JPS63238364A - Refrigeration cycle controller - 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 [Industrial Application Field] The present invention relates to a refrigeration cycle control device, and is suitable for use in, for example, a refrigeration cycle control device for an automobile air conditioner.

[Prior Art] When the amount of refrigerant in a refrigeration cycle device is insufficient, the compressor lubricating oil that circulates in the cycle together with the refrigerant accumulates in various parts of the cycle, making it difficult for the oil to return to the compressor, which can lead to compressor seizure. There is a risk that such problems may occur. For this reason, various types of refrigerant deficiency detection devices have been proposed in refrigeration cycle devices such as automobile air conditioners.

In addition, as such a means for detecting refrigerant shortage, the present inventors have previously proposed detecting refrigerant shortage based on fluctuations in the refrigerant temperature at the outlet of the evaporator (Japanese Patent Application No. 173306/1982), but If the refrigerant repeatedly starts and stops in short cycles, it may become difficult to accurately detect the refrigerant temperature at the outlet of the evaporator.

[Problems to be Solved by the Invention] The present invention provides a refrigeration cycle control device equipped with a refrigerant shortage detection means as described above, in which the control means for detecting an abnormal state of the refrigeration cycle caused by refrigerant shortage etc. operates accurately. This is to check whether the refrigerant is running low or not, and ultimately determine whether or not there is a refrigerant shortage.

[Means for solving problems]

In order to achieve the above object, the present invention provides a refrigeration cycle with a temperature detection means for detecting the refrigerant temperature on the evaporator outlet side, and a control means for determining an abnormal operating state of the refrigeration cycle. When an abnormal condition is detected and a signal is output, the compressor is stopped, and the difference in temperature of the refrigerant at the outlet of the evaporator before and after the compressor is stopped is calculated. If the temperature difference is greater than a predetermined value, the control means has made an incorrect decision. On the other hand, when the temperature difference is not greater than a predetermined value, it can be determined that the determination by the control means is correct.

[Effect]

If there is enough refrigerant in the refrigeration cycle,
The refrigeration cycle is working well, so after the compressor is stopped, the refrigerant temperature on the evaporator outlet side will rise. In other words, if the refrigerant temperature on the evaporator outlet side rises by a predetermined value or more after the compressor stops, the refrigeration cycle will not operate normally in the state before the compressor stopped, that is, the state in which the refrigeration cycle was operating. That means you were doing it. In the present invention, this state can be accurately detected by the misjudgment detection means.

〔Effect of the invention〕

Therefore, in the present invention, whether or not the control means has accurately detected the malfunctioning state of the refrigeration cycle can be accurately checked again by the misjudgment means, and finally an abnormal state such as a refrigerant shortage state is detected. . Therefore, it is extremely effective as a protection device for refrigeration cycles.

〔Example] The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a refrigeration cycle for automobile air conditioning. Reference numeral 10 denotes a compressor, which is driven by an automobile engine 12 via an electromagnetic clutch 11.

A condenser 13 is connected to the discharge side of the compressor 10, and the condenser 13 cools and condenses the gas refrigerant discharged from the compressor 10 using cooling air blown by a cooling fan 14. The cooling fan 14 is driven by a motor 14a.

On the downstream side of the condenser 13, there is a receiver 15 that stores liquid refrigerant.
An electric inflatable type 16 is connected via. The expansion valve 16 has its opening degree electrically controlled, and serves as a pressure reducing device that expands the liquid refrigerant from the receiver 15 under reduced pressure.

An evaporator 17 is connected to the downstream side of the electric expansion valve 16, and this evaporator 17 connects the gas-liquid two-phase refrigerant that has passed through the expansion valve 16 to the interior of the vehicle or outside the vehicle, which is blown by the ventilation fan 18. The liquid refrigerant is evaporated by exchanging heat with the air. The cold air cooled by the latent heat of evaporation of the refrigerant is blown into the vehicle interior through the heater unit 24. As is well known, the heater unit 24 includes a heater core 24 which uses engine cooling water as a heat source, and adjusts the ratio of the air volume of warm air heated by passing through the heater core 241 and cold air passing through a bypass passage 242 of the heater core 241. A temperature control damper 243 and the like for adjusting the temperature of air blown into the vehicle interior is built-in. The downstream side of the evaporator 17 is connected to the suction side of the compressor 10.

