JP7102298B2 - Injection device and injection molding machine - Google Patents

Description

Embodiments of the present invention relate to injection devices and injection molding machines.

The injection molding machine molds the resin by pouring the molten resin into a cavity between a plurality of molds that have been molded. In this injection molding, a foam molding method is used in which the resin is foamed by adding a foaming agent to the resin or the like. In the foam molding method, when the actual pressure in the cavity is low, foaming gas may pop out from the tip of the molten resin that flows in the injection process, resulting in poor appearance such as swirl marks on the product surface. Therefore, a CP (Counter Pressure) method is known in which the inside of the cavity is pressurized to a foaming pressure or higher by supplying gas before the injection step. In order to pressurize the inside of the cavity, for example, the mold is first molded. After mold clamping, gas is supplied into the cavity to further pressurize the inside of the cavity.

However, in this case, it takes time for mold clamping, and further, it takes time for gas supply after mold clamping. Therefore, there is a problem that the cycle time, which is the time required for the operation of molding the molded product once, is long and the production efficiency is low.

Japanese Unexamined Patent Publication No. 2006-159898

Provided are an injection device and an injection molding machine capable of shortening a cycle time and improving production efficiency.

The injection device according to the present embodiment is an injection device that injects a molding material into a cavity between a first mold and a second mold that is closed, and is at least one of a first mold and a second mold. A gas supply unit provided in the cavity to supply gas to the cavity, a flow meter provided in the gas supply unit to measure the flow rate of the gas supplied to the cavity, and a first mold based on the flow value of the flow meter. A control unit for calculating the gas supply start timing or the supply start mold position for starting the gas supply to the cavity between the start of the mold closing operation of the second mold and the completion of the mold clamping is provided. The supply start timing is the time point from the start of the mold closing operation of the first mold and the second mold to the completion of mold clamping, and the supply start mold position is the first mold and the gas supply start timing. This is the position of the second mold.

The block diagram which shows an example of the structure of the injection molding machine by 1st Embodiment. The block diagram which shows an example of the structure of the injection device, the control part, the fixed mold and the moving mold by 1st Embodiment. The figure which shows the operation of the injection molding machine in the molding flow of the CP method by 1st Embodiment. The graph which shows the relationship between the actual pressure in a cavity, the pressure value of a gas pressure gauge, and the flow rate value of a gas flow meter in the first flow rate test. The graph which shows the relationship between the actual pressure in a cavity, the pressure value of a gas pressure gauge, and the flow rate value of a gas flow meter in the second flow rate test. The figure which shows the position in the gas supply start timing of the fixed mold and the moving mold by 1st Embodiment.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. The present embodiment is not limited to the present invention.

The drawings are schematic or conceptual, and the ratio of each part is not always the same as the actual one. In the specification and the drawings, the same elements as those described above with respect to the existing drawings are designated by the same reference numerals, and detailed description thereof will be omitted as appropriate.

(First Embodiment)
FIG. 1 is a block diagram showing an example of the configuration of the injection molding machine 1 according to the first embodiment. The injection molding machine 1 is a machine capable of repeatedly executing a series of injection molding operations. For example, an operation of molding a molded product once is repeated as a cycle operation. The time to execute a series of cycle operations is called cycle time.

The injection molding machine 1 includes a frame 2, a fixing plate 3, a moving plate 4, a tie bar 5, a mold clamping drive mechanism 6, an injection device 7, a control unit 8, an extrusion mechanism 9, and a human machine. It includes an interface 60, a storage unit 110, an injection pressure sensor S1, and a screw position sensor S2.

The frame 2 is the base of the injection molding machine 1. The fixing plate 3 is fixed on the frame 2. A fixed mold 11 as a first mold is attached to the fixed plate 3. One end of the tie bar 5 is fixed to the fixing plate 3, and the other end is fixed to the support plate 10. The tie bar 5 extends from the fixed plate 3 through the moving plate 4 to the support plate 10.

The moving board 4 is mounted on a linear guide (not shown) provided on the frame 2. The moving board 4 can be guided by the tie bar 5 or the linear guide and can move toward or away from the fixed board 3. A moving mold 12 as a second mold is attached to the moving board 4. The moving mold 12 faces the fixed mold 11, approaches the fixed mold 11 together with the moving plate 4, and is combined with the fixed mold 11. When the moving mold 12 and the fixed mold 11 are brought into contact with each other, a space corresponding to the product shape is formed between the moving mold 12 and the fixed mold 11.

The mold clamping drive mechanism 6 includes a toggle mechanism 13 and a toggle mechanism drive unit 14. The toggle mechanism drive unit 14 includes a mold clamping servomotor 21, a ball screw 22, and a transmission mechanism 23 for driving the toggle mechanism 13. A crosshead 15 is attached to the tip of the ball screw 22. As the ball screw 22 rotates, the crosshead 15 moves so as to approach the moving board 4 or move away from the moving board 4. The transmission mechanism 23 transmits the rotation of the mold clamping servomotor 21 to the ball screw 22 to move the crosshead 15.

