Pressing device, load correction method and storage medium

Abstract

Pressing device comprising: a position detection unit (14) that detects a position of a plunger (1); a load detecting unit (27) that detects a load value exerted on the plunger (1); a determination unit that determines whether or not a press-fitting operation on a workpiece is performed normally based on the position of the ram and the load value at the position; a storage unit (25) that stores a moving average and a scatter average of the load value, which are calculated in advance; a load drop determination unit (34) that determines whether the load value detected by the load detection unit exceeds a load drop determination value set based on the stored moving average and the stored dispersion average; a data substitution unit (35) which substitutes the load value determined by the load drop determination unit to exceed the load drop determination value with a predetermined value; and a press-fitting operation determining unit (36, 44) that determines whether or not the press-fitting operation is normally performed on a workpiece based on a load value data series of the press-fitting operation including the load value data substituted by the data substitution unit.

Description

TECHNICAL FIELDThe present invention relates to a pressing apparatus, a load correction method, and a storage medium.BACKGROUND ARTA servo press for driving a slide by a servo motor is well known (for example, shown in JP 2008-137 015 A). In the servo press, the position and speed of the slide can be controlled with high accuracy. The servo press can therefore be combined in a simple manner with peripheral devices, for example with a conveying device which is used for the input / output of a workpiece. The servo press thus has a productivity enhancing feature.The above-described type of servo press is also characterized in that whether or not press-fitting work is successfully performed is determined, for example, by continuously monitoring a load value in the press-fitting work. As an example of the concrete determination criteria as shown in FIG. 17, a function called "load determination" has been provided. In the load determination, the position range and the load range are set, and it is determined that the press-fit work is successful when performed within a rectangular range of the position range and the load range.In the above-described load determination, a "determination start position" and a "determination end position" are set, and "maximum load" and "minimum load" are set, respectively, for both positions. As shown in FIG. 17, four points form a rectangular determination frame. It is then determined that the press-fit work is successful when the position and load value during the work are within the determination frame, and that it is unsuccessful when they are outside the determination frame.DE 699 09 579 T2 discloses a method for determining the success or failure of press-fitting a workpiece into an object element with a linearly driven punch, comprising the steps of: obtaining the thrust information and the position information of the punch when the punch press-fits the workpiece in a predetermined stroke range; characterized in that: the object element has a contact end; a near press-fit end position is detected at which the ratio of the change of the thrust information with respect to the position information exceeds a predetermined value; the success or failure of the press-fitting operation is determined according to whether the thrust information during the press-fitting operation is included in a predetermined range of a section from a predetermined determination start position to a determination end position; and the determination end position corresponding to the detected near-press-fit end position is determined.US 2011 / 0 301 875 A1 discloses a female press-fit inspection device that can perform inspection in any state between the start of press-fit and the end of press-fit to determine whether or not the press-fit has been satisfactorily performed. The bush press-fit inspection device is used in a bush press-fit device that supports a bush at one end of the bush press-fit device using a press-fit mechanism and that presses the bush into a bush press-fit portion formed as part of a cylindrical-shape structure included in a workpiece over a certain stroke at a certain load. The socket press-fit inspection device includes setting means, storage means, input means, judgment means and output means.WO 2008 / 009 299 A1 discloses a joining unit which contains a spindle drive in the form of a hollow shaft motor which encloses a spindle. The hollow shaft motor serves to achieve a linear movement of a joining tool for carrying out a joining process. The joining unit contains instruments for presetting and / or determining the exerted forces and / or the movement of the joining tool during the joining process.CN 1 0 1 288 934 A discloses a power device consisting of a servomotor controlled by an embedded industrial control system and a driving part matched with the servomotor in a transmission manner; the driving part is matched with a press mounting head through a screw thread; the press mounting head is provided with a pressure sensor for sending signals to the embedded industrial control system and connected to a displacement sensor; the embedded industrial control system is connected to a display and a control keyboard.CN 1 05 955 192 A discloses a real time monitoring method for press mounting of a servo press machine. The method comprises in particular the following steps: creating a real-time displacement pressure curve on the basis of displacement pressure data read in real time, creating a speed displacement curve and a speed-time curve of an initial press assembly process on the basis of the displacement pressure curve, using the speed displacement curve for setting anomalies of the press assembly process which are caused by minute changes in the speed in the displacement change process, using the speed-time curve for carrying out a further fine tuning of the press assembly press, subsequent introduction of an external detection, carrying out a real-time comparison of normal travel and pressure data, correction of deviations, determining abnormal points in press assembly and adjusting the process according to the slope of each collection point on the path-pressure curve, performing the final adjustment, and obtaining precise final process data. According to the invention, the press mounting time, the parameters such as the press mounting speed, currents, dot pitches and additional analog quantities are introduced, and any two parameters may be selected to form a press mounting curve, so that a targeted monitoring and judgment of the press mounting process is realized.DE 10 2014 012 637 A1 discloses a detection means for detecting a data series of a pressing position and a load at the pressing position; an input / storage means for inputting and storing a load value, a value of an increase of the load, a value of a second-order difference quotient of