JP3490758B2 - Internal gear and its injection mold - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal gear formed by injection molding and an injection molding die for molding the internal gear.

[0002]

2. Description of the Related Art A cylindrical member having an internal gear (internal gear) causes an undercut in the radial direction, so that the teeth are located on the end surface of the cylindrical member and the inner die is axially moved. The method of pulling out was taken. But,
This method was only possible if the tooth trace was an internal gear running parallel to the axis and had no other undercuts.

Further, in order to injection-mold an internal gear, it is necessary to use an internal slide core obtained by dividing an internal mold into a plurality of parts. Here, the problem is where to place the parting line of the inner slide core. In order to make the mold thicker, it is desirable to place the parting line on the bottom of the tooth, avoiding the tooth surface, but in consideration of the internal tooth pitch, all parting lines should be placed on the bottom of the mold. It was difficult to establish.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an internal gear which facilitates the construction of an injection mold, a drive mechanism, drive control, and the like, and an injection molding die for injection molding the internal gear.

[0005]

SUMMARY OF THE INVENTION In order to achieve this object, the present invention according to claim 1 comprises a pair of first and second inner slide cores which are adjacent to each other and move radially at different speeds to open and close the inner mold. Do
An internal gear formed by an injection molding die having six or more sets of first and second internal slide cores, the number of teeth of the internal gear being
Z is set according to the following formula based on the number S of divisions of the first and second inner slide cores: Z = (n / 2) S , where n is a positive integer . The present invention according to claim 3 is such that six or more sets of first and second inner slide cores, which are adjacent to each other and move in the radial direction at different speeds to open and close the inner mold, as one set,
An injection molding die for forming an internal gear with a second internal slide core, wherein the number of teeth Z of the internal gear is set by the following formula based on the number S of divisions of the first and second internal slide cores: Z = (N / 2) S , where n is a positive integer .

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments. FIG. 1 is a front view of a cam ring which is an embodiment of an internal gear of the present invention.

The cam ring 11 has internal teeth 13 on its inner circumference. The internal teeth 13 are internal gears whose tooth lines extend in parallel with the central axis of the cam ring 11 and whose end faces are continuous in the spiral direction, and are formed for about 2/3 of the internal circumference of the cam ring 11. . The inner peripheral portion of the cam ring 11 has two inner mold portions 32,
It is formed by a plurality of sets of inner mold parts 32 and 42, one set of which is 42. The tooth surfaces of the inner teeth 13 have inner die parts 32, 42 (first,
The second inner slide cores 31, 41) form a flat surface from which the inner slide cores 31, 41) can be pulled out in the radial direction. In this embodiment, the inner mold part 3
Parting lines 2, 42 are formed so as to be located at the roots of the outer teeth 35, 45 forming the inner teeth 13.
Here, the number of teeth per revolution of the inner teeth 13 is Z, and the inner die part 3
When the number of 2, 42 is S, Z = (n / 2) S ... However, n has a relation of a positive integer.

Thus, the number of teeth Z of the inner teeth 13 and the inner die 3
By setting the number of divisions of 2 and 42 so as to satisfy the above formula, the parting line of the inner mold parts 32 and 42 can be formed at the tooth bottom. In this embodiment, S
= 12 and n = 18 are set, so Z = 108. However, the cam ring 11 of the present embodiment is not the entire circumference of the inner peripheral surface,
It has a structure in which the internal teeth 13 are provided in approximately half of the circumference. Therefore, it goes without saying that not all of the inner mold parts 32, 42 have the outer teeth 35, 45, but only the corresponding parts. On the contrary, the number of teeth Z may be set first and the number of divisions S may be set.

Further, the first and second sets of each set of this embodiment are
The slide cores 31 and 41 are formed in the same basic shape as the first and second slide cores 31 and 41 of the other sets, but as described above, the inner mold parts 32 and 42 are shaped like the molded product. It has a mold part according to.

