Note: Descriptions are shown in the official language in which they were submitted.
CA 02358005 2001-09-24
METHOD OF CONSTRUCTING DATABASE FOR CORRECTING OUTPUTS OF
LOAD MEASUREMENT SENSING DEVICES AND WEIGHT VESSEL
TECHNICAL FIELD
The present invention relates to a method of constructing an output correction
database indicating output characteristics of a plurality of load measurement
sensing devices
such as strain gauge sensors, or the like, in the condition that the sensing
devices are attached
to a vehicle such as a truck, ship, train, airplane, or the like, so that the
database is used for
calculating correction values for correcting vehicle characteristics, or the
like, in which loads
imposed on the respective sensing devices are changed in accordance with the
variations in
output characteristics of the sensing devices and the structure of the
vehicle, when the load of
the vehicle is measured on the basis of the sum of the outputs of the sensing
devices, or the
like. The present invention further relates to a weight vessel adapted to be
used when the
database is constructed by the above method.
BACKGROUND ART
The measurement of load of a vehicle may be provided for a large-sized vehicle
such
as a truck, etc., for example, for the purpose of preventing traffic accidents
such as rolling
accidents caused by overload, etc., and preventing acceleration of
deterioration of the vehicle.
Conventionally, the measurement of load of a vehicle is performed in the
condition
that the vehicle, which is a subject of the measurement, is placed on a
platform weighing
machine sa called "FCA~TItAN" in Japanese. However, because a large-scaled
equipment and
a large installation space are required for the measurement, the number of
platform weighing
machines allowed to be installed in the space is limited so that numbers of
vehicles cannot be
measured. Furthermore, the cost for installing the platform weighing machines
increases.
CA 02358005 2001-09-24
Recently, therefore, a load measUring_apparatus which is mounted on the
vehicle per
se to measure the load of the vehicle is provided.
In an on-vehicle type conventional load measuring apparatus, for example, load
measurement sensing devices such as strain gauge sensors, or the like, are
designed to be
attached to suitable positions between front, rear, left and right places of
carrier frames and
circular-arc-Iike leaf springs interposed between left and right opposite end
portions of front
and rear axles so that the load is measured on the basis of the sum of signals
outputted from
the sensing devices respectively proportional to the loads imposed on the
front, rear, left and
right sensing devices.
When the outputs of the respective sensing devices are used directly for the
measurement of the Ioad of the vehicle by the aforementioned load measuring
apparatus, the
outputs of the sensing devices may become values which do not correspond to
the loads
actually imposed on the respective sensing devices because of the variations
in the output
characteristics of the sensing devices even in the case where the center of
gravity of a
baggage is located substantially at a center of a carrier so that the load
from the baggage or
carrier is evenly imposed on the respective sensing devices. That is, there is
a risk that the
correct values of the load of the baggage placed on the carrier cannot be
obtained on the basis
of the sum of the outputs of the respective sensing devices.
Further, the outputs of the sensing devices depend also on vehicle
characteristics
defined in accordance with the structure of the vehicle.
In measurement of a load on a vehicle by using such a plurality of sensing
devices, it
becomes necessary to correct the outputs of the sensing devices in accordance
with the
individual output characteristics and vehicle characteristics.
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As described above, calculation of correction values for correcting the output
characteristics of the respective sensing devices and calculation of the
output correction
values of the respective sensing devices in accordance with the vehicle
characteristics are
performed on the basis of calculation of coefficients to make the sum of the
outputs of the
respective sensing devices accord with a value corresponding to a known load
value in the
condition that the value of the load on the carrier is known. Particularly,
correction values
corresponding to the output characteristics of the sensing devices are
calculated after the
loaded state is adjusted so that the center of gravity of the carrier in the
loaded state is made
coincident with the center of gravity of the carrier in the tare or non-loaded
state.
Both the calculation of the output characteristics of the sensing devices and
the
calculation of the output correction values of the sensing devices in
accordance with the
vehicle characteristics are performed each time by suitably
inereasing/decreasing the weight
value of a weight on the carrier.
That is, the calculation of the output correction values of the load
measurement
sensing devices is equivalent to the calculation of correction values or
correction equations
for the sensing devices on the basis of a database constructed by calculation
of the changes of
the output characteristics of the respective sensing devices corresponding tv
the weight. It is
therefore necessary to fetch the outputs of the respective sensing devices to
construct the
database while the load on the carrier is increased/decreased gradually and
while the load per
se after the increase/decrease is always made known.
Therefore, in order to make the load per se after increased/decreased always
known
while the load of the carrier is increased/decreased gradually at the time of
the work of
calculating the output correction values, it is considered that weights such
as balance weights.
etc., each having a known mass value are placed on a single position or a
plurality of places
on the carrier so that the load is evenly imposed on the sensing devices and
the number of
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CA 02358005 2001-09-24
weights per place is increased/decreased equally whenever the outputs of the
sensing devices
have been measured and fetched as data.
Because such balance weights to be used by being mounted on the carrier. are,
however, large both in weight and in external size, a conveying apparatus such
as a forklift, a
crane, etc. must be used separately for carrying the balance weights and
inereasing/decreasing
the number of the balance weights on the carrier. Accordingly, there is a
disadvantage that
not only surplus labor and equipment are required but also dangerous work such
as slinging
work for the balance weights must be carried out in the case of a crane.
Further, the weight per balance weight is predetermined so that the pitch for
increasin~decreasing the load is limited by_the predetermined balance weight.
There arises a
disadvantage that the change of the output of each sensing device cannot be
calculated in a
pitch smaller than the weight of one balance weight or various kinds of
balance weights
different in weight must be prepared in order to calculate the change of the
output in a pitch
as small as possible.
