U.S. patent application number 09/767267 was filed with the patent office on 2001-08-09 for curved helical compression spring.
Invention is credited to Hasegawa, Keiji, Imaizumi, Toshiyuki.
Application Number | 20010011791 09/767267 |
Document ID | / |
Family ID | 18546699 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010011791 |
Kind Code |
A1 |
Hasegawa, Keiji ; et
al. |
August 9, 2001 |
Curved helical compression spring
Abstract
The present invention is directed to a curved helical
compression spring having a plurality of coils along a curved coil
axis. Each coil constituting the helical compression spring is
increased and decreased in diameter, and the order of the increased
diameter and the decreased diameter of each coil is reversed at a
predetermined position on the longitudinal axis of the helical
compression spring, so as to provide the curved coil axis, such as
the coil axis curved in C-shape. For example, one section of each
coil having approximately a half of the circumference of each coil,
which is divided by a plane including the coil axis, is increased
in diameter, whereas the other one section of approximately a half
of the circumference of each coil is decreased in diameter. The
curved helical compression spring may be mounted on a vehicle
suspension.
Inventors: |
Hasegawa, Keiji; (Toyoake,
JP) ; Imaizumi, Toshiyuki; (Toyoake, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
277 S. WASHINGTON STREET, SUITE 500
ALEXANDRIA
VA
22314
US
|
Family ID: |
18546699 |
Appl. No.: |
09/767267 |
Filed: |
January 23, 2001 |
Current U.S.
Class: |
267/166 |
Current CPC
Class: |
B60G 15/07 20130101;
B60G 2202/12 20130101; B60G 2206/426 20130101; F16F 1/04 20130101;
B60G 2202/312 20130101; B60G 11/14 20130101; B21F 3/06 20130101;
B60G 2206/42 20130101 |
Class at
Publication: |
267/166 |
International
Class: |
F16F 001/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 2000 |
JP |
2000-20082 |
Claims
What is claimed is:
1. A helical compression spring having a plurality of coils along a
curved coil axis, wherein each coil constituting the helical
compression spring is increased and decreased in diameter, and
wherein the order of the increased diameter and the decreased
diameter of each coil is reversed at a predetermined position on
the longitudinal axis of the helical compression spring.
2. The helical compression spring of claim 1, wherein each coil
constituting the coils between one end of the helical compression
spring and the predetermined position is increased in diameter and
then decreased in diameter, and wherein each coil constituting the
coils between the predetermined position and the other one end of
the helical compression spring is decreased in diameter and then
increased in diameter.
3. The helical compression spring of claim 2, wherein one section
of each coil having approximately a half of the circumference of
each coil divided by a plane including the coil axis is increased
in diameter, the other one section having approximately a half of
the circumference of each coil is decreased in diameter.
4. A method for producing a helical compression spring having a
plurality of coils along a curved coil axis, comprising: forming
each coil constituting the helical compression spring to be
increased and decreased in diameter; and reversing the order of
forming each coil to be increased in diameter and decreased in
diameter at a predetermined position on the longitudinal axis of
the helical compression spring.
5. The method for producing the helical compression spring of claim
4, wherein each coil constituting the coils between one end of the
helical compression spring and the predetermined position is formed
to be increased in diameter and then decreased in diameter, and
wherein each coil constituting the coils between the predetermined
position and the other one end of the helical compression spring is
formed to be decreased in diameter and then increased in
diameter.
6. The method for producing the helical compression spring of claim
5, wherein one section of each coil having approximately a half of
the circumference of each coil divided by a plane including the
coil axis is formed to be increased in diameter, the other one
section having approximately a half of the circumference of each
coil is formed to be decreased in diameter.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a curved helical
compression spring and a method for producing the same, and more
particularly to the curved helical compression spring for use in a
strut type vehicle suspension, and to the method for producing the
spring.
[0003] 2. Description of the Related Arts
[0004] Various types of helical compression spring have been known
heretofore. Among them, is known a compression spring having a coil
axis curved in a predetermined direction. In Japanese Utility Model
Publication No.48-39290, proposed is a method for forming a coil
spring with the center line thereof curved in advance in an
unloaded state, and mounting it on the vehicle in such a state that
the center line is straightened, to produce a moment by the
reactive side force of the spring. Also disclosed in British Patent
No.1198713 is a helical spring which is coiled about an arc axis of
the unloaded spring, and two support surfaces which extend
obliquely at an angle to one another. When the helical spring is
fitted between the parallel plates, and the longer surface line of
the unloaded helical spring faces the outside of the vehicle, the
outer half of the helical spring is compressed to a greater extent
than the half which faces the inside of the vehicle.
[0005] Furthermore, a wheel suspension having a helical compression
spring, the center line of which has an approximately S-shaped
course in an unloaded state, has been proposed in Japanese patent
No. 2642163, which corresponds to U.S. Pat. No. 4,903,985. The
suspension was aimed to enable reduce a side force applied to a
piston rod of a shock absorber to a great extent, in view of the
fact that because tires are becoming wider and wider, hence
shifting the wheel-to-road contact point outward, larger and larger
angles between the line of support action and the shock absorber
axis arise, so that the helical compression spring can not be
positioned as obliquely with respect to the shock absorber axis as
would actually be desired. In FIG. 5 of the Japanese patent No.
