Die cushion control device and method, and die cushion apparatus

Abstract

To provide a die cushion control device and method capable of suppressing abnormal operation of a cushion pin, and to provide a die cushion device.SOLUTION: A compression spring model 100 included in a processor of a die cushion control device refers to a load characteristic curve of a compression spring when a hydraulic cylinder 12 is assumed to be the compression spring, generates a cushion load command according to a spring constant and a deflection amount of the compression spring, and generates a control command based on a deviation between the generated cushion load command and an actual cushion load. The drive motor 50 and the hydraulic motor 60 are driven in accordance with the control command, and an upward load is generated in the cushion pin 14 by the hydraulic cylinder 12. Thus, even when the cushion pin 14 is raised by the setting mistake of the press die height or the like, the cushion load command is reduced according to the deflection amount of the compression spring, and the abnormal pushing-up operation of the cushion pin 14 is suppressed.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a cushion control device and method and a cushion device, and particularly to a technique for preventing the upward push of a cushion pin.

Background Art

[0002] A cushion device is a device that generates an upward pressure on a cushion pin and generates a reaction force for suppressing wrinkles during the drawing process of a workpiece.

[0003] The cushion device holds the position of the cushion pin at a predetermined position in order to support the workpiece when the height of the lower surface of the upper die fixed to the press slide of the press machine is higher than the workpiece disposed on the lower die. When the height of the lower surface of the upper die becomes lower than or equal to the workpiece disposed on the upper surface of the lower die, the cushion pin generates a reaction force for the drawing process and plays a role in suppressing the periphery of the workpiece.

[0004] Generally, for the switching from the position control for holding the position of the cushion pin to the pressure control for generating the reaction force for the drawing process on the cushion pin, a switching method in accordance with the height of the press slide (the lower surface of the upper die) is used (Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the method of switching between position control and pressure control as described in Patent Documents 1 and 2, when the timing of contact between the upper die and the workpiece does not match the timing at which the control state of the cushioning device switches from position control to pressure control, the following problems occur.

[0007] For example, if the pressure control switches before the upper die contacts the workpiece, the cushion pin will continue to rise until it is mechanically restrained, which may damage the workpiece or break the die.

[0008] Factors for the non - matching switching timing include setting errors of the press die height, thickness errors of the upper and lower dies, and thickness variations of the workpiece. Even if the controller detects the abnormal operation caused by these incorrect operations or settings in some way and cuts off the position holding force or pressure applied to the cushion pin, it is impossible to completely suppress the abnormal operation of the cushion pin due to inertial force and residual pressure.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide a cushioning control device, a method, and a cushioning device capable of suppressing abnormal operation of a cushion pin.

Means for Solving the Problems

[0010] In order to achieve the above object, the invention according to the first aspect includes a hydraulic cylinder that supports a cushion load generating member that generates a cushion load, a drive motor, and a hydraulic pump driven by the drive motor, and a hydraulic cylinder drive device that drives the hydraulic cylinder. A cushion target position command device and a cushion target load command device that output a cushion target position command and a cushion target load command, respectively, according to the crank angle of the press machine or the position of the press slide, a position sensor that detects the position of the cushion load generating member, and a pressure sensor that detects the pressure in the lower chamber of the hydraulic cylinder. In the cushion control device of the die cushion device, the cushion control device includes a processor and a controller that controls the drive motor according to an input control command. When the hydraulic cylinder is assumed to be a compression spring model, the processor obtains the deflection length of the compression spring when the upward load of the cushion load generating member reaches a preset load as the target deflection length, and based on the cushion target load command, the target deflection length, the cushion target position command, and the cushion position, which is the position of the cushion load generating member detected by the position sensor, generates a cushion load command or a pressure command obtained by converting the cushion load command by the cylinder area, and generates the control command based on the second deviation between the cushion load command and the cushion load converted from the pressure detected by the pressure sensor, or the second deviation between the pressure command and the pressure detected by the pressure sensor. It is a cushion control device.

[0011] According to the first aspect of the present invention, referring to the load characteristic curve of the compression spring when the hydraulic cylinder is assumed to be a compression spring, a cushion load command or a pressure command is generated from the cushion position detected by the position sensor. Then, a control command is generated based on the second deviation between the generated cushion load command and the cushion load converted from the pressure detected by the pressure sensor, or the second deviation between the pressure command and the pressure detected by the pressure sensor, and the drive motor is controlled according to this control command. Therefore, even if there is a setting error in the press die height or the like, it is possible to control so that there is no abnormal pushing up of the cushion pin.

[0012] In the second aspect of the present invention, in the first aspect, 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 based on the calculated deflection length, the target deflection length, and the cushion target position command using the following formula: Cushion load command = (Cushion target load command / Target deflection length) × Deflection length It is preferably calculated by.

[0013] Accordingly, when the deflection length is zero, the cushion load command or the pressure command becomes zero, the cushion load command or the pressure command increases in proportion to the deflection length, and when 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 when contact with the upper die of the press slide cannot be obtained, the cushion pin does not rise beyond the position where the deflection length becomes zero.

[0014] In the third aspect of the present invention, in the first or second aspect, the processor preferably generates a cushion position command based on the cushion target position command and the cushion position, and generates the control command based on a first deviation between the cushion position command and the cushion position.

[0015] In the fourth aspect of the present invention, in the third aspect, when the cushion load command or the pressure command is zero or less than a set predetermined value, the processor preferably generates the cushion target position command as the cushion position command, and when the cushion load command or the pressure command is zero or exceeds the predetermined value, the processor preferably generates the cushion position as the cushion position command. Thereby, when controlled by the cushion load command or the pressure command, the position loop gain ratio becomes 0%, and control is substantially performed only by the cushion load command or the pressure command.

[0016] In the fifth aspect of the present invention, the cushion control device, in the fourth aspect, in order to move the position of the cushion load generating member to the cushion position corresponding to the cushion position command based on the first deviation, the first supply amount of the hydraulic fluid supplied to the upper chamber or the lower chamber of the hydraulic cylinder is calculated, and the second supply amount of the hydraulic fluid supplied to the lower chamber of the hydraulic cylinder to make the upward load of the cushion load generating member the cushion load corresponding to the cushion load command based on the second deviation is calculated. Then, based on the first supply amount, the second supply amount, and the discharge amount of the hydraulic fluid per one rotation of the hydraulic pump, the rotation angle of the drive motor is calculated, and it is preferable to generate the control command based on the rotation angle.

[0017] In the sixth aspect of the present invention, the cushion control device, in any one of the third aspect to the fourth aspect, the processor includes a cushion position control unit that generates a first speed command based on the first deviation, and a cushion position control unit or a pressure control unit that generates a second speed command based on the second deviation, and it is preferable to add the first speed command and the second speed command to generate the control command.

[0018] According to the fifth aspect or the sixth aspect of the present invention, the switching between the cushion load control (or pressure control) and the cushion position control in the control device is abolished, and the cushion load control (or pressure control) and the cushion position control are always operated. Referring to the load characteristic curve of the compression spring from the information of the cushion position, the cushion load control (pressure control) and the cushion position control can be performed.

[0019] In the seventh aspect of the present invention, the cushion control device, in the sixth aspect, the processor preferably generates a cushion free position command obtained by adding the cushion target position command and the target deflection length, generates a third speed command based on the cushion free position command, and adds the first speed command, the second speed command, and the third speed command to generate the control command. The control by this third speed command is a feedforward control, and highly responsive control can be performed.

[0020] In the eighth aspect of the present invention, in the seventh aspect, it is preferable that the processor obtains the displacement amount of the hydraulic cylinder per unit time by time-differentiating the cushion free position command, and converts the displacement amount per unit time into the speed of the drive motor to generate the third speed command.

