U.S. patent application number 09/934577 was filed with the patent office on 2001-12-27 for exhaust gas recirculation valve device.
This patent application is currently assigned to MITSUBISHI DENKI KABUSHIKI KAISHA. Invention is credited to Ikai, Takeshi, Kato, Yasuhiko, Yokoyama, Hisashi.
Application Number | 20010054417 09/934577 |
Document ID | / |
Family ID | 14237694 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010054417 |
Kind Code |
A1 |
Kato, Yasuhiko ; et
al. |
December 27, 2001 |
Exhaust gas recirculation valve device
Abstract
An exhaust gas recirculation valve device is provided with a
motor shaft, a stepping motor main body driving the motor shaft, a
valve shaft having a tip functioning as a proximal end which faces
one end of the motor shaft and a distal end provided with a valve,
a spring pushing the valve shaft in a closing direction, and a
spring holder retaining the spring. In the case that the valve is
closed, the tip of the valve shaft and the spring holder are
caulked together at a distance between the tip of the valve shaft
and the one end of the motor shaft so that a distance between the
facing ends of the motor shaft and the valve shaft is equivalent to
a difference between a stroke of the motor shaft of the stepping
motor main body and a stroke of the valve on opening.
Inventors: |
Kato, Yasuhiko; (Tokyo,
JP) ; Yokoyama, Hisashi; (Tokyo, JP) ; Ikai,
Takeshi; (Tokyo, JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037
US
|
Assignee: |
MITSUBISHI DENKI KABUSHIKI
KAISHA
|
Family ID: |
14237694 |
Appl. No.: |
09/934577 |
Filed: |
August 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09934577 |
Aug 23, 2001 |
|
|
|
PCT/JP99/07293 |
Dec 24, 1999 |
|
|
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Current U.S.
Class: |
123/568.23 ;
251/129.11 |
Current CPC
Class: |
F02M 26/54 20160201;
F16K 31/04 20130101; F02M 26/67 20160201 |
Class at
Publication: |
123/568.23 ;
251/129.11 |
International
Class: |
F02M 025/07 |
Claims
What is claimed is:
1. An exhaust gas recirculation valve device, comprising: a first
shaft arranged reciprocally in an axial direction; a driving means
driving the first shaft; a second shaft having a proximal end which
faces one end of the first shaft and a distal end provided with a
valve; a pushing means pushing the second shaft in a closing
direction; and a retaining means retaining the pushing means,
wherein a length of the second shaft subjected to a caulking
processing with respect to the retaining means is determined so
that a distance between the facing ends of the first and second
shafts is equivalent to a specific value with the valve
closure.
2. An exhaust gas recirculation valve device according to claim 1,
wherein the driving means is a stepping motor.
3. An exhaust gas recirculation valve device according to claim 1,
wherein the second shaft has a central hole extending from the
proximal end to the vicinity of the retaining means.
4. An exhaust gas recirculation valve device according to claim 2,
wherein the second shaft has a central hole extending from the
proximal end to the vicinity of the retaining means.
5. An exhaust gas recirculation valve device according to claim 1,
wherein the proximal end of the second shaft includes a caulking
fixation section and a height-adjustment section formed at a bottom
of the caulking fixation section and formed its diameter smaller
than the caulking fixation section.
6. An exhaust gas recirculation valve device according to claim 2,
wherein the proximal end of the second shaft includes a caulking
fixation section and a height-adjustment section formed at a bottom
of the caulking fixation section.
Description
CROSS-REFERENCE TO THE RELATED APPLICATION
[0001] This application is a continuation of International
Application No. PCT/JP99/07293, whose international filing date is
Dec. 24, 1999, the disclosure of which Application are incorporated
by reference herein. The present application has not published in
English.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an exhaust gas
recirculation valve device disposed in an exhaust gas recirculation
passage of an internal combustion engine for example of an
automobile.
[0004] 2. Prior Art 1.
[0005] FIG. 1 is a cross sectional figure showing the internal
structure of a conventional exhaust gas recirculation valve device.
