JP4825616B2 - Injection molding machine and control method of injection molding machine - Google Patents

Description

  The present invention relates to, for example, an injection molding machine for molding a molded product and a control method for the injection molding machine.

  Conventionally, various injection molding machines (see, for example, Patent Documents 1 and 2) have been used to form molded products such as connector housings, harness protectors, and wiring clips. In this type of injection molding machine, a molding material heated and fluidized (plasticized) in a cylinder is injected into a mold by a high pressure, cooled and solidified or cured therein, and then the mold is opened as a molded product. Take out.

The injection molding machine described in Patent Documents 1 and 2 described above sequentially performs a filling (also referred to as injection) step and a pressure holding step when injecting a plasticized molding material into a mold. In the injection molding machine described in Patent Documents 1 and 2, first, in the filling process, the pressing member that pushes the plasticized molding material in the cylinder into the cavity of the mold, the volume of the extruded molding material, and the cavity It is moved by a predetermined distance that is equal to the internal volume. The injection molding machine switches from the filling process to the pressure holding process after the pressing member has moved the predetermined distance from the start of injection of the molding material. Thus, the above-described injection molding machine manufactures a molded product.
JP 2003-326573 A JP 2003-11192 A

  The injection molding machine described in Patent Document 1 described above moves the pressing member described above away from the cavity described above in the pressure holding process described above. The injection molding machine described in Patent Document 2 described above stops the pressing member described above using a brake in the pressure holding process described above. As described above, the injection molding machine described in Patent Documents 1 and 2 described above moves or stops the pressing member from the cavity in the pressure-holding step, so that the volume of the extruded molding material is within the cavity in the filling step. The pressing member has to be moved until it is approximately equal to the volume of.

  For this reason, the above-described conventional injection molding machine moves the pressing member until the volume of the extruded molding material becomes substantially equal to the volume in the cavity in the filling process, so that the pressure of the extruded molding material is very high. Get higher. For this reason, in order to withstand the pressure of the molding material, the conventional injection molding machine described above needs to ensure the mechanical strength of the mold and the injection molding machine itself more than necessary, which increases the size and cost. It was a tendency to.

  Further, since the pressure of the extruded molding material becomes very high, the conventional injection molding machine described above requires a higher mechanical strength when manufacturing a relatively thin molded product. For this reason, in order to manufacture a comparatively thin molded article, there was a tendency to increase in size and cost.

  Furthermore, in the injection molding machine described in Patent Document 1 described above, the pressing member is retracted in the pressure-holding step, so that the molding material may not sufficiently reach the cavity. For this reason, in particular, in the injection molding machine described in Patent Document 1, appearance defects such as sink marks occur in the molded product, and variation in the mass of the molded product (amount of molding material constituting the molded product) is large. That is, the injection molding machine described in Patent Document 1 described above tends to reduce the yield of molded products.

  Accordingly, an object of the present invention is to provide an injection molding machine and an injection molding machine control method capable of suppressing the increase in size and cost of the injection molding machine itself and improving the yield of molded products. is there.

  In order to solve the above problems and achieve the object, an injection molding machine according to claim 1 includes a pressing member and is filled with a plasticized molding material and is molded through an opening at one end. A cylindrical cylinder capable of injecting material into the cavity of the mold, a drive source for moving the pressing member along the longitudinal direction of the cylinder, and filling the molding material into the cylinder to hold the pressing member The pressing member is moved away from the opening, the pressing member is brought close to the opening to the driving source, the molding material is injected into the cavity of the mold through the opening, and the pressing member is predetermined in the opening. An injection molding machine comprising: a control unit that performs a pressure-holding step of controlling the movement of the pressing member based on the pressure of the molding material in the cavity after performing the filling step approaching the distance of The predetermined distance is a distance in which the volume of the molding material injected from the opening from the start of injection of the molding material becomes smaller than the volume of the cavity, and the control means includes the filling step from the filling step. Immediately after shifting to the pressure holding step, the backward movement of the pressing member is restricted until the pressure of the molding material decreases to a predetermined pressure setting pressure.

  An injection molding machine according to a second aspect of the present invention is the injection molding machine according to the first aspect, wherein the control means is configured to maintain a predetermined pressure of the molding material in the cavity in the pressure holding step. When the pressure setting pressure is reached, the restriction of the retraction of the pressing member is released, and the pressing member is moved so that the pressure of the molding material in the cavity maintains the holding pressure setting pressure.

  According to a third aspect of the present invention, there is provided a method for controlling an injection molding machine according to the present invention, wherein a pressing member is accommodated and a plasticized molding material is filled, and the molding material is injected into a mold cavity through an opening at one end. In a control method of an injection molding machine comprising a possible cylindrical cylinder and a drive source that moves the pressing member along the longitudinal direction of the cylinder, the cylinder is filled with the molding material and the pressing A member is kept away from the opening, the pressing member is made to approach the opening by the driving source, and the molding material is injected into the cavity of the mold through the opening, and the pressing member is predetermined in the opening. And performing a pressure holding step for controlling the movement of the pressing member based on the pressure of the molding material in the cavity after performing the filling step approaching the predetermined distance, and the predetermined distance is: The volume of the molding material injected from the opening from the start of injection of the molding material is a distance smaller than the volume of the cavity, and immediately after the filling process is shifted to the pressure holding process, the molding The retraction of the pressing member is restricted until the pressure of the material drops to a predetermined holding pressure setting pressure.

  The method for controlling an injection molding machine according to a fourth aspect of the present invention is the method for controlling an injection molding machine according to the third aspect, wherein the pressure of the molding material in the cavity is predetermined in the pressure holding step. When the holding pressure setting pressure is reached, the restriction of the backward movement of the pressing member is released, and the pressing member is moved so that the pressure of the molding material in the cavity maintains the holding pressure setting pressure.