the load as reference values for determining a stop or a rating; a calculation means of the value of the increase of the load for calculating the value of the increase of the load based on the pressing position and the load at the pressing position which are detected; a calculation means of the value of the second-order difference quotient of the load for calculating the value of the second-order difference quotient of the load based on the calculated value of the increase of the load; and determining means for comparing the calculated value of the second-order difference quotient of the load with the values serving as references for determining a stop or a score.SUMMARY OF THE INVENTIONOBJECTS TO BE SOLVED BY THE INVENTIONThe principle of load generation during press-in work is different from that during shaping or bending work. In press-fitting work, the load is generated as a resistance force corresponding to the friction coefficient or as a repulsive force as in a damper. In addition, the load value generated in press-fitting work tends to be constant.However, during press-in operations, a sudden increase in the load value (e.g., seizure) or a brief decrease in the press load may occur due to slippage. At this time, the seizure at which the load value suddenly increases can be judged by adjusting the pressing-in maximum value. However, for load drops due to temporary slipping, depending on the extent of the load drop, some values should be considered normal. Therefore, the minimum load for the load determination is sufficiently lowered, or the determination is performed based on a moving average value of the load.As described above, a sudden load drop can be alleviated to some extent by calculating the moving average value of the load value to perform the determination.However, when the moving average is used, the value falls as the load decreases. The minimum load value for the determination should therefore be lowered by this amount. On the other hand, it is also desirable to keep the load value determination margin of a normal press-in for fault detection small. Thereby, although it is determined that the operation is successful per se, it is determined that appropriate measures such as preventive maintenance are necessary. In addition, there is doubt about the validity of the evaluation of the press-in work when unintended load jumps are involved in the calculation of the moving average.FIG. 16 is a graph showing the moving average value of the load value in the data having the load value at which the load drop occurs due to slipping of the load. As shown in FIG. 16, the load drop is smoothed to some extent by calculating the moving average value of the load value. In addition, if a wide window is selected for the moving average of the load value, the load drop is considerably more smoothed. Thus, the effect of eliminating the influence of the load drop can be expected. However, calculating the moving average value of the load value from the data having the load value at which the load drop occurs due to slipping of the load has no meaningful meaning. It is believed that calculating an "average" does not make any sense for situations with different load generation mechanisms.The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a pressing apparatus, a load correction method, and a program capable of evaluating press-in work by appropriately determining the load upon occurrence of slipping.MEANS FOR ACHIEVING THE OBJECTAspect 1: One or more embodiments of the present invention propose a pressing device having the features of claim 1.Aspect 2: One or more embodiments of the present invention propose the pressing apparatus in which the data substituting unit substitutes the load value determined by the load drop determination unit to exceed the load drop determination value with an average value of the load value before determining that the load value applied to the workpiece exceeds the load drop determination value.Aspect 3: One or more embodiments of the present invention propose the pressing apparatus in which the data substituting unit substitutes the load value determined to exceed the load drop determination value by the load drop determination unit with a normal load value determined to be normal before determining that the load value applied to the workpiece exceeds the load drop determination value.Aspect 4: One or more embodiments of the present invention propose the pressing apparatus in which the data substituting unit substitutes the load value determined to exceed the load drop determination value by the load drop determination unit with a normal load value determined to be normal after determining that the load value applied to the workpiece exceeds the load drop determination value.Aspect 5: One or more embodiments of the present invention propose the pressing apparatus further including a press-fit operation determination unit that determines whether or not the press-fit operation is normally performed on a workpiece based on a load value data series of the press-fit operation including the load value data substituted by the data substitution unit.Aspect 6: One or more embodiments of the present invention propose the pressing apparatus further including a counting unit that counts the number of determinations in which it is determined by the load-dropping determination unit that the load value exceeds the load-dropping determination value, wherein the press-fitting operation determination unit determines whether or not the press-fitting operation is normally performed on the workpiece in consideration of the number counted by the counting unit.Aspect 7: One or more embodiments of the present invention propose a load correction method in a pressing apparatus, the pressing apparatus including: a position detection unit that detects a position of a plunger; a load detection unit that detects a load value applied to the plunger; a determination unit that determines whether or not a press-fitting operation is normally performed on a workpiece based on the position of the plunger and the load value at the position; a storage unit that stores a moving average value and a scattering average value of the load value calculated in advance; a load drop determination unit; a data substitution unit; An injection operation determination unit, the method comprising: a first operation of determining, by the load dump determination unit, whether the load value detected by the load detection unit exceeds a load dump determination value set based on the stored moving average and the stored scattering average; and a second operation of substituting, by the data substitution unit, the (one) load value determined by the load dump determination unit to exceed the load dump determination value by a predetermined value.Aspect 8: One or more embodiments of the present invention propose a storage medium in which a computer program for causing a computer to execute a load correction method in a pressing apparatus is stored, the pressing apparatus including: a position detection unit that detects a position of a plunger; a load