Press forming equipment

Abstract

To provide a press molding device for correcting a clearance of a die and performing stable processing.SOLUTION: A press molding device includes: a punch; a die having a slope inclined toward a hollow part to which the punch is inserted; a die plate holding the die; a wrinkle presser having a presser surface facing the slope of the die; a die load sensor for detecting a load in a press direction, a load in a first direction vertical to the press direction, and a load in a second direction vertical to the first direction; a control part for calculating a vertical drag of the die on the basis of each of the load in the press direction, the load in the first direction and the load in the second direction detected by the die load sensor, and calculating a clearance correction amount between the die and the wrinkle presser on the basis of the die vertical drag; a first drive part for moving the die in the press direction on the basis of the clearance correction amount; and a second drive part for driving the punch in the press direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a press forming apparatus. [Background technology]

[0002] When performing bending or drawing of metal materials by press forming, it is common to carry out production after determining processing conditions in advance for each material or in response to environmental changes.

[0003] For example, Patent Document 1 discloses a press working condition setting device that sets working conditions so as to obtain a predetermined press quality even when there is variation in the material quality or plate thickness. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-266100 Summary of the Invention [Problem to be solved by the invention]

[0005] The press working condition setting device described in Patent Document 1 still has room for improvement in terms of working stability.

[0006] The present disclosure provides a press molding apparatus capable of performing stable processing by correcting die clearance. [Means for solving the problem]

[0007] The press forming apparatus according to the present disclosure is a press forming apparatus for processing a plate-shaped workpiece, and includes a punch moving in a press direction, a die formed with a hollow portion into which the punch is inserted and having a slope inclined toward the hollow portion, a die plate for holding the die, a blank holder arranged between the punch and the die and having a pressing surface facing the slope of the die, a die load sensor for detecting a load generated on the slope of the die as loads in three directions, namely, a load in the press direction, a load in a first direction perpendicular to the press direction, and a load in a second direction perpendicular to the press direction and the first direction, a control unit for calculating a normal force of the die based on each of the load in the press direction, the load in the first direction, and the load in the second direction detected by the die load sensor, and for calculating a clearance correction amount between the die and the blank holder based on the normal force of the die, a first drive unit for moving the die in the press direction based on the clearance correction amount, and a second drive unit for driving the punch in the press direction. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a press molding apparatus capable of performing stable processing by correcting clearance. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a press molding apparatus according to a first embodiment. [Diagram 2] Schematic diagram showing the top dead center state of the punch of the press forming device of FIG. [Diagram 3] Schematic diagram showing the bottom dead center state of the punch of the press forming device of FIG. [Figure 4] Enlarged view of area R1 in Figure 3 [Diagram 5] FIG. 2 is a plan view of the die and die plate of the press molding apparatus of FIG. [Figure 6] 2 is a flowchart illustrating a clearance correction process in the press forming apparatus of FIG. 1. [Figure 7] A graph showing the relationship between the normal force of the die and the processing time from the start of forming. [Figure 8]A graph showing the relationship between the normal force of the die and the processing time from the start of forming when the impulse difference is within ±20%. [Figure 9] Graph showing the relationship between impulse difference and clearance correction amount [Figure 10] A graph showing the relationship between the load on the punch and the processing time from the start of forming. [Figure 11] A graph showing the relationship between the load on the punch and the processing time from the start of forming when the impulse difference is within ±20%. [Figure 12] Graph showing the relationship between impulse difference and correction amount of push-in amount DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Background to this disclosure) When bending or drawing is performed using a press forming apparatus, processing conditions are determined in advance, taking into consideration material factors such as the quality or thickness of the metal material to be processed, or environmental factors caused by the press forming apparatus. The processing conditions can be determined, for example, by experience or experiment, or by using simulation. The effects of material factors or environmental factors are often difficult to predict, and various methods for controlling the processing conditions in consideration of these effects have been studied.

[0011] For example, Patent Document 1 discloses a method in which the relationship between physical quantities such as the shape of the press material (metal material) and the appropriate blank holding load (appropriate press processing conditions) is determined in advance, and the appropriate blank holding amount is determined from that relationship according to the actual physical quantities.

