JP3114053B2 - Work joining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of setting two or more works on a jig on which a clamp unit is mounted, and connecting the works while clamping the works by the clamp unit.

[0002]

2. Description of the Related Art Conventionally, according to Japanese Patent Application Laid-Open No. Hei 1-153387, a clamp unit is made movable, and at the first time, a work is clamped to a position where the clamp unit is positioned at a predetermined reference position determined from design data. Combine
Next, the accuracy of the product assembled by this connection is optically measured, the position of the clamp unit is corrected based on the measurement result, the next work is connected, and the accuracy measurement is performed. A method is known in which the process is repeated until the product is obtained.

[0003]

When two products Wa and Wb as shown in FIG. 1 are connected to assemble a product having a closed cross-sectional shape, for example, a distortion δ as shown in FIG. 2B, the workpiece Wa is forcibly bent by the amount of the strain δ during clamping as shown in FIG. 2 (b). As shown in FIG. 2C, a distortion δ ′ due to springback occurs.

In the above-mentioned prior art, the distortion δ 'of such a product is measured, and the position of the clamp unit is corrected in the direction of reducing the distortion, so that the next work is joined. However, in such a feedback-type correction, a highly accurate product cannot be obtained from the first time, and waste is increased.
In addition, in the work, in addition to the variation for each lot, the variation of each work within the same lot is inherent.If the distortion of the current work is different from the distortion of the previous work, it can be obtained by combining the previous work. The correction based on the measured data of the product is not suitable for the current work, and after all, the conventional correction of the feedback method cannot cope with the variation of each work.

[0005] In view of the above, it is an object of the present invention to provide a method of joining workpieces in which a high-precision product can be obtained from the first time and variations in individual workpieces can be dealt with. .

[0006]

In order to solve the above-mentioned problems, a work connecting method according to the present invention comprises, as a clamp unit, a reference clamp unit for clamping a specific portion of a work at a fixed position, and a plurality of other portions of the work. A plurality of movable clamp units, each of which can be controlled to move in the clamp direction, are clamped, and the workpiece is clamped by the reference clamp unit, and the plurality of movable clamp units are respectively positioned at predetermined reference positions in the clamp direction. A first step of clamping the workpiece by the movable clamp unit and measuring the amount of bending of each of the workpieces at the time of clamping by the movable clamping unit; Second step of calculating the amount of distortion of Based on the amount of distortion, a third step of calculating the amount of work correction at each clamp location required to prevent the amount of distortion from remaining after joining the works, and moving each movable clamp unit, A fourth step of further bending each clamp point by the correction amount calculated for each clamp point, and a fifth step of joining works while maintaining the bent state in the fourth step are sequentially executed. It is characterized by.

According to the present invention, the distortion of the work set this time on the jig can be known. Here, when joining a workpiece having a distortion, the workpieces Wa and Wb are clamped as shown in FIG. 2B, the workpiece Wa is bent by the distortion δ, and then the workpieces Wa and Wb are combined as shown in FIG. ), The workpiece W is further bent by a predetermined correction amount A, and when the workpieces are joined together in this state, the product W springs back by the correction amount A as shown in FIG.
No distortion remains.

[0008] A unique relationship is established between the correction amount and the distortion amount of the work, and the correction amount is calculated based on the measured distortion amount, and the work is further bent by the correction amount. If the workpieces are joined together in the bent state, no distortion remains in the product.

By the way, it is conceivable to clamp one end and the other end of the work with the reference clamp unit and the movable clamp unit, respectively, and join the work with the intermediate part of the work being free. There is a possibility that distortion remains in the middle part of. On the other hand, according to the present invention, a plurality of movable clamp units clamp a plurality of locations on a work, and each of the clamp locations is further bent by a correction amount calculated based on the amount of distortion of the work between the clamp locations. As a result, no distortion remains throughout the product.

As described above, according to the present invention, the correction is performed by the feedforward method according to the distortion of the current work, so that a high-precision product can be obtained from the first time and it is possible to cope with the variation of each work. , Can greatly improve productivity.

