JP2009031026A - Thermocouple and its mounting structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermocouple and its mounting structure capable of detecting a temperature stably and accurately, and having excellent mounting/dismounting work efficiency. <P>SOLUTION: In this covered wire type thermocouple 3 having a tip joint of a thermocouple wire exposed from an insulation coating, for example, a chip-shaped holding member 6 comprising brass is brazed on the tip joint of the thermocouple wire, and the holding member 6 is fitted into a groove 5 formed in a die 1, and thereby the thermocouple 3 can be mounted on/dismounted from the die 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thermocouple and a mounting structure thereof, and more particularly, to a thermocouple in which a tip joint portion of a thermocouple wire is exposed and a mounting structure thereof.

  Conventionally, as a temperature control method for reducing interference between control points when controlling a temperature of a controlled object such as a mold at multiple points, a plurality of detected temperatures corresponding to a plurality of control points are There is a method (hereinafter also referred to as “gradient temperature control”) that converts the average temperature into a temperature difference (gradient temperature) based on a plurality of detected temperatures and controls the average temperature and the gradient temperature as control amounts (hereinafter also referred to as “gradient temperature control”). Patent Document 1).

  FIG. 18 is a configuration diagram when the above-described gradient temperature control method is applied to two-channel temperature control.

  The detected temperatures at the two control points of the controlled object 30 are converted by the mode converter 31 into an average temperature that is an average value of both detected temperatures and a gradient temperature that is a temperature difference between the detected temperatures, and the average temperature and the target average temperature. Or a deviation between the gradient temperature and the target gradient temperature is input to each PID control unit 32.

  Each PID control unit 32 calculates and outputs an operation amount so as to eliminate an average temperature deviation or a gradient temperature deviation. In the precompensator 33, only the gradient temperature reacts to a change in the gradient temperature manipulated variable. The control output is distributed to control the output so that the response to the average temperature is small, and conversely, the response to the gradient temperature is small with respect to the change in the control amount of the average temperature. The temperature of the controlled object 30 is controlled.

Conventionally, in order to control each of the two points to be controlled individually, the control of one point has an effect on the control of the other point, making it difficult to control with high accuracy. In the gradient temperature control, high-precision control is enabled by controlling the average temperature at two points and the gradient temperature, which is the temperature difference between the two points, as control amounts.
Japanese Patent No. 3278807

  Such tilt temperature control is to reduce the interference and enable uniform temperature control.For example, in injection molding of precision parts such as optical lens parts, when trying to control the temperature of the mold at multiple points, If the detection ends of multiple temperature sensors that detect the temperature at each point are not in contact with the detection point of the mold without being displaced even if an impact is applied due to the opening and closing of the mold, Therefore, it is difficult to control the temperature of the mold with high accuracy.

  In addition, in order to shorten the time required for mold replacement work and increase productivity, it is desirable that the workability of attaching and detaching the temperature sensor to and from the mold is good, especially in multi-point temperature control. As the number of sensors increases, the demand becomes even higher.

  In general, a resistance temperature detector, a thermocouple, or the like is used as the temperature sensor, but the thermocouple has an advantage that it is inexpensive and has a high degree of freedom in installation.

  In such a thermocouple, as shown in FIG. 19, a sheath type in which a thermocouple wire 21 is enclosed with a filler 22 such as high-purity magnesia in a metal sheath tube 20, and as shown in FIG. In addition, the thermocouple element 21 is covered with a glass fiber-coated tube 23, a heat-resistant resin-coated tube 24, and the like, and the end of the thermocouple element that becomes the detection end is exposed from the insulating coating. is there.

  The sheath type uses a sheath tube 20 made of a metal material such as stainless steel, so that the thermocouple wire 21 is protected, but has a drawback that it is difficult to bend due to its rigidity.

  On the other hand, the covered wire type has an advantage that it is easy to bend and handle, and it is preferable to use such a covered type from the viewpoint of the workability of attachment to and removal from the mold described above. .

