1. A marker for mobile communications comprising: a housing including an electronic board inside; a pedestal retaining the housing; and a fastening body fastening the housing and the pedestal, wherein the housing is molded from a resin that expands or contracts in accordance with a variation in temperature, and the fastening body has a coefficient of linear expansion substantially the same as a coefficient of linear expansion of the housing.

2. The marker for mobile communications according to claim 1, wherein the fastening body has a coefficient of linear expansion so as to cause a ratio between the coefficient of linear expansion of the housing and the coefficient of linear expansion of the fastening body to be in a predetermined constant range.

3. The marker for mobile communications according to claim 1, wherein the fastening body is a bolt, and directly fastens the housing and the pedestal by causing a head portion of the bolt to come in contact with one end of the housing so as to press downward and by screwing an end portion of the bolt in the pedestal so as to come in contact. 22

4. The marker for mobile communications according to claim 1, wherein the housing is set to have an area that is a sum of a contact area with the fastening body and a contact area with the pedestal, based on a conditional expression calculated from the number of the fastening body, yield stress of the housing, mass of the marker for mobile communications, a coefficient of axial force degradation of the fastening body, and acceleration acting on the marker for mobile communications.

5. The marker for mobile communications according to claim 4, wherein when the number of the fastening body is defined as N, the yield stress of the housing is defined as σy, the mass of the marker for mobile communications is defined as m, the coefficient of axial force degradation of the fastening body is defined as K, the acceleration acting on the marker for mobile communications is defined as a, and the sum area of the contact area between the housing and the fastening body and the contact area between the housing and the pedestal is defined as A, the conditional expression satisfies A > (ma)/NKσy.

6. The marker for mobile communications according to claim 1, wherein the pedestal is fixed on a ground, a wall surface, or a ceiling. 23

7. The marker for mobile communications according to claim 1, wherein the housing is constituted by molding fiber reinforced plastic.

8. The marker for mobile communications according to claim 7, wherein the fiber reinforced plastic is a composite material including a glass fiber or a carbon fiber.

9. The marker for mobile communications according to claim 7, wherein the fiber reinforced plastic is molded so as to cause an orientation of a fiber in proximity to the fastening body to be substantially the same as an axial direction of the fastening body.

10. The marker for mobile communications according to claim 1, wherein the fastening body is a stainless bolt.

11. The marker for mobile communications according to claim 1, wherein a ratio (αR/αB) between the coefficient of linear expansion of the housing (αR) and the coefficient of linear expansion of the fastening body (αB) satisfies 0.80 < (αR/αB) < 1.20.

