JPH03190680A - Fastening method for screw - Google Patents

Abstract

PURPOSE:To perform tightening irrespective of the presence, etc., of a resistance torque until reaching a seating point, by performing tightening to the initial torque or equivalent to the initial torque, in addition to the fastening at the specific angle, only in the case of the initial torque corresponding to the seating point being larger than the preset decision torque. CONSTITUTION:The torque corresponding to a seating point is detected by a transducer 8 as the initial torque and this initial torque and decision torque are compared by comparator circuits 9-11. In the case of the initial torque being smaller than the decision torque from this comparison result, it is completed at the time when the fastening by a nut runner including a motor 2 of the specific angle is performed from the seating point. On the other hand, in case of the initial torque being larger than the decision torque, the screw and bolt fitted by a torque runner into the socket 2a thereof are subjected to tightening at the tightening angle equivalent to the initial torque or the initial torque, further, after the fastening by the nut runner of the specific angle being performed from the seating point.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for tightening a screw at a predetermined angle from a seating point.
Furthermore, the present invention relates to a method of tightening a screw by retightening it at a predetermined angle or with a predetermined torque.

[Conventional technology]

For example, engine connecting rods and bearing caps are usually assembled by tightening multiple bolts. Generally, the above-mentioned tightening is performed by a torque method, but since it is difficult to uniformly manage the axial forces of all bolts, a method that can uniformly manage the above-mentioned axial forces is desired.

Therefore, for example, in Japanese Patent Application Laid-open No. 60-245133,
A tightening method using the angle method has been proposed. In this tightening method, a seating point is determined during tightening, and tightening is performed at a predetermined angle starting from this seating point. As a result, the bolts tightened using the above angle method are
Compared to bolts tightened using the torque method, the axial force is sufficiently stable.

[Problem to be solved by the invention]

'However, it has become clear that the above tightening method may cause fluctuations in the axial force due to the torque during tightening.

That is, as shown in FIG. 5, when fastening the upper fastening member 31 and the lower fastening member 32, such as a cap, for example,
Bolt holes 31a and 32a are formed in the upper fastening member 31 and the lower fastening member 32, and these bolt holes 31a
- The fastening may be performed by screwing the bolt 33 into the bolt 32a and tightening it.

At this time, if there is a pitch misalignment between the bolt holes 31a and 32a, the bolt 33 and the bolt hole 31a may overlap while the bolt 33 is being tightened, and the bolt 33 may overlap.
A large resistance torque is generated before the seat portion 33a of No. 3 reaches the seating point where it comes into contact with the upper fastening member 31.

Further, as shown in FIG. 6, this resistance torque also occurs when a deformed screw 34 is used for the purpose of preventing the screw from loosening. If the above-mentioned angle method tightening is performed with this resistance torque generated, as shown by the solid line in Fig. 7, the initial torque TS, which is the resistance torque at the time when the axial force is generated, will rise up. The seating point θS is determined from the torque gradient RT (T2-Tl/Δθ), and tightening is performed at a predetermined angle θ from this seating point θS.

In general, the above-mentioned seating point θS is the seating point θ determined by the axial force gradient RF indicated by the - dotted chain line. is equal to .

However, the seating point θS of the torque gradient RT determined in the state where the above-mentioned resistance torque is generated is the seating point θ of the axial force gradient RF. This results in a seating deviation θα as shown by the following equation.

θα = Ts/RT Therefore, the bolt tightened at a predetermined angle θ1 from the seating point θS is at the seating point θ. compared to a bolt tightened at a predetermined angle θ from the seating point θ.

This results in an insufficient axial force corresponding to the seating deviation θα, which is the difference between the position and the seating point θS. Incidentally, this insufficient axial force naturally occurs even when tightening is performed after determining the seating point θS by the torque method.

As described above, the above-mentioned angle tightening method has a problem in that it is difficult to sufficiently stabilize the axial force, especially when the tightening torque is different for each bolt.

Therefore, as a method to solve the above problem, the seating point θS
The largest resistance torque T before reaching
smax, and set a predetermined angle θ1 from the seating point θS.
After tightening is performed, the above resistance torque Tsma
One possible method is to tighten the bolts by an additional amount of x. However, with this method, as shown in Fig. 8, if the memorized resistance torque TSmax is significantly larger than the initial torque Ts at the seating point θS, it is difficult to prevent the bolt from stretching and breaking due to excessive retightening. There is a possibility that it will be invited.