Taking the aforementioned circumstances into consideration, a first object of
the
present invention is to provide a method of constructing a database for
correcting outputs of a
plurality of load measurement sensing devices such as strain gauge sensors,
etc., for
measuring load of a vehicle so that the database is used for calculating
correction values for
correcting the outputs of the sensing devices in accordance with output
characteristics of the
sensing devices and vehicle characteristics, and so that the database
indicating the output
characteristics of the sensing devices can be constructed by simple labor.
A second object of the present invention is to provide a weight vessel adapted
for
carrying out the database constructing method so that the weight can be
changed in a desired
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CA 02358005 2001-09-24
arbitrary pitch without requiring any surplus labor, any equipment such as
balance weights,
and any dangerous work.
DISCLOSURE OF THE INVENTION
In order to achieve the above first object, according to the present
invention, there is
provided a method of constructing an output characteristic correction database
indicating
output characteristics of a plurality of load measurement sensing devices
disposed in a
vehicle at portions supporting a carrier of the vehicle so that the database
is to be used to
calculate correction values for correcting the outputs of the sensing devices
in accordance
with vehicle characteristics determined on the basis of variations in output
characteristic of
the sensing devices and a structure of the vehicle, comprising the steps of:
changing an
amount of a liquid contained in a weight vessel placed on the carrier to
thereby change
weight of the weight vessel containing the liquid while making a value of the
weight of the
weight vessel containing the liquid known; and collecting and storing at least
one ofthe
amount of the liquid and the weight of the weight vessel while relating it to
the outputs of the
sensing devices whenever the amount of the liquid in the weight vessel is
changed.
In the above method of constructing a database for correcting outputs of load
measurement sensing devices, according to the present invention, a plurality
of the weight
vessels are placed at lengthwise and widthwise equal intervals on the carrier;
and the outputs
of the sensing devices are collected and stored so as to be related to at
least one of the
amounts of the liquid in the weight vessels and the weight values of the
weight vessels in a
condition that the weight values of the weight vessels are made equal to each
other.
In order to achieve the above second object, according to the present
invention, the
above-mentioned weight vessel comprises. a vessel body shaped like a hollow
box so that a
liquid can be reserved in the inside of the vessel body; an injection inlet
formed in an upper
portion of the vessel body; a discharge outlet formed in a lower portion of
the vessel body;
CA 02358005 2001-09-24
and a scale formed on a side portion of the vessel body so as to indicate a
value
corresponding to the amount of the liquid reserved in the vessel body; wherein
at least the
side portion provided with the scale in side portions of the vessel body is
formed of a
transparent or semitransparent member so that the amount of the liquid in the
vessel body can
be seen through the transparent or semitransparent member.
In the above weight vessel, according to the present invention, rotatable
caster wheels
are attached to at least three corner portions on a lower end of the vessel
body to thereby
make the vessel moveable.
In the above weight vessel, according to the present invention, shock
absorbers are
interposed between corner portions of the vessel body and the caster wheels
respectively so
that the shack absorbers can be expanded/contracted to come near to/go far
from a ground
surface of the caster wheels and so that the vessel body is urged to go far
from the ground
surface with respect to the caster wheels against loads of the vessel body and
the liquid in the
vessel body.
In the above weight vessel, according to the present invention, the shock
absorbers are
contracted to bring the vessel body into contact with the ground surface when
the amount of
the liquid in the vessel body reaches a predetermined value, and wherein
contraction limiting
members are further provided so that the contraction of the shock absorbers is
limited in the
condition that the vessel body is brought into contact with the ground
surface.
In the method of constructing a database for connecting the outputs of load
measurement sensing devices according to the present invention, the known
weight of the
weight vessel containing the liquid in the weight vessel is
increased/decreased by
increasing/decreasing the amount of the liquid in the weight vessel.
Accordingly, the weights
imposed on the sensing devices can be changed easily in an arbitrary pitch
without requiring
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CA 02358005 2001-09-24
any troublesome balance weight increasing/decreasing work using a conveying
apparatus
such as a forklift, a crane, or the like, as in the conventional case where
balance weights are
used and without the necessity of separately preparing in advance various
kinds of balance
weights different in weight. Accordingly, the database indicating the changes
of the output
characteristics of the sensing devices corresponding to the changes of the
weights imposed on
the sensing devices can be constructed easily..
Further, in the method of constructing a database for correcting the outputs
of the load
measurement sensing devices according to the present invention, the balance of
weight
imposed on the carrier is made uniform by the plurality of weight vessels
having weights
made equal to each other. Accordingly, the changes of the weights in the
output
characteristics of the sensing devices containing the influence of the vehicle
characteristics
determined on the basis of the structure of the vehicle can be collected
easily and stored in
the form of a database.
Further, in the weight vessel according to the present invention, the amount
of liquid
reserved in a box-like vessel body can be confirmed easily by means of the
scale provided at
a side portion of the vessel body. Furthermore, by confirming the weight of
the vessel body
per se and the specific gravity of the liquid in advance, the weight of the
whole of the vessel
body can be calculated easily on the basis of the amount of the liquid in the
vessel body
observed by means of the scale.
Further, by making the vessel body empty, the weight vessel can be carried
only with
the light weight of the weight vessel per se. The weight vessel can be carried
safely without
use of any conveying apparatus such as a forkliR, a crane, or the like, unlike
the conventional
case where balance weights are used. Further, the inerease/deerease of the
weight of the
weight vessel can be performed easily by injecting the liquid into the vessel
body through the
injection inlet and discharging the Liquid out of the vessel body through the
discharge outlet.
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CA 02358005 2001-09-24
Further, in the weight vessel according to the present invention as, by
providing caster
wheels at least at three comer portions so as to rotate on a lower end of the
vessel body, the
vessel body can be moved easily so as not to be lifted from the ground
surface.