The measurement of the amount of deflection in the first step can be performed optically, but this requires a large-scale measuring equipment and increases costs. By the way, if the work is distorted,
The pressing reaction force of the work deviates from the reference value of the pressing reaction force by the force required to deflect the work by the distortion. Therefore, in the first step, it is possible to detect the pressing reaction force of the workpiece by each movable clamp unit, and calculate the amount of bending at each clamp location from the detected value of the pressing reaction force. According to this, it is only necessary to incorporate a detecting means such as a load cell for detecting the pressing reaction force into the movable clamp unit, which is advantageous in cost. In addition, a total deflection reaction force (spring-back force) of a plurality of works clamped by the movable clamp unit can be detected, and calculation of the correction amount can be easily performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to assembling a product W having a closed cross-section by joining the workpieces Wa and Wb shown in FIG. 1 by spot welding, arc welding, bonding or the like will be described below. I do.

Referring to FIG. 3, reference numeral 1 denotes a jig, on which a pair of reference clamp units 2 and 2 for clamping one ends of works Wa and Wb at fixed positions, and a work W
a, clamping the middle part of the Wb, the first movable clamp units 3 ₁ mobile controllable pair vertically, 3 ₁ and to clamp the other end portion of the workpiece Wa, Wb, can be controlled to move up and down 1 the second movable clamp units 3 ₂ pairs 3 ₂ and is provided.

Each of the movable clamp units 3 ₁ and 3 ₂ is shown in FIG.
As shown in the figure, a lower fixed clamp piece 31 fixed to the bracket 30 and an upper movable clamp piece 32 pivotally mounted on the bracket 30 so as to be able to open and close vertically are provided. The piston rod 33a of the pressure cylinder 33, which is freely mounted on the shaft, is
2, when the movable clamp piece 32 is closed by the operation of the pressurizing cylinder 33, the workpieces Wa, Wb are clamped between the contact tips 31a, 32a attached to the clamp pieces 31, 32, respectively. I have.

The above arrangement is the same as that of the reference clamp unit 2. However, the movable clamp units 3 ₁ and 3 ₂ further include a moving mechanism 34 for moving the bracket 30 in the vertical direction, ie, the clamp direction, and both clamp pieces 31. , 32, the fixed clamp piece 3 in the illustrated example.
Detecting means 35 for detecting a pressing reaction force of the workpiece
And

The moving mechanism 34 includes a lifting rod 341 having a mounting base 341a for the bracket 30 at an upper end, and a lower end of the lifting rod 341. A nut 342, which is screwed to a threaded rod 341b attached to the casing 340, is rotatably supported on a lower inner periphery of the casing 340 via a holder 342a, and a belt 34 is connected to a pulley 342b connected to a lower end of the holder 342a.
3a, a pulley 343b on the output shaft connected to the servomotor 343 as a drive source. The nut 342 is rotated forward and reverse by the servomotor 343, so that the bracket 30 moves up and down via the lifting rod 341. Be moved. A spline groove (not shown) is formed on the outer peripheral surface of the elevating rod 341, and a ball spline sleeve 344 containing a ball that engages with the spline groove is fitted in the casing 340 by a key 344 a so as not to rotate. It is inserted.

The detecting means 35 includes a fixed clamp piece 31.
And a load cell embedded in the
1a is fixed to the fixed clamp piece 31 by the shaft portion 31 of the tip 31a.
b so as to be freely movable in the vertical direction,
Is brought into contact with the load cell 35, so that the load cell 35 receives the pressing reaction force of the work via the contact tip 31a. Note that the contact tip 31a has a shaft portion 31b.
Is fixed to the fixed clamp piece 31 by a circlip 31c attached thereto, and the chip insertion portion 31d of the fixed clamp piece 31 is detachably attached to the main body of the clamp piece 31 to separate the chip insertion portion 31d. By removing the circlip 31c in this state, the contact tip 31a can be replaced.

The detection signal of the load cell 35 is transmitted to the personal computer 4 as shown in FIG. 3, and the computer 4 calculates the amount of distortion of the work based on the detected value of the reaction force of the work, and calculates the amount of distortion of the work. Based on the amount, a correction amount of the work required to prevent distortion from remaining when the works are combined is calculated, and the data of the correction amount is transmitted to the control panel 5 for the jig 1, in a command signal from the control panel 5 by operating the servomotor 343 of each of the movable clamp units 3 _1, 3 ₂ of the moving mechanism 34, the movable clamp units 3 _1, 3 ₂ in the vertical direction of a predetermined in movement of the bracket 30 The workpiece is displaced from the reference position by the correction amount, and in this state, the workpieces are joined by a welding robot or the like (not shown).

