JPH02162019A - Frp forming jig - Google Patents

Abstract

PURPOSE:To shorten production cycle, while the efficiency of heating and cooling is improved, and the temperature control is easily achieved with the uniform temperature distribution by a method in which the heat-radiating fines radiating uniformly the heat amount obtained by substracting the heat amount radiated from the surface plate from the heat content of the surface plate are arranged in parallel on the rear of the surface plate, and the fences projected in the direction perpendicular to wind flow are firmly stuck onto the side of the heat-radiating fins. CONSTITUTION:Heat conductivity is calculated by estimating the wind speed in each part of a surface plate 2, and vents 3a, 3b, 4a or wind-guiding plates are provided in the part into which the wind does not flow easily, whereby minimum necessary wind speed is kept, and then the heat conductivity is again calculated, and thus the heat conductivity in each part of the surface plate 2 is calculated. The large difference between these heat conductivities is designed not to be generated. A plurality of heat radiating fins 5 extending in parallel with a transverse frame 3 are arranged in each area of the rear of the surface plate 2. The heat amount of the value obtained by substracting the heat amount radiated from the surface plate 2 in some time from the heat content of the surface plate 2 is caused to be uniformly radiated along the direction of its length. The fences 6 perpendicular to the flow are provided on the side of the heat radiating fins 5, whereby the flow near the heat radiating fins is dispersed, and excellent heat conduction is obtained.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an FRP molding treatment used when molding FRP (m-fiber reinforced plastic) by controlling the temperature with hot air, for example in the aviation and space industries. The present invention relates to tools, and in particular to FRP molding jigs that reduce production costs and improve quality by increasing heating and cooling efficiency.

[Conventional technology]

For the above-mentioned forming jig, the applicant first made the tip edges of the plurality of plates constituting the envelope surface arcuate in cross section, and provided each plate with a notch opening at the tip edge and a hole penetrating the plate surface. We proposed a method in which the processing viscosity and shape were made uniform by creating a hot air circulation passage, and the processing temperature was also controlled according to the container (Japanese Patent Application Laid-open No. 177923/1983).
.

Regarding cooling, a metal pipe is passed through the mold, and cooling water is introduced into the metal pipe to uniformly cool the hot plate (for example, Japanese Patent Laid-Open No. 62-2971
No. 25), a type that spouts cooling water to the outside of the mold, and which aims to shorten the cooling time by providing a plurality of rod-shaped or plate-shaped fins on a plane parallel to the direction in which the cooling water is jetted (also, Various proposals have been made, such as Japanese Patent Application Laid-Open No. 13735/1983.

[Problem to be solved by the invention]

However, although the method described in JP-A No. 63-177923 has the desired effect, due to the influence of the difference in heat radiation between the windward side and the leeward side, it is difficult to manufacture the jig as shown in Fig. 8. Afterwards, we actually applied hot air and measured the temperature (+i), and based on this result, we blocked the ventilation holes to prevent hot air from blowing directly into areas where the temperature rise was too high (hereinafter referred to as temperature-sensitive areas). It was necessary to perform a heat insulation treatment such as covering the surface with a rubber sheet or the like, and repeat this process usually about 3 to 5 times to make the temperature distribution uniform.

For this reason, the hot air application time (autoclave use time) becomes longer, and as a result, the number of products that can be cured in a given period of time decreases. Furthermore, molding temperatures such as FRP using thermoplastic resins are much higher than those using commonly used thermosetting resins, and the molding temperature is required to be close to the limit of the capacity of general autoclaves. Even in cases where
Since the temperature must be adjusted to insensitive areas, it is not possible to obtain the necessary temperature with such a general autoclave.

In addition, it is generally quite difficult to make the temperature distribution accurate and uniform, so especially when crystalline resins are used, variations occur in the crystallization rate that is affected by the cooling rate, resulting in poor product strength and toughness. This will affect various performances of the device.

Furthermore, every time a new jig is manufactured, the temperature 6i is changed to fl.
It takes a lot of time and effort, especially when the jig is large and has a complicated shape, to perform the work of determining the temperature, applying temperature adjustment measures at appropriate locations based on the results, and measuring the temperature distribution again. It takes.

