first embodiment, when the pressure inside the evaporator 15 fluctuates, the compressor capacity fluctuates, and the Bring the pressure closer to the desired set point. Furthermore, when the temperature of the air blown from the evaporator changes due to changes in the cooling load, the compressor capacity changes in the same way, and the cooling capacity is changed to maintain a constant cooling condition in the vehicle interior. When gas leaks from the refrigerated Nicle and the evaporation pressure in the evaporator 15 drops abnormally, the electromagnetic clutch of the compressor 11 is disconnected, and the compressor 11
operation will be stopped. Therefore, seizure of the compressor due to an abnormal decrease in lubricating oil is prevented. In addition, in the initial stage when a gas leak occurs, the temperature of the blown air increases because the cooling capacity decreases when the gas leaks.

This rise is detected by thermistor 30 and puts the compressor into high capacity operation. Therefore, until the compressor stops due to the electromagnetic clutch disengaging as described above, the compressor shifts to high-capacity operation, making it less likely that lubricating oil will run out. Reps are prevented.

Second Embodiment FIG. 7 is an overall configuration diagram of an automobile air conditioner having a refrigeration cycle control device according to a second embodiment of the present invention.
The figure is an electrical circuit diagram of a control device used in the second embodiment. As shown in FIG. 7, in this second embodiment,
A humidity sensor is used to detect the humidity inside the vehicle as a cooling load. The relationship between humidity and potential Ve is shown in FIG.

That is, as the humidity increases, the potential decreases. As shown in FIG. 7, the humidity inside the vehicle is detected by a humidity sensor 60, amplified by an amplifier circuit 61, and input to the control device 50. If the humidity inside the vehicle increases and there is a risk that the windows may fog up, the potential Ve at the J contact e shown in FIG. 8 decreases, and the current flowing through the transistor 515 decreases. the result,
The potential Va of the contact a rises, the duty ratio of the output of the comparator 504 decreases, the compressor capacity increases, and the evaporation pressure of the evaporator 15 decreases. Therefore, the dehumidifying ability of the refrigeration cycle is improved and the humidity inside the vehicle is reduced.

In summary, the present invention detects physical quantities related to the evaporation pressure in the evaporator and physical quantities related to the cooling load in a control device for a refrigeration cycle having a variable displacement compressor, and changes the capacity of the compressor using them. In addition to maintaining the optimal cooling condition in the vehicle interior, the electromagnetic clutch of the compressor is disconnected in the event of refrigerant scum leaking from the refrigeration cycle, thereby preventing the compressor from burning out.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an automobile air conditioner having a refrigeration cycle control device according to a first embodiment of the present invention.
The figure is an electrical circuit diagram of a control device used in the first embodiment. FIG. 3 is an explanatory diagram showing the installation state of the pressure detection device used in this embodiment, and FIG. 4 is a sectional view of the pressure detection device. FIG. 5 is a diagram showing the relationship between the evaporation pressure and potential of the evaporator of this embodiment, and FIG. FIG. 5 is an explanatory diagram showing the output of the comparator 504 determined by the potential of . FIG. 7 is an overall configuration diagram of an automobile air conditioner having a refrigeration cycle control device according to a second embodiment of the present invention, and FIG. 8 is an electric circuit diagram of a control device used in the second embodiment. FIG. 9 is a graph 1c showing the output potential of the 9 degree sensor (used in the second embodiment) and the amplifier circuit with humidity as the horizontal axis. 11... Variable capacity compressor 15... Evaporator 40... Pressure saw detection device 50... Control device Patent applicant Nippondenso Co., Ltd. Agent Patent attorney Hirotoshi Okawa Patent attorney Shudo Fujitani Patent attorney Akio Maruyama Figure 1 Figure 3 Figure 6 Figure 4. 7 □・ Fig. 5, P (evaporation pressure) Fig. 7 Fig. 9 0 50 100 5x degrees ('10)

Claims (1)

[Claims] <1) A refrigeration cycle having a variable displacement compressor, an electromagnetic clutch that transmits driving force to the compressor, and detecting physical quantities related to the evaporation pressure of an evaporator included in the refrigeration cycle. It has a first sensor, a second sensor that detects a physical quantity related to the cooling load, and a control device, and the control device receives the electric signal detected from the second sensor and a setting section for setting a physical quantity related to a first reference evaporation pressure of the device; a capacity control section that performs feedback control on the capacity of the compressor; a measurement value detected from the first sensor; and a predetermined second sensor.
1. A refrigeration cycle control device comprising: an electromagnetic clutch control unit that puts the electromagnetic clutch in a disengaged state according to a relationship with a set value corresponding to a physical quantity related to a reference evaporation pressure. (2) The refrigeration cycle control if according to claim 1, wherein the physical quantity related to the evaporation pressure is the temperature of the evaporator.
f device.