When the toggle mechanism drive unit 14 moves the crosshead 15, the toggle mechanism 13 operates. For example, when the crosshead 15 moves toward the moving board 4, the moving board 4 moves toward the fixed board 3, and the molds 11 and 12 are clamped. On the contrary, when the crosshead 15 moves away from the moving board 4, the moving board 4 moves away from the fixed board 3, and the molds 11 and 12 are opened.

The extrusion mechanism 9 includes an extrusion servomotor 71, a ball screw 72, a transmission mechanism 73, and an extrusion pin 74 in order to remove the molded product from the moving mold 12. As the ball screw 72 rotates, the extrusion pin 74 pushes out the product adhering to the inner surface of the moving mold 12. The transmission mechanism 73 transmits the rotation of the extrusion servomotor 71 to the ball screw 72, and the ball screw 72 rotates to move the extrusion pin 74 in the left-right direction of FIG.

The injection device 7 includes a heating barrel (band heater) 41, a screw 42, a weighing drive unit 43, and an injection drive unit 44. The heating barrel 41 includes a nozzle 41a for injecting the molten resin into the cavity of the molded mold. The heating barrel 41 stores the resin from the hopper 45 while heating and melting it, and ejects the molten resin from the nozzle. The screw 42 is provided so as to be movable while rotating or not rotating inside the heating barrel 41. In the weighing step, the screw 42 rotates, and the injection amount of the molten resin injected from the barrel 41 is measured and determined by the rotation amount (moving distance) of the screw 42. In the injection process, the screw 42 moves without rotating and ejects the molten resin from the nozzle.

The weighing drive unit 43 includes a weighing servomotor 46 and a transmission mechanism 47 that transmits the rotation of the weighing servomotor 46 to the screw 42. When the metering servomotor 46 is driven and the screw 42 is rotated in the heating barrel 41, the resin is introduced from the hopper 45 into the heating barrel 41. The introduced resin is sent to the tip end side of the heating barrel 41 while being heated and kneaded. The resin is melted and stored in the tip portion of the heating barrel 41. By moving the screw 42 in the direction opposite to that at the time of weighing, the molten resin is ejected from the barrel 41. At this time, the screw 42 moves without rotating and pushes the molten resin out of the nozzle. In the present embodiment, the molten resin is used as the molding material, but the molding material is not limited to the molten resin, and may be a metal, glass, rubber, a carbonized compound containing carbon fibers, or the like.

The injection drive unit 44 includes an injection servomotor 51, a ball screw 52, and a transmission mechanism 53. As the ball screw 52 rotates, the screw 42 moves in the left-right direction of FIG. 1 in the heating barrel 41. The transmission mechanism 53 transmits the rotation of the injection servomotor 51 to the ball screw 52. As a result, when the injection servomotor 51 rotates, the screw 42 moves. When the screw 42 pushes out the molten resin stored in the tip portion of the heating barrel 41 from the nozzle 41a, the molten resin is ejected from the nozzle 41a.

The injection pressure sensor S1 detects the filling pressure when the molten resin is filled from the barrel 41 to the mold and the holding pressure in the holding pressure step. In the injection process, the injection pressure sensor S1 detects the injection pressure of the molten resin material from the barrel 41 to the mold. In the pressure holding step, the injection pressure sensor S1 detects the pressure holding pressure of the molten resin after the pressure holding is switched from the speed control to the pressure control.

The screw position sensor S2 detects the position of the screw 42. Since the screw 42 moves with the rotation of the injection servomotor 51, the screw position sensor S2 may detect the position of the screw 42 from the rotation speed and the angular position of the injection servomotor 51. By detecting the position of the screw 42 at a predetermined control cycle, the speed and acceleration of the screw 42 can be known.

The human machine interface (HMI / F) 60 displays various information about the injection molding machine 1. The HMI / F60 may include, for example, a display unit and a keyboard, or may be a touch panel display. The user can input settings such as commands related to the operation of the injection molding machine 1 through the HMI / F60. For example, in injection molding, a product is molded by an injection step of injecting molten resin into a mold and a pressure holding step of controlling the holding pressure of the molten resin in the mold.

The control unit 8 monitors sensor information received from various sensors (not shown) during the injection process, and controls the injection device 7 based on the sensor information. Further, the control unit 8 controls the screw 42 according to the above set value set through the HMI / F60. Further, the control unit 8 causes the display unit 100 to display necessary data. The injection device 7 may include a control unit 8.

The storage unit 110 stores a plurality of operation information of the injection molding machine 1. The operation information is information indicating the operation of the molds 11 and 12, the mold clamping drive mechanism 6, or the injection device 7. The injection device 7 may include a storage unit 110.