[0012] The press working condition setting device described in Patent Document 1 has a problem that the clearance between the blank holder and the die cannot be properly maintained due to difficult-to-predict variable factors, and stable working cannot be performed. The difficult-to-predict variable factors refer to variations due to the characteristics of the material of the workpiece or environmental changes due to temperature. The difficult-to-predict variable factors also refer to environmental changes due to the forming speed, bottom dead center accuracy, processing dimensional accuracy of the die, blank holder force, clearance between the blank holder and the die, surface roughness of the die, or lubricity between the workpiece and the die, etc., related to the press forming device and the die. Since such environmental changes are difficult to predict, there is a problem that it is difficult to determine an appropriate blank holder load in advance, and it is difficult to maintain the clearance between the blank holder and the die at an appropriate value.

[0013] Therefore, the present inventors have investigated a press forming apparatus capable of performing stable processing by correcting the clearance, and have arrived at the following invention.

[0014] A press forming apparatus according to a first aspect of the present disclosure is a press forming apparatus for processing a plate-shaped workpiece, and includes a punch moving in a press direction, a die formed with a hollow portion into which the punch is inserted and having a slope inclined toward the hollow portion, a die plate for holding the die, a blank holder arranged between the punch and the die and having a pressing surface facing the slope of the die, a die load sensor for detecting a load generated on the slope of the die as loads in three directions, namely, a load in the press direction, a load in a first direction perpendicular to the press direction, and a load in a second direction perpendicular to the press direction and the first direction, a control unit for calculating a normal force of the die based on each of the load in the press direction, the load in the first direction, and the load in the second direction detected by the die load sensor, and for calculating a clearance correction amount between the die and the blank holder based on the normal force of the die, a first drive unit for moving the die in the press direction based on the clearance correction amount, and a second drive unit for driving the punch in the press direction.

[0015] With this configuration, the clearance correction amount between the blank holder and the die is calculated based on the normal force of the die, so that a press forming device can be provided that can properly maintain the clearance and perform stable processing.

[0016] In the press forming apparatus according to the second aspect of the present disclosure, the clearance correction amount may be calculated based on the difference between an impulse calculated from the normal force of the die and the processing time in the case of an appropriate clearance, and an impulse calculated from the normal force of the die during processing and the processing time.

[0017] With this configuration, the clearance correction amount can be calculated more accurately.

[0018] The press forming apparatus according to the third aspect of the present disclosure may further include a punch load sensor that detects the load of the punch applied in the press direction, and the control unit may calculate a punch push-in correction amount based on the punch load detected by the punch load sensor, and the second drive unit may drive the punch based on the punch push-in correction amount.

[0019] With this configuration, the punch depression amount can be corrected, allowing for more stable machining.

[0020] In the press forming apparatus according to the fourth aspect of the present disclosure, the punch push-in correction amount may be calculated based on the difference between an impulse calculated from the punch load and processing time in the case of an appropriate push-in amount, and an impulse calculated from the punch load and processing time during processing.

[0021] With this configuration, the correction amount for the punch depression amount can be calculated more accurately.

[0022] The press forming apparatus according to the fifth aspect of the present disclosure may further include a first gap sensor that detects when the punch is at the bottom dead center.

[0023] With this configuration, it is possible to detect whether any misalignment has occurred between the upper mold including the punch and the lower mold including the die of the press molding device.

[0024] The press forming apparatus according to the sixth aspect of the present disclosure may further include a second gap sensor that detects contact between the blank holder and the die plate.

[0025] With this configuration, it is possible to detect whether the relative position of the blank holder with respect to the die plate is appropriate.

[0026] In the press molding apparatus according to the seventh aspect of the present disclosure, the die may be composed of a plurality of die pieces, and the die load sensor may be disposed in each of the plurality of die pieces.

[0027] With this configuration, even when machining a complex shape, the clearance correction amount can be accurately calculated, enabling more stable machining.

[0028] Hereinafter, an embodiment will be described with reference to the drawings.

