JP3494715B2 - Weight calibration method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for calibrating a weight meter mounted on a freight vehicle such as a truck or a dump truck for measuring the weight of a loaded cargo. In particular, the weight meter uses a displacement of a suspension spring as a weight. The present invention relates to a calibration method and apparatus for calibrating a spring constant that changes with time when the conversion is performed based on the spring constant.

[0002]

2. Description of the Related Art Conventionally, a freight vehicle such as a truck or a dump truck may be equipped with a self-weight meter as a weight scale for measuring the weight of loaded cargo.
A strain gauge is attached to the axle of a freight vehicle, and a weak electric signal from this strain gauge is amplified by an amplifier to measure the weight, and the sinking of the spring used in the suspension of the freight vehicle, that is, the displacement is measured. There was something that tried to measure the weight.

The spring constant of the spring of the suspension is used for the latter weight measurement. A value at the design stage or a value at the time of factory shipment is used for this spring constant. However, since this spring constant changes within a few years due to aging, it is necessary to calibrate the spring constant each time in order to accurately measure the weight.

In the conventional calibration, a predetermined heavy object is simply loaded on a freight vehicle and the displacement of the spring is measured to obtain the spring constant after aging based on the weight and the displacement.

[0005]

However, the suspension of a freight vehicle or the like has friction, and a shock absorber or the like is attached in parallel with the spring. Therefore, the suspension as a whole draws a hysteresis loop in the weight / displacement characteristics.

Due to the secular change of the hysteresis loop, the spring constant changes in the above calibration, and accurate weight measurement cannot be performed. In addition, even if an object of a predetermined weight is loaded, a difference in displacement occurs due to the method of loading and how to stop swinging of the suspension that occurs during loading, so it is difficult to obtain the correct spring constant, Therefore, accurate calibration could not be performed.

In view of the above, the present invention measures the displacement of a spring of a vehicle suspension to measure the weight of a load based on the spring constant, and the weight / displacement characteristic of the spring surrounds a straight line due to the spring constant to form a hysteresis loop. In the method and apparatus for calibrating the spring constant of the self-weighting machine, the correct spring constant can be obtained even if the hysteresis loop changes due to the secular change of the spring, and an accurate calibration can be performed.

[0008]

[Means for Solving the Problems]

[1] In order to achieve the above object, a method for calibrating a self-weighting meter according to the present invention is a flexure line in which a straight line representing a predetermined weight in a weight / displacement characteristic of a spring of a vehicle suspension is obtained from a spring constant before aging. The ratio of two line segments formed by intersecting the figure and the hysteresis loop at three points is obtained in advance, and during calibration, the hysteresis loop after aging is obtained by actual measurement, and the straight line representing the predetermined weight is the hysteresis after aging. A line segment formed by intersecting the loop at two points is divided by the ratio, and a spring constant giving a straight line passing through the divided point and the origin is set as a spring constant at the predetermined weight after aging.

[2] In addition, the apparatus for calibrating a self-weight meter according to the present invention comprises a load device that changes the displacement of the spring of the suspension by pulling the vehicle downward or pushing it upward, and a predetermined weight based on the weight / displacement characteristic. The straight line represented is obtained from the spring constant before aging, and is changed by a storage device that stores and previously stores the ratio of two line segments formed by intersecting the deflection diagram and the hysteresis loop at three points, and the load device. The displacement of the spring to be input is input from the weight meter to obtain the hysteresis loop, and a line segment formed by a straight line representing the predetermined weight intersecting the hysteresis loop at the time of calibration at two points is divided by the ratio, A calculation device for calculating a spring constant that gives a straight line passing through the origin, and a calibration execution means for making the calculated spring constant the spring constant at the predetermined weight after aging have been provided. It is characterized in.

[0010]

In the present invention, in order to calibrate the spring constant that changes with the lapse of time, first, the displacement of the spring of the suspension is changed by pulling the vehicle downward or pushing it upward by the load device. As a result, the hysteresis loop of the weight / displacement characteristic after aging is obtained by actual measurement.

Then, a line segment where a straight line representing a predetermined weight intersects with the hysteresis loop after aging at two points is obtained. A spring constant that gives a straight line passing through the origin and a division point that divides this line segment into a ratio of m: n is calculated.

The above-mentioned ratio m: n is obtained in advance by experiments when the vehicle is shipped from the factory and is stored in the storage device. In this experiment, the load device pulls the vehicle downwards or pushes it upwards in the same manner as described above, and the calculation device obtains the hysteresis loop in the weight / displacement characteristic based on the measurement result of the weight meter.

Then, the arithmetic unit obtains two line segments formed by intersecting the hysteresis loop before the aging and the straight line by the spring constant with the above-mentioned straight line representing the predetermined weight at three points. The ratio of these two line segments is the ratio of m: n obtained in advance. From this ratio, the spring constant after aging is obtained as described above, and the calibration of the spring constant is executed by the calibration executing means.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. As shown in FIGS. 1 to 3, the rear wheels 2 of the freight vehicle 1 are mounted on a bottom plate 3. This wheel 2 has a propeller shaft 4 and a rear axle 5
The rotational driving force of the engine (not shown) is transmitted via the. These wheels 2 and the like are suspended via a suspension 6 on a frame 7 of the vehicle body.

