KR100931800B1 - Electric Injection Molding Machine - Google Patents

Abstract

The present invention relates to a load cell mounting structure of an electric drawing-molding machine, which prevents assembly error and deformation of a load cell that detects a molding material pressure received by a screw during injection, thereby enabling accurate measurement and control of the molding material pressure. In front of the load cell 120, a first shaft portion 122a protrudes from a point located radially inward of the pressure sensing sensor 121, and the thrust housing 130 is provided with the first shaft part 122a. A first hole portion 132a into which the first shaft portion 122a is loosely fitted is formed, and the front end surface 123 of the first shaft portion 122a of the load cell 120 and the first hole of the thrust housing 130 are formed. The inner end surface 133 of the portion 132a is an axial contact surface for transmitting molding material pressure to the load cell 120, and is radially outward from the pressure sensing sensor 121 of the load cell 120. At the position where the second shaft portion 125 protrudes, The transfer base 60 is formed with an annular engaging groove 65 corresponding to the second shaft portion, so that the second shaft portion 125 of the second shaft portion 125 with respect to the inner diameter D2 of the engaging groove 65 of the transfer base 60 is formed. The outer diameter d2 is fitted to fit the inner diameter D2 of the coupling groove 65 of the transfer base 60 and the outer diameter d2 of the second shaft portion 125 of the load cell 120 and the thrust housing 130. A radial fitting portion is used.

Injection, Screw, Load Cell, Mounting, Deformation, Assembly, Machining, Error, Tolerance

Description

Electric injection molding machine {ELECTRICALLY DRIVEN INJECTION MOLDING MACHINE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motorized draw molding machine in which a screw is inserted into a heating cylinder in a rotatable and movable manner, and more particularly, to prevent an assembly error and deformation of a load cell that detects a molding material pressure applied to the screw during injection. The present invention relates to an electric drawing molding machine that enables accurate measurement and control of molding material pressure.

The electric injection molding machine is an apparatus for molding a product in the form of a cavity by injecting a molten resin into a cavity of a mold at high pressure, cooling and solidifying it.

An injection apparatus in such an injection molding machine is a part for heating and melting a molding material (raw material resin) and injecting the molten molding material into the cavity of the mold, as shown in FIG. 1, in front of the nozzle 11. And a heating cylinder (10) for heating and storing the molding material introduced from the hopper (12) while the hopper (12) is connected to one rear side thereof, and is rotatable and movable inside the heating cylinder (10). The screw 20, the motor 30 for rotating the screw 20, and the screw 20 are connected together with the screw 20, for example, by spline coupling. , The shaft 40 which is slidably coupled in the axial direction, and supports the shaft 40, and is moved forward and backward in the axial direction by a conveying device 50 such as, for example, a ball screw, to thereby move the shaft 40. ) And advance screw (20) And a pressure detecting unit 100 which detects the conveying base 60 to retreat and the molding material pressure acting on the screw 20 to enable metering control and injection pressure control according to molding conditions. And the pressure detection unit 100, the load cell 120 is mounted to the rear of the support block 110 which is mounted directly to the rear of the transfer base 60 or the transfer base 60, and the shaft 40 And a thrust housing 130 that rotatably supports and transmits a molding material pressure acting on the screw 20 to the load cell 120.

In such an injection molding machine, the molding material (raw resin or the like) injected into the heating cylinder 10 through the hopper 12 is melted inside the heating cylinder 10 and kneaded by the rotation of the screw 20 and the front thereof. Is transferred to. When such a process is performed while the screw 20 is slowly retracted by the set stroke by the conveying device 50, the molten molding material is the front part of the heating cylinder 10 at an amount and pressure corresponding to the stroke. Stored in the weighing process. Subsequently, the injection apparatus is advanced, the nozzle 11 at the tip of the heating cylinder 10 is brought into close contact with the sprue of the molded mold, and the screw 20 is advanced by the transfer apparatus 50 to be heated. The molten molding material stored in front of the cylinder 10 is injected at a predetermined pressure through the nozzle 11 (injection step), and then cooled and solidified while maintaining a predetermined holding pressure. .