[0029] (Embodiment 1) [Overall configuration] Fig. 1 is a schematic diagram showing a press forming apparatus 100 according to a first embodiment. Fig. 2 is a schematic diagram showing a top dead center state of a punch 1 of the press forming apparatus 100 of Fig. 1. Fig. 3 is a schematic diagram showing a bottom dead center state of a punch 1 of the press forming apparatus 100 of Fig. 1. Fig. 4 is an enlarged view of a region R1 of Fig. 3. Fig. 5 is a plan view of a die 2 and a die plate 4 of the press forming apparatus 100 of Fig. 1. Some components are omitted in Figs. 2 to 5.

[0030] 1, the press forming apparatus 100 is an apparatus that includes a punch 1, a die 2, a blank holder 3, a die plate 4, a die load sensor 14, a control unit 30, a first drive unit 11, and a second drive unit 18, and presses a workpiece such as a metal plate. In this embodiment, bending and drawing is performed by the press forming apparatus 100. In this embodiment, the press forming apparatus 100 further includes a punch load sensor 13, a first gap sensor 15, and a second gap sensor 16.

[0031] In the press forming apparatus 100, the clearance between the die 2 and the blank holder 3 is corrected based on the loads applied to the die 2 and punch 1 detected by the die load sensor 14 and the punch load sensor 13. By correcting the clearance based on the load applied during processing, stable processing can be performed.

[0032] The punch 1 is a tool for pressing against a workpiece 5 to process it, and is attached to a slide 7.

[0033] 2, the die 2 has a hollow portion into which the punch 1 is inserted, has an inclined surface 2a that slopes from an upper surface 2b toward the hollow portion, and is attached to a bolster 8. An ejector 6 that separates the machined workpiece 5 from the die 2 is disposed in the hollow portion of the die 2. The ejector 6 is driven by an air cylinder 17.

[0034] 5, the die 2 includes four die pieces 2c to 2f. The die pieces 2c and 2d have symmetrical shapes, and the die pieces 2e and 2f have symmetrical shapes. In this embodiment, the die pieces 2c and 2d are arranged to face each other in the Y direction, and the die pieces 2e and 2e are arranged to face each other in the X direction.

[0035] Since the die 2 is composed of multiple die pieces 2c to 2f, by adjusting the position of each die piece 2c to 2f, it is possible to reduce the effects that may occur due to the processing accuracy, surface roughness, or wear condition of the punch 1, etc., and perform stable processing.

[0036] The blank holder 3 is attached to the slide 7 together with the punch 1, and during press working, presses the workpiece 5 against the inclined surface 2a of the die 2. The blank holder 3 has a pressing surface 3a that faces the inclined surface 2a of the die 2 (see FIG. 2).

[0037] The die plate 4 is a member that holds the die 2 .

[0038] The slide 7 is connected to a servo motor 11 via a ball screw 12. The servo motor 11 rotates the ball screw 12, thereby driving the slide 7 in the pressing direction (Z direction) at a predetermined speed. The slide 7 is guided by a shaft 10 so as to be driven up and down in the Z direction relative to the bolster 8. As the slide 7 drives up and down relative to the bolster 8, the punch 1 moves toward the die 2, and the workpiece 5 placed on the die 2 can be bent and drawn. The servo motor 11 corresponds to a second drive unit in this embodiment.

[0039] The punch 1, the die 2, the blank holder 3, the die plate 4, the ejector 6, the slide 7, the bolster 8, and the shaft 10 are attached to a forming apparatus body 9.

[0040] The die 2 is moved in the pressing direction (Z direction) by the actuator 18 based on a clearance correction amount described later. The actuator 18 corresponds to a first driving unit in this embodiment.

[0041] The die load sensor 14 is a sensor that detects the load applied to the die 2 during processing. The die load sensor is a three-axis load sensor that detects the load applied to the die 2 as load components in three directions. In this embodiment, the die load sensor 14 detects the load applied to the die 2 as load components in the press direction (Z direction), a first direction (X direction) perpendicular to the Z direction, and a second direction (Y direction) perpendicular to the press direction and the first direction.

[0042] In this embodiment, the die load sensor 14 includes four die load sensors 14c to 14f, one for each of the die pieces 2c to 2f, as shown in Fig. 5. The die load sensor 14c and the die load sensor 14d are arranged symmetrically facing each other in the Y direction. The die load sensor 14e and the die load sensor 14f are arranged symmetrically facing each other in the X direction.

