JP2010099858A - Injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve circularity of the inside diameter of a bore by uniformly filling with resin at a bore molding part side and a motor case molding part side, and preventing the occurrence of turbulent flow in the resin flowing in the bore molding part side and the motor case molding part side in the filling in molding of a throttle body. <P>SOLUTION: A cylinder A for filling with resin in a cavity 25 for molding the bore, and a cylinder B for filling resin in a cavity 26 for molding the motor case are independently provided respectively. In filling with the resin, the filled resin pressure and the holding pressure are set lower at the cavity 26 side for molding the motor case than at the cavity 25 side for molding the bore. Alternatively, the timing for filling with resin is more delayed at the cavity 26 side for molding the motor case than at the cavity 25 for molding the bore. By molding like this, the circularity of the inside diameter of the bore 1 becomes better into the circularity of 105 μm with respect to that of 187 μm performed by using the conventional molding method. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a molded article such as a so-called throttle body, which forms a part of an intake passage of an internal combustion engine (engine) such as an automobile, and has a bore and a motor case for controlling the intake air amount. The present invention relates to a molding method for injection molding using a resin.

  2. Description of the Related Art Conventionally, an internal combustion engine (engine) such as an automobile has an intake passage for taking combustion air into the engine, and a throttle body for controlling the amount of intake air is attached to the intake passage. ing. One type of throttle body is a drive-by-wire type throttle body (hereinafter referred to as “DBW throttle body”). In the configuration, a bore portion in which a throttle valve for adjusting the amount of intake air is incorporated, and a motor case portion for housing a motor and gear for rotating the throttle valve are integrated.

  Conventionally, this DBW throttle body requires a high drive control accuracy during operation, and therefore has been made by cutting a metal such as aluminum.

  However, in recent years, automobile parts have been reduced in weight due to environmental problems and economic reasons such as low fuel consumption, and the DBW throttle body has also been made into a resin that is manufactured using an injection molding method. It came to be able to.

  In general injection molding, a molded product is obtained by filling a molten resin into a mold cavity and then increasing the resin pressure to apply a holding pressure and cooling and solidifying the molten resin. Is solidified under the influence of various factors such as mold cavity shape, mold structure, molding conditions (especially filling pressure and holding pressure), mold temperature, etc. It is difficult to make them completely the same. Due to this non-uniform shrinkage rate, deformation such as sink marks and warpage appears in the injection molded product.

  In particular, in the case of a throttle body, a high dimensional accuracy (roundness) is required because a throttle valve for controlling the flow rate of air is attached to the bore inner diameter. For this reason, it is necessary to uniformly fill the molten resin in the mold cavity during the molding process.

  Furthermore, since the DBW throttle body also integrally forms a motor case that houses the motor that drives the throttle valve, the resin flow that forms the bore and the resin flow that forms the motor case when the resin is filled are affected. It is an obstacle to increase the roundness of the bore.

  As described above, when the DBW throttle body is injection-molded, it is very difficult to increase the dimensional accuracy of the roundness of the target bore inner diameter portion for the reason described above. Furthermore, considering the heat-resistant temperature and chemical resistance of the resin in consideration of the DBW throttle body usage environment, the resin to be molded contains a high content of fillers such as glass fibers and glass flakes, which prevents resin shrinkage. In addition to being uniform, it is also affected by the orientation of the filler, resulting in an increasingly complicated deformation process, and it is difficult to increase the dimensional accuracy of the molded product, not limited to the molding of the DBW throttle body.

  Various inventions have been filed so far regarding methods for injection molding of resin throttle bodies. For example, an invention related to the structure of a molding die, an invention related to a molding method using insert molding, or an invention related to the type and components of a resin to be molded can be cited. Resin pressure is increased by mold insert operation to hold pressure, and deformation of the molded product due to uneven resin shrinkage is inevitable.

  Thus, as a method for reducing non-uniformity of resin shrinkage, Japanese Patent Application Laid-Open No. 2006-2675 introduces a temperature control circuit for making the surface temperature of a mold cavity for insert injection molding uniform. By this method, the resin filled in the mold cavity shrinks by obtaining a uniform temperature profile as a whole, and as a result, deformation of the molded product can be reduced.

  However, the shrinkage of the resin is greatly influenced not only by the temperature, but also by the resin pressure during the filling process and the pressure holding process. Can not. Further, when this method is adopted, there is a problem that the mold structure becomes complicated and the manufacturing cost of the mold becomes high.

  On the other hand, a molding method using an inert gas has been proposed as a technique for reducing deformation such as sink marks and warpage of a molded product in injection molding. This is a method in which after a molten resin is filled in a mold, an inert gas is injected to form a hollow inside the thickness of the molded product.

  However, when a throttle body molded product is molded using this molding method, since a hollow is formed inside the molded product, the strength of the molded product is lowered, which is not practical.

  Furthermore, Japanese Patent Laid-Open No. 53-47457 discloses that a molded product shape that requires roundness outside the cylinder is used to fill the mold cavity with molten resin and then invisible from the invisible back surface inside the cylinder. A method has been introduced to improve the roundness accuracy of the visible surface side cylinder by injecting an active gas and pressing the gas to the visible surface side. According to this method, the inert gas is moved to the invisible surface side. Since the injection is performed, the dimensional accuracy on the visible surface side can be easily increased.

However, according to this method, resin shrinkage occurs on the gas injection side of the invisible surface, and significant sink marks are generated. For example, in order to improve the roundness in the bore portion of the throttle body taken up in the present invention, after filling the mold cavity with molten resin and injecting an inert gas outside the bore portion, the inner diameter in the bore portion Although the roundness of the portion is improved, it is difficult to improve the surface accuracy of the flange formed on the end surface of the bore portion.
JP 2006-2675 A JP-A-53-47457

  As described above, when the DBW throttle body in which the cylindrical bore portion and the motor case portion are integrally molded is molded using the conventional injection molding method, the motor case portion side formed around the bore portion is formed. There is a problem that the roundness in the bore part is affected.

  The purpose of this explanation is to fill and hold a resin under the optimum conditions for molding in each molded part in a method of integrally molding a complex molded product such as a DBW throttle body using a cavity having a plurality of molded parts. An object of the present invention is to provide a molding method in which the roundness of a bore inner diameter portion is increased by applying pressure and filling timing, particularly when a DBW throttle body is injection molded.

In order to achieve the above object, according to the first aspect of the present invention, in the injection molding method, in a mold in which a plurality of molding parts are formed in a cavity, a resin filling cylinder is provided for each of the plurality of molding parts. In addition, at the time of product molding, the plurality of cylinders are simultaneously filled with resin from the plurality of cylinders to form the plurality of molding parts integrally.
According to this invention, it is possible to obtain a highly accurate molded product by setting optimum molding conditions for each molded part.
A molding method using a plurality of cylinders includes a two-color molding method, which is a method of molding by moving or rotating a part of a mold. On the other hand, according to the present invention, a resin-filling cylinder is provided for each of a plurality of different molding parts to improve the quality of a molded product. Therefore, a part of the mold is not moved.

Furthermore, in the invention according to claim 2, in the injection molding method according to claim 1, when the resin is filled from the plurality of cylinders, the filling pressure of the resin and / or the filling timing and / or the holding pressure are used. Is performed for each forming part.
According to this invention, it is possible to obtain a highly accurate molded product by setting optimum molding conditions for each molded part.

Furthermore, in the invention according to claim 3, in the injection molding method according to claim 1 or 2, when filling the resin from the plurality of cylinders, the type or color of the resin is changed for each cylinder to form a molded part. Each is characterized by simultaneously molding merged regions of different types or colors of resin.
According to this invention, various molded products can be obtained at low cost.

  Furthermore, in the invention according to claim 4, in the injection molding method according to any one of claims 1 to 3, the plurality of molding parts include a motor that drives a bore molding part and a valve in the bore, and A throttle body molding cavity that integrally molds a gear case, and this cavity comprises a cavity part for bore molding and a cavity part for molding a motor case, and the cylinder comprises the cavity part for bore molding and the cavity for molding a motor case. It is provided for each part.

  Furthermore, in the invention according to claim 5, in the injection molding method according to claim 4, the timing of filling the molten resin into the bore molding cavity is determined by the timing of the molten resin into the motor case molding cavity. It is characterized by being simultaneously with the filling start timing.

  Furthermore, in the invention according to claim 6, in the injection molding method according to claim 4, the start timing of filling the molten resin into the cavity for molding the motor case is the timing of the molten resin into the cavity for bore molding. It is characterized by being immediately after the start of filling.

  Furthermore, in the invention according to claim 7, in the injection molding method according to any one of claims 4 to 6, when filling the molten resin into the bore molding cavity and the motor case molding cavity. The resin pressure and holding pressure of the cylinder that fills the cavity resin for the bore molding and the cylinder that fills the cavity resin for the motor case molding are adjusted so that the molten resin is uniformly filled in each cavity. It is characterized by being adjusted individually.