In the figure, the valve housing 1 has an input port 2
communicating with an exhaust system (not shown) of an engine which
is an internal combustion engine, an output port 3 communicating
with an air intake system (not shown) of the engine and a passage 4
interposed between the output port 3 and the input port 2. A valve
seat 5 is press fitted into the passage 4. 6 is a valve rod passing
through a bush 7. A valve 8 is mounted on the lower end of the
valve rod 6 to abut or separate with the valve seat 5. 9 is a
spring holder pushed upwardly by a coil spring 10. A through hole
11 is formed in the central section of the spring holder 9. A tip
6a of the valve rod 6 is fixed by caulking through the through hole
11. The valve rod 6 and the spring holder 9 are integrated by such
a caulking and the valve 8 mounted on the lower end of the valve
rod 6 is normally pushed in a closed positioning with respect to
the valve seat 5 by the coil spring 10. 12 is a cooling water
passage cooling the valve body and the motor to be described
below.
[0006] 20 is a stepping motor main body, and is mounted on the top
section of the valve housing 1 so that the axial centers are
aligned by a mounting screw 21. 22 is a motor housing, 23 is a
motor holder disposed concentrically between the motor housing 22
and the valve housing 1. 24 are bobbins which are wound coils 25.26
and 27 are yokes. A magnetic path is formed through the outer
periphery of the yokes 26 and 27. 28 is a terminal which is
electrically connected to the coils 25. The terminal 28 and the
motor housing 22 form a connector. 29 is a plate which shields the
two coil sections magnetically. 30 is a magnet. 31 is a rotor
retaining the magnet 30. The rotor 31 has a threaded section 31a
threadably attached to a threaded section 32a of the motor shaft
32. 33 is a bushing mounted on the upper end of the rotor 31. 34 is
a ball supported by the bushing 33. 35 is an adjustment plate, and
36 is a ball bearing mounted at the lower end of the rotor 31.
[0007] In the case that the valve housing 1 and the motor housing
22 above are assembled so that the axial centers are aligned by the
mounting screw 21, an upper face of the tip 6a of the valve rod 6
near the valve housing 1 is set to oppose a lower face of the motor
shaft 32 near the motor housing 22 at a required distance from the
tip 6a.
[0008] The operation of the invention will be described below.
[0009] Firstly, when the engine is started and the valve is
completely closed, the rotor 31 which contains a magnet 30 rotates
in a stepwise manner in a direction of valve opening due to a
pulsed voltage sent from the control unit (not shown) to the
terminal 28 during the valve opening operation. The stepwise
rotation is converted into linear motion by the threaded section
31a of the rotor 31 and the threaded section 32a of the motor shaft
32 and the motor shaft 32 displaces in a direction of valve opening
(downwardly). As the displacement continues, at the moment when the
upper face of the tip 6a of the valve rod 6 near the valve housing
1 touches to the lower face of the motor shaft 32 near the motor
housing 22, the valve rod 6 is depressed by the drive force of the
motor shaft 32 against the pushing upward force of the spring 10.
Also the valve 8 which is mounted on the lower section of the valve
rod 6 is lowered and opens with respect to the valve seat 5 and the
input port 2 and the output port 3 are connected by the passage
4.
[0010] During the valve closure operation, the rotor 31 which
contains a magnet 30 rotates in a stepwise manner in a direction of
valve closure due to a pulsed voltage sent from the control unit
(not shown) to the terminal 28 in an operation which is the
opposite of the above. The motor shaft 32 displaces in a direction
of valve closure (upwardly) due to the rotation. In addition to the
rotation, the valve rod 6 is raised by the upward pushing force of
the spring 10 and the valve 8 shuts the passage between the valve 8
and the valve seat 5.
[0011] It is noted that in the above exhaust gas recirculation
valve device which uses a stepping motor, when a valve opening step
varies, the rate of exhaust gas flow also varies. Therefore, in
order to pass a target flow rate of the exhaust gas, the valve
opening step must be constant. The valve opening step is determined
by a distance L between the tip 6a of the valve rod 6 and the lower
face of the motor shaft 22. However, the distance L depends on the
accuracy of dimension of parts such as bushing 33 and the ball 34,
which are disposed on the upper section of the motor shaft 32.
