Mold buffer control apparatus and method, and mold buffer apparatus

Abstract

A compression spring model included in a processor in the mold buffer control equipment refers to a load characteristic curve of a compression spring when a hydraulic cylinder is set as the compression spring, and a buffer load instruction is generated according to a spring constant and deflection of the compression spring; and generating a control command based on a deviation between the generated buffer load command and the actual buffer load. According to the control instruction, the driving motor and the hydraulic pump are driven, and an upward load is generated on the buffer pin through the hydraulic cylinder. Therefore, even if the cushion pin rises due to a setting error of the height of the press die, the cushion load command is reduced according to the amount of deflection of the compression spring, and the abnormal upward pushing action of the cushion pin is suppressed.

Description

Technical Field

[0001] The present disclosure relates to a die cushion control device and method and a die cushion device, and particularly to a technique for preventing a cushion pin from being pushed upward. Background Art

[0002] A die cushion device is a device that generates a pressure in the upward direction on a cushion pin during flattening of a workpiece and generates a reaction force for holding wrinkles.

[0003] The function of the die cushion device is to squeeze the periphery of the workpiece downward in the following manner: in a state where the height of the lower surface of the upper die fixed to the pressing slider in a press is higher than the workpiece placed in the lower die, by holding the position of the cushion pin at a predetermined position to support the workpiece, and when the height of the lower surface of the upper die is equal to or lower than the workpiece placed on the upper surface of the lower die, a reaction force is generated on the cushion pin during the drawing process.

[0004] Generally, the switching from position control for holding the position of the cushion pin to pressure control for generating a drawing reaction force on the cushion pin uses a method of switching according to the height of the pressing slider (the lower surface of the upper die) (PTL1 and PTL2).

[0005] List of Cited Documents

[0006] PTL1: Japanese Patent Application Laid-Open No. 2009-279620

[0007] PTL2: Japanese Patent Application Laid-Open No. 2017-225998. Summary of the Invention

[0008] In the method of switching between position control and pressure control as in PTL1 and PTL2, the following problems may occur when the time when the upper die contacts the workpiece does not match the time when the control mode on the die cushion device switches from position control to pressure control.

[0009] For example, if the pressure control is switched before the upper die contacts the workpiece, the cushion pin will inadvertently continue to rise until it is mechanically constrained, which may damage the workpiece or the die.

[0010] The reasons for the mismatch in the switching time include setting errors in the height of the press die, thickness errors between the upper die and the lower die, fluctuations in the thickness of the workpiece, etc. Even if an abnormal operation caused by these incorrect operations and / or improper settings is detected on the controller side according to a certain method and the position holding force and pressure to be applied to the cushion pin are blocked, due to inertial force and residual pressure, the abnormal movement of the cushion pin may not be completely suppressed.

[0011] The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a die cushion control device and method and a die cushion device that allow suppression of abnormal operation of a cushion pin.

[0012] To achieve this object, a die cushion control device according to a first aspect of the present invention is a die cushion control device for a die cushion device, the die cushion device including: a hydraulic cylinder that supports a cushion load generating member that generates a cushion load; a hydraulic cylinder driving device that includes a driving motor and a hydraulic pump to be driven by the driving motor, and the hydraulic cylinder driving device drives the hydraulic cylinder; a cushion target position instruction device and a cushion target load instruction device that output a cushion target position instruction and a cushion target load instruction according to a crank angle of a press or a position of a squeezing slider, respectively; a position sensor that detects a position of the cushion load generating member; and a pressure sensor that detects a pressure in a lower chamber of the hydraulic cylinder, wherein the die cushion control device includes a processor and a controller that controls the driving motor according to an input control instruction, the processor sets the hydraulic cylinder to include a compression spring model, when an upward load of the cushion load generating member is equal to a preset load, obtains a deflection length of the compression spring as a target deflection length, generates a cushion load instruction or a pressure instruction obtained by converting the cushion load instruction with a cylinder area based on the cushion target load instruction, the target deflection length, the cushion target position instruction, and a cushion position that is the position of the cushion load generating member detected by the position sensor, and generates the control instruction based on a second deviation between the cushion load instruction and a cushion load converted from the pressure detected by the pressure sensor or a second deviation between the pressure instruction and the pressure detected by the pressure sensor.

[0013] According to a first aspect of the present disclosure, referring to a load characteristic curve of a compression spring when the hydraulic cylinder is set as a compression spring, a cushion load instruction or a pressure instruction is generated according to a cushion position detected by a position sensor. Then, a control instruction is generated based on a second deviation between the generated cushion load instruction and a cushion load converted from the pressure detected by the pressure sensor or a second deviation between the pressure instruction and the pressure detected by the pressure sensor, and the driving motor is controlled according to the control instruction. Therefore, even if there is a setting error in the die height of the press, control can be performed to prevent abnormal upward pushing of the cushion pin.

[0014] In the die cushion control device according to the second aspect of the present disclosure theme, the processor in the first aspect preferably calculates the deflection length of the compression spring based on the cushion target position command, the target deflection length, and the cushion position, and calculates the cushion load command through the following equation based on the calculated deflection length, the target deflection length, and the cushion target position command:

[0015] Cushion load command = (cushion target load command / target deflection length) × deflection length.

[0016] Therefore, if the deflection length is equal to zero, the cushion load command or the pressure command is equal to zero, and the cushion load command or the pressure command increases proportionally with the deflection length; and if the deflection length reaches the target deflection length, the cushion load command or the pressure command becomes a command corresponding to the cushion target load. Therefore, even if the contact with the upper die of the extrusion slider is not achieved, the cushion pin does not rise beyond the position where the deflection length is zero.

[0017] In the die cushion control device according to the third aspect of the present disclosure theme, the processor in the first aspect or the second aspect preferably generates a cushion position command based on the cushion target position command and the cushion position, and generates a control command based on the first deviation between the cushion position command and the cushion position.

[0018] In the die cushion control device according to the fourth aspect of the present disclosure theme, the processor in the third aspect preferably generates the cushion target position command as the cushion position command when the cushion load command or the pressure command is less than or equal to zero or a preset predetermined value, and generates the cushion position as the cushion position command when the cushion load command or the pressure command is greater than zero or the predetermined value. Therefore, when controlling the cushion load command or the pressure command, the position loop gain ratio is equal to 0%, and the control is basically performed only using the cushion load command or the pressure command.

[0019] In the die cushion control device according to the fifth aspect of the present disclosure theme, the processor in the fourth aspect preferably calculates the first supply amount of the hydraulic fluid to be supplied to the upper chamber or the lower chamber of the hydraulic cylinder required to make the position of the cushion load generating member reach the cushion position corresponding to the cushion position command based on the first deviation, and calculates the second supply amount of the hydraulic fluid to be supplied to the lower chamber of the hydraulic cylinder required to make the upward load of the cushion load generating member reach the cushion load corresponding to the cushion load command based on the second deviation, and calculates the rotation angle of the drive motor based on the first supply amount, the second supply amount, and the amount of the hydraulic fluid ejected per rotation of the hydraulic pump, and generates a control command based on the rotation angle.

[0020] In the die cushion control device according to the sixth aspect of the present disclosure theme, the processor in any one of the third aspect to the fourth aspect preferably includes a cushion position controller that generates a first speed command based on a first deviation and a cushion position controller or a pressure controller that generates a second speed command based on a second deviation, and the processor generates a control command by adding the first speed command and the second speed command.

[0021] According to the fifth aspect or the sixth aspect of the present disclosure theme, instead of applying the switching between the cushion load control (or pressure control) and the cushion position control within the control device, the cushion load control (or pressure control) and the cushion position control are always operated, and with reference to the load characteristic curve of the compression spring from the information regarding the cushion position, thus the cushion load control (pressure control) and the cushion position control can be executed.

[0022] In the die cushion control device according to the seventh aspect of the present disclosure theme, the processor in the sixth aspect preferably generates a cushion unloaded position command obtained by adding a cushion target position command and a target deflection length, generates a third speed command based on the cushion unloaded position command, and generates a control command by adding the first speed command, the second speed command, and the third speed command. The control by the third speed command is a feedforward control, so highly responsive control can be performed.

[0023] In the die cushion control device according to the eighth aspect of the present disclosure theme, the processor in the seventh aspect preferably obtains the displacement of the hydraulic cylinder per unit time by differentiating the cushion unloaded position command with respect to time, and converts the displacement per unit time into the speed of the drive motor to generate a third speed command.

