JPH0198868A - Controller for refrigeration cycle - Google Patents

Abstract

PURPOSE: To reduce a shock as caused by the starting of a compressor by shifting the travel of an electric type expansion valve to a closure upon the start of a compressor to decrease the flow rate of a refrigerant of a refrigeration cycle for lowering a compression workload of the compressor. CONSTITUTION: A refrigerant temperature sensor 19 detects the temperature TE of a refrigerant on the inlet side of an evaporator and a sensor 20 detects the temperature TR of the refrigerant on the outlet side of the evaporator. A CPU 25 controls the travel of an electric type expansion valve 7 so that the temperature difference of the refrigerant between an inlet and an outlet of the evaporator 12 as given by the temperatures TE and TR of the refrigerant, namely, the degree of superheat coincides with a target temperature difference. Under such a condition, when a heat load decreases, a control is performed to reduce the travel of the valve 7 corresponding to a load. The CPU 25 outputs a control signal to an electromagnetic clutch 2 through an output circuit 24 to perform an ON-OFF control of the clutch 2. When the clutch 2 is linked, the travel of the expansion valve 7 is fully closed and no refrigerant flows to a refrigeration cycle to put the compressor 1 out of work. This enables relaxing of a shock as caused when the clutch 2 is linked (at the start of the compressor 1).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to a control device for a refrigeration cycle.

(Prior Art) Conventionally, in an automobile air conditioner, a compressor forming part of a refrigeration cycle is connected to an engine via a clutch.
The compressor is driven by an engine. Generally speaking, in order to prevent the evaporator from frosting in the refrigeration cycle, the automotive air conditioner detects the evaporation temperature of the refrigerant in the evaporator and disengages the clutch when the temperature falls below a predetermined temperature. The drive of the compressor was stopped, and when the temperature exceeded a predetermined temperature, the clutch was connected (connected) and the drive of the compressor was restarted.

(Problem to be solved by the invention) However, because this clutch is frequently turned on and off (connection/disconnection operation), the driver is shocked by the start of the compressor when the clutch is turned on (primary operation). There was a problem of giving.

Incidentally, as a related technique, there is cited Japanese Patent Application Laid-open No. 62-66064, which was previously filed by the applicant of the present invention.

(Object of the Invention) An object of the present invention is to provide a refrigeration cycle control device that solves the above-mentioned problems and can reduce the shock caused by the start-up of the compressor accompanying the clutch operation.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a compressor connected to an engine via a clutch and driven by the engine;
a condenser that condenses the gas refrigerant compressed by the compressor; an electric expansion valve that depressurizes and expands the liquid refrigerant condensed in the condenser and electrically controls the valve opening; In the refrigeration cycle, the refrigeration cycle includes an evaporator that evaporates refrigerant that has passed through an expansion valve, and a clutch control unit that connects and disconnects the clutch, and a clutch control unit that operates the clutch to start the compressor. The gist of the present invention is a refrigeration cycle control device including an expansion valve control means for controlling the electric expansion valve to close the opening of the electric expansion valve.

(Operation) The expansion valve control means controls the electric expansion valve so that the opening degree of the electric expansion valve is closed when the clutch control means operates the clutch and starts the compressor.

As a result, the opening degree of the electric expansion valve is closed when the compressor is started, so the refrigerant flow rate in the refrigeration cycle is reduced, the compression work of the compressor is reduced, and there is less shock when the compressor is started.

(Example) An example embodying the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a compressor 1 disposed in the refrigeration cycle receives driving force from an engine 3 via an electromagnetic clutch 2, and the compressor 1 is driven to supply refrigerant during the refrigeration cycle. supply

The condenser 4 is equipped with an engine cooling fan 5,
The high-temperature, high-pressure gaseous refrigerant sent from the compressor 1 is liquefied by cooling air. The liquid refrigerant obtained in the condenser 4 is sent to an electric expansion valve 7 through a receiver 6. This expansion valve 7 is an expansion valve having a mechanism in which the valve opening degree is electrically controlled.