  Furthermore, in the invention according to claim 8, in the injection molding method according to any one of claims 4 to 7, filling with molten resin through a plurality of gates formed in the cavity for cavity molding. When the holding pressure is applied, the amount of resin passing through each gate or runner is controlled so that the molten resin is uniformly filled and molded.

  Furthermore, in the invention according to claim 9, in the injection molding method according to claim 8, the filling of the molten resin is performed through a plurality of gates formed in the bore molding cavity and the motor case molding cavity. When applying holding pressure, adjust the cross-sectional area of each gate or runner to control the resin pressure and holding pressure for each cavity part so that the molten resin is uniformly filled and molded. It is a feature.

The effects of the present invention are as follows.
1. According to the first to third aspects of the present invention, when molding a product having a complicated molded portion, molding can be performed under optimum conditions for each molded portion, and a highly accurate molded product can be obtained and a part of the molded product can be obtained. You can change the resin or change the color.

  2. According to the invention of claim 4, when molding the bore part and the motor case part in the molding of the DBW throttle body, each molding cavity is provided with a dedicated cylinder. Injection molding can be performed at a lower filling pressure and holding pressure than when each molten resin is filled into each molding part. Accordingly, the molten resin is uniformly filled in each molded part and is uniformly shrunk during solidification, so that the roundness of the bore inner diameter part can be molded with high accuracy.

  3. According to the inventions of claims 5 and 6, since the timing of the molten resin filling start and the holding pressure loading to the bore molding cavity and the motor case molding cavity can be selected at the same time or the delay, the optimum molding conditions Can be set.

  4). According to the seventh to ninth aspects of the present invention, since the resin filling pressure and the holding pressure for the bore molding cavity and the motor case molding cavity can be individually selected, the optimum molding conditions can be set.

  5. According to the inventions described in claims 8 and 9, by selecting the gate diameter of the plurality of gates in the bore molding cavity and the sprue diameter or runner diameter following each gate, the bore molding cavity is uniformly filled with the molten resin. In addition, a highly accurate product can be obtained by applying holding pressure.

  In the injection molding method for the DBW throttle body, etc. of the present invention, the molten resin is uniformly filled and held in each molded part by using a cylinder that can be filled with resin for each molded part and applied with holding pressure. Further, since the solidification is also performed for each molded part, the molded product is uniformly shrunk, so that the roundness of the inner diameter part of the bore can be particularly increased.

  Further, by selecting the molten resin filling pressure, holding pressure, the diameter of the gate, sprue, runner, etc., it is possible to set the optimum molding conditions for each molding part.

  The resin used in the present invention is a thermoplastic resin excellent in resin characteristics (for example, moldability, dimensional stability, heat resistance and chemical resistance) required in the case of a throttle body. For example, polyamide, polyphenylene sulfide, Polyetherimide is desirable. In addition, the type of resin is not limited as long as it is a thermoplastic resin that satisfies the above resin characteristics. Moreover, fillers such as glass filler, glass flakes, glass beads, carbon fiber, talc, and mica may be mixed in the resin. Further, by changing the color of the resin, a multicolor molded product can be simultaneously molded in one cavity.

  Next, an example in which the injection molding method according to the present invention is applied to molding of a throttle body will be described in detail with reference to the drawings.

In the first embodiment, an embodiment corresponding to the invention described in claims 1 to 9 will be described with reference to the drawings.
1 is a perspective view of a DBW throttle body injection-molded in this embodiment, FIG. 2 is a cross-sectional view of an injection mold used in this embodiment, and FIG. 3 is an explanatory view of a cavity shape for molding the DBW throttle body. 4 is a schematic view showing a state in which the DBW throttle body is connected to the runner and the sprue, FIG. 5 is an explanatory view showing a state where the injection mold is closed, and FIG. FIG. 7 is an explanatory diagram in which the molten resin is filled into the cavity and the motor case cavity, FIG. 7 is an explanatory diagram in which the molten resin is filled and the pressure holding step is started, and FIG. 8 is an explanatory diagram in which the injection mold is opened, FIG. 9 is an explanatory view in which the DBW throttle body is released from the mold by the ejector pins.

  The DBW throttle body 100 obtained in the first embodiment will be described with reference to FIG. As the resin, polyphenylene sulfide (PPS) resin was used. In FIG. 1, reference numeral 1 denotes a cylindrical bore that accommodates a throttle valve (not shown) therein, 2 is a flange (not shown) when assembled to a manifold (3), and 3 is a assembly to the manifold. , A bolt mounting boss having a hollow shape for penetrating the mounting bolt, 4 a bearing for incorporating a shaft of a rotating throttle valve, 5 a motor case for housing a motor and a gear, and 6 for one of the motor case 5 A motor storage portion, which is a portion, and 7 is a gear storage portion. The bore 1 has an inner diameter W of 65 mm and a height H from the flange 2 of 60 mm. The capacity of the bore 1 and the motor case 5 is larger in the bore 1.

  The DBW throttle body 100 molded according to the first embodiment incorporates a throttle valve using a bearing 4 in the bore 1 and a motor for driving the throttle valve is assembled in the motor housing 6 of the motor case 5. After the gear that transmits the drive to the throttle valve is assembled in the gear housing 7, the cover 8 is attached to the gear housing 7 and the gear housing 7 is closed in an airtight state.

A mold for molding the DBW throttle body 100 having such a shape will be described with reference to FIG.
The fixed-side mounting plate 7 is provided with two sprue bushes, a sprue bush 8 and a sprue bush 9. A cylinder A is connected to the sprue bush 8 and a cylinder B is connected to the sprue bush 9 as shown in FIG.

  Further, a runner stripper plate 10 and a fixed side template 11 are provided on the front surface of the fixed side mounting plate 7.

  12 is a fixed side insert built in the front of the runner stripper plate 10, 13 is a fixed side cavity forming insert built in the front of the insert 12, 14 is a sprue, 15 is a cross-shaped primary runner, 16 Are four secondary runners and 17 are four gates.

  In FIG. 2, 18 is a movable side mounting plate, 19 is a mounting plate of an eject pin 20 assembled on the front side of the movable side mounting plate 18, 19a is a pressing plate of the eject pin 20, and 21 is a front side of the movable side mounting plate 18. This is a cradle to which the movable side template 22 is assembled.

  Reference numeral 23 denotes a movable-side cavity molding insert assembled on the front side of the movable-side mold plate 22. By facing the fixed-side insert 13, the throttle body molding cavity 24 shown in FIG. 4 is formed. .

  In FIG. 4, reference numeral 25 denotes a bore forming portion of the throttle body forming cavity 24, and 26 denotes a forming portion of the motor housing portion 6. The forming portion 26 of the motor housing portion 6 is connected to the sprue 29, the primary runner from the cylinder B. 30, resin filling is performed via the secondary runner 31 and the gate 27.

  As described above, the fixed side template 11 incorporates the insert 13 that bears a part of the product shape. Further, the sprue bushing 8 is formed from the sprue bush 8 as a molten resin runway to the nest 13 as described above, and further passes from the nest 12 through the nest 13 to the cavity 24 and branches from the sprue 14 to four runners. The primary runner 15 and the secondary runner 16 are formed.

  Similarly, the resin is filled from the sprue bush 9 to the surface of the molded part 26 of the motor case 5 of the cavity 24 through the primary runner 30, the secondary runner 31, and the gate 27, which are molten resin runners, up to the nest 12. The

  The movable side mounting plate 18 is assembled with a movable side template 22 assembled with a nesting 23 that bears a part of the product shape, and a cradle 21 is assembled. Further, a plurality of ejector pins 20 are attached so as to be sandwiched between the ejector plate 19 and the presser plate 19 a of the ejector pin 20. The front end penetrates the receiving table 21 and the movable side mold plate 22 and reaches the surface of the cavity 24.

  By closing the fixed side mold plate 11 and the movable side mold plate 22, the cavity 24 has the product shape shown in FIG.

  FIG. 4 shows a schematic view of the DBW throttle body forming cavity 24, the sprue 14 (29), the primary runner 15 (30), the secondary runner 16 (31), and the gate 17 (27). Four gates 17 are provided on the bore forming portion 25 side, and resin is supplied from the cylinder A to the gates 17 via the sprue 14, the first runner 15, and the second runner 16. In addition, two gates 27 are provided on one motor case molding portion 26 side, and resin is supplied from the cylinder B to the gates 27 via a sprue 29, a primary runner 30, and a secondary runner 31. Thus, since the cylinder A dedicated for bore molding and the cylinder B dedicated for motor case molding are independent, the resin can be filled from the respective cylinders A and B at an arbitrary filling pressure, holding pressure and timing. .

  Next, an injection molding method of the DBW throttle body 100 using the cylinders A and B described in the first embodiment will be described with reference to FIGS.

