JP2798171B2 - Method of detecting mold clamping force of mold clamping device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a mold clamping force in a mold clamping device having a toggle mechanism such as a molding device such as an injection molding machine or a die casting machine. The present invention relates to a method for detecting a mold clamping force of a mold clamping device intended for accurate detection.

[0002]

2. Description of the Related Art In general, a mold clamping device of an injection molding machine requires a high-speed, shock-free opening and closing operation of a mold and a clamping force (mold clamping force) that is not inferior to the resin pressure at the time of injection. It is roughly classified into a direct pressure type and a toggle type. The toggle type requires a smaller amount of oil when opening and closing the mold than the direct pressure type. To maintain the clamping force, the direct pressure type requires supply of high-pressure oil, whereas the toggle type requires the self-locking function of the toggle mechanism. Since it works, there are various advantages such as energy saving as compared with the direct pressure type. FIG. 6 is a longitudinal sectional view showing a toggle type mold clamping device. The upper half from the center line shows a state before mold closing starts, and the lower half shows a mold closing completed state (toggle link extension completed state). . The mold clamping device 100 shown in the figure includes a link housing 1, a fixed platen (fixed platen) 2, a movable platen (movable platen) 3, a mold 4
(Fixed mold 4b and movable mold 4a), bed 5, toggle mechanism 6, crosshead 7, mold clamping cylinder (die lock cylinder) 8, piston rod 9 and guide rod 1.
It is composed of 0. The double toggle mold clamping device 100 of the injection molding machine includes a pair of upper and lower link mechanisms 6 including three links 6a, 6b, 6c between the movable platen 3 and the link housing 1, as shown in the figure. Housing 1
A die clamping cylinder (die lock cylinder) 8 is attached to a substantially central portion of the outer end surface of the, and the tip of a piston rod 9 of the clamping cylinder 8 is connected to the crosshead 7, and the guide is inserted through the crosshead 7 so as to be able to move forward and backward. The movable platen (movable platen) 3 is moved forward and backward along the rod 10 and the toggle mechanism 6 is operated via the crosshead 7 to move the movable platen (movable platen) 3 with respect to the fixed platen 2 to perform a mold clamping operation. ing.
Specifically, as shown in FIG. 7, the mold 4 is tightened by advancing the mold clamping cylinder 8 from the mold open state in which the toggle links 6a, 6b, 6c of the toggle mechanism 6 are folded.
The amount of oil sent to the mold clamping cylinder 8 is adjusted to obtain a smooth and fast mold clamping operation. Immediately before FIG. 8 where the mold 4 touches, if a product remains between the molds 4a and 4b or foreign matter enters the mold 4, the mold 4 may be damaged. Set the oil level and oil pressure to low and low pressure and tighten. In order to generate a mold clamping force from the state in which the molds of FIG. 8 are touched and to firmly mold the molds 4a and 4b,
High-speed, high-pressure oil is sent to the clamping cylinder 8 and the toggle mechanism 6
Toggle link 6a of, 6b and the stretched state, to generate a clamping force to the mold by extending the length L _t of the tie bar -11 between the link housing 1 and fixed platen 2. Tie bar 11
FIG. 9 shows the state in which the mold has been stretched and completed, and at this time, the toggle links 6a and 6b have completed the extension and are in a straight line state. However, since this state is maintained, energy saving is superior to the direct pressure type. Adjustment of the mold clamping force is performed by changing the amount of extension of the tie bar 11 from the state of the mold touch shown in FIG. When increasing the mold clamping force, the link housing 1 is further advanced in the direction of the fixed platen 2, and when decreasing, the link housing 1 is retracted. This link housing 1
Is carried out by driving a chain wrapped around four tie bar nuts fastened to the four tie bars 11 by a die height motor (not shown). The movement amount is controlled by the rotation amount of the die height motor.