  According to the injection molding machine of the present invention as set forth in claim 1, the cylinder is switched from the filling process to the pressure holding process at the rear position of the pressing member rather than the known injection molding machine conventionally used. The maximum value of the pressure of the molding material in the inside and the cavity can be suppressed, and the molding material near the tip of the compressed pressing member in the cylinder is gradually released into the cavity. Pressure can be suppressed.

  Further, in the pressure holding process, the pressing member is prevented from retreating until the pressure of the molding material in the cavity drops to the pressure setting pressure, so that the pressure of the molding material in the cavity becomes the pressure setting pressure. The pressing member is stopped. For this reason, in the pressure holding process, the molding material near the tip of the compressed pressing member in the cylinder is gradually released into the cavity, and the molding material reaches the cavity.

  According to the injection molding machine of the second aspect of the present invention, in the pressure holding step, once the molding material in the cavity reaches the pressure setting pressure, the pressing member is moved so as to maintain the pressure setting pressure. The molding material in the cavity is kept at the holding pressure setting pressure by the pressing member until the molding material is sufficiently spread in the cavity.

  According to the control method of the injection molding machine of the present invention according to claim 3, the predetermined distance that the pressing member moves in the filling step is a distance in which the injected volume of the molding material is smaller than the volume of the cavity. . In other words, it switches from the filling process to the pressure-holding process at a position behind the pressing member rather than the known injection molding machine that has been used in the past, and therefore suppresses the maximum pressure of the molding material in the cylinder and in the cavity. In addition, since the molding material near the tip of the compressed pressing member in the cylinder is gradually released into the cavity, the pressure of the molding material in the cylinder and in the cavity can be suppressed.

  Further, in the pressure holding process, the pressing member is prevented from retreating until the pressure of the molding material in the cavity drops to the pressure setting pressure, so that the pressure of the molding material in the cavity becomes the pressure setting pressure. The pressing member is stopped. For this reason, in the pressure holding process, the molding material near the tip of the compressed pressing member in the cylinder is gradually released into the cavity, and the molding material reaches the cavity.

  According to the control method of the injection molding machine of the present invention described in claim 4, in the pressure holding step, once the molding material in the cavity reaches the pressure setting pressure, the pressure is set on the cavity side so as to maintain the pressure setting pressure. Since the pressing member is moved, the pressing material keeps the molding material in the cavity at the holding pressure setting pressure until the molding material is sufficiently spread in the cavity.

  As described above, according to the first aspect of the present invention, the pressure of the molding material in the cylinder and the cavity can be suppressed, so that it is not necessary to secure the mechanical strength of the cylinder and the mold more than necessary. Therefore, the increase in size and cost of the injection molding machine itself can be suppressed.

  In addition, since it is not necessary to secure the mechanical strength of cylinders and molds more than necessary, even a relatively simple (low mechanical strength) injection molding machine has a relatively thin molded product. Can be molded stably. Therefore, it is possible to suppress a rise in the cost of a relatively thin molded product and improve the quality.

  Furthermore, in the pressure holding process, the molding material near the tip of the compressed pressing member in the cylinder is gradually released into the cavity, and the molding material reaches the cavity. Can be prevented and the mass of the molded product can be prevented from varying. Therefore, the yield of molded products can be improved.

  According to the second aspect of the present invention, since the molding material in the cavity is kept at the pressure setting pressure by the pressing member until the molding material is sufficiently spread in the cavity, the molding material is surely sufficiently molded in the cavity. Material goes around. Therefore, the yield of molded products can be improved reliably.

  According to the third aspect of the present invention, since the pressure of the molding material in the cylinder and in the cavity can be suppressed, it is not necessary to secure the mechanical strength of the cylinder and the mold more than necessary. Increase in size and cost of itself can be suppressed.

  In addition, since it is not necessary to secure the mechanical strength of cylinders and molds more than necessary, even a relatively simple (low mechanical strength) injection molding machine has a relatively thin molded product. Can be molded. Therefore, it is possible to suppress a rise in the cost of a relatively thin molded product.

  Furthermore, in the pressure holding process, the molding material near the tip of the compressed pressing member in the cylinder is gradually released into the cavity, and the molding material reaches the cavity. Can be prevented and the mass of the molded product can be prevented from varying. Therefore, the yield of molded products can be improved.

  According to the fourth aspect of the present invention, since the molding material in the cavity is kept at the pressure setting pressure until the molding material is sufficiently spread in the cavity, the molding material is surely sufficiently molded in the cavity. Material goes around. Therefore, the yield of molded products can be improved reliably.

  Hereinafter, an injection molding machine 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 12. An injection molding machine 1 (shown in FIG. 1) according to an embodiment of the present invention is an apparatus for molding a connector housing 3 (corresponding to a molded product) of a connector 2 shown in FIG.

  The connector housing 3 is made of an insulating synthetic resin as a molding material and is formed in a box shape. The connector housing 3 includes a plurality of terminal accommodating chambers 4. The terminal accommodating chamber 4 is a hole (space) that extends linearly and penetrates the connector housing 3. The terminal accommodating chamber 4 accommodates a terminal fitting 6 to which an electric wire 5 is attached.

  The connector housing 3 accommodates a terminal fitting 6 in which an electric wire 5 is attached to a predetermined terminal accommodating chamber 4 to constitute the connector 2. The connector 2 is fitted with a mating connector or the like to constitute a wire harness routed in an automobile or the like.

  As shown in FIG. 1, the injection molding machine 1 includes a mold part 7, an injection machine 8, and a control device 9 as control means. The mold part 7 includes a pair of molds 10 and 11 provided so as to be able to contact and separate from each other, and a moving mechanism 12 that brings the molds 10 and 11 into and out of contact with each other.