  In advance, the final filling positions of the bore molding part 25 and the motor case molding part 26 were set at points E and F, and the injection speeds of the cylinders A and B were adjusted so that the molten resin reached at the same time.

An injection molding process performed so that the final filling position is at points E and F will be described.
As shown in FIG. 5, the movable side mounting plate 18 is advanced to close the fixed side template 11 and the movable side template 22. At this time, in the cylinder A and the cylinder B, after the resin is weighed, the resin is melted by heating with a heater and kneading with a screw and is waiting.

  Next, as shown in FIG. 6, filling of the molten resin into the cavity 24 is started at the same time in both the cylinder A and the cylinder B. The filling pressure at this time is 80 MPa for cylinder A and 70 MPa for cylinder B. The setting of the filling pressure is based on the capacity of each molding part.

  Finally, as shown in FIG. 7, the molten resin is simultaneously filled in the cavity of the bore molding portion 25 and the cavity of the motor case molding portion 26 to complete the filling. Thus, by determining the molding conditions of the cylinder A and the cylinder B, the bore molding part 25 side and the motor case molding part 26 side are individually filled with resin, and the bore molding part 25 and the motor case molding part 26 are joined. Since the resin merges at the portion, the occurrence of turbulent flow due to the merge of the resin is suppressed particularly in the bore forming portion 25, and the molten resin can be uniformly filled in the respective cavities.

  In the pressure holding process, the holding pressure of the cylinder A is set to 93 Mpa and the holding pressure of the cylinder B is set to 48 Mpa in proportion to the capacity, and the resin pressure is set for a set time. After the cooling process, the movable side mounting plate 17 is moved. It was made to move backward and away from the fixed side mounting plate 7 side (FIG. 8). As a result, the stationary side template 7 and the runner stripper plate 10 were separated from each other, and the primary runner 15 (30) and the secondary runner 16 (31) were peeled off from the DBW throttle body 100 and separated.

  Thereafter, as shown in FIG. 9, when the eject plate 19 and the presser foot 19a of the eject pin 20 move forward, the eject pin 20 moves through the guide holes of the receiving base 21 and the movable side mold plate 22, and the DBW throttle body 100 is moved. Extrude and release. Through this molding process, the injection molding was completed, and the DBW throttle body 100 shown in FIG. 1 could be obtained.

  As a result, when the roundness (longest inner diameter−shortest inner diameter) of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured using a cylinder gauge (model: CG-100A manufactured by Mitutoyo Corporation), it was as good as 105 μm. It was a measured value.

  The second embodiment has the same shape as the DBW throttle body 100 molded in the first embodiment, but the bore 1 has an inner diameter W of 35 mm and a height H from the flange 2 of 45 mm. 100 molding methods.

  The volume of the bore 1 portion and the volume of the motor case 5 portion are substantially the same. For this reason, both the filling pressure and the holding pressure of the cylinders A and B were set to 48 Mpa.

  As a result, it was possible to obtain the DBW throttle body 100 having the same roundness as in Example 1.

  In the first embodiment described above, filling of the molten resin into the cavity 24 is started at the same time in both the cylinder A and the cylinder B. However, in this third embodiment, the timing of filling the molten resin into the motor case molding cavity 26 is determined by bore molding. After the start of filling of the molten resin into the cavity 25 for use, it was performed at a timing to delay the time (claim 6).

  When the cavity capacity of the bore molding cavity 25 is larger than that of the motor case molding cavity 26, a time difference until reaching the final filling position is generated, which causes turbulence.

  First, the fixed side mold plate 11 and the movable side mold plate 22 are closed as shown in FIG. At this time, in the cylinder A and the cylinder B, after the resin is weighed, the resin is melted by heating with a heater and kneading with a screw and is waiting.

  Next, as shown in FIG. 11, filling of the molten resin into the bore forming cavity 25 from the cylinder A is started.

  Thereafter, as shown in FIG. 12, the injection from the cylinder B is started 0.7 seconds after the start of the injection from the cylinder A. The delay time can be set by performing a flow analysis by CAE in advance.

  Finally, as shown in FIG. 13, the bore molding cavity 25 and the motor case molding cavity 26 are simultaneously filled with molten resin, and the filling is completed. Since the molding conditions of cylinder A and cylinder B can be determined according to each cavity, the molten resin is uniformly filled into each molded part without turbulent flow between the bore molding resin and the motor case molding resin. I was able to.

  After passing through the pressure holding and cooling steps, the movable side mounting plate 17 was moved backward from the fixed side mounting plate 7. When the stationary side template 11 and the runner stripper plate 10 are separated from each other, the primary runner 15 (30) and the secondary runner 16 (31) are both separated from the DBT throttle body 100 (FIG. 14).

  Thereafter, as shown in FIG. 15, the eject plate 19 and the retainer plate 19a of the eject pin 20 move forward, so that the eject pin 20 moves through the guide holes of the cradle 21 and the movable side mold plate 22, and the DBW throttle body 100 is moved. The DBW throttle body 100 can be obtained after the injection molding is completed.

  As a result, when the roundness of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured, it was a good measured value of 76 μm.

In the fourth embodiment, an embodiment corresponding to the invention described in claims 8 and 9 will be described with reference to the drawings.
The DBW throttle body 100 in which the bore 1 and the motor case 5 are integrated has a portion where the bore forming cavity 25 and the motor case forming cavity 26 are connected. If the molten resin first reaches the connecting portion, it may flow into another cavity, and a situation may occur where the amount of resin is insufficient.

  For example, in FIG. 4, the portion C is the thickest portion among the locations where the bore forming cavity 25 and the motor case forming cavity 26 are connected. Therefore, in the secondary runner 16 closest to the part C in FIG. 4, the cross-sectional area in the vicinity of the gate 17 is made 1.0 mm thicker than the diameter of the other secondary runners 16. The value for making the diameter of the nearest secondary runner 16 larger than that of the other secondary runners 16 can be set in advance by performing flow analysis by CAE. Naturally, the diameter of the gate 17 is larger than that of the other gates 17.

  As a result, when the roundness of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured, it was a good measured value of 70 μm. In each of the above embodiments, the resins in the cylinders A and B are the same. However, by changing the resin in the cylinders A and B or changing the color, different parts or colors in one molded product can be obtained. It is also possible to make the product different (claim 3).

Comparative Example 1

In this comparative example, the sprue 14 and sprue 29 in FIG. 4 were connected, and the molten resin was injected only from the sprue 14. That is, only A was used as the cylinder.
Other primary runners, secondary runners, and gates are the same as those in the second embodiment.

  As a result, when the roundness of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured, it was 187 μm, which was considerably inferior as shown in Table 1 when compared with the measured values of Examples 1 to 4. Value.

External view of throttle body Explanatory drawing of the mold and injection device for throttle body molding concerning the present invention Side view of throttle body Explanatory drawing of throttle body molding cavity and runner and sprue following this cavity Explanatory drawing of the state using a mold Explanatory drawing of the state of filling halfway with resin Explanatory drawing of the state where resin filling is completed Explanatory drawing of mold open Explanatory drawing of the state where the product is released Explanatory drawing of Example 2. Explanatory drawing of Example 2. Explanatory drawing of Example 2. Explanatory drawing of Example 2. Explanatory drawing of Example 2. Explanatory drawing of Example 2.

Explanation of symbols

100 DBW Throttle body 1 Bore 5 Motor case 11 Fixed side template 13 Fixed side inserts 14 and 29 Sprue 15 and 30 Primary runners 16 and 31 Secondary runners 17 and 27 Gate 22 Movable side plate 23 Movable side insert 24 Cavity 25 Bore molding part 26 Motor case molding part A Bore side cylinder B Motor case side cylinder

  The present invention relates to a molded article such as a so-called throttle body, which forms a part of an intake passage of an internal combustion engine (engine) such as an automobile, and has a bore and a motor case for controlling the intake air amount. The present invention relates to a molding method for injection molding using a resin.

  2. Description of the Related Art Conventionally, an internal combustion engine (engine) such as an automobile has an intake passage for taking combustion air into the engine, and a throttle body for controlling the amount of intake air is attached to the intake passage. ing. One type of throttle body is a drive-by-wire type throttle body (hereinafter referred to as “DBW throttle body”). In the configuration, a bore portion in which a throttle valve for adjusting the amount of intake air is incorporated, and a motor case portion for housing a motor and gear for rotating the throttle valve are integrated.

  Conventionally, this DBW throttle body requires a high drive control accuracy during operation, and therefore has been made by cutting a metal such as aluminum.

  However, in recent years, automobile parts have been reduced in weight due to environmental problems and economic reasons such as low fuel consumption, and the DBW throttle body has also been made into a resin that is manufactured using an injection molding method. It came to be able to.