Further, in the weight vessel according to the present invention, the vessel
body
comes far from the ground surface of the caster wheels by the urging force of
the shock
absorbers. Accordingly, the carrying of the weight vessel can be performed
easily by means
of the rotation of the caster wheels.
Further, in the weight vessel according to the present invention, by making
the
amount of the liquid in the vessel body reach a predetermined value to make
the shock
absorbers contract, the vessel body is brought into contact with the ground
surface.
Accordingly, if the weight of the weight vessel is increased to some degree,
the weight vessel
can be fixed by the contact of the vessel body with the ground surface.
Furthermore, the
contraction of the shock absorbers is limited by the contraction limiting
members in this
condition. Accordingly, the shock absorbers are prevented from being worn out
and being
damaged in the continuous contracting state due to continuous reception of
overload.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a weight vessel according to an embodiment of
the
present invention;
Figs. 2(a) and 2(b) are explanatory views of a caster wheel portion of the
weight
vessel depicted in Fig. 1, Fig. 2(a) shows an empty state in the weight
vessel, and Fig. 2(b)
shows a state in which a predetermined amount of water is reserved in the
weight vessel;
Fig. 3 is an explanatory view showing a modified configuration example of the
caster
wheel depicted in Figs. 2(a) - 2(b);
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Fig. 4 is an explanatory view showing a procedure for constructing a database
concerning output characteristics of load measurement sensing devices using a
plurality of
weight vessels;
Figs. 5(a) and 5(b) are explanatory side and plan views, respecrively, showing
places
of a vehicle in which the load measurement sensing devices having outputs
corrected in
accordance with correction values obtained on the basis of the database
constructed by the
procedure in Fig. 4 are disposed;
Fig. 6 is an exploded perspective view of a structure in which leaf springs
depicted in
Figs. 5(a) and 5(b) are supported to carrier frames of a vehicle;
Fig. 7 is a sectional view showing a sensing device provided in a shackle pin
depicted
in Fig. 6;
Fig. 8 is a circuit diagram, partly in block, showing the configuration of the
sensing
device depicted in Fig. 7;
Fig. 9 is a front view of a load meter for calculating the load of a vehicle
on the basis
of the outputs of the respective sensing devices depicted in Fig. 7; and
Fij. 10 is a block diagram showing the hardware configuration of a micro-
computer
depicted in Fig. 9.
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference
to
Figs. 1 through 10.
First, referring to Figs. S(a) and 5(b), description will be made about the
places in a
ground type of vehicle where sensing devices of a load measuring apparatus,
which is a
subject of construction of an output-correcting database, are disposed by
using weight vessels
according to an embodiment of the present invention.
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Fig. 5(a) is a side view of a vehicle and Fig. 5(b) is a plan view of the
vehicle. The
vehicle 1 has wheels 3, carrier frames 5, and a carrier 7.
The wheels 3 are provided by six in total, in the front, middle and rear
portions on the
left and right sides, respectively. The pairs of front, middle and rear wheels
are supported by
front, middle and rear axles 9, respectively, at their widthwise or laterally
opposite ends,
respectively.
The carrier 7 is supported on the carrier frames 5. Pairs of front, middle and
rear
positions separated on the Ieft and right sides at a distance on the carrier
frames 5 are
supported, through leaf springs 11, by pairs of left and right end positions
of the respective
front, middle and rear axles 9.
As shown in Fig. 6 which is an exploded perspective view of a structure for
making
the carrier frames support the leaf springs 11 of Figs. 5(a) and 5(b), each of
the leaf springs
11 is formed from belt-like spring leaves which are placed one upon another so
as to be
substantially shaped like a substantially circular arc curved convexly toward
the ground. The
longitudinal opposite ends of the leaf spring 11 are supported by two brackets
13 attached on
the carrier frame 5 at front and rear positions separated at a distance.
Particularly, the rear end
portion of the leaf spring 11 on the rear side of the vehicle 1 is supported
by a shackle 15
interposed between the bracket 13 and the leaf spring 11 so as to be rockable
with respect to
the bracket 13.
In Fig. 6, the reference numeral 17 designates a shackle pin (corresponding to
the
"portions supporting a carrier of the vehicle") which connects the bracket 13
and the shackle
15 to each other so as to be rockable.
In the vehicle 1 configured as described above, load measuring sensing devices
21
(corresponding to the "sensors") are disposed in six shackle pins 17 which are
disposed in the
CA 02358005 2001-09-24
pairs of front, middle and rcar places on the left and right sides of the
vehicle 1 so as to
connect the brackets 13 and the shackles 15 to each other.
In this embodiment, each of the sensing devices 21 is constituted by a
magnetostriction type gauge sensor. As shown in Fig. 7 which is a sectional
view showing a
sensing device provided in the shackle pin depicted in Fig. 6, the sensing
device 21 is
attached to a web 19a of a retaining member 19 received in a hole 17a formed
along the axial
direction from one end of the shackle pin 17.
Incidentally, in the case where the sensing s device 21 is of a
magnetostriction type,
the sensing device 21 is fitted into a receiving hole (not shown) formed in
the web 19a.
Each of the six sensing devices 2.1 respectively disposed in the shackle pins
17 located
in the front, middle and rear places on the left and right sides is
constituted by a sensor 23,
and a voltage-to-frequency conversion portion (hereinafter referred to as V/F
conversion
portion) 25 as shown in Fig. 8 which is a block diagram of the sensing device
21.
The sensor 23 is constituted by a magnetostriction element 23a, and a
transformer 23b
using the magnetostTiction element 23a as a magnetic circuit.
The V/F conversion portion 25 has an oscillator 25a connected to a primary
winding
of the transformer 23b, a detector 25b connected to a secondary winding of the
transformer
23b, and a V/F conversion circuit 25c connected to the detector 25b.
