JP2005024379A - Torsion spring testing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torsion spring testing machine that has superior reproducibility as compared with before and can evaluate hysteresis in a torsion spring itself. <P>SOLUTION: The torsion spring testing machine comprises a rotary table 1; a guide bar 2 that is provided at the center of the rotary table 1 and is fitted to a cylindrical section for installing the torsion spring; a torsion pin 3 that is provided on the rotary surface of the rotary table 1 for fixing one end of the torsion spring; a torque measurement pin 4 that is provided outside the rotary table 1 for fixing the other end of the spring and is connected to a torque measurement means 6 for measuring the torque of the spring; and a measuring instrument 5 for measuring a twist angle in the torsion spring. Additionally, the torsion spring testing machine has a torque measurement means for measuring torque T<SB>1</SB>while the spring is twisted without allowing the torsion spring to stand still in a specified twist angle α<SB>1</SB>preset by rotating the rotary table. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spring testing machine for measuring the rotational torque of a torsion spring (torsion spring, hereinafter simply referred to as “spring”).
[0002]
[Prior art]
A customer (orderer) who needs a torsion spring designates a moment at a specified twist angle to a spring manufacturer (orderer). In response to this, the spring designer designs so as to generate a predetermined torque at a specified twist angle specified by the orderer.
[0003]
Each of the contractor and the orderer measures the rotational torque of the completed torsion spring using their own torsion spring testing machine, and tests whether a predetermined torque value is obtained at a specified twist angle. For this reason, the accuracy of the measuring instrument is important.
[0004]
In order to make a first-class torsion spring testing machine in accordance with JIS standards, accuracy within a measurement error of 1% is required. For that purpose, it must be measured with an accuracy of at least 4 significant figures.
[0005]
For this reason, the conventional torsion spring testing machine is stopped at the specified twist angle, and the torque is measured in a stationary state at this time.
[0006]
[Problems to be solved by the invention]
The torsion spring has inherent hysteresis in the torque due to the terminal shape and friction. For this reason, even if the contractor evaluates with a JIS class 1 torsion spring testing machine and delivers a spring that has passed the inspection, if the orderer actually uses it, the desired torque cannot be obtained at the specified twist angle. There was a problem. Further, when the measuring method is different between the ordering parties, there is a problem that the measurement result is greatly different between the two.
[0007]
The difference between the torque value at the time of inspection and the torque value at the time of actual use is not due to the accuracy of the measuring instrument, but the hysteresis in the spring itself (the torsion caused by the friction of the spring itself and the friction of the measuring instrument). This is because the torque difference generated between the direction and the return direction is inherent.
[0008]
Friction includes static friction and dynamic friction. The value of the static friction changes within the range of the maximum static friction or less depending on the degree of deceleration at the time of transition from the dynamic friction state to the static state and the stop accuracy at the static time. For this reason, in order to increase the accuracy of measuring the torque of the measuring instrument, when the spring is brought into a stationary state, a variation in the static friction state occurs, and on the contrary, the measurement is not reproducible.
[0009]
By the way, the conventional torsion spring testing machine cannot evaluate the magnitude of hysteresis as the characteristic of the torsion spring. For this reason, the displayed torque value is the only torque information that can be obtained, and the magnitude of the hysteresis is not included in the basic data indicating the spring characteristics.
[0010]
For this reason, if the measured values differ between the ordering parties, it is because of the low reproducibility (or accuracy) of the measuring instrument or the low reproducibility due to the hysteresis of the spring itself. I couldn't judge it.
[0011]
The present invention has been made in view of the above, and has as its first object to provide a torsion spring testing machine with higher reproducibility than before, and provides a torsion spring testing machine capable of evaluating the hysteresis of the torsion spring itself. This is the second purpose.
[0012]
[Means for Solving the Problems]
The torsion spring testing machine according to the present invention has the following configuration in order to reduce the poor reproducibility due to the variation in the frictional state when measuring the torque of the torsion spring.
[0013]
A torsion spring testing machine according to the present invention includes a rotary table 1 for rotating a torsion spring, and a guide rod 2 provided at the center of the rotary table and fitted in a cylindrical portion of the torsion spring to install the torsion spring. And a torsion pin 3 provided on the rotating surface of the rotary table for fixing one end of the torsion spring, and a torque provided by the torsion spring for fixing the other end of the torsion spring provided on the outer side of the rotary table. Torque measuring pin 4 to which torque measuring means for measuring the torque is connected, and measuring instrument 5 for measuring the torsion angle of the torsion spring without stopping the rotary table at a preset specified torsion angle α ₁ . characterized in that it comprises a torque measuring means for measuring the torque T ₁ while twisting the spring.
