JP5098542B2 - Bolt fastening method and apparatus - Google Patents

Description

  The present invention relates to a bolt fastening method and an apparatus therefor.

  In order to ensure the fastening quality of the bolt fastening parts, it is important to appropriately manage the bolt fastening axial force so that the desired design value is satisfied. However, it is difficult to perform tightening management while directly measuring and confirming the bolt tightening axial force. Until now, tightening torque and tightening angle (rotation angle) have been used as substitute characteristics of tightening axial force. In general, a method of managing data is used. Among them, for example, as shown in Patent Document 1, there is a seating point angle method. In the seating point angle method, the torque gradient (dT / dθ) is calculated from the measured torque curve at the time of bolt tightening, the intersection of the gradient slope line and the torque zero (horizontal axis) is obtained, and the intersection is the theoretical seating point. This is a tightening method in which tightening is performed by a predetermined angle as a (tightening start point) (see FIG. 17). If this seating point angle method is used, since the bolt tightening angle θ (bolt rotation angle) and the tightening axial force F are in a proportional relationship, the theoretical seating point can be accurately obtained with an ideal straight line of the torque curve. If this is done, the influence of the friction coefficient μ is completely eliminated, and an extremely stable tightening axial force can be obtained.

By the way, when the bolt and the member to be tightened have the same degree of hardness, the torque characteristic line (torque curve) tends to be a straight line, and an excellent axial force stabilization effect can be obtained by applying the above-described seating point angle method. Can demonstrate.
Japanese Patent Laid-Open No. 62-102978

  However, when the hardness of the member to be tightened is relatively low compared to the hardness of the bolt, the seating surface of the member to be tightened is likely to be loose or galling in the bolt tightening process. At the initial stage of tightening, the seating surface of the tightened member is loosened due to local contact between the outer periphery of the bolt seating surface and the seating surface of the tightening member, and the friction torque of the seating surface increases and the tightening friction coefficient μ It is easy to cause. Further, when the seating surface of the member to be tightened progresses in the tightening process, the bolt seat surface and the member to be tightened come into surface contact, and torque fluctuations are likely to occur, for example, reducing the friction torque of the seating surface. For this reason, when the hardness of the member to be tightened is relatively low compared to the hardness of the bolt, the torque characteristic line (tightening torque curve) in the relationship between the tightening torque and the tightening angle in tightening the member to be tightened The seating point angle method using the torque gradient (dT / dθ) is often curved in the middle of tightening, and a large deviation occurs in the calculated seating point, which is accompanied by the final tightening angle (θA1). There is a problem in that the tightening axial force greatly fluctuates (see FIG. 18).

The present invention has been made in view of such circumstances, and a first technical problem thereof is to provide a bolt fastening method capable of preventing a fastening axial force from fluctuating based on a state of a torque characteristic line. There is.
The second technical problem is to provide a bolt fastening device using the bolt fastening method.

In order to achieve the first technical problem, in the present invention (the invention according to claim 1),
In a bolt fastening method for obtaining a target fastening axial force by fastening a bolt to a member to be fastened,
During the tightening of the bolt, a state of a torque characteristic line indicating a change in the tightening torque accompanying a change in the tightening angle is obtained,
When it is determined that the torque characteristic line is in a straight line state, the bolt is tightened until the first set angle set in advance is reached from the theoretical seating point obtained based on the initial torque gradient in the torque characteristic line. To obtain the target tightening axial force,
When it is determined that the state of the torque characteristic line is a curved state that is curved more than the linear state, the bolt is tightened until reaching a preset snag torque, and the bolt tightening angle when the snag torque is reached As a reference, the bolt is further tightened by the second set angle to obtain the target tightening axial force. A preferred embodiment of claim 1 is as described in claims 2-7.

In order to achieve the second technical problem in the present invention (the invention according to claim 8),
In a bolt fastening device that obtains a target fastening axial force by fastening a bolt to a member to be fastened,
A bolt tightening adjusting means for adjusting the tightening of the bolt;
Torque characteristic line state detecting means for detecting a state of a torque characteristic line indicating a change in tightening torque accompanying a change in tightening angle during tightening of the bolt;
Torque characteristic line state determining means for determining whether the state of the torque characteristic line is in a straight line state or a curved state curved from the straight line state based on information from the torque characteristic line state detection unit;
Based on the information from the torque characteristic line state determining means, the bolt tightening adjusting means is controlled to determine that the torque characteristic line is in a straight line state. When the bolt is tightened from the theoretical seating point calculated based on the theoretical setting point until a first preset angle is reached to obtain the target tightening axial force, and when it is determined that the torque characteristic line is in a curved state The bolt is tightened until the preset snag torque is reached, and the bolt is further tightened by the second set angle based on the bolt tightening angle at the time when the snag torque is reached, to obtain the target tightening axial force Control means to
It is set as the structure provided. The preferred embodiment of claim 8 is as described in claim 9 and below.