Therefore, in the present invention, the initial torque Ts, which is the resistance torque at the time when the axial force is generated, is determined, and this initial torque Ts is determined.
By retightening the seating deviation θα caused by the initial torque Ts or the initial torque Ts, the bolt can be tightened to have a stable axial force regardless of the presence or absence, magnitude, or change of resistance torque. The purpose is to provide a tightening method.

[Means to solve the problem]

In order to solve the above-mentioned problems, the screw tightening method according to the present invention has, during tightening, at least two tightening angles and the tightening torque corresponding to these tightening angles, for example, using an angle input means or a torque input means. The seating point is determined from the torque gradient obtained by the tightening angle and tightening torque, and tightening is performed at a predetermined angle using this seating point as the starting point, and the initial torque corresponding to the seating point is is larger than the preset judgment torque, in addition to tightening at the predetermined angle, the initial torque or initial torque is tightened. It is characterized by retightening at the retightening angle corresponding to the IJI torque.

[Operation] According to the above configuration, the seating point is determined from the torque gradient obtained from the tightening angles at at least two points during tightening and the tightening torques corresponding to these tightening angles. Then, the tightening is performed by rotating a predetermined angle from this seating point as a starting point.

At this time, the torque corresponding to the seating point is detected as the initial torque, and this initial torque and the determination torque are compared. As a result of this comparison, if the initial torque is smaller than the determination torque, the tightening process ends when the tightening is performed at a predetermined angle from the seating point. On the other hand, when the initial torque is larger than the determination torque, after tightening is performed at a predetermined angle from the seating point, additional tightening is performed at the initial torque or at a ground line angle corresponding to the initial torque.

Therefore, in the screw tightening method according to the present invention, even if the seating point determined from the l·lux slope is significantly different from the point in time when the axial force is generated, the screw tightening method according to the present invention can be used to It is possible to obtain stable axial force by retightening. In addition, since retightening is performed based on the initial 31Jl l-lux corresponding to the seating point, the presence or absence of resistance torque until reaching the seating point,
It is not described by size or change.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

As shown in FIG. 3, the screw tightening method according to this embodiment involves a processing unit 1 (CPU) to which angle input means, torque input means, etc. are connected, and a motor controlled by this processing unit 1. This is carried out using a tightening device consisting of a second type of tightening means.

The above motor 2 is connected to the arithmetic processing unit 1 via a servo amplifier 7, and this servo amplifier 7 receives a nut runner start (N/R5TA) from the arithmetic processing unit 1.
RT) The motor 2 is rotated by receiving the signal. The motor 2 also has a rotatable socket 2a for tightening screws, and is configured to rotate by fitting screws or bolts (not shown) into the socket 2a.

The rotation angle caused by the above rotation is detected by an angle manual means provided between the motor 2 and the arithmetic processing unit 1. This angle input means includes an angle encoder 3 provided on the rotating shaft of the motor 2 and a pulse signal outputted from the angle encoder 3, which is counted by the arithmetic processing unit 1.
It consists of angle gates 4, 5, and 6 that are manually operated.

Further, although not shown, the above-mentioned pulse signal is also directly input to the arithmetic processing device 1.

The angle gates 4, 5, and 6 have an input terminal into which the pulse signal from the angle encoder 3 is input, and an output terminal which outputs the count value of the input pulse signal to the arithmetic processing device 1. . The input terminals are the gate terminals 4a and 4a.
0N-OF of whether or not to input pulse signals at 5a and 6a
The F state can be switched, and these gate terminals 4a, 5a, 6a are connected to the arithmetic processing unit 1, respectively.
is connected to the output terminal of

Further, the arithmetic processing device 1 described above is provided with a torque input means. This torque input means has a torque transducer 8 that converts the tightening torque generated by the motor 2 into an analog signal such as voltage, and this torque transducer 8 converts the tightening torque generated by the motor 2 into an analog signal such as a voltage. It is connected to one input terminal of comparator circuits 9, 10, and 11 that compare the signals and output operating signals based on the comparison results. Further, the analog signal from the torque transducer 8 is converted into a digital signal via an A/D converter (not shown), etc., and then sent to the arithmetic processing unit in units of pulse signals.
The information is entered and stored in the .

