JPH06297530A - Clamping force-measuring method for injection molding machine and its apparatus - Google Patents

Abstract

PURPOSE:To provide a clamping force-measuring method for an injection molding machine capable of measuring clamping force surely and smoothly and its apparatus. CONSTITUTION:A plurality of detecting shafts 4, 20 provided inside a tie bar 2, the first and second springs 21, 22 which are provided to the detecting shafts 4, 20 and push tips P1, P2 of respective detecting shafts 4, 20 against the tie bar 2, a displacement sensor 23 which measures variation (Lc'-Lc)=(t'-t) in an axial distance between the tips P1, P2 of respective detecting shafts 4, 20, and a clamping force display 24 which calculates clamping force on the basis of the measured value are provided. Then, the variation (t'-t) in the axial distance between respective tips P1 and P2 is measured with the displacement sensor 23 under a state wherein the tips P1, P2 of respective detecting shafts 4, 20 are pushed against the tie bar 2 with the first and second springs 21, 22, and the clamping force is calculated with the clamping force display 24 on the basis of the measured value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a tie bar installed between a fixed platen and an end plate which are arranged to face each other.
In an injection molding machine in which a movable platen supported and guided by the tie bar is provided so as to be able to approach and separate from the fixed platen, a mold clamping for measuring the mold clamping force between the movable platen and the fixed platen. The present invention relates to a force measuring method and its device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 8, as an injection molding machine of this type, a plurality of tie bars are provided between a stationary platen 1 and end plates (not shown) which are erected in a state of facing each other. 2 are arranged horizontally, a movable platen (not shown) is reciprocally supported and guided by these tie bars 2, and the movable platen is brought close to the fixed platen 1 between the end plate and the movable plate. A mold clamping mechanism (not shown) for separating the mold is provided, and the mold clamping force measurement for measuring the mold clamping force between the fixed mold and the movable mold attached to the fixed plate 1 and the movable plate on the tie bar 2 is measured. It is known that the device 10 is installed. Then, the mold clamping force measuring device 10 includes a tie bar 2 according to the mold clamping force applied between the fixed platen 1 and the movable platen.
Is used to calculate the mold clamping force,
The base end portion of the tie bar 2 is inserted into the fixed platen 1, and the tie bar nut 3 is attached to the screw portion 2a formed at the base end portion of the tie bar 2.
The tie bar 2 is attached to the fixed platen 1 by screwing the tie bar 2 into the mounting hole 2b formed in the base end surface of the tie bar 2, and the detection shaft 4 has its tapered tip end portion of the mounting hole 2b. The tie bar 2 is mounted in a state of abutting against the inner part of the cone, and the cover 5 is mounted on the base end surface of the tie bar 2, while the spring 6 is mounted between the base end of the detection shaft 4 and the cover 5. Further, a displacement sensor 7 that faces the end face of the base end small diameter portion 4a of the detection shaft 4 and detects the position of the end face is screwed into a screw hole 5a formed in the center of the cover 5 and mounted. Further, the displacement sensor 7 is electrically connected to a mold clamping force display device 8 for calculating and displaying the mold clamping force based on the detection value detected by the displacement sensor 7.

When measuring the mold clamping force using the conventional mold clamping force measuring device 10 having the above-described structure, first, as shown in step SP1 of FIG. 9, it is determined whether the mold is open. If it is in the mold open state, the process proceeds to step SP2 as it is, and if it is not in the mold open state, as shown in step SP3, after the movable platen is separated from the fixed platen 1 by the mold clamping mechanism to be in the mold open state, In step SP2, the distance t between the displacement sensor 7 and the end surface of the base end small diameter portion 4a of the detection shaft 4 when the mold clamping force is not applied is measured. Next, as shown in step SP4, a cycle start command is awaited. When this cycle start command is issued, the process moves to step SP5 and the movable platen is moved closer to the fixed platen 1 by the mold clamping mechanism to perform mold clamping. After the completion of clamping, as shown in step SP6, the distance t ′ between the displacement sensor 7 and the end surface of the base end small diameter portion 4a of the detection shaft 4 when the mold clamping force is applied is measured.

