U.S. patent application number 10/132146 was filed with the patent office on 2002-11-21 for electromagnetic actuator.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Asano, Masahiko, Hattori, Hiroyuki, Iida, Tatsuo, Izuo, Takashi, Sakuragi, Takeshi.
Application Number | 20020170512 10/132146 |
Document ID | / |
Family ID | 18995635 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020170512 |
Kind Code |
A1 |
Izuo, Takashi ; et
al. |
November 21, 2002 |
Electromagnetic actuator
Abstract
An electromagnetic actuator includes a pair of core assemblies
and a spacer. An armature is provided between the pair of core
assemblies. The spacer is molded to be integral with a coil
provided in electromagnets of the core assemblies. The spacer is
located between the electromagnets. A relative position of the pair
of electromagnets with respect to each other can be determined by
the size of the spacer. A space that allows the armature to
reciprocate is securely defined by the spacer located between the
core assemblies.
Inventors: |
Izuo, Takashi; (Toyota-shi,
JP) ; Asano, Masahiko; (Toyota-shi, JP) ;
Iida, Tatsuo; (Anjo-shi, JP) ; Hattori, Hiroyuki;
(Toyota-shi, JP) ; Sakuragi, Takeshi; (Toyota-shi,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
18995635 |
Appl. No.: |
10/132146 |
Filed: |
April 26, 2002 |
Current U.S.
Class: |
123/90.11 |
Current CPC
Class: |
H01F 7/127 20130101;
H01F 7/1638 20130101; F01L 9/20 20210101 |
Class at
Publication: |
123/90.11 |
International
Class: |
F01L 009/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 21, 2001 |
JP |
2001-150651 |
Claims
What is claimed is:
1. An electromagnetic actuator comprising: an armature that
reciprocates along an axis; a pair of electromagnets, each having a
coil, the pair of electromagnets provided along the axis and on
opposite sides of the armature; and a spacer formed by molding to
be integral with the coil and located between the pair of
electromagnets, the spacer secures a space for the armature to
reciprocate along the axis.
2. The electromagnetic actuator according to claim 1, wherein the
electromagnetic actuator has at least two of the spacers.
3. The electromagnetic actuator according to claim 2, wherein the
spacers are located on opposite sides of the armature as viewed in
a direction perpendicular to the axis.
4. The electromagnetic actuator according claim 1, wherein a noise
absorbing material is provided between a first surface defined by
at least one of the spacer and the coil opposite to a side adjacent
to the armature and a second surface defined matingly opposite to
the first surface.
5. The electromagnetic actuator according claim 4, wherein the
noise absorbing material is provided at least one of the spacer and
the coil.
6. The electromagnetic actuator according to claim 4, wherein the
noise absorbing material comprises a foam metal.
7. The electromagnetic actuator according to claim 1, wherein a
surface of the armature is hardened by a surface-hardening
treatment.
8. The electromagnetic actuator according claim 1, wherein the
electromagnetic actuator is provided in an internal combustion
engine to drive a valve body of an intake valve.
9. The electromagnetic actuator according claim 1, wherein the
electromagnetic actuator is provided in an internal combustion
engine to drive a valve body of an exhaust valve.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2001-150651 filed on May 21, 2001, including the specification,
drawings and abstract is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The invention relates to an electromagnetic actuator.
[0004] 2. Description of Related Art
[0005] It has been suggested that an electromagnetic actuator can
be used to open and close intake and exhaust valves in an internal
combustion engine.
[0006] Conventionally, the electromagnetic actuator includes an
armature, which moves integrally with a valve body, and a pair of
core assemblies (electromagnets), between which the armature is
provided. These core assemblies provide a coil and a core that
retains the coil. These core assemblies exert an electromagnetic
attraction on the armature as an electromagnet. When the pair of
core assemblies alternatively exert the electromagnetic attraction
on the armature, the armature reciprocates so that the
electromagnetic actuator is driven and the intake and exhaust
valves in an internal combustion engine are opened and closed.
[0007] In the above-described electromagnetic actuator, it is
necessary that a space be secured for the armature to reciprocate
between the pair of core assemblies. Therefore, it is conceivable
that a spacer is used to secure the space for the armature to
reciprocate like an electromagnetic actuator according to a
Laid-Open Japanese patent Publication No. JP 11-260638.
[0008] FIG. 4 is a side cross-sectional view showing the
arrangement of the spacer and the core assemblies of the
electromagnetic actuator according to JP-A-11-260638. The
conventional structure shown in FIG. 4 illustrates the space
required for the armature to move by the spacer.