Details of the mold 20 for injection molding the cam ring 11 will be described with reference to FIGS. 4 to 7 and FIG. 4 and 5 are perspective views showing a main part of an inner slide core of an embodiment of an injection molding die for injection molding the cam ring in a closed state and an open state, respectively, and FIGS. It is the front view.

The mold 20 has a first inner slide core 31 as an inner slide core for molding the inner peripheral surface of the cam ring 11.
And a plurality of sets of inner slide cores 31 and 41 (6 sets in this embodiment, a total of 12 sets)
And a fixed plate 21 for movably supporting the inner slide cores 31 and 41 in a radial direction orthogonal to the central axis O of the mold coinciding with the central axis of the cam ring 11, and the first and second The lock core 23, which is located in the axial center space formed by the inner peripheral surfaces 31a and 41a of the inner slide cores 31 and 41 and moves back and forth in parallel with the central axis O about the central axis O, is provided. A movable plate 25 that moves forward and backward, and an angular pin 27 that is fixed to the movable plate 25 and that drives the first and second inner slide cores 31 and 41 at different speeds in the opening and closing directions when the movable plate 25 moves backward and forward. , 28 are provided. The lock core 23 presses and holds the first and second inner slide cores 31 and 41 in the closed state at the forward movement position. Although not shown in detail, the fixed plate 21 is fixed to a fixed block or the like of the injection molding machine, and the moving plate 25 is driven by a hydraulic cylinder, a press shaft or the like mounted on the fixed block or the like.

Each of the first and second inner slide cores 31, 41
The inner mold parts 32, 42 are formed integrally with the tip parts of the base parts 33, 43, and the inner mold parts 32, 42 are in close contact with the other inner mold parts 32, 42 adjacent to each other in the closed state. The inner peripheral surface of the cam ring 11 is formed. Further, the base portions 33 and 43 include first and second inner slide cores 31 and 41 (inner die portion 3).
2, 42) are formed in the opening / closing direction (diameter direction). Hereinafter, the first and second inner slide cores 31 and 41 of each set are, except for the mold part formed on the outer peripheral surface of the inner mold parts 32 and 42, the basic structure and the configuration and mechanism of the parts related thereto. Are the same, a description will be given of the pair of first and second inner slide cores 31 and 41.

The guide portions 34 and 44 are formed to have a cross section (details are not shown). On the other hand, the fixed plate 21 is formed with groove-shaped guide grooves 21b in the diametrical direction orthogonal to the central axis O (the central axis of the cam ring 11), and the guide portions 34 and 44 slide on these guide grooves 21b. It is movably fitted. In this fitted state, each inner mold part 32, 42 projects forward from the opening 21a formed in the fixed plate 21, and is constrained by the guide parts 34, 44 and the guide groove 21b to move in the radial direction.

When the inner mold parts 32 and 42 move toward the central axis O, they separate from each other to be in an open state in which the mold is opened. Further, when the inner mold parts 32, 42 move in the radial direction away from the central axis O and the outer peripheral surfaces contact the edge part 21c of the opening 21a, and further outward movement is blocked,
Close to each other and close the mold. This inner mold part 3
The positions and states of 2, 42 are the closed position, which is the closed state.

External gear portions 35 and 45 that form the internal teeth 13 in the closed state are formed on the outer peripheral surfaces of the inner mold portions 32 and 42. The cam ring 11 is not limited to the internal teeth 13,
There may be grooves, holes, ridges, protrusions, etc., and in such a case, the ridges that form them in the inner mold parts 32, 42,
Protrusions, grooves, holes, etc. are formed.

The front surface of the fixed plate 21 forms the end surface of the cam ring 11.
Adult Subeku, the inner diameter of the opening 21a is formed into substantially the same as the inner diameter of the cam ring 11, the inner peripheral surface of the cam ring 11 is formed by the inner mold part 32, 42 projecting from the opening 21a.

