JP2020189314A - Press load measuring device and method for press machine - Google Patents

Abstract

To provide a press load measuring device and a method for a press machine that can accurately measure a press load of a press machine.SOLUTION: A press load measuring device for a press machine has a pressure detector 11 for detecting a pressure of a hydraulic fluid filled in a head-side hydraulic chamber of a hydraulic cylinder contained a slide of the press machine at the time of action of a press load, a differential pressure computation unit 50 for computing a differential pressure between a pressure PS detected by the pressure detector 11 and an initial pressure P0 during non-action of a press load of the hydraulic fluid pressurized and filled in the head-side hydraulic chamber, a variable acquisition unit 56 for acquiring a variable kh in a current operation time of the press machine, the variable kh corresponding to a bulk moduli of the hydraulic fluid which varies according to the operation condition (operation time) of the press machine, and a press load computation unit 54 for computing a press load acting on the slide, based on the differential pressure computed by the differential pressure computation unit 50 and the variable kh acquired by the variable acquisition unit.SELECTED DRAWING: Figure 5

Description

The present invention relates to a press load measuring device and method of a press machine, and more particularly to a technique of measuring a press load based on the pressure of a hydraulic cylinder built in a slide of a press machine.

Conventionally, a technique for measuring a press load based on the pressure of a hydraulic cylinder built in a slide of a press machine is known (Patent Document 1).

The press load measuring device described in Patent Document 1 has a hydraulic chamber formed in a slide portion, and when the press load becomes larger than a predetermined value, the hydraulic pressure in the hydraulic chamber is released to avoid an overload. In a press machine equipped with a load protector (HOLP: Hydraulic Overload Protection) function, a means for detecting the pressure of a hydraulic chamber formed in a slide portion by a pressure sensor and converting the pressure detected by the pressure sensor into a press load. I have.

This prevents the slide load from being overloaded and makes it possible to measure the press load.

In the press load measuring device described in Patent Document 1, the pressure in the hydraulic chamber detected when the press load is applied is Ph, the pressure (preload) detected when the press load is not applied is Pc, and the constant is K. , Press load P,
P = √ {(Ph-Pc) / K}
It is calculated by.

JP-A-58-68500

Patent Document 1 describes that by obtaining the square root of (Ph-Pc) / K as the press load P, the calculated value of the press load and the actual value match with each other with an accuracy that does not hinder practical use. However, when the press machine was operated after adjusting the constant K and shipping the press machine, the error of the press load measured value with respect to the actual press load was about 10% at the maximum.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a press load measuring device and method for a press machine capable of accurately measuring the press load of the press machine.

In order to achieve the above object, the press load measuring device of the press machine according to one aspect of the present invention measures the pressure of the hydraulic fluid filled in the head side hydraulic chamber of the hydraulic cylinder built in the slide of the press machine. The differential pressure between the pressure detector detected when the press load is applied, the pressure detected by the pressure detector, and the initial pressure of the working fluid pressure-filled in the head side hydraulic chamber when the press load is not applied. A differential pressure calculator that calculates the above, and a variable corresponding to the volume elastic coefficient or the volume elastic coefficient of the working fluid that changes according to the operating condition of the press machine, and is under the current operating condition of the press machine. A variable acquisition unit that acquires the variable, a press load calculator that calculates a press load acting on the slide based on the differential pressure calculated by the differential pressure calculator and the variable acquired by the variable pressure calculator, and a press load calculator. To be equipped.

According to the present inventor, the volume elastic modulus of the hydraulic fluid filled in the hydraulic chamber on the head side of the hydraulic cylinder changes according to the operating condition of the press machine, and the change in the volume elastic modulus affects the measurement of the press load. I found that.

According to one aspect of the present invention, a variable corresponding to the volume elastic modulus of the working fluid or the volume elastic modulus that changes according to the operating condition of the press machine, and the variable under the current operating condition of the press machine get. Then, by calculating the differential pressure between the pressure of the working fluid detected when the press load is applied and the initial pressure of the working fluid when the press load is not applied, and the press load acting on the slide based on the acquired variables. The press load can be measured accurately regardless of the press operation status.

In the press load measuring device of the press machine according to another aspect of the present invention, it corresponds to the operation time of the press machine or the operation time from the time when the hydraulic chamber on the head side of the hydraulic cylinder is first filled with the hydraulic fluid. From the initial value of the variable corresponding to the number of presses to be performed and the content of bubbles contained in the working fluid at the time when the working fluid is first filled, to the convergence value of the variable in which the content of the bubbles is minimized. The variable acquisition unit includes a first storage unit that stores a first function or a lookup table that shows the relationship with the variable, and the variable acquisition unit stores the first function or the lookup table stored in the first storage unit. It is preferred to use and obtain the variable from the first function or lookup table based on the current operating time or number of presses of the press.

The volume elastic modulus of the working fluid changes according to the content of air bubbles contained in the working liquid, and the content of air bubbles contained in the working liquid depends on the operating time of the press machine or the number of presses corresponding to the operating time. Change.

According to another aspect of the present invention, the operating time of the press machine from the time when the hydraulic chamber on the head side of the hydraulic cylinder is first filled, or the number of presses corresponding to the operating time, and the hydraulic fluid are first applied. The first function or lookup table showing the relationship between the initial value of the variable corresponding to the content of air bubbles contained in the working fluid at the time of filling in, and the convergence value of the variable that minimizes the content of air bubbles. A first storage unit is prepared, and the first function or the lookup table stored in the first storage unit is used, and the first is based on the operating time or the number of times of pressing of the press machine to date. Obtain the appropriate variable used to calculate the press load from the function or lookup table.

In the press load measuring device of the press machine according to still another aspect of the present invention, the first storage unit stores a plurality of the first functions or the lookup table corresponding to a plurality of press loads having different press loads. It is preferable that the variable acquisition unit selects and uses the first function or the lookup table corresponding to the press load of the press machine from the first storage unit.

Since the content of bubbles that determines the volume elastic modulus of the working fluid changes due to the repeated action of the press load (pressure corresponding to the press load), the first function or the look-up table is used for each press load with a different press load. It is preferable to prepare and use a first function or look-up table corresponding to the press load.

In the press load measuring device of the press machine according to still another aspect of the present invention, the first storage unit is a plurality of the first functions or the lookup table corresponding to each mold of a plurality of dies of different types. The variable acquisition unit selects the first function or the lookup table corresponding to the exchanged die from the first storage unit every time the die used for the press machine is exchanged. To use.

The degree of change in the volume elastic modulus of the working fluid changes depending on the press load, but the press load differs for each die. Therefore, the first function or the look-up table is prepared for each die having a different press load, and the first function or the look-up table corresponding to the die to be used is used.

In the press load measuring device of the press machine according to still another aspect of the present invention, when the hydraulic pressure of the hydraulic fluid in the head side hydraulic chamber of the hydraulic cylinder reaches an abnormal pressure, the hydraulic fluid in the head side hydraulic chamber The variable acquisition unit has an overload protection function that releases the overload protection function, and when the operation of the press machine is started after the operation of the overload protection function, the variable acquisition unit is lowered in relation to the operation of the overload protection function. It is preferable to obtain the variable in consideration of the decrease of the variable.

In the press load measuring device of the press machine according to still another aspect of the present invention, the operation time of the press machine or the operation time from the time when the hydraulic chamber on the head side of the hydraulic cylinder is first filled with the hydraulic fluid is set. From the initial value of the variable corresponding to the corresponding number of presses and the content of bubbles contained in the working fluid at the time when the working fluid is first filled, the convergence value of the variable that minimizes the content of the bubbles. The variable acquisition unit includes a first storage unit that stores a first function indicating the relationship with the variable up to, and the variable acquisition unit uses the first function stored in the first storage unit and is currently used in the press machine. The variable is acquired from the first function based on the operation time up to or the number of presses, and the first function is a function showing a first-order approximation curve approximated to a first-order lag system from the initial value to the convergence value.

In the press load measuring device of the press machine according to still another aspect of the present invention, a second function that stores a second function showing the relationship between the press load and the time constant of the first-order approximation curve that changes according to the press load is stored. A storage unit is provided, and the variable acquisition unit acquires the time constant of the first-order approximation curve from the second storage unit based on the press load of the press machine, and stores the time constant of the linear approximation curve in the first storage unit according to the acquired time constant. It is preferable to specify the first-order approximation curve which is the first function.

That is, by acquiring the time constant of the linear approximation curve from the second function based on the press load to be used and using the acquired time constant as the time constant of the linear approximation curve, the linear approximation curve corresponding to the press load to be used can be obtained. The indicated function (first function) can be specified.

In the press load measuring device of the press machine according to still another aspect of the present invention, the initial value of the variable is kh ₀ , the convergence value is kh _C , the time constant of the linear approximation curve is T, and the operation time of the press machine is set. When t, the variable kh is expressed by the following equation.
kh = kh ₀ + (kh _C −kh ₀ ) · e ^{(−t / T)}
Represented by.

