JPH0433585B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a proof-tightening system that enables switching between main tightening, which is tightening with a predetermined proof stress, and pre-tightening, which is tightening with a predetermined pre-tightening torque. This invention relates to a detection bolt tightening machine.

(Background of the Invention) The applicant has already proposed a proof stress detection bolt tightening machine for tightening with accurate proof stress in Japanese Patent Application No. 60-42688 and Japanese Patent Application Laid-Open No. 61-203275. This tightening machine calculates the rate of increase in tightening torque based on the tightening torque within the elastic range of the bolt and its primary lag amount, and calculates the increase rate of the tightening torque from the specified torque within the elastic range on the characteristic curve showing the time change of the tightening torque. Find a straight line with a slope equal to the rate of increase that passes through the time required to tighten the specified amount from this starting point with the same torque as the starting point, and the point where this straight line intersects with the tightening torque curve is the tightening end point. (proof point) and stops tightening.

On the other hand, when tightening bolts, preliminary tightening is often required. For example, in most construction projects such as construction and bridges, preliminary tightening is performed.
Since the set torques for pre-tightening and final tightening are different, it may be possible to use separate tightening machines for each, but in this case multiple tightening machines would be required and the operating rate of the tightening machines would be low. A problem arises.

Therefore, in the case of a tightening machine that uses the torque method or the rotation angle method, it has been considered in the past to make the set torque variable so that it can be used for both preliminary tightening and final tightening. However, when using the above-mentioned proof stress detection method, the rate of increase in tightening torque is determined from the primary lag amount of tightening torque, so calculations must be continued within a certain range within the elastic range. However, it is not possible to tighten with the desired pre-tightening torque simply by changing the set value. In other words, according to this proof force detection method, it is possible to change the tightening end point when the elastic range is exceeded by changing the set value, but it is possible to end the tightening at a pre-tightening torque within the elastic range. I couldn't do that.

In addition, when applying main tightening using this proof force detection method to a product in which pre-tightening was performed with a torque greater than the torque at which calculation of the primary lag amount is started in order to find the rate of increase in tightening torque, the pre-tightening torque must be The tightening speed becomes faster, and the increase rate calculated by calculation becomes larger. For this reason, there was a problem in that a malfunction occurred in which the tightening was completed before the desired proof stress was reached.

(Objective of the Invention) The present invention has been made in view of the above circumstances, and makes it possible to perform preliminary tightening with a torque within or below the elastic range, and furthermore, uses a proof force detection method after this preliminary tightening to check the tightening operation. It is an object of the present invention to provide a strength detection bolt tightening machine that is free from the risk of malfunctions when it is inserted into the machine.

(Structure of the Invention) According to the present invention, in a bolt tightening machine using a prime mover 10, a tightening torque detecting means 1 for determining a tightening torque T within an elastic range of a bolt.
6, a primary lag circuit 20 that starts calculating the primary lag amount of the tightening torque T from the calculation start torque T ₁ set by the setting device 28, and a subtractor 24 that calculates the difference between the tightening torque T and this primary lag amount. , a first hold circuit 26 that determines and stores the tightening torque increase rate K based on this difference, and a starting point setting device 3 that sets the tightening torque of the starting point B located within the elastic range of the bolt.
4, an integration start determination circuit 38 that outputs an integration start signal at the elapsed time point C of the tightening time β of the predetermined tightening angle from the starting point B, and an integration start determination circuit 38 that starts integrating the increase rate K based on the integration start signal. A circuit 40;
An addition circuit 42 that calculates the sum of the tightening torque T ₂ at the starting point B and the integral value outputted by the integration circuit 40, and the output of this addition circuit 42 is the tightening torque T.
a first comparator circuit 44 that outputs a tightening stop signal S ₁ upon determining that the torque has become equal to , and a pre-tightening torque T ₃ that is smaller than the calculation start torque T ₁ for the primary lag
a pre-tightening torque setting device 46 for setting the pre-tightening torque, and a second comparison circuit 48 for determining that the tightening torque T has become equal to the pre-tightening torque _T3 and outputting a pre-tightening stop signal _S2 . , a changeover switch 50 that selects either the tightening stop signal S ₁ or the preliminary tightening stop signal S ₂ to stop tightening, and the changeover switch 50 can switch between preliminary tightening and main tightening. This is achieved by a strength-detecting bolt tightening machine featuring the following features:

(Function) When final tightening is selected with the changeover switch, first, when the tightening torque T reaches the calculation start torque T ₁ , the increase rate K of the tightening torque is calculated from the difference between the tightening torque T and the primary delay amount. and stored in the first hold circuit 26. When the tightening torque T reaches the tightening torque T ₂ at the predetermined starting point B, on the tightening characteristic diagram showing the time change of the tightening torque, the increase rate K is calculated from the time point C when the time β for tightening the predetermined tightening angle has elapsed. Integration starts at the tightening time t (or tightening angle θ), and when the first comparison circuit 44 detects the point at which the tightening torque T reaches T=Kt+T ₂ , the tightening ends. This makes it possible to tighten at the stress-bearing point, which is faithful to the theory.

