U.S. patent application number 14/543083 was filed with the patent office on 2015-06-11 for ring-shaped insert molded article.
The applicant listed for this patent is NAKANISHI METAL WORKS CO., LTD.. Invention is credited to Yoshihiro ITO, Nobumasa OKA.
Application Number | 20150158216 14/543083 |
Document ID | / |
Family ID | 52146054 |
Filed Date | 2015-06-11 |
United States Patent
Application |
20150158216 |
Kind Code |
A1 |
ITO; Yoshihiro ; et
al. |
June 11, 2015 |
RING-SHAPED INSERT MOLDED ARTICLE
Abstract
A molded article 1 is configured such that an insert 2 is made
of a steel plate and includes a cylindrical part 2A and an annular
part 2B, a plastic 4 is annular in shape so as to be joined to the
annular part 2B, inner diameter D1 of the plastic 4 is larger than
inner diameter D2 of the annular part 2B so that no burrs at a gate
mark E protrude to the inner diameter side of the molded article 1,
the injection molding is conducted with a disc gate arranged on an
inner peripheral surface F of the plastic 4 at a position separated
from a surface of the annular part 2B, and the gate mark E resides
on the inner peripheral surface F of the plastic 4 at a position
separated from the surface of the annular part 2B.
Inventors: |
ITO; Yoshihiro; (Osaka-shi,
JP) ; OKA; Nobumasa; (Osaka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NAKANISHI METAL WORKS CO., LTD. |
Osaka-shi |
|
JP |
|
|
Family ID: |
52146054 |
Appl. No.: |
14/543083 |
Filed: |
November 17, 2014 |
Current U.S.
Class: |
428/66.6 ;
264/161 |
Current CPC
Class: |
B29C 2045/2716 20130101;
B29K 2101/10 20130101; G01D 5/12 20130101; B29C 45/14418 20130101;
B29K 2103/06 20130101; Y10T 428/218 20150115; B29K 2105/16
20130101; B29C 45/38 20130101; B29C 2045/0027 20130101; B29K
2905/00 20130101; G01D 5/00 20130101; B29K 2105/251 20130101; B29C
45/0025 20130101; B29K 2077/00 20130101; B29C 45/1459 20130101;
B29K 2995/0008 20130101; G01D 5/244 20130101; B29C 2045/2714
20130101; B29K 2705/00 20130101; B29K 2081/04 20130101; B29C
45/2708 20130101; B29C 45/14836 20130101 |
International
Class: |
B29C 45/00 20060101
B29C045/00; B29C 45/14 20060101 B29C045/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 5, 2013 |
JP |
2013-251941 |
Claims
1. A ring-shaped insert molded article manufactured by injection
molding in a state where a thermoset adhesive is applied to a
joining surface of a ring-shaped insert to a plastic and then the
insert and the plastic are placed in a metal mold, wherein the
insert, is made of a steel plate and includes a cylindrical part
and an annular part extended radially outward from one end edge of
the cylindrical part, the plastic is annular in shape so as to be
joined to the annular part of the insert, the inner diameter of the
plastic is larger than the inner diameter of the annular part so
that no burrs at a gate mark protrude to the inner diameter side of
the molded article, the injection molding is conducted with a disc
gate arranged on an inner peripheral surface of the plastic at a
position separated from a surface of the annular part, and in the
gate-cut state, the gate mark resides on the inner peripheral
surface of the plastic at a position separated from the surface of
the annular part so that no foreign matter resulting from gate
cutting sticks to the surface and no shearing load is applied by
gate cutting to the joining surface to prevent degradation of
adhesive performance.
2. The ring-shaped insert molded article according to claim 1,
wherein the ring-shaped insert molded article is an axial magnetic
encoder in which the ring-shaped insert is a support member and the
plastic is a plastic magnet, the inner diameter of the plastic is
0.6 mm or more larger than the inner diameter of the annular part,
and the gate mark resides at a position separated 0.1 mm or more
from the surface of the annular part.