  A cavity 13 and a sprue runner 14 connected to the cavity 13 are provided between the pair of molds 10, 11, and the one mold 10 located on the right side in FIG. A communication injection hole 15 is provided. The cavity 13 is a space provided between the molds 10 and 11 when the molds 10 and 11 described above approach each other. The shape of the cavity 13 is along the outer shape of the connector housing 3 described above. The sprue runner 14 is a hole having one end penetrating the molds 10 and 11 connected to the cavity 13. The injection hole 15 is a hole that opens on the outer surface of the above-described one mold 10 and continues to the sprue runner 14.

  The moving mechanism 12 includes a toggle link 17 that is swingably connected to a movable plate 16 to which the other mold 11 is attached, a hydraulic cylinder (not shown) that swings the toggle link 17, and the like. In the moving mechanism 12, the hydraulic cylinder swings the toggle link 17 to bring the other mold 11 into and out of contact with the one mold 10. In addition, approaching / separating means approaching or separating from each other.

  The injection machine 8 includes an injection machine main body 19, a cylinder part 21, a rotational movement part 22, a slide movement part 23, and a linear encoder 44 as position detection means. The injection machine main body 19 is provided so as to be able to contact and separate from the mold part 7 by a moving means (not shown).

  The cylinder part 21 includes a heating cylinder 24 as a cylinder and a screw 25 as a pressing member. The heating cylinder 24 is formed in a cylindrical shape and is fixed to the injection machine main body 19. The heating cylinder 24 is arranged such that its longitudinal direction (axial center direction) is parallel to the direction in which the pair of molds 10 and 11 come in contact with each other. In the heating cylinder 24, the opening 26 of the one end portion 24 a is opposed to the injection hole 15 of one mold 10 along the direction in which the pair of molds 10 and 11 come in contact with and away from each other. Further, the one end 24 a of the heating cylinder 24 is formed so that its inner diameter gradually becomes thinner toward the opening 26.

  The heating cylinder 24 accommodates the screw 25 inside. A plurality of heating heaters are attached to the outer surface of the heating cylinder 24. In addition, a cylindrical hopper 27 is attached to the heating cylinder 24. The heating cylinder 24 is filled with a chip-shaped synthetic resin I as a molding material via a hopper 27. The heating cylinder 24 heat-fluidizes (plasticizes) the filled chip-shaped synthetic resin I. Thus, the heating cylinder 24 is filled with the plasticized synthetic resin I. Further, the heating cylinder 24 has an opening 26 approaching the injection hole 15, and the synthetic resin plasticized through the opening 26 can be injected into the cavity 13 through the injection hole 15 and the sprue runner 14.

  The screw 25 is formed in a rod shape and is accommodated in the heating cylinder 24. When the screw 25 is accommodated in the heating cylinder 24, the longitudinal direction (axial core direction) is parallel to the longitudinal direction (axial core direction) of the heating cylinder 24. The screw 25 is provided so as to be movable along the longitudinal direction of the heating cylinder 24. On the outer peripheral surface of the screw 25, a spiral projection 28 is provided.

  The screw 25 rotates around the axis to move the synthetic resin I located between the protrusions 28 toward the opening 26, that is, the one end 24 a of the heating cylinder 24, and the opening 26, that is, the cavity 13 by the synthetic resin I. It is pressed in the direction away from. Further, the screw 25 is pushed toward the opening 26 to push out the plasticized synthetic resin I in the heating cylinder 24 toward the opening 26.

  The rotational movement unit 22 includes a motor 29 and a pulley 30. The motor 29 is a well-known electric motor, and includes an output shaft 31 that is fixed to a slide member 37 to be described later and that rotates around an axis. A pulley 32 is attached to the output shaft 31. The output shaft 31 and the pulley 32 are arranged coaxially with each other.

  The pulley 30 is attached to the end of the screw 25 on the side away from the opening 26. The pulley 30 is arranged in parallel with the screw 25. An endless annular belt 33 is stretched between the pulley 30 and the pulley 32 attached to the output shaft 31 of the motor 29.

  In the rotational movement unit 22 described above, the pulley 33 is rotated by the output shaft 31 of the motor 29, whereby the belt 33 circulates around the outer circumferences of the pulleys 30 and 32. Then, the rotational movement unit 22 rotates the screw 25 together with the pulley 30 around the axis.

  The slide moving unit 23 includes a motor 34 as a drive source, a pulley 35, a ball screw 36, and a slide member 37. The motor 34 is a well-known electric motor, and is provided with an output shaft 38 that is fixed to the injector body 19 and rotates around an axis. A pulley 39 is attached to the output shaft 38. The output shaft 38 and the pulley 39 are arranged coaxially with each other.

  The pulley 35 is rotatably provided. The rotation center of the pulley 35 is parallel to the axis of the output shaft 38 of the motor 34. The pulley 35 is arranged coaxially with the screw 25. An endless annular belt 40 is wound around the pulley 35 and a pulley 39 attached to the output shaft 38 of the motor 34. When the output shaft 38 is rotated around the axis by the motor 34, the belt 40 circulates around the outer periphery of the pulleys 35 and 39, and the pair of pulleys 35 and 39 rotate in synchronization with each other.

  The ball screw 36 includes a screw shaft 41 and a nut 42 screwed onto the screw shaft 41. The screw shaft 41 is parallel to the longitudinal direction (axial direction) of the screw 25. The screw shaft 41 is fixed to the pulley 35 and rotates around the shaft core integrally with the pulley 35. Of course, the screw shaft 41 is arranged coaxially with the pulley 35. The nut 42 moves along the longitudinal direction of the screw shaft 41 as the screw shaft 41 rotates around the axis.

  The slide member 37 is attached to the nut 42 of the ball screw 36. The slide member 37 rotatably supports the opening 26 of the screw 25, that is, the base end portion on the side away from the cavity 13. A bearing 43 that rotatably supports the screw 25 is provided between the slide member 37 and the base end portion of the screw 25.

