JP3185130B2 - Clamping device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a clamp device mounted on other jigs for welding.

[0002]

2. Description of the Related Art Conventionally, this type of clamping device is configured such that a fixed clamp piece and a movable clamp piece are attached to a bracket, and the work is clamped between the fixed clamp piece and the movable clamp piece by closing operation. And is fixed to the jig via a bracket.

[0003]

When the workpieces Wa and Wb are set on a jig and the movable clamp piece is closed in order to couple the two workpieces Wa and Wb as shown in FIG. Even if there is a distortion δ as shown in FIG. 2A, the work is positioned and clamped at a fixed position as shown in FIG. 2B using the fixed clamp piece as a reference seat in the clamping direction.
However, when the movable clamp piece is opened and unclamped, the work is distorted again due to springback, and therefore, even if the works are connected to each other in the clamped state, the product W taken out by unclamping as shown in FIG. 2 (c). Distortion δ 'remains, and it becomes difficult to secure the assembly accuracy of the product.

Further, a contacting tip for a workpiece is attached to a clamp piece, and the abrasion of the contact tip of the fixed clamp piece shifts the clamping position of the workpiece in the clamping direction. The position is adjusted, and the work is troublesome.

The present invention has been made in view of the above points, and provides an apparatus capable of automatically adjusting a work clamp position in a clamp direction by automatically measuring work distortion and abrasion of a contact tip. It is an issue.

[0006]

Means for Solving the Problems In order to solve the above problems,
The present invention relates to a clamp device in which a fixed clamp piece and a movable clamp piece are mounted on a bracket, and the work is clamped between the fixed clamp piece and the movable clamp piece by closing the movable clamp piece. A moving mechanism, a detecting means provided on at least one of the fixed clamp piece and the movable clamp piece for detecting a reaction force of pressing the work, and a fixed clamp piece and a movable clamp piece.
Control means for controlling a moving mechanism such that the bracket is moved to a predetermined position determined based on a signal from the detection means when the work is clamped between the work piece and the clamp piece .

When the work has a distortion, when the work is clamped, the pressing reaction force of the work deviates from the reference value of the pressing reaction force by the force required to bend the work by the amount of the distortion. Therefore, the amount of bending of the work, that is, the amount of distortion δ can be measured from the deviation between the detected value of the pressing reaction force by the detecting means and the reference value. Here, as shown in FIG.
When the workpieces are joined by being further bent by a predetermined correction amount A according to the above, the product W springs back by the correction amount A during unclamping as shown in FIG. Thus, the correction amount A is calculated from the distortion amount δ, and the bracket is moved by the correction amount A, whereby the assembly accuracy of the product can be ensured.

Further, even when the contact tip of the fixed clamp piece is worn and a gap is formed between the contact tip and the work, the work is bent by the amount of the gap when the work is clamped, and this bending is required. The pressing reaction force of the work deviates from the reference value by the force. Therefore, the gap amount is measured from the deviation between the detected value of the pressing reaction force by the detecting means and the reference value, and the bracket is moved by the gap amount to compensate for the wear of the contact tip.

By the way, as the detecting means, a strain gauge attached to the contact tip can be used. However, the contact tip is a consumable, and if the strain gauge is attached to this, the detecting means is attached together with the chip. Must be replaced, which increases maintenance costs. On the other hand, if the contacting tip is movably inserted in the clamping direction of the work on the clamp piece, and a load cell receiving a pressing reaction force via the contacting tip is embedded, and the load cell constitutes a detecting means. It is only necessary to replace the contact tip, which is advantageous in cost.

[0010]

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 1 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 configuration 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 as a 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 pressing the work, and calculates the 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, the distortion amount δ can be calculated from the deviation ΔP (= Ps−P) of the detected value P of the pressure reaction force from the reference value Ps.

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 distortion amount δ12 at C2 is δ12 = δ2-β · δ1 = {(α11 + βα21) ΔP2- (α12 + βα22) ΔP1} / (α11α22−α12α21) (5)

FIG. 6 shows the relationship between the amount of deflection and the pressure 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 non-deflection state, a force corresponding to ΔPb obtained from the b-line corresponding to the amount of bending is determined by the 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.

In the bending test for obtaining the empirical formulas representing the a-line and the b-line, the moving pitch of the movable clamp units 3 ₁ and 3 ₂ is set by the personal computer 4, and the movable clamp unit is instructed by 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 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).