  According to the first aspect of the present invention, when the state of the torque characteristic line is obtained during tightening of the bolt, and it is determined that the state of the torque characteristic line is in a straight line state that does not cause the problem of deviation of the theoretical seating point. When the tightening based on the seating point angle method is performed in principle, the torque characteristic line is determined to be in a curved state that causes a problem of deviation of the theoretical seating point. The bolts are tightened until the snag torque is reached, and tightening is performed based on the bolt tightening angle at the time when the snag torque is reached. The tightening axial force can be made substantially constant (after the snag torque, tightening is performed by the angle method, and before reaching the snag torque, The fluctuation of the valence diameter is suppressed and the fluctuation of the tightening axial force is suppressed), and the target tightening axial force is based on the seating point angle method even under tightening by the torque + angle method. By adjusting to the target tightening axial force, the tightening axial force based on the tightening by the seating point angle method can be made equal. For this reason, it is possible to suppress fluctuations in the tightening axial force regardless of whether the torque characteristic line is in a straight state or a curved state.

  According to the invention of claim 2, the state of the torque characteristic line is obtained from the predetermined parameter value related to the torque characteristic line, and it is determined that the torque characteristic line is in a curved state. Therefore, it can be specifically determined that the state of the torque characteristic line is a curved state.

  According to the invention of claim 3, since the predetermined parameter value is the difference between the torque gradients in the low and high torque regions on the torque characteristic line, it is accurately and easily determined whether or not the state of the torque characteristic line is a curved state. it can.

  According to the invention of claim 4, since the predetermined parameter value is the difference between the tightening torque at the predetermined tightening angle calculated based on the torque gradient of the torque characteristic line and the measured tightening torque at the predetermined tightening angle, Whether the line state is a curved state or not can be determined more specifically and accurately.

  According to the invention of claim 5, when it is determined that the state of the torque characteristic line is in a predetermined bending state, the bolt is tightened until reaching a preset snag torque, and the bolt at the time when the snag torque is reached is tightened. With the tightening angle as a reference, tightening the bolt by the second set angle is continued by offsetting the tightening angle executed up to the time of the judgment, so that the bolt tightening can be completed by one continuous tightening. The bolt can be quickly tightened while suppressing fluctuations in the tightening axial force.

  According to the invention of claim 6, when it is determined that the state of the torque characteristic line is in a predetermined curved state, the bolt is tightened until reaching a preset snag torque, and the bolt at the time when the snag torque is reached is tightened. With the tightening angle as a reference, tightening the bolt by the second set angle is started again by loosening the bolt, so that the tightening axial force varies without complicated control in tightening the bolt. This can be suppressed.

  According to the seventh aspect of the present invention, since the hardness of the bolt is higher than the hardness of the member to be tightened, the tightening axial force fluctuates even when the torque characteristic line is likely to be bent in tightening the bolt. This can be suppressed.

  According to the invention of claim 8, in operation, the bolt fastening method according to claim 1 is used, and a bolt fastening device using the bolt fastening method according to claim 1 can be provided.

  According to the invention of claim 9, the bolt fastening method according to claim 2 is used in operation, and a bolt fastening device using the bolt fastening method according to claim 2 can be provided.

  According to the invention of claim 10, the bolt fastening method according to claim 3 is used in operation, and a bolt fastening device using the bolt fastening method according to claim 3 can be provided.

  According to the invention of claim 11, the bolt fastening method according to claim 4 is used in operation, and a bolt fastening device using the bolt fastening method according to claim 4 can be provided.

  According to the twelfth aspect of the present invention, the bolt fastening method according to the fifth aspect is used in operation, and a bolt fastening device using the bolt fastening method according to the fifth aspect can be provided.

  According to the invention of claim 13, in the operation, the bolt fastening method according to claim 6 is used, and a bolt fastening device using the bolt fastening method according to claim 6 can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the bolt fastening method according to the first embodiment will be described.

(1) The bolt fastening method according to the first embodiment uses a bolt rotating means such as a nut runner to fasten a member to be fastened (for example, an engine bearing component) by tightening the bolt. In this fastening method, By initial bolt tightening (bolt tightening), a state of a torque characteristic line indicating a change in tightening torque accompanying a change in the tightening angle is obtained during the initial tightening.

  (i) The state of the torque characteristic line during initial tightening is determined by determining whether the torque characteristic line is a curved state that causes a deviation of the theoretical seating point or a linear state in which the deviation of the theoretical seating point does not matter, This is to reflect the result of the determination in the tightening of the bolt.

  (ii) As the state of the torque characteristic line, in the bolt fastening method according to the first embodiment, as shown in FIG. 1, a predetermined parameter value related to the torque characteristic line, that is, a low torque region in the torque characteristic line A torque gradient difference α−β between the torque gradient α and the torque gradient β in the high torque region higher than the low torque region is used. This is because the torque gradient difference α−β is optimal for determining whether the torque characteristic line is in a curved state. In this case, as shown in FIG. 2, when the torque gradient difference ΔRT is less than or equal to a threshold value ΔRT0 (for example, 0.10) (for example, α≈β), as shown in FIG. When the torque gradient difference ΔRT exceeds the threshold value ΔRT0 as shown in FIG. 1, it is determined that the torque characteristic line is in a curved state. In order to increase the accuracy of the determination, more torque gradients may be obtained in the low torque region and the high torque region.

  (iii) The initial tightening is performed based on a seating point angle method. The seating point angle method is a fastening method in which the theoretical seating point is used as a reference for fastening by a set angle. In the initial fastening, θ00 (initial fastening angle) is set as the set angle. In this case, when the theoretical seating point is obtained, the torque gradient β in the torque stable region is used, and based on this, the theoretical seating point (specifically, the tightening that is tangent to the torque gradient β measurement point and the horizontal axis is used. The angle axis (intersection with the line where the tightening torque is 0) is obtained.

