Electric press equipment

Abstract

To provide an electric press device which can optimize a deceleration load ratio even when difference in work and press environment is caused, and thereby can reduce variation in load at a stop position and a stop time of a ram.SOLUTION: An electric press device includes: a ram 1 pressing a work W; a load detection part 31 detecting load on the ram 1; a target stop load storage part 15 storing a target stop load value LT; a stop part 21 stopping the ram 1 when the load detection part 31 detects the target stop load value LT; a speed reduction load rate storage part 16 storing a speed reduction load rate R; a speed control part 22 controlling the speed of the ram 1 to be reduced to a set speed VL when the load detection part 31 detects a load value obtained by multiplying the speed reduction load rate R and the target stop load value LT; and a determination part 23 determining whether or not the speed reduction load rate R is proper on the basis of a result of comparison between a ram speed at the target stop load value LT and the set speed VL.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an electric press device. [Background technology]

[0002] BACKGROUND ART Electric press devices are known that use an electric motor such as a servo motor as a drive source to move a ram up and down and press an object with the ram (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-33563 Summary of the Invention [Problem to be solved by the invention]

[0004] Electric presses have a drive stop mode such as "load stop." In "load stop," the drive command is stopped when the set "target stop load value" is detected. However, at this time, the ram may overshoot from the position where it should stop. The ram moves forward the overshoot distance and stops, causing the load to exceed the set "target stop load value." The distance of the overshoot generally depends on the drive speed of the ram; the higher the drive speed, the greater the distance of the overshoot.

[0005] In order to reduce this overshoot phenomenon, a method is provided in which, when the "deceleration start load value" is detected, the pressure is applied by decelerating to a preset value or a fixed value, "set speed VL." In this method, the "deceleration start load value" is not directly specified, but is set by setting a "deceleration load rate" expressed as a ratio to the "target stop load value." In other words, the "deceleration start load value" can be expressed as "target stop load value x deceleration load rate."

[0006] Ideally, it would be sufficient if the ram could be decelerated quickly to the set deceleration speed VL when the set value of the "deceleration start load value," i.e., "target stop load value x deceleration load rate," reaches a predetermined set value. However, in reality, it takes a certain amount of time to decelerate the ram. Therefore, if the set value of the "deceleration load rate" is inappropriate, the ram speed will reach the "target stop load value" before it reaches the set deceleration speed VL, resulting in variation in the ram speed when the drive command is stopped. This variation leads to variation in the overshoot distance, which in turn leads to variation in the overshoot load, which ultimately leads to unnecessary variation in the ram stop position and load value.

[0007] In addition, the "deceleration load rate," which is set to reduce work time and reduce overshoot, has an appropriate value that varies depending on the workpiece and press environment. Even if the "deceleration load rate" is set to a value that allows for a certain degree of tolerance, the variation may increase and exceed the tolerance range if additional equipment is added or a small change is made to the workpiece. Press operation without checking that the deceleration load rate is not exceeding the tolerance range may result in large variations in the ram stop position and load.

[0008] In view of the above problems, the present invention provides an electric press device that can optimize the deceleration load rate even when differences occur in the workpiece or press environment, and that can reduce variations in the ram stopping position and load at the time of stopping. [Means for solving the problem]

[0009] In order to solve the above problem, according to one embodiment of the present invention, an electric press device includes a ram that applies pressure to a workpiece, a load detection unit that detects the load on the ram, a target stopping load memory unit that stores a target stopping load value for the ram, a deceleration load rate memory unit that stores a deceleration load rate, expressed as a percentage of the target stopping load value, at which the ram starts to decelerate just before the target stopping load value is reached, a speed control unit that controls the ram speed to decelerate to a set speed from the time the load detection unit detects a load value obtained by multiplying the deceleration load rate and the target stopping load value, and a judgment unit that judges whether the deceleration load rate is appropriate based on the result of comparing the ram speed at the target stopping load value with the set speed. [Effects of the Invention]