[0021] In the ninth aspect of the present invention, in the seventh or eighth aspect, it is preferable that the processor includes a delay unit that delays the cushion position command used for calculating the first deviation and the cushion load command or the pressure command used for calculating the second deviation.

[0022] In the tenth aspect of the present invention, in any one of the first to ninth aspects, it is preferable that the processor calculates the target deflection length based on the flow path volume information of the hydraulic circuit including the hydraulic cylinder, the volume elastic modulus of the working fluid, and the hydraulic circuit parameters including the cylinder diameter of the hydraulic cylinder and the set load.

[0023] In the eleventh aspect of the present invention, in any one of the first to ninth aspects, it is preferable that the processor calculates the target deflection length based on the spring constant of the compression spring and the set load.

[0024] The invention according to the twelfth aspect is a cushioning device including the cushioning control device according to any one of the first to eleventh aspects.

[0025] The invention according to the 13th aspect includes a hydraulic cylinder that supports a cushion load generating member that generates a cushion load, a drive motor, and a hydraulic pump driven by the drive motor, and a hydraulic cylinder drive device that drives the hydraulic cylinder. A cushion target position command device and a cushion target load command device that output a cushion target position command and a cushion target load command respectively according to the crank angle of the press machine or the position of the press slide, 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 the lower chamber of the hydraulic cylinder. In the cushion control method of the cushion control device of the die cushion device, when the hydraulic cylinder is assumed to be a compression spring model, the step of obtaining the deflection length of the compression spring when the upward load of the cushion load generating member reaches a preset load as the target deflection length, and the cushion target load command, the target deflection length, the cushion target position command, and the step of generating a cushion load command based on the cushion position, or a pressure command obtained by converting the cushion load command by the cylinder area, and the second deviation between the cushion load command and the cushion load obtained by converting the pressure detected by the pressure sensor, or the second deviation between the pressure command and the pressure detected by the pressure sensor. The step of generating a control command based on the above, and the step of outputting the generated control command to a speed controller that controls the drive motor are respectively executed by a processor.

[0026] The cushion control method according to the 14th aspect of the present invention is, in the 13th aspect, 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 based on the calculated deflection length, the target deflection length, and the cushion target position command, the cushion load command is calculated by the following formula: Cushion load command = (Cushion target load command / Target deflection length) × Deflection length It is preferably calculated as follows.

[0027] The cushion control method according to the 15th aspect of the present invention is, in the 13th aspect or the 14th aspect, the step in which the processor generates a cushion position command based on the cushion target position command and the cushion position, and the step in which the processor generates the control command based on a first deviation between the cushion position command and the cushion position. It is preferable to include these steps.

[0028] The cushion control method according to the 16th aspect of the present invention is, in the 15th aspect, when the cushion load command or the pressure command is zero or less than a predetermined value set, the processor generates the cushion target position command as the cushion position command, and when the cushion load command or the pressure command is zero or exceeds the predetermined value, it is preferable to generate the cushion position as the cushion position command.

[0029] The cushion control method according to the 17th aspect of the present invention is, in the 16th aspect, the step in which the processor calculates a first supply amount of the hydraulic fluid supplied to the upper chamber or the lower chamber of the hydraulic cylinder necessary for reaching the position of the cushion load generating member to the cushion position corresponding to the cushion position command based on the first deviation, and a second supply amount of the hydraulic fluid supplied to the lower chamber of the hydraulic cylinder necessary for making the upward load of the cushion load generating member the cushion load corresponding to the cushion load command based on the second deviation, and the step in which the processor calculates the rotation angle of the drive motor based on the first supply amount, the second supply amount, and the discharge amount of the hydraulic fluid per rotation of the hydraulic pump, and generates the control command based on the rotation angle. It is preferable to include these steps.

[0030] The cushion control method according to the 18th aspect of the present invention is, in any one of the 15th aspect to the 17th aspect, the step in which the processor generates a first speed command based on the first deviation, the step in which the processor generates a second speed command based on the second deviation, and the step in which the processor adds the first speed command and the second speed command to generate the control command. It is preferable that the processor executes each of these steps.

[0031] In the cushion control method according to the 19th aspect of the present invention, in the 18th aspect, the steps of generating a cushion free position command obtained by adding the cushion target position command and the target deflection length, generating a third speed command based on the cushion free position command, and generating the control command by adding the first speed command, the second speed command, and the third speed command are preferably executed by the processor respectively.

[0032] In the cushion control method according to the 20th aspect of the present invention, in the 19th aspect, it is preferable that the processor time-differentiates the cushion free position command to calculate the displacement amount of the hydraulic cylinder per unit time, and converts the calculated displacement amount into the speed of the drive motor to generate the third speed command.

Advantages of the Invention

[0033] According to the present invention, even if the cushion load control is started before the upper die and the workpiece come into contact due to a setting error of the press die height or the like, the cushion pin does not rise beyond the preset cushion standby position, thereby preventing damage to the workpiece and the die caused by the upward push of the cushion pin.

Brief Description of the Drawings

[0034]

Figure 1

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Figure 12

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Figure 17

Figure 18

Embodiments for Carrying Out the Invention

[0035] The die cushion control device and method according to the present invention and preferred embodiments of the die cushion device will be described in detail below with reference to the accompanying drawings.

[0036] [Press Machine Equipped with Die Cushion Device] Figure 1 is a configuration diagram showing a press machine equipped with a die cushion device according to the present invention.

[0037] The press machine 1 shown in Figure 1 has a crank mechanism including a crankshaft 2 and a connecting rod 3, and the crankshaft 2 is rotated by a servo motor (not shown). The rotational driving force of the crankshaft 2 is transmitted to a press slide 4 via the connecting rod 3 to reciprocate the press slide 4 in the vertical direction. It is a crank press.

[0038] A crankshaft encoder 5 for detecting the crank angle of the crankshaft 2 is provided on the crankshaft 2. A crank angle signal indicating the crank angle detected by the crankshaft encoder 5 is output to a cushion target load command device 20 and a cushion target position command device 22.

[0039] An upper die (not shown) is mounted on the press slide 4, and a lower die is mounted on a bolster.

[0040] A blank holder 15 is disposed between the upper die and the lower die. The lower side of the blank holder 15 is supported by a cushion pin 14, and a workpiece (work material) 16 is set (contacted) on the upper side.

[0041] The press machine 1 performs press working (drawing in this example) on the workpiece 16 between the upper die and the lower die by lowering the press slide 4. Note that the press machine 1 in this example is a crank press, but the press machine to which the cushioning device according to the present invention is applied is not limited to a crank press and can be applied to various press machines.

[0042] The cushioning device applies a pressing force (cushion load) from below to the periphery of the workpiece 16 to be drawn and plays a role of holding the periphery of the workpiece 16 between the upper die and the blank holder 15.

[0043] The cushioning device is composed of a cushioning device main body 10 and a cushioning control device according to the present invention.

[0044] The cushioning device main body 10 includes a cushion load generating member that generates a cushion load including a cushion pin 14 and a blank holder 15, a hydraulic cylinder (in this example, "hydraulic cylinder") 12 that supports the cushion load generating member, a drive motor 50 and a hydraulic pump (hydraulic pump) 60 driven by the drive motor 50, a hydraulic cylinder drive device (hydraulic cylinder drive device) that drives the hydraulic cylinder 12, a cushion target load command device 20 and a cushion target position command device 22 that output a cushion target load command C1 and a cushion target position command C2 respectively based on a crank angle signal indicating the crank angle detected by the crankshaft encoder 5 or a slide position signal converted from the crank angle to the position of the press slide 4, a position sensor 17 that detects the position of the cushion load generating member (in this example, the tip position of the cushion pin 14), and a pressure sensor 18 that detects the pressure in the lower chamber 12a of the hydraulic cylinder 12.