In the press load measuring device of the press machine according to still another aspect of the present invention, assuming that the number of calculations this time is M and the calculation cycle is ΔT, the variable acquisition unit operates the press machine at the Mth number of calculations. t _M is the following equation,
t _M = t _M-1 + ΔT (where t ₀ = 0)
The intermediate operation parameter Pd _M , which means the first-order lag response of the first function, is obtained by
Pd _M = Pd _M-1 + ΔT / T · (1-Pd _M-1 ) (However, Pd ₀ = 0)
The variable kh _M at the operating time t _M of the press machine is calculated by the following equation.
kh _M = kh ₀ + (kh _C −kh ₀ ) · Pd _M
Calculated by

In the press load measuring device of the press machine according to still another aspect of the present invention, when the hydraulic pressure of the hydraulic fluid in the head side hydraulic chamber reaches an abnormal pressure, the hydraulic cylinder is in the head side hydraulic chamber. It has an overload protection function that releases the working fluid, and when the operation of the press machine is started after the operation of the overload protection function, the variable acquisition unit acquires it immediately before the operation of the overload protection function. The value kh _h obtained by subtracting a constant value Δkh from the variable kh _M is obtained, the obtained value kh _h is used in place of the initial value kh ₀ , and the intermediate calculation parameter Pd _M is reset to 0, and the excess The variable kh _M after the operation of the load protection function is expressed by the following equation.
kh _M = kh _h + (kh _C -kh _h ) · Pd _M
Calculated by

In addition the press load measuring apparatus of a press machine according to another aspect of the present invention, the differential pressure calculator, the press load the detected pressure during the action P _S, the initial pressure at the time of press load inoperative P ₀ When the calculated differential pressure _(P S -P ₀₎ between the pressure _{P S} and the initial pressure _{P 0,} the pressing load calculator, the differential pressure _(P S -P ₀₎ and the first function the press load _{F R} on the basis of the kh, the following equation,
_{F R = 1/10 × a} × (kh + 1) / kh × (P S -P 0)
(However, a is the cross-sectional area of the hydraulic chamber on the head side of the hydraulic cylinder)
Calculated by

The press load measuring method of the press machine according to still another aspect of the present invention detects the pressure of the working fluid filled in the hydraulic chamber on the head side of the hydraulic cylinder built in the slide of the press machine when the press load is applied. A step, a step of calculating the difference pressure between the detected pressure and the initial pressure when the press load of the hydraulic fluid filled under pressure in the head side hydraulic chamber is not applied, and the operating state of the press machine. A variable corresponding to the volume elastic coefficient of the working fluid or the volume elastic coefficient, which changes according to the above, and the step of acquiring the variable under the current operating conditions of the press machine, the calculated differential pressure, and the calculated differential pressure. Includes a step of calculating the press load acting on the slide based on the acquired variables.

In the press load measuring method of the press machine according to still another aspect of the present invention, the operating time of the pressing machine or the operating time from the time when the hydraulic chamber on the head side of the hydraulic cylinder is first filled with the hydraulic fluid is set. From the initial value of the variable corresponding to the corresponding number of presses and the content of bubbles contained in the working fluid at the time when the working fluid is first filled, the convergence value of the variable that minimizes the content of the bubbles. The step of acquiring the variable includes the step of preparing the first storage unit for storing the first function or the lookup table showing the relationship with the variable up to, and the step of acquiring the variable is the first storage unit stored in the first storage unit. It is preferable to use the function or the lookup table and obtain the variable from the first function or the lookup table based on the operating time or the number of presses of the press machine to date.

In the press load measuring method of the press machine according to still another aspect of the present invention, the operating time of the pressing machine or the operating time from the time when the hydraulic chamber on the head side of the hydraulic cylinder is first filled with the hydraulic fluid is set. From the initial value of the variable corresponding to the corresponding number of presses and the content of bubbles contained in the working fluid at the time when the working fluid is first filled, the convergence value of the variable that minimizes the content of the bubbles. The step of acquiring the variable includes the step of preparing the first storage unit for storing the first function indicating the relationship with the variable up to, and the step of acquiring the variable uses the first function stored in the first storage unit. , The variable is acquired from the first function based on the operating time of the press machine up to the present or the number of presses, and the first function is a first-order approximation curve that approximates a first-order lag system from the initial value to the convergence value. It is a function indicating.

In the press load measuring method of the press machine according to still another aspect of the present invention, the step of preparing the first storage unit is when the hydraulic chamber on the head side of the hydraulic cylinder is first filled with the hydraulic fluid. A step of mounting a load die for a load test on the press machine, cycling the press machine until the content of air bubbles contained in the working fluid is minimized, and repeatedly applying a press load to the slide, and the above. The step of stopping the slide of the press machine at each predetermined operation time from the start of the cycle operation of the press machine to the end of the operation or at each predetermined number of presses, and the step of stopping the slide of the press machine. A step of applying a preset press load to the slide by an external pressurizing device and detecting the pressure of the working fluid filled in the hydraulic chamber on the head side of the hydraulic cylinder, and the applied press load. Based on the detected pressure of the working fluid, the step of calculating the variable for each predetermined operation time or for each predetermined number of presses, and the operation time of the press machine or the operation time of the press machine based on the calculation result of the variable. The first storage unit includes the step of creating the first function or lookup table showing the relationship between the number of presses corresponding to the operation time and the variable, and the created first function or lookup table. To memorize.

In the press load measuring method of the press machine according to still another aspect of the present invention, a second function for storing the second function showing the relationship between the press load and the time constant of the first-order approximate curve that changes according to the press load is stored. The step of acquiring the variable, including the step of preparing the storage unit, acquires the time constant of the first-order approximation curve from the second storage unit based on the press load of the press machine, and uses the acquired time constant to obtain the time constant. The first-order approximation curve, which is the first function stored in the first storage unit, is specified.

In the press load measuring method of the press machine according to still another aspect of the present invention, the initial value of the variable is kh ₀ , the convergence value is kh _C , the time constant of the linear approximation curve is T, and the operating time of the press machine is set. Assuming that t, the first function kh is expressed by the following equation.
kh = kh ₀ + (kh _C −kh ₀ ) · e ^{(−t / T)}
Represented by.

In the press load measuring method of the press machine according to still another aspect of the present invention, in the step of acquiring the variable, assuming that the number of calculations this time is M and the calculation cycle is ΔT, the press machine at the Mth number of calculations The operating time t _M is _calculated by the following equation.
t _M = t _M-1 + ΔT (where t ₀ = 0)
The intermediate operation parameter Pd _M , which means the first-order lag response of the first function, is obtained by
Pd _M = Pd _M-1 + ΔT / T · (1-Pd _M-1 ) (However, Pd ₀ = 0)
The variable kh _M , which is the value of the first function kh at the operating time t _M of the press machine, is calculated by the following equation.
kh _M = kh ₀ + (kh _C −kh ₀ ) · Pd _M
Calculated by

In the press load measuring method of the press machine according to still another aspect of the present invention, when the hydraulic pressure of the hydraulic fluid in the head side hydraulic chamber reaches an abnormal pressure, the hydraulic cylinder is in the head side hydraulic chamber. The step of acquiring the variable, which has an overload protection function for releasing the working fluid, is immediately before the operation of the overload protection function when the operation of the press machine is started after the operation of the overload protection function. The value kh _h obtained by subtracting a constant value Δkh from the acquired variable kh _M is obtained, the obtained value kh _h is used in place of the initial value kh ₀ , and the Pd _M is reset to 0 to obtain the excess. The variable kh _M after the operation of the load protection function is expressed by the following equation.
kh _M = kh _h + (kh _C -kh _h ) · Pd _M
Calculated by

In addition the press load measurement method of a press machine according to another aspect of the present invention, the step of calculating the differential pressure, the press the detected pressure at the load acting P _S, the initial pressure during the press load inoperative When P _0, the calculated differential pressure _(P S -P ₀₎ between the pressure _{P S} and the initial pressure _{P 0,} the step of calculating the pressing load, and the differential pressure _(P S -P ₀₎ the press load F _R on the basis of said variables kh, the following equation,
_{F R = 1/10 × a} × (kh + 1) / kh × (P S -P 0)
(However, a is the cross-sectional area of the hydraulic chamber on the head side of the hydraulic cylinder)
Calculated by

According to the present invention, when measuring the press load based on the pressure of the hydraulic cylinder built in the slide of the press machine, the press load can be measured accurately regardless of the press operation condition.

FIG. 1 is a diagram showing an embodiment of a press machine to which the press load measuring device of the press machine according to the present invention is applied. FIG. 2 is a diagram showing a pressure or the like applied to the hydraulic cylinder shown in FIG. 1, and is a diagram showing a pressure or the like when a press load is not applied (when no load is applied). FIG. 3 is a diagram showing a pressure or the like applied to the hydraulic cylinder shown in FIG. 1 and is a diagram showing a pressure or the like when a press load is applied (when a press load is applied). FIG. 4 is a graph showing the volume elastic modulus when air bubbles are mixed in the hydraulic oil. FIG. 5 is a block diagram showing a first embodiment of a press load measuring device of a press machine. FIG. 6 is a graph showing an example of a first function showing the relationship between the operating time t of the press machine and the variable kh. FIG. 7 is a graph showing another example of the first function showing the relationship between the operating time t of the press machine and the variable kh. Figure 8 is a graph showing the relationship between the constant T and the pressing load F _{R 'when} the first function. FIG. 9 is a block diagram showing a second embodiment of the press load measuring device of the press machine. FIG. 10 is a graph showing the relationship between the operating time of the press machine and the variable kht calculated by sequentially changing the press load. FIG. 11 is a chart showing numerical values such as a variable kh in the vicinity of the 1800th calculation count M in FIG. FIG. 12 is a graph corresponding to the graph shown in FIG. 10, and is a graph particularly when the HOLP is broken when the number of operations M is the 5100th time (operating time is 51000 (s)). FIG. 13 is a chart showing numerical values such as a variable kh in the vicinity of the 5100th calculation count M in FIG. FIG. 14 is a flowchart showing an embodiment of a press load measuring method of a press machine. FIG. 15 is a flowchart showing an embodiment of a method for acquiring the first function.