A first refrigerant temperature sensor 20 is installed at the inlet piping of the evaporator 17 and detects the refrigerant temperature TE on the evaporator inlet side, and is made of a thermistor.

A second refrigerant temperature sensor 21 is installed at the outlet piping of the evaporator 17 to detect the refrigerant temperature TR on the evaporator outlet side, and is composed of a thermistor. These first and second refrigerant temperature sensors 20
．． 21 is installed in the inlet/outlet pipe to directly detect the refrigerant temperature, and is closely fixed to the surface of the inlet/outlet pipe.
Although any method may be used to detect the pipe surface temperature by covering the sensor mounting portion with a heat insulating material, the former method is practically advantageous in terms of accuracy of detected temperature.

Reference numeral 22 designates a control circuit, which includes an input circuit 22a into which the detection signals of the sensors 20 and 21 are input, a microcomputer 22b that performs predetermined arithmetic processing based on the input signals from the input circuit 22a, and the microcomputer 22.
It has an output circuit 22c that controls energization of the electromagnetic clutch 11 and the electric expansion valve 16 based on the output signal of the output circuit 22c.

The input circuit 22a has a built-in A-D converter etc. that converts an analog signal into a digital signal, and the output circuit 22a
c has a built-in relay circuit etc. that drives the load.

On the other hand, the microcomputer 22b is a single-chip L
The microcomputer 22b is formed by a digital computer consisting of SI, and this microcomputer 22b has a constant voltage circuit (
(not shown) and is placed in a ready state for operation. In this case, the constant voltage circuit is
In response to the closing of the ignition switch (not shown) No. 2, the constant voltage is generated by receiving a DC voltage from an on-vehicle DC power source (battery). The microcomputer 22b includes a central processing unit (hereinafter referred to as CPU), a memory (RO
The CPU, memory (ROM, RAM), and clock circuit are connected to each other via a path line. The memory (RAM) of the microcomputer 22b receives and temporarily stores each digital signal from the input circuit 22a, and selectively provides each of these signals to the CPU. The clock circuit of the micro combinator 22b generates a clock signal having a predetermined frequency in cooperation with a crystal oscillator, and allows the microcomputer 22b to execute a predetermined control program based on this clock signal.

In the memory (ROM) of the microcomputer 22b, the microcomputer 22b stores arithmetic processing as described below.
The predetermined control program is stored in advance to be executed within the controller.

FIG. 2 illustrates a specific structure of the electric expansion valve 16, and 160 is a base member, which has a refrigerant inlet passage 161 at one end and a refrigerant outlet passage 162 at the other end. ing. 163 is a cylindrical member made of a non-magnetic material, and has two valve holes 163a and 163b opened at symmetrical positions for decompressing and expanding the refrigerant. 164 is a plunger made of a magnetic material that is slidably inserted into the inner circumference of the cylindrical member 163;
When the excitation coil 166 is not energized, the plunger 164 is pressed by the coil spring 165 and is at the lowest position, and the two valve holes 163a are closed.

163b is fully closed by the side surface of the plunger.

A fixed magnetic pole member 167 is arranged opposite to the plunger 164, and is fixed to the upper end of the cylindrical yoke 16B. 1
Reference numeral 69 denotes a magnetic end plate that constitutes a magnetic circuit of the excitation coil 166 together with the members 164, 167 and 168. When the excitation coil 166 is energized, a magnetic attraction force is generated between the plunger 164 and the fixed magnetic pole member 167, and the plunger 1
64 is attracted to the fixed magnetic pole member 167 against the spring force of the coil spring 165, and opens the valve holes 163a and 163b. Therefore, by applying a pulse waveform voltage to the excitation coil 166, the plunger 164 is continuously reciprocated to repeatedly open and close the valve holes 163a and 163b. Then, the duty ratio (on-off ratio in a predetermined period) of the pulse waveform input voltage to the excitation coil 166
By changing the opening/closing ratio of the valve holes 163a and 163b, the refrigerant flow rate can be adjusted. That is, by changing the duty ratio of the input voltage to the excitation coil 166, the opening degree of the expansion valve 16 can be substantially adjusted.