3. A ring-shaped insert molded article manufactured by injection
molding in a state where a thermoset adhesive is applied to a
joining surface of a ring-shaped insert to a plastic and then the
insert and the plastic are placed in a metal mold, wherein the
insert is made of a steel plate and includes a cylindrical part and
an annular part extended radially inward from one end edge of the
cylindrical part, the plastic is cylindrical in shape so as to be
joined to an outer peripheral surface of the cylindrical part of
the insert and has a curve part over the annular part, the
injection molding is conducted with a disc gate arranged on an
inner peripheral surface of the plastic at a position separated
from a surface of the annular part, and in the gate-cut state, a
gate mark resides on the inner peripheral surface of the plastic at
a position separated from the surface of the annular part so that
no foreign matter resulting from gate cutting sticks to the surface
and no shearing load is applied by gate cutting to the joining
surface to prevent degradation of adhesive performance.
4. The ring-shaped insert molded article according to claim 3,
wherein the ring-shaped insert molded article is a radial magnetic
encoder in which the ring-shaped insert is a support member and the
plastic is a plastic magnet, and the gate mark resides at a
position separated 0.1 mm or more from the surface of the annular
part.
Description
TECHNICAL FIELD
[0001] The present invention relates to a ring-shaped insert molded
article that is manufactured by injection molding in a state where
a thermoset additive is applied to a joining surface of a
ring-shaped insert to a plastic.
BACKGROUND ART
[0002] As ring-shaped insert molded articles manufactured by
injection molding in a state where a thermoset additive is applied
to a joining surface of a ring-shaped metallic part as an insert to
a plastic and then the insert and the plastic are placed in a metal
mold, there have been suggested axial (axially opposed-type)
magnetic encoders (for example, refer to Patent Documents 1 and 2,
and Patent Document 3, FIG. 2) and radial (radial opposed-type)
magnetic encoders (for example, refer to Patent Document 3, FIG. 9
and Patent Document 4), which are used in devices for detecting the
rotation speed of a rotating body.
[0003] Such injection molding of magnetic encoders is performed in
many cases such that a molten resin is injected into a metal mold
from a disc gate placed at the radially inner side of the insert
molded article for the viewpoint of the orientation of magnetic
substance powder in the molten resin (refer to Patent Document 2,
paragraphs [0017] to [0023], Patent Document 3, paragraph [0034],
and Patent Document 4, the description in the prior art
section).
CITATION LIST
Patent Literatures
[0004] Patent Document 1: JP-A No. 2012-098125
[0005] Patent Document 2: JP-A No. 2006-133018
[0006] Patent Document 3: JP-A No. 2011-081008
[0007] Patent Document 4: JP-B No. H07-27833
SUMMARY OF INVENTION
Technical Problems
[0008] In the magnetic encoders manufactured by disc gate-type
insert molding as described above, an additive layer intervenes
between a support member as an insert and a plastic magnet (for
example, refer to Patent Document 1, paragraph [0026], Patent
Document 2, paragraph [0035], and Patent Document 8, paragraph
[0034]).
[0009] At manufacture of conventional magnetic encoders by disc
gate-type insert molding, gate cutting is conducted in many cases
at a boundary surface between the support member and the plastic
magnet, as can be seen from the gate placement in the axial
magnetic encoder shown in FIG. 5 of Patent Document 2 or the gate
placement in the radial magnetic encoder shown in FIG. 4 of Patent
Document 4.
[0010] Thus, since foreign matter such as dust generated from the
cut resin may remain on the insert (for example, slinger 16
described in Patent Document 2 or rotor yoke 1 described in Patent
Document 4). it is necessary to perform a post-process for removing
the foreign matter. In addition, when the gate cutting is conducted
on the boundary surface, a shearing load is applied to the boundary
surface (joining surface between the insert and the plastic magnet)
that is low in strength, which may cause degradation of adhesive
performance.
[0011] In addition, if a metal mold structure with the gate
position aligned to the inner peripheral surface of cylindrical
part (annular part) of the ring-shaped support member is used in
the axial magnetic encoder, the foreign matter does not remain on
the insert, but burrs at the gate mark protrudes to the inner
diameter side of the molded article. This requires additional work
for removing the burrs.