FIG. 2 is a block diagram showing an example of the configuration of the injection device 7, the control unit 8, the fixed mold 11, and the moving mold 12 according to the first embodiment. In the following, the cavity is provided between the mold-closed fixed mold 11 and the moving mold 12. Even before the mold is closed, the space between the fixed mold 11 and the moving mold 12 may be referred to as a cavity.

The injection device 7 is used, for example, in a foam molding method. Therefore, a foamable molten resin is used as the molding material. The foamable molten resin is a molten resin having foamability due to the addition of a foaming agent or the like. The foaming agent generates bubbles inside the molten resin by supplying a foaming gas to the molten resin. As a result, the weight of the product and the material can be reduced. Further, the injection device 7 is used, for example, in the CP method. The CP method is a method of molding a product by applying a gas pressure that opposes the foaming gas to suppress foaming on the surface of the molten resin and foaming the inside thereof. For example, the injection device 7 pressurizes the inside of the cavity to a pressure equal to or higher than the foaming pressure of the foamable molten resin by supplying gas before the injection step. The foaming pressure is the pressure of the foaming gas contained in the molten resin. Therefore, the injection device 7 suppresses the foaming gas from jumping out from the surface of the foamable molten resin that flows in the injection step by making the gas pressure against the foaming gas higher than the foaming pressure. As a result, the surface of the foamable molten resin is cooled by the molds 11 and 12 to form a solidified layer before the inside, while suppressing the ejection of the foaming gas from the surface of the foamable molten resin. That is, the injection device 7 suppresses the foaming gas from jumping out from the surface of the foamable molten resin before the surface of the foamable molten resin solidifies. As a result, it is possible to suppress the occurrence of appearance defects such as swirl marks on the product surface.

On the other hand, since it takes time to solidify the inside of the foamable molten resin, it solidifies later than the surface. The injection device 7 removes the supplied gas from the cavity after the surface of the foamable molten resin is solidified and before the inside of the foamable molten resin is solidified. As a result, the gas pressure becomes lower than the foaming pressure, and the inside of the foamable molten resin is foamed.

As described above, in the CP method, in the injection step, the inside of the foamable molten resin can be foamed while suppressing the ejection of the foaming gas from the surface. As a result, it is possible to suppress the occurrence of appearance defects such as swirl marks on the product surface, and to reduce the weight of the product or the material. The injection device 7 is not limited to the foam molding method and the CP method, and may be used when the inside of the cavity is pressurized by supplying gas.

The injection device 7 further includes a gas supply unit 120, a gas discharge unit 130, a gas flow meter 140, and a gas pressure meter 150.

The gas supply unit 120 has a gas supply pipe 121 and a gas supply valve 122. The gas supply pipe 121 is provided in, for example, the fixed mold 11. Further, the gas supply valve 122 is provided in the gas supply pipe 121. The gas supply valve 122 is controlled by, for example, the control unit 8. The gas supply unit 120 supplies gas into the cavity by opening the gas supply valve 122 before the injection process. As a result, the gas supply unit 120 can increase the actual pressure in the cavity and prevent the foaming gas from jumping out from the surface of the foamable molten resin that flows in the injection process. The gas is, for example, air, but may be an inert gas. The gas supply pipe 121 may be provided in at least one of the fixed mold 11 and the moving mold 12.

The gas discharge unit 130 has a gas discharge pipe 131 and a gas discharge valve 132. The gas discharge pipe 131 is provided in, for example, the fixed mold 11. Further, the gas discharge valve 132 is provided in the gas discharge pipe 131. The gas discharge valve 132 is controlled by, for example, the control unit 8. The gas discharge unit 130 discharges gas from the cavity by opening the gas discharge valve 132 after the injection step. As a result, the gas discharge unit 130 can reduce the actual pressure in the cavity. The gas discharge unit 130 discharges gas from the cavity by opening to the atmosphere, for example. The gas discharge pipe 131 may be provided in at least one of the fixed mold 11 and the moving mold 12. Further, the gas discharge unit 130 may not be provided, and a vacuum pump may be connected to the gas supply unit 120 to discharge the gas from the cavity.

The gas flow meter 140 is provided in the gas supply pipe 121 and measures the flow rate of the gas supplied to the cavity. The gas flow meter 140 sends the measured flow rate value to the control unit 8.

The gas pressure gauge 150 is provided in the gas supply pipe 121 and measures the pressure in the gas flow path. The gas pressure gauge 150 sends the measured pressure value to the control unit 8.