The other input terminals of the comparator circuits 9, 10, and 11 are connected to setting signal generation circuits 2, 3, and 14 that output predetermined analog signals. These setting signal generation circuits 12, 13, and 14 output analog signals equal to the analog signals from the torque transducer 8 when the tightening torque of the motor 2 becomes torque Tm-Tl and T2, respectively. It has become. This allows the comparator circuit 9 to receive these analog signals.
1o-ii is analog switch 1 when the tightening torque of motor 2 becomes torque Tm-T1 and T2, respectively.
Operation signals are output at 5, 16, and 17.

Note that the above torque Tm is set to a value that can be used as a determination torque for determining whether the resistance torque is larger than a predetermined value, and torque T1 and torque T2 are The applied torque is set to a value that is in the middle of increasing.

One terminal of the analog switches 15, 16, and 17 is connected to the arithmetic processing device 1, and the other terminal (not shown) is connected to, for example, a power source via a pull-up resistor. The above both terminals are connected to the comparator circuit 9.
・The open/close state can be switched by operation signals from 10 and 11. As a result, the analog switches 15, 16, and 17 cause the motor 2 to output each torque Tm-Tl-.
The arithmetic processing unit 1 outputs a detection signal indicating that T2 has reached T2.
It is designed to output to .

The arithmetic processing unit 1 to which the above detection signal and the pulse signal from the angle encoder 3 are inputted is a RAM (not shown).
(Random Access Memory)
and ROM (Read Only Memory)
), and the RAM has a calculation area that stores at least the count values and calculated values of the pulse signals input from each angle gate 4, 5, and 6, and a calculation area that stores the count values and calculation values of the pulse signals input from the torque transducer A torque characteristic area is formed in which the tightening torque of is stored in units of pulse signals indicating the tightening angle. On the other hand, the ROM contains analog switches 15 and 16.
・A routine for controlling the motor 2 by switching the opening/closing states of the angle gates 4, 5, and 6 based on the detection signal from the motor 17, and calculating the seating point, ground line angle, etc. from the count value in the counter area is programmed as a subroutine, for example. ing.

In the above configuration, the operation for tightening the bolts will be described below based on the flowchart shown in FIG. 1 and the graph shown in FIG. 2.

First, in step (hereinafter referred to as S) 1, the third
A bolt is fitted into the socket 2a of the motor 2 shown in the figure,
A nut runner start (N/R5TART) signal is output from the arithmetic processing unit 1 to the servo amplifier 7 (Sl)
. The servo amplifier 7 that has received the above signal rotates the socket 2a via the motor 2 and starts tightening the bolt (S2).

The tightening torque generated during the tightening described above is converted into an analog signal by the torque transducer 8, and this analog signal is compared with the analog signal from the setting signal generation circuit 12 in the comparator circuit 9. At this time, the analog signal from the setting signal generation circuit 12 is equal to the analog signal obtained by converting the torque Tm that determines the magnitude of the resistance torque, and the analog signal from the torque transducer 8 is output from the setting signal generation circuit 12. If the analog signal is smaller than the analog signal, the comparator circuit 9 will not operate, and the detection signal from the analog switch 5 will not be input to the arithmetic processing unit 1. Therefore, the arithmetic processing device 1
The determination is NO since no resistance torque larger than the torque Tm is generated, and the process returns to S2 to continue tightening the bolt.

On the other hand, when tightening progresses and the analog signal from the torque transducer 8 becomes larger than the analog signal from the setting signal generation circuit 12, the comparator circuit 9
outputs an operation signal to the analog switch 15, and the analog switch 15 that receives this operation signal outputs the operation signal to the arithmetic processing unit 1.
A detection signal will be output to the

Then, the arithmetic processing device 1 that has received the above detection signal,
Assuming that a resistance torque larger than torque Tm occurs, Y
If it is determined to be ES (S3), an operation signal is output to the gate terminals 4a, 5a, and 6a of the angle gates 4, 5, and 6. As a result, the angle gates 4, 5, and 6 are turned on and count the pulse signals output from the angle encoder 3 (S4).

Subsequently, while the bolts are continued to be tightened (S5),
The tightening torque obtained from the torque transducer 8 is stored for each pulse signal indicating the rotation angle in the torque characteristic area. As a result, T=f(θ), which is the relationship between the rotation angle and the tightening torque, is obtained. Note that the storage of this tightening torque is continued at least until the angle gate 6 is turned off at step 58, which will be described later (S6).