  In general injection molding, a molded product is obtained by filling a molten resin into a mold cavity and then increasing the resin pressure to apply a holding pressure and cooling and solidifying the molten resin. Is solidified under the influence of various factors such as mold cavity shape, mold structure, molding conditions (especially filling pressure and holding pressure), mold temperature, etc. It is difficult to make them completely the same. Due to this non-uniform shrinkage rate, deformation such as sink marks and warpage appears in the injection molded product.

  In particular, in the case of a throttle body, a high dimensional accuracy (roundness) is required because a throttle valve for controlling the flow rate of air is attached to the bore inner diameter. For this reason, it is necessary to uniformly fill the molten resin in the mold cavity during the molding process.

  Furthermore, since the DBW throttle body also integrally forms a motor case that houses the motor that drives the throttle valve, the resin flow that forms the bore and the resin flow that forms the motor case when the resin is filled are affected. It is an obstacle to increase the roundness of the bore.

  As described above, when the DBW throttle body is injection-molded, it is very difficult to increase the dimensional accuracy of the roundness of the target bore inner diameter portion for the reason described above. Furthermore, considering the heat-resistant temperature and chemical resistance of the resin in consideration of the DBW throttle body usage environment, the resin to be molded contains a high content of fillers such as glass fibers and glass flakes, which prevents resin shrinkage. In addition to being uniform, it is also affected by the orientation of the filler, resulting in an increasingly complicated deformation process, and it is difficult to increase the dimensional accuracy of the molded product, not limited to the molding of the DBW throttle body.

  Various inventions have been filed so far regarding methods for injection molding of resin throttle bodies. For example, an invention related to the structure of a molding die, an invention related to a molding method using insert molding, or an invention related to the type and components of a resin to be molded can be cited. Resin pressure is increased by mold insert operation to hold pressure, and deformation of the molded product due to uneven resin shrinkage is inevitable.

  Thus, as a method for reducing non-uniformity of resin shrinkage, Japanese Patent Application Laid-Open No. 2006-2675 introduces a temperature control circuit for making the surface temperature of a mold cavity for insert injection molding uniform. By this method, the resin filled in the mold cavity shrinks by obtaining a uniform temperature profile as a whole, and as a result, deformation of the molded product can be reduced.

  However, the shrinkage of the resin is greatly influenced not only by the temperature, but also by the resin pressure during the filling process and the pressure holding process. Can not. Further, when this method is adopted, there is a problem that the mold structure becomes complicated and the manufacturing cost of the mold becomes high.

  On the other hand, a molding method using an inert gas has been proposed as a technique for reducing deformation such as sink marks and warpage of a molded product in injection molding. This is a method in which after a molten resin is filled in a mold, an inert gas is injected to form a hollow inside the thickness of the molded product.

  However, when a throttle body molded product is molded using this molding method, since a hollow is formed inside the molded product, the strength of the molded product is lowered, which is not practical.

  Furthermore, Japanese Patent Laid-Open No. 53-47457 discloses that a molded product shape that requires roundness outside the cylinder is used to fill the mold cavity with molten resin and then invisible from the invisible back surface inside the cylinder. A method has been introduced to improve the roundness accuracy of the visible surface side cylinder by injecting an active gas and pressing the gas to the visible surface side. According to this method, the inert gas is moved to the invisible surface side. Since the injection is performed, the dimensional accuracy on the visible surface side can be easily increased.

However, according to this method, resin shrinkage occurs on the gas injection side of the invisible surface, and significant sink marks are generated. For example, in order to improve the roundness in the bore portion of the throttle body taken up in the present invention, after filling the mold cavity with molten resin and injecting an inert gas outside the bore portion, the inner diameter in the bore portion Although the roundness of the portion is improved, it is difficult to improve the surface accuracy of the flange formed on the end surface of the bore portion.
JP 2006-2675 A JP-A-53-47457

  As described above, when the DBW throttle body in which the cylindrical bore portion and the motor case portion are integrally molded is molded using the conventional injection molding method, the motor case portion side formed around the bore portion is formed. There is a problem that the roundness in the bore part is affected.

  The purpose of this explanation is to fill and hold a resin under the optimum conditions for molding in each molded part in a method of integrally molding a complex molded product such as a DBW throttle body using a cavity having a plurality of molded parts. An object of the present invention is to provide a molding method in which the roundness of a bore inner diameter portion is increased by applying pressure and filling timing, particularly when a DBW throttle body is injection molded.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a throttle body injection molding method comprising: a. A cylindrical bore forming part for assembling a throttle valve therein, a throttle valve driving motor case forming part formed on the side of the bore forming part, and a driving force from the throttle valve driving motor to the throttle valve In a mold formed by forming a throttle body molding cavity composed of a gear case molding portion containing a gear group for transmitting
b. Provided with a cylinder for filling the bore molding part and the throttle valve drive motor case molding part, respectively,
c. When the resin is filled into the cavities from the two cylinders, the resin filling pressure and the filling start timing and / or the holding pressure are controlled so that the flow heads of the filled resins are merged in the gear case molding portion. Is.

According to a second aspect of the present invention, in the throttle body injection molding method according to the first aspect, the resin filling pressure and filling start timing and / or holding pressure control performed by the two cylinders are controlled. This is characterized in that it is performed by a throttle provided in a runner part or a gate part from the cylinder to the cavity.

The effects of the present invention are as follows.
According to the present invention, when molding a product having a complicated molded part, molding is performed under optimum conditions for each molded part, a highly accurate molded product can be obtained and the resin can be changed for each part of the molded product, You can change the color.

Also , when molding the bore part and motor case part in the molding of the DBW throttle body, each molding cavity is equipped with a dedicated cylinder, so it has conventionally been filled with molten resin from one cylinder to each molding part. Injection molding can be performed at a lower filling pressure and holding pressure than when performing the above. Accordingly, the molten resin is uniformly filled in each molded part and is uniformly shrunk during solidification, so that the roundness of the bore inner diameter part can be molded with high accuracy.

In addition , since the timing of the start of filling the molten resin into the bore molding cavity and the motor case molding cavity and the timing of loading with holding pressure can be selected at the same time or delay, the optimum molding conditions can be set.

Further , since the resin filling pressure and the holding pressure in the bore molding cavity and the motor case molding cavity can be individually selected, the optimum molding conditions can be set.

In addition , by selecting the gate diameter of multiple gates in the bore molding cavity and the sprue diameter or runner diameter following each gate, the molten resin is uniformly filled into the bore molding cavity, and holding pressure is applied to achieve high precision. You can get a product.

  In the injection molding method for the DBW throttle body, etc. of the present invention, the molten resin is uniformly filled and held in each molded part by using a cylinder that can be filled with resin for each molded part and applied with holding pressure. Further, since the solidification is also performed for each molded part, the molded product is uniformly shrunk, so that the roundness of the inner diameter part of the bore can be particularly increased.

  Further, by selecting the molten resin filling pressure, holding pressure, the diameter of the gate, sprue, runner, etc., it is possible to set the optimum molding conditions for each molding part.

  The resin used in the present invention is a thermoplastic resin excellent in resin characteristics (for example, moldability, dimensional stability, heat resistance and chemical resistance) required in the case of a throttle body. For example, polyamide, polyphenylene sulfide, Polyetherimide is desirable. In addition, the type of resin is not limited as long as it is a thermoplastic resin that satisfies the above resin characteristics. Moreover, fillers such as glass filler, glass flakes, glass beads, carbon fiber, talc, and mica may be mixed in the resin. Further, by changing the color of the resin, a multicolor molded product can be simultaneously molded in one cavity.

  Next, an example in which the injection molding method according to the present invention is applied to molding of a throttle body will be described in detail with reference to the drawings.

In the first embodiment, an embodiment corresponding to the invention described in claims 1 to 9 will be described with reference to the drawings.
1 is a perspective view of a DBW throttle body injection-molded in this embodiment, FIG. 2 is a cross-sectional view of an injection mold used in this embodiment, and FIG. 3 is an explanatory view of a cavity shape for molding the DBW throttle body. 4 is a schematic view showing a state in which the DBW throttle body is connected to the runner and the sprue, FIG. 5 is an explanatory view showing a state where the injection mold is closed, and FIG. FIG. 7 is an explanatory diagram in which the molten resin is filled into the cavity and the motor case cavity, FIG. 7 is an explanatory diagram in which the molten resin is filled and the pressure holding step is started, and FIG. 8 is an explanatory diagram in which the injection mold is opened, FIG. 9 is an explanatory view in which the DBW throttle body is released from the mold by the ejector pins.

  The DBW throttle body 100 obtained in the first embodiment will be described with reference to FIG. As the resin, polyphenylene sulfide (PPS) resin was used. In FIG. 1, reference numeral 1 denotes a cylindrical bore that accommodates a throttle valve (not shown) therein, 2 is a flange (not shown) when assembled to a manifold (3), and 3 is a assembly to the manifold. , A bolt mounting boss having a hollow shape for penetrating the mounting bolt, 4 a bearing for incorporating a shaft of a rotating throttle valve, 5 a motor case for housing a motor and a gear, and 6 for one of the motor case 5 A motor storage portion, which is a portion, and 7 is a gear storage portion. The bore 1 has an inner diameter W of 65 mm and a height H from the flange 2 of 60 mm. The capacity of the bore 1 and the motor case 5 is larger in the bore 1.

