JPS6239347B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration system in which a refrigeration cycle is formed using a variable capacity compressor as a compressor and an electric expansion valve whose throttling amount can be controlled by an electric signal as a throttling device.

The refrigeration cycle of this type of refrigeration system is shown in FIG. In Figure 1, 1 is a variable capacity compressor, 2 is a condenser,
3 is an electric expansion valve, and 4 is an evaporator. 5 is a temperature T ₁ detected by a first temperature sensor 50 provided at the middle part (or the inlet part) of the evaporator 4
and the temperature T 2 detected by the second temperature sensor 51 provided at the outlet of the evaporator 4 SH' = T _{2 -} T ₁
Detects the condition of the refrigeration cycle and calculates this difference.
Electric expansion valve ₃
This is a control device that outputs a signal to control the amount of aperture. Reference numeral 6 denotes a detection control device that controls the capacity of the variable capacity compressor in accordance with the output of a state detector 61 that detects the target state of the refrigeration system. If the refrigeration equipment is an air conditioner, for example, the state detection device 61
It is a room temperature detector.

FIG. 2 is a diagram showing the temperature difference SH' with respect to the throttle amount O _v of the electric expansion valve 3. Cycle 1 is when the compressor capacity is relatively low, and cycle 2 is when the compressor capacity is large. Assume that the compressor 1 is currently operating at a capacity corresponding to cycle 1, the throttle amount O _v is O _v1 , and the temperature difference SH' is controlled to a predetermined value SH' _R. At this time,
When the output of the state detection device 61 requests large capacity, the capacity of the compressor 1 requests large capacity operation, and the cycle changes to cycle 2, the temperature difference SH' is set to a predetermined value SH' _R
In order to maintain this, the aperture amount needs to change from O _v1 to O _v2 .

However, the first and second temperature sensors 50, 5
Due to the detection delay of 1 and the response delay of the electric expansion valve 3, a considerable amount of time is required for the throttle amount to change to _Ov2 when changing from cycle 1 to cycle 2. Therefore, the operating point gradually moves from point A in cycle 1 to point B in cycle 2.

Since the temperature difference SH' is lower than SH' _R , the control device 5
tries to further reduce the throttle amount O _v to increase SH', and the evaporator 4 becomes too dry. However, as is clear from FIG. 2, in this state SH' cannot be increased even if the amount of aperture is reduced, that is, it is in an uncontrollable region. That is, in a region where the slope of the cycle curve is positive, the temperature difference SH' cannot be controlled by the control device 5 and is in an uncontrollable state. Once in this area, it is impossible to escape from this area, so it is clear that normal operation of the refrigeration system cannot be expected.

The present invention eliminates the drawbacks of the conventional devices described above and provides a refrigeration device that can maintain stable operation without entering an uncontrollable region.

FIG. 3 shows an improved capacity control device 7 of the capacity control device 6 according to one embodiment of the present invention. 71 is an amplifier that amplifies the difference between the temperature detected by the temperature detection thermistor 61' as the state detector 61 and a predetermined value; 72 is the capacitor 7 in accordance with the amplifier output V _A ;
74 is a voltage follower that amplifies the voltage V _C of the capacitor 73; 75 is a capacity control circuit that controls the capacity of the compressor 1 according to the output of the voltage follower 74; , for example, an inverter device. Here, the capacity control circuit 75 operates to increase the compressor capacity when the output of the voltage follower 74 increases.