In addition, as shown in Figure 8, only conceptual data (reference data) can be obtained, and a firm temperature
! Since it is not possible to obtain measurement data, the designer has to rely heavily on the experience of the designer, which not only slows down progress in jig design technology regarding heat transfer characteristics, but also causes problems when designers use different jigs. If several pieces are placed in an autoclave at the same time, the rate of temperature rise and cooling will be significantly different, and heating may be required for a longer period of time than necessary, which will affect the life of the jig and the production cycle. It has been found that there are problems such as sometimes giving

Furthermore, in the method described in JP-A No. 62-297125, although cooling is promoted by the cooling water passing through the vibrator in the mold, the temperature of the cooling water increases as it approaches the cooling water outlet side of the vibrator. Because of this, uniform cooling cannot be achieved. Furthermore, in the method described in JP-A No. 63-13735, although the heat radiation efficiency is improved by the fins, the fins simply increase the heat radiation area and assist in heat radiation, improving the heat transfer promoted by the diffusion of the flow. Therefore, even if the cooling fluid is turbulent at the mold surface where the temperature is most desired to be controlled, the fluid close to the mold surface becomes close to a laminar flow, which is called heat transfer. It is thought that there is a problem that it is not very good in terms of points.

In view of the above, the present invention provides a hot air circulation type heating furnace.
By maximizing the use of hot air, we can improve the efficiency of heating and cooling, make the temperature distribution even, and easily control the temperature, shortening the production cycle.
The purpose of the present invention is to provide data that can be used to plan efficient jigs regarding uniform temperature distribution, heating, and cooling.

[Means to solve the problem]

In order to achieve the above object, the FRP molding jig according to the present invention is a molding jig for molding FRP in a hot air circulation type heating furnace. The face plate is configured to ensure the minimum required wind speed on the back surface so that there is no large difference in heat transfer at each part of the surface plate, and a plurality of strips are formed on the back surface of the face plate along the flow direction of the wind. Radiation fins set to uniformly radiate heat along the length direction are installed in parallel, and this heat radiation is A fence that protrudes in a direction perpendicular to the wind flow is fixed to the side surface of the fin.

[For production]

According to the present invention configured as described above, hot air is actively taken in to the back surface of the front plate, and moreover, the hot air is taken in through the radiating fins installed parallel to the flow of the hot air and the fence fixed perpendicularly to the radiating fins. By making the most of the heat, not only can temperature rise and cooling efficiency be improved, but also the temperature distribution can be improved by dissipating all the heat from the surface plate through heat dissipation from the surface plate and radiation fins. This load roll can be done uniformly and easily. Furthermore, since the heat transfer amount of the surface plate can be calculated in advance at the design stage, quantitative data for the next design can be obtained by comparing with the data of the actual nI value.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of the FRP molding jig 1 seen from the back.
A plurality of vertical frames 3, 3... and structural frames 4, 4... are erected on the back side of the surface plate 2 whose surface has a shape that determines the shape of the product. It is divided into shape areas.

Each vertical frame 3 extends in a direction perpendicular to the direction of flow of hot air, etc., and has a plurality of circular ventilation holes 3a in its peripheral wall.

3a... and the surface plate 2, rectangular ventilation holes 3b, 3b... are formed. In addition, each horizontal frame 4 is
It extends in the flow direction of hot air, etc., and a plurality of circular ventilation holes 4a, 4a, . . . are formed in its peripheral wall.

The above ventilation ports 3a, 3a..., 3b, 3b,...
The positions, shapes, numbers, etc. of 4a, 4a, .

That is, as shown in FIG. 4, after designing the basic structure, the wind speed at each part of the surface plate 2 is multiplied by rΔy1, and the heat transfer coefficient is calculated based on this p side. Then, there are ventilation holes 3a, 3a..., 3b, 3b in places where it is difficult for the wind to flow.

