JPH047986B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mold clamping device for an injection molding machine, a die casting machine, etc., and particularly to a toggle type mold clamping device.

[Prior Art] Conventionally, mold clamping devices for injection molding machines, die-casting machines, etc. are of the so-called direct pressure type, in which the stroke of the mold clamping cylinder and the stroke of the moving plate are the same, and the A so-called toggle type is known in which the stroke of the moving plate differs near the completion of mold clamping and near mold opening.

Comparing the two, in the toggle type mold clamping device, the movable die plate only moves very little when the mold clamping is completed, but as the mold opens a little, it moves quickly, which protects the mold and molded product and protects the mold. This is advantageous in that it satisfies both opening and closing speed requirements.

FIG. 2 shows a schematic structure of a conventional toggle type mold clamping device, in which the upper half of the center line in the figure shows the state when mold clamping is completed, and the lower half shows the state when the mold is opened.

As shown in the figure, a movable die plate 2 is movably attached to a fixed die plate 1 via tie bars 10, and the movable die plate 2 is connected to a tail stock 3 via a plurality of links.

This link includes a first link 5 that connects one end to the tail stock 3, a second link 4 that connects one end to the other end of the first link 5 and the other end to the movable die plate 2, and a second link 4 that connects the other end of the first link 5 to the moving die plate 2. The third link 6 has one end connected to the middle part of the first link 5 and a third link 6 connected to the crosshead 9 at the other end.

In the figure, 7 and 8 are toggle pins for connecting the links 4, 5, and 6, 12 is a piston rod for the clamping cylinder 11, 13 is a stationary mold, and 14 is a movable mold.

The crosshead 9 is fixed to the piston 15 of the mold clamping cylinder 11 by a piston rod 12, and when the piston 15 of the mold clamping cylinder 11 moves due to hydraulic drive or the like, the crosshead 9 transmits the driving force to the links 4, 5, and 6. It's getting old.

As is clear from the figure, in the conventional mold clamping device,
When the mold clamping is completed, that is, the moving die plate 2
When the first die is closest to the fixed die plate 1, the first
The link 5 and the second link 4 are aligned approximately in a straight line in the longitudinal direction (the line connecting the centers of the toggle pins 7, 7), and the third link 6 is aligned in the longitudinal direction (the line connecting the centers of the toggle pins 8, 8). ) faces the direction perpendicular to the moving direction of the movable die plate 2.

[Problems to be Solved by the Invention] However, in this conventional toggle type mold clamping device, in order to obtain a predetermined stroke of the movable die plate, the mold clamping cylinder stroke inevitably becomes long, which makes the device large and long. , there are problems such as a long time required for mold clamping and poor molding cycle efficiency.

Furthermore, conventionally, for example, Japanese Patent Application Laid-open No. 57-64532, Japanese Patent Application Publication No. 137127-1982, and Japanese Patent Publication No. 50-6857 disclose a first link connecting one end to the tail stock, and a first link connecting the other end to the tail stock. a second end connected at one end to the movable die plate and the other end connected to the movable die plate;
and a third link that connects one end to an intermediate position of the first link and the other end to the crosshead, and when the mold clamping is completed, the third link moves in the longitudinal direction. The toggle clamping device is shown inclined with respect to the direction perpendicular to the direction of movement of the die plate.

However, these toggle type mold clamping devices do not take into account the relationship between the tightening coefficient with respect to the elongation of the tie bar at the time of completion of mold clamping and the inclination angle of the third link at the time of completion of mold clamping. As a result, the excess mold clamping force, which indicates the smallest difference between the mold clamping force characteristics and the tie bar elastic force characteristics, is smaller than that of the conventional type, and as a result, the mold clamping operation cannot be performed smoothly, and the equipment does not operate smoothly. There are reliability problems.

The purpose of the present invention is to eliminate such drawbacks, to enable precision molding, and to provide a mold clamping cylinder that can be used after passing the point of maximum load applied to the mold clamping cylinder just before the mold clamping is completed, until the mold clamping is completed. To provide a toggle type mold clamping device capable of shortening the stroke, shortening the mold clamping time, increasing the cycle without reducing the excess mold clamping force, and downsizing the device.

[Means for Solving the Problems] In order to achieve this object, the present invention provides the following features: A movable die plate is movably attached to a fixed die plate via a tie bar, and the movable die plate is attached to a fixed die plate via a link mechanism. A first link connected to a tail stock, the link mechanism having one end connected to the tail stock, and a second link connecting one end to the other end of the first link and connecting the other end to the movable die plate. and a third link having one end connected to an intermediate position of the first link and the other end connected to a crosshead, a mold clamping cylinder being connected to the crosshead,
The tightening coefficient for the elongation of the tie bar upon completion of mold clamping is
It has a high rigidity of 2.5 or less, and is characterized in that the longitudinal direction of the third link is inclined within a range of 10 to 20 degrees with respect to the direction perpendicular to the moving direction of the movable die plate when the mold clamping is completed. It is something to do.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a toggle type mold clamping device according to an embodiment.