That is, when a mold clamping force is applied between the fixed platen 1 and the movable platen, and the tie bar 2 expands in response to the mold clamping force, the spring 6 causes the spring 6 to move deep inside the mounting hole 2b of the tie bar 2. Since the distance t from the end surface of the base end small diameter portion 4a of the detection shaft 4 pressed against the portion and the displacement sensor 7 changes from the distance t to the distance t ′, the distance t ′ is measured by the displacement sensor 7. . continue,
As shown in step SP7, the mold clamping force display device 8 calculates and displays the mold clamping force based on the difference (t-t ') between the measured distances, and then, as shown in step SP8. The steps of injection, supply, cooling, and mold opening are sequentially performed, and the molded product is released from the mold, thereby completing one molding cycle. Further, as shown in step SP9, it is determined whether or not the molding is continued, and if it is continued, the process returns to step SP4.

Further, step SP1 to step S in FIG.
In P3, mold open state (when mold clamping force is not applied)
Instead of measuring the distance t between the displacement sensor 7 and the end face of the base end small-diameter portion 4a of the detection shaft 4,
Small-diameter portion 4a of the base end of the detection shaft 4 when the mold clamping force is not applied
The distance t between the end surface of the displacement sensor 7 and the displacement sensor 7 is input to the mold clamping force display device 8 or whether the distance t is input as shown in steps SP10 and SP11 of FIG. Upon confirmation, a method has been conventionally used in which the distance t is input to the mold clamping force display device 8 and then the process proceeds to step SP4.

[0006]

However, in each of the conventional methods for measuring the mold clamping force, the mold clamping force display device 10 is used.
There is a problem that the mold clamping force displayed on may differ from the actual value. Therefore, as a result of the investigation by the inventors of the present invention, the temperature or the mold temperature changes with time during repeated molding, and the dimensions of the tie bar 2 and the detection shaft 4 due to the thermal expansion according to the temperature change. Therefore, the distance t between the displacement sensor 7 and the end surface of the base end small diameter portion 4a of the detection shaft 4 changes when the mold clamping force is not applied due to the dimensional change due to the thermal expansion. I understood. As described above, in the conventional mold clamping force measuring methods, the distance t is measured at the start of the molding program, as shown in FIG. 9, even though the distance t varies with time. Alternatively, as shown in FIG. 10, the previously input measurement value is used as the distance t, and in any case, the distance t is not changed during repeated molding. It was found that the mold clamping force cannot be calculated accurately because it is handled as a constant value.

Further, in the conventional mold clamping force measuring device 10, the base end of the detection shaft 4 when the tie bar 2 extends in accordance with the mold clamping force applied between the fixed platen 1 and the movable platen. A change in the distance between the end surface of the small diameter portion 4a and the displacement sensor 7 is measured by the displacement sensor 7, and the mold clamping force display device 8 calculates and displays the mold clamping force based on the measured value. When the mold clamping force is measured in this way, the mold clamping force cannot be accurately measured because the screw portion 2a and the screw relief portion 2c connected to the screw portion 2a are formed at the base end portion of the tie bar 2. There is. That is, the length of the measurement target range of the tie bar 2 when the mold clamping force f is not applied is La, the length of the portion where the screw portion 2a and the screw relief portion 2c are formed is Ld, and the length of the cylindrical portion is Let be Le, the length of the measurement target range of the tie bar 2 when the mold clamping force f is applied is La ′, the length of the portion where the screw portion 2a and the screw relief portion 2c are formed is Ld ′, the cylindrical portion Let Le ′ be the length of A, let Ae be the cross-sectional area of the length Le portion, and E be Young's modulus (modulus of elasticity), La′−La = (Ld′−Ld) + (Le′−Le) = (Ld′−Ld) + f · Le / (Ae · E), the force per tie bar f
Is f = {(La'-La)-(Ld'-Ld)} * E * Ae / Le = (La'-La) * E * Ae / Le- (Ld'-Ld) * E * Ae / It becomes Le (1). As is clear from this equation, the change (La'-La) in the length of the measurement target range of the tie bar 2 is (La '
Since −La) = (t′−t), it can be measured by the displacement sensor 7, but the change in the length of the portion where the screw portion 2a and the screw relief portion 2c are formed (Ld′−L)
Since it is difficult to theoretically calculate d) due to changes in the shapes of the screw relief portion 2c and the screw portion 2a and changes in the screw position of the screw portion 2a, the force f per tie bar is calculated from the above formula (1). Could not be calculated accurately.