  The DBW throttle body 100 molded according to the first embodiment incorporates a throttle valve using a bearing 4 in the bore 1 and a motor for driving the throttle valve is assembled in the motor housing 6 of the motor case 5. After the gear that transmits the drive to the throttle valve is assembled in the gear housing 7, the cover 8 is attached to the gear housing 7 and the gear housing 7 is closed in an airtight state.

A mold for molding the DBW throttle body 100 having such a shape will be described with reference to FIG.
The fixed-side mounting plate 7 is provided with two sprue bushes, a sprue bush 8 and a sprue bush 9. A cylinder A is connected to the sprue bush 8 and a cylinder B is connected to the sprue bush 9 as shown in FIG.

  Further, a runner stripper plate 10 and a fixed side template 11 are provided on the front surface of the fixed side mounting plate 7.

  12 is a fixed side insert built in the front of the runner stripper plate 10, 13 is a fixed side cavity forming insert built in the front of the insert 12, 14 is a sprue, 15 is a cross-shaped primary runner, 16 Are four secondary runners and 17 are four gates.

  In FIG. 2, 18 is a movable side mounting plate, 19 is a mounting plate of an eject pin 20 assembled on the front side of the movable side mounting plate 18, 19a is a pressing plate of the eject pin 20, and 21 is a front side of the movable side mounting plate 18. This is a cradle to which the movable side template 22 is assembled.

  Reference numeral 23 denotes a movable-side cavity molding insert assembled on the front side of the movable-side mold plate 22. By facing the fixed-side insert 13, the throttle body molding cavity 24 shown in FIG. 4 is formed. .

  In FIG. 4, reference numeral 25 denotes a bore forming portion of the throttle body forming cavity 24, and 26 denotes a forming portion of the motor housing portion 6. The forming portion 26 of the motor housing portion 6 is connected to the sprue 29, the primary runner from the cylinder B. 30, resin filling is performed via the secondary runner 31 and the gate 27.

  As described above, the fixed side template 11 incorporates the insert 13 that bears a part of the product shape. Further, the sprue bushing 8 is formed from the sprue bush 8 as a molten resin runway to the nest 13 as described above, and further passes from the nest 12 through the nest 13 to the cavity 24 and branches from the sprue 14 to four runners. The primary runner 15 and the secondary runner 16 are formed.

  Similarly, the resin is filled from the sprue bush 9 to the surface of the molded part 26 of the motor case 5 of the cavity 24 through the primary runner 30, the secondary runner 31, and the gate 27, which are molten resin runners, up to the nest 12. The

  The movable side mounting plate 18 is assembled with a movable side template 22 assembled with a nesting 23 that bears a part of the product shape, and a cradle 21 is assembled. Further, a plurality of ejector pins 20 are attached so as to be sandwiched between the ejector plate 19 and the presser plate 19 a of the ejector pin 20. The front end penetrates the receiving table 21 and the movable side mold plate 22 and reaches the surface of the cavity 24.

  By closing the fixed side mold plate 11 and the movable side mold plate 22, the cavity 24 has the product shape shown in FIG.

  FIG. 4 shows a schematic view of the DBW throttle body forming cavity 24, the sprue 14 (29), the primary runner 15 (30), the secondary runner 16 (31), and the gate 17 (27). Four gates 17 are provided on the bore forming portion 25 side, and resin is supplied from the cylinder A to the gates 17 via the sprue 14, the first runner 15, and the second runner 16. In addition, two gates 27 are provided on one motor case molding portion 26 side, and resin is supplied from the cylinder B to the gates 27 via a sprue 29, a primary runner 30, and a secondary runner 31. Thus, since the cylinder A dedicated for bore molding and the cylinder B dedicated for motor case molding are independent, the resin can be filled from the respective cylinders A and B at an arbitrary filling pressure, holding pressure and timing. .

  Next, an injection molding method of the DBW throttle body 100 using the cylinders A and B described in the first embodiment will be described with reference to FIGS.

  In advance, the final filling positions of the bore molding part 25 and the motor case molding part 26 were set at points E and F, and the injection speeds of the cylinders A and B were adjusted so that the molten resin reached at the same time.

An injection molding process performed so that the final filling position is at points E and F will be described.
As shown in FIG. 5, the movable side mounting plate 18 is advanced to close the fixed side template 11 and the movable side template 22. At this time, in the cylinder A and the cylinder B, after the resin is weighed, the resin is melted by heating with a heater and kneading with a screw and is waiting.

  Next, as shown in FIG. 6, filling of the molten resin into the cavity 24 is started at the same time in both the cylinder A and the cylinder B. The filling pressure at this time is 80 MPa for cylinder A and 70 MPa for cylinder B. The setting of the filling pressure is based on the capacity of each molding part.

  Finally, as shown in FIG. 7, the molten resin is simultaneously filled in the cavity of the bore molding portion 25 and the cavity of the motor case molding portion 26 to complete the filling. Thus, by determining the molding conditions of the cylinder A and the cylinder B, the bore molding part 25 side and the motor case molding part 26 side are individually filled with resin, and the bore molding part 25 and the motor case molding part 26 are joined. Since the resin merges at the portion, the occurrence of turbulent flow due to the merge of the resin is suppressed particularly in the bore forming portion 25, and the molten resin can be uniformly filled in the respective cavities.

  In the pressure holding process, the holding pressure of the cylinder A is set to 93 Mpa and the holding pressure of the cylinder B is set to 48 Mpa in proportion to the capacity, the resin pressure is set for a set time, and after the cooling process, the movable side mounting plate 17 is moved. It was made to move backward and away from the fixed side mounting plate 7 side (FIG. 8). As a result, the stationary side template 7 and the runner stripper plate 10 were separated from each other, and the primary runner 15 (30) and the secondary runner 16 (31) were peeled off from the DBW throttle body 100 and separated.

  Thereafter, as shown in FIG. 9, when the eject plate 19 and the presser foot 19a of the eject pin 20 move forward, the eject pin 20 moves through the guide holes of the receiving base 21 and the movable side mold plate 22, and the DBW throttle body 100 is moved. Extrude and release. Through this molding process, the injection molding was completed, and the DBW throttle body 100 shown in FIG. 1 could be obtained.

  As a result, when the roundness (longest inner diameter−shortest inner diameter) of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured using a cylinder gauge (model: CG-100A manufactured by Mitutoyo Corporation), it was as good as 105 μm. It was a measured value.

  The second embodiment has the same shape as the DBW throttle body 100 molded in the first embodiment, but the bore 1 has an inner diameter W of 35 mm and a height H from the flange 2 of 45 mm. 100 molding methods.

  The volume of the bore 1 portion and the volume of the motor case 5 portion are substantially the same. For this reason, both the filling pressure and the holding pressure of the cylinders A and B were set to 48 Mpa.

  As a result, it was possible to obtain the DBW throttle body 100 having the same roundness as in Example 1.

  In the first embodiment, filling of the molten resin into the cavity 24 is started at the same time in both the cylinder A and the cylinder B. However, in this third embodiment, the timing of filling the molten resin into the motor case molding cavity 26 is determined by bore molding. After the start of filling of the molten resin into the cavity 25 for use, it was performed at a timing that was delayed.

  When the cavity capacity of the bore molding cavity 25 is larger than that of the motor case molding cavity 26, a time difference until reaching the final filling position is generated, which causes turbulence.

  First, the fixed side mold plate 11 and the movable side mold plate 22 are closed as shown in FIG. At this time, in the cylinder A and the cylinder B, after the resin is weighed, the resin is melted by heating with a heater and kneading with a screw and is waiting.

  Next, as shown in FIG. 11, filling of the molten resin into the bore forming cavity 25 from the cylinder A is started.

  Thereafter, as shown in FIG. 12, the injection from the cylinder B is started 0.7 seconds after the start of the injection from the cylinder A. The delay time can be set by performing a flow analysis by CAE in advance.

  Finally, as shown in FIG. 13, the bore molding cavity 25 and the motor case molding cavity 26 are simultaneously filled with molten resin, and the filling is completed. Since the molding conditions of cylinder A and cylinder B can be determined according to each cavity, the molten resin is uniformly filled into each molded part without turbulent flow between the bore molding resin and the motor case molding resin. I was able to.

  After passing through the pressure holding and cooling steps, the movable side mounting plate 17 was moved backward from the fixed side mounting plate 7. When the stationary side template 11 and the runner stripper plate 10 are separated from each other, the primary runner 15 (30) and the secondary runner 16 (31) are both separated from the DBT throttle body 100 (FIG. 14).

