JP2782368B2 - Thread bush screwing control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a screwing control method when a thread bush is screwed into a work by a nut runner.

(Prior Art) An operation of assembling an upper arm shaft constituting an attachment portion to an A-shaped upper arm in a suspension of a vehicle such as an automobile is generally performed by screwing a thread bush by a nut runner. At this time, both ends of the upper arm shaft are inserted into the mounting holes formed at the opposite ends of the upper arm, and then thread bushes are inserted into both the mounting holes of the upper arm from the outside. A female thread formed on the inner periphery of the bush is screwed into each male thread formed on both ends of the upper arm shaft, and at the same time, a male thread formed on the outer periphery of each thread bush is formed in each mounting hole of the upper arm. Screwed into the female screw part. Here, the male screw portion usually formed on the outer periphery of the thread bush is constituted by an incomplete male screw portion on the distal end side and a complete male screw portion following the male screw portion, while the female screw portion on the upper arm side has a different angle. It is still an incomplete screw, and when the thread bush is screwed in,
First, the incomplete threaded portions of the outer periphery of the thread bush and the upper arm are screwed together, and then the threaded bush is tightened while the incompletely female portion of the upper arm is threaded by the complete male thread. And
The screwing is stopped when the incomplete male screw part comes off from the upper arm. For this reason, chips generated by the threading of the upper arm remain at the threaded portion between the upper arm and the thread bush, thereby strengthening the connection between the two.

By the way, in the thread bush screwing by such a nut runner, accurate control cannot be performed only by checking the value of the screwing torque at the end. That is, when the thread bush is inserted into the mounting hole of the upper arm and screwed in as described above, the tightening torque gradually increases initially, and a complete external thread portion on the outer periphery of the thread bush is formed in the mounting hole. The maximum torque is reached when the thread enters the female thread and starts threading, after which the tightening torque decreases until the thread bush is seated, and after seating, the torque increases sharply. In some cases, the tightening torque may reach the set value at the time of completion of the screwing, which causes a problem that the screwing operation of the nut runner stops before the tightening is actually completed. Therefore, in order to prevent such a malfunction of the nut runner and to secure a good screwing state, for example, in Japanese Patent Application Laid-Open No. Sho 61-103874, the maximum point of the tightening torque in threaded bush screwing is detected. Then, the seating point at which the torque becomes minimum is detected, and the screwing is completed and stopped at a predetermined torque value after the seating point, and the screwing angle from the seating point to the stop point is within the set range. A control method for determining whether the screwing state is good or not is adopted based on the above.

However, according to the control method described in the above-mentioned publication, it is possible to perform much more accurate control than in the case where the screwing torque reaches a set value and the screwing is completed and stopped. Malfunctions cannot be completely eliminated due to the following phenomena, which is still not practically sufficient. That is, when the thread bush is screwed, the screwing torque changes as described above, and the minimum point, which is the seating point, comes after the maximum point, and the tightening torque rapidly rises therefrom to reach the set value. However, during this time, there is a possibility that the maximum torque and the seating point will be erroneously detected due to the rising and falling phenomenon before reaching the maximum point because the tightening torque has microscopic waves. . Therefore, another accurate control cannot be realized.

(Object of the Invention) The present invention has been made in view of the above problems,
It is an object of the present invention to provide a thread bush screwing control method capable of smoothly performing screwing without erroneously detecting a true maximum point of a tightening torque and a seating point that comes after the true maximum point.

(Structure of the Invention) The present invention focuses on the fact that there is a clear difference in torque gradient characteristics between before the torque reaches a maximum point before the seating point and after the seating point in threaded bush screwing. Accurate control is realized by adding the torque gradient characteristic to the determination condition, and the configuration is as follows. That is, in the thread bush screwing control method according to the present invention, a thread bush in which an internal thread portion is formed on the inner periphery and an incomplete male thread portion and a complete male thread portion are continuously formed on the outer periphery from the distal end side is formed as the first thread bush. While inserting the female thread of the thread bush into the male thread formed at the end of the second assembly to be assembled to the first assembly, by inserting the thread into the assembly hole of the assembly. First, the incomplete male screw portion is screwed into the incomplete female screw portion formed in the mounting hole of the first mounting component, and then the incomplete female screw portion of the first mounting component is screwed by the complete male screw portion. In a thread bush screwing control method using a nut runner for screwing a female screw portion to a predetermined tightening state while cutting the female screw portion,
The threaded bush is screwed in while detecting the screwing angle and the screwing torque, and a torque increasing rate is obtained from the detected screwing torque and the screwing angle as a torque gradient characteristic, and the detected screwing torque and the torque increasing rate are obtained. Is compared with a preset set value, the maximum point of the screwing torque that appears when the complete male thread portion enters the incomplete female thread portion of the first assembly part, and the maximum point After that, a seating point at which the screwing torque is minimized, and a stop point at which the thread bush can be further tightened to the set torque value from the seating point to determine that the threaded bush is in a completely tightened state are determined, and the stop point is reached. It is characterized in that the screwing is stopped when it is done.

