JPS63169456A - Refrigeration cycle device - 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 [Field of Industrial Application] The present invention relates to a control device for a refrigeration cycle, and is effective for use in, for example, an air conditioner for an automobile.

[Conventional technology and its problems]

Conventionally, as a method of controlling an electric expansion valve in a refrigeration cycle, as shown in Japanese Utility Model Application No. 60-146267, the control constant is increased at startup to speed up the response, and the control constant is increased as time elapses. There is a way to achieve stability by making it smaller.

However, actual refrigeration cycles are extremely complex; for example, if the load conditions, cycle operating conditions, etc. change, the response of the cycle will also change, and even if stable superheat control had previously been achieved, it suddenly becomes unstable. There are times when it becomes. That is, the control constants that are stable during steady operation vary depending on the control conditions and load conditions at that time, and it is difficult to determine the control constants in a regular manner.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above points, and automatically determines the operating conditions of the refrigeration cycle, that is, whether stable superheat control is obtained or unstable, and automatically optimizes the operating conditions and load conditions. The purpose of this study is to determine appropriate control constants and to perform appropriate superheat control under all conditions.

[Structure and Operation] In order to achieve the above object, the present invention makes the control constant for controlling the electric expansion valve variable depending on the state of the refrigeration cycle, that is, the degree of hunting. If the hunting is large, the hunting is reduced by decreasing the control constant. That is, in the present invention, the valve opening degree of the electric expansion valve is controlled by PID control so that the refrigerant temperature difference between the inlet and outlet of the evaporator (superheat 5H=TR-TB) matches the target superheat SHO.

Here, if 5H-3HO=en, the hunting period can be detected by detecting the change in the deviation en. When the period is short, control gains (proportional gain Kp, integral time Ti, differential time Td
Hunting is reduced by reducing the

〔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 F collects the gas-liquid two-phase refrigerant that has passed through the expansion valve 6 and the air inside or outside the vehicle blown by the blower fan 18. The liquid refrigerant is evaporated by exchanging heat with the refrigerant. The cold air cooled by the latent heat of vaporization 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 241 that uses engine cooling water as a heat source.
A temperature control damper 243 and the like is built in to adjust the air volume ratio of warm air heated by passing through the heater core 241 and cold air passing through the bypass path 242 of the heater core 241 to adjust the temperature of the air blown into the vehicle interior. There is. 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 composed 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 denotes 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 22b.
The output circuit 22c controls energization of the electromagnetic clutch 11 and the electric expansion valve 16 based on the output signal.

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 an operation standard completion state. 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 microcomputer 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, completely closing the two valve holes 163a and 163b by the side surface of the plunger.

A fixed magnetic pole member 167 is installed opposite the plunger 164, and is fixed to the upper end of the cylindrical yoke 168. 1
69 is a magnetic end plate that constitutes the 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 continuously reciprocates, and the valve holes 163a and 163b are continuously opened and closed. By changing the duty ratio (on-off time ratio in a predetermined period) of the pulse waveform input voltage to the excitation coil 166, the opening/closing ratio of the valve holes 163a, 163b changes, and the refrigerant flow rate can be adjusted. That is, by changing the duty ratio of the input terminal to the excitation coil 166, the valve opening degree of the expansion valve 16 can be substantially adjusted.

The specific control method is as shown in Figure 3.
The number of changes in the magnitude relationship between the target superheat (SHO) and the actual superheat is counted, and if the number of changes is greater than or equal to a predetermined number of times, the control constant is changed to reduce the control gain. (In Fig. 3, Ti is increased.) In other words, section 1. If we count the points within which the magnitude relationship between the target super heat and the actual super heat changes, there are four points, a to d. Therefore, the integration time Ti is T, from T
Stabilization is achieved by increasing the control gain to 2 and decreasing the control gain 1/Ti.

Furthermore, in the interval t2, there are four points from e to h where the magnitude relationship between the target super heat and the actual super heat changes.

Therefore, Ti is further increased from T't to T, and the control gain is decreased.