Hereinafter, preferred embodiments of the press load measuring device and method of the press machine according to the present invention will be described in detail with reference to the accompanying drawings.

[Press machine]
FIG. 1 is a diagram showing an embodiment of a press machine to which the press load measuring device of the press machine according to the present invention is applied.

The press machine 10 shown in FIG. 1 has a column (frame) 20, a slide 26, a bolster 27 on a bed 28, and the like, and the slide 26 is movably guided in the vertical direction by a guide portion provided on the column 20. ing.

A hydraulic cylinder (hydraulic cylinder) 25 including a cylinder portion 25a and a piston portion 25b is built in the slide 26, and the tip portion of the connecting rod 22 provided on the crankshaft 21 is connected to the piston portion 25b. .. A rotational driving force is transmitted to the crankshaft 21 via a servomotor 33, a gear 34, and a main gear 35. When the crankshaft 21 is rotated by the servomotor 33, the slide 26 slides the crankshaft 21. And the driving force applied via the connecting rod 22, the hydraulic cylinder 25 is moved in the vertical direction on FIG.

The crankshaft 21 is provided with an encoder 14 that detects the angle of the crankshaft 21 in order to detect the position and speed of the slide 26. The slide position is calculated from the angle signal output from the encoder 14, and the crank angular velocity of the crankshaft 21 is calculated by differentiating the angle signal, and the slide speed of the slide 26 is calculated from the angle signal and the angular velocity of the crankshaft. be able to.

The head-side hydraulic chamber (head-side hydraulic chamber) 24 of the hydraulic cylinder 25 is pressurized and filled with the hydraulic fluid (hydraulic oil) at the initial pressure when the press load is not applied by the hydraulic device 9. When a press load acts on the slide 26, the hydraulic cylinder 25 is made of metal formed by a joint surface between the cylinder portion 25a and the piston portion 25b, which are pressurized by an initial pressure or the like when the press load becomes larger than a predetermined value. It has a hydraulic overload protection (HOLP) function that breaks the seal and allows the pressure oil in the head side hydraulic chamber 24 to escape to avoid overload. The details of the HOLP function of the hydraulic cylinder 25 will be described later.

The upper die 31a is mounted on the slide 26, and the lower die 31b is mounted on the bolster 27. The mold 31 (upper mold 31a, lower mold 31b) in this example is for molding a hollow cup-shaped (drawing shape) product closed upward.

The hydraulic device 9 is a hydraulic device for initial pressure charging that supplies pressure oil of a predetermined initial pressure to the head side hydraulic chamber 24 of the hydraulic cylinder 25, and is used for the accumulator 1, the hydraulic pump 2, and the rotary shaft of the hydraulic pump. It is composed of an electric motor 3 to which a connected drive shaft is connected, a check valve 4, an electromagnetic valve 5, and a relief valve 6.

The accumulator 1 is set with a low-pressure gas pressure, accumulates low-pressure hydraulic oil at a substantially constant pressure, and acts as a tank.

One port of the hydraulic pump is connected to the head-side hydraulic chamber 24 of the hydraulic cylinder 25 via the check valve 4 and the pipe 15, and the other port is connected to the accumulator 1. The hydraulic pump 2 is driven by the torque applied from the electric motor 3 so as to supply the hydraulic oil at the initial pressure.

The check valve 4 applies the pressure of the head side hydraulic chamber 24 of the hydraulic cylinder 25 even when the electric motor 3 is in a no-load state (torque 0 state) in the region where the press load is not applied during the press (slide) one-cycle operation. The slide 26 is held at the descending end (limit) with respect to the piston portion 25b so that it can be held at a predetermined initial pressure.

The solenoid valve 5 plays a role of forcibly depressurizing the pressure acting on the head-side hydraulic chamber 24 of the hydraulic cylinder 25. Do not use it normally, but use it during maintenance (before dismantling the machine).

The relief valve 6 drives the electric motor 3 to control the initial pressure of the head side hydraulic chamber 24 of the hydraulic cylinder 25, and also plays a role of releasing excess oil amount other than generating the initial pressure to the accumulator 1 side. ..

Further, the pressure in the head-side hydraulic chamber 24 of the hydraulic cylinder 25 is detected by the pressure detector 11. The pressure detected by the pressure detector 11 is used to measure the press load when the press load is applied.

[Problems of press load measurement method and prior art]
2 and 3 are diagrams showing the pressure and the like applied to the hydraulic cylinder 25 shown in FIG. 1, respectively, FIG. 2 shows the pressure and the like when the press load is not applied (when there is no load), and FIG. 3 is the press load. It shows the pressure at the time of action (when the press load is applied).

2, the pressure of the head-side hydraulic chamber 24 of the hydraulic cylinder 25 has an initial pressure P ₀ at the time of no load, the initial pressure P _0, the steel cylinder portion of the cylinder portion 25a (M site (hereinafter M)) Generates a tensile force F ₀ .

This action, in press load application, pressing load F _R is, M and H share in accordance with the rigidity ratio of the liquid column part of the M and the head-side hydraulic chamber 24 (H sites (hereinafter H)) (Fig. 3) .. As a result, the tensile force acting on M decreases from _{F 0} to _{F T,} the pressure acting on the H is increased from _{P 0} to _{P S.} Any (tolerance) unless the action of P ₀ which F _T is greater than zero even for press load, this property is maintained. This is generally done from the viewpoint of effectively utilizing the rigidity of M to keep the press machine more rigid.

Further, the joint surface 23 between the cylinder portion 25a and the piston portion 25b of the hydraulic cylinder 25 is a metal seal portion for sealing the pressure oil in the head side hydraulic chamber 24, and is an initial stage of the pressure oil sealed in the head side hydraulic chamber 24. By setting the pressure P ₀ to a pressure corresponding to the permissible value of the press load, the metal sealing function is performed for the press load within the permissible range. Further, in the hydraulic cylinder 25, when a press load exceeding the permissible range is applied, the joint surfaces 23 are separated (HOLP is broken), and the pressure oil in the head side hydraulic chamber 24 is released to avoid an overload. Has a protective function.

The cross-sectional volume of M is S (cm ² ), the longitudinal elastic modulus of M is E (GPa), the length of influence is L (cm), and the cross-sectional volume of H (hydraulic cylinder 25) is a (cm ² ), H. If the volume of H including the communicating pipe 15 is V ₀ (cm ³ ), the volume elastic modulus of the hydraulic oil staying in H is _Khydro (GPa), and the acceleration of gravity is g (m / s ² ), then M The rigidity of H, K _M (kg / cm) and K _H (kg / cm), can be expressed by the following equations.

[Number 1]
^{_{K M = 10 5 S × E}} / g / L
[Number 2]
K _H = 10 ⁵ K _hydro × a ² / g / V ₀
The K _M and 1 while maintaining the rigidity ratio of the M and H, when the kh stiffness ratio of H to M, kh can be shown in the following equation.

[Number 3]
kh _{= K} H / K _M
F _R, from _kh, F T, PS can be shown in the following equation.

[Number 4]
_{F T = F 0 -1 / (} kh + 1) × F R
[Number 5]
_{P S = kh / (kh +} 1) × 10F R / a + P 0
After all, the pressure _{P S} of the hydraulic cylinders 25 when the pressing load _{F R} is applied, using kh is a function (first function) of the bulk modulus _{K hydro} hydraulic oil is determined by [Equation 5] where .. That, _{P S} will be affected by the bulk modulus _{K hydro} of hydraulic fluid in addition to the initial pressure _{P 0} and _{F R.}

The volume elastic modulus of the hydraulic fluid is affected by the air mixing rate in the hydraulic fluid.

FIG. 4 is a graph showing the volume elastic modulus when air bubbles are mixed in the hydraulic oil. The graph shown in FIG. 4 is an excerpt from the technical data "Volume elastic modulus when air bubbles are mixed" of Tokyo Keiki Co., Ltd.

As also shown in FIG. 4, the degree of decrease (change) in the volume elastic modulus K'of the hydraulic oil with respect to the air mixing ratio in the hydraulic oil decreases as the pressure increases. However, the initial pressure P ₀ of the hydraulic cylinder 25, even about 20 MPa (correspondingly, also to reduce the degree of reduction in volume elastic coefficient K '), as indicated by a rectangular frame on the 4, aeration rate When is changed from 0.2 to 1%, the volume fraction K'changes from about 1.6 GPa to 1.3 GPa.

In order to calculate the pressing load F _R, Transforming Equation 5 Equation [6] is obtained.

[Number 6]
_{F R = 1/10 × a} × (kh + 1) / kh × (P S -P 0)
The pressing load signal indicating the pressing load F _R from the pressure signal indicating the pressure of the hydraulic cylinder 25 detected by the pressure detector 11 (the pressure signal P ₀ sig initial pressure, the pressure signal at the time of press load acting P _S sig) F _R sig can be expressed by the following equation.

