JPS61203275A - Bearing-force detecting bolt screwing machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a strength detection bolt tightening machine that enables fastening with accurate yield strength at all times.

(Prior Art) Various methods have been proposed in the past for tightening bolts with a predetermined load. Since the rotation angle method is inaccurate in detecting the snug point, and the torque method has variations in the coefficient of friction, both methods are unable to tighten with an accurate load. In addition, the axial force method was not practical because it was impossible to actually measure the bolt axial force.

The proof stress method is a method in which bolts are tightened so that the permanent elongation of the bolt is 0.2%, and is theoretically very preferable. However, in the past, the point at which the rate of increase in tightening torque after passing through the bolt's elastic range reached a set value of 1/2 to 1/3 of the maximum rate of increase was conveniently regarded as proof strength, and tightening was stopped. I was trying to stop it.

Therefore, if the rate of change in the tightening torque changes due to differences in the tightening conditions due to the washer or the object to be tightened, it will not be possible to tighten with an accurate yield strength, and the tightening load will still vary. There was a problem. Also, the tightening torque
Some methods detect the tightening stop point from the next differential value, but in this case there is a problem in that malfunctions are likely to occur due to noise.

(Purpose of the Invention) The present invention was made in view of the above circumstances, and provides a proof-strength detection bolt tightening system that enables high-accuracy control of the tightening load at the proof stress level even if the tightening conditions change. The purpose is to provide a machine.

(Structure of the Invention) According to the present invention, the object is to maximize the amount of tightening torque equivalent in a bolt tightening machine using a prime mover based on the amount of tightening torque equivalent within the elastic range of the bolt and its primary lag amount. a maximum rate of increase detection circuit that determines and stores the rate of increase; an integral start determination circuit that detects tightening by an amount equivalent to a predetermined tightening angle from a starting point located within the elastic range of the bolt and outputs an integral start signal; an integrating circuit that starts integrating the maximum rate of increase based on a start signal; an adding circuit that calculates the sum of the tightening torque equivalent amount at the starting point and the integral value output by the integrating circuit; Achieved by a strength-detecting bolt tightening machine, which is equipped with a comparison circuit that outputs a tightening stop signal when it determines when the tightening torque has become equal to the amount equivalent to the tightening torque, and stops tightening based on the tightening stop signal. be done.

(Embodiment) FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is a diagram of its tightening characteristics.

In FIG. 1, reference numeral 10 denotes a DC series motor, and the bolts are tightened by the rotation of this motor 10. This electric motor 10 includes an AC power source 12, a thyristor 14, and a current detection resistor 16.
and the main switch 18 form a closed circuit. The tightening torque T is proportional to the current l of the electric motor 10. This current 11
That is, the tightening torque T is detected by the resistor 16.

In order to eliminate the influence of the starting current of the motor 10, it is desirable to provide a soft start circuit in the gate circuit of the thyristor 14, or to configure the output of the resistor 16 to be cut off for a predetermined period of time by a timer.

This embodiment detects the proof strength of a bolt in an analog manner, and is formed entirely of an analog circuit.

First, a maximum increase rate detection circuit I that calculates and stores the maximum increase rate of tightening torque based on the tightening torque T within the elastic range of the bolt and its primary lag amount will be explained.

20.22 are the first and second primary delay circuits, each having a series resistor 20a, 22a1 and a parallel capacitor 20b.
, 22b and operational amplifier 20c.

22c. The time constant of the first delay circuit 20 is set to be extremely small compared to the time constant of the second delay circuit 22. In particular, the time constant of the first primary lag circuit 20 is the current i
It is preferable to set it as small as possible to eliminate high frequency noise.

Of course, if there is no noise, the first primary delay circuit 20 is not necessary.

24 is the output AI of these two-order delay circuits 20 and 22.
, A2 is a subtraction circuit that calculates the difference (AI - A2). 26 is a first hold circuit that determines and stores the maximum increase rate K of tightening torque from the output (AI-A2) of this subtraction circuit 24, and includes an ideal diode 26a with zero forward resistance, an integrating capacitor 26b, and an operational amplifier 26c. It is formed by

By the way, the feature of the present invention is that the maximum increase rate K of the tightening torque is determined based on the difference (AI-A2) between the outputs of the first and second primary delay circuits 10.20.

Within the elastic range of the bolt, the first primary delay circuit 10
Assuming that the delay time of is minute, the change in the output A1 can be considered to be linear, so AI=Kt (K is a spring constant) On the other hand, let T=RC be the time constant of the second primary delay circuit 20. The characteristic equation for the output A2 of the bus is therefore A2=KT (e ”T-1)÷K TA+-A2=
KT(1-e ''/T) Here, for example, if t is the time constant T, then AI-A2=0.632KT;, then = (At-A2)10.632T and t is 2T.
Then, = (AI-A2)10.863T In any case, if t is determined, K can be obtained by calculation.