TITLE OF THE INVENTION
MARKER FOR MOBILE COMMUNICATIONS
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a marker for mobile
communications used upon wireless communications with a mobile
object, and, in particular, is preferably applied to a marker
for mobile communications fixed on the ground by a fastening
body.
2. Description of the Related Art
A marker for mobile communications is, for example, fixed
on the ground by a fastening body, and used upon wireless
communications with a mobile object, such as a motor vehicle.
The marker for mobile communications includes an electronic
board including electronic components for communications
mounted thereon and a resin-based housing that fixes the
electronic board. The housing includes a supplementary metal
member for fastening. A fastening body, such as a bolt, fastens
the supplementary metal member for fastening and a pedestal
previously disposed on the ground so that the marker for mobile
communications can be fixed on the ground due to axial force
of the fastening body (fastening force).
The metal member of the housing is integrally fixed upon
resin-molding of the housing. In this case, when adhesion
3
between the metal member and an interface of the resin is small,
detachment of adhering surfaces occurs. Thus, the marker for
mobile communications cannot be sometimes sufficiently fixed
on the ground (pedestal). Furthermore, using the metal member
increases manufacturing cost. JP-2006-183678-A discloses a
structure in which a bolt directly fastens a resin-based
housing, decommissioning the metal member. It is disclosed
that this structure can reduce manufacturing cost and stably
fix a marker for mobile communications on the ground.
SUMMARY OF THE INVENTION
However, with the technique described in
JP-2006-183678-A, when a long time has passed since the marker
for mobile communications has been fixed on the ground, axial
force of the bolt is degraded. In a state where the bolt has
been degraded, when a mobile object passes over the marker for
mobile communications, the marker for mobile communications
vibrates so as to cause the bolt to loosen. Therefore, there
is a problem that the marker for mobile communications cannot
be stably fixed for a long time.
Note that, when a bolt directly fastens a resin without
using a supplementary body for fastening, such as a metal member,
axial force of the bolt is degraded due to stress relaxation
of the resin as time passes. JP-2006-183678-A discloses that
performing fastening so as to satisfy a conditional expression
4
acquired based on a contact area of the bolt, temperature, a
resin, and a coefficient of linear expansion of the bolt, and
the like, can retain the axial force even after a certain period
of time has passed (for example, 1000 hours). However, the axial
force extremely decreases after a long time has passed (for
example, after one year). In this case, the remaining axial
force falls below axial force capable of preventing the
loosening with respect to the vibration, and the loosening
occurs in the bolt due to the vibration when the mobile object
passes over.
The present invention has been made in consideration of
the above problems. An object of the present invention is to
propose a marker for mobile communications capable of retaining
axial force of a fastening body, preventing loosening, and being
fixed stably.
In order to solve the problems, according to one
embodiment of the present invention, there are provided a
housing including an electronic board inside, a pedestal
retaining the housing, a fastening body fastening the housing
and the pedestal. The housing is molded from a resin that
expands or contracts in accordance with a variation in
temperature. The fastening body has a coefficient of linear
expansion substantially the same as a coefficient of linear
expansion of the housing.
5
According to one embodiment of the present invention,
even after a long time has passed since fastening, axial force
of a fastening body can be retained, loosening can be prevented,
and a marker for mobile communications can be stably fixed.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a top configuration view of a marker for mobile
communications;
Fig. 2 is a schematic view of wireless communications
performed between the marker for mobile communications and a
mobile object;
Fig. 3 is a cross-sectional configuration view of the
marker for mobile communications;
Fig. 4 is a graphical representation of relationship
between axial force retention time and axial force retention;
Fig. 5 is a graphical representation of relationship
between axial force retention time and axial force retention;
Fig. 6 is a graphical representation of relationship
between axial force retention time and axial force retention;
Fig. 7 is a cross-sectional configuration view of another
marker for mobile communications;
Fig. 8 is an enlarged cross-sectional configuration view
of another marker for mobile communications;
Fig. 9 is an enlarged cross-sectional configuration view
of another marker for mobile communications;
6
Fig. 10 is an enlarged cross-sectional configuration
view of another marker for mobile communications; and
Fig. 11 is a top configuration view of the marker for
mobile communications fixed by another fastening method.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
(1) Entire configuration
A schematic configuration of a marker for mobile
communications 1 will be described with reference to Figs. 1
and 2.
Fig. 1 is a top configuration of the marker for mobile
communications 1. Fig. 2 is a schematic view of wireless
communications 11 performed between the marker for mobile
communications 1 and a mobile object 9.
The marker for mobile communications 1 is fixed on a road
surface 3 by a fastening body 2. The fastening body 2 is, for
example, a bolt including a metal, such as stainless steel. The
mobile object 9, such as a motor vehicle, travels on the road
surface 3. When the mobile object 9 passes over the marker for
mobile communications 1, an antenna 10 included in the mobile
object 9 and the marker for mobile communications 1 fixed on
the road surface 3 perform the wireless communications 11 at
the passing timing.
For example, in a case where the marker for mobile
communications 1 has been fixed on the road surface 3 of a toll
7
road, the marker for mobile communications 1 receives