Conventionally, a method of detecting the clamping force of the mold clamping apparatus 100 having the above-described configuration employs a displacement sensor 20 attached to a detection rod 20a set on a tie bar 11, as shown in FIG.
Of the tie bar 11 in a specific section is detected, and the value is coefficient-corrected and converted into an industrial value (TON value) to calculate the mold clamping force. Tie bar 11
Is determined by the drilling depth of the tie bar 11 shown in FIG. 10, but is usually drilled almost to the center between the fixed platen 2 and the movable platen 3.

[0004]

In this method, the amount of elongation in a specific section of the tie bar 11 is about 0.5 mm, and an expensive high-resolution sensor is required to measure the amount of elongation accurately and accurately. There is a drawback that it is necessary, and even if such a high-resolution sensor is used, it is not stable to detect a minute displacement. Also, when measuring the elongation of the tie bar length, a sensor was attached to only one of the four tie bars and detected. The elongation was different, and the measurement results were not always representative of the elongation of all tie bars, and were one of the causes of measurement errors.

[0005]

SUMMARY OF THE INVENTION In order to solve such a problem and detect a mold clamping force with high accuracy and ease, in the present invention, a mold provided with a toggle mechanism is provided with a toggle mechanism. A method of detecting a mold clamping force of a clamping device, wherein a mold clamping force applied to a mold is provided between a link housing and a movable plate, and a difference (amount of change) in a distance between the link housing and the movable plate. Is calculated based on the difference (change amount) between the distance between the link housing and the movable plate at the time of no load when the toggle link of the toggle mechanism is completely extended and at the time of load via the mold opening / closing sensor for measuring the distance. The configuration was adopted.

[0006]

According to the present invention, the distance between the link housing and the movable platen in the state where the toggle link of the toggle mechanism is completely extended, and the two dies are metal-touched with no load.
After the link housing is brought close to the movable platen side by any die height adjustment, the displacement between the link housing and the movable platen in the mold clamped state where the toggle link is in the extension completed state is measured by a sensor (mold open / close sensor). The mold clamping force was converted from this value and calculated. As a result,
A highly accurate mold clamping force is detected from a relatively large sensor displacement.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
This will be described in detail. 1 to 5 relate to an embodiment of the present invention.
FIG. 1 is a side view of a main part of a mold clamping device of an injection molding machine, and FIGS.
Is a schematic side view illustrating the operation of the mold clamping device, and FIG.
FIG. 3 is a correlation diagram of a displacement amount and a mold clamping force. As shown in FIG.
Of an injection molding machine to which the method for detecting a mold clamping force according to the present invention is applied.
In the mold clamping device 100, the link housing 1 and the movable
Toggle link 6 between panel 3 and the same as described in the prior art.
a, 6b, 6c
In both cases, the distance L between the link housing 1 and the movable platen 3
Opening / closing sensor 30 for measuring the change ΔS
It is installed in the lower center between the ring 1 and the movable platen 3. Mold opening and closing
The sensor 30 includes a pinion 30 that rolls on a rack 30a.
By detecting the rotation angle of b, the travel distance between
The change is measured, and the rack 30a and the
The pinion 30b has a movable platen 3 and a link housing, respectively.
1 is fixedly mounted. Mold clamping device configured as above
Principle of measuring method for mold clamping force detection method in 100
The measurement procedure will be described below. Figure 2 shows both
A state in which the metal dies 4a and 4b are metal-touched with no mold clamping force.
Is shown. At this time, the thickness of the link housing 1 is P₁ ,
The thickness of the movable platen 3 is P_Two , Fixing plate 2 thickness is P_Three And
The distance between the ink housing 1 and the movable platen 3 is L₁ , Movable board 3
And the distance between the fixed board 2 and K₁ And In addition, tie bar 11
T is the total length of₁ And FIG. 3 does not show from the state of FIG.
Penetrates the link housing 1 with a die height adjustment device
Four tie bars 11
Turn the nut 11a in the same direction (right-hand
The housing 1 has been moved in the direction of the movable platen 3
And the amount of movement of the link housing 1 (that is, Daiha
Adjustment amount) d_i When the link housing 1
Distance to moving platen 3 is L₁ -D_i And tie bar length T₁ 
Is T₁ -D _i Changes to In the state of FIG. 3, the link how
Jing 1 is the die height adjustment amount d_i Only, close to movable platen 3
The toggle links 6a, 6b, 6c of the toggle mechanism 6
Etc. are bent from the stretched state as shown in the figure
You. From the state shown in FIG. 3, the operation of the mold clamping cylinder 8 is started.
Move the piston rod 9 to the right and toggle again
The metal mechanism 6 is extended to apply a mold clamping force to both the molds 4a and 4b.
FIG. 4 shows the state of the link housing at this time.
L is the distance between_Two And the amount of shrinkage of both molds is
If ΔK, the distance between movable platen 3 and fixed platen 2 is K₁ −
ΔK. The tie bar length at this time is T_Two Toss
You.