Therefore, the distance L, which is defined between the tip 6a of
the valve rod 6 and the lower face of the motor shaft 22, must be
adjusted when the valve housing 1 and the motor housing 22 do
assembly about every exhaust gas recirculation valve device.
[0012] According to the conventional adjustment method, firstly a
distance L1 between the upper face of the tip 6a of the valve rod 6
and the upper face of the valve housing 1 and a distance L2 between
the lower face of the motor shaft 32 and the lower face of the
motor housing 22 are measured. In order to determine an appropriate
distance L, a stroke of the motor shaft 32 is then considered to
calculate an adjustment thickness L3. The adjustment plate 35
having a thickness corresponding to the adjustment thickness L3 is
interposed between the both abutting sections of the valve housing
1 and the motor housing 22 to adjust the distance L so as to be
constant. In other words, with the conventional adjustment method,
since the distance L satisfies an equation of L=(L1-L2)+L3 and the
distances L1 and L2 vary in all products, the distance L is
adjusted by varying the adjustment thickness L3.
[0013] However, since the conventional exhaust gas recirculation
valve device is constituted as described above, when one kind of
metallic plate functioning as the adjustment plate 35 having a
thickness of 0.1 mm, for example, is prepared, there are occasions
when many metallic plates must be interposed there-between. This
results in the manufacturing costs being raised. Therefore, in
order to reduce the number of metallic plates interposed
there-between, various kinds of metallic plate which function as an
adjustment plate 35 are prepared with a thickness varying from 0.1
mm to 0.5 mm in increments of 0.1 mm. Therefore the use of the
plates differs as a result of this processing. As a result, there
are problems in time and effort with respect to the
stock-control.
[0014] 3. Prior Art 2.
[0015] JP-A-1997/256916 discloses an exhaust gas recirculation
valve including a seat valve for opening/closing an exhaust gas
circulation passage, and a valve actuator moving a valve body of
the seat valve in a forward or backward direction to open/close the
passage above. With the exhaust gas recirculation valve, seat parts
with a variety of thicknesses are disposed between a valve shaft of
the seat valve and a central piston of the valve actuator. Thus,
the axial variations in component dimensions are absorbed in order
to control a stroke of the valve on opening.
[0016] However, with the exhaust gas recirculation valve, the seat
parts for adjustment of thicknesses are also used, and the axial
variations in component dimensions of the valve shaft and so on,
are absorbed in a like manner of the prior art 1. Since the seat
parts prepared have a variety of thicknesses, there are problems
with respect to increases in manufacturing costs and in the time
and effort expended in stock control.
[0017] The present invention is made to resolve the problems above,
and it is an object of the present invention to provide an exhaust
gas recirculation valve device controlling a valve open timing with
high accuracy without using the adjustment plates or the seat
parts.
SUMMARY OF THE INVENTION
[0018] The exhaust gas recirculation valve device according to the
present invention includes a first shaft arranged reciprocally in
an axial direction, a driving means driving the first shaft, a
second shaft having a proximal end which faces one end of the first
shaft and a distal end provided with a valve, a pushing means
pushing the second shaft in a closing direction, and a retaining
means retaining the pushing means. Here, in the exhaust
recirculation valve, a caulking length of the second shaft is
determined to fix the retaining means so that a distance between
the facing ends of the first and second shafts is equivalent to a
specific value with the valve closure. In this way, it is not
necessary to use the adjustment plates or the seat parts which have
been used conventionally to control the distance and thus it is
possible to simplify stock-control and to reduce the manufacturing
costs of the exhaust gas recirculation valve device. It is also
possible to perform flexibly stepless control of the distance and
thus it is possible to control a valve open timing with high
accuracy.
[0019] With the exhaust gas recirculation valve device, the driving
means is a stepping motor. In this way, it is possible to absorb
effectively the distance between the facing ends of the first and
second shafts due to a single working step of determining the
amount of caulking of the second shaft.
