KR950007676B1 - Deflection yoke - Google Patents

Abstract

The shaping method of coil separator minimizes the modification modeling by modeling of the metal for coil separator. The method comprises the steps of: forming the gate for injecting the row material, injecting the raw material of coil separator by the pressure of 70MPa for a second, and cooling it in a cavity of the metallic model for 18˜25 seconds.

Description

Molding method of coil separator of deflection yoke

The drawing shows the forming state of the coil separator through computer simulation, and FIGS. 1 to 8 show the forming state of the coil separator by a conventional side gate.

1 is a diagram showing a pressure distribution when raw material filling is completed.

2 is a diagram showing a temperature distribution when raw material filling is completed.

3 is a diagram showing the pressure distribution in the packing process.

4 is a diagram showing a temperature distribution after cooling.

5 is a diagram showing the shrinkage per unit volume after injection.

6 is a view showing the warpage state of the coil separator after injection.

7 is a view showing a bending state by cooling after injection.

8 is a view showing a state of shrinkage deformation due to uneven pressure retention.

9 to 14 are diagrams showing the forming state of the coil separator by the one-point pin point gate method according to the present invention.

9th graph showing the pressure distribution when the raw material filling is completed.

10 is a diagram showing a temperature distribution when raw material filling is completed.

11 shows shrinkage per unit volume after injection.

12 is a diagram showing a bending state of the coil separator after injection.

FIG. 13 is a view showing a bending state in consideration only of the effect of cooling after injection.

14 is a view showing the results of the deflection analysis considering only the effect of the holding pressure.

15 to 17 are views showing another example by the one-point pin point gate according to the present invention,

FIG. 15 is a diagram showing a bending deformation state in a state where a part of the thickness of the coil separator is adjusted. FIG.

FIG. 16 is a view showing a state in which ribs are formed at the joint portion of the curved surface portion and the screen side of the loil separator. FIG.

FIG. 17 is a view showing the bending deformation results in FIG.

The present invention relates to a deflection yoke. More specifically, a deflection yoke coil has a coil separator that has a large influence on the distribution of characteristics of a deflection yoke so that the shape deformation can be minimized during injection molding by a mold. It relates to a separator molding method. In general, a deflection yoke mounted on a cathode ray tube such as a TV or a monitor to deflect a beam emitted from an electron gun, as is well known, is a horizontal coil inside a pair of coil separators consisting of a neck portion and a screen portion. Is mounted, and a ferrite core wound around the vertical coil is assembled by the core clamp.

Such a deflection yoke is mounted to the rear of the cathode ray tube, so that an image can be constructed by deflecting a beam emitted from an electron gun to each dice on the screen.

However, since the deflection yoke as described above is difficult to accurately scan the beam in place due to its mechanical error or its own characteristics, it causes various misconvergences on the screen. Correction means are used.

The most influential cause is due to the deformation of the coil separator, which occurs during the injection molding of the coil separator by the mold, causing the mutual assembly instability of the horizontal and vertical coils. It has a large effect on the dispersion and is a direct cause of the deterioration of the deflection yoke.

In addition, due to the deformation of the coil separator, the deformation must be forcibly corrected by using a jig immediately after the injection, and the molding cycle time becomes long, which greatly affects productivity.

Therefore, it is very urgent to prevent the deformation occurring in the coil separator as described above and to secure the technology thereof. Until now, it was only possible to speculate that the cause of the deformation was simply caused by uneven cooling. Deformation has been slightly reduced by methods such as thickness control or rib formation, but the exact cause of the coil separator is poor in design and manufacturing technology.

Therefore, the inventors have tried to minimize the adverse effects on the characteristics distribution of the deflection yoke caused by the deformation of the coil separator by analyzing the causes of deformation of the coil separator described above and establishing the fundamental countermeasures. In addition, it was found that the temperature distribution and the pressure distribution were changed by the runner system 1 on the mold, which greatly influenced the warpage or shrinkage. Thus, computer simulation based on this fact was performed. Through this, the basic design method to minimize the deformation of the coil separator was derived.