Hereinafter, a method of calculating the distortion amount and the correction amount will be described. Work Wa, Wb is used as the reference clamp unit 2.
Can be considered as a cantilever as shown in FIG. 5 in which the clamped position by the reference clamp unit 2 is the fixed end C0. Figure C1 is clamped position by the first movable clamp units 3 _1, C2 is the clamping portion of the second movable clamp units 3 _2. The work has a strain amount of δ1 between C0 and C1, and C1
And C2 have a distortion amount of δ12. Note that C
2 is originally displaced by β · δ1 due to the influence of the distortion in C1, and therefore, the apparent distortion amount δ2 with respect to the reference position in C2.
Becomes δ2 = δ12 + β · δ1. Where β is the distance between C0 and C1 as L1, C
Assuming that the distance between 1 and C2 is L2, β ≒ (L1 + L2)
/ L1. The amount of distortion is positive when the direction of the distortion is upward, and negative when the direction is downward.

When the work is clamped at the reference position, the work is forcibly bent by the amount of distortion δ, and the pressing reaction force received by the lower fixed clamp piece 31 by the force required to bend the work is reduced. Decrease. Assuming that the force required to bend the work at the clamping point by the unit length is α, the force required to bend the work by the amount of distortion δ is δ · α, the reference value of the clamping force is Ps, and the load cell 35 Assuming that the detected pressure reaction force is P, P = Ps−δ · αδ = (Ps−P) / α. Thus, from the deviation ΔP (= Ps−P) of the detected value P of the pressure reaction force with respect to the reference value Ps,
That is, the distortion amount δ can be calculated.

When clamping C1 and C2 as in this embodiment, the pressing reaction force at C1 and the pressing reaction force at C2 affect each other, and the first movable clamp unit 3
If the deviation from the reference value of the detected value of the load cell 35 provided in the ₁ Delta] P1, deviation and ΔP2 the reference value of the detected value of the load cell 35 provided in the second movable clamp units _{3 2, ΔP1 = δ1 · α11} + δ2 · α21 ... (1) ΔP2 = δ1 · α12 + δ2 · α22 (2) Here, α11... Α22 are coefficients obtained by clamping the master work of the works Wa and Wb and performing a bending test. That is, when the first movable clamp units 3 ₁ is displaced unit length in a state of fixing the second movable clamp units 3 ₂ to the reference position is detected by the load cell 35 provided on the first movable clamp units 3 ₁ the amount of change in pressure reaction force alpha 11, the change amount of the pressurizing reaction force detected by the second movable clamp units 3 ₂ load cell 35 provided in is Arufa12, fixing the first movable clamp units 3 ₁ to the reference position the second movable clamp units 3 ₂ when displaced unit length in a state, variation of pressurizing reaction force detected by the load cell 35 provided on the first movable clamp units 3 ₁ a21, the second movable clamp variation of pressurizing reaction force detected by the load cell 35 provided in the unit 3 ₂ are Arufa22.

When δ1 and δ2 are obtained from the equations (1) and (2), δ1 = (α22 · ΔP1−α21 · ΔP2) / (α11 · α22−α12 · α21) (3) δ2 = (α11 · ΔP2−α12 · ΔP1) / (α11 · α22−α12 · α21) (4), and the true amount of strain δ12 at C2 is calculated from the amount of deflection δ2 at C2 by the amount of δ1 at C1. Displacement β
By subtracting δ1, δ12 = δ2-β · δ1 = {(α11 + βα21) ΔP2- (α12 + βα22) ΔP1} / (α11α22-α12α21) (5)

FIG. 6 shows the relationship between the amount of bending and the pressing reaction force detected by the load cell 35 when the master work is bent by moving the clamp unit up and down while the master work is clamped. The line a in the drawing is a relation line before the work is joined, and the line b is a relation line after the work is joined. The horizontal axis represents the amount of deflection with the clamp unit as the reference position, that is, the case where the master work is bent upward from a state where there is no bending, and the case where the master work is bent downward is negative. Represents the deviation ΔP of the detected value of the pressure reaction force with respect to the reference value (the pressure reaction force when the clamp unit is set at the reference position). I have.

