JPS62155473A - 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 control of an electric expansion valve in a refrigeration cycle, particularly in a refrigeration cycle having an electric expansion valve. It is suitable for use in cycles.

[Conventional technology]

The expansion valve in the refrigeration cycle generally controls the flow rate of the refrigerant so that the degree of superheat (superheat) of the refrigerant at the outlet of the evaporator remains constant.

The degree of superheating of the refrigerant can be determined from the refrigerant pressure and refrigerant temperature, so when using an electric expansion valve that electrically controls the opening of the expansion valve, the pressure at which the refrigerant pressure at the evaporator outlet is generally detected is The valve opening degree is controlled based on a detection signal from a sensor and a temperature sensor that detects refrigerant temperature.

[Problem that the invention seeks to solve]

By the way, when the refrigeration cycle for automobile air conditioning is started immediately after parking in the hot summer sun, the evaporator suction air temperature becomes extremely high, exceeding 40 degrees Celsius, so the cooling load on the evaporator becomes extremely large. When starting in the intermediate temperature range during the period, the cooling load on the evaporator becomes extremely small.

In this way, in a bath freezing cycle where the cooling load at startup varies greatly, if the opening of the expansion valve at startup is not set appropriately, the degree of superheating of the refrigerant at the evaporator outlet will become excessive at high loads. However, there are problems in that the cooling performance deteriorates and, conversely, the degree of superheating of the refrigerant at the outlet of the evaporator cannot be maintained at low loads, causing liquid refrigerant to return to the compressor.

The present invention has been made in view of the above points, and an object of the present invention is to accurately control the valve opening degree of an electric expansion valve at the time of activation according to cooling load conditions.

[Means for solving problems]

In order to achieve the above object, the present invention includes (a) a compressor; (b) a condenser connected to the discharge side of this compressor and condensing a gas refrigerant; (C1 connected to the downstream side of this condenser and said an electric expansion valve that depressurizes and expands liquid refrigerant from the condenser and electrically controls the valve opening degree; an evaporator that evaporates the refrigerant that has passed through the evaporator; (f) temperature detection means for detecting the refrigerant temperature on the outlet side of the evaporator; (a) the refrigerant temperature detection signal of the temperature detection means is manually input;
a second control means that calculates a valve opening signal of the electric expansion valve based on the refrigerant temperature on the outlet side of the evaporator, and controls the electric expansion valve after activation based on the valve opening signal. Adopt technical means to do so.

[Effect]

According to the above technical means, when the refrigeration cycle is started, the electric expansion valve can be started by the first control means with a valve opening degree that directly corresponds to the cooling load.

On the other hand, during steady operation after startup, the degree of superheating of the refrigerant at the evaporator outlet can be well controlled by controlling the valve opening degree of the electric expansion valve according to the refrigerant temperature at the evaporator outlet side using the second control means. .

〔Effect of the invention〕

Therefore, in the present invention, even when starting under various cooling load conditions, the electric expansion valve can be started with an appropriate valve opening degree corresponding to the cooling load, thereby improving cooling performance (cool-down performance) under high loads. Problems such as deterioration of refrigerant, increased power loss due to refrigerant liquid returning to the compressor at low loads, and damage to compressor valves can be successfully resolved.

〔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. Numeral 10 is a variable capacity compressor ν that can change the discharge capacity. Driven.

A condenser 13 is connected to the discharge side of the variable capacity 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 I4. cooling fan 14
is moved by the motor 14a.

On the downstream side of the condenser 13, there is a receiver 15 that stores liquid refrigerant.
An electric expansion valve 16 is connected via the. The expansion valve 16 has its opening degree electrically controlled, and 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 is connected to a gas-liquid two-phase refrigerant that has passed through the expansion valve 16 and has been depressurized, and is blown into the passenger compartment or the vehicle by a blower fan 18. The liquid refrigerant is evaporated by exchanging heat with outdoor air.

The cold air cooled by the latent heat of evaporation of the refrigerant is
It is blown out into the vehicle interior through the port 24. Heater unit 24
As is well known, the heater core 241 uses engine cooling water as a heat source, and the ratio of the amount of warm air heated through the heater core 241 to the cold air passing through the bypass passage 242 of the heater core 241 is adjusted to supply the air into the vehicle interior. A temperature control damper 243' etc. for adjusting the temperature of the blown air is built-in.

