JPH1044179A - Hollow injection forming method and its device, and inspection method for hollow injection molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a hollow part of a hollow injection molded product at a favorable precision, and stably prevent an unfavorable appearance from generating by a method wherein The shape of the hollow part which is formed by an injection gas, is detected, and the injection condition of the gas is controlled depending on the detected state. SOLUTION: A hollow part is formed by injecting nitrogen gas in a specified area of a molten resin which is injected in a cavity between the molding surfaces 3a, 2a of upper and lower dies 3, 2. The resin temperatures are measured and compared by an infrared ray camera 54 at the border regions between the hollow part both ends and a solid part of a bumper W which is on the way to be taken out after the cooling of the injected resin is almost completed, and if the temperature difference is a specified temperature, it is judged that the hollow part has been formed into the aimed shape, and a next injection molding is performed. If there is no temperature difference, and the resin temperatures are all high, it is judged that the length of the hollow part is insufficient, and the injection pressure of the gas which is injected in the resin, is increased, and the gas injection amount is increased. When the resin temperatures are all low, it is judged that the length of the hollow part is too long, and the gas injection pressure to be injected in the resin, is decreased, and the gas injection amount is changed so as to be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of injecting a resin into a cavity of a molding die and then injecting a gas into the resin (hereinafter referred to as "gas containing air"). The present invention belongs to a technical field related to a hollow injection molding method and apparatus for molding a hollow injection product (molded product) having a hollow portion therein, and a method for inspecting a hollow injection product.

[0002]

2. Description of the Related Art Conventionally, as this kind of hollow injection molding method, as shown in, for example, Japanese Patent Application Laid-Open No. 2-215516, a resin reservoir communicating with a cavity deep portion is formed in a molding die and a cavity is formed. After injecting the resin inside,
When injecting a gas therein, of the resin in the cavity, by discharging a resin having a volume corresponding to a hollow portion formed by gas injection and injection into the resin reservoir,
It has been known that even a thin injection product can be satisfactorily injected and injected with gas while enhancing its surface appearance.

[0003]

By the way, in such a hollow injection product having a hollow portion inside, there is an advantage that the internal hollow portion can prevent sink of the product outer surface and increase the strength of the product. is there.

However, in practice, when a hollow portion is formed by injecting a gas into an injection resin in a cavity, it is difficult to always accurately form the hollow portion in a portion where the hollow portion should be formed. The shape of the hollow portion varies due to variations in molding depending on pressure and pressure, and the hollow portion cannot be formed with high accuracy. As a result, there is a possibility that appearance defects such as sink marks and gas protrusion may occur on the product surface to some extent. Whenever such a defective appearance of the product occurs, the molding process is stopped each time, and conditions such as the temperature and pressure of the resin and the pressure of the gas to be injected are changed. .

[0005] The present invention has been made in view of the above, and an object of the present invention is to always control the conditions when injecting and injecting a gas into a resin of a cavity as described above, thereby making it possible to form a hollow resin. An object of the present invention is to make it possible to accurately form a hollow portion of an injection product in real time, and to stably prevent appearance defects of the product.

[0006]

In order to achieve the above object, according to the present invention, the shape of a hollow portion formed by a gas injected into a resin is directly or indirectly detected, and the shape of the hollow portion is detected. The gas injection conditions are controlled according to the shape.

More specifically, the inventions of claims 1 to 17 are inventions of a hollow injection molding method. In the invention of claim 1, after injecting a resin into a cavity in a molding die, a gas nozzle is inserted into the resin. In a hollow injection molding method for injecting a gas and molding a hollow injection product having a hollow portion therein, a shape of the hollow portion formed by the injection gas is detected, and a shape of the hollow portion is detected based on the detected state of the detected hollow portion. To control the gas injection conditions.

With this configuration, at the stage of forming a hollow portion by injecting a gas into the resin of the cavity, the shape of the hollow portion is detected, and the gas is detected based on the detected state of the hollow portion. The injection conditions are controlled, so the shape of the actually formed hollow part can be accurately detected, and the gas injection conditions can be changed so that the hollow part has the desired shape. By accurately forming the hollow portion, the occurrence of poor appearance can be stably prevented.

According to the second aspect of the present invention, the shape of the hollow portion is detected based on the resin temperature in the boundary region between the hollow portion and the solid portion formed by the injection gas. This makes it possible to indirectly detect the shape of the hollow portion.

According to a third aspect of the present invention, in the hollow injection molding method according to the second aspect of the present invention, the shape of the hollow portion is detected based on a difference in resin temperature between the hollow portion and the solid portion. That is, although the respective resin temperatures of the hollow portion and the solid portion are variously changed in the molding process, the temperature difference between the two is always substantially constant.
By utilizing this fact and detecting the difference in the resin temperature, the shape of the hollow portion can be accurately detected.

According to a fourth aspect of the present invention, in the hollow injection molding method of the second or third aspect, the gas injection conditions are controlled by changing the gas injection pressure. According to the fifth aspect of the present invention, the gas injection conditions are controlled by changing the gas injection timing. This makes it possible to easily control the gas injection conditions.

According to a sixth aspect of the present invention, in the hollow injection molding method of the fourth aspect, the gas injection pressure is changed by adjusting a variable pressure mechanism for varying the gas injection pressure from the gas injector. . Thus, control for changing the gas injection pressure can be easily performed.

According to a seventh aspect of the present invention, in the hollow injection molding method according to the first aspect of the present invention, an actual pattern of the gas injection pressure over time is compared with a preset standard pattern. The gas injection conditions are controlled based on the deviation of the gas injection pressure. The standard pattern indicates a change in gas injection pressure when a hollow portion is normally formed in the resin, and when the pattern of the gas injection pressure that changes with the formation of the hollow portion deviates from the standard pattern, What is necessary is just to change the gas injection pressure so as to reduce the deviation. Therefore, the shape of the hollow portion can be accurately detected in the present invention.

According to an eighth aspect of the present invention, in the hollow injection molding method of the seventh aspect, similarly to the fourth aspect, the gas injection conditions are controlled by changing the gas injection pressure. . Therefore, the same function and effect as the fourth aspect of the invention can be obtained.

In this case, according to the invention of claim 9, specifically, when the gas injection pressure of the actual pattern is larger than the standard pattern, the gas injection pressure is increased. That is, the fact that the gas injection pressure of the actual pattern is higher than the standard pattern means that the gas injection pressure is high because the formation of the hollow portion inside the resin pattern is insufficient due to the high resin pressure and the like. And to make up for it,
The injection pressure of the gas is increased more than usual to promote the formation of the hollow portion. In this case, control for changing the gas injection pressure can be realized.

According to a tenth aspect of the present invention, in the hollow injection molding method of the seventh aspect, the gas injection conditions are controlled by changing the gas injection timing. In this case, the same operation and effect as the fifth aspect of the invention can be obtained.