When the product is assembled with the workpieces bent and assembled, in order to return the product to a state without bending, a force corresponding to ΔPb obtained from the b-line corresponding to the amount of bending is defined by a bending direction. Must be added in the opposite direction. Here, a restoring force corresponding to ΔPa obtained from the line a corresponding to the amount of bending remains in the work, and when a force F1 corresponding to a deviation between ΔPb and ΔPa is applied to the product, the product is in a state without bending. Return. When the work is distorted, a bending reaction force (spring-back force) F2 corresponding to the amount of distortion δ is applied to the product. Thus, when F1 and F2 become equal, the product returns to the state without bending. No distortion remains in the product.

[0025] a line, upon deflection test for determining the empirical formula representing the b lines, sets the movement pitch of the movable clamp unit 3 _1, 3 ₂ in the personal computer 4, the movable clamp unit by a command from the control panel 5 Each time 3 ₁ and 3 ₂ are moved up and down at a set pitch, the detection data of the load cell 35 is read into the personal computer 4 each time the pitch is moved by 1 pitch, and the computer uses the computer to perform a regression process or the like from the sampling data to the a line and the b line. The empirical formula representing is calculated. Here, assuming that the amount of deflection is x, the equation of line a is ΔPa
= Fa (x), if the equation of the b-line is ΔPb = fb (x), then F1 = fa (x) −fb (x) F2 = fa (δ), so that no distortion remains in the product. Is required to satisfy the following equation: fa (A) −fb (A) = fa (δ). From this equation, it is necessary to determine the correction amount A that is suitable for the distortion amount δ. Can be.

If the a-line and the b-line are straight lines as shown, and ΔPa = Ka · x ΔPb = Kb · x, then Ka · A−Kb · A = Ka · δ, and α = Ka / A = α · δ as (Ka−Kb).

[0027] As in the present embodiment, when clamping the C1 and C2, the master work is clamped at a reference clamp unit 2 and the first movable clamp units 3 _1, escape the second movable clamp units 3 ₂ from the work in state by moving the first movable clamp units 3 ₁ vertically, and coefficient Ka1 representing the relationship between the deflection amount and the pressurizing reaction force at the C1 before coupling the master work, bending at C1 after binding the master work A coefficient Kb1 representing the relationship between the amount and the pressing reaction force is obtained, and a coefficient α1 for calculating the correction amount A1 at C1 is obtained.
Is calculated by the following equation: α1 = Ka1 / (Ka1−Kb1). Further, the clamps at each reference position by the master work the reference clamp units 2 first movable clamp units 3 _1, move the second movable clamp units 3 ₂ up and down in a state of clamping the master work, master work And a coefficient Kb2 representing the relationship between the amount of deflection and the pressure reaction force at C2 after the coupling of the master work and the coefficient Kb2 representing the relationship between the deflection amount and the pressure reaction force at C2 after the coupling of the master work. Is calculated by the following equation: α2 = Ka2 / (Ka2−Kb2).

Then, the correction amount A1 at C1 is calculated by the following equation based on the work distortion amount δ1 at C1 as follows: A1 = α1 · δ1 (6) The correction amount A2 at C2 is equal to the correction amount A12 corresponding to the true distortion amount δ12 of the workpiece at C2.
1, the displacement amount β · A1 of C2 due to the correction amount A1 (however,
β ≒ (L1 + L2) / L1). Therefore, A2 is A2 = β · A1 + A12 = β · A1 + α2 · δ12 (7) = β · α1 · δ1 + α2 (δ2-β · δ1) = α2 · δ2 + β (α1-α2) δ1 (8)

When assembling the product W by combining the workpieces Wa and Wb, the workpiece Wa is placed in a state where the reference clamp unit 2 and the first and second movable clamp units 3 ₁ and 3 ₂ are all positioned at the reference positions. , Wb are clamped, and the detection data of the load cells 35 of the movable clamp units 3 ₁ , 3 ₂ at the time of the clamping are read into the personal computer 4, and the computer 4 calculates C 1 from the above equation (3).
Δ1 is calculated, and C2 is calculated from the above equation (4).
The apparent distortion amount δ2 in the above, or C2 from the above equation (5)
Is calculated. Then, the calculated value of δ1 is substituted into the above equation (6) to calculate the correction amount A1 at C1, and the calculated value of δ12 is substituted into the above equation (7).
The correction value A2 at C2 is calculated by substituting the calculated value of δ2 into the equation.