[Number 7]
_{F R sig = 1/10 ×} a × (kh + 1) / kh × (P S sig-P 0 sig)
Now, in a certain press machine (temporarily No. 1 machine), a is 714.3 (cm ² ), and the air bleeding of the hydraulic oil in the hydraulic cylinder 25 is done (by performing a sufficient trial run of the machine as in this example). ideally completed, hydraulic oil aeration rate of the hydraulic cylinder 25, almost the final converged to equilibrium value of 0.2% (minimum) _{(K hydro} is the number corresponding to 1.6 GPa) at calibrate the press load measuring device, when the _{P 0} sig and 22 (MPa), press load signal _{F R} sig when _{P S} sig is 34 (MPa) was 2000 kN.

At this time, the numerical value of "1/10 x a x (kh + 1) / kh" in the equation [Equation 7] is 166.67, and kh is 0.75. Such a result was obtained at Unit 1.

On the other hand, in another press machine (temporarily Unit 2) having the same mechanical structure as Unit 1, air bleeding is ideally completed (due to insufficient test run of the press machine) after assembly is completed. not aerated rate of the hydraulic oil in the hydraulic cylinder 25 is the final value not convergence of 1% when the (K _hydro considerable number to 1.3 GPa) to calibrate the press load measuring apparatus at the time, unit 1 when _{P 0} sig 22 adjusted to the same (MPa) and, _{P S} sig is press load signal _{F R} sig when 32.6 (MPa) was 2000 kN.

At this time, the numerical value of "1/10 x a x (kh + 1) / kh" in the equation [Equation 7] is 188.72, and kh is 0.609. The change in the numerical value of "1/10 x a x (kh + 1) / kh" between Units 1 and 2 (that is, the change in kh) is that the rigidity of H of Unit 2 is 81.25 with respect to the rigidity of Unit 1. This is a change caused by a decrease to% (= 1.3 / 1.6 × 100). Such a result was obtained at Unit 2.

In this way, conventionally, the physical phenomenon in which the rigidity of H changes according to the content of air mixed in the hydraulic oil in the hydraulic cylinder 25 is not recognized, and it is inevitable for each press machine to have "1 /" of the formula [Equation 7]. 10 × a × (kh + 1 ) / kh "numerical mistaking shall changes in, was calibrated press load signal F _R sig.

This means that in the press machine having the same structure, just beyond which cause inefficiencies and the calibration work of good press load signal F _R sig in nature once, it is necessary to perform for each press machine (increasing the error of actual and) reduce the accuracy of the press load signal F _R sig is a factor.

That is, as the second car operating time increases, gradually air intrusion degree of hydraulic fluid converges to the final value, the stiffness of H increases equivalent to Unit 1, at the time of calibration of the press load signal F _R sig The numerical value (188.72) of "1/10 x a x (kh + 1) / kh" in the obtained formula [Equation 7] changes to 166.7 shown by Unit 1. Then, an error occurs in the press load signal F _R sig at this stage.

Specifically, for example, press load signal _{F R} sig when the press load is actually 1766kN action outputs 2000 kN, resulting in errors of 244KN.

In the present invention, the operation that changes depending on the press operation status (press operation time, press count, etc.) of the press machine is not obtained as a constant of "1/10 × a × (kh + 1) / kh" of the equation [Equation 7]. The value (variable) of the volume elastic modulus K- _hydro of the oil or the variable (in this example, the rigidity ratio kh shown in the equation [Equation 3]) that changes according to the volume elastic modulus K- _hydro is used in the press operation of the press machine. Get according to the situation. The initial pressure P _o and the pressure detecting the _{P S} Searching for the differential pressure _(P S -Po), the pressing load acting on the slide on the basis of the differential pressure _(P S -P _o) and the obtained variable kh Is calculated.

In a press machine having the same structure, for one of them, a function indicating the correspondence between the press operation status of the press machine and the volume elastic modulus K- _hydro of the hydraulic oil or the variable kh corresponding to the volume elastic modulus K- _hydro ( If the first function) is obtained, the first function can be applied to other press machines having the same structure, and as in the conventional case, for each press machine, "1/10 × a × (1/10 × a ×) of the formula [Equation 7] The work efficiency is improved as compared with the case where "kh + 1) / kh" is obtained as a constant.

Further, if kh can be obtained based on the first function, the calibration portion of "1/10 x a x (kh + 1) / kh" in the equation [Equation 7] can be obtained by calculation. In addition, since the volume elastic modulus _Khydro of the hydraulic oil, which changes depending on the air content in the hydraulic oil of the hydraulic cylinder, is taken into consideration in this calibration part, the measurement accuracy of the press load is improved as compared with the conventional method. ..

[First Embodiment of Press Load Measuring Device of Press Machine]
FIG. 5 is a block diagram showing a first embodiment of a press load measuring device of a press machine.

The press load measuring device of the press machine of the first embodiment shown in FIG. 5 is mainly composed of a pressure detector 11, a differential pressure calculator 50, a press load calculator 54, and a variable acquisition unit 56.

The pressure detector 11 detects the pressure in the head-side hydraulic chamber 24 of the hydraulic cylinder 25, and indicates a pressure signal P ₀ sig, which indicates an initial pressure P ₀ when the press load of the head-side hydraulic chamber 24 is not applied (when there is no load). or outputs the pressure signal P _S sig showing the pressure P _S in press load is applied.

The initial pressure holding unit 52 temporarily holds and holds the pressure signal output from the pressure detector 11 when the press load is not applied (when there is no load) as the pressure signal P ₀ sig indicating the initial pressure P ₀ . The pressure signal P ₀ sig is output to the differential pressure calculator 50.

Differential pressure calculator 50, the pressure signal output from the pressure detector 11 at the time of press load acting, obtained as a pressure signal P _S sig, the differential pressure between the pressure P _S and the initial pressure P ₀ at the time of press load acting ( P _S -P ₀₎ calculates a differential pressure signal of _{(P S sig-P 0 sig} ) showing the outputs the result to the press load operator 54.

The variable acquisition unit 56 is a variable kh corresponding to the volume elastic coefficient K _hydr of the hydraulic oil in the hydraulic cylinder 25 that changes according to the operating condition of the press machine 10, and is a variable under the current operating condition of the press machine 10. The kh is acquired, and the acquired variable kh is output to the press load calculator 54.

<Method of acquiring variable kh when operating with a constant press load (1000 kN) applied to a specific model A of a press machine>
Next, a method of acquiring the variable kh by the variable acquisition unit 56 will be described.

The first embodiment of the press load measuring device shown in FIG. 5 further includes a first storage unit 58, an operation time calculator 60, and a press count counter 62.

In the first storage unit 58 of this example, the operating time t of the press machine 10 from the time when the hydraulic chamber 24 on the head side of the hydraulic cylinder 25 is first filled with hydraulic oil, and the variable kh that changes according to the operating time t A function (first function) indicating the relationship with (variable corresponding to the volume elastic modulus K _hydro ) is stored.

This first function is obtained as follows.

By modifying the above-described [Equation 4] where the variables kh as a function of the press load F _R '(kN) and the hydraulic cylinder pressure P _S, represented by the following equation.

[Number 8]
_{kh = a (P S -P 0} ) / (10 · F R '+ a (P 0 -P S))
Press load F _{R 'is} a state where the slide is stationary at the bottom dead center, using a hydraulic jack or the like, the slide 26 a force which is generated by pressurizing upward, its value is clear It is a press load.

Now, to produce a press machine maximum pressure pressure capability 2000 kN (tentatively specific model A-1 Unit) (to complete the assembly), by the action of 1000 kN) as press load F _R by using the load die for load test Then, the operation is performed for 50,000 cycles (150,000 s) with a slide stroke number N (average 20 rpm). During this operation, once approximately every 1000 cycles (run time 3000 s), remove the load die, to measure the pressure _{P S} in a state in which the action of pressing load _{F R} '(= _1500kN) using a hydraulic jack, [ The variable kh is obtained by the equation [Equation 8].

FIG. 6 is a graph showing an example of the first function showing the relationship between the operating time t of the press machine and the variable kh, and the variable kh is set at intervals of 3000s (3000s, 6000s, ...) With respect to the operating time t. It is a graph which is plotted at 150,000s) and finally shows the variable kh as a first-order approximation curve which approximates the first-order lag system with respect to the operation time t.

In the equation [Equation 8], the other parameters are a = 714.3 (cm ² ) and the initial pressure P ₀ = 22 (MPa).

The reason for the press load F _{R 'to} 1500kN, while by applying a pressing load as large as possible, to reduce the amount of oil leaking through the joint surface from the hydraulic cylinder, is order to reduce the measurement error of the measured value of kh.

In other words, the larger the pressing load, the difference in the initial pressure P ₀ and the pressure P _S is increased, although not easily affected by variations of the initial pressure P ₀ or the pressure P _S, acting on the joint surface of the hydraulic cylinder on the opposite decrease pressing load F _{T (surface} pressure generated by) the amount of oil leaking into the tank is increased over the site, the pressure P _S is reduced by the influence of leakage, uncertain values to calculate the variable kh become. Given these balance, and the pressing load _{F R} 'to 1500KN.

Here, assuming that the number of slide strokes of the press machine is N (rpm) and the number of presses of the press machine from the time when the hydraulic oil is first filled in the hydraulic chamber on the head side of the hydraulic cylinder to the present time is n (times), the hydraulic cylinder The operating time t (s) from the time when the hydraulic oil is first filled in the hydraulic pressure chamber on the head side to the present time can be expressed by the following equation.