Whether it is before reaching the maximum point of the screwing torque or after the seating is determined by comparing with the set value of the torque increase rate.

(Operation) When the thread bush is screwed, a screwing angle and a screwing torque are detected, and a torque gradient characteristic is obtained.
Then, based on the torque value and the torque gradient characteristic, the maximum point of the torque before sitting is determined, and then the seating point with the minimum torque is determined. Then, the screwing is further continued beyond the seating point obtained in this way, and when the set torque is reached, and when the stop point at which the torque gradient characteristic can be determined as a completely tightened state is reached, the screwing is stopped. You. Whether it is before reaching the maximum point of the screwing torque or after the seating is determined by comparing with the set value of the torque increase rate.

(Example) Hereinafter, an example of the present invention will be described.

FIG. 1 shows an assembling structure of an upper arm and an upper arm shaft of a vehicle suspension according to one embodiment of the present invention. In the drawing, reference numeral 1 denotes a so-called A-shaped upper arm, and reference numeral 2 denotes an upper arm shaft that is assembled to the upper arm 1. Female threads 4 are formed on the inner periphery of the mounting holes 3 provided at both ends of the upper arm 1 facing each other. In addition, this female screw part 4 is initially
The thread is formed in an imperfect shape with a slightly larger thread angle with respect to the male thread portion on the thread bush side described later, and is threaded by screwing the thread bush into a complete female thread. On the other hand, both ends of the upper arm shaft 2 are made smaller than the inner diameter of the assembling hole 3, and a male screw portion 5 is formed on each. Then, both ends of the upper arm shaft 2 are inserted into the mounting holes 3 at both ends of the upper arm 1 with a gap, and the thread bush 6 is inserted into the gap from the outside.

The thread bush 6 has a substantially cylindrical shape, and has a female screw portion 7 screwed into the male screw portion 5 at the end of the upper arm shaft 2 on the inner circumference, and a trapezoidal incomplete male screw portion from the front end side on the outer circumference. 8a and a complete male thread 8b following it are provided. In the drawing, reference numeral 10 denotes a dust cover.

Next, the thread bush screwing control according to this embodiment will be described. The thread bush 6 is screwed by a nut runner 11 shown in FIG. Nutrunner 11
Is a socket portion 11 that engages with the head of the thread bush 6.
a built-in motor for rotating a at a predetermined speed, and a torque detecting means for detecting a screwing torque (T);
Angle detecting means for detecting the screwing angle (θ). The detected screwing torque (T) and screwing angle (θ) are input to the control means 13 of the controller 12.

The controller 12 includes a control unit 13, a driving unit 14 that drives and controls the motor of the nut runner 11 based on a signal from the control unit 13, and a scheduled value setting unit 15. Based on the characteristics shown in FIG. 3, the scheduled value setting means 15 determines the upper limit (T ₁ ) of the maximum torque point, the torque setting value (T _F ) for stopping the screwing, and the upper and lower limits thereof, and until the maximum point is reached. And the torque increase rate characteristic between the seating point and the screw stop point are set in advance. Then, the control means 13 calculates the inputted torsion torque (T) and the inputted torsion angle (θ)
The torque increase rate (ΔT / Δθ) obtained from the above is compared with a predetermined value, the maximum point of A in the torque characteristic diagram of FIG. 3 is obtained, the seating point B is obtained, and the stop point is passed after the seating point B. It is determined whether or not C has reached C, and when it is finally determined that the stop point C has been reached, a stop signal is output to the drive control means 14 to stop the operation of the nut runner 11.

FIG. 4 shows a flowchart for executing the above control of this embodiment. Note that S represents each step. When started first detects the rotation angle of the nut runner 11 (Hinekomi angle .theta.n) in S1, it detects the torque T _n at S2. And S3
To see if T _n ≦ T ₁ .

