JPH07118985B2 - Tightening method for equalizing mold clamping force in toggle type mold clamping device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention makes it possible to automatically apply a mold clamping force evenly to four tie bars in a toggle type mold clamping device of an injection molding machine or a tie casting machine. The present invention relates to a mold clamping force equalizing structure and a tightening method for equalizing the mold clamping force.

[Conventional technology and its problems]

Hydraulic mold clamping devices such as injection molding and die casting machines
The direct pressure type and toggle type have been put into practical use.

The direct pressure type has the advantage that the mold clamping force is determined by the pressure receiving area of the piston body of the mold clamping cylinder x the operating hydraulic pressure, but in order to produce a large mold clamping force, the pressure receiving area of the piston body must be increased. First, many techniques were required to prevent oil leaks such as packing, and a special hydraulic circuit was required to quickly open and close the mold with a hydraulic pump with an appropriate discharge rate.

In the toggle type, a toggle mechanism increases the mold opening force of a small diameter mold clamping cylinder to obtain a large mold clamping force.High-speed mold opening and closing can be performed with a simple hydraulic circuit. The mold clamping force is not determined by the area × operating hydraulic pressure, but when the toggle mechanism is clamped, the four tie bars are stretched and the mold clamping force is obtained by the reaction force. That is, after the parting surface of the mold comes into contact with the operation of the mold clamping cylinder, the toggle arm is fully extended while the small force generated by the mold clamping cylinder is increased by the toggle mechanism.
Up to the so-called dead point, the four tie bars are stretched to perform the tightening operation.

In such a toggle type mold clamping, it is important that the four tie bars are stretched evenly and the mold clamping force is evenly shared. If the shared mold clamping force of each tie bar becomes unbalanced, an overload occurs. The tie bar that has become dead may be damaged.

For this equalization, the stress generated in each tie bar is measured by a sensor such as a strain gauge, and if the imbalance becomes excessive, the molding is interrupted and the tie nut corresponding to the excessively extended tie bar is interrupted. There were many problems in the maintenance of the molding machine, as I loosened a little and adjusted it.

〔Purpose〕

The present invention has been made in view of the problems of the conventional example, and an object thereof is to provide a toggle-type mold clamping device,
Another object of the present invention is to provide a tightening method at the time of equalizing the mold clamping force, which has a structure capable of equalizing the mold clamping force in the four tie bars by utilizing hydraulic pressure.

[Means for solving problems]

The present invention is to solve the above problems by claim (1); in a toggle mechanism (7), a toggle type mold for moving a movable mold (14) with respect to a fixed mold (13) in a pressure contact / separable manner. In the tightening device, a gap (20a) for filling pressure oil is provided between the link housing (2) serving as the force application point of the toggle mechanism (7) and the tie nuts (10) screwed to the plurality of tie bars (5). ) ...
Are formed respectively, and the respective gaps (20a) ... Are made to communicate with each other by the pressure pipes (23). The contraction amount of the pressure oil in the axial direction is calculated in advance, and prior to the mold clamping, the toggle mechanism (7) is moved to the fixed plate (1) side according to the contraction amount to perform the tightening.

Is adopted as a technical means.

[Action]

In the toggle type mold clamping device of the present invention configured as described above,
When the fixed and movable molds (13) and (14) are attached to the fixed plate (1) and the movable plate (4), respectively, and the tie nuts (10) are tightened by increasing the tightening amount by an equal rotation angle. A constant hydraulic pressure is generated by the pressure oil filled in the gaps (20a) communicating with each other, and the tie bars (5) are uniformly stretched. As a result, a uniform mold clamping force is automatically applied to each tie bar (5). At this time, the pressure oil is also slightly compressed in the axial direction of the tie bar (5), and the mold clamping force becomes insufficient accordingly. Therefore, the axial contraction amount of this pressure oil is calculated in advance, and This pressure oil shrinkage is added to the tightening amount before tightening. As a result, a necessary and sufficient mold clamping force can be obtained.