[Number 9]
t = n / N × 60
If the number of slide strokes N _If the N _1, N 2, and changes.. _{N N,} the press count n _accordingly, n _1, n 2, changes.., And _{n N,} operation time t (s) can be expressed by the following equation.

[Number 10]
t = t ₁ + t ₂ + ... + t _N
= N ₁ / N ₁ x 60 + n ₂ / N ₂ x 60 + ... + n _N / N _N x 60
Now, assuming that the initial value of the variable kh is kh ₀ , the convergence value is kh _C , the time constant of the linear approximation curve is T, and the operation time is t, the variable kh (operation time t and the variable kh) approximated to the first-order lag system. The first function indicating the relationship) can be expressed by the following equation.

[Number 11]
kh = kh ₀ + (kh _C −kh ₀ ) · e ^{(−t / T)}
However, e is the base of the natural logarithm (= 2.71828 ...)
The time constant T of the linear approximation curve shown in the equation [Equation 11] is T = 25000 (s). The initial value kh ₀ of the variable kh is 0.609, and the final convergence value kh _C of the variable kh is 0.75.

In the future, if another press machine (ex. Model A-2) is manufactured with the same model A and then operated with a press load of 1000 kN, the operation time t will be integrated in the press load measuring device. Or, the operation time t is calculated from the number of presses n counted as the number of slide strokes N by the formula [Equation 9] or the formula [Equation 10], or the operation time t and the initial value kh ₀ are calculated by the formula [Equation 11]. , The convergence value kh _C , and the time constant T, the variable kh can be calculated.

The formula [Equation 11] obtained by load testing the model A-1 of the press machine can also be applied to the model A-2 of the same model. It is preferable that the model A-2 is subjected to a load test for obtaining the initial value kh ₀ and calculated by the formula [Equation 8]. After the assembly of the press machine is completed, the volume elastic modulus (content of air bubbles contained in the hydraulic oil) of the hydraulic oil when the hydraulic chamber on the head side of the hydraulic cylinder is first filled with the hydraulic oil is different from that of the model A-1. This is because there are cases.

Returning to FIG. 5, the first storage unit 58 stores the first function ([Equation 11]) obtained as described above.

The press count counter 62 counts the number of presses of the press machine 10 from the time when the hydraulic oil chamber 24 on the head side of the hydraulic cylinder 25 is first filled with hydraulic oil to the present time, and is used as an angular velocity signal output from the encoder 14. One cycle operation of the press machine 10 is detected from the crank angle calculated based on this, and the number of presses n (times) is counted.

The number of slide strokes N (rpm) is set in the operation time calculator 60, and the operation time calculator 60 has the number of presses n input from the press number counter 62 and the number of slide strokes N (rpm) of the press machine 10. ), The operating time t (s) of the press machine 10 from the time when the hydraulic oil chamber 24 on the head side of the hydraulic cylinder 25 is first filled with hydraulic oil to the present time is calculated by the equation [Equation 9]. Further, the operation time calculator 60 calculates the operation time t (s) by the equation [Equation 10] when the number of slide strokes N changes.

The variable acquisition unit 56 uses the first function ([Equation 11]) stored in the first storage unit 58, and is based on the operation time t (s) of the press machine 10 calculated by the operation time calculator 60. Then, the variable kh is calculated (acquired) from the equation [Equation 11]. The initial value kh ₀ of the variable kh in the equation [Equation 11] is 0.609, the convergence value kh _C is 0.75, and the time constant T is 25000 (s).

Press load operator 54, based on the variable kh obtained by differential pressure signal calculated by the differential pressure calculator _{50 (P S sig-P 0} sig) and variable obtaining section 56, the press machine 10 slides 26 the press load signal F _R sig showing the current press load F _R applied to calculating the [equation 7 equation. In this example, the cross-sectional area a of the hydraulic cylinder in the equation [Equation 7] is 714.3 (cm ² ).

Press load operator 54, a computed press load signal F _R sig, a monitor device (not shown), a printer, and outputs to the storage device, etc., to be provided to the user.

<Method of acquiring variable kh when operating by applying a constant other press load (1500 kN) on a specific model A of a press machine>
As in the case of operating with a press load (1000 kN) applied, temporarily remove the piping of the hydraulic cylinder of a specific model A-1 of the press machine with a maximum pressurizing capacity of 2000 kN (air in the hydraulic cylinder and hydraulic piping). after been filled is), and reset by connecting again piping state just after the assembly, by the use of the load die for load test, this time by acting 1500kN as press load F _R, the number of slide strokes N (average Operate at 50,000 cycles (150,000 s) at 20 rpm). During this operation, once approximately every 1000 cycles (run time 3000 s), remove the load die, to measure the pressure _{P S} in a state in which the action of pressing load _{F R} '(= _1500kN) using a hydraulic jack, [ The variable kh is obtained by the equation [Equation 8].

FIG. 7 is a graph showing another example of the first function showing the relationship between the operating time t of the press machine and the variable kh, and the variable kh is set at intervals of 3000s (3000s, 6000s, ...) With respect to the operating time t. ·, 150000s), and finally the variable kh is shown as a first-order approximation curve that approximates the first-order lag system with respect to the operation time t.

In the equation [Equation 8], the other parameters are a = 714.3 (cm ² ) and the initial pressure P ₀ = 22 (MPa).

The time constant T of the first function (first-order approximation curve shown in FIG. 7) shown in the equation [Equation 11] thus obtained is T = 13000 (s). Press load _F with respect to _R 'time constant of the first-order approximation curve shown in FIG. 6 by the action of 1000kN T (= 25000 (s) ), when the convergence value constant T decreases (variable kh from the initial value kh ₀ kh _C The reason for shortening the time to converge) is that in Fig. 7, where the press load is larger, the amount of oil leaking from the joint surface of the hydraulic cylinder to the tank increases every cycle, and the initial pressure charge is charged by that amount during operation. This is because the circulation of the hydraulic oil in the hydraulic cylinder is accelerated by supplementing with the hydraulic device 9 for the purpose.

Since the first function (time constant of the linear approximation curve) indicating the relationship between the operation time t and the variable kh differs depending on the press load used for the press processing, the first storage unit 58 is used for the press processing. A plurality of first functions corresponding to each press load are stored, and the variable acquisition unit 56 selects and uses the first function corresponding to the press load used for the press processing, and acquires the variable kh. Is preferable.

Further, since the press load differs depending on the type of die, and as a result, the first function differs. Therefore, the first storage unit 58 stores a plurality of first functions corresponding to each die used for press working. The variable acquisition unit 56 may select and use the first function corresponding to the die used for press working to acquire the variable kh.

In the future, if another press machine (ex. Model A-2) is manufactured with the same model A and then operated with a press load of 1500 kN, the operation time t will be integrated in the press load measuring device. Or, the operation time t is calculated from the number of presses n counted as the number of slide strokes N by the formula [Equation 9] or the formula [Equation 10], or the operation time t and the initial value kh ₀ are calculated by the formula [Equation 11]. The variable kh can be calculated from the convergence value kh _C and the time constant T corresponding to the press load of 1500 kN.

<Method of acquiring variable kh when operating by applying various press loads on a specific model A of a press machine>
The hydraulic cylinder of a specific model A-1 of a press machine with a maximum pressurizing capacity of 2000 kN, as in the case of operating with a press load (1000 kN) applied and operating with a press load (1500 kN) applied. After removing the piping (filling the hydraulic cylinder and hydraulic piping with air), reconnect the piping and reset it to the state immediately after assembly, and use the load die for load test to perform various press loads. by the action of F _R, obtaining the time constant T of the variable kh for the driver time t.

Figure 8 is a graph showing the relationship between the constant T and the pressing load F _{R 'when} determined as described above, it became curve as shown in FIG. When this curve is approximated by a quadratic curve, the quadratic curve (quadratic function) can be expressed by the following equation.

[Number 12]
^{_{T = 0.0132F R '2 -58.364F R}} ' +70627
Incidentally, the time constant T for the pressing load F _{R 'obtained} by experiments, in some cases appropriate better approximated (the model) primary (linear).

[Second Embodiment of Press Load Measuring Device of Press Machine]
FIG. 9 is a block diagram showing a second embodiment of the press load measuring device of the press machine. In FIG. 9, the same reference numerals are given to the parts common to the press load measuring apparatus of the first embodiment shown in FIG. 5, and detailed description thereof will be omitted.

The press load measuring device of the second embodiment shown in FIG. 9 has a second storage unit 59 added as compared with the press load measuring device of the first embodiment shown in FIG. 5, and also has a variable acquisition unit 56'and a variable acquisition unit 56'. The first storage unit 58'is different from the variable acquisition unit 56 and the first storage unit 58 of the first embodiment.

The first function ([Equation 11]) indicating the relationship between the operation time t and the variable kh is stored in the first storage unit 58', but the time constant T in the equation [Equation 11] is pressed. It is stored as a variable corresponding to the load.

On the other hand, the second storage unit 59 stores a second function ([Equation 12]) showing the curve shown in FIG.

The variable acquisition unit 56'uses the first function ([Equation 11]) stored in the first storage unit 58, but stores it in the second storage unit 59 based on the press load used for the press processing. The time constant T (the time constant T in the [Equation 11] equation) is acquired using the obtained [Equation 12] equation, and the acquired time constant T is applied to the time constant T of the [Equation 11] equation. The variable kh is calculated (acquired) from the equation [Equation 11] based on the time constant T and the operation time t (s) calculated by the operation time calculator 60. The initial value kh ₀ of the variable kh in the equation [Equation 11] is 0.609, and the convergence value kh _C is 0.75.