In addition, the force f is applied (changed) experimentally in advance, and the change (La'-La) in the length of the measurement target range of the tie bar 2 at that time is measured in advance to obtain the above-mentioned force f. Change in length of measurement range of tie bar 2 (La'-L
(a) in the form of a table or graph, the change in the distance between the measured end surface of the base end small diameter portion 4a of the detection shaft 4 and the displacement sensor 7 (t'-t) {= (La ' -L
a)} is used to convert the force f per tie bar, but in this case, the measurement accuracy can be improved, but the above correlation table or graph must be created. At the same time, it has to be converted based on these correlation tables or correlation graphs, which is extremely troublesome and has a problem of poor workability.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to ensure the influence of a disturbance such as a change in air temperature or mold temperature even if molding is continuously repeated for a long period of time. To provide a method for measuring the mold clamping force of an injection molding machine, which can be eliminated and can measure the mold clamping force accurately and smoothly, and to measure the mold clamping force and the tie bar as in the conventional method. It is not necessary to create a table or graph for the relationship with the change in the length of the range, and the effect is irrelevant regardless of the shape or structure of the tie bar end such as the screw part or the screw relief part formed on the tie bar. It is an object of the present invention to provide a mold clamping force measuring device for an injection molding machine that can be excluded and can measure the mold clamping force reliably and smoothly.

[0010]

In order to achieve the above object, the mold clamping force measuring method according to claim 1 of the present invention is such that a detection shaft is mounted inside a tie bar so as to be movable in the axial direction, and the detection shaft is attached. While pressing the tie bar, the change in the position of the detection axis between the mold open state and the mold clamp state is measured for each fixed molding cycle, and the mold clamping force is calculated based on this measured value. is there.

According to a second aspect of the present invention, there is provided a mold clamping force measuring apparatus, wherein a plurality of detection shafts are mounted inside the tie bar so as to be movable in the axial direction, and the detection shafts are provided on these detection shafts. Of the pressing member that presses the contact end with the tie bar against the tie bar, and the change in the axial distance between the contact ends of the detection shafts with the tie bar is measured, and the mold is determined based on this measurement value. And a mold clamping force calculating means for calculating the clamping force.

[0012]

In the mold clamping force measuring method according to the first aspect of the present invention, the change in the position of the detection axis between the mold open state and the mold clamped state after the start of molding is measured, so that the repetitive molding is performed. The mold clamping force can be reliably measured by flexibly responding to changes in the air temperature or the mold temperature, etc., and eliminating the influence that the dimensions of the tie bar and the detection shaft change due to thermal expansion.

Further, in the mold clamping force measuring apparatus according to the second aspect of the present invention, the contact ends of the plurality of detection shafts mounted inside the tie bar with the tie bar are connected to the tie bar by the pressing member. In the pressed state, the mold clamping force calculating means measures the change in the axial distance between the contact ends of the respective detection shafts with the tie bar, and calculates the mold clamping force based on the measured value. Thus, the measurement accuracy is improved by excluding a portion that adversely affects the mold clamping force measurement accuracy such as a screw portion or a screw relief portion formed on the tie bar from the measurement target range of the tie bar.

[0014]

Embodiments of the present invention will be described below with reference to FIGS. In the present embodiment, parts having the same configurations as those of the conventional example shown in FIG. 8 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, reference numeral 20 is a second detection shaft formed in a bottomed cylindrical shape.
Is loosely fitted to the first detection shaft 4 with the base end bottom located on the base end face side of the tie bar 2. And these 1st, 2nd detection shafts 4 and 20 are mounted in the mounting hole 2f of the tie bar 2 which consists of the small hole part 2d and the thick hole part 2e. The tip portion of the second detection shaft 20 is brought into contact with the step portion 2g between the small hole portion 2d and the thick hole portion 2e of the mounting hole 2f, and the tip portion position thereof is the screw. It is set at a position that is sufficiently distant in the axial direction of the tie bar 2 from the screw escape portion 2c formed to be continuous with the portion 2a. Further, between the base end portion of the first detection shaft 4 and the inner bottom portion of the second detection shaft 20, the first detection shaft 4 is pressed against the inner portion of the mounting hole 2f of the tie bar 2. The spring 21 is attached, and the second detection shaft 20 is pressed between the base end portion of the second detection shaft 20 and the cover 5 against the step portion 2g of the attachment hole 2f of the tie bar 2. Two springs 22
Is installed. Then, the second spring 22
Is set to be stronger than the urging force of the first spring 21. Further, a displacement sensor 23 for detecting the position of the end face of the base end small diameter portion 4a of the first detection shaft 4 is screwed and attached to the base end bottom portion of the second detection shaft 20. Furthermore, the displacement sensor 23 is electrically connected to a mold clamping force display device 24 that calculates and displays the mold clamping force based on the detection value detected by the displacement sensor 23.

