JPH0457680A - Fastening method for screw member - Google Patents

Abstract

PURPOSE:To prevent a seating point from slippage and to stabilize the fastening axial force, by calculating the seating point with the torque rate between two points of a wider angle range at the torque rate side of the latter half of the torque rate changing point which is the starting point of the latter half torque rate and a 4th set point. CONSTITUTION:A former half torque rate RTA=(T2-T1)/a is found with the fastening angle (a) between 1st and 2nd set points that fastening torques T1, T2 differ in the specific quantity at the fastening time former half being measured by an encoder 5. Then, the latter half torque rate RTB=(T4-T3)/(c-b) is found with the fastening angle between 3rd and 4th set points that the latter half torques T3, T4 differ in the specific quantity at the fastening time latter half being measure by the encoder 5. The fastening angle and torque at the torque rate change point are found thereby, a logical seating point is calculated from the 1 torque rate between the torque rate change point and 4th set point and the fastening is performed until reaching the specific angle from the seating point.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a tightening method for tightening a screw member at a predetermined angle from its seating point.

(Prior Art) Conventionally, as a method for tightening screw members of this type, as disclosed in Japanese Patent Application Laid-Open No. 62-102978, a tightening method between two points in which the tightening torque differs by a predetermined amount during tightening has been used. Measure the tightening angle to find the torque rate (that is, the ratio of the tightening torque increase to the tightening angle increase), calculate the theoretical seating point from the torque rate, and tighten until the specified angle is reached from the seating point. It is known that the tightening axial force can be stabilized without being affected by the friction coefficient of the threaded member by performing the following steps.

(Problem to be Solved by the Invention) However, when the screw member to be tightened is partially press-fitted in advance, the relationship between the tightening torque and the tightening angle is as shown in FIG. In the first half and the second half of the time (
(before and after the fastening angle θX corresponding to the torque Tx) is different,
The torque rate in the first half is greater than the torque rate in the second half. This is because in the first half of the tightening process, the press-fitted portion of the screw member has no relation to the tightening process and has a high spring constant.

In such a case, two points T sandwiching the torque rate change point
When the torque rate is determined by measuring the tightening angle between I and T2, the seating point θ0- calculated from this torque rate is:
A deviation from the true seating point θ0 occurs. In order to prevent this deviation from occurring, it is necessary to make T1 larger than the torque Tx at the torque rate change point, but if a value close to T2 is set, the angular range becomes small and becomes a factor of error in the seating point θ0.

The present invention has been made in view of these points, and its purpose is to accurately determine the seating point θ0 when tightening a screw member in which the torque rate is different between the first half and the second half. It is an object of the present invention to provide a method for tightening a screw member that can stabilize the axial force.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention measures the tightening angle between first and second set points where the tightening torque differs by a predetermined amount in the first half of tightening. In addition, in the second half of tightening, the tightening angle between the third and fourth set points where the tightening torque differs by a predetermined amount is measured to find the torque rate in the second half, and from this, the torque rate change point is determined. A configuration in which the tightening angle and tightening torque are determined, a theoretical seating point is calculated from the torque rate between the torque rate change point and the fourth set point, and tightening is performed from the seating point until a predetermined angle is reached. That is.

(Function) With the above configuration, the present invention provides a torque rate between two points with a wide angle range on the second half torque rate side, namely the torque rate change point, which is the starting point of the second half torque rate, and the fourth setting point. Since the seating point is calculated, the theoretical seating point can be found accurately.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows the overall configuration of a bolt tightening device used in the method of tightening a screw member according to the present invention. This bolt tightening device is specifically used for tightening press-fit type connecting rod bolts, and when tightening press-fit type connecting rod bolts, due to the influence of press-fitting, as shown in Fig. 3. As such, the torque rate, which is the ratio of the increase in tightening torque to the increase in tightening angle, is different between the first half and the second half.

In FIG. 2, 1 is a nut runner, which includes a socket 2 that fits into a bolt head, a motor 3 that rotationally drives the socket 2 via a main shaft (not shown), and a main shaft. It includes a torque transducer 4 that detects torque, and an angle encoder 5 that detects the rotation angle of the main shaft.