[0024] In the die cushion control device according to the ninth aspect of the present disclosure theme, the processor in the seventh aspect or the eighth aspect preferably includes a delay unit that delays the cushion position command to be used for calculating the first deviation and the cushion load command or pressure command to be used for calculating the second deviation.

[0025] In the die cushion control device according to the tenth aspect of the present disclosure theme, the processor in any one of the first aspect to the ninth aspect preferably calculates a target deflection length based on hydraulic circuit parameters and a set load, and these hydraulic circuit parameters include: the flow path volume information of the hydraulic circuit including the hydraulic cylinder, the bulk modulus of the hydraulic fluid, and the cylinder diameter of the hydraulic cylinder.

[0026] In the die cushion control device according to the eleventh aspect of the present disclosure theme, the processor in any one of the first aspect to the ninth aspect preferably calculates a target deflection length based on the spring coefficient of the compression spring and the set load.

[0027] The invention according to the twelfth aspect is a die cushion device, which includes a die cushion control device according to any one of the first aspect to the eleventh aspect.

[0028] The invention according to the thirteenth aspect is a die cushion control method for a die cushion control device of a die cushion device, the die cushion device including: a hydraulic cylinder that supports a cushion load generating member for generating a cushion load; a hydraulic cylinder driving device including a driving motor and a hydraulic pump to be driven by the driving motor, and the hydraulic cylinder driving device driving the hydraulic cylinder; a cushion target position instruction device and a cushion target load instruction device that respectively output a cushion target position instruction and a cushion target load instruction according to the crank angle of a press or the position of a ram; a position sensor that detects the position of the cushion load generating member as a cushion position; and a pressure sensor that detects the pressure in a lower chamber of the hydraulic cylinder, wherein a processor performs the following steps: setting a compression spring model for the hydraulic cylinder, and when the upward load of the cushion load generating member is equal to a preset load, obtaining the deflection length of the compression spring as a target deflection length; generating a cushion load instruction or a pressure instruction obtained by converting the cushion load instruction with a cylinder area based on the cushion target load instruction, the target deflection length, the cushion target position instruction, and the cushion position; generating a control instruction based on a second deviation between the cushion load instruction and the cushion load converted from the pressure detected by the pressure sensor or a second deviation between the pressure instruction and the pressure detected by the pressure sensor; and outputting the generated control instruction to a speed controller for controlling the driving motor.

[0029] In the die cushion control method according to the fourteenth aspect of the subject matter of the present disclosure, the processor according to the thirteenth aspect preferably calculates the deflection length of the compression spring based on the cushion target position instruction, the target deflection length, and the cushion position, and calculates the cushion load instruction through the following equation based on the calculated deflection length, the target deflection length, and the cushion target position instruction:

[0030] Cushion load instruction = (cushion target load instruction / target deflection length) × deflection length.

[0031] The die cushion control method according to the fifteenth aspect of the subject matter of the present disclosure preferably includes the following steps in the thirteenth aspect or the fourteenth aspect: generating a cushion position instruction by the processor based on the cushion target position instruction and the cushion position, and generating a control instruction by the processor based on a first deviation between the cushion position instruction and the cushion position.

[0032] In the die cushion control method according to the sixteenth aspect of the present disclosure theme, the processor in the fifteenth aspect preferably generates a cushion target position instruction as a cushion position instruction when the cushion load instruction or the pressure instruction is less than or equal to zero or a preset predetermined value, and generates a cushion position as a cushion position instruction when the cushion load instruction or the pressure instruction is greater than zero or the predetermined value.

[0033] The die cushion control method according to the seventeenth aspect of the present disclosure theme preferably includes the following steps in the sixteenth aspect: based on the first deviation, calculating, by the processor, a first supply amount of hydraulic fluid to be supplied to the upper chamber or the lower chamber of the hydraulic cylinder required to bring the position of the cushion load generating member to a cushion position corresponding to the cushion position instruction, and based on the second deviation, calculating a second supply amount of hydraulic fluid to be supplied to the lower chamber of the hydraulic cylinder required to bring the upward load of the cushion load generating member to a cushion load corresponding to the cushion load instruction, and based on the first supply amount, the second supply amount, and the amount of hydraulic fluid ejected per revolution of the hydraulic pump, calculating, by the processor, the rotation angle of the drive motor, and generating a control instruction based on the rotation angle.

[0034] In the die cushion control method according to the eighteenth aspect of the present disclosure theme, the processor in any one of the fifteenth aspect to the seventeenth aspect preferably performs the following steps: generating a first speed instruction based on the first deviation; generating a second speed instruction based on the second deviation; and generating a control instruction by adding the first speed instruction and the second speed instruction.

[0035] In the die cushion control method according to the nineteenth aspect of the present disclosure theme, the processor in the eighteenth aspect preferably performs the following steps: generating a cushion unloaded load position instruction obtained by adding the cushion target position instruction and the target deflection length; generating a third speed instruction based on the cushion unloaded load position instruction; and generating a control instruction by adding the first speed instruction, the second speed instruction, and the third speed instruction.

[0036] In the die cushion control method according to the twentieth aspect of the present disclosure theme, the processor in the nineteenth aspect preferably calculates the displacement of the hydraulic cylinder per unit time by performing a time differentiation on the cushion unloaded load position instruction, and converts the calculated displacement into the speed of the drive motor to generate a third speed instruction.

[0037] According to the present disclosure theme, even if the cushion load control starts before the upper die contacts the workpiece due to the setting error of the press die height, the cushion pin will not rise beyond the preset cushion standby position, thereby preventing damage to the workpiece or the die caused by the upward push of the cushion pin. Description of the Drawings

[0038] Figure 1 is a configuration diagram of a press showing a die cushion device according to the subject matter of the present disclosure;

[0039] Figure 2 is a graph showing the load characteristics of a compression spring model, which represents the relationship between the deflection length of the compression spring and the upward load of the buffer pin when the hydraulic cylinder is set as the compression spring;

[0040] Figure 3 is a schematic diagram showing the respective operating states of a die cushion device body and the like controlled by a die cushion control device according to the subject matter of the present disclosure;

[0041] Figure 4 is a diagram showing Figure 1 a functional block diagram of an embodiment of a compression spring model of the illustrated processor;

[0042] Figure 5 is a diagram showing Figure 1 a block diagram of the main part of the illustrated die cushion device;

[0043] Figure 6 is a diagram showing an example of a method by which a die cushion control device generates a speed command for controlling a buffer position;

[0044] Figure 7 is a diagram showing an example of a method by which a die cushion control device generates a speed command for controlling a buffer load;

[0045] Figure 8 is a diagram showing an example of a method by which a die cushion control device generates speed commands for controlling a buffer position and a buffer load;

[0046] Figure 9 is a diagram showing another example of a method by which a die cushion control device generates speed commands for controlling a buffer position and a buffer load;

[0047] Figure 10 is a graph showing an extrusion slider position, a buffer position, a buffer load, and a buffer unloaded position, which is a graph showing the effects of a die cushion control device according to the subject matter of the present disclosure;

[0048] Figure 11 is a schematic diagram showing a state where the extrusion slider is above the buffer pin and separated from the buffer pin;

[0049] Figure 12 is a schematic diagram showing a state where the extrusion slider is in contact with the buffer pin and the buffer pin is slightly pressed downward;

[0050] Figure 13 is a diagram showing the extrusion slider from Figure 12Schematic diagram of the state where the shown state further drops and the buffer load reaches the set load;

[0051] Figure 14 It shows the extrusion slider from Figure 13 Schematic diagram of the state where the shown state further drops and maintains the set load during the drop (extrusion process);

[0052] Figure 15 It is a chart showing the operations of each component in the case of normal extrusion processing operation using a conventional die cushion control device;

[0053] Figure 16 It is a chart showing the operations of each component in the case of abnormal operation of the conventional die cushion control device;

[0054] Figure 17 It is a chart showing the operations of each component in the case of controlling the die cushion device body by the die cushion control device according to the subject matter of the present disclosure; and

[0055] Figure 18 It is a flowchart showing an embodiment of the die cushion control method according to the subject matter of the present disclosure. Detailed Description of the Invention

[0056] Hereinafter, embodiments of a die cushion control device and method according to the subject matter of the present disclosure and a die cushion device will be described in detail with reference to the accompanying drawings.

[0057] [Press including die cushion device]

[0058] Figure 1 It is a configuration diagram showing a press including a die cushion device according to the subject matter of the present disclosure.