  A load cell 20 as a pressure sensor is provided between the proximal end portion of the screw 25 and the slide member 37. The load cell 20 is sandwiched between the screw 25 and the slide member 37 along the axis of the screw 25. The load cell 20 is distorted when the screw 25 is pressed from the plasticized synthetic resin I when the plastic resin I plasticized by the screw 25 is injected into the cavity 13. This strain (elastic deformation amount) corresponds to the pressure of the synthetic resin I in the cavity 13.

  The load cell 20 is connected to the control device 9. The load cell 20 outputs information corresponding to the above-described strain (elastic deformation amount) toward the control device 9. The load cell 20 detects the above-described distortion, thereby detecting the pressure of the synthetic resin I applied to the tip surface of the screw 25, that is, the pressure of the synthetic resin I in the cavity 13. The load cell 20 outputs information corresponding to the pressure of the synthetic resin I in the cavity 13 to the control device 9 by outputting the information corresponding to the strain to the control device 9.

  In the slide moving unit 23 having the above-described configuration, the belt 40 circulates around the outer circumferences of the pulleys 35 and 39 and the pulley 35 rotates in conjunction with the rotation of the output shaft 38 of the motor 34. When the output shaft 38 of the motor 34 rotates, the slide moving unit 23 slides the nut 42 along the longitudinal direction of the screw shaft 41 and moves the screw 25 along the longitudinal direction of the heating cylinder 24. The slide moving unit 23 causes the motor 25 to slide the screw 25 and the rotary moving unit 22 together along the longitudinal direction of the heating cylinder 24.

  Further, in the injection machine 8 having the above-described configuration, the cylinder part 21, the rotation movement part 22, and the slide movement part 23 are integrally formed in the longitudinal direction of the heating cylinder 24 by moving means attached to the injection machine main body 19 and the like. It is possible to move along. The injection machine 8 moves along the longitudinal direction of the heating cylinder 24, whereby the opening 26 of the heating cylinder 24 is in close contact with and in communication with the injection hole 15 of the mold 10, and the position shown in FIG. The opening 26 of the cylinder 24 moves over the injection hole 15 of the mold 10 and a position shown in FIG. Thus, in the injection machine 8, the cylinder part 21, the rotational movement part 22, and the slide movement part 23 are integrated with each other and come into and out of the mold 10, that is, the mold part 7.

  The linear encoder 44 includes a main scale 45 and an index scale 46. The main scale 45 is formed in a rod shape, and its longitudinal direction is arranged in parallel with the longitudinal direction of the screw 25. The main scale 45 is attached to the slide member 37. That is, the main scale 45 contacts and separates from the mold part 7, that is, the cavity 13 together with the slide member 37. The index scale 46 is attached to the main scale 45 so as to be movable along the longitudinal direction of the main scale 45. The index scale 46 is attached to the injection machine main body 19.

  The linear encoder 44 is connected to the control device 9. The linear encoder 44 outputs information corresponding to the relative position of the index scale 46 to the main scale 45 toward the control device 9. This relative position corresponds to the position of the screw 25 in the heating cylinder 24.

  The linear encoder 44 detects the position of the screw 25 in the heating cylinder 24 by detecting the relative position of the index scale 46 to the main scale 45. The linear encoder 44 outputs information corresponding to the position of the index scale 46 relative to the main scale 45 toward the control device 9, thereby obtaining information corresponding to the position of the screw 25 in the heating cylinder 24. Output toward.

  The control device 9 is a computer including a known RAM, ROM, CPU, and the like. The control device 9 stores a program for operating the injection molding machine 1. The control device 9 is connected to the mold unit 7 and the injection machine 8 and controls the whole injection molding machine 1 by controlling them based on the program described above. The control device 9 is connected to an input device 47 composed of a keyboard, a mouse and the like for inputting the product number and the number of manufactured connector housings 3 as molded products.

  The control device 9 is connected to both the load cell 20 as a pressure sensor and the linear encoder 44 through an amplifier (not shown). Information corresponding to the pressure of the synthetic resin I in the cavity 13 detected by the load cell 20 is amplified and input to the control device 9 by the amplifier. Information corresponding to the position of the screw 25 in the heating cylinder 24 detected by the linear encoder 44 is amplified and input to the control device 9 by the amplifier. The control device 9 is connected to each of the motor 29 of the rotational movement unit 22 and the motor 34 of the slide movement unit 23 via a driver (not shown), and controls these.

  The control device 9 is filled with the plasticized plastic I in the heating cylinder 24 with the screw 25 farthest from the opening 26, and the opening 26 of the heating cylinder 24 and the injection hole 15 are in contact with each other. The motor 34 is controlled so that the screw 25 moves toward the opening 26 at a predetermined speed determined based on information from the linear encoder 44.

  Further, the control device 9 sets the screw 25 to a predetermined distance L (FIG. 10C) determined in advance based on information from the linear encoder 44 while the screw 25 is moving at the predetermined speed. Determine whether it has moved. The synthetic resin I is injected into the cavities 13 of the molds 10 and 11 while the screw 25 is moved by the predetermined distance L from the state farthest from the opening 26, that is, at the aforementioned predetermined speed and the screw 25 is brought close to the opening 26. Between, the filling step A (shown in FIG. 10C) described in the present specification is performed.

  The predetermined distance L is the volume of the synthetic resin I injected from the opening 26 from the start of injection of the synthetic resin I into the cavity 13 by the movement of the screw 25. Is a smaller distance.