6 is a CPU that controls the operation of the nut runner 1.

Further, reference numerals 11 to 14 are first to fourth torque setting devices for setting predetermined torques T1 to T4, respectively, and the following magnitude relationship exists between these set torques T1 to T4 (the third (see figure).

Tl <T2 <T3 <T4 The first and second set torques Tl and T2 are set to relatively small values on the torque rate side in the first half of the engagement, and the third
and fourth setting torque T3. T4 is set to a relatively large value on the torque rate side in the latter half of the engagement period.

Further, 15 to 18 are comparators, and each of the comparators 15 to 18 is connected to the torque transducer 4.
The tightening torque detected by and the corresponding torque setting device 11~
14 are compared with set torques T1 to T4, and when the two match, a signal is sent to the CPU 6 via the corresponding torque gates 19 to 22. 24-2
7 receives a control signal from the CPU 6, and an angle encoder 5
The rotation angle signals detected by the first to fourth signals are sent to the CPU 6, respectively.
The angle gate 28 is a servo amplifier that transmits the output from the CPU 6 to the motor 3 of the nut runner 1.

Next, a method for tightening a press-fit type connecting rod bolt using the bolt tightening device described above will be explained with reference to a flowchart shown in Fig. '1s1.

In FIG. 1, first, in step S1, in response to a nut runner start signal from the outside, the CPU 6 rotates the motor 3 of the nut runner 1 via the servo amplifier 28 to start tightening the bolts. Then, in step S2, wait until the tightening torque T detected by the torque transducer 4 matches the set torque TI set by the first torque setting device 11, and then in step S3, the first to third angle gates 24
Turn on ~26.

Subsequently, in step S4, the tightening torque T and the set torque T2 set by the second torque setting device 12 are waited for to match, and the first angle gate 24 is turned OFF in step S5. Then, in step S6, the first angle gate 24
ON period (that is, the tightening torque T is the first setting torque T1)
to the second setting torque T2) is determined, and the torque rate RTA during the first half of tightening is determined using the following formula (see FIG. 3).

RTA - (T2 - TI ) /a Here, the linear equation of the torque rate RTA is, in Fig. 3, the first set torque T1 of the torque rate RT A.
If the intersection with .

T proverb RTA・θ −((T2−Tl ) /at “θ −fl)
Next, in step S7, the tightening torque T and the set torque T3 set by the third torque setting device 13 are waited for to match, and the second angle gate 25 is turned OFF in step S8. Then, in step S, the tightening angle S during the ON period of the first angle gate 24 (that is, the period until the tightening torque T reaches the set torque T3 from the set torque T1) is determined.

After that, in step SIO, wait until the tightening torque T matches the fourth setting torque T2 set by the torque setting device 14, and then turn off the third angle gate 26 in step S11.
Make it. Then, in step S12, the tightening angle C during the ON period of the third angle gate 24 (that is, the period until the tightening torque T becomes the set torque T3 from the set torque T1) is determined, and the tightening angle C in the second half of the tightening time is calculated.RTB is calculated using the following formula.

RTB-(T4-T3)/(c-b) Also, the linear equation of the above torque rate RTB is the above torque rate RT
As in A, the setting torque T of the torque rate RTA
1 is the origin, and the tightening angle from this origin is θ, it is expressed as follows.

T-RTB・(θ-b) 10(T3-Tl)-((T
4-T3) (θ-b)/(c-b)) ten (T3-
Tl )...(2 above step S12
In addition, find the tightening angle θX and tightening torque Tx at the torque rate change point where the torque rate changes (
(See Figure 3).

The tightening angle θX at the torque rate change point is determined as the intersection of the above equations (1) and (2), and is expressed as follows.

e x-a 1b(T 4 T 3) (c b
) (T 3 T 1) Ja (T4-T3)-(
T2-TI) (c-b) Also, the tightening torque Tx at the torque rate change point is determined by the following formula.

Tx -RTA・ (θl+θX) -((T2-Tl) /al (θl+θX) However, θ1 is the torque rate R during the first half of the engagement in Fig. 3.
This is the tightening angle between the point where the straight line representing the slope of TA intersects the horizontal axis and the first set point (the set point of torque T1).