[0045] Still, in this example, for simplicity of explanation, the piston rod of the hydraulic cylinder 12 is used as a cushion pin. However, the cushion load generating member includes a blank holder 15, a plurality of cushion pins supporting the blank holder, and a cushion pad (not shown) supporting the plurality of cushion pins. The piston rod of the hydraulic cylinder 12 is connected to the cushion pad. Normally, the hydraulic cylinder 12 supports the blank holder 15 via the plurality of cushion pins by supporting the cushion pad.

[0046] The drive shaft of the drive motor 50 is connected directly or via a speed reducer to the rotating shaft of the hydraulic pump 60. The hydraulic pump 60 driven by the drive motor 50 supplies the hydraulic fluid (hydraulic oil) necessary to reach the cushion position of the cushion pin 14 (cushion position) to the lower chamber 12a or the upper chamber 12b of the hydraulic cylinder 12, and supplies the pressure fluid (pressure oil) necessary to make the upward load of the cushion pin 14 the cushion load corresponding to the cushion load command to the lower chamber 12a of the hydraulic cylinder 12.

[0047] Still, the tank 62 stores the surplus hydraulic oil discharged during the cushion position control and the cushion load control from the hydraulic pump 60, or supplies the insufficient hydraulic oil to the hydraulic pump 60.

[0048] The die cushion control device according to the present invention is composed of a processor 30 and a controller (speed controller) 40.

[0049] The processor 30 is composed of a CPU (Central Processing Unit) or the like, and receives a cushion target load command C1 and a cushion target position command C2 from the cushion target load commander 20 and the cushion target position commander 22 respectively. It also receives a cushion position signal D1 indicating the tip position of the cushion pin 14 and a pressure signal D2 indicating the pressure in the lower chamber 12a of the hydraulic cylinder 12 from the position sensor 17 and the pressure sensor 18 respectively, and generates a control command (speed command) to be output to the speed controller 40 based on the cushion target load command C1, the cushion target position command C2, the cushion position signal D1, and the pressure signal D2.

[0050] The processor 30 functions as a compression spring model 100, a cushion load command delay unit 110, a cushion load converter 114, a cushion load control unit 116, a cushion position command delay unit 120, a cushion position control unit 126, and adders 112, 122, 118. The details of the processing of each part of the processor 30 will be described later.

[0051] <Load characteristics of the compression spring model> FIG. 2 is a graph showing the load characteristics of the compression spring model, which shows the relationship between the deflection length of the compression spring and the upward load of the cushion pin when the hydraulic cylinder is assumed to be a compression spring.

[0052] As shown in FIG. 2, when the press slide 4 is located above the tip of the cushion pin 14 and is separated from the tip of the cushion pin 14, the tip position of the cushion pin is defined as the cushion free position.

[0053] Here, the hydraulic circuit including the hydraulic cylinder 12 is filled with hydraulic oil, and the hydraulic pump 60 is stationary, and the hydraulic circuit model is such that the cushion load is 0 [kN].

[0054] No cushion load is applied to the compression spring at the cushion free position, the compression spring is at its free length, and the deflection length is zero.

[0055] When the press slide 4 descends and contacts the cushion pin 14, the cushion pin 14 then descends together with the press slide 4. In practice, the upper die, the workpiece 16, and the blank holder 15 are interposed between the press slide 4 and the cushion pin 14, but they are omitted in this example.

[0056] When the cushion pin 14 is pressed down (when the compression spring deflects), an upward load is generated on the cushion pin 14 as a reaction force proportional to the pressing length (deflection length) (see the graph in Figure 2). And the deflection length of the compression spring when the upward load of the cushion pin 14 reaches a preset load is defined as the "target deflection length" in this example.

[0057] <Overview of Die Cushion Control> Figure 3 is a schematic diagram showing each operating state of the die cushion device body and the like controlled by the die cushion control device according to the present invention.

[0058] (1) Deviation When the press slide 4 is in the upper position and is separated from the cushion pin 14, the cushion load command to the cushion load control unit 116 is set to zero, the position loop gain ratio to the cushion position control unit 126 is set to 100%, and the tip position (cushion position) of the cushion pin 14 is position-controlled to be held at the cushion free position.

[0059] (2) Contact / Pressing When the press slide 4 descends, contacts the cushion pin 14, and presses down the cushion pin 14, the cushion load command to the cushion load control unit 116 becomes a load command according to the compression spring characteristic, the position loop gain ratio to the cushion position control unit 126 becomes 0%, and the upward load (cushion load) of the cushion pin 14 is controlled with a cushion load command according to the compression spring characteristic.

[0060] (3) Reaching the Set Load When the press slide 4 further descends and reaches the target deflection length, the cushion load command to the cushion load control unit 116 becomes a cushion target load command corresponding to a preset set load, and the cushion position control unit 126 does not generate a reaction force against the press position. That is, the cushion pin 14 is controlled to push up the press slide 4 with the set load.

[0061] (4) Holding of Set Load When the press slide 4 further descends, a descent command based on the target deflection length is given to the cushion position control unit 126. The cushion position control unit 126 outputs the motor rotation speed that becomes the oil discharge amount of the hydraulic cylinder 12 corresponding to the descent command, so that the cushion pin 14 continues the descent operation while pushing up the press slide 4 with the set load.

[0062] FIG. 4 is a functional block diagram showing an embodiment of the compression spring model of the processor shown in FIG. 1.

[0063] The compression spring model 100 shown in FIG. 4 is composed of a target deflection length calculator 101, a cushion load command generator 102, a motor speed converter 104, a cushion position command generator 106, and adders 103 and 105.

[0064] The compression spring model 100 receives a cushion target load command C1 and a cushion target position command C2 from a cushion target load commander 20 and a cushion target position commander 22 respectively, and also receives a cushion position signal D1 from a position sensor 17. As will be described later, based on the cushion target load command C1, the cushion target position command C2, and the cushion position signal D1, a third speed command S3, which is a feedforward speed command (FF speed command), a cushion position command S5, and a cushion load command S6 are generated.

[0065] The target deflection length calculator 101 inputs information indicating the cushion target load (set load preset by the user) C1 set in the cushion target load commander 20 and the hydraulic circuit parameters (hydraulic circuit parameters) 107, and calculates the target deflection length based on these input information. The cushion target load is not limited to being obtained from the cushion target load commander 20, and may also be obtained from an input unit where the user inputs the set load.

[0066] The hydraulic circuit parameters are parameters including the flow path volume information of the 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, and can be stored in the storage unit. Note that the flow path volume information of the hydraulic circuit parameters also includes information on the flow path volume determined by the length and diameter of the hydraulic rubber hose between the hydraulic cylinder 12 and the hydraulic pump 60, and the elastic modulus of the hydraulic rubber hose can also be included in the hydraulic circuit parameters.

[0067] The target deflection length calculator 101 creates a cushion hydraulic circuit model in which the hydraulic circuit including the hydraulic cylinder 12 and the hydraulic rubber hose is filled with hydraulic oil based on the hydraulic circuit parameters 107, the hydraulic pump 60 is stationary, and the cushion load is 0 [kN].

[0068] The target deflection length calculator 101 uses the created cushion hydraulic circuit model, calculates the displacement amount of the hydraulic cylinder 12 required to apply the cushion target load command C1 using the hydraulic circuit parameters 107, and outputs this displacement amount as the target deflection length.