[0010] According to the present invention, an electric press device can be provided that can optimize the deceleration load rate even when differences occur in the workpiece or press environment, and can reduce variations in the ram stopping position and load when stopped. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing an example of an electric press apparatus according to an embodiment of the present invention; [Figure 2] 1 is a cross-sectional view showing a configuration of a mechanical portion of an electric press apparatus according to an embodiment of the present invention. [Figure 3] 1 is a block diagram showing a configuration example of a controller portion and its peripheral portion of an electric press apparatus according to an embodiment of the present invention. FIG. [Figure 4] 10 is a graph showing an example of the relationship between the load and speed of a ram when the deceleration load rate is appropriate. [Figure 5] 10 is a graph showing an example of the relationship between the load and speed of a ram when the deceleration load rate is not appropriate. [Figure 6] 10 is a graph showing the variation in the load of the ram when the deceleration load rate is not appropriate. [Figure 7] 5 is a flowchart showing a first example (automatic setting method) of a method for calculating a deceleration load rate of an electric press apparatus according to an embodiment of the present invention. [Figure 8] 8 is a graph showing an example of the results when the end condition δ is set to 2 and the deceleration load rate is calculated according to the flowchart of FIG. 7. [Figure 9] 8 is a graph showing an example of the results when the end condition δ is set to 4 and the deceleration load rate is calculated according to the flowchart of FIG. 7. [Figure 10] 5 is a flowchart showing a second example (semi-automatic setting method) of the method for calculating the deceleration load rate of the electric press apparatus according to the embodiment of the present invention. [Figure 11] 1 is a graph showing an example of the relationship between the load and speed of a ram when the speed of the ram is calculated based on equation (1). [Figure 12] 10 is a graph showing an example of the relationship between the load and speed of a ram when the speed of the ram is calculated using the least squares method. [Figure 13] 10 is a graph showing an example of the relationship between load and speed when operation is performed multiple times under the same conditions. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, identical or similar parts are designated by identical or similar reference numerals. Note that the embodiments shown below are merely examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not limit the structure, arrangement, etc. of component parts to those described below.

[0013] <Structure of electric press device> An electric press apparatus according to an embodiment of the present invention comprises a main body mechanism portion as shown in Figures 1 and 2, and a controller portion as shown in Figure 3. The main body mechanism portion is equipped with a conversion mechanism that converts rotational force into linear motion of a press ram 1 using a screw mechanism. As shown in Figure 2, for example, the conversion mechanism comprises a press ram 1 that applies a desired pressure to a workpiece W (workpiece) through linear motion, and a ball screw 2 that applies linear motion to the ram 1, and these are provided inside an upper body 4 of the press apparatus.

[0014] The ram 1 is provided inside the upper body 4. The upper body 4 also includes a servo motor 3 as an electric motor that powers the ram 1. The drive of the servo motor 3 is transmitted to the ball screw 2 via a pulley and a belt. The upper body 4 is fixed to a support 7 located at the bottom of the upper body 4, and the support 7 is fixed to a base 8. The base 8 is made of a material such as aluminum or iron, and the workpiece W to be pressed is placed on this base 8. The guide unit 6 extends axially adjacent to the ram 1 and is configured to guide the ram 1 along the axial direction. Switches 9a and 9b are connected to the ends of the base 8 and are operated by the operator when starting or stopping the pressing operation of the workpiece W.

[0015] The ram 1 has a hollow portion formed along the axial direction inside its cylindrical body, and the screw shaft 2a of the ball screw 2 can be inserted into this hollow portion. A nut body 2b of the ball screw 2 is fixed to the axial end of the cylindrical body of the ram 1. A strain-flexible pillar 1b can be freely attached to the tip of the cylindrical body. The strain-flexible pillar 1b abuts against the workpiece W to apply an appropriate pressure. A strain gauge is arranged on the strain-flexible pillar 1b so that it can be attached, and this strain gauge can detect the load value applied to the workpiece W.