When selecting temporary tightening, the tightening torque T is set by the setting device 46.
When the second comparison circuit 48 detects that the pre-tightening torque T ₃ matches the pre-tightening torque set in , the tightening is stopped. Here, the preliminary tightening torque T ₃ is set smaller than the calculation start torque T ₁ during final tightening, so
When performing main tightening after preliminary tightening, normal tightening can always be performed.

(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, 10 is a DC motor, and the bolts are tightened by the rotation of this motor 10. This electric motor 10 forms a closed circuit with an alternating current 12, a thyristor 14, a current detection resistor 16, and a main switch 18. The tightening torque T is the current i of the electric motor 10
is proportional to. This current i, that is, the tightening torque T
is detected by a resistor 16, and in this embodiment, the resistor 16 serves as tightening torque detection means. 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 syleister 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, an explanation will be given of the increase rate detection circuit I that calculates and stores the increase rate of the tightening torque T based on the tightening torque T within the elastic range of the bolt and its primary delay amount.

20 is a first-order delay circuit, which includes a series resistor 20a,
Parallel capacitor 20b and operational amplifier 20c
Consists of.

24 is _the difference _{(A 1 −}
It is a subtracter that calculates A ₂ ). 26 is a first hold circuit that determines and stores the tightening torque increase rate K from the output (A ₁ −A ₂ ) of this subtracter 24, and includes an ideal diode 26a with zero forward resistance, an integrating capacitor 26b, and an operational amplifier. 26c.

By the way, one of the features of the present invention is that the tightening torque is determined based on the difference ( _{A 1 −A} 2 ) between the output A 1 of the resistor 16 indicating the tightening torque T and the output A ₂ of the first primary lag circuit ₂₀ . The point is to find the rate of increase K of applied torque.

Within the elastic range of the bolt, the change in the output A1 of the resistor ₁₆ is considered to be a straight line, so this slope is considered to be equal to the rate of increase K, and it can be set as A=KT.

On the other hand, if the time constant of the first-order lag circuit 20 is τ=RC, the characteristic equation of its output A ₂ is RdA ₂ /dt+A ₂ /C=Kt Therefore, A ₂ =KT(exp(-t/T)-1 )+Kt A ₁ −A ₂ =KT(1−exp(−t/T)) Here, for example, if t is the time constant τ, A ₁ −A ₂ =0.632Kτ ∴K=(A ₁ −A ₂ )/ 0.632τ Furthermore, if t is 2τ, then K=(A ₁ −A ₂ )/0.863τ In any case, once t is determined, K can be obtained by calculation.

In this embodiment, the tightening torque T ₁ at point A within the elastic range is preset in the setting device 28, and the comparator 30 determines when this tightening torque T has reached T ₁ , and the normally open contact SW1 is set. After closing, the output _A1 of the resistor 16 indicating the tightening torque T is started to be input to the first-order delay circuit 20, and from this point _t1 , the predetermined time t=α is set by the timer 3.
2, and at that time t ₂ (i.e. t ₂ - t ₁ = α), the normally closed contact SW2 is opened, and (A ₁ -
A ₂ ) 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.

34 is a starting point setter for setting the tightening torque _T2 at the starting point B within the elastic range of the bolt, and 36 is a comparator. The comparator 36 determines the starting point B, and the timer 38
starts calculation based on the output of the comparator 36, and measures the time β corresponding to a predetermined tightening angle. Note that this timer 38 functions as an integration start determination circuit.

40 is an integrating circuit. This integration circuit 40 integrates the rate of increase K over time t via a normally open contact SW4 which is closed in response to an integration start signal output by the timer 38 at time _t4 . That is, the integration is started with time _t4 , when the tightening is done by a predetermined tightening angle equivalent from the starting point B, as the integration start point C.

42 is an adder circuit, which calculates the sum of the output Kt of this integrating circuit 40 and the torque T ₂ set by the setting device 34. Note that SW5 is set to time t ₄ by the timer 38.
The circuit is closed to The output Kt+T ₂ of this adder circuit 42 means a straight line extending with a slope K from the integration starting point C. This output is compared with the output A ₁ of the resistor 16 in a first comparator circuit 44 . This comparison circuit 44 outputs a tightening stop signal _S1 when both match (proof point D). The SW5 is connected to the comparison circuit 4 before the starting point B.
4 is provided to prevent output of the tightening stop signal _S1 .

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 be set to 1% of the idle screw length (the length of the threaded portion of the portion to which tensile force is applied).
In any case, once a predetermined elongation ε is determined, the tightening angle ψ required to generate this elongation ε is determined. The elapsed time (t ₄ −t ₃ )=β corresponding to the predetermined tightening angle stored in the timer 38 in this embodiment is
By setting the time to be equal to this tightening angle ψ, it becomes possible to tighten with proof stress in accordance with the theory.