  Immediately after the filling process A is performed by moving the screw 25 by a predetermined distance L after the screw 25 has moved in advance, the pressure in the cavity 13 is set to a predetermined pressure holding pressure P0 (FIG. 10 ( The motor 34 is stopped until it decreases to (shown in b), and a backward restriction signal for restricting the backward movement of the screw 25 (moving away from the opening 26, that is, the cavity 13) is output to the motor 34.

  Then, when the pressure of the synthetic resin I in the cavity 13 detected by the load cell 20 reaches the above-described pressure holding pressure P0, the control device 9 causes the motor 34 to retract the screw 25 (in the direction away from the opening 26, that is, the cavity 13). A reverse restriction release signal that permits movement) is output. The control device 9 controls the motor 34 so that the pressure of the synthetic resin I in the cavity 13 detected by the load cell 20 becomes the above-described holding pressure setting pressure P0, so that the screw 25 is moved along the longitudinal direction of the heating cylinder 24. And move it.

  Then, when a predetermined time elapses from the start of injection, the control device 9 stops the motor 34 of the slide moving unit 23 and ends the filling of the synthetic resin I. The pressure holding step B (shown in FIG. 10 (c)) described in the present specification is performed after outputting the above-described backward restriction signal, that is, while the screw 25 is temporarily stopped and the filling of the synthetic resin I is finished. There is no.

  Then, the control device 9 controls the motor 29 so as to rotate the screw 25 in the direction in which the projection 28 moves the synthetic resin I from the hopper 27 toward the opening 26, and performs the measuring process. Based on the information from the linear encoder 44, the control device 9 stops the motor 29 when the screw 25 is farthest from the opening 26 and sends a desired amount of the synthetic resin I toward the opening 26. And after performing the cooling process, the control apparatus 9 leaves | separates the injection machine 8 from the metal mold | die part 7, once molds 10 and 11 are once separated, and shape | molds the next connector housing 3 again.

  Next, the molding process of the connector housing 3 as a molded product using the injection molding machine 1 of the above-described embodiment will be described. In step S1 in FIG. 2, first, as shown in FIG. 3, the control device 9 is filled with plasticized synthetic resin I in the heating cylinder 24 and the screw 25 is moved away from the opening 26. The pair of molds 10 and 11 are brought close to each other by the moving mechanism 12 or the like. Thus, the control device 9 closes the molds 10 and 11 by bringing the molds 10 and 11 closer to each other and in close contact with each other. Further, the control device 9 keeps the entire injection machine 8 away from the mold part 7. That is, the control device 9 arranges the opening 26 of the heating cylinder 24 of the injection machine 8 at a distance from the mold 10. Then, the process proceeds to step S2.

  In step S2, the control device 9 brings the entire injection machine 8 close to the mold part 7 and brings the opening 26 of the heating cylinder 24 into close contact with the injection hole 15 of the mold 10 as shown in FIG. Let Then, the process proceeds to step S3. In step S <b> 3, the control device 9 drives the motor 34 to bring the screw 25 closer to the opening 26 at a predetermined speed stored in advance based on information from the linear encoder 44. Then, the control device 9 injects the plasticized synthetic resin I in the heating cylinder 24 into the cavity 13 through the injection hole 15 and the sprue runner 14. Thus, the motor 34 brings the screw 25 close to the opening 26 at a predetermined speed, and the synthetic resin I is injected into the cavities 13 of the molds 10 and 11 through the opening 26.

  Thus, the control device 9 injects the synthetic resin I into the cavity 13, that is, into the molds 10 and 11, as shown in FIG. Then, most of the inside of the cavity 13, that is, the inside of the molds 10 and 11 is filled with the plasticized synthetic resin I. Then, the process proceeds to step S4.

  In step S4, the control device 9 determines whether or not the screw 25 has moved a predetermined distance L stored in advance based on information from the linear encoder 44. If the control device 9 determines that the screw 25 has not moved the predetermined distance L stored in advance, the control device 9 repeats step S4. When the control device 9 determines that the screw 25 has moved the predetermined distance L stored in advance, the control device 9 proceeds to step S5. That is, the control device 9 proceeds to the pressure holding step B after the predetermined distance L screw 25 stored in advance in the filling step A moves.

  Steps S3 and S4 described above constitute the filling step A described above. In this filling step A, the synthetic resin I is filled in the heating cylinder 24 and the screw 25 is moved away from the opening 26, and the motor 25 is moved closer to the opening 26 and the synthetic resin I is molded through the opening 26. 10 and 11 are injected into the cavities 13 and the screw 25 approaches a predetermined distance L in the opening 26. Further, in the filling step A, as indicated by a solid line in FIG. 10A, after the injection speed of the synthetic resin I is rapidly increased, the injection speed is maintained at a preset speed, and FIG. As shown by the solid line in (b), the pressure of the synthetic resin I in the cavity 13 increases rapidly. At the end of the filling step A, the pressure of the synthetic resin I in the cavity 13 is maximized. Further, in this filling step A, of course, as shown by the solid line in FIG. 10C, the screw 25 moves by the predetermined distance L as described above, and the V / P switching position L0 (from the filling step A to the pressure holding step). Move to position B).

  In step S5, the control device 9 temporarily stops the motor 34, outputs the above-described reverse regulation signal to the motor 34, and proceeds to step S6. The reverse regulation signal is a signal that regulates that the motor 34 moves the screw 25 in the direction away from the opening 26, that is, the cavity 13. In step S6, the control device 9 determines whether or not the pressure of the synthetic resin I in the cavity 13 detected by the load cell 20 has reached the above-described holding pressure setting pressure P0 immediately after shifting from the filling process A to the holding pressure process B. Determine. When the control device 9 determines that the pressure of the synthetic resin I in the cavity 13 has not reached the above-described pressure holding pressure P0, the control device 9 repeats step S6 and maintains the stopped state. When the control device 9 determines that the pressure of the synthetic resin I in the cavity 13 has reached the above-described pressure holding set pressure P0, the control device 9 proceeds to step S7.