[0012] In view of the foregoing circumstances, an issue to be
solved by the present invention is to provide a ring-shaped insert
molded article manufactured by injection molding using a disc gate
in a state where a thermoset adhesive is applied to a joining
surface of a ring-shaped insert to a plastic and then the insert
and the plastic are placed in a metal mold, wherein there is no
need for the foregoing post-process or additional work after gate
cutting and the adhesive performance does not deteriorate.
Solution to Problems
[0013] To solve the foregoing problems, a ring-shaped insert molded
article according to the present invention is a ring-shaped insert
molded article manufactured by injection molding in a state where a
thermoset adhesive is applied to a joining surface of a ring-shaped
insert to a plastic and then the insert and the plastic are placed
in a metal mold, wherein the insert is made of a steel plate and
includes a cylindrical part and an annular part extended radially
outward from one end edge of the cylindrical part, the plastic is
annular in shape so as to be joined to the annular part of the
insert, the inner diameter of the plastic is larger than the inner
diameter of the annular part so that no burrs at a gate mark
protrude to the inner diameter side of the molded article, the
injection molding is conducted with a disc gate arranged on an
inner peripheral surface of the plastic at a position separated
from a surface of the annular part, and in the gate-cut state, the
gate mark resides on the inner peripheral surface of the plastic at
a position separated from the surface of the annular part so that
no foreign matter resulting from gate cutting sticks to the surface
and no shearing load is applied by gate cutting to the joining
surface to prevent degradation of adhesive performance.
[0014] According to this configuration, the inner diameter of the
annular plastic is larger than the inner diameter of the annular
part of the ring-shaped insert so that no burrs at the gate mark
protrude to the inner diameter side of the molded article, which
thus eliminates the need for additional work to remove the
burrs.
[0015] In addition, in the gate-cut state, the gate mark resides on
the inner peripheral surface of the plastic at a position separated
from the surface of the annular part so that no foreign matter
resulting from the gate cutting sticks to the surface and no
shearing load is applied by gate cutting to the joining surface to
prevent deterioration in adhesive performance. This eliminates the
need to perform the post-process for removing the foreign matter
because of absence of the foreign matter on the surface and
prevents degradation of adhesive performance caused by the gate
cutting.
[0016] It is preferred that the ring-shaped insert molded article
is an axial magnetic encoder in which the ring-shaped insert is a
support member and the plastic is a plastic magnet, the inner
diameter of the plastic is 0.6 mm or more larger than the inner
diameter of the annular part, and the gate mark resides at a
position separated 0.1 mm or more from the surface of the annular
part.
[0017] According to this configuration, in the case where the
ring-shaped insert molded article is an axial magnetic encoder, it
is ensured that the additional work and post-process are not needed
after the gate cutting and degradation of adhesive performance
caused by the gate cutting is prevented.
[0018] In addition, to solve the foregoing problems, a ring-shaped
insert molded article according to the present invention is a
ring-shaped insert molded article manufactured by injection molding
in a state where a thermoset adhesive is applied to a joining
surface of a ring-shaped insert to a plastic and then the insert
and the plastic are placed in a metal mold, wherein the insert is
made of a steel plate and includes a cylindrical part and an
annular part extended radially inward from one end edge of the
cylindrical part, the plastic is cylindrical in shape so as to be
joined to an outer peripheral surface of the cylindrical part of
the insert and has a curve part over the annular part, the
injection molding is conducted with a disc gate arranged at a
position separated from a surface of the annular part on an inner
peripheral surface of the plastic, and in the gate-cut state, the
gate mark resides on the inner peripheral surface of the plastic at
a position separated from the surface of the annular part so that
no foreign matter resulting from gate cutting sticks to the surface
and no shearing load is applied by gate cutting to the joining
surface to prevent degradation of adhesive performance.
[0019] According to this configuration, the inner diameter of the
curve part of the cylindrical plastic is sufficiently larger than
the inner diameter of the annular part of the ring-shaped insert so
that, no burrs at the gate mark protrude to the inner diameter side
of the molded article, which thus eliminates the need for
additional work to remove the burrs. In addition, in the gate-cut
state, the gate mark resides on the inner peripheral surface of the
plastic at the position separated from the surface of the annular
part so that no foreign matter resulting from the gate cutting
sticks to the surface and no shearing load is applied by gate
cutting to the joining surface to prevent deterioration in adhesive
performance. This eliminates the need to perform the post-process
for removing the foreign matter because of absence of the foreign
matter on the surface and prevents degradation of adhesive
performance caused by the gate cutting.