2642163, there is disclosed a compression spring to be compared
with the present invention, the center line of which is curved in
an unloaded state, and about which it is stated that the radius of
curvature of the spring center line is constant and the center line
is curved on only one plane, and that the line of the spring action
is merely shifted from the center line of the helical spring, so
that it is difficult to reduce the side force sufficiently. In
other words, it has been concluded that the helical compression
spring with its center line curved in the unloaded state is not to
be employed.
[0006] In any of the publications as mentioned above, a structure
of the helical compression spring having a coil axis formed to be
curved in a predetermined direction, i.e., a curved helical spring,
has not been disclosed, nor a method for producing the same has
been disclosed. If the curved helical spring is produced on the
basis of a prior cylindrical type of the helical compression
spring, for example, it may be produced by varying the pitch of the
spring between the inside and the outside of the curved plane.
Therefore, the pitch of the curved helical spring will be varied
alternately in dependence upon the number of coils, along the coil
axis. However, it is very difficult to produce the compression
spring for creating a predetermined side force, holding it in a
predetermined curved shape, by varying the pitch of the spring
between the inside and the outside of the curved plane. Therefore,
it is presumed that the helical compression spring with its center
line curved in the unloaded state was not to be employed, and it
was proposed to employ the S-shaped center line according to the
Japanese patent No. 2642163.
[0007] In the mean time, there exists a helical spring that is
formed to vary a diameter of each coil along the coil axis, such as
a truncated cone-shaped helical spring, a barrel-shaped helical
spring, or the like. However, it is hardly assumed to employ the
helical spring having the varying diameter of the coil, with its
coil axis curved, for the helical compression springs as disclosed
in the prior publications. It is natural to be considered that the
cylindrical helical compression spring was formed, with the pitches
thereof varied between the outside and the inside of the curved
plane, because there is no disclosure about such a specific spring
that the diameter of the coil is varied along the coil axis, for
example, in any of the publications as described above.
SUMMARY OF THE INVENTION
[0008] Accordingly, it is an object of the present invention to
provide a curved helical compression spring for applying a desired
side force to a strut of a vehicle suspension appropriately, when
mounted on a vehicle.
[0009] And, another object of the present invention is to provide a
method for producing the curved helical compression spring
easily.
[0010] In accomplish the above and other objects, a curved helical
compression spring according to the present invention includes a
plurality of coils along a curved coil axis. Each coil constituting
the helical compression spring is increased and decreased in
diameter, and the order of the increased diameter and the decreased
diameter of each coil is reversed at a predetermined position on
the longitudinal axis of the helical compression spring. Thus, the
curved helical compression spring according to the present
invention has the curved coil axis, such as the coil axis curved in
C-shape.
[0011] The helical compression spring may be formed in such a
manner that each coil constituting the coils between one end of the
helical compression spring and the predetermined position is
increased in diameter and then decreased in diameter, and that each
coil constituting the coils between the predetermined position and
the other one end of the helical compression spring is decreased in
diameter and then increased in diameter. More practically, one
section of each coil having approximately a half of the
circumference of each coil divided by a plane including the coil
axis may be increased in diameter, whereas the other one section of
approximately a half of the circumference of each coil may be
decreased in diameter.
[0012] The method for producing a helical compression spring having
a plurality of coils along a curved coil axis, may comprise the
steps of forming each coil constituting the helical compression
spring to be increased and decreased in diameter, and reversing the
order of forming each coil to be increased in diameter and
decreased in diameter at a predetermined position on the
longitudinal axis of the helical compression spring.
[0013] In the method as defined above, each coil constituting the
coils between one end of the helical compression spring and the
predetermined position may be formed to be increased in diameter
and then decreased in diameter, and each coil constituting the
coils between the predetermined position and the other one end of
the helical compression spring may be formed to be decreased in
diameter and then increased in diameter.
[0014] Preferably, one section of each coil having approximately a
half of the circumference of each coil divided by a plane including
the coil axis is formed to be increased in diameter, and the other
one section having approximately a half of the circumference of
each coil the spring is formed to be decreased in diameter.
[0015] In the case where an appropriate side force is to be
applied, when the curved helical compression spring as constituted
above is mounted on a strut-type vehicle suspension, it is
necessary to provide a relative relationship between the shape of
the curved helical spring in its unloaded state, and an upper seat
and/or a lower seat to be mounted thereon, as described
hereinafter. In any case, when the curved helical compression
spring as constituted above, such as the curved spring having a
C-shaped coil axis, is employed, that relationship may be provided
easily.
[0016] Firstly, the curved helical compression spring is disposed
between the upper seat and the lower seat, with the upper seat
an/or lower seat tilted by a predetermined angle. For example, the
helical compression spring is mounted on the lower seat tilted in
the direction for shortening the longitudinal length of the spring
at the outside of the curvature of the spring in its unloaded
state, and/or it is mounted on the upper seat tilted in the
direction for shortening the longitudinal length of the spring at
the inside of the curvature of the spring in its unloaded
state.
[0017] Secondly, the upper seat and the lower seat are held in
parallel without being tilted, and the pitch of an upper end coil
and/or a lower end coil of the C-shaped curved helical compression
coil is set to tilt the end plane of the upper end coil and/or the
lower end coil at a predetermined angle against the upper seat or
the lower seat to be seated. For example, the pitch of the lower
end coil may be set to tilt the end plane of the lower end coil at
a predetermined angle against the lower seat to be seated, in the
direction for shortening the longitudinal length of the spring at
the inside of the curvature, and/or the pitch of the upper end coil
may be set to tilt the end plane of the upper end coil at a
predetermined angle against the upper seat to be seated, in the
direction for shortening the longitudinal length of the spring at
the outside of the curvature.