Specifically, as shown in FIG. 2, a valve member 10 elastically supported in the closed state by a spring 9 on the narrow diameter portion 8a of the refrigerant flow path 8 is moved by the electromagnetic force of the electromagnetic coil 11, and the refrigerant flow path 8 is closed. is opened and closed. By changing the duty ratio of the input voltage to the electromagnetic coil 11, the opening/closing ratio of the refrigerant flow path 8 is changed, and the refrigerant flow mountain is adjusted. In other words, the electromagnetic coil 11
By changing the duty ratio of the input voltage to the expansion valve 7, the opening degree of the expansion valve 7 can be substantially adjusted.

At the electric expansion valve 7, the liquid refrigerant becomes a low-temperature, low-pressure mist.
It flows into the next evaporator 12. The evaporator 12 is an air passage 13
A blower motor 14 is provided nearby. By driving the blower motor 14, air inside or outside the vehicle passes through the evaporator 12. At this time, the mist refrigerant that has flowed into the evaporator 12 absorbs heat from the air inside or outside the vehicle, evaporates, is roughly heated, becomes a gaseous refrigerant, and is sucked into the compressor 1.

The cold air cooled by the latent heat of evaporation of the refrigerant in the evaporator 12 is blown into the vehicle interior via the heater unit 15. The heater unit 15 includes a heater core 16 that uses engine cooling water as a heat source, and adjusts the proportion of warm air heated by passing through the heater core 16 and cold air passing through a bypass passage 17 of the heater core 16 to blow into the vehicle interior. A temperature control damper 18 and the like for adjusting air temperature is built-in.

A first refrigerant temperature sensor 19 is provided on the refrigerant inlet side of the evaporator 12, and the sensor 19 detects the refrigerant temperature TE on the evaporator inlet side. Further, a second refrigerant temperature sensor 20 is provided on the refrigerant outlet side of the evaporator 12, and the second refrigerant temperature sensor 20 detects the refrigerant temperature TR on the evaporator exit side.

A control circuit 21 serving as a clutch control means and an expansion valve control means includes an input circuit 22 that inputs detection signals from the first and second refrigerant temperature sensors 19 and 20, and this input circuit 22.
a microcomputer 23 that performs predetermined arithmetic processing based on input signals from the microcomputer 2;
The output circuit 24 controls energization of the electromagnetic clutch 2 and the electric expansion valve 7 based on the output signal No. 3. The input circuit 22 has a built-in A/D converter etc. that converts analog signals into digital signals, and the output circuit 24
has a built-in relay circuit etc. that drives the load.

The microcomputer 23 is a central processing unit (hereinafter referred to as
CPU) 24, read-only memory (ROM>
26. Readable and rewritable memory (RAM>2
7, is equipped with a clock circuit 28, etc., and these CPU2
5. The ROM 26, RAM 27, and clock circuit 28 are connected to each other via a pass line. The ROM 26 has a built-in control program, and the CPU 25 executes various calculation processes based on this control program. RAM2
7 receives and temporarily stores each digital signal from the input circuit 22, and selectively provides each of these signals to the CPU 25. The clock circuit 28 works with a crystal oscillator to output a clock signal having a predetermined frequency, and based on this, the CPU
25 predetermined control programs are allowed to be executed.

The CPU 25 is connected to the first and second refrigerant temperature sensors 19.2.
A signal is input from 0 to detect the evaporator inlet side refrigerant temperature TE and the evaporator outlet side refrigerant temperature TR. Also, CPU25
is the electromagnetic coil 1 of the electric expansion valve 7 via the output circuit 24.
A drive signal is output to 1, and its valve opening degree (duty ratio > D
It is designed to adjust T.

The CPU 25 calculates the refrigerant temperature difference between the inlet and the outlet of the evaporator 12 given by the refrigerant temperatures TE and TR detected by the refrigerant temperature sensors 19 and 20 (=TR-TE>, that is, the temperature difference at which the degree of superheating is targeted) ( The valve opening degree DT of the electric expansion valve 7 is controlled to match the super heat) SHO, and when the heat load decreases in this state, the valve opening degree D is adjusted according to the load.
It is controlled to narrow down the T.