After securing the minimum required wind speed by installing 4g, 4a, etc. and a wind guide plate (not shown), the thermal conductivity is calculated again and the heat of each part of the surface plate 2 is calculated. They calculate the heat transfer and consider air guide methods to avoid large differences in heat transfer.

A plurality of radiation fins 5, 5, . . . extending in the direction of flow of hot air, that is, in one row of the horizontal frames 3, 3, etc., are arranged in each area on the back surface of the surface plate 2. ing.

The heat dissipation fins 5, 5... are intended to make the temperature distribution uniform, increase temperature, and improve cooling efficiency.The heat dissipation fins 5, 5, . . . It is set to radiate heat equal to the amount of heat subtracted by the amount of heat evenly along its length.

An example of this calculation will be explained based on FIG.

First, it is confirmed by the Reynolds number that there is a laminar flow on the surface plate 2.

That is, the Reynolds number R when the fluid flows along the flat plate is x OX ν where, V: fluid velocity [m/s x;・I distance from the tip of the plate i! T! [m]ν; can be expressed as kinematic viscosity coefficient of fluid [r&/s].

The Reynolds number Red when fluid flows in a circular pipe is V
・dRed”.

Here, d; diameter of the circular tube [m It can be expressed as.

The Reynolds number indicates the ratio of the temporal change in the momentum of a fluid per unit area corresponding to the shear force and the shear force acting per unit area based on the viscosity of the fluid, and is a dimensionless number that characterizes the flow state and velocity distribution. It is a number.

Here, the Reynolds number when transitioning from laminar flow to turbulent flow is called the critical Reynolds number, and this is R and C. For the flow on a flat plate, R-3X105 C For the flow in a circular pipe, R -2320C. That is, if the Reynolds number determined by the above equations is greater than or equal to this critical Reynolds number, the flow will be turbulent, and if it is less than this, the flow will be laminar.

Next, find the Nusselt number at each point.

・In the case of a laminar flow, the Nusselt number N at a local distance of x [ml] from this tip of a single plate is The developed flow is divided into the flow within this speed run-up section and the flow after it, and the speed run-up section length Ω [ml, in the case of laminar flow, (P > 0.5) where, α ; distance fix [local thermal conductivity in ml [K
cal/rrf h'CI λ; Thermal conductivity of fluid [Kcal/ m h'CIP
; Prandtl number " In the case of turbulent flow, it is expressed as , and the Nusselt number Nudx within this interval is
In the case of laminar flow, as shown in the graph of Figure 6, in the case of turbulent flow, - For example, (P > 107) Furthermore, in the case of flow inside a pipe, the liquid flowing into the pipe with a velocity distribution like - As the flow progresses, the boundary layer develops along the inner wall, and after the boundary layer fills the pipe at a certain point, this state is maintained until the flow + (G − P )”14.
10-3] 115d r g・β・Δθ・d3 Grd”' 2 ν Here, G: Grashoff number g: Gravitational acceleration [m/s2] β: Volumetric expansion coefficient [/deg] Δθ: Temperature difference (wall surface - between fluids) [deg].

After the speed run-up section, the Nusselt number N in the case of laminar flow indicates the ratio of temperature conductivity based on, for example, and is determined by the material properties of the fluid.

Next, find the local heat transfer coefficient at each part.

For flow over a flat plate, N number λ 0.8 17
3 N-0,023R fist P udm od r Here, N
udffl; Can be expressed as the average Nusselt number within the tube.

The above Nusselt number indicates the ratio of the amount of heat transfer per unit area per unit time + 1 due to heat transfer to the amount of heat transfer per unit area per unit time due to heat conduction when the fluid is stopped, and the Prandtl number is , the momentum conductivity based on the viscosity of the fluid and the heat conduction of the fluid can be expressed as 'dx', the local heat transfer coefficient within the tube, or α7: the average heat transfer coefficient within the tube.