[0069] Note that the target deflection length calculator 101 may also calculate the target deflection length based on the compression spring characteristics (spring constant) of the hydraulic cylinder 12 and the cushion target load (set load). In this case, the spring constant of the hydraulic cylinder 12 can be calculated from the displacement amount of the hydraulic cylinder due to applying a known load by applying a known load to the hydraulic cylinder 12.

[0070] The target deflection length output from the target deflection length calculator 101 and the cushion target position command C2 output from the cushion target position command device 22 are added by the adder 103, and the added value is output to the motor speed converter 104 as a cushion free position command.

[0071] The motor speed converter 104 time-differentiates the input cushion free position command to obtain the displacement amount of the hydraulic cylinder 12 per unit time, and converts the displacement amount per unit time into the rotational speed of the drive motor 50 to generate an FF speed command (third speed command) S3.

[0072] The motor speed converter 104 obtains the amount of oil supplied from the hydraulic pump 60 to the hydraulic cylinder 12 per unit time from the displacement amount per unit time and the cylinder area, and divides the obtained amount of oil by the volume of oil displaced per revolution of the hydraulic pump 60 (discharge amount) to obtain the rotational angle of the hydraulic pump 60 per unit time, that is, the rotational angle of the drive motor 50 connected to the drive shaft of the hydraulic pump 60 per unit time, and generates a third speed command indicating this.

[0073] The cushion load command generator 102 inputs the cushion target load command C1 output from the cushion 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 cushion target position command C2 output from the adder 105 and the cushion position signal D1, calculates the deflection length of the compression spring when the hydraulic cylinder 12 is assumed to be a compression spring, and based on the calculated deflection length, the cushion target load command C1, and the target deflection length, calculates a cushion load command S6 according to the following formula: [Equation 1] Cushion load command S6 = (cushion target load command / target deflection length) × deflection length for calculation.

[0074] Here, the adder 105 subtracts the cushion position signal D1 indicating the tip position of the cushion pin 14 detected by the position sensor 17 from the cushion target position command C2 output from the cushion target position command generator 22, and outputs information indicating the position deviation, which is the subtraction result, to the cushion load command generator 102.

[0075] The cushion load command generator 102 calculates the deflection length by adding the target deflection length and the position deviation. The deflection length becomes equal to the target deflection length when the position deviation is 0 [mm]. As the position deviation increases in the negative direction, the deflection length becomes shorter. When the magnitude of the position deviation in the negative direction becomes equal to the target deflection length, the deflection length becomes 0 [mm]. Note that the deflection length is not limited to being obtained by adding the target deflection length and the position deviation as described above. It may also be obtained by adding the target deflection length and the cushion target position, and then subtracting the cushion position indicated by the cushion position signal D1 from the added value (corresponding to the cushion free position).

[0076] The above [Equation 1] is an equation showing Hooke's law, and (cushion target load command / target deflection length) indicates the spring constant k (kN / mm). The cushion load command generator 102 generates a cushion load command S6 by multiplying the spring constant k and the deflection length (mm) according to [Equation 1].

[0077] Therefore, when the deflection length reaches the target deflection length, the cushion load command generator 102 outputs a cushion load command S6 that becomes the cushion target load command C1 (command indicating the set load). As the deflection length becomes shorter, the cushion load command generator 102 outputs a cushion load command S6 that decreases in proportion to the deflection length. When the deflection length becomes 0 [mm], the cushion load command generator 102 outputs a cushion load command S6 indicating 0 [kN].

[0078] The cushion position command generator 106 is applied with a cushion target position command C2, a cushion position signal D1, and a cushion load command S6. When the cushion load command S6 is zero, the cushion target position command C2 is output as the cushion position command S5. When the cushion load command S6 exceeds zero, the cushion position signal D1 is output as the cushion load command S6. Note that the switching between the cushion target position command C2 and the cushion position signal D1 is not limited to whether the cushion load command S6 is zero or less, and may be performed according to whether it is less than or equal to a set predetermined value (for example, the cushion load command S6 corresponding to the holding load of the cushion pin 14, the blank holder 15, etc. that the hydraulic cylinder 12 supports when unloaded).

[0079] Returning to FIG. 2, the third speed command S3 of the feedforward speed command generated by the compression spring model 100 is output to the adder 118, and the cushion load command S6 and the cushion position command S5 generated by the compression spring model 100 are output to the cushion load command delay unit 110 and the cushion position command delay unit 120, respectively.

[0080] The cushion load command delay unit 110 and the cushion position command delay unit 120 delay the cushion load command S6 and the cushion position command S5, respectively, and then output them to the positive inputs of the adders 112 and 122.

[0081] The cushion position signal D1 is applied from the position sensor 17 to the negative input of the adder 122. The adder 122 calculates the deviation (first deviation) between the delayed cushion position command S5 and the cushion position signal D1, and outputs the calculated first deviation to the cushion position control unit 126.

[0082] Also, a signal indicating the cushion load indicating the upward load of the cushion pin 14 is applied from the cushion load converter 114 to the negative input of the adder 112. The adder 112 calculates the deviation (second deviation) between the delayed cushion load command S6 and the signal indicating the cushion load, and outputs the calculated second deviation to the cushion load control unit 116.

[0083] Still, the cushion load converter 114 receives a pressure signal D2 indicating the pressure in the lower chamber 12a of the hydraulic cylinder 12 from the pressure sensor 18, calculates the upward load applied to the cushion pin 14 from the hydraulic cylinder 12 based on the pressure in 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 (cushion load) to the negative input of the adder 112.

[0084] The cushion position control unit 126 generates a first speed command S1, which is part of the control command, based on the input first deviation, outputs the first speed command S1 to the adder 118, the cushion load control unit 116 generates a second speed command S2, which is part of the control command, based on the input second deviation, and outputs the second speed command S2 to the adder 118.

[0085] 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.

[0086] The speed controller 40 outputs a drive signal to the drive motor 50 so that the rotational speed of the drive motor 50 becomes the target speed indicated by the input speed command, and can be configured by, for example, a proportional integral derivative (PID) controller.

[0087] The drive shaft of the drive motor 50 and the drive shaft of the hydraulic pump 60 are directly connected or connected via a speed reducer. The hydraulic pump 60 supplies an oil volume corresponding to the rotational speed of the drive motor 50 to the hydraulic cylinder 12, or is rotated by the pressure oil discharged from the hydraulic cylinder 12. Still, when the hydraulic pump 60 is rotated by the pressure oil discharged from the hydraulic cylinder 12, the hydraulic pump 60 functions as a hydraulic motor.

[0088] Furthermore, although the compression spring model 100 of the above embodiment outputs the cushion load command S6, it may output the pressure command obtained by converting the cushion load command S6 by the cylinder area instead of the cushion load command S6. That is, the cushion load indicated by the cushion load command S6 may be divided by the cross-sectional area of the lower chamber 12a of the hydraulic cylinder 12 to be converted into pressure, and the pressure designation indicating the pressure may be output. In this case, the cushion load converter 114 for converting the pressure signal D2 into a cushion load signal becomes unnecessary. Also, the cushion load command delay unit 110 becomes a delay unit for delaying the pressure command, and the cushion load control unit 116 becomes a pressure control unit.

[0089] The cushion position is controlled to be the cushion free position by the feedforward control by the third speed command S3. However, since there are errors between the theoretical values and the cushion position and cushion load associated with the operation of the press slide 4 during this control, feedback control by the first speed command S1 and the second speed command S2 is performed to correct the position error and load error respectively.