In this embodiment, PID control is used to control the opening degree of this valve. That is, the target superheat S as input
The valve opening degree DTn as an output is calculated using the following equation with respect to the deviation en between HO and the actual superheat degree 5t-1.

DT,= ...(1) However, DT, 1 is the previous valve opening, Kp, Td.

Ti is a control constant, en-1' and en-2 are deviations between the target superheat and the actual superheat degree from the previous time and the time before the previous time, and e is the sampling time.

Further, the CPU 25 outputs a control signal to the electromagnetic clutch 2 via the output circuit 24 to control the clutch 2 on and off (connection/disconnection).

That is, it is determined whether the evaporator inlet side refrigerant temperature TE detected by the refrigerant temperature sensor 19 is below a predetermined temperature device O or above a predetermined temperature TEH, and when the refrigerant temperature is below O, the clutch 2 is activated. is turned off (cut) and the predetermined temperature -r
E+: Turn on clutch 2 (connect) when it is above
It looks like this.

Next, the operation of the refrigeration cycle control device configured as described above will be explained.

When the CPU 25 determines that the air conditioner switch (not shown) has been turned on, it starts the process shown in FIG. 3. First, the CPU 25 sets initial conditions (step 1). This is the target superheat 5HO = 5°C, the first setting device o for the evaporator inlet refrigerant temperature = -1°C, the second setting value TEHi -4°C for the evaporator inlet refrigerant temperature, and the control constant for PID control. Kp=0.005, T+=40, Td=1, en-
1=O' en-2=O.

When turning on the air conditioner, step 1 described above
After the predetermined setting operation by
When reaching step 20), proceed to the next step.

The CPU 25 determines the valve opening degree DTrl of the expansion valve 7 =O (fully open)
After setting (step 2), the clutch 2 is turned on (connected), the timer operation is started, and the timer operation is waited for a predetermined time e (for example, 5 seconds) (steps 3 and 4).CPU 25
executes the interrupt routine shown in FIG. 4 at predetermined minute intervals, that is, reads the valve opening degree DTn at each time in the main routine shown in FIG. (Step 21)
. Therefore, in steps 2 to 4 of the main routine, the valve opening degree is kept fully closed until the starting time θ of the compressor 1 has elapsed. This state is shown by Pl in FIG. The time e during which the valve opening is fully closed (DTn = O) is the time during which the degree of superheating SH becomes equal to or higher than the target superheat level -8380, and the time e is determined in advance.

After that, the CPU 25 adds a certain ratio (ΔDT> to the valve opening degree of the expansion valve 7 at the time of startup set above DTn = O (fully closed) (step 5).
25 is the evaporator inlet refrigerant temperature TE.

Incorporating the evaporation outlet refrigerant temperature TR (step 6)
, the degree of superheating SH is determined by calculating the temperature difference SH (=TR-TE>) (step 7).Then, CP
U25 compares the obtained superheat degree SH with the set target super heat SHO (step 8). Initially, the superheat degree SH is higher than the target super heat SHO, so 1
Wait for seconds (Step 9) Repeat steps 5 to 9.

That is, the opening degree of the expansion valve 7 is gradually increased by a constant rate (ΔDT>).The expansion valve 7 is opened by executing the interrupt routine shown in FIG. 4 to increase this valve opening degree DT. In this state, the valve opening increasing operation shown at P2 in FIG. 5 is performed.

Thereafter, in step 8, the CPU 25 determines that when the degree of superheat SH becomes equal to or less than the target superheat SHO (SH
<5HO), while reading the evaporator inlet side refrigerant temperature TE measured by the first refrigerant temperature sensor 19 and the evaporator outlet side refrigerant temperature TR measured by the second refrigerant temperature sensor 20 (Step 1
0), the evaporator inlet side refrigerant temperature TE is compared with the first set position O of the evaporator inlet refrigerant temperature (step 11).