As a result, the points at which the magnitude relationship changes in the interval t are 2 of i and j.
Therefore, Ti at this time, that is, T, is the optimal control constant under this operating condition, and from now on, this T
, to perform control.

A block diagram showing a control method in the control circuit 22 is shown in FIG. 4. The control method shown in FIG. 4 will be explained below using the flowchart in FIG. 5.

Started at step 600 (by turning on the A/C switch), set target 5HO-5°C1 sampling time θ=2 s e c, proportional gain Kp at step 601
=0.005, integration time Ti=2) differentiation time Td-0,
Initialize the counter N, I=O, and interval time to -60 seconds. In step 602, the clutch is set to 110N and the compressor 10 is started. In step 603, the evaporator 17 artificial refrigerant Tt and the evaporator 17 outlet refrigerant temperature TR are measured.

Then, based on this measurement value, in step 604, TR-T
Super heat SH is calculated by t. Further, in step 605, the target SHO and the measured super heat S
Calculate the deviation e from H. In step 606, the current efi is multiplied by the previous er+-1 to obtain Z. The sign of this Z is determined in the next step 607. That is, Z becomes positive when e, . . . and all-1 have the same sign, and 2 becomes negative only when el and e+q-1 have different signs. Therefore, by determining the sign of Z, it is possible to count the number of times the magnitude relationship between the target SHO and the measured super heat changes. this is,
In Figure 3, the number of each point 3-, = j is counted. That is, if Z is negative, the magnitude relationship has been reversed, and in this case, the process advances to step 614 and the target S
The number N of times the magnitude relationship between HO and super heat changes is counted. Further, in step 6O8, a counter (2) for defining a fixed time interval is added, and in step 609, this counter (2) is multiplied by the sampling time θ to calculate the elapsed time Time. In step 610, the elapsed time Ti
It is determined whether or not me has passed a predetermined time to (60 s e c), and if T'ime>t, the process proceeds to step 615, and the number of changes in the size of SHO and super heat N is determined to be a predetermined number of times (5 times). ). If N>5, the integration time Ti=TiX1.5, and by increasing Ti, the control gain is decreased to stabilize the cycle. In step 616, the elapsed time T
ime has passed for a predetermined period of time, the counter I is cleared, and in step 617, the counter N is cleared. In step 611, the valve opening D of the electric expansion valve 16 is determined by PID control (using Ti changed in step 618).
Calculate Tn. Then, in step 612, DT...
Replace (update) e, , e, , -. After performing the above flow, the process waits for sampling time θ in step 613.

Thereafter, the process returns to step 603, and the above-described cycle is repeated, and the electric expansion valve 16 is driven with the duty ratio DT and the valve opening is controlled according to the interrupt flowchart shown in FIG. In the above example, the stability or instability of the refrigeration cycle was determined based on how many times the magnitude relationship between the target superheat value SHO and the measured superheat value SH changed within the predetermined time T0, but conversely, the stability or instability of the refrigeration cycle was determined based on how many times the magnitude relationship between the target superheat value SHO and the measured superheat value SH changed. By measuring the time required for the size relationship to change,
By comparing that time with a predetermined time, it may be determined whether the refrigeration cycle is stable or unstable.

FIG. 6 shows a flowchart in this embodiment.

The difference from the above-described embodiment shown in FIG.
Go to 1. In this step 651, it is determined whether the time required for conversion a predetermined number of times is less than or equal to a predetermined time to (60 seconds). If it is less than the predetermined time, it is determined that the refrigeration cycle is in an unstable operating state and the process proceeds to step 618.

Furthermore, in the above example, the control gain is reduced when the number of changes in the magnitude relationship between the target superheat value SHO and the measured superheat value SH is greater than or equal to the predetermined number of times within the predetermined time t0. For example, within a predetermined time t0, (1) the number of changes in the magnitude relationship between the target superheat value SHO and the measured superheat value SH is greater than or equal to the predetermined number of times, and (2) the maximum and minimum values of the measured superheat value SH The control gain is reduced when the temperature difference is greater than or equal to a predetermined value.

