JPH0512680Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a control sensor for giving a control signal to an expansion valve when refrigerant is supplied to a cooler, and the invention relates to a control sensor that provides a control signal to an expansion valve when refrigerant is supplied to a cooler. are housed in the same protection tube, and the vapor pressure characteristics of the refrigerant at the same point are detected.
These outputs are used to control the refrigerant liquid expansion valve.

Conventionally, there are two types of expansion valves: temperature-type expansion valves in which the sensor and actuator functions are mechanically integrated, and separate type expansion valves in which the sensor and actuator functions are separated and connected by electrical signals, but the present invention is based on the latter. It is one of the types.

When refrigerant is supplied into the cooler using an expansion valve, if there is an excess of refrigerant in the cooler, the refrigerant is stored in the cooler, and the heat exchange area of the cooler is reduced by this excess storage. This will reduce the cooling capacity of the cooler, and furthermore, it will be returned to the suction side of the compressor as liquid refrigerant, causing trouble in compressor operation. On the other hand, when the refrigerant supply is insufficient, the refrigerant liquid has already been gasified in the heat exchange section near the outlet side of the cooler, and the so-called superheated refrigerant simply passes through, reducing the cooling area. ,
On the compressor side, the superheated gas is also compressed, resulting in a reduction in the capacity of the compressor, resulting in a reduction in the capacity of the cooling system.

Therefore, the refrigerant supply must be controlled so that the refrigerant liquid is completely vaporized only at the point on the outlet side of the cooler. Both refrigerant temperature sensors were installed individually, and their outputs were used to control the throttle expansion valve. In this case, since the refrigerant pressure sensor and the refrigerant temperature sensor are not detected at the same point, it is not possible to fully understand and detect the refrigerant vapor pressure characteristics, and it is necessary to output a highly accurate control signal to the expansion valve to control it. There were some drawbacks to both, and the mounting structures for both were not satisfactory.

The present invention was developed in view of these points, and its feature is that the expansion valve for supplying refrigerant to the cooler can be controlled by detecting the degree of superheating of the refrigerant. The valve control sensor includes a protection tube having a pressure-receiving surface that can directly face the refrigerant on the suction side of the compressor, and the refrigerant pressure sensing element and the refrigerant temperature sensing element are respectively brought into contact with the back surface of the pressure-receiving surface to protect the refrigerant pressure sensing element and the refrigerant temperature sensing element. The refrigerant pressure sensing element and the three fixed resistors form an electric bridge (bridge circuit), and the power supply voltage of the electric bridge is applied to the input terminal side of the pressure sensing element to detect the pressure. The pressure sensing element is configured to be able to detect pressure based on the output voltage of the electric bridge taken out from the output terminal side of the element, and the input terminal side of the temperature sensing element is connected to the output terminal side of the pressure sensing element, so that the voltage component of the power supply voltage is connected to the output terminal side of the pressure sensing element. It is characterized by functioning as a piezoresistor.

In this case, the pressure receiving surface may be formed by a diaphragm provided at the pointed end of the protective tube, or may be constructed by other means.

Furthermore, if the calculations for controlling the expansion valve are performed within the protection tube, the circuit structure within the regulator can be simplified, the protection tube can be easily installed, and the number of output conductors can be reduced, which is economically advantageous. Become.

This will be explained with reference to the diagram. FIG. 1A is a system diagram of a conventional cooler, and FIG. 1B is a system diagram of a cooler using the expansion valve control sensor of the present invention. In the figure, 1 is a cooler equipped with a cooling fan, 2 is a refrigerant expansion valve that throttles and controls the amount of refrigerant, 3 is an air temperature sensor that detects the cooled air temperature, and 4 is a compressor (in the diagram, 5 is a refrigerant pressure sensing element attached to the suction pipe 4 and detects the pressure of the refrigerant; 6 is the suction pipe 4;
7 is a refrigerant temperature detection sensor provided on the inlet side of the cooler 1, and 8 is a regulator. In Figure A, the refrigerant pressure sensing element 5 and the refrigerant temperature sensing element 6 are individually independent conversion elements, so they are inserted into the suction pipe 4 individually, or a branch pipe is provided from the suction pipe 4 to detect the refrigerant. This means that the temperature and pressure are being detected. Therefore, as mentioned above, it is clear that this is not necessarily ideal for understanding the state of the refrigerant as it is.