According to the eleventh aspect, when the gas injection pressure of the actual pattern is higher than the standard pattern, the gas injection timing is advanced. That is, as described above, when the gas injection pressure of the actual pattern is higher than the standard pattern and the injection pressure is high due to insufficient formation of the hollow portion inside the resin, the gas injection timing is normally The formation of the hollow portion is promoted earlier. Therefore, control for changing the gas injection timing can be realized.

According to a twelfth aspect of the present invention, in the hollow injection molding method of the first aspect, each of the plurality of hollow portions is formed by injecting gas from a plurality of gas nozzles into the same region of the resin in the cavity. The actual pattern of the gas injection pressure from the gas nozzle over time is compared with a preset standard pattern, and the gas injection conditions from each gas nozzle are controlled based on the deviation of the gas injection pressure in both patterns. . This makes it possible to accurately detect the shape of each hollow portion when a plurality of hollow portions are formed by injection gas from a plurality of gas nozzles in the same region of the resin in the cavity. Similar effects can be obtained.

According to a thirteenth aspect of the present invention, in the hollow injection molding method of the twelfth aspect, the gas injection conditions are controlled by changing the gas injection pressure from each gas nozzle. By doing so, the same effect as the invention of claim 8 can be obtained.

According to a fourteenth aspect of the present invention, in the hollow injection molding method of the thirteenth aspect, when the gas injection pressure of the actual pattern is higher than the standard pattern, the gas injection pressure is increased. Thus, the same operation and effect as the ninth aspect can be obtained.

According to a fifteenth aspect of the present invention, in the hollow injection molding method of the fourteenth aspect, when a hollow portion larger than the other hollow portions is formed, the hollow portion is further enlarged to form an adjacent hollow portion. To communicate with That is, even if it is detected that the shapes of the plurality of hollow portions vary, a gas is injected so as to further enlarge the large hollow portion therein, and the hollow portion is communicated with the adjacent hollow portion. It is sufficient that the occurrence of sink marks on the surface of the injection product can be satisfactorily prevented.

According to a sixteenth aspect, in the hollow injection molding method of the twelfth aspect, the gas injection conditions are controlled by changing the gas injection timing from each gas nozzle. In this case, the same effect as the ninth aspect can be obtained.

Further, according to the seventeenth aspect, in the sixteenth aspect,
In the hollow injection molding method of the invention, when the gas injection pressure of the actual pattern is higher than the standard pattern, the gas injection timing is advanced. In this case, the same effect as that of the eleventh aspect can be obtained.

The inventions of claims 18 and 19 are both
This is an invention of an inspection method for injecting a resin into a cavity in a molding die and then injecting a gas from a gas nozzle into the resin to inspect a hollow injection product having a hollow portion inside. A feature of the eighteenth aspect is that the shape of the hollow portion is inspected based on the temperature difference between the hollow portion and the solid portion formed by the injection gas. According to the present invention, the hollow portion can be accurately detected as in the third aspect of the present invention.

On the other hand, a feature of the invention of claim 19 is that the shape of the hollow portion is inspected based on a pattern of the gas injection pressure over time. Also in this invention, the shape of the hollow portion can be detected accurately, similarly to the invention of claim 7.

The inventions of claims 20 to 26 are inventions of a hollow injection molding apparatus. In the invention of claim 20, after injecting a resin into a cavity in a mold, a gas is injected into the resin from a gas nozzle. A hollow injection molding apparatus configured to mold a hollow injection product having a hollow portion therein; a temperature detecting means for detecting a temperature of a boundary region between the hollow portion and the solid portion formed by the injection gas; Control means for controlling the gas injection conditions based on the temperature of the boundary region between the hollow portion and the solid portion detected by the detection means.

According to the present invention, the temperature of the boundary region between the hollow portion and the solid portion formed in the resin by the injection gas is detected by the temperature detecting means, and the temperature is detected by the control means by the temperature detecting means. The gas injection condition is controlled based on the temperature of the boundary region between the hollow portion and the solid portion. This makes it possible to accurately detect the shape of the hollow portion based on the temperature of the boundary region between the hollow portion and the solid portion, and change the gas injection conditions so that the hollow portion has the desired shape. The hollow portion of the product can be formed with high accuracy, and the appearance defect can be stably prevented.

According to a twenty-first aspect of the present invention, in the hollow injection molding apparatus of the twentieth aspect, the temperature detecting means detects a difference in resin temperature between the hollow portion and the solid portion. Thus, the same effect as the third aspect of the invention can be obtained.

In the invention of claim 22, a temperature sensor for measuring the temperature of the resin in the cavity is provided in the mold. This facilitates the arrangement of the temperature sensor. In this case, the temperature sensor is provided on the back surface of the mold. This allows the temperature sensor to be hidden behind the mold.

In the invention of claim 24, claim 20 or 2
In the hollow injection molding apparatus according to the first aspect of the present invention, a temperature sensor for measuring a resin temperature is provided in a take-out means for taking out an injection product from a mold. With this arrangement, the temperature sensor can be arranged using the existing take-out means, and the step of taking out the product by the take-out means can also be used as the step of measuring the resin temperature.

According to a twenty-fifth aspect of the present invention, in a hollow injection molding apparatus similar to the premise of the twentieth aspect, an actual pattern of gas injection pressure over time is compared with a preset standard pattern. Pressure pattern detection means for detecting a deviation of gas injection pressure in both patterns, and control means for controlling gas injection conditions based on the deviation of gas injection pressure in both patterns detected by the pressure pattern detection means. It is characterized by having.

According to the present invention, the actual pattern of the gas injection pressure over time is compared with the standard pattern by the pressure pattern detection means, and the deviation of the gas injection pressure between the two patterns is detected. The gas injection conditions are controlled based on the difference between the gas injection pressures in both patterns detected by the pressure pattern detection means. This makes it possible to accurately form the hollow portion and stably prevent the appearance of the hollow injection product from being defective in appearance, similarly to the seventh aspect of the present invention.

According to the twenty-sixth aspect of the present invention, after injecting a resin into a cavity in a mold, a plurality of gas nozzles respectively inject a gas into the resin to form a hollow injection product having a plurality of hollow portions inside. In the hollow injection molding apparatus, the actual pattern of the gas injection pressure from each of the gas nozzles over time is compared with a preset standard pattern to detect a deviation of the gas injection pressure between the two patterns. A pressure pattern detecting means and a control means for controlling gas injection conditions based on a deviation of the gas injection pressure in both patterns detected by the pressure pattern detecting means are provided. Also in this case, the same operation and effect as the above-mentioned invention can be obtained.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 shows an injection molding apparatus A according to Embodiment 1 of the present invention.
A vehicle bumper W as a hollow injection product (molded product) as shown in FIG. 1 is injection-molded with its back surface facing downward. In the bumper W, a flange portion W1 at the upper end thereof is provided.
Left-right direction from the left-right central part of the bumper W (vehicle width direction)
, A hollow portion W2 having a predetermined length is formed.

Referring to FIG. 1, reference numeral 1 denotes a molding die made of a metal mold. As shown in FIG. And an upper die 3 as a movable die. The upper die 3 can be moved up and down by a lifting drive mechanism (not shown) so as to be able to come in contact with and separate from the lower die 2. Lower mold 2
Has a convex lower mold forming surface 2a on the upper surface thereof, and a concave upper mold forming surface 3 corresponding to the lower mold forming surface 2a on the lower surface of the upper mold 3.
a are respectively formed. The peripheral portions of the molding surfaces 3a, 2a of the upper and lower dies 3, 2 are flat mating surfaces, and when the upper and lower dies 3, 2 are combined with the lower dies 2, The two surfaces are in close contact with each other,
The closed space formed between the molding surfaces 3a and 2a is a cavity 5.

The upper die 3 has the cavity 5
A runner 7 for supplying a molten resin W 'to be a product (bumper W) is formed therein. This runner 7 is upper die 3
One end of which is connected to a resin injection mechanism (not shown) through a resin injection port 8 opened on the upper surface (back surface) of the upper mold 3, and the other end is opened to the cavity 5. ing. When the upper and lower dies 3 and 2 are matched, the cavity 5
Then, the molten resin W 'is injected and filled from the resin injection mechanism via the resin injection port 8 and the runner 7 to be molded.

As shown in FIG. 1, between the upper and lower dies 3, 2, the molded bumper W is sandwiched by the clampers 9, 9,. A take-out jig 10 (take-out means) to be taken out is arranged.
It is designed to move between a position in between and another position.

Further, a gas for forming a hollow portion W2 inside the resin W 'by injecting and injecting a nitrogen gas (hereinafter, simply referred to as a gas) into a predetermined portion of the resin W' in the cavity 5 between the upper and lower dies 3,2. An injection mechanism 13 is provided. The gas injection site (the position of the gas nozzle 14 described later) in the resin W 'in the cavity 5 is a central portion on the left and right of a portion serving as a flange portion W1 at the upper end of the bumper W as shown in FIG. As shown in FIG. 4 (only the left half of the bumper W is shown in FIG. 4), gas is injected and injected from the gas injection portion, so that the flange portion W1 of the bumper W is positioned from the left and right central portions. 1 that extends the same length in the left-right direction
One hollow portion W2 is formed.

The gas injection mechanism 13 has a gas nozzle 14 formed on the lower die 2, and the gas nozzle 14 is connected to a nitrogen gas cylinder 15 for storing gas via a gas pipe 16. The gas pipe 16 is branched in the middle into main and sub pipes 16a and 16b in parallel, respectively.
In the middle of the main pipe 16a, a normally-injected injector 18 that sucks gas from the cylinder 15 and discharges the same, and an electromagnetic valve that is located downstream of the main injector 18 and opens and closes the main pipe 16a. An injection valve 21 is provided in the middle of the sub-pipe 16b, and a sub-injector 23 that sucks and discharges gas from the cylinder 15 and an electromagnetic valve that is located downstream of the sub-injector 23 and opens and closes the sub-pipe 16b. A normally closed injection valve 26 composed of a valve is provided. The main and sub-injectors 18 and 23 have the same structure except that the gas discharge amounts (injection injection amounts) are different, and the suction ports 19 a and 24 connected to the cylinder 15 are provided.
a and discharge ports 19b, 24b communicating with the gas nozzle 14
The cylinder body 19, 24 is provided with a measuring cylinder comprising a cylinder body 19, 24 having an opening, and pistons 20, 25 reciprocally fitted in the cylinder body 19, 24. Each of the pistons 20, 25 is provided with a servo motor 22. When the pistons 20 and 25 are driven in the cylinder extending direction, the servo motors 22 and 27 draw the gas into the cylinder bodies 19 and 24 from the suction ports 19a and 24a, while the pistons 20 and 25 draw the gas. , 25 in the cylinder contraction direction when the cylinder body 19,
The gas in 24 is discharged from discharge ports 19b and 24b by a fixed amount.

In the middle of the gas pipe 16 and its main and sub pipes 16a, 16b, each pipe 1
Vents 29 to 31 each of which is a normally closed solenoid valve that opens 6, 16a, 16b and discharges gas therein are arranged.

In this embodiment, the sub-injector 23 and the vent 29 in the middle of the gas pipe 16 constitute a variable pressure mechanism 32 for varying the gas injection pressure from the main injector 18. Reference numeral 33 denotes a check valve connected in the middle of the gas pipe 16.

The servo motor 2 of each of the injection machines 18 and 23
The operation of the motor controllers 2 and 27 is controlled by a motor controller 53. The motor controller 53 is connected to a control unit 51 with a built-in CPU via a sequence controller 54. The control unit 51 is configured to control the opening and closing of the injection valves 21 and 26 and the vents 29 to 31 although signal lines are not shown. Output signals of a pair of infrared cameras 54, 54 as temperature sensors are input to the control unit 51. Each of the infrared cameras 54 is provided with a gas injection mechanism in the resin W 'in the cavity 5 between the upper and lower dies 3, 2. The resin temperature (surface temperature) of the boundary region between the hollow portion W2 formed by the injection gas injected from 13 and the solid portion W3 adjacent thereto is detected. As shown in FIG.
The pair of infrared cameras 54, 54
0, the bumper W taken out by the take-out jig 10
And are mounted so as to face.
The imaging range of each infrared camera 54 is, as shown in FIG. 4, the position P of the right and left ends of the normal hollow portion W2 which is to be originally formed in the resin W 'by the injection gas.
1, P1 and the boundary area between the positions P2 and P2 of the solid part W3, and the infrared camera 54
The resin surface temperature in the boundary region between the solid portion 2 and the solid portion W3 is measured.

Here, the injection molding operation controlled by the control unit 51 will be described with reference to FIG. First, conditions such as the injection pressure of the gas to be injected are set in step S1. Next, in step S2, the upper mold 3
Is moved downward to close the upper and lower dies 3 and 2, and then the step S3 is performed.
Then, the cavity 5 formed between the molding surfaces 3a, 2a of the upper and lower dies 3, 2 is provided from the resin injection mechanism to the runner 7 of the upper die 3.
And the molten resin W ′ is injected.

Thereafter, in step S4, the gas injection mechanism 1
3, the piston 20 of the main injector 18 is contracted by the servo motor 22, and a certain amount of gas discharged from the main injector 18 is discharged from the gas nozzle 14 of the lower die 2 to the resin W ′. Predetermined part (left and right central part of the part to be the flange part W1 of the bumper W)
Inject into the inside. Next, in Step S5, after the pressure of the injected gas is maintained for a predetermined time, Step S6 is performed.
Then, the vent 29 in the middle of the gas pipe 16 is opened to discharge the gas.

Next, in step S7, the piston 20 of the main injector 18 is extended by the servo motor 22 to measure the amount of injection gas to be injected and injected next time. After the amount of the injection resin W 'to be injected is measured, it is determined in step S9 whether the cooling of the injection resin W' is substantially completed and solidified. When this determination is NO, the same step S9 is repeated, but when YES, the process proceeds to step S10, in which the upper die 3 is lifted to open the upper and lower dies 3, 2, and then the molded hollow bumper in step S11 is opened. W is taken out by the take-out jig 10.

Thereafter, in step S12, the resin temperature in the boundary region between both ends of the hollow portion W2 and the solid portion W3 of the bumper W in the middle of being removed by the removal jig 10 is measured by the infrared cameras 54 and 54, respectively. It is determined whether the measurement result is normal. That is, as shown in FIGS. 3 and 4, the hollow portion W2 and the solid portion W
When the resin temperature corresponding to each of the hollow portions W2 and W3 is compared, the hollow portion W2 is cooled by the injected gas.
The resin temperature of the portion where 2 is inside is always lower by a predetermined temperature (for example, 20 ± 5 ° C.) than the resin temperature of the solid portion W3. Therefore, if the temperature difference between the temperature of the position P1 corresponding to the end of the hollow portion W2 originally intended to be formed in the resin W 'and the temperature of the position P2 corresponding to the solid portion W3 is the above-mentioned predetermined temperature. By detecting that, the hollow portion W
2 can be determined to have been formed into the desired shape.

On the other hand, when the temperature at the position P1 corresponding to the end of the target hollow portion W2 and the temperature at the position P1 corresponding to the solid portion W3 are the same and there is no temperature difference,
Both portions are the same solid portion W3 or hollow portion W2. When both temperatures are high (for example, 65 ± 5 ° C.), the target position P1 where the hollow portion W2 is to be formed is still the solid portion W
In 3, it is determined that the hollow portion W2 is not formed up to that portion and the length of the hollow portion W2 is insufficient. on the other hand,
When both temperatures are low (for example, 45 ± 5 ° C.), the target position P1 where the hollow portion W2 is to be formed is already the hollow portion W2, but the hollow portion W2 is beyond the original position and is a solid portion W3. The position P2 is determined to be in a state where the length is too long. Thus, after injecting the resin W 'into the cavity 5, the gas nozzle 1 is inserted into the resin W'.
As a method for inspecting a hollow bumper W having a hollow portion W2 therein by injecting gas from the hollow portion 4, a hollow portion is formed based on a temperature difference between the hollow portion W2 and the solid portion W3 formed by the injection gas. The shape of W2 is being inspected.

If the determination in step S12 is YES, that is, "the temperature measurement result is normal", the flow returns to step S2 to perform the next injection molding. Proceeding to S13, the condition of the gas to be injected next time is changed from the initially set one, and then the process returns to Step S2. That is, as described above, the resin temperature at the position P1 which is the end of the target hollow portion W2 and the resin temperature at the position P2 which is the solid portion W3 are the same, and the hollow portion W2 is sufficiently formed up to the target position P1. If it is determined that the injection has not been performed, the injection valve 26 is opened and the sub-injector 2
Also from 3, the gas is discharged by the contraction operation of the piston 25, so that the injection pressure of the gas injected into the resin W 'is increased, and the gas injection amount is increased.

On the other hand, the resin temperature at the position P1 which is the end of the target hollow portion W2 and the resin temperature at the position P2 which is the solid portion W3 are both low, and the hollow portion W2 is formed beyond the target position P1. When the determination is made, the vent 29 in the middle of the gas pipe 16 is opened to lower the injection pressure of the gas and change the gas injection amount so as to decrease.

In this embodiment, the resin temperature in the boundary region between the hollow portion W2 and the solid portion W3 formed by the injection gas, specifically, the difference between the resin temperatures of the hollow portion W2 and the solid portion W3 is determined by the step S12. And a temperature detecting means 59 for detecting the shape of the hollow portion W2 from the temperature difference.

In step S13, the injection condition of the gas is controlled based on the detection state of the hollow portion W2 detected by the temperature detecting means 59. When the length of the hollow portion W2 is insufficient, the injection pressure of the gas is reduced. On the other hand, when the length of the hollow portion W2 is excessive, the control means 60 is configured to change the gas injection pressure so as to decrease the gas injection pressure when the length of the hollow portion W2 is excessive.

Next, the operation of injection molding of the hollow bumper W by the injection molding apparatus A of the above embodiment will be described. In advance, the piston 20 of the main injector 18 in the gas injection mechanism 13 is extended by the servomotor 22, whereby a predetermined amount of gas is sucked from the cylinder 15 and stored in the main injector 18.

Then, the upper mold 3 moves down and the upper and lower molds 3,
When the mold 2 is closed, a cavity 5 is formed between the molding surfaces 3a, 2a of the upper and lower molds 3, 2. In this state, cavity 5
The molten resin W 'is injected from the resin injection mechanism via the runner 7 of the upper mold 3. Thereafter, the injection valve 21 is opened, and at the same time, the piston 20 of the main injector 18 is contracted by the servo motor 22, and the main injector 1 is opened.
8 discharges a predetermined amount of gas, and the discharged gas is injected and injected into a predetermined portion of the resin W 'in the cavity 5 from the gas nozzle 14 of the lower die 2 through the main pipe 16a and the gas pipe 16. After the pressure of the injected gas is maintained for a predetermined time, the vent 29 in the gas pipe 16 is opened to discharge the gas. Thus, the hollow bumper W as an injection product having the hollow portion W2 formed therein is formed.

Next, similarly to the first operation, the piston 20 of the main injector 18 is extended by the servo motor 22 to measure the amount of the injection gas to be injected and injected next time, and to perform the next injection. The amount of the injection resin W 'is measured similarly. Then, when the cooling of the injected resin W 'is completed and the resin W' is solidified, the upper die 3 rises and the upper and lower dies 3, 2 are opened, and in the opened state, the upper and lower dies 3, 2 are opened. The take-out jig 10 moves in the meantime, and the formed bumper W is taken out by the clampers 9, 9,. Thus, molding of one bumper W is completed, and thereafter, the same operation as described above is repeated.

When the bumper W is taken out by the take-out jig 10, the hollow portion W2 of the bumper W to be taken out is taken out.
The resin temperature in the boundary region between the both ends of the solid portion W3 and the solid portion W3 is measured by the infrared cameras 54, 54, and it is determined whether the measurement result is normal. Specifically, as shown in FIGS. 3 and 4, the difference between the resin temperature corresponding to the position P1 of the end of the hollow portion W2 originally intended to be formed and the position P2 of the solid portion W3 is a predetermined temperature. (For example, 20 ± 5 ° C.), it is determined that the hollow portion W2 is formed in a desired shape,
At this time, the next injection molding is performed under the same conditions without changing the injection gas injection conditions.

On the other hand, when the resin temperature at the position P1 of the end of the target hollow portion W2 and the resin temperature at the position P2 of the solid portion W3 are the same and both temperatures are high (for example, 65 ± 5).
° C), the target position P1 of the hollow portion W2 is still the solid portion W
3, and it is determined that the length of the hollow portion W2 is insufficient. At this time, the condition of the gas to be injected next time is
In addition to the main injector 18, the sub-injector 23 also discharges gas by contracting the piston 25 to increase the gas injection pressure injected into the resin W ′ and increase the gas injection amount. Is changed to

On the other hand, when the resin temperature at the position P1 of the end of the target hollow portion W2 and the resin temperature at the position P2 of the solid portion W3 are all the same and low (for example, 45 ± 5 ° C.), the target position It is determined that the hollow portion W2 is formed beyond P1, and the length thereof is too long. At this time, the condition of the gas to be injected next time depends on the vent 29 in the gas pipe 16.
Is opened, the injection pressure of the gas injected into the resin W 'is reduced, and the gas injection amount is changed. Then, at the next molding, gas is injected under the changed conditions.

Therefore, in this embodiment, the shape of the hollow portion W2 is detected from the position of the end while the hollow portion W2 is formed by injecting gas into the resin W 'of the cavity 5, and the shape of the hollow portion W2 is detected. Since the gas injection condition of the next injection molding cycle is controlled based on the detection state, the shape of the actually formed hollow portion W2 is accurately detected so that the hollow portion W2 has the desired shape. In addition, the gas injection conditions can be changed, and the hollow portion W2 of the hollow bumper W can be formed with high accuracy, and the appearance defect can be stably prevented.

In order to detect the shape of the hollow portion W2, the fact that the difference between the resin temperatures of the hollow portion W2 and the solid portion W3 is always substantially constant is used. The shape of the portion W2 can be accurately detected.

Further, since the injection pressure is changed as the gas injection condition, the gas injection condition can be easily controlled.

Further, the infrared cameras 54, 54
Since the bumper W is positioned and attached to the take-out jig 10 for taking out the bumper W from the upper and lower dies 3, 2, the infrared cameras 54, 54 can be attached using the existing take-out jig 10. In addition, the temperature can be detected at the same time in the step of removing the bumper W, and both steps can be used.

(Embodiment 2) FIGS. 6 to 9 show Embodiment 2 of the present invention (note that the same parts as in FIGS. 1 to 5 are denoted by the same reference numerals and detailed description thereof is omitted). In the first embodiment, the surface temperature of the resin W 'in the cavity 5 is measured by the infrared cameras 54, 54.
The temperature is directly measured by a temperature sensor arranged on the lower mold 2. In the second embodiment, instead of changing the next gas injection condition as in the first embodiment, the current gas injection condition is controlled.

That is, in this embodiment, as shown in FIG. 6, the molding die 1 is the same as the molding die of the first embodiment (see FIG. 1), but its take-out jig 10 (not shown).
Are not provided with infrared cameras 54, 54.
Instead, as shown in FIG. 7, two pairs of left and right temperature sensors 5 are provided on the lower surface of the lower mold 2 (the back surface opposite to the upper molding surface 2a).
5, 55, 56, 56 (only one pair is shown) are attached, and the two temperature sensors 55, 56 of each pair
Are inserted into sensor mounting holes 2b, 2b passing through the lower surface of the sensor. Of the two temperature sensors 55 and 56 of each pair, FIG.
The tip of the hollow portion temperature sensor 55 shown on the left side at the position P1 corresponding to the end portion 2 of the hollow portion W to be originally formed in the resin W ', and the solid portion temperature shown on the right side in FIG. The tip of the sensor 56 is located at a position P2 in the resin W 'that is separated from the target hollow portion W2. These temperature sensors 55 and 56 are connected to the control unit 51 as shown in FIG.

The injection molding operation controlled by the control unit 51 will be described with reference to FIG. 8. First, after the upper and lower dies 3 and 2 are closed in step T1, the upper and lower dies 3 and 2 are formed in step T2. The molten resin W ′ is injected into the cavity 5 via the runner 7 of the upper mold 3. Thereafter, in step T3, the injection valve 21 of the gas injection mechanism 13 is opened, and the piston 20 of the main injection machine 18 is contracted by the servomotor 22 to discharge a certain amount of gas from the main injection machine 18. From the gas nozzle 14 of the lower mold 2 into a predetermined portion of the resin W '. In the next step T4, it is determined whether or not there is a temperature drop point at which the temperature detected by the hollow portion temperature sensor 55 falls within a predetermined time after the gas is injected.

That is, looking at the change in the surface temperature of the injection resin W 'during the period from the resin injection step to the gas injection step, as shown in FIG. 9, a sharp temperature drop point P is caused by the formation of the hollow portion W2. Resulting characteristics. From this, it can be seen that if there is this temperature drop point D, a hollow portion W2 is formed in that portion. If the determination in step T4 is NO for "no temperature drop point D", it is determined that the hollow portion W2 has not yet been formed at the target position P1, and the process proceeds to step T5.
Then, the injection valve 26 of the gas injection mechanism 13 is opened, the sub-injector 23 is turned on, and the gas from the sub-injector 23 is injected by the gas nozzle 14 to increase the injection pressure of the gas. Later step T6
Proceed to.

On the other hand, if the determination in step T4 is YES for "there is a temperature drop point D", it is determined that the hollow portion W2 is already formed at the target position P1, and the process proceeds to step T6.

In step T6, it is determined whether or not a counter for counting the pressure-holding time after gas injection has counted up. If the determination is YES, the process directly proceeds to step T8, but if NO, the process proceeds to step T7. This time, it is determined whether or not the temperature detected by the solid portion temperature sensor 56 has a temperature drop point D. If the determination is NO for "no temperature drop point D", it is determined that the hollow portion W2 is not yet formed at the position P2 of the solid temperature sensor 56, and the process returns to step T6. If "Yes" is determined, the process proceeds to step T8. In the above steps T6 to T8, after the gas injection, the dwell time elapses (counting up of the counter).
Earlier, it is determined whether or not a temperature drop point D has occurred in the temperature detected by the solid portion temperature sensor 56. If the temperature drop point D is present, the position where the hollow portion W2 deviates from the target position is determined. That is, it is considered that the solid portion temperature sensor 56 is formed up to the position P2.

In step T8, the vent 29 in the gas pipe 16 is opened to discharge the gas. Then, in step T9, the piston 20 of the main injector 18 is extended by the servomotor 22 to measure the amount of the next injection gas. In step T10, the amount of the next injection resin W 'is similarly measured. In step T11, it is determined whether the cooling of the injection resin W 'has been substantially completed. When this determination is NO, the same step T11 is repeated. However, when YES is determined, the process proceeds to step T12 to open the upper and lower dies 3 and 2, and then, at step T13, the molded hollow bumper W is formed.
The jig 10 is taken out, and the process is terminated thereafter.

Therefore, this embodiment can also provide the same functions and effects as those of the first embodiment. In particular, in the case of this embodiment, the temperature of the injected resin W '
Are directly detected by the temperature sensors 55 and 56 provided in the apparatus, the position of the hollow portion W2 is determined from the detected temperature, and the pressure of the injection gas is increased or decreased based on the position of the hollow portion W2. There is an advantage that the size of the hollow portion W2 can be changed in real time, while accurately detecting the hollow portion W2 that is coming.

Further, since the temperature sensors 55, 56 are provided in the sensor mounting holes 2b, 2b on the lower surface of the lower mold 2 of the molding die 1, the temperature sensors 55, 56 can be easily arranged and the temperature sensors 55, 56 The sensors 55 and 56 can be hidden and arranged on the lower surface of the lower mold 2 at positions that are hardly noticeable.

(Embodiment 3) FIGS. 10 to 13 show Embodiment 3 (the same parts as those in FIGS. 1 to 5 are denoted by the same reference numerals and detailed description thereof is omitted). In the above, the shape of the hollow portion W2 is detected based on the temperature of the resin W ', whereas the shape is detected based on a change in the pressure of the gas injected into the resin W'. In this embodiment, the gas is injected and injected by a plurality of gas nozzles 14, 14,... Instead of one gas nozzle 14 as in each of the above embodiments.

That is, in this embodiment, 3
Are arranged at predetermined intervals in the center and on both left and right sides of a portion of the cavity 5 that becomes the flange portion W1 of the bumper W. The three gas nozzles 14, 14,...
6c,... And these three branch pipes 16c, 1
6c are assembled in one gas pipe 16 and connected to the main and sub injectors 18, 23. Each of the branch pipes 16c is connected to a pressure sensor 57 for detecting the pressure of the gas ejected from each gas nozzle 14, and the signals of these three pressure sensors 57, 57,. . The same vents 29 and injection valves 35 as those described in the first embodiment are connected to the respective branch pipes 16c.

The injection molding operation controlled by the control unit 51 will be described with reference to FIG. First, after setting the conditions of the gas to be injected in step U1, the upper mold 3 is moved downward by the upper mold 3 in step U2.
2, the molten resin W 'is injected into the cavity 5 between the upper and lower dies 3, 2 in step U3. After this, step U4
, And the piston 20 of the main injector 18 is connected to the servo motor 2.
, And a certain amount of gas is dispersed from the main injector 18 so that the gas nozzles 14, 14,.
Is injected into a predetermined portion of the resin W '.

In the next step U5, it is determined whether or not the actual pattern of the gas injection pressure detected by each of the pressure sensors 57 is normal. That is, when a normal hollow portion W2 is formed by injecting a gas into the resin W 'from the gas nozzle 14, a pattern of the injection pressure of the gas over time becomes as shown in FIG. Then, this pattern (or its integral value) is stored in advance as a standard pattern, the actual pattern is compared with the standard pattern, and when the actual pattern matches the standard pattern, the hollow portion W2 is normally When the formed state is different from the standard pattern, it is determined that the hollow portion W2 is not formed normally.

Specifically, as shown in FIG.
Gas is ejected from the three gas nozzles 14, 14,.
As each hollow portion W2 formed by the gas from each gas nozzle 14 becomes larger in the resin W ', each hollow portion W2
When 2 is formed in a substantially uniform size, the pattern of the gas injection pressure from each gas nozzle 14 with the passage of time becomes the standard pattern shown in FIG.

However, like the central hollow portion W2 shown in FIG. 12B, the hollow portion W2 is formed faster than the other portions due to the reason that the pressure of the resin W 'in that portion is partially low. As the pressure increases, the gas injection pressure from the central gas nozzle 14 decreases.
It changes from the standard pattern as shown by the dashed line in (b). Conversely, the right hollow portion W2 shown in FIG.
When the hollow portion W2 is formed later and smaller than the other portions and is small due to the reason that the pressure of the resin W 'at that portion is partially high, the gas injection pressure from the gas nozzle 14 on the right side increases. Therefore, also in this case, the pattern is as shown in FIG.
It changes from the standard pattern as shown by the broken line in FIG.
The pattern shown by the solid line in FIG.
Like the hollow portion W2 on the left side of (b), when the hollow portion W2 is formed normally, it becomes a standard pattern. Therefore, by comparing the actual pattern of the gas injection pressure with the passage of time with the standard pattern in this manner, each hollow portion W
2 can be detected. In other words, here
After injecting the resin W 'into the cavity 5 in the upper and lower dies 3, 2, a gas is injected from the gas nozzle 14 into the resin W' to inspect the hollow bumper W having the hollow portion W2 therein. The shape of the hollow portion W2 is inspected based on the actual pattern of the gas injection pressure over time.

Then, in step U5, "the pattern of the gas injection pressure from each gas nozzle 14 is standard" Y
If it is determined that the gas nozzle 14 is the ES,
Is determined to be NO, the gas injection pressure pattern from the gas nozzle 14 having the abnormal pattern is changed in step U6.
Go to step U7.

The processing in step U6 is specifically as follows.
As shown by the broken line in FIG. 13B, the gas injection pressure increased from the standard pattern
Is opened, the injection valve 35 of the other branch pipe 16c is closed, and in this state, the injection valve 26 is opened and the sub-injector 2 is opened.
The gas injection pressure is further increased by causing the third piston 25 to contract by the servomotor 27. on the other hand,
As shown by the one-dot chain line in FIG. 13 (b), for the gas injection pressure decreased from the standard pattern, only the vent 29 of the branch pipe 16c corresponding to the gas nozzle 14 is opened, and the vent 29 is connected to the other branch pipe 16c. By closing,
Further reduce the gas injection pressure.

In step U7, the upper and lower dies 3 and 2 are opened by raising the upper die 3, and in the next step U8, the hollow bumper W after molding is removed by the removal tool 10 and the process is terminated.

In this embodiment, the deviation of the gas injection pressure between the two patterns is detected by comparing the actual pattern of the gas injection pressure with the passage of time with a preset standard pattern in step U5. The pressure pattern detecting means 61 is constituted.

In step U6, the gas injection condition is controlled based on the deviation of the gas injection pressure between the two patterns detected by the pressure pattern detecting means 61, and when the actual pattern is larger than the standard pattern. Control means 60 'for increasing the gas injection pressure is provided.

Therefore, in this embodiment, after the resin W 'is injected into the cavity 5 between the upper and lower dies 3, 2, the three gas nozzles 14, 14,
.. Are simultaneously injected from the... Respectively, whereby three hollow portions W2, W2,.

At this time, the actual pattern of the gas injection pressure from each gas nozzle 14 with the lapse of time is compared with a preset standard pattern, and when the actual pattern is significantly different from the standard pattern, The gas injection conditions are changed. That is, FIG.
With respect to the gas injection pressure that has increased from the standard pattern as shown by the broken line in (b), only the injection valve 35 of the branch pipe 16c corresponding to the gas nozzle 14 is opened, and the injection valves 35 of the other branch pipes 16c are closed. Then, the gas from the sub-injector 23 is supplied to the gas nozzle 14 with the injection valve 35 opened, and the gas injection pressure increases. Thus, even if the hollow portion W2 is small in size, the hollow portion W2 is formed due to the increased gas injection pressure.
2 quickly grows into a normal shape.

On the other hand, as shown by the alternate long and short dash line in FIG. 13B, with respect to the gas injection pressure reduced from the standard pattern, only the vent 29 of the branch pipe 16c corresponding to the gas nozzle 14 is opened, and the other The vent 29 of the branch pipe 16c is closed, and the gas injection pressure decreases. Thus, even if the hollow portion W2 has a large size, the hollow portion W2 becomes small and has a normal shape due to the reduced gas injection pressure. As a result, the gas is injected from the three gas nozzles 14, 14,... Into the same region of the resin W 'in the cavity 5, and the three hollow portions W2, W2,.
Can be formed normally while accurately detecting the shape of each hollow portion W2.

In the third embodiment, when the gas injection mechanism 13 does not include the sub-injector 23, the injection timing of the gas from each nozzle 14 is changed to control the gas injection conditions, as shown in FIG. The small hollow W2
May be closed later than the other injection valves 35, in other words, the other injection valves 35 may be closed earlier.
That is, when the actual pattern of the gas injection pressure is larger than the standard pattern, the gas injection timing is advanced. As a result, the same effect as above can be obtained.

In the third embodiment, when a hollow portion W2 (the central portion shown in FIG. 12B) larger than the other hollow portions W2 is formed, the gas nozzle 14 corresponding to the large hollow portion W2 is formed. By increasing the pressure from the opposite direction, the hollow portion W2 may be further enlarged to communicate with the adjacent hollow portion W2. Due to this, even if it is detected that the shapes of the plurality of hollow portions W2, W2,.
Is further injected so that is larger, and the hollow portion W2 communicates with the adjacent hollow portion W2. As a result, the occurrence of sink marks on the surface of the bumper W can be favorably prevented.

In each of the above embodiments, the case where the vehicle bumper W is injection-molded is described. However, the present invention can be applied to the case where another resin product having a hollow portion is injection-molded. Of course you can.

[0088]

As described above, according to the first aspect of the present invention, after the resin is injected into the cavity of the molding die, the gas is injected into the resin from the gas nozzle, and the hollow having the hollow portion therein is formed. When molding an injection product, the shape of the hollow portion formed by the injection gas is detected, and the injection condition of the gas is controlled based on the detection state of the hollow portion. The gas injection conditions can be changed so that the shape is accurately detected and the hollow part has the desired shape, and the hollow part of the hollow injection product is accurately formed to prevent the appearance defect from occurring stably. Can be achieved.

According to the second or twentieth aspect of the present invention, the shape of the hollow portion can be accurately detected by detecting the resin temperature in the boundary region between the hollow portion and the solid portion. it can.

According to the present invention, the shape of the hollow portion can be accurately detected by detecting the difference between the resin temperature of the hollow portion and the resin temperature of the solid portion which is always substantially constant.

In the fourth aspect of the present invention, the gas injection conditions are controlled by changing the gas injection pressure. Further, in the invention of claim 5, the gas injection conditions are controlled by changing the gas injection timing. Therefore, according to these inventions, control of gas injection conditions can be facilitated.

According to the sixth aspect of the invention, the variable pressure mechanism for varying the gas injection pressure from the gas injector is adjusted to change the gas injection pressure.
Control for changing the gas injection pressure can be facilitated.

According to the invention of claim 7 or 25, by controlling the gas injection conditions based on the deviation between the actual pattern of the gas injection pressure over time and a preset standard pattern, The shape of the hollow portion can be accurately detected.

According to the ninth aspect of the present invention, when controlling the gas injection pressure as the gas injection condition, the gas injection pressure is increased when the gas injection pressure of the actual pattern is larger than the standard pattern. Accordingly, the control for changing the gas injection pressure can be realized.

According to the eleventh aspect of the present invention, when changing the injection timing as the gas injection condition, when the actual pattern is larger than the standard pattern, the gas injection timing is advanced so that the gas injection timing is increased. Can be realized.

According to the twelfth aspect of the present invention, when a plurality of hollow portions are formed by injecting gas from a plurality of gas nozzles into the same region of the resin in the cavity, the injection pressure of the gas from each gas nozzle is reduced. By controlling the gas injection conditions based on the deviation between the actual pattern over time and a preset standard pattern, the shape of each of the plurality of hollow portions can be accurately detected.

According to the fifteenth aspect, in forming a plurality of hollow portions in the resin, when controlling the gas injection conditions by changing the gas injection pressure, the hollow portion is larger than the other hollow portions. Is formed, the hollow portion is further enlarged so as to communicate with the adjacent hollow portion, whereby the occurrence of sink marks on the surface of the injection product can be favorably prevented.

According to the eighteenth aspect, after injecting a resin into a cavity in a molding die and then injecting a gas from a gas nozzle into the resin to inspect a hollow injection product having a hollow portion therein, the injection gas is used. The shape of the hollow portion is inspected based on the difference in resin temperature between the formed hollow portion and the solid portion. According to the nineteenth aspect of the invention, the shape of the hollow portion is inspected based on the actual pattern of the gas injection pressure over time. According to these inventions, the shape of the hollow portion can be accurately detected.

According to the twenty-second aspect of the present invention, the temperature sensor for measuring the resin temperature is provided in the molding die,
The arrangement of the temperature sensor can be facilitated.

In this case, according to the twenty-third aspect of the present invention, since the temperature sensor is provided on the back surface of the mold, the temperature sensor can be concealed.

According to the twenty-fourth aspect of the present invention, since the temperature sensor is provided in the take-out means for taking out the injection product from the molding die, the temperature sensor can be arranged using the existing take-out means, and the product can be taken out. The process and the step of performing temperature measurement can be shared.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of an injection molding apparatus according to Embodiment 1 of the present invention.

FIG. 2 is an enlarged sectional view of a molding die.

FIG. 3 is a front view showing a temperature measurement state by an infrared camera.

FIG. 4 is a perspective view partially showing a temperature measurement state by an infrared camera.

FIG. 5 is a flowchart illustrating an injection molding operation performed by the control unit according to the first embodiment.

FIG. 6 is a view corresponding to FIG. 1 showing a second embodiment.

FIG. 7 is a front view showing a state where the temperature sensor is attached to the lower mold.

FIG. 8 is a flowchart illustrating an injection molding operation performed by a control unit according to the second embodiment.

FIG. 9 is a diagram showing a pattern of a temperature characteristic of the injection resin with time.

FIG. 10 is a view corresponding to FIG. 1 showing a third embodiment.

FIG. 11 is a flowchart illustrating an injection molding operation performed by a control unit according to the third embodiment.