The control unit 8 is connected to a gas supply valve 122, a gas discharge valve 132, a gas flow meter 140, a gas pressure gauge 150, a metering drive unit 43, and an injection drive unit 44. The control unit 8 calculates the gas supply start timing at which the gas supply to the cavity is started based on the flow rate value of the gas flow meter 140. In the present embodiment, the gas supply start timing is set at a time when it is estimated that the fixed mold 11 and the moving mold 12 come into contact with each other after the start of the mold closing operation of the fixed mold 11 and the moving mold 12. .. As a result, gas can be efficiently supplied without wasting gas. The mold closing operation is an operation of bringing the moving mold 12 away from the fixed mold 11 closer to the fixed mold 11 and closing the mold. The mold clamping operation is an operation of pressing the moving mold 12 against the fixed mold 11 after the fixed mold 11 and the moving mold 12 come into contact with each other. The mold clamping operation may be included in the mold closing operation. In this case, the mold closing is completed at the same time as the mold closing is completed. As described above, in the present embodiment, the gas supply start timing is set at the start of the mold clamping operation in which the fixed mold 11 and the moving mold 12 come into contact with each other. Therefore, the injection device 7 starts the gas supply earlier than the case where the gas supply start timing is set after the mold clamping is completed, and performs the mold clamping operation and the gas supply in parallel. As a result, the injection device 7 can shorten the cycle time and improve the production efficiency. The control unit 8 causes the gas supply unit 120 to supply gas at the gas supply start timing. As a result, the injection device 7 can automatically start the gas supply at the calculated gas supply start timing. Further, the control unit 8 controls the metering drive unit 43 and the injection drive unit 44 after pressurizing the inside of the cavity by molding and supplying gas to inject the foamable molten resin into the injection device 7. The gas supply start timing is calculated before injection molding by the CP method. The calculation of the gas supply start timing will be described in detail later with reference to FIGS. 4 and 5.

Next, the molding flow of the CP method will be described with reference to FIG.

FIG. 3 is a diagram showing the operation of the injection molding machine 1 in the molding flow of the CP method according to the first embodiment. FIG. 3 shows the molding flow (A) in the present embodiment and the molding flow (B) in the comparative example. L1A, L2A, and L3A in FIG. 3 indicate the actual pressure in the cavity, the injection pressure of the injection device 7, and the movement distance of the moving mold 12 in the core back operation, respectively. The injection pressure is a pressure value detected by the injection pressure sensor S1. L1B indicates the actual pressure in the cavity when the gas supply is started after the mold clamping is completed. The injection pressure of the injection device 7 in the molding flow (B) and the moving distance of the moving mold 12 in the core back operation are not shown in FIG.

As shown in the molding flow (A), first, in the mold closing operation, the moving mold 12 moves so as to approach the fixed mold 11. When the moving mold 12 and the fixed mold 11 come into contact with each other at t1, lockup (mold tightening) starts. That is, at t1, the mold clamping operation starts. The gas supply unit 120 starts supplying gas into the cavity when the fixed mold 11 and the moving mold 12 come into contact with each other (at the start of mold clamping). Due to the supply of gas, the actual pressure (L1A) in the cavity rises at t1.

Next, when the mold clamping is completed at t2 and the gas supply time elapses, the actual pressure (L1A) in the cavity becomes a set pressure value equal to or higher than the foaming pressure of the foamable molten resin. If the actual pressure in the cavity is greater than a certain upper limit, defects may easily occur. Therefore, there is an upper limit to the set pressure value. The set pressure value may be any pressure value within a range in which defects are unlikely to occur in the product (that is, above the foaming pressure and below the upper limit pressure value). In FIG. 3, the foaming pressure of the foamable molten resin is 0.7 MPa as an example, and the upper limit of the pressure is 1.0 MPa as an example. The set pressure value is an arbitrary pressure value within the range of 0.7 MPa to 1.0 MPa. Hereinafter, the set pressure value is described as being, for example, 1.0 MPa.

Next, the injection device 7 injects the foamable molten resin into the cavity at t3 after the lapse of the gas supply time. As a result, the injection pressure (L2A) rises.

Next, at t4 after the start of injection and before the completion of filling, the gas discharge unit 130 discharges the gas in the cavity and lowers the actual pressure (L1A) in the cavity. This is to prevent the gas in the cavity from becoming hot due to adiabatic compression and to suppress the burning of the product. Further, it is also for suppressing air entrainment in the subsequent core back operation. In the core back operation, the moving mold 12 moves away from the fixed mold 11, that is, the molds 11 and 12 open. Air entrainment means that the pressurized gas in the cavity suddenly escapes from the contact surfaces of the molds 11 and 12, a load is applied to the molded product, and the surface of the molded product becomes uneven.

Next, the injection molding machine 1 starts a core back operation at t5. The core back operation is an operation of increasing the volume in the cavity by moving the moving mold 12 away from the fixed mold 11. The core back operation lowers the actual pressure (L1A) in the cavity. When the actual pressure (L1A) in the cavity becomes smaller than the foaming pressure, the foamable molten resin in the uncured layer begins to foam, and the bubbles in the uncured layer can be expanded. As a result, the weight of the product and the material can be reduced.

The difference between the molding flow (A) in the present embodiment and the molding flow (B) in the comparative example is the gas supply start timing. As shown in the molding flow (B), in the comparative example, the gas supply unit 120 supplies gas to the cavity after the mold closing operation is completed, that is, at t2 after the mold clamping is completed. Therefore, as shown in L1B, the actual pressure (L1B) in the cavity rises at t2 after the mold clamping is completed.