  However, in the coated wire type, the tip junction of the thin thermocouple wire that becomes the detection end is exposed, and the joint consisting of this thin strand can be contacted stably without being displaced from the mold. There is a problem that it is not easy to do.

  The present invention has been made in view of the above points, and provides a thermocouple capable of detecting temperature stably and accurately and having good workability in attachment and detachment, and an attachment structure thereof. For the purpose.

  (1) The thermocouple of the present invention is a thermocouple in which a tip joint portion of a thermocouple wire is exposed, and a holding member is attached to the tip joint portion so that the thermocouple is held by a temperature detection target. Are joined.

  The holding member preferably has elasticity, and is preferably held on the temperature detection target using an elastic restoring force.

  According to the thermocouple of the present invention, the holding member is joined to the tip joining portion of the thin thermocouple wire, and the thermocouple is held on the temperature detection target. It is possible to stably detect the temperature by holding the end joint portion of the wire stably on the temperature detection target.

   (2) In one embodiment of the thermocouple of the present invention, the holding member is made of metal.

  According to this embodiment, since the holding member is made of a metal having good thermal conductivity, the heat of the temperature detection target is efficiently transmitted to the tip joint portion of the thermocouple wire via the holding member. As a result, the thermal response is improved.

   (3) In another embodiment of the thermocouple of the present invention, the holding member is a spring.

  The spring is only required to be held on the temperature detection target by an elastic restoring force, and may be a string winding shape, a plate shape, or other shapes.

  According to this embodiment, using the elastic restoring force of the spring of the holding member, the tip joint portion of the thermocouple wire can be stably held on the temperature detection target and the temperature can be detected.

   (4) In still another embodiment of the thermocouple of the present invention, the holding member has a chip shape.

  The chip shape is a strip shape and may be any size as long as it can be held by the temperature detection target. The shape is also arbitrary such as a columnar shape, a rectangular parallelepiped shape, or a cylindrical shape.

  According to this embodiment, using the chip-shaped holding member, the tip joint portion of the thermocouple wire can be stably held on the temperature detection target to detect the temperature.

  (5) The thermocouple mounting structure of the present invention is a structure for mounting the thermocouple according to any one of (1) to (4) above to a temperature detection target, and is formed on the surface of the temperature detection target. The thermocouple is housed in the groove, and the holding member is in contact with the inner wall of the groove to hold the thermocouple in the groove.

  According to the thermocouple mounting structure of the present invention, the holding member is fitted into the groove formed in the temperature detection target and the thermocouple is held, so the thermocouple is attached to and removed from the temperature detection target. Is easy.

  In addition, the heat of the temperature detection target is efficiently transmitted to the tip junction of the thermocouple element via the holding member that contacts the inner wall of the temperature detection target groove, and the temperature can be measured accurately and the thermal response. Property is improved.

  (6) In one embodiment of the thermocouple mounting structure of the present invention, the temperature detection target is a mold, and a plurality of thermocouples are mounted.

  According to this embodiment, it can be applied to multi-point temperature control of a mold, for example, the workability of attaching and removing a large number of thermocouples at the time of mold replacement is improved, and productivity is increased. Can do.

  According to the present invention, since the thermocouple is held on the temperature detection target by the holding member, the tip junction of the thermocouple wire is stably held on the temperature detection target to detect the temperature. can do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of a temperature control system including a thermocouple according to an embodiment of the present invention.

  This temperature control system includes a mold 1 as an object to be controlled, a heater 2 that heats the mold 1, a thermocouple 3 that detects a temperature of the mold 1, and a detected temperature from the thermocouple 3. And a temperature regulator 4 for controlling the temperature of the mold 1 by controlling energization of the heater 2.

  The mold 1 of this embodiment is, for example, a mold on the fixed side of an injection molding machine. A plurality of heaters 2 and thermocouples 3 are provided, but only one representative is shown in FIG.

  FIG. 2 is a front view showing the arrangement of the mold 1, the heater 2 and the thermocouple 3 of FIG. A concave portion (not shown) for forming a cavity is formed on the surface of the mold 1, but is omitted in FIG. 2.