[0020] With the exhaust gas recirculation valve device, the second
shaft has a central hole extending from the proximal end to the
vicinity of the retaining means. In this way, it is possible to
reduce the volume of the caulking fixation section in the second
shaft and thus it is possible to shorten the time required in order
to fix the second shaft with caulking.
[0021] With the exhaust gas recirculation valve device, the
proximal end of the second shaft includes a caulking fixation
section and a height-adjustment section formed at a top of the
caulking fixation section and formed its diameter smaller than the
caulking fixation section. In this way, it is possible to ensure a
sufficient caulking force of the second shaft with respect to the
retaining means due to the caulking fixation section. It is also
possible to ensure a sufficient height of the proximal end of the
second shaft after caulking-with respect to the retaining means due
to the height-adjustment section and thus it is easy to control the
distance above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a cross sectional figure showing the internal
structure of an exhaust gas recirculation valve device according to
the prior art 1.
[0023] FIG. 2 is a cross sectional figure showing the internal
structure of an exhaust gas recirculation valve device according to
a first embodiment of the present invention.
[0024] FIG. 3A and FIG. 3B are enlarged views showing a caulking
section of a valve shaft in the exhaust gas recirculation valve
device of FIG. 2, FIG. 3A is a plan view, and FIG. 3B is a front
view.
[0025] FIG. 4A and FIG. 4B are enlarged views showing a caulking
section of a valve shaft in an exhaust gas recirculation valve
device according to a second embodiment of the present invention,
FIG. 4A is a plan view, and FIG. 4B is a front view.
[0026] FIG. 5 is an enlarged view showing a caulking section of a
valve shaft in an exhaust gas recirculation valve device according
to a third embodiment of the present invention.
PREFERRED EMBODIMENTS OF THE INVENTION
[0027] In order to describe the invention in greater detail, the
preferred embodiments will be outlined below with reference to the
accompanying figures.
[0028] Embodiment 1
[0029] FIG. 2 is a cross sectional figure showing the internal
structure of an exhaust gas recirculation valve device according to
a first embodiment of the present invention. FIG. 3A and FIG. 3B
are enlarged views showing a caulking section of a valve shaft in
the exhaust gas recirculation valve device of FIG. 2, FIG. 3A is a
plan view, and FIG. 3B is a front view. Those components of the
first embodiment of the present invention which are the same as
those of the conventional exhaust gas recirculation valve device as
shown in FIG. 1 are denoted by the same reference numerals and
further description will be omitted.
[0030] With the embodiment 1, as shown in FIG. 3A and FIG. 3B, the
tip (made in a solid line) 6a, which is a proximal end of the valve
rod 6 acting as the second shaft, is formed as a cylindrical solid
section. The tip 6a of the valve rod 6 is inserted into the through
hole 11 of the spring holder 9. A shoulder section 6b is caulked
and fixed to the spring holder 9 with a state that the shoulder
section 6b abuts with a lower face 9a of the spring holder 9 which
is arranged around the through hole 11. A height of the tip 6a
after caulked and fixed to an upper face 9b of the spring holder 9
is set so that the distance L, which is defined between a lower end
of the motor shaft 32 acting as the first shaft and an upper end of
the tip (made in a broken line) 6a of the valve shaft 6 after
caulked, is equivalent to a difference between a stroke of the
motor shaft 32 of the stepping motor main body 20 acting as the
driving means and a stroke of the valve 8 on opening when the motor
housing 22 is mounted on the valve housing 1 so that the axial
centers are aligned by the mounting screw 21. In this way, it is
not necessary to prepare the adjustment plates 35 or the seat
parts, which have been used conventionally for controlling the
distance L, and thus it is possible to simplify the stock-control
and to reduce the manufacturing costs of the exhaust gas
recirculation valve device. It is also possible to perform flexibly
stepless control of the distance and thus it is possible to control
a valve open timing with ease and high accuracy without using the
adjustment plates 35 or the seat parts.