  That is, immediately after shifting to the pressure holding process B, the control device 9 stops the screw 25 and stops the screw 25 until the pressure of the synthetic resin I in the cavity 13 drops to a predetermined pressure holding pressure P0. Regulate the retreat. In this way, in step S5 and step S6, of course, the injection speed of the synthetic resin I becomes zero as shown by the solid line in FIG. 10A, and the cavity as shown by the solid line in FIG. 10B. The pressure of the synthetic resin I in 13 is reduced to the holding pressure setting pressure P0, and the screw 25 is stopped as shown by a solid line in FIG. From step S6 to step S7, as shown in FIG. 6, the synthetic resin I in the cavity 13 is injected into the cavity 13, that is, into the molds 10 and 11 by its own pressure. The generated cavity 13, that is, the gap in the molds 10 and 11 is slightly filled.

  In step S <b> 7, the control device 9 outputs a reverse regulation release signal to the motor 34. The reverse restriction release signal is a signal that allows the motor 34 to move the screw 25 in the direction away from the opening 26, that is, the cavity 13. The control device 9 moves the screw 25 by driving the motor 34 so that the pressure of the synthetic resin I in the cavity 13 detected by the load cell 20 becomes the above-described holding pressure setting pressure P0.

  Then, as shown in FIG. 7, the screw 25 slightly approaches the opening 26, and the plasticized synthetic resin I in the heating cylinder 24 is injected into the cavity 13, that is, into the molds 10 and 11, and the filling process A The synthetic resin I is filled in the cavity 13, that is, the gaps in the molds 10 and 11 generated in step (1). The gaps described above are completely filled with the synthetic resin I. Then, the process proceeds to step S8.

  In step S8, the control device 9 temporarily stops the screw 25 in step S5, and determines whether or not a predetermined time has elapsed from the start of injection. The control device 9 repeats step S8 until a predetermined time elapses, and proceeds to step S8a after the predetermined time elapses. During this step S8, the synthetic resin I in the cavity 13 is cured, and the connector housing 3 having the above-described configuration is manufactured.

  In step S7 and step S8 described above, the injection speed of the synthetic resin I becomes slightly positive as shown by the solid line in FIG. 10A, and as shown by the solid line in FIG. While the pressure of the synthetic resin I is maintained at the above-described holding pressure setting pressure P0, the screw 25 slightly moves toward the opening 26, that is, the cavity 13, as indicated by a solid line in FIG. Thus, this embodiment is clearly different from the method shown in Patent Document 2 described above (indicated by a two-dot chain line in FIGS. 10A to 10C) in the movement of the screw 25. Of course, the pressure change of the synthetic resin I in the cavity 13 is also different.

  Steps S5 to S8 described above constitute the pressure holding step B described above. In this pressure holding step B, the control device 9 controls the movement of the screw 25 based on the pressure of the synthetic resin I in the cavity 13 after performing the filling step A. Further, in the pressure holding process B, when the pressure of the synthetic resin I in the cavity 13 detected by the load cell 20 reaches the pressure setting pressure P0, the control device 9 releases the restriction on the backward movement of the screw 25 and The screw 25 is moved so that the pressure of the synthetic resin I is maintained at the holding pressure setting pressure P0.

  In step S8a, the control device 9 performs a weighing process and a cooling process. First, the control device 9 stops the motor 34 of the slide moving unit 23 and moves the motor 29 of the rotary moving unit 22 in a direction in which the projection 28 of the screw 25 moves the synthetic resin I in the hopper 27 toward the opening 26. Driven to feed a desired amount of synthetic resin I toward the opening 26, the process proceeds to step S8b. Then, since the motor 34 of the slide moving unit 23 is stopped, the screw 25 is gradually separated from the opening 26 as the protrusion 28 moves the synthetic resin I toward the opening 26.

  Then, as shown in FIG. 8, the screw 25 is positioned at the position farthest from the opening 26, and the heating cylinder 24 is filled with the synthetic resin I. The heating heater of the heating cylinder 24 heat-fluidizes (plasticizes) the synthetic resin I in the heating cylinder 24. In step S8b, based on the information from the linear encoder 44, it is determined whether or not the screw 25 has moved a predetermined distance in advance, that is, whether or not a predetermined amount of the synthetic resin I is filled in the heating cylinder 24. Step S8b is repeated until a predetermined amount of synthetic resin I is filled in the cylinder 24, and when a predetermined amount of synthetic resin I is filled in the heating cylinder 24, the process proceeds to step S8c. Thus, in step S8a and step S8b, the heating cylinder 24 is filled with a predetermined amount of synthetic resin I.

  In step S8c, the molds 10, 11 and the like are cooled to a predetermined temperature. That is, in order to harden the synthetic resin I in the cavity 13, step S8c is repeated until the preset cooling time ends, and when the cooling time ends, the process proceeds to step S9. In step S <b> 9, the control device 9 separates the entire injection machine 8 from the mold part 7 as shown in FIG. 9. That is, the opening 26 of the heating cylinder 24 is separated from the injection hole 15 of one mold 10 of the mold part 7. Then, the process proceeds to step S10. In step S10, the control device 9 causes the moving mechanism 12 of the mold part 7 to move to the other mold when a predetermined time has elapsed after the pressure holding process, that is, the injection of the synthetic resin I into the molds 10 and 11 is completed. The mold 11 is moved away from one mold 10. Thus, in step S10, the control device 9 separates the pair of molds 10 and 11 from each other, that is, opens the molds 10 and 11, after the connector housing 3 as a molded product is cooled and solidified or cured. Then, the process proceeds to step S11.