[0020] It is preferred that the ring-shaped insert molded article
is a radial magnetic encoder in which the ring-shaped insert is a
support member and the plastic is a plastic magnet, and the gate
mark resides at a position separated 0.1 mm or more from the
surface of the annular part.
[0021] According to this configuration, in the case where the
ring-shaped insert molded article is a radial magnetic encoder, it
is ensured that the additional work and post-process are not needed
after the gate cutting and degradation of adhesive performance
caused by the gate cutting is prevented.
Advantageous Effects of Invention
[0022] According to each of the ring-shaped insert molded articles
according to the present invention as described above, the
ring-shaped insert molded article is manufactured by injection
molding in a state where a thermoset adhesive is applied to the
joining surface of the ring-shaped insert to the plastic and then
the insert and the plastic are placed in a metal mold, which
eliminates the need for the additional work to remove the burrs at
the gate mark and the need to perform the post-process for removing
the foreign matter because of absence of the foreign matter on the
surface resulting from the gate cutting, and prevents degradation
of adhesive performance caused by the gate cutting.
BRIEF DESCRIPTION OF DRAWINGS
[0023] FIG. 1 is a longitudinal cross-sectional view of a
ring-shaped insert molded article (axial magnetic encoder)
according to a first embodiment of the present invention;
[0024] FIG. 2 is a longitudinal cross-sectional view of one example
of an injection mold for manufacturing the ring-shaped insert
molded article;
[0025] FIG. 3 is an enlarged longitudinal cross-sectional view of
major components of the injection mold;
[0026] FIG. 4 is an enlarged longitudinal cross-sectional view of
major components, showing one example of a metal mold structure
(insert core-type): FIG. 4(a) shows a state in which, after mold
clamping, a molten plastic is injected into the metal mold; FIG.
4(b) shows a state where the metal mold is cooled and then opened;
and FIG. 4(c) shows a state where the molded article is removed
from the metal mold, set on a jig, and then cut at a gate;
[0027] FIG. 5 is an enlarged longitudinal cross-sectional view of
major components, showing one example of another metal mold
structure (slide core-type): FIG. 5(a) shows a state in which,
after mold clamping, a molten plastic is injected into the metal
mold; FIG. 5(b) shows a state where the metal mold is cooled and
then opened; and FIG. 5(c) shows a state where the molded article
is removed from the metal mold, set on a jig, and then cut at a
gate;
[0028] FIG. 6 is a longitudinal cross-sectional view of a
ring-shaped insert molded article (radial magnetic encoder)
according to a second embodiment of the present invention;
[0029] FIG. 7 is an enlarged longitudinal cross-sectional view of
major components, showing one example of a metal mold structure
(insert core-type): FIG. 7(a) shows a state in which, after mold
clamping, a molten plastic is injected into the metal mold; FIG.
7(b) shows a state where the metal mold is cooled and then opened;
and FIG. 7(c) shows a state where the molded article is removed
from the metal mold, set on a jig, and then cut at a gate;
[0030] FIG. 8 is an enlarged longitudinal cross-sectional view of
major components, showing one example of another metal mold
structure (slide core-type): FIG. 8(a) shows a state in which,
after mold clamping, a molten plastic is injected into the metal
mold; FIG. 8(b) shows a state where the metal mold is cooled and
then opened; and FIG. 8(c) shows a state where the molded article
is removed from the metal mold, set on a jig, and then cut at a
gate.
DESCRIPTION OF EMBODIMENTS
[0031] Embodiments of the present invention will now be described
below with reference to the drawings. The present invention is not
limited to the embodiments shown in the drawings but includes all
of embodiments meeting the requirements described in the patent
claims.