[0059] Figure 1 The shown press 1 is a crank press having a crank mechanism including a crankshaft 2 and a connecting rod 3, wherein the crankshaft 2 is rotated by a servo motor (not shown), and the rotational driving force of the crankshaft 2 is transmitted to the extrusion slider 4 through the connecting rod 3, so that the extrusion slider 4 reciprocates in the vertical direction.

[0060] The crankshaft 2 is provided with a crankshaft encoder 5 for detecting the crank angle of the crankshaft 2. A crank angle signal indicating the crank angle detected by the crankshaft encoder 5 is output to the buffer target load command device 20 and the buffer target position command device 22.

[0061] An upper die (not shown) is attached to the extrusion slider 4, and a lower die is attached to the bolster.

[0062] The blank holder 15 is placed between the upper die and the lower die. The lower side of the blank holder 15 is supported by the cushion pins 14, and the workpiece 16 is disposed on (contacts) its upper side.

[0063] The press 1 lowers the extrusion slider 4 so that the workpiece 16 can be subjected to extrusion processing (flattening in this example) between the upper die and the lower die. It should be noted that although the press 1 in this example is a crank press, the press applying the die cushion device according to the subject matter of the present disclosure is not limited to such a crank press, and the subject matter of the present disclosure can be applied to various presses.

[0064] The die cushion device applies an extrusion force (cushion load) to the circumferential edge of the workpiece 16 to be drawn from the lower side and serves to hold the circumferential edge of the workpiece 16 between the upper die and the blank holder 15.

[0065] The die cushion device includes a die cushion device body 10 and a die cushion control device according to the present invention.

[0066] The die cushion device body 10 includes: a cushion load generating member, which includes cushion pins 14 and a blank holder 15 and generates a cushion load; a hydraulic cylinder (an "oil hydraulic cylinder" in this example) 12, which supports the cushion load generating member; a hydraulic cylinder driving device (an oil hydraulic cylinder driving device), which includes a driving motor 50 and a hydraulic pump (an oil pump) 60 to be driven by the driving motor 50 and drives the hydraulic cylinder 12; a cushion target load command device 20 and a cushion target position command device 22, which respectively output a cushion target load command C1 and a cushion target position command C2 based on a crankshaft angle signal indicating the crankshaft angle detected by the crankshaft encoder 5 or a slider position signal indicating the position of the extrusion slider 4 converted from the crankshaft angle; a position sensor 17, which detects the position of the cushion load generating member (the tip position of the cushion pin 14 in this example); and a pressure sensor 18, which detects the pressure in the lower chamber 12a of the hydraulic cylinder 12.

[0067] It should be noted that although for simplicity of description, the piston rod of the hydraulic cylinder 12 is a cushion pin in this example, the cushion load generating member includes a blank holder 15, a cushion pin holding the blank holder, and a cushion pad (not shown) supporting the cushion pin. The piston rod of the hydraulic cylinder 12 is connected to the cushion pad, and the hydraulic cylinder 12 typically supports the cushion pad to support the blank holder 15 through the cushion pin.

[0068] The drive shaft of the drive motor 50 is directly or via a speed reducer connected to the rotary shaft of the hydraulic pump 60. The hydraulic pump 60 driven by the drive motor 50 supplies the hydraulic fluid (hydraulic oil) required to bring the position (buffer position) of the buffer pin 14 to the buffer target position to the lower chamber 12a or the upper chamber 12b of the hydraulic cylinder 12, and supplies the pressure fluid (pressure oil) required to make the upward load of the buffer pin 14 become the buffer load corresponding to the buffer load command to the lower chamber 12a of the hydraulic cylinder 12.

[0069] It should be noted that the oil tank 62 retains the excessive hydraulic oil discharged from the hydraulic pump 60 during the buffer position control and the buffer load control, or supplies hydraulic oil to the hydraulic pump 60 when needed.

[0070] The die buffer control device according to the subject matter of the present disclosure includes a processor 30 and a controller (speed controller) 40.

[0071] The processor 30 includes a central processing unit (CPU), and receives inputs of a buffer target load command C1 and a buffer target position command C2 from a buffer target load command device 20 and a buffer target position command device 22 respectively, and also receives inputs of a buffer position signal D1 indicating the end position of the buffer pin 14 and a pressure signal D2 indicating the pressure in the lower chamber 12a of the hydraulic cylinder 12 from a position sensor 17 and a pressure sensor 18 respectively, and generates a control command (speed command) to be output to the speed controller 40 based on the buffer target load command C1, the buffer target position command C2, the buffer position signal D1, and the pressure signal D2.

[0072] The processor 30 acts as a compression spring model 100, a buffer load command delay unit 110, a buffer load converter 114, a buffer load controller 116, a buffer position command delay unit 120, a buffer position controller 126, and adders 112, 122, and 118. It should be noted that the processing details of each component of the processor 30 are described below.

[0073] [Load characteristics of the compression spring model]

[0074] Figure 2 is a graph showing the load characteristics of the compression spring model, and the load characteristics represent the relationship between the deflection length of the compression spring and the upward load of the buffer pin when the hydraulic cylinder is set as the compression spring.

[0075] As Figure 2 shown, the extrusion slider 4 is located above the end of the buffer pin 14, and the end position of the buffer pin is set to the buffer unloaded position separated from the end of the buffer pin 14.

[0076] Here, a hydraulic circuit model is set in which the hydraulic circuit including the hydraulic cylinder 12 is filled with hydraulic oil, the hydraulic pump 60 remains stationary, and the buffer load is equal to 0 [kN].

[0077] In the buffer unloaded position, no buffer load is applied to the compression spring, and the compression spring has a free length with a deflection length equal to zero.

[0078] When the fall of the extrusion slider 4 causes the extrusion slider 4 to contact the buffer pin 14, the buffer pin 14 then falls together with the extrusion slider 4. It should be noted that although in reality the upper die, the workpiece 16, and the blank holder 15 are between the extrusion slider 4 and the buffer pin 14, they are omitted in this example.

[0079] When the buffer pin 14 is squeezed downward (when the compression spring is deflected), an upward load appears in the buffer pin 14 as a reaction force proportional to the extrusion length (deflection length) (see the graph in Figure 2 ). Then, the deflection length of the compression spring when the upward load of the buffer pin 14 is equal to a preset load is treated as the "target deflection length".

[0080] [Outline of Die Buffer Control]

[0081] Figure 3 is a schematic diagram showing the respective operating states of the die buffer device body and the like controlled by the die buffer control device according to the subject matter of the present disclosure.

[0082] (1) Separation

[0083] In a state where the extrusion slider 4 is in the upper part and deviated from the buffer pin 14, position control is performed such that the buffer load command to the buffer load controller 116 is equal to zero, the position loop gain ratio to the buffer position controller 126 is equal to 100%, and the end position (buffer position) of the buffer pin 14 is maintained at the buffer unloaded position.

[0084] (2) Contact / Extrusion

[0085] When the extrusion slider 4 falls, the extrusion slider 4 contacts the buffer pin 14 and squeezes the buffer pin 14 downward. The buffer load command to the buffer load controller 116 is a load command depending on the compression spring characteristics, the position loop gain ratio to the buffer position controller 126 is equal to 0%, and the upward load (buffer load) of the buffer pin 14 is controlled by a buffer load command depending on the compression spring characteristics.

[0086] (3) Reaching the Set Load

[0087] When the extrusion slider 4 further drops to the target deflection length, the buffer load command for the buffer load controller 116 is a buffer target load command corresponding to a preset set load, and the buffer position controller 126 does not cause a reaction force corresponding to the extrusion position. In other words, the buffer pin 14 is controlled to push the extrusion slider 4 upward with the set load.

[0088] (4)Maintain the set load

[0089] When the extrusion slider 4 further drops, a drop command for the reference target deflection length is executed on the buffer position controller 126. The buffer position controller 126 outputs a motor speed (i.e., the oil discharge amount of the hydraulic cylinder 12) corresponding to the drop command, so that the buffer pin 14 continues its dropping action while pushing the extrusion slider 4 upward with the set load.

[0090] Figure 4 is shown Figure 1 The functional block diagram of an embodiment of the compression spring model of the illustrated processor.

[0091] Figure 4 The illustrated compression spring model 100 includes a target deflection length calculator 101, a buffer load command generator 102, a motor speed converter 104, a buffer position command generator 106, and adders 103 and 105.

[0092] The compression spring model 100 receives inputs of a buffer target load command C1 and a buffer target position command C2 from a buffer target load command device 20 and a buffer target position command device 22, respectively, and also receives an input of a buffer position signal D1 from a position sensor 17, and generates a third speed command S3 (i.e., a feedforward speed command (FF speed command)), a buffer position command S5, and a buffer load command S6 based on the buffer target load command C1, the buffer target position command C2, and the buffer position signal D1, as described later.

