JP2004249365A - Press die device for thin sheet and press forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To impart proper frictional force regardless of variable elements such as lubricity, surface condition, etc., between a metallic die and a work, and to constantly provide superior formed products regardless of variance of material property or environmental change. <P>SOLUTION: This press die device for a sheet is characterized in that it is equipped with a punch 1, a die 2, a blank holder die 3, a frictional force measuring means 4 which is installed between the die 2 and the blank holder die 3, and a means 5 for adjusting a blank holding load. It is desirable that the blank holder die 3 is split into a plurality of pieces and that the frictional force measuring means 4 is provided for each of the split blank holder dies 3. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a thin plate press mold apparatus and a press molding method, and more particularly to a mold apparatus and a molding method capable of adjusting the distribution of wrinkle holding load during press working.

  Various inventions have been disclosed for molding methods for controlling the wrinkle holding force. For example, Patent Document 1 discloses the shape, mechanical properties, chemical properties, lamination characteristics such as plating, and the surface of oil amount, etc. of the press material. The relationship between the physical quantity such as the situation and the appropriate wrinkle holding load that obtains the predetermined press quality is obtained in advance, and the appropriate wrinkle holding load is obtained from the relationship according to the actual physical quantity, and pressing is performed with the appropriate wrinkle holding load. A method of adjusting the air pressure of the air cylinder so that the above is performed is disclosed.

In Patent Document 2, the wrinkle holding force at the time of drawing molding is increased from the initial stage to the middle stage to suppress wrinkle generation and growth, while at the latter stage of molding, the pressure is reduced to an appropriate value to generate cracks and excess material. A method of preventing wrinkle residue due to inflow is disclosed. Further, Patent Document 3 discloses an invention for controlling a wrinkle holding load by temporarily changing a hydraulic pressure in a hydraulic cylinder by opening control of a flow rate control valve in a die cushion device including a hydraulic cylinder for equalizing pressure. Has been.
JP 7-266100 A JP-A-9-38728 JP-A-6-190464

Even if the invention for controlling the wrinkle holding load is disclosed in Patent Documents 1 to 3, etc., an appropriate wrinkle holding load in advance for a large number of fluctuation factors such as changes in material characteristics, mold wear, mold temperature, etc. It is difficult to seek. In particular, the lubrication characteristics with the mold are constantly fluctuating, and measuring the above characteristics every time significantly reduces productivity.
Controlling the wrinkle holding load with a die cushion device or the like requires a significant modification of the press device, and it is difficult to predict an appropriate wrinkle holding load in advance.
The present invention provides a press die apparatus capable of obtaining a wrinkle holding load on the spot and setting an appropriate load without obtaining an appropriate wrinkle holding load in advance for various fluctuation factors, and a press molding method using the same. For the purpose.

In order to solve the problem, means of the present invention are as follows.
(1) Punch, die and wrinkle holding die, friction force measuring means attached between the die and the wrinkle holding die, and a wrinkle holding load adjusting means, and a thin plate pressing die device .
(2) A thin plate press die apparatus comprising a punch, a die and a wrinkle holding die, a frictional force measuring means attached to the die shoulder, and a wrinkle holding load adjusting means.
(3) The thin plate pressing die apparatus according to (1) or (2), wherein the wrinkle holding die is divided into a plurality of pieces, and each of the divided wrinkle holding die has a frictional force measuring means.
(4) The thin plate pressing die apparatus according to any one of (1) to (3), wherein the frictional force measuring means is a piezo element or a strain gauge.
(5) The thin plate pressing die apparatus according to any one of (1) to (3), wherein a temperature measuring unit is provided instead of the frictional force measuring unit.
(6) The thin plate pressing die apparatus according to (5), wherein the temperature measuring means is a thermocouple.
(7) A thin plate press mold apparatus comprising a punch, a die and a wrinkle pressing mold, a press reaction force measuring means attached to the punch, and a wrinkle pressing load adjusting means.
(8) The thin plate pressing die apparatus according to (7), wherein the wrinkle holding die is divided into a plurality of pieces.
(9) The thin plate press according to any one of (3) to (6) or (8), characterized in that it has a wrinkle pressing load adjusting means that can be independently controlled for each divided wrinkle pressing die. Mold equipment.
(10) A thin plate press forming method using the press die apparatus according to any one of (1) to (4) or (9), wherein the frictional force is measured by the frictional force measuring means. A thin plate press-molding method characterized by controlling at least one of a wrinkle holding load and a punch speed so that is within a predetermined range during processing.
(11) A press forming method of a thin plate using the press die apparatus according to any one of (1) to (4) or (9), wherein the frictional force is measured by the frictional force measuring means. Is used to control at least one of the wrinkle holding load and the punch speed so that the friction force falls within a predetermined range based on the relationship between the friction force measured in the previous molding and the wrinkle holding load and the punch speed. A thin plate press molding method.
(12) A thin plate press forming method using the press die apparatus according to (5), (6) or (9), wherein the temperature measured by the temperature measuring means falls within a predetermined range during processing. , A press forming method for a thin plate, wherein at least one of a wrinkle holding load and a punch speed is controlled.
(13) A press forming method of a thin plate using the press die apparatus according to (5), (6) or (9), wherein the temperature is measured by the previous molding using the temperature measured by the temperature measuring means. A thin plate press forming method, wherein at least one of the wrinkle holding load and the punch speed is controlled so that the temperature falls within a predetermined range based on the relationship between the temperature and the wrinkle holding load and the punch speed.
(14) A thin plate press forming method using the press die apparatus according to (7) or (8), wherein the press reaction force measured by the press reaction force measuring means falls within a predetermined range during processing. , A press forming method for a thin plate, wherein at least one of a wrinkle holding load and a punch speed is controlled.
(15) A thin plate press forming method using the press die apparatus according to (7) or (8), wherein the press reaction force measured by the press reaction force measuring means is used and measured in the previous molding. A thin plate characterized by controlling at least one of the wrinkle pressing load and the punch speed so that the press reaction force falls within a predetermined range based on the relationship between the pressed reaction force, the wrinkle pressing load and the punch speed. Press molding method.

