JP3369962B2 - Method and apparatus for molding resin products by gas assist molding method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a molding method and a molding apparatus for a resin product having a hollow portion such as a side molding of an automobile.

[0002]

2. Description of the Related Art Resin products having hollow portions, such as automobile side moldings, are often molded by a gas assist molding method. The gas-assisted molding method refers to the thick-walled part ("gas channel") of a molded product when injection molding is performed.
Called. ) Is injected with a gas to obtain an injection-molded article having a hollow portion, which is also called "gas injection".

FIG. 7 shows a conventional gas-assist molding apparatus 100 for molding a side molding of an automobile. This device is a mold 120 consisting of two mold elements.
A cavity 122 corresponding to the shape of the side molding M to be manufactured is formed between the two mold elements, and a gas channel portion 124 extending in the longitudinal direction is provided at the center of the cavity 122 in the width direction. Has been. As shown in FIG. 7, normally, a plurality of cavities 122 are formed in the mold 120 in order to mold a plurality of side moldings M at the same time.

The mold 120 has sprues 127 for supplying molten resin into the mold 120 from the outside, a runner 128 for guiding the molten resin into the cavity 122, and the mold 12.
A gas injection port 129 for injecting gas into the zero gas channel portion 124 is formed. The runner 128 and the gas inlet 129 are connected to the cavity 122 via the gate 126. Sprue 127 to runner 12
8 and through the gate 126, after filling each cavity 122 with molten resin, or while filling,
Before the molten resin is solidified, gas is supplied to the gas channel portion 124 via the gas injection port 129 and the gate 126 to form a hollow portion.

FIG. 8 shows a side molding M molded using the mold 120 of FIG. 7, FIG. 8 (a) is a front view seen from the gas channel side, and FIG. 8 (b) is FIG. 8 (a). 8b is a vertical sectional view taken along line bb, and FIG. 8C is a vertical sectional view taken along line cc of FIG. 8A. As shown in FIGS. 8B and 8C, a hollow portion 150 is formed in the gas channel 124 ′ by the pressure of the gas.

Further, FIG. 9 shows a side molding M'of another embodiment, which is molded by the gas assist molding method described above. FIG. 9 (a) is a front view and FIG. 9 (b) is FIG.
9A is a vertical sectional view taken along the line bb of FIG. 9A, and FIG. 9C is a vertical sectional view taken along the line cc of FIG. 9A. The mold (not shown) used to mold the side molding M ′ is the gas channel unit 1 of the mold 120 used in the apparatus 100 of FIG.
The width of 24 is gradually widened from the middle along the longitudinal direction,
Then, it is finally converged to a certain width.

[0007]

However, according to the conventional method, since the molten resin is filled from one end of the cavity 122 through the gate 126, a long product such as the side molding M shown in FIG. 8 is obtained. When the long die 120 is used for molding, the temperature of the molten resin filled decreases as the end of the die 120 approaches, and the fluidity of the resin decreases.

Therefore, the hollow portion 1 is caused by the pressure of the gas.
It becomes difficult to form 50, and as shown by the broken line in FIG. 8A, the cross-sectional area of the hollow portion 150 is gradually reduced, and the wall thickness of the hollow portion 150 is correspondingly increased. As shown in FIG. 8C, the cross-sectional area of the hollow portion 150c becomes smaller,
If the gas channel 124 corresponding to the hollow portion 150c becomes thick, sink marks S are generated on the surface of the product, the strength is lowered, and the appearance is deteriorated.

Further, in the side molding M'shown in FIG. 9, as shown by the broken line in FIG. 9 (a), the cross-sectional area of the hollow portion 150 'gradually decreases as it approaches the end, while the width of the gas channel increases. Since it becomes wider from the middle, the wall thickness of the gas channel 124 'corresponding to the hollow portion 150c' near the end becomes thicker, and sink marks S are more likely to occur on the product surface.

[0010]

According to the present invention, in a method for molding a resin product having a gas channel by a gas assist molding method, the temperature of a portion of a mold corresponding to the gas channel is gradually increased with increasing distance from the gas inlet. By the molding method, which is characterized by
The above problems have been solved.

According to a second aspect of the present invention, there is provided an apparatus for carrying out the above method, which comprises a plurality of heaters and temperature sensors along the longitudinal direction of the portion corresponding to the gas channel of the mold, and gradually becomes farther from the gas inlet. It is an apparatus for molding a resin product by a gas-assisted molding method, the temperature of which is controlled to be a high temperature.

[0012]

In the present invention, the temperature of the portion corresponding to the gas channel of the mold filled with the molten resin is gradually increased as the distance from the gas inlet is increased. The property can be made uniform in the longitudinal direction of the mold. Therefore, it becomes possible to mold a product having a hollow portion with a uniform wall thickness along the longitudinal direction of the gas channel. That is, it has become possible to obtain a resin product having the same thickness around the hollow portion by the gas assist molding method.

