JP2006053009A - Pressure switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure switch having no wrong signal caused by a noise at the transmission time, and connectable in common to a plurality of control devices, relative to the control device for controlling an opening of an electrically-driven expansion valve in a refrigerating cycle. <P>SOLUTION: A single-chip semiconductor pressure sensor is used as a pressure sensor 10g, and digital data corresponding to a detected pressure are transmitted to a microcomputer 10a. A low-pressure cut value and an MOP set value in the refrigerating cycle are set by operation of an operation switch 10h, and stored in EEPROM 10d. The low-pressure cut value, the MOP set value and detected pressure data are transmitted as digital data to the control device through a communication interface 10e. A detected pressure value is displayed in blue by using a blue LED in a digital pressure display 10j, and the power consumption is suppressed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pressure switch that is provided in a pipe line of a refrigeration cycle, particularly for controlling the refrigeration cycle, and suitable for detecting the pressure of a refrigerant.

  Conventionally, as prior literature relating to the present invention, for example, there are Japanese Patent No. 312229 (Patent Literature 1) and Japanese Patent Laid-Open No. 2003-302300 (Patent Literature 2).

The one of Patent Document 1 is provided with a plurality of digital pressure indicators and relay drive circuits that A / D convert analog electric signals from the pressure sensor, perform arithmetic processing by the CPU, and display the output value of the pressure sensor. Output means and output means for D / A converting and outputting the output value of the pressure sensor. Further, the one disclosed in Patent Document 2 is a pressure sensor that outputs a digital signal.
Japanese Patent No. 3212229 JP 2003-302300 A

  The conventional technology of Patent Document 1 performs A / D conversion on an analog signal from a pressure sensor and performs D / A conversion for analog voltage output, so that an extra processing step is required, and A / D conversion is performed. Since conversion errors accompanying D / A conversion are accumulated, there remains room for improvement in these respects.

  Further, in the prior art of Patent Document 1, when controlling a plurality of evaporators with respective temperature control devices, for example, when pressure data is used for superheat degree control, analog voltage output (for example, 0.25 to 4.75 V) is used. When signals are sent to a plurality of temperature control devices, there remains room for improvement in that there is a possibility of an erroneous signal due to noise. Furthermore, even if the most common analog current output (4 to 20 mA) is used, there is a limitation on the loop resistance value for voltage conversion (generally 250Ω or less), so that a plurality of temperature control devices cannot be connected. .

  Furthermore, the prior art of Patent Document 1 describes that the paragraph [0036] is limited to the pressure control device on the low pressure side of the compressor constituting the refrigerator, but also includes the pressure control device on the high pressure side. Needless to say. When the pressure control device of this prior art is used on the high pressure side and the low pressure side of the compressor, the pressure indicator is connected to the pressure control device on the high pressure side with a red 7 segment LED in order to distinguish and visually recognize the two pressure control devices. When the pressure indicator of the low-pressure side pressure control device is configured with a green 7-segment LED, the green LED has a low luminance, and in order to ensure a luminance equivalent to that of the red LED, a forward current of approximately twice is passed. There is room for improvement in that it is necessary and consumes extra power.

  An object of the present invention is to solve the above-described problems and to provide a pressure switch that can be commonly connected to a plurality of temperature control devices without an erroneous signal due to noise when transmitting detected pressure data. Another object is to provide a pressure switch with reduced power consumption.

  The pressure switch according to claim 1 is a pressure sensor for sending digital data from a single-chip semiconductor pressure sensor for processing an electrical signal detected by a piezoresistive element in accordance with an applied pressure by an electronic circuit, a setting device, a storage means, And an arithmetic processing means, a digital pressure indicator, and an output means for outputting data calculated by the arithmetic processing means as a digital signal by communication.

  A pressure switch according to a second aspect is the pressure switch according to the first aspect, wherein the setter sets a low pressure cut value and sets a MOP value.