The sensing device 21 is configured to make a current flow into the primary
winding
of the transformer 23b on the basis of the output signal of the oscillator 25a
to thereby induce
an AC voltage in the secondary winding of the transformer 23b, make the
detector 25b
convert the AC voltage into a DC voltage and make the V/F conversion circuit
25c convert
the DC voltage into a pulse signal of a frequency proportional to the value of
the DC voltage
to output the pulse signal to the outside.
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Incidentally, a resistor 25d having a high resistance value is connected
between the
oscillator 25a and the primary winding of the transformer 23b. The voltage
value of the AC
voltage induced in the primary winding of the transformer 23b is prevented
from changing by
the resistor 25d even in the case where the output signal of the oscillator
25a more or less
changes.
Further, the conversion of the AC voltage, 10 induced in the secondary winding
of the
transformer 23b, into the DC voltage by the detector 25b is performed by
multiplication of
the AC voltage by a voltage generated between the opposite ends of the
resistor 25d, so that
noise components contained in the AC voltage are reduced by detection based on
the
multiplication.
Further, in the sensing device 21, the permeability ofthe magnetostriction
element
23a changes correspondingly to the load imposed on the magnetostriction
element 23a. As a
result, the AC voltage induced in the secondary winding of the transformer 23b
changes
correspondingly to the output signal of the oscillator 25a, so that the
frequency of the pulse
signal outputted from the V/F conversion circuit 25c changes.
The detection of one-sided load of the vehicle 1 and the measurement of load
on the
basis of the outputs of the respective sensing devices 21 disposed in the
shackle pins 17 in the
front, middle and rear places on the left and rZght sides are performed by a
micro-computer
33 disposed in a load meter 31 shown in Fig. 9 which is a front view thereof.
A load indication portion 37 which is 35 constituted, for example, by a group
of 7-
segment light-emitting diodes for indicating the load measured by the micro-
computer 33,
three load indication lamps 40a to 40c for indicating a left-sided state, a
uniform state and a
right-sided state respectively, an overload indication lamp 41 for indicating
the fact that the
measured load exceeds a predetermined maximum load value, an alarm buzzer 43
for
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reporting a state of one-sided load and a state of overload, an offset
adjustment value setting
key 45, an overload value setting key 47, ten keys 53, a rest key 54 and a set
key 55 are
disposed on a front surface 31a of the load meter 3l.
As shown in Fig. 10, the micro-computer 33 is constituted by a central
processing unit
(CPU) 33a, a random access memory (RAM) 33b and a read-only memory (ROlVi]
33c.
A nonvolatile memory (NVM) 35 for preventing stored data from disappearing
even
in the case where an electric supply is turned off, the offset adjustment
value setting key 45,
the overload value setting key 47, the ten keys 53, the reset key 54 and the
set key 55 are
directly connected to the CPU 33a. Further, the respective sensing devices 21
and a running
sensor 57 for genezating running pulses correspondingly to the running of the
vehicle 1 are
connected to the CPU 33a through an input interface 33d.
Further, the load indication 37, the left-sided state, uniform state and right-
sided state
load indication lamps 40a to 40c, the overload indication lamp 41 and the
alarm buzzer 43 are
connected to the CPU 33a through an output interface 33e.
The RAM 33b has a data area for storing various kinds of data, and a work area
for
various kinds of processing. Control programs far making the CPU 33a perform
various
kinds of operations are stored in the 8014 33c.
Tables of offset adjustment values and characteristic correction values for
the
respective output pulse signals of the sensing devices 2I, weighting
coefficients ql to q3
peculiar to the axles 9, used for calculating vehicle one-sided load values p
(unit: %) which
will be described later and which indicates the magnitude and direction of
lateral deviation of
load imposed on the vehicle 1, a table of gain correction values for the sum
of frequencies of
the output pulse signals of the sensing devices 21 after the offset adjustment
and
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characteristic correction, load conversion equations, overload values and
values for judgment
of load deviation in the left and right directions are stored in the NVM 35 in
advance.
Adjustment values in the offset adjustment value table are provided to
eliminate the
variations in frequency of the output pulse signals of the six sensing devices
21 in the tare
state of the vehicle 1. The adjustment values are set for the sensing devices
21 respectively by
a setting process in the tare state of the vehicle 1.
Each of the adjustment values for the sensing 25 devices 21 is a difference
(unit: Hz)
between the frequency of the output pulse signal of the sensing device 21 in
the tare state and
the reference frequency 200 Hz of the pulse signal at the time the load is 0
ton. The specific
range of the adjustment value is between +170 Hz and -SOOHz.
Accordingly, each of the sensing devices 21 which can be offset-adjusted by
the
adjustment values respectively is set so that the frequency of the output
pulse signal in the
tare state is in a range of from 30 Hz to 700 Hz.
Characteristic correction values in the characteristic correction value table
are
provided to correct the variations in characteristic of the sensing devices 21
which concerns
the correlation between the loads imposed on the sensing devices Z1 and the
output pulse
signals of the sensing devices 21. The characteristic correction values are
set respectively for
the sensing devices 21 in the stage before the sensing devices 21 are disposed
in the
respective shackle pins 17.
Each of the characteristic correction values for the sensing devices 21 is a
correction
coefficient by which the frequency of the output pulse signal of the sensing
device 21 is
multiplied so that the slope of a line indicating the correlation between the
load imposed on
the sensing device 21 and the output pulse signal of the sensing device 21 is
made coincident
with the slope of a line indicating the reference characteristic.
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In the case where the sensing device 21 has non-linear characteristic so that
the
characteristic of the pulse signal changes from one characteristic to another
characteristic
correspondingly to the frequency band of the output pulse signal, a plurality
of characteristic
correction values to be applied to frequency bands between adjacent turning
points are set for
one sensing device 21.