On the other hand, in the molding flow (A) of the present embodiment, since the injection molding machine 1 performs the mold clamping operation and the gas supply in parallel, the timing of the injection step and the core back operation is earlier than that of the molding flow (B). That is, the molding flow (A) in the present embodiment has a shorter cycle time than the molding flow (B) in the comparative example.

Next, the calculation of the gas supply start timing by the control unit 8 will be described with reference to FIGS. 4 and 5.

As described above, the control unit 8 calculates the gas supply start timing based on the flow rate value of the gas flow meter 140 before the injection molding by the CP method. In the first embodiment, the gas supply start timing is set when the fixed mold 11 and the moving mold 12 come into contact with each other (t1 in FIG. 3). The control unit 8 calculates when the molds 11 and 12 come into contact with each other (t1 in FIG. 3) by the first flow rate test shown in FIG. 4 and the second flow rate test shown in FIG. As will be described later, the control unit 8 calculates the first period Xa shown in FIG. 4 in the first flow rate test, and calculates the second period Xc shown in FIG. 5 in the second flow rate test. The control unit 8 calculates the third period Y2 based on the first period Xa and the second period Xc. When the third period Y2 elapses, it is presumed that the molds 11 and 12 come into contact with each other (t1 in FIG. 3). Therefore, the gas supply start timing is set when the third period Y2 elapses. The first flow rate test and the second flow rate test are carried out before injection molding by the CP method. Further, the calculated gas supply start timing is stored in the storage unit 110. Hereinafter, the first flow rate test and the second flow rate test will be described in detail.

(1st flow rate test)
FIG. 4 is a graph showing the relationship between the actual pressure in the cavity, the pressure value of the gas pressure gauge 150, and the flow rate value of the gas flow meter 140 in the first flow rate test. The vertical axis shows the pressure value and the flow rate value, and the horizontal axis shows the time from the start of gas supply. L11, L41, and L51 indicate the actual pressure in the cavity, the pressure value of the gas pressure gauge 150, and the flow rate value of the gas flowmeter 140, respectively.

At the start of the first flow rate test, the fixed mold 11 and the moving mold 12 before the mold closing operation are open. First, in the first flow rate test, the gas supply unit 120 supplies a substantially constant flow rate of gas to the cavity before the mold closing operation. The flow rate value (L51) of the gas flow meter 140 rises at t10 when the gas supply starts, becomes stable with the passage of time, and becomes substantially constant. The flow rate value (L51) of the gas flow meter 140 becomes substantially constant at the upper limit of the supply flow rate, for example. In FIG. 4, the upper limit of the supply flow rate is set to 10 L / min as an example. Further, although the gas supply is started at t10, since the fixed mold 11 and the moving mold 12 are not in contact with each other, the supplied gas escapes from the cavity and the pressure value (L41) of the gas pressure gauge 150 does not increase. Therefore, the actual pressure (L11) in the cavity is also substantially zero.

Next, at t11, the moving mold 12 starts the mold closing operation. While the fixed mold 11 and the moving mold 12 are not in contact with each other, the supplied gas escapes from the cavity, so that the flow rate value (L51) of the gas flow meter 140 is substantially constant. However, when the moving mold 12 comes into contact with the fixed mold 11 at t12 and the inside of the cavity is sealed, the gas does not escape from the cavity, so that the actual pressure (L11) in the cavity starts to rise. When the inside of the cavity is sealed and the actual pressure (L11) in the cavity rises, it becomes difficult for the gas to enter the cavity, so that the flow rate value (L51) of the gas flow meter 140 begins to decrease. However, the flow rate value of the gas flowmeter 140 starts to decrease with a delay from t12 due to the pressure loss of the piping, the delay of the flow rate value of the gas flowmeter 140, and the like. The delay in the flow rate value of the gas flow meter 140 means that the gas flow meter 140 is separated from the molds 11 and 12, so that the flow value of the gas flow meter 140 (L11) increases with respect to the increase in the actual pressure (L11) in the cavity. The decrease of L51) is delayed. As shown in FIG. 4, the flow rate value (L51) of the gas flow meter 140 begins to decrease at t13 after the period Xb has passed from t12. Further, when the actual pressure (L11) in the cavity becomes higher, it becomes more difficult for gas to enter the cavity. Therefore, the flow rate value (L51) of the gas flow meter 140 decreases after t13. After a further lapse of time, the actual pressure (L11) in the cavity reaches the set pressure value (for example, 1.0 MPa) at t14. The pressure value (L41) of the gas pressure gauge 150 on the gas supply side and the actual pressure (L11) in the cavity become substantially equal, and the gas supply to the cavity is stopped. That is, at t14, the flow rate value (L51) of the gas flow meter 140 becomes substantially zero.