(2) The bolt fastening method according to the first embodiment, when it is determined that the state of the torque characteristic line is in a straight line state, the theory obtained based on the torque gradient in the torque characteristic line as shown in FIG. The bolt is tightened from the seating point until a first set angle θA1 set in advance is reached to obtain a target tightening axial force. When the torque characteristic line is in a straight line state, the problem of deviation of the theoretical seating point does not occur. By tightening only the first set angle θA1 with the theoretical seating point as a reference (sitting point angle method), This is because a uniform tightening axial force can be obtained in bolt tightening. That is, when the torque characteristic line is in a straight line state, a theoretical seating point reflecting the torque characteristic line can be accurately obtained, and if the exact theoretical seating point is tightened as a tightening start reference of the first set angle θA1, the tightening is performed. Attached axial force = Bolt tightening angle θ / 360 · P · K Based on the fact that each bolt is tightened, an equal tightening axial force can be obtained. Here, P is a bolt pitch, and K is a coefficient determined from the material and shape of the bolt and the member to be tightened.

  (i) In this case, as the theoretical seating point, the same theoretical seating point as that in the initial tightening using the torque gradient β in the torque stable region is used. The target tightening axial force is determined in advance from the shape and material of the bolt, the shape and material of the member to be tightened, and the first set angle θA1 is determined from the target tightening axial force. .

  (ii) Also, in this case, when it is determined that the torque characteristic line is in a straight line state, the tightening angle (in the initial tightening) in which the tightening of the bolt according to the above aspect is performed until the time of the determination based on the theoretical seating point. Offset the executed tightening angle) and continue. This is to quickly tighten the bolt. At this time, since the theoretical seating point is common in the initial tightening and the tightening after the above determination, as shown in FIG. 2, after the initial tightening is performed to the initial tightening angle θ00, the initial tightening angle θ00. Then, you may make it further tighten | tighten the amount of shortage (theta) A1- (theta) 00. Of course, the initial tightening is stopped when it is determined that the torque characteristic line is in a straight line state, the bolt is then loosened, and the first set angle θA1 is tightened again from the theoretical seating point. Good.

(3) On the other hand, the bolt fastening method according to the first embodiment is preset as shown in FIG. 3 when it is determined that the torque characteristic line is in a curved state that is curved rather than a linear state. The bolt is tightened until it reaches a snag torque (tightening torque at the start of effective (substantial) tightening) Ts, and a second setting is made based on the tightening angle θs of the bolt when the snag torque Ts is reached. The bolt is tightened by the angle θA2 to obtain the target tightening axial force.

  (i) Judgment that the state of the torque characteristic line is in the curved state is that when the state of the torque characteristic line is in the curved state, the theoretical seating point is larger than the theoretical seating point in the linear state. Since the tightening axial force fluctuates in tightening by the seating point angle method using the theoretical seating point (see FIG. 18 described above), other tightening methods that do not use the angle method based on the theoretical seating point are used. This is for switching. Such a curved torque characteristic line is likely to occur when the hardness of the bolt is higher than the hardness of the member to be tightened.

(Ii) When it is determined that the state of the torque characteristic line is in a curved state, the bolt is tightened until a preset snag torque Ts is reached, and the bolt tightening angle θs (theoretical seating when the snag torque is reached) The tightening method (torque + angle method) for tightening the bolt by the second set angle θA2 with the point specified as a reference) is used as the reference. This is because the final tightening axial force has characteristics that can be made substantially equal. That is, if the torque + angle method is used, after the snag torque Ts, the tightening is performed by the angle method, and the desired tightening axial force can be obtained accurately only by controlling the tightening angle (the tightening axial force and the tightening force). Before the snag torque Ts is reached, the tightening axial force is low at this stage, and there is a variation in the location (equivalent diameter) that causes friction between the bolt seat surface and the member to be tightened. Suppressed and stable friction occurs, and variations in the tightening axial force up to the snag torque Ts are suppressed. Therefore, as long as the torque + angle method is used, the final tightening axial force of each bolt can be made substantially equal. In the bolt fastening method according to the first embodiment, the characteristics of this torque + angle method will be used. It is.

  (iii) As the target tightening axial force of the tightening by the torque + angle method, the same as the target tightening axial force by the seating point angle method (the target tightening axial force when the torque characteristic line is in a straight state) is obtained. As long as the tightening is performed under the torque + angle method, the final tightening axial force by tightening each bolt can be made almost equal, but the target tightening axial force by the seating point angle method is the seating point. Unless it matches the target tightening axial force of the angle method, the tightening axial force based on the torque + angle method cannot be made equal to the tightening axial force based on the seating point angle method. Because. Therefore, the snag torque Ts and the second set angle θA2 used in the torque + angle method are set based on the target tightening axial force.

  (iv) When it is determined that the torque characteristic line is in a curved state, the bolt is tightened (the bolt is tightened until the preset snag torque Ts is reached, and the bolt at the time when the snag torque Ts is reached). Using the tightening angle as a reference, the bolt is further tightened by the second set angle θA2), and the tightening angle executed until the determination (the tightening angle performed in the initial tightening) is canceled. This is to quickly tighten the bolt. In this case, the initial tightening may be performed up to the initial tightening angle θ00, and the portion insufficient at the initial tightening angle θ00 may be further tightened. Of course, when it is determined that the state of the torque characteristic line is in a curved state, the initial tightening is stopped, and then the bolt is loosened, and the bolt is tightened again until the preset snag torque Ts is reached. The bolt may be further tightened by the second set angle θA2 with reference to the bolt tightening angle when the snag torque Ts is reached.