[0016] Fig. 3 is a schematic diagram of the periphery of a controller (control mechanism) that controls the main body mechanical parts of Fig. 1 and Fig. 2. The controller includes a processor (CPU) 20. The processor 20 is connected to a control program storage unit 11, a display unit 12, an operation unit 13, a primary storage unit 14, a target stopping load storage unit 15, and a deceleration load rate storage unit 16.

[0017] The control program storage unit 11 stores various control programs for controlling the processor 20. The display unit 12 displays processing results such as graphs shown in Figs. 4 to 6, which show the relationship between the speed of the ram 1 and the detection results of the load on the ram 1. The operation unit 13 is composed of a mouse, keyboard, etc., which can input the operating conditions of the ram 1 and various parameters required for pressing the workpiece W. The primary storage unit 14 is composed of a memory, etc., which can store temporary data used in the calculation process.

[0018] The target stopping load memory unit 15 stores a target stopping load value (Load of Target) LT [N], which is the target load when stopping the press operation of the ram 1. The deceleration load rate memory unit 16 stores a deceleration load rate (Ratio) R [%], which is expressed as a ratio (%) of the target stopping load value, when deceleration of the ram 1 starts before the target stopping load value.

[0019] The processor 20 is further connected to a load detection unit 31, a command pulse generator 32, a servo motor driver 33, and an encoder position counter 35, all of which are connected to the strain-flexible column 1b. The load detection unit 31 amplifies a signal corresponding to a change in resistance of the strain gauge attached to the strain-flexible column 1b, converts the analog signal into a digital signal by A / D conversion, and outputs the converted signal to the processor 20. The command pulse generator 32 generates desired drive command pulses based on commands from the processor 20, and outputs the generated drive command pulse signal to the servo motor driver 33 via the processor 20. The servo motor driver 33 then controls the servo motor 3 to drive the ram 1, thereby moving the ram 1 up and down.

[0020] The servo motor 3 is connected to an encoder 34. The encoder 34 detects the rotation angle of the servo motor and functions as a position detector that detects the position of the ram 1. The information from the encoder 34 provides position information to the servo motor driver 33 for feedback control. The position information from the encoder 34 is also output to the processor 20 via an encoder position counter 35, which allows the position of the ram 1 to be detected.

[0021] Processor 20 includes a stop unit 21, a speed control unit 22, a determination unit 23, a search unit 24, and an informing unit 25. When load detection unit 31 detects a target stop load value LT for stopping the pressurizing operation of ram 1, stop unit 21 outputs a control signal to servo motor 3, which is an electric motor, to stop servo motor 3, thereby stopping ram 1. Speed ​​control unit 22 controls the speed of ram 1, and when load detection unit 31 detects a deceleration start load value, which is a load value obtained by multiplying deceleration load rate R and target stop load value LT, controls the speed of ram 1 to decelerate to a set speed (Velocity of Low) VL [mm / sec] that is slower than a preset pressing speed (Velocity of Pressing) VP [mm / sec].

[0022] The determination unit 23 compares the speed of the ram 1 at the target stopping load value LT with the set speed VL during deceleration, and determines based on the comparison result whether the deceleration load rate R is appropriate, i.e., whether the speed control unit 22 is correctly decelerating the ram 1. If the speed of the ram 1 at the target stopping load value LT is equal to or less than the set speed VL, the determination unit 23 determines that the deceleration load rate R is appropriate. On the other hand, if the speed of the ram 1 at the target stopping load value LT is greater than the set speed VL during deceleration, the determination unit 23 determines that the deceleration load rate R is inappropriate.

[0023] If the deceleration load rate R is inappropriate, the ram 1 will overshoot from the position where it should stop, resulting in variations in the stop position and load of the ram 1 when it stops. When the speed of the ram 1 at the target stop load value LT is greater than the set speed VL during deceleration, the search unit 24 changes the value of the deceleration load rate R in stages and performs a test to operate and execute the press operation of the ram 1 at the changed deceleration load rate R, thereby searching for and finding an appropriate deceleration load rate R for properly decelerating the ram 1 just before the stop position.

