Electric press, bend-point detection method, and program

Abstract

A detection unit for detecting a press position and a load at the press position; an input/storage unit for inputting and storing a value serving as a reference for determining a bend point in a relation between the press position and the load at the press position; a slope calculation unit for calculating a slope of the load based on the press position and the load at the press position, which have been detected; and a bend-point determination unit for determining a point, at which the calculated slope of the load exceeds the value serving as the reference for determining the bend point, as the bend point are provided.

Claims

1. An electric press comprising: a detection unit configured to detect a press position and a first data sequence of a load at the press position; an input and storage unit configured to input and store a value serving as a reference that determines a bend point in a relation between the press position and the first data sequence of the load at the press position; a slope calculation unit configured to calculate a slope of the load based on the press position and the first data sequence of the load at the press position detected, according to a first regression line, wherein the slope of the load is calculated by the following formula, (i), $\begin{array}{cc}\mathrm{the}\mathrm{slope}\mathrm{of}\mathrm{the}\mathrm{load}=\frac{n\underset{i=1}{\overset{n}{.Math.}}{x}_i{y}_i-\underset{i=1}{\overset{n}{.Math.}}{x}_i\underset{i=1}{\overset{n}{.Math.}}{y}_i}{n\underset{i=1}{\overset{n}{.Math.}}{x}_i^2-\left(\underset{i=1}{\overset{n}{.Math.}}{x}_i\right)}& \left[\mathrm{Formula}\left(i\right)\right]\end{array}$ a slope-of-slope calculation unit configured to calculate a slope of the slope of the load calculated by the slope calculation unit as an amount of change of an amount of change of a load value with respect to the press position by using the formula (i) for calculating a slope of the first regression line, according to a second regression line, wherein, in the formula (i), n denotes a number of data, xi denotes position data of a pressurization part, and yi denotes data of a load; and a bend-point determination unit configured to determine a point, at which the calculated slope of the slope of the load exceeds the value serving as the reference for determining the bend point, as the bend point.

2. The electric press according to claim 1, wherein the slope calculation unit smoothes the press position and the first data sequence of the load at the press position detected, and calculates the slope of the load based on the press position and the load at the press position smoothed, and wherein the slope-of-slope calculation unit smoothes the press position and the second data sequence of the slope of the load at the press position smoothed, and calculates the slope of the slope of the load based on the press position and the load at the press position smoothed.

3. A bend-point detection method of an electric press having at least a detection unit, an input and storage unit, a slope calculation unit, and a bend-point determination unit, the bend-point detection method including: a first step of detecting a press position and first data sequence of a load at the press position by the detection unit; a second step of inputting and storing a value serving as a reference for determining a bend point in a relation between the press position and the load at the press position by the input and storage unit; a third step of calculating a slope of the load based on the press position and the first data sequence of the load at the press position detected by the slope calculation unit, according to a first regression line, wherein the slope of the load is calculated by the following formula (i), $\begin{array}{cc}\mathrm{the}\mathrm{slope}\mathrm{of}\mathrm{the}\mathrm{load}=\frac{n\underset{i=1}{\overset{n}{.Math.}}{x}_i{y}_i-\underset{i=1}{\overset{n}{.Math.}}{x}_i\underset{i=1}{\overset{n}{.Math.}}{y}_i}{n\underset{i=1}{\overset{n}{.Math.}}{x}_i^2-\left(\underset{i=1}{\overset{n}{.Math.}}{x}_i\right)}& \left[\mathrm{Formula}\left(i\right)\right]\end{array}$ a fourth step of calculating a slope of the slope calculated by the slope calculation unit, as an amount of change of an amount of change of a load value with respect to the press position by using the formula (i) for calculating a slope of the first regression line, according to a second regression line, wherein, in the formula (i), n denotes a number of data, xi denotes position data of a pressurization part, and yi denotes data of a load; and a fifth step of determining a point, at which the calculated slope of the slope of the load exceeds the value serving as the reference for determining the bend point, as the bend point by the bend-point determination unit.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an overall view of an electric press according to one or more embodiments of the present invention.

(2) FIG. 2 is a cross-sectional view of an electric press according to one or more embodiments of the present invention.

(3) FIG. 3 is a drawing showing a configuration of a control unit of the electric press according to a first embodiment of the present invention.