As a result, the variable acquisition unit 56'can acquire the variable kh corresponding to an arbitrary press load and operation time.

<Method of acquiring variable kh when operating by applying various press loads in any unit (ex. Units 1 to 10) of a specific model A of a press machine>
In a press machine having a maximum pressurizing capacity of 2000 kN of a specific model A, assuming that the calculation cycle in which the variable acquisition unit 56'acquires (calculates) the variable kh is ΔT (s), the operation time calculator 60 has n press times. The operation time t (s) can be calculated by integrating the calculation cycle ΔT (s) only during operation, instead of calculating the operation time t (s) based on the number of slide strokes N.

Now, assuming that the operation time at the Mth arbitrary calculation number is t _M , the operation time t _M can be calculated by the following equation.

[Number 13]
t _M = t _M-1 + ΔT
(However, the initial value of the operation time t ₀ = 0)
Further, the variable kh at operating time _{t M,} when a variable kh _M, variable kh _M can be expressed by the following equation.

[Number 14]
kh _M = kh ₀ + (kh _C −kh ₀ ) · Pd _M
The equation [Equation 14] is an equation corresponding to the equation [Equation 11], and Pd _M in the equation [Equation 14] is an intermediate that means a first-order lag response based on the time constant T calculated by the equation [Equation 12]. It is an operation parameter and is calculated by the following equation.

[Number 15]
Pd _M = Pd _M-1 + ΔT / T · (1-Pd _M-1 )
(However, Pd ₀ = 0)
Variable obtaining section 56 ', a variable kh _M in operating time _{t M,} on the basis of the _{Pd M-1} was constant T and the previous operation when calculated in Equation 12] where the current by [Expression 15] where the intermediate The calculation parameter Pd _M is calculated, and the variable kh at the current operation time t _M can be calculated by the equation [Equation 14] using the calculated intermediate calculation parameter Pd _M.

In the future, when another press machine (ex. Model A-2) is manufactured with the same model A and then operated by applying various press loads, various press loads will be applied in the press load measuring device. The corresponding time constant T is timely calculated from the formula [Equation 12], and the variable kh at an arbitrary press load and an arbitrary operation time is calculated in a timely manner using the equations [Equation 13] to [Equation 15]. Can be done.

For example, the operating time t to 0～12000S, produced by pressing load _{F R} is 1000kN using certain mold (mold No.11), the operating time t to 12000S～18000s, another mold is replaced pressing load _{F R} in (mold No.12) produced in 1500KN, the operating time t to 18000S～36000s, a further die replacement and pressing load _{F R} in (mold No.13) produced in 1200KN, operation time t is produced by replacement pressing load _{F R} is 600kN to yet another mold until 36000S～60000s (mold No.14), the operating time t is more than 60000s again mold No. The variable kh when replacement pressing load _{F R} is that produced by the 1000kN to 11, calculates by using the number 12] formula ~ [Expression 15] expression.

FIG. 10 is a graph showing the relationship between the operating time of the press machine and the variable kht calculated by sequentially changing the press load as described above.

In this example, the calculation cycle ΔT for calculating the variable kh of the press load measuring device (variable acquisition unit 56'in FIG. 9) is 10 s, and the number of calculations M is the 1800th time (near x in FIG. 10) in FIG. An example of calculation of the variable kh is shown in the chart of FIG.

In FIG. 11, the operation time t ₁₇₉₉ , the intermediate operation parameter Pd ₁₇₉₉ , the variable kh ₁₇₉₉ , the operation time t ₁₈₀₀ , the intermediate operation parameter Pd ₁₈₀₀ , and the variable kh ₁₈₀₀ are calculated when the number of operations M is 1799 and 1800. , [Equation 16] to [Equation 18] and [Equation 19] to [Equation 21].

<M = 1799>
[Number 16]
t ₁₇₉₉ = t ₁₇₉₈ +10
[Number 17]
Pd ₁₇₉₉ = Pd ₁₇₉₈ + 10 / T ₁₇₉₉ · (1-Pd ₁₇₉₈ )
[Number 18]
kh ₁₇₉₉ = 0.609 + (0.75-0.609) · Pd ₁₇₉₉
<M = 1800>
[Number 19]
t ₁₈₀₀ = t ₁₇₉₉ +10
[Number 20]
Pd ₁₈₀₀ = Pd ₁₇₉₉ + 10 / T ₁₈₀₀ · (1-Pd ₁₇₉₉ )
[Number 21]
kh ₁₈₀₀ = 0.609 + (0.75-0.609) · Pd ₁₈₀₀
In this way, by calculating the variable kh every fixed calculation cycle ΔT using the formulas [Equation 12] to [Equation 15], the variable kh can be calculated even when the press load changes variously. Can be done. Further, since the time constant T of the variable kh is relatively large, there is no problem even if the calculation cycle ΔT is slow.

<When operating an arbitrary unit (ex. Units 1 to 10) of a specific model A of a press machine by applying various press loads, a press load abnormality (overload) further occurs, and a hydraulic cylinder (ex. 1 to 10) How to obtain the variable kh when the joint surface of HOLP) composed of
When the HOLP breaks, the variable kh decreases by Δkh. Reason, the bonding surface of the hydraulic cylinder is broken, after which the hydraulic cylinder is contracted, when the charging pressure of the hydraulic cylinder the initial pressure P _0, is because the air enters from the gap of the joint surface.

Δkh is a substantially constant value for each model of the press machine, and Δkh = 0.03 for this model A. This is experimentally break the HOLP, initial pressure charge press load F using a hydraulic jack immediately _R 'measures the pressure P _S in (= 1500kN) was reacted with state variables from [Equation 8] where It is a value that can be obtained by obtaining kh and using this and the variable kh calculated immediately before the HOLP breaks.

Δkh is hardly affected by the value of the variable kh before the HOLP breaks, and the variable kh does not fall below the initial value kh ₀ (0.609 in this machine).

Further, when the HOLP is broken, the intermediate calculation parameter Pd _M shown in the equation [Equation 15] is temporarily reset to 0. Then, the variable kh _M immediately HOLP break, if held as a variable kh _h obtained by subtracting only decrease (Derutakh min) by HOLP break from broken just before the variable kh _M, variable kh _M after HOLP break, the following equation Can be shown.

[Number 22]
kh _M = kh _h + (kh _C −kh _h ) · Pd _M
For example, as in the case of the graph shown in FIG. 10, the operating time t to 0～12000S, the press load _{F R} by using a certain mold (mold No.11) produced in 1000 kN, driving time t until 12000s~18000s is another mold replacement pressing load _{F R} in (mold No.12) produced in 1500KN, the operating time t until 18000S～36000s, yet another mold (mold pressing load FR is replaced with No.13) is produced in 1200KN, the operating time t until 36000S～60000s, further exchanged pressing load _{F R} to another mold (mold No.14) is produced in 600kN The HOLP broke during the process, and after that, it was restored and production was continued. When the operation time t was 60,000 s or more, the mold No. The variable kh when replacement pressing load _{F R} is that produced by the 1000kN to 11, calculates by using the number 12] formula ~ [Expression 15] expression.

In this example, the calculation cycle ΔT for calculating the variable kh of the press load measuring device (variable acquisition unit 56'in FIG. 9) is 10 s, and the number of calculations M in which the HOLP is broken in FIG. 12 is the 5100th (in FIG. 12). An example of calculation of the variable kh (near x) is shown in the chart of FIG.

In FIG. 13, the operation time t ₅₀₉₉ , the intermediate operation parameter Pd ₅₀₉₉ , the variable kh ₅₀₉₉ , the operation time t ₅₁₀₀ , the intermediate operation parameter Pd ₅₁₀₀ , and the variable kh _{5100 when the} number of operations M is the 5099th, 5100th, and _5101th operations. The operation time t ₅₁₀₁ , the intermediate calculation parameter Pd ₅₁₀₁ , and the variable kh ₅₁₀₁ are calculated by [Equation 23] to [Equation 25], [Equation 26] to [Equation 28], and [Equation 29]. ] Expression to [Equation 31].

<M = 5099>
[Number 23]
t ₅₀₉₉ = t ₅₀₉₈ +10
[Number 24]
Pd ₅₀₉₉ = Pd ₅₀₉₈ + 10 / T ₅₀₉₉ · (1-Pd ₅₀₉₈ )
[Number 25]
kh ₅₀₉₉ = 0.609 + (0.75-0.609) · Pd ₅₀₉₉
<M = 5100>
[Number 26]
t ₅₁₀₀ = t ₅₀₉₉ +10
[Number 27]
Pd ₅₁₀₀ = 0
[Number 28]
kh ₅₁₀₀ = 0.707 + (0.75-0.707) · Pd ₅₁₀₀
(Kh _h = kh _5099- Δkh = 0.737-0.03 = 0.707)
<M = 5101>
[Number 29]
t ₅₁₀₁ = t ₅₁₀₀ +10
[Number 30]
Pd ₅₁₀₁ = Pd ₅₁₀₀ + 10 / T ₅₁₀₁ · (1-Pd ₅₁₀₀ )
[Number 31]
kh ₅₁₀₁ = 0.707 + (0.75-0.707) · Pd ₅₁₀₁
In this way, by calculating the variable kh every fixed calculation cycle ΔT using the equations [Equation 12] to [Equation 15], even if the press load changes variously and the HOLP breaks, The variable kh that takes into account the HOLP break can be calculated.