Next, the data of A1 and A2 are transmitted from the personal computer 4 to the control panel 5, and the first and second movable clamp units 3 ₁ and 3 ₂ are unclamped once according to a command from the control panel 5. The workpieces Wa and Wb are clamped again by being displaced from the reference position by A1 and A2, respectively, and the workpieces Wa and Wb are combined in this state.

[0031] In the above embodiment are provided with the first and second two sets of movable clamp units 3 _1, 3 _2, but it is also possible to provide a movable clamp unit 3 sets or more.

In the above-described embodiment, the correction amount is calculated from the measured distortion amount using an empirical formula. However, various test works having different distortions are created, and an optimum test work corresponding to the distortion amount is created. It is also possible to experimentally determine the correction amount, store the correction amount as a data table, and determine the correction amount corresponding to the measured distortion amount by searching a table.

After the workpieces are joined together, the movable clamp units 3 ₁ and 3 ₂ are returned to the reference positions and the product is re-clamped. The presence or absence of the distortion may be confirmed, and the calculation coefficient of the correction amount may be corrected by learning control.

[Brief description of the drawings]

FIG. 1 is a perspective view of a work.

2 (a) to 2 (e) are diagrams showing the principle of distortion generation and the principle of distortion removal of a product.

FIG. 3 is a perspective view of equipment used for carrying out the present invention.

FIG. 4 is a sectional view of a movable clamp unit.

FIG. 5 is a diagram showing a distortion amount and a correction amount of a work.

FIG. 6 is a graph showing the relationship between the amount of deflection of a work and the pressure reaction force.

[Explanation of symbols]

Wa, Wb Work W Product 1 Jig 2 Reference clamp unit 3 ₁ , 3 ₂ Movable clamp unit 34 Moving mechanism 35 Load cell (detection means) 4 Personal computer 5 Control panel

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuya Takeishi 1-10-1, Shinsayama, Sayama-shi, Saitama Prefecture Honda Engineering Co., Ltd. (72) Inventor Isao Kudou 1-10-10, Shin-Sayama, Sayama-shi, Saitama 1 Honda Engineering Co., Ltd. (56) References Japanese Utility Model Sho 61-172609 (JP, U) Japanese Utility Model Hei 4-54509 (JP, U) Japanese Utility Model Utility Model 4-60787 (JP, U) (58) Field (Int.Cl. ⁷ , DB name) B23K 11/11 593 B21D 1/14

Claims (2)

(57) [Claims] 1. A jig on which a clamp unit is mounted is mounted on a jig.
In a method of setting one or more workpieces and joining the workpieces while the workpieces are clamped by a clamp unit, the clamp unit includes a reference clamp unit that clamps a specific portion of the workpiece at a fixed position, and a plurality of other workpieces. A state in which a plurality of movable clamp units that can be moved in the clamp direction and that can be controlled in the clamping direction are provided, and the workpiece is clamped by the reference clamp unit, and the plurality of movable clamp units are respectively positioned at predetermined reference positions in the clamp direction. The first step of clamping the work with these movable clamp units and measuring the amount of bending at the time of clamping each work piece by each movable clamp unit; The amount of work distortion at And a third step of calculating, based on the amount of distortion between the clamp points, a correction amount of the work at each clamp point necessary to prevent the amount of distortion from remaining after the works are joined to each other. A fourth step of moving each movable clamp unit and further bending each of the clamp points by the correction amount calculated for each of the clamp points; and joining the workpieces while maintaining the bent state in the fourth step A work combining method, wherein the fifth step and the following steps are sequentially performed. 2. The method according to claim 1, wherein in the first step, a reaction force applied to the workpiece by each movable clamp unit is detected, and a bending amount of each clamp portion is calculated from a detected value of the pressure reaction force. 3. The method of joining workpieces according to 1.