The downstream side of the evaporator 17 is connected to the suction side of the variable capacity compressor 10.

A refrigerant temperature sensor 19 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. This refrigerant temperature sensor 19 can be installed in the outlet piping to directly detect the refrigerant temperature, or it can be fixed tightly to the surface of the outlet piping and the sensor mounting part is covered with heat insulating material to detect the piping surface temperature. Either method may be used, but the latter method is more advantageous in practice due to ease of installation.

Since this refrigerant temperature sensor 19 detects the evaporator ambient temperature ta when the refrigeration cycle is stopped, in this example, it also serves as an ambient temperature sensor that detects the evaporator ambient temperature ta when the refrigeration cycle is started. It has become. Here, the evaporator ambient temperature ta is detected as one of the physical quantities related to the cooling load.

Reference numeral 20 denotes an air volume detection circuit, which detects the air volume Va to the evaporator 17, and in this example, includes a fan motor control circuit and an electric circuit that control the speed of the drive motor 18a of the ventilation fan 18 by a manual operation switch or automatic control. connected to
The air volume (a) is detected by determining the fan motor speed set by this fan motor control circuit.

Reference numeral 21 denotes an engine rotation speed detection circuit that detects the rotation speed N of the automobile engine 12, and detects the engine rotation speed by, for example, detecting the frequency of a pulse signal generated in the primary circuit of the ignition coil of the automobile engine 12. It is.

22 is a control circuit which receives detection signals 7'R, ta, V'a, of the refrigerant temperature sensor 19 and detection circuit 20.
An input circuit 22a to which N is input, and this input circuit 22
a microcomputer 22b that performs predetermined arithmetic processing based on an input signal from a;
The output circuit 22C controls energization of the electromagnetic clutch 11 and the electric expansion valve 16 based on the output signal of the output circuit 2b.

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 (R
The CPU, memory (ROM, RAM), and clock circuit are connected to each other via a path line. The memory (RAM) of the microcomputer 22b is the input circuit 2.
It receives each digital signal from 2a and temporarily stores it.
Each of these signals is selectively applied 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.

The memory (ROM) of the microcomputer 22b contains the arithmetic processing described above.
The predetermined control program is stored in advance for execution within the controller 2b.

Next, the variable capacity mechanism 101 of the variable capacity compressor 10
For example, this mechanism 101 is disclosed in Japanese Unexamined Patent Publication No. 5
As is known from Publication No. 8-155287,
By controlling the back pressure of the first section member by opening and closing the solenoid valve 102, the capacity adjusting member is displaced and the discharge capacity is changed.The opening and closing of the solenoid valve 102 is controlled by the duty of the output signal of the capacity control circuit 103. Control by changing the ratio. A detection signal from a low-pressure side pressure sensor 104 that detects compressor suction pressure (evaporation pressure) Pt is input to the control circuit 103, and this suction pressure PL is maintained at a predetermined value (for example, 2.1 kg/cm!G). By changing the duty ratio of the output signal, compressor 1
Controls the capacity of 0. That is, when the suction pressure PL becomes higher than the predetermined value, the compressor capacity is increased, and when it becomes lower than the predetermined value, the compressor capacity is decreased, thereby maintaining the suction pressure Pt at the predetermined value. Changes in compressor capacity can be continuous or discontinuous (
(in stages) is also acceptable. Note that the predetermined value is not a completely fixed value, and control may be added to slightly correct the predetermined value using a signal depending on the cooling heat load, for example.

Further, the variable capacity mechanism 101 of the variable capacity compressor 10
In addition to the one that electrically controls the capacity based on the detection signal PL of the pressure sensor 104 as described above, the one that controls the capacity electrically based on the detection signal PL of the pressure sensor 104, the one that controls the capacity electrically based on the detection signal PL of the pressure sensor 104, as well as the one that controls the capacity in response to the compressor suction pressure PL as described in the above-mentioned Japanese Patent Application Laid-Open No. 155287/1987. A purely mechanical structure may be used in which a valve is provided and the back pressure of the capacity adjustment member is controlled by the pressure-responsive valve to control the capacity.