  The pressure switch according to claim 3 is the pressure switch according to claim 1, wherein the output by communication of the detected pressure data calculated by the arithmetic processing means, the set low-pressure cut value, and the set MOP value. It sends out using a means, It is characterized by the above-mentioned.

  A pressure switch according to claim 4 is the pressure switch according to claim 1, wherein a blue 7-segment LED is used for the digital pressure indicator, and a blue color is displayed when at least low pressure data is displayed on the digital pressure indicator. It was made to do.

  According to the pressure switch of the first aspect, the output means for outputting by communication of the (low pressure side) pressure switch is connected to the communication line, and digital data, for example, detected pressure data is sent as a digital signal. There is no error signal at the time of transmission, and it can be commonly connected to a plurality of temperature control devices. Further, since the pressure sensor outputs digital data from the single chip semiconductor pressure sensor, there is no need for A / D conversion and D / A conversion, and no conversion error occurs.

  According to the pressure switch of the second aspect, the same effect as that of the first aspect can be obtained, and the MOP set value and the low pressure cut set value can be set by the setting device.

  According to the pressure switch of the third aspect, the same effect as that of the first aspect can be obtained, and the detected pressure data, the MOP set value, and the low pressure cut set value are transmitted. There is no need to provide pressure detection means. In addition, the configuration of the refrigeration cycle is simplified, the MOP set value and the low pressure cut set value are sent via the communication function, the refrigeration cycle is controlled by the detected pressure data / each set value, and the transient at the start of the compressor Since the refrigeration cycle can be favorably controlled regardless of the time delay of the temperature sensor, such as when the operating state is suddenly changed due to a disturbance, the refrigeration cycle reliability is improved.

  According to the pressure switch of the fourth aspect, the same effect as in the first aspect can be obtained, and the low pressure data is displayed by the digital pressure indicator using the blue 7 segment LED, so that it is connected in series with the LED. Since the resistance value of the resistor to be used is the same for both the red LED and the blue LED, the arrangement of the members is simplified and the visibility is improved compared to the green color, and further compared to the red / green color. As the current value is small, a significant energy saving effect can be obtained.

  According to the pressure switch of the first aspect, there is no error signal when the pressure data is transmitted, and it can be commonly connected to a plurality of temperature control devices, and no conversion error is caused by the single-chip semiconductor pressure sensor.

  According to the pressure switch of the second aspect, the same effect as that of the first aspect can be obtained, and the MOP set value and the low pressure cut set value can be set by the setting device. Here, the MOP and the low pressure cut will be described. MOP (Maximum Operating Pressure) is originally a function of a temperature type expansion valve. As a result of the MOP regulation, it is possible to prevent liquid return at the start of the compressor and overload of the compressor motor. In general, this is a high limit function. The low pressure cut is the main function of the low pressure switch. When an abnormality occurs in the refrigeration cycle, such as an expansion valve or an evaporator, and the refrigerant stops flowing, the low-pressure side pressure decreases. At that time, a low-pressure cut acts to protect the refrigeration cycle. In general, this is a low limit function.

  According to the pressure switch of the third aspect, the same effect as in the first aspect can be obtained, and it is not necessary to separately provide a pressure sensor or the like (low pressure side) as the detection pressure means, and the configuration of the refrigeration cycle is simplified. In addition, the refrigeration cycle can be favorably controlled regardless of the time delay of the temperature sensor, such as a transient operation state at the time of starting the compressor, a sudden load change due to disturbance, and the reliability of the refrigeration cycle is improved.

  According to the pressure switch of the fourth aspect, the same effect as in the first aspect can be obtained, the arrangement of the members is simplified, the visibility is improved, the remarkable energy saving effect is obtained, and the global environment is maintained. A great deal of contribution can be made.