NO in S3, that is, if T _n> T _1, that the abnormal state, to stop the narrowing twisting go to S4, an abnormality display. Then, check the reset signal in S5, and if it is reset,
At S6, the abnormal signal is turned off, and the process returns to the initial state.

YES in S3, that is, if T _n ≦ T _1, that the torque is in the normal range, then go to S7 T _n> T _n-1, that the torque detection value T _n is the previous detection value T _n See if it is greater than _-1 .

If YES in S7, it means that the torque is increasing, and in this case, go to S8 to check whether the torque increase rate is equal to or more than a specified value. If NO in S8, that is, if the torque increase rate is smaller than the specified value, it is determined that the current point is on the near side of the maximum point A in FIG. 3, and the torque data (T _1n ) of the maximum point is taken in or updated. If YES in S8, that is, if the torque increase rate is equal to or more than the specified value, the process returns to S1. If NO in S7, that is, if T _n ≦ T _n−1, the process directly proceeds to S10.

In S10, it is checked whether T _n <T _n-1 . Then, if YES, that is, if T _n <T _n−1 , go to S11 to determine whether the data is after the torque data of T _1n is captured, that is, when the torque once increases toward the maximum point and then decreases. Then, if YES, the torque data (T _2n ) at the seating point is fetched in S12. If NO, go to the next step.

Next, in S13, it is checked whether or not the torque increase rate is equal to or higher than a set value, that is, whether or not the torque increase rate is a size that can be determined to be after sitting. Then, when it is judged that after YES, that seated, then S14 in T _n to see whether reached the set value T _F, go to step S15 if YES, stops the narrowing twisting, the stop T _n is determined the quality of the tightened state depending on whether you are within the allowable range of T _F, and outputs the judgment result as a signal. Then, it returns to the initial state. Also, S1
If NO in 3, that is, if it is determined that the torque increase rate is not after seating, the process returns to S1, and if NO in S14, that is, if the set value of _TF has not been reached, the process also returns to S1.

By such control, the screwing is stopped only after the set torque is reached after sitting, and at the same time, the quality of the tightened state is determined.

The present invention is not limited to the assembly of the upper arm and the upper arm shaft of the suspension, but can be applied to the threaded bushing of various other assembled parts.

(Effect of the Invention) Since the present invention is configured as described above, when screwing the thread bush, it is possible to smoothly screw the thread bush without erroneously detecting the maximum point and the seating point by the wave of torque before sitting. It can be carried out.

[Brief description of the drawings]

FIG. 1 is an assembly structure diagram according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a control device in the embodiment, FIG. 3 is a screw torque characteristic diagram in the embodiment, and FIG. It is a flowchart which performs the control of the same Example. 1: Upper arm, 2: Upper arm shaft, 3: Assembly hole,
4: Female thread, 5: Male thread, 6: Thread bush, 7: Female thread, 8a, 8b: Male thread, 11: Nut runner, 12: Controller, 13: Control means, 14: Drive control means, 15: Scheduled Value setting means.

Claims (2)

(57) [Claims] 1. A threaded bush having an internal thread formed on an inner periphery and an incomplete male thread and a complete male thread continuously formed on the outer periphery from the distal end side into a mounting hole of a first mounting component. Inserting the threaded female thread of the thread bush into the male thread formed at the end of the second assembled component to be inserted into the first assembled component while assembling the first assembled component First, the incomplete male screw portion is screwed into the incomplete female screw portion formed in the attachment hole, and then a predetermined tightening is performed while the incomplete female screw portion of the first assembled part is cut off by the complete male screw portion. In the thread bush screwing control method using a nut runner for screwing up to the attached state, the threading bush is screwed in while detecting the screwing angle and the screwing torque, and the detected screwing torque and the screwing are obtained as torque gradient characteristics. angle By calculating the torque increase rate from the above, and comparing the detected screwing torque and the torque increase rate with a preset set value, the complete male screw part is replaced with the incomplete female screw part of the first assembled part. The maximum point of the screwing torque that appears at the point of entry, the seating point at which the screwing torque is minimized after passing the maximum point, and the thread bush is further tightened from the seating point to the set torque value to complete tightening. A thread bush screwing control method, comprising: judging a stop point at which a state can be determined; and stopping the screwing when the stop point is reached. 2. The thread bush screw-in control method according to claim 1, wherein it is determined whether the torque rise rate is before reaching the maximum point of the screw torque or after the seat is seated by comparing with the set value. .