A displacement sensor 8 (see FIG. 4) such as a stroke sensor for measuring the displacement of the spring 6a constituting the suspension 6 is attached to the suspension 6.

The detection signal of the displacement detected by the displacement sensor 8 is converted into the weight based on the spring constant and the like by the conversion circuit 9 and displayed by the display 10, as shown in FIG. These displacement sensor 8, control device 15, display 1
Zeros and the like constitute the own weight 20. This deadweight 20
Is mounted on the freight vehicle 1.

Since the spring 6a deteriorates over time, its spring constant also changes over time. Therefore, accurate weight measurement cannot be performed without calibrating the spring constant. Therefore, a calibration device 30 that calibrates the spring constant is provided.

The calibration device 30 includes a load device 11 for pulling down the freight vehicle 1 in addition to the weight meter 20. In this load device 11, a hand portion 13 provided on an upper end of a hydraulic cylinder 12 grips a part of a frame 7 of a vehicle body, and a lower end of the hydraulic cylinder 12 is locked to a rail 14 provided on the bottom plate 3. It has a structure. The rails 14 are arranged on the bottom plate 3 in the left-right direction with respect to the vehicle body. Two such rails 14 are provided in parallel, and a total of four hydraulic cylinders 12 are provided so that the vehicle body is pulled down in parallel with the bottom plate 3.

Such a load device 11 is a control device 15
(See FIG. 4) is controlled by the load device control circuit 16. A pressure sensor 17 constituting a calibration device 30 is provided in the hydraulic cylinder 12 used in the load device 11 to measure the pressure.

Both the measured pressure signal and the spring displacement signal measured by the displacement sensor 8 are input to the arithmetic circuit 17 to perform an operation regarding a hysteresis loop as described later. In the memory circuit 18, in addition to data for controlling the load device 11 and data for performing the above calculation, a ratio m to be described later, which is necessary for calculating the spring constant after aging from the hysteresis loop: n is stored.

The operation of this embodiment will be described below with reference to FIG. First, when the weight meter 20 mounted on the freight vehicle 1 is shipped from the factory, the deflection diagram 21 obtained from the hysteresis loop 20 and the spring constant in the weight / displacement characteristics
Experiment to find the relationship with.

That is, the freight vehicle 1 is pulled down by the load device 11 and the suspension 6 is contracted. The displacement sensor 8 measures the displacement of the spring 6a of the suspension 6 at this time. Further, the pressure in the hydraulic cylinder 12 used in the load device 11 is measured by the pressure sensor 17, is given to the arithmetic circuit 17, and is converted into weight.
The above displacement is also input from the displacement sensor 8 to the arithmetic circuit 17 and converted into weight.

When the load device 11 gradually changes the load by the load device control circuit 16 to change the spring displacement, a hysteresis loop 20 shown in FIG. 5 is drawn. That is, when the load (weight) increases, the origin O to A
When the load is reduced after passing through the points C and C, the point O returns to the origin O through the points D and E. If it is shipped, no secular change has occurred, and the deflection diagram 21 (line segment OH) obtained from the spring constant at the design stage is known.

These hysteresis loop 20 and line segment OH
On the other hand, three points B, G, and
By F, two line segments BG and GF are obtained. It is considered that the ratio m: n between the line segments BG and GF does not change even if the hysteresis loop 20 or the line segment OH changes with time.

This is because the hysteresis loop 20 and the line segment OH change by falling down in the lower right direction in FIG. 5 due to aging, but the hysteresis loop 20 itself maintains a similar shape.

In this way, the arithmetic circuit 17 obtains the hysteresis loop 20 and the ratio m: n in advance and stores it in the memory circuit 18. Then, when the spring 6a of the suspension deteriorates due to aging and the spring constant needs to be calibrated, the hysteresis loop 20 (this hysteresis loop may be tilted downward in the lower right direction in FIG. 5 due to aging) by the same procedure as described above. However, the same reference numeral "20" is used for convenience of explanation. That is, the freight vehicle 1 is pulled down by the load device 11 to obtain the weight / displacement characteristics.

At this time, since the spring constant has already changed due to aging, it is unknown what kind of inclination the straight line representing the spring constant has. Therefore, the spring constant is obtained by using the previously known ratio m: n.

For this reason, the line segment BF formed by intersecting the straight line XI representing the predetermined weight of the same value at two points with respect to the hysteresis loop 20 obtained after the aging is divided by this ratio m: n. A straight line OG passing through the division point G and the origin O is
Gives the spring constant after aging. In this way, the spring constant can be calculated.

This calculation is performed by the calculation device 17,
The calculated spring constant after aging is stored in the memory circuit 18.
Will be updated and stored. Based on this new spring constant, the conversion circuit 9 converts the displacement of the spring 6a into weight. And
The converted weight is displayed on the display 10.

In this way, since the correct spring constant that has changed over time can be calculated, accurate calibration can be performed. Therefore, the weight displayed on the display 10 has less error.