[0008] Under the above premise, the mold clamping device 10
Assuming that the mold clamping force of 0 is W and the elongation of the tie bar 11 is ΔT,

[0009]

ΔT = T ₂ − (T ₁ −d _i ) (1)

[0010] From FIGS. 2 to 4

[0011]

T ₂ = P ₁ + L ₂ + P ₂ + K ₁ − △ K + P ₃ (2) T ₁ −d _i = P ₁ + L ₁ −d _i + P ₂ + K ₁ + P ₃ (3)

Therefore, equation (1) is replaced by equation (2) and equation (3).
Substitute the expression

[0013]

ΔT = L ₂ −ΔK−L ₁ + d _i (4)

## EQU1 ## On the other hand, the relationship between ΔT and the clamping force W is such that the sliding resistance between the movable platen 3 and the tie bar 11 is neglected as a high-order minute amount, the tie bar diameter is d _t , the Young's modulus of the steel is E, and When the tie bar length as the extension of the target and T _1,

[0015]

(Equation 4)

[0016] Here, if the d _i with respect to T ₁ Ignore d _i from a small amount of higher order

[0017]

(Equation 5)

Where α is a constant,

[0019]

(Equation 6)

## EQU1 ## Further, the relationship between the amount of compressive strain ΔK of the dies 4a and 4b and the mold clamping force W is obtained by setting the dimensions of the dies 4a and 4b to a.
× b

[0021]

(Equation 7)

Where β is a constant,

[0023]

(Equation 8)

## EQU1 ## The displacement amount (sensor displacement amount) の S of the distance between the link housing 1 and the movable platen 3 measured by the die opening / closing sensor 30 after the die height adjustment is obtained by:

[0025]

ΔS = L ₂ − (L ₁ −d _i ) = L ₂ −L ₁ + d _i (10)

Therefore, substituting (4) into this gives:

[0027]

１０S = △ T + △ K (11)

## EQU1 ## Therefore, by substituting equations (6) and (8) into equation (11),

[0029]

ΔS = (α + β) W (12)

## EQU1 ## α and β are, as described above, (7)
Since the constant is determined by the equation (9) and the equation (9), the sensor displacement △ S is eventually proportional to the mold clamping force W. In other words, the sensor displacement △ S is measured indirectly by measuring the sensor displacement △ S. The tightening force W can be detected. The above is the measurement principle of the mold clamping force detection method of the present invention. In addition, according to a trial calculation in an actual machine, β is on the order of 1/10 to 1/100 of α, and the amount of shrinkage ΔK of the mold is larger than the expansion ΔT of the tie bar 11. It may be ignored and △ S = αW. FIG. 5 is a correlation diagram showing the measurement results obtained by the above method, and the mold clamping force W is proportional to the sensor displacement ΔS.
In the above calculation, the bending deformation of the link housing 1 and the movable platen 3 is neglected. However, the correction can be made in consideration of the amount of deformation.