An object of the present invention is to provide a coil separator molding method of a deflection yoke capable of minimizing the shape deformation occurring during injection molding of the coil separator constituting the deflection yoke as described above.

A feature of the present invention for achieving the above object is a molding method for minimizing the shape deformation in the case of injection molding a coil separator of a deflection yoke for deflecting a beam emitted from an electron gun mounted on a cathode ray tube. The method may further include: selecting a position at which a flow balance is formed in a cavity having a shape with the coil separator on a pair of molds so that a gate for raw material injection is formed at this point; Injecting a raw material of a coil separator at about 200 ° to 220 ° C. at a pressure of about 70 MPa for about 1 second into the cavity of the mold through the gate; A method of forming a coil separator for a deflection yoke, comprising: cooling a raw material filled in a cavity of the mold for about 18 to 25 seconds to form a coil separator and then taking it out of the mold.

Hereinafter, an embodiment of the coil separator molding method of the deflection yoke according to the present invention will be described in detail according to the accompanying drawings.

First, the inventors found that deformation was generated on both the screen side, the neck side, and the curved portion as a result of measuring the deformation phenomenon by presenting general injection conditions during injection molding of the coil separator. In other words, on the screen side, the left and right edges of the coil separator sag toward the curved surface, which is the main cause of the loule separator's cracking, and the cycle time during the actual injection molding to reduce the deformation even a little. It also increases productivity, as well as quality.

In addition, since the neck side has a problem in assembling the coil as the deformation that is driven inwards during the injection molding of the coil separator, the deformation is forcibly corrected by using a jig immediately after the injection. Therefore, it is difficult to automate the injection molding process, causing labor costs to increase due to manpower input.

In addition, the curved portion of the rib portion formed in the center of the coil separator (Rib) and the left and right edge portion of the deformation occurs that the length is different. Such deformation of the curved portion has a deformation in the coil during assembly to affect the characteristics of the deflection yoke a lot. do.

The following <Table 1> is the value which measured these three deformation | transformation quantities, and the measurement object model made the 19 ＂VA with a comparatively large deformation amount.

TABLE 1

Here, the numerical values used for the injection of the coil separator were analyzed using a package for injection molding analysis developed by Cornell University, Novolen-1320HX of BASF of the United States of America. Boundary warning was set to be as similar as possible by examining the actual injection conditions.

<Table 2> shows various conditions used for the above analysis.

TABLE 2

As described above, in order to solve the deformation of the coil separator, a purified cause analysis is required. For this, the flow, holding pressure, cooling, and bending deformation analysis during injection molding are performed through computer simulation.

Example 1

The model to be analyzed was 14 ＂0.41P coil separator, and the runner system (SIDE CATE TYPE) was used in most coil separators. The analysis results for the side gate tapped are shown in FIGS. 1 to 8.

Figure 1 shows the pressure distribution at the completion of filling. The maximum pressure is 69.4 MPa, and there is no possibility of unmolding, but it can be seen that the pressure drop occurs because the flow length from the gate to the last filled neck portion is long.

2 shows the temperature distribution at the completion of filling, the temperature distribution on the curved surface and the screen side is severely different between the left and right portions and the center portion, so that if the cooling is not effective, many deformations may occur.

3 is a pressure distribution during the holding pressure process after 2 seconds. As can be seen from the drawing, the screen side and the curved portion receive some pressure in a linear direction with respect to the gate, but the left and right edge portions are hardly pressurized. The neck part does not receive pressure at all. That is, the resin filled with the cavity (cavity) due to the pressure non-uniformity in the process of holding pressure occurs due to the non-uniformity of the density, thereby causing a shrinkage rate for each site.

4 shows the temperature distribution after cooling, while the screen and the curved portion have relatively uniform cooling, but the neck side shows a partial deviation of about 15 ° C.

5 shows the shrinkage per unit volume after injection, which is determined as a function of temperature, pressure and specific volume.