Furthermore, while the bolts continue to be tightened (37)
, the comparator circuit 10 determines whether the tightening torque from the torque transducer 8 has reached torque T1. If the torque T1 has not yet been reached, the process returns to step S7 and the bolt tightening is continued.

On the other hand, when the torque Tl is reached, an operating signal is output from the comparator circuit 10, and a detection signal is sent to the processing unit 1 from the analog switch 16 that received this operating signal.
is output to. As a result, the arithmetic processing device 1 determines YES because a tightening torque larger than the torque T1 has been generated (S8).

The arithmetic processing unit 1 that has determined YES stops the operation signal that was being output to the gate terminal 6a, and outputs the operation signal to the gate terminal 6a.
The angle gate 6 having the angle is turned off. Therefore, the angle gate 6 stops counting the pulse signal output from the angle encoder 3, and holds the count value a shown in FIG. 2 as the tightening angle at the time when the torque T1 is reached (S9). .

Further, while tightening of the bolt continues (310)
, the comparator circuit 11 determines whether the tightening torque from the torque transducer 8 has reached torque T2. If the torque T2 has not yet been reached, the process returns to step S10 and the bolt tightening is continued.

On the other hand, when the torque T2 is reached, the comparator circuit 11 outputs an operation signal, and the analog switch 17 that receives this operation signal outputs a detection signal to the processing unit 1.
is output to. As a result, the arithmetic processing device 1 determines YES because a torque larger than the torque T2 has been generated (3.11).

The arithmetic processing device 1 that has determined YES outputs an operation signal to the gate terminal 5a, and turns the angle gate 5 having the gate terminal 5a into an OFF state. Therefore, the angle gate 5 is
Counting of the pulse signal output from the angle encoder 3 is stopped, and the counted value is held as the tightening angle at the time when the torque T2 is reached (S12).

Next, the count values a-b counted by the angle gates 5 and 6 are taken into the calculation area on the calculation processing unit lORAM,
Torque gradient RT is calculated using the following formula.

RT = (T2-'ri), / (ba-a) Furthermore,
T'2 and Tl are the torque T1 and torque T
This is about number 2. Further, b is the count value of the pulse signal when the angle gate 6 is turned off when the torque T1 is reached, and a is the count value of the pulse signal when the angle gate 5 is turned off when the torque T2 is reached.
This is the count value of the pulse signal when

Then, the seating point θS is calculated from the above torque gradient RT using the following formula.

θs ='a-Tl/RT Furthermore, the torque and rotation angle stored in the torque characteristic area are stored in the above-mentioned torque characteristic area T=f (0)
Since the relational expression holds true, the initial torque Ts at the seating point θS can be determined.

Ts=r(θS) Then, using the above initial torque Ts and torque gradient RT, the ground line angle θα, which is equal to the seating deviation θα from the seating point θS to the initial torque Ts, is calculated using the following formula. Ru.

θα = Ts/RT Further, the initial torque Ts at the seating point θS is compared with the torque Tm. Then, when the torque Tm is greater than or equal to the initial torque Ts, the operations from 318 onward, which will be described later, are performed, and when the torque Tm is less than the initial torque Ts, the operations from 514 onward, which will be described later, are performed (513).

Therefore, when the torque Tm becomes less than the initial torque Ts, the bolt is continued to be tightened (318), and the count value of the pulse signal is input from the angle gate 4 to the arithmetic processing unit 1. At this time, the input count value is the addition angle θ which is the predetermined angle θ from the seating point θS and the ground line angle θα.
1+θα, and tightening is performed until the addition angle θ1+θα and the count value become equal (S
19). Then, when the addition angle θ1+θα and the count value become equal, the nut runner stop (N/R5
TOP) signal is output to the servo amplifier 7 (S20),
Bolt tightening (=) Ends when injury motor 2 stops (E
ND) (S21).

On the other hand, as shown in Fig. 4, the torque Tm is the initial torque T
s or more, bolt tightening continues (
S14), the count value of the pulse signal is input from the angle gate 4 to the arithmetic processing unit l.