[0093] The target deflection length calculator 101 receives inputs of information indicating a buffer target load (a set load preset by the user) C1 set in the buffer target load command device 20 and a hydraulic circuit parameter (hydraulic circuit parameter) 107, and calculates the target deflection length based on the input information. The buffer target load can be obtained from an input unit through which the user inputs the set load, and is not limited to being obtained from the buffer target load command device 20.

[0094] The hydraulic circuit parameters are the following parameters and can be stored in a storage unit. The parameters include: flow path volume information regarding a hydraulic circuit (hydraulic circuit) including the hydraulic cylinder 12, the bulk modulus of the hydraulic fluid (hydraulic oil), and the cylinder diameter of the hydraulic cylinder 12. It should be noted that the information regarding the flow path volume in the hydraulic circuit parameters can include information regarding the flow path volume depending on the length of the hydraulic rubber hose and the diameter of the hydraulic rubber hose between the hydraulic cylinder 12 and the hydraulic pump 60, and the modulus of the hydraulic rubber hose can also be included in the hydraulic circuit parameters.

[0095] The target deflection length calculator 101 creates a buffered hydraulic circuit model based on the hydraulic circuit parameters 107, in which the hydraulic circuit including the hydraulic cylinder 12 and the hydraulic rubber hose is filled with hydraulic oil, the hydraulic pump 60 remains stationary, and the buffering load is equal to 0 [kN].

[0096] The target deflection length calculator 101 applies the created buffered hydraulic circuit model and uses the hydraulic circuit parameters 107 to calculate the displacement of the hydraulic cylinder 12 required to give the buffering target load command C1, and outputs this displacement as the target deflection length.

[0097] It should be noted that the target deflection length calculator 101 can calculate the target deflection length based on the compression spring characteristic (spring constant) of the hydraulic cylinder 12 and the buffering target load (set load). In this case, the spring constant of the hydraulic cylinder 12 can be calculated by applying a known load to the hydraulic cylinder 12 and according to the displacement of the hydraulic cylinder caused by the application of the known load.

[0098] The adder 103 adds the target deflection length output from the target deflection length calculator 101 and the buffering target position command C2 output from the buffering target position command device 22, and outputs the added value as the buffering unloaded load position command to the motor speed converter 104.

[0099] The motor speed converter 104 obtains the displacement of the hydraulic cylinder 12 per unit time by taking the time derivative of the input buffering unloaded load position command, and converts the displacement per unit time into the rotational speed of the drive motor 50 to generate an FF speed command (third speed command) S3.

[0100] The motor speed converter 104 obtains the amount of oil per unit time to be supplied from the hydraulic pump 60 to the hydraulic cylinder 12 according to the displacement per unit time and the cylinder area, and divides the obtained amount of oil by the volume of oil pushed out by one rotation of the hydraulic pump 60 (ejection amount) to generate the rotational angle of the hydraulic pump 60 per unit time, that is, the third speed command indicating the rotational angle of the drive motor 50 connected to the drive shaft of the hydraulic pump 60 per unit time.

[0101] The buffer load command generator 102 receives as inputs the buffer target load command C1 output from the buffer target load command device 20, the information indicating the target deflection length output from the target deflection length calculator 101, and the position deviation between the buffer target position command C2 and the buffer position signal D1 output from the adder 105, calculates the deflection length of the compression spring when the hydraulic cylinder 12 is set as the compression spring, and calculates the buffer load command S6 based on the calculated deflection length, the buffer target load command C1, and the target deflection length, by the following equation:

[0102] [Equation 1] Buffer load command S6 = (buffer target load command / target deflection length) × deflection length.

[0103] Here, the adder 105 subtracts the buffer position signal D1 indicating the end position of the buffer pin 14 detected by the position sensor 17 from the buffer target position command C2 output from the buffer target position command device 22, and outputs the information indicating the position deviation as the subtraction result to the buffer load command generator 102.

[0104] The buffer load command generator 102 adds the target deflection length and the position deviation to calculate the deflection length. When the position deviation is equal to 0 [mm], the deflection length is equal to the target deflection length. When the position deviation increases in the negative direction, the deflection length decreases. When the magnitude of the position deviation in the negative direction is equal to the target deflection length, the deflection length is equal to 0 [mm]. It should be noted that the deflection length can be obtained by adding the target deflection length and the buffer target position and then subtracting the buffer position (corresponding to the buffer unloaded position) indicated by the buffer position signal D1 from the added value, and is not limited to being obtained by adding the target deflection length and the position deviation.

[0105] The above equation [Equation 1] is an equation under Hooke's law, and (buffer target load command / target deflection length) represents the spring constant k (kN / mm). The buffer load command generator 102 generates the buffer load command S6 by multiplying the spring constant k by the deflection length (mm) according to Equation [Equation 1].

[0106] Therefore, when the deflection length reaches the target deflection length, the buffer load command generator 102 outputs the buffer load command S6 as the buffer target load command C1 (the command indicating the set load), outputs the buffer load command S6 that decreases proportionally with the decrease in the deflection length as the deflection length decreases, and outputs the buffer load command S6 indicating 0 [kN] when the deflection length is equal to 0 [mm].

[0107] The buffer position instruction generator 106 receives a buffer target position instruction C2, a buffer position signal D1, and a buffer load instruction S6, and outputs the buffer target position instruction C2 as a buffer position instruction S5 when the buffer load instruction S6 is zero, and outputs the buffer position signal D1 as the buffer load instruction S6 when the buffer load instruction S6 exceeds zero. It should be noted that the switching between the buffer target position instruction C2 and the buffer position signal D1 is not limited to whether the buffer load instruction S6 is equal to or less than zero, but can be based on whether it is equal to or less than a set predetermined value (for example, the buffer load instruction S6 corresponding to the holding load of the buffer pin 14, the blank holder 15, etc. supported by the hydraulic cylinder 12 when there is no load).

[0108] Return reference Figure 2 , the third speed instruction S3, which is a feedforward speed instruction generated by the compression spring model 100, is output to the adder 118, and the buffer load instruction S6 and the buffer position instruction S5 generated in the compression spring model 100 are output to the buffer load instruction delay unit 110 and the buffer position instruction delay unit 120, respectively.

[0109] The buffer load instruction delay unit 110 and the buffer position instruction delay unit 120 delay the buffer load instruction S6 and the buffer position instruction S5, respectively, and output them to the positive input terminals of the adder 112 and 122.

[0110] The negative input terminal of the adder 122 is applied with the buffer position signal D1 from the position sensor 17. The adder 122 calculates the deviation (first deviation) between the delayed buffer position instruction S5 and the buffer position signal D1, and outputs the calculated first deviation to the buffer position controller 126.

[0111] In addition, the negative input terminal of the adder 112 is applied with a signal indicating the upward load of the buffer pin 14 from the buffer load converter 114. The adder 112 calculates the deviation (second deviation) between the delayed buffer load instruction S6 and the signal indicating the buffer load, and outputs the calculated second deviation to the buffer load controller 116.

[0112] It should be noted that the buffer load converter 114 receives an input of a pressure signal D2 indicating the pressure of the lower chamber 12a of the hydraulic cylinder 12 from the pressure sensor 18, calculates the upward load applied to the buffer pin 14 from the hydraulic cylinder 12 based on the pressure of the lower chamber 12a of the hydraulic cylinder 12 and the cross-sectional area of the lower chamber 12a of the hydraulic cylinder 12, and outputs a signal indicating the calculated load (buffer load) to the negative input terminal of the adder 112.

[0113] The buffer position controller 126 generates a first speed command S1 as part of a control command based on a first deviation input thereto, and outputs the first speed command S1 to the adder 118, while the buffer load controller 116 generates a second speed command S2 as part of a control command based on a second deviation input thereto, and outputs the second speed command S2 to the adder 118.

[0114] The adder 118 adds the first speed command S1, the second speed command, and the third speed command S3 and outputs the added speed command to the speed controller 40.

[0115] The speed controller 40 outputs a drive signal to the drive motor 50 such that the rotational speed of the drive motor 50 is equal to the target speed indicated by the input speed command, and the speed controller 40 can be configured by, for example, a proportional-integral-derivative (PID) controller.

[0116] The drive shaft of the drive motor 50 is directly connected to the drive shaft of the hydraulic pump 60 or connected through a speed reducer, and the hydraulic pump 60 supplies an oil amount depending on the rotational speed of the drive motor 50 to the hydraulic cylinder 12 or rotates using the pressure oil ejected from the hydraulic cylinder 12. It should be noted that in the case where the hydraulic pump 60 rotates using the pressure oil ejected from the hydraulic cylinder 12, the hydraulic pump 60 acts as a hydraulic motor.