In other words, conventionally, a heavy object was simply loaded statically to displace the spring, which was affected by hysteresis, making it difficult to accurately calibrate the spring constant. In the example, when calibrating the spring constant, the spring displacement is, so to speak, quasi-dynamically continuously changed to draw the entire hysteresis loop, and the spring constant after aging is obtained based on this entire hysteresis loop. With this, the correct spring constant can be obtained without being affected by hysteresis, and accurate calibration can be performed.

Since the four hydraulic cylinders 12 for calibrating the load device 11 can move on the rails 14, they can be commonly used for freight vehicles 1 having different vehicle widths.

Although FIG. 5 is drawn as a straight line for the sake of convenience, the actual drawing is a curved line. This is because the laminated leaf spring acts as the main spring to the auxiliary spring as the load increases, and the spring constant also changes depending on the number of leaf springs that are acting.

In the above embodiments, the load device 11 pulls the cargo vehicle 1 downward to change the displacement of the spring 6a, but in other embodiments, the cargo vehicle 1 is pushed upward. The displacement of the spring 6a may be changed. In this case, it is desirable that a cargo with sufficient weight be loaded in the freight vehicle beforehand.

Further, in the above embodiment, the predetermined weight for obtaining the ratio m: n in advance and the predetermined weight for obtaining the dividing point G by this ratio m: n are the same, and are one kind. However, if a plurality of types of predetermined weights are used, an accurate ratio m: n can be obtained by averaging the calculation results obtained from these, and thus a more accurate division point G can be obtained and a more accurate spring constant can be obtained. It becomes possible to obtain.

Further, in the above embodiment, the load device 1
Although 1 is calibrated by the hydraulic cylinder 12, it may be a device using another power source such as an electric motor.

[0037]

As described above, according to the method and apparatus of the present invention, the straight line representing the predetermined weight in the weight / displacement characteristics of the spring of the vehicle suspension is the deflection diagram and hysteresis obtained from the spring constant before aging. The ratio of two line segments formed by intersecting the loop at three points is obtained in advance, and during calibration, the hysteresis loop after aging is obtained by actual measurement, and the straight line representing the predetermined weight is 2 times the hysteresis loop after aging. A line segment that intersects at points is divided by the ratio, and the spring constant that gives a straight line passing through the divided point and the origin is configured to be the spring constant at the predetermined weight after aging. Accurate calibration of the spring constant can be performed without being affected by, and thus accurate weight measurement can always be performed regardless of changes over time.

[Brief description of drawings]

FIG. 1 is a rear view of a freight vehicle for explaining an embodiment of the method and apparatus for calibrating a weight meter according to the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a plan view of FIG.

FIG. 4 is a block diagram showing an embodiment of a method and apparatus for calibrating a weight meter according to the present invention.

FIG. 5 is a diagram showing a weight / displacement characteristic for explaining a method for calibrating a self-weight meter according to the present invention.

[Explanation of symbols]

20 self-weight meter 30 Calibration device 6 suspension 6a spring 11 load device 17 arithmetic unit 18 storage 20 Hysteresis loop In the drawings, the same reference numerals indicate the same or corresponding parts.

Front page continued (72) Inventor Nobuo Sugamura 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Transtron Co., Ltd. (56) References JP-A-6-294679 (JP, A) JP-A-52-102762 (JP) , A) JP 62-195518 (JP, A) JP 7-260558 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01G B60G G01D G01L

Claims (2)

(57) [Claims] 1. A displacement of a spring of a vehicle suspension is measured to measure a weight of a load based on a spring constant, and a weight / displacement characteristic of the spring is obtained from the spring constant. A method for calibrating the spring constant of a self-weighting meter that draws a loop, in which a straight line representing the predetermined weight in the weight / displacement characteristic intersects the deflection diagram and the hysteresis loop obtained from the spring constant before aging at three points. The ratio of the two line segments created in advance is calculated in advance, the hysteresis loop after aging is found by actual measurement during calibration, and the line segment created by intersecting the line representing the predetermined weight with the hysteresis loop after aging at two points Is divided by the ratio, and a spring constant that gives a straight line passing through the dividing point and the origin is set as a spring constant at the predetermined weight after aging, and a self-weight calibration method. 2. The displacement of a spring of a vehicle suspension is measured to measure the weight of a load based on the spring constant, and the weight / displacement characteristic of the spring is obtained from the spring constant. A device for calibrating the spring constant of a self-weighting meter that draws a loop, a load device for changing the displacement of the spring of the suspension by pulling down or pushing up the vehicle, and a straight line that represents a predetermined weight with the weight / displacement characteristics. Was obtained from the spring constant before aging, and
A storage device for previously obtaining and storing a ratio of two line segments formed by intersecting points, and a displacement of a spring which is changed by the load device are input from a weight meter to obtain the hysteresis loop and the predetermined weight. A line segment formed by intersecting the represented straight line in the hysteresis loop at the time of calibration at two points is divided by the ratio, and an arithmetic unit for calculating a spring constant that gives a straight line passing through the divided point and the origin, and the calculated spring constant A self-weight scale calibrating device, comprising: a calibration execution unit that sets a spring constant at the predetermined weight after aging.