Then, the evaporator inlet side refrigerant temperature TE is set at the first setting position 10 or more of the evaporator inlet refrigerant temperature (TE≧TE L
o >, the CPU 25 sets the superheat degree SH (=TR-TE
Step 12) Subtract the target overheat SHO from the superheat degree SH and find the deviation en (=
SH-3HO) is determined (step 13). And C
The PU 25 calculates the valve opening degree DTn using the above equation (1) (step 14), changes the variables (DTn, e, eo-i) (step 15), waits for 2 seconds (step 16), and performs steps 10 to 16 described above. Repeat.

The valve opening degree DTn obtained in this manner is used to drive the opening degree of the expansion valve 7 by executing the interrupt routine shown in FIG. In this state, superheat control indicated by P3 in FIG. 5 is performed.

Further, in step 11, when the evaporator inlet side refrigerant temperature TE reaches the first set position O of the evaporator inlet refrigerant temperature (TE<position Lo>), the CPU 25 performs the following steps to prevent the evaporator 12 from frosting. The CPU 25 sets the opening degree DTn of the expansion valve 7 to 0 (fully closed) (Step 17) and turns off the clutch 2 (Step 1).
8).

Then, the CPU 25 measures the evaporator inlet refrigerant temperature RE (step 19), and when the temperature RE becomes equal to or higher than the second set value TEHi (TE≧TEHi) (step 20), the process returns to step 2.

As described above, in this embodiment, when the clutch 2 is connected, the expansion valve 7 is fully closed, so the refrigerant does not flow in the refrigeration cycle and the compressor 1 does not perform any work, so the clutch 2 The shock that occurs when the compressor 1 is connected (when the compressor 1 is started) can be alleviated.

Note that this invention is not limited to the above embodiment; for example, in the above embodiment, when the clutch 2 is connected, the expansion valve 7 is
Although the valve opening was set to close, it may be the minimum valve opening to return the compressor oil to the compressor together with the refrigerant.In short, it is the valve opening to alleviate the shock when the compressor starts up. Good to have.

Further, in the above embodiment, the valve opening degree is determined for a predetermined time e after the clutch is connected.
Although the valve opening was increased until 5t-1 reached the target value after the elapse of time, the valve opening may be returned to the valve opening when the clutch 2 was disengaged, and then the superheat control may be performed.

Further, in the above embodiment, the degree of superheating is detected by the difference in temperature of the refrigerant at the outlet and outlet of the evaporator, but the degree of superheating may be detected by the pressure and temperature of the refrigerant at the outlet of the evaporator.

Roughly speaking, in each of the above embodiments, the case where the clutch 2 is engaged/disengaged to prevent frosting has been explained, but in other cases, for example, in a refrigeration cycle where the clutch is disengaged during an acceleration state, the engagement/disengagement operation may be used. The present invention may be implemented at the time of.

Effects of the Invention As described in detail above, the present invention exhibits an excellent effect of alleviating the shock caused by the start-up of the compressor accompanying the clutch engagement operation.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a υNB device of a refrigeration cycle embodying the present invention, Fig. 2 is a cross section 1 to 5 of an electric expansion valve, and Fig.
The figure is a time chart showing the degree of superheating and the opening degree of the expansion valve. 1 is a compressor, 2 is an electromagnetic clutch, 3 is an engine, 4 is a condenser, 7 is an electric expansion valve, 12 is an evaporator, and 21 is a control circuit as clutch control means and expansion valve control means.

Claims (1)

[Claims] 1. a compressor connected to the engine via a clutch and driven by the engine; a condenser that condenses the gas refrigerant compressed by the compressor; and a depressurized and expanded liquid refrigerant condensed by the condenser. In the refrigeration cycle, the refrigeration cycle includes an electric expansion valve that electrically controls a valve opening degree, and an evaporator that evaporates refrigerant that has passed through the electric expansion valve, and a clutch control means that connects and disconnects the clutch. and an expansion valve control means for controlling the electric expansion valve so that the opening degree of the electric expansion valve is closed when the clutch is engaged by the clutch control means to start the compressor. A unique refrigeration cycle control device.