First Embodiment
[0032] As shown in the longitudinal cross-sectional view of FIG. 1,
a ring-shaped insert molded article 1 according to a first
embodiment of the present invention is manufactured by injection
molding in a state where a thermoset adhesive is applied to a
joining surface of a ring-shaped insert 2 to a plastic 4 and then
the ring-shaped insert 2 and the plastic 4 are placed in a metal
mold. An adhesive layer 6 intervenes between the ring-shaped insert
2 and the plastic 4.
[0033] In addition, the ring-shaped insert molded article 1 is an
axial magnetic encoder A in which the ring-shaped insert 2 is a
support member and the plastic 4 is a plastic magnet.
[0034] The insert 2 is made of a steel plate and includes a
cylindrical part 2A and an annular part 2B extended radially
outward from, one end edge of the cylindrical part 2A. The
ring-shaped insert 2 is formed by pressing a stainless-steel plate
of 0.6 mm thick, for example.
[0035] The shape of the ring-shaped insert 2 is not limited to that
shown in FIG. 1 as far as it includes at least the cylindrical part
2A and the annular part 2B.
[0036] The plastic 4 is annular in shape so as to be joined to the
annular part 2B of the ring-shaped insert 2. Inner diameter D1 of
the plastic 4 is larger than an inner diameter D2 of the annular
part 2B (inner diameter of the cylindrical part 2A) (D1>D2) so
that no burrs at a gate mark E protrude to the inner diameter side
of the molded article 1. Radial distance G between an inner
peripheral surface F of the plastic 4 and an inner peripheral
surface of the ring-shaped insert 2 (inner peripheral surface of
the annular part 2B) is 0.3 mm or more (G.gtoreq.0.3 mm). Thus, a
difference between the inner diameter D1 of the plastic 4 and the
inner diameter D2 of the annular part 2B is 0.6 mm or more
(D1-D2.gtoreq.0.8 mm) and thickness T1 of the plastic 4 is 0.9 mm,
for example.
[0037] In addition, the plastic 4 is formed by injection molding
such that a disc gate described later is arranged on an inner
peripheral surface F at a position separated from the surface of
the annular part 2B. In the gate-cut state, the gate mark E resides
on the inner peripheral surface F of the plastic 4 at a position
separated from the surface of the annular par 2B, and a distance L1
from the surface of the annular part 2B to the gate mark E is 0.1
mm or more (L1.gtoreq.0.1 mm), so that no foreign, matter resulting
from gate cutting sticks to the surface and no shearing load is
applied by gate cutting to the joining surface between the
ring-shaped insert 2 and the plastic 4 to prevent degradation of
adhesive performance as described later.
[0038] The plastic (plastic magnet) 4 is formed by a magnetic
material containing magnetic substance powder, a binder, and an
additive. The magnetic substance powder may be preferably magnetic
powder based on ferrite such as strontium ferrite or barium
ferrite, or rare-earth magnetic powder based on neodymium or
samarium. The binder may be preferably a thermoplastic resin
material such as polyamides (PA6, PA12, PA612, and the like) or
polyphenylene sulfide (PPS). The additive may be preferably an
organic additive such as carbon fiber, or an inorganic additive
such as glass beads, glass fiber, talc, mica, silicon nitride
(ceramic), or crystalline (non-crystalline) silica.
[0039] Next, an example of injection molding for manufacturing the
ring-shaped insert molded article 1 according to the first
embodiment of the present invention will be described.
[0040] As shown in the longitudinal cross-sectional view of FIG. 2
and the enlarged longitudinal cross-sectional view of major
components of FIG. 3, an injection mold 8 is intended to mold the
ring-shaped insert molded article 1 (axial magnetic encoder A) and
is attached to an injection molding machine by fixing a fixed
attachment plate 9 to a fixed platen with a bolt and fixing a
movable attachment plate 10 to a movable disc with a bolt.
[0041] In a state where a thermoset adhesive is applied to the
joining surface of the ring-shaped insert 2 to the plastic 4 and
then the ring-shaped insert 2 and the plastic 4 are placed in a
fixed mold plate 11 and a movable mold plate 12 and then the mold
plates are clamped, when a molten plastic P is poured into a sprue
13, the molten plastic P flows through a disc gate 15 via a runner
14 and is filled into a cavity C between the fixed mold plate 11
and the movable mold plate 12 (refer also to the enlarged
longitudinal cross-sectional view of major components of FIG.