  With the present invention, appropriate frictional force can be applied regardless of fluctuation factors such as lubricity and surface properties between the mold and the workpiece, and it is always good regardless of variations in material characteristics and environmental changes. Can be obtained.

Details will be described below with reference to the drawings.
FIG. 1 shows a cross-sectional view of a press mold apparatus incorporating the mold apparatus described in (1). A mold apparatus incorporating the friction force measuring means 4 is attached to the surface of the wrinkle pressing mold 3, and the wrinkle pressing force is controlled via the wrinkle pressing load adjusting means 5 in accordance with the detected friction force. FIG. 4 shows an enlarged view of one side of the die 2 and the wrinkle holding mold 3 in FIG. 1 and shows a cross-sectional view of a mold apparatus incorporating the frictional force measuring means 4.

  As the punch 1 rises, the workpiece 6 sandwiched between the crease pressing die 3 and the die 2 is drawn into the cavity of the die 2 while being pulled by the frictional force, and the shape along the punch 1 is drawn. To be molded. At this time, if the tension is excessive, the material may be broken, and if it is excessively small, there is a problem that a shape defect such as generation of wrinkles or inability to form the shape along the lower mold occurs. . Therefore, in order to obtain a good product shape, it is necessary to set an appropriate wrinkle holding load. On the other hand, the tension acting on the material is caused by the frictional force between the workpiece 6 and the punch 1 and the die 2, and lubrication is performed to change the relationship between the surface pressure and the frictional force, that is, the friction coefficient. Generally, changing the characteristics of the oil, the surface roughness of the punch and the die, and applying beads are performed. However, since the friction coefficient changes every moment due to the influence of temperature, surface pressure, surface properties, etc., it is necessary to adjust the wrinkle holding force each time.

On the other hand, with the configuration shown in FIG. 1, the frictional force between the workpiece 6 and the wrinkle holding die 3 and the die 2 is directly measured by the frictional force measuring means 4, and the frictional force becomes a predetermined value. By adjusting at least one of adjusting the wrinkle holding load force using the wrinkle holding load adjusting means 5 and adjusting the punch speed, an appropriate tension is always applied regardless of the fluctuation of the friction coefficient. It can be applied to the material (the invention described in (1), (10) and (11) above).
FIG. 2 shows a cross-sectional view of a press mold apparatus incorporating the mold apparatus described in (2). In this example, a die apparatus incorporating the friction force measuring means 4 is attached to the shoulder of the die 2 and the wrinkle pressing force is controlled via the wrinkle pressing load adjusting means 5 according to the detected friction force. In FIG. 2, the frictional force measuring means 4 is incorporated not only in the die shoulder but also in the surface of the wrinkle pressing mold 3, but the frictional force measuring means 4 may be installed only in the die shoulder.
Further, as shown in FIG. 3, if the wrinkle pressing mold 3 is divided into a plurality of parts, the frictional force for each of the divided wrinkle pressing molds can be measured by the frictional force measuring means 4 (the above ( Invention according to 3)).
Moreover, the distribution of the wrinkle holding force can be adjusted appropriately by installing the wrinkle holding load adjusting means 5 for each of the divided wrinkle holding molds so that it can be controlled independently (see (( The invention according to 9).

FIG. 3 shows the wrinkle holding die described in (3) above. As shown in the figure, the wrinkle holding die is divided into a plurality of pieces, and each of the divided wrinkle holding die has a friction force measuring means 4.
Next, the principle of directly measuring the frictional force will be described with reference to FIG. The workpiece 6 is gripped by a pair of dies, that is, a die 2 and a flat plate 7, and the flat plate 7 is fastened to the crease pressing die 3 in the left-right direction in the drawing, for example, with bolts or the like. Further, a strain measuring element 4 is sandwiched between the flat plate 7 and the wrinkle holding mold 3. At this time, when the workpiece 6 slides in the direction of the arrow (leftward in the drawing), a shear strain is generated in the strain measuring element 4, and a piezo element (piezoelectric element) or a strain gauge is used as the strain measuring element 4. For example, it is possible to easily extract the strain as a voltage and measure the frictional force (the invention described in (4) above).
FIG. 3 shows a case where the frictional force is measured only on one side of the wrinkle holding die 3. For example, the front and back surfaces of the workpiece 6, the pair of dies 2, and the surface properties of the wrinkle holding die 3 are different. In this case, the measurement accuracy can be further improved by measuring the frictional force on the upper and lower surfaces of the workpiece 6. As the flat plate 7, structural carbon steel, tool steel, or the like can be used.