detection unit that detects a load value applied to the plunger; a determination unit that determines whether or not a press-fitting operation is normally performed on a workpiece based on the position of the plunger and the load value at the position; a storage unit that stores a moving average value and a scattering average value of the load value that are calculated in advance; a load drop determination unit; a data substitution unit; An injection operation determination unit, the method comprising: a first operation of determining, by the load dump determination unit, whether the load value detected by the load detection unit exceeds a load dump determination value set based on the stored moving average and the stored scattering average; and a second operation of substituting, by the data substitution unit, the (one) load value determined by the load dump determination unit to exceed the load dump determination value by a predetermined value.Aspect 9: One or more embodiments of the present invention propose the pressing device in which the press-fit operation determination unit determines that the press-fit operation on the workpiece is not normal when the number counted by the counting unit exceeds a predetermined number.Aspect 10: One or more embodiments of the present invention propose the pressing apparatus in which the press-fit operation determination unit determines that the press-fit operation on the workpiece is not normal when a number of continuous occurrences counted by the counting unit exceeds a predetermined number of continuous occurrences.Aspect 11: One or more embodiments of the present invention propose the pressing apparatus in which the press-fit operation determination unit determines that the press-fit operation on the workpiece is not normal when a continuous occurrence distance corresponding to a number of continuous occurrences counted by the counting unit exceeds a predetermined continuous occurrence distance.EFFECT OF THE INVENTIONIn one or more embodiments of the present invention, by appropriately determining the load upon occurrence of slipping, the effect that evaluation of the press-fit work becomes possible can be obtained.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a drawing showing the configuration of a pressing apparatus according to the first embodiment of the present invention. FIG. 2 is a drawing showing the electrical configuration of the pressing apparatus according to the first embodiment of the present invention. FIG. 3 is a drawing showing the electrical configuration of a central processing unit according to the first embodiment of the present invention. FIG. 4 is a drawing showing the relationship among an upper limit value, a lower limit value, and a load drop determination value of the pressing apparatus according to the first embodiment of the present invention. FIG. 5 is a drawing showing the operations of the pressing apparatus according to the first embodiment of the present invention. FIG. 6 is a drawing illustrating data substituting operations in the pressing apparatus according to the first embodiment of the present invention. FIG. 7 is a drawing illustrating the data substituting operations in the pressing apparatus according to the first embodiment of the present invention. FIG. 8 is a drawing illustrating the data substituting operation in the pressing apparatus according to the first embodiment of the present invention. FIG. 9 is a drawing illustrating the position / load data in the pressing apparatus according to the first embodiment of the present invention. FIG. 10 is a drawing illustrating the position / load data in the pressing apparatus according to the first embodiment of the present invention in which the data is substituted when the load is slipping. FIG. 11 is a drawing illustrating a standard deviation in the pressing apparatus according to the first embodiment of the present invention. FIG. 12 is a drawing showing the electrical configuration of the pressing apparatus according to the second embodiment of the present invention. FIG. 13 is a drawing showing the electrical configuration of a central processing unit according to the second embodiment of the present invention. FIG. 14 is a drawing showing the operations of the pressing apparatus according to the second embodiment of the present invention. FIG. 15 is a drawing showing the operations of the pressing apparatus according to the second embodiment of the present invention. FIG. 16 is a drawing illustrating the position / load data in the pressing apparatus according to the first embodiment of the present invention in which the data is substituted when the load is slipping. FIG. 17 is a drawing showing the conventional determination method.EMBODIMENTS OF THE INVENTIONFirst EmbodimentNext, the first embodiment of the present invention will be explained with reference to FIGS. 1 to 11.Configuration of the Pressing DeviceThe configuration of a pressing apparatus 100 according to the present embodiment will be explained with reference to FIG. 1.As shown in FIG. 1, the pressing apparatus 100 according to the present embodiment includes a pressing ram 1 that applies a desired pressure to a workpiece W (object to be processed) by upward and downward movement, and a ball screw 2 that transmits the upward and downward movement (linear movement) to the ram 1. The plunger 1 and the ball screw 2 are provided inside a press housing 3. In addition, a servo motor 4, such as an AC servo motor, is housed in a frame body located at the head portion of a casing 5 connected to the press housing 3 to serve as a drive source. The drive of the servomotor 4 is transmitted to the ball screw 2 via a pulley and a belt.The plunger 1 is formed in a cylindrical shape as shown in FIG. 1. Specifically, a tubular body 1 ais formed in a cylindrical shape, and a hollow portion is formed inside the tubular body 1 ain the axial direction. A screw shaft 2 aof the ball screw 2 can be inserted into the hollow portion. In addition, a nut 2 bof the ball screw 2 is fixed to the axial direction end portion of the tubular body 1 aof the plunger 1.To the tip portion of the tubular body 1a, an expanding cylinder 9 may be attached as desired.In practice, the stretching cylinder 9 is brought into contact with the workpiece W to apply the desired pressure. In addition, a strain gauge may be attached to the strain cylinder 9. The force applied to the workpiece W can be detected by the strain gauge.A tubular guide 6 is provided so as to cover the outer circumferential side surface of the tubular body 1 a. The tubular guide 6 is fixed inside the fairing 5. The punch 1 can move up and down along the tubular guide 6.Electrical Configuration of the Pressing DeviceAs shown in FIG. 2, the pressing apparatus 100 according to the present embodiment includes a servo motor driving device 13, an encoder 14, a control program storage unit 21, a display unit 22, an operation section 23, a temporary storage unit 24, a calculation value storage unit 25, a circuit section 27, a drive command pulse generation unit 28, an encoder position counter 