[0117] It should be noted that although the buffer load command S6 is output according to the compression spring model 100 of the above-described embodiment, a pressure command obtained by converting the buffer load command S6 by the cylinder area may be output instead of the buffer load command S6. In other words, the buffer load indicated by the buffer load command S is divided by the cross-sectional area of the lower chamber 12a of the hydraulic cylinder 12 to convert it into pressure, and a pressure name indicating the pressure may be output. In this case, the buffer load converter 114 for converting the pressure signal D2 into a buffer load signal is no longer required. Further, the buffer load command delay unit 110 is now a delay unit for delaying a pressure command, and the buffer load controller 116 is now a pressure controller.

[0118] Although the feedforward control using the third speed command S3 is controlled such that the buffer position is equal to the buffer unloaded position, since there are errors between the buffer position and the buffer load involved in the operation of the extrusion slider 4 during the control and the theoretical values, in order to correct the position error and the load error respectively, feedback control is performed using the first speed command S1 and the second speed command S2.

[0119] Figure 1The die cushion control device of the illustrated embodiment eliminates the switching between position control and load control, and is characterized by always operating the position control and the load control, referring to the load characteristic curve of the compression spring according to the cushion position signal D1 indicating the end position of the cushion pin 14 detected by the position sensor 17, and outputting a cushion position command S5 and a cushion load command S6 for cushion position control and cushion load control.

[0120] Figure 5 is a diagram showing Figure 1 the main part of the die cushion device shown.

[0121] Referring to Figure 5 , the drive motor 50 is controlled by Figure 1 the die cushion control device including a processor 30 and a speed controller 40 shown, and the hydraulic cylinder 12 is controlled by a hydraulic pump 60 whose drive shaft is connected to the drive motor 50.

[0122] When the rotational driving force is transmitted from the drive motor 50 to the hydraulic pump 60 and the hydraulic oil flows from the upper chamber 12b in the hydraulic cylinder 12 to the lower chamber 12a (when the hydraulic oil flows in the direction shown by the solid line arrow), the cushion pin 14 moves in the upward direction, and when the upward movement of the cushion pin 14 is restricted by the squeeze slider 4, the upward load (cushion load) on the cushion pin 14 increases.

[0123] In addition, when the hydraulic oil flows from the lower chamber 12a in the hydraulic cylinder 12 to the upper chamber 12b through the hydraulic pump 60 (when the hydraulic oil flows in the direction shown by the dashed line arrow), the cushion pin 14 moves in the downward direction and the cushion load also decreases. It should be noted that the excessive or insufficient hydraulic oil caused by the difference in the cross-sectional areas of the lower chamber 12a and the upper chamber 12b in the hydraulic cylinder 12 is supplied from or discharged to the oil tank 62.

[0124] Figures 6 to 9 Each of

[0125] [Cushion position control]

[0126] Figure 6 is a diagram showing an example of a method by which the die cushion control device generates a speed command for controlling the cushion position.

[0127] As Figure 6 shown, time 0 [s] is set as a reference, the end position of the cushion pin 14 at time 0 [s] is at a height of H [mm] from the top surface of the moving platen (MB), and the target position of the cushion position is 0 [mm] ( Figure 6(height H in ), the buffer position command is 0 [mm]. The height of the lower chamber 12a of the hydraulic cylinder 12 is also set to 0 [mm] ( Figure 6 L [mm] in ).

[0128] Thereafter, if at time ΔT, the buffer position is lowered by X [mm] from the reference, the buffer position command (first deviation) of the buffer position relative to the reference is -X [mm] (i.e., the target height of the lower chamber 12a of the hydraulic cylinder 12 is equal to -X [mm]), and the amount of oil M1 (first supply amount) to be supplied to the lower chamber 12a of the hydraulic cylinder 12 can be expressed by the following equation:

[0129] [Equation 2] M1 = -X × piston area (lower chamber) [mm 3 .

[0130] In this case, since the amount of oil M1 is negative, the amount of oil M1 is discharged from the lower chamber 12a of the hydraulic cylinder 12.

[0131] The rotation angle θ1 of the drive motor 50 for discharging the amount of oil M1 from the lower chamber 12a of the hydraulic cylinder 12 is set, and the rotation angle θ1 can be expressed by the following equation:

[0132] [Equation 3] θ1 = (M1 / volume of oil pushed by one revolution of the hydraulic pump 60) × 360,

[0133] The angular velocity ω1 is expressed as ω1 = θ1 / ΔT. Figure 1 The buffer position controller 126 shown outputs a speed command indicating the angular velocity ω1 as the first speed command S1.

[0134] Based on the speed command calculated in this way, the rotational speed of the drive motor 50 (the rotational speed of the hydraulic pump 60 whose drive shaft is connected to the drive motor 50) is controlled by the speed controller 40 so that the end position (buffer position) of the buffer pin 14 can be lowered by X [mm].

[0135] [Buffer load control]

[0136] Figure 7 is a diagram showing an example of a method by which the die cushion control device generates a speed command for controlling the buffer load.

[0137] As Figure 7 shown, time 0 [s] is set as the reference, and the upward load (buffer load) of the buffer pin 14 at time 0 [s] is set to 0 [kN].

[0138] Thereafter, if at time ΔT, the buffer load increases by P [kN] from the reference, the buffer load command (second deviation) for the buffer position relative to the reference is P [kN], and the amount of oil M2 (second supply amount) to be supplied to the lower chamber 12a of the hydraulic cylinder 12 can be obtained by the following equation:

[0139] [Equation 4] M2 = P × (oil volume in the hydraulic circuit) / bulk modulus.

[0140] By supplying the hydraulic oil amount M2 to the lower chamber 12a of the hydraulic cylinder 12, the upward load (buffer load) of the buffer pin 14 can be increased by P [kN].

[0141] If the rotation angle of the drive motor 50 for supplying the oil amount M2 to the lower chamber 12a of the hydraulic cylinder 12 is set as θ2, the rotation angle θ2 can be expressed by the following equation:

[0142] [Equation 5] θ2 = (M2 / oil amount pushed by the hydraulic pump 60 in one rotation) × 360,

[0143] The angular velocity ω2 is expressed as ω2 = θ2 / ΔT. Figure 1 The shown buffer load controller 116 outputs a speed command indicating the angular velocity ω2 as the second speed command S2.

[0144] Based on the speed command calculated in this way, the rotational speed of the drive motor 50 is controlled by the speed controller 40 so that the upward load (buffer load) of the buffer pin 14 can be increased by P [kN].

[0145] [Buffer position control + buffer load control]

[0146] Figure 8 is a diagram showing an example of a method by which the die buffer control device generates speed commands for controlling the buffer position and buffer load.

[0147] As Figure 8 shown, time 0 [s] is set as the reference, the end position (buffer position) of the buffer pin 14 at time 0 [s] is at a height of H [mm] from the top surface of the moving platen (MB), and the upward load (buffer load) of the buffer pin 14 is 0 [kN].

[0148] Then, at time ΔT, when the buffer position is lowered by X [mm] from the reference and the buffer load is increased by P [kN], the amounts of oil M1 and M2 to be supplied to the lower chamber 12a of the hydraulic cylinder 12 are calculated by using the aforementioned equations [Equation 2] and [Equation 4]. Further, the rotation angles θ1 and θ2 of the drive motor 50 are obtained by using equations [Equation 3] and [Equation 5] based on the calculated M1 and M2, and the first speed command S1 for buffer position control and the second speed command S2 for buffer load control are obtained.

[0149] Based on the speed command obtained by adding the first speed command S1 and the second speed command S2, the speed controller 40 controls the rotational speed of the drive motor 50 so that the end position (buffer position) of the buffer pin 14 can be lowered by X [mm] and the upward load (buffer load) of the buffer pin 14 can be increased by P [kN].

[0150] [Variant Example of Buffer Position Control + Buffer Load Control]

[0151] Figure 9 is a diagram showing another example of a method for generating speed commands for controlling buffer position and buffer load by a die cushion control device.

[0152] Figure 9 The method for generating speed commands shown is Figure 8 a variant example of the method for generating speed commands shown, and the key point of calculating the amounts of oil M1 and M2 to be supplied to the lower chamber 12a of the hydraulic cylinder 12 for controlling the buffer position and buffer load is the same as Figure 8 the method for generating speed commands shown.