[0024] If the speed of the ram 1 at the target stop load value LT is greater than the set speed VL, the notification unit 25 notifies the operator that the deceleration load rate R is inappropriate, for example, via the display unit 12. This urges the operator to optimize the deceleration load rate R, so that even if there are differences in the workpiece W or press environment, it is possible to quickly respond to variations in the stop position of the ram 1 and the load at the time of stop.

[0025] When the ram 1 is in operation, a control program stored in the control program storage unit 11 issues a drive command to the servo motor driver 33, which drives the ram 1 at a speed (also called the "pressurization speed") VP. When the load value detected by the load detection unit 31 reaches a deceleration load value, which is the product of the deceleration load rate R and the target stopping load value LT, deceleration begins so that the speed VP of the ram 1 reaches the set speed VL. Thereafter, when the load value detected by the load detection unit 31 reaches the target stopping load value LT, the stop unit 21 stops the servo motor 3, thereby stopping the drive of the ram 1.

[0026] Figure 4 is a graph showing the relationship between the load value (detected load) of the ram 1 and the speed when the ram 1 is decelerated and stopped appropriately. Here, an example is shown where the set conditions are: ram 1 speed (pressure speed) VP = 5 mm / sec, set speed during deceleration VL = 1 mm / sec, target stopping load value LT = 10,000 N, and deceleration load rate R = 90%. In the example shown in Figure 4, as expected, the load reaches 10,000 N after decelerating to 1 mm / sec and stops. In the example in Figure 4, it can be evaluated that an appropriate deceleration load rate R is set.

[0027] In contrast, Figure 5 shows an example in which the deceleration load rate R is inappropriate. The setting conditions are the same as in the example in Figure 4. In Figure 5, deceleration of the ram 1 speed begins when the deceleration load rate R multiplied by the target stopping load value LT is 9,000 N, but the target stopping load value of 10,000 N is reached before the set speed during deceleration, VL = 1 mm / sec, is reached. In reality, in Figure 5, the target stopping load value LT is reached when ram 1 is decelerated to 3 mm / sec. When the drive of ram 1 is stopped, an overshoot occurs, and it stops at a load value of 10,300 N.

[0028] The problem in Figure 5 is not simply that the overshoot load is getting larger. Differences in the workpiece and press environment change the speed at which the target stop load value LT is reached, which can ultimately cause variations in the pressure application speed. Variations in the pressure application speed then cause variations in the overshoot distance, which ultimately manifests as variations in the load overshoot.

[0029] Figure 6 shows an example where an inappropriate setting for the deceleration load rate R caused variations in the overshoot load. The graph in Figure 6 shows three example operating operation results. The solid line shows the same results as the operating operation in Figure 5. In the example shown by the dotted line above the solid line, the speed of ram 1 at the time the target stopping load value LT of 10,000 N was detected was high at 4 mm / sec. As a result, both the overshoot distance and overshoot load when ram 1 stopped were large, and the load exceeded by approximately 400 N. Additionally, in the example shown by the dashed line below the solid line, the speed at the target stopping load value LT of 10,000 N was low at 2 mm / sec, and the overshoot load was also small, staying at around 200 N.

[0030] The problem in Figure 6 is that deceleration starts at 9000N and the target stopping load value LT of 10,000N is reached before the speed drops to 1mm / sec, resulting in load overshoot variations.

[0031] If the phenomenon shown in Figure 6 is occurring, the problem can be resolved by lowering the deceleration load rate R. If the deceleration load rate R is lowered, for example from R = 90% to R = 80%, deceleration will begin at 10,000N x 80% = 8,000N, which is earlier than the stopping position of ram 1 than in the case of 9,000N. This will lengthen the time it takes to reach the target stopping load value LT = 10,000N, so it will be possible to reach the target stopping load value LT after decelerating to the set speed VL for deceleration at the target stopping load value LT, which is 1mm / sec.