[0009] As shown in FIG. 4, a pair of core assemblies 102 are
provided on both sides of the moving directions of an armature 101
(e.g., as shown by the up and down direction in FIG. 4). A
horizontal hole 103 is formed and extends along the width direction
of each core assembly 102 (e.g., as shown by the right and left
direction in FIG. 4). Spacers 104 are provided on both sides of the
pair of core assemblies 102 along the width direction. At each
location corresponding to one of the horizontal holes 103, a pin
hole 105 is provided in the spacer 104. A constant distance between
the pair of core assemblies 102 is maintained by the spacers 104.
Pins 106 are inserted into the pin holes 105 aligned with the
horizontal holes 103 to ensure the constant distance.
[0010] If the pins 106 are inserted into the pin holes 105 and the
horizontal holes 103 inaccurately, relative positions between the
pair of core assemblies 102 deviate from appropriate positions. For
example, the relative positions deviate in the reciprocating
directions of the armature 101. As a result, an appropriate size of
space for the armature 101 to move between the core assemblies 102
cannot be maintained and maximum displacement of the armature 101
will deviate from appropriate values. If the armature 101 contacts
one of the core assemblies 102 as the armature 101 reciprocates, an
impact generated from the contact is translated among the
horizontal hole 103, the pin holes 105, and the pin 106. Therefore,
if the pin 106 is inserted into the pin holes 105 and the
horizontal hole 103 inaccurately, a contact force between the
armature 101 and one of the core assemblies 102 deviates in the
reciprocating direction of the armature 101 due to the impact. As a
result, there is a great chance that the relative position of the
core assemblies 102, with respect to a neutral position of the
armature 101, will deviate from the appropriate values by many
degrees.
[0011] Furthermore, in addition to requiring spacers 104, the pin
106 must be inserted into each core assembly 102 in order to secure
the space for the armature 101 to move by inserting the pin 106
into the horizontal hole 103 and the pin holes 105. As a result, an
increase in the number of components is necessary.
SUMMARY OF THE INVENTION
[0012] It is an object of the invention to provide an
electromagnetic actuator to prevent a deviation of the relative
positions of a pair of electromagnets with respect to a neutral
position of an armature from an appropriate position and to change
a maximum displacement of the armature without increasing the
number of components parts.
[0013] A first aspect of the invention relates to an
electromagnetic actuator. The electromagnetic actuator reciprocates
an armature between a pair of electromagnets by an electromagnetic
attraction. The pair of electromagnets is provided in both sides of
the moving path direction of the armature with a coil being
provided inside the pair of electromagnets. In the electromagnetic
actuator described above, a spacer is formed by molding to be
integral with a coil and is located between the pair of
electromagnets. The spacer secures a space for the armature to
reciprocate.
[0014] According to the above-described structure of the
electromagnetic actuator, the spacer, which determines relative
positions of a pair of the electromagnets to the neutral position
of the armature, does not deviate in the reciprocating directions
of the armature since the spacer is located between the
electromagnets. The spacer is formed by molding to be integral with
the coil, so that the number of components is not increased.
Therefore, deviation of the relative position of the pair of core
assemblies to the neutral position of the armature from the
appropriate position and to change a maximum displacement of the
armature can be prevented without increasing the number of
components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The foregoing and further objects, features and advantages
of the invention will become apparent from the following
description of exemplary embodiments with reference to the
accompanying drawings, wherein like numerals are used to represent
like elements and wherein:
[0016] FIG. 1 is a cross-sectional view of an electromagnetically
driven valve applied by an electromagnetic actuator according to an
exemplary embodiment of the invention;
[0017] FIG. 2 is an exploded perspective view which shows an
interior structure of the electromagnetic actuator;
[0018] FIG. 3 is a schematic view of a modified embodiment of a
shape of a coil unit according to the exemplary embodiment; and
[0019] FIG. 4 is a side cross-sectional view illustrating a
structure for securing a space for an electromagnetic actuator to
move with a spacer.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0020] The following is an explanation of an exemplary embodiment
of the invention applying an electromagnetic actuator to an
electromagnetically driven valve as an intake valve or an exhaust
valve in an internal combustion engine.
[0021] FIG. 1 shows an electromagnetically driven valve 1 having a
valve body 4 which opens and closes a port 3 connected to a
combustion chamber 2, a valve shaft 6 which projects from the valve
body 4 and is reciprocatingly supported by a cylinder head 5 . An
electromagnetic actuator 7 reciprocates the valve shaft 6. The port
3 is opened and closed when the valve body 4 seats to and moves
away from a valve seat 3a as the valve shaft 6 reciprocates.