[0018] Thirdly, the upper end coil and/or the lower end coil of the
C-shaped curved helical compression spring are arranged to be
offset. For example, the center of the end plane of the upper end
coil may be arranged to be offset to the center of the end plane of
the lower end coil in the direction of the inside of the curvature
of the spring. Or, the center of the end plane of the lower end
coil may be arranged to be offset to the center of the end plane of
the upper end coil in the direction of the outside of the curvature
of the spring. Accordingly, when the curved helical compression
spring is disposed between the upper seat and the lower seat
arranged in parallel with each other, can be obtained the same
effect as those obtained in the case where the pitch of the upper
end coil and/or lower end coil is set to tilt the end plane of the
upper end coil and/or lower end coil at a predetermined angle
against the upper seat and/or lower seat.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above stated object and following description will
become readily apparent with reference to the accompanying
drawings, wherein like reference numerals denote like elements, and
in which:
[0020] FIG. 1 is a perspective view of a curved helical spring
according to an embodiment of the present invention;
[0021] FIG. 2 is a diagram showing a relationship between the
number of coils and pitches of a curved helical spring according to
an embodiment of the present invention;
[0022] FIG. 3 is a diagram showing a relationship between the
number of coils and diameters of coils of a curved helical spring
according to an embodiment of the present invention;
[0023] FIG. 4 is a front view of a coiling machine for producing a
curved helical spring according to an embodiment of the present
invention;
[0024] FIG. 5 is a front view showing one process for producing a
curved helical spring according to an embodiment of the present
invention;
[0025] FIG. 6 is a front view showing another process for producing
a curved helical spring according to an embodiment of the present
invention;
[0026] FIG. 7 is a plan view showing an example of a part of a
curved helical spring under a coiling process in one process for
producing the curved helical spring according to an embodiment of
the present invention;
[0027] FIG. 8 is a sectional view of one example of a curved
helical spring, which is disposed between an upper seat and a lower
seat arranged in parallel with each other, according to an
embodiment of the present invention;
[0028] FIG. 9 is a sectional view of one example of a curved
helical spring, which is disposed between an upper seat and a
tilted lower seat, according to an embodiment of the present
invention;
[0029] FIG. 10 is a perspective view showing a model of helical
compression spring for experimenting a curved helical spring to
investigate influence on spring reaction force by tilting a lower
end plane to an upper end plane of the spring;
[0030] FIG. 11 is a diagram showing a variation of the reaction
force axis of the helical spring as shown in FIG. 10 in the case
where the lower end plane is rotated about the x-axis
counterclockwise with the helical spring compressed to a
predetermined height;
[0031] FIG. 12 is a diagram showing a variation of reactive side
force of the helical spring as shown in FIG. 10 in the case where
the lower end plane is rotated about the x-axis counterclockwise
with the helical spring compressed to a predetermined height;
[0032] FIG. 13 is a diagram showing a variation of reactive side
force of the helical spring as shown in FIG. 10 in the case where
the lower end plane is rotated about the x-axis counterclockwise
and the upper end plane is rotated about the x-axis clockwise with
the helical spring compressed to a predetermined height;
[0033] FIG. 14 is a diagram showing a variation of the reaction
force axis of the helical spring as shown in FIG. 10 in the case
where the upper end plane is rotated about the x-axis
counterclockwise with the helical spring compressed to a
predetermined height;
[0034] FIG. 15 is a characteristic diagram showing a relationship
of reaction force in the case where the lower end plane of the
helical spring as shown in FIG. 10 is rotated about the x-axis
counterclockwise with the helical spring compressed to a
predetermined height;
[0035] FIG. 16 is a diagram showing a variation of the reactive
side force of the helical spring as shown in FIG. 10 according to a
tilting angle .alpha. of the lower plane, in the case where the
lower end plane is rotated about the x-axis counterclockwise with
the helical spring compressed to a predetermined height;
[0036] FIG. 17 is a diagram showing a displacement of the point of
application of reaction force caused according to a variation of a
tilting angle .alpha. of the lower plane of the helical spring as
shown in FIG. 10, in the case where the lower end plane is rotated
about the x-axis counterclockwise with the helical spring
compressed to a predetermined height;
[0037] FIG. 18 is a front view of a curved helical spring of an
embodiment of the present invention mounted on a vehicle
suspension;
[0038] FIG. 19 is a sectional view of a curved helical spring
according to another embodiment of the present invention;
[0039] FIG. 20 is a front view of a curved helical spring according
to a further embodiment of the present invention;
[0040] FIG. 21 is a front view of a curved helical spring according
to a yet further embodiment of the present invention;
[0041] FIG. 22 is a perspective view of a curved helical spring
according to a yet further embodiment of the present invention;
[0042] FIG. 23 is a diagram showing a relationship between the
number of coils and pitches of the curved helical spring as shown
in FIG. 22; and
[0043] FIG. 24 is a diagram showing a relationship between the
number of coils and diameters of coils of the curved helical spring
as shown in FIG. 22.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] Referring to FIG. 1, there is schematically illustrated a
curved helical compression spring (hereinafter, simply referred to
as a curved helical spring). The curved helical spring 5 according
to an embodiment of the present invention has a body portion 5c
between an upper end coil 5b and a lower end coil 5a, with each
coil constituting the body portion 5c increased and decreased in
diameter, and with its coil axis CA curved in C-shape. That is,
each coil constituting the body portion 5c according to the present
embodiment is increased and decreased in diameter, and formed at a
substantially constant pitch, and it is so arranged that the order
of the increased diameter and the decreased diameter of each coil
is reversed at a predetermined position on the longitudinal axis of
the curved helical spring 5, to provide the coil axis CA which is
curved in a predetermined direction (rightward in FIG. 1) to be
formed in C-shape.