A press mold apparatus having the temperature measuring means described in (5) or (6) will be described. FIG. 5 shows a cross-sectional view of a press mold apparatus having the temperature measuring means 10. In FIG. 5, the temperature measuring means 10 is incorporated not only on the die shoulder but also on the surface of the wrinkle holding die 3, but it is measured on at least one of the surface of the wrinkle holding die 3 and the shoulder of the die 2. If a mold having a temperature means is attached and at least one of adjusting the wrinkle pressing load via the wrinkle pressing load adjusting means 5 and adjusting the punch speed according to the detected temperature is controlled, Since an appropriate tension can always be applied to the material regardless of the fluctuation of the friction coefficient, the effects of the present invention can be obtained (the inventions described in (5), (12) and (13) above).
It is economically preferable to use a thermocouple as the temperature measuring means (the invention described in (6) above).
The temperature measuring means will be described with reference to FIG. FIG. 7 is an enlarged view of one side of the die 2 and the wrinkle holding die 3 of FIG. The temperature measuring means 10 is sandwiched between the flat plate 7 and the wrinkle holding die 3. During press molding, the processing heat generation is large where the frictional force on the flat plate 7 is large, and the processing heat generation is small where the frictional force is small. That is, when the temperature on the flat plate 7 is high, the frictional force is large and the inflow of the material is hindered. Therefore, the material may be broken. Since this is not possible, problems such as wrinkles and poor shape occur. Therefore, the effect of the present invention can be obtained by directly measuring the temperature on the flat plate 7 during molding using the temperature measuring means 10.
Further, as shown in FIG. 6, if the wrinkle pressing mold 3 is divided into a plurality of parts, the temperature of each divided wrinkle pressing mold can be measured by the temperature measuring means 10. Moreover, the distribution of the wrinkle holding force can be adjusted appropriately by installing the wrinkle holding load adjusting means 5 for each of the divided wrinkle holding molds so that it can be controlled independently of each other (see above). Invention according to (9)).
The configuration in FIG. 5 is the same as that in which the frictional force measuring unit 4 in FIG. 2 is replaced with the temperature measuring unit 10, and the frictional force measuring unit 4 and the temperature measuring unit 10 may be used in combination.

A press mold apparatus having the press reaction force measuring means described in the above (7) to (9) will be described.
When processing the workpiece 6 with the configuration as shown in FIG. 8, the resultant force of the friction force and the force required for deformation of the workpiece 6, that is, the press reaction force acts on the punch. During processing, if the press reaction force is excessive, the material may break, and if it is excessive, problems such as generation of wrinkles and defective shape occur. Therefore, in order to obtain a good product shape, it is necessary to set an appropriate press reaction force. However, since the frictional force described above changes from time to time depending on the temperature and the surface shape, the press reaction force having the frictional force as a component also changes from time to time. Until now, in order to change the press reaction force to an appropriate value, the relationship between the surface pressure and the friction force, that is, the friction coefficient, the surface roughness of the punch and the die, Giving beads is generally performed.

On the other hand, as shown in FIG. 8, the pressing reaction force acting on the punch is directly measured by the pressing reaction force measuring means 9, and the wrinkle pressing load adjusting means 5 is used so that the pressing reaction force becomes a predetermined value. By adjusting the wrinkle holding force and adjusting the punch speed, proper processing can always be performed regardless of fluctuations in the press reaction force (the invention described in (7) above).
Also in this case, as shown in FIG. 3, the wrinkle pressing mold 3 is divided into a plurality of pieces, and the wrinkle pressing load adjusting means 5 is installed for each divided wrinkle pressing mold and can be controlled independently. By doing so, the distribution of the wrinkle pressing force can also be adjusted appropriately (the inventions described in (8) and (9) above).
In FIG. 8, the frictional force measuring means 4 is incorporated not only in the press reaction force measuring means 9 but also on the surface of the wrinkle holding die 3 and the shoulder of the die 2, but the surface of the wrinkle holding die 3 or the die 2. Any one or more of the shoulder frictional force measuring means 4 may be used in combination with the press reaction force measuring means 9 as necessary. The frictional force measuring means may be used in place of the temperature measuring means.