4(a)).
[0042] The direction of extension of the sprue 13 (in which the
molten plastic P is poured) is horizontal.
[0043] After the molten plastic P is cooled and hardened, as shown
in the enlarged longitudinal cross-sectional view of major
components of FIG. 4(b), the movable mold plate 12 is opened from a
parting line PL and a pre-gate cutting molded article and an insert
core 18A are projected and ejected by ejectors 16 and 17 (refer to
FIGS. 2 and 3), thereby obtaining the pre-gate cutting molded
article and the insert core 18A.
[0044] Next, as shown in the enlarged longitudinal cross-sectional
view of major components of FIG. 4(c), while the pre-gate cutting
molded article and the insert core 18A removed from the metal mold
are set on a jig 20A, the molded article is pressurized by a pusher
21A to cut the gate. Thus, the gate mark E remains on the
ring-shaped insert molded article 1 (axial magnetic encoder A).
[0045] At the gate cutting as shown in FIG. 4(c), the insert core
18A is placed along the gate cutting part of the plastic such that
the insert core 18A serves as a cutting blade to cut the gate by
shearing action. This reduces load on the product at the time of
gate cutting.
[0046] Next, an example of a metal mold structure different from
the insert core type as shown in FIG. 4 will be described.
[0047] The enlarged longitudinal cross-sectional view of major
components of FIG. 5 shows a slide core-type metal mold
structure.
[0048] After the molten plastic P is filled into the cavity C and
then is cooled and hardened as shown in FIG. 5(a), a slide core 19A
is slid radially inward and separated from the molded article as
shown in FIG. 5(b). In this state, the movable mold plate 12 is
opened from the parting line PL and a pre-gate cutting molded
article is projected and ejected by the ejector 16 (refer to FIG.
2), Thus, the pre-gate cutting molded article is obtained.
[0049] Next, as shown in FIG. 5(c), while the pre-gate cutting
molded article removed from the metal mold is set on the jig 20A,
the molded article is pressurized by the pusher 21A to cut the
gate. The gate mark E remains on the ring-shaped insert molded
article 1 (axial magnetic encoder A).
[0050] According to the configuration of the ring-shaped insert
molded article 1 (axial magnetic encoder A) in the first
embodiment, the inner diameter D1 of the annular plastic 4 is
larger than the inner diameter D2 of the annular part 2B of the
ring-shaped insert 2 so that no burrs at the gate mark E protrude
to the inner diameter side of the molded article 1, which thus
eliminates the need for additional work to remove the burrs.
[0051] In addition, in the gate-cut state, the gate mark E resides
on the inner peripheral surface F of the plastic 4 at a position
separated from the surface of the annular part 2B so that no
foreign matter resulting from the gate cutting sticks to the
surface and no shearing load is applied by gate cutting to the
joining surface between the ring-shaped insert 2 and the plastic 4
to prevent deterioration in adhesive performance. This eliminates
the need to perform a post-process for removing the foreign matter
because of absence of the foreign matter on the surface and
prevents degradation of adhesive performance caused by the gate
cutting.
[0052] In addition, in the case where the ring-shaped insert molded
article 1 is an axial magnetic encoder A in which the ring-shaped
insert 2 is a support member, the plastic 4 is a plastic magnet,
the inner diameter D1 of the plastic 4 is 0.6 mm or more larger
than the inner diameter D2 of the annular part 2B, and the gate
mark E resides at a position separated 0.1 mm or more from the
surface of the annular part 2B, and further in the case where the
ring-shaped insert molded article 1 is an axial magnetic encoder A,
it is ensured that the additional work and post-process are not
needed after the gate cutting and degradation of adhesive
performance caused by the gate cutting is prevented.
Second Embodiment
[0053] As shown in the longitudinal cross-sectional view of FIG. 8,
the ring-shaped insert molded article 1 according to a second
embodiment of the present invention is manufactured by injection
molding in a state where a thermoset adhesive is applied to a
joining surface of a ring-shaped insert 3 to a plastic 5 and then
the ring-shaped insert 3 and the plastic 5 are placed in a metal
mold, and the adhesive layer 6 intervenes between the ring-shaped
insert 3 and the plastic 5.