In this injection process, the reaction force (molding material pressure) acting at the same magnitude as the force pushing the molding material, that is, the back pressure in the weighing process, the injection pressure in the injection process, and The holding pressures are all transmitted to the thrust housing 130 through the shaft 40, the force transmitted to the thrust housing 130 is detected at the load cell 120, and injection control of the pressure signal applied from the load cell 120 is performed. It is used as data for feedback control of process by molding condition in module.

2 and 3 are shown in detail the coupling state of the components of the pressure detection unit 100, Figure 2 is a cross-sectional view of the main part of the coupling state, Figure 3 is a state in which the load cell 120 is separated A cross-sectional view of is shown. In the following description and claims, the support block 110 is referred to as a 'transfer base 60' by being treated as a part of the body of the transfer base 60. Because, depending on the injection device, the structure for mounting the load cell 120 and the thrust housing 130 directly to the transfer base 60 may be employed, or after mounting the support block 110 to the transfer base 60, Since the structure for mounting the load cell 120 and the thrust housing 130 to the support block 110 is also employed, in either case, the load cell 120 and the thrust housing 130 are mounted on the transfer base 60 side. It is because it is the same.

First, as shown in FIG. 2 and as described above, the transfer base 60 is fitted with a thrust housing 130, and the load cell 120 has a rear end and a thrust housing of the transfer base 60. It is attached to the rear end of 130 by means such as screws 141 and 142. The load cell 120 is provided with an annular pressure sensor (eg, a strain gauge) 121, and the molding material pressure, which is the axial pressure of the screw 20, is applied to the thrust housing 130. When the force is transmitted to the load cell 120 in the fitting portion A of FIG. 2, the load cell 120 is deformed finely, and the deformation amount is detected by the pressure sensor 121 and is not shown. It is sent to the injection control module via the signal line.

Here, in order for the force (molding material pressure) applied from the thrust housing 130 to be accurately transmitted to the load cell 120, three components of the thrust housing 130, the load cell 120, and the transfer base 60 are provided. The parts joining each other, that is, the 'axially fitting surface' and the 'radial fitting', should be combined very precisely and accurately.

Conventionally, the load cell 120 is configured to be mainly configured in the fitting portion A (see FIG. 2). That is, the fitting portion A of the load cell 120 and the thrust housing 130 is used to align the radial center of the load cell 120 and the thrust housing 130 and to make the axial contact surface coincide. .

Specifically, as shown in FIG. 3, the shaft portion 122 of the load cell 120 and the hole 132 of the thrust housing 130 are fitted to each other so that the radial direction of the load cell 120 and the thrust housing 130 is provided. Align the center and closely contact the front end surface 123 of the shaft portion 122 of the load cell 120 with the inner end surface 133 of the hole portion 132 of the thrust housing 130 to form an axial contact surface. The molding material pressure applied to the thrust housing 130 by the screw 20 (see FIG. 1) is transmitted to the load cell 120 through its axially close contact surface. In addition, the mounting surface 124 of the load cell 120 is in close contact with the mounting surface 64 of the transfer base 60.