(Examples) Hereinafter, the present invention will be described in detail with reference to illustrated examples.

As shown in FIG. 1, FIG. 2, and FIG. 3, the fixed plate (1) on the machine frame and the link housing (2) are vertically opposed to each other, and four holes are provided in the four holes of the moving plate (4). Insert the tie bar (5). The right end screw part (5a) of the tie bar (5) is inserted into the four holes of the fixing plate (1), and the left end screw part (5b) is inserted into the four holes of the link housing (2). A mold opening / closing cylinder (6) is attached to the link housing (2), and a toggle mechanism (7) is attached between the link housing (3) and the moving plate (4).

Screw part (5a) of the tie bar (5) on the fixed plate (1) side
Tighten with the fixed side tie nut (8) and lock with the rotation stop device (9). The four tie nuts (10) from the left of the link housing (2) are screwed into the threaded portion (5b) at the left end of the tie bar (5) to form a tie nut holder formed on the inner surface of the outside of the link housing (2). Tighten until the right end (10a) of the tie nut (10) contacts the inner surface (3a) of (3). In this state, tie nut presser (1
1) is fixed to the link housing (2) with bolts (12) to form a toggle type mold clamping device.

Next, the fixed mold (13) is attached to the fixed plate (1), the movable mold (14) is attached to the movable plate (4), and the cylinder (6) is operated to extend the toggle to extend the mold parting surface. Close the mold so that (15) matches. This time,
In the toggle type mold clamping device, the entire toggle mechanism (7) is moved forward according to the size (height in the axial direction) of the mounted molds (13) (14) (right in Figs. 1 and 2). Direction) or back (left side of the figure). There is a mold thickness adjusting device for performing the operation. This will be described with reference to FIGS. 3 to 6. (16)
Is a motor for adjusting the mold thickness, and is fixed to the link housing (2) by a bracket (17). Electric motor (16)
The main gear (18) is screwed into the screw of the shaft (16a) to simultaneously drive the four gears (19) in the same direction by the same rotation angle.
Since the gears (19) are fixed to the tie nuts (10), the four tie nuts (10) are rotated by equal rotation angles by the normal rotation and the reverse rotation of the mold thickness adjusting motor (16), so that the link housing ( It is possible to adjust the parting surface (15) of the mold with the toggle fully extended by moving the entire toggle mechanism including 2) forward and backward to match the thickness of the mold.

Next, the right end surface (10a) of the four tie nuts (10) and the pressure contact point (2) of the inner surface (3a) of the tie nut holder (3).
The four pipe holes (21) communicating with (0) are drilled, and the hydraulic nipple (22) is tightly screwed so that there is no oil leak in the holes (21). Then, in the pressure pipe section (23), as shown in FIGS. 5 and 6, these four hydraulic nipples (22) are connected so as to communicate with each other, and a check valve (24) and a direction switching valve (25) are further connected. Through a hydraulic source.

When pressure oil is sealed in the pressure contact point (20) with the above structure, a slight gap (20a) is generated in the pressure contact point (20). The pressure oil filled in the gap (20a) is passed through the hydraulic nipple (22) and the pipe member (23) to form four gaps (20).
It can flow freely between a), but because of the check valve (24), it cannot flow back to the hydraulic pressure source.

Next, in order to obtain the required mold clamping force, the mold is once opened slightly, and then the mold thickness adjusting motor (16) is normally rotated by an additional tightening amount corresponding to the mold clamping force to move the fixed mold (13 ), Moving mold (1
When the face-to-face spacing in 4) is reduced by the specified amount and the mold is clamped again, a predetermined mold clamping force is generated. In this state, a force in the direction opposite to the mold clamping acts as a reaction force on the extended toggle member, and the link housing (2) which is the force application point of the toggle.
Is pressed in the direction of FIG. That is, the inner end surface (3b) of the four tie nut holders (3a) is moved to the left by the right end surface (10a) of the four tie nuts (10) through the pressure oil filled in the gap (20a). Press on. Therefore, the tie nut (1
The four tie bars (5) screwed together with (0) are evenly stretched to the left and generate a predetermined mold clamping force in balance with the restoring force due to the elasticity of the tie bars (5).