Among the control methods of the mold apparatus shown in FIG. 1 or FIG. 2, the control method described in (10), that is, the wrinkle presser so that the frictional force measured by the frictional force measuring means 4 falls within a predetermined range during processing. A method for controlling at least one of the load and the punch speed during machining will be described with reference to a flowchart shown in FIG. Here, the subscript i represents the number of times of control during molding.
101: Start of molding, i = 1 at this time.
102: Here, the punch stroke is advanced by ΔS _i [mm]. For example, when i = 1, since S ₀ = 0 [mm], S ₁ = ΔS ₁ [mm]. ΔS ₁ [mm] is determined before processing.
103: The process of measuring the frictional force Fm _i [N] when the stroke is S _i [mm] is performed here.
104: Here, the frictional force Fm _i [N] measured in 103 is compared with the frictional force control target value Fc _i [N] (preset before processing).
As a result of comparing the magnitudes at 105: 104, if Fm _i > Fc _i , according to the difference in the frictional force between the measured value and the target value (Fm _i -Fc _i ) as indicated by the formula 105 in the figure. At least one of the processes of reducing the wrinkle holding load BHF _{i + 1} [N] or reducing the punch stroke increment ΔS _{i + 1} [mm] is performed.
As a result of comparing the magnitudes at 106: 104, if Fm _i <Fc _i , according to the difference in the frictional force between the measured value and the target value (Fm _i -Fc _i ), as indicated by the equation 106 in the figure. At least one of the processes of increasing the wrinkle holding load BHF _{i + 1} [N] or increasing the punch stroke increment ΔS _{i + 1} [mm] is performed.
107: As described above, processing is performed while performing feedback control in one molding, and if the stroke S [mm] is equal to or greater than the stroke S _max [mm] at the end of processing, the processing is completed, and below If so, the loop returns to 102. At this time, the value of i increases by one.
The specific wrinkle holding load BHF _{i + 1} [N] or punch stroke increment ΔS _{i + 1} [mm] is calculated from the relational expression in the figure using proportional constants α, β, γ, and δ. This loop is repeated until the punch stroke S _i [mm] reaches the punch stroke S _end [mm] at the end of molding.
If the above control is performed at regular time intervals Δt [sec], the punch speed Vp _i [mm / s] is obtained by ΔS _i / distance Δt, and therefore the punch speed can be controlled by the punch stroke increment.
FIG. 10 shows an example of the punch stroke history of the frictional force measured value Fm [N] and the wrinkle holding load BHF [N] when this control method is used. It can be seen that the BHF control target value changes by a value corresponding to the difference between the frictional force actual measurement value Fm and the frictional force control target value Fc [SI unit], and the BHF actual measurement value changes during machining to match it.

Next, the invention (11), which is one of the control methods of the mold apparatus shown in FIG. 1, will be described with reference to the flowchart shown in FIG. Here, the subscript j represents the number of moldings in the press working process.
201: First molding, j = 1
202: The frictional force history Fm _j ^(t) [N] at the time t [sec] at the j-th molding is measured.
203: When the time t [sec] at the time of the j-th molding is arbitrarily divided and the predetermined frictional force lower limit value is Fcl (t) [N], Fm _j (t )> Fcl _j (t), BHF _{j + 1} (t) [N] or punch velocity Vp _{j + 1} (t) [mm / s] in the range of the minute time t at the time of (j + 1) -th molding As shown in the equation, the wrinkle pressing load BHF _{j + 1} is reduced according to the difference between the measured value and the frictional force between the predetermined lower limit value (Fm _j (t) −Fcl _j (t)) or the punch speed Vp _{j + 1} ( At least one of the processes for delaying t) is performed.
204: When the predetermined upper limit of frictional force is Fcu (t) [N], if Fm _j (t) <Fcu _j (t) at each minute time t [sec], (j + 1) th molding As shown in the figure for the BHF _{j + 1} (t) [N] or punch velocity Vp _{j + 1} (t) in the minute time t range of time, the difference between the measured value and the frictional force (Fm _j (t) -Fcu _j (t)) at least one of the processes of increasing the wrinkle holding load BHF _{j + 1} [N] or increasing the punch speed Vp _{j + 1} (t) [mm / s]. Do.
205: As described above, the molding conditions for the (j + 1) -th molding are set in advance based on the molding conditions for the j-th molding, and if j is the total number of moldings _jmax , the molding ends. Otherwise, return to 202.
The specific wrinkle holding load BHF _{j + 1} (t) [N] or the punch speed Vp _{j + 1} (t) [mm / s] is calculated from the relational expression in the figure using proportional constants α, β, γ, and δ. . Using the wrinkle pressing load BHF _{j + 1} (t) [N] or the punch speed Vp _{j + 1} (t) [mm / s] obtained in this way, the ( _{j + 1} ) th molding is performed. This control is repeated until the number of moldings j reaches the maximum number of moldings _jmax .
FIG. 12 shows an example of a time history of the frictional force actual measurement value Fm [N] and the wrinkle pressing force BHF [N] when this control method is used. Frictional force upper limit value _Fcu j (t) [N] than the frictional force _Fm j (t) [N] is large, or friction force limit value _Fcl j (t) [N] than the frictional force _Fm j (t) [N] In the range of t [sec] where is small, the BHF control target value is changed from BHF _j to BHF _{j + 1,} and the _{j +} 1th machining is performed using the changed BHF control target value BHF _{j + 1} .