[0031] As shown above, according to the embodiment 1, it is not
necessary to prepare the adjustment plates 35 or the seat parts,
which have been used conventionally for controlling the distance L,
and thus it is possible to simplify the stock-control and to reduce
the manufacturing costs of the exhaust gas recirculation valve
device. According to the embodiment 1, if the variations in
dimension of the parts and the stroke of the driving means occur,
it is not necessary to use the adjustment plates 35 or the seat
parts and it is possible to perform flexibly stepless control of
the distance L. In this way, it is possible to control a valve open
timing with high accuracy and thus is it possible to keep the valve
opening step constant.
[0032] With the embodiment 1, the stepping motor is taken as an
example of the driving means. Alternatively, a DC motor or a
variety of pushing means may be used as the driving means.
[0033] Embodiment 2
[0034] FIG. 4A and FIG. 4B are enlarged views showing a caulking
section of a valve shaft in an exhaust gas recirculation valve
device according to a second embodiment of the present invention,
FIG. 4A is a plan view, and FIG. 4B is a front view.
[0035] The embodiment 2 is characterized in that a central hole 6c
is formed at the tip 6a of the valve rod 6. In the case that the
height of the tip 6a after caulked is set to a minimum level for
example, it is necessary to caulk the tip 6a more which is
subjected to a caulking processing and thus to take a long time for
the caulking processing. Therefore, it is possible to shorten the
time for caulking processing considerably due to the central hole
6c by reducing the volume of the tip 6a. The central hole 6c
extends from the upper end of the tip 6a to the vicinity of the
spring holder 9. The size and length of the central hole 6c are
determined as appropriate by making a comparison between a point in
that it is necessary to ensure a sufficient caulking force applied
to the spring holder 9 due to the caulking processing with respect
to the tip 6a of the valve rod 6 and the other point in that it is
necessary to ensure a sufficient height of the tip 6a with respect
to the upper face 9b of the spring holder 9 after caulking in order
to keep the distance L constant.
[0036] As shown above, according to the embodiment 2, the central
hole 6c is arranged at the tip 6a of the valve rod 6 and thus it is
possible to have the same effect as the embodiment 1. It is also
possible to shorten extensively the time for the caulking
processing by reducing the volume of the tip 6a.
[0037] Embodiment 3
[0038] FIG. 5 is an enlarged view showing a caulking section of a
valve shaft in an exhaust gas recirculation valve device according
to a third embodiment of the present invention.
[0039] The embodiment 3 is characterized in that the tip 6a of the
valve rod 6 includes a caulking fixation section 6d and a
height-adjustment section 6e formed at a top of the caulking
fixation section and formed its diameter smaller than the caulking
fixation section. In the case that the height of the tip 6a after
being caulked is set to a maximum level for example, the length of
the tip 6a which is subjected to a caulking processing is short and
thus it is difficult to ensure a sufficient caulking force. In this
way, the caulking fixation section 6d for ensuring the sufficient
caulking force with a slight length subjected to the caulking
processing and the height-adjustment section 6e for ensuring a
sufficient height of the tip 6a after caulked are stacked.
[0040] In order to caulk and fix the tip 6a to the spring holder 9,
a tool is rotated on an outermost of the caulking fixation section
6d about a center axis of the caulking fixation section 6d and the
height-adjustment section 6e and thus it is possible to perform
effectively a working of the caulking processing.
[0041] As shown above, according to the embodiment 3, it is
possible to have the same effect as the embodiment 1. It is
possible to ensure a sufficient caulking force applied to the
spring holder 9 due to the tip 6a of the valve rod 6 and to ensure
the sufficient height of the tip 6a with respect to the upper face
9b of the spring holder 9 after caulking.
[0042] As shown above, with the exhaust gas recirculation valve
device according to the present invention, a length of the second
shaft subjected to a caulking processing with respect to the
retaining means is determined so that a distance between the facing
ends of the first and second shafts is equivalent to a specific
value with the valve closure. In this way, it is not necessary to
prepare the adjustment plates or the seat parts which have been
used conventionally to control the distance and thus it is possible
to simplify the stock-control and to reduce the manufacturing costs
of the exhaust gas recirculation valve device. It is also possible
to perform flexibly a stepless control of the distance and thus it
is possible to control a valve open timing with high accuracy.
* * * * *