29, and a CPU (Central Processing Unit) 30.In the control program storage unit 21, control programs are stored such that the CPU (central processing unit) 30 controls the operation and operations of the entire pressing apparatus 100. For example, in the present embodiment, the control program storage unit 21 stores a main program concerning the pressing operation; also, there are stored the programs described later, such as a program for determining whether or not the pressing operation is normally performed, a program for calculating a moving average, a program for calculating a deviation value, a program concerning the data substitution, and a program concerning the display. The display unit 22 is a display device for displaying various information. In the present embodiment, the display unit 22 displays information such as the determination result of the press-fitting operation.The operation section 23 includes, for example, a touch screen for setting the press-fit conditions or the like, and a button. Temporary data is stored in the temporary storage unit 24. In the present embodiment, the temporary storage unit 24 stores, for example, acquired position and load value. In the calculation value storage unit 25, for example, the calculated moving average value and deviation value are stored.The circuit portion 27 serving as a load detection unit amplifies the signal corresponding to the resistance change of the strain measurement device mounted on the strain cylinder 9, converts an analog signal into a digital signal by an A / D conversion process, and then outputs the signal to the CPU (central processing unit) 30.The drive command pulse generation unit 28 generates the desired drive command pulse based on the command from the CPU (central processing unit) 30, and outputs the generated drive command pulse signal to the servo motor drive device 13 via the CPU (central processing unit) 30. Then, the servomotor 4 is driven by the control of the servomotor drive device 13 to vertically displace the plunger 1.The encoder 14 is a device for detecting the rotation angle of the servomotor 4, and is used for detecting the position of the plunger 1. In addition, the information of the encoder 14 transmits position information to the servo motor driving device 13 to form a control loop. The CPU (central processing unit) 30 can further read the position information of the encoder 14 via the encoder position counter 29. Thereby, the amount of movement of the plunger 1 is detected.The CPU (central processing unit) 30 controls the operation of the entire pressing apparatus 100 according to the control program stored in the control program storage unit 21. In the present embodiment, specifically and mainly, the CPU 30 performs the control related to the determination of the press-fitting operation.Electrical Configuration of the Central Processing UnitAs shown in FIG. 3, the central processing unit 30 according to the present embodiment includes a moving average calculation unit 32, a moving average calculation unit 33, a load drop determination unit 34, a data substitution unit 35, and a press-in operation determination unit 36.The moving average value calculation unit 32 calculates the moving average value of the load value acquired from the circuit portion 27 and stored in the temporary storage unit 24. Specifically, the moving average value calculation unit 32 calculates the moving average value of the load value data after the start of the press-fitting work until the load value used for the determination is obtained. The calculated moving average value is then stored in the arithmetic value storage unit 25.The mean-of-scattering calculation unit 33 calculates the standard deviation from the moving average calculated by the moving average calculation unit 32 and the load value stored in the temporary storage unit 24, calculates the mean-of-scattering value, and calculates the mean-of-scattering value of the calculated mean-of-deviation value. The calculated average scattering value is then stored in the calculation value storage unit 25. When a test was made on a real device, the load drop actually occurred was about 300 N as shown in Fig. 9. In the present embodiment, three times the standard deviation σ is defined as a deviation value.The load-droop determination unit 34 determines (judges) whether the load value acquired by the circuit portion 27 and stored in the temporary storage unit 24 exceeds a load-droop determination value determined based on the moving average calculated by the moving average calculation unit 32 and the moving average calculated by the moving average calculation unit 33. The relationship among the upper limit value, the lower limit value, and the load-down determination value behaves as shown in FIG. 4. It is determined that there is a load drop caused by load slipping when the load value acquired from the circuit portion 27 is smaller than the load drop determination value set from "moving average value and deviation (3σ)".The data substituting unit 35 substitutes the predetermined value for the load value obtained from the circuit section 27 and stored in the temporary storage unit 24, when the load value exceeds the load-decrease determination value determined by the load-decrease determination unit 34 based on the moving average calculated by the moving average calculation unit 32 and the moving average calculated by the moving average calculation unit 33. Specifically, as shown in FIG. 6, the load value (shaded circle in the figure) exceeding the load-down determination value is substituted by the previous moving average value. Alternatively, as shown in FIG. 7, the load value (hatched circle in the figure) exceeding the load-down determination value is substituted with the normal load value which has been found to be normal before the detection of the load value exceeding the load-down determination value. Alternatively, as shown in FIG. 8, the load value (hatched circle in the figure) exceeding the load-down determination value is substituted with the normal load value which is found to be normal after the detection of the load value exceeding the load-down determination value.The press-fit operation determination unit 36 determines whether or not the press-fit operation is normally (correctly) performed on a workpiece based on the load value data series of the press-fit operation including the load value data substituted by the data substitution unit 35. Then, the determination result is outputted to the display unit 22 to display the determination result.Operations in the Pressing ApparatusNext, the operations in the pressing apparatus 100 according to the present embodiment will be explained with reference to FIG. 5.First, the load dump determination unit 34 reads out the moving average value and the scattering average value from the calculation value storage unit 25 (step S 101). In addition, the load dump determination unit 34 acquires the current load value from the temporary storage unit 24 (step S 102).The load-decrease determining unit 34 determines whether the acquired current load