information on a type of car and an inlet tollgate from the mobile
object 9 (antenna 10). Based on the information, the marker
for mobile communications 1 calculates and transmits toll
information to the mobile object 9. Onboard equipment (not
illustrated) included in the mobile object 9 notifies a driver
of the toll information that has been received, by a voice or
an image.
The marker for mobile communications 1 may transmit
regulation speed information during a traveling section, to the
mobile object 9. In this case, the mobile object 9 compares
and collates the regulation speed with current speed by using
the onboard equipment. In a case where the current speed exceeds
the regulation speed, voice information is generated so that
the driver can be alerted.
As described above, since the wireless communications
11 due to the marker for mobile communications 1 are sometimes
used for a transfer of money and improvement of security, high
reliability is required. Note that, here, the marker for mobile
communications 1 has been fixed on the road surface 3. The
marker for mobile communications 1 is not limited to this, and
may be, for example, fixed on a wall surface or a ceiling.
(2) Cross-sectional configuration
Fig. 3 is a cross-sectional configuration of the marker
for mobile communications 1. Specifically, the
8
cross-sectional configuration taken along line A-A of Fig. 1
is illustrated. An electronic board 7 is disposed on a tray
6. The electronic board 7 is sealed with a filler 8 so as to
be protected. Furthermore, a housing 5 covers the filler 8 from
the upper side. As a result, the marker for mobile
communications 1 is made. Note that an electronic component
for the wireless communications is disposed on the electronic
board 7.
The marker for mobile communications 1 is directly
fastened and fixed to a pedestal 4 that has been previously fixed
on the road surface 3, using the fastening body 2. Axial force
is applied to the metal bolt that is the fastening body 2 so
that the marker for mobile communications 1 can be fixed on the
ground.
The tray 6 and the housing 5 are made from a resin.
Examples of the resin include fiber reinforced plastics (FRP).
The FRP include a glass fiber or a carbon fiber. Examples of
the filler 8 include a potting resin and a polyurethane resin.
The filler 8 may seal the electronic board 7 so as to be partially
filled as illustrated in Fig. 3 or be entirely filled.
According to the present embodiment, the marker for
mobile communications 1 has been directly fastened to the
pedestal 4 by the fastening body 2. Therefore, there is no need
to adhere a metal member for supplementing fastening of the
9
fastening body 2, to the marker for mobile communications 1.
Thus, manufacturing cost can be reduced.
Furthermore, according to the present embodiment, the
marker for mobile communications 1 is made so that a coefficient
of linear expansion of the housing 5 and a coefficient of linear
expansion of the fastening body 2 are substantially the same.
The detailed descriptions will be given later. Making the
coefficient of linear expansion of the housing 5 and the
coefficient of linear expansion of the fastening body 2 in
contact with the housing 5 substantially the same, the axial
force of the fastening body 2 from degrading due to a variation
in temperature can be prevented. Therefore, loosening of the
fastening body 2 caused in accordance with the degradation of
the axial force can be prevented. Substantially the same
between the coefficient of linear expansion of the housing 5
and the coefficient of linear expansion of the fastening body
2 may be made so as to set the coefficient of linear expansion
of the fastening body 2 based on the coefficient of linear
expansion of the housing 5. Substantially the same includes
a case where both of the coefficients are completely the same,
or a case where both of the coefficients are in a range of identity
in terms of retaining the axial force of the fastening body 2,
preventing the loosening, and fixing the marker for mobile
communications 1 stably. For example, a case where a ratio
(αR/αB) between the coefficient of linear expansion (αR) of the
10
housing 5 and the coefficient of linear expansion (αB) of the
fastening body 2 satisfies 0.80 ≤ (αR/αB) ≤ 1.20, is included.
(3) Relationship between axial force retention time and axial
force retention
Relationship between axial force retention time and
axial force retention will be described with reference to Figs.
4 to 6.
Fig. 4 is relationship of axial force retention time and
axial force retention of the fastening body 2 after the marker
for mobile communications 1 has been directly fixed to the
pedestal 4 by the fastening body 2, in a case where the
coefficient of linear expansion αR of the housing 5 and the
coefficient of linear expansion αB of the fastening body 2 are
substantially the same.
As illustrated in Fig. 4, the axial force of the fastening
body 2 decreases as time passes. However, the axial force is
retained higher than axial force generating loosening X. Even
in a case where the mobile object 9 passes over the marker for
mobile communications 1 and then the marker for mobile
communications 1 vibrates, since the axial force of the
fastening body 2 is higher than the axial force generating
loosening X, no loosening of the fastening body 2 occurs.
Therefore, in this case, even after a long time has passed since
the fastening, the axial force of the fastening body 2 can be
retained and the loosening can be prevented.
11
Figs. 5 and 6 each illustrate relationship between axial
force retention time and axial force retention in a case where
a variation in temperature occurs. Figs. 5 and 6 each also
illustrate relationship between axial force retention time and
axial force retention in a case where the coefficient of linear
expansion αR of the housing 5 and the coefficient of linear
expansion αB of the fastening body 2 are not substantially the
same. The marker for mobile communications 1 is usually set
outdoors. Thus, the marker for mobile communications 1 is
influenced by a variation in temperature due to day and night
or a seasonal variation.
Fig. 5 will be described first. Fig. 5 is the
relationship between the axial force retention time and the
axial force retention in a case where the following conditional
expression is satisfied: (the coefficient of linear expansion