  Nine plate heaters 2-1, 2-2a, 2-2b, 2-3, 2-4a, 2-4b, 2-5, 2-in total, three on each side of the mold 1 respectively. 6a, 2-6b, 2-7, 2-8a, 2-8b are respectively attached to constitute the heater 2 of FIG.

  Nine heaters 2-1, 2-2a, 2-2b, 2-3, 2-4a, 2-4b, 2-5, 2-6a, 2- attached to each side surface of the square mold 1 6b, 2-7, 2-8a, 2-8b, heaters 2-2a, 2-2b; 2-4a, 2-4b; 2-6a, 2-6b; 8a and 2-8b are a set of two heaters 2-2a and 2-2b; 2-4a and 2-4b; 2-6a and 2-6b; 2-8a and 2-8b, respectively. Therefore, there are eight heaters 2-1, 2-2, 2-3, 2-4, 2-5, 2-6, 2-7, 2-8 that are individually controlled.

  In this embodiment, eight thermocouples 3a to 3h constituting the thermocouple 3 of FIG. 1 are housed and held in a mounting groove 5 formed on the surface of the mold 1, and each temperature sensor 3a to 3h is stored. The holding member 6 at the tip of 3h is disposed so as to be located along the same circumference from the center of the mold 1 so as to correspond to the eight control points A to H.

  The temperature controller 4 shown in FIG. 1 includes eight heaters 2-1, 2-2, 2 via SSR (not shown) based on the detected temperatures of the thermocouples 3a to 3h at the control points A to H. −3, 2-4, 2-5, 2-6, 2-7, and 2-8 are controlled, and in this embodiment, temperature control of 8 channels is performed.

  The temperature controller 4 of this embodiment does not individually control the temperature for each channel, but uses the temperature control method disclosed in the above-mentioned Patent Document 1 or the like.

  As described above, this temperature control method converts a plurality of detected temperatures corresponding to a plurality of control points into, for example, an average temperature of a plurality of detected temperatures and a temperature difference (gradient temperature) based on the plurality of detected temperatures. The temperature is controlled using the average temperature and the gradient temperature as control amounts.

  FIG. 3 is a block diagram showing the configuration of the gradient temperature control in the temperature controller 4 of this embodiment.

  The temperature controller 4 of this embodiment converts the input temperatures PV1 to PV8 from the eight temperature sensors 3a to 3h into one average temperature (average PV) and seven gradient temperatures (gradient PV1 to gradient PV7). The operation amount is calculated based on the mode converter 14 and the deviation between each temperature (average PV, slope PV1 to slope PV7) from the mode converter 14 and the target temperature (average SP, slope SP1 to slope SP7). The eight PID control units 15 and the operation amount from each PID control unit 15 are distributed so that the influence of the control by each PID control unit 15 on the control by the other PID control unit 15 is eliminated or reduced. And a pre-compensation unit 16 for supplying control outputs MV1 to MV8 to the heaters 2-1, 2-2, 2-3, 2-4, 2-5, 2-6, 2-7, 2-8. Yes.

  The mode conversion unit 14 converts the eight input temperatures PV1 to PV8 into an average temperature (average PV) that is an average value thereof and, for example, a temperature difference (PV1-PV2, PV2-PV3, PV3-PV4) between adjacent input temperatures. ,..., PV7-PV8) are converted into seven gradient temperatures (gradient PV1 to gradient PV7).

  Note that the gradient temperature is not limited to the temperature difference with the adjacent input temperature. For example, the temperature difference between the average temperature (average PV) and each input temperature (PV1-average PV, PV2-average PV, PV3-average). PV, ... PV7-average PV). Thus, by using the temperature difference between each input temperature and the average temperature as the gradient temperature, it becomes possible to control the temperature of the symmetrical mold more evenly.