The inner peripheral surfaces 31a, 41a of the first and second inner slide cores 31, 41 are formed in a mortar shape that becomes thinner toward the fixed mold 51 (front), and the lock core 23 is
The tapered portion 23a that contacts the inner peripheral surfaces 31a and 41a is formed in a truncated cone shape corresponding to the inner peripheral surfaces 31a and 41a. The central axis O is the taper portion 23a and the inner peripheral surfaces 31a and 41a.
Let θ _G be the angle formed with.

Further, the movable plate 25 is fixed with angular pins 27, 28 for transmitting a linear motion in the front-rear direction parallel to the central axis O to the first and second inner slide cores 31, 41 as a motion in the opening / closing direction. Has been done. The tip end shaft portions 27a, 28a of the angular pins 27, 28 are formed in the guide holes 36, 4 formed in the first and second inner slide cores 31, 41, respectively.
6 are slidably fitted respectively.

The angular pins 27 and 28 are the first and second
In order to move the inner slide cores 31 and 41 at different speeds, they are fixed to the moving plate 25 at predetermined angles θ _D and θ _E with respect to the central axis O, respectively. The moving plate 25 has a screw hole 25 with a seat support whose axial center extension intersects with the central axis O and forms angles θ _D and θ _E with the central axis O, respectively.
a, 25b are formed, while angular pins 27, 2 are formed.
Male screw parts 27c, 28c near the heads 27b, 28b of No. 8
Are formed. And Angular Pins 27, 28
The front end shaft portions 27a, 28a are inserted into the screw holes 25a, 25b from the rear of the moving plate 25, and the male screw portions 27c, 28
c is screwed into the screw holes 25a and 25b. As a result, the angular pins 27 and 28 are fixed to the moving plate 25 at angles θ _D and θ _E with respect to the central axis O.

The angles θ _D and θ _E are different so as to drive the first and second inner slide cores 31 and 41 at different speeds. In the present embodiment, the second inner slide core 41 is attached to the central axis O
Since it is configured to contact the first slide core 31 from the side,
When the fixed plate 25 moves back and forth, the second inner slide core 41
In order to move faster than the first inner slide core 31, the relationship of θ _D <θ _E is set. The first and second inner slide cores 3 for advancing and retracting the lock core 23.
The moving speeds (speed ratios) in the opening / closing direction (radial direction) of Nos. 1 and 41 are tan θ _D and tan θ _E , respectively.

The means for driving the first and second inner slide cores 31, 41 at different speeds is not limited to the angular pins 27, 28. For example, the inclined surface provided on the lock core 23 and the slide cores 31, 41 A structure in which the inclined surface provided on the peripheral surface is in sliding contact, or a structure in which a groove provided on one side and a ridge provided on the other side are slidably fitted may be used.

Further, in this embodiment, the taper portion 23a of the lock core 23 has the inner peripheral surface 3 at and near the closed position.
The inclination angle θ _G of the taper portion 23a is set to θ _D <θ so as not to interfere with the 1a and 41a and to interfere with other retracted positions.
The relationship is _E <θ _G.

A more detailed structure of the first and second inner slide cores 31, 41 will be described with reference to FIGS. 2 and 3. 2 is an enlarged front view showing the inner mold portions 32, 42 (first and second inner slide cores 31, 41), and FIG. 3 is a further enlarged front view showing the inner mold portions 32, 42. .

As shown in FIG. 2, the adjoining first and second inner slide cores 31 and 41 are formed such that their basic shapes are symmetrical with respect to the slide direction lines O ₁ and O ₂ passing through the central axis O thereof. , The first and second slide direction lines O ₁ and O ₂ move in parallel.

The contact and separation angle θ _C formed by the first and second sliding direction lines O ₁ and O ₂ with respect to the central axis O is set. This contact angle θ _C
Is determined by the total number of the first and second inner slide cores 31, 41, but in the present embodiment, the first and second inner slide cores 31, 4 are
Since there are 12 in total, θ _C = 360/12 = 30
(Degree).