Among the control methods for the mold apparatus shown in FIG. 5, the control method described in (12) above, that is, at least the wrinkle pressing load or the punch speed so that the temperature measured by the temperature measuring means falls within a predetermined range during processing. A method for controlling any one of them during machining will be described with reference to the flowchart shown in FIG. Here, the subscript i represents the number of times of control during molding.
301: Start of molding, i = 1 at this time.
302: Here, the punch stroke is advanced by ΔS _i [mm]. For example, when i = 1, since S ₀ = 0, S ₁ = ΔS ₁ [mm]. ΔS ₁ [mm] is determined before processing.
303: Here, the process of measuring the temperature Tm _i [° C.] when the stroke is S _i [mm] is performed.
304: Here, the magnitude of the temperature Tm _i [° C.] measured in 3 is compared with the temperature control target value Tc _i [° C.] (preset before processing).
As a result of comparing the magnitudes at 305: 304, if Tm _i > Tc _i , wrinkles according to the temperature difference (Tm _i −Tc _i ) between the measured value and the target value as indicated by the equation in 305 in the figure. At least one of processing of reducing the pressing load BHF _{j + 1} [N] or decreasing the punch stroke increment ΔS _{i + 1} [mm] is performed.
As a result of comparing the magnitudes at 306: 304, if Tm _i <Tc _i , wrinkles are formed according to the temperature difference (Tm _i −Tc _i ) between the measured value and the target value, as indicated by the equation in 306 in the figure. At least one of the processing of increasing the pressing load BHF _{j + 1} [N] or increasing the punch stroke increment ΔS _{i + 1} [mm] is performed.
307: As described above, processing is performed while performing feedback control in one molding, and if the stroke S [mm] is equal to or greater than the stroke S _max [mm] at the end of the processing, the processing is completed, and less If so, the loop returns to before 302. At this time, the value of i increases by one.
The specific wrinkle holding load BHF _{i + 1} [N] or punch stroke increment ΔS _{i + 1} [mm] is calculated from the relational expression in the figure using proportional constants α, β, γ, and δ. This loop is repeated until the punch stroke S _i [mm] reaches the punch stroke S _end [mm] at the end of molding.
If the above control is performed at regular time intervals Δt [sec], the punch speed Vp _i [mm / s] is obtained by ΔS _i / Δt, and therefore the punch speed can be controlled by the punch stroke increment.

As for the control method of the mold apparatus shown in FIG. 5, the control method described in (13) will be described with reference to the flowchart shown in FIG. Here, the subscript j represents the number of moldings in the press working process.
401: First molding, j = 1
402: A temperature history Tm _j (t) [° C.] at a time t [sec] at the j-th molding is measured.
403: Time t [sec] at the time of j-th molding is arbitrarily divided, and Tm _j (t) at each minute time t [sec] when a predetermined temperature lower limit value is Tcl (t) [° C.] If> Tcl _j (t), BHF _{j + 1} (t) [N] or punch speed Vp _{j + 1} (t) [N] in the range of the minute time t at the time of (j + 1) -th molding is shown by an expression in the figure. As shown, the wrinkle holding load BHF _{j + 1} is decreased or the punch speed Vp _{j + 1} (t) is decreased according to the difference between the measured value and the predetermined lower limit temperature (Tm _j (t) −Tcl _j (t)). At least one of the processes to be performed is performed.
404: When the predetermined upper temperature limit value is Tcu (t), if Tm _j (t) <Tcu _j (t) at each minute time t [sec], the minute value at the time of (j + 1) -th molding As shown in the figure for BHF _{j + 1} (t) [N] or punch velocity Vp _{j + 1} (t) [mm / s] in the range of time t, the difference in temperature between the measured value and the predetermined upper limit value (Tm _j (t) −Tcu _j (t)), at least one of the processes of increasing the wrinkle holding load BHF _{j + 1} [N] or increasing the punch speed Vp _{j + 1} (t) [mm / s]. Do.
405: As described above, the molding conditions for the (j + 1) -th molding are set in advance based on the molding conditions for the j-th molding. If j is the total number of moldings j _max , the molding ends. Otherwise, return to the front of 402.
The specific wrinkle holding load BHF _{j + 1} (t) [N] or the punch speed Vp _{j + 1} (t) [mm / s] is calculated from the relational expression in the figure using proportional constants α, β, γ, and δ. . The temperature Tm _j (t) [° C.] measured in advance in the previous molding is higher than the temperature upper limit value Tcu _j (t) [° C.], or the temperature Tm _j (t) [° C.] is the temperature lower limit value Tcl _j (t). The BHF control target value is changed from BHF _j (t) [N] to BHF _{j + 1} (t) [N] and the punch speed control target value is set to Vp _j (t) [mm / s] to Vp _{j + 1} (t) [mm / s], the changed BHF control target value BHF _{j + 1} (t) [N], and the punch speed control target value Vp _{j + 1} (t) [mm / s] Is used for the (j + 1) th molding.
This control is repeated until the number of moldings j reaches the maximum number of moldings _jmax .