value is smaller than the load-decrease determining value (moving average value and deviation value (3σ)) (step S 103). In the above-described step, when the load dump determination unit 34 determines that the acquired current load value is smaller than the load dump determination value ("Yes" in step S 103), the load value acquired from the data substitution unit 35 is substituted by a predetermined value (e.g., the moving average) or substituted by forward substitution or backward substitution (step S 104). In the above-described step, the substituted load value is overwritten and stored in the temporary storage unit 24.On the other hand, when the load dump determination unit 34 determines that the acquired current load value is not less than the load dump determination value ("No" in step S 103), the process proceeds to step S 105.The load dump determination unit 34 then determines whether or not the determination of step S 103 is completed for all load values (step S 105). When the load dump determination unit 34 determines that the determination of step S 103 is not completed for all load values ("No" in step S 105), the process returns to step S 103. On the other hand, when the load dump determination unit 34 determines that the determination of step S 103 is completed for all load values ("Yes" in step S 105), the process proceeds to step S 106.In addition, the press-fit operation determination unit 36 determines whether or not the load values including the substituted load value are within the range between the upper limit value and the lower limit value (step S 106). Here, when the press-fit operation determination unit 36 determines that the load values including the substituted load value are not within the range between the upper limit value and the lower limit value ("No" in step S 106), a failure determination operation is performed (step S 107), and all operations are ended.However, when the press-fit operation determination unit 36 determines that the load values including the substituted load value are within the range between the upper limit value and the lower limit value ("Yes" in step S 106), the determination result information is output to the display unit 22, and the operation is ended.As explained above, in the present embodiment, the load drop determination unit 34 determines whether the detected load value exceeds the load drop determination value set based on the stored moving average and the stored scattering average. The data substituting unit 35 substitutes a load value determined by the load dump determination unit 34 to exceed the load dump determination value with the predetermined value. The press-fit operation determination unit 36 determines whether or not the press-fit operation is normally performed on a workpiece based on the load value data series of the press-fit operation including the load value data substituted by the data substitution unit 35. Therefore, the press-fit work can be evaluated by appropriately determining the load upon occurrence of slipping. In addition, the determination range can be narrowed by evaluating the press-fit work excluding the load at which slipping occurs. As a result, it is expected that the information can be used to find errors and prevent errors in press-fit operations. The concrete effects of the present embodiment will now be considered with reference to FIGS. 9 and 10. For example, FIG. 9 shows data in which slipping occurs. It can be seen from the figure that the pressing-in begins at a position somewhat above 40.00 mm and the load reaches approximately 1000 N at a position of 40.7 mm. Thereafter, an approximately constant load is applied as the pressing operation proceeds. In addition, in the figure, at the position around 41.5 mm, a sudden and momentary load drop having a value of about 700 N can be observed. On the other hand, FIG. 10 is a graph in which the instantaneous load drop has been removed. It is apparent from the figure that the momentary load drop shown in Fig. 9 has been removed.The press-fit operation determination unit 36 also determines whether or not the press-fit operation is normally performed on a workpiece based on the load value data series of the press-fit operation including the load value data substituted by the data substitution unit 35. Thus, when the press-fit operation is not normally performed for reasons other than creating chutes, it can be determined that the press-fit operation is not normal and that the press-fit operation has failed.In addition, the data substituting unit 35 substitutes the load value determined by the load dump determination unit 34 to exceed the load dump determination value with an average value of the load values before determining that the load value applied to the workpiece exceeds the load dump determination value. Thereby, even if the load drop caused by slipping occurs, it is not determined that the press-fitting operation is not normal. It is thus possible to improve the manufacturing yield while maintaining the quality of the press-fit.In addition, the data substituting unit 35 substitutes the load value determined by the load drop determination unit 34 to exceed the load drop determination value with an average value of the load values after determining that the load value applied to the workpiece exceeds the load drop determination value. Thereby, even if the load drop caused by slipping occurs, it is not determined that the press-fitting operation is not normal. It is thus possible to improve the manufacturing yield while maintaining the quality of the press-fit.In the example of the present embodiment, the data substituting unit 35 substitutes the load value with the moving average or substitutes it with forward substitution or backward substitution. However, it is also possible to substitute the load value with an average value of the load value found to be normal after the exceeding load value and the load value found to be normal before the exceeding load value, or an ideal value at the position of the load value.In the example of the present embodiment, it is also determined whether or not the press-fitting operation is normally performed on the workpiece based on the load value data substituted by the data substituting unit 35. However, it is also possible to determine whether or not the press-fit operation is normally performed based on corrected data without substituting the load value upon occurrence of slipping.Second EmbodimentNext, the second embodiment of the present invention will be explained with reference to FIGS. 12 to 15.Electrical Configuration of the Pressing DeviceAs shown in FIG. 12, a pressing apparatus 110 according to the present embodiment includes a servo motor driving device 13, an encoder 14, a control program storage unit 21, a display unit 22, an operation section 23, a temporary storage unit 24, a calculation value storage unit 25, an occurrence number storage unit 26, a circuit section 27, a drive command pulse generation unit 28, an encoder position counter 29, a continuous occurrence number storage unit 31, and a CPU (central processing