Therefore, the first and second inner slide cores 3
When the 1, 41 are opened and closed, the parting surface 31c,
The moving speed ta of the first and second inner slide cores 31 and 41 is adjusted so that 41c does not interfere with each other except at or near the closed position.
n θ _D , tan θ _E and the contact angle θ _C satisfy the relationship of tan θ _D <tan θ _E cos θ _C.

The first and second inner slide cores 31, 41 are
Both sides in the circumferential direction (parting surfaces 31c, 41c)
Contact each other in the closed state to close the inner mold parts 32, 42. The parting surfaces 31c and 41c of the first and second inner slide cores 31 and 41 correspond to the first inner slide core 31.
The angle θ _B is measured with respect to the first sliding direction line O ₁ in the counterclockwise direction in the figure. This angle θ _B
Is formed so that the parting surface 41c of the second inner slide core 41 contacts the parting surface 31c of the first inner slide core 31 from the central axis O side. First, second
Parting surfaces 31 on both sides of the inner slide cores 31, 41
c and 41c are formed symmetrically with respect to a plane in which the slide direction lines O ₁ and O ₂ are extended along the axis.

The maximum angle θ _A is such that the outer teeth 35 interfere with the mold part 42 or the outer teeth 45 when the first and second inner slide cores 31, 41 are opened and closed. As for the maximum angle θ _A , as in the illustrated embodiment, a straight line connecting the corner portion 35 a of the outer tooth 35 and the outermost vertex (corner portion) 45 a of the outer tooth 45 is the first slide direction line O ₁ . It is an angle. This maximum angle θ
_A changes depending on the position of the parting line (the position where the external teeth 35 and 45 are divided), but it is desirable that the divided position be located at the valley bottom by avoiding the tooth surface in terms of strength.

Further, the minimum angle θ _F formed by the parting surfaces 31c and 41c with respect to the first sliding direction line O ₁ which can be moved to the open / close position without interfering with each other is defined by the following equation. It θ _F = tan ^-1 {sin θ _C tan θ _E / (tan θ _E cos θ _C
− Tan θ _D )} However, as described above, θ _C is the angle formed by the sliding direction lines O ₁ and O ₂ of the first and second inner slide cores 31 and 41, and θ _D is the angular pin 27 with the central axis O. Angle to make,
θ _E is the angle that the angular pin 28 makes with the central axis O.

The angle θ _B formed by the parting surfaces 31c and 41c with respect to the sliding direction line O ₁ of the first inner slide core 31 is larger than the minimum angle θ _F and smaller than the maximum angle θ _A. That is, by setting so as to satisfy θ _F ≦ θ _B ≦ θ _A , the first and second inner slide cores 31, 41, that is, the inner mold parts 32, 42 move without interfering with each other. It is opened and closed in conjunction with the movement of the plate 25.

The opening / closing operation of the first and second inner slide cores 31, 41 will be described with reference to FIGS. 8, 10 and 12 show the first and second inner slide cores 31 and 4.
9, 11 and 13 are sectional views taken along the planes passing through the slide direction lines O ₁ and O ₂ of FIGS. 8, 10 and 12, respectively, and the first inner slide core 31 is located on the lower side. 2 is a cross-sectional view showing the second inner slide core 41 on the upper side. FIG.

In the closed state where the inner mold parts 32 and 42 are in close contact with each other, the lock core 23 advances, and the taper part 23a of the lock core 23 causes the inner peripheral surfaces 31a and 41a of the first and second inner slide cores 31 and 41 to move. And presses in the closing direction (outward direction). The first and second inner slide cores 31 and 41 that have received this pressing force are urged in the closing direction (outward direction) along the guide groove 21b, and the parting surfaces 31c and 41c are in close contact with each other and the inner mold The parts 32 and 42 are closed (see FIGS. 4, 6, 8 and 9).