[0153] Figure 9 For the method for generating speed commands shown, the amounts of oil M1 and M2 are converted, and the total oil supply amount M3 (= M1 + M2) to the lower chamber 12a of the hydraulic cylinder 12 is calculated.

[0154] If the rotation angle of the drive motor 50 for supplying the amount of oil M3 to the lower chamber 12a of the hydraulic cylinder 12 is set as θ3, the rotation angle θ3 can be expressed by the following equation:

[0155] [Equation 6] θ3 = (M3 / the amount of oil displaced by one rotation of the hydraulic pump 60) × 360,

[0156] The angular velocity ω3 is expressed as ω3 = θ3 / ΔT. Then, the die cushion control device outputs a speed command indicating the angular velocity ω3 to the speed controller 40.

[0157] Based on the calculated speed command in this way, the rotational speed of the drive motor 50 is controlled by the speed controller 40 so that the end position (buffer position) of the buffer pin 14 can be lowered by X [mm], and the upward load (buffer load) of the buffer pin 14 can be increased by P [kN].

[0158] [Effect of Die Buffer Control Device]

[0159] Figure 10 is a graph showing the position of the extrusion slider, the buffer position, the buffer load, and the buffer unloaded load position, and it is a graph showing the effect of the die buffer control device according to the subject matter of the present disclosure.

[0160] Figure 10 The graph shown in (B) in Figure 10 is an enlarged graph of the main part of the graph shown in (A) in

[0161] Refer to Figure 10 , in order to make the hydraulic cylinder work as a compression spring, the loop gain of the position control and the target value of the load control (buffer load command) are changed. When the hydraulic cylinder 12 is pushed downward by the extrusion slider 4 and is in the contact position (the position where the workpiece 16 is extruded), the buffer target load in the die buffer device (test device) of this example is equal to 200 [kN], which causes the position loop gain to be equal to zero and realizes the control following the set load (200 [kN]).

[0162] When the extrusion slider 4 and the buffer pin 14 are not in contact and no pressure (buffer load) appears, the hydraulic cylinder 12 rises, but as the hydraulic cylinder 12 rises, the target load (buffer load command) gradually decreases as shown in the graph in Figure 10 (C), the target load reaches zero at the unloaded load position, and the rising stops. In this example, when the buffer pin 14 rises 10 [mm] relative to the contact position (reaches the buffer unloaded load position), the buffer load command is equal to zero, and the buffer pin 14 will not be pushed upward beyond the buffer unloaded load position.

[0163] Although the target load reaches zero at the buffer unloaded load position and there is no position binding force acting under the buffer load control in this way, the position loop gain is 100%, and the buffer position control starts, thereby constraining the end position (buffer position) of the buffer pin 14 at the buffer unloaded load position.

[0164] In Figure 10In the example shown in (A), the extrusion slider 4 contacts the end position of the buffer pin 14 (the extrusion slider reaches the buffer position). Then, as the extrusion slider 4 gradually drops, the deflection length of the compression spring gradually increases. Then, when the extrusion slider 4 reaches the contact position with the buffer pin 14, the deflection length is equal to the target deflection length (10 [mm] in this example), and the buffer load is equal to the target load (set load).

[0165] Then, when the extrusion slider 4 drops further, the target deflection length is maintained. In other words, during the extrusion process, the buffer load is maintained at the set load.

[0166] Figures 11 to 14 Each of which shows Figure 3 A schematic diagram of the operating states of the die buffer device body and the like shown. Therefore, from Figures 11 to 14 The illustration of the common part with Figure 3 Is partially omitted.

[0167] Figure 11 Is a schematic diagram showing the state where the extrusion slider 4 is above the buffer pin 14 and separated from the buffer pin 14.

[0168] In the separated state, position control is performed such that the buffer load command is equal to zero, the position loop gain ratio of the buffer position controller 126 is equal to 100%, and the end position (buffer position) of the buffer pin 14 is maintained at the buffer unloaded position. Therefore, when the hydraulic cylinder 12 is set as the compression spring, the deflection length of the compression spring is equal to zero.

[0169] Figure 12 Is a schematic diagram showing the state where the extrusion slider 4 contacts the buffer pin 14 and the buffer pin 14 is slightly pressed downward.

[0170] In the contact / press-down state, the buffer load command is a load command depending on the compression spring characteristics, and the upward load (buffer load) of the buffer pin 14 is controlled by a buffer load command depending on the compression spring characteristics (buffer load command corresponding to the deflection length).

[0171] In other words, the hydraulic cylinder 12 is controlled to generate a buffer load corresponding to the deflection length of the compression spring. It should be noted that the length of the lower chamber 12a of the hydraulic cylinder 12 is shortened by a length corresponding to the deflection length of the compression spring relative to the separated state.

[0172] On the other hand, the position loop gain ratio of the buffer position controller 126 is equal to 0%, and the position constraint of the buffer position controller 126 on the hydraulic cylinder 12 does not work.

[0173] Figure 13 Is a schematic diagram showing the extrusion slider 4 fromFigure 12 Schematic diagram of the state where the shown state further drops and the buffer load reaches the set load.

[0174] In the state where the set load is reached, the buffer load command is a buffer load command corresponding to the target deflection length, and the buffer load is controlled to be the set load.

[0175] It should be noted that the length of the lower chamber 12a of the hydraulic cylinder 12 is shortened by a length corresponding to the target deflection length relative to the separated state. Additionally, similar to the contact / downward extrusion state, the buffer position controller 126 does not act on the position constraint of the hydraulic cylinder 12.

[0176] Figure 14 Shows the extrusion slider 4 falling from Figure 13 Schematic diagram of the state where the shown state further drops and maintains the set load during the fall (during the extrusion process).

[0177] In the state where the set load is maintained, the buffer load command is maintained as a buffer load command corresponding to the target deflection length, and the buffer load is controlled to be the set load.

[0178] Therefore, the pressure in the lower chamber 12a of the hydraulic cylinder 12 is maintained as Figure 13 The pressure when the set load is reached as shown. In other words, the hydraulic pump 60 driven by the drive motor 50 maintains the pressure in the lower chamber 12a of the hydraulic cylinder 12 as a pressure corresponding to the set load, and at the same time is driven to eject an amount of oil corresponding to the fall of the extrusion slider 4 from the lower chamber 12a of the hydraulic cylinder 12.

[0179] [Comparison between the subject matter of the present disclosure and conventional techniques]

[0180] Figure 15 Is a chart showing the operations of each component in the case of performing a normal extrusion process operation using a conventional die buffer control device.

[0181] In Figure 15 In the example of the normal operation as shown, when the falling extrusion position (the position of the lower surface of the upper die attached to the extrusion slider 4) and the standby buffer position (100 [mm] in this example) match, the buffer control switches from the buffer position control mode to the buffer load control mode, and the extrusion process is performed with a set buffer load (200 [kN] in this example).

[0182] Figure 16 Is a chart showing the operations of each component in the case of an abnormal operation of a conventional die buffer control device.

[0183] Figure 16The example shown is an example of extrusion processing in a state where the actual extrusion value at the extrusion position is higher than the planned extrusion value due to, for example, a die height setting error of a press. The conventional buffer control device starts applying pressure to the hydraulic oil in the lower chamber of the hydraulic cylinder at the timing of the start angle of the buffer load control obtained from the crankshaft encoder to increase the buffer load. However, the buffer pin cannot contact the upper die of the extrusion slider, and the buffer position continuously rises beyond the standby position (100 [mm]).

[0184] The rising operation of the buffer is an abnormal detection condition, and the press system performs an emergency stop. However, the buffer pin continuously rises beyond the standby position (100 [mm]) (the buffer pin is pushed upward beyond the standby position). Applying a large buffer force (buffer load) when pushing the buffer pin upward may damage the die and / or the workpiece.

[0185] Measures to advance the abnormal detection timing can be regarded as a damage prevention solution, but it is difficult to manage the relationship between the pressure reduction after abnormal detection and the runaway stroke. Additionally, when designing the die, it is necessary to consider the runaway stroke when a buffer abnormality occurs, which may cause disadvantages such as an increase in die cost.

[0186] Figure 17 It is a diagram showing the operation of each component when controlling the die buffer device body by the die buffer control device according to the subject matter of the present disclosure.

[0187] Same as Figure 16 the example in Figure 17 The example shown is an example of extrusion processing in a state where the actual extrusion value at the extrusion position is higher than the planned extrusion value due to, for example, a die height setting error of a press.