unit) 40. Note that the detailed description of the elements having the same reference numerals as in the first embodiment will be omitted because they have the same function.In the occurrence number storage unit 26, the number of occurrences counted by the counting unit 43 that counts how many times it is determined that the load value acquired by the circuit portion 27 and stored in the temporary storage unit 24 exceeds the load drop determination value set in the later-described load drop determination unit 34 for a series of press-fitting operation applied to a particular workpiece based on the moving average calculated by the moving average calculation unit 32 and the moving average calculated by the moving average calculation unit 33.In the continuous occurrence number storage unit 31, the continuously counted value of the count of the count unit 43 is stored as the continuous occurrence number.Electrical Configuration of the Central Processing UnitAs shown in FIG. 13, the central processing unit 40 according to the present embodiment includes a moving average calculation unit 32, a moving average calculation unit 33, a load decrease determination unit 34, a data substitution unit 35, a counting unit 43, and a press-in operation determination unit 44.The counting unit 43 includes a counter for counting how many times it is determined that the load values in the load values acquired from the circuit portion 27 and stored in the temporary storage unit 24 exceed the load-down determination value determined by the load-down determination unit 34 based on the moving average calculated by the moving average calculation unit 32 and the moving average calculated by the moving average calculation unit 33. The counted value is stored in the occurrence number storage unit 26 and the continuous occurrence number storage unit 31 via a not-illustrated control unit.The press-fit operation determination unit 44 determines whether or not the press-fit operation is normally performed on the workpiece by taking into account the load value data substituted by the data substitution unit 35 and taking into account the count (number) counted by the counting unit 43. Specifically, the press-fit operation determination unit 44 determines that the press-fit operation on the workpiece is not normal when the number counted by the counting unit 43 exceeds the predetermined number. In addition, the press-fit operation determination unit 44 determines that the press-fit operation on the workpiece is not normal when the number of continuous occurrences counted by the counting unit 43 exceeds the predetermined number of continuous occurrences. In addition, the press-fit operation determination unit 44 determines that the press-fit operation on the workpiece is not normal when the continuous occurrence distance corresponding to the continuous occurrence number counted by the counting unit 43 exceeds the continuous occurrence distance determined in advance.Operations in the Pressing ApparatusNext, the operations in the pressing device 110 according to the present embodiment will be explained with reference to FIGS. 14 and 15.First, the load dump determination unit 34 acquires the current position and the current load value from the temporary storage unit 24 (step S 201), and reads out the moving average value and the deviation value from the calculation value storage unit 25 to calculate the lower limit value (step S 202).The load-dump determination unit 34 determines whether the acquired current load value is smaller than the load-dump determination value (step S 203). In the above-described step, when the load dump determination unit 34 determines that the acquired current load value is not less than the load dump determination value ("No" in step S 203), a continuous occurrence counter is cleared (step S 204), and the process proceeds to step S 209.On the other hand, when the load dump determination unit 34 determines that the acquired current load value is smaller than the load dump determination value ("Yes" in step S 203), the acquired load value is substituted by the predetermined value (step S 205), and then determines whether or not the counter value of the continuous occurrence counter is "0" (step S 206). When it is determined in the above-described step that the counter value of the continuous occurrence counter is "0" ("Yes" in step S 206), the counter value of the occurrence counter is increased by "1" (step S 207), and the counter value of the continuous occurrence counter is increased by "1" (step S 208). When it is determined that the counter value of the continuous occurrence counter is not "0" ("No" in step S 206), the value of the continuous occurrence counter is increased by "1" (step S 208), and the process proceeds to step S 209. When it is determined that the counter value of the continuous occurrence counter is not "0" ("No" in step S 206), it is assumed that there is continuous slipping. Therefore, the counter value of the occurrence counter is not increased and the counter value of the continuous occurrence counter is increased by "1" (step S 208), and the process proceeds to step S 209.Then, the load dump determination unit 44 determines whether or not the current load value is less than the lower limit value (step S 209). When it is determined that the current load value is less than the lower limit value ("Yes" in step S 209), the failure determination process is performed (step S 210), all the processes are ended, and the failure determination result is output to the display unit 22.On the other hand, when the press-fit operation determination unit 44 determines that the current load value is larger than the lower limit value ("No" in step S 209), it is determined whether or not the counter value of the occurrence counter is within the predetermined count value range (step S 211). In the above-described step, when the press-fit operation determination unit 44 determines that the counter value of the occurrence counter is outside the predetermined count value range ("No" in step S 211), the failure determination operation is performed (step S 210), all operations are ended, and the failure determination result is output to the display unit 22.On the other hand, when the press-fit operation determination unit 44 determines that the counter value of the occurrence counter is not outside the predetermined count range ("Yes" in step S 211), it is determined whether or not the counter value of the continuous occurrence counter is within the predetermined count range (step S 212). In the above-described step, when the press-fit operation determination unit 44 determines that the counter value of the continuous occurrence counter is outside the predetermined count value range ("No" in step S 212), the failure determination operation is performed (step S 210), all operations are ended, and the failure determination result is output to the display unit 22.On the other hand, when the press-fit operation determination unit 44 determines that the counter value of the continuous occurrence counter is not outside the predetermined count