(4) FIG. 4 is a drawing showing a process flow of the electric press according to the first embodiment of the present invention.

(5) FIG. 5 is a drawing showing the relation of position/load data of the electric press according to the first embodiment of the present invention.

(6) FIG. 6 is a drawing showing the relation of position/load slope data of the electric press according to the first embodiment of the present invention.

(7) FIG. 7 is a graph showing data sequences of x and y (original data) of the electric press according to the first embodiment of the present invention and the values of y on a regression line (y).

(8) FIG. 8 is a drawing showing the relation of slope data of the slope of position/pressurization-load of the electric press according to the first embodiment of the present invention.

(9) FIG. 9 is a graph in which FIG. 5, FIG. 6, and FIG. 8 are mutually overlapped.

(10) FIG. 10 is a drawing showing a configuration of a control unit of an electric press according to a first embodiment of the present invention.

(11) FIG. 11 is a drawing showing a process flow of the electric press according to the first embodiment of the present invention.

(12) FIG. 12 is a drawing showing a bend point.

(13) FIG. 13 is an example that draws a position/simple-second-order difference graph based on actual data of press-fitting.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(14) Hereinafter, embodiments of the present invention will be explained in detail by using drawings.

(15) Note that constituent elements in the present embodiments can be arbitrarily replaced with existing constituent elements, etc., and various variations including combinations with other existing constituent elements can be also employed. Therefore, the description of the present embodiments does not limit the substance of the invention described in claims.

First Embodiment

(16) A first embodiment of the present invention will be explained by using FIG. 1 to FIG. 9.

(17) As shown in FIG. 1 and FIG. 2, an electric press according to the present embodiment consists of: a pressing ram 1, which applies a desired pressure to a workpiece W by up/down movement; a ball screw 2, which applies the up/down movement to the ram 1; and an electric motor 3. These are provided in a head frame body of a casing 4.

(18) First, as shown in FIG. 1, the structure of the ram 1 is formed into a tubular body. Specifically, a hollow part is formed in a tubular main body 1a, which is formed into a cylindrical shape, along the axial direction thereof, a screw shaft 2a of the ball screw 2 can be inserted in the hollow part, and a nut body 2b of the ball screw 2 is fixed to a shaft-length-direction end location of the tubular main body 1a of the ram 1.

(19) A pressing body 1b is configured to be attachable to a lowermost part of the tubular main body 1a. In practice, the pressing body 1b abuts the workpiece W and applies an arbitrary pressure thereto. Furthermore, in some cases, a strain gauge is configured to be attachable to the pressing body 1b so that the pressure applied to the workpiece W can be detected by the strain gauge.

(20) A tubular guide 5 is provided so as to surround an outer peripheral side surface of the tubular main body 1a. The tubular guide 5 is fixed in the casing 4, and the ram 1 is configured to be movable upward/downward along the tubular guide 5. The ram 1 is provided with an anti-vibration guide 6 so as not to rotate on a plane orthogonal to the axial direction. Specifically, as show in FIG. 1 and FIG. 2, the anti-vibration guide 6 consists of an anti-vibration rod 6a, a guiding part 6b, and a coupling plate 6c; the anti-vibration rod 6a is provided via the coupling plate 6c so as to be directed upward from a lower end location of the ram 1 and be parallel to the ram 1; and the anti-vibration rod 6a is configured to be moved in a top-bottom direction along up and down of the ram 1.

(21) Furthermore, the guiding part 6b for causing the anti-vibration rod 6a to pass a predetermined location is fixed in the casing 4, the anti-vibration rod 6a is configured to be moved up and moved down along the guiding part 6b, and the ram 1 is configured so as not to idle in the tubular guide 5 when moved in the top-down direction.

(22) Below the casing 4, a base 8 is provided in the front side via a perpendicular column 7 and immediately below the ram 1, and manipulation buttons 9a and 9b are provided in front of the base 8 and has functions to move down, pause, and move up the ram 1. Specifically, if the ram 1 is to be moved down, the manipulation buttons 9a and 9b are simultaneously pressed; and, if it is to be paused, the manipulation button 9a is pressed, and only the manipulation button 9b is released. Furthermore, the ram 1 is configured to be moved up when the manipulation buttons 9a and 9b are simultaneously released. Moreover, a control unit 10, which is provided in a lateral front side of the casing 4, has a display device 12 and a manipulation device 13.