  Next, a bolt fastening device using the method according to the first embodiment will be described. As shown in FIG. 4, the bolt fastening device 1 includes a nut runner 2 as a bolt rotating means, and a control system 3 that controls the nut runner 2. The nut runner 2 includes a socket 4 that is engaged with the head of the bolt, a drive motor (bolt tightening adjusting means) 5 that rotationally drives the socket 4, and torque for detecting torque applied to the bolt by the socket 4. A transducer (torque detecting means) 6 and an angle encoder (tightening angle detecting means) 7 for measuring the tightening angle of the bolt by detecting the rotation angle of the drive motor 5 are provided.

  The control system 3 includes an arithmetic control device (CPU) 8. In addition to the direct input of the tightening torque signal from the torque transducer 6 and the tightening angle signal from the angle encoder 7, the arithmetic and control unit 8 has various information for torque gradient calculation and tightening by the torque + angle method. Are input and output. First, the tightening torque signal from the torque transducer 6 and the tightening angle signal from the angle encoder 7 will be described. The tightening torque and the tightening angle based on these signals are measured at the same time as the bolt tightening is started. Of these, the tightening angle is calculated with reference to the theoretical seating point after the theoretical seating point is obtained as described later. The tightening angle is specified (as a tightening angle value of 0).

  Next, the input / output relationship for torque gradient calculation will be described. The control system 3 includes a reference torque setter 9a for setting a reference torque T0. A reference torque signal from the reference torque setter 9a and a bolt tightening torque signal detected by the torque transducer 6 are supplied to the comparator 10a. Have been entered. The comparator 10a compares the reference torque signal and the tightening torque signal, and outputs a coincidence signal when the two values coincide with each other, and the coincidence signal reaches the reference torque via the analog gate 11a. The signal is input to the arithmetic and control unit 8 as a signal. On the other hand, a bolt tightening angle signal detected by the angle encoder 7 is input to the arithmetic control device 8 via the angle gates 12a to 12d, and the angle gates 12a to 12d are turned on and off. ON / OFF signals are input from the arithmetic and control unit 8. In this case, the ON signal from the arithmetic and control unit 8 is output on condition that the reference torque arrival signal is input to the arithmetic and control unit 8, whereby each of the angle gates 12 a to 12 d is output. When turned ON, the arithmetic and control unit 8 (storage means) stores the reference tightening angle θ0 at the reference torque T0. On the other hand, the OFF signal from the arithmetic control device 8 reaches the angle set according to each angle gate 12a to 12d when the tightening angle input after each angle gate 12a to 12d is turned ON. Are output respectively. That is, the control system 3 includes an angle setter 14a for setting the tightening angle Δθ1, an angle setter 14b for setting the tightening angle Δθ2, an angle setter 14c for setting the tightening angle Δθ3, and an angle setter for setting the tightening angle Δθ4. The arithmetic control unit 8 stores the sum θ0 + Δθ1, θ0 + Δθ2, θ0 + Δθ3, θ0 + Δθ4 of the reference tightening angle θ0 and the angles Δθ1, Δθ2, Δθ3, Δθ4 set by the angle setting devices 14a to 14d, respectively. When it is determined that the tightening angles from the angle encoder 7 have sequentially reached θ0 + Δθ1, θ0 + Δθ2, θ0 + Δθ3, θ0 + Δθ4, OFF signals are sequentially output to the respective angle gates 14a to 14d accordingly. When the tightening angle from the angle encoder 7 reaches θ0 + Δθ1, θ0 + Δθ2, θ0 + Δθ3, θ0 + Δθ4, the arithmetic and control unit 8 inputs the input tightening torques T1, T2, T3 at the timing of reaching θ0 + Δθ1, θ0 + Δθ2, θ0 + Δθ3, θ0 + Δθ4. , T4 are stored. Based on these, as described later, a torque gradient is calculated, and a theoretical seating point, a torque gradient difference, and the like, which are substantial tightening starting points, are obtained using the torque gradient β. Note that Δθ1, Δθ2, Δθ3, and Δθ4 have a relationship of Δθ1 <Δθ2 <Δθ3 <Δθ4.

  Next, the input / output relationship for tightening by the torque + angle method will be described. The control system 3 is provided with a snag torque setting device 9b for setting the snag torque Ts. The snag torque signal from the snag torque setting device 9b and the bolt tightening torque signal detected by the torque transducer 6 are compared with each other. Has been entered. The comparator 10b compares the snag torque signal and the tightening torque signal, and outputs a coincidence signal when the two values coincide with each other, and the coincidence signal is output via the analog gate 11b. The arrival signal is input to the arithmetic and control unit 8. On the other hand, a bolt tightening angle signal detected by the angle encoder 7 is input to the arithmetic control device 8 via an angle gate 12e, and an ON / OFF signal for turning ON / OFF is supplied to the angle gate 12e. Input from the arithmetic and control unit 8. The ON signal from the arithmetic control device 8 is output on condition that the snag torque reaching signal is input. As a result, the angle gate 12e is turned ON, and the arithmetic control device 8 (memory) Means) stores the tightening angle at the time of the snag torque Ts. The OFF signal from the arithmetic control device 8 is output on condition that the set angle θA2 has been reached after the snag torque arrival signal has been input.