[0014]
With such a configuration, the measurement can be performed in a state close to the state where the orderer actually uses, so that the accuracy of torque measurement is improved. In addition, since the torsion spring is measured in a dynamic friction state because the measurement is performed while rotating, the reproducibility of the measurement is improved. That is, “without static” means that measurement is performed in a dynamic friction state without shifting to a static friction state.
[0015]
In addition, this torsion spring can change the torsion angle of the torsion spring by being rotated by rotating means such as a motor. Further, it is preferable that the rotational speed of the table in the vicinity of the specified twist angle alpha ₁ is as constant as possible speed. Further, it is preferable that the rotational speed in advance unified by agreement between ordering party in the specified twist angle alpha _1.
[0016]
The spring tester measures the torque T _P and T _Q in each of the torque measurement as it passes through the specified twist angle alpha ₁ forward (twisting direction) and backward (return direction), both arithmetic mean torque value it may further comprise a means for outputting as an average torque value Tav of the specified torsion angle alpha _1.
[0017]
The spring testing machine calculates a value R _TH = ΔT ÷ T _av obtained by dividing the reciprocal torque difference ΔT = | T _P −T _Q | when passing the specified twist angle α ₁ by the average torque value T _av. It may further comprise a calculation means and an output means.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
(Basic configuration of torsion spring testing machine)
FIG. 1A is an overall view showing an example of a torsion spring testing machine. Moreover, FIG.1 (b) is the figure which expanded the torque measurement mechanism part of the torsion spring testing machine. The basic configuration of the torque measuring mechanism is composed of a rotary table 1 for rotating a torsion spring S (hereinafter simply referred to as “spring S”) and a center of the rotary table 1 and is fitted to a cylindrical portion of the spring S. A guide rod 2 for installation, a torsion pin 3 for fixing one end of the torsion spring S provided on the rotating surface of the rotary table 1, and the other end of the torsion spring provided on the outer side of the rotary table. A torque measuring pin 4 to which a load cell 6 (an example of a torque measuring means) for measuring the torque of the spring S is connected and a measuring instrument 5 for measuring the torsion angle of the spring S are provided. Further, the entire apparatus includes a display 7 for displaying measured torque values, an input panel 8 for inputting set values such as measurement conditions, and a printer 9 for printing measurement results.
[0019]
You may provide the drive means (for example, a motor etc.) for driving a rotary table, and the reduction gear (rotation speed adjustment means) for adjusting a rotation speed. The measuring instrument 5 may be a rotary encoder that can be connected to a driving system of a rotary table such as a motor and can measure the rotation angle, but may be any other method.
[0020]
Furthermore, a computer program and memory (for example, ROM: read only memory) for analyzing measurement data and registering test conditions, a computer for executing these programs, and the like may be included. If these are included, there is an advantage that the accuracy of control of the drive system can be improved and complicated statistical processing can be automatically performed. However, in view of the problem of the present invention that suppresses the reproducibility of measured values due to friction, a primitive manual torsion spring testing machine that is not computer-controlled is also included in the present invention, which includes a measurement mechanism described later. It is.
[0021]
FIG. 2A shows a block diagram of the entire torsion spring testing machine of the present invention. FIG. 2B illustrates a block diagram of the rotational drive system 10 among them. A motor 10A, a speed reducer 10B, the rotary drive system 10 including a rotary table 10C (= 1) is applied to the torsion spring S, to measure the torque in the specified torsion angle alpha _1.
[0022]
(Measuring mechanism)
The torsion spring testing machine of the present invention comprises torque measuring means for measuring torque T ₁ while twisting the spring without rotating the torsion spring at a specified torsion angle α ₁ set in advance by rotating the rotary table 1. Yes. In the example of the block diagram in FIG. 2A, this is realized by a program for performing motor control.
[0023]
Conventionally, it was measured by stopping the rotary table at a specified twist angle alpha _1, thus, continues to rotate without also reaching the specified torsion angle alpha ₁ to stop the rotary table. Then, read the torque value _{T 1} in the specified torsion angle alpha _1. When the rotary table is stopped and brought into a stationary state, the friction existing in the spring itself or the friction between the guide rod and the spring reduces the reproducibility of the measurement. This is because, when shifting from the dynamic friction state to the static friction state, variations in measurement occur depending on the degree of deceleration and stop accuracy.
[0024]
FIGS. 3A and 3B are graphs showing the twist angle on the horizontal axis and the torque generated by the torsion spring on the vertical axis. A normal torsion spring testing machine does not draw a graph in this way, and only a torque value is displayed when measured, but this time it is specially graphed for experiments. (A) is a result of measuring a densely wound torsion spring, and (b) is a result of measuring a roughly wound torsion spring.