[0013]

1 shows a schematic front view of a gas-assisted molding apparatus 10 according to the present invention, and FIG.
It is a 2-line vertical cross-sectional view. This device 10 is similar to a conventional device in that a mold 20 including two mold elements 20a and 20b is used.
(See FIG. 2). A cavity 22, a gate 26, a sprue 27, a runner 28, and a gas injection port 29 are formed in the mold 20, but the structure thereof is the same as that of the conventional one, and the description thereof will be omitted.

As shown in FIG. 2, a set of temperature control means 30 consisting of two heaters 32, 32 and one temperature sensor 34 is provided along the longitudinal direction on both wall surfaces corresponding to the gas channels of the product. , Multiple sets are installed. This is because the gas-assisted molding method utilizes the characteristic that the molten resin preferentially flows in the gas channel portion. Each temperature control means 30 is connected to a control section 38 having a data input section 36. The temperature to be maintained by each temperature control unit 30 is preset in the data input unit 36, and the heating input to each temperature control unit 30 is controlled by the control unit 38 based on this set temperature. The temperature of the mold of the portion corresponding to the gas channel is set so as to gradually become higher as it moves away from the gate port 26 'of the product.

1 and 2, the temperature control means 30 has two
Although it is composed of one heater 32, 32 and one temperature sensor 34, one temperature sensor 34 is not necessarily required for two heaters 32. Further, the arrangement of the heater 32 and the temperature sensor 34 is not limited to this, and any arrangement may be used as long as the temperature is appropriately detected at each position and the temperature can be controlled.

The gas-assisted molding apparatus 10 is provided with a cooling water supply unit 40, and the mold heated by the temperature control means 30 is cooled by the cooling water passing through the pipe provided along the cavity 22. After being properly cooled, the cooling water is discharged from the discharge port 44. The valve 42 of the cooling water supply unit 40 is connected to the control unit 38, and the amount of cooling water is appropriately controlled by the control unit 38. Therefore, the combined use of the heater 32 and the cooling water supply unit 40 enables fine temperature control.

FIG. 3A is a front view of a side molding M having a hollow portion 50 formed by using the gas assist molding apparatus 10 of the present invention shown in FIGS. 1 and 2, and FIG. 3] is a diagram showing the relationship between the channel temperature and the distance from the gate opening 26 'of the side molding M to the end when molding the side molding M of FIG. 3 (a). In this case, a mold in which the temperature control means 30 is installed every 100 mm from the gate opening 26 ′ to the terminal end is used, and in FIG. 3B, the channel temperature at each position where the temperature control means 30 is installed is measured. Plotted. As shown by the broken line in FIG. 3A, since the hollow portion 50 of the side molding M is molded with a constant width along the longitudinal direction, the wall thickness of the gas channel 24 corresponding to the hollow portion 50 is also increased. It is constant. Figure 3 (b)
As shown in, when molding the side molding M, the channel temperature is set to gradually increase in proportion to the distance from the gate opening 26 'to the terminal end.

Next, FIG. 4 is a side molding M ′ of the second embodiment, which is molded by the resin product molding apparatus 10 by the gas assist molding method of the present invention, and FIG.
4A is a front view, FIG. 4B is a vertical sectional view taken along the line bb of FIG. 4A, and FIG. 4C is a vertical sectional view taken along the line cc of FIG. 4A. Compared to the side molding M of FIG. 3, this side molding M ′ has the width of the gas channel 24 ′ gradually increased from the middle along the longitudinal direction as in the case of FIG. 9, and thereafter, at a constant width, The last is to make it converge. As compared with the hollow portion 50b ′ of FIG. 4 (b), in FIG. 4 (c), the hollow portion 50c ′ is formed so as to have a larger cross-sectional area corresponding to the width of the gas channel 24 ′. The wall thickness of the gas channel 24 'corresponding to the portion 50' is always constant.

FIG. 5 is a diagram showing the relationship between the temperature of the channel portion and the distance from the gate opening 26 'of the side molding M'to the end when molding the side molding M'of FIG. Also in this case, as in FIG. 3, a mold in which the temperature control means 30 is installed every 100 mm from the gate opening 26 ′ to the terminal end is used, and the channel temperature at each position where the temperature control means 30 is installed is measured. Plotted. This side molding M'is shown in FIG.
As shown in (a), as the width of the hollow portion 50 ′ changes from the middle along the longitudinal direction and the cross-sectional area of the hollow portion 50 ′ increases, the channel temperature also changes in the longitudinal direction. , Is set to be higher temperature, but then
Since the width of the hollow portion 50 'is constant, the set temperature rises gradually.

Next, FIG. 6 is a side molding M ″ of the third embodiment, which is molded by the resin product molding apparatus 10 by the gas assist molding method of the present invention.
6A is a front view, FIG. 6B is a vertical sectional view taken along the line bb of FIG. 6A, and FIG. 6C is a vertical sectional view taken along the line cc of FIG. 6A. In the side molding M ″, not only the portion of the gas channel 24 ″ but also the entire width of the molding M ″ is complicatedly changed along the longitudinal direction. Also in this case, as compared with the hollow portion 50b ″ of FIG. 6 (b), in FIG. 6 (c), the cross-sectional area of the hollow portion 50c ″ also becomes large corresponding to the width of the gas channel 24 ″. Since the gas channel 24 ″ corresponding to the hollow portion 50 ″ is formed, the wall thickness of the gas channel 24 ″ is always constant.