In the first flow rate test, the control unit 8 calculates or measures the first period Xa from the start of the mold closing operation to the start of the flow rate value (L51) of the gas flow meter 140 starting to decrease. The first period Xa is the period from the start of the mold closing operation (t11) to the contact (t12) between the fixed mold 11 and the moving mold 12 (period Y in FIG. 4), the pressure loss of the pipe, and the gas flow meter. It is a period obtained by adding the loss time (period Xb in FIG. 4) due to the delay of the flow rate value of 140 or the like. The loss time due to the pressure loss of the piping or the delay of the flow rate value of the gas flow meter 140 means that the flow rate value (L51) of the gas flow meter 140 decreases after the fixed mold 11 and the moving mold 12 come into contact (t12). It is a period until (t13). The period Xb of the loss time occurs because the increase in the actual pressure in the cavity is slower than the increase in the pressure value of the gas pressure gauge 150 due to the pressure loss of the pipe. Further, the loss time period Xb is also caused by the delay of the flow rate value of the gas flow meter 140 as described above. On the other hand, as the number of gas supply units 120 increases, the pressure loss in the piping becomes smaller and the loss time period Xb becomes shorter.

(Second flow rate test)
FIG. 5 is a graph showing the relationship between the actual pressure in the cavity, the pressure value of the gas pressure gauge 150, and the flow rate value of the gas flow meter 140 in the second flow rate test. In the first flow rate test, the mold closing operation starts from the state of supplying gas. On the other hand, in the second flow rate test, the gas supply starts from the state where the molds 11 and 12 are already closed and the inside of the cavity is sealed. In the second flow rate test, the moving mold 12 does not have to move, and is carried out, for example, in a state where mold clamping is completed. The vertical axis shows the pressure value and the flow rate value, and the horizontal axis shows the time from the start of gas supply. L12, L42, and L52 indicate the actual pressure in the cavity, the pressure value of the gas pressure gauge 150, and the flow rate value of the gas flowmeter 140, respectively.

At the start of the second flow rate test, the fixed mold 11 and the moving mold 12 are molded. First, the gas supply unit 120 supplies gas to the molded cavity in the second flow rate test. At t20, the flow rate value (L52) of the gas flow meter 140 increases with the start of gas supply. Further, the pressure value (L42) of the gas pressure gauge 150 rises at t20 when the gas supply is started, and reaches the set pressure value (1.0 MPa). Since the fixed mold 11 and the moving mold 12 are in contact with each other, the actual pressure (L12) in the cavity also rises when the gas supply is started. When the actual pressure (L12) in the cavity becomes high, it becomes difficult for gas to enter the cavity. Therefore, the flow rate value (L52) of the gas flow meter 140 decreases at t21 when the second period Xc elapses from the start of gas supply. In FIG. 5, as an example, the flow rate value (L52) of the gas flow meter 140 shows a peak at t21 and decreases. After a further lapse of time, the actual pressure (L12) in the cavity reaches the set pressure value (1.0 MPa) at t22. Since the pressure value (L42) of the gas pressure gauge 150 on the gas supply side and the actual pressure (L12) in the cavity become substantially equal, the gas supply to the cavity is stopped. That is, at t22, the flow rate value (L52) of the gas flow meter 140 becomes substantially zero. The flow rate value (L52) of the gas flow meter 140 may be substantially constant without showing a peak. In this case, the timing of t21 is when the flow rate value (L52) of the gas flow meter 140 starts to decrease from substantially constant.

In the second flow rate test, the control unit 8 calculates or measures the second period Xc from the start of gas supply to the cavity (t20) to the start of the flow rate value (L52) of the gas flow meter 140 (t21). .. The second period Xc is the time from the start of gas supply until the inflow of gas into the cavity approaches the maximum inflow of the cavity to some extent. On the other hand, the loss time period Xb shown in FIG. 4 is a period caused by the pressure loss of the pipe and the delay of the flow rate value of the gas flow meter 140 when the gas starts to enter the cavity. Therefore, the second period Xc includes the period Xb of the loss time. That is, the second period Xc is longer than the period Xb of the loss time due to the pressure loss of the pipe and the delay of the flow rate value of the gas flow meter 140 described above.

Next, the control unit 8 calculates the third period Y2 (Y2 = Xa-Xc) obtained by subtracting the second period Xc from the first period Xa. As described above, since the second period Xc includes the loss time period Xb, the loss time period Xb is subtracted from the third period Y2.

The gas supply start timing is when the third period Y2 has elapsed from the start of the mold closing operation. When the third period Y2 elapses, it is presumed that the molds 11 and 12 are in contact with each other or the mold clamping is started at t12 in FIG. The control unit 8 sets the gas supply start timing at a time when the mold is contacted or when the mold is presumed to be started. Therefore, according to the present embodiment, the gas supply can be started without delay from the time of contact of the molds 11 and 12 capable of pressurizing with the gas. As a result, the pressurization in the cavity can be completed quickly by supplying gas in parallel with the mold clamping operation from the time when the molds 11 and 12 are in contact with each other. As a result, the cycle time can be shortened and the production efficiency can be improved.