αR of the housing 5) ≈ (the coefficient of linear expansion αB
of the fastening body 2), in a case where the temperature
increases. As a comparative example, Fig. 5 also illustrates
the relationship between the axial force retention time and the
axial force retention in a case where the following conditional
expression is satisfied: (the coefficient of linear expansion
αR of the housing 5) << (the coefficient of linear expansion
αB of the fastening body 2).
As illustrated in Fig. 5, in the case where the following
conditional expression is satisfied: (the coefficient of linear
12
expansion αR of the housing 5) ≈ (the coefficient of linear
expansion αB of the fastening body 2), even when the temperature
increases, there is no influence due to the increase in
temperature with respect to the axial force of the fastening
body 2. The axial force of the fastening body 2 is retained
higher than the axial force generating loosening X. Therefore,
in this case, even after a long time has passed since the
fastening, the axial force of the fastening body 2 can be
retained and the loosening can be prevented.
In contrast, in the case where the following conditional
expression is satisfied: (the coefficient of linear expansion
αR of the housing 5) << (the coefficient of linear expansion
αB of the fastening body 2), when the temperature increases,
the fastening body 2 expands in an axial force energizing
direction (direction perpendicular to the pedestal 4). The
housing 5 also expands in the same direction. However, an amount
of expansion of the fastening body 2 in the axial force
energizing direction is larger than an amount of expansion of
the housing 5 in the same direction. Thus, the axial force is
degraded, and the axial force retention time until falling below
the axial force generating loosening X, shortens.
Therefore, in a case where a long time has passed since
the fastening, the axial force of the fastening body 2 becomes
lower than the axial force generating loosening X. In this case,
when the marker for mobile communications 1 vibrates after a
13
long time has passed since the fastening, the fastening body
2 is influenced by the vibration to loosen. Thus, the marker
for mobile communications 1 cannot stably fixed.
Next, Fig. 6 will be described. Fig. 6 is relationship
between axial force retention time and axial force retention
in a case where the following conditional expression is
satisfied: (the coefficient of linear expansion αR of the housing
5) ≈ (the coefficient of linear expansion αB of the fastening
body 2), in a case where the temperature increases. As a
comparative example, Fig. 6 also illustrates relationship
between axial force retention time and axial force retention
in a case where the following conditional expression is
satisfied: (the coefficient of linear expansion αR of the housing
5) >> (the coefficient of linear expansion αB of the fastening
body 2).
In the case where the following conditional expression
is satisfied: (the coefficient of linear expansion αR of the
housing 5) ≈ (the coefficient of linear expansion αB of the
fastening body 2), as described above, there is no influence
due to the increase in temperature with respect to the axial
force of the fastening body 2. Therefore, even after a long
time has passed since the fastening, the axial force of the
fastening body 2 can be retained and the loosening can be
prevented.
14
In contrast, in the case where the following conditional
expression is satisfied: (the coefficient of linear expansion
αR of the housing 5) >> (the coefficient of linear expansion
αB of the fastening body 2), when the temperature increases,
the fastening body 2 expands in an axial force energizing
direction (direction perpendicular to the pedestal 4) and the
housing 5 also expands in the same direction. In this case,
since an amount of expansion of the fastening body 2 in the axial
force energizing direction is smaller than an amount of
expansion of the housing 5, the axial force increases once.
However, in contrast, when the temperature decreases,
the housing 5 expands larger than the fastening body 2. Thus,
the axial force of the fastening body 2 decreases. As a result,
the axial force of the fastening body 2 becomes lower than the
axial force generating loosening X. In this case, when the
marker for mobile communications 1 vibrates, the fastening body
2 is influenced by the vibration to loosen. Thus, the marker
for mobile communications 1 cannot be stably fixed.
(4) Effects of the present embodiment
As described above, according to the present embodiment,
the marker for mobile communications 1 is directly fastened to
the pedestal 4 by using the fastening body 2. Accordingly, there
is no need to dispose a metal member for supplementing the
fastening of the fastening body 2, to the marker for mobile
communications 1. Thus, manufacturing cost can be reduced.
15
Furthermore, according to the present embodiment, the
marker for mobile communications 1 is made so that the
coefficient of linear expansion αR of the housing 5 and the
coefficient of linear expansion αB of the fastening body 2 are
substantially the same. Thus, the axial force of the fastening
body 2 can be prevented from degrading due to the influence of
a variation in temperature.
Therefore, even after a long time has passed since the
fastening, the axial force of the fastening body 2 can be
retained and the loosening can be prevented. The marker for
mobile communications 1 can be stably fixed.
Note that, in a case where the FRP are used as a material
of the housing 5, a reinforced fiber direction varies due to
a flow of a resin upon molding of the housing 5. As a result,
discrepancies occur in the coefficient of linear expansion αR
of the housing 5. The ratio αR/αB between the coefficient of
linear expansion αR of the housing 5 and the coefficient of linear
expansion αB of the fastening body 2 preferably satisfies 0.80
< αR/αB < 1.20 in consideration of the discrepancies.
(5) Other embodiments
Fig. 7 is a cross-sectional configuration of another
marker for mobile communications 1A. Specifically, the
cross-sectional configuration taken along line A-A of Fig. 1
is illustrated. The marker for mobile communications 1A is
different from the marker for mobile communications 1 in Fig.
16
3 in that no tray 6 is provided and a filler 8 fixes an electronic