As another embodiment when the HOLP was broken, to measure the pressure P _S in a state in which the action of a known press load using a hydraulic jack immediately after the initial pressure charge after HOLP fracture, [Expression 8] The variable kh is obtained from the equation, the operation time is calculated from the first function showing the relationship between the operation time t and the variable kh, and the calculated operation time is corrected to the current operation time so that the first function is applied. You may.

[Embodiment of Press Load Measuring Method of Press Machine]
FIG. 14 is a flowchart showing an embodiment of a press load measuring method of a press machine. The press load measuring method of the press machine shown in FIG. 14 is a method corresponding to the press load measuring device of the press machine of the first embodiment shown in FIG.

In FIG. 14, the operation time calculator 60 acquires the operation time t of the press machine from the time when the hydraulic oil on the head side of the hydraulic cylinder 25 is first filled (step S10).

The variable acquisition unit 56 uses the first function ([Equation 11]) stored in the first storage unit 58 to calculate (acquire) the variable kh from the [Equation 11] equation based on the operation time t. (Step S12). The variable kh is a variable corresponding to the volume elastic modulus of the hydraulic oil that changes according to the operating time t of the press machine.

Here, a method of acquiring the first function to be stored in the first storage unit 58 will be described.

FIG. 15 is a flowchart showing an embodiment of a method for acquiring the first function.

In FIG. 15, first, a load die for a load test is attached to the press machine (step S50). Then, after filling the air slide internal hydraulic cylinder and the hydraulic within piping, to use the hydraulic system 9 for initial pressure charge filling the pressurized oil of the initial pressure P ₀ to the head side hydraulic chambers of the hydraulic cylinder (Step S52).

Next, the slide is stopped at the bottom dead center, and the press load F _{R 'set} in advance to act on the slide by a hydraulic jack (step S54), detects the pressure P _S of the head side hydraulic chambers of the hydraulic cylinder by hydraulic pressure detector (Step S56).

Then, press load _{F R} ', the initial pressure _{P 0,} on the basis of the pressure _{P S,} calculates the variable kh by [Expression 8] type (step S58). Since the volume elastic modulus of the hydraulic oil changes depending on the mixing rate of air bubbles in the hydraulic oil, the volume elastic modulus cannot be ignored for calculating the press load, but the variable kh is a variable corresponding to the volume elastic modulus of the hydraulic oil. Therefore, finding the variable kh indirectly means finding the volume elastic modulus of the hydraulic fluid.

Subsequently, it is determined whether or not the pressure P _S which is detected at step S56 has converged (whether bulk modulus, or variable kh has reached the convergence value) (step S60).

If it has not converged, the press machine is driven for a predetermined operation time t (or a predetermined number of presses) (step S62). For example, the predetermined operation time t can be 3000 s, and the predetermined number of presses can be 1000 times.

After that, the process returns to step S54, and the processes of steps S54 to S60 are repeated. As a result, the variable kh for each predetermined press operation time is acquired.

When the pressure P _S is converged (variable kh is reaches the convergence value) is calculated and the operating time t, the function indicating the relationship between the variables kh obtained in correspondence with the operation time of the (first function) (step S64). The first function calculated in this way is stored in the first storage unit 58 (step S66).

Returning to FIG. 14, the press load measuring device determines whether or not the crank angle (or press / slide position) is within the press load calculation range (step S14). Whether or not it is within the press load calculation range can be determined by whether or not the angle of the crankshaft 21 is within the angle range where press molding may be performed (for example, greater than 90 degrees and less than 270 degrees).

In the case the press load is outside the press load operation range (when the press load inoperative), detecting the pressure detected by the pressure detector 11 as the initial pressure P _0, temporarily holds the initial pressure P ₀ (Step S16).

If the crank angle is press load operation range (when the press load is likely to act), the pressure detected by the pressure detector 11 and the pressure P _S in the press load operation range (step S18). Differential pressure calculator 50 calculates a differential pressure between the pressure _{P S} and the initial pressure _{P 0} of the pressing load operation range detected by the pressure detector 11 _(P S -P _{0) (step} S20).

The press load calculator 54, a variable kh acquired in step S12, on the basis of the differential pressure calculated in step S20 _(P S -P _0), calculates the pressing load _{F R} by [6] Formula (step S22). Such pressing load F _R calculated by the monitor device, a printer, output to the storage device, is provided to the user. Pressing load F _R, for example can be used when assess a causal relationship between press load F _R and pressing result.

The press load measuring device determines whether or not the crank angle is out of the press load calculation range (step S26).

If not degreased pressing load operation range, the process returns to step S18, by repeating the processing of step S26 from step S18, it is possible to continuously obtain a pressing load F _R of the press load operation range.

When the press load calculation range is exceeded once, the number of presses is counted up (step S28). As a result, the number of presses is counted. This number of presses can be used to calculate the operation time t based on the number of presses and the number of slide strokes.

Subsequently, the press load measuring device determines whether or not the press operation is completed (step S30). If the press operation is not completed, the process proceeds to step S10, and the press load in the next press cycle is measured. When the press operation is completed, the measurement of the press load by the press load measuring device is completed.

[Other]
In the present embodiment, the variable kh is acquired from the first function according to the operating time of the press machine. However, by making the first function a function of the number of presses of the press machine, the variable is based on the number of presses. You may try to get kh. Further, since the variable kh is a variable corresponding to the volume elastic modulus of the hydraulic oil, the first function may be a function of the volume elastic modulus of the hydraulic oil that changes according to the operating time of the press machine or the number of presses. In this case, the variable kh is calculated based on the volume elastic modulus obtained from the first function.

Further, the first storage unit that stores the first function may store the lookup table corresponding to the first function instead of the first function. The look-up table in this case is a table in which the operating time or the number of presses of the press machine is associated with the variable kh or the volume elastic modulus of the hydraulic oil. By acquiring the operating time or the number of presses of the press machine by using this lookup table, the variable kh corresponding to the acquired operating time or the number of presses or the volume elastic modulus of the hydraulic oil can be read from the lookup table. Can be done.

Further, the case where oil is used as the hydraulic fluid for the cylinder built in the slide has been described, but the present invention is not limited to this, and water or other liquid may be used.

Further, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

1 Accumulator 2 Hydraulic pump 3 Electric motor 4 Check valve 5 Electromagnetic valve 6 Relief valve 9 Hydraulic device 10 Press machine 11 Pressure detector 14 Encoder 15 Piston 20 Column 21 Crank shaft 22 Conrod 23 Joint surface 24 Head side hydraulic chamber 25 Hydraulic cylinder 25a Cylinder part 25b Piston part 26 Slide 27 Bolster 28 Bed 31 Mold 31a Upper mold 31b Lower mold 33 Servo motor 34 Gear 35 Main gear 50 Differential pressure calculator 52 Initial pressure holding unit 54 Press load calculator 56, 56'Variable acquisition unit 58, 58'1st storage unit 59 2nd storage unit 60 Operation time calculator 62 Press count counter

Claims (20)

