JP2996498B2 - Mold clamping drive mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a machine for molding a product by injecting a molding material into a mold by pressure, for example, a mold clamping drive mechanism in a plastic injection molding apparatus and the like. More specifically, the present invention relates to a mold clamping drive mechanism in which the control of the clamping pressure is performed by pressure control means provided in the mold clamping drive mechanism.

[Prior Art] A machine for molding a product by injecting a molding material into a mold by pressure, for example, a mold clamping operation in a plastic injection molding apparatus means a mold provided on a movable die plate.
This refers to closing the mold by moving toward the mold provided on the fixed die plate, and pressing the mold so as to oppose the pressure in the mold.

Conventional mold clamping drive mechanisms that use hydraulic cylinders, those that use ball screws, ball nuts, electric servomotors, those that use link levers, link cams, gear groups, and electric motors are known. ing.

In the case of using hydraulic cylinders, there is a risk that the environment may be deteriorated due to oil leakage, and hydraulic oil is specified as dangerous goods under the Fire Service Law, and there are places where machines can not be installed depending on conditions. There is a point.

In the case of using a ball screw, ball nut and electric servo motor, it is difficult to optimize the design of the drive mechanism because one electric servo motor performs different operations such as moving the moving die plate and pressing the mold. There is also a problem that, when the pressing pressure of the mold increases,
There is a disadvantage that the life of the ball screw and the ball nut is extremely shortened.

When using a link lever, link cam, gear group, and electric motor, a brake plate is inserted as a torque limiter between the link cam and gear group to control the pressing pressure. There is a problem that it is very large, and its operation is sometimes not perfect, and there is a problem that the tie bar is damaged.

As a means to solve the above problem, there is a method of replacing the electric motor with an electric servo motor. However, since the operation of the link lever and the link cam is non-linear, it is difficult to control the pressing pressure, and it is also necessary to use a sensor or the like. Has to be added, and the driving mechanism becomes complicated.

[Problems to be Solved by the Invention] The non-linear operation of the link lever and the link cam described above will be described in detail below. That is, as shown in FIGS. 4a and 4b, this mold clamping drive mechanism 10 is a movable die plate that moves along tie bars 36a to 36d.
12, comprising a fixed die plate 16a and a fixed die plate 16b, and also moving the movable die plate 12, a mold 14 provided on the movable die plate 12, and a fixed die plate 16b
And a link mechanism 20, which is a drive mechanism for pressing the dies 14, 18 so as to oppose the pressure in the dies so as to oppose the pressure inside the dies.

The link mechanism 20 includes a link lever 22, a link lever 24, a link lever 26, a link cam 28 mounted on a base 34, a gear group 30, and an electric servomotor 32.

In this mold clamping drive mechanism 10, the electric servo motor 32 is operated, the link cam 28 is rotated via the gear group 30, and the link levers 22 and 24 are operated via the link lever 26, whereby the movable die plate 12 Is moved to close the dies 14, 18, and the electric servomotor 32 is driven to clamp the dies 14, 18 so as to oppose the pressure in the dies.

Here, the control targets in the operation of the link levers 22, 24, 26 and the link cam 28 are the tip position of the link lever 24 connected to the movable die plate 12 and the thrust of the link, and the control is performed correspondingly. The amount should be an electric servo motor
32 rotation positions and rotation torque.

FIG. 5A is a view showing a model of the above link mechanism 20, and FIG. 5B is a view showing the tip position of the link lever 24, the thrust of the link, and the rotation of the electric servomotor 32 in the model of FIG. FIG. 4 is a diagram illustrating a relationship between a position and a rotational torque.

In FIG. 5a, L1 is the length between the nodes of the link lever 22, L2 is the length between the nodes of the link lever 24, L3 is the horizontal length from the fixed end of the link lever 22 to the center of the link cam 28,
L4 is the vertical length from the fixed end of the link lever 22 to the center of the link cam 28, and L5 is the length between the nodes of the link lever 26.

FIG. 5B shows the result of a simulation of this model using the above parameters. In FIG. 5b, T1 is the acceleration time of the electric servomotor 32, T2 is the constant speed rotation time of the electric servomotor 32, and T3 is the electric servomotor.
A deceleration time of 32, and N indicates a rotation speed of the electric servomotor 32.

The graph is unitized, the unit reference value is FS, the vertical axis is the unit reference value FS, and the horizontal axis is the elapsed time from the start to the end of the operation. In the graph, P is the horizontal distance from the fixed end of the link lever 22 to the moving die plate 12 side joint of the link lever 24, AF is the angle formed horizontally with the link lever 24, and V is the angle of the moving die plate side joint of the link lever 24. The moving speed, N is the rotation speed of the electric servomotor 32, and TFG is the conversion ratio of the torque of the electric servomotor 32 to the thrust at the moving die plate side section of the link lever 24.