[0090] The die cushion control device of the embodiment shown in FIG. 1 abolishes the switching between position control and load control, and always operates position control and load control. Referring to the load characteristic curve of the compression spring from the cushion position signal D1 indicating the tip position of the cushion pin 14 detected by the position sensor 17, it is characterized by outputting the cushion position command S5 and the cushion load command S6 for cushion position control and cushion load control.

[0091] FIG. 5 is a block diagram showing the main part of the die cushion device shown in FIG. 1.

[0092] In FIG. 5, the drive motor 50 is controlled by the die cushion control device including the processor 30 and the speed controller 40 shown in FIG. 1, and the hydraulic cylinder 12 is controlled by the hydraulic pump 60 having a drive shaft connected to the drive motor 50.

[0093] The rotational driving force is transmitted from the drive motor 50 to the hydraulic pump 60. When the hydraulic pump 60 causes the hydraulic oil to flow from the upper chamber 12b to the lower chamber 12a of the hydraulic cylinder 12 (when flowing in the direction indicated by the solid arrow), the cushion pin 14 moves in the upward direction. Also, when the upward movement of the cushion pin 14 is restricted by the press slide 4, the upward load (cushion load) on the cushion pin 14 increases.

[0094] Also, when the hydraulic pump 60 causes the hydraulic oil to flow from the lower chamber 12a to the upper chamber 12b of the hydraulic cylinder 12 (when flowing in the direction indicated by the dotted arrow), the cushion pin 14 moves in the downward direction, and the cushion load decreases. Note that due to the difference in the cross-sectional areas of the lower chamber 12a and the upper chamber 12b of the hydraulic cylinder 12, the excess or insufficient hydraulic oil is supplied from the tank 62 or discharged to the tank 62.

[0095] Figures 6 to 9 are diagrams showing the generation of the speed command and the control state of the die cushion device main body, respectively.

[0096] <Cushion position control> Figure 6 is a diagram showing an example of a method for generating a speed command when the cushion position is controlled by the die cushion control device.

[0097] As shown in Figure 6, with time 0 [s] as a reference, the tip position of the cushion pin 14 at this time 0 [s] is located at a height of H [mm] from the upper surface of the moving bolster (MB), the target position of the cushion position is 0 [mm] (the height of H in Figure 6), and the cushion position command is set to 0 [mm]. Also, the height of the lower chamber 12a of the hydraulic cylinder 12 is set to 0 [mm] (L [mm] in Figure 6).

[0098] Thereafter, at time ΔT, when the cushion position is lowered by X [mm] from the above reference, the cushion position command (first deviation) with respect to the reference cushion position is -X [mm] (that is, the target height of the lower chamber 12a of the hydraulic cylinder 12 is -X [mm]), and the amount of oil M1 (first supply amount) supplied to the lower chamber 12a of the hydraulic cylinder 12 is given by the following formula, [Equation 2] M1 = -X × piston area (lower chamber) [mm 3 In this case, since the oil quantity M1 becomes negative, the oil quantity M1 is discharged from the lower chamber 12a of the hydraulic cylinder 12.

[0099] If the rotation angle of the drive motor 50 for discharging the oil quantity M1 from the lower chamber 12a of the hydraulic cylinder 12 is θ1, the rotation angle θ1 is given by the following equation, [Equation 3] θ1 = (M1 / volume of oil displaced per revolution of the hydraulic pump 60) × 360 and the angular velocity ω1 is ω1 = θ1 / ΔT. The cushion position control unit 126 shown in FIG. 1 outputs the speed command indicating the above angular velocity ω1 as the first speed command S1.

[0100] By controlling the rotational speed of the drive motor 50 (the rotational speed of the hydraulic pump 60 to which the drive motor 50 and the drive shaft are connected) via the speed controller 40 based on the speed command calculated in this way, the tip position (cushion position) of the cushion pin 14 can be lowered by X [mm].

[0101] <Cushion load control> FIG. 7 is a diagram showing an example of a method for generating a speed command when controlling the cushion load by the die cushion control device.

[0102] As shown in FIG. 7, with time 0 [s] as a reference, the upward load (cushion load) of the cushion pin 14 at this time 0 [s] is assumed to be 0 [kN].

[0103] Thereafter, when increasing the cushion load by P [kN] from the above reference at time ΔT, the cushion load command (second deviation) with respect to the reference cushion load is P [kN], and the oil quantity M2 (second supply quantity) supplied to the lower chamber 12a of the hydraulic cylinder 12 is given by the following equation, [Equation 4] M2 = P × (oil volume of the hydraulic circuit) / bulk modulus of elasticity and can be obtained by. ​

[0104] By supplying hydraulic oil to the lower chamber 12a of the hydraulic cylinder 12 by an amount M2 of oil, the upward load (cushion load) on the cushion pin 14 can be increased by P [kN].

[0105] When the rotation angle of the drive motor 50 for supplying the amount M2 of oil to the lower chamber 12a of the hydraulic cylinder 12 is θ2, the rotation angle θ2 is given by the following equation: [Equation 5] θ2 = (M2 / volume of oil displaced per revolution of the hydraulic pump 60) × 360 and the angular velocity ω2 is ω2 = θ2 / ΔT. The cushion load control unit 116 shown in FIG. 1 outputs a speed command indicating the above angular velocity ω2 as a second speed command S2.

[0106] By controlling the rotational speed of the drive motor 50 via the speed controller 40 based on the speed command calculated in this way, the upward load (cushion load) on the cushion pin 14 can be increased by P [kN].

[0107] <Cushion position control + cushion load control> FIG. 8 is a diagram showing an example of a method for generating a speed command when controlling the cushion position and the cushion load by the die cushion control device.

[0108] As shown in FIG. 8, with time 0 [s] as a reference, the tip position (cushion position) of the cushion pin 14 at this time 0 [s] is located at a height of H [mm] from the upper surface of the moving bolster (MB), and the upward load (cushion load) on the cushion pin 14 is 0 [kN].

[0109] After that, when the cushion position is lowered by X [mm] and the cushion load is increased by P [kN] from the above reference at time ΔT, the oil supply amounts M1 and M2 to the lower chamber 12a of the hydraulic cylinder 12 are calculated by the above-described equations [2] and [4], and further, based on the calculated M1 and M2, the rotation angles θ1 and θ2 of the drive motor 50 are obtained by the equations [3] and [5], and the first speed command S1 for cushion position control and the second speed command S2 for cushion load control are obtained.

[0110] By controlling the rotational speed of the drive motor 50 via the speed controller 40 based on the speed command obtained by adding these first speed command S1 and second speed command S2, the tip position (cushion position) of the cushion pin 14 can be lowered by X [mm], and the upward load (cushion load) of the cushion pin 14 can be increased by P [kN].

[0111] <Modification Example of Cushion Position Control + Cushion Load Control> FIG. 9 is a diagram showing another example of a method for generating a speed command when controlling the cushion position and the cushion load by the die cushion control device.

[0112] The method for generating a speed command shown in FIG. 9 is a modification example of the method for generating a speed command shown in FIG. 8, and the point of calculating the oil supply amounts M1 and M2 to the lower chamber 12a of the hydraulic cylinder 12 in order to control the cushion position and the cushion load is the same as the method for generating a speed command shown in FIG. 8.

[0113] The method for generating a speed command shown in FIG. 9 converts the oil supply amount M1 and the oil supply amount M2, and calculates the oil supply amount M3 (= M1 + M2) of the total oil supply amount to the lower chamber 12a of the hydraulic cylinder 12.