  As shown in FIG. 13, the arithmetic control device 8 processes the various input information and the like, as shown in FIG. 13, storage means, first torque gradient calculation means, second torque gradient calculation means, theoretical seating point calculation means, tightening angle. Readjustment means, initial tightening angle arrival detection means, torque gradient difference calculation means, torque characteristic line state determination means, snag torque point angle detection means, tightening mode selection means, additional tightening angle calculation means, and control means.

  The storage unit stores various information (Δθ1, Δθ2, Δθ3, Δθ4, T1 to T4) and the like in addition to the preset initial tightening angle θ00, the first set angle θA1, the snag torque Ts, and the second set angle θA2. Is set to

  The first torque gradient calculation means includes a reference tightening angle θ0 corresponding to the reference torque T0 in the low torque region, tightening angles Δθ1, Δθ2 tightened with reference to the reference tightening angle θ0, and torques T1, T2 corresponding to Δθ1, Δθ2. Are set as information, and the torque gradient α is calculated based on them (see FIG. 1). That is, the first torque gradient calculation means reads Δθ1, Δθ2, T1, T2 from the storage means described above, and sets the first torque gradient α in the low torque region to α = (T2-T1) / (Δθ2-Δθ1). Calculate based on

  The second torque gradient calculation means corresponds to the tightening angles Δθ3, Δθ4 and the Δθ3, Δθ4 tightened with the reference tightening angle θ0 as a reference in a torque region (high torque region) higher than the low torque region and stable in torque. Torques ΔT3 and ΔT4 to be received are received as information, and based on these, the torque gradient β is set to be calculated (see FIG. 1). That is, the second torque gradient calculation means reads Δθ3, Δθ4, T3, T4 from the storage means described above, and sets the second torque gradient β in the high torque region to β = (T4-T3) / (Δθ4-Δθ3). Calculate based on

  The theoretical seating point calculation means calculates T4 / β using the torque gradient β and the tightening torque T4 in the stable region of the tightening torque, and tightens on the tightening angle axis (horizontal axis) in FIG. A point that is back by T4 / β from the tightening angle point corresponding to the torque T4 is set as the theoretical seating point.

  The tightening angle readjustment means resets the tightening angle measured from the start of tightening and the tightening angle to be measured from now on, with the tightening angle value at the theoretical seating point obtained by the theoretical seating point calculating means as 0. Is set to

  The initial tightening angle arrival detection means is specially provided in the first embodiment. In the first embodiment, for the time being, the bolt tightening is performed up to the initial tightening angle θ00 (based on the theoretical seating point). It is set to detect that the initial fastening angle θ00 has been reached with reference to the theoretical seating point obtained by the computing means.

  The torque gradient difference calculation means (torque characteristic line state detection means) calculates the torque gradient α and the second torque gradient calculated by the first torque gradient calculation means when the initial tightening angle arrival detection means detects the arrival of the initial tightening angle θ00. The torque gradient difference ΔRT = α−β, which is the difference between them, is set based on the torque gradient β calculated by the means.

  The torque characteristic line state determining means determines whether or not the torque gradient difference ΔRT = α−β calculated by the torque gradient difference calculating means is less than or equal to a threshold value ΔRT0, and determines that the torque gradient difference ΔRT is less than or equal to the threshold value ΔRT0. Is determined to be in a straight line state, and when it is determined that the torque gradient difference ΔRT exceeds the threshold value ΔRT0, it is determined that the torque characteristic line is in a curved state.

  When the torque characteristic line state determination unit determines that the torque characteristic line is in a straight line state, the tightening mode selection unit executes a tightening mode from the theoretical seating point to the first set angle θA1 under the seating point angle method. Accordingly, the first set angle θA1 set in advance is read, the tightening angle θA1 from the theoretical seating point to the first set angle θA1 is set, and the torque characteristic line state discriminating means is in the curved state of the torque characteristic line. When the determination is made, the snag is tightened under the torque + angle method until the snag torque Ts is reached, and the tightening mode is performed to tighten the second set angle θA2 based on the tightening angle when the snag torque Ts is reached. Reads the tightening angle θs at the time when the torque Ts is reached (based on the theoretical seating point) and the preset second set angle θA2. , After adding them, the added value [theta] s + [Theta] a2, are set so as to to be fastening angle executed based on the theoretical seating point.

  The additional tightening angle calculation means is specially provided in the first embodiment. In the first embodiment, for the time being, the bolt is tightened to the initial tightening angle θ00, and after the bolt is tightened to the initial tightening angle θ00, the predetermined calculation is performed to compensate for the shortage at the initial tightening angle θ00. Control is to be done. For this reason, the additional tightening angle calculating means additionally tightens the shortage θA1-θ00 that is insufficient for tightening up to the initial tightening angle θ00 when performing tightening by the seating point angle method according to the selection setting of the tightening mode selecting means. When the tightening is performed using the torque + angle method, the shortage θs + θA2-θ00 that is insufficient for the tightening up to the initial tightening angle θ00 is determined as the additional tightening angle.

  When the control means detects that the initial tightening angle arrival detecting means has reached the initial tightening angle θ00 so as to perform the control provided with the initial tightening angle arrival detecting means and the additional tightening angle calculating means, After that, when the additional tightening angle calculation means finishes the calculation, the drive signal is output to the drive motor 5 again via the servo amplifier 13 and the calculated increase is performed. The bolt is set to be further tightened by the nut runner 2 by the tightening angle.