[0022] A lower retainer 8 is provided at an opposite end to the
valve body 4 side end of the valve shaft 6. A lower spring 9 is
compressed and provided between the lower retainer 8 and the
cylinder head 5. The valve body 4 and the valve shaft 6 are biased
in the direction of closing the valve (e.g., upwardly as shown in
FIG. 1) by the lower spring 9.
[0023] The electromagnetic actuator 7 includes an armature shaft 10
which is provided along the same axis as the valve shaft 6, an
armature 11 which is plate-shaped and contains a material with high
magnetic permeability, and a pair of core assemblies 12a and 12b
which are provided on both sides of a thickness direction of the
armature 11. The armature 11 is fixed at approximately the center
of the armature shaft 10. An upper cap 14 is provided on top of the
core assembly 12a. An adjustment bolt 29 is screwed into and out of
the upper cap 14 to adjust a neutral position of the armature 11.
Furthermore, the upper cap 14 and the pair of core assemblies 12a
and 12b are fixed by pins 15, which extends parallel to the
armature shaft 10, and a bolt 16. The upper cap 14 and the pair of
core assemblies 12a and 12b are located at orthogonal angles to the
armature shaft 10.
[0024] The armature shaft 10 penetrates through the pair of core
assemblies 12a and 12b. One end (e.g., the lower end as shown in
FIG. 1) of the armature shaft 10 is contacted with the lower
retainer 8 side end of the valve shaft 6. An upper retainer 13 is
fixed on the other end of the armature shaft 10. An upper spring 17
is compressed and provided between the upper retainer 13 and the
upper cap 14. The armature shaft 10 is biased on the side of the
valve shaft 6 by the upper spring 17. The valve shaft 6 and the
valve body 4 are biased in the direction of opening the valve
(e.g., downwardly as shown in FIG. 1) by the biased armature
10.
[0025] A core 18 which contains a material with high magnetic
permeability and a coil unit 19 retained by the core 18 are
provided in the pair of core assemblies 12a and 12b. A coil 20 is
embedded in the coil unit 19. The core assemblies 12a and 12b work
as an electromagnet by conducting electricity to the coil 20 and
exert electromagnetic attraction on the armature 11. In this
connection, the core 18, a core block 22, and a coil part 23
(mentioned later) as an electromagnet according to the exemplary
embodiment. Therefore, the core 18, a core block 22, and the coil
part 23 are called electromagnets 30a and 30b according to the
exemplary embodiment. The electromagnet 30a is side of the core
assembly 12a and the electromagnet 30b is side of the core assembly
12b. As the armature shaft 10 and the armature 11 reciprocate in
the direction along the axis of the valve shaft 6, the valve body 4
opens and closes by controlling electricity conduction to the two
coils 20 located on both sides of the core assemblies 12a and 12b
and by alternately exerting electromagnetic attraction from the
core assemblies 12a and 12b on the armature 11.
[0026] The surface of the armature 11 is treated to improve
anti-abrasion. In other words, anti-abrasion improvement of the
surface of the armature 11 is carried out by colliding metal
particles with the surface of the armature 11 at a high speed by
air to increase the hardness of the surface. Therefore, when the
armature 11 comes into contact with the core assemblies 12a and
12b, and as the armature 11 reciprocates, abrasion of the armature
11 can be restrained.
[0027] FIG. 2 is an exploded perspective view which shows an
interior structure of an electromagnetic actuator 7. The core
assemblies 12a and 12b are arranged symmetrically from the armature
11. The two core assemblies 12a and 12b are identical except for
their arrangement and working timing such that only the core
assembly 12b is referred to hereafter.
[0028] As shown in FIG. 2, in addition to the core 18 and the coil
unit 19, the core assembly 12b includes a core plate 21 with which
the core 18 contacts, and a pair of core blocks 22. The pair of
core blocks 22 contact the core plate 21 and is provided in a way
such that the core 18 is located between the core blocks 22.
[0029] The coil unit 19 having an annular shape includes a coil
part 23 into which the coil 20 (e.g., shown in FIG. 1) is embedded,
and a pair of spacers 24 which is formed integrally with the coil
part 23 at the outer margins of and on top of the coil part 23
(e.g., as shown in FIG. 2). The coil part 23 is molded out of a
thermoplastic resin to be integral with the coil 20. The spacers 24
are also molded out of thermoplastic to be integral with the coil
20. On a side opposite to the armature 11 (the under-side of the
coil part 23 and the spacers 24, e.g., as shown in FIG. 2), the
coil unit 19 has a noise absorbing material 25 attached, which is a
sheet-shape and contains a foam metal such as a foam cast iron.
[0030] A retaining groove 26 with an annular shape, which houses
the coil part 23, is formed in the core 18 and the core blocks 22.