The mold clamping force f in the mold clamping force display device 24 is calculated as follows. That is, the length from the base end surface of the tie bar 2 to the step portion 2g of the mounting hole 2f when the mold clamping force f is not applied is Lb.
From the base end face of the tie bar 2 when the mold clamping force f is applied to the step portion 2g of the mounting hole 2f
Is Lb 'and the length from the stepped portion 2g to the tip is Lc', then Lc'-Lc = (La'-Lb ')-(La-Lb) = (La'-La) Since there is a relationship of-(Lb'-Lb) = t'-t, if Ac is the cross-sectional area of the length Lc portion, the mold clamping force f per tie bar is f = (Lc'-Lc). -E * Ac / Lc = (t'-t) * E * Ac / Lc (2) is calculated. Therefore, the total mold clamping force is the above mold clamping force f.
Is multiplied by the number of tie bars 2 (4 in this embodiment).

Next, referring to FIG. 2, a case of carrying out the method of the present invention using an injection molding machine incorporating the mold clamping force measuring device 40 constructed as described above will be described. As shown in step SP20, it is determined whether or not a cycle start command is output, and when this cycle start command is issued, the process proceeds to step SP21 to determine whether or not the mold is open. If the mold is not in the mold open state while moving to SP22, as shown in step SP23, the movable platen is separated from the fixed platen 1 by the mold clamping mechanism to be in the mold open state, and then the process moves to step SP22 to apply the mold clamping force. The displacement sensor 2 and the end surface of the base end small diameter portion 4a of the first detection shaft 4 when not performing
3 is measured and the measured value is used as the mold clamping force display device 2
Enter in 4. Next, as shown in step SP24, the movable platen is moved closer to the fixed platen 1 by the mold clamping mechanism, and the movable platen and the fixed platen mounted on the movable platen and the fixed platen 1 are closed and strongly closed. Clamp the mold.

After the completion of the mold clamping, as shown in step SP25, the first detection shaft 4 when the mold clamping force is acting.
The distance t ′ between the displacement sensor 23 and the end surface of the base small diameter portion 4a of FIG. That is, when the mold clamping force is applied, the tie bar 2 is extended, and with the extension of the tie bar 2,
The tip P1 of the first detection shaft 4 pressed by the first spring 21 into the inner part of the mounting hole 2f of the tie bar 2 and the mounting hole 2 by the second spring 22.
The second detection shaft 2 pressed against the stepped portion 2g of f
The distance from 0 to the tip P2 changes. A displacement sensor attached to the end surface of the base end small diameter portion 4a of the first detection shaft 4 and the base end portion of the second detection shaft 20 according to the change in the distance (Lc'-Lc). 23 changes from the distance t when the mold clamping force is not applied to the distance t ′ when the mold clamping force is applied, so that the changed distance t ′
Is measured by the displacement sensor 23.

Then, as shown in step SP26,
In the mold clamping force display device 24, the difference (t'-t) is obtained based on these measured distances t and t ', and the mold clamping force is calculated and displayed according to the above equation (2). In this case, since the change in the distance is measured between the two points P1 and P2 which are sufficiently separated from the screw portion 2a or the screw escape portion 2c, the influence of the screw portion 2a and the screw escape portion 2c is not exerted. The mold clamping force is surely required and displayed smoothly. Next, as shown in step SP27, each step of injection, supply, cooling, and mold opening is sequentially performed to release the molded product from the mold, thereby completing one molding cycle. Further, as shown in step SP28, it is determined whether or not the molding is continued, and after repeating a predetermined molding cycle, the molding is finished.