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, it is pressed by the coil spring 165 and is at the lowest position, connecting the two valve holes 163a and 163b to the ring-shaped groove 164a on the outer periphery.
It is fully opened.

A fixed magnetic pole member 167 is arranged opposite to the plunger 164 and is fixed to the upper end of the cylindrical yoke 168. 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 closes 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 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 voltage to the excitation coil 166, the opening degree of the expansion valve 16 can be substantially adjusted.

In addition, in this example, the above-mentioned sawtooth is used as the electricity bill expansion valve 16.
The plunger 164 continuously reciprocates the valve hole 163a,
Although the description has been given of a duty control type in which the opening and closing of the plunger 163b is continuously repeated, a linear control type in which the amount of displacement of the plunger 164 is continuously changed by a servo motor or the like to thereby adjust the valve opening degree can also be used.

Next, the operation of the apparatus of this embodiment with the above configuration will be explained. First, to explain the basic operation mode, in the refrigeration cycle shown in Fig. 1, a variable capacity compressor that performs low pressure control is used as the compressor 1, so the low pressure PL is kept at a constant value by the capacity control of the compressor. (For example, 2.1 kg/ci
G). Therefore, the electric expansion valve 16 is operated at the refrigerant temperature T on the evaporator outlet side (in other words, on the compressor suction side).
By simply controlling I to a constant value, the superheat (degree of superheating) SH of the refrigerant at the evaporator outlet can be adjusted to the target value TR0 (for example, about 10
'c).

Therefore, the refrigerant temperature T on the evaporator outlet side is detected by the refrigerant temperature sensor 19, and this refrigerant temperature TR is the target temperature T.
. The control circuit 22 performs feedbank control of the valve opening degree of the electric expansion valve 16 so as to match the .

The operation of this embodiment will be specifically explained below with reference to the flowcharts shown in FIGS. 3 and 4. Step 100 is started by turning on the air conditioner operation switch (not shown), and in the next step 1゜1, the preset reference temperature of the evaporator ambient temperature tao = 30°C, the reference air volume V' aO”300m3/h, standard engine speed N,
. '=180Orpm.

Reference valve opening signal (duty ratio") DT, = 0.5, target refrigerant temperature TR0-10"C1 constant C, = 1/150,
c, = 1/1000. Read C,=1/16000. Next, in step 102, the evaporator ambient temperature ta detected by the refrigerant temperature sensor 19, the air volume Va and the engine rotation speed NE detected by the detection circuit 20.21 are read.

The next steps 103 to 106 are for calculating the expansion valve opening signal (duty signal) DT at the time of startup, and in this example, the reference cooling load at the time of startup is the ambient temperature tao=30°C, Air volume■a o=300m'/
h (when the speed of the blower fan motor is set to Hi) and set the standard engine rotation speed NEO to 1800 rpm.
m, and the reference valve opening degree at startup under this condition is D.
TO=0.5, and if it differs from the reference cooling load at the time of actual startup, the valve opening at the time of startup is corrected from the reference valve opening DTO according to the difference.

That is, in step 103, a correction value ΔDT based on the ambient temperature ta is calculated, and in step 1.4, the air volume Va is calculated.
In step 105, a correction value ΔDT is calculated based on the engine rotational speed NE. FIGS. 5 to 7 schematically show these correction values ΔDT, -ΔDT3.

Then, in step 106, an actual starting valve opening signal DT is calculated. In the next step 107, the electromagnetic clutch 11 is turned on (connected state B), compression [12] is started, and in the next step 108, the process waits for 2 seconds.

Here, FIG. 4 is a flowchart for driving the electric expansion valve 16, and the control flowchart shown in FIG. 3 is interrupted every predetermined time (for example, 0.005 seconds) and the memory ( The electric expansion valve 16 is driven by the valve opening signal (duty ratio signal) DT stored in the RAM.

In this case, in the example of FIG. 2, the expansion valve I6 is the valve hole 163a when the ii1 power to the exciting coil 166 is turned off.

Since the type in which the excitation coil 163b is open is used, the above duty ratio DT indicates the ratio of energization off to the excitation coil 166, and 1-DT) indicates the ratio of energization on to the excitation coil 166. And step 108 is 1 for 2 seconds!
During this period, the electric expansion valve 16 is driven according to the interrupt flowchart shown in FIG.
set by ′.