[0025] 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 this clamping are read into the personal computer 4, and the computer 4 calculates the distortion amount δ1 at C1 from the above equation (3). At the same time, the apparent distortion amount δ2 at C2 is calculated from the above equation (4), or the true distortion amount δ12 at C2 is calculated from the above equation (5). Then, the correction value A1 at C1 is calculated by substituting the calculated value of δ1 into the above equation (6),
The correction value A2 at C2 is calculated by substituting the calculated value of δ12 into the above equation (7) or by substituting the calculated value of δ2 into the equation (8).

Next, the data of A1 and A2 is 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 once unclamped 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.

[0029] Incidentally, it is also possible to omit the first movable clamp units 3 _1, this is likely to strain remains in the middle portion of the product W, To increase the accuracy of the product W, the present embodiment movable clamp units 3 ₁ first and second two sets as in the three ₂ we are desirable to provide. It is also possible to provide three or more movable clamp units.

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 the 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, and the pressure reaction force detected at this time is deviated from the reference value by a deviation from the reference value. The presence or absence of the distortion may be confirmed, and the calculation coefficient of the correction amount may be corrected by learning control.

As described above, the movable clamp units 3 ₁ and 3 ₂
Has been described embodiment was used to deflect the workpiece as distortion in the product is not left, the movable clamp units 3 _1, 3 ₂ other applications, for example, to compensate for the displacement of the clamping position by chip abrasion Can also be used. That is, when the contact tip 31a of the fixed clamp piece 31 is worn, but the clamping position of the workpiece is shifted by the wear amount of the contact tip 31a, the movable clamp unit 3 _1, 3 ₂ having a load cell 35, such as above, Since the pressing reaction force detected by the load cell 35 deviates from the reference value due to the bending of the work by the amount of wear of the contact tip 31a generated at the time of clamping, the contact tip is determined from the deviation between the detection value of the pressing reaction force and the reference value. detecting the wear amount of the 31a, the wear amount movable clamp units 3 _1, 3 ₂ are moved, it is possible to compensate for displacement of the clamping position.

In the above embodiment, the load cell 35 is provided on the fixed clamp piece 31. However, the load cell may be provided on the movable clamp piece 32. However, if the load cell 35 is provided on the fixed clamp piece 31, the clamp position can be automatically adjusted according to the set height of the work without clamping the work. That is, after setting the workpiece to a predetermined height, when moved upward the movable clamp unit 3 _1, 3 ₂ in the open state of the movable clamp piece 32, the contact tip 31a of the fixed clamp piece 31 is in contact with the workpiece instant change detection signal of the load cell 35, by stopping the movable clamp unit 3 _1, 3 ₂ detects this change point, it can be automatically adjusted to suit the clamping position to the set height of the workpiece.

[Brief description of the drawings]

FIG. 1 is a perspective view of an example of a work to be clamped by the apparatus of the present invention.

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

FIG. 3 is a perspective view showing a work joining apparatus provided with the apparatus of the present invention.

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

FIG. 5 is a view 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 3 ₁ , 3 ₂ Movable clamp unit 30 Bracket 31 Fixed clamp piece 31a Contact tip 32 Movable clamp piece 34 Moving mechanism 35 Load cell (detection means) 4 Personal computer (control means) 5 Control panel (control means)

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shinji Imai 1-10-1, Shinsayama, Sayama City, Saitama Prefecture Honda Engineering Co., Ltd. (72) Inventor Nobuya Takeishi 1-10-1, Shinsayama, Sayama City, Saitama Prefecture (56) References JP-A-6-201301 (JP, A) JP-A-4-336937 (JP, A) JP-A-62-15053 (JP, A) JP-A-2-167687 (JP, A) JP-A-58-196116 (JP, A) JP-A-61-148000 (JP, A) JP-B-3-27290 (JP, B2) JP-B-3-37779 (JP, Y2) ( 58) Field surveyed (Int. Cl. ⁷ , DB name) B23Q 3/06 B23K 37/04

Claims (2)

(57) [Claims] In a clamp device, a fixed clamp piece and a movable clamp piece are mounted on a bracket, and the work is clamped between the fixed clamp piece and the movable clamp piece by closing operation. A moving mechanism that moves, detecting means provided on at least one of the fixed clamp piece and the movable clamp piece for detecting a reaction force of pressing the work, and a fixed clamp piece and a movable clamp piece.
A clamp device comprising: a control unit that controls a moving mechanism so that a bracket is moved to a predetermined position determined based on a signal from a detection unit when a workpiece is clamped between the clamp piece and the clamp piece . 2. A load chip receiving a press reaction force via a contact tip is buried in a clamp piece provided with a detecting means, and a contact tip for a work is freely movably inserted in a clamp direction of the work. 2. The clamp device according to claim 1, wherein the load cell constitutes a detecting unit.