[0114] When the rotation angle of the drive motor 50 for supplying the oil amount M3 to the lower chamber 12a of the hydraulic cylinder 12 is θ3, the rotation angle θ3 is given by the following equation, [Equation 6] θ3 = (M3 / Volume of oil displaced per one rotation of the hydraulic pump 60) × 360 It can be represented by [formula], and the angular velocity ω3 is ω3 = θ3 / ΔT. Then, the cushion control device outputs a speed command indicating the above angular velocity ω3 to the speed controller 40.

[0115] By controlling the rotational speed of the drive motor 50 via the speed controller 40 based on the speed command calculated in this way, the tip position (cushion position) of the cushion pin 14 can be lowered by X [mm], and the upward load (cushion load) of the cushion pin 14 can be increased by P [kN].

[0116] <Function of the cushion control device> FIG. 10 is a graph showing the press slide position, the cushion position, the cushion load, and the cushion free position, and is a graph showing the function of the cushion control device according to the present invention.

[0117] The graph shown in FIG. 10(B) is an enlarged graph of the main part of the graph shown in FIG. 10(A).

[0118] In FIG. 10, the loop gain of the position control and the target value of the load control (cushion load command) change in order to operate the hydraulic cylinder as a compression spring. When the hydraulic cylinder 12 is pressed by the press slide 4 and is at the touch position (the position where press working is performed on the workpiece 16), the cushion target load in the cushion device (test machine) of this example is 200 [kN], the position loop gain is zero, and the control is in accordance with the set load (200 [kN]).

[0119] When the press slide 4 and the cushion pin 14 do not come into contact and no pressure (cushion load) is generated, the hydraulic cylinder 12 rises. As it rises, the target load (cushion load command) gradually decreases as shown in the graph of FIG. 10(C), and the target load becomes zero at the free position and the rise stops. In this example, when the cushion pin 14 rises 10 [mm] with respect to the touch position (reaches the cushion free position), the cushion load command becomes zero, and the cushion pin 14 is not pushed up beyond the cushion free position.

[0120] In this way, at the cushion free position, the target load becomes zero and the position restraining force by the cushion load control disappears. However, the position loop gain becomes 100% and the cushion position control starts, restraining the tip position (cushion position) of the cushion pin 14 at the cushion free position.

[0121] In the example shown in FIG. 10(B), the press slide 4 contacts the tip position of the cushion pin 14 (the press slide position reaches the cushion position). Then, as the press slide 4 gradually descends, the deflection length of the compression spring gradually becomes longer. When the press slide 4 reaches the touch position with the cushion pin 14, the deflection length becomes the target deflection length (in this example, 10 [mm]), and the cushion load becomes the target load (set load).

[0122] After that, when the press slide 4 further descends, the target deflection length is maintained. That is, the cushion load is maintained at the set load during the press working.

[0123] FIGS. 11 to 14 are schematic views showing each operating state of the die cushion device main body and the like shown in FIG. 3. Therefore, in FIGS. 11 to 14, the description of the parts common to FIG. 3 is partially omitted.

[0124] FIG. 11 is a schematic view showing a state where the press slide 4 is above the cushion pin 14 and separated from the cushion pin 14.

[0125] In this separated state, the cushion load command is zero, the position loop gain ratio to the cushion position control unit 126 is 100%, and the tip position (cushion position) of the cushion pin 14 is position-controlled to be held at the cushion free position. Therefore, the deflection length of the compression spring when the hydraulic cylinder 12 is assumed to be a compression spring is zero.

[0126] FIG. 12 is a schematic view showing a state where the press slide 4 contacts the cushion pin 14 and slightly pushes down the cushion pin 14.

[0127] In the case of this contact / press state, the cushion load command becomes a load command according to the compression spring characteristic, and the upward load (cushion load) of the cushion pin 14 is controlled by the cushion load command (cushion load command corresponding to the deflection length) according to the compression spring characteristic.

[0128] That is, the hydraulic cylinder 12 is controlled to generate a cushion load corresponding to the deflection length of the compression spring. Incidentally, the length of the lower chamber 12a of the hydraulic cylinder 12 becomes shorter by a length corresponding to the deflection length of the compression spring with respect to the separated state.

[0129] On the other hand, the position loop gain ratio to the cushion position control unit 126 becomes 0%, and the position restraint on the hydraulic cylinder 12 by the cushion position control unit 126 does not act.

[0130] FIG. 13 is a schematic view showing a state in which the press slide 4 further descends from the state shown in FIG. 12 and the cushion load reaches the set load.

[0131] In the case of this state where the set load is reached, the cushion load command becomes a cushion load command corresponding to the target deflection length, and the cushion load is controlled to be the set load.

[0132] Incidentally, the length of the lower chamber 12a of the hydraulic cylinder 12 becomes shorter by a length corresponding to the target deflection length with respect to the separated state. Also, similar to the contact / press state, the position restraint on the hydraulic cylinder 12 by the cushion position control unit 126 does not act.

[0133] FIG. 14 is a schematic view showing a state in which the press slide 4 further descends from the state shown in FIG. 13 and maintains the set load during this descent (during press working).

[0134] In the case of this state where the set load is maintained, the cushion load command is maintained as a cushion load command corresponding to the target deflection length, and the cushion load is controlled to be the set load.

[0135] Therefore, the pressure in the lower chamber 12a of the hydraulic cylinder 12 is maintained at the pressure at the time of reaching the set load shown in FIG. 13. That is, the hydraulic pump 60 driven by the drive motor 50 is driven to discharge the amount of oil corresponding to the lowering of the press slide 4 from the lower chamber 12a of the hydraulic cylinder 12 while maintaining the pressure in the lower chamber 12a of the hydraulic cylinder 12 at the pressure corresponding to the set load.

[0136] [Comparison between the present invention and the prior art] FIG. 15 is a graph showing the operations of respective parts when a normal press working operation is performed by a conventional cushion control device.

[0137] In the example of the normal operation shown in FIG. 15, at the timing when the descending press position (the position of the lower surface of the upper die attached to the press slide 4) coincides with the standby cushion position (in this example, 100 [mm]), the cushion control switches from the cushion position control mode to the cushion load control mode, and the press working is performed with the set cushion load (in this example, 200 [kN]).

[0138] FIG. 16 is a graph showing the operations of respective parts when an abnormal operation occurs by a conventional cushion control device.

[0139] The example shown in FIG. 16 is an example in which the press working is performed in a state where the actual press value is higher than the planned press value due to a die height setting error of the press or the like. In the conventional cushion control device, the hydraulic pressure of the hydraulic oil in the lower chamber of the hydraulic cylinder is started to increase in order to increase the cushion load at the timing of the start angle of the cushion load control obtained from the crankshaft encoder, but the cushion pin cannot obtain contact with the upper die of the press slide, and the cushion position exceeds the standby position (100 [mm]) and continues to rise.

[0140] The upward movement of this cushion becomes an abnormal detection condition, and the press system performs an emergency stop, but the cushion pin continues to rise beyond the standby position (100 [mm]) (the cushion pin is pushed up beyond the standby position). Due to the application of a steep cushion force (cushion load) when pushing up this cushion pin, there is a risk of damaging the mold or the workpiece.

[0141] As a measure to prevent damage, a measure to speed up the abnormal detection timing can be considered, but it is difficult to manage the relationship between the pressure reduction after abnormal detection and the fall stroke. Also, considering the fall stroke during cushion abnormality, a mold design with a margin is required, which also causes demerits such as an increase in mold cost.

[0142] FIG. 17 is a graph showing the operations of respective parts when the die cushion device main body is controlled by the die cushion control device according to the present invention.

[0143] The example shown in FIG. 17 is an example in which press working is performed in a state where the actual press value is higher than the press planned value due to a die height setting error or the like of the press, similar to FIG. 16.