Next, a control example of the bolt fastening device 1 will be described more specifically based on the flowchart shown in FIG.
First, when the bolt fastening device 1 is activated, various information is read in S (indicating steps) 1. As various information, the snag torque Ts, the first set angle θA1, the second set angle θA2, the initial fastening angle θ00, and the like are read.

  Next, the drive of the nut runner 2 is started and the tightening of the bolt is started, and accordingly, the detection of the tightening torque and the tightening angle is started (S2, S3). A torque characteristic line (tightening torque-tightening angle line) is obtained based on the detection data of S3, and based on the torque characteristic line data, the torque gradient α in the low torque region is higher than the low torque region, and the tightening torque is A torque gradient β in a stable region is obtained (S4, S5). In the next S6, the torque gradient β of S5 is used to obtain the theoretical seating point where the substantial tightening angle is 0 as described above, and when the theoretical seating point is found, The tightening angle with respect to the starting point is readjusted to that with respect to the theoretical seating point, and the readjusted tightening angle is related to the tightening torque (S7: data readjustment). When the initial tightening angle θ00 is reached with the theoretical seating point as a reference, tightening by the nut runner 2 is stopped (the control means outputs a drive stop signal to the drive motor 5) (S8, S9).

  In the next S10, a torque gradient difference ΔRT = α−β is calculated using the torque gradient α in S4 and the torque gradient β in S6, and whether or not ΔRT is a threshold value ΔRT0 (for example, 0.10) or less. Is discriminated (S11). This determination is to determine whether or not the actually measured torque characteristic line is in a straight line state. When this S11 is YES, it is determined that the torque characteristic line is in a straight line state, and initial bolt tightening by the seating point angle method is performed. The shortage θA1-θ00 that is insufficient for tightening up to the tightening angle θ00 is calculated as the additional tightening angle (S12). When this calculation is finished, the tightening by the nut runner 2 is resumed (the control means outputs a drive signal to the drive motor 5) (S13). When the tightening angle θA1-θ00 is executed, the tightening by the nut runner 2 is stopped. (S14, S15).

  On the other hand, when S11 is NO (when the measured torque characteristic line is in a curved state), the tightening angle θs and the second set angle θA2 at the time of the snag torque Ts are read to perform tightening by the torque + angle method (S16). ), A tightening angle θs + θA2 to be executed with the theoretical seating point as a reference is calculated (S17), and then an insufficient amount θs + θA2-θ00 that is insufficient for tightening up to the initial tightening angle θ00 is calculated as the additional tightening angle (S18). When this calculation is finished, the tightening by the nut runner 2 is resumed (S19), and when the additional tightening angle θs + θA2-θ00 is executed, the tightening by the nut runner 2 is stopped (S20, S15). In this case, in the tightening based on the torque + angle method, the snag torque Ts and the second set angle are set so that the target tightening axial force is equal to the target tightening axial force based on the seating point angle method. θA2 is preset. For this reason, even when the torque characteristic line during the bolt tightening is in a curved state, the tightening by the torque + angle method can obtain substantially the same tightening axial force as the tightening by the seating point angle method.

  7 and 8 are experimental examples using the bolt fastening method according to the first embodiment (combined use of tightening by the seating point angle method and tightening by the torque + angle method), and FIGS. An experimental example using such a bolt fastening method (use only fastening by the seating angle method) is shown. According to this, in the bolt fastening method according to the first embodiment, when the torque + angle method is used only for the bolts a and b whose seating point shift is larger than the bolts c and d, the conventional method is used. Compared with the bolt fastening method, the bolt fastening method according to the first embodiment showed excellent axial force stability (about 1/3 of the conventional) with respect to fluctuations in the fastening axial force. In this case, as shown in FIG. 11, the bolts a to d were tightened at each position of the cylinder block bearing portion B, and steel bolts were used as the bolts a to d.

Next, a bolt fastening method according to the second embodiment will be described.
The bolt fastening method according to the second embodiment shows a modification of the method for detecting the state of the torque characteristic line. In the bolt fastening method according to the second embodiment, the state of the torque characteristic line is calculated based on a predetermined parameter value related to the torque characteristic line, that is, the torque gradient β of the torque characteristic line, as shown in FIG. The difference ΔT = Tf1−Tf2 between the tightening torque Tf1 at the initial tightening angle θ00 (the tightening torque at the initial tightening angle θ00 position) = α × θ00 and the actually measured torque Tf2 at the initial tightening angle θ00 is used. This is because such a difference ΔT = Tf1−Tf2 can also accurately determine whether or not the torque characteristic line is in a curved state. In this case, as for the difference ΔT = Tf1−Tf2, as shown in FIG. 13, when the difference ΔT is equal to or smaller than a threshold value ΔT0 (for example, Tf1≈Tf2), it is determined that the torque characteristic line is in a linear state. As shown in FIG. 12, when the difference ΔT exceeds the threshold value ΔT0, it is determined that the torque characteristic line is in a curved state. Thereafter, based on the determination result, as in the first embodiment, the bolt tightening method is selected from tightening by the seating point angle method or tightening by the torque + angle method.