[0025]
Here, how to display the angle of the torsion spring is defined with reference to FIG. The angle when the torsion spring is twisted is expressed by the angle formed by the linear portions at both ends of the spring (this is called the “outer peripheral angle θ”), and the angle formed by the portion where torque is obtained and the center of the cylinder (this is expressed as There are various display methods such as “center angle φ” (see FIG. 5A).
[0026]
However, since the twist angle α can be defined as the difference between the outer peripheral angles θ, in the present invention, the twist angle α is defined as α = θ ₀ −θ ₁ (where θ ₀ is the outer peripheral angle in the natural state, and θ ₁ is the twist torque. Represents the outer peripheral angle in a state where is added (see FIG. 5B).
[0027]
As is clear from the results of FIG. 3A, the torque values are greatly different between the forward path and the return path. For example, even when an attempt is made to measure torque when the specified twist angle α ₁ = 40 °, there is a large difference in torque values between the forward path and the return path. This difference is called hysteresis. Hysteresis depends largely on the shape of the spring or the like, large enough generally designated torsion angle alpha ₁ is larger. On the other hand, in FIG. 3B, there is almost no hysteresis. This is a spring with a small friction of the spring itself. It can be said that this spring is an excellent spring having a reproducibility of almost 99%.
[0028]
Since the torque value differs between reciprocations even at the same specified twist angle α ₁ , only the forward path or the return path may be measured. However, in order to improve the accuracy, the average torque T _{av is} obtained by arithmetically averaging the values of the forward path and the return _path. May be output as As the method of arithmetic averaging, the simplest method is to take an arithmetic average, but an optimal calculation formula can also be obtained by data analysis.
[0029]
-Comparative example-
FIG. 4 is a diagram showing the relationship between the twist angle and the torque measured using a conventional torsion spring testing machine. In this example, the purpose is to accurately obtain the torque T at the specified twist angle α ₁ = 40 °. Rotate slowly turntable of the torsion spring tester, torsion angles alpha ₁ stops rotating at the time when a 40 °, read the torque value displayed at that time.
[0030]
However, although the read torque T ₁ at the point A in FIG ideal, gradually increasing the twist angle, when he then stops, the torque value is reduced within a certain range. The magnitude of the torque value that decreases at this time varies each time due to slight differences in conditions, such as the stop speed of the turntable and the accuracy of the stop position. For this reason, the torque decreases from the position of the point A to the position of the point B on the graph in some cases, and the torque decreases to the position of the point C in some cases. Conversely, when the torsion angle is decreased and then stopped, the torque value increases within a certain range (not shown).
[0031]
(Means for quantifying the reproducibility of springs)
Torsion spring hysteresis is large, than the hysteresis is small torsion springs, the torque value at the specified torsion angle alpha ₁ is, for that varies with a certain width in each time of measurement, poor reproducibility of the torque value.
[0032]
Since the conventional torsion spring testing machine could not evaluate the magnitude of hysteresis as the characteristic of the torsion spring, it had to read the displayed torque value, and the hysteresis was not included in the basic data indicating the spring characteristic.
[0033]
As described above, it is considered that there are two causes for the occurrence of hysteresis. One is due to the friction between the spring and the guide rod of the testing machine, and the other is due to the friction of the torsion spring itself. In particular, the friction of the torsion spring itself is larger as the torsion spring is tightly wound. In addition, there are elements due to the shape and the like, which is actually quite complicated.
[0034]
At the time of measurement, when a force exceeding the maximum static friction is first applied from the initial static state, the torsion spring is twisted in the dynamic friction state and then stops when it reaches a predetermined angle and becomes static.
[0035]
Friction varies depending on the shape of the spring and the mechanism of the spring testing machine. For example, the closer the spring is wound, the greater the friction of the spring itself. In the case of a method in which the guide rod rotates together with the rotary table, the influence of friction between the guide rod and the spring is small, but in the case of the method in which the guide rod does not rotate even if the rotary table rotates. The friction between the guide rod and the spring is large.
[0036]
Therefore, in the present invention, “torque hysteresis content R _TH ” is defined as a new parameter that has not _existed before. The formula for calculating R _TH is obtained as follows.
[0037]
R _TH = ΔT ÷ Tav × 100 [%]
[0038]
Here, ΔT is the difference between the forward torque value T _P and the return torque value T _{Q at} the specified twist angle α ₁ (ΔT = T _P −T _Q ), and Tav is the forward torque value T _P. When the arithmetic mean value of the return torque value _{T Q (Tav = f (T} P, T Q), where, f is an arithmetic mean function.) represent. As the arithmetic mean function, for example, an arithmetic mean, that is, f = 0.5 × ( _TP + _TQ ) or the like can be considered. Various arithmetic expressions can be used for the arithmetic average function by fitting one of the values to a weighted average or fitting an optimal calculation expression such as a mean square.