A specific section of the conventional tie bar 11 (movable platen 3
The length of the tie bar 11 to which the present invention is applied is 1.5 to 1.5 times smaller than the distance between the movable plate and the fixed plate. Since the distance is between the link housing 1 and the movable platen 3 having twice the length, a high-resolution sensor as in the related art is not essential, and a sufficiently high-precision measurement can be performed even with a low-resolution sensor. . Also,
According to the present invention, the mold opening / closing sensor is disposed near the center in the width direction between the link housing and the movable platen, even with respect to the error caused by the non-uniform elongation of the four tie bars inherent in the conventional measuring method based on the tie bar length. , High-precision detection is possible. The maximum measured amount in the conventional method is about 0.5 mm for the same mold clamping force, but the maximum measured amount is about 2 to 3 mm in the method of the present invention, so that highly accurate detection is possible.

[0032]

As described above, in the method of the present invention, the length of the target tie bar is long and the displacement of the sensor is correspondingly large, so that the detection can be performed with high accuracy. Also, the length of the tie bar to be measured is the length between the link housing and the movable platen, and does not depend on the thickness of the mold. Furthermore, since the sensor displacement is large, existing sensors with low resolution can be detected with sufficiently high accuracy, and the equipment cost is low (the link housing and movable plate used to detect the position of the movable plate in the past). Intermediate sensors can be substituted).

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a mold clamping device according to an embodiment of the present invention.

FIG. 2 is a schematic side view illustrating the operation of the mold clamping device according to the embodiment of the present invention.

FIG. 3 is a schematic side view illustrating the operation of the mold clamping device according to the embodiment of the present invention.

FIG. 4 is a schematic side view for explaining the operation of the mold clamping device according to the embodiment of the present invention.

FIG. 5 is a correlation diagram of a sensor displacement amount and a mold clamping force according to the embodiment of the present invention.

FIG. 6 is a longitudinal sectional view of a conventional toggle-type mold clamping device.

FIG. 7 is a side view illustrating the operation of a conventional toggle-type mold clamping device.

FIG. 8 is a side view illustrating the operation of a conventional toggle-type mold clamping device.

FIG. 9 is a side view illustrating the operation of a conventional toggle-type mold clamping device.

FIG. 10 is a side view of a main part showing an embodiment of a conventional mold clamping force detecting method.

[Explanation of symbols]

Reference Signs List 1 link housing 2 fixed platen (fixed platen) 3 movable platen (movable platen) 4 mold 4a movable mold 4b fixed mold 5 bed 6 toggle mechanism 6a toggle link 6b toggle link 6c toggle link 7 crosshead 8 mold clamping cylinder ( die lock cylinder) 9 the distance between the piston rod 10 guide rod 11 tie bar 20 a displacement sensor 20a detects the rod 20b probe 30 type close sensor 100 mold clamping device L link housing and the distance L ₁ link housing and the movable platen and the movable platen (no load h) the distance between the L ₂ link housing and the movable platen (load) K ₁ distance T ₁ tie bar length between movable platen and the fixed platen (no load) T ₂ tie bar length (load) △ and S link housing The amount of change in the distance from the movable platen (the amount of sensor displacement) △ T The extension of the tie bar △ K The shrinkage of the mold The amount d _i die height adjustment amount P ₁ link thickness P ₂ movable plate thickness of the housing P ₃ of the fixing plate thickness d _t tie bar diameter E steel modulus of elongation (Young's modulus) W clamping force α constant β constant a Mold width b Mold height

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-258216 (JP, A) JP-A-5-200522 (JP, A) JP-A-4-197714 (JP, A) JP-A-4-197714 307219 (JP, A) JP-A-61-252126 (JP, A) JP-A-6-71716 (JP, A) JP-A-61-268424 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) B22D 17/26 B29C 33/22 B29C 45/67 B29C 45/76

Claims (1)

(57) [Claims] 1. A method for detecting a mold clamping force of a mold clamping device having a toggle mechanism for opening and closing a mold, wherein a mold clamping force applied to the mold is set between a link housing and a movable platen. Of the distance between the link housing and movable plate (change amount)
Is calculated based on the difference (change amount) between the distance between the link housing and the movable plate at the time of no load when the toggle link of the toggle mechanism is completely extended and at the time of load via the mold opening / closing sensor for measuring the distance. A method for detecting the mold clamping force of the mold clamping device.