  Thereafter, as shown in FIG. 15, the eject plate 19 and the retainer plate 19a of the eject pin 20 move forward, so that the eject pin 20 moves through the guide holes of the cradle 21 and the movable side mold plate 22, and the DBW throttle body 100 is moved. The DBW throttle body 100 can be obtained after the injection molding is completed.

  As a result, when the roundness of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured, it was a good measured value of 76 μm.

In the DBW throttle body 100 in which the bore 1 and the motor case 5 of Example 4 are integrated, there are places where the bore molding cavity 25 and the motor case molding cavity 26 are connected. If the molten resin first reaches the connecting portion, it may flow into another cavity, and a situation may occur where the amount of resin is insufficient.

  For example, in FIG. 4, the portion C is the thickest portion among the locations where the bore forming cavity 25 and the motor case forming cavity 26 are connected. Therefore, in the secondary runner 16 closest to the part C in FIG. 4, the cross-sectional area in the vicinity of the gate 17 is made 1.0 mm thicker than the diameter of the other secondary runners 16. The value for making the diameter of the nearest secondary runner 16 larger than that of the other secondary runners 16 can be set in advance by performing flow analysis by CAE. Naturally, the diameter of the gate 17 is larger than that of the other gates 17.

  As a result, when the roundness of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured, it was a good measured value of 70 μm. In each of the above embodiments, the resins in the cylinders A and B are the same. However, by changing the resin in the cylinders A and B or changing the color, different parts or colors in one molded product can be obtained. It is possible to make different products.

Comparative Example 1

In this comparative example, the sprue 14 and sprue 29 in FIG. 4 were connected, and the molten resin was injected only from the sprue 14. That is, only A was used as the cylinder.
Other primary runners, secondary runners, and gates are the same as those in the second embodiment.

  As a result, when the roundness of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured, it was 187 μm, which was considerably inferior as shown in Table 1 when compared with the measured values of Examples 1 to 4. Value.

Fig. 1 Appearance explanatory view of throttle body Fig. 2 Explanatory drawing of throttle body molding die and injection device according to the present invention Fig. 3 Side view of throttle body Fig. 4 Explanation of throttle body molding cavity and runner and sprue following this cavity Fig. 5 An explanatory diagram of a state using a mold. Fig. 6 An explanatory diagram of an intermediate state in which resin is filled. Fig. 7 An explanatory diagram of a state in which resin filling is completed. Fig. 8 An explanatory diagram of a state in which a mold is opened. 9 Explanatory drawing of the state where the product is released FIG. 10-15 Explanatory drawing of Example 2

100 DBW Throttle body 1 Bore 5 Motor case 11 Fixed side template 13 Fixed side inserts 14 and 29 Sprue 15 and 30 Primary runners 16 and 31 Secondary runners 17 and 27 Gate 22 Movable side plate 23 Movable side insert 24 Cavity 25 Bore molding part 26 Motor case molding part A Bore side cylinder B Motor case side cylinder

  The present invention relates to a molded article such as a so-called throttle body, which forms a part of an intake passage of an internal combustion engine (engine) such as an automobile, and has a bore and a motor case for controlling the intake air amount. The present invention relates to a molding method for injection molding using a resin.

  2. Description of the Related Art Conventionally, an internal combustion engine (engine) such as an automobile has an intake passage for taking combustion air into the engine, and a throttle body for controlling the amount of intake air is attached to the intake passage. ing. One type of throttle body is a drive-by-wire type throttle body (hereinafter referred to as “DBW throttle body”). In the configuration, a bore portion in which a throttle valve for adjusting the amount of intake air is incorporated, and a motor case portion for housing a motor and gear for rotating the throttle valve are integrated.

  Conventionally, this DBW throttle body requires a high drive control accuracy during operation, and therefore has been made by cutting a metal such as aluminum.

  However, in recent years, automobile parts have been reduced in weight due to environmental problems and economic reasons such as low fuel consumption, and the DBW throttle body has also been made into a resin that is manufactured using an injection molding method. It came to be able to.

  In general injection molding, a molded product is obtained by filling a molten resin into a mold cavity and then increasing the resin pressure to apply a holding pressure and cooling and solidifying the molten resin. Is solidified under the influence of various factors such as mold cavity shape, mold structure, molding conditions (especially filling pressure and holding pressure), mold temperature, etc. It is difficult to make them completely the same. Due to this non-uniform shrinkage rate, deformation such as sink marks and warpage appears in the injection molded product.

  In particular, in the case of a throttle body, a high dimensional accuracy (roundness) is required because a throttle valve for controlling the flow rate of air is attached to the bore inner diameter. For this reason, it is necessary to uniformly fill the molten resin in the mold cavity during the molding process.

  Furthermore, since the DBW throttle body also integrally forms a motor case that houses the motor that drives the throttle valve, the resin flow that forms the bore and the resin flow that forms the motor case when the resin is filled are affected. It is an obstacle to increase the roundness of the bore.

  As described above, when the DBW throttle body is injection-molded, it is very difficult to increase the dimensional accuracy of the roundness of the target bore inner diameter portion for the reason described above. Furthermore, considering the heat-resistant temperature and chemical resistance of the resin in consideration of the DBW throttle body usage environment, the resin to be molded contains a high content of fillers such as glass fibers and glass flakes, which prevents resin shrinkage. In addition to being uniform, it is also affected by the orientation of the filler, resulting in an increasingly complicated deformation process, and it is difficult to increase the dimensional accuracy of the molded product, not limited to the molding of the DBW throttle body.

  Various inventions have been filed so far regarding methods for injection molding of resin throttle bodies. For example, an invention related to the structure of a molding die, an invention related to a molding method using insert molding, or an invention related to the type and components of a resin to be molded can be cited. Resin pressure is increased by mold insert operation to hold pressure, and deformation of the molded product due to uneven resin shrinkage is inevitable.

  Thus, as a method for reducing non-uniformity of resin shrinkage, Japanese Patent Application Laid-Open No. 2006-2675 introduces a temperature control circuit for making the surface temperature of a mold cavity for insert injection molding uniform. By this method, the resin filled in the mold cavity shrinks by obtaining a uniform temperature profile as a whole, and as a result, deformation of the molded product can be reduced.

  However, the shrinkage of the resin is greatly influenced not only by the temperature, but also by the resin pressure during the filling process and the pressure holding process. Can not. Further, when this method is adopted, there is a problem that the mold structure becomes complicated and the manufacturing cost of the mold becomes high.

  On the other hand, a molding method using an inert gas has been proposed as a technique for reducing deformation such as sink marks and warpage of a molded product in injection molding. This is a method in which after a molten resin is filled in a mold, an inert gas is injected to form a hollow inside the thickness of the molded product.

  However, when a throttle body molded product is molded using this molding method, since a hollow is formed inside the molded product, the strength of the molded product is lowered, which is not practical.

  Furthermore, Japanese Patent Laid-Open No. 53-47457 discloses that a molded product shape that requires roundness outside the cylinder is used to fill the mold cavity with molten resin and then invisible from the invisible back surface inside the cylinder. A method has been introduced to improve the roundness accuracy of the visible surface side cylinder by injecting an active gas and pressing the gas to the visible surface side. According to this method, the inert gas is moved to the invisible surface side. Since the injection is performed, the dimensional accuracy on the visible surface side can be easily increased.

However, according to this method, resin shrinkage occurs on the gas injection side of the invisible surface, and significant sink marks are generated. For example, in order to improve the roundness in the bore portion of the throttle body taken up in the present invention, after filling the mold cavity with molten resin and injecting an inert gas outside the bore portion, the inner diameter in the bore portion Although the roundness of the portion is improved, it is difficult to improve the surface accuracy of the flange formed on the end surface of the bore portion.
JP 2006-2675 A JP-A-53-47457

  As described above, when the DBW throttle body in which the cylindrical bore portion and the motor case portion are integrally molded is molded using the conventional injection molding method, the motor case portion side formed around the bore portion is formed. There is a problem that the roundness in the bore part is affected.

  The purpose of this explanation is to fill and hold a resin under the optimum conditions for molding in each molded part in a method of integrally molding a complex molded product such as a DBW throttle body using a cavity having a plurality of molded parts. An object of the present invention is to provide a molding method in which the roundness of a bore inner diameter portion is increased by applying pressure and filling timing, particularly when a DBW throttle body is injection molded.

In order to achieve the above object, according to the first aspect of the present invention, in the injection molding method for a throttle body, a. A cylindrical bore forming part for assembling a throttle valve therein, a throttle valve driving motor case forming part formed on the side of the bore forming part, and a driving force from the throttle valve driving motor to the throttle valve In a mold formed by forming a throttle body molding cavity composed of a gear case molding portion containing a gear group for transmitting
b. Provided with a cylinder for filling the bore molding part and the throttle valve drive motor case molding part, respectively,
c. When the resin is filled into the cavities from the two cylinders, the filling pressure of the resin and the filling start timing are controlled so that the flow heads of the filled resin merge at the gear case molding portion.