[0043] The punch load sensor 13 is a sensor that detects a load applied to the punch 1 during processing. The punch load sensor 13 is a uniaxial load sensor that detects a load Pz (see FIG. 3) applied to the punch 1 in the press direction.

[0044] The control unit 30 calculates the normal force of the die 2 based on the load detected by the die load sensor 14, and calculates a clearance correction amount between the die 2 and the blank holder 3 based on the normal force of the die 2. The control unit 30 will be described in detail later.

[0045] The first gap sensor 15 detects that the punch 1 is at the bottom dead center, i.e., at the lowest possible position of the punch 1. The first gap sensor 15 is attached to an arbitrary position of the lower die of the press forming apparatus 100 including, for example, the die 2, the die plate 4, the ejector 6, and the bolster 8, and detects that the punch 1 is at the bottom dead center by detecting contact between the upper die including the punch 1, the blank holder 3, and the slide 7 and the lower die. For example, by arranging the first gap sensors 15 at the four corners of the lower die, it is possible to detect whether the upper die and the lower die are parallel to each other.

[0046] The second gap sensors 16 are arranged at the four corners of the die plate 4 and detect contact between the blank holder 3 and the die plate 4. In this embodiment, as shown in Fig. 5, the second gap sensors 16a to 16d are arranged at the four corners of the die plate 4. Whether the blank holder 3 and the die plate 4 are parallel or not can be detected based on the difference in the timing of contact between the blank holder 3 and the die plate 4 at each of the second gap sensors 16a to 16d arranged at the four corners of the die plate 4.

[0047] The control unit 30 has a first drive control unit 19, a second drive control unit 20, a sensor controller 21, a calculation unit 22, and a determination unit 23. The control unit 30 is configured with digital circuits such as a microcomputer, a CPU, an MPU, a GPU, a DSP, an FPGA, an ASIC, etc.

[0048] The first drive control unit 19 drives the servo motor 11 to rotate the ball screw 12, thereby driving the slide 7 up and down in the pressing direction (Z direction) at a predetermined speed.

[0049] The second drive control unit 20 drives the actuator 18 based on a clearance correction amount, which will be described later, to move the die 2 in the pressing direction (Z direction).

[0050] The sensor controller 21 is electrically connected to the die load sensor 14, the punch load sensor 13, the first gap sensor 15, and the second gap sensor 16, and outputs the detection values ​​of each sensor to the calculation unit 22 or the determination unit .

[0051] The calculation unit 22 calculates the normal force and the impulse difference based on the detection values ​​from the die load sensor 14 or the punch load sensor 13. The details will be described later.

[0052] The determination unit 23 determines, based on the calculation result of the calculation unit 22, whether or not to perform clearance correction.

[0053] In the press forming apparatus 100, the workpiece 5 is placed on the upper surface 2b of the die 2 when the punch 1 is at its top dead center, as shown in Fig. 2. The top dead center state of the punch 1 refers to the state in which the punch 1 is at the highest possible position. With the workpiece 5 placed on the upper surface 2b of the die 2, the punch 1 is lowered in the pressing direction to start processing.

[0054] As the punch 1 descends, the blank holder 3 attached to the slide 7 also descends. As a result, as shown in Fig. 3, the workpiece 5 is pressed between the pressing surface 3a of the blank holder 3 and the inclined surface 2a of the die 2, while being formed by the punch 1. Here, the inclined surface 2a of the die 2 is formed so as to be inclined at an angle θ1 with respect to the upper surface 2b, as shown in Fig. 4. The pressing surface 3a of the blank holder 3 is formed so as to face the inclined surface 2a of the die 2, i.e., so as to be inclined at an angle θ1 with respect to the upper surface 2b of the die 2.

[0055] As the punch 1 descends, the tip of the punch 1 comes into contact with the workpiece 5 to form the workpiece 5. When the blank holder 3 and the die plate 4 come into contact with each other (see FIG. 3), the punch 1 reaches the bottom dead center. At this time, as shown in FIG. 4, a predetermined clearance CL is provided between the blank holder 3 and the die 2, or in this embodiment, between the pressing surface 3a of the blank holder 3 and the inclined surface 2a of the die 2.