[0188] Although the die buffer control device according to the subject matter of the present disclosure starts applying pressure to the hydraulic oil in the lower chamber 12a of the hydraulic cylinder 12 at the timing of the start angle of the buffer load control (extrusion slider position of the planned extrusion value) obtained from the crankshaft encoder 5 to increase the buffer load, when the buffer position reaches the buffer unloaded position as the standby position (100 [mm]), even if the buffer pin 14 does not contact the upper die of the extrusion slider 4, the buffer load command is zero, and the end position (buffer position) of the buffer pin 14 does not rise beyond the buffer unloaded position.

[0189] Refer to Figure 17 the diagram showing the buffer position in

[0190] Therefore, the dropping operation can be performed according to the planned / managed buffer operation, thereby preventing damage to the die and the like.

[0191] [Die Buffer Control Method]

[0192] Figure 18 is a flowchart showing an embodiment of a die buffer control method according to the subject matter of the present disclosure.

[0193] It should be noted that Figure 18 the shown die buffer control method is a method to be executed by Figure 1 the processor 30 in the shown die buffer control device.

[0194] Referring to Figure 18 , the compression spring model 100 in the processor 30 obtains a target deflection length (step S10). The target deflection length can be obtained by calculation by the target deflection length calculator 101 ( Figure 4 ), or can be obtained by reading out the target deflection length pre-calculated and stored in the storage unit.

[0195] Then, based on the crank angle signal indicating the crank angle detected by the crankshaft encoder 5 or the slider position signal indicating the position of the extrusion slider 4 converted from the crank angle, each of the buffer target load command C1 and the buffer target position command C2 is obtained, the buffer position signal D1 is obtained from the position sensor 17, and a buffer load signal indicating the buffer load converted from the pressure detected by the pressure sensor 18 is obtained (step S12).

[0196] In step S14, based on the buffer target position command C2, the buffer position signal D1, and the buffer load command obtained in step S12, a buffer position command S5 is generated. The buffer load command is the buffer load command S6 generated by step S16, and for example, if the buffer load command S6 is less than or equal to the holding load of the blank holder 15 or the like, the buffer target position command C2 is output as the buffer position command S5, and if the buffer load command S6 exceeds the holding load, the buffer position signal D1 is output as the buffer position command S5. Since if the latter buffer position command S5 is output, the buffer position command S5 matches the buffer position signal D1, the buffer position control operation does not limit the operation of the hydraulic cylinder 12.

[0197] In addition, in step S16, a buffer load command S6 is generated based on the target deflection length obtained in step S10 and the buffer target load command C1, buffer target position command C2, and buffer position signal D1 obtained in step S12. More specifically, the buffer load command S6 is calculated by the aforementioned equation [Equation 1]. In addition, the "deflection length" in Equation [Equation 1] can be obtained by adding the target deflection length to the position deviation obtained by subtracting the buffer position signal D1 from the buffer target position command C2.

[0198] If the deflection length is equal to the target deflection length, the buffer load command S6 is the buffer target load command C1 (a command indicating the set load), and the buffer target load command C1 is a command indicating a buffer load that decreases proportionally with the decrease in the deflection length, and is a command indicating a buffer load of 0 [kN] when the deflection length is equal to 0 [mm].

[0199] Further, in step S18, the target deflection length obtained in step S10 and the buffer target position command C2 obtained in step S12 are added, and the added value is generated as the buffer unloaded load position command.

[0200] Next, in step S20, based on the deviation (the first deviation) between the buffer position command S5 generated in step S14 and the buffer position signal D1, a first speed command S1 required to process the buffer position as the target position is generated.

[0201] The generation of the first speed command S1 is performed as follows. The amount of oil M1 to be supplied to the hydraulic cylinder 12 is obtained by multiplying the first deviation by the piston area (see Equation [Equation 2]). The rotation angle θ1 of the drive motor 50 for supplying the amount of oil M1 from the hydraulic pump 60 to the hydraulic cylinder 12 is calculated by dividing the amount of oil M1 by the discharge amount of one rotation of the hydraulic pump 60 (see Equation [Equation 3]). Then, the first speed command S1 of the drive motor 50 is generated by obtaining the rotation angle θ1 of the drive motor 50 based on the first deviation per unit time.

[0202] In addition, in step S22, based on the deviation (the second deviation) between the buffer load command S6 generated in step S16 and the buffer load signal obtained in step S12, a second speed command S2 required to process the buffer load as the target load is generated.

[0203] The generation of the second speed command S2 is performed as follows. Based on the second deviation, the oil volume in the hydraulic circuit, and the bulk modulus of the hydraulic oil, the oil volume M2 required to increase the buffer load by only the second deviation is calculated for the hydraulic cylinder 12 (see Equation [Equation 4]). By dividing the oil volume M2 by the discharge volume per revolution of the hydraulic pump 60, the rotation angle θ2 of the drive motor 50 for supplying the oil volume M2 from the hydraulic pump 60 to the hydraulic cylinder 12 is calculated (see Equation [Equation 5]). Then, the second speed command S2 for the drive motor 50 is generated by obtaining the rotation angle θ2 of the drive motor 50 based on the second deviation per unit time.

[0204] Further, in step S24, a third speed command S3 is generated based on the buffer unloaded position command generated in step S18. The generation of the third speed command S3 is performed as follows: the displacement of the hydraulic cylinder per unit time is obtained by time-differentiating the buffer unloaded position command, and the displacement per unit time is converted into the speed of the drive motor 50.

[0205] Next, the first speed command S1, the second speed command S2, and the third speed command S3 generated in steps S20, S22, and S24 are added together to obtain a speed command, and the obtained speed command is output to the speed controller 40 (step S26).

[0206] Subsequently, the processor 30 determines whether the extrusion process (die cushion control) of the press is completed, and if the die cushion control is to continue (if "no"), it returns to step S12 and repeats the processing from step S12 to step S28, while if the die cushion control is completed (if "yes"), the processing is ended (step S28).

[0207] [Other]

[0208] Although one hydraulic cylinder 12 is provided in the die cushion device of this embodiment, the number of hydraulic cylinders 12 is not limited to this. In addition, although one set of drive motor 50 + hydraulic pump 60 is used for one hydraulic cylinder 12, the number is not limited to this, and two or more sets may be arranged in parallel for one hydraulic cylinder 12.

[0209] In addition, the case where oil is used as the hydraulic fluid for the hydraulic cylinder 12 and the hydraulic pump 60 is described, but the hydraulic fluid is not limited to this, and water or other liquids may also be used.

[0210] In an embodiment, the hardware structure of a processing unit that performs various processes (such as the processor 30 in a die buffer control device) is, for example, various processors as will be described below. The various processors include: a central processing unit (CPU), which is a general-purpose processor that executes software (program) and serves as various processing units; a programmable logic device (PLD), which is a processor having a circuit configuration that can be changed after manufacturing, such as a field-programmable gate array (FPGA); and an application-specific circuit, which is a processor having a circuit configuration specifically designed to execute a specific process, such as an application-specific integrated circuit (ASIC).

[0211] A processing unit may be configured by one of these various processors, or may be configured by two or more processors of the same type or different types (for example, a combination of an FPGA or a CPU and an FPGA). Additionally, a processing unit may be configured by one processor. As an example of a processing unit being configured by one processor, first, there is an aspect in which one processor is configured by a combination of one or more CPUs and software, represented by a computer such as a client or a server, where the processor serves as the processing unit. Second, there is an aspect in which a processor is used that applies an integrated circuit (IC) chip to implement the functions of an entire system including the processing unit, represented by a system-on-chip (SoC). In this way, various processing units are configured by adopting one or more of the various processors as described above as the hardware structure.

[0212] Additionally, the hardware structure of those various processors is more specifically a circuit system in which circuit elements such as semiconductor elements are combined.

[0213] Furthermore, the subject matter of the present disclosure is not limited to the above-described embodiments, and it is needless to say that various variations are possible without departing from the scope and spirit of the subject matter of the present disclosure.

[0214] List of reference numerals

[0215] 1: Press, 2: Crankshaft, 3: Connecting rod, 4: Extrusion slider, 5: Crankshaft encoder, 10: Die cushion equipment body, 12: Hydraulic cylinder, 14: Buffer pin, 15: Blank holder, 16: Workpiece, 17: Position sensor, 18: Pressure sensor, 20: Buffer target load command device, 22: Buffer target position command device, 30: Processor, 40: Speed controller, 50: Drive motor, 60: Hydraulic pump, 62: Oil tank, 100: Compression spring model, 101: Target deflection length calculator, 102: Buffer load command generator, 103, 105, 112, 118, 122: Adder, 104: Motor speed converter, 106: Buffer position command generator, 107: Hydraulic circuit parameter, 110: Buffer load command delay unit, 114: Buffer load converter, 116: Buffer load controller, 120: Buffer position command delay unit, and 126: Buffer position controller.