[0144] The die cushion control device according to the present invention starts pressurizing the hydraulic oil in the lower chamber 12a of the hydraulic cylinder 12 to increase the cushion load according to the timing of the start angle of the cushion load control (the press slide position of the press planned value) obtained from the crankshaft encoder 5. However, even when the cushion pin 14 cannot make contact with the upper die of the press slide 4, when the cushion position reaches the cushion free position which is the standby position (100 [mm]), the cushion load command becomes zero, so the tip position (cushion position) of the cushion pin 14 does not rise beyond the cushion free position.

[0145] According to the graph showing the cushion position in FIG. 17, when the cushion load control is started, the cushion position turns to an upward movement, but it does not rise beyond the cushion free position which is the standby position (100 [mm]), and no cushion load is generated.

[0146] Accordingly, a lowering operation can be performed in accordance with a planned and managed cushion operation to prevent damage to a mold or the like.

[0147] [Die Cushion Control Method] FIG. 18 is a flowchart showing an embodiment of a die cushion control method according to the present invention.

[0148] Note that the die cushion control method shown in FIG. 18 is a method performed by the processor 30 of the die cushion control device shown in FIG. 1.

[0149] In FIG. 18, the compression spring model 100 of the processor 30 acquires a target deflection length (step S10). The target deflection length may be acquired by executing a calculation by a target deflection length calculator 101 (FIG. 4), or may be acquired by reading out a target deflection length calculated in advance and stored in a storage unit.

[0150] Subsequently, a cushion target load command C1 and a cushion target position command C2 are acquired based on a crank angle signal indicating a crank angle detected by the crankshaft encoder 5 or a slide position signal converted from the crank angle to the position of the press slide 4, respectively. Also, a cushion position signal D1 is acquired from the position sensor 17, and a cushion load signal indicating a cushion load converted from the pressure detected by the pressure sensor 18 is acquired (step S12).

[0151] In step S14, a cushion position command S5 is generated based on the cushion target position command C2, the cushion position signal D1, and the cushion load command obtained in step S12. The cushion load command is the cushion load command S6 generated in step S16. When the cushion load command S6 indicates a value equal to or less than the holding load of, for example, the blank holder 15, the cushion target position command C2 is output as the cushion position command S5. When the cushion load command S6 exceeds the holding load, the cushion position signal D1 is output as the cushion position command S5. When the latter cushion position command S5 is output, since the cushion position command S5 coincides with the cushion position signal D1, the cushion position control operates so as not to restrict the operation of the hydraulic cylinder 12.

[0152] Also, in step S16, a cushion load command S6 is generated based on the target deflection length obtained in step S10, and the cushion target load command C1, the cushion target position command C2, and the cushion position signal D1 obtained in step S12. Specifically, the cushion load command S6 is calculated by the above-mentioned [Equation 1]. Also, the "deflection length" in [Equation 1] can be obtained by adding the target deflection length and the position deviation obtained by subtracting the cushion position signal D1 from the cushion target position command C2.

[0153] This cushion load command S6 becomes the cushion target load command C1 (a command indicating the set load) when the deflection length is the target deflection length, and becomes a command indicating a cushion load that decreases in proportion to the deflection length as the deflection length becomes shorter. When the deflection length becomes 0 [mm], it becomes a command indicating a cushion load of 0 [kN].

[0154] Furthermore, in step S18, the target deflection length obtained in step S10 and the cushion target position command C2 obtained in step S12 are added, and the added value is generated as the cushion free position command.

[0155] Next, in step S20, based on the deviation (first deviation) between the cushion position command S5 generated in step S14 and the cushion position signal D1, a first speed command S1 necessary to set the cushion position to the target position is generated.

[0156] The generation of this 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 [2]). By dividing this amount of oil M1 by the discharge amount per revolution of the hydraulic pump 60, 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 (see Equation [3]). Then, based on the first deviation per unit time, the rotation angle θ1 of the drive motor 50 is obtained, thereby generating the first speed command S1 for the drive motor 50.

[0157] Also, in step S22, based on the deviation (second deviation) between the cushion load command S6 generated in step S16 and the cushion load signal acquired in step S12, a second speed command S2 necessary to set the cushion load to the target load is generated.

[0158] The generation of this second speed command S2 is performed as follows. The amount of oil M2 to the hydraulic cylinder 12 necessary to increase the cushion load by the second deviation is calculated based on the second deviation, the oil volume of the hydraulic circuit, and the bulk modulus of the hydraulic oil (see Equation [4]). By dividing this amount of oil M2 by the discharge amount per revolution of the hydraulic pump 60, the rotation angle θ2 of the drive motor 50 for supplying the amount of oil M2 from the hydraulic pump 60 to the hydraulic cylinder 12 is calculated (see Equation [5]). Then, based on the second deviation per unit time, the rotation angle θ2 of the drive motor 50 is obtained, thereby generating the second speed command S2 for the drive motor 50.

[0159] Furthermore, in step S24, a third speed command S3 is generated based on the cushion free position command generated in step S18. The generation of the third speed command S3 is performed by time-differentiating the cushion free position command to obtain the displacement amount of the hydraulic cylinder per unit time, and converting the displacement amount per unit time into the speed of the drive motor 50.

[0160] 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 to obtain a speed command, and the obtained speed command is output to the speed controller 40 (step S26).

[0161] Subsequently, the processor 30 determines whether or not the press working (die cushion control) by the press machine has ended. If the die cushion control is to be continued (in the case of "No"), the process returns to step S12, and the processing from step S12 to step S28 is repeatedly executed. On the other hand, if the die cushion control is to be terminated (in the case of "Yes"), this process is terminated (step S28).

[0162] [Others] In the die cushion device of this embodiment, one hydraulic cylinder 12 is provided, but the number of hydraulic cylinders 12 is not limited to this. Also, for one hydraulic cylinder 12, one drive motor 50 + hydraulic pump 60 is used, but this is not the only case. For one hydraulic cylinder 12, two or more units can be provided in parallel.

[0163] Also, although the case where oil is used as the working fluid of the hydraulic cylinder 12 and the hydraulic pump 60 has been described, this is not the only case, and water or other liquids may be used.

[0164] Also, in the present embodiment, for example, the hardware structure of a processing unit that executes various processes, such as the processor 30 of the dicing control device, is various processors as shown below. The various processors include a CPU (Central Processing Unit), which is a general-purpose processor that executes software (program) and functions as various processing units, a Programmable Logic Device (PLD) such as an FPGA (Field Programmable Gate Array), which is a processor whose circuit configuration can be changed after manufacturing, and a dedicated electric circuit, which is a processor having a circuit configuration designed specifically to execute specific processes such as an ASIC (Application Specific Integrated Circuit).

[0165] One processing unit may be composed of one of these various processors, or may be composed of two or more processors of the same or different types (for example, a plurality of FPGAs, or a combination of a CPU and an FPGA). Also, a plurality of processing units may be composed of one processor. Examples of composing a plurality of processing units with one processor include, firstly, a form in which one processor is composed of a combination of one or more CPUs and software, as represented by a computer such as a client or a server, and this processor functions as a plurality of processing units. Secondly, there is a form in which a processor that realizes the functions of an entire system including a plurality of processing units with one IC (Integrated Circuit) chip, as represented by a System On Chip (SoC). Thus, as a hardware structure, the various processing units are composed using one or more of the above various processors.

[0166] Furthermore, the hardware structure of these various processors is more specifically an electric circuit that combines circuit elements such as semiconductor elements.

[0167] Furthermore, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications are possible without departing from the spirit of the present invention.

