JPS59197760A - Controller for refrigerator - 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 The present invention relates to a control device for a refrigerator suitable for a refrigerator in which suction is strictly performed.

For refrigerators that have a wide temperature control range (-25°C to +25°C) and require strict temperature accuracy, such as the two-wheeled refrigeration system "Umi", it is necessary to use a temperature sensing element for temperature control. However, from a practical point of view, it also has the drawbacks mentioned above, although platinum temperature resistors have been used for a long time because they are usually highly accurate and have excellent linearity.

(1) It is an extremely expensive element.

(2) Because the temperature coefficient is small (approximately 04Ω/'C),
It is easily affected by the resistance of the IJ-wire and the contact resistance of the connection part, and the accuracy may deteriorate.

This poses a problem in terms of stability (reliability).

(3) Methods to improve the drawback of (2) above include a method of compensating for error resistance in the adjustment stage and a method of using a Blinozi circuit configuration (4-wire type), but the former method is effective against environmental stresses such as vibration and shock. The change in contact resistance due to influence is due to the addition of force, and the latter has the disadvantage of making the already expensive product even more expensive.

The present invention has been proposed in view of the above points, and its purpose is to provide an inexpensive and inexpensive temperature control device for use in refrigerators that have a wide temperature control range and require high temperature accuracy. The aim is to realize something that has accuracy and surface reliability.

The present invention (lt) as a temperature detection element for temperature control.

An element with non-linearity is used as an output characteristic with respect to temperature in the temperature control range required for the refrigerator, and the characteristics of the element are corrected so that the temperature can be controlled with the required accuracy in the required temperature control range. The gist of this is a control device for a refrigerator, which is characterized by the provision of a correction means, and is generally used as a temperature detection element, is inexpensive, has a wide temperature control range, and requires strict temperature accuracy When non-linearity is noticeable and accuracy cannot be ensured up to that temperature, an element with non-linear output characteristics is used, and a means for correcting the non-linear characteristics of this element is provided. Since problems in terms of accuracy are covered by the correction, it is possible to obtain a control device that is inexpensive, highly accurate, and highly reliable.

The present invention will be explained below based on seven examples.

In FIGS. 1 to 4, l is a compressor, 2 is a condenser,
3 is a throttle device and a 4-place evaporator, and the above constitutes a refrigeration cycle. Reference numeral 5 denotes a control device that controls the compressor 1 via a temperature control circuit 8 based on the temperature detected by the thermistor-side temperature resistance element 7 that detects the temperature of the indoor air 6 and the temperature set by the digital temperature setting device 9. It is designed for ON/OFF control. In addition, in the above-mentioned refrigeration cycle and control device, only relevant parts are shown and other parts are omitted.

Figure 2 shows the temperature detection circuit, vl is the constant voltage source, v2 is the bridge output voltage + R4 is the series resistance, Rt is the internal temperature air resistance, AI) is the analog/digital converter + D
J indicates a non-linear internal temperature digital quantity.

FIG. 3 shows a temperature correction circuit, which includes a correction temperature digital quantity storage circuit 10. Linearization correction amount selection circuit 11. This circuit has an auxiliary circuit 12 and corrects a non-linear internal temperature digital quantity 1) to a linear internal temperature digital quantity Dt.

Figure 4 shows the temperature comparison circuit, which measures the internal temperature digital M:D.
Comparator C compares t and set temperature digital quantity D8, and compares the internal temperature digital quantity 1) When t is large, an operation command is issued to the compressor 1, when it is small, a stop command is issued;
It is designed to issue commands to stop.

In the above configuration, the high-temperature, high-pressure refrigerant gas compressed by the compressor 1, which is operated according to a command from the refrigerator control device 50, radiates heat in the condenser 2, is condensed and liquefied, and reaches the throttling device 3. The decompressed refrigerant enters the evaporator 4, absorbs heat from the internal air 6 flowing through the evaporator 4, evaporates and vaporizes, and returns to the compressor 1, completing the refrigeration cycle.

During this period, the internal temperature of the internal air 6 is - temperature vs. M (
It can be sensed through resistance by the thermistor-side temperature resistor 7, which has a non-linear resistance characteristic and a large temperature coefficient of several +00Ω/C. This sensed resistance is converted and detected by the temperature control circuit 8, and the set temperature digital quantity 1)s of the digital temperature 18 setting device 9 is detected.
compared to

When the temperature inside the refrigerator becomes lower than the set temperature digital 'fVj-D8, the temperature control circuit 8 stops the operation of the compressor 1 and stops the cooling operation. Further, when the temperature inside the refrigerator rises due to heat intrusion from the outside and becomes higher than the set temperature digital amount D8, the temperature control circuit 8 is activated again.