[0054] In addition, the ring-shaped insert molded article 1 is a
radial magnetic encoder B in which the ring-shaped insert 3 is a
support member and the plastic 5 is a plastic magnet.
[0055] The ring-shaped insert 3 is made of a steel plate and
includes a cylindrical part 3A and an annular part 3B extended
radially inward from one end edge of the cylindrical part 3A. The
ring-shaped insert 3 is formed by pressing a stainless-steel plate
of 0.6 mm thick, for example.
[0056] The shape of the ring-shaped insert 3 is not limited to that
shown in FIG. 6 as far as it includes at least the cylindrical part
3A and the annular part 3B.
[0057] The material for the plastic (plastic magnet) 5 is the same
as that in the first embodiment. The plastic 5 is cylindrical in
shape so as to be joined to the outer peripheral surface of the
cylindrical part 3A of the ring-shaped insert 3, and has a curve
part 7 over the annular part 3B. Thickness T2 of the plastic 5 is
0.9 mm, for example.
[0058] In addition, the plastic 5 is injection-molded such that a
disc gate is arranged on the inner peripheral surface F at a
position separated from the surface of the annular part 3B. In the
gate-cut state, the gate mark E resides on the inner peripheral
surface F of the plastic 5 at a position separated from the surface
of the annular part 3B, and a distance L2 from the surface of the
annular part 3B to the gate mark E is 0.1 mm or more (L2.gtoreq.0.1
mm), so that no foreign matter resulting from gate cutting sticks
to the surface and no shearing load is applied by gate cutting to
the joining surface between the ring-shaped insert 3 and the
plastic 5 to prevent degradation of adhesive performance as
described later.
[0059] Next, an example of injection molding for manufacturing the
ring-shaped insert molded article 1 according to the second
embodiment of the present invention will be described.
[0060] The ring-shaped insert molded article 1 (radial magnetic
encoder B) can be manufactured using the same metal mold as the
injection mold 8 shown in FIG. 2. After the molten plastic P is
filled into the cavity C and then is cooled and hardened as shown
in the enlarged longitudinal cross-sectional view of major
components of FIG. 7(a), the movable mold plate 12 is opened from
the parting line PL and a pre-gate cutting molded article and an
insert core 18B are projected and ejected by the ejectors 16 and 17
(refer to FIG. 2), thereby obtaining the pre-gate cutting molded
article and the insert core 18B as shown in the enlarged
longitudinal cross-sectional view of major components of FIG.
7(b).
[0061] Next, as shown in the enlarged longitudinal cross-sectional
view of major components of FIG. 7(c), while the pre-gate cutting
molded article and the insert core 18B removed from the metal mold
are set on a jig 20B, the molded article is pressurized by a pusher
21B to cut the gate. The gate mark E remains on the ring-shaped
insert molded article 1 (radial magnetic encoder B).
[0062] At the gate cutting as shown in FIG. 7(c), the insert core
18B is placed along the gate cutting part of the plastic such that
the insert core 18B serves as a cutting blade to cut the gate by
shearing action. This reduces load on the product at the time of
gate cutting.
[0063] Next, an example of a metal mold structure different from
the insert core type shown in FIG. 7 will be described.
[0064] The enlarged longitudinal cross-sectional view of major
components of FIG. 8 shows a slide core-type metal mold
structure.
[0065] After the molten plastic P is filled into the cavity C and
then is cooled and hardened as shown in FIG. 8(a), a slide core 19B
is slid radially inward and separated from the molded article as
shown in FIG. 8(b). In this state, the movable mold plate 12 is
opened from the parting line PL and a pre-gate cutting molded
article is projected and ejected by the ejector 18 (refer to FIG.
2). Thus, the pre-gate cutting molded article is obtained.
[0066] Next, as shown in FIG. 8(c), while the pre-gate cutting
molded article removed from the metal mold is set on the jig 20B,
the molded article is pressurized by the pusher 21B to cut the
gate. The gate mark E remains on the ring-shaped insert molded
article 1 (radial magnetic encoder B).