In this closed state, the outer mold 51 is fitted into the inner mold parts 32 and 42, and the space between the outer peripheral surfaces of the inner mold parts 32 and 42 and the inner peripheral surface of the outer mold 51 and the fixing plate 21. A cavity for molding the cam ring 11 is formed between the cavity and the front surface of the. Although not shown in the drawing, a synthetic resin is injected by an injection plunger or the like and solidified or cured to mold the cam ring 11.

In order to take out the formed cam ring 11,
When the moving plate 25 is retracted from this closed state, the lock core 23 and the angular pins 27 and 28 are integrally retracted. Then, due to these retreats, the first and second inner slide cores 31, 41, that is, the inner mold parts 32, 42 are movable in the opening direction (direction toward the central axis O) by releasing the constraint by the taper part 23a. Become. In addition, Angular Pin 2
Since 7 and 28 are retracted at the same time, the inner mold parts 32 and 42 are
The outer teeth 35, 45 are constrained by the angular pins 27, 28 and move in the opening direction, and the outer teeth 35, 45 separate from the inner teeth 13 (FIG. 10,
11).

When the moving plate 27 is further retracted and reaches the open position, the outer gear parts 35 and 45 of the inner mold parts 32 and 42 are completely removed from the inner teeth 13 of the cam ring 11, and the cam ring 11 is pulled out. Is possible (see FIGS. 2, 3, 5, 12, and 13). At the open position, the outer mold 51 is separated from each other, the cam ring 11 is pulled out from the inner mold parts 32 and 42, and the cam ring 11 is further pulled out from the outer mold 51. In this open state, the first and second inner slide cores 31, 4 are
1 is an inclined surface 31a, 41a and a parting surface 31c,
The connecting surfaces 31b and 41b connecting to 41c are in the closest state. It goes without saying that these connecting surfaces 31b, 41b are formed in a shape that does not interfere with each other when the first and second inner slide cores 31, 41 move between the closed position and the open position. When the outer periphery of the cam ring 11 also has an undercut, the outer die 51 is also a split die.

As described above, in this embodiment, the cam ring 11 is
Since the number of the inner teeth 13 is set based on the number of divisions of the inner mold part, each inner mold part can be formed in a constant basic shape, and the structure of the mold and the structure of the opening / closing drive means thereof. Became easier. Moreover, the external tooth portion 35 forming the internal tooth 13,
It became easier to form parting lines at the roots of 45 teeth. Further, in this embodiment, the inner slide core 31,
When the number of divisions of 41 is S and the number of teeth of the internal gear 13 is Z, the number of teeth Z is expressed by the formula: Z = (n / 2) S;
Although n is a positive integer), the coefficient n is usually set in consideration of a gear meshing with the internal gear 13 and the like, and is an even number.

In the present embodiment, the inner mold is composed of a plurality of sets, each of which is composed of the first and second inner slide cores 31 and 41. Therefore, the number of teeth Z is an integer in the above formula. Number of teeth Z
However, in this case, the number of divisions may not be an integer in some cases. Therefore, some of the first and second inner slide cores 31, 41 are used for adjustment.

Although the embodiment of the cam ring 11 and the mold for molding the cam ring 11 has been described as an example of the injection molded product having the internal gear in the present embodiment, the present invention is not limited to the internal teeth other than the cam ring 11. It is needless to say that the present invention can be applied to a molded product having the above and a mold for injection molding thereof.

[0039]

As is apparent from the above description, the present invention is
Injection having six or more sets of first and second inner slide cores, which are adjacent to each other and move in the radial direction at different speeds to open and close the inner mold to form one set of first and second inner slide cores Since the number Z of teeth of the internal gear formed by the forming die is set by the formula Z = (n / 2) S (where n is a positive integer) based on the number S of divisions of the inner slide core, It became very easy to configure the mold, as it became possible to position all the parting lines of the inner mold forming the teeth at the root of the tooth. Further, the present invention relating to an injection molding die includes six or more first and second inner slide cores which are adjacent to each other and move in the radial direction at different speeds to open and close the inner die. An injection molding die for forming an internal gear by an inner slide core,
Since the number of teeth Z of the internal gear is set by the equation, Z = (n / 2) S (where n is a positive integer) based on the number S of divisions of the first and second inner slide cores, It became very easy to configure the mold, as it became possible to position all the parting lines of the inner mold to be formed on the tooth bottom.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment in which an internal gear of the present invention is applied to a cam ring.