  For the target temperature SP, the difference between the target average temperature (average SP), which is the average value of the set temperatures (target temperatures) SP1 to SP8 of the eight control points A to H, for example, the adjacent set temperature (SP1- SP2, SP2-SP3, SP3-SP4,... SP7-SP8) are set as seven target gradient temperatures (gradient SP1 to gradient SP7).

  Each PID control unit 15 performs a PID calculation so as to eliminate a deviation between the input temperature PV and the target temperature SP, and outputs an operation amount.

  The pre-compensation unit 16 decomposes the operation amount from the PID control unit 15 and has the same configuration as the configuration disclosed in Patent Document 1 and the like, and the distribution ratio matrix of the pre-compensation unit 16 Gc is the pre-compensation matrix, and the mode conversion matrix Gm is a matrix for converting the detected temperatures (PV1 to PV8) by the above-described mode converter 14 into gradient temperatures (gradients PV1 to PV7) and average temperatures (average PV). If the interference matrix, which is information indicating the degree of interference, is Gp, the pre-compensation matrix Gc can be obtained as an inverse matrix as follows.

Gc = (Gm · Gp) ⁻¹
When each of the eight control points A to H is individually controlled, a certain control point influences another control point, that is, it is difficult to perform high-precision temperature control due to interference. In the temperature control, the average temperature and the gradient temperature based on the detected temperatures at the eight control points A to H are controlled as control amounts, so that highly accurate temperature control with reduced influence of interference becomes possible.

  The thermocouple 3 of this embodiment is, for example, a thermocouple called K type (chromel alumel), and is a covered wire type thermocouple. The thermocouple 3 is not limited to the K type, and various types such as an E type, a J type, and a T type can be selected according to accuracy, temperature range, and the like.

  As shown in FIG. 20, the coated wire type thermocouple is obtained by coating a thermocouple wire 21 with a glass fiber-coated tube 23 and a heat-resistant resin-coated tube 24, and serving as a detection end. The tip joint portion 21 a of the pair of wires is exposed from the covered tubes 23 and 24.

  The thermocouple 3 of this embodiment has an outer shape of the covered wire, for example, the major axis is 1.5 mm, the minor axis is 0.8 mm, and the thermocouple strand diameter is 0.2 mm. is there.

  In such a covered wire type thermocouple 3, it is necessary to sufficiently bring the tip joint portion of the thermocouple element exposed from the covered wire into contact with the detection point of the mold 1. That is, since the thermoelectromotive force, which is the thermocouple measurement principle, is generated at the tip joint portion of the thermocouple wire, if the contact is insufficient or the contact position is shifted, it causes a measurement error.

  In this embodiment, as shown in FIG. 4 and FIG. 1 described above, the mold 1 is provided so that the tip joint portion of the thermocouple wire of the thermocouple 3 can be stably and sufficiently brought into contact with the mold 1. A groove 5 for attaching the thermocouple 3 is formed on the surface of the thermocouple 3, and the thermocouple 3 is accommodated in the groove 5, and the tip of the thermocouple 3 is made of metal, for example, as shown in FIG. The chip-shaped holding member 6 made of brass is joined by brazing using, for example, silver brazing. In FIG. 4, a movable mold 7 is shown in pressure contact with the fixed mold 1 as indicated by arrows. The holding member 6 is not limited to brass, and may be composed of other metal materials such as stainless steel, copper, aluminum, silver, or alloys thereof.

  As described above, in the coated wire type thermocouple, since the thin thermocouple element portion is exposed at the tip, the contact portion is small and unstable compared to the width of the groove 5.

  Therefore, in this embodiment, the holding member 6 made of brass is integrally joined to the tip of the thermocouple 3 as described above, so that the rectangular parallelepiped holding member 6 is attached to the tip of the groove 5 of the mold 1. The thermocouple 3 can be stably held in the groove 5 so as to be fitted.

  Moreover, since the holding member 6 is made of brass and has appropriate metal elasticity, it can be easily attached and detached.

  Therefore, for example, compared to a configuration in which a thermocouple is attached to a mold using screws, the working time can be shortened and productivity can be improved, and the thermocouple is fixed to the die with resin. Thus, there is no risk of contamination due to the scattering of the resin, and it is particularly useful for molding precision parts.