  Next, an embodiment of a pressure switch of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of the pressure switch 10 of the embodiment, and FIG. 2 is a front view of the pressure switch 10. As will be described later, the pressure switch 10 is connected to the refrigeration cycle of the cooling temperature control system. As shown in FIG. 1, the pressure switch 10 includes a microcomputer 10a, a RAM 10b, a ROM 10c, an EEPROM 10d, a communication interface 10e, an input / output interface 10f, a pressure sensor 10g, an operation switch 10h, a relay drive circuit and relay switch 10i, and a digital pressure indicator. 10j and a power supply circuit 10k. The microcomputer 10a controls the entire pressure switch 10, inputs various setting values with the operation switch 10h, various arithmetic processes, and exchanges communication data with the control device of the cooling temperature control system via the communication interface 10e. Give and receive. The digital pressure indicator 10j includes 4 to 8 digits of 7-segment LED elements, and the 7-segment LED elements are composed of blue LEDs.

  The pressure sensor 10g is a single-chip semiconductor pressure sensor including a piezoresistive element and an electronic circuit disposed on, for example, a diaphragm exposed to a refrigerant, and the piezo element outputs an electric signal according to an applied pressure. The electrical signal is processed by an electronic circuit to send digital data corresponding to the detected pressure. Therefore, there is no problem of conversion errors associated with A / D conversion of analog signals and D / A conversion for voltage output.

  As shown in FIG. 2, the display units 11 and 12 of the digital pressure indicator 10 j are disposed on the operation panel of the pressure switch 10. The display units 11 and 12 display various set values during the setting operation, and display the low pressure (measured pressure) of the cooling temperature control system. The measurement value (PV) of the low pressure is displayed in blue on the display unit 11, and the set value (SV) is displayed in blue on the display unit 12. Further, an up / down operation element 13, a function selection operation element 14, and a determination operation element 15 of the operation switch 10h are disposed on the operation panel, and further, an LED indicator lamp 16a for displaying a depressurization state, and an LED for displaying a pressurization state. An indicator lamp 16b, an LED indicator lamp 17a for displaying an operation state, and an LED indicator lamp 17b for displaying an alarm state are provided. The LED indicator lights 16a and 17a are lit in blue, and the LED indicator lights 16b and 17b are lit in red.

  FIG. 3 shows an example of a circuit for driving each LED element a of the digital pressure indicator 10j. A control signal from the microcomputer 10a is supplied to the switch circuit c through the inverter b, and is divided by the resistor R of the reference voltage + 5V. Is applied to the LED element a and lights up. The resistance value of the resistor R is set according to the color (type) of the LED element a. The following table 1 is a constant table of the display circuit corresponding to the type of the LED element a, and shows the resistance value of the resistor R, the forward voltage during lighting, and the forward current during lighting.

  As can be seen from the above table, the resistance value of the resistor R is the same in the case of red and blue, but is different in the case of green. Therefore, as compared with the case where a red LED element and a green LED element are used as LED elements as in the prior art, a blue 7-segment LED as in the embodiment, even when the resistance value of the resistor R is a red LED, the blue LED In this case, the same value may be used, so that the arrangement of the members is simplified, the visibility is improved as compared with the green color, and the current value is smaller than that of the red / green color.

  FIG. 4 is a configuration diagram of the cooling temperature control system of the embodiment. In this embodiment, with respect to one compressor 1 and one condenser 2, a refrigeration cycle is constituted by four evaporators 41 to 44 and electric expansion valves 31 to 34 corresponding thereto. . The electric expansion valve driving units 51 to 54 are valve driving units that control the valve opening degree by opening and closing the electric expansion valves 31 to 34 in response to signals from the control devices 91 to 94 described later. In a broad sense, the electric expansion valves 31 to 34 are included. Control devices 91 to 94 are connected to the evaporators 41 to 44, respectively. In addition, the temperature sensors 61 to 64 on the outlet side of the evaporators 41 to 44 and the temperature sensors 71 to 74 on the inlet side are connected to the control devices 91 to 94 below. Further, a control device 91 as a parent device among the control devices 91 to 94 is connected to the personal computer 100, and an internal temperature sensor 8 is connected to the control device 91 of the parent device. The pressure switch 10 of the embodiment is connected to the outlet sides of the evaporators 41 to 44, and the pressure switch 10 and the control devices 91 to 94 are connected by a communication cable 200 via communication terminals. A terminal resistor R is connected to the communication device of the control device 91 of the master unit and the pressure switch 10. As indicated by broken lines in the figure, the outlet side and inlet side temperature sensors 61 to 64 and 71 to 74 of the evaporators 41 to 44 may be connected only to the control device 91 of the master unit. In the drawing, the pressure switch 10 is shown in two places, in the piping of the refrigeration cycle and in the connection of the communication line, but this pressure switch 10 is one installed at the same position.