[0056] In this embodiment, based on the loads detected by the die load sensor 14 and the punch load sensor 13, the position of the die 2 in the pressing direction or the pressing amount of the punch 1 is adjusted so that the clearance CL becomes an appropriate value.

[0057] The die load sensor 14 detects the load applied to the die 2 from when the punch 1 starts descending until it reaches the bottom dead center state. Specifically, the load applied to the die 2 is detected as three-directional load components, namely, a load Fz in the press direction (Z direction), a load Fx in the first direction (X direction), and a load Fy in the second direction (Y direction), as shown in FIG. 4. The load Fz in the press direction is a load component acting in the press direction of the die 2. The load Fx in the first direction and the load Fy in the second direction are load components in a direction perpendicular to the press direction. The load Fy in the second direction is omitted from the drawing. Since the load Fy is a very small value compared to the loads Fx and Fz, the influence of the load Fy on the loads Fx and Fz can be ignored. In this embodiment, the die load sensor 14 includes four die load sensors 14c to 14f arranged on the die pieces 2c to 2f, respectively. Therefore, the four die load sensors 14c to 14f detect the loads Fx, Fy, Fz in three directions and the normal force N for each of the die pieces 2c to 2f.

[0058] The punch load sensor 13 detects the load applied to the punch 1 in the pressing direction.

[0059] A method for correcting the clearance between the pressing surface 3a of the blank holder 3 and the inclined surface 2a of the die 2 based on the loads detected by the load sensors 13 and 14 will be described with reference to Fig. 6. Fig. 6 is a flowchart illustrating the clearance correction process in the press forming apparatus 100 of Fig. 1.

[0060] The clearance CL between the pressing surface 3a of the blank holder 3 and the inclined surface 2a of the die 2 is adjusted to an appropriate value in advance, and forming is started (step S1). Next, the load applied to the die 2 is detected by the die load sensor 14 (step S2). The load F (Fx, Fy, Fz) detected by the die load sensor 14 is output to the calculation unit 22 via the sensor controller 21. At the same time as the load is detected by the die load sensor 14, the load applied to the punch 1 is detected by the punch load sensor 13 (step S3). The load Pz (see FIG. 3) detected by the punch load sensor 13 is output to the calculation unit 22 via the sensor controller 21. When forming is completed (step S4), the normal force N of the die 2 is calculated by the calculation unit 22 (step S5).

[0061] The normal force N of the die 2 is calculated using equation (1) from the load F (Fx, Fy, Fz) of the die 2. In equation (1), θ1 is the angle of inclination of the slope 2a with respect to the upper surface 2b of the die 2 (see FIG. 4).

[0062]

number

[0063] When the normal force N is calculated, the calculation unit 22 calculates an impulse difference with respect to the normal force N of the die 2 (step S6).

[0064] Fig. 7 is a graph showing the relationship between the normal force N of the die 2 and the processing time t from the start of molding. As shown in Fig. 7, the magnitude of the normal force N of the die 2 calculated by the calculation unit 22 is acquired as waveform data showing the relationship with the processing time from the start of molding.

[0065] When the magnitude of clearance CL is an appropriate value (standard clearance), the waveform data of normal force N is as shown by the solid line in Fig. 7. When the magnitude of clearance CL is larger than the standard clearance, the waveform data of normal force N is as shown by the dashed line in Fig. 7. When the magnitude of clearance CL is smaller than the standard clearance, the waveform data of normal force N is as shown by the dashed line in Fig. 7.

[0066] 7, when the clearance CL during molding is larger than the reference clearance, the normal force N of the die 2 is smaller throughout the molding time than in the case of the reference clearance. Conversely, when the clearance CL is smaller than the reference clearance, the normal force N of the die 2 is larger throughout the molding time than in the case of the reference clearance.