From this, the maximum shrinkage is 10.8% and the negative value is generated at the gate area, so it can be seen that excessive pressure retention occurs.In general, the neck value tends to be large, and the screen side and the curved part are located at the center and left and right along the gate. It can be seen that there is some difference in the edge portion.

Based on the results of the injection molding analysis, the flexural analysis was performed in order to grasp the exact aspect of the deformation. The results of the bending analysis are shown in FIGS. 6 to 8.

Figure 6 shows the shape of the product bent after injection, showing the same aspect as the actual product. That is, the screen side is pulled out, inwardly pulled out, and the uneven shrinkage of the curved portion occurs. In order to specifically visualize the cause of such deformation, an independent analysis was performed on the effects of cooling and shrinkage, respectively. FIG. 7 shows the bending shape caused by cooling. However, the neck side was somewhat deformed. That is, the present cooling system has no problem in cooling the screen side and the curved surface ', but the neck side can be seen that the cooling state is uneven.

FIG. 8 shows the deformation state caused by the nonuniform shrinkage caused by the non-uniform pressure holding. The deformation is caused to some extent on the neck side, and particularly, the deformation is generated on the curved surface and the screen side. The above result is summarized in the following <Table 3>.

TABLE 3

Therefore, it can be seen that the curved portion and the screen side are deformed due to the shrinkage unevenness due to the uneven pressure of the curved portion, and the neck side is somewhat affected by the pressure of the pressure, although the neck is the main cause of the uneven cooling.

Thus, the main cause of the curved portion and the screen-side deformation is the nonuniformity of shrinkage due to the nonuniformity of the packing pressure, so the position of the gate is important to make the packing pressure uniform. The optimal position of the gate can be determined from the flow analysis and the most optimal position is where the flow balance during filling is filled and filled at the same time. For this reason, the analysis was conducted by setting the gate to the curved part as a one-point pin point type. The results were not very effective on the screen side. Was used.

Example 2

Through the flow analysis, it is confirmed that the position of the gate having the best balance of flow is the center of the curved portion, and the results of the analysis are shown in FIGS. 9 to 14.

FIG. 9 shows the pressure distribution at the completion of filling. The maximum pressure is 59.3 MPa, which is easier to fill than when the side gate is used. Therefore, the shear stress is less likely to occur, and the possibility of the post deformation will be less.

In addition, it can be seen that the pressure distribution on the screen side and the neck side is similar, so that filling is completed at the same time.

FIG. 10 shows the temperature distribution at the completion of filling, and the deviation is reduced by about 10 ° C. compared with the case where the side gate is used at the minimum temperature of 174 ° C., and the temperature on the neck side is generally lowered. In addition, since the curved portion and the screen side also form a relatively uniform distribution, it can be seen that the temperature distribution is improved due to the shift of the gate position.

11 shows the shrinkage per unit volume. The maximum value is 10.3%, which is similar to that of the side gate, but the distribution of the curved portion is relatively uniform, especially on the neck side, and the value is reduced much. Reduction of deformation due to uniformity of holding pressure is expected. Using these result data, the bending deformation after injection molding when the one-point pin point gate is installed at the center of the curved portion was analyzed. The results are shown in FIGS. 12 to 14.

Figure 12 shows the overall bending shape, the amount of deformation of the curved portion is 0.101mm, the neck side is significantly reduced to 0.096mm, but the screen side is only slightly improved to 0.202mm. In order to understand the cause, the bending analysis was conducted with the influence of cooling and packing pressure independently.

FIG. 13 shows the results of bending analysis considering only the effect of cooling, from which it can be seen that the cooling process proceeds very efficiently and hardly causes deformation.

14 is a result of the bending analysis considering only the influence of the holding pressure, the curved portion and the neck side can be seen that the deformation is fine, but the screen side is a certain rough deformation occurs.

In summary, the deformation of the curved part and the neck side is reduced by using the one-point gate in the center of the curved part, but the deformation of the screen side is still not satisfactory. Therefore, further countermeasures are required to reduce deformation on the screen side. The analysis results using the one-point pin point gate in the center of the curved portion are summarized in the following <Table 4>.