Claims

1. A die buffer control device for a die buffer device, the die buffer device comprising: a hydraulic cylinder supporting a buffer load generating member, wherein the buffer load generating member generates a buffer load; a hydraulic cylinder driving device, the hydraulic cylinder driving device comprising a driving motor and a hydraulic pump to be driven by the driving motor, and the hydraulic cylinder driving device drives the hydraulic cylinder; A buffer target position instruction device and a buffer target load instruction device, wherein the buffer target position instruction device and the buffer target load instruction device respectively output a buffer target position instruction and a buffer target load instruction according to a crank angle of a press machine or a position of an extrusion slide; a position sensor that detects a position of the buffer load generating member as a buffer position; as well as A pressure sensor, the pressure sensor detecting the pressure of the lower chamber of the hydraulic cylinder, wherein The die buffer control device includes a processor and a controller for controlling the drive motor according to an input control instruction; The processor: The hydraulic cylinder is set to include a compression spring model, and when the upward load of the buffer load generating member is equal to a preset set load, the deflection length of the compression spring is obtained as a target deflection length; generating a buffer load command or a pressure command obtained by converting the buffer load command into a cylinder area based on the buffer target load command, the target deflection length, the buffer target position command, and the buffer position; and The control command is generated based on a second deviation between the cushion load command and the cushion load converted from the pressure detected by the pressure sensor or a second deviation between the pressure command and the pressure detected by the pressure sensor.

2. The die cushion control device according to claim 1, wherein the processor calculates a deflection length of the compression spring based on the cushion target position command, the target deflection length, and the cushion position, and calculates the cushion load command by the following equation based on the calculated deflection length and the target deflection length and the cushion target position command: Buffer load command = (buffer target load command / target deflection length) × deflection length.

3. The die cushion control device according to claim 1, wherein the processor: generating a buffer position instruction based on the buffer target position instruction and the buffer position, and The control command is generated based on a first deviation between the buffer position command and the buffer position.

4. The die cushion control device according to claim 3, wherein: If the buffer load instruction or the pressure instruction is less than or equal to zero or a predetermined value, the processor generates the buffer target position instruction as the buffer position instruction, and If the buffer load command or the pressure command is greater than zero or the predetermined value, the processor generates the buffer position as the buffer position command.

5. The die cushion control device according to claim 4, wherein the processor: calculating a first supply amount of hydraulic fluid to be supplied to an upper chamber or a lower chamber of the hydraulic cylinder required to make the position of the buffer load generating member reach a buffer position corresponding to the buffer position command based on the first deviation, and calculating a second supply amount of hydraulic fluid to be supplied to the lower chamber of the hydraulic cylinder required to make the upward load of the buffer load generating member reach a buffer load corresponding to the buffer load command based on the second deviation, and The rotation angle of the drive motor is calculated based on the first supply amount and the second supply amount and the amount of hydraulic fluid ejected by the hydraulic pump during one rotation, and the control command is generated based on the rotation angle.

6. The die cushion control device according to any one of claims 3 to 5, wherein: The processor comprises: a buffer position controller, the buffer position controller generating a first speed instruction based on the first deviation; and the buffer position controller or the pressure controller, the buffer position controller or the pressure controller generates a second speed instruction based on the second deviation, and The processor generates the control command by adding the first speed command to the second speed command.

7. The die cushion control device according to claim 6, wherein: The processor: generating a buffer unloaded position command obtained by adding the buffer target position command and the target deflection length; generating a third speed command based on the buffered unloaded position command; as well as The control command is generated by adding the first speed command, the second speed command, and the third speed command.

8. The mold buffer control device according to claim 7, wherein the processor obtains the displacement of the hydraulic cylinder per unit time by time-differentiating the buffer unloaded position instruction, and converts the displacement per unit time into the speed of the drive motor to generate the third speed instruction.

9. The die cushion control apparatus according to claim 7, the processor comprising a delay unit that delays the cushion position instruction to be used for calculating the first deviation and the cushion load instruction or the pressure instruction to be used for calculating the second deviation.

10. The die cushion control apparatus according to any one of claims 1 to 5, wherein the processor calculates the target deflection length based on hydraulic circuit parameters and the set load, the hydraulic circuit parameters comprising: Flow path volume information about a hydraulic circuit of the hydraulic cylinder, a bulk modulus of the hydraulic fluid, and a cylinder diameter of the hydraulic cylinder. 11 . The die cushion control apparatus according to claim 1 , wherein the processor calculates the target deflection length based on a spring constant of the compression spring and the set load. 12 . A die cushion device, comprising the die cushion control device according to claim 1 .

13. A die buffer control method for a die buffer control device of a die buffer device, the die buffer device comprising: a hydraulic cylinder supporting a buffer load generating member, wherein the buffer load generating member generates a buffer load; a hydraulic cylinder driving device, the hydraulic cylinder driving device comprising a driving motor and a hydraulic pump to be driven by the driving motor, and the hydraulic cylinder driving device drives the hydraulic cylinder; A buffer target position instruction device and a buffer target load instruction device, wherein the buffer target position instruction device and the buffer target load instruction device respectively output a buffer target position instruction and a buffer target load instruction according to a crank angle of a press machine or a position of an extrusion slide; a position sensor that detects a position of the buffer load generating member as a buffer position; and A pressure sensor, the pressure sensor detecting the pressure of the lower chamber of the hydraulic cylinder, wherein The processor performs the following steps: The hydraulic cylinder is set to include a compression spring model, and when the upward load of the buffer load generating member is equal to a preset set load, the deflection length of the compression spring is obtained as a target deflection length; Based on the buffer target load command, the target deflection length, the buffer target position command, and the buffer position, generating a buffer load command or a pressure command obtained by converting the buffer load command with a cylinder area; generating a control command based on a second deviation between the buffer load command and the buffer load converted from the pressure detected by the pressure sensor or a second deviation between the pressure command and the pressure detected by the pressure sensor; and The generated control command is output to a speed controller for controlling the drive motor.

14. The die cushion control method according to claim 13, wherein the processor calculates the deflection length of the compression spring based on the cushion target position command, the target deflection length, and the cushion position, and calculates the cushion load command by the following equation based on the calculated deflection length, the target deflection length, and the cushion target position command: Buffer load command = (buffer target load command / target deflection length) × deflection length.

15. The die cushion control method according to claim 13, comprising the following steps: generating, by the processor, a buffer position instruction based on the buffer target position instruction and the buffer position, and The control command is generated, by the processor, based on the buffer position command and a first deviation between the buffer position.

16. The die cushion control method according to claim 15, wherein: If the buffer load instruction or the pressure instruction is less than or equal to zero or a predetermined value, the processor generates the buffer target position instruction as the buffer position instruction, and If the buffer load command or the pressure command is greater than zero or the predetermined value, the processor generates the buffer position as the buffer position command.

17. The die cushion control method according to claim 16, comprising the following steps: calculating, by the processor, a first supply amount of the hydraulic fluid to be supplied to the upper chamber or the lower chamber of the hydraulic cylinder required to make the position of the buffer load generating member reach the buffer position corresponding to the buffer position instruction based on the first deviation, and calculating a second supply amount of the hydraulic fluid to be supplied to the lower chamber of the hydraulic cylinder required to make the upward load of the buffer load generating member reach the buffer load corresponding to the buffer load instruction based on the second deviation, and The processor calculates a rotation angle of the drive motor based on the first supply amount and the second supply amount and the amount of hydraulic fluid ejected by the hydraulic pump during one rotation, and generates the control command based on the rotation angle.

18. The die cushion control method according to any one of claims 15 to 17, wherein the processor performs the following steps: generating a first speed instruction based on the first deviation; generating a second speed command based on the second deviation; and The control command is generated by adding the first speed command to the second speed command.

19. The die cushion control method according to claim 18, wherein the processor performs the following steps: generating a buffer unloaded position command obtained by adding the buffer target position command and the target deflection length; generating a third speed command based on the buffered unloaded position command; and The control command is generated by adding the first speed command, the second speed command, and the third speed command.

20. The die buffer control method according to claim 19, wherein the processor obtains the displacement of the hydraulic cylinder per unit time by time-differentiating the buffer unloaded position command, and converts the calculated displacement into the speed of the drive motor to generate the third speed command.

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