Next, the operation of the device of this embodiment will be explained as shown in FIGS. 3, 4 and 5.
This will be explained based on the flowchart shown in the figure. Furthermore, the fourth
The figure shows a control means portion of the control circuit 22 that determines whether the amount of refrigerant charged is appropriate or not, and FIG. shows. Step 400 in FIG. 3 is started by turning on the air conditioner operation switch (not shown), and in the next step 401, the initial conditions are the refrigerant superheat degree SHO, the gas shortage judgment temperature Tc, which is the target for expansion valve control,
Proportional gain Kp of PID control, integral time Ti, differential time Td, valve opening at startup, that is, duty ratio DTO,
Set counter N and judgment value Z. next step 40
2, the evaporator outlet refrigerant temperature before the compressor is started, that is, the ambient temperature, is measured by the second temperature sensor 21 and stored as TRO. In the next step 403, the clutch 11 is turned off.
N and start the compressor 10. next step 40
4, the refrigerant temperature at each inlet and outlet of the evaporator 17 is set to the first,
Measured by the second temperature sensors 20 and 21 and stored as TE and TR. In the next step 405, it is determined whether the elapsed time after starting the compressor 10 is more than 1 minute and less than 2 minutes. In this step 405, the count of the counter N is N>3.
0. The reason why N>60 is determined is that step 412 (stitch for calculating counter N), which will be described later, is followed by step 412 in which the process waits for two seconds. If the determination in step 405 is YES, step 41
Proceed to step 3, and calculate the temperature difference ΔTR (=TPO−TR) between the refrigerant temperature TRO before the compressor starts and the refrigerant temperature TR after the compressor starts.
and the judgment temperature Tc (=5°C), ΔTR is 5°
If it is equal to or higher than C, the answer is YES, and the determination value Z is set to 1 in step 414.

On the other hand, if the determination in step 405 is No, the process directly proceeds to step 406, where the refrigerant temperature difference between the entrance and exit of the evaporator is calculated and set as SH. In the next step 407, the deviation e7 between the target SHO and the actual SH is calculated, and in the next step 408, the duty ratio DT,
Calculate.

This duty ratio DT is a control signal that determines the valve opening degree of the electric expansion valve 16. In the next step 409, DT,
,,e, ,-2,e,-, is updated, and the counter is calculated in step 410. Next step 411
Two minutes after starting the compressor, the judgment value is 2.
When is 0, it is determined that there is a refrigerant shortage, and the process proceeds to the step of the erroneous determination means shown in FIG.

Further, when the judgment value 2=1 in step 411, that is, when the amount of refrigerant is normal, the judgment becomes NO, and in the next step 412, the process waits for 2 seconds and returns to step 404 again.

If the amount of refrigerant charged is appropriate, proceed to step 4 described above.
04 to 412 are repeatedly executed, and the electric expansion valve 16 is driven with the duty ratio DT according to the interrupt flowchart shown in FIG. 3, and the valve opening degree is controlled.

In the above embodiment, since the detection signal of the second refrigerant temperature sensor 21 used to control the valve opening of the electric expansion valve 16 is directly used to detect refrigerant shortage, the refrigerant The present invention has the advantage of not requiring a dedicated sensor for detecting refrigerant shortage and having a simple configuration. Therefore, the present invention can be similarly applied to a refrigeration cycle device that uses a temperature-operated expansion valve or the like as a pressure reducing device. However, in this case, it is necessary to newly provide a refrigerant temperature sensor on the outlet side of the evaporator 17 for detecting refrigerant shortage.