  Next, the bolt fastening device 1 using the method according to the second embodiment will be described. In the bolt fastening device 1 using the method according to the second embodiment, the same components as those of the bolt fastening device 1 using the method according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

In the bolt fastening device 1, as shown in FIG. 14, the angle gates 12a and 12b and the angle setting devices 14a and 14b are omitted from the configuration according to the first embodiment, and the torque gradient α in the low torque region is reduced. It is not to be requested. On the other hand, when the arithmetic and control unit 8 determines that the initial tightening angle θ00 has been reached with reference to the theoretical seating point, it stops driving the nut runner 2 and stores the actual tightening torque Tf2 at the initial tightening angle θ00. It is set to be.
Further, as shown in FIG. 15, the arithmetic control device 8 is provided with torque gradient calculation means for calculating the torque gradient β in the stable region of the tightening torque, but the second torque gradient calculation means in the first embodiment, Torque gradient difference calculating means (torque characteristic line state detecting means) is not provided, and instead, torque calculating means and torque difference calculating means (torque characteristic line state detecting means) are provided. The torque calculation means is set to calculate the calculated torque Tf1 at the initial tightening angle θ00 position using the torque gradient β calculated based on the torque gradient calculation means. The torque difference calculation means The difference ΔT = Tf1−Tf2 between the calculated torque Tf1 calculated by the means and the actual tightening torque Tf2 at the initial tightening angle θ00 is calculated. Accordingly, the torque characteristic line state determining means determines that the torque characteristic line is in a straight state when the difference ΔT is equal to or less than the threshold value ΔT0, and the torque characteristic line is in a curved state when the difference ΔT exceeds the threshold value ΔT0. It is set to be judged.

  Next, a control example of the bolt fastening device 1 using the method according to the second embodiment will be specifically described based on a flowchart shown in FIG.

  First, when the bolt fastening device 1 is activated, the same processes Q1 to Q8 as S1 to S9 (except S4) of the first embodiment are performed, and the initial fastening angle θ00 is reached with respect to the theoretical seating point, respectively. Then, tightening by the nut runner 2 is stopped. In the next Q9, using the torque gradient β in S4, the tightening torque (calculated torque when the torque characteristic line is in a straight line state) Tf1 at the initial tightening angle θ00 is calculated based on Tf1 = β × θ00. On the other hand, in the next Q10, the actual measured value (actual tightening torque) Tf2 of the tightening torque at the initial tightening angle θ00 is read, and the difference ΔT = Tf1 using the actual tightening torque Tf2 of Q10 and the calculated torque Tf1 of Q9. -Tf2 is calculated (Q11). This difference ΔT indicates the state of the torque characteristic line, and in the next Q12, the difference ΔT ≦ the threshold value ΔT0 is determined.

  When Q12 is YES, the torque characteristic line is in a straight line state. At this time, the same processes Q13 to Q16 as S12 to S15 of the first embodiment are performed in order to perform tightening by the seating point angle method. Is called. On the other hand, when Q12 is NO, the torque characteristic line is in a curved state. At this time, the same processing Q17 as S16 to S20, S15 of the first embodiment is performed in order to perform tightening by the torque + angle method. -Q21 and Q16 are performed. Of course, also in this case, in the tightening by the torque + angle method, the snag torque Ts and the second set angle θA2 so that the target tightening axial force becomes equal to the target tightening axial force of the tightening by the seating point angle method. Is set in advance, and even when the torque characteristic line during bolt tightening is in a curved state, substantially the same tightening axial force as the tightening by the seating point angle method is obtained.

Explanatory drawing explaining the method of discriminating whether the state of the actual measurement torque characteristic line is a straight state or a curved state in the bolt fastening method according to the first embodiment. In the bolt fastening method which concerns on 1st Embodiment, explanatory drawing which shows the case where the state of a measured torque characteristic line is a linear state. Explanatory drawing explaining the bolt fastening method (when the state of a torque characteristic line is a curved state) which concerns on 1st Embodiment. Explanatory drawing which shows the bolt fastening apparatus used for the bolt fastening method which concerns on 1st Embodiment. Explanatory drawing which shows the means contained in the calculation control apparatus of the control system in 1st Embodiment. The flowchart which shows the control example of the bolt fastening apparatus which uses the bolt fastening method which concerns on 1st Embodiment. The figure which shows the experimental result of the bolt fastening method which concerns on 1st Embodiment. The figure which showed the experimental result shown in FIG. 7 concretely. The figure which shows the experimental result of the bolt fastening method which concerns on the past (when the seating point angle method is used uniformly). The figure which showed the experimental result shown in FIG. 9 concretely. The figure which shows the bolting position in the experiment shown in FIGS. Explanatory drawing explaining the method of discriminating whether the state of the actual measurement torque characteristic line is a straight state or a curved state in the bolt fastening method according to the second embodiment. In the bolt fastening method which concerns on 2nd Embodiment, explanatory drawing which shows the case where the state of the actual measurement torque characteristic line is a linear state. Explanatory drawing which shows the bolt fastening apparatus used for the bolt fastening method which concerns on 2nd Embodiment. Explanatory drawing which shows the means contained in the calculation control apparatus of the control system in 2nd Embodiment. The flowchart which shows the example of control of the bolt fastening apparatus which uses the bolt fastening method which concerns on 2nd Embodiment. Explanatory drawing explaining the bolt fastening method (sitting point angle method) which concerns on the former. Explanatory drawing explaining the problem of the bolt fastening method (sitting point angle method) which concerns on the former.