[0039]
(Difference from tolerance)
Note that tolerance (tolerance of error with respect to the reference) is set for the spring and may be expressed as a plus or minus percentage tolerance, but the above-mentioned hysteresis content is completely different from the tolerance. is there. If the tolerance is set including the hysteresis, the tolerance must be set in a wider range including the hysteresis width (ΔT) at the specified twist angle α ₁ . Thus, by indicating the hysteresis width as the ratio of the reciprocal arithmetic average value at the specified twist angle α ₁ measured in the dynamic friction state, the hysteresis content that could not be expressed conventionally can be expressed numerically. . The measurement method for the torsion spring is preferably a measurement method that is standardized by agreement between the parties concerned with delivery. On that basis, the hysteresis content rate is clearly specified, and the reproducibility is reduced by the hysteresis of the spring itself. It is clearly communicated to the contractor that it is caused by
[0040]
(Other)
The rotation speed of the rotary table at the time of measurement should be changed by a spring. These measurement conditions are preferably agreed in advance so that both the delivery parties (such as the contractor and the orderer) can perform measurement under the same conditions. In the experiment, the reciprocation was measured in about 30 seconds. It should be noted that a constant speed needs to be maintained near the measurement point (designated twist angle), and the forward path to the measurement point or the return path from the measurement point may be rotated at a high speed. In this way, the measurement time is shortened. This is a range of matters that can be arbitrarily designed by those skilled in the art.
[0041]
The torque may be measured using a load cell or a torque cell. When a load cell is used, there is a merit that the measurement range can be expanded by increasing the length of the arm. Therefore, an example using a load cell is shown as an example. In addition, since there exists a merit which can measure a rotational torque directly when a torque cell is used, a torque cell can also be used if the resolution is within an allowable range. Any one of them is advantageous, and any other method may be used as long as it is a torque measuring means.
[0042]
The measurement program can be provided by being stored in a ROM (Read Only Memory) or other medium.
[0043]
【The invention's effect】
The torsion spring testing machine according to the present invention can provide a highly accurate torsion spring testing machine with high reproducibility, and further provides a torsion spring testing machine having an output including the hysteresis content of the torsion spring itself. can do.
[Brief description of the drawings]
FIG. 1 shows an example of a torsion spring testing machine according to the present invention, and FIG. (B) is the figure which expanded the torque measurement mechanism part of the torsion spring testing machine.
FIG. 2A is a block diagram of the entire torsion spring testing machine of the present invention. (B) is a figure which shows the block diagram of a rotational drive system.
FIGS. 3A and 3B are graphs measured with the torsional angle on the horizontal axis and the torque generated by the torsion spring on the vertical axis. FIGS.
FIG. 4 is a diagram showing a relationship between a twist angle and a torque measured using a conventional torsion spring testing machine.
FIGS. 5A and 5B are diagrams for explaining how to display the angle of the torsion spring. FIGS.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotary table 2 Guide rod 3 Torsion pin 4 Torque measurement pin 5 Torsion angle measuring device 6 Load cell 7 Display 8 Input panel 9 Printer 10A, 10B, 10C Each block S of a rotational drive system S Torsion spring

Claims (3)

A rotary table 1 for rotating the torsion spring, a guide rod 2 provided in the center of the rotary table and fitted in a cylindrical portion of the torsion spring to install the torsion spring, and a rotary surface of the rotary table A torsion pin 3 for fixing one end of the torsion spring, and a torque measuring means provided on the outside of the rotary table for fixing the other end of the torsion spring and for measuring the torque of the torsion spring. A torque measuring pin 4 and a measuring instrument 5 for measuring a torsion angle of the torsion spring are provided, and a torque T ₁ is measured while twisting the spring without stopping the rotary table at a preset specified torsion angle α ₁ . A torsion spring testing machine comprising torque measuring means for performing For torque measurement when passing through the specified twist angle α ₁ , the torque values T _P and T _Q are measured in each of the forward path and the return path, and the torque value obtained by arithmetically averaging the two is the average torque value T _av at the specified twist angle α ₁ . The torsion spring testing machine according to claim 1, further comprising means for outputting as Calculation means for calculating a value R _TH = ΔT ÷ T _av obtained by dividing a reciprocal torque difference ΔT = | T _P −T _Q | when passing through the specified twist angle α ₁ by the average torque value T _av , and The torsion spring testing machine according to claim 2, further comprising output means.

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