A pressure detector that detects the pressure of the hydraulic fluid filled in the hydraulic chamber on the head side of the hydraulic cylinder built into the slide of the press machine when a press load is applied.
A differential pressure calculator that calculates the differential pressure between the pressure detected by the pressure detector and the initial pressure when the press load of the hydraulic fluid filled in the hydraulic chamber on the head side is not applied.
A variable acquisition unit that is a variable corresponding to the volume elastic modulus of the working fluid or the volume elastic modulus that changes according to the operating condition of the press machine and acquires the variable under the current operating condition of the press machine. ,
A press load calculator that calculates the press load acting on the slide based on the differential pressure calculated by the differential pressure calculator and the variables acquired by the variable acquisition unit.
Press load measuring device for press machines equipped with. The operating time of the press machine from the time when the hydraulic chamber on the head side of the hydraulic cylinder is first filled, or the number of presses corresponding to the operating time, and the operation when the hydraulic liquid is first filled. Stores a first function or look-up table showing the relationship with the variable from the initial value of the variable corresponding to the content of bubbles contained in the liquid to the convergence value of the variable that minimizes the content of bubbles. Equipped with a first storage unit
The variable acquisition unit uses the first function or the look-up table stored in the first storage unit, and uses the first function or the lookup table based on the operating time or the number of presses of the press machine to date. The press load measuring device for a press machine according to claim 1, wherein the variable is acquired from a table. The first storage unit stores a plurality of the first functions or the look-up tables corresponding to a plurality of press loads having different press loads.
The press load measuring device for a press machine according to claim 2, wherein the variable acquisition unit selects and uses the first function or the lookup table corresponding to the press load of the press machine from the first storage unit. The first storage unit stores a plurality of the first functions or the lookup table corresponding to each mold of a plurality of molds of different types.
The variable acquisition unit selects and uses the first function or the look-up table corresponding to the exchanged mold from the first storage unit each time the mold used for the press machine is exchanged. Item 2. The press load measuring device of the press machine according to Item 2. It has an overload protection function that releases the hydraulic fluid in the hydraulic chamber on the head side when the hydraulic pressure of the hydraulic fluid in the hydraulic chamber on the head side of the hydraulic cylinder reaches an abnormal pressure.
When the operation of the press machine is started after the operation of the overload protection function, the variable acquisition unit obtains the variable in consideration of the decrease of the variable that decreases in relation to the operation of the overload protection function. The press load measuring device for a press machine according to any one of claims 1 to 4 to be acquired. The operating time of the press machine from the time when the hydraulic chamber on the head side of the hydraulic cylinder is first filled, or the number of presses corresponding to the operating time, and the operation when the hydraulic liquid is first filled. A first memory that stores a first function indicating the relationship with the variable from the initial value of the variable corresponding to the content of bubbles contained in the liquid to the convergence value of the variable that minimizes the content of the bubbles. With a part
The variable acquisition unit uses the first function stored in the first storage unit, and acquires the variable from the first function based on the operating time or the number of presses of the press machine up to the present.
The press load measuring device of a press machine according to claim 1, wherein the first function is a function showing a linear approximation curve approximated to a linear delay system from the initial value to the convergence value. A second storage unit for storing a second function showing the relationship between the press load and the time constant of the linear approximation curve that changes according to the press load is provided.
The variable acquisition unit acquires the time constant of the first-order approximation curve from the second storage unit based on the press load of the press machine, and the first storage unit stores the time constant of the first-order approximation curve by the acquired time constant. The press load measuring device of a press machine according to claim 6, which specifies the first-order approximation curve which is a function. Assuming that the initial value of the variable is kh ₀ , the convergence value is kh _C , the time constant of the linear approximation curve is T, and the operating time of the press machine is t, the variable kh is expressed by the following equation.
kh = kh ₀ + (kh _C −kh ₀ ) · e ^{(−t / T)}
The press load measuring device of the press machine according to claim 6 or 7. The variable acquisition unit
The current calculation number M, when the calculation cycle and [Delta] T, the press machine operating time in the calculation number M th t _M, the following equation,
t _M = t _M-1 + ΔT (where t ₀ = 0)
Asked by
The intermediate parameter Pd _M , which means the first-order delayed response of the first function, is expressed by the following equation.
Pd _M = Pd _M-1 + ΔT / T · (1-Pd _M-1 ) (However, Pd ₀ = 0)
Calculated by
The variable kh _M at the operating time t _M of the press machine is expressed by the following equation.
kh _M = kh ₀ + (kh _C −kh ₀ ) · Pd _M
The press load measuring device of the press machine according to claim 8, which is calculated according to the above. The hydraulic cylinder has an overload protection function that releases the hydraulic fluid in the head side hydraulic chamber when the hydraulic pressure of the hydraulic fluid in the head side hydraulic chamber reaches an abnormal pressure.
When the operation of the press machine is started after the operation of the overload protection function, the variable acquisition unit has a value kh obtained by subtracting a constant value Δkh from the variable kh _M acquired immediately before the operation of the overload protection function. _h is obtained, the obtained value kh _h is used in place of the initial value kh ₀ , the intermediate parameter Pd _M is reset to 0, and the variable kh _M after the operation of the overload protection function is set to the next. formula,
kh _M = kh _h + (kh _C -kh _h ) · Pd _M
9. The press load measuring device for a press machine according to claim 9. The differential pressure calculator, the press the detected pressure at the load acting P _S, the initial pressure during the press load inoperative and P _0, the pressure P _S and the differential pressure between the initial pressure P ₀ ( calculates the P _S -P _0),
The pressing load arithmetic unit, the press load _{F R} based the differential pressure and _(P S -P ₀₎ to said variable kh, the following equation,
_{F R = 1/10 × a} × (kh + 1) / kh × (P S -P 0)
(However, a is the cross-sectional area of the hydraulic chamber on the head side of the hydraulic cylinder)
The press load measuring device of the press machine according to any one of claims 6 to 10, which is calculated according to the above. A step of detecting the pressure of the working fluid filled in the hydraulic chamber on the head side of the hydraulic cylinder built in the slide of the press machine when the press load is applied.
A step of calculating the difference pressure between the detected pressure and the initial pressure when the press load of the working fluid filled under pressure in the head side hydraulic chamber is not applied, and
A variable corresponding to the volume elastic modulus of the working fluid or the volume elastic modulus, which changes according to the operating condition of the press machine, and the step of acquiring the variable under the current operating condition of the press machine.
A step of calculating the press load acting on the slide based on the calculated differential pressure and the acquired variable, and
How to measure the press load of a press machine, including. The operating time of the press machine from the time when the hydraulic chamber on the head side of the hydraulic cylinder is first filled, or the number of presses corresponding to the operating time, and the operation when the hydraulic liquid is first filled. Stores a first function or look-up table showing the relationship with the variable from the initial value of the variable corresponding to the content of bubbles contained in the liquid to the convergence value of the variable that minimizes the content of bubbles. Including the step of preparing the first storage part to be
The step of acquiring the variable uses the first function or the look-up table stored in the first storage unit, and the first function or the first function or the number of presses based on the operating time or the number of presses of the press machine to date. The press load measuring method of a press machine according to claim 12, wherein the variable is acquired from a look-up table. The operating time of the press machine from the time when the hydraulic chamber on the head side of the hydraulic cylinder is first filled, or the number of presses corresponding to the operating time, and the operation when the hydraulic liquid is first filled. A first memory that stores a first function indicating the relationship with the variable from the initial value of the variable corresponding to the content of bubbles contained in the liquid to the convergence value of the variable that minimizes the content of the bubbles. Including the steps to prepare the department
The step of acquiring the variable uses the first function stored in the first storage unit, and acquires the variable from the first function based on the operating time or the number of presses of the press machine up to the present. ,
The press load measuring method of a press machine according to claim 12, wherein the first function is a function showing a first-order approximation curve approximated to a first-order lag system from the initial value to the convergence value. The step of preparing the first storage unit is
When the hydraulic chamber on the head side of the hydraulic cylinder is first filled with the hydraulic fluid, a load die for a load test is attached to the press machine until the content of air bubbles contained in the hydraulic fluid is minimized. A step of cycling the press machine to repeatedly apply a press load to the slide,
A step of stopping the slide of the press machine every predetermined operation time from the start of the cycle operation of the press machine to the end of the operation or every predetermined number of presses.
With the slide of the press machine stopped, a press load preset by an external pressurizing device is applied to the slide, and the working fluid filled in the hydraulic chamber on the head side of the hydraulic cylinder is charged. Steps to detect pressure and
A step of calculating the variable for each predetermined operation time or for each predetermined number of presses based on the applied press load and the detected pressure of the working fluid.
A step of creating the first function or a look-up table showing the relationship between the operating time of the press machine or the number of presses corresponding to the operating time and the variable based on the calculation result of the variable is included.
The press load measuring method of a press machine according to claim 13 or 14, wherein the created first function or lookup table is stored in the first storage unit. A step of preparing a second storage unit for storing a second function showing the relationship between the press load and the time constant of the linear approximation curve that changes according to the press load is included.
In the step of acquiring the variable, the time constant of the linear approximation curve is acquired from the second storage unit based on the press load of the press machine, and the time constant stored in the first storage unit is stored by the acquired time constant. The method for measuring a press load of a press machine according to claim 14, wherein the first-order approximation curve is specified as a first function. Assuming that the initial value of the variable is kh ₀ , the convergence value is kh _C , the time constant of the linear approximation curve is T, and the operating time of the press machine is t, the variable kh is expressed by the following equation.
kh = kh ₀ + (kh _C −kh ₀ ) · e ^{(−t / T)}
The method for measuring a press load of a press machine according to claim 14 or 16. The step of getting the variable is
The current calculation number M, when the calculation cycle and [Delta] T, the press machine operating time in the calculation number M th t _M, the following equation,
t _M = t _M-1 + ΔT (where t ₀ = 0)
Asked by
The intermediate parameter Pd _M , which means the first-order delayed response of the first function, is expressed by the following equation.
Pd _M = Pd _M-1 + ΔT / T · (1-Pd _M-1 ) (However, Pd ₀ = 0)
Calculated by
The variable kh _M at the operating time t _M of the press machine is expressed by the following equation.
kh _M = kh ₀ + (kh _C −kh ₀ ) · Pd _M
The press load measuring method of the press machine according to claim 17, which is calculated according to The hydraulic cylinder has an overload protection function that releases the hydraulic fluid in the head side hydraulic chamber when the hydraulic pressure of the hydraulic fluid in the head side hydraulic chamber reaches an abnormal pressure.
In the step of acquiring the variable, when the operation of the press machine is started after the operation of the overload protection function, a constant value Δkh is subtracted from the variable kh _M acquired immediately before the operation of the overload protection function. The value kh _h is obtained, the obtained value kh _h is used in place of the initial value kh ₀ , the Pd _M is reset to 0, and the variable kh _M after the operation of the overload protection function is set to the next. formula,
kh _M = kh _h + (kh _C -kh _h ) · Pd _M
The press load measuring method of the press machine according to claim 18, which is calculated according to the above. The step of calculating the differential pressure, the difference between the press the detected pressure at the load acting P _S, the initial pressure during the press load inoperative When P _0, the pressure P _S and the initial pressure P ₀ calculates the pressure _(P S -P _0),
The step of calculating the pressing load, the pressing load F _R based the differential pressure and (P S _{-P 0)} to said variable kh, the following equation,
_{F R = 1/10 × a} × (kh + 1) / kh × (P S -P 0)
(However, a is the cross-sectional area of the hydraulic chamber on the head side of the hydraulic cylinder)
The method for measuring a press load of a press machine according to any one of claims 16 to 19, which is calculated according to the above.

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