The weighting coefficients ql to q3 peculiar to the respective axles 9 are
provided to
give weight, correspondingly to the ratios of load distributed to the
respective axles 9, to the
wheelset deviation load values pl to p3 (unit: %), which will be described
later, which
indicate the magnitude and direction of lateral deviation of loads imposed on
the respective
axles 9, and which are calculated on the basis of the frequencies of the
output pulse signals of
the sensing devices 2I after the offset adjustment and characteristic
correction. The weighting
coefficients qI to q3 are set correspondingly to the structure of the vehicle
1 in advance.
In this embodiment, the weighting coefficient ql of the front axle 9 is set to
0.1, the
weighting coefficient q2 of the middle axle 9 is set to 0.2 and the weighting
coefficient q3 of
the rear axle 9 is set to 0.7.
The gain correction value table in the gain correction value table area is
provided to
correct the outputs of the sensing devices 21 to adjust the gains of the
sensing devices 21
correspondingly to the error between the sum of the frequencies of the actual
output pulse
signals of the six sensing devices 21 and the sum of the frequencies of the
originally expected
output pulse signals of the sensing devices 21 in accordance with the loads
imposed on the
six sensing devices 21.
Further, first to sixth correction values Z1 to Z6 are stored in the gain
correction value
table so that one of the six correction values Z1 to Z6 is suitably selected
on the basis of the
combination of the deviation state of the load imposed on the vehicle 1 as to
in which
CA 02358005 2001-09-24
laterally (widthwise) deviated state the load is, among left-sided deviation,
no-deviation, and
right-sided deviation, and the running state of the vehicle 1 as to whether
the vehicle 1 has
run or not after the load measurement is performed previously.
The first, third and fifth correction values Zl, Z3 and z5 are calculated as
follows.
Before the vehicle 1 is made to run, weights (not shown) of lrnown weight
values are placed
successively on positions where the loads are evenly imposed on the respective
sensing
devices 21 on the carrier 7, on positions where loads are imposed on the
respective sensing
devices 21 in the left-sided state, and on positions where the loads are
imposed on the
respective sensing devices 21 in the right-sided state. The sum of the
frequencies of the
output pulse signals of the respective sensing devices 21 is measured at each
of the load-
mount states and then the first, third and fifth correction values Z1, Z3 and
ZS are
respectively calculated in a manner so that the thus obtained sum values at
each load-mount
state is divided by the sum of the frequencies of the originally expected
output pulse signals
of the respective sensing devices 21 correspondingly to the weight values of
the weights.
The second, fourth, and sixth correction values Z2, Z4 and Z6 are calculated
as
follows. Before the vehicle 1 is made to run, weights (not shown) of lrnown
weight values
are placed successively on positions where the loads are evenly imposed on the
respective
sensing devices 21 on the carrier 7, on positions where loads are imposed on
the respective
sensing devices 21 in the left-sided state, and on positions where the loads
are imposed on the
respective sensing devices 21 in the right-sided state. After the vehicle 1 is
made to run in this
state and then stopped, the sum of the frequencies of the output pulse signals
of the respective
sensing devices 21 is measured at each of the load-mount states and then the
second, fourth
and sixth correction values Z2, Z4 and Z6 are respectively calculated in a
manner so that the
thus obtained sum values at each load-mount state is divided by the sum of the
frequencies of
the originally expected output pulse signals of the respective sensing devices
21
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correspondingly to the weight values of the weights, the frequencies of the
output pulse
signals of the respective sensing devices 21 is measured at each of the
respective positions
where the known weight is placed. The first, third and fifth correction values
Z1, Z3 and ZS
are respectively calculated in a manner so that the thus obtained sum values
at various
positions is divided by the sum of the frequencies of the originally expected
output pulse
signals of the respective sensing devices 21 in accordance with the weight
values of the
weights.
The work of constructing the database concerning the output characteristics of
the
sensing devices 21 used for calculating the characteristic correction values
in the
characteristic correction value table and the first to sixth correction values
Z1 to Z6 will be
described below with reference to Figs. 1 through 4.
Fig. 1 is a perspective view of a water injection tank type weight vessel used
as the
aforementioned weight according to an embodiment of the present invention. In
Fig. 1, the
weight vessel 60 in this embodiment has a vessel body 61 shaped like a hollow
box, caster
wheels 63 attached to four corners of the lower portion of the vessel body 61.
The vessel body 61 is formed of, for example, a reinforced plastic filin of
transparent
resin, semitransparent resin, or the like, so that the inside can be seen.
Concave portions 61a
(corresponding to the "corner portions of the vessel body") each of which has
such a size that
a corresponding caster wheel 63 can be received are formed in the Iower four
corner portions
to where the caster wheels 63 are attached.
Further, a water injection port 61c (corresponding to the "injection inlet")
is formed
substantially in the center position of an upper surface 61b (corresponding to
an upper portion
of the vessel body) of the vessel body 61 so that water can be injected into
the inside of
vessel body 61. A scale 61e indicating the amount of water injected and
reserved in the inside
17
CA 02358005 2001-09-24
of the vessel body 61 is formed on one side 61d of the vessel body 61
(corresponding to the
"side portion of the vessel body"). A drain port 61 f (corresponding 'to the
"discharge outlet")
for discharging water from the inside of the vessel body 61 is formed at a
position below the
scale 61 a and on the side surface 6I d of the vessel body 61. As occasion
demands, a water
stopper (not shown), for example, which is formed of soft rubber serving also
as a water
sealing material is suitably attached to the drain port 61 f.
Incidentally, the lower portion of the vessel body 61 at least containing the
concave
portions 61a is formed with such hardness that the rectangular shape as shown
in Fig. 1 can
be kept regardless of the reservation of water in the vessel body 61.