As described above, in this embodiment, the distance between the displacement sensor 23 and the end face of the base end small diameter portion 4a of the first detection shaft 4 when the mold clamping force is not applied in each molding cycle. Since t is measured and the distance t is updated when the mold clamping force is calculated, there is only a small time difference between the measurement of the distance t and the measurement of the distance t ′. Changes in air temperature or mold temperature are reliably eliminated,
In addition, thermal expansion does not affect the tie bar and the detection shaft. Therefore, the measurement accuracy is remarkably improved as compared with the conventional mold clamping force measuring method.

In the above embodiment, the first detection shaft 4 when the mold clamping force is not applied in each molding cycle.
Distance t between the end surface of the base end small-diameter portion 4a and the displacement sensor 23
However, the present invention is not limited to this, and the distance t may be measured every predetermined number of molding cycles, as shown in step SP30 of FIG.
Further, in each of the above embodiments, the distance t is measured by the displacement sensor 23 and is input to the mold clamping force display device 24 as shown in step SP22 of FIGS. 2 and 3, but the invention is not limited thereto. At this time, the mold clamping force display device 2
In step 4, the distance t may be reset to 0 (set to 0). By doing so, in step SP25 of FIGS. 2 and 3, when measuring the distance when the mold clamping force is acting, the measured value by the displacement sensor 23 is Since the difference between the distance when the mold clamping force is applied and the distance when the mold clamping force is not applied (t'-t) is represented, by substituting this difference (t'-t) into the above formula (2). , The mold clamping force is easily calculated.

Further, in the above-described mold clamping force measuring method shown in FIGS. 2 and 3, the mold clamping force measuring device 40 shown in FIG. 1 is used.
However, the method of the present invention is not limited to this.
It is needless to say that the present invention can be applied to the conventional mold clamping force measuring device 10 shown in FIG. In this case, similarly to the above-mentioned respective embodiments, the change of the air temperature or the mold temperature during the repeated molding is surely eliminated, and the measurement accuracy is higher than that of the conventional mold clamping force measuring method shown in FIG. 9 or 10. Is improved.

Here, the mold clamping force measuring device 4 shown in FIG.
0 and the conventional mold clamping force measuring device 10 shown in FIG. 8 are compared with each other, the mold clamping force measuring device 10 is not affected by the screw part 2a and the screw relief part 2c. Measuring the mold clamping force using the clamping force measuring device 40 improves the measurement accuracy. That is, as is apparent from the above formula (1), the change (La′−La) {= (t′−t)} in the length of the measurement target range of the tie bar 2 can be measured by the displacement sensor 7. However, there is a change in the length of the portion where the screw portion 2a and the screw relief portion 2c are formed (Ld'-L
Since it is difficult to theoretically calculate d) as described above, the mold clamping force according to the above mathematical formula (2) is correspondingly compared with the mold clamping force calculated by the conventional mold clamping force measuring device 10. The mold clamping force calculated by the measuring device 40 improves the measurement accuracy. When measuring the mold clamping force using the conventional mold clamping force measuring device 10 shown in FIG.
The mold clamping force is applied (changed) experimentally in advance, and the length of the measurement target range of the tie bar 2 at that time is changed (La'-L).
a) {= (t'-t)} is measured in advance, and the mold clamping force and the change in the length of the measurement target range of the tie bar 2 (La'-L) are measured.
The relationship between (a) and (a) is input to the mold clamping force display device 8, and this correlation and the change in the length measured during actual operation (L
The mold clamping force may be converted based on a′−La) {= (t′−t)}. As a result, the threaded portion 2 in the case where the conventional mold clamping force measuring device 10 is used.
The influence of a or the screw escape portion 2c is reliably eliminated.

Further, the mold clamping force measuring device 4 shown in FIG.
Although the displacement sensor 23 is housed inside the tie bar 2 in 0, the lengths La and Lb are the length L.
If it is set large enough for d, the tie bar 2
The same effect can be obtained even if it is provided outside. Further, in the embodiment shown in FIG. 1, the case where the mold clamping force measuring device is provided on one tie bar 2 has been described, but the present invention is not limited to this.
As shown in FIG. 4, a plurality of (four) tie bars 2 are provided with the displacement sensors 23 of the mold clamping force measuring device, and the measurement values measured by these displacement sensors 23 are input to the displacement gauge control unit 25. At the same time, a digital display 27 is electrically connected to these displacement gauge control units 25 via a switching unit 26, and signals from each displacement gauge control unit 25 are selected and switched by this switching unit 26. The mold clamping force applied to each tie bar 2 may be digitally displayed on the digital display 27.