Note that if the outside temperature is detected in view of the characteristics shown in Figure 6 and the refrigerant shortage judgment temperature Tc is corrected to increase as the outside temperature rises, refrigerant shortage can be detected at an earlier point in time during high loads. can be detected.

Next, an embodiment of the erroneous discrimination means will be described based on FIG.

In this embodiment, the above-mentioned refrigerant shortage detection means is further provided with a function of checking for erroneous determination of refrigerant shortage. That is,
When it is determined in step 415 that there is a refrigerant shortage and the clutch 11 is turned off, the evaporator 17 outlet temperature TII during the refrigeration cycle operation and the outlet temperature T, 1 after the refrigeration cycle operation is stopped.
The temperature difference ΔT,I between the refrigerant and the refrigerant is detected, and it is determined that there is a refrigerant shortage only when the outlet temperature T, does not rise after a predetermined period of time. This is intended to prevent erroneous judgments due to a drop in outside temperature, etc.

That is, in the above example, the evaporator 1 before and after starting the compressor
Since the lack of refrigerant charge is detected based on the temperature difference TR0-TR of the refrigerant temperature at the 7th outlet, it may not be possible to make an accurate determination, for example, if the compressor is restarted at short intervals after it has stopped once. be.

In this case, the refrigerant temperature TRO at the outlet of the evaporator 17 before starting the compressor is low, so even if a sufficient amount of refrigerant is filled in the cycle, the temperature difference TR0 - TR
may not exceed the predetermined value Tc.

Hereinafter, the operation of the erroneous discrimination means will be explained based on FIG. 5.

If YES in step 411, step 42
Evaporator 17 outlet refrigerant temperature TRE during refrigeration cycle operation at 0
is measured, and then the clutch is temporarily turned off (step 421).

Clear counter N in step 422;
3 and 424, the elapsed time after the clutch is turned off is measured. Evaporator 17 after clutch 11 is turned off in step 425
Measure the outlet refrigerant temperature TR, and set TR at step 426.
-TRE, that is, the rise in the refrigerant temperature at the outlet of the evaporator 17 after the clutch 11 is turned off, is calculated and compared with the set temperature Tc.

Here, if (TR-TRE)>Tc, it is determined that the refrigerant charging amount is appropriate, and in step 427, the clutch 11 is turned on to perform normal operation, and the cycle returns to the start (step 400). If (TR-THE)≦Tc
In this case, the process proceeds to step 428, and it is determined whether the elapsed time after the clutch 11 is turned off is a set time (60 sec). Here, in the case of N>60, the clutch 11
Even though sufficient time has elapsed since the evaporator 17 was turned off, the temperature of the refrigerant at the outlet of the evaporator 17 does not rise, and in this case, it is determined that the amount of refrigerant charged is insufficient.

Therefore, in this state, the clutch 11 remains off. In this case, an indicator indicating refrigerant shortage may be displayed (step 429).

Incidentally, when it is determined in step 428 that N≦60, it is determined that sufficient time has not elapsed, and the process proceeds to step 423.
Go back and repeat the cycle.

In the example shown in FIG. 4, the control circuit for detecting refrigerant shortage detects the temperature difference between the refrigerant temperature at the outlet of the evaporator 17 before and after the compressor is started, but other methods may be used to detect refrigerant shortage, etc. Good too.

That is, when the superheat of the refrigerant on the outlet side of the evaporator 17 reaches a predetermined temperature or higher and this state continues for a preset time or more, it may be determined that an abnormal state such as refrigerant shortage has occurred. Of course, in this case as well, the clutch 11 is temporarily turned off by the erroneous determination means, and the erroneous determination of refrigerant shortage is detected when the temperature rises thereafter. Alternatively, in the case of using the electric expansion valve 16, the clutch 11 may be temporarily turned off when the valve opening is fully open, or when it becomes fully open, and the refrigerant shortage corridor may be detected by the subsequent temperature rise. good. Alternatively, the temperature of the air after passing through the evaporator 17 is detected by a blowing air temperature sensor, and the control means is activated when abnormal signs are observed, such as when the detected temperature continues to be higher than the set temperature for a set time or more. An abnormality may be determined.