Further, it is a matter of course that the shape of the vessel body 6I is not
limited to
the box shape in this embodiment as shown in Fig. 1 and any shape such as a
columnar shape,
an undefined format bag shape, etc. may be used.
Further, the size of the vessel body 61 is preferably formed so that the
weight of the
weight body 60 takes an even value such as 1 ton, or the like, when the vessel
body 61 is
filled up with water.
As shown in Fig. 2(a), each of the caster wheels 63 is configured so that a
pipe-like
receiving member 63b opened upward is integrally formed at the upper portion
of a frame
63a of the caster wheel 63. A shock absorber 65 is constituted by a coiled
spring 63c received
in the receiving member 63b and a shaft 61h projected from a bottom surface
61g of the
ZO concave portion 61a of the vessel body 61 and having a forward end inserted
into the coiled
spring 63c.
As shown in Fig. 2(a), the shack absorber 65 is configured so that a gap H is
formed
between the upper end of the receiving member 63b and the bottom surface 61 g
of the
concave portion 61 a by means of the elastic force of the coiled spring 63c to
thereby separate
18
CA 02358005 2001-09-24
a bottom surface 61j of the vessel body 61 up far from the ground surface G of
the caster
wheel 63 because of the gap H in the condition that the vessel body 61 is
empty of water. On
the other hand, as shown in Fig. 2(b), the shock absorber 65 is configured so
that the shaft
61h is inserted into the receiving member 63b against the elastic force of the
coiled spring
63c by the weight of water per se contained in the inside of the vessel body
61 to thereby
bring the bottom surface 61 g of the concave portion 61 a into contact with
the upper end of
the receiving member 63b and so as to bring the bottom surface 61 j of the
vessel body 61 into
contact with the ground surface G of the caster wheel 63 in the condition that
an amount of
water not smaller than a predetermined value is reserved in the vessel body
In the shock absorber 65 shown in Figs. 2(a) and 2(b), the receiving member
63b
corresponds to a contraction limiting member.
As shown in Fig. 3, the shock absorber 6.5 may be configured such that a pipe-
like
receiving member 61k opened downward is attached to the bottom surface 61g of
the
concave portion 61a so that the coiled spring 63c is received in the inside of
the receiving
member 61k and a shaft 63d projected from the upper end of the frame 63a of
the caster
wheel 63 is inserted into the coiled spring 63c.
In Fig. 3, the reference numeral 63e designates a flange projected from the
outer
circumference of the shaft 63d in order to receive the coiled spring 63c. In
the shock absorber
65 shown in Fig. 3, the receiving member 61k and the flange 63e correspond to
the
contraction limiting member.
The procedure of constructing the database concerning the output
characteristics of
the sensing devices 21 by using a plurality of weight vessels 60 as defined
above will be
described below with reference to Fig. 4.
19
CA 02358005 2001-09-24
As shown in Fig. 4, ten weight vessels 60 are mounted in the form of a matrix
of two
lines and five columns at both widthwise and lengthwise equal intervals and
placed on the
carrier 7 of the vehicle 1. A water supply pump 70 and a water tank 80 are
disposed on a side
of the vehicle 1.
Each weight vessel 60 and the water supply pump 70 are connected to each other
by
two hoses 71, 71 represented by one line in Fig. 4. One hose 71 connects the
drain port 61 f of
the vessel body 61 of the weight vessel 60 to a water suction port (not shown)
of the water
supply pump 70 and the other hose 71 connects the water injection port 61c of
the vessel
body 61 to a water outlet (not shown) of a drain pump 70.
Incidentally, the gap between the outer circumference of the hose 71 connected
to the
drain port 61 f of the weight vessel 60 and the inner circumference of the
drain port 61 f is
sealed by a not-shown water sealing member so that water leakage is prevented.
In this condition, water is supplied from the water supply tank 80 to the
weight
vessels 60 or water is discharged from the weight vessels 60 to the water
supply tank 80 by
the water supply pump 70 to thereby increase/decrease amounts of water in the
vessel bodies
61 of the weight vessels 60 step by step by a predetermined value while the
amounts of water
are made equal to each other. The frequencies of output signals of the sensing
devices 21 at
each step and the weight of each weight vessel 60 or the amount of water in
each weight
vessel 60 at that time are fetched into the computer not shown. These data are
stored in an
external or internal storage means. As a result, the database concerning the
output
characteristics of the sensing devices 2I is constructed.
Although the above description has bcen made about the case where the amounts
of
water in the vessel bodies 61 of the weight vessels 60 are increased/decreased
by the water
supply pump 70, the present invention can be applied also to the case where
the amounts of
CA 02358005 2001-09-24
water are increased/decreased manually without the water supply pump 70 while
the
respective scales 61 a of the weight vessels 60 are observed.
Taking into consideration the differences between the output frequencies of
the
sensing devices 21 in the respective amounts of water in the database, the
disposition of the
sensing devices 21, etc., the characteristic correction values for the
respective sensing devices
21 and the first to sixth correction values Z1 to Z6 are calculated by means
of the computer
on the basis of predetermined correction value calculation equations. The
correction values
thus calculated are stored in the NVM 35 of the load meter 31.
Although the above description has been made about the case where the
processing
work for constructing the database and calculating the characteristic
correction values and the
first to sixth correction values Z1 to Z6 may be performed by the computer not
shown, the
present invention can be applied also to the case where necessary programs are
stored in the
ROM 33c of the load meter 31 to operate the CPU 33a on the basis of the
programs so that
the processing work may be performed by the micro-computer 33.
In the weight vessel 60 configured as described above in this embodiment, the
weight
of the weight vessel 60 can be adjusted to an arbitrary value when the amount
of water
reserved in the vessel body 61 is adjusted. Furthermore, only by adjusting the
amount of
water, the weight of the weight vessel 60 can be increasedldecreased in a
delicate pitch.