  Furthermore, since the holding member 6 is made of a metal having a high thermal conductivity, the heat of the mold 1 is efficiently transmitted to the tip joint portion of the thermocouple strand of the thermocouple 3 and the temperature can be accurately measured. In addition, the thermal responsiveness is good.

  As another embodiment of the present invention, instead of the chip-shaped holding member 6, as shown in FIG. 6, a holding member 6a made of a metal spring may be used. In this thermocouple 3 a, the thermocouple 3 a can be held in the groove 5 of the mold 1 by spring elasticity, and the mold 1 is in contact with the mold 1 via the metallic holding member 6 a that is in contact with the mold 1. Heat is efficiently transferred to the junction of the thermocouple strands.

  Next, the characteristics of the thermocouple of this embodiment will be described.

  First, thermal response will be described.

  The thermal responsiveness of the thermocouple 3 provided with the chip-like holding member 6 and the conventional covered wire type thermocouple 25 shown in FIG. 20 was compared as follows.

  That is, on the surface of the heater 2 for heating the mold 1 shown in FIG. 7, as shown in the plan view of FIG. 8, the conventional coated wire type thermocouple 25 and the above-described chip-like shape are formed by the aluminum tape 8. A thermocouple 3 having the holding member 6 was attached and a temperature increase test was performed.

FIG. 9 shows the result. The solid line indicates the heater temperature detected by the thermocouple 3 having the chip-like holding member 6, and the broken line indicates the heater detected by the conventional covered wire type thermocouple 25. Each temperature is shown. As shown in FIG. 9, the thermocouple 3 having the chip-like holding member 6 rises slightly later than the conventional thermocouple 25.
However, there are individual differences in thermocouples, and the temperature of the heater surface is slightly different depending on the location.

  FIG. 10 shows the result. The differential value is simply calculated by how many times the temperature changes per second or the difference of a certain time.

  In FIG. 10, the triangular plot shows the result of measuring the heater temperature with the conventional coated wire type thermocouple 25, and the solid line shows the differential value of the detected temperature by the thermocouple 3 having the chip-shaped holding member 6. The broken line shows the transition of the differential value of the detected temperature by the conventional coated wire type thermocouple 25, respectively.

  As shown in FIG. 10, it can be seen that there is no difference of 1 ° C./second or more between the two. That is, it can be seen that the thermocouple 3 having the holding member 6 exhibits the same thermal responsiveness as a conventional coated wire type thermocouple.

  Next, the stability of the thermocouple attached was evaluated.

  Evaluation of stability by mounting means whether a stable contact surface can be secured when the thermocouple is repeatedly mounted and removed, that is, whether the same measurement conditions can be secured stably. It is something to evaluate.

  As shown in the plan view of FIG. 11 and FIG. 12 which is a cross-sectional view thereof, a groove 5 having a width and a depth of 1.6 mm and a length of 20 mm is cut in the mold 1, and the thermocouple 3 is placed near the mounting position. A conventional coated wire type thermocouple 9 is attached with a heat-resistant aluminum tape 8 as a temperature sensor for measuring the reference temperature. In this state, it is heated at a constant output by the heater 2 shown in FIG. Thereafter, the thermocouple 3 is repeatedly attached to and removed from the groove 5 to check whether the temperature can be reproduced.

  In consideration of the possibility of variation, the thermocouple 3 includes two types of thermocouples 3 having the chip-like holding member 6 shown in FIG. 5 having the same specifications, and a holding member 6a made of a spring shown in FIG. A total of four types including one type of thermocouple 3a having the above and one type of conventional coated wire type thermocouple 25 shown in FIG. 20 for comparison.

  With respect to the mounting strength, the covered wire type thermocouple 25 is not fixed and simply detached by being fitted in the groove 5, so the groove 5 is closed with an aluminum seal, and the thermocouple 25 is inserted and attached thereto. For this reason, the thermocouple 25 comes off only by touching the hand. On the other hand, the thermocouples 6 a and 6 having the holding member 6 a made of a spring and the chip-like holding member 6 are stable because the holding members 6 a and 6 are fitted into the groove 5.