The difference in the structure of the toggle type mold clamping device in this embodiment from the conventional one is that when the mold clamping is completed, the straight line connecting the connecting toggle pins 8, 8 of the third link 6 is in the direction of movement of the movable die plate 2. It is a point that is tilted within a range of 10 to 20 degrees with respect to the direction perpendicular to the direction.

The reason for this will be explained below.

FIGS. 3A, 3B, and 3C are diagrams for explaining toggle performance such as mold clamping cylinder stroke Xc, die plate stroke Xd, and torque expansion ratio F/P in the toggle type mold clamping device.

That is, a: Length of toggle link A, b: Length of toggle link B, c: Length of toggle link C, l, m: Length between pins 7 and 8 of toggle link B, e, f: Length as shown, φ: Angle between side h and side m, ε: Angle between side h and side l, δ: Form between toggle links A and B, which are aligned when mold clamping is completed, and the machine axis line Angle, θ: Angle between toggle link C and a line perpendicular to the machine axis when mold clamping is completed, α: Angle between toggle link B and the machine axis, γ: Angle between toggle link A and the machine axis, Xco : Distance between the crosshead forward position and the moving die plate forward position when mold clamping is completed, Xd: Stroke of the movable die plate with the origin at mold clamping completion, Xc: Stroke of the mold clamping cylinder with Xco as the origin, F: Mold clamping force, P: Thrust force of the mold clamping cylinder, F/P: Torque expansion ratio, then, It can be calculated using the following (Formula 2).

sinγ={b・sinα−(a+b) ・sin δ}/a ... (Formula 2) Xc=(a+b)・cosδ−l・cos(α+ε) +c・sinθ−Xco...(Formula 3) Here, the above-mentioned θ can be calculated using the following (Formula 4).

cosθ={e−fl・sin(α+ε)}/c
...(Formula 4) Also, Xco=a・cosδ+m・cos(φ−δ) +c・cosθ……(Formula 5) l=√(−・) ² +(・) ²
...(Formula 6) F/P={l·cosγ·cos(α+ε-θ)}/{b·sinθ·sin(α+γ)} ...(Formula 7) Calculated as follows.

FIG. 4 shows the relationship between the stroke Xc of the mold clamping cylinder and the stroke Xd of the movable die plate, and the intersection point 0 between the vertical and horizontal axes in the figure indicates the mold clamping completion point.

Starting from the mold clamping completion point 0, gradually open the mold, and while increasing α in Fig. 3 b by a certain angle from δ at mold clamping completion, move the stroke Xd of the moving die plate on the vertical axis. , the stroke Xc of the mold clamping cylinder is plotted on the horizontal axis and their intersection point is found, and in the end, when the mold clamping is completed, the toggle link C
The angle θ formed by the line perpendicular to the machine axis is 0 degrees, 10
FIG. 4 shows the characteristic curves when the angle is set to 15 degrees, 15 degrees, and 20 degrees. In addition, the straight line of two-dot chain line in the figure shows the relationship between the stroke of the movable die plate and the stroke of the mold clamping cylinder in the case of a direct pressure type mold clamping device.

As is clear from this figure, in the case of the conventional toggle type mold clamping device, that is, the inclination angle θ = 0 degrees, in order to ensure a constant die plate stroke Xd, a long mold clamping cylinder stroke Xc is required, and the device There are drawbacks such as not only the length of the process becoming longer but also the mold clamping time taking longer.

In addition, looking at the enlarged view near the completion of mold clamping in Fig. 5, when the inclination angle θ = 0 degrees as in the conventional case, the clamping cylinder will move from the position where the most load is applied to the mold clamping cylinder until the mold clamping is completed. A long stroke Xc is required.

On the other hand, as the inclination angle θ increases to 10 degrees, 15 degrees, and 20 degrees, the mold clamping cylinder stroke
Die plate stroke The tightening cylinder stroke Xc also becomes shorter (see Figure 5).

Next, Figure 6 shows the die plate stroke on the horizontal axis.
Xd is the toggle magnification rate F/P on the vertical axis (formula 7)
It is a characteristic curve diagram that calculates the mold clamping force in the case of a molding machine with a nominal mold clamping force of 180 tons. This figure shows that as the completion of mold clamping approaches, the toggle enlargement ratio F/P rapidly increases, and the mold clamping force F that propels the moving die plate increases.

The straight line (tie bar elastic force line shown by solid line and broken line) connecting point P (mold clamping force generation point) and point B (maximum mold clamping force point) in the figure is the generated mold clamping measured by attaching a strain gauge to the tie bar. It is power.

As is clear from this experimental result, in the conventional toggle type mold clamping device (the tie bar elastic force line shown by the solid line), the parting surfaces of both the movable and stationary molds come into contact 1.8 [mm] before the mold clamping is completed. The tie bar begins to stretch, and mold clamping force is generated as a reaction force.