[0067] According to the configuration of the ring-shaped insert
molded article 1 (radial magnetic encoder B) in the second
embodiment, the inner diameter of the curve part 7 of the
cylindrical plastic 5 is sufficiently larger than the inner
diameter of the annular part 3B of the ring-shaped insert 3, and
thus no burrs at the gate mark E protrude to the inner diameter
side of the molded article 1, which thus eliminates the need for
additional work to remove the burrs.
[0068] In addition, in the gate-cut state, the gate mark E resides
on the inner peripheral surface F of the plastic 5 at a position
separated from the surface of the annular part 3B so that no
foreign matter resulting from the gate cutting sticks to the
surface and no shearing load is applied by gate cutting to the
joining surface between the ring-shaped insert 3 and the plastic 5
to prevent deterioration in adhesive performance. This eliminates
the need to perform a post-process for removing the foreign matter
because of absence of the foreign matter on the surface and
prevents degradation of adhesive performance caused by the gate
cutting.
[0069] In addition, in the case where the ring-shaped insert molded
article 1 is a radial magnetic encoder B in which the ring-shaped
insert 3 is a support member, the plastic 5 is a plastic magnet,
and the gate mark E resides at a position separated 0.1 mm or more
from the surface of the annular part 3B, and further in the case
where the ring-shaped insert molded article 1 is a radial magnetic
encoder B, it is ensured that the additional work and post-process
are not needed after the gate cutting and degradation of adhesive
performance caused by the gate cutting is prevented.
[0070] In the foregoing descriptions, the ring-shaped insert molded
article is an axial magnetic encoder or a radial magnetic encoder.
However, the ring-shaped insert molded article of the present,
invention is not limited to them but can be manufactured in any
manner by injection molding in the state where a thermoset adhesive
is applied to the joining surface of the ring-shaped insert to the
plastic and then the insert and the plastic are placed in the metal
mold, such as an insert molded article with replacement of a
ring-shaped metal.
[0071] In addition, the ring-shaped molded article of the present
invention is configured such that, in the gate-cut state, the gate
mark resides on the inner peripheral surface of the plastic at a
position separated from the surface of the annular part so that no
foreign matter resulting from the gate cutting sticks to the
surface and no shearing load is applied by gate cutting to the
joining surface between the insert and the plastic to prevent
deterioration in adhesive performance. This eliminates the need to
perform the post-process for removing the foreign matter because of
absence of the foreign matter on the surface and prevents
degradation of adhesive performance caused by the gate cutting.
Besides, no burrs at the gate mark protrude to the inner diameter
side of the molded article, which thus eliminates the need for
additional work to remove the burrs. However, the process for
removing the burrs may be performed on the ring-shaped insert
molded article, depending on the specifications for the ring-shaped
insert molded article.
REFERENCE SIGNS LIST
[0072] A Axial magnetic encoder [0073] B Radial magnetic encoder
[0074] C Cavity [0075] D1 Inner diameter of plastic [0076] D2 Inner
diameter of annular part [0077] E Gate mark [0078] F Inner
peripheral surface of plastic [0079] G Radial distance between
inner peripheral surface of plastic and inner peripheral surface of
insert [0080] L1, L2 Distance from surface of annular part to gate
mark [0081] P Molten plastic [0082] PL Parting line [0083] T1, T2
Thickness [0084] 1 Ring-shaped insert molded article [0085] 2, 3
Ring-shaped insert [0086] 2A, 3A Cylindrical part [0087] 2B, 3B
Annular part [0088] 4, 5 Plastic [0089] 6 Adhesive layer [0090] 7
Curve part [0091] 8 Injection mold [0092] 9 Fixed attachment plate
[0093] 10 Movable attachment plate [0094] 11 Fixed mold plate
[0095] 12 Movable mold plate [0096] 13 Sprue [0097] 14 Runner
[0098] 15 Disc gate [0099] 16, 17 Ejector [0100] 18A, 18B Insert
core [0101] 19A, 19B Slide core [0102] 20A, 20B Jig [0103] 21A, 21B
Pusher
* * * * *