In this embodiment, the illustration of the relationship between the temperature of the channel portion and the distance from the gate opening 26 'of the side molding M "is omitted, but it is almost the same as the side molding M'of FIG. Hollow part 5
The channel temperature is set to a higher temperature as the width of 0 ″ becomes wider.

In the resin product molding apparatus 10 according to the gas assist molding method of the present invention, the gas channels 24 and 2 are provided.
The temperature of the mold corresponding to each of the positions 4 ′ and 24 ″ is appropriately set according to the conditions such as the molding material, the shape of the product, and the degree of the wall thickness of the channel portion. Also, gas channel 2
The number of temperature control means 30 provided in the mold part corresponding to 4, 24 ', 24''and the arrangement thereof can also be changed depending on the conditions.

The resin product molded by the gas assisted molding method 10 of the present invention is not limited to the side molding.
By appropriately controlling the temperature of the portion corresponding to the gas channel of the mold, it is possible to mold a resin product of a complicated shape having a hollow portion with a uniform wall thickness throughout.

[0024]

According to the molding method and molding apparatus for a resin product by the gas assist molding method of the present invention, the molten resin injected into the cavity can maintain uniform fluidity in the longitudinal direction of the cavity. . Therefore, it is possible to form a hollow portion having a uniform wall thickness in the longitudinal direction in the gas channel, and as a result, sink marks or the like do not occur on the surface of the product and the design is improved.

Furthermore, even if the width of the gas channel changes from the middle of the product or the product has a complicated shape, it has a hollow portion of a predetermined size by appropriately controlling the temperature of the mold. In addition, there is an effect that the wall thickness of the gas channel around the hollow portion can be formed to be equal.

[Brief description of drawings]

FIG. 1 is a schematic view of a molding apparatus for resin products by a gas assist molding method of the present invention.

2 is a vertical sectional view taken along line 2-2 of the molding apparatus of FIG.

3 (a) is a front view of a side molding molded by the molding device of FIG. 1, and FIG.
3A is a relational diagram of the distance from the gate opening of the side molding and the channel temperature when the side molding of FIG. 3A is formed.

FIG. 4 shows a side molding of a second embodiment, which is molded by a resin product molding apparatus by the gas assist molding method of the present invention, FIG. 4 (a) is a front view and FIG.
4B is a vertical sectional view taken along the line bb of FIG. 4A, and FIG. 4C is a vertical sectional view taken along the line cc of FIG. 4A.

FIG. 5 is a relationship diagram between the distance from the gate opening of the side molding and the channel temperature when the side molding of FIG. 4 is molded.

FIG. 6 shows a side molding of a third embodiment, which is molded by a molding apparatus for resin products by the gas assist molding method of the present invention, and FIG. 6 (a) is a front view and FIG.
6B is a vertical sectional view taken along the line bb of FIG. 6A, and FIG. 6C is a vertical sectional view taken along the line cc of FIG. 6A.

FIG. 7 is a schematic diagram of a molding apparatus for a resin product by a conventional gas assist molding method.

8 shows a side molding formed by the apparatus of FIG. 7, FIG. 8 (a) is a front view, FIG. 8 (b) is a vertical sectional view taken along line bb of FIG. 8 (a), and FIG. ) Is shown in FIG.
3 is a vertical cross-sectional view taken along line cc of FIG.

9 shows another form of the side molding formed by the apparatus of FIG. 7, FIG. 9 (a) is a front view, and FIG.
9B is a vertical sectional view taken along the line bb of FIG. 9A, and FIG. 8C is a vertical sectional view taken along the line cc of FIG. 9A.

[Explanation of symbols]

10: Molding apparatus for resin products by the gas assist molding method 20: Mold 24: Gas channel 30: Temperature control means 32: heater 34: Temperature sensor 38: control unit 40: Cooling water supply unit 50: hollow part

Claims (3)

(57) [Claims] 1. A method for molding a resin product having a gas channel by a gas assist molding method, wherein the temperature of a portion of the mold corresponding to the gas channel is gradually increased as the distance from the gas injection port increases. And a method of molding a resin product by the gas assist molding method. 2. A molding apparatus for a resin product having a gas channel by a gas assist molding method, comprising a plurality of heaters and a temperature sensor along a longitudinal direction of a portion of a mold corresponding to the gas channel, and a gas injection port. An apparatus for molding a resin product by a gas-assisted molding method, which is characterized in that the temperature is controlled so that the temperature becomes gradually higher as the distance from the resin product increases. 3. The apparatus according to claim 2, further comprising a cooling water supply unit.
Molding equipment for resin products by the gas-assisted molding method.