Explanation of symbols

1 Bolt fastening device 3 Control system 5 Drive motor (Bolt tightening adjusting means)
7 Angle encoder 8 Arithmetic controller 12e Angle gate 12f Angle gate 12g Angle gate Ts Snag torque α Torque gradient β Torque gradient ΔRT Torque gradient difference ΔRT0 Threshold value Tf1 Calculated torque Tf2 Actual torque ΔT Difference ΔT0 Threshold value

Claims (13)

In a bolt fastening method for obtaining a target fastening axial force by fastening a member to be fastened by tightening a bolt,
During the tightening of the bolt, a state of a torque characteristic line indicating a change in the tightening torque accompanying a change in the tightening angle is obtained,
When it is determined that the state of the torque characteristic line is in a straight line state, the bolt is tightened from the theoretical seating point obtained based on the torque gradient in the torque characteristic line until a first set angle set in advance is reached, and the target To obtain the tightening axial force,
When it is determined that the state of the torque characteristic line is a curved state that is curved more than the linear state, the bolt is tightened until reaching a preset snag torque, and the bolt tightening angle when the snag torque is reached , The bolt is further tightened by a second set angle to obtain the target tightening axial force.
The bolt fastening method characterized by the above-mentioned. In claim 1,
The state of the torque characteristic line is obtained by a predetermined parameter value related to the torque characteristic line,
Determining that the torque characteristic line is in a curved state is that the predetermined parameter value deviates from a threshold value indicating the linear state of the torque characteristic line.
The bolt fastening method characterized by the above-mentioned. In claim 2,
The predetermined parameter value is a difference in torque gradient in a low / high torque region in the torque characteristic line.
The bolt fastening method characterized by the above-mentioned. In claim 2,
The predetermined parameter value is a difference between a tightening torque at a predetermined tightening angle calculated based on a torque gradient of the torque characteristic line and an actually measured tightening torque at the predetermined tightening angle.
The bolt fastening method characterized by the above-mentioned. In claim 1,
When it is determined that the state of the torque characteristic line is in the predetermined bending state, the bolt is tightened until a preset snag torque is reached, and the bolt tightening angle at the time when the snag torque is reached is further used as a reference. Tightening the bolt by the second set angle is continued by offsetting the tightening angle executed up to the time of the determination,
The bolt fastening method characterized by the above-mentioned. In claim 1,
When it is determined that the state of the torque characteristic line is in the predetermined bending state, the bolt is tightened until a preset snag torque is reached, and the bolt tightening angle at the time when the snag torque is reached is further used as a reference. Tighten the bolt by the second set angle, loosen the bolt and start a new one,
The bolt fastening method characterized by the above-mentioned. In any one of Claims 1-6,
The bolt has a hardness higher than that of the member to be tightened,
The bolt fastening method characterized by the above-mentioned. In a bolt fastening device that obtains a target fastening axial force by fastening a member to be fastened by tightening a bolt,
A bolt tightening adjusting means for adjusting the tightening of the bolt;
Torque characteristic line state detecting means for detecting a state of a torque characteristic line indicating a change in tightening torque accompanying a change in tightening angle during tightening of the bolt;
Torque characteristic line state determining means for determining whether the state of the torque characteristic line is in a straight line state or a curved state curved from the straight line state based on information from the torque characteristic line state detection unit;
Based on the information from the torque characteristic line state discriminating means, when the bolt tightening adjusting means is controlled to determine that the state of the torque characteristic line is in a straight line state, it is obtained based on the torque gradient in the torque characteristic line. The bolt is tightened from the theoretical seating point until a preset first set angle is reached to obtain the target tightening axial force. When it is determined that the state of the torque characteristic line is in a curved state, the bolt is set in advance. The bolt is tightened until the snag torque is reached, and the bolt is tightened by a second set angle based on the bolt tightening angle when the snag torque is reached to obtain the target tightening axial force. Control means;
With
A bolt fastening device characterized by that. In claim 8,
The torque characteristic line state detecting means is set to detect a predetermined parameter value related to the torque characteristic line when detecting the state of the torque characteristic line,
The torque characteristic line state determining means sets the torque characteristic line to a curved state on condition that a predetermined parameter value detected by the torque characteristic line state detecting means is out of a threshold value indicating a linear state of the torque characteristic line. Set to judge that there is,
A bolt fastening device characterized by that. In claim 9,
The predetermined parameter value detected by the torque characteristic line state detecting means is a difference in torque gradient between low and high torque regions in the torque characteristic line.
A bolt fastening device characterized by that. In claim 9,
The predetermined parameter value detected by the torque characteristic line state detecting means is a difference between a tightening torque at a predetermined tightening angle calculated based on a torque gradient of the torque characteristic line and an actually measured tightening torque at the predetermined tightening angle.
A bolt fastening device characterized by that. In claim 8,
When the control means controls the bolt tightening adjustment means and determines that the state of the torque characteristic line is in the predetermined bending state, the control means tightens the bolt until a preset snag torque is reached, and Based on the bolt tightening angle at the time when the torque is reached, further tightening the bolt by the second set angle is set so that the tightening angle executed up to the time of the determination is canceled and continued.
A bolt fastening device characterized by that. In claim 8,
When the control means controls the bolt tightening adjustment means and determines that the state of the torque characteristic line is in the predetermined bending state, the control means tightens the bolt until a preset snag torque is reached, and Based on the tightening angle of the bolt at the time when the torque is reached, further tightening the bolt by the second set angle is set so that the bolt is loosened and newly started.
A bolt fastening device characterized by that.

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