range ("Yes" in step S 212), the load average (moving average) is calculated again, the load average (moving average) is updated with a new value (step S 213), the standard deviation is calculated again, and the standard deviation is updated with a new value (step S 214).Then, the CPU 40 determines whether or not the determination of step S 203 is completed for all load values (step S 215). When it is determined that the determination of step S 203 is completed for all load values ("Yes" in step S 215), all operations are ended and the success determination result is output to the display unit 22. When it is determined that the determination of step S 203 is not completed for all load values ("No" in step S 215), the process returns to step S 201.As explained above, in the present embodiment, the load drop determination unit 34 determines whether the detected load value exceeds the load drop determination value set based on the stored moving average and the stored scattering average. The data substituting unit 35 substitutes the detected value with the predetermined value when the detected load value exceeds the load-down determination value set based on the stored moving average and the stored scattering average from the load-down determination unit 34. The counting unit 43 counts how many times the detected load value exceeds the load-down determination value set based on the stored moving average and the stored scattering average from the load-down determination unit 34. Then, the press-fit operation determination unit 44 determines whether or not the press-fit operation is normally performed on the workpiece from the load value data series of the press-fit operation including the load value data substituted by the data substitution unit 35 and the count of the count unit 43. The press-fit work is evaluated by making determinations on the data group in which the load generated upon occurrence of slipping is substituted with an appropriate value, and determinations according to the count of the counting unit 43. The load generated upon slipping is therefore appropriately determined, and the press-fit work can thus be evaluated more accurately. In addition, frequently occurring load drop and continuously occurring load drop are detected and corresponding fault determinations are carried out. The error can thus be accurately determined. In addition, when the situation is inspected at the position where the continuous load drop occurs, the cause of the failure can be accurately recognized.The press-fit operation determination unit 44 also determines whether or not the press-fit operation is normally performed on a workpiece from the load value data series of the press-fit operation including the load value data substituted by the data substitution unit 35 and the count of the count unit 43. Thus, when the press-fit operation is not normally performed for reasons other than creating chutes, it can be determined that the press-fit operation is not normal and that the press-fit operation has failed.The press-fit operation determination unit 44 also determines that the press-fit operation on the workpiece is not normal when the number counted by the counting unit 43 exceeds a predetermined number. Even if it is originally determined that the press-fitting operation has been normally performed, it is determined that a certain cause of failure may have occurred when the number counted by the counting unit 43 exceeds the predetermined number. It is therefore determined that the press-fit work is not normal. Accordingly, the press-fit work can be evaluated more accurately because a certain cause of failure is predicted in the evaluation.In addition, the press-fit operation determination unit 44 determines that the press-fit operation on the workpiece is not normal when the number of continuous occurrences counted by the counting unit 43 exceeds the predetermined number of continuous occurrences. Even if it was originally determined that the press-fitting operation was normally performed, it is determined that a certain cause of failure may have occurred when the number of continuous occurrences counted by the counting unit 43 exceeds the predetermined number. It is therefore determined that the press-fit work is not normal. Accordingly, the press-fit work can be evaluated more accurately because a certain cause of failure is predicted in the evaluation.In addition, the press-fit operation determination unit 44 determines that the press-fit operation on the workpiece is not normal when the continuous occurrence distance corresponding to the continuous occurrence number counted by the counting unit 43 exceeds the continuous occurrence distance determined in advance. Even if it was originally determined that the press-fitting operation was normally performed, it is determined that a certain cause of failure may have occurred when the continuous occurrence distance corresponding to the number of continuous occurrences counted by the counting unit 43 exceeds the predetermined continuous occurrence distance. It is therefore determined that the press-fit work is not normal. Accordingly, the press-fit work can be evaluated more accurately because a certain cause of failure is predicted in the evaluation.Although the example shown in FIGS. 14 and 15 described above shows the continuous occurrence count method, the determination may be performed based on the continuous occurrence distance. In step S206 of Fig. 14, if the continuous occurrence counter is "0", this point may also be regarded as a beginning point of the continuous occurrence. Instead of step S 207, the current position Pc is stored as the continuous occurrence start position Pcs, and in step S 206, the continuous occurrence distance may be calculated by subtracting the continuous occurrence start position Pcs from the current position Pc when the continuous occurrence counter is not "0" (i.e., at continuous occurrence).In this case, in step S 211 of FIG. 15, the failure determination process may be performed by determining whether or not the above-calculated continuous occurrence start position Pcs is within the range instead of comparing the value of the continuous occurrence counter.It is noted that the pressing apparatus of the present invention can be realized by storing the operations of the pressing apparatus on a recording medium readable by a computer system or computer and causing the pressing apparatus to read the program stored on the recording medium to execute the program. The computer system or computer described above includes hardware such as an operating system and peripheral devices."Computer system or computer" also includes a homepage providing environment (or display environment) when the WWW (World Wide Web) system is used.The above-described program can also be transmitted from the computer system or computer in which the program is stored in a storage medium or the like to other computer systems or computers via a transmission medium or through a transmission wave in the transmission medium. "Transmission medium" for transmitting the program means here