By the way, in the conventional electric injection molding machine having the load cell mounting structure made as described above, the radial fitting portion of the load cell 120 and the thrust housing 130 is located radially inward than the pressure sensor 121. Because of the structure, when assembling the load cell 120 and the thrust housing 130, there is a high possibility that a force other than the molding material pressure (force due to misassembly or the like) is transmitted to the pressure sensing sensor 121 as it is, and thus molding It impedes accurate measurement and accurate control of material pressure. For example, in the shaft portion 122 of the load cell 120 and the hole portion 132 of the thrust housing 130, it is allowed between the outer diameter d1 of the shaft portion 122 and the inner diameter D1 of the hole portion 132. If a tolerance occurs due to a fastening or a tolerance occurs between the outer diameter d1 of the shaft portion 122 and the inner diameter D1 of the hole portion 132, a fastening occurs, so that the shaft portion 122 and the hole portion 132 may be assembled. When it is forcibly fitted, an axial load (usually a deflection force) is applied to the shaft portion 122 by the force, so that the pressure sensor 121 deforms in advance. In addition, when the shaft portion 122 of the load cell 120 and the hole portion 132 of the thrust housing 130 are assembled to be inclined to one side even slightly, the force (deflection force) caused by the load cell 120 It is transmitted to the shaft portion 122 as it is to cause deformation of the pressure sensor 121. In this case, since the front end surface 123 of the shaft portion 122 and the inner end surface 133 of the hole portion 132 are likely to come into close contact with one side but not the other, the thrust housing 130 From the inner end surface 133 of the hole 132 of the hole 132 to the whole of the front end surface 123 of the shaft portion 122 of the load cell 120, the molding material pressure is not uniformly acting but biased to one side, Molding material pressure is not transmitted accurately.

In addition, due to the structure in which the radial fitting of the load cell 120 and the thrust housing 130 is radially inward from the pressure sensing sensor 121, conventionally, the shaft portion 122 of the load cell 120 may be connected to the shaft portion 122 of the load cell 120. Since the hole 132 of the thrust housing 130 has to be made of a relatively small diameter, precise machining of the hole 132 is difficult, thereby amplifying the aforementioned problems. For example, the shaft portion 122 of the load cell 120 and the hole portion 132 of the thrust housing 130 are typically important coupling parts that serve as a reference for the radial assembly of the load cell 120 and the thrust housing 130. Grinding their surface precisely. However, since the outer diameter d1 of the shaft portion 122 is circumscribed with the grinding wheel, the diameter of the grinding wheel for polishing the shaft portion 122 is several to tens of times larger than the outer diameter d1 of the shaft portion 122. It has a larger diameter and therefore less wear of the grinding wheel so that the shaft 122 can be precisely ground. On the other hand, in the grinding wheel for polishing the hole 132, the grinding wheel having a diameter smaller than the inner diameter D1 of the hole 132 must be used so that the grinding wheel wears badly. If the grinding wheel wears badly, when the grinding wheel is transferred from the inlet to the inner end of the hole 132, grinding is performed properly at the inlet side of the hole 132, but the grinding is performed less toward the inner end, so that the hole 132 ) May be processed in a tapered form, such that precision grinding is difficult and tolerances are difficult to match with the outer diameter grinding of the shaft portion 122. For example, when applying the IT fitting tolerance to the actual machining part, the reason for applying the grade of the hole portion to the grade larger than that of the shaft portion is here. The larger the IT grade, the wider the tolerance range. Therefore, the tolerance is applied to the tolerance grade larger than the tolerance grade of the shaft in consideration of the difficulty of grinding.

Therefore, according to the structure in which the shaft portion 122 and the hole portion 132, which are radial fitting portions of the load cell 120 and the thrust housing 130, are located radially inward from the pressure sensor 121, according to the related art. The fitting state of the shaft 122 and the hole 132 is likely to directly affect the pressure sensor 121, resulting in deformation of the pressure sensor 121 during assembly, and in addition, the hole 132. Inner diameter (D1) of the) is difficult to precision machining is to amplify the deformation of the pressure sensor 121 during assembly.

The present invention was developed in order to solve the conventional problems as described above, an object of the present invention, while preventing the deformation of the load cell during assembly, reducing the processing and assembly error of the load cell, accurate measurement of the molding material pressure It is to provide an electric injection molding machine which enables control.