FIG. 2 is a front view showing the structure of an embodiment of an injection molding die having a plurality of sets of first and second inner slide cores, to which the present invention is applied.

FIG. 3 is an enlarged front view for explaining the configuration of the first and second inner slide cores in more detail.

FIG. 4 is a perspective view showing an embodiment of an inner die for injection-molding the inner gear of the present invention, with the first and second inner slide cores closed.

FIG. 5 is a perspective view showing the first and second inner slide cores of the same embodiment in an open state.

FIG. 6 is a front view showing the first and second inner slide cores of the same embodiment in a closed state.

FIG. 7 is a front view showing the first and second inner slide cores of the same embodiment in an open state.

FIG. 8 is a state in which the first and second inner slide cores of the embodiment are closed, and cut along a plane that passes through the sliding direction of the first and second inner slide cores so that the first inner slide core portion is located on the lower side. FIG. 7 is a sectional view showing the second inner slide core portion on the upper side.

9 is a front view for explaining the positional relationship between the first and second inner slide cores in the closed state of FIG.

FIG. 10 is a view showing a state in which the first and second inner slide cores are being opened and closed in the same embodiment, cut along a plane passing through a sliding direction of the first and second inner slide cores to lower the first inner slide core portions. It is a sectional view which shows the 2nd inner slide core part on the side and the upper side.

FIG. 11 is a diagram illustrating a state in which the first and second states of FIG.
It is a front view explaining the positional relationship of an inner slide core.

FIG. 12 is a sectional view of the first and second inner slide cores in the open state of the same embodiment taken along a plane that passes through the sliding direction of the first and second inner slide cores, so that the first inner slide core portion faces downward. ,
It is sectional drawing which shows the 2nd inner slide core part on the upper side.

FIG. 13 is a front view illustrating the positional relationship between the first and second inner slide cores in the open state of FIG.

[Explanation of symbols]

11 cam ring 13 internal teeth 21 Fixed plate 23 Rock Core 23a taper part 25 moving plate 27 First Angular Pin 28 Second Angular Pin 31 1st inner slide core 31a taper inner peripheral surface 31c Parting surface 32 Inner mold part 35 External teeth 41 Second inner slide core 41a taper inner peripheral surface 41c Parting surface 42 Inner mold part 45 External teeth O central axis

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B29C 45/26-45/38 B29C 33/00-33/76 F16H 1/28-3/78 F16H 51 / 00-55/30 G02B 7/08

Claims (4)

(57) [Claims] 1. Six or more sets of first and second inner slide cores, which are adjacent to each other and move in the radial direction at different speeds to open and close the inner die, as one set. An internal gear formed by an injection molding die, wherein the number of teeth Z of the internal gear is set by the following formula based on the number S of divisions of the first and second internal slide cores. And internal gear. Z = (n / 2) S where n is a positive integer 2. The internal gear according to claim 1, wherein the parting line of the first and second internal slide cores forming the internal gear is formed at a tooth die of the internal tooth forming portion or a position corresponding to a tooth bottom of the gear. Internal gear that has been. 3. Inner by six or more sets of first and second inner slide cores, which are adjacent to each other and move in the radial direction at different speeds to open and close the inner mold to form one set. An injection molding die for forming a gear, characterized in that the number of teeth Z of the internal gear is set by the following formula based on the number S of divisions of the first and second internal slide cores. Mold for. Z = (n / 2) S where n is a positive integer 4. The mold for injection molding according to claim 3, wherein the first and second inner slide cores have a tooth pattern of an internal tooth forming portion whose inner part forms the internal gear or teeth of the gear. Injection molding die formed on the bottom equivalent part.