  In this cooling temperature control system, each control device 91-94 controls the valve opening degree of the electric expansion valves 31-34 based on the evaporation pressure at the evaporator outlet. For this reason, in the pressure switch 10, the MOP set value and the low pressure cut set value in the refrigeration cycle are input and set from the operation switch 10h, and these set values are stored in the EEPROM 10d. Then, these set values and detected pressure data are transmitted from the pressure switch 10 to the control devices 91 to 94, and the control devices 91 to 94 send the set values and detected pressure data to the control devices 91 to 94 based on these set values and detected pressure data. The opening degree of the corresponding electric expansion valves 31 to 34 is controlled. At this time, each of the control devices 91 to 94 controls the valve opening so that the detected pressure based on the detected pressure data is MOP set value> detected pressure> low pressure cut set value.

  Here, when the MOP set value and the low pressure cut set value are input and set, each setting mode of the MOP set value or the low pressure cut set value is selected by operating the function selector 14 on the operation panel shown in FIG. To do. Then, the up / down operation element 13 is operated to input the MOP set value or the low pressure cut setting value, and the determination operation element 15 is operated to complete the setting. Each set value is stored in the EEPROM 10d. Is done.

  FIG. 5A is a diagram showing transmission data from the pressure switch 10 to the control device 91 of the parent device, and the detected pressure, MOP set value, and low pressure cut set value are transmitted as text data. FIG. 5B is a diagram showing transmission data from the control device 91 of the master unit to the control devices 92 to 94 of the slave units. In addition to the detected pressure, MOP set value, and low pressure cut set value similar to the above, Temperature and valve opening data are also transmitted as text data. Note that these data are transmitted and received together with data such as text start, text end, and checksum. Thus, since the pressure switch 10 outputs data as digital data by communication, there is no error signal when transmitting the pressure data, and it can be connected to a plurality of control devices in common.

It is a block diagram of the pressure switch of the embodiment by the present invention. It is a front view of the pressure switch. It is an example of the circuit which drives each LED element of the digital pressure indicator in an embodiment. It is a block diagram of the temperature control system for cooling in embodiment. It is a figure which shows the transmission / reception data in embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pressure switch 10a Microcomputer 10e Communication interface 10g Pressure sensor 10h Operation switch 10j Digital pressure indicator 11, 12 Display part 13 Up / down operation element 14 Function selection operation element 15 Determination operation element 91-94 Control apparatus

Claims (4)

A pressure sensor that sends digital data from a single-chip semiconductor pressure sensor that processes an electrical signal detected by a piezoresistive element in response to an applied pressure in an electronic circuit;
A setting device;
Storage means;
Arithmetic processing means;
A digital pressure indicator;
Output means for outputting calculation data by the arithmetic processing means as a digital signal by communication; and
A pressure switch characterized by comprising:   The pressure switch according to claim 1, wherein the setter sets a low pressure cut value and sets a MOP value.   2. The pressure switch according to claim 1, wherein the detected pressure data calculated by the arithmetic processing means, the set low pressure cut value, and the set MOP value are sent out using the output means by communication. Using a blue 7 segment LED for the digital pressure indicator,
2. The pressure switch according to claim 1, wherein when the pressure data of at least a low pressure is displayed on the digital pressure indicator, a blue color is displayed.

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