(23) As shown in FIG. 3, the control unit 10 has a central processing unit 20 and is controlled by a program stored by a control-program storage device 11. Moreover, it has a temporary storage device 14, which stores temporary data, and it further has a reference-value storage device 15, which stores reference values input by using the display device 12 and the manipulation device 13. On the other hand, a motor-drive control device 21 drives the electric motor 3 by commands of the central processing unit 20. An encoder 22, which detects the position of the ram 1, is coupled to the electric motor 3, thereby detecting the moved distance and speed of the ram 1.

(24) Hereinafter, explanations will be given in accordance with a detection process flow of a bend point shown in FIG. 4. First, in step S110, while the ram 1 is moved down, the position of the ram and the load applied to a work are obtained at a constant time interval. The position of the ram can be obtained from the signals from the encoder 22, which is coupled to the electric motor 3, as the moved distance from an initialization position serving as a reference. Moreover, load values can be obtained from the signals from the strain gauge. For example, position/load data as shown in FIG. 5 is obtained. In the graph of FIG. 5, a bend point is observed near a position of 52.8 [mm].

(25) Then, in step S120, the slope of the graph (the amount of change of the load value with respect to the position) is calculated by a slope calculating formula of a regression line. For example, regarding n-pieces of data, a position data sequence of a pressurization part is (x.sub.1, x.sub.2 . . . xn) and a data sequence of the load is (y.sub.1, y.sub.2 . . . yn); in this case, it is assumed that a regression line is drawn with respect to these values. The slope of the regression line is expressed by Formula 1. Thus, the slope of the load, in other words, the values corresponding to first-order differentials are calculated. FIG. 6 shows an example of the graph of the slope of position/load.

(26) $\begin{array}{cc}\mathrm{Slope}=\frac{n\underset{i=1}{\overset{n}{.Math.}}{x}_i{y}_i-\underset{i=1}{\overset{n}{.Math.}}{x}_i\underset{i=1}{\overset{n}{.Math.}}{y}_i}{n\underset{i=1}{\overset{n}{.Math.}}{x}_i^2-{\left(\underset{i=1}{\overset{n}{.Math.}}{x}_i\right)}^2}& \left[\mathrm{Formula}1\right]\end{array}$

(27) Hereinafter, the slope calculation of the regression line will be shown by specific numerical values. For example, there are data sequences of x={1, 3, 4, 6, 7, 10} and y={5.7, 10.4, 11.1, 19.5, 21.8, 26.2}. The slope is calculated by using all of the six pairs of data. In Formula 1, n=6. The results of calculating the terms of sums in Formula 1 are shown in Table 1.

(28) TABLE-US-00001 TABLE 1 i x y xy x.sup.2 1 1 5.7 5.7 1 2 3 10.4 31.2 9 3 4 11.1 44.4 16 4 6 19.5 117.0 36 5 7 21.8 152.6 49 6 10 26.2 262.0 100 31 94.7 612.9 211

(29) With respect to i of 1 to 6 in a first column, the values of x are provided in a second column, and the vertical sum thereof is shown in a lowermost row . Similarly, y is provided in a third column, xy is provided in a fourth column, x.sup.2 is provided in a fifth column, and the sums thereof are shown in the lowermost level. According to these values, the slope according to Formula 1 becomes 2.432 as shown by Formula 2.
{(6612.9)(3194.7)}{(6211)(3131)}=741.7305=2.432[Formula 2]

(30) As reference, an intercept of the regression line is calculated, and the results of obtaining values of y on the regression line (y) from the slope, the intercept, and the values of x are shown in Table 2.

(31) TABLE-US-00002 TABLE 2 i x y y: y on the regression line 1 1 5.7 5.650 2 3 10.4 10.514 3 4 11.1 12.946 4 6 19.5 17.810 5 7 21.8 20.241 6 10 26.2 27.537

(32) Note that the results of showing the data sequences (original data) of x and y of Table 2 by black points and showing the values (y) of y on the regression line by hollowed points are as shown in FIG. 7.