The pressure oil sealed in the gap (20a) in the device of the present invention is compressed during mold clamping, which causes a change in volume and reduces the effective axial length of the tie bar (5). There may be a concern that only a small mold clamping force can be obtained, but when measuring the hydraulic pressure that rises during mold clamping with the example machine (nominal mold clamping force 80 tons machine), The hydraulic pressure for raising the clearance (20a) is 280 kg / c when the pressure is 80 tons.
It was about m ² . In the case of petroleum-based hydraulic oil, the volumetric shrinkage rate due to pressurization of about 280 kg / cm ² is 0.995, so the gap length of the gap (20a), for example, 10 mm, is shortened by 10 mm × (1-0.995) = 0.05 mm. Therefore, if the effective length of the tie bar (5) (span from the inside of the fixed side tie nut (8) to the inside of the link housing side tie nut (10)) is 1000 mm, in the case of 80 tons mold clamping, about 0.4 mm during mold clamping. Although it is stretched, it is reduced by about 0.05 mm. That is, in the case of 80 tons machine, in order to generate the mold clamping force of 80 tons, when setting the mold clamping force, 0.4 mm of the amount of extension of the tie bar is preset.
Only the span of 1000 mm is shortened, the tightening work is carried out by sending the entire toggle device in the direction of the fixed plate, but when applying the present invention, the tightening amount of 0.4 mm is 0.4-0.05. It becomes as short as = 0.35 mm. If left as it is, the mold clamping force will be as small as 0.35 ÷ 0.4 = 87.5%.

However, the rate at which this mold clamping force becomes smaller is constant because it is due to the volumetric contraction rate of the pressure oil, so the RAM memory value that stores the table of mold clamping force vs. tightening amount during the tightening work. By increasing it (adding only the axial shrinkage rate of the pressure oil tie bar), the correct mold clamping force will always be obtained.

In the toggle type mold clamping device of the present invention configured as described above,
When the molds (13) (14) with a high degree of parallelism of the mounting surface are mounted and the tie nuts (10) are tightened with the tightening amount equal to the rotation angle, the gaps (20a) communicating with each other become A constant hydraulic pressure is generated and the four tie bars (5) are uniformly stretched. During long-term use, it is assumed that one of the four tie bars (5) has a stretching force larger than the other three due to unbalanced wear of the bushing of the toggle member. The force of tightening the die in the direction of FIG. 5 generated on the tie bar is also larger than the other points, and the tie nut screwed on the tie bar is also pressed to the left more than the other tie nuts. Now, in the conventional structure where the tightening force is applied to each tie bar independently, the right end surface (10a) of the tie nut (10) is directly pressed against the inner back surface (3b) of the tie nut holder (3a), As a result, this large unbalanced pressing force is maintained as it is, and the four tie bars do not evenly share the mold clamping force, and only one tie bar excessively bears the mold clamping force. Become. Therefore, in an extreme case, one overloaded tie bar may be cut off.

On the other hand, in the case of the present invention, only the gap (20a) pressed by the tie nut (10) where the imbalance occurs is narrowed, and the pressure oil filled in the gap (20a) is not The pressure of the pressure oil transferred to the three gaps (20a), (20a), (20a) and filled in the four gaps (20a) becomes equal. Therefore, even if, for example, an unbalanced large tensile force is to be generated in only one tie bar (5), the other tie bar (5) can be formed by the configuration of the present invention.
(5) Since the tensile force is evenly distributed to (5), the four tie bars (5) always share an even mold clamping force.

(Example 1) An example of how the apparatus of the present invention automatically equalizes the mold clamping forces shared by the four tie bars will be described.