Furthermore, as shown in FIG. 7(a), when the width of the heat dissipation fin 2 is set as w1, the height as g1, and the thickness b, the amount of heat dissipated from the first heat dissipation fin shown in FIG. 7(b) is calculated as follows:Q1 ■(θ.-θ)2αl” A p k) Wt
(b + Wttanl+ (m, II l) [
Kcallh ] However, here, C1; heat transfer coefficient between the first radiation fins [Kca
llrrrh”c] θ0; Surface plate temperature [deg] θ; Fluid temperature [dcg] W11 First radiation fin section width [m1 g1; First radiation fin height [m] λ,; Thermal conductivity of radiation fin material [ It can be expressed as Kcall m h ”C1.

Based on the above, determine the height of the radiation fins at each point.

In order to make the amount of heat radiation from each radiation fin section the same, the height g of the radiation fin is determined as follows.

Each heat radiation), the heat radiation port QX from between the ins is Qx#(θ0-〇a)2α8・λ1. -b building Wx・(b
+ W

As this QX-01, when solving for gx, however, Lanh(m”j!) x (θ −θ) −C8・p xIW a W) Y becomes.

Next, determine the number of heat radiation fins.

The amount of heat Q that the surface plate 2 has at a temperature difference of Δθ.

[Kcall is Q - M - C - Δθ [Keal1 here, M
; Mass of surface plate [Kg] Δθ; Temperature difference between fluid and surface plate [deglC; Specific heat of surface plate material [Keal/Kg'C].

Next, the amount of heat that can be radiated by the surface plate 2 within a certain period of time is calculated.

The heat dissipation WQ from the entire surface plate is Q-Δθ.
s A Here, C8; Average heat transfer coefficient [Kcal/rrrII] using the value at the center of the wind direction; S; Surface plate area [r
yrl Here, if the allowable delay time from the atmospheric temperature inside the autoclave is t minutes, then Q -1 Δθ・aA-S [Kcall in minutes] L60 The amount of heat ΔQ that should be radiated by the N heat radiation fins in this t minutes The number N of heat dissipation fins is determined by:

-The heat radiation ff1QF from the heat radiation fins for t minutes is t
anb (mA) [Minute Kcall] The amount of heat ΔQ to be radiated from the N heat radiating fins is ΔQ−Qo−
Qst [Kcall Therefore, the number N of radiation fins is N-ΔQ/Q.

It is determined by

A specific example of the above will be explained below.

The number of heat dissipation fins to be laminated on the outer circumferential side of a cylindrical jig with a diameter of 30 marks and a length of 50 cm is determined.

Here, the flow velocity inside the autoclave is 3.4 m/s, the temperature of the surface plate is 350°C during cooling, and the atmosphere inside the tube is 300°C.
As a representative case, the condition is that the jig temperature follows the ambient temperature with a delay of 10 minutes.

In addition, both the radiation fins and the surface plate are made of steel with a thickness of 2 mm.

First, since the pipe is extremely short at p/d-1.3, it is treated as a flat plate, and the flow is checked, and R and N are measured every 0.1m from the tip.
and α.

The physical property value of air at an average temperature of 325° C. between the air and the flat plate is λ-0,038 [Kcallmh”c].

Therefore, at a position of 0.1 m, N -0,458x6355""xo,720"3
uxO,1 −32,72 Next, the heat radiation mQ1 from the first radiation fin section is Q=(
θ −θ ) −“xo, I P 1 11
0 a W ″ tanh (
mlI) l) Mouth (350-300) x tanh (14,24X0.015) -1,87[Keal/hko x 32.72xO,038 -12,43 Kcal/rrfh'c] -14,24.

Here・λF′″ θ0− θ ~ ΩXO, J″″ becomes.

62, 5 [Kcal/mh℃ 350 ['C 300[℃] 2 cities - 0,002 [m] 100mm - 0,1 [ml I 5mm = 0. 015 [ml To make the amount of heat radiation between each radiation fin the same (θ −
θ ) −αx ” p ” Wx 10wX
As a, here, 7-7.87x103 [Kg/rrt co M-7
,42 [Kg] C-0,108 [Kcal/Kg'C] The amount of heat Q that the surface plate can dissipate in 10 minutes is calculated as follows:
28.20 [Kcal/10 minutes] However, αA is
17 at the center of the heat dissipation fins Next, determine the number of heat dissipation fins.