[0045] Thus, the pitch of the body portion 5c is set to a
substantially constant value as shown in FIG. 2, except for the
case where a variation of pitch is necessitated so as to avoid any
contact between neighboring coils. That is, the variation of pitch
is not used for forming the curved coil axis. Furthermore,
according to the present embodiment, in order to provide the coil
axis CA of the curved helical spring 5 to be curved in C-shape,
each coil constituting the body portion 5c is increased and
decreased in diameter, and it is so arranged that the order of
increasing the diameter and decreasing the diameter in each coil is
reversed at a predetermined position on the longitudinal axis of
the curved helical spring 5. Therefore, the diameter of each coil
is increased and decreased according to the number of coils (i.e.,
along the longitudinal axis), as shown in FIG. 3.
[0046] In practice, the diameter of one coil of the body portion 5c
is set in such a manner that one section of the one coil having
approximately a half of the circumference of the one coil divided
by a plane including the coil axis CA is gradually increased in
diameter from its minimum diameter (Db) in the one coil, and
reaches its maximum diameter (Da) in the one coil, and the other
one section following that one section having approximately a half
of the circumference of the one coil is gradually decreased from
the maximum diameter (Da) and reaches its minimum diameter (Db) in
the one coil. Each coil constituting the coils is varied in
diameter at a predetermined position on the longitudinal axis (a
target position to be bent, i.e., approximately center of the body
portion 5c according to the present invention). That is, each one
coil constituting the coils is increased in diameter between the
upper end coil 5b and the approximately center of the body portion
5c, and then decreased in diameter between the approximately center
of the body portion 5c and the lower end coil 5a.
[0047] According to the present embodiment, the upper end coil 5b
and the lower end coil 5a are set to be of the same diameter as the
portion of the minimum diameter, while they are not limited to that
dimension. The maximum diameter (Da) and the minimum diameter (Db)
indicate the maximum value and the minimum value in each one coil
(or, one turn). According to the present embodiment, they are set
to be of different values by one coil according to a target
configuration. Thus, the maximum diameter (Da) and the minimum
diameter (Db) are set to be of different values in the longitudinal
direction (by the number of coils), respectively. The relationship
in one coil increased and decreased in diameter is held to be of a
predetermined relationship at either side of a predetermined
position (the position to be bent) on the longitudinal axis of the
spring.
[0048] FIG. 4 illustrates a part of a coiling machine for producing
the curved helical spring 5 as described above, wherein a basic
structure is the same as those distributed in the market. According
to the present embodiment, a couple of coiling pins of a first pin
101 and a second pin 102 are provided, and the second pin 102 is
adapted to move toward and away from a center of each coil to be
formed, as indicated by a two-way arrow, so as to adjust the
diameter of the spring. And, the pitch and diameter of the coil as
shown in FIGS. 2 and 3 are stored in a program in advance by a
numerical control machine (not shown), so that the coiling machine
is actuated according to the program. According to a rotation of a
feed roller 103, therefore, an element wire of the coil
(hereinafter, referred to as wire W) is guided by a wire guide 104
and delivered rightward in FIG. 4. Then, the wire W is bent by the
first pin 101, and bent by the second pin 102 to be coiled in a
predetermined diameter. During this process, pitches between
neighboring coils are controlled to be of a constant value by a
pitch tool 105. When the wire W is coiled to provide a
predetermined number of coils, it is cut by a cutter 106. Although
the first and second pins 101, 102 are employed in the present
embodiment, a single coiling pin may be employed.
[0049] When the curved helical spring 5 is produced by the coiling
machine as described above, the first and second pins 101 and 102
are actuated as follows. At the outset, it is so arranged that the
diameter of a section extending from [a reference
position-{fraction (1/2)} of one coil] to [the reference position],
wherein the reference position of each coil is placed in a bending
side (extending side) of the curved helical spring to be formed,
i.e., the diameter of one section of each coil having approximately
a half of the circumference of each coil divided by a plane
including the coil axis (i.e., the plane including the reference
position, and perpendicular to a drawing plane of FIG. 4) is
increased in diameter. In this case, the wire W is bent by the
first and second pins 101 and 102, with the second pin 102 being
retracted, and formed to gradually increase the diameter of the
coil up to the maximum diameter (Da) as shown in FIG. 5. Then, it
is so arranged that the diameter of a section following the
above-described section having approximately a half of the
circumference of each coil, i.e., the diameter of a section
extending from [the reference position] to [the reference
position+{fraction (1/2)} of one coil] is decreased in diameter. In
this case, the wire W is bent, with the second pin 102 being
advanced, and formed to gradually decrease the diameter of the coil
down to the minimum diameter (Db) as shown in FIG. 6.