This value is directly related to the overall rigidity of the entire toggle type mold clamping device, and in the conventional type, the ratio of the amount of additional tightening to the elongation of the tie bar when mold clamping is completed, that is, the additional tightening coefficient is 3.0, and the overall rigidity of the entire mold clamping device is The rigidity was relatively small.

As this tightening coefficient becomes smaller, the slope of the straight line of the generated mold clamping force becomes steeper from the solid line to the broken line.

Furthermore, in the same figure, the minimum difference between the upper curve of mold clamping force F and the lower straight line of generated mold clamping force represents the excess mold clamping force, and this surplus mold clamping force must be secured above a certain level. This is extremely important when designing a toggle type mold clamping device.

As mentioned above, as the inclination angle θ increases from 0 degrees to 20 degrees, the mold clamping cylinder stroke becomes shorter. However, if the tightening coefficient of the mold clamping device remains the same as the conventional one, which is 3.0 (the tie bar elastic force line shown by the solid line), as the inclination angle θ increases, the mold clamping force F increases, as is clear from Fig. 6. Since the curve tends to fall, the excess mold clamping force is equal to the conventional surplus mold clamping force Y ₀ −
Y will be smaller than ₀ . When the excess mold clamping force becomes small, the mold clamping operation does not proceed smoothly due to the elastic force of the tie bars, causing a problem in operational reliability.

Therefore, in the present invention, the tightening coefficient of the mold clamping device is set to 2.5.
(the tie bar elastic force line shown by the broken line). By doing so, even if the inclination angle θ is increased to 10 to 20 degrees and the mold clamping cylinder stroke is shortened as much as possible, the excess mold clamping force can be made larger than the conventional surplus mold clamping force Y ₀ −Y ₀ (e.g. Y ₁₅ −Y ₁₅ > Y ₀ −
Y ₀ ), the mold clamping operation is further improved. In this way, it is technically important to keep the inclination angle θ in the range of 10 to 20 degrees and to keep the retightening coefficient to 2.5 or less.

If the inclination angle θ is greater than 20 degrees, the mold clamping force curve F in FIG. 6 drops too much, and even if the additional tightening coefficient is made small, the excess mold clamping force will be insufficient. On the other hand, if the inclination angle θ is less than 10 degrees, the stroke of the clamping cylinder cannot be shortened as in the conventional case. From this, the inclination angle θ is
It is necessary to regulate the temperature within the range of 10 to 20 degrees.

In addition, in recent years, the demand for precision molding has increased, and if a mold clamping device with a relatively low rigidity with a tightening factor of 3.0 is used as in the past, highly precise molding cannot be performed. Therefore, there is a trend to increase the rigidity of the die plate, minimize deflection, and reduce the tightening factor to 2.5 or less.
In this way, by increasing the amplification factor to 2.5 or less, that is, by increasing the rigidity of the entire toggle type mold clamping device, highly precise molding is possible, and there are advantages as described above.

[Effects of the Invention] As described above, the present invention provides high rigidity with an amplification factor of 2.5 or less for the elongation of the tie bar when the mold clamping is completed, and when the mold clamping is completed, the longitudinal direction of the third link is It is configured to be inclined within a range of 10 to 20 degrees with respect to a direction perpendicular to the moving direction of the moving die plate.

Therefore, the mold clamping cylinder stroke necessary for mold clamping can be shortened, the device can be made smaller, the mold clamping time can be shortened, and sufficient margin clamping force can be obtained.
It is possible to provide a toggle-type mold clamping device that provides stability in mold clamping operation and is highly reliable.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a toggle type mold clamping device according to an embodiment of the present invention, Figure 2 is a schematic configuration diagram of a conventional toggle type mold clamping device, and Figures 3 a, b, and c are toggle type mold clamping devices. A diagram for explaining the mold clamping characteristics of the device. Figure 4 is a characteristic diagram showing the relationship between the mold clamping cylinder stroke and die plate stroke. Figure 5 is an enlarged characteristic diagram of Figure 4 near the completion of mold clamping. FIG. 6 is a characteristic diagram showing mold clamping force characteristics, tie bar elasticity characteristics, and margin mold clamping force characteristics. 1... Fixed die plate, 2... Moving die plate, 3... Tail stock, 4... Second link, 5... First link, 6... Third link,
9...Crosshead, 10...Tie bar, 11...
...Mold clamping cylinder, θ...Inclination angle.

Claims (1)

[Scope of Claims] 1. A movable die plate is movably attached to a tie bar with respect to a fixed die plate, the movable die plate is connected to a tail stock via a link mechanism, and the link mechanism connects one end to the tail stock. a first link to be connected; a second link having one end connected to the other end of the first link and the other end to the movable die plate; and a second link having one end connected to an intermediate position of the first link. a third link connecting the other end to the crosshead, a mold clamping cylinder being connected to the crosshead;
The tightening coefficient for the elongation of the tie bar upon completion of mold clamping is
2.5 or less, and the longitudinal direction of the third link is inclined within a range of 10 to 20 degrees with respect to the direction perpendicular to the moving direction of the movable die plate when the mold clamping is completed. Type mold clamping device.