The effects of the present invention are as follows.
According to the present invention, when molding a product having a complicated molded part, molding is performed under optimum conditions for each molded part, a highly accurate molded product can be obtained and the resin can be changed for each part of the molded product, You can change the color.

  Also, when molding the bore part and motor case part in the molding of the DBW throttle body, each molding cavity is equipped with a dedicated cylinder, so it has conventionally been filled with molten resin from one cylinder to each molding part. Injection molding can be performed at a lower filling pressure and holding pressure than when performing the above. Accordingly, the molten resin is uniformly filled in each molded part and is uniformly shrunk during solidification, so that the roundness of the bore inner diameter part can be molded with high accuracy.

  In addition, since the timing for starting the filling of the molten resin into the bore molding cavity and the motor case molding cavity can be selected either simultaneously or delayed, it is possible to set optimum molding conditions.

  In addition, since the resin filling pressure into the bore molding cavity and the motor case molding cavity can be individually selected, optimum molding conditions can be set.

  In the injection molding method for the DBW throttle body, etc. of the present invention, the molten resin is uniformly filled and held in each molded part by using a cylinder that can be filled with resin for each molded part and applied with holding pressure. Further, since the solidification is also performed for each molded part, the molded product is uniformly shrunk, so that the roundness of the inner diameter part of the bore can be particularly increased.

  Furthermore, the optimal molding conditions can be set for each molded part by selecting the filling pressure and holding pressure of the molten resin.

  The resin used in the present invention is a thermoplastic resin excellent in resin characteristics (for example, moldability, dimensional stability, heat resistance and chemical resistance) required in the case of a throttle body. For example, polyamide, polyphenylene sulfide, Polyetherimide is desirable. In addition, the type of resin is not limited as long as it is a thermoplastic resin that satisfies the above resin characteristics. Moreover, fillers such as glass filler, glass flakes, glass beads, carbon fiber, talc, and mica may be mixed in the resin. Further, by changing the color of the resin, a multicolor molded product can be simultaneously molded in one cavity.

  Next, an example in which the injection molding method according to the present invention is applied to molding of a throttle body will be described in detail with reference to the drawings.

In the first embodiment, an embodiment corresponding to the invention described in claim 1 will be described with reference to the drawings.
1 is a perspective view of a DBW throttle body injection-molded in this embodiment, FIG. 2 is a cross-sectional view of an injection mold used in this embodiment, and FIG. 3 is an explanatory view of a cavity shape for molding the DBW throttle body. 4 is a schematic view showing a state in which the DBW throttle body is connected to the runner and the sprue, FIG. 5 is an explanatory view showing a state where the injection mold is closed, and FIG. FIG. 7 is an explanatory diagram in which the molten resin is filled into the cavity and the motor case cavity, FIG. 7 is an explanatory diagram in which the molten resin is filled and the pressure holding step is started, and FIG. 8 is an explanatory diagram in which the injection mold is opened, FIG. 9 is an explanatory view in which the DBW throttle body is released from the mold by the ejector pins.

  The DBW throttle body 100 obtained in the first embodiment will be described with reference to FIG. As the resin, polyphenylene sulfide (PPS) resin was used. In FIG. 1, reference numeral 1 denotes a cylindrical bore that accommodates a throttle valve (not shown) therein, 2 is a flange (not shown) when assembled to a manifold (3), and 3 is a assembly to the manifold. , A bolt mounting boss having a hollow shape for penetrating the mounting bolt, 4 a bearing for incorporating a shaft of a rotating throttle valve, 5 a motor case for housing a motor and a gear, and 6 for one of the motor case 5 A motor storage portion, which is a portion, and 7 is a gear storage portion. The bore 1 has an inner diameter W of 65 mm and a height H from the flange 2 of 60 mm. The capacity of the bore 1 and the motor case 5 is larger in the bore 1.

  The DBW throttle body 100 molded according to the first embodiment incorporates a throttle valve using a bearing 4 in the bore 1 and a motor for driving the throttle valve is assembled in the motor housing 6 of the motor case 5. After the gear that transmits the drive to the throttle valve is assembled in the gear housing 7, the cover 8 is attached to the gear housing 7 and the gear housing 7 is closed in an airtight state.

A mold for molding the DBW throttle body 100 having such a shape will be described with reference to FIG.
The fixed-side mounting plate 7 is provided with two sprue bushes, a sprue bush 8 and a sprue bush 9. A cylinder A is connected to the sprue bush 8 and a cylinder B is connected to the sprue bush 9 as shown in FIG.

  Further, a runner stripper plate 10 and a fixed side template 11 are provided on the front surface of the fixed side mounting plate 7.

  12 is a fixed side insert built in the front of the runner stripper plate 10, 13 is a fixed side cavity forming insert built in the front of the insert 12, 14 is a sprue, 15 is a cross-shaped primary runner, 16 Are four secondary runners and 17 are four gates.

  In FIG. 2, 18 is a movable side mounting plate, 19 is a mounting plate of an eject pin 20 assembled on the front side of the movable side mounting plate 18, 19a is a pressing plate of the eject pin 20, and 21 is a front side of the movable side mounting plate 18. This is a cradle to which the movable side template 22 is assembled.

  Reference numeral 23 denotes a movable-side cavity molding insert assembled on the front side of the movable-side mold plate 22. By facing the fixed-side insert 13, the throttle body molding cavity 24 shown in FIG. 4 is formed. .

  In FIG. 4, reference numeral 25 denotes a bore forming portion of the throttle body forming cavity 24, and 26 denotes a forming portion of the motor housing portion 6. The forming portion 26 of the motor housing portion 6 is connected to the sprue 29, the primary runner from the cylinder B. 30, resin filling is performed via the secondary runner 31 and the gate 27.

  As described above, the fixed side template 11 incorporates the insert 13 that bears a part of the product shape. Further, the sprue bushing 8 is formed from the sprue bush 8 as a molten resin runway to the nest 13 as described above, and further passes from the nest 12 through the nest 13 to the cavity 24 and branches from the sprue 14 to four runners. The primary runner 15 and the secondary runner 16 are formed.

  Similarly, the resin is filled from the sprue bush 9 to the surface of the molded part 26 of the motor case 5 of the cavity 24 through the primary runner 30, the secondary runner 31, and the gate 27, which are molten resin runners, up to the nest 12. The

  The movable side mounting plate 18 is assembled with a movable side template 22 assembled with a nesting 23 that bears a part of the product shape, and a cradle 21 is assembled. Further, a plurality of ejector pins 20 are attached so as to be sandwiched between the ejector plate 19 and the presser plate 19 a of the ejector pin 20. The front end penetrates the receiving table 21 and the movable side mold plate 22 and reaches the surface of the cavity 24.

  By closing the fixed side mold plate 11 and the movable side mold plate 22, the cavity 24 has the product shape shown in FIG.

  FIG. 4 shows a schematic view of the DBW throttle body forming cavity 24, the sprue 14 (29), the primary runner 15 (30), the secondary runner 16 (31), and the gate 17 (27). Four gates 17 are provided on the bore forming portion 25 side, and resin is supplied from the cylinder A to the gates 17 via the sprue 14, the first runner 15, and the second runner 16. In addition, two gates 27 are provided on one motor case molding portion 26 side, and resin is supplied from the cylinder B to the gates 27 via a sprue 29, a primary runner 30, and a secondary runner 31. Thus, since the cylinder A dedicated for bore molding and the cylinder B dedicated for motor case molding are independent, the resin can be filled from the respective cylinders A and B at an arbitrary filling pressure, holding pressure and timing. .

  Next, an injection molding method of the DBW throttle body 100 using the cylinders A and B described in the first embodiment will be described with reference to FIGS.

  In advance, the final filling positions of the bore molding part 25 and the motor case molding part 26 were set at points E and F, and the injection speeds of the cylinders A and B were adjusted so that the molten resin reached at the same time.

An injection molding process performed so that the final filling position is at points E and F will be described.
As shown in FIG. 5, the movable side mounting plate 18 is advanced to close the fixed side template 11 and the movable side template 22. At this time, in the cylinder A and the cylinder B, after the resin is weighed, the resin is melted by heating with a heater and kneading with a screw and is waiting.

  Next, as shown in FIG. 6, filling of the molten resin into the cavity 24 is started at the same time in both the cylinder A and the cylinder B. The filling pressure at this time is 80 MPa for cylinder A and 70 MPa for cylinder B. The setting of the filling pressure is based on the capacity of each molding part.

  Finally, as shown in FIG. 7, the molten resin is simultaneously filled in the cavity of the bore molding portion 25 and the cavity of the motor case molding portion 26 to complete the filling. Thus, by determining the molding conditions of the cylinder A and the cylinder B, the bore molding part 25 side and the motor case molding part 26 side are individually filled with resin, and the bore molding part 25 and the motor case molding part 26 are joined. Since the resin merges at the portion, the occurrence of turbulent flow due to the merge of the resin is suppressed particularly in the bore forming portion 25, and the molten resin can be uniformly filled in the respective cavities.