Although the caster wheels 63 attached to the lower four comers of the vessel
body 61
may be omitted, the caster wheels 63 function as follows if the caster wheels
63 are attached
to the lower four corners of the vessel body 61. When the weight vessel 60 is
placed or
removed, the vessel body 61 can be made empty of water so that the weight of
the weight
vessel 60 is lightened. Further, when the caster wheels 63 are rotated in the
condition that the
bottom surface 61 j of the vessel body 61 is separated up from the ground
surface G of the
21
CA 02358005 2001-09-24
caster wheels 63 by the shock absorber 65, the weight vessel 60 can be moved
easily without
any special equipment and without any dangerous work.
Further, such a configuration that when an amount of water not smaller than a
predetermined value is reserved in the vessel body 61, the coiled spring 63c
of the shock
absorber 65 is contracted by the weight of the weight vessel 60 which is the
sum of the
weight of the vessel body 61 and the weight of water in the inside of the
vessel body 61 so
that the bottom surface 61j of the vessel body 61 is brought into close
contact with the ground
surface G of the caster wheels 63 may be omitted or replaced by wheel
stoppers, or the like,
attached to/detached from the caster wheels 63.
In the aforementioned configuration, when the weight of the weight vessel 60
is made
heavy to some degree, the weight vessel 60 can be fixed onto the ground
surface G of the
carrier 7, or the like. Furthermore, because the bottom surfaces 61g ofthe
concave portions
61 a are brought into close contact with the upper ends of the receiving
members 63b
respectively in this condition, reaction force received in the shock absorber
65 from the
ground surface G can be dispersed to and received by the whole of the vessel
body 61.
Accordingly, the reaction force (load) can be prevented from being
concentrated into one
place to damage the weight vessel 60, etc.
Furthermore, the shock absorber 65 per se can 25 be also omitted. By providing
the
shock absorber 65, however, the load imposed on the support shaft of the
caster wheel 63 can
be relaxed by the elastic force of the coiled spring 63c.
Although the specific description about the 30 correction process of the
outputs of the
sensing devices 21 using the aforementioned database and using the
characteristic correction
values and the first to sixth correction values Z1 to Z6 calculated on the
basis of the database
and the specific description about the calculation of load based on the
outputs of the sensing
22
CA 02358005 2001-09-24
devices 21 corrected by the aforementioned correction process are omitted, the
details of
these processes can follow the contents described preliminarily in the load
calculation
apparatus according to JP-A-7-58899 proposed by this Applicant.
Although this embodiment has been described upon the case where a scale 61 a
and a
drain port 61f are formed in one side surface 6Id of each vessel body 61, the
present
invention can be applied also to the case where a scale 61e and a drain port
61f are formed in
two sides respectively or a plurality of scales 61 a and a plurality of drain
ports 61f are formed
in two or more side surfaces, or any scale 61e is not provided.
Although this embodiment has been described about the case where caster wheels
63
are attached to and disposed at the lower four corners of the vessel body 61
through shock
absorbers 65, the present invention may be applied also to the case where the
shock absorbers
65 are omitted or both the shock absorbers 65 and the caster wheels 63 are
omitted.
Although this embodiment has been described about the case where the whole of
the
vessel body 61 is formed from transparent resin or semitransparent resin so
that the inside of
the vessel body 61 can be seen through, the present invention may be applied
also to the case
where, for example, only the side 61 d having the scale 61 a and its vicinity
are formed from
transparent resin or semitransparent resin so that the inside of the vessel
body 61 can been
seen through while the other sides 61 d are formed from opaque resin so that
the inside of the
vessel body 61 cannot be seen through.
Although this embodiment has been described about the case where the gain
adjustment correction values Z1 to Z6 are provided to be separated from the
characteristic
correction values, the present invention may be applied also to the case where
these values
are collected to be one kind of correction values so that the weight vessels
60 are used when
the database for calculation of the correction values collected to be one kind
is constructed. In
23
CA 02358005 2001-09-24
this case, if the characteristics of the sensing devices 21 change
correspondingly to the
frequency bands of the output pulse signals of the sensing devices 21, the
gain adjustment
correction values Z1 to Z6 may be set to different values corresponding to the
frequency
bands as occasion demands.
Although this embodiment has shown the case where the sensing devices 21 are
disposed in the respective shackle pins 17, it is a matter of course that the
locations of the
sensing devices 21 are not limited to the positions shown in this embodiment,
but they are
freely selected so only as the sensing devices 21 are disposed in spindles of
steering lrnuckles
(in the case of steering wheels) or in the portions in the vehicle 1 in which
the load is
imposed from the carrier 7 onto the wheel 3.
Although this embodiment has been described about the case where six sensing
devices 21 are provided because the number of wheels 3 is six and the number
of axles 9 is
three, that is, front, middle and rear axles are provided, it is a matter of
course that the present
invention can be applied also to a vehicle in which the number of wheels is
not six, for
example, four wheels 3 and two axles 9 are provided, etc., so long as the
number of the
sensing devices 21 corresponds to the number of the wheels.
Although this embodiment has been described about the case where
magnetostriction
type sensing devices 21 are used as the sensors, the present invention may be
applied also to
the case where weight measuring sensors having another configuration are used.
Further, the
subject of gain adjustment in accordance with the load deviation or the fact
as to whether the
vehicle 1 has run or not before the load measurement is not limited to the
frequencies of the
output pulse signals of the sensing devices 21 as described above in this
embodiment. Other
v2lues may be used as the subject in accordance with the difference in
configuration of the
sensors such as the voltage level, the current level, the weight value after
weight conversion,
etc.