Figure 1(b) is based on the present invention, and the refrigerant pressure detection element 5 and refrigerant temperature detection element 6, which detect the pressure and temperature of the refrigerant in the suction pipe 4 taken in by the compressor, are housed in the same protection tube. It is possible to grasp and detect the state of the refrigerant in the pipe 4 with high precision, and output a control signal for the expansion valve.

FIG. 2A is a view of an example of an expansion valve control sensor in which converting elements 5 and 6 for refrigerant pressure and refrigerant temperature are housed in the same protection tube 9, and FIG. 2B is an enlarged view of the converting element portion. In the figure, a refrigerant pressure sensing element 5 is a semiconductor silicon thin film or a strain gauge, and is attached to the back surface of a diaphragm 10 provided at the pointed end of a protective tube 9. The diaphragm 10 is strained by the refrigerant pressure in the suction pipe 4, its resistance value changes, and a pressure signal is output as the refrigerant pressure sensing element 5.

If a thermocouple or thermistor is used as the refrigerant temperature sensing element 6, its joint is attached to the back surface of the diaphragm 10 and placed on the pressure sensing element 5 to output a temperature signal. Therefore, both conversion elements 5 and 6 can detect and output the state of the refrigerant with high precision at the same point.

FIG. 3 is an example of a processing circuit diagram of the outputs of both conversion elements 5 and 6. Since a semiconductor is generally used for the refrigerant pressure sensing element 5, its output is susceptible not only to diaphragm distortion but also to temperature.

This correction utilizes the temperature sensing element 6 and is performed by an electric bridge 11 (hereinafter referred to as a bridge circuit).

The detailed configuration will be explained below based on the same figure.

In the figure, fixed resistors 11a, 11b, and 11c constitute a bridge circuit 11 together with the refrigerant pressure sensing element 5. 13c/13d are voltage input lines of the bridge circuit 11 drawn out from the circuit voltage power source in the arithmetic circuit 12, 13c, which is a positive input line, is connected to the input terminal side of the refrigerant pressure detection element 5, and 13d is connected to the resistor 1.
It is connected to the connection point between 1a and 11b.

Reference numerals 13a and 13b are output signal lines of the bridge circuit drawn out between the connection points between the output terminal side of the refrigerant pressure sensing element 5 and the resistors 11b and 11c.

According to this configuration, when a constant voltage power source is applied to the bridge circuit through 13c/13d, when distortion occurs in the diaphragm 10 and the resistance value of the refrigerant pressure sensing element 5 changes, the resistance value of the refrigerant pressure sensing element 5 changes accordingly.
The output voltages of 3a and 13b change, and by detecting the output voltages on the arithmetic circuit 12 side, the refrigerant pressure in the suction pipe 4 can be detected via the diaphragm 10.

However, since the detection element 5 uses a semiconductor, the resistance value of the refrigerant pressure detection element 5, that is, the output voltage of the bridge circuit 11, changes even when the temperature of the refrigerant in the suction pipe 4 changes. , it is impossible to accurately detect pressure unless this is compensated for.

Therefore, in this embodiment, the input terminal side of the refrigerant temperature sensing element 6 is connected to the output terminal side of the refrigerant pressure sensing element 5, and the signal line 13e connected to the output terminal side of the refrigerant temperature sensing element 6 is connected to the arithmetic circuit. leading to the side.

According to this embodiment, the refrigerant temperature sensing element 6 substantially functions as a voltage dividing resistor of the circuit voltage power source applied via the input line 13c between the refrigerant temperature sensing element 5 and the refrigerant pressure sensing element 5. Even if the resistance value of the refrigerant pressure sensing element 5 changes due to a change in refrigerant temperature,
Since the element resistance of the refrigerant temperature sensing element 6 changes in proportion to this, the input voltage applied to the bridge circuit 11 becomes approximately constant, thereby making temperature compensation possible.