In order to achieve the above object, the present invention provides a screw rotatably inserted into a heating cylinder, a shaft connecting the screw and the motor, and supporting the shaft and moving in the axial direction back and forth by a conveying device. A transfer base for advancing and retracting the shaft and the screw, a load cell mounted behind the transfer base and equipped with a pressure sensor, and inserted into the transfer base while rotatably supporting the shaft to act on the screw. An electric injection molding machine including a thrust housing for transmitting a molding material pressure to the load cell, wherein the first shaft portion protrudes from the front of the load cell at a position radially inward from the pressure sensing sensor, and the thrust housing The first hole portion to which the first shaft portion of the load cell is loosely inserted And an end surface of the first shaft portion of the load cell and an inner end surface of the first hole portion of the thrust housing to be in close contact with each other to form an adhesion surface of the first shaft portion end surface and the inner end surface of the first hole portion of the thrust housing. It acts as an axial contact surface for transferring molding material pressure applied from the screw to the thrust housing to the load cell, and protrudes a second shaft portion at a point located radially outward from the pressure sensing sensor of the load cell. And forming an annular engaging groove corresponding to the second shaft portion in the conveying base to fit the outer diameter of the second shaft portion with respect to the inner diameter of the engaging groove of the conveying base, and the inner diameter of the engaging groove of the conveying base and the second shaft portion. To act as a radial fit to match the radial center of the load cell and thrust housing. It consists of a configuration.

In the electric injection molding machine of the present invention described above, the inner diameter of the coupling groove of the transfer base is preferably the inner diameter of the coupling hole for coupling the thrust housing to the transfer base.

In the electric injection molding machine of the present invention described above, it is preferable that the axial protrusion length of the second shaft portion is made of 1 mm to 10 mm.

In addition, the radial position of the second shaft portion is preferably disposed between the screw fastening hole for fastening the load cell to the transfer base and the pressure sensor.

According to the present invention, since the radial fitting portion of the load cell is formed radially outward of the pressure sensing sensor, it does not affect the pressure sensing sensor at the time of assembly, thereby enabling accurate transmission and measurement of the molding material pressure. In addition, the diameter of the radial fitting area is increased, which helps to improve the machining accuracy, thereby enabling more precise and stable fitting.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 and 5 are cross-sectional views showing the mounting structure of the load cell according to the present invention. The same reference numerals are given to the same parts as those shown in Figs. 1 to 3, and repeated description thereof will be omitted.

As shown in Figures 4 and 5, the load cell mounting structure of the electric injection molding machine according to the present invention, the fitting portion of the load cell 120 to the thrust housing 130, that is, the axial contact surface is a conventional By using the axial contact surface as it is, the front end surface of the first shaft portion 122a and the inner end surface of the first hole 132a ('C' portion of Figure 4), the radial fitting portion, The second shaft portion 125 is further formed on the radially outer side from the pressure sensor 121, and the second shaft portion 125 is formed by fitting the second shaft portion 125 with the engaging groove 65 of the transfer base 60. ('B' portion of Figure 4).

Specifically, the first shaft portion 122a is formed to protrude at a point located radially inward of the pressure sensing sensor 121 in front of the load cell 120, and corresponds to the first hole portion 132a. ) Is formed at the rear of the thrust housing 130 to correspond to the first shaft portion 122a of the load cell 120. In the present invention, in particular, the first shaft portion 122a and the first hole 132a, the role of the radial fitting portion for matching the radial center of the load cell 120 and the thrust housing 130 is It is excluded and only serves as an axial contact surface for transmitting the molding material pressure. Therefore, since the outer diameter d1-1 of the said 1st shaft part 122a and the inner diameter D1-1 of the 1st hole part 132a may be comprised so loosely that any fastening may not be produced, processing precision is required. It is not necessary to keep it higher than usual, and the machining precision of the axial contact surface formed only by the front end surface 123 of the first shaft portion 122a and the inner end surface 133 of the first hole 132a is high. Just keep the same level).