board 7.
The marker for mobile communications 1A made in this
manner can acquire an effect similar to that of the marker for
mobile communications 1 that has been described above. That
is, manufacturing cost can be reduced, for a long time, axial
force of a fastening body 2 can be retained, and loosening can
be prevented.
Figs. 8 to 10 are enlarged cross-sectional
configurations of the marker for mobile communications 1A and
other markers for mobile communications 1B and 1C, respectively.
Fig. 11 is a top configuration of the marker for mobile
communications 1 (1A to 1C) fixed by another fastening method.
The marker for mobile communications 1A illustrated in
Fig. 8 is different from the marker for mobile communications
1 in Fig. 3 in that as described above no tray 6 is provided
and the filler 8 fixes the electronic board 7. Reference numeral
14 denotes a contact area of a contact portion at which one end
of the housing 5 comes in contact with another member (in this
case, the fastening body 2). Reference numeral 15 denotes a
contact area of a contact portion at which the other end of the
housing 5 comes in contact with another member (in this case,
the pedestal 4). Conditions of an area A [mm2] that is the sum
of these contact areas, will be described later.
17
The marker for mobile communications 1B illustrated in
Fig. 9 including the configuration of the marker for mobile
communications 1A in Fig. 8, is different from the marker for
mobile communications 1 in Fig. 3 in that a spacer 12A is disposed
between a housing 5 and a fastening body 2, and a nut 13 is
previously disposed on a pedestal 4, and a spacer 12B is disposed
between the housing 5 and the pedestal 4 or the nut 13.
Similarly to the marker for mobile communications 1 that
has been described above, the marker for mobile communications
1B made in this manner can reduce manufacturing cost, for a long
time, retain axial force of the fastening body 2, and prevent
loosening.
Note that, reference numeral 14 in Fig. 9 denotes a
contact area of a contact portion at which one end of the housing
5 comes in contact with another member (in this case, the spacer
12A). Reference numeral 15 denotes a contact area of a contact
portion at which the other end of the housing 5 comes in contact
with another member (in this case, the spacer 12B). Conditions
of an area A [mm2] that is the sum of these contact areas, will
be described later.
The marker for mobile communications 1C illustrated in
Fig. 10 including the configuration of the marker for mobile
communications 1A in Fig. 8, is different from the marker for
mobile communications 1 in Fig. 3 in that an orientation
direction of a reinforced fiber 16 of the housing 5 is made so
18
as to be substantially the same as an axial direction of the
fastening body 2. Making the orientation direction of the
reinforced fiber 16 substantially the same as the axial
direction of the fastening body 2 can reduce influence of stress
relaxation of a resin, and retain an amount of axial force to
be degraded as time passes, to be minimized. Note that reference
numerals 14 and 15 denote contact areas similar to those in Fig.
8.
The fastening method illustrated in Fig. 11 is different
from the fastening method in Fig. 1 in that four fastening bodies
2 fasten the marker for mobile communications 1 (1A to 1C). In
this manner, by fastening the marker for mobile communications
1 (1A to 1C) by making a plurality of fastening bodies 2 that
is not limited to two, the marker for mobile communications 1
(1A to 1C) can acquire an effect similar to that of the marker
for mobile communications 1 that has been described above. That
is, manufacturing cost can be reduced, for a long time, axial
force of a fastening body 2 can be retained, and loosening can
be prevented.
Here, the conditions of the contact area A will be
described below. In a case where the sum area of the contact
areas 14 and 15 is defined as A [mm2], mass of the marker for
mobile communications 1 (1A to 1C) is defined as m [kg], maximum
acceleration received by the marker for mobile communications
1 (1A to 1C) is defined as a [m/s2], the number of fastening
19
bodies 2 to be used for fixing the marker for mobile
communications 1 (1A to 1C) is defined as N [pieces], yield
stress or a proof stress of 0.2% of the housing 5 is defined
as σy [MPa], and a coefficient of axial force degradation is
defined as K, the marker for mobile communications 1 (1A to 1C)
is constituted so as to satisfy the following Mathematical
Formula 1.
[Mathematical Formula 1]
... (1)
A function of the above Mathematical Formula 1, will be
described. The axial force of the fastening body 2 degrades
as time passes. Thus, when an initial axial force is defined
as F1 [N], a remaining axial force after the degradation is
defined as Fn [N], the coefficient of axial force degradation
is defined as K, the remaining axial force Fn can be expressed
as KF1. Note that the coefficient of axial force degradation
K results in, for example, a value of 0.36 after one year, and
a value of 0.23 after 30 years.
Meanwhile, when the maximum acceleration a is loaded to
the marker for mobile communications 1 (1A to 1C) having the
mass m, force that acts on one fastening body 2 results in ma/N
[N]. When the force ma/N acting on per unit fastening body 2
exceeds the remaining axial force KF1 of the fastening body 2,
loosening occurs in the fastening body 2. Therefore, it is
20
necessary to satisfy KF1 > ma/N in order to prevent the loosening
from occurring in the fastening body 2 after a certain period
of time has passed.
The initial axial force F1 is required to be set so as
to be smaller than strength of the housing 5. Specifically,
when the yield stress or a proof stress of 0.2% of the housing
5 is defined as σy [MPa] and the contact area to be in contact
with the housing 5 is defined as A [mm2], it is necessary to
have a set in order to satisfy F1/A < σy. The above Mathematical
Formula 1 can be acquired based on the above considerations.
The marker for mobile communications 1 (1A to 1C)
constituted so as to satisfy the above Mathematical Formula 1
can prevent the housing 5 from being damaged, and, for a long
time, retain the axial force of the fastening body 2, and prevent
the loosening. Therefore, the marker for mobile communications
1 (1A to 1C) can be stably fixed.
21