[0067] The impulse of the normal force N is the normal force N multiplied by time, and is calculated by determining the area of ​​the waveform data in Fig. 7. The impulse difference of the die 2 is the difference between the impulse in the case of the standard clearance and the impulse based on the normal force N calculated in step S5. In this embodiment, the difference between the impulse based on the calculated normal force N and the impulse in the case of the standard clearance is calculated, and it is determined whether or not to correct the size of the clearance CL based on the difference value.

[0068] For example, the difference in impulse when the size of clearance CL is larger than the reference clearance is calculated by determining the area of ​​region 70 in Fig. 7. Also, the difference in impulse when the size of clearance CL is smaller than the reference clearance is calculated by determining the area of ​​region 71 in Fig. 7.

[0069] Based on the impulse difference of the normal force N of the die 2, the determination unit 23 determines whether or not to perform clearance correction (step S7). For example, an upper limit value and a lower limit value of the impulse difference are set in advance, and it can be determined that clearance correction is to be performed when the value of the impulse difference exceeds the upper limit value or falls below the lower limit value.

[0070] For example, if the impulse difference exceeds ±10% of the impulse for the reference clearance, that is, if the difference from the area of ​​the waveform for the reference clearance exceeds ±10%, it is determined that clearance correction is to be performed (Yes in step S7). In other words, if the impulse difference exceeds ±10% of the impulse for the reference clearance, it is determined that clearance correction is to be performed. If the impulse difference is included within ±10% of the reference clearance, it is determined that the impulse difference is within the standard and clearance correction is not to be performed (No in step S7).

[0071] When it is determined that clearance correction is to be performed (Yes in step S7), the calculation unit 28 calculates a correction amount (step S8). The correction amount is a value indicating how much the size of the clearance CL is to be increased or decreased.

[0072] Fig. 8 is a graph showing the relationship between the normal force N and the machining time t when the impulse difference is within ±20%. Fig. 9 is a graph showing the relationship between the impulse difference and the correction amount of the clearance CL. In Fig. 8, region 72 shows the case where the impulse difference is -20%, and region 73 shows the case where the impulse difference is +20%. Fig. 9 is a graph plotting the correction amount of the clearance CL obtained by experiment when the impulse difference is -20% or more and +20% or less. In Fig. 8, the horizontal axis shows the impulse difference (%), and the vertical axis shows the clearance correction amount (μm).

[0073] According to the graphs of FIG. 8 and FIG. 9, for example, when the impulse difference is -20%, it indicates that the clearance is larger than the reference, and the correction amount of the clearance is -10 μm. That is, it indicates that the size of the clearance CL is corrected to be 10 μm smaller. That is, it indicates that the die 2 is moved upward (-Z direction). When the impulse difference is +20%, it indicates that the clearance is smaller than the reference, and the correction amount of the clearance is +10 μm. In this case, it indicates that the size of the clearance CL is corrected to be 10 μm larger. That is, it indicates that the die 2 is moved downward (+Z direction).

[0074] The correction amount based on the experimental results is as shown in the graph in FIG. 9. If the correction amount is ΔCL and the impulse difference is D1, then equation (2) is established.

[0075]

number

[0076] Here, the coefficient a changes depending on the wear state of the punch 1, etc., so that an accurate correction amount ΔCL can be calculated by obtaining experimental results such as those shown in the graph of FIG. 9 every few shots and changing the coefficient a.

[0077] Next, the calculation unit 22 calculates the movement amount of the die 2 (step S9). The movement amount of the die 2 refers to the movement amount of the die 2 in the pressing direction.

[0078] Here, if the amount of movement is ΔH and the size of the reference clearance is CL1, the relationship of formula (3) holds between the amount of movement ΔH and the reference clearance CL1.

[0079]

number

[0080] When the movement amount ΔH is a positive number, it means that the die 2 is moved in the −Z direction, and when the movement amount ΔH is a negative number, it means that the die 2 is moved in the +Z direction.

[0081] Next, based on the calculated movement amount ΔH, the actuator 18 is driven to move the die 2, and the size of the clearance CL is corrected (step S10), and the process proceeds to step S11.

[0082] Returning to step S7, if it is determined that the clearance is not to be corrected based on the impulse difference of the die 2 (No in step S7), the calculation unit 22 calculates the impulse difference for the load Pz applied to the punch 1 (step S12).