In this embodiment, the time t1 of point A within the elastic range is preset in the timer 28, and at this time t1, the normally open contact SWI is closed and the tightening torque T is started to be input to the second primary delay circuit 22. Time t2 after a predetermined time t=α from time t1
(i.e. j2 - jl=α), the normally closed contact SW2
is opened and (AI-A2) at this time is stored in the first hold circuit 26. Note that the amplification factor of the operational amplifier 26c is set so that its output becomes K.

The timer 28 receives the output A1 of the first primary delay circuit 20.
A signal is output at time t3 when the starting point B is within the elastic range of the bolt, and at t4 after a period of time β corresponding to a predetermined tightening angle has elapsed from time t3.

This signal at time t4 is an integration start signal.

30 is a second hold circuit, which sequentially stores the output A1 of the first primary lag circuit 20 via a normally closed contact SW3.

The normally closed contact SW3 is opened based on the signal output by the timer 28 at time t3. As a result, this second hold circuit 30
As shown in Figure 2, the starting point B is within the elastic range of the bolt.
The tightening torque T2 will be stored.

32 is an integrating circuit. This integrating circuit 32 is connected to the timer 28
The maximum rate of increase K is integrated over time t via a normally open contact SW4 which is closed by an integration start signal outputted at time t4. That is, the integration is started with time t4, when the tightening is done by an amount equivalent to a predetermined tightening angle from the starting point B, as the integration start point C.

34 is an adder circuit, and the output K t of this integrating circuit 32
and the output T2 of the second hold circuit 30. The output Kt+'l''2 of this adder circuit 34 means a straight line extending from the integration start point C with a slope K. This output is compared with the output A1 of the first primary lag circuit 20 in the comparator circuit 36. This comparison The circuit 36 sends a tightening stop signal to the thyristor 14 when both match (the tightening stop point D).
to the gate circuit 38 to stop tightening.

Generally, if the type of bolt, tightening thickness, etc. are determined, the elongation under load that will result in a predetermined permanent elongation can be determined in advance. Normally, this permanent elongation is set to 0.2% of the length to which tensile force is applied, but it may also be set to 1% of the length of the threaded part of the part to which tensile force is applied. be. In any case, once a predetermined elongation ε is determined, the tightening angle ψ required to generate this elongation ε is determined. If the predetermined tightening angle equivalent amount (t4 to t3) = β stored in the timer 28 in this embodiment is set to a time equal to this tightening angle ψ, tightening at proof stress can be performed faithfully to the theory. It becomes possible.

Note that if the delay time of the first primary delay circuit 20 with respect to the actual tightening torque 2T is sufficiently small and this delay becomes visible as mI, the predetermined tightening angle equivalent amount + t4 - t3) is calculated as described above. It is sufficient to set it to match the tightening angle ψ. However, if the delay of this first primary delay circuit 20 cannot be ignored, this predetermined tightening angle equivalent amount (t4-
Of course, t3) must be set shorter than the time corresponding to the tightening angle ψ.

In the above embodiment, the timer 28 sets the times jl, j2 . j3
t4 is stored, and the integrating circuit 32 integrates K with respect to time. However, in the present invention, the rotation angle θ of the electric motor 10 is detected, the timer stores the amount equivalent to a predetermined tightening angle in θ, and the integrator may be integrated over θ.

Further, the first-order delay amount in the present invention may be calculated digitally at each predetermined time or each predetermined rotation angle (or may be configured entirely or partially by a digital circuit.

Furthermore, in the embodiment, the time point A and the starting point B at which the tightening torque starts to be input to the second primary delay circuit 22 are determined by the timer 2.
8, the time is calculated from the start of tightening, but the present invention is not limited to this, and it is sufficient if the point A1B falls within the elastic range of the output of the first primary delay circuit 20.

For example, the tightening torques at points A and B within the elastic range are preset in a setting device, the output of this setting device is compared with the output of the first primary lag circuit, and the point when the two become equal is determined at points A and B. It may also be the starting point B. FIG. 3 is a configuration diagram showing an embodiment in such a case.

In this figure, 40a is a setting device for setting the tightening torque T1 at point A, and 42a is a setting device for setting the tightening torque T2 at starting point B.
b, 42b are comparators.