[0050] Likewise, the next section of approximately a half of the
circumference of the coil is bent, with the second pin 102 being
retracted, until it becomes to be of the maximum diameter (Da).
And, the following section of approximately a half of the
circumference of the coil is bent, with the second pin 102 being
advanced, until it becomes to be of the minimum diameter (Db). If
the order of increasing and decreasing the diameter of each coil is
reversed at a predetermined position (bent position) on the
longitudinal axis of the spring, e.g., at the approximate center of
the longitudinal axis of body portion 5c to be formed, and the
increasing and decreasing the diameter of each coil are repeated,
then the diameter of the coil is formed to be varied as follows.
That is, the diameter of one coil from the upper end coil 5b to the
approximate center of the body portion 5c is first increased then
decreased, and thereafter the diameter of one coil from the
approximate center of the body portion 5c to the lower end coil 5a
is first decreased then increased. Accordingly, if the diameter of
the coil is set as shown in FIG. 3 for example, and the coiling is
made by the advancing movement and retracting movement of the
second pin 102 repeated alternately, by each approximately half
portion of the circumference of the coil, then the curved helical
spring having the curved coil axis, such as the coil CA axis curved
in C-shape as shown in FIG. 1, will be formed.
[0051] The diameter of the coil may be set to provide the maximum
diameter (Da) and the minimum diameter (Db) every approximately
half portion of the circumference of the coil, and the diameters Da
and Db may be of a constant value along the longitudinal axis. In
this case, however, there is caused a difference between the
configuration of the outer surfaces of the one side and the
configuration of the outer surfaces of the other one side, which
are divided by a plane including the coil axis CA. As a result, the
spring is formed to extend rightward in FIG. 7, thereby to provide
a coil axis having a sharp bent portion, so that the coil axis does
not become smooth, while it constitutes approximately C-shaped.
[0052] Next will be explained an embodiment of the curved helical
spring 5 as constituted above, which is used for a compression
spring for use in a strut type suspension. In this case, if the
curved helical spring 5 is simply installed between the upper seat
3 and the lower seat 4 mounted in parallel with each other as shown
in FIG. 8, the reaction force axis RA will be shifted parallel as
shown by oen-dot chain line in FIG. 8, so that the point of
application of the reaction force will be displaced from the coil
axis CA by a displacement (e). According to the present embodiment,
therefore, the curved helical spring 5 is compressed, with the
lower plate 4 tilted by the tilting angle .alpha. counterclockwise
as shown in FIG. 9, for example. Consequently, the angle of the
reaction force axis RA is changed as shown in FIG. 9, so that the
point of application of the reaction force is positioned
approximately on the center of the upper end plane, and it is
positioned on the coil axis CA, as will be described in detail as
follows.
[0053] FIG. 10 illustrates a model of a helical compression spring
5x, which is used for experimenting the helical compression spring
with the initial curvature, the coil axis of which passes the
center of the upper end plane and curves in approximate C-shape in
an unloaded state, to investigate the influence on the spring
reaction force by tilting the upper seat and/or the lower seat.
Hereinafter, will be described results of the experiments in the
case where the helical spring 5x is compressed to shorten the
longitudinal length of either side of the helical spring 5x, i.e.,
the lower end plane of the helical spring 5x is rotated about the
x-axis counterclockwise by a degree as shown in FIG. 10, and the
case where the upper end plane of the helical spring 5x is rotated
about the x-axis clockwise by / degree.
[0054] In FIG. 11 which shows the result obtained from the
experiment, solid lines indicate variation of the reaction force
axis of the helical spring 5x, in the case where the lower end
plane is rotated about the x-axis counterclockwise, with the
helical spring 5x compressed to a predetermined height, and broken
lines indicate variation of the reaction force axis of the
conventional helical compression spring in the same case as the
former case. When a rotational angle which is rotated about the
x-axis in FIG. 10, i.e., tilting angle .alpha. of the lower end
plane, is increased, the upper end of the reaction force axis will
move as indicated by the arrow. In FIG. 11, the arrow indicates the
direction to which the tilting angle .alpha. increases. The
reaction force axis lies on the line for connecting the points of
application of the reaction forces acting on the upper end plane
and lower end plane.
[0055] As shown in FIG. 11, the following results are obtained from
the experiment.
[0056] (1) By initially curving the helical spring, the reaction
force axis of the spring is displaced parallel in the y-direction,
i.e., in the direction to which the spring is initially curved to
extend.
[0057] (2) With increase of the tilting angle .alpha. in the
counterclockwise direction in FIG. 10, the inclination of the
reaction force axis of the spring in the y-direction increases. In
other words, the reactive side force of the helical compression
spring increases, with increase of the tilting angle .alpha. of the
lower end plane.
[0058] (3) With increase of the tilting angle .alpha. of the lower
end plane, the point of application of the reaction force on the
upper end plane of the helical spring 5x gets close to the center
of the upper end plane, i.e., z-axis in FIG. 11, as indicated by
the solid lines, whereas the conventional spring gets away from the
center of the upper end plane as indicated by the broken lines.
[0059] In the case where the upper end plane of the helical spring
5x is rotated clockwise about the x-axis, with the helical spring
5x compressed to the predetermined height, the inclination of the
reaction force axis of the spring in the y-direction decreases,
i.e., the reactive side force of the helical spring 5x decreases,
with increase of the tilting angle .beta. of the upper end plane in
the clockwise direction (Figure showing this relationship is
omitted).