At this time, the input count value is compared with a predetermined angle θ from the seating point θS (315). Then, when this predetermined angle θ and the count value become equal, a nut runner stop (N/R5TOP) signal is output to the servo amplifier 7 (S16), and the bolt tightening is finished by stopping the motor 2 (END). ) (S17).

In this way, the screw tightening method of this embodiment, as shown in FIG. 2, involves determining the initial torque Ts at the seating point θS,
By comparing this initial torque Ts with a preset torque Tm, it is determined whether the resistance torque is large enough to require additional tightening. If it is determined that additional tightening is required, the ground line angle θα corresponding to obtaining the above initial torque Ts is added to the predetermined angle θ1 and tightened, while if it is determined that additional tightening is not required, the specified It is designed to end by tightening at the angle θ. Therefore, the bolt tightened by this method can obtain a stable axial force without being affected by the presence or absence, magnitude, or change of resistance torque up to the initial torque Ts.

In this embodiment, additional tightening after the predetermined angle θ1 is performed using the ground line angle θα, but the present invention is not limited to this, and may be performed using the initial torque Ts at the seating point θS. That is, for additional tightening after the predetermined angle θ1, after tightening at the predetermined angle θ, monitor the torque obtained from the torque transducer 8, and tighten until the torque after the predetermined angle θ1 becomes equal to the initial torque Ts. It may also be done by

Furthermore, in this embodiment, the torque gradient RT for calculating the seating point θS is determined using the tightening torque and tightening angle at two points, but the present invention is not limited to this, and for example, the tightening angle at three or more points. A more accurate torque gradient RT may be determined by the tightening torque and tightening angle.

Furthermore, the above-mentioned tightening torque and tightening angle can be obtained by hardware such as the setting signal generation circuits 12, 13, 14 and angle gates 4, 5, 6, but the memory of the arithmetic processing unit 1 It may also be possible to obtain the information using software. In this case, the tightening device can be constructed at low cost.

[Effects of the Invention] As described above, the screw tightening method according to the present invention detects at least two tightening angles and the tightening torques corresponding to these tightening angles during tightening, and detects the tightening torques corresponding to these tightening angles. The seating point is determined from the torque gradient obtained from the seating angle and the tightening torque, and tightening is performed at a predetermined angle starting from this seating point, and the initial torque corresponding to the seating point is the preset judgment torque. In addition to tightening at the predetermined angle, additional tightening is performed at the initial torque or at a ground line angle corresponding to the initial torque only when the torque is larger than the initial torque.

As a result, only when the initial torque is larger than a preset judgment torque, retightening is performed at the initial torque or at the ground line angle corresponding to the initial torque. , or it becomes possible to retighten without being affected by the change,
Even if the seating point determined from the torque gradient is significantly different from the point at which axial force is generated, stable axial force can be obtained by retightening at the initial torque or at the ground line angle equivalent to the initial torque. It has the effect of becoming

[Brief explanation of drawings]

1 to 4 show one embodiment of the present invention. FIG. 1 is a flowchart 1 showing the operating procedure according to the screw tightening method. FIG. 2 is a graph showing the relationship between tightening angle and torque. FIG. 3 is a block diagram of the tightening device. FIG. 4 is a graph showing the relationship between tightening angle and torque. 5 to 8 show conventional examples. FIG. 5 is an explanatory diagram showing a state in which the bolt is leaning. FIG. 6 is a plan view of the deformed screw. FIG. 7 is a graph showing the relationship between torque and axial force with respect to the tightening angle. FIG. 8 is a graph showing the relationship between tightening angle and torque. 1 is an arithmetic processing unit, 2 is a motor, 3 is an angle encoder,
4, 5, and 6 are angle gates, 7 is a servo amplifier, 8 is a torque transducer, 9, lO, and 11 are comparator circuits, 12, 13, and 14 are setting signal generation circuits, 15 and 16
・17 is an analog switch.

Claims (1)

[Claims] 1. During tightening, detect the tightening angles at at least two points and the tightening torques corresponding to these tightening angles, find the seating point from the torque gradient obtained from the tightening angles and tightening torques, and Tightening is performed at a predetermined angle starting from the seating point, and only when the initial torque corresponding to the seating point is larger than a preset judgment torque, in addition to tightening at the predetermined angle, the initial torque or A screw tightening method characterized by retightening at an additional tightening angle corresponding to the torque.