Classifications

• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D23/00—Control of temperature
  • G05D23/19—Control of temperature characterised by the use of electric means
  • G05D23/1917—Control of temperature characterised by the use of electric means using digital means
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D23/00—Control of temperature
  • G05D23/19—Control of temperature characterised by the use of electric means
  • G05D23/1927—Control of temperature characterised by the use of electric means using a plurality of sensors
  • G05D23/193—Control of temperature characterised by the use of electric means using a plurality of sensors sensing the temperaure in different places in thermal relationship with one or more spaces
  • G05D23/1932—Control of temperature characterised by the use of electric means using a plurality of sensors sensing the temperaure in different places in thermal relationship with one or more spaces to control the temperature of a plurality of spaces
  • G05D23/1934—Control of temperature characterised by the use of electric means using a plurality of sensors sensing the temperaure in different places in thermal relationship with one or more spaces to control the temperature of a plurality of spaces each space being provided with one sensor acting on one or more control means
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D23/00—Control of temperature
  • G05D23/19—Control of temperature characterised by the use of electric means
  • G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
  • G05D23/22—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element being a thermocouple

Definitions

• the present invention relates to a system for regulating high temperature electrical heating equipment mounted on a press intended for the manufacture of plastic or composite material products, said heating equipment being distributed in several heating zones each equipped with a heating element.
• heating and a temperature sensor having two terminals subjected to an electric voltage, the heating elements being electrically supplied independently by means of electronic power supply means, said regulation system comprising a computer intended to regulate the electronic power supply means as a function of predetermined set points per heating zone and as a function of the indications provided by said temperature sensors.
• the international application published under No. WO 90/1173 relates to heating elements multizoncs, wherein each heating zone is equipped with a thcrmocouple connected to a calculator for piloting the electronic power supply means according to the points of setpoint for each heating zone. Thermocouples and heating elements can naturally be incorporated in the tools or molds for the production of parts or in the heating elements themselves.
• thermocouples are of good quality.
• these indications can be disturbed by external parasites resulting in particular from high-intensity currents which supply the heating elements. These parasites are all the more important since in general one of the terminals of the thermocouples is connected to ground, and the temperature indication is noted on the second terminal of the thermocouple.
• the computer is located at a sufficient distance from the heating elements and the connecting cables connecting the thermocouples to the computer have a long length, which results in additional noise and inevitable current leaks.
• the connecting cables connecting the thermocouples to the computer have a long length, which results in additional noise and inevitable current leaks.
• the purpose of the present invention is to propose a significant improvement in the above-mentioned regulation system, and to ensure that the temperature indications received by the computer are of better quality. And that the cooking can continue in good conditions in the event of a failure of a temperature measurement sensor.
• the proposed regulation system is characterized in that it further comprises means for transforming the voltages detected at the two terminals of any one of said temperature sensors chosen by said computer in an established sequence, in a digital value representative of the temperature of the heating zone associated with said temperature sensor, said digital value being transmitted to said computer for the purpose of regulating the electronic supply means, the means for detecting the state of good or malfunction of said chosen temperature sensor, and means for determining a replacement digital value in the event of detection of a state of malfunction by said detection means.
• the means for transforming voltages into numerical values are preferably located near the press. This makes it possible to reduce the length of the voltage transmission wires and thereby the influence of parasites.
• the cables for transmitting the digital value representative of the temperature can be very long, since it is known that digital digital signals are less sensitive to interference.
• each temperature sensor transmitting the voltages from its two terminals to said transformation means the voltage variations due to external parasites can be compensated.
• the means for transforming the voltages read into a digital value include ⁇ : a multiplexer connected to said computer by wiring used for addressing a temperature sensor and connected to each of said measurement sensors by two electric wires, said multiplexer providing output the two voltages recorded at the two terminals of the temperature sensor chosen by said computer, an operational amplifier connected to said multiplexer to receive said two voltages and providing a differential voltage as output, means for linearizing said differential voltage, and an analog-to-digital converter connected to said computer and intended to transform the differential voltage supplied by said linearization means into a numerical value representative of the measured temperature.
• the means for detecting the state of good or bad functioning of the chosen temperature sensor are interposed between said operational amplifier and said computer and supply to said computer a fault signal when the differential voltage is zero.
• the transformation means and the detection means are preferably mounted on a single electronic plate.
• the means for determining the replacement digital value in the event of detection of a poor operating condition of the chosen temperature sensor are provided in said computer.
• the means for determining the replacement digital value in the event of detection of a malfunction state of the chosen temperature sensor comprise a microcontroller connected to said detection means to said converter and to said computer.
• Said ⁇ r Ocontroller is further connected to said computer by said wiring serving for the addressing of a temperature sensor and comprises a memory for storing the operating state of each temperature sensor.
• the system further comprises means for detecting an overheating of the heating zone associated with the chosen temperature sensor, said means being interposed between said linearization means and said computer and providing said computer with an overheating signal when the differential voltage is greater than a predetermined maximum voltage.