  The measurement results are shown in FIG. In FIG. 13, the thick solid line rising to the right indicates the reference temperature of the mold, the broken line indicates one of the two types of thermocouples 3 (chip 1) having the chip-shaped holding member 6, and the alternate long and short dash line indicates the chip-shaped holding member. 6 is a thermocouple 3a (spring) having a holding member 6a made of a spring, and a thin solid line is a conventional thermocouple 25 of a conventional coated wire type (coating). Each is shown.

  As shown in FIG. 13, the temperature waveform is rising to the right because it is not completely in thermal equilibrium, but it can be seen that there is a beard on the waveform. This beard is caused by removing the thermocouple. When the thermocouple tip is removed from the mold, the temperature at the tip of the thermocouple drops sharply, and when the thermocouple is attached to the mold, the temperature rises abruptly, resulting in a beard-like waveform.

  In order to express stability more easily in the graph of FIG. 13, the temperature difference from the reference temperature is plotted for each thermocouple in FIGS. In both cases, the reproducibility of mounting is ensured. However, since the conventional thermocouple 25 of the covered wire type is in a state of being lightly fixed with a seal, it will come off when the mold is vibrated.

  As described above, the thermocouples 3 and 3 a having the holding member have good mounting stability to the mold 1.

  The present invention is useful for multipoint temperature control and the like.

It is a schematic structure figure of a system provided with a thermocouple concerning one embodiment of the present invention. It is a front view which shows the metal mold | die, heater, and thermocouple of FIG. It is a block diagram of the principal part of the temperature controller of FIG. It is a figure which shows the groove | channel formed in the metal mold | die, and the thermocouple accommodated in this groove | channel. It is a figure which shows the thermocouple which concerns on embodiment. It is a figure which shows the thermocouple which concerns on other embodiment. It is a front view of the metal mold | die with which the heater was attached. It is a top view which shows the thermocouple attached to the heater of FIG. It is a figure which shows the measurement result of heater temperature. It is a figure which shows the differential waveform of FIG. It is a top view for demonstrating the evaluation test of attachment and removal of a thermocouple. It is sectional drawing of the principal part of FIG. It is a figure which shows the change of the measurement temperature by attachment and detachment of a thermocouple. It is a figure which shows the change of the temperature difference from the reference temperature of the thermocouple which has a chip-shaped holding member. It is a figure which shows the change of the temperature difference from the reference temperature of the thermocouple which has another chip-shaped holding member. It is a figure which shows the change of the temperature difference from the reference temperature of the thermocouple which has the holding member which consists of a spring. It is a figure which shows the change of the temperature difference from the reference temperature of the conventional coating type thermocouple. It is a block diagram of inclination temperature control. It is a figure which shows a sheath type thermocouple. It is a figure which shows a coated wire type thermocouple.

Explanation of symbols

1 Mold 2 Heater 3 Thermocouple 4 Temperature Controller 5 Groove 6 Holding Member 14 Mode Conversion Unit 15 PID Control Unit 16 Precompensation Unit

Claims (6)

A thermocouple with exposed end of the thermocouple strand,
A thermocouple, wherein a holding member is joined to the tip joint portion so that the thermocouple is held on a temperature detection target.   The thermocouple according to claim 1, wherein the holding member is made of metal.   The thermocouple according to claim 1, wherein the holding member is a spring.   The thermocouple according to claim 1, wherein the holding member has a chip shape. A structure for attaching the thermocouple according to any one of claims 1 to 4 to a temperature detection target,
The thermocouple is housed in a groove formed on the surface of the temperature detection target, and the holding member abuts against an inner wall of the groove to hold the thermocouple in the groove. Mounting structure of thermocouple.   The thermocouple mounting structure according to claim 5, wherein the temperature detection target is a mold, and a plurality of the thermocouples are mounted.

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