[0083] Fig. 10 is a graph showing the relationship between the load Pz applied to the punch 1 and the processing time t from the start of forming. As shown in Fig. 10, the magnitude of the load Pz applied to the punch 1 calculated by the calculation unit 22 is acquired as waveform data showing the relationship with the processing time from the start of forming.

[0084] When the magnitude of the push-in amount of punch 1 is an appropriate value (reference push-in amount), the waveform data of load Pz will be the waveform shown by the solid line in Fig. 10. When the magnitude of the push-in amount is greater than the reference push-in amount, the waveform data of load Pz will be the waveform shown by the dashed line in Fig. 10. When the magnitude of the push-in amount is less than the reference push-in amount, the waveform data of load Pz will be the waveform shown by the dashed line in Fig. 10. Note that the push-in amount of punch 1 indicates the position of punch 1 when punch 1 reaches the bottom dead center.

[0085] The impulse of the load Pz is the product of the load Pz and time, and is calculated by determining the area of ​​the waveform data in Fig. 10. The impulse difference of the punch 1 is the difference between the impulse in the case of the reference push-in amount and the impulse of the load Pz applied to the punch 1 detected in step S3. In this embodiment, the difference between the impulse based on the detected load Pz and the impulse in the case of the reference push-in amount is calculated, and it is determined whether or not to correct the push-in amount of the punch 1 based on the difference value.

[0086] For example, the difference in impulse when the magnitude of the push-in amount is larger than the reference push-in amount is calculated by finding the area of ​​region 120 in Fig. 10. Also, the difference in impulse when the magnitude of the push-in amount is smaller than the reference push-in amount is calculated by finding the area of ​​region 121 in Fig. 10.

[0087] Based on the impulse difference of the load Pz, the determination unit 23 determines whether or not to correct the amount of push-in (step S13). For example, an upper limit value and a lower limit value of the impulse difference are set in advance, and it can be determined that the amount of push-in is to be corrected when the value of the impulse difference exceeds the upper limit value or falls below the lower limit value.

[0088] For example, if the impulse difference exceeds ±10% of the impulse for the reference push-in amount, it is determined that the push-in amount is to be corrected (Yes in step S13). In other words, if the impulse difference exceeds ±10% of the reference push-in amount, it is determined that the push-in amount is to be corrected. If the impulse difference is included within ±10% of the reference push-in amount, it is determined that the impulse difference is within the standard and that the push-in amount is not to be corrected (No in step S13).

[0089] If it is determined that the push-in amount is to be corrected (Yes in step S13), the calculation unit 28 calculates the correction amount (step S14). The correction amount is a value indicating the position of the punch 1 when it is at the bottom dead center, and how much it is to be moved in the press direction (Z direction).

[0090] Fig. 11 is a graph showing the relationship between the load Pz and the processing time t when the impulse difference is within ±20%. Fig. 12 is a graph showing the relationship between the impulse difference and the correction amount of the push-in amount. In Fig. 11, region 122 shows the case where the impulse difference is -20%, and region 123 shows the case where the impulse difference is +20%. Fig. 12 is a graph plotting the correction amount of the push-in amount when the impulse difference is -20% or more and +20% or less, which is obtained by experiment. In Fig. 12, the horizontal axis shows the impulse difference (%), and the vertical axis shows the correction amount of the push-in amount (mm).

[0091] 11 and 12, for example, when the impulse difference is -20%, it indicates that the push-in amount is smaller than the reference amount, and the correction amount of the push-in amount is +0.2 mm. In other words, it indicates that the position of punch 1 at the bottom dead center is to be moved 0.2 mm downward in the press direction (+Z direction). Also, when the impulse difference is +20%, it indicates that the push-in amount is larger than the reference amount, and the correction amount of the push-in amount is -0.2 mm. In this case, it indicates that the position of punch 1 at the bottom dead center is to be moved 0.2 mm downward in the press direction (+Z direction).

[0092] The correction amount based on the experimental results is as shown in the graph in FIG. 10. If the correction amount is ΔPR and the impulse difference is D2, then equation (4) is established.