[0032] The appropriateness of the deceleration load rate R can be determined by checking the speed of the ram 1 when it reaches the target stopping load value LT = 10,000 N. In other words, if the speed of the ram 1 is the set speed during deceleration VL = 1 mm / sec when it reaches the target stopping load value LT, then the deceleration load rate R is appropriate, and if it is greater than 1 mm / sec, then the deceleration load rate R is determined to be inappropriate.

[0033] Generally, if the deceleration load rate R is made smaller, it becomes more likely that the speed of ram 1 will be decelerated to the set speed VL at deceleration by the time the ram 1 stops, but the distance over which it is driven after deceleration becomes longer, which increases the pressurization time, increases the takt time, and reduces productivity. Currently, the deceleration load rate R is set based on the experience and intuition of an experienced worker, and an appropriate method for setting the deceleration load rate R has not been established.

[0034] One tool for determining the appropriate value for the deceleration load rate R is PC application software for analyzing time-series data. Time-series data is a sequence of position and detected load values ​​sampled at regular time intervals, such as 1 msec. The PC application software has a function that allows test pressurized processing operations to be performed during the setup stage, imports the time-series data, and displays it as a position-load graph. This function is primarily used to verify the validity of the judgment function and the judgment values. The judgment function here specifies the position range and upper and lower load limits as set values, and detects whether the position and load during actual processing operations pass within this judgment frame, outputting an error if they go outside the judgment frame.

[0035] However, such PC application software is difficult to use for verifying the validity of the set value of the deceleration load rate R. As a result, it has been necessary for an experienced person to use a spreadsheet program or similar to find a valid value based on the time series data.

[0036] On the other hand, according to the electric press device of the embodiment of the present invention, a judgment unit 23 is provided that judges whether the deceleration load rate R is appropriate based on the results of comparing the ram speed at the target stopping load value LT with the set speed VL. This makes it possible to optimize the deceleration load rate R even when differences arise in the workpiece W or press environment, thereby providing an electric press device that can reduce variations in the stopping position of the ram 1 and the load when stopped.

[0037] <Method for automatically searching the deceleration load rate R by the search unit 24> A specific example of an algorithm for searching for the deceleration load rate R is shown in the flowchart of Figure 7. This algorithm is based on a dichotomous approach. Here, we will explain a method of increasing or decreasing the deceleration load rate R% by a deceleration load rate adjustment range ΔR%, and halving the deceleration load rate adjustment range ΔR%.

[0038] In step 71, the search unit 24 sets an initial value for the deceleration load rate adjustment width ΔR [%]. The initial value can be, for example, a negative value, such as -16 [%]. Next, in step 72, the search unit 24 sets an initial value for the deceleration load rate R [%]. The initial value can be, for example, 84 [%]. Next, in step 73, the press process operation of the ram 1 is performed using the initial values ​​set in steps 71 and 72. In step 74, from the data on the position of the ram 1 and the load of the ram 1 detected by the encoder position counter 35 and the load detection unit 31, the search unit 24 calculates the speed of the ram 1 when the load of the ram 1 reaches the target stop load value LT.

[0039] In step 75, the judgment unit 73 determines whether the calculated speed of the ram 1 is greater than the set speed VL. If the calculated speed of the ram 1 is greater than the set speed VL, the judgment unit 73 determines that the deceleration load rate R is not an appropriate value, and the process proceeds to step 76. In step 76, the search unit 24 updates the deceleration load rate R so that the deceleration load rate R becomes R + ΔR, and the process returns to step 73. As described above, ΔR has a negative value. Here, the deceleration load rate R is gradually reduced until it becomes an appropriate value within the deceleration load rate adjustment range ΔR.

[0040] In step 75, if the calculated speed of ram 1 is equal to or less than the set speed VL, it indicates that the ram 1 has been decelerated appropriately and that the deceleration load rate R is an appropriate value. In this case, the process proceeds to step 77. In step 77, the search unit 24 sets the deceleration load rate adjustment width ΔR to 1 / 2, and to a positive value.