24
CA 02358005 2001-09-24
The liquid reserved in the vessel body 61 of the weight vessel 60 is not
limited to
water as described above in this embodiment, and any liquid higher or lower in
specific
gravity than water may be used as the liquid. So long as the specific gravity
of the liquid is
known, the weight of the liquid can be calculated on the basis of the amount
of the reserved
liquid recognized by the scale 61e so that the total weight of the weight
vessel 61 can be
managed on the basis of the sum of the weight of the weight vessel 61 and the
weight of the
liquid.
INDUSTRIAL UTILITY
As described above, according to the present invention, provided is a method
of
constructing an output characteristic correction database indicating output
characteristics of a
plurality of load measurement sensing devices disposed in a vehicle at
portions supporting a
carrier of the vehicle so that the database is to be used to calculate
correction values for
correcting the outputs of the sensing devices in accordance with vehicle
characteristics
determined on the basis of variations in output characteristic of the sensing
devices and a
structure of the vehicle, comprising the steps of: changing an amount of a
liquid contained in
a weight vessel placed on the carrier to thereby change weight of the weight
vessel containing
the liquid while making a value of the weight of the weight vessel containing
the liquid
known; and collecting and storing at least one of the amount of the liquid and
the weight of
the weight vessel while relating it to the outputs of the sensing devices
whenever the amount
of the liquid in the weight vessel is changed.
Therefore, the known weight of the weight vessel containing the liquid in the
weight
vessel is increased/decreased by increasing/decreasing the amount of the
liquid in the weight
vessel. Accordingly, the weights imposed on the sensing devices can be changed
easily in an
arbitrary pitch without requiring any troublesome balance weight
increasing/decreasing work
using a conveying apparatus such as a forklift, a crane, or the like, as in
the conventional case
CA 02358005 2001-09-24
where balance weights are used and without the necessity of separately
preparing in advance
various kinds of balance weights different in weight. Accordingly, the
database indicating the
changes of the output characteristics of the sensing devices corresponding to
the changes of
the weights imposed on the sensing devices can be constructed easily.
In the above method of constructing a database for correcting outputs of load.
measurement sensing devices, according to the present invention, a plurality
of the weight
vessels are placed at lengthwise and widthwise equal intervals on the carrier;
and the outputs
of the sensing devices are collected and stored so as to be related to at
least one of the
amounts of the liquid in the weight vessels and the weight values of the
weight vessels in a
condition that the weight values of the weight vessels are made equal to each
other.
Therefore, the balance of weight imposed on the carrier is made uniform by the
plurality of
weight vessels having weights made equal to each other, and the changes of the
weights in
the output characteristics of the sensing devices containing the influence of
the vehicle
characteristics determined on the basis of the structure of the vehicle can be
collected easily
and stored in the form of a database.
Further, according to the present invention, the about-mentioned weight vessel
comprises: a vessel body shaped like a hollow box so that a liquid can be
reserved in the
inside of the vessel body; an injection inlet formed in an upper portion of
the vessel body; a
discharge outlet formed in a lower portion of the vessel body; and a scale
formed on a side
portion of the vessel body so as to indicate a value corresponding to the
amount of the liquid
reserved in the vessel body; wherein at least the side portion provided with
the scale in side
portions of the vessel body is formed of a transparent or semitransparent
member so that the
amount of the liquid in the vessel body can be seen through the transparent or
semitransparent member.
26
CA 02358005 2001-09-24
Therefore, the amount of liquid reserved in a box-like vessel body can be
confirmed
easily by means of the scale provided at a side portion of the vessel body.
Furthermore, by
confirming the weight of the vessel body per se and the specific gravity of
the liquid in
advance, the weight of the whole of the vessel body can be calculated easily
on the basis of
the amount of the liquid in the vessel body observed by means of the scale.
Further, by making the vessel body empty, the weight vessel can be carried
only with
the light weight of the weight vessel per se. The weight vessel can be carried
safely without
use of any conveying apparatus such as a forklift, a crane, or the like,
unlike the conventional
case where balance weights are used. Further, the increase/decrcase of the
weight of the
weight vessel can be performed easily by injecting the liquid into the vessel
body through the
injection inlet and discharging the liquid out of the vessel body through the
discharge outlet.
In the above weight vessel, according to the present invention, rotatable
caster wheels
are attached to at least three corner portions on a lower end of the vessel
body to thereby
make the vessel moveable. Thus, by providing caster wheels at least at three
corner portions
so as to rotate on a lower end of the vessel body, the vessel body can be
moved easily so as
not to be lifted from the ground surface.
In the above weight vessel, according to the present invention, shock
absorbers are
interposed between comer portions of the vessel body and the caster wheels
respectively so
that the shock absorbers can be expanded/contracted to come near to/go far
from a ground
surface of the caster wheels and so that the vessel body is urged to go far
from the ground
surface with respect to the caster wheels against loads of the vessel body and
the liquid in the
vessel body. Accordingly, the carrying of the weight vessel can be performed
easily by means
of the rotation of the caster wheels.
27
CA 02358005 2001-09-24
In the above weight vessel, according to the present invention, the shock
absorbers are
contracted to bring the vessel body into contact with the ground surface when
the amount of
the liquid in the vessel body reaches a predetermined value, and wherein
contraction limiting
members are further provided so that the contraction of the shock absorbers is
limited in the
condition that the vessel body is brought into contact with the ground
surface.
Therefore, by making the amount of the liquid in the vessel body reach a
predetermined value to make the shock absorbers contract, the vessel body is
brought into
contact with the ground surface.
Accordingly, if the weight of the weight vessel is increased to some degree,
the
weight vessel can be fixed by the contact of the vessel body with the ground
surface.
Furthermore, the contraction of the shock absorbers is limited by the
contraction limiting
members in this condition. Accordingly, the shock absorbers are prevented from
being wom
out and being damaged in the continuous contracting state due to continuous
reception of
overload.
28