The coil unit 19 is matingly fixed on the core 18 and the core
blocks 22 by inserting the coil part 23 into the retaining groove
26. The spacers 24 are located above the core blocks 22 as shown in
FIG. 2. The noise absorbing material 25 attached on the coil unit
19 is located between two groups. One group comprises the coil part
23 and the spacers 24. The other group comprises the core 18 and
the core blocks 22.
[0031] Pin holes 27, through which pins 15 penetrate, and bolt
holes 28 into which bolts 16 are screwed, are formed in the spacers
24, core blocks 22, and the core plate 21. The pins 15 and the
bolts 16 are shown in FIG. 1. The core assemblies 12a and 12b are
fixed to meet at least the following two requirements. The first
requirement is that the armature 11 is arranged between the core
assemblies 12a and 12b. The second requirement is that the spacers
24 on both sides of the core assembly 12a and 12b are contacted
together. This arrangement is fixed by tightening the bolts 16
screwed into the bolt holes 28 after inserting the pins 15 into the
pin holes 27.
[0032] As described above, when the core assemblies 12a and 12b are
fixed, the spacers 24 are located on both sides of the armature 11
(along the moving path of the armature shaft 10) and between the
electromagnet 30a of the core assembly 12a and the electromagnet
30b of the core assembly 12b. The relative position of the
electromagnets 30a and 30b to the neutral position of the armature
11 is determined by the spacers 24. A space 11a for the armature 11
to reciprocate between the core assemblies 12a and 12b is secured.
Maximum displacement of the armature 11 is determined in proportion
to the length of moving direction of the armature 11 in the space
11a.
[0033] According to the exemplary embodiment described above, the
following characteristics can be obtained. The spacers 24, for
determining the relative positions of the electromagnets 30a and
30b to the neutral position of the armature 11, are located between
the electromagnets 30a and 30b. Therefore, the spacers 24 do not
deviate in the reciprocating direction of the armature 11 (e.g., in
the direction of the axis of the armature shaft 10). The spacers 24
are formed by molding to be integral with the coils 20 as the coil
unit 19. Therefore, the number of components of the electromagnetic
actuator 7 are few and is not increased. Furthermore, deviation of
the relative position of the electromagnets 30a and 30b from the
neutral position of the armature 11 from an appropriate position
can be prevented. Change in the maximum displacement of the
armature 11 accompanied by the above-mentioned deviation can also
be prevented.
[0034] The spacers 24 are located on opposite sides of the armature
11 as viewed in a direction perpendicular to the moving direction
of the armature 11. Because of the above-described relation of the
positions among the spacers 24 and the armature 11, the spacers 24
are located between the electromagnets 30a and 30b. Both
electromagnets 30a and 30b are located along the axis of the
armature shaft 10. Therefore, the position of the electromagnets
30a and 30b relative to the neutral position of the armature 11 can
be determined by the spacers 24 appropriately and the maximum
displacement of the armature 11 can be maintained within an
appropriate value with greater certainty.
[0035] The level of contact noise caused by contacting the armature
11 with the core assemblies 12a and 12b, as the armature 11
reciprocates, can be lowered by the noise absorbing materials 25
located between the two groups of components. As mentioned before,
one group comprises the coil part 23 and the spacers 24. The other
group comprises the core 18 and the core blocks 22.
[0036] The exemplary embodiment may be modified as follows.
[0037] According to the exemplary embodiment, two of the spacers 24
are provided at each coil unit 19. On the other hand, as shown in
FIG. 3, for example, each spacer 24 may be provided at each coil
unit 19. And the two coil units 19 may be installed in the
electromagnetic actuator in the way that spacers 24 of coil units
19 are located on opposite sides of the armature 11 as viewed in a
direction perpendicular to the moving direction of the armature
11.
[0038] According to the exemplary embodiment, the noise absorbing
material 25 is attached to the coil part 23 and the spacers 24 on
the side opposite to the armature 11 (e.g., the under-side of the
coil part 23 and the spacers 24 as shown in FIG. 2). In the
alternative, the noise absorbing material 25 may be attached either
on the coil part 23 or the spacers 24.
[0039] The noise absorbing material 25 is optional and can be
omitted to reduce the number of components. The electromagnetic
actuator 7 may be applied to structures other than an engine
valve.
[0040] While the invention has been described with reference to the
exemplary embodiments thereof, it is to be understood that the
invention is not limited to the exemplary embodiments or
constructions. To the contrary, the invention is intended to cover
various modifications and equivalent arrangements. In addition,
while the various elements of the exemplary embodiments are shown
in various combinations and configurations, which are exemplary,
other combinations and configurations, including more, less or only
a single element, are also within the spirit and scope of the
invention.
* * * * *