[0041] In step 78, the search unit 24 updates the deceleration load rate R so that the deceleration load rate R becomes R+ΔR, and the process proceeds to step 79, where the ram 1 performs press processing operation at the updated deceleration load rate R. In step 80, from the data on the position and load of the ram 1 detected by the encoder position counter 35 and the load detection unit 31, the search unit 24 calculates the speed of the ram 1 when the load of the ram 1 reaches the target stop load value LT.

[0042] In step 81, the judgment unit 73 determines whether the calculated speed of the ram 1 is greater than the set speed VL. If the calculated speed of the ram 1 is greater than the set speed VL, the judgment unit 73 determines that the deceleration load rate R is not a valid value (inappropriate), and proceeds to step 82. In step 82, the deceleration load rate adjustment width ΔR is halved to make it negative. In step 83, the judgment unit 73 determines whether the absolute value of the deceleration load rate adjustment width ΔR is smaller than a preset termination condition width δ. If the absolute value of the deceleration load rate adjustment width ΔR is not smaller than the termination condition width δ, the process returns to step 73. If the absolute value of the deceleration load rate adjustment width ΔR is smaller than the termination condition width δ, the process returns to step 84. The termination condition width δ [%] is the preset value of ΔR at the end, and if the absolute value of ΔR becomes smaller than δ, the process proceeds to step 84. Next, since the deceleration load rate R is an inappropriate value in step 84, it is returned to the previous valid value. Here, ΔR is half and is therefore negative, so by doubling it and adding it, the deceleration load rate R is reset to a reasonable value, and the process proceeds to step 87 and ends.

[0043] On the other hand, if the calculated speed of the ram 1 is not greater than the set speed VL, it is determined that the deceleration load rate R is appropriate (suitable), and the process proceeds to step 85. In step 85, the search unit 24 halves the deceleration load rate adjustment width ΔR to make it positive. In step 86, the determination unit 73 determines whether the magnitude of the absolute value of the deceleration load rate adjustment width ΔR is not smaller than the termination condition width δ. If the magnitude of the absolute value of the deceleration load rate adjustment width ΔR is not smaller than the termination condition width δ, the process returns to step 78. If the magnitude of the absolute value of the deceleration load rate adjustment width ΔR is smaller than the termination condition width δ, the process proceeds to step 87 and ends.

[0044] FIG. 8 is a table showing the results of the automatic search for the deceleration load rate R when the termination condition width δ is set to 2 in the flowchart shown in FIG. 7. In No. 1, when the initial conditions R = 84 and ΔR = -16 were set, the driving results were inappropriate, so in step 76 the value of the deceleration load rate R was updated to R + ΔR, resulting in the deceleration load rate R being updated to 76%. In No. 2, if the execution with the deceleration load rate R = 68% was deemed appropriate, ΔR and R are updated in steps 77 and 78. In No. 3, ΔR becomes a positive value of 8, and the deceleration load rate R = 76%. If the driving results under these conditions are deemed appropriate, the values ​​are updated in steps 85 and 78. Here, in step 86, the absolute values ​​of the termination condition width δ = 2 and ΔR = 8 are compared, and it is determined that the termination condition has not yet been met. In No. 4, if the driving is deemed inappropriate with ΔR = 4 and the deceleration load rate R = 80%, the values ​​are updated in steps 82 and 78. If operation is appropriate in No. 5 with ΔR = -2 and deceleration load rate R = 78%, then when ΔR is halved in step 85, the termination condition in step 86 is met and the process ends in step 87. In the example of Figure 8, when No. 6 ends, the deceleration load rate R = 78%.

[0045] Fig. 9 is a table showing the results of automatic search for the deceleration load rate when the termination condition width δ is set to 4 in the flowchart shown in Fig. 7. In this case, the search ends when the operation result of No. 4 is inappropriate, so the value is returned in step 84 and the search ends when the deceleration load rate R = 76%.