Point A is determined based on the output of the comparator 40b, and SWI is closed, and SW2 is opened after time α set by timer 28A. Further, the timer 28B starts counting based on the output of the comparator 42b, and sends a signal to the normally open contacts SW4 and SW5 to start the integration after the elapse of time β corresponding to a predetermined tightening angle. In this case, the setting device 42
Since the output of a becomes the tightening torque at the starting point B, if the output of the setting device 42a is used as is and inputted to the adder 34, the second hold circuit 30 in the embodiment of FIG. 1 can be omitted. become. Note that SW5 is provided to prevent the comparison circuit 36 from outputting a tightening stop signal before the starting point B. Further, in FIG. 3, the same parts as in FIG. 1 are given the same reference numerals, so the description thereof will not be repeated.

The present invention may set tl = t3 in FIG. In this case, it is necessary to set α to β.By doing this, the timer 28 in the embodiment of FIG.
a and the comparator 42b become unnecessary. Furthermore, the present invention j2
Of course, it may be set to =j3.

(Effects of the Invention) As described above, the present invention calculates the maximum rate of increase in the tightening torque equivalent amount based on the tightening torque equivalent amount and its primary lag amount, and calculates the maximum rate of increase in the tightening torque equivalent amount from the starting point within the elastic range to a predetermined tightening angle equivalent. After tightening the amount, this maximum rate of increase is integrated and added to the amount equivalent to the tightening torque at the starting point, and this added value is compared with the amount equivalent to the tightening torque.

Therefore, the tightening end point can be detected in accordance with the definition of proof stress, making it possible to perform highly accurate tightening.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a diagram of its tightening characteristics, and FIG. 3 is a block diagram of another embodiment. DESCRIPTION OF SYMBOLS 10... DC series motor, 20... First primary lag circuit, 22... Second primary lag circuit, 24... Subtractor, 26... First hold circuit, 28.28A, 28B...Timer, 30...Second halt circuit, 32...Integrator circuit, 38...Addition circuit, 40...Comparison circuit, ■...Maximum rate of increase detection circuit B...Starting point. Patent Applicant Shibaura Seisakusho Co., Ltd. Agent Patent Attorney Yama 1) Letter A Figure 1-A2 Procedural Amendment Form (Sealed) 1'? 1. Indication of the case Patent Application No. 42688 of 1933 2. Name of the invention Strength detection bolt tightening machine 3. Person making the amendment Relationship to the case Patent applicant address 1-12 Akasaka, Minato-ku, Tokyo Name Name (2
42) Shibaura Seisakusho Co., Ltd. Representative: Ryo Watanabe 4, Agent address: 1-6-21 Nishi-Shinbashi, Minato-ku, Tokyo, Voluntary 6, Number of inventions increased by amendment: 07, Subject of amendment

Claims (8)

[Claims] (1) In a bolt tightening machine using a prime mover, the maximum rate of increase is detected by determining and storing the maximum rate of increase in the amount of tightening torque equivalent to the amount of tightening torque within the elastic range of the bolt and its primary lag amount. an integral start determination circuit that detects tightening of an amount equivalent to a predetermined tightening angle from a starting point located within the elastic range of the bolt and outputs an integral start signal, and integrates the maximum rate of increase based on the integral start signal. an integrating circuit to start, an adding circuit for calculating the sum of the tightening torque equivalent amount at the starting point and the integral value output by the integrating circuit, and determining when the output of this adding circuit has become equal to the tightening torque equivalent amount. and a comparison circuit that outputs a tightening stop signal, and stops tightening based on the tightening stop signal. (2) The strength detecting bolt tightening machine according to claim 1, wherein the prime mover is a DC series-wound motor, and the motor current is an amount equivalent to the tightening torque. (3) The maximum rate of increase detection circuit determines the maximum rate of increase of the amount equivalent to the tightening torque from the change over time in the output difference of the first and second primary delay circuits having different time constants. A strength-detecting bolt tightening machine according to scope 1 or 2. (4) The strength detection bolt tightening machine according to any one of claims 1 to 3, characterized in that the delay time of the first primary delay circuit is approximately zero. (5) The predetermined tightening angle equivalent amount is set by the tightening time, and the integrating circuit integrates the maximum increase rate of the tightening torque equivalent amount over time. The strength detection bolt tightening machine described in any of the above. (6) The predetermined tightening angle equivalent amount is set by the tightening angle, and the integrating circuit integrates the maximum increase rate of the tightening torque equivalent amount with respect to the tightening angle. The strength detection bolt tightening machine described. (7) The proof stress according to any one of claims 1 to 6, wherein the predetermined tightening angle equivalent amount is set to give a permanent elongation of 0.2% to the bolt. Detection bolt tightening machine. (8) The starting point within the elastic region is defined as the point in time when the output of the first primary delay circuit becomes equal to the tightening torque preset by the setting device.
The proof stress detection bolt tightening machine described in any of the paragraphs.