a medium having the function of transmitting the information. For example, a network (communication network) such as the Internet and a communication line (communication cable) such as a telephone line may be used.In addition, the above-described program may be a program for realizing a part of the above-described functions. Further, the program may be a so-called difference file (difference program) which is combined with the programs already stored on the computer system or computer to achieve the above-described functions.The embodiments of the present invention have been explained in detail above. However, the specific configuration is not limited to the above-described embodiments. The present invention encompasses design variations without departing from the scope of the invention. For example, although the determination function is included in a part of the function of the pressing apparatus according to the embodiments, the present invention is not limited to such a configuration. Determination means having the determination function may be provided separately from the pressing device.In addition, a server or a cloud may have the determination function.LIST OF REFERENCE CHARACTERS1 Plunger 1 a Röhrenförmige body 2 Kugelgewinde screw 2 a Gewindespindel screw 2 b Mutter 3 Presse housing 4 Electric motor 5 Case 6 Röhrenförmige guide 9 Stretching cylinder 13 Servomotor driving device 14 Encoder 21 Control program storage unit 22 Display unit 23 Operation section 24 Temporary storage unit 25 Arithmetic value storage unit 26 Occurrence number storage unit 27 Circuit section 28 Drive command pulse generation unit 29 Encoder position counter 30 CPU 31 Continuous occurrence number storage unit 32 Moving average calculation unit 33 Moving average calculation unit 34 Load decrease determination unit 35 Data substitution unit 36 Press-in operation determination unit 40 CPU 43 Count unit 44 Press-in operation determination unit

Claims

A pressing apparatus comprising: a position detection unit (14) that detects a position of a plunger (1); a load detection unit (27) that detects a load value applied to the plunger (1); a determination unit that determines whether or not press-fitting is normally performed on a workpiece based on the position of the plunger and the load value at the position; a storage unit (25) that stores a moving average value and a spreading average value of the load value that are calculated in advance; a load drop determination unit (34) that determines whether or not the load value detected by the load detection unit exceeds a load drop determination value set based on the stored moving average value and the stored spreading average value; a data substituting unit (35) that substitutes a predetermined value for the load value determined to exceed the load drop determination value by the load drop determination unit; and a press-fit operation determining unit (36, 44) that determines whether or not the press-fit operation is normally performed on a workpiece based on a load value data series of the press-fit operation including the load value data substituted by the data substituting unit.The pressing apparatus according to claim 1, wherein the data substituting unit substitutes the load value determined by the load decay determining unit to exceed the load decay determining value with an average value of the load value before determining that the load value applied to the workpiece exceeds the load decay determining value.The pressing apparatus according to claim 1, wherein the data substituting unit substitutes the load value determined to exceed the load drop determination value by the load drop determination unit with a normal load value determined to be normal before the determination that the load value applied to the workpiece exceeds the load drop determination value.The pressing apparatus according to claim 1, wherein the data substituting unit substitutes the load value determined to exceed the load drop determination value by the load drop determination unit with a normal load value determined to be normal after determining that the load value applied to the workpiece exceeds the load drop determination value.The pressing apparatus according to any one of claims 1 to 4, further comprising: a counting unit (43) that counts the number of determinations at which it is determined by the load decay determining unit (34) that the load value exceeds the load decay determining value, wherein the press-fit operation determining unit (36, 44) determines whether or not the press-fit operation is normally performed on the workpiece in consideration of the number counted by the counting unit.A load correction method in a pressing apparatus, the pressing apparatus comprising: a position detection unit (14) that detects a position of a plunger (1); a load detection unit (27) that detects a load value applied to the plunger; a determination unit that determines whether or not a press-fitting operation is normally performed on a workpiece based on the position of the plunger and the load value at the position; a storage unit (25) that stores a moving average value and a spreading average value of the load value calculated in advance; a load drop determination unit (34); a data substitution unit (35); An injection operation determination unit (36, 44), the method comprising: a first operation of determining (S103), by the load dump determination unit, whether the load value detected by the load detection unit exceeds a load dump determination value set based on the stored moving average and the stored scattering average value; and a second operation of substituting (S104), by the data substitution unit, the load value determined by the load dump determination unit to exceed the load dump determination value by a predetermined value.A storage medium in which a computer program for causing a computer to execute a load correction method in a pressing apparatus is stored, the pressing apparatus comprising: a position detection unit (14) that detects a position of a plunger (1); a load detection unit (27) that detects a load value applied to the plunger; a determination unit that determines whether or not a press-fitting operation is normally performed on a workpiece based on the position of the plunger and the load value at the position; a storage unit (25) that stores a moving average value and a spreading average value of the load value calculated in advance; a load drop determination unit (34); a data substitution unit (35); An injection operation determination unit (36, 44), the method comprising: a first operation of determining (S103), by the load dump determination unit, whether the load value detected by the load detection unit exceeds a load dump determination value set based on the stored moving average and the stored scattering average value; and a second operation of substituting (S104), by the data substitution unit, the load value determined by the load dump determination unit to exceed the load dump determination value by a predetermined value.

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