[0060] Therefore, in the case where the tilting angle of the upper
end plane of the helical spring 5x is zero, with the helical spring
5x compressed to the predetermined height, when the lower end plane
is rotated about the x-axis counterclockwise in FIG. 10 by the
tilting angle .alpha., the reactive side force will be varied as
indicated by the solid lines in FIG. 12. The abscissa in FIG. 12
represents the tilting angle .alpha. of the lower end plane, and
the ordinate represents the reactive side forces Fx, Fy in the
x-direction and the y-direction, respectively. Solid lines indicate
variations of the reactive side forces Fxb, Fyb of the curved
helical spring 5 according to the present embodiment, whereas the
broken lines indicate the variation of the reactive side forces
Fxn, Fyn according to the conventional helical compression
spring.
[0061] As shown in FIG. 12, the following results are obtained.
[0062] (1) If the helical spring 5x is initially curved in the
y-direction, the reactive side force Fxb in the x-direction is
increased, whereas the reactive side force Fyb in the y-direction
is decreased, comparing with the reactive side forces Fxn, Fyn of
the conventional helical compression spring.
[0063] (2) In the case where the lower end plane is rotated about
the x-axis counterclockwise in FIG. 10 by the tilting angle
.alpha., the reactive side force Fyb in the y-direction is largely
increased, with increase of the tilting angle .alpha., whereas the
reactive side force Fxb in the x-direction is slightly reduced.
[0064] (3) The absolute value of the reactive side force Fxb in the
x-direction is not negligible, in order to have the reaction force
axis of the spring coincide with an ideal offset line. In this
respect, the reactive side force Fxb in the x-direction can be
minimized by coinciding the curving direction of the spring with
the direction of the reactive side force exerted when the spring is
compressed between parallel seats, to adjust the position of end
turn of the spring.
[0065] On the contrary, in the case where the lower end plane of
the helical spring 5x is rotated about the x-axis counterclockwise
in FIG. 10 by the tilting angle .alpha. of 8.0 degree, with the
helical spring 5x compressed to the predetermined height, and at
the same time the upper end plane of the helical spring 5x is
rotated about the x-axis clockwise in FIG. 10, the reactive side
forces Fxb, Fyb of the helical spring 5x will vary as indicated by
the solid lines in FIG. 13, with increase of the tilting angle
.beta. of the upper end plane. The broken lines indicate the
variation of the reactive side forces in the same case as the above
case. Thus, referring to FIG. 13, it can be concluded that with
increase of the tilting angle .beta. of the upper end plane in the
clockwise direction, the reactive side forces Fyb, Fyn in the
y-direction are largely decreased, and the reactive side forces
Fxb, Fxn are slightly increased.
[0066] In conclusion, according to the initially curved helical
compression spring,
[0067] (1) The reaction force axis is shifted parallel in the
extending direction of the curved spring.
[0068] (2) When the lower end plane is tilted about the x-axis
counterclockwise in FIG. 10, the reactive side force in the
y-direction is largely increased, and the angle between the coil
axis and the reaction force axis of the spring is increased.
[0069] (3) In the case where the lower end plane is rotated about
the x-axis counterclockwise in FIG. 10 by the tilting angle
.alpha., the point of application of the reaction force on the
upper end plane gets close to the center of the upper end plane,
with increase of the tilting angle .alpha..
[0070] (4) If the upper end plane is rotated about the x-axis
clockwise in FIG. 10 by the tilting angle .beta., however, the
reactive side force in the y-direction is largely decreased, with
increase of the tilting angle .beta., to compensate the effect
obtained when the lower end plane was tilted.
[0071] (5) Although the reactive side force in the direction
vertical to the extending direction of the curved spring (i.e., the
reactive side force in the x-direction) is large in value, it can
be reduced as described before, and its variation caused by tilting
the end plane will be as small as negligible.
[0072] In FIG. 14, solid lines indicate variation of the reaction
force axis of the helical spring 5x, in the case where the upper
end plane is rotated about the x-axis counterclockwise with the
helical spring 5x compressed to the predetermined height, i.e., a
reverse direction to the direction indicated by the arrow in FIG.
10. Since the direction of the arrow in FIG. 10 corresponds to the
direction for increasing the angle .beta., the reverse direction
corresponds to the direction for decreasing the angle .beta.. And,
the broken lines indicate variation of the reaction force axis of
the conventional helical compression spring in the same case as the
former case. FIG. 14 shows the variation of the reaction force axis
of the spring, when a rotational angle which is rotated about the
x-axis in FIG. 14, i.e., tilting angle .beta. of the upper end
plane, is increased in the direction opposite to the direction as
indicated by the arrow in FIG. 10 (in other words, the decreasing
direction of the angle .beta.). By increasing the tilting angle
.beta. of the upper end plane in the direction opposite to the
clockwise direction as indicated by the arrow in FIG. 10, i.e.,
counterclockwise direction, the inclination of the upper end plane
in the y-direction will be increased. In other words, the reactive
side force of the curved helical spring 5 is increased, with
decrease of the tilting angle .beta. of the upper end plane in the
clockwise direction as indicated by the arrow in FIG. 10.