• the computer then comprises means for cutting off the electrical supply to the heating elements in the event of reception of the overheating signal.
• FIG. 1 shows a diagram general of a press equipped with two multi-zone heating elements and the regulation system of the present invention
• Figure 2 shows the block diagram of the regulatory system of the present invention.
• FIG. 1 there is shown by reference 1, a first electrically heating element of a press for the implementation of products made of composite materials and by reference 2, a second heating element of the same press not shown. Said heating elements 1 and 2 are mounted on the fixed frame or the table of said press.
• heating elements 1, 2 are divided into several heating zones, referenced 3, each heating zone 3 is equipped with a heating element 4 and a temperature sensor 5.
• the heating elements 4 are electrically powered independent via electronic power supply means 6.
• These electronic power supply means 6 are regulated by a computer 7 as a function of instructions determined by the computer 7 and by heating zone 3, as a function of the temperature indications provided by the temperature sensors 5 associated with each heating zone. 3.
• the electronic power means 6 are connected to the electrical network by a terminal block 8 and comprising, in known manner, either solid state relays, power triacs or thyristors controlled in the train of waves by external instructions delivered by the computer 7.
• an electronic card 9 is interposed between the temperature sensors 5 and the computer 7. This electronic card 9 constitutes, with the computer 7, the system for regulating the heating equipment 1 and 2.
• This electronic card 9 is shown in detail in FIG. 2. It essentially comprises a multiplexer 10 which is connected to the computer 7 by wiring 10a, and to each of the temperature sensors 5 by two electric wires 11, 12 respectively connected to the two terminals 13, 14 of the corresponding temperature sensor 5.
• the temperature sensor 5 preferably consists of a thermocouple which delivers on its two terminals 13, 14 voltages whose difference is a function of the temperature to which the thermocouple is subjected.
• the multiplexer 10 has two output terminals 15 and 16 to which the voltages A and B supplied by the temperature sensor 5 will be applied, which is chosen as a function of an address transmitted on the wiring 10a by the computer 7.
• the voltages A and B supplied by the multiplexer 10 are applied to the input terminals of an operational amplifier 17 which outputs a voltage equal to the difference of the voltages A and B.
• This differential voltage AB is then adjusted by means of linearization 18 and a cold junction compensation device 19 and finally it is transformed into a digital value V, representative of the temperature recorded in the heating zone 3 associated with the chosen temperature sensor 5, by an analog digital converter 20.
• the value digital V is transmitted to the computer 7 by a wiring21 connecting the converter 20 to the computer 7.
• This digital value N is used by the computer 7 to regulate the electronic power supply means 6 for the heating element 4 associated with the temperature 5 previously chosen by the computer 7.
• the electronic plate 9 further comprises means 22 for detecting a zero differential voltage at the output of the operational amplifier 17, that is to say a state of non-operation or failure of the temperature sensor 5 chosen.
• These means 22 are connected, on the one hand, to the output of the operational amplifier 17 and, on the other hand, to the computer 7, which allows the latter to know the non-functioning state of the temperature 5 chosen.
• the electronic plate 9 finally comprises means 23 for detecting at the output of the compensation device 19 a differential voltage greater than a predetermined maximum voltage, that is to say a state of overheating of the corresponding heating zone 3. These means 23 are connected, on the one hand, to the output of the compensation device 19 and, on the other hand, to the computer 7 in order to transmit an overheating signal to it when the differential voltage is greater than the predetermined maximum voltage.
• the computer 7 includes means for cutting off the electrical supply to the heating elements 4 in the event of reception of the overheating signal.
• the computer 7 comprises, according to a first alternative embodiment, means for determining a digital value of probable temperature, replacing the digital value supplied by the converter analog digital 20, which is transmitted to the electronic power supply means 6 in order to determine the intensity of the current supplying the heating element 4 associated with the faulty temperature sensor 5.
• this replacement digital value is determined by a microcontroller 24 mounted on the electronic plate 9, which makes it possible to discharge the computer 7.
• This microcontroller 24 is connected to the detection means 22, to the addressing wiring 10a to the analog digital converter 20 and to the computer 7.
• the microcontroller 24 is also connected to the means 23 for detecting the overheating state of a heating zone 3, which enables it to store this information in the storage memory 25.
• the electronic plate 9 can be placed in the vicinity of the heating elements 1 and 2. It includes means for transforming the voltages detected at the two terminals 11, 12 of any of the temperature sensors 5 chosen by the computer. 7 according to a preset sequence, in a digital value representative of the temperature of the heating zone 3 associated with the chosen temperature sensor, as well as the means 22 for detecting the non-operating state of the chosen temperature sensor.
• the electronic plate 9 transmits a replacement digital value to the computer 7 in the event of failure of the chosen temperature sensor. The latter receives at the same time a non-operating signal which makes it possible to output a message on the operator console of the computer 7.
• the information stored in the memory 25 can be further processed by preset programs in order to know the state of the areas of heater 3, heater elements 4 and temperature sensors 5 during maintenance.
• the digital value N representative of the temperature recorded and supplied by the analog converter 20 is transmitted to the microcontroller 24 by the wiring 21.
• the microcontroller 24 then transmits this value V or the replacement value by the wiring 21a.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Automation & Control Theory (AREA)
• Remote Sensing (AREA)
• Control Of Temperature (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9430145

Family Applications (1)

Country Status (4)

Cited By (1)

Citations (6)

• 1992
  • 1992-05-25 FR FR9206376A patent/FR2691555B1/fr not_active Expired - Fee Related
• 1993
  • 1993-01-12 TW TW082104681A patent/TW232764B/zh active
  • 1993-05-25 AU AU43300/93A patent/AU4330093A/en not_active Abandoned
  • 1993-05-25 WO PCT/FR1993/000507 patent/WO1993024877A1/fr active Application Filing

Patent Citations (6)

Non-Patent Citations (1)

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