Issue a command to operate compressor 1 and restart cooling operation.

The operation of the temperature control circuit 8 will be explained below with reference to FIGS. 2 to 4.

FIG. 2(a) shows a temperature detection circuit in which when the power is turned on and the constant voltage source v1 is activated, the Brinon output voltage V2 is determined by the internal temperature air resistance i<
A non-linear electric current 11F is generated which is correlated with t.

Fig. 2 (b) shows the relationship between the internal temperature air resistance R, t and the internal temperature, and Fig. 2 (, ) shows the relationship between the output voltage v2 and the internal temperature (non-linear voltage). FIG. 2(d) shows the relationship between the digital tDt+ and the internal temperature (non-direct internal lung temperature digital quantity).

In this circuit, the bridge output voltage V2 is determined by the following equation.

Bridge output voltage V2== Note that the above equation originally takes into account the lead wire resistance of the thermistor resistance temperature detector 7 and the contact resistance of the connection part, but since the thermistor resistance temperature detector 7 has a large temperature coefficient, it can be ignored. is also omitted as it has no effect. In this example, a temperature sensing element with negative characteristics is used.

Now, the non-linear bridge output voltage v2, which is correlated with this temperature, is compared with the set temperature digital gDs of the digital temperature setting device 9, and in order to match the level, it is correlated with the internal air temperature using analog/digital converters A and Dl. is converted into a non-linear internal temperature digital value 1Dv1. Next, FIG. 3(a) shows a temperature correction circuit that calculates the non-linear internal temperature digital amount Dt detected by the temperature detection circuit of FIG. 2(a).
l is.

Furthermore, in order to facilitate comparison with the linear set temperature digital amount Ds, it is taken into the linearization correction amount selection circuit 11,
By the linearization correction amount selection circuit 11.

A correction temperature digital amount is selected according to the non-linear internal temperature digital amount DJ from the correction temperature digital amount storage circuit 10 which predefines the temperature error amount from the straight line of the standard thermistor resistance temperature detector 7. , is added to the non-linear internal temperature digital quantity DJ in the adder circuit 12 to correct it into a linear internal temperature digital quantity Dt. Figure 3 (
1)) is the relationship between the internal temperature digital quantity Dt and the internal temperature (
Represents the linear internal temperature (digital quantity). - Next, FIG. 4 shows a comparator circuit, and t is a setter for the internal temperature digital value linearly corrected by the temperature correction circuit shown in FIG. 3(a).

A comparator C compares the digital value Da with the internal temperature digital value Dt, and issues an operation command to the compressor 1 if the internal temperature digital value Dt is large. If it is still small, a stop command is issued to compressor 1 to control the temperature.

As described above, this embodiment uses a control device in which a thermistor resistance temperature detector, which is inexpensive and has a characteristic of a large temperature coefficient, is subjected to easy digital correction, so that the following effects can be obtained.

(1) Accuracy equivalent to when using a platinum resistance thermometer! I get caught.

(2) Temperature errors due to lead wire resistance and connection resistance are eliminated, and stability (reliability) is improved.

(3) Since an inexpensive temperature detection element is used, the overall cost can be reduced.

In the above embodiments, a thermistor resistance temperature detector was used as an example of the fd and temperature detection element, but it is not necessarily limited to this. It does not matter if the number of elements is small. It is not necessary to limit the output to "resistance change" as an element with respect to temperature.
It may be '+i pressure change'.

[Brief explanation of drawings]

1 to 4 show an embodiment of the present invention, in which FIG. 1 is a block diagram of a refrigerator, and FIG. 2 (a). (b), (c), and (d) are diagrams showing the temperature detection circuit, (a) is a circuit diagram, (b) is a diagram showing the relationship between internal temperature air resistance and outside internal temperature, and (C ) is a diagram showing the relationship between output voltage and internal temperature, (d) is a diagram showing the relationship between output voltage and internal temperature,
Figure 3 (-) and (b) are diagrams showing the temperature correction circuit, (a) is a circuit diagram, and (b) is a linear digital quantity and internal temperature. Diagram showing the relationship between
The figure is a circuit diagram of a temperature comparison circuit. 1. Compression, 2. Condenser, 3° throttling device, 4.2 evaporator, 5.
Control device, 7 thermistor 41]j temperature resistance element, 8: temperature control circuit, 9゛digital flow setting device, 10゛corrected temperature digital quantity storage circuit. 11 Linearization correction amount selection circuit, 12' Addition trowel circuit.

Claims (1)

[Claims] As a temperature detection element for temperature control, we use an element that has nonlinear output characteristics with respect to temperature in the temperature control range required for the refrigerator, and also 1. A control device for a refrigerator, characterized in that a correction means is provided for correcting the temperature so that temperature control can be performed with accuracy.