[0073] Referring to FIGS. 15-17, it can be concluded that by
tilting the lower end plane of the helical spring 5x with the
initial curvature as shown in FIG. 10, the reaction force axis RA
will pass approximately the center of the upper end plane. FIG. 15
illustrates a state of forces exerted in the case where the lower
end plane of the helical spring 5x as shown in FIG. 10 is rotated
about the x-axis counterclockwise in FIG. 10, with the helical
spring 5x compressed to the predetermined height. As can be seen in
FIGS. 16 and 17, the reactive side force Fy and the displacement
(e) of the point of application of force will vary according to the
tilting angle .alpha. of the lower end plane of the helical spring
5x to the lower seat (not shown in FIG. 15).
[0074] FIGS. 16 and 17 show the results obtained from the
experiment, wherein solid lines indicate the result of the
experiment for a helical compression spring without being curved,
one-dot chain lines indicate the result for a helical compression
spring which was curved by 10 mm of the curved amount (d), two-dot
chain lines indicate the result for a helical compression spring
which was curved by 13 mm, and broken lines indicate the result for
a helical compression spring which was curved by 16 mm. As can be
seen from the results of those experiments, with increase of the
radius of curvature, the reactive side force Fy is decreased, and
the point of application of reaction force on the upper end plane
is sifted in the extending direction of the curvature. And, in the
case where the lower end plane is tilted by the tilting angle
.alpha., with increase of the angle .alpha., the reactive side
force Fy is increased, and the point of application of force on the
upper end plane is sifted in the direction opposite to the
extending direction of the curvature of the helical spring.
[0075] FIG. 18 illustrates a first embodiment of the curved helical
spring 5 for use in a strut type suspension (hereinafter, simply
referred to as suspension). As shown in FIG. 18, the curved helical
spring 5 as shown in FIG. 1 is mounted on the suspension, most
parts of which are illustrated by two-dot chain lines except for a
portion for supporting the upper end of the curved helical spring
5. A strut 2 is elastically mounted at its upper end on a vehicle
body 1, and the upper seat 3 is mounted on the vehicle body 1. The
lower seat 4 is fixed to a middle portion of the strut 2. Between
the upper seat 3 and the lower seat 4, the curved helical spring 5
is arranged to encircle therein the strut 2. The lower end of the
strut 2 is fixed to a knuckle 6, which is pivotally mounted on the
vehicle body 1 through a lower arm 7. Accordingly, a wheel 8 is
mounted on the knuckle 6, which is connected to the vehicle body 1
through the strut 2 and the curved helical spring 5, and which is
connected to the vehicle body 1 through the lower arm 7. The upper
end of the strut 2 and the upper seat 3 are mounted on the vehicle
body 1 thorough a strut mount 10, explanation of which is omitted.
The strut 2 is provided with a cylinder 2a and a rod 2b which is
slidably mounted in the cylinder 2a, to form a shock absorber. The
rod 2b is mounted at its upper end on the vehicle body 1 through
the strut mount 10, and the cylinder 2a is fixed at its lower end
to the knuckle 6, to form a structure similar to that disclosed in
the aforementioned Japanese Utility Model No. 48-39290.
[0076] As shown in FIG. 18, the lower seat 4 of the present
embodiment is fixed to the cylinder 2a of the strut 2 so as to be
tilted at the predetermined angle .alpha. in the direction for
shortening the longitudinal length of the curved helical spring 5
at the outside of the vehicle body. In the case where the curved
helical spring 5 is arranged to be offset to the strut 2, as shown
in FIG. 18, the lower seat 4 is supported to be tilted at the
predetermined angle .alpha. in the direction for shortening the
longitudinal length of the curved helical spring 5 at the outside
of the vehicle body toward the offset direction (rightward in FIG.
18).
[0077] According to the suspension as shown in FIG. 18, the
reaction force axis RA does not coincide with the load input axis
AA. That is, the strut axis SA of the strut 2 and the load input
axis AA form an angle .theta.1, whereas the strut axis SA and the
reaction force axis RA form an angle .theta.2. In FIG. 18, "LA"
designates the axis of the lower arm 7, "KA" designates the axis of
a king pin (not shown). Due to the relationship between the
reaction force axis RA and the strut axis SA which do not coincide
with each other, sliding resistance may be caused between the
cylinder 2a and the rod 2b of the strut 2. However, the sliding
resistance will be prevented, by the side force of the curved
helical spring 5, from being created, thereby to ensure a smooth
sliding motion of the rod 2b.
[0078] FIG. 19 illustrates a second embodiment of the curved
helical spring mounted on the suspension, wherein a curved helical
spring 15 has an initial curvature of curved amount (d), and a
pitch of a lower end coil 15a of the curved helical spring 15 has
been set to tilt the end plane of the lower end coil 15a at a
predetermined angle .alpha. to the lower seat 14 on which the lower
end coil 15a is seated in its unloaded state, in the direction for
shortening the longitudinal length of the curved helical spring 15
at the inside of the curvature (i.e., left side in FIG. 19). In
FIG. 19, the upper seat 13 and lower seat 14 on which the curved
helical spring 15 is seated are indicated by two-dot chain line, a
seat plane of the upper end coil 15b which abuts the upper seat 13,
i.e., the upper end plane is indicated by (US), and a seat plane of
the lower end coil 15a which abuts the lower seat 14, i.e., the
lower end plane is indicated by (LS).