TABLE 4

As described above, the main cause of the deformation on the screen side is shrinkage unevenness due to uneven pressure, and as a first countermeasure, uniformity of shrinkage is achieved by adjusting the thickness of the product. Prevented

Example 3

In the case of the one-point pin point gate method, as shown in FIG. 14, the thickness of the curved portion is increased from 1.0 mm to 1.1 for the expansion of the holding pressure range from the gate. In addition, the thickness of the screen side was also set to 1.1 mm uniformly in order to make the shrinkage ratio of the screen side uniform, and the neck side was analyzed without changing the thickness because the deformation was fine. Fig. 5 shows the state of bending deformation in the analysis result in which a part of the thickness is adjusted. It can be seen that the deformation of the screen side as well as the neck side and the curved portion is very small.

As another method for preventing the deformation of the screen side in the state where the thickness was not deformed, an analysis was performed by installing ribs at the joint portion between the curved surface portion and the screen side as shown in FIG. The result of the bending deformation at this time is shown in FIG. 17, and it can be seen that the deformation is very small, similar to when the thickness is adjusted. The analysis results when adjusting the thickness and when installing the ribs are summarized in the following <Table 5>.

TABLE 5

Summarizing the above analysis results, the deformation amount in each case is shown in the following <Table 6>.

TABLE 6

In the case of the conventional side gate method, the analysis results show that the screen, neck, and curved portions are 0.34 mm, 0.15 mm, and 0.221 mm, respectively, than the 0.855 mm, 0.71 mm, and 0.53 mm actual measurement results for the 19 ＂VA model. It can be seen that the value is small. Therefore, it can be said that the difference in the relative value of each case is meaningful rather than the absolute value of the deformation amount in each case.

In the case of the one-point pin point gate method, compared with the conventional side gate method, the deformation is reduced by about 40% on the screen and neck sides and about 55% on the curved parts.

When ribs are installed in the one-point pin point gate method, the screen side is deformed about 80% compared to the conventional side gate method, the neck side is about 45%, and the curved part about 75%. In addition, when the thickness of the product was uniformly adjusted to 1.1mm in the one-point pin point gate method, the screen side improved about 90%, the neck side about 60%, and the curved side about 70%. Can be.

As described above, according to the coil separator forming method of the deflection yoke according to the present invention, the coil separator is provided at the position where the flow balance of the curved portion is provided by using the one-point pin point gate in the injection molding of the coil separator. The holding pressure is good on the neck side of the neck and the temperature distribution is improved, so that the deformation of the neck side can be considerably improved.The thickness of the screen side and the curved part can be made as uniform as possible to maintain a constant shrinkage rate and it is difficult to make the thickness uniform. In this case, it is possible to minimize the deformation caused during injection molding of the loil separator by using the rib.

Claims (4)

Selecting a position in the cavity having a shape of a loule separator on a pair of mold molds in order to balance the flow of the curved portion so that a one-point pin point gate for raw material injection is formed at this point; and through the one-point pin point gate Injecting the coil separator raw material into the cavity of the mold at a predetermined pressure for a few seconds, and cooling and holding the raw material filled in the cavity of the mold for several seconds to form a coil separator and then taking it out of the mold. A method of forming a coil separator of a deflection yoke, the shape of which is minimized by injection molding. The method of claim 1, wherein the one-point pin point gate is located at the center of the area of the cavity constituting the coil separator on the mold, and the raw material is simultaneously filled to the neck side and the screen side. The method of forming a coil separator for a deflection yoke according to claim 1 or 2, wherein the thickness of the screen portion and the curved portion is uniformly maintained during injection molding of the coil separator. 4. The method of forming a coil separator of a deflection yoke according to claim 3, wherein reinforcing ribs are further formed at the connection portions of the screen side and the curved portion when the screen and curved portions of the coil separator have different thicknesses.