Furthermore, in the above embodiment shown in FIG. 1, two points P1 and P2 are provided by one displacement sensor 23.
Although it is configured to measure the change in distance (t′−t) between the two, the present invention is not limited to this, and as shown in FIG. 5, the second detection shaft 20 includes a cylindrical first tubular portion 20a, Tip locking part 20
b and a second tubular portion 20d having a base end flange portion 20c, the base end portion of the first detection shaft 4 and the second detection shaft 2 described above.
The first spring 21 is mounted between the front end locking portion 20b of the second cylindrical portion 20d of 0 and the cover attached to the base end surface of the tie bar 2 and the front end locking portion 20b of the second cylindrical portion 20d. The second spring 22 having a stronger urging force than the first spring 21 is mounted between the first and second springs 28 and 28, and the base 28 of the first detection shaft 4 has a small-diameter portion 4a.
The displacement sensors 30 and 31 for detecting the respective positions of the end surface of the second detection shaft 20 and the end surface of the base end flange portion 20c of the second detection shaft 20 may be attached by screwing. With this configuration, the displacement sensors 30 and 31 change the distance (La'-La) from the base end face of the tie bar 2 at two points P1 and P2 (La'-La) = (ta'-ta),
Since (Lb'-Lb) = (tb'-tb) is measured independently, the difference between these measured values (Lc'-L)
The mold clamping force is calculated by obtaining c) and substituting it in the above equation (2). The second detection shaft 20 is divided into a first tubular portion 20a and a second tubular portion 20d,
The first tubular portion 20a and the second tubular portion 20d may be integrally configured.

Further, as shown in FIG. 6, two mounting holes 2h and 2i are formed in one tie bar 2, and these mounting holes 2h and 2i are urged by springs 34 and 35, respectively. A configuration in which the solid first and second detection shafts 32 and 33 are mounted may be used. In this case, similarly to the above-described embodiment shown in FIG. 5, the displacement sensors 30 and 31 measure the changes in the distance from the base end surface of the tie bar 2 at the two points P1 and P2, respectively. The mold clamping force can be obtained by calculating the difference between the measured values and substituting it in the above formula (2) for calculation. In each of the embodiments shown in FIGS. 5 and 6, the tie bar 2 is provided with the two displacement sensors 30 and 31, respectively. However, these displacement sensors 30 and 31 are provided to the two tie bars. It may be divided into two parts.

In each of the embodiments shown in FIGS. 5 and 6, the tie bar 2 is provided with the mold clamping force measuring device having the two displacement sensors 30 and 31, respectively. However, as shown in FIG. 7, the displacement sensors 30, 30 of the mold clamping force measuring device are respectively attached to the plurality of tie bars 2.
31 is provided, and the measured values measured by these displacement sensors 30, 31 are respectively input to the displacement gauge control unit 25, and the digital display 27 is provided to these displacement gauge control units 25 via the calculation / switch 36. It is electrically connected and a pair of displacement sensors 30, 3 are connected by the operation / switch 36.
Based on the change in the distance from the base end face of the tie bar 2 at the two points P1 and P2 measured by the pair of displacement sensors 30 and 31, the signals from the displacement gauge control units 25 corresponding to 1 are selected. After calculating the mold clamping force, the mold clamping force may be digitally displayed on the digital display 27. Furthermore, in each of the above-described embodiments, the non-contact type displacement sensors 23, 30, 31 are used for description, but the present invention is not limited to this, and for example, a dial gauge or the like may be used.
The change (Lc'-Lc) in the distance from the base end surface of the tie bar 2 at the points P1 and P2 is read, and the measured value is multiplied by the coefficient (E · Ac / Lc) to calculate and display the mold clamping force. Good.

[0028]

As described above, according to the method for measuring the mold clamping force of the injection molding machine of the present invention, the detection shaft is mounted inside the tie bar so as to be movable in the axial direction, and the detection shaft is pressed against the tie bar. Since the change in the position of the detection axis between the mold opening state and the mold clamping state after the start of molding is measured and the mold clamping force is calculated based on this measured value, the mold clamping force is fixed every fixed cycle. By measuring the change in the position of the detection axis between the mold open state and the mold clamped state, it is possible to flexibly respond to changes in air temperature or mold temperature during repetitive molding, and tie bars due to thermal expansion. Further, it is possible to reliably eliminate the influence of the variation of the size of the detection shaft, and it is possible to measure the mold clamping force accurately and smoothly.