Next, the control method according to (14), which is one of the control methods of the mold apparatus shown in FIG. 9, that is, the press reaction force measured by the press reaction force measuring means is within a predetermined range during processing. A method of controlling at least one of the wrinkle holding load and the punch speed during machining will be described with reference to the flowchart shown in FIG. Here, the subscript i represents the number of times of control during molding.
501: Molding started, i = 1 at this time.
502: Here, the punch stroke is advanced by ΔS _i [mm]. For example, when i = 1, since S ₀ = 0 [mm], S ₁ = ΔS ₁ [mm]. ΔS ₁ [mm] is determined before processing.
503: Here, the punch reaction force Pm _i [N] at the stroke S _i [mm] is measured.
504: Here, the magnitudes of the punch reaction force Pm _i [N] measured in 503 and the punch reaction force control target value Pc _i [N] (preset before processing) are compared.
As a result of comparing the magnitudes at 505: 504, if Pm _i > Pc _i [N], the difference in the press reaction force between the measured value and the target value (Pm _i −Pc _i ) as indicated by the formula 505 in the figure. ) To reduce the wrinkle pressing load BHF _{j + 1} [N] or at least one of the processes to reduce the punch stroke increment ΔS _{i + 1} [mm].
When Pm _i > Pc _i [N] as a result of comparing the magnitudes at 506: 505, the difference between the press reaction force of the measured value and the target value (Pm _i −Pc _i ) as indicated by the equation 506 in the figure. ) To increase the wrinkle holding load BHF _{j + 1} [N] or increase the punch stroke increment ΔS _{i + 1} [mm].
507: As described above, processing is performed while performing feedback control in one molding, and if the stroke S is equal to or greater than the stroke S _max [mm] at the end of processing, the processing is completed, and if it is less, the loop is performed. Returns to before 502. At this time, the value of i increases by one.
The specific wrinkle holding load BHF _{i + 1} [N] or punch stroke increment ΔS _{i + 1} [mm] is calculated from the relational expression in the figure using proportional constants α, β, γ, and δ. This loop is repeated until the punch stroke S _i [mm] reaches the punch stroke S _end [mm] at the end of molding.
If the above control is performed at regular time intervals Δt [sec], the punch speed Vp _i [mm / s] is obtained by ΔS _i / Δt, and therefore the punch speed can be controlled by the punch stroke increment.

The invention (15), which is one of the control methods for the mold apparatus shown in FIG. 9, will be described with reference to the flowchart shown in FIG. Here, the subscript j represents the number of moldings in the press working process.
601: First molding, j = 1
602: Punch reaction force history Pm _j (t) at time t [sec] at the j-th molding is measured.
603: When the time t [sec] at the j-th molding is arbitrarily divided and the lower limit value of the predetermined press reaction force is Pcl (t) [N], Pm _{j at} each minute time t [sec] If (t)> Pcl _j (t), the figure shows BHF _{j + 1} (t) [N] or punch velocity Vp _{j + 1} (t) [mm / s] in the range of the minute time t at the time of (j + 1) -th molding. As shown in the equation, the wrinkle holding load BHF _{j + 1} [N] is reduced according to the difference (Pm _j (t) −Pcl (t)) between the measured reaction value and the predetermined lower limit press reaction force, At least one of the processes for reducing the punch speed Vp _{j + 1} (t) [mm / s] is performed.
604: When the upper limit value of the predetermined press reaction force is Pcu (t) [N], if Pm _j (t) <Pcu _j (t) at each minute time t [sec], (j + 1) As shown by the formula in the figure for BHF _{j + 1} (t) [N] or punch velocity Vp _{j + 1} (t) [mm / s] in the minute time t range at the time of the second molding, the measured value and the predetermined upper limit value At least one of the processes of increasing the wrinkle holding load BHF _{j + 1} [N] or increasing the punch speed Vp _{j + 1} (t) according to the temperature difference (Tm _j (t) −Tcu (t)) Do.
605: As described above, the molding conditions for the (j + 1) -th molding are set in advance based on the molding conditions for the j-th molding, and if j is the total number of moldings _jmax , the molding ends. Otherwise, return to 602.
The specific wrinkle holding load BHF _{j + 1} (t) [N] or the punch speed Vp _{j + 1} (t) [mm / s] is calculated from the relational expression in the figure using proportional constants α, β, γ, and δ. . The press reaction force Pm _j (t) [N] measured in advance in the previous molding is larger than the press reaction force upper limit Pcu _j (t) [° C.], or the press reaction force Pm _j (t) [N] is the press reaction force. The BHF control target value is changed from BHF _j (t) [N] to BHF _{j + 1} (t) [N], and the punch speed control target value is set within a range of t [sec] smaller than the force lower limit value Pcl _j (t) [N]. Vp _j (t) [mm / s] is changed to Vp _{j + 1} (t) [mm / s], the changed BHF control target value BHF _{j + 1} (t) [N], and the punch speed control target value Vp _{j + 1} (T) Perform the (j + 1) th molding using [mm / s]. This control is repeated until the number of moldings j reaches the maximum number of moldings _jmax .

  Further, the punch 1 may have a divided structure as in the case of the wrinkle holding mold 3 and may be pressurized by a hydraulic cylinder for each divided punch. However, since the mold apparatus becomes complicated and the equipment becomes expensive, the punch 1 is integrated. The pressure chamber is uniformly reduced by a normal outer cylinder, and is clamped (fixed) to the surface of the punch 1 by the method described above, and the hydraulic chamber 8 is built in the wrinkle presser mold 3 as shown in FIG. By adjusting, it is possible to control the wrinkle holding load for each of the wrinkle holding molds divided at low cost.