In the above embodiment, the timers 32 and 38 operate at times α and β.
is stored, and the integrating circuit 40 integrates K with respect to time. However, in the present invention, the rotation angle θ of the electric motor 10 is detected, and the timer calculates a predetermined tightening angle equivalent amount by θ.
Alternatively, the integrator may integrate over θ.

The above describes the process of final tightening in which the stress point is detected and tightening is stopped by the tightening stop signal _S1 .

Next, a configuration for performing preliminary tightening will be explained. The pre-tightening torque T ₃ is taken out via a setting device 46 that divides the output of the setting device 28 , and this pre-tightening torque T ₃ is applied to the resistor 1 by a second comparator circuit 48 .
₆ , that is, the tightening torque T.
The comparison circuit 48 indicates that the tightening torque T is the preliminary tightening torque.
When _T3 matches, a pre-tightening stop signal _S2 is output.
50 is a changeover switch, which outputs the tightening stop signal S ₁
and the pre-tightening stop signal _S2 are selected and inputted to the gate circuit 52 of the thyristor 14 to stop the tightening.

Therefore, if the selector switch 50 is set to select the pre-tightening stop signal _S2 as shown by the solid line in FIG. 1, it becomes possible to tighten with the pre-tightening torque _T3 (pre-tightening). Moreover, if the changeover switch 50 is switched to the other direction, the tightening stop signal _S1 can be selected and tightening can be performed at the stress-proof point D (main tightening). Further, by adjusting the setting device 46, the pre-tightening torque can be adjusted.
T ₃ can be freely adjusted within a torque range lower than the calculation start torque T ₁ for the primary lag amount.

Here, the pre-tightening torque T ₃ is set lower than the torque T ₁ at point A used for final tightening, that is, the starting point for calculating the primary lag amount, so malfunctions may occur when performing further final tightening after pre-tightening. will no longer occur. In particular, it is desirable to set the preliminary tightening torque T ₃ so that the torque when additional tightening is performed due to the inertia of the rotating part at the end of the preliminary tightening is lower than the torque T ₁ at point A.

(Effects of the Invention) As described above, the present invention uses a changeover switch to select the tightening stop signal used for final tightening and the preliminary tightening stop signal used for preliminary tightening. Pre-tightening is possible with any tightening torque within or below the elastic range. In addition, since the pre-tightening torque is set smaller than the calculation start torque for the primary lag amount during final tightening, malfunctions will not occur even if one tightening machine is used for both preliminary tightening and final tightening. Enables tightening with accurate yield strength.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a diagram of its tightening characteristics. 10... DC motor, 16... Resistor as tightening torque detection means, 20... First-order delay circuit, 24
...Subtractor, 34...Starting point setter, 38...Timer as an integration start determination circuit, 40...Integrator circuit, 42...Addition circuit, 44...First comparison circuit, 46...Pre-tightening Torque setting device, 48...
Second comparison circuit, 50... changeover switch, I...
Maximum rate of increase detection circuit, S ₁ ... Tightening stop signal, S ₂ ...
... Pre-tightening stop signal, T ₁ ... Calculation start torque,
T ₂ ...Tightening torque at the starting point, T ₃ ...Preliminary tightening torque.

Claims (1)

[Claims] 1. A bolt tightening machine using a prime mover 10,
A tightening torque detecting means 16 that determines the tightening torque T within the elastic range of the bolt, a primary lag circuit 20 that starts determining the primary lag amount of the tightening torque T from the calculation start torque _T1 set by the setting device 28, A subtractor 24 that calculates the difference between the tightening torque T and this first-order delay amount, a first hold circuit 26 that calculates and stores the tightening torque increase rate K based on this difference, and a starting point located within the elastic range of the bolt. a starting point setter 34 that sets the tightening torque of B; an integral start determining circuit 38 that outputs an integral start signal at the elapsed time point C of the tightening time β for a predetermined tightening angle from the starting point B; an integrating circuit 40 that starts integrating the increase rate K based on the above, an adding circuit 42 that calculates the sum of the tightening torque T ₂ at the starting point B and the integral value outputted by the integrating circuit 40;
a first comparison circuit 4 that determines that the output of has become equal to the tightening torque T and outputs a tightening stop signal _S1 ;
4, a pre-tightening torque setting device 46 for setting a pre-tightening torque T ₃ smaller than the calculation start torque T ₁ for the primary delay amount, and a setting device 46 for setting the pre-tightening torque T 3 to be equal to the pre-tightening torque T ₃ . a second comparison circuit 48 that determines the pre-tightening stop signal _S2 and outputs the pre-tightening stop signal
, the tightening stop signal _S1 and the pre-tightening stop signal
A strength detection bolt tightening machine comprising a changeover switch 50 that selects either one of _S2 and stops tightening, and the changeover switch 50 can switch between preliminary tightening and main tightening. 2. The strength detecting bolt tightening machine according to claim 1, wherein the prime mover 10 is a DC motor, and the motor current is the tightening torque T. 3. The strength detection bolt tightening machine according to claim 1, wherein the preliminary tightening torque _T3 set by the setting device 46 is adjustable.