Even in these cases, the erroneous determination means temporarily turns off the clutch 11, and after a predetermined period of time has elapsed, the refrigerant temperature rising at the outlet of the evaporator 17 confirms the detection of refrigerant shortage. As a result of the confirmation, if the temperature of the refrigerant at the outlet of the evaporator 17 rises by a predetermined value or more within a predetermined time, it is determined that the amount of refrigerant charged is an appropriate amount. In that case, the clutch 11 is turned on again and the operation is restarted. Conversely, if the temperature of the refrigerant at the outlet of the evaporator 17 does not rise by a predetermined value or more within a predetermined period of time, it is determined that the amount of refrigerant charged is insufficient. In that case, the clutch 11 is kept in the off state, and an indicator or the like displays the gas shortage.

Further, the present invention can be implemented in exactly the same manner with respect to a refrigeration cycle apparatus using a variable capacity type compressor 10.

Furthermore, in the above-described embodiment, the case where the control means for the electric expansion valve 16, the control means for determining refrigerant shortage, etc. are all configured using the microcomputer 22b has been described, but each of the above means can be configured individually. It is also possible to construct an electric circuit that is a combination of electric circuit elements.

Furthermore, it goes without saying that the present invention is not limited to use in automobile air conditioning, but is widely applicable to refrigeration cycles for various uses.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram including a refrigeration cycle and an electric control system, FIG. 2 is a sectional view illustrating the specific structure of an electric expansion valve, and FIG. figure,
4 and 5 are flowcharts illustrating control by a microcomputer, and FIG. 6 is a graph illustrating a refrigerant shortage determination method according to the present invention. 10... Compressor, 11... Electromagnetic clutch, 1
3... Condenser, detector, 16... Electric expansion valve (pressure reducing device). 17... Evaporator, 20.21... Refrigerant temperature sensor (temperature detection means), 22... Control circuit, 22b... Microcomputer. 2, Ning 40 method Figure 1 M2 Figure 3 Figure 5 - 〇 I.

Claims (4)

[Claims] (1) A compressor, a condenser connected to the discharge side of the compressor to condense gas refrigerant, a pressure reducing device connected to the downstream side of the condenser to depressurize and expand the liquid refrigerant from the condenser; an evaporator that is connected between the downstream side of the pressure reducing device and the suction side of the compressor and evaporates the liquid refrigerant that has passed through the pressure reducing device; and a control that detects an abnormal operating state of the refrigeration cycle and stops the operation of the compressor. means, a temperature detection means for detecting the refrigerant temperature on the outlet side of the evaporator, and a refrigerant temperature detection signal is inputted from the temperature detection means when the control means stops the operation of the compressor, and A difference in refrigerant temperature on the evaporator outlet side is detected, and if the temperature difference is greater than a predetermined value, the abnormal operation state signal detected by the control means is determined to be an erroneous signal, and if the temperature difference is less than a predetermined value. In this case, the refrigeration cycle control device includes erroneous discrimination detection means for determining that the signal output by the control means is a positive signal. (2) The control means receives a refrigerant temperature detection signal from the temperature detection means, calculates a difference in refrigerant temperature on the evaporator outlet side before and after starting the compressor, and if the temperature difference is less than a predetermined value, there is a refrigerant shortage. The refrigeration cycle control device according to claim 1, wherein the refrigeration cycle control device determines that . (3) The refrigeration cycle control device according to claim 1, wherein the pressure reducing means is an electric expansion valve that electrically controls the valve opening. (4) The refrigeration cycle according to claim 3, wherein the control means detects whether the valve opening of the pressure reducing device is at a maximum opening or a minimum opening. Control device.