Another embodiment will be described based on the flowcharts shown in FIGS. 7 and 8. The different parts from the example shown in FIG. 6 will be explained. In step 711, a predetermined time to (=60s
Compare the superheat maximum (1i7SHmax) in ec) with the superheat value SH measured this time, and if S
If Hmax<SH, SHmax is updated in step 712. In step 713, the minimum value SHmin of superheat within the predetermined time L0 is compared with the superheat value SH measured this time, and if SHmin>SH, SH
Update min. Next, in step 715, the predetermined time L
0 (=60 sec), and if a predetermined time has elapsed, step 716 determines that the number of changes N in the magnitude relationship between the measured superheat value SH and the target superheat value SHO is greater than or equal to the predetermined number of times (=5). Determine if N>5
In this case, the process advances to step 717. In step 717, the maximum superheat value SHmax within the predetermined time t0
and the minimum value SHmin, that is, 5HDIF is calculated.

Then, based on this calculation result, in step 718, 5H
DIF and a predetermined temperature difference (=5° C.) are compared. 5HDI
When F is 5°C or more, the integration time is Ti=TiX1.
5 and reduce the control gain to stabilize the cycle.

If it is determined in step 715 that the predetermined time t0 has elapsed,
At step 720, the counter ■, at step 721, the counter N, at step 722, SHmax, and at step 723, SHmin are cleared. Note that step 724
The subsequent steps are the same as the flowchart shown in FIG.

In addition, in the above example, the maximum super heat (isl(max
S due to the temperature difference between and the minimum superheat value SHmin
Although HD IF has been calculated, 5HDIF may be calculated based on the temperature difference between the maximum superheat (fisHmax) and the target superheat value SHO, as shown in step 757 in the flowcharts shown in FIGS. 9 and 10.

Conversely, step 7 in the illustrated flowchart in Figure 11.12
As shown at 67, 5HDIF may be calculated based on the temperature difference between the target superheat value SHO and the minimum superheat value SHmin.

Further, in the above example, superheat was determined based on the temperature difference between the inlet and outlet of the evaporator 17, but it may also be determined based on the outlet pressure of the evaporator 17 and the outlet refrigerant temperature. Furthermore, the structure of the electric expansion valve is not limited to the above-mentioned embodiment, but may be any other structure as long as it can be electrically controlled from the outside.Also, the compressor 10 may be a variable capacity compressor whose discharge capacity can be variably controlled. You can also use it as The control gain may be obtained by changing only Kp, only Ti, or a combination of Kp, Ti, and Td.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an example of the cycle of the present invention, Fig. 2 is a sectional view showing the expansion valve shown in Fig. 1, and Fig. 3 shows the relationship between the reversal of the superheat measurement value and the operating state of the refrigeration cycle. 4 is a block diagram showing the control method of the control circuit shown in FIG. 1, FIG. 5 is a flowchart showing the control method shown in FIG. 4, and FIGS. 7 to 12 show other control methods of the present invention. FIG. 13 is a flowchart showing the interrupt operation of the electric expansion valve. 10... Compressor, 13... Condenser, 16...
- Electric expansion valve, 17...evaporator, 22... control circuit.

Claims (8)