As described above, since the second period Xc is longer than the loss time period Xb, the third period Y2 (Y2 = Xa-Xc) is shorter than the period Y (Y = Xa-Xb). Therefore, assuming that the start point of the third period Y2 is the start of the mold closing operation (t11), the end point of the third period Y2 is before t12 where the molds 11 and 12 come into contact with each other. In this case, the molds 11 and 12 come into contact with each other within a short time from the start of gas supply. On the other hand, the second period Xc may be close to the loss time period Xb depending on the pressure loss of the pipe and the magnitude of the delay of the flow rate value of the gas flow meter 140. In this case, the third period Y2 becomes a value close to the period Y. Therefore, the timing of starting the gas supply approaches the time when the molds 11 and 12 come into contact with each other (t12).

FIG. 6 is a diagram showing the positions of the fixed mold 11 and the moving mold 12 according to the first embodiment at the gas supply start timing. FIG. 6 shows the states of the fixed mold 11 and the moving mold 12 at the time of contact of the mold (t1 in FIG. 3). The gas supply start timing will be further described with reference to FIG.

As shown in FIG. 6, a packing 160 is provided on the contact surface of the moving mold 12 that comes into contact with the fixed mold 11. When the fixed mold 11 and the moving mold 12 come into contact with each other via the packing 160, the packing 160 seals the inside of the cavity. FIG. 6 shows a state in which the fixed mold 11 and the moving mold 12 are in contact with each other via the packing 160 during the mold closing operation. This state is the state at the time of contact of the mold (t1 in FIG. 3). The packing 160 may be provided on at least one of the fixed mold 11 and the moving mold 12. Further, the packing 160 may be an elastic body or the like that can seal the inside of the cavity.

As shown in FIG. 6, when the molds 11 and 12 come into contact with each other during the mold closing operation and the inside of the cavity is sealed (t1 in FIG. 3), the gas supply of the molding flow (A) in FIG. 3 is started. To.

When the molding cycle is repeated, the packing 160 may deteriorate. In this case, the appropriate gas supply start timing at which the inside of the cavity is sealed may change due to cycle repetition. Therefore, considering the deterioration of the packing 160 due to the repetition of the molding cycle, the first flow rate test and the second flow rate test are performed, for example, before the first molding of the day. On the first day of the day, the gas supply start timing calculated on that day is used in injection molding by the CP method. Further, for example, even when the packing 160 is replaced, the first flow rate test and the second flow rate test are carried out. Thereby, an appropriate gas supply start timing can be set in consideration of a state such as deterioration of the packing 160.

So far, the first period Xa, the second period Xc, the third period Y2, and the gas supply start timing have been described as times. However, since the mold clamping drive mechanism 6 controls the movement of the moving mold 12, the time can be converted into the mold opening amount (moving distance). Therefore, the first period Xa, the second period Xc, the third period Y2, and the gas supply start timing may be the mold opening amount (moving distance) or position of the moving mold 12. In this case, the supply start mold position, which is the gas supply start timing after conversion, is the position of the fixed mold 11 and the moving mold 12 at the gas supply start timing.

Further, the order of carrying out the first flow rate test and the second flow rate test is not limited, and either of them may be carried out first.

Further, the gas supply start timing may be any time point between the start of the mold closing operation and the completion of the mold clamping. For example, the gas supply start timing may be when the first period Xa has elapsed from the start of the mold closing operation. The first period Xa includes the period Xb of the loss time due to the pressure loss of the pipe, the delay of the flow rate value of the gas flow meter 140, and the like. However, since the gas can be supplied in parallel with the mold clamping operation, the cycle time can be shortened and the production efficiency can be improved. Further, the second flow rate test can be omitted, and the gas supply start timing can be calculated more easily.

Further, in the case of omitting the second flow rate test as described above, when the user determines that the time when the molds 11 and 12 come into contact with each other and the time when the first period Xa elapses are different, the first period Xa may be corrected. For example, the control unit 8 calculates a first correction period obtained by subtracting a predetermined period from the first period Xa. The predetermined period may be set according to the user's rule of thumb or intuition. In this case, the gas supply start timing is when the first correction period has elapsed from the start of the mold closing operation. When the first correction period elapses, it is closer to the time when the molds 11 and 12 come into contact with each other for a predetermined period than when the first period Xa elapses. Therefore, it is possible to start supplying gas earlier than before the correction while suppressing waste of gas. Even in this case, since the gas can be supplied in parallel with the mold clamping operation, the cycle time can be shortened and the production efficiency can be improved. Further, the second flow rate test can be omitted, and the gas supply start timing can be calculated more easily.

As described above, according to the first embodiment, the control unit 8 from the start of the mold closing operation of the fixed mold 11 and the moving mold 12 to the completion of mold clamping based on the flow rate value of the gas flow meter 140. Calculate the gas supply start timing set in between. The gas supply start timing is set so that the mold clamping operation and the gas supply are performed in parallel. Therefore, the injection device 7 can shorten the cycle time and improve the production efficiency.