  In step S11, the connector housing 3 is taken out as a molded product of the cavity 13 between the molds 10 and 11. When the connector housing 3 as a molded product is taken out, the process returns to step S1, and the next injection molding cycle is started. In this way, the injection molding machine 1 repeats the above-described steps S1 to S11 to mold (manufacture) a predetermined number of connector housings 3 as molded products.

  In addition, the predetermined distance L, the predetermined time, the holding pressure setting pressure P0, and the like in the above-described embodiment are values determined in advance for each connector housing 3 as a molded product, and differ for each product number of the connector housing 3 and the like. It is a value. The control device 9 performs injection molding by appropriately changing the predetermined distance L, the predetermined time, the holding pressure setting pressure P0, etc. described above according to the product number of the molded product such as the connector housing 3 to be manufactured.

  According to this embodiment, the predetermined distance L in which the screw 25 moves in the filling step A is a distance where the injected volume of the synthetic resin I is smaller than the volume of the cavity 13. In other words, the filling process is switched to the pressure-holding process at a position behind the screw 25 rather than the known injection molding machine that has been used conventionally. For this reason, the pressure of the synthetic resin I in the heating cylinder 24 and the cavity 13 is changed. The maximum value can be suppressed, and the synthetic resin I near the tip of the compressed screw 25 in the heating cylinder 24 is gradually released into the cavity 13. Therefore, since it is not necessary to ensure the mechanical strength of the heating cylinder 24 and the molds 10 and 11 more than necessary, the increase in size and cost of the injection molding machine 1 itself can be suppressed.

  Moreover, since it is not necessary to ensure the mechanical strength of the heating cylinder 24 and the molds 10 and 11 more than necessary, even the injection molding machine 1 that is relatively simple (low mechanical strength) A relatively thin molded product can be formed. Therefore, it is possible to suppress a rise in the cost of a relatively thin molded product.

  Further, in the pressure holding process B, the screw 25 is restricted to move backward until the pressure of the synthetic resin I in the cavity 13 drops to the pressure setting pressure P0, so that the pressure of the synthetic resin I in the cavity 13 is maintained. The screw 25 is stopped until the pressure setting pressure P0 is reached. For this reason, in the pressure holding step B, the synthetic resin I near the tip of the compressed screw 25 in the heating cylinder 24 is gradually released into the cavity 13, and the synthetic resin I reaches the cavity 13. Become. For this reason, it is possible to prevent the appearance of defects such as sink marks from occurring in the connector housing 3 as a molded product and the variation in the mass of the connector housing 3 as the molded product. Therefore, the yield of the connector housing 3 as a molded product can be improved.

  In the pressure holding step B, once the synthetic resin I in the cavity 13 reaches the holding pressure setting pressure P0, the screw 25 is moved so as to keep the holding pressure setting pressure P0. The synthetic resin I in the cavity 13 is maintained at the holding pressure setting pressure P0 by the screw 25 until it spreads. For this reason, the synthetic resin I reaches the cavity 13 sufficiently. Therefore, the yield of the connector housing 3 as a molded product can be reliably improved.

  Next, the inventors of the present invention confirmed the effects of the injection molding machine 1 of the above-described embodiment. The results are shown in Table 1 below.

  In Table 1, the connector housing 3 as a molded product was molded. In Comparative Example 1 in Table 1, the retraction speed of the screw immediately after shifting from the filling process A to the pressure holding process B is 5 mm / sec, and in Comparative Example 2, the screw retraction speed immediately after shifting from the filling process A to the pressure holding process B. The screw retraction speed was set to 15 mm / sec, and Comparative Example 3 was carried out using the method described in Patent Document 1 described above, assuming that the screw retraction speed immediately after shifting from the filling process to the pressure holding process was 30 mm / sec. 3 was molded. As shown in the above-described embodiment, the product of the present invention in Table 1 was molded with the connector housing 3 with the retraction speed of the screw 25 immediately after the transition from the filling step A to the pressure holding step B being 0 mm / sec. .

  Further, the coefficient of variation in Table 1 indicates a variation in the mass of the molded connector housing 3, and indicates that the greater the variation coefficient, the greater the variation in the mass of the connector housing 3.

  According to Table 1, it was found that the product of the present invention has the smallest coefficient of variation in product weight than Comparative Examples 1 to 3. Therefore, as shown in Table 1, it became clear that the connector housing 3 having a high yield can be formed by not retracting the screw 25 immediately after the transition from the filling step A to the pressure holding step B.

  In the embodiment described above, the connector housing 3 is molded as a molded product. However, in the present invention, for example, a case of an electrical junction box constituting a wire harness routed in an automobile or the like, a harness protector and a wiring clip constituting the above-described wire harness may be formed. In short, in the present invention, any material can be molded as long as it can be molded by injection molding. In the above-described embodiment, the injection machine 8 is once separated from the molds 10 and 11, and then the molds 10 and 11 are brought into contact with and separated from each other (that is, so-called repetitive molding is performed). However, in the present invention, the molds 10 and 11 may be brought into contact with or separated from each other while the injector 8 is in contact with the molds 10 and 11 (that is, so-called touch molding may be performed).

  In the embodiment described above, a synthetic resin is used as the molding material. However, in the present invention, a silicon-based material or a metal may be used as the molding material. Furthermore, the present invention is not limited to the injection molding machine 1 shown in the above-described embodiment, and can be applied to any injection molding machine. For example, in the embodiment described above, the screw 25 is used as the pressing member. However, in the present invention, a well-known piston or plunger may be used as the pressing member, and a sensor other than the load cell 20 is used as a pressure sensor as the detecting means. Any known type of electric motor such as a hydraulic control type may be used as a drive source. In the present invention, the pressure sensor described above may be provided in the cavity 13, and the pressure in the cavity 13 may be directly detected by the pressure sensor.