[Claims] (1) (a) a compressor; (b) a condenser connected to the discharge side of the compressor for condensing the gas refrigerant; and (c) a condenser connected to the downstream side of the condenser for condensing the liquid refrigerant from the condenser. (d) an electric expansion valve that expands under reduced pressure and electrically controls the valve opening degree; (e) target superheat setting means for setting a target value of superheat of the refrigerant at the outlet of said evaporator; and (f) actual means for determining the actual superheat of the refrigerant at the outlet of said evaporator. (g) determining a deviation between the target superheat determined by the setting device and the actual superheat determined by the determining device, and controlling the proportional-integral-differential control of this deviation to determine the valve opening of the electric expansion valve; (h) determining the number of times the magnitude relationship between the target super heat and the actual super heat is reversed within a predetermined time;
A refrigeration cycle device comprising control constant changing means for comparing this number of times with a preset set number of times and changing a control constant of proportional-integral-derivative control in the valve opening control means. (2) In the refrigeration cycle apparatus according to claim 1, the control constant changing means determines the temperature difference between the maximum value and the minimum value of superheat measured within a predetermined time, and It is characterized in that the control constant is changed when the temperature difference is greater than a predetermined temperature difference and the number of reverse rotations is greater than or equal to a set number of times. (3) In the refrigeration cycle device according to claim 1, the control constant changing means determines a temperature difference between the maximum value or minimum value of superheat measured within a predetermined time and a target superheat value. The control constant is changed when this temperature difference reaches a preset temperature difference and the number of reverse rotations is equal to or greater than a set number of times. (4) (a) a compressor; (b) a condenser connected to the discharge side of the compressor to condense the gas refrigerant; and (c) a condenser connected to the downstream side of the condenser to condense the liquid refrigerant from the condenser. (d) an electric expansion valve that expands under reduced pressure and electrically controls the valve opening degree; (e) target superheat setting means for setting a target value of superheat of the refrigerant at the outlet of said evaporator; and (f) actual means for determining the actual superheat of the refrigerant at the outlet of said evaporator. (g) determining a deviation between the target superheat determined by the setting device and the actual superheat determined by the determining device, and controlling the proportional-integral-differential control of this deviation to determine the valve opening of the electric expansion valve; (h) determining the temperature difference between the maximum value and the minimum value of superheat measured within a predetermined time, and when this temperature difference is greater than or equal to a predetermined temperature difference, controlling the valve opening degree; A refrigeration cycle device comprising control constant changing means for changing a control constant of proportional-integral-derivative control in the means. (5) (a) a compressor; (b) a condenser connected to the discharge side of the compressor to condense the gas refrigerant; and (c) a condenser connected to the downstream side of the condenser to condense the liquid refrigerant from the condenser. (d) an electric expansion valve that expands under reduced pressure and electrically controls the valve opening degree; (e) target superheat setting means for setting a target value of superheat of the refrigerant at the outlet of said evaporator; and (f) actual means for determining the actual superheat of the refrigerant at the outlet of said evaporator. (g) a valve opening for controlling the valve opening of the electric expansion valve by proportional-integral-derivative control of the deviation between the target superheat determined by the setting device and the actual superheat determined by the determining device; (h) determining the time required for the magnitude relationship between the target superheat and the actual superheat to reverse a predetermined number of times, and comparing this time with a preset time to control the valve opening degree; A refrigeration cycle device comprising: control constant changing means for changing a control constant of proportional-integral-derivative control. (6) In the refrigeration cycle device according to claim 5, the control constant changing means determines the temperature difference between the maximum value and the minimum value of superheat measured within a predetermined time, and It is characterized in that the control constant is changed when the temperature difference is greater than a predetermined temperature difference and the reversal time is greater than or equal to a set time. (7) In the refrigeration cycle device according to claim 5, the control constant changing means determines a temperature difference between the maximum value or minimum value of superheat measured within a predetermined time and a target superheat value. The control constant is changed when this temperature difference reaches a preset temperature difference and the reversal time is longer than a set time. (8) (a) a compressor; (b) a condenser connected to the discharge side of the compressor to condense the gas refrigerant; and (c) a condenser connected to the downstream side of the condenser to condense the liquid refrigerant from the condenser. (d) an electric expansion valve that expands under reduced pressure and electrically controls the valve opening degree; (e) target superheat setting means for setting a target value of superheat of the refrigerant at the outlet of said evaporator; and (f) actual means for determining the actual superheat of the refrigerant at the outlet of said evaporator. (g) a valve opening for controlling the valve opening of the electric expansion valve by proportional-integral-derivative control of the deviation between the target superheat determined by the setting device and the actual superheat determined by the determining device; (h) determining the temperature difference between the maximum or minimum value of superheat measured within a predetermined time and the target superheat value, and when this temperature difference reaches a preset temperature difference, opening the valve; A refrigeration cycle device comprising control constant changing means for changing a control constant of proportional-integral-derivative control in the temperature control means.