The four data numbers in Table 1 are the actual measurements of the mold clamping force shared by the four tie bars when normal mold thickness adjustment and retightening were performed with the conventional mold clamping device. It is written according to the position of the tie bar. The machine to be measured is a machine with a nominal clamping force of 80 tons, and the measuring method is the strain gauge method. The variation of the mold clamping force applied to each tie bar is ± (2 to 7)% centering on the average of this measured value of 20.48 tons.

As shown in Table 2, the apparatus of the present invention was applied to the same machine to be measured and the distribution of mold clamping force was measured again. As shown in Table 2, the variation of the mold clamping force applied to each tie bar is ± (0.4 to 0.9)%. It is contained in a small range, and the effect is clear.

Further, it was possible to feel from the outside of the hose that the pressure oil reciprocates in the high-pressure rubber hose, which is the pressure pipe that connects the four gaps each time the mold is opened and closed.

〔effect〕

The tightening method at the time of equalizing the mold clamping force in the present invention forms a pressure oil filling gap between the link housing, which is the force application point of the toggle mechanism, and the tie nuts screwed to the plurality of tie bars. Since each gap is configured to communicate with each other by pressure piping, when the toggle mechanism is operated to perform mold clamping, pressure oil moves in the gaps through the pressure piping, and as a result, all gaps The hydraulic pressure is equalized, and the mold clamping force applied to the tie bar is automatically equalized, resulting in variations in the mold clamping force applied to the tie bar, resulting in damage to the tie bar to which excessive mold clamping force is applied. In addition to the advantage of being able to prevent the above, the amount of pressure oil contraction in the axial direction of the tie bar during mold clamping is calculated in advance, and the toggle mechanism is moved to the fixed plate side according to the amount of pressure oil contraction before mold clamping. Tightening Since Tsu, despite performing mold clamping through the pressure oil, in which it is possible to obtain a necessary and sufficient clamping force.

[Brief description of drawings]

1 is a front sectional view of a toggle type mold clamping device of the present invention in a mold clamping state. FIG. 2 is a front sectional view of a toggle type mold clamping device of the present invention in a mold open state. FIG. 3 is a link housing part of the present invention. Detailed sectional view of Fig. 4 ... View of Fig. 3 in the direction of arrow Fig. 5 ... XX sectional view of the tie nut holder portion of the present invention Fig. 6 ... Perspective view from the back side of Fig. 3 (1) ... Fixed plate, (2) ... Link housing (3a) ... Tie nut holder, (4) ... Moveable plate (5) ... Tie bar, (5a) ... Right side thread (5b) ... Right side thread, (6) ... Mold open / close cylinder (7) ... toggle mechanism, (8) ... fixed side tie nut (9) ... rotation stop device, (10) ... tie nut (10a) ... right end surface of sliding part, (10b) ... left end of sliding part Surface (11)… Tie nut retainer, (11a)… Right end face of tie nut retainer (12)… Bolt, (13)… Fixed mold (14)… Move Mold, (15)… Mold parting surface (16)… Mold thickness adjusting motor, (16a)… Shaft (17)… Bracket, (18)… Main gear (19)… Gear, (20)… Pressure contact point (20a) ... Gap, (21) ... Piping hole (22) ... Hydraulic nipple, (23) ... Pressure piping (24) ... Check valve, (25) ... Direction switching valve

Claims (1)

[Claims] 1. A link housing which serves as a force application point of a toggle mechanism of a toggle type mold clamping device for moving a movable mold with respect to a fixed mold in a pressure contact / separable manner by a toggle mechanism, and is screwed to a plurality of tie bars. A gap for pressure oil filling is formed between each tie nut and the tie nut, and each gap is communicated with each other by pressure piping to form a structure for equalizing the mold clamping force. The pressure oil shrinks in the axial direction of the tie bar during mold clamping. When the mold clamping force is equalized in the toggle-type mold clamping device, the amount is calculated in advance and the toggle mechanism is moved to the fixed plate side in advance according to the contraction amount to perform additional tightening prior to mold clamping. Tightening method.