  Furthermore, in the above-described embodiment, the weighing process is performed after a predetermined time has elapsed since the injection was started in step S8. However, in the present invention, the metering step may be performed after a predetermined time has elapsed after the synthetic resin I is injected into the cavity 13 and the screw 25 is temporarily stopped.

  Further, in the above-described embodiment, when the pressure of the synthetic resin I injected into the cavity 13 becomes the above-described holding pressure setting pressure P0 in the holding pressure step B, the control device 9 outputs a reverse restriction release signal, The screw 25 is moved so that the pressure of the synthetic resin I in the cavity 13 becomes the above-described holding pressure setting pressure P0. However, in the present invention, in the pressure holding process B, as shown in FIG. 11, even when the pressure of the synthetic resin I injected into the cavity 13 becomes the pressure setting pressure P0 described above, the control device 9 restricts the backward movement. The screw 25 may be stopped without outputting the release signal.

  In addition, embodiment mentioned above only showed the typical form of this invention, and this invention is not limited to embodiment. That is, various modifications can be made without departing from the scope of the present invention.

It is explanatory drawing which shows the structure of the injection molding machine which concerns on one Embodiment of this invention. It is a flowchart which shows the process of shape | molding the connector housing as a molded article using the injection molding machine shown by FIG. It is explanatory drawing which shows the state from which the injection machine of the injection molding machine shown by FIG. It is explanatory drawing explaining the state which brought the injection machine close | similar to the metal mold | die from the state shown by FIG. It is explanatory drawing explaining the state which injected the synthetic resin as a molding material in a heating cylinder in the metal mold | die in the filling process from the state shown by FIG. It is explanatory drawing explaining the state by which the synthetic resin as a molding material in a heating cylinder was open | released in the metal mold | die, with the screw stopped in the pressure-holding process from the state shown in FIG. It is explanatory drawing explaining the state which inject | poured the synthetic resin as a molding material in a heating cylinder in the metal mold | die by the pressure-holding process from the state shown by FIG. It is explanatory drawing explaining the state which filled the molding material in the heating cylinder from the state shown by FIG. It is explanatory drawing explaining the state which separated the injection machine from the metal mold | die from the state shown by FIG. (A) is explanatory drawing which shows the change of the injection speed of the synthetic resin of the injection molding machine shown by FIG. 1, (b) is the pressure of the synthetic resin in the cavity of the injection molding machine shown by FIG. It is explanatory drawing which shows a change, (c) is explanatory drawing which shows the change of the position of the screw of the injection molding machine shown by FIG. (A) is explanatory drawing which shows the change of the injection speed of the synthetic resin of the modification of the injection molding machine shown by FIG. 1, (b) is in the cavity of the injection molding machine shown by FIG. 11 (a). It is explanatory drawing which shows the change of the pressure of this synthetic resin, (c) is explanatory drawing which shows the change of the position of the screw of the injection molding machine shown by Fig.11 (a). FIG. 2 is a perspective view of a connector housing or the like as a molded product molded by the injection molding machine shown in FIG. 1.

Explanation of symbols

1 Injection molding machine 3 Connector housing (molded product)
9 Control device (control means)
10, 11 Mold 13 Cavity 24 Heating cylinder (cylinder)
24a one end 25 screw (pressing member)
26 Opening 34 Motor (drive source)
A Filling process B Holding pressure process I Synthetic resin (molding material)
L Predetermined distance P0 Holding pressure setting pressure

Claims (4)

A cylindrical cylinder that contains a pressing member and is filled with a plasticized molding material and can be injected into the cavity of the mold through an opening at one end;
A drive source for moving the pressing member along the longitudinal direction of the cylinder;
Filling the cylinder with the molding material, keeping the pressing member away from the opening, causing the driving source to bring the pressing member closer to the opening, and passing the molding material into the cavity of the mold through the opening. Control that performs a pressure-holding step of controlling the movement of the pressing member based on the pressure of the molding material in the cavity after performing the filling step of injection and the pressing member approaching the opening a predetermined distance. An injection molding machine comprising:
The predetermined distance is a distance in which the volume of the molding material injected from the opening from the start of injection of the molding material is smaller than the volume of the cavity;
The control means regulates the backward movement of the pressing member until the pressure of the molding material decreases to a predetermined holding pressure setting pressure immediately after shifting from the filling step to the holding pressure step. Injection molding machine.   When the pressure of the molding material in the cavity reaches a predetermined holding pressure setting pressure in the pressure holding step, the control means releases the restriction of the retraction of the pressing member, and the molding material in the cavity The injection molding machine according to claim 1, wherein the pressing member is moved so that the pressure maintains the holding pressure setting pressure. A cylindrical cylinder that accommodates the pressing member and is filled with the plasticized molding material and can inject the molding material into the mold cavity through the opening at one end, and the pressing member in the longitudinal direction of the cylinder In a control method of an injection molding machine provided with a drive source that moves along
Filling the cylinder with the molding material, keeping the pressing member away from the opening, causing the driving source to bring the pressing member closer to the opening, and passing the molding material into the cavity of the mold through the opening. After performing a filling step of injection and the pressing member approaching the opening a predetermined distance, a pressure holding step for controlling the movement of the pressing member based on the pressure of the molding material in the cavity is performed. ,
The predetermined distance is a distance in which the volume of the molding material injected from the opening from the start of injection of the molding material is smaller than the volume of the cavity;
Immediately after shifting from the filling step to the pressure-holding step, the backward movement of the pressing member is restricted until the pressure of the molding material drops to a predetermined pressure-holding pressure setting pressure. Control method.   In the pressure-holding step, when the pressure of the molding material in the cavity reaches a predetermined pressure-holding setting pressure, the restriction of the retraction of the pressing member is released, and the pressure of the molding material in the cavity is the pressure-holding pressure. The method of controlling an injection molding machine according to claim 3, wherein the pressing member is moved so as to maintain a set pressure.

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