Further, the mold clamping force measuring device of the injection molding machine of the present invention comprises a plurality of detection shafts mounted inside the tie bar so as to be movable in the axial direction, and the detection shafts provided on these detection shafts. Of the pressing member that presses the contact end with the tie bar against the tie bar, and the change in the axial distance between the contact ends of the detection shafts with the tie bar is measured, and the mold is determined based on this measurement value. Since the mold clamping force calculating means for calculating the clamping force is provided, the mold clamping force calculating means is provided in a state where the contact ends of the detection shafts with the tie bars are pressed against the tie bars by the pressing member. Depending on the above detection axes,
By measuring the change in the axial distance between the contact end with the tie bar and calculating the mold clamping force based on this measurement value, the mold clamping force and the range of the tie bar to be measured are measured as in the conventional case. It is not necessary to create a table or graph for the relationship with the change in length, and it adversely affects the accuracy of mold clamping force measurement of the screw part or screw relief part formed on the tie bar from the measurement range of the tie bar. Since the part can be removed, the mold clamping force can be measured reliably and smoothly regardless of the shape and structure of the end of the tie bar, and the accuracy of mold clamping force measurement can be improved. The tightening force can be measured automatically.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a mold clamping force measuring device of the present invention.

FIG. 2 is a flow chart showing an embodiment of the mold clamping force measuring method of the present invention.

FIG. 3 is a flowchart showing another embodiment of the mold clamping force measuring method of the present invention.

FIG. 4 is a schematic configuration diagram in the case where a plurality of mold clamping force measuring devices of FIG. 1 are provided.

FIG. 5 is a cross-sectional view showing another embodiment of the mold clamping force measuring device of the present invention.

FIG. 6 is a cross-sectional view showing another embodiment of the mold clamping force measuring device of the present invention.

7 is a schematic configuration diagram in the case where a plurality of mold clamping force measuring devices of FIG. 5 or 6 are provided.

FIG. 8 is a cross-sectional view showing a conventional mold clamping force measuring device.

FIG. 9 is a flowchart showing an example of a conventional mold clamping force measuring method.

FIG. 10 is a flowchart showing another example of the conventional method for measuring the mold clamping force.

[Explanation of symbols]

 1 Fixed Plate 2 Tie Bar 4 First Detection Axis 10/40 Mold Clamping Force Measuring Device 20 Second Detection Axis 21 First Spring (Pressing Member) 22 Second Spring (Pressing Member) 23 ・ 30 ・ 31 Displacement Sensor (Mold Clamping Force Calculator) 24 Mold Clamping Force Display Device (Mold Clamping Force Calculator) 32 First Detecting Shaft 33 Second Detecting Shaft 34 First Spring (Pressing Member) 35 Second Spring (Pressing Member)

Claims (2)

[Claims] 1. A tie bar is installed between a fixed platen and an end plate, which are arranged to face each other, and a movable platen supported and guided by the tie bar is provided so as to be close to and away from the fixed platen. In the method of measuring the mold clamping force of an injection molding machine for measuring the mold clamping force between the movable platen and the fixed plate, a detection shaft is mounted inside the tie bar so as to be movable in the axial direction, and the detection shaft is attached to the tie bar. It is characterized in that the change in the position of the detection axis between the mold opening state and the mold clamping state is measured at fixed molding cycles and the mold clamping force is calculated based on the measured value. Measuring method of mold clamping force of injection molding machine. 2. A tie bar is installed between a fixed platen and an end plate which are arranged opposite to each other, and a movable platen supported and guided by the tie bar is provided so as to be able to approach and separate from the fixed platen, and In a mold clamping force measuring device of an injection molding machine for measuring the mold clamping force between these movable platen and stationary platen, a plurality of detection shafts mounted movably in the axial direction inside the tie bar, and these Measures the change in the axial distance between the pressing member that is provided on the detection shaft and that presses the contact end of each detection shaft with the tie bar against the tie bar and the contact end of each detection shaft with the tie bar. The mold clamping force measuring device for an injection molding machine, further comprising a mold clamping force calculating means for calculating the mold clamping force based on the measured value.