Explanation of Reference Numerals

[0168] 1... Press machine 2... Crankshaft 3... Connecting rod 4... Press slide 5... Crankshaft encoder 10... Die cushion device body 12... Hydraulic cylinder 14... Cushion pin 15... Blank holder 16... Workpiece 17... Position sensor 18... Pressure sensor 20... Cushion target load commander 22... Cushion target position commander 30... Processor 40... Speed controller 50... Drive motor 60... Hydraulic pump 62... Tank 100... Compression spring model 101... Target deflection length calculator 102... Cushion load command generator 103, 105, 112, 118, 122,... Adder 104... Motor speed converter 106... Cushion position command generator 107... Hydraulic circuit parameter 110... Cushion load command delay unit 114... Cushion load converter 116... Cushion load control unit 120... Cushion position command delay unit 126... Cushion position control unit

Claims

1. A hydraulic cylinder that supports a cushion load generating member that generates a cushion load, a hydraulic cylinder drive device that includes a drive motor and a hydraulic pump driven by the drive motor and drives the hydraulic cylinder, a cushion target position command device and a cushion target load command device that output a cushion target position command and a cushion target load command respectively according to the crank angle of the press machine or the position of the press slide, 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 the lower chamber of the hydraulic cylinder. In the cushion control device of the die cushion device, the die cushion control device includes a processor and a controller that controls the drive motor according to an input control command, the processor when the hydraulic cylinder is assumed to be a compression spring model, obtains the deflection length of the compression spring when the upward load of the cushion load generating member reaches a preset load as the target deflection length, generates a cushion load command based on the cushion target load command, the target deflection length, the cushion target position command, and the cushion position, or generates a pressure command obtained by converting the cushion load command by the cylinder area, generates the control command based on the second deviation between the cushion load command and the cushion load converted from the pressure detected by the pressure sensor, or the second deviation between the pressure command and the pressure detected by the pressure sensor. A die cushion control device.

2. 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 based on the calculated deflection length, the target deflection length, and the cushion target position command according to the following formula: Cushion load command = (Cushion target load command / Target deflection length) × Deflection length The die cushion control device according to Claim 1.

3. The processor generates a cushion position command based on the cushion target position command and the cushion position, generates the control command based on the first deviation between the cushion position command and the cushion position. The die cushion control device according to Claim 1.

4. ​ When the cushion load command or the pressure command is zero or below a preset value, the processor generates the cushion target position command as the cushion position command, and when the cushion load command or the pressure command exceeds zero or the preset value, the processor generates the cushion position as the cushion position command. The die cushion control device according to claim 3.

5. The processor calculates a first supply amount of hydraulic fluid to be supplied to the upper chamber or the lower chamber of the hydraulic cylinder necessary to move the position of the cushion load generating member to a cushion position corresponding to the cushion position command based on the first deviation, and a second supply amount of hydraulic fluid to be supplied to the lower chamber of the hydraulic cylinder necessary to set the upward load of the cushion load generating member to a cushion load corresponding to the cushion load command based on the second deviation. The processor calculates the rotation angle of the drive motor based on the first supply amount, the second supply amount, and the discharge amount of hydraulic fluid per rotation of the hydraulic pump, and generates the control command based on the rotation angle. The die cushion control device according to claim 4.

6. The processor includes a cushion position control unit that generates a first speed command based on the first deviation, and includes a cushion position control unit or a pressure control unit that generates a second speed command based on the second deviation, and adds the first speed command and the second speed command to generate the control command. The die cushion control device according to any one of claims 3 to 5.

7. The processor generates a cushion free position command obtained by adding the cushion target position command and the target deflection length, generates a third speed command based on the cushion free position command, and adds the first speed command, the second speed command, and the third speed command to generate the control command. The die cushion control device according to claim 6.

8. The processor differentiates the cushion free position command with respect to time to obtain the displacement amount of the hydraulic cylinder per unit time, converts the displacement amount per unit time into the speed of the drive motor, and generates the third speed command. The die cushion control device according to claim 7.

9. The processor includes a delay unit that delays the cushion position command used for calculating the first deviation and the cushion load command or the pressure command used for calculating the second deviation. The cushion control device according to claim 7.

10. The processor calculates the target deflection length based on the flow path volume information of the hydraulic circuit including the hydraulic cylinder, the volume elastic modulus of the hydraulic fluid, the hydraulic circuit parameters including the cylinder diameter of the hydraulic cylinder, and the set load. The cushion control device according to any one of claims 1 to 5.

11. The processor calculates the target deflection length based on the spring constant of the compression spring and the set load. The cushion control device according to any one of claims 1 to 5.

12. A cushion device provided with the cushion control device according to any one of claims 1 to 5.

13. A hydraulic cylinder that supports a cushion load generating member that generates a cushion load, a hydraulic cylinder driving device that includes a drive motor and a hydraulic pump driven by the drive motor and drives the hydraulic cylinder, a cushion target position command and a cushion target load command are output according to the crank angle of the press machine or the position of the press slide, respectively. A cushion control method for a cushion control device of a cushion device, comprising: a cushion target position command device and a cushion target load command device, 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 the lower chamber of the hydraulic cylinder. When the hydraulic cylinder is assumed to be a compression spring model, a step of obtaining the deflection length of the compression spring when the upward load of the cushion load generating member reaches a preset set load as the target deflection length. A step of generating a cushion load command or a pressure command obtained by converting the cushion load command by a cylinder area based on the cushion target load command, the target deflection length, the cushion target position command, and the cushion position. A step of generating a control command 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. A step of outputting the generated control command to a speed controller that controls the drive motor. A cushion control method executed by a processor respectively.

14. 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 based on the calculated deflection length, the target deflection length, and the cushion target position command using the following formula: Cushion load command = (Cushion target load command / Target deflection length) × Deflection length and The die cushion control method according to claim 13.

15. The step of the processor generating a cushion position command based on the cushion target position command and the cushion position; The step of the processor generating the control command based on a first deviation between the cushion position command and the cushion position; The die cushion control method according to claim 13, including these steps.

16. When the cushion load command or the pressure command is zero or less than a predetermined value set, the processor generates the cushion target position command as the cushion position command, and when the cushion load command or the pressure command is zero or exceeds the predetermined value, the processor generates the cushion position as the cushion position command. The die cushion control method according to claim 15.

17. The processor calculates a first supply amount of hydraulic fluid to be supplied to the upper chamber or the lower chamber of the hydraulic cylinder necessary for reaching the position of the cushion load generating member to a cushion position corresponding to the cushion position command based on the first deviation, and a second supply amount of hydraulic fluid to be supplied to the lower chamber of the hydraulic cylinder necessary for making the upward load of the cushion load generating member a cushion load corresponding to the cushion load command based on the second deviation, The processor calculates the rotation angle of the drive motor based on the first supply amount, the second supply amount, and the discharge amount of hydraulic fluid per rotation of the hydraulic pump, and generates the control command based on the rotation angle. The die cushion control method according to claim 16, including these steps.

18. The step of generating a first speed command based on the first deviation; The step of generating a second speed command based on the second deviation; The step of adding the first speed command and the second speed command to generate the control command; The die cushion control method according to any one of claims 15 to 17, each executed by the processor.

19. generating a cushion free position command by adding the cushion target position command and the target deflection length; generating a third speed command based on the cushion free position command; generating the control command by adding the first speed command, the second speed command, and the third speed command; The die cushion control method according to claim 18, wherein each of the above steps is executed by the processor.

20. The processor time-differentiates the cushion free position command to calculate the displacement amount of the hydraulic cylinder per unit time, and converts the calculated displacement amount into the speed of the drive motor to generate the third speed command. The die cushion control method according to claim 19.

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