[0093]

number

[0094] Here, since the coefficient b changes depending on the wear state of the punch 1, etc., an accurate correction amount ΔPR can be calculated by obtaining experimental results such as those shown in the graph of FIG. 10 every few shots and changing the coefficient b.

[0095] Next, based on the calculated correction amount ΔPR, the servo motor 11 is controlled to correct the push-in amount of the punch 1 (step S15).

[0096] The die 2 is moved (step S10) or the pushing amount of the punch 1 is corrected (step S15), and the process ends.

[0097] [effect] According to the embodiment described above, the clearance correction amount between the blank holder and the die is calculated based on the normal force of the die, so that it is possible to provide a press forming apparatus that can properly maintain the clearance and perform stable processing.

[0098] In the above-described embodiment, an example has been described in which the press forming apparatus 100 is equipped with a punch load sensor 13 and corrects the amount of pressing of the punch 1 based on the load Pz applied to the punch 1, but the punch load sensor 13 is not a required component.

[0099] In the above embodiment, the die 2 is configured with four die pieces 2c to 2f, but is not limited thereto. The die 2 may be configured with one die piece, or may be configured with two or more die pieces. In this case, it is preferable that the die load sensor 14 is disposed in each die piece.

[0100] Further, in the above-described embodiment, an example has been described in which the press forming apparatus 100 includes the first gap sensor 15 and the second gap sensor 16, but the first gap sensor 15 and the second gap sensor 16 are not essential components. [Industrial Applicability]

[0101] The press molding apparatus of the present disclosure can be applied to bending or drawing of workpieces that are thin, hard, and difficult to stretch, such as home appliances and medical device parts. [Explanation of symbols]

[0102] 1 Punch 2 Die 2a slope 2c~2f Die Pieces 4 Die Plate 5 Work 11 Servo motor (first drive unit) 13 Punch load sensor 14, 14cc~14f Die load sensor 15 First gap sensor 16, 16a to 16d Second gap sensor 18 Actuator (second drive unit) 100 Press molding equipment

Claims

1. A press forming apparatus for processing a plate-shaped workpiece, A punch moving in the press direction; a die having a hollow portion into which the punch is inserted and having a slope inclined toward the hollow portion; A die plate for holding the die; a blank holder disposed between the punch and the die and having a pressing surface facing the inclined surface of the die; a die load sensor that detects a load generated on the inclined surface of the die as loads in three directions, including a load in the press direction, a load in a first direction perpendicular to the press direction, and a load in a second direction perpendicular to the press direction and the first direction; a control unit that calculates a normal force of the die based on each of the load in the press direction, the load in the first direction, and the load in the second direction detected by the die load sensor, and calculates a clearance correction amount between the die and the blank holder based on the normal force of the die; A first drive unit that moves the die in the press direction based on the clearance correction amount; A second drive unit that drives the punch in the pressing direction; Equipped with Press forming equipment.

2. The clearance correction amount is calculated based on a difference between an impulse calculated from the normal force of the die and the processing time in the case of an appropriate clearance and an impulse calculated from the normal force of the die during processing and the processing time. The press forming apparatus according to claim 1 .

3. moreover, a punch load sensor for detecting the load of the punch applied in the press direction; Equipped with the control unit calculates a punch push-in correction amount based on the load of the punch detected by the punch load sensor, The second driving unit drives the punch based on a push-in correction amount of the punch. The press molding apparatus according to claim 1 or 2.

4. The punch push-in correction amount is calculated based on a difference between an impulse calculated from the load of the punch and the processing time in the case of an appropriate push-in amount and an impulse calculated from the load of the punch and the processing time during processing. The press forming apparatus according to claim 3 .

5. moreover, a first gap sensor for detecting when the punch is at the bottom dead center; Equipped with The press molding apparatus according to any one of claims 1 to 4.

6. moreover, a second gap sensor that detects contact between the blank holder and the die plate; Equipped with The press molding apparatus according to any one of claims 1 to 5.

7. The die is composed of a plurality of die pieces, The die load sensor is disposed on each of the plurality of die pieces. The press molding apparatus according to any one of claims 1 to 6.

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