[0046] According to the electric press apparatus of the embodiment of the present invention, the searching unit 24 determines an appropriate deceleration load rate R under predetermined conditions based on, for example, the flowchart of Fig. 7, and repeats press process operation execution tests using the determined deceleration load rate R, thereby searching for an appropriate deceleration load rate R. This makes it possible to provide an electric press apparatus that can reduce variations in the stopping position of the ram 1 and the load at the time of stopping, even when differences occur in the workpiece or press environment.

[0047] <Semi-automatic search method for deceleration load rate R using notification unit 25> FIG. 10 is a flowchart showing a modified example of the method for searching for the deceleration load rate R. After starting in step 90, in step 91 the operator inputs and sets the deceleration load rate R via the operation unit 13. In step 92, the operation of the press process of the ram 1 is executed. This operation may also be started by the operator. In step 93, the judgment unit 23 calculates the speed of the ram 1 at the target stopping load value LT. In step 94, the judgment unit 23 compares the calculated speed of the ram 1 at the target stopping load value LT with the set speed VL. If the calculated speed is greater than the set speed VL, the judgment unit 23 determines that the deceleration load rate R is inappropriate, and the process proceeds to step 95. The notification unit 25 notifies the operator via the display unit 12 that the deceleration load rate R is inappropriate, and the process returns to step 91. On the other hand, if the calculated speed is equal to or less than the set speed VL, the judgment unit 23 judges that the deceleration load rate R is appropriate, and in step 96, the notification unit 25 notifies the operator via the display unit 12 that the deceleration load rate R is appropriate, and the process returns to step 91.

[0048] In step 95, in addition to informing the operator via the display unit 12 that the deceleration load rate R is inappropriate, the notification unit 25 may also display a graph of time-series data showing the relationship between the speed of the ram 1 and the load (detected load) applied to the ram 1, as shown in Figures 4 and 5. By referring to the displayed graph, the operator can adjust the value of the deceleration load rate R input in step 91, and therefore can more quickly obtain an appropriate value for the deceleration load rate R.

[0049] The calculated speed of the ram 1 at the target stopping load value LT calculated in steps 74 and 80 in FIG. 7 and step 93 in FIG. 10 can be calculated by the following calculation method.

[0050] The velocity can be calculated from the position of ram 1 observed at regular time intervals. For example, assume that position information of positions P1, P2, ... is detected at a certain time Tc. At this time, the instantaneous velocities V2, V3, VN of ram 1 are expressed by equation (1): V2=(P2-P1) / Tc V3=(P3-P2) / Tc VN=(PN-P(N-1)) / Tc...Equation (1)

[0051] Figure 11 shows a graph plotting the relationship between the speed and the detected load calculated based on equation (1). Here, the pressurizing speed VP of the ram 1 is set to 5 mm / sec, and the set speed VL during deceleration is set to 1 mm / sec.

[0052] When calculating the speed by simply taking the difference as shown in equation (1), the value fluctuates as shown in Figure 11. In reality, the speed does not fluctuate, but rather it appears to fluctuate in the calculation, and this is thought to be due to an error associated with the quantization of the position of the ram 1. Alternatively, this fluctuating calculation occurs because the sampling time interval Tc is not completely constant. Incidentally, the sampling time interval Tc in Figure 11 is 5 msec.

[0053] The speed calculated as the slope of linear regression using the least squares method is shown in the graph in Figure 12. It can be seen from Figure 12 that the speed value is relatively stable. It can also be seen from Figure 12 that at the target stopping load value of 10,000 N, the speed has not yet dropped to 1 mm / sec, but is around 2 mm / sec.

[0054] To calculate the speed of ram 1, instead of using a calculation method based on two points like equation (1), we can use m pieces of data (here m = 6) as shown in equation (2), assume that these m pieces of data are on a straight line, and find the slope of this line using the least squares method. The calculation formula is shown in equation (2) below.