Next, in step S13, the torque rate R during the first half of tightening is determined.
It is determined whether TA and the torque rate RTB in the second half of tightening are substantially equal. If this determination is YES, the torque detection range is set between the first set point (torque T1 set point) and the fourth set point (torque T4 set point) in step S14, and the theoretical Assuming a seating point θ0, the tightening angle θA from the seating point θ0 to the fourth set point is determined (see FIG. 3). The tightening angle θ^ is determined by the following formula.

θA − (c/ (T4 − Tl ) ) Fist T4 After calculating this tightening angle θA, in step S15, the additional tightening angle of 7 (θα − θ^) is increased from the fourth set point to the set tightening angle θα.
seek.

On the other hand, when the determination in step S1B is No, in step S16, the torque detection range is changed between the torque rate change point (tightening torque Tx point) and the fourth set point (torque T4 set point).
A theoretical seating point θO is assumed from the torque rate during this period, and the tightening angle θB from the seating point θ0 to the fourth set point is determined (see FIG. 3). The tightening angle θB is determined by the following formula.

θB −1(c−θx) / (T4−Tx)l
・T4 After calculating this tightening angle θB, in step S17, the retightening angle (θα
−θB).

After determining the retightening angle in step S15 or S17, the fourth angle gate 27 is turned on in step S18. After waiting for the bolt to be tightened by an additional tightening angle (θα-θA) or (θα-θB) from the fourth set point in step S19, the fourth angle gate 27 is turned off in step S20, and the nut runner Stop the operation of 1 and finish the bolt tightening work.

When tightening a press-fit type connecting rod bolt with different torque rates in the first and second halves of the tightening process using the method described above, the torque detection range can be set to the torque rate change point, which is the starting point of the torque rate RTB in the second halves. (Tightening torque Tx point) and the fourth setting point (Torque T4 setting point), which is the widest range on the latter torque rate side, and from this range of torque rate, the theoretical seating point θ0 Assuming that, the theoretical seating point θ0 can be accurately determined without deviation, and the tightening axial force can be stabilized.

As in the embodiment, when the first half torque rate RTA and the second half torque rate RTB are approximately equal, the torque detection range is set between the first set point (the set point of torque T1) and the fourth set point (
Setting point of torque T4) can be used to more accurately determine the theoretical seating point θ0, so when the torque rate changes during tightening and does not change, effective for use.

(Effects of the Invention) As described above, according to the method of fastening a screw member of the present invention, in a screw member in which the torque rate is different between the first half and the second half when tightening, the torque rate that is the starting point of the second half torque rate is Since the seating point is calculated using the torque rate between two points with a wide angle range on the latter half torque rate side, namely the change point and the fourth set point, it is possible to prevent the seating point from shifting, and the tightening shaft It is possible to stabilize the force.

[Brief explanation of the drawing]

Figures 1 to 3 show embodiments of the present invention; Figure 1 is a flowchart of the tightening method, Figure 2 is an overall configuration diagram of a bolt tightening device used in the tightening method, and Figure 3 is a diagram of the overall configuration of a bolt tightening device used in the tightening method. The figure is a diagram showing the relationship between the tightening characteristics of a press-fit bolt and the tightening method. FIG. 4 is a diagram showing the relationship between the tightening characteristics of a press-fit bolt and a conventional tightening method. 1...Nut runner 4...Torque transducer 5...Angle encoder 15-18...Comparator 19-22...Torque gate 24-27...Angle gate 4 Fig.

Claims (1)

[Claims] (1) When tightening a threaded member, the torque rate, which is the ratio of the increase in tightening torque to the increase in tightening angle, differs between the first half and the second half, and the tightening torque differs by a predetermined amount in the first half of tightening. The tightening angle between the first and second set points is measured to determine the torque rate in the first half, and the tightening angle between the third and fourth set points, where the tightening torque differs by a predetermined amount, is measured in the second half of tightening. Find the torque rate in the second half,
From this, find the tightening angle and tightening torque at the torque rate change point, calculate the theoretical seating point from the torque rate between the torque rate change point and the fourth set point, and set a predetermined angle from the seating point. A method for tightening a threaded member, characterized by tightening the screw member until it reaches .