In addition, as described above, the second shaft 125 protrudes radially outward from the pressure sensing sensor 121 in front of the load cell 120, and correspondingly, the transfer base 60. At the rear end thereof, an annular coupling groove 65 is formed. The second shaft 125 and the coupling groove 65 may serve as a radial fitting portion of the load cell 120, that is, a fitting portion for centering the load cell 120 and the thrust housing 130. One configuration. That is, as the outer diameter d2 of the second shaft portion 125 is fitted to the inner diameter D2 of the coupling groove 65 of the transfer base 60, the load cell 120 and the thrust housing 130 are disposed. The radial center is aligned. As such, when the second shaft 125 and the engaging groove 65 are formed radially outward of the pressure sensing sensor 121, the portion of the transfer cell (not the thrust housing 130) of the transfer housing 120 is formed. Since it is adjacent to the portion to be screwed to 60, even if a fastening occurs or the biasing force according to the interference fit is to have little effect on the pressure sensor 121.

Here, the inner diameter (D2) of the coupling groove 65 of the transfer base 65, as shown in the figure, and the inner diameter of the coupling hole for coupling the thrust housing 130 to the transfer base 60 It is preferable to use in common. Then, the groove base 135 may be formed only at the rear end of the thrust housing 130 without forming a separate groove for fitting the second shaft portion 125 to the transfer base 60. The radial fitting portion (or assembly reference surface) of the thrust housing 130 and the load cell 120 for the 60) can be commonly used as one coupling groove (coupling hole) 65 to help improve machining and assembly accuracy. do. In this case, the axial depth of the groove portion 135 formed in the thrust housing 130 to form the coupling groove 65 is naturally formed deeper than the protruding length of the second shaft portion 125, the groove portion 135 Of the second shaft portion 125 is sufficiently smaller than the inner diameter d3 of the second shaft portion 125, and is sufficient between the inner diameter d3 of the second shaft portion 125 and the outer diameter D3 of the groove portion 135. Make sure the gap is maintained.

Here, the axial protrusion length of the second shaft portion 125 is preferably made of 1mm ~ 10mm. If the axial protrusion length of the second shaft portion 125 is too short, less than 1 mm, processing and assembly safety may decrease. If the length of the second shaft 125 is too long, the second shaft 125 may be damaged during transportation or assembly.

In addition, the second shaft 125 may be disposed between the screw fastening hole 126 for fastening the load cell 120 to the transfer base 60 and the pressure sensor 121. In this way, the radial fitting portion of the second shaft portion 125 of the load cell 120 with respect to the transfer housing 60 and the radial fitting portion of the thrust housing 130 are combined without causing inconvenience to screwing. One groove (coupling hole) 65 can be used in common.

In the electric injection molding machine of the present invention, the first shaft portion 122a and the first hole portion 132a positioned radially inward of the pressure sensing sensor 121 have the first shaft portion of the load cell 120 ( Only the front end surface 123 of 122a and the inner end surface 133 of the first hole 132a of the thrust housing 130 are utilized as the axial contact surface, and the rod is radially outward from the pressure sensor 121. The coupling hole 65 of the second shaft portion 125 and the transfer base 60 of the cell 120 is further formed, so that the outer diameter d2 and the transfer base of the second shaft portion 125 of the load cell 120 thereof are formed. The inner diameter D2 of the coupling hole 65 of 60 is utilized as a radial fitting part.

Conventionally, since the radial fitting portion of the load cell 120 has a structure that is radially inwardly formed than the pressure sensing sensor 121 of the load cell 120, an assembly error and corresponding biasing force of the corresponding radial fitting portion are caused. Since it was transmitted to the load cell 120 almost intact, causing deformation of the pressure sensor 121, it was difficult to accurately measure the molding material pressure. However, according to the present invention, as the radial fitting portion of the load cell 120 is formed by the second shaft portion 125 and the coupling groove 65 formed radially outward of the pressure sensing sensor 121, the deflection during assembly Even if a force is applied, the force hardly affects the pressure sensing sensor 121, so that the molding material pressure can be measured more accurately, and as the diameter of the radial fitting portion increases, precise machining is possible, thereby making it more precise and stable. Assembly is possible.