  Based on the above-mentioned invention, the mold apparatus shown in FIG. 1 was made as an example of the present invention, and press forming using a thin steel plate was performed. A piezo element was used as the frictional force measuring means 4 and the flat plate 7 was made of surface-quenched S45C. Table 1 shows the characteristics of the steel sheet used. Each was an alloyed hot-dip galvanized steel sheet with a thickness of 1: 2 mm, and two kinds of steel sheets with different degrees of alloying were used.

In the forming test, 50 mm × 50 mm square tube deep drawing was continuously performed, and the forming load at that time and the presence or absence of wrinkling of the formed product were investigated. From a 100 mm × 100 mm square base plate, a molding experiment was performed using a wrinkle pressing die whose periphery was divided into eight as shown in FIG. Table 2 shows the test results of 100 consecutive moldings.
As a comparative example, Table 3 shows the results when a mold apparatus without wrinkle pressing load adjusting means is used and the wrinkle pressing pressure is made constant.

  In Example 1 of the present invention formed so that the frictional force is constant (0:25 [kN / die]) for all the divided molds, the wrinkle pressing load is constant 20 [kN] (the friction coefficient is 0: 1). Assuming that the total frictional force is 2 [kN]), the comparative example 1 and the wrinkle holding load are constant 40 [kN] (when the friction coefficient is assumed to be 0: 1, the total frictional force is 4 [kN]). Compared with Comparative Example 2, the molding load fluctuated very little, and generally good molding was obtained. However, in the material B having a low alloying degree, as the number of moldings increased, zinc adhered to the mold, the friction became non-uniform, and slight wrinkles were observed at the corners. Therefore, the molding experiment was performed with the frictional force of the parallel part where the material flowed in greatly decreased to 0: 2 [kN / die] and the frictional force of the corner part increased to 0: 3 [kN / die]. In Inventive Example 2, good molding results were obtained regardless of the number of moldings for any material.

  Based on the above-mentioned invention, a mold apparatus shown in FIG. 5 was made as an example of the present invention, and press forming using a thin steel plate was performed. A thermocouple was used as the temperature measuring means 10, and the flat plate 7 was S45C that had been surface-hardened. The steel plate used in the experiment is the same as that used in Example 1.

  In the forming test, 50 mm × 50 mm square tube deep drawing was continuously performed, and the forming load at that time and the presence or absence of wrinkling of the formed product were investigated. A molding experiment was performed from a 100 mm × 100 mm square base plate using a wrinkle pressing die whose periphery was divided into eight as shown in FIG. Table 4 shows the test results of 100 consecutive moldings. The comparative example is the same as that of Example 1.

  In Example 3 of the present invention formed so that the temperature is constant (180 [° C.]) for all the divided molds, the wrinkle holding load is constant 20 [kN] (if the friction coefficient is assumed to be 0: 1, the friction is Comparative Example 1 in which the total force is 2 [kN]) and Comparative Example 2 in which the wrinkle holding load is constant at 40 [kN] (when the friction coefficient is assumed to be 0: 1, the total frictional force is 4 [kN]) In comparison, the molding load fluctuated very little, and generally good molding was obtained. However, with the material B having a low alloying degree, as the number of moldings increased, zinc adhered to the mold, the temperature became uneven, and slight wrinkles were observed at the corners. For this reason, in Example 4 of the present invention in which the molding experiment was performed with the temperature of the parallel portion where the inflow of material was large lowered to 150 [° C.] and the frictional force of the corner portion increased to 200 [° C.], any material was used. Good molding results were obtained regardless of the number of moldings.

  Based on the above-mentioned invention, a mold apparatus shown in FIG. 8 was prototyped as an example of the present invention, and press forming using a thin steel plate was performed. A strain gauge was used as the press reaction force measuring means 9, and the flat plate 7 was S45C which had been surface-hardened. The steel plate used in the experiment is the same as that used in Example 1.

  In the forming test, 50 mm × 50 mm square tube deep drawing was continuously performed, and the forming load at that time and the presence or absence of wrinkling of the formed product were investigated. From a 100 mm × 100 mm square base plate, a molding experiment was performed using a wrinkle presser mold whose periphery was divided into eight as shown in FIG. Table 5 shows the test results of 100 consecutive moldings. The comparative example is the same as that of Example 1.

  In Example 5 of the present invention formed by controlling the wrinkle pressing force so that the press reaction force is constant (65 [kN]), the wrinkle pressing load is constant at 20 [kN] (when the friction coefficient is assumed to be 0: 1). Comparative Example 1 in which the total frictional force is 2 [kN]) and Comparative Example in which the wrinkle holding load is constant at 40 [kN] (when the friction coefficient is assumed to be 0: 1, the total frictional force is 4 [kN]) Compared with 2, molding load fluctuation was very small, and generally good molding was obtained. However, with the material B having a low alloying degree, as the number of moldings increased, zinc adhered to the mold, the press reaction force became uneven, and slight wrinkles were observed at the corners. Therefore, in Example 6 of the present invention in which the molding experiment was performed with the setting of the press reaction force at the initial stage of machining with a large inflow of material lowered to 20 kN, while the press reaction force at the latter stage of machining was increased to 70 kN, the number of moldings was increased for any material. Regardless, good molding results were obtained.