  In the pressure holding process, the holding pressure of the cylinder A is set to 93 Mpa and the holding pressure of the cylinder B is set to 48 Mpa in proportion to the capacity, the resin pressure is set for a set time, and after the cooling process, the movable side mounting plate 17 is moved. It was made to move backward and away from the fixed side mounting plate 7 side (FIG. 8). As a result, the stationary side template 7 and the runner stripper plate 10 were separated from each other, and the primary runner 15 (30) and the secondary runner 16 (31) were peeled off from the DBW throttle body 100 and separated.

  Thereafter, as shown in FIG. 9, when the eject plate 19 and the presser foot 19a of the eject pin 20 move forward, the eject pin 20 moves through the guide holes of the receiving base 21 and the movable side mold plate 22, and the DBW throttle body 100 is moved. Extrude and release. Through this molding process, the injection molding was completed, and the DBW throttle body 100 shown in FIG. 1 could be obtained.

  As a result, when the roundness (longest inner diameter−shortest inner diameter) of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured using a cylinder gauge (model: CG-100A manufactured by Mitutoyo Corporation), it was as good as 105 μm. It was a measured value.

  The second embodiment has the same shape as the DBW throttle body 100 molded in the first embodiment, but the bore 1 has an inner diameter W of 35 mm and a height H from the flange 2 of 45 mm. 100 molding methods.

  The volume of the bore 1 portion and the volume of the motor case 5 portion are substantially the same. For this reason, both the filling pressure and the holding pressure of the cylinders A and B were set to 48 Mpa.

  As a result, it was possible to obtain the DBW throttle body 100 having the same roundness as in Example 1.

  In the first embodiment, filling of the molten resin into the cavity 24 is started at the same time in both the cylinder A and the cylinder B. However, in this third embodiment, the timing of filling the molten resin into the motor case molding cavity 26 is determined by bore molding. After the start of filling of the molten resin into the cavity 25 for use, it was performed at a timing that was delayed.

  When the cavity capacity of the bore molding cavity 25 is larger than that of the motor case molding cavity 26, a time difference until reaching the final filling position is generated, which causes turbulence.

  First, the fixed side mold plate 11 and the movable side mold plate 22 are closed as shown in FIG. At this time, in the cylinder A and the cylinder B, after the resin is weighed, the resin is melted by heating with a heater and kneading with a screw and is waiting.

  Next, as shown in FIG. 11, filling of the molten resin into the bore forming cavity 25 from the cylinder A is started.

  Thereafter, as shown in FIG. 12, the injection from the cylinder B is started 0.7 seconds after the start of the injection from the cylinder A. The delay time can be set by performing a flow analysis by CAE in advance.

  Finally, as shown in FIG. 13, the bore molding cavity 25 and the motor case molding cavity 26 are simultaneously filled with molten resin, and the filling is completed. Since the molding conditions of cylinder A and cylinder B can be determined according to each cavity, the molten resin is uniformly filled into each molded part without turbulent flow between the bore molding resin and the motor case molding resin. I was able to.

  After passing through the pressure holding and cooling steps, the movable side mounting plate 17 was moved backward from the fixed side mounting plate 7. When the stationary side template 11 and the runner stripper plate 10 are separated from each other, the primary runner 15 (30) and the secondary runner 16 (31) are both separated from the DBT throttle body 100 (FIG. 14).

  Thereafter, as shown in FIG. 15, the eject plate 19 and the retainer plate 19a of the eject pin 20 move forward, so that the eject pin 20 moves through the guide holes of the cradle 21 and the movable side mold plate 22, and the DBW throttle body 100 is moved. The DBW throttle body 100 can be obtained after the injection molding is completed.

  As a result, when the roundness of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured, it was a good measured value of 76 μm.

Reference example

In the DBW throttle body 100 in which the bore 1 and the motor case 5 of this reference example are integrated, there are places where the bore molding cavity 25 and the motor case molding cavity 26 are connected. If the molten resin first reaches the connecting portion, it may flow into another cavity, and a situation may occur where the amount of resin is insufficient.

  For example, in FIG. 4, the portion C is the thickest portion among the locations where the bore forming cavity 25 and the motor case forming cavity 26 are connected. Therefore, in the secondary runner 16 closest to the part C in FIG. 4, the cross-sectional area in the vicinity of the gate 17 is made 1.0 mm thicker than the diameter of the other secondary runners 16. The value for making the diameter of the nearest secondary runner 16 larger than that of the other secondary runners 16 can be set in advance by performing flow analysis by CAE. Naturally, the diameter of the gate 17 is larger than that of the other gates 17.

  As a result, when the roundness of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured, it was a good measured value of 70 μm. In each of the above embodiments, the resins in the cylinders A and B are the same. However, by changing the resin in the cylinders A and B or changing the color, different parts or colors in one molded product can be obtained. It is possible to make different products.

Comparative Example 1

In this comparative example, the sprue 14 and sprue 29 in FIG. 4 were connected, and the molten resin was injected only from the sprue 14. That is, only A was used as the cylinder.
Other primary runners, secondary runners, and gates are the same as those in the second embodiment.

  As a result, when the roundness of the inner diameter portion of the bore 1 in the obtained DBW throttle body 100 was measured, it was 187 μm, which was considerably inferior as shown in Table 1 when compared with the measured values of Examples 1 to 4. Value.

Fig. 1 Appearance explanatory view of throttle body Fig. 2 Explanatory drawing of throttle body molding die and injection device according to the present invention Fig. 3 Side view of throttle body Fig. 4 Explanation of throttle body molding cavity and runner and sprue following this cavity Fig. 5 An explanatory diagram of a state using a mold. Fig. 6 An explanatory diagram of an intermediate state in which resin is filled. Fig. 7 An explanatory diagram of a state in which resin filling is completed. Fig. 8 An explanatory diagram of a state in which a mold is opened. 9 Explanatory drawing of the state where the product is released FIG. 10-15 Explanatory drawing of Example 2

100 DBW Throttle body 1 Bore 5 Motor case 11 Fixed side template 13 Fixed side inserts 14 and 29 Sprue 15 and 30 Primary runners 16 and 31 Secondary runners 17 and 27 Gate 22 Movable side plate 23 Movable side insert 24 Cavity 25 Bore molding part 26 Motor case molding part A Bore side cylinder B Motor case side cylinder

Claims (9)

  In a mold formed by forming a plurality of molded parts in a cavity, a resin-filling cylinder is provided for each of the plurality of molded parts, and resin is respectively supplied from the plurality of cylinders to the molded part in each cavity during product molding. An injection molding method in which a plurality of molded parts are integrally molded by filling at the same time.   The injection molding method according to claim 1, wherein when filling the resin from the plurality of cylinders, the filling pressure and / or filling timing and / or holding pressure of the resin is changed for each molding part.   The injection molding according to claim 1 or 2, wherein when the resin is filled from the plurality of cylinders, the type or color of the resin is changed for each cylinder, and a merged region having a different type or color of the resin is simultaneously molded for each molding part. Method.   The plurality of molding parts are throttle body molding cavities for integrally molding a bore molding part, a motor for driving a valve in the bore, and a gear case, and the cavities include a cavity part for bore molding and a motor case molding The injection molding method according to any one of claims 1 to 3, wherein the injection molding method comprises a cavity part, and a cylinder is provided for each of the bore molding cavity part and the motor case molding cavity part.   5. The injection molding method according to claim 4, wherein the filling resin filling timing into the bore molding cavity is the same as the melting resin filling start timing into the motor case molding cavity.   The injection molding method according to claim 4, wherein the start timing of filling the molten resin into the motor case molding cavity is immediately after the start of filling the molten resin into the bore molding cavity.   Cylinder and motor for filling the cavity molding cavity with the molten resin so that the cavity resin is uniformly filled with the molten resin when filling the cavity molding cavity and the motor case molding cavity. The injection molding method according to any one of claims 4 to 6, wherein the injection molding method is performed by individually adjusting a resin pressure and a holding pressure of a cylinder that fills the case molding cavity with a molten resin.   When filling and holding pressure of the molten resin through a plurality of gates formed in the cavity for cavity molding, the molten resin is uniformly filled and molded so as to pass through each gate or runner. The injection molding method according to any one of claims 4 to 7, wherein a resin amount is controlled. When applying molten resin and holding pressure through a plurality of gates formed in the bore molding cavity portion and the motor case molding cavity portion, the molten resin is uniformly filled and molded. 9. The injection molding method according to claim 8, wherein a resin pressure and a holding pressure to be filled for each cavity portion are controlled by adjusting a cross-sectional area of the gate or the runner.

Images