As described above, when the structure for mounting the load cell according to the present invention is applied to an electric injection molding machine, a very precise and stable assembly state can be realized, thereby preventing deformation of the load cell (pressure sensing sensor) and accurate molding material pressure. It can be measured, it is possible to implement an injection molding machine capable of producing a product of excellent quality.

In the above, specific embodiments of the present invention shown in the accompanying drawings have been described in detail, but these are merely illustrative of the preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. In addition, the embodiments of the present invention as described above can be variously modified and equivalent other embodiments by those of ordinary skill in the art within the technical spirit of the present invention, such modifications and equivalent other embodiments are naturally It belongs to the appended claims of the present invention.

1 is a view schematically showing a general electric injection molding machine.

2 is a cross-sectional view of an essential part showing a mounting structure of a conventional load cell.

3 is a view illustrating the load cell separated from FIG. 2.

4 is a cross-sectional view of an essential part showing a mounting structure of a load cell according to the present invention.

FIG. 5 is a diagram illustrating the load cell separated from FIG. 4.

<Explanation of symbols for the main parts of the drawings>

10: heating cylinder 11: nozzle

12: hopper 20: screw

30: motor 40: shaft

50: transfer device 60: transfer base

65: coupling groove 120: load cell

121: pressure sensor 122a: first shaft portion

123: end surface (of the first shaft) 125: second shaft

126: screw fastener 130: thrust housing

132a: first hole 133: inner end surface (first hole)

135: groove

Claims (4)

A screw 20 rotatably and movable inserted into the heating cylinder 10, a shaft 40 connecting the screw 20 and a motor, and the shaft 40 are supported in an axial direction by a conveying device. A transfer base 60 moving forward and backward to move the shaft and screws forward and backward, a load cell 120 mounted behind the transfer base 60 and provided with a pressure sensor 121, and the shaft 40 An electric injection molding machine including a thrust housing 130 that is rotatably supported) and is inserted into the transfer base 60 to transmit a molding material pressure acting on the screw 20 to the load cell 120. In front of the load cell 120, a first shaft portion 122a protrudes from a point located radially inward from the pressure sensing sensor 121, and the thrust housing 130 of the load cell 120 is formed. A first hole 132a is formed through which the first shaft portion 122a is loosely inserted, so that the front end surface 123 of the first shaft portion 122a of the load cell 120 and the first of the thrust housing 130 are formed. The inner end surface 133 of the hole portion 132a is brought into close contact with each other so that the first end portion 123 of the first shaft portion 122a and the inner end surface 133 of the first hole portion 132a of the thrust housing 130 are closed. The contact surface to be formed acts as an axial contact surface for transmitting the molding material pressure applied from the screw 20 to the thrust housing 130 to the load cell 120, The second shaft portion 125 protrudes from a point located radially outward from the pressure sensing sensor 121 of the load cell 120, and the transfer base 60 has an annular coupling corresponding to the second shaft portion. The groove 65 is formed to fit the outer diameter d2 of the second shaft portion 125 to the inner diameter D2 of the coupling groove 65 of the transfer base 60, thereby engaging the coupling groove of the transfer base 60. (65) The inner diameter D2 and the outer diameter d2 of the second shaft portion 125 serve as radial fitting portions for matching the radial center of the load cell 120 and the thrust housing 130. Electric injection molding machine comprising a configuration. The method of claim 1, The inner diameter (D2) of the coupling groove (65) of the transfer base (65) is an electric injection molding machine, characterized in that the inner diameter of the coupling hole for coupling the thrust housing (130) to the transfer base (60). The method of claim 1, The axial protrusion length of the second shaft portion 125 is 1mm ~ 10mm, characterized in that the electric injection molding machine. The method according to claim 1 or 3, The radial position of the second shaft portion 125 is provided between the screw fastening hole 126 for fastening the load cell 120 to the transfer base 60 and the pressure sensor 121. Injection molding machine.

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