(33) In the above described manner, the slope of the load, in other words, the values corresponding to the amounts of changes with respect to the positions can be calculated by Formula 1 for obtaining the slope of the regression line. FIG. 7 shows a graph of the slope of the regression line obtained based on the data sequences of position/load shown in FIG. 6. It can be understood from this graph that the slope is increased from around the position of 52.8 mm, the amount of increase thereof is reduced from a point after a position of 53 mm, and the slope becomes approximately constant at 8000 [N/mm].

(34) In step S130, based on the data of the slope, the slope of the slope of the load is calculated as the amounts of changes of the amounts of changes of the load values with respect to the positions by using Formula 1 for calculating the slope of a regression line again. The calculation per se is similar. A graph of the slope of the slope of position/pressurization-load obtained as a result is shown in FIG. 8. It can be understood from this graph that a peak is at a point slightly after the position of 52.8 mm. FIG. 9 shows a graph in which FIG. 5, FIG. 6, and FIG. 8 are mutually overlapped. The vertical direction thereof is in an appropriate scale so as to facilitate viewing.

(35) Then, in step S140, a reference set value, which is set in advance, and the calculated value of the slope of the load are compared with each other, a point that exceeds the reference set value is determined as a bend point, and, when the bend point is determined, movement of the pressurization part is stopped (step S150).

(36) As explained above, according to the present embodiment, the slope of the slope of the load can be calculated as significant amounts, and the bend point can be detected based on that.

Second Embodiment

(37) An electric press according to the present embodiment will be explained by using FIG. 10 and FIG. 11. The first embodiment has shown an example of calculating the slope of the load by using the regression line. In the present embodiment, a smoothing process is added thereto.

(38) Therefore, as shown in FIG. 10, the control unit 10 is provided with a low-pass filter (for example, a digital filter).

(39) In an actual process, as shown in FIG. 11, after a data sequence of the position of the ram and a data sequence of the load applied to the work are obtained by sampling at every constant time, and, after the slope of the load is calculated by a regression line, the smoothing process by the low-pass filter (for example, a digital filter) is carried out.

(40) In this manner, according to the present embodiment, a graph is smoothed by the smoothing so that a next processing calculation can be carried out well. Note that, as the smoothing process, for example, smoothing such as obtaining a moving average is conceivable.

(41) Note that the electric press of one or more embodiments of the invention can be realized by recording the process of the electric press in a recording medium, which can be read by a computer system and causing the electric press to read and execute the program recorded in the recording medium. The computer system referred to herein includes an OS and hardware such as peripheral devices.

(42) If a WWW (World Wide Web) system is utilized, the computer system also includes a homepage providing environment (or display environment). The above described program may be transmitted from the computer system, which stores the program in a storage device or the like, to another computer system via a transmission medium or by transmission waves in the transmission medium. Herein, the transmission medium, which transmits the program, refers to a medium having a function to transmit information like a network (communication network) such as the Internet or a communication line (communication wire) such as a telephone line.

(43) The above described program may be a program for realizing part of the above described functions. Furthermore, the above described program may be a so-called difference file (difference program), which can realize the above described functions by combination with a program(s) already recorded in the computer system.

(44) Hereinabove, the embodiments of this invention have been described in detail with reference to drawings. However, specific configurations thereof are not limited to the embodiments, but include designs, etc. within a range not departing from the gist of this invention.

DESCRIPTION OF REFERENCE NUMERALS

(45) 1; RAM 2; BALL SCREW 3; ELECTRIC MOTOR 4; CASING 1a; TUBULAR MAIN BODY 2a; SCREW SHAFT 2b; NUT BODY 1b; PRESSING BODY 5; TUBULAR GUIDE 6; ANTI-VIBRATION GUIDE 6a; ANTI-VIBRATION ROD 6b; GUIDING PART 6c; COUPLING PLATE 7; COLUMN 8; BASE 9a; MANIPULATION BUTTON 9b; MANIPULATION BUTTON 10; CONTROL UNIT 11; CONTROL-PROGRAM STORAGE DEVICE 12; DISPLAY DEVICE 13; MANIPULATION DEVICE 14; TEMPORARY STORAGE DEVICE 15; REFERENCE-VALUE STORAGE DEVICE 16; LOW-PASS FILTER 20; CENTRAL PROCESSING UNIT (CPU) 21; MOTOR-DRIVE CONTROL DEVICE 22; ENCODER