A sectional view of a press mold apparatus having a frictional force measuring means 4 on the surface of the wrinkle pressing mold 3 is shown. Sectional drawing of the press die apparatus which has the frictional force measurement means 4 on the surface of a wrinkle pressing die 3, and a die shoulder is shown. The top view of the wrinkle pressing die divided | segmented into plurality and the frictional force measuring means is shown. FIG. 2 shows an enlarged cross-sectional view of one side of the die 2 and the wrinkle holding mold 3 in FIG. 1. Sectional drawing of the press die apparatus which has the temperature measuring means 10 on the surface of the wrinkle pressing die 3, and a die shoulder is shown. The top view of the wrinkle pressing die divided | segmented into plurality and the temperature measuring means is shown. FIG. 6 shows an enlarged cross-sectional view of one side of the die 2 and the crease holding die 3 in FIG. 5. A sectional view of a press die apparatus having a frictional force measuring means 4 on the surface of the wrinkle pressing mold 3 and a die shoulder and a press reaction force measuring means 9 on the punch 1 is shown. The flowchart of the example of this invention which controls a frictional force is shown. FIG. 10 shows the relationship between the wrinkle pressing load or friction force and the stroke when the control method shown in the flowchart of FIG. 9 is applied. 6 shows a flowchart of another example of the present invention for controlling the frictional force. The time history of a wrinkle pressing load or a friction force when the control method shown in the flowchart of FIG. 11 is applied is shown. The flowchart of the example of this invention which controls temperature is shown. 6 shows a flowchart of another example of the present invention for controlling temperature. The flowchart of the example of the present invention which controls press reaction force is shown. The flowchart of another example of the present invention which controls press reaction force is shown. The expanded sectional view of the wrinkle pressing load adjusting means incorporating a hydraulic chamber is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Punch 2 Dies 3 Wrinkle pressing die 4 Friction force measuring means (strain measuring element)
5 Wrinkle holding load adjustment means 6 Workpiece (thin plate)
7 Flat plate 8 Hydraulic chamber 9 Press reaction force measuring means 10 Temperature measuring means

Claims (15)

  A thin plate die apparatus comprising a punch, a die and a wrinkle holding mold, a frictional force measuring means attached between the die and the wrinkle holding mold, and a wrinkle holding load adjusting means.   A thin plate press die apparatus comprising a punch, die and wrinkle holding die, a frictional force measuring means attached to the die shoulder, and a wrinkle holding load adjusting means.   The thin plate pressing die apparatus according to claim 1 or 2, wherein the wrinkle holding die is divided into a plurality of pieces, and each of the divided wrinkle holding die has a frictional force measuring means.   The thin plate pressing die apparatus according to any one of claims 1 to 3, wherein the frictional force measuring means is a piezo element or a strain gauge.   The thin plate press die apparatus according to any one of claims 1 to 3, further comprising a temperature measuring means instead of the frictional force measuring means.   6. The thin plate pressing die apparatus according to claim 5, wherein the temperature measuring means is a thermocouple.   A thin plate press die apparatus comprising a punch, a die and a wrinkle holding die, a press reaction force measuring means attached to the punch, and a wrinkle holding load adjusting means.   The thin plate pressing die apparatus according to claim 7, wherein the wrinkle holding die is divided into a plurality of pieces.   The thin plate pressing die apparatus according to any one of claims 3 to 6 or 8, further comprising a wrinkle pressing load adjusting means that can be independently controlled for each of the divided wrinkle pressing dies.   A thin plate press molding method using the press die device according to any one of claims 1 to 4, or 9, wherein the frictional force measured by the frictional force measuring means falls within a predetermined range during processing. Thus, the thin plate press forming method characterized by controlling at least one of the wrinkle holding load and the punch speed.   A thin plate press molding method using the press die device according to any one of claims 1 to 4, or 9, wherein the previous molding is performed using the frictional force measured by the frictional force measuring means. The thin plate is characterized in that at least one of the wrinkle holding load and the punch speed is controlled so that the friction force falls within a predetermined range based on the relationship between the friction force measured in Step 1 and the wrinkle holding load and the punch speed. Press molding method.   A thin plate press forming method using the press die apparatus according to claim 5, 6 or 9, wherein the wrinkle holding load and the punch speed are adjusted so that the temperature measured by the temperature measuring means falls within a predetermined range during processing. A method for press forming a thin plate, wherein at least one of the above is controlled.   A thin plate press molding method using the press die device according to claim 5, 6 or 9, wherein the temperature measured by the temperature measurement means, the temperature measured in the previous molding, the wrinkle holding load, and A thin plate press forming method, wherein at least one of a wrinkle holding load and a punch speed is controlled so that the temperature falls within a predetermined range based on a relationship between punch speeds.   A thin plate press forming method using the press die apparatus according to claim 7 or 8, wherein the press reaction force measured by the press reaction force measuring means is within a predetermined range during processing, A method for press-forming a thin plate, wherein at least one of punch speeds is controlled.   A press forming method of a thin plate using the press die apparatus according to claim 7 or 8, wherein the press reaction force measured in the previous molding is measured using the press reaction force measured by the press reaction force measuring means. A thin plate press forming method, wherein at least one of a wrinkle holding load and a punch speed is controlled based on a relationship between a wrinkle holding load and a punch speed so that the press reaction force falls within a predetermined range.

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