The amount of heat Q that the surface plate has. teeth, Qo-MCΔT-40,07 [Kcal].

During these 10 minutes, all the heat dissipation fins radiate the remaining amount of heat, but the amount of heat dissipated QPA for the 10 minutes of the hk heat rough-ins is QFA-50x, x, x, x.

Conflict Lan1+ (IO, 82X0.02B) XI/6-1
．． 533 [Kcal/10 minutes] The amount of heat emitted by all the heat radiation fins is ΔQ - 40.07 - 28.
2-11.87 [Kcal] Therefore, the number N of radiation fins is N-11,87/1.533-7.7 8 pieces.

Furthermore, fences 6.6 are fixed to the side surfaces of the radiation fins 5.5, which protrude in a direction perpendicular to the flow direction of the hot air, that is, in a direction parallel to the horizontal frame.

These fences 6, 6, . . . are forcibly agitating the wind to create a turbulent flow, thereby improving heat transfer.

That is, as shown in FIG. 3(b), when the heat dissipation fins 5, 5,... are provided in the flow direction, the heat dissipation fins 5,5,...
In the vicinity of ..., the flow velocity becomes extremely low, and the heat transfer coefficient also becomes small.

Therefore, as shown in Figure (a), by providing fences 6.6 perpendicular to the flow, by applying fluid to these fences 6.6, turbulent flow is forced. This improves heat transfer by separating and diffusing the flow near the radiation fins.

The relationship between the pitch p of the fence and the height h of the fence is determined experimentally, but is generally about p-5h.

As shown in Figure 4, after the jig is fabricated, the temperature distribution is actually measured, and it is determined whether the temperature distribution is uniform or not before heat insulation treatment is applied. This can be done in one or two times in total, and since this measured data can be compared with design data, it can be standardized, and mechanical design can be performed using this standardized data. It is possible to do so.

〔Effect of the invention〕

Since the present invention has the above-described configuration, it is possible to actively take in hot air and make maximum use of it, thereby improving the temperature rise and cooling efficiency. By making temperature-insensitive areas more sensitive through the process, the temperature distribution can be made uniform, thereby increasing the efficiency of the autoclave.

Furthermore, since it is possible to specifically compare the data at the time of design and actual measurement, it is possible to reflect more accurate data on the next jig, and it is possible to standardize the design based on the collected data. This has the effect that variations in jig performance due to the influence of the designer's level of experience can be reduced as much as possible.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a jig according to an embodiment of the present invention seen from the back side, Fig. 2 is an enlarged view showing section A in Fig. 1, and Figs. 3 (a) and (b) are An explanatory diagram to explain the difference in the flow of hot air depending on the presence or absence of a fence, Fig. 4 is a flowchart from the design of the present invention to the post-production process, Fig. 5 is a block diagram showing an overview of the calculation method, and Fig. 6 is a diagram showing the flow of hot air in the pipe. Graph for determining the Nusselt number during laminar flow in the speed run-up area, Figure 7 is a diagram showing symbols for determining the heat radiation amount of each fin section of the heat radiation fin, and Figure 8 is from the design of the conventional example. It is a flowchart after production. ]...FRP molding jig, 2...surface plate, 3...vertical frame, 3a, 3b...ventilation opening, 4...picture frame, 4a...
... Ventilation opening, 5... Radiation fin, 6... Fence.

Claims (1)

[Claims] In a molding jig designed to mold FRP in a hot air circulation type heating furnace, a front plate whose front surface has a shape that determines the shape of the product is used, and a minimum air velocity is secured on the back side of the front plate. The structure is configured so that there is no large difference in heat transfer in each part, and there are multiple strips extending along the wind flow direction on the back side of the top plate, and the amount of heat dissipated from the top plate within a certain time based on the amount of heat the top plate has. Radiation fins set to uniformly dissipate the amount of heat equal to the value of An FRP molding jig that is characterized by: