JP6808980B2 - How to manufacture rubber products - Google Patents

Description

The present invention relates to a method for manufacturing a rubber product, and more specifically, when unvulcanized rubber is injected into a molding mold to manufacture a rubber product, the rubber pressure in the molding mold is maintained within an appropriate range. The present invention relates to a method for manufacturing a rubber product that can suppress the occurrence of manufacturing defects.

Some rubber products are manufactured by extruding unvulcanized rubber into a molding mold with an extruder or injecting it with an injector (see, for example, Patent Document 1). For example, a tire vulcanizing bladder or the like is manufactured by injecting unvulcanized rubber into a molding mold, injecting it, molding it into a predetermined shape, and vulcanizing it. When manufacturing such a rubber product, the injection pressure of unvulcanized rubber in an injector (extruder or injector) is generally controlled to a predetermined pressure.

In this manufacturing method, even if an abnormality occurs in the fluidity of the unvulcanized rubber due to the blending of the unvulcanized rubber or the variation in the temperature of the molding mold, the injection pressure in the injector is within the predetermined pressure range. If so, the abnormality cannot be detected. This abnormality can be detected when the molding mold is opened after the rubber product is manufactured. Therefore, the rubber product manufactured at this time becomes a defective product, and the materials and time used are wasted.

It is conceivable to directly detect the rubber pressure in the molding mold and control this rubber pressure within an appropriate range, but it is difficult to install a pressure gauge that detects the rubber pressure in the molding mold. Even if this rubber pressure can be detected, it may not be in time to change the injection pressure in the injector to an appropriate pressure after detecting this rubber pressure.

Therefore, in order to avoid insufficient rubber pressure in the molding mold, the injection pressure is often intentionally set high. However, if the injection pressure becomes higher than necessary, unvulcanized rubber flows out at the seams of the molding mold, and so-called burrs are likely to occur. Further, if the injection pressure is increased, it may cause distortion of the molding mold and its accompanying equipment, and a larger and stronger molding mold and equipment are required.

Japanese Unexamined Patent Publication No. 2001-239565

An object of the present invention is to maintain the rubber pressure in the molding mold within an appropriate range and suppress the occurrence of manufacturing defects when the unvulcanized rubber is injected into the molding mold to manufacture a rubber product. The purpose is to provide a method for manufacturing a rubber product that can be produced.

In order to achieve the above object, the method for producing a rubber product of the present invention is a rubber in which unvulcanized rubber is injected from an injection machine into a molding mold through a flow path, and the unvulcanized rubber is molded and vulcanized by the molding mold. In the product manufacturing method, the injection pressure of the unvulcanized rubber is measured at the first measurement position and the second measurement position spaced apart from each other in the flow direction of the unvulcanized rubber being injected, and the first measurement position and The first measurement was performed by setting both of the second measurement positions to predetermined positions in the flow path, or setting one of them to a predetermined position in the injection machine and one of the other to a predetermined position in the flow path. The injection of the unvulcanized rubber into the molding mold is completed based on the injection pressure at the measurement position and the second measurement position and the pressure gradient of the injection pressure between the first measurement position and the second measurement position. It is characterized in that the rubber pressure in the molding mold is maintained within a predetermined range set in advance before the vulcanization.

Injection by setting both the first measurement position and the second measurement position at predetermined positions in the flow path, or by setting one of them at a predetermined position in the injector and one of them at a predetermined position in the flow path. The injection pressure of the unvulcanized rubber is measured at the first measurement position and the second measurement position spaced apart from each other in the flow direction of the unvulcanized rubber, and these injection pressures, the first measurement position and the second measurement position are measured. The rubber pressure in the molding mold can be accurately predicted based on the pressure gradient of the injection pressure between. Therefore, it becomes possible to vulcanize and mold the unvulcanized rubber while maintaining the rubber pressure in the molding mold within an appropriate predetermined range set in advance. Along with this, it is possible to suppress the occurrence of manufacturing defects in rubber products.

It is explanatory drawing which illustrates the main part of the rubber product manufacturing apparatus in a vertical cross-sectional view. It is explanatory drawing which illustrates the molding mold of FIG. 1 in a plan view. It is explanatory drawing which illustrates the state in which the unvulcanized rubber is flowing in the flow path of FIG. It is explanatory drawing which illustrates the state which the unvulcanized rubber is vulcanized by the molding mold of FIG. It is explanatory drawing which illustrates the manufactured vulcanization bladder in a vertical cross-sectional view. It is explanatory drawing which illustrates the vulcanization bladder of FIG. 5 in a plan view. It is a graph which illustrates the relationship between the elapsed time (injection time) from the start of injection of unvulcanized rubber and the injection pressure. It is a graph which illustrates the relationship between the position in the flow direction of unvulcanized rubber and the injection pressure. It is a graph which illustrates the relationship between the injection tip position of unvulcanized rubber and the injection pressure at the first measurement position. It is a graph which illustrates the relationship between the injection tip position of unvulcanized rubber and the injection pressure at the 2nd measurement position. It is a graph which illustrates the relationship between the injection tip position of unvulcanized rubber and the pressure gradient of the injection pressure between the 1st measurement position and the 2nd measurement position. It is explanatory drawing which illustrates another manufacturing apparatus in a longitudinal side view.

Hereinafter, the method for producing a rubber product of the present invention will be described based on the embodiment shown in the figure, taking the case where the rubber product is a tire vulcanization bladder as an example.

In the method for manufacturing a rubber product of the present invention, the rubber product manufacturing apparatus 1 illustrated in FIGS. 1 and 2 is used. The manufacturing apparatus 1 includes an injection machine 2 for unvulcanized rubber R, and in this embodiment, the injection machine 2 is a rubber injection machine. As the injection machine 2, a rubber extruder may also be used.

The injection machine 2 has a tubular cylinder 3 in which the unvulcanized rubber R is housed, a plunger 4 arranged inside the cylinder 3, and a drive mechanism 5 for moving the plunger 4. The operation of the drive mechanism 5 is controlled by the calculation unit 10. Various computers and the like can be used as the calculation unit 10. One end of the flow path 6 is connected to the tip of the cylinder 3. The other end of the flow path 6 is connected to the molding mold 7.

The molding mold 7 is composed of a core mold 7b and two split molds 7a that are vertically assembled on the outside of the core mold 7b. The gap formed between the inner peripheral surface of each of the split molds 7a and the outer peripheral surface of the core mold 7b is the cavity 7c. The molding mold 7 is not limited to this form, and various forms can be adopted.

In this embodiment, the flow path 6 is formed between a straight line portion 6a extending from the tip of the cylinder 3 and an inner peripheral surface of one of the split molds 7a and an outer peripheral surface of the core mold 7b connected to the straight line portion 6a. It is composed of a disk-shaped portion 6b. The outer edge of the disk-shaped portion 6b is connected to the upper end portion of the cavity 7c. The inside of the cylinder 3 and the cavity 7 are in a state of communicating with each other through the flow path 6.

Pressure sensors 9a and 9b are installed at predetermined positions (first measurement position D1 and second measurement position D2) spaced apart from each other in the extending direction of the flow path 6, respectively. The pressure sensors 9a and 9b sequentially measure the injection pressures P1 and P2 of the unvulcanized rubber R at the first measurement position D1 and the second measurement position D2, respectively. The injection pressures P1 and P2 measured by the pressure sensors 9a and 9b are sequentially input to the calculation unit 10.

The molding mold 7 is provided with a heating unit 8. The heating, stopping, and heating degree of the molding mold 7 by the heating unit 8 are controlled by the calculation unit 10. Further, the injection pressure of the unvulcanized rubber R in the injection machine 2, the injection time of the unvulcanized rubber R into the cavity 7c (moving speed of the plunger 4), and the like are controlled by the calculation unit 10. ..

Next, a procedure for manufacturing the rubber product RP according to the present invention will be described.

As illustrated in FIG. 1, the upper and lower split molds 7a are assembled to the outside of the core mold 7b to form the cavity 7c. The unvulcanized rubber R is housed in the cylinder 3 of the rubber injection machine 2.

Next, as illustrated in FIG. 3, the plunger 4 is moved downward to send the unvulcanized rubber R from the cylinder to the flow path 6. The unvulcanized rubber R sent out to the flow path 6 is injected into the cavity 7c as illustrated in FIG. 4, and the cavity 7c is filled with the unvulcanized rubber R.

At this time, the split mold 7a is heated at a predetermined temperature. The filled unvulcanized rubber R is molded into a predetermined shape by the molding mold 7 and vulcanized. When this state elapses for a predetermined time, the vulcanization of the unvulcanized rubber R is completed.

Next, the assembled split mold 7a is separated into upper and lower parts. As a result, the rubber product RP in a state of covering the core mold 7b appears. Next, the core mold 7b is extracted from the rubber product RP. After that, the rubber product RP illustrated in FIGS. 5 and 6 is manufactured through steps such as removing an excess portion (a portion in which the unvulcanized rubber R filled in the disk-shaped portion 6b is vulcanized and molded). Complete.

Here, the positions of the first measurement position D1, the second measurement position D2, and the predetermined positions of the cavity 7c (referred to as reference numeral D3 in FIG. 4) when the unvulcanized rubber R is injected from the injection machine 2 into the cavity 7c. The time course of the injection pressures P1, P2, and P3 of the unvulcanized rubber R in FIG. 7 is illustrated in FIG. In FIG. 7, the pressure curve when a non-defective product is manufactured is shown by a solid line, and the pressure curve when a defective product is manufactured is shown by a broken line. The position of reference numeral D3 is the upper end of the cavity 7c in FIG. 4, but can be any position of the cavity 7c.

The injection pressure (rubber pressure) of the unvulcanized rubber R injected from the injection machine 2 into the cavity 7c has a characteristic of linearly decreasing with respect to the flow direction thereof. The present invention makes use of this property. When the horizontal axis of FIG. 7 is rewritten from the elapsed time to the measurement position of the injection pressure, it is as illustrated in FIG.

In FIG. 8, the data when the injection of the unvulcanized rubber R in the case of producing a non-defective product is completed is shown by a thick solid line, and the data at an arbitrary time point X before the completion is shown by a thin solid line. On the other hand, the data when the injection of the unvulcanized rubber R in the case of producing a defective product is completed is shown by a thick dashed line, and the data at an arbitrary time point before the completion is shown by a thin broken line.

In the thick solid line of FIG. 8, the injection pressure (rubber pressure) at the position D3 at the time (E) when the cavity 7c is filled with the unvulcanized rubber R and the injection is completed is P3 (E). This P3 (E) has reached the required rubber pressure. On the other hand, in the thick broken line in FIG. 8, the injection pressure (rubber pressure) at the position D3 at the time (E) when the injection of the unvulcanized rubber R is completed is P3'(E). This P3'(E) does not reach the required rubber pressure.

Referring to FIG. 8, the injection pressures P1 (X) and P1'(at the first measurement position D1 and the second measurement position D2 at an arbitrary time point X after the injection of the unvulcanized rubber R is started from the injection machine 2). Based on X), P2 (X), P2'(X), the injection tip positions D (X), D'(X) of the unvulcanized rubber R being injected and the cavity 7c (position D3) at the completion of injection ), It becomes possible to predict the injection pressures P3 (E) and P3'(E). That is, the injection of the unvulcanized rubber R being injected is based on the injection pressure at the first measurement position D1 and the second measurement position D2 at an arbitrary time point X and the pressure gradient of the injection pressure between these positions. It becomes possible to predict the tip position.

As illustrated in FIG. 9, the relationship between the injection tip position of the unvulcanized rubber R being injected and the injection pressure of the unvulcanized rubber R at the first measurement position D1 differs depending on the injection pressure at the initial stage of injection. It becomes a relational line, and the larger the initial injection pressure, the more it shifts to the upper side of the graph. As illustrated in FIG. 10, the relationship between the injection tip position of the unvulcanized rubber R being injected and the injection pressure of the unvulcanized rubber R at the second measurement position D2 also differs depending on the injection pressure at the initial stage of injection. It becomes a relational line, and the larger the initial injection pressure, the more it shifts to the upper side of the graph.

FIG. 11 shows the relationship between the injection tip position of the unvulcanized rubber R being injected and the pressure gradients A of the injection pressures P1 and P2 between the first measurement position D1 and the second measurement position D2. .. That is, the pressure gradient A = (P2-P1) / (distance between D2 and D1).

If the initial injection pressures are the same, the states of the injection pressures P1 and P2 at the first measurement position D1 and the second measurement position D2 are always the same. Therefore, the pressure gradient of the injection pressure at any position and the injection pressure between these positions is the injection pressure P1, P2 between the initial injection pressure and the first measurement position D1 and the second measurement position D2. It is possible to make a prediction based on the pressure gradient A of.

Therefore, specifically, the following procedure is performed. First, the pressure curve (data shown by the solid line) illustrated in FIG. 7 when a non-defective product is manufactured is acquired in advance. Next, in the cavity 7c (position D3), based on the first measurement positions D1 and the second measurement position D2 and the injection pressures P1 (E) and P2 (E) at the completion of injection at the respective positions D1 and D2, respectively. The injection pressure P3 (E) of the above and the injection tip position D (E) of the unvulcanized rubber at which the injection pressure becomes zero are calculated.

Then, when the rubber product PR is manufactured, the injection pressures P1'(X) and P2 at the first measurement position D1 and the second measurement position D2 at an arbitrary time point X after the injection of the unvulcanized rubber R is started. 'Measure (X). The injection tip position of the unvulcanized rubber at which the injection pressure becomes zero based on the distance between the first measurement position D1 and the second measurement position D2 and the injection pressures P1'(X) and P2'(X). D'(X) is calculated by the calculation unit 10.

Next, in the relational lines of FIGS. 9, 10 and 11, P1'(X), P2'(X) and the pressure gradient A'(X) with respect to the calculated injection tip position D'(X) are plotted and corresponded. Determine each relationship line. Next, the calculation unit 10 calculates the injection pressure P1'(E) at the position D (E) when a non-defective product is manufactured.

Next, the injection pressure P3'(E) is calculated by the calculation unit 10. This injection pressure P3'(E) is calculated by the following equation (1).
P3'(E) = A'(E) x (distance between D3 and D1) ... (1)
Here, A'(E) = P1'(E) / (distance between D (E) and D1)

Next, the calculated injection pressure P3'(E) and the injection pressure P3 (E) are compared by the calculation unit 10. The injection pressure P3 (E) is calculated by the following equation (2).
P3 (E) = A (E) × (distance between D3 and D1) ... (2)
Here, A (E) = P1 (E) / (distance between D (E) and D1)

When the injection pressure P3'(E) is equal to or higher than the injection pressure P3 (E), it is determined that the rubber pressure in the cavity 7c is sufficient, and the manufacturing conditions are maintained. On the other hand, when the calculated injection pressure P3'(E) is less than the injection pressure P3 (E), it is determined that the rubber pressure in the cavity 7c is insufficient, and the injection pressure in the injection machine 2 is increased. Change the manufacturing conditions. Alternatively, discontinue production.

For example, the manufacturing conditions are changed based on the deviation between the measured injection pressures P1 and P2 and the preset target values of the injection pressures P1 and P2 at the first measurement position D1 and the second measurement position D2. That is, control is performed to change the manufacturing conditions so that the measured injection pressures P1 and P2 approach the target values, respectively. The target values of the injection pressures P1 and P2 are input to the calculation unit 10 and stored.

Specifically, the calculation unit 10 controls the heating unit 8 based on these measured data to change the temperature of the molding mold 7 (each divided mold 7a). Alternatively, at least one of the viscosity of the unvulcanized rubber R, the injection time of the unvulcanized rubber R by the injection machine 2, and the injection pressure of the injection machine 2 is changed. As described above, in the present invention, the injection pressures P1 and P2 measured at the initial stage of injecting the unvulcanized rubber R from the injection machine 2 into the molding mold 7 and the pressure gradient A of the injection pressures P1 and P2 are used. Based on this, the rubber pressure in the molding mold 7 is maintained within an appropriate predetermined range set in advance, that is, P3 (E) or higher, and the production is performed.

According to the present invention, the rubber pressure in the molding mold 7 can be accurately predicted based on the measured pressure gradient (pressure difference) between the injection pressures P1 and P2, so that the rubber in the molding mold 7 can be predicted accurately. It becomes possible to vulcanize and mold the unvulcanized rubber R while maintaining the pressure within an appropriate predetermined range set in advance. Along with this, it is possible to suppress the occurrence of manufacturing defects of the rubber product RP. That is, since the rubber pressure in the molding mold 7 can be maintained within an appropriate predetermined range before the rubber product RP is manufactured, it is possible to avoid becoming a defective product due to insufficient rubber pressure in the molding mold 7.

Therefore, according to the present invention, it is possible to avoid a defect in the conventional method in which the material (unvulcanized rubber R) and time used for producing the defective product are wasted, which is advantageous for improving productivity. Further, unlike the conventional method, it is not necessary to intentionally set the injection pressure of the unvulcanized rubber R to be high, so that there is an advantage that so-called burrs are less likely to occur in the manufactured rubber product PR. It is also advantageous for avoiding problems such as distortion of the molding mold 7 and its ancillary equipment due to the high injection pressure of the unvulcanized rubber R.

In the case of resin molding, the injection speed and extrusion speed are significantly faster than those of rubber molding. Therefore, even if the injection pressures P1 and P2 are measured as in the present invention, injection and extrusion are completed immediately. Therefore, it is practically impossible to maintain the resin pressure in the molding mold 7 within a preset predetermined range based on the measured injection pressures P1 and P2 and the pressure gradients of the injection pressures P1 and P2. is there. That is, the present invention is exclusively applied when the unvulcanized rubber R is injected into the molding mold 7.

The positions (first measurement position D1, second measurement position D2) at which the injection pressures P1 and P2 of the unvulcanized rubber R are measured by the pressure sensors 9a and 9b are not limited to the positions exemplified in this embodiment and are other positions. It can also be set to. For example, as shown in FIG. 12, the pressure sensors 9a and 9b can be installed at the first measurement position D1 in the injector 2 and the second measurement position D2 in the flow path 6, respectively. However, as in the embodiment illustrated in FIG. 1, the injection pressures P1 and P2 are measured more stably when the first measurement position D1 and the second measurement position D2 are set in the flow path 6 having a constant cross-sectional area. be able to.

The present invention is not limited to the bladder for tire vulcanization, and can be applied to various rubber product RPs in which unvulcanized rubber R is injected or extruded and vulcanized and molded.

1 Manufacturing equipment 2 Injection machine 3 Cylinder 4 Plunger 5 Drive mechanism 6 Flow path 7 Molding mold 7a Split type 7b Core type 7c Cavity 8 Heating part 9a, 9b Pressure sensor 10 Calculation part R Unvulcanized rubber RP Rubber product

Claims (3)

In a method for manufacturing a rubber product, in which unvulcanized rubber is injected from an injection machine into a molding mold through a flow path and the unvulcanized rubber is molded and vulcanized by the molding mold.
The injection pressure of the unvulcanized rubber is measured at the first measurement position and the second measurement position spaced apart from each other in the flow direction of the unvulcanized rubber being injected, and both the first measurement position and the second measurement position are measured. Is set at a predetermined position in the flow path, or one of them is set at a predetermined position in the injection machine and one of the other is set at a predetermined position in the flow path.
The unvulcanized rubber in the molded mold based on the measured injection pressures at the first and second measurement positions and the pressure gradient of the injection pressure between the first and second measurement positions. A method for producing a rubber product, which comprises maintaining the rubber pressure in the molding mold within a predetermined range set in advance before the injection of the rubber product is completed. A claim for changing the manufacturing conditions based on the deviation between the measured injection pressures at the first and second measurement positions and the preset target values of the injection pressures at the first measurement position and the second measurement position. Item 2. The method for manufacturing a rubber product according to Item 1. The rubber product according to claim 2, wherein the production conditions are at least one of the temperature of the molding mold, the viscosity of the unvulcanized rubber, the injection time by the injection machine, and the injection pressure by the injection machine. Production method.

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