FIG. 12 is a front view showing a state of a plurality of hollow portions formed in a resin in a third embodiment.

FIG. 13 is a diagram showing a characteristic of changing a gas injection pressure with respect to a standard pattern over time of a gas injection pressure according to a third embodiment.

FIG. 14 is a diagram showing a characteristic of changing a gas injection timing with respect to a standard pattern with time of a gas injection pressure according to a third embodiment.

[Explanation of symbols]

 A Injection molding apparatus 1 Mold 2 Lower mold 3 Upper mold 5 Cavity 10 Extraction jig 13 Gas injection mechanism 14 Gas nozzle 18 Main injection machine 21, 26, 35 Injection valve 22, 27 Servo motor 23 Sub-injector 29-31 Vent 32 Variable pressure mechanism 51 Control unit 54 Infrared camera (Temperature detecting means) 55, 56 Temperature sensor (Temperature detecting means) 57 Pressure sensor 59 Temperature detecting means 60, 60 'Control means 61 Pressure pattern detecting means P1 End of hollow portion in injection resin Part P2 Position to be solid in injection resin D Pressure drop point W Vehicle bumper (injection product) W 'Injection resin W2 Hollow part W3 Solid part

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasuyuki Suga 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd.

Claims (26)

[Claims] 1. A hollow injection molding method for injecting a resin into a cavity in a molding die and then injecting a gas from a gas nozzle into the resin to form a hollow injection product having a hollow portion therein. A shape of a hollow portion formed by the method, and controlling the gas injection condition based on the detected state of the hollow portion. 2. The hollow injection molding method according to claim 1, wherein the shape of the hollow portion is detected based on a resin temperature in a boundary region between the hollow portion and the solid portion formed by the injection gas. Injection molding method. 3. The hollow injection molding method according to claim 2, wherein the shape of the hollow portion is detected based on a difference in resin temperature between the hollow portion and the solid portion. 4. The hollow injection molding method according to claim 2, wherein the gas injection conditions are controlled by changing the gas injection pressure. 5. The hollow injection molding method according to claim 2, wherein the gas injection conditions are controlled by changing the gas injection timing. 6. The hollow injection molding method according to claim 4, wherein the gas injection pressure is changed by adjusting a variable pressure mechanism that changes the gas injection pressure from the gas injector. Molding method. 7. The hollow injection molding method according to claim 1, wherein an actual pattern of the gas injection pressure over time is compared with a predetermined standard pattern, and a deviation of the gas injection pressure between the two patterns is calculated. A hollow injection molding method comprising controlling gas injection conditions on the basis of the method. 8. The hollow injection molding method according to claim 7, wherein the gas injection conditions are controlled by changing the gas injection pressure. 9. The hollow injection molding method according to claim 8, wherein the gas injection pressure is increased when the gas injection pressure of the actual pattern is higher than the standard pattern. 10. The hollow injection molding method according to claim 7, wherein the gas injection conditions are controlled by changing the gas injection timing. 11. The hollow injection molding method according to claim 10, wherein when the gas injection pressure of the actual pattern is higher than the standard pattern, the gas injection timing is advanced. 12. The hollow injection molding method according to claim 1, wherein a plurality of gas nozzles are used to form a plurality of hollow portions by injecting gas from a plurality of gas nozzles into the same region of the resin in the cavity. Comparing the actual pattern with the passage of pressure with a preset standard pattern, and controlling the gas injection condition from each gas nozzle based on the deviation of the gas injection pressure in both patterns. Injection molding method. 13. The hollow injection molding method according to claim 12, wherein the injection pressure of the gas from each gas nozzle is changed.
A hollow injection molding method comprising controlling gas injection conditions. 14. The hollow injection molding method according to claim 13, wherein when the gas injection pressure of the actual pattern is higher than the standard pattern, the gas injection pressure is increased. 15. The hollow injection molding method according to claim 14, wherein when a hollow portion larger than another hollow portion is formed, the hollow portion is further enlarged to communicate with an adjacent hollow portion. Hollow injection molding method. 16. The hollow injection molding method according to claim 12, wherein a gas injection condition is controlled by changing a gas injection timing from each gas nozzle. 17. The hollow injection molding method according to claim 16, wherein the gas injection timing is advanced when the gas injection pressure of the actual pattern is higher than the standard pattern. 18. An inspection method for injecting a resin into a cavity in a molding die and then injecting a gas from a gas nozzle into the resin to inspect a hollow injection product having a hollow portion therein, wherein the injection gas A method for inspecting a hollow injection product, comprising inspecting a shape of a hollow portion based on a temperature difference between a hollow portion and a solid portion formed by the method. 19. An inspection method for injecting a resin into a cavity in a molding die, and then injecting a gas from a gas nozzle into the resin to inspect a hollow injection product having a hollow portion therein, A method for inspecting a hollow injection product, comprising: inspecting a shape of a hollow portion based on a pattern of an injection pressure with time. 20. A hollow injection molding apparatus for injecting a resin into a cavity in a molding die and then injecting a gas from a gas nozzle into the resin to mold a hollow injection product having a hollow portion therein. A temperature detecting means for detecting a resin temperature in a boundary region between the hollow portion and the solid portion formed by the injection gas; and a resin temperature in a boundary region between the hollow portion and the solid portion detected by the temperature detecting device. And a control means for controlling the gas injection condition based on the gas injection condition. 21. The hollow injection molding apparatus according to claim 20, wherein the temperature detecting means detects a difference in resin temperature between the hollow part and the solid part. 22. The hollow injection molding apparatus according to claim 20, wherein the molding die is provided with a temperature sensor for measuring a resin temperature in the cavity. 23. The hollow injection molding apparatus according to claim 22, wherein the temperature sensor is provided on a back surface of the molding die. 24. A hollow injection molding apparatus according to claim 20, wherein a temperature sensor for measuring a resin temperature is provided in a take-out means for taking out an injection product from a molding die. . 25. A hollow injection molding apparatus for injecting a resin into a cavity in a mold, and then injecting a gas into the resin from a gas nozzle to form a hollow injection product having a hollow portion therein. Pressure pattern detecting means for comparing the actual pattern of the gas injection pressure with the passage of time with a preset standard pattern to detect a deviation of the gas injection pressure between the two patterns, and the pressure pattern detection means Control means for controlling gas injection conditions based on a difference between gas injection pressures in both patterns. 26. A hollow in which a resin is injected into a cavity in a molding die, and a gas is then injected into the resin from a plurality of gas nozzles to form a hollow injection product having a plurality of hollow portions therein. In the injection molding apparatus, pressure pattern detection means for detecting the deviation of the gas injection pressure in both patterns by comparing the actual pattern of the gas injection pressure from each gas nozzle with the passage of time with a standard pattern set in advance. And a control means for controlling gas injection conditions based on a difference between gas injection pressures in both patterns detected by the pressure pattern detection means.