Furthermore, in this embodiment, the bridge circuit 11
The pressure detection output obtained through the output signal lines 13a, 13b and the signal line 13e of the refrigerant temperature detection element 6
The temperature detection output obtained through the calculation circuit 12 calculates the degree of superheat of the refrigerant and outputs the calculation for controlling the expansion valve 2. On the other hand, the temperature of the output of the air temperature sensor 3 of the cooling air of the cooler 1 is set and compared with the output of the arithmetic circuit 12, and the expansion valve 2 is controlled by the output of the temperature controller 7.

As described above, the present invention integrates the refrigerant pressure sensing element and the refrigerant temperature sensing element into one protective tube, thereby making it possible to detect the characteristics of the refrigerant at the same time and at the same point, resulting in high accuracy. It is possible to detect the temperature of the refrigerant, and its installation is easy because it is just a single sensor, and the temperature compensation of the refrigerant pressure conversion element and the calculation of the characteristics of the refrigerant passing through the suction pipe, that is, the degree of superheat, can be adjusted within the compensation pipe. It is economical because the device is simplified and the number of conductors leading to the expansion valve is reduced, and the operating efficiency of the cooler can be maximized.

Furthermore, in the present invention, the refrigerant pressure sensing element is configured as a part of the bridge circuit, and the output error caused by temperature fluctuations of the refrigerant pressure sensing element can be compensated for by using the temperature sensing element. This makes it possible to simplify the circuit configuration and eliminate the influence of temperature and the influence of noise from the conversion element mounting portion, thereby making it possible to detect pressure with high accuracy.

Furthermore, since the temperature sensing element constitutes the output compensation circuit of the refrigerant pressure sensing element, the circuit configuration is simplified accordingly, and the compensation circuit itself can also be housed within the protective tube.

In particular, the present invention provides a protection tube with a pressure-receiving surface that can directly face the refrigerant on the suction side of the compressor, and by integrally attaching both of the sensing elements to the back of the pressure-receiving surface, temperature can be detected using a simple strain gauge or the like. At the same time, pressure detection can be performed with high precision, and compensation for distortion of the pressure receiving surface can be easily performed using a bridge circuit configured using a part of the temperature sensing element, resulting in high precision. Detection accuracy can be maintained.

It has various effects such as

[Brief explanation of drawings]

Fig. 1A is a system diagram of a conventional cooler, B is a system diagram of a cooler of the present invention, Fig. 2A is a diagram of the expansion valve control sensor, B is an enlarged view of the conversion element section, and Fig. 3 is a system diagram of a conventional cooler. An example of a conversion element processing circuit is shown. 1...Cooler, 2...Refrigerant liquid expansion valve, 3...Air temperature sensor, 4...Suction pipe, 5...Refrigerant pressure detection element, 6...Refrigerant temperature detection element, 7...Refrigerant temperature detection sensor , 8...Adjuster, 9...Expansion valve control sensor, 10...Diaphragm, 11...
Electric bridge, 12... Arithmetic circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] 1) In an expansion valve control sensor configured to be able to control an expansion valve for supplying refrigerant to a cooler by detecting the degree of superheat of the refrigerant, refrigerant on the suction side of the compressor a protection tube having a pressure-receiving surface that can directly face the pressure-receiving surface, a refrigerant pressure detection element and a refrigerant temperature detection element are housed and integrated within the protection tube by being brought into contact with the back surface of the pressure-reception surface, respectively, and the refrigerant pressure detection element is integrated. An electric bridge (bridge circuit) is formed by the element and three fixed resistors, and the power supply voltage of the electric bridge is applied to the input terminal side of the pressure sensing element, and the output of the electric bridge is taken out from the output terminal side of the pressure sensing element. 1. A sensor for controlling an expansion valve, which is configured to be capable of detecting pressure based on voltage, and further comprising: an input terminal side of the temperature sensing element connected to an output terminal side of the pressure sensing element. 2) The expansion valve control sensor according to claim 1, wherein the pressure-receiving surface is a diaphragm provided at the tip of the protection tube.