WE claim:
1. A marker for mobile communications comprising:
a housing including an electronic board inside;
a pedestal retaining the housing; and
a fastening body fastening the housing and the pedestal,
wherein the housing is molded from a resin that expands
or contracts in accordance with a variation in temperature, and
the fastening body has a coefficient of linear expansion
substantially the same as a coefficient of linear expansion of
the housing.
2. The marker for mobile communications according to
claim 1,
wherein the fastening body has a coefficient of linear
expansion so as to cause a ratio between the coefficient of
linear expansion of the housing and the coefficient of linear
expansion of the fastening body to be in a predetermined constant
range.
3. The marker for mobile communications according to
claim 1,
wherein the fastening body is a bolt, and directly fastens
the housing and the pedestal by causing a head portion of the
bolt to come in contact with one end of the housing so as to
press downward and by screwing an end portion of the bolt in
the pedestal so as to come in contact.
22
4. The marker for mobile communications according to
claim 1,
wherein the housing is set to have an area that is a sum
of a contact area with the fastening body and a contact area
with the pedestal, based on a conditional expression calculated
from the number of the fastening body, yield stress of the
housing, mass of the marker for mobile communications, a
coefficient of axial force degradation of the fastening body,
and acceleration acting on the marker for mobile communications.
5. The marker for mobile communications according to
claim 4,
wherein when the number of the fastening body is defined
as N, the yield stress of the housing is defined as σy, the mass
of the marker for mobile communications is defined as m, the
coefficient of axial force degradation of the fastening body
is defined as K, the acceleration acting on the marker for mobile
communications is defined as a, and the sum area of the contact
area between the housing and the fastening body and the contact
area between the housing and the pedestal is defined as A, the
conditional expression satisfies A > (ma)/NKσy.
6. The marker for mobile communications according to
claim 1,
wherein the pedestal is fixed on a ground, a wall surface,
or a ceiling.
23
7. The marker for mobile communications according to
claim 1,
wherein the housing is constituted by molding fiber
reinforced plastic.
8. The marker for mobile communications according to
claim 7,
wherein the fiber reinforced plastic is a composite
material including a glass fiber or a carbon fiber.
9. The marker for mobile communications according to
claim 7,
wherein the fiber reinforced plastic is molded so as to
cause an orientation of a fiber in proximity to the fastening
body to be substantially the same as an axial direction of the
fastening body.
10. The marker for mobile communications according to
claim 1,
wherein the fastening body is a stainless bolt.
11. The marker for mobile communications according to
claim 1,
wherein a ratio (αR/αB) between the coefficient of linear
expansion of the housing (αR) and the coefficient of linear
expansion of the fastening body (αB) satisfies 0.80 < (αR/αB)
< 1.20.