[0079] In other words, according to the present embodiment, the
curved amount (d) and the pitch of the lower end coil 15a for
providing the tilting angle .alpha. (i.e., the rotational angle
rotating clockwise in FIG. 19) are set, so as to be in the same
state as that the lower seat is rotated counterclockwise by the
tilting angle .alpha., with the helical spring 5x as shown in FIG.
10 compressed to the predetermined height, when the curved helical
spring 15 is mounted between the upper seat 13 and the lower seat
14 as shown in FIG. 19. Accordingly, if the curved helical spring
15 formed as shown in FIG. 19 is mounted between the upper seat 13
and the lower seat 14 which are arranged in parallel with each
other in the same manner as in the prior art, and the curved
helical spring 15 is installed so that the extending direction of
the curve of the coil axis CA directed to the outside of the
vehicle body, the same effect as in the case where the helical
spring 5x in FIG. 10 is tilted to the lower seat, as shown in FIG.
9, can be obtained.
[0080] Or, the pitch of the upper end coil 15b of the curved
helical spring may be set to tilt the end plane of the upper end
coil 15b at the predetermined angle .beta. to the upper seat 13 to
be seated, in the direction for shortening the longitudinal length
of the helical spring at the outside of the curvature (i.e., right
side in FIG. 19). That is, in view of the property as shown in FIG.
14, the curved amount (d) and the pitch of the upper end coil 15b
for providing the tilting angle .beta. in an unloaded state may be
set, so as to be in the same state as that the upper end plane US
is rotated counterclockwise by the tilting angle .beta., with the
helical spring 5x in FIG. 10 compressed to the predetermined
height.
[0081] The helical spring may be formed such that the tilting
angles .gamma., .delta. of the lower end plane LS and upper end
plane US, and the pitches of the upper end coil 15b and lower end
coil 15a are set, so as to be in the same state, when the helical
spring is mounted between the upper seat and the lower seat which
were arranged in parallel with each other (not shown), the lower
end plane of the helical spring 5x as shown in FIG. 10 is rotated
about the x-axis counterclockwise by the angle .gamma., and also
the upper end plane of the helical spring 5x is rotated about the
x-axis counterclockwise by the angle .delta., with the helical
spring 5x compressed to the predetermined height. Accordingly, when
the curved helical spring 15 is mounted between the upper seat and
the lower seat which were arranged in parallel with each other, the
same effects as those in the embodiment as disclosed in FIG. 19 can
be obtained.
[0082] Referring to FIGS. 20 and 21, will be explained a third
embodiment of the present invention, wherein curved helical
compression springs 25, 35 as shown in FIGS. 20 and 21 are formed
so that the coil axes CA2, CA3 are curved at their unloaded states,
respectively, in such a manner that the center of the upper end
coil 25b and the center of the upper end coil 35b are offset to the
center of the lower end coil 25a and the center of the lower end
coil 35a, in the direction of the inside of the curvature (left
side in FIGS. 20, 21), by the horizontal distances S1, S2,
respectively. Likewise, the coil axes may be set, in such a manner
that the center of the lower end coil is offset to the center of
the upper end coil in the direction of the outside of the curvature
(rightward in FIGS. 20, 21). When the curved helical spring 25 or
35 as shown in FIGS. 20 and 21 is mounted between the upper seat 13
and the lower seat 14, the center of the end plane of the upper end
coil 25b or 35b, which is offset by the distance S1 or S2 to the
center of the end plane of the lower end coil 25a or 35a,
respectively, will coincide with the center of the upper seat 13
which is not offset to the center of the lower seat 14. As a
result, the curved helical spring 25 or 35 is held in the same
state that the upper end plane of the upper end coil 25b or 35b is
rotated counterclockwise by the angle .delta., so that
substantially the same effect as the effect obtained by using the
helical spring with the pitch of its upper end coil adjusted.
[0083] Next, FIG. 22 illustrates a curved helical spring 45
according to a yet further embodiment of the present invention,
wherein the curved helical spring 45 is formed in a truncated
cone-shape with a curved coil axis. According to the curved helical
spring 45, the pitch is provided so as to be increased in
proportion to the number of coils, as shown in FIG. 23. However,
the variation of the pitch is caused by forming the configuration
of the spring to be the conical shape with a curved coil axis, so
that it is provided as an independent condition, without any
relationship with forming the coil axis to be curved. Also, FIG. 24
shows a graph in which the diameter of the coil is increased in
proportion to the number of coils, this variation is also caused by
forming the configuration of the spring to be the truncated
cone-shape, so that it is provided without any direct relationship
with forming the coil axis to be curved. In order to curve the coil
axis, however, the diameter of the coil is gradually increased
along the longitudinal axis, maintaining a relative relationship
between the diameters of the approximately halves of circumferences
in one coil. In the case where the spring is formed to provide a
specific configuration as shown in the curved helical spring 25,
the pitch is to be varied, or the diameter of the coil is to be
varied. In this case, in order to provide a curved coil axis, the
relative relationship between the diameters of the approximately
halves of circumferences in one coil has to be maintained.
[0084] It should be apparent to one skilled in the art that the
above-described embodiments are merely illustrative of but a few of
the many possible specific embodiments of the present invention.
Numerous and various other arrangements can be readily devised by
those skilled in the art without departing from the spirit and
scope of the invention as defined in the following claims.
* * * * *