Next, we will explain this operation. When the temperature sensor detected by the temperature detection thermistor 61' rises, its resistance value decreases, so the output V _A of the amplifier 71 becomes high V _A1 , V _A1 > V _C , and the capacity of the compressor 1 increases. is required. Since V _A1 >V _C , the charging/discharging circuit 72 charges the capacitor 73 and increases the voltage V _C by the following operation. Since V _A1 >V _C , the output of the operational amplifier 72A becomes Hi since the positive input > the negative input. This turns off transistor 72B, and
2C turns on. As a result, the operational amplifier 72G
Since the positive input of the operational amplifier 72 is zero V,
G, the transistor 72G has a negative input of the operational amplifier 72G, that is, the voltage across the resistor 72i is zero V.
In other words, the transistor 72H operates so that
is in the off state. On the other hand, the positive input of the operational amplifier 72E is the voltage V _RC obtained by dividing the power supply voltage by the resistors 72j and 72k, and the operational amplifier 72E and the transistor 72F are connected to the voltage V _D across the resistor 72D and the resistor 7.
In other words, a constant current flows through the resistor 72D such that the voltage Vj at both ends of the resistor 2j becomes equal, I _D =Vj/ _RD , and the capacitor 73 is charged with a constant current by this current _ID . Here, R _D is the resistance value of the resistor 72D. Due to this constant current charging, the current V _C of the capacitor 73 increases at a constant speed, the voltage of the voltage follower 74 increases accordingly, and the capacity control circuit 75 increases the capacity of the compressor at a constant rate.
As a result of this charging, when V _A1 <V _C , the output of the operational amplifier 72A becomes L ₀ . transistor 72
B is turned on and transistor 72C is turned off. Since the positive input of the operational amplifier 72E becomes the power supply voltage and the voltage Vj across the resistor 72j becomes zero V, the transistor 72F is turned off, the current _ID disappears, and charging stops. On the other hand, since the transistor 72C is turned off, a voltage V _L obtained by dividing the power supply voltage by the resistors 72K and 72L is generated across the resistor 72L, and this voltage V _L becomes equal to the voltage Vi across the resistor 72i. A constant current Ii flows, and the capacitor 73 is discharged by this current. As a result, the capacitor voltage V _C decreases so that V _A1 >V _C again, and the charging cycle begins again. Once the capacitor voltage V _C reaches V _A , charging and discharging of the capacitor 73 occurs near V _A1 ≈V _C , so it appears to substantially stop at V _A1 ≒ V _C . Conversely, when the temperature detected by the thermistor 61' decreases,
Since the resistance value increases, the output V of the amplifier 71
_A is low and becomes V _A2 , and V _A2 < V _C , compressor 1
capacity reduction is required. Since V _A2 <V _C , as described above, a constant current Ii flows through resistor 72i, which discharges capacitor 73 at a constant rate, and its V _C decreases at a constant rate. As a result, the output of the voltage follower 74C decreases at a constant rate, which causes the capacity control circuit 75 to decrease the compressor capacity at a constant rate. In the same way as when increasing the capacity, with V _A2 = V _C , the charging/discharging circuit 72
stops working. Therefore, in response to a request for capacity increase from cycle 1 to cycle 2 in FIG. 2, the transition from cycle 1 to cycle 2 is gradually made in accordance with the above-mentioned charging speed. Here, if this charging speed is selected to an appropriate value, the temperature difference SH' caused by the previous transition can be detected while following it with some delay, and the temperature sensors 50, 51, the control device 5, The refrigerant flow rate control system constituted by the electric expansion valve 3 will follow this and will not fall into an uncontrollable region. That is, by limiting the rate of change in compressor capacity to a speed at which the refrigerant flow control system can follow changes in compressor capacity using a charging/discharging circuit, which is a speed limiting device consisting of a charging circuit and a discharging circuit, the refrigerant flow rate can be The control system does not fall into an uncontrollable state.

As described in detail above, according to the present invention, the refrigerant flow control system consisting of the refrigeration cycle state detector, the control device, and the electric expansion valve does not fall into an uncontrollable state, and the refrigeration system always operates stably. This has the effect of providing the following benefits.

[Brief explanation of the drawing]

Figure 1 is a refrigeration cycle diagram, Figure 2 is the throttle amount O _v
FIG. 3 is a capacity control circuit diagram of a refrigeration system according to an embodiment of the present invention. 1... Variable displacement compressor, 3... Electric expansion valve,
5...Control device, 7...Capacity control device, 50,5
1... Temperature sensor as a refrigeration cycle state detector, 61... Status detector, 72... Charging/discharging circuit as a speed limiting device.

Claims (1)

[Claims] 1 A refrigeration cycle is formed using a variable capacity compressor as a compressor and an electric expansion valve as a throttling device, and a state detector that detects the target state of the refrigeration system, and a system that responds to the output of the state detector. a capacity control device that controls the capacity of the variable displacement compressor; a refrigeration cycle state detector that detects the state of the refrigeration cycle; and a throttle amount of the electric expansion valve according to the output of the refrigeration cycle state detector. The capacity control device controls the rate of change in capacity to a rate at which a refrigerant flow rate control system comprising the refrigeration cycle state detector, control device, and electric expansion valve can follow changes in compressor capacity. A refrigeration device configured to include a speed limiting device.