When the two seconds according to step 108 have elapsed, step 1
Proceed to step 09 and read the evaporator outlet side refrigerant temperature TR. In the next step 110, the deviation ΔT between the actual refrigerant temperature T and the target refrigerant temperature TRo is determined, and in the next step 111, the proportional-integral-derivative control (
The valve opening degree signal DT after startup is calculated using a method (PID control).

More specifically, the above DT is calculated from the following equation.

In the above equation, Kp, Ti, and Td are constants determined in advance through experiments and the like, and are stored in the memory (ROM). Further, subscripts n-n 1 and n-2 indicate the calculation order.

In the next step 112, wait for 2 seconds and step 10
9, and repeat steps 109 to 112. Then, according to the interrupt flowchart shown in FIG. 4, the electric expansion valve 16 is driven by the valve opening signal DT11 calculated in step 111, and the valve opening is set.

In the refrigeration cycle shown in FIG. 1, a variable capacity type is used as the compressor 10, and the low pressure PL is maintained at a predetermined value through capacity control. This is a type of refrigeration cycle in which the degree of superheating of the refrigerant at the evaporator outlet is controlled by controlling the valve opening degree of the electric expansion valve 16 according to the refrigerant temperature T at the evaporator outlet side and the refrigerant pressure PL. The present invention can also be applied to.

Furthermore, in the above-mentioned embodiment, a case has been described in which all the control means for the electric expansion valve 16 are configured using the microcomputer 22b, but the control means is configured by an electric circuit that is a combination of individual electric circuit elements. It is also possible to do so.

In the example shown in FIG. 1, the refrigerant temperature sensor 19 also has the function of detecting the ambient temperature of the evaporator before starting the compressor, but if necessary, the refrigerant temperature sensor 19
A dedicated temperature sensor may be separately provided to detect the ambient temperature of the evaporator.

In addition, as a physical quantity related to the cooling load of the evaporator 17,
In addition to the evaporator ambient temperature ta and the air volume (a) to the evaporator, the humidity of the air taken into the evaporator, the amount of solar radiation to the automobile, the outside temperature, etc. may be detected.

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 drawings]

The drawings show an embodiment of the present invention; FIG. 1 is an overall configuration diagram, FIG. 2 is a sectional view illustrating the specific structure of an electric expansion valve, and FIGS. 3 and 4 are diagrams showing a microcomputer. A flowchart illustrating the control according to the present invention, and FIGS. 5, 6, and 7 are operation explanatory diagrams. 10... Variable capacity compressor, 11... Electromagnetic clutch, 101... Variable capacity mechanism, 13... Pseudo compressor,
16... Electric expansion valve, 17... Evaporator, 19...
- Refrigerant temperature sensor (temperature detection means), 22...control circuit, 22b...microcomputer.

Claims (6)

[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) calculating a valve opening signal at the time of activation of the electric expansion valve based on a physical quantity related to the cooling load of the evaporator, and controlling the electric expansion valve using this valve opening signal; (f) a temperature detection means for detecting the temperature of the refrigerant on the outlet side of the evaporator; (g) a refrigerant temperature detection signal of the temperature detection means is inputted to detect the temperature of the refrigerant on the outlet side of the evaporator; A refrigeration cycle device comprising: a second control means that calculates a valve opening signal of the electric expansion valve based on temperature, and controls the electric expansion valve after activation based on the valve opening signal. (2) The refrigeration cycle device according to claim 1, wherein the evaporator ambient temperature is detected as a physical quantity related to the cooling load of the evaporator. (3) The refrigeration cycle device according to claim 1, wherein the air flow rate to the evaporator is detected as a physical quantity related to the cooling load of the evaporator. (4) The refrigeration cycle device according to claim 2, wherein the temperature detection means also serves as a detection means for detecting the ambient temperature of the evaporator. (5) The refrigeration cycle device according to any one of claims 1 to 4, wherein the electric expansion valve is configured to be duty-controlled. (6) Claim 1, wherein the compressor is a variable capacity compressor having a variable capacity mechanism that changes the discharge capacity, and is configured to maintain the compressor suction pressure at a predetermined value by changing the discharge capacity. The refrigeration cycle device according to any one of items 5 to 6.