If the gas supply start timing is set so that the gas supply starts before the fixed mold 11 and the moving mold 12 come into contact with each other, it is not necessary to calculate the gas supply start timing, and the gas supply start timing does not need to be calculated. The cycle time can also be shortened. However, if the gas is supplied before the fixed mold 11 and the moving mold 12 come into contact with each other, the gas is supplied to the fixed mold 11 and the moving mold 12 for a long time. In this case, the gas may significantly lower the surface temperature of the molds 11 and 12. For example, in the foam molding method, the temperature of the molds 11 and 12 may be adjusted from 60 ° C. to 70 ° C. In such a case, if the temperature of the molds 11 and 12 drops due to the gas supply for a long time, the temperature adjustment of the molds 11 and 12 may become unstable.

Further, if the gas supply is started before the fixed mold 11 and the moving mold 12 come into contact with each other, the gas stays with the fixed mold 11 and the moving mold until the fixed mold 11 and the moving mold 12 come into contact with each other. It means that it is leaking from the mold 12. This wastes gas.

On the other hand, the injection device 7 according to the first embodiment sets the gas supply start timing at a time when it is estimated that the fixed mold 11 and the moving mold 12 come into contact with each other based on the flow rate of the gas flow meter 140. .. That is, the injection device 7 can start the gas supply at the timing when the inside of the cavity is sealed. As a result, the molds 11 and 12 are not supplied with gas for an excessively long time. Moreover, the gas supply is started without delay after the cavity is sealed. Therefore, it is possible to suppress a wasteful decrease in the temperature of the molds 11 and 12, and also to suppress a wasteful consumption of gas.

Further, the portion (gas gate) of the gas supply pipe 121 connected to the cavity is usually designed to be narrow in order to suppress the inflow of the resin. When the gas gate is provided on the contact surface of the fixed mold 11 and the moving mold 12, the gas gate is further narrowed by the mold clamping. Therefore, when the gas supply is started after the mold is compacted, the gas gate is narrow and it is difficult for the gas to enter the cavity, so that the gas supply time becomes long.

On the other hand, the injection device 7 according to the first embodiment starts supplying gas after the molds 11 and 12 come into contact with each other and before the mold clamping is completed. Therefore, since the gas supply is started before the gas gate is narrowed, the gas can easily enter the cavity and the gas supply time can be shortened. That is, the user can set the gas supply time shorter than when the gas supply is started after the mold clamping is completed. As a result, the cycle time can be further shortened and the production efficiency can be improved.

Further, as shown in FIG. 4, the actual pressure (L11) in the cavity rises at t12 where the molds 11 and 12 come into contact with each other. Therefore, a pressure sensor can be provided in the cavity to calculate or measure the period Y shown in FIG. 4, and the time when the period Y elapses can be set as the gas supply start timing. However, in this case, since it is necessary to make the sensor detection portion of the pressure sensor face the cavity, the mold design becomes complicated.

On the other hand, the injection device 7 according to the first embodiment can calculate the time estimated at the time of contact with the mold or the start of mold clamping by the gas flow meter 140 provided outside the molds 11 and 12. can. Therefore, it is possible to calculate the time point estimated to be at the time of contacting the mold or at the start of mold clamping without complicating the mold design.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

1 injection molding machine, 7 injection device, 8 control unit, 11 fixed mold, 12 mobile mold, 120 gas supply unit, 140 gas flow meter

Claims (4)

An injection device that injects molding material into the cavity between the mold-closed first mold and the second mold.
A gas supply unit provided in at least one of the first mold and the second mold to supply gas to the cavity, and
A flow meter provided in the gas supply unit to measure the flow rate of the gas supplied to the cavity, and
A control unit for calculating a supply start timing or a supply start mold position for starting gas supply to the cavity based on the flow rate value of the flow meter is provided.
In the first flow rate test carried out in advance, the gas supply unit supplies gas to the cavity before the mold closing operation, and the control unit performs the flow rate from the start of the mold closing operation in the first flow rate test. Calculate or measure the first period until the flow value of the meter starts to decrease,
The gas supply unit supplies gas to the closed cavity in the second flow rate test conducted in advance, and the control unit starts supplying gas to the cavity in the second flow rate test. Calculate or measure the second period until the flow value of the flow meter starts to decrease,
The supply start timing is a time when a third period obtained by subtracting the second period from the first period has elapsed from the start of the mold closing operation of the first mold and the second mold.
The supply start mold position is an injection device that is the position of the first mold and the second mold at the supply start timing. The injection device according to claim 1 , wherein the control unit supplies gas to the gas supply unit at the supply start timing. The injection device according to claim 1 or 2, wherein the molding material is a foamable resin. An injection molding machine comprising the injection device according to any one of claims 1 to 3 .

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