[0055]

number

[0056] Since the sampling time interval Tc is 5 msec, when m = 6, the result is 5 msec x (6 - 1) = 25 msec, and 6 points will fall on a straight line. The number of data points m can be fixed, but as the speed slows, the amount of movement decreases, so a small number of points will result in larger errors. On the other hand, if m is made too large, the assumption that the data falls on a straight line will be incorrect. Also, if m is large, tracking will be poor when the speed fluctuates.

[0057] The number of data m may be variable depending on the speed. First, the speed is roughly calculated using equation (1), the number of data m is determined depending on that speed, and the slope of the line is calculated using equation (2), thereby calculating the speed of ram 1.

[0058] Figure 13 shows a load-speed graph when an operation is performed multiple times (three times) under the same conditions. Even under the same conditions, the graph results will change depending on the variations in the workpiece, etc. When automatically finding the deceleration load rate as shown in the flow chart in Figure 7, the calculated speed used for judgment may vary as a result of the operations performed in steps 73 and 79. Therefore, to determine whether the deceleration load rate R is "appropriate," it is necessary to perform the operation multiple times (for example, 10 times) without changing the deceleration load rate R, and only judge it to be appropriate if all of the results are appropriate. If it is judged to be inappropriate, it can be judged to be inappropriate if it occurs just once. This makes it possible to determine a deceleration load rate R [%] that is reliably appropriate.

[0059] While the present invention has been described using the above embodiments, the descriptions and drawings that form part of this disclosure should not be understood as limiting the present invention, and various modifications are possible. For example, while the "load stop" process has been described in the embodiments of the present invention, a "load gradient stop" process that monitors the load change, particularly the load change per unit distance, and stops the vehicle when it exceeds a certain set value can also be considered similar to the present invention. In other words, by applying the above embodiments to a function that sets a percentage of a set load gradient value and decelerates when this value is exceeded, an appropriate "deceleration load gradient rate" can be automatically calculated. [Explanation of symbols]

[0060] 1...Rum 1b...Strain column 2...Ball screw 2a...Screw shaft 2b...Nut body 3...Servo motor 6...Guide section 7...Strut 8...Bass 9a, 9b...Switch 10...Casing 11...Control program storage unit 12...Display section 13...Operation unit 14…Primary storage section 15...Target stopping load storage section 16...Deceleration load rate storage section 20...Processor 21...Stop part 22...Speed ​​control section 23…Judgment section 24…Exploration Department 25...Information Department 31...Load detection unit 32...Command pulse generator 33...Servo motor driver 34...Encoder 35...Encoder position counter

Claims

1. A ram that applies pressure to the workpiece; a load detection unit that detects a load applied to the ram; a target stopping load memory unit that stores a target stopping load value when the pressurizing operation of the ram is stopped; a deceleration load rate storage unit configured to store a deceleration load rate, which is indicated as a ratio to the target stopping load value, when deceleration of the ram is started just before the target stopping load value is reached; a speed control unit that controls the speed of the ram to be decelerated to a set speed from when the load detection unit detects a load value obtained by multiplying the deceleration load rate and the target stop load value; a determination unit that determines whether the deceleration load rate is appropriate based on a comparison result between the speed of the ram at the target stopping load value and the set speed; An electric press device comprising:

2. a search unit that searches for an appropriate deceleration load rate when the speed of the ram at the target stopping load value is greater than the set speed; The electric press apparatus according to claim 1 , further comprising:

3. a notification unit that notifies that the deceleration load rate is inappropriate when the speed of the ram at the target stopping load value is greater than the set speed; The electric press apparatus according to claim 1 or 2, further comprising:

4. an operation unit that allows input of a set value of the deceleration load rate based on time-series data that indicates the relationship between the speed of the ram and the detection result of the load applied to the ram; The electric press apparatus according to claim 1 or 2, further comprising:

5. 3. The electric press apparatus according to claim 1, further comprising: calculating the speed of the ram at the target stopping load value by finding a slope by applying a least squares method to time-series data representing a relationship between the speed of the ram and a detection result of the load acting on the ram.

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