As described above, the control targets in the operation of the link levers 22, 24, 26 and the link cam 28 are the tip position of the link lever 24 connected to the movable die plate 12 and the thrust of the link. The amounts to be controlled are the rotational position and rotational torque of the electric servomotor 32.

Here, looking at the relationship between the tip position of the link lever 24 and the rotation position of the electric servo motor 32, V (the moving speed of the link die 24 at the side of the movable die plate 12) which is the differential amount of the tip position of the link lever 24 is shown. ) And a graph of N (the rotational speed of the electric servomotor 32), which is the differential amount of the rotational position of the electric servomotor 32, are non-similar, and the relationship between them is not linear but non-linear.

Also, looking at the relationship between the thrust of the link lever 24 and the rotational torque of the electric servomotor 32, the graph of the conversion ratio TFG of the rotational torque of the electric servomotor 32 into the thrust at the tip of the link lever 24 is not linear. It can be seen that the relationship between the two is not linear but nonlinear.

Since the operation of the link mechanism 20 is nonlinear, it is difficult to control the pressing pressure. That is, a correction table is prepared so that both operations are substantially linear, and can be controlled by controlling the electric servomotor 32 according to the correction data of the correction table. Since the mold thickness varies, L2 (link lever 24
It is necessary to prepare a correction table in which the length of the internode is changed variously.

Thus, it is not practical to prepare various correction tables due to the large amount of data, and it takes a lot of data calculation time to sequentially calculate data for correction, and the molding per unit time is required. It is not realistic, resulting in a decrease in the number.

The present invention is intended to overcome the above-described disadvantages, and in the above-described mold clamping drive mechanism, noise during operation is small, control of the clamping pressure is easy, and sharing of functions and operations is achieved. It is an object of the present invention to provide a mold clamping drive mechanism which is appropriate and does not require the use of components that shorten the life even if the mold clamping pressure increases.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a driving unit for moving a mold provided on a movable die plate toward a mold provided on a fixed die plate. A mold clamping drive mechanism for closing and pressing the mold, wherein the driving means comprises: a driving source; and a driving force from the driving source being transmitted to the moving die plate. A displacement means for displacing the fixed die plate with respect to the fixed die plate; and a pressure control means for absorbing a part of the pressure for clamping the mold by the displacement means and controlling the pressure for clamping the mold to be constant. The pressure control means comprises: a fluid pressure damper that absorbs a part of the clamping pressure in a fluid storage unit; a relief valve connected to the fluid storage unit; and a fluid storage unit connected to the relief valve. , Is connected between the serial fluid reservoir and the fluid storage portion,
A check valve that allows only the flow of the fluid from the fluid storage unit to the fluid storage unit.

[Operation] In the mold clamping drive mechanism according to the present invention, when the movable die plate is moved by the displacement means via the pressure control means to clamp the mold, a part of the pressure generated by the pressure clamping acts on the pressure control means. The fluid pressure damper is displaced, whereby the fluid in the fluid storage flows into the fluid reservoir via the relief valve. In this case, by adjusting the relief valve, the pressing pressure can be optimally controlled. In addition,
When the movable die plate returns to the position before the mold clamping, the fluid is returned from the fluid storage unit to the fluid storage unit via the check valve.

Next, a preferred embodiment of a mold clamping drive mechanism according to the present invention will be described in detail with reference to the accompanying drawings.

1a and 1b are schematic structural views of a mold clamping drive mechanism according to the present embodiment.

As shown in FIGS. 1A and 1B, the mold clamping drive mechanism 10 according to the present invention includes a moving die plate 12, which moves along tie bars 36a to 36d, a fixed die plate 16a, a fixed die plate 16b, and a moving die. The plate 12 is moved, and the die 14 and the fixed die plate 16b provided on the movable die plate 12 are moved.
And a link mechanism 20 as a displacement means for closing the mold 18 provided in the apparatus.

The link mechanism 20 includes a link lever 22, a link lever 24, a link lever 26, a link cam 28, and a gear group 30, and the gear group 30 includes an electric servomotor 32 as a driving source mounted on a base 34. Are connected.

Link lever 2 of fixed die plate 16a and link mechanism 20
A fluid pressure damper 40 constituting a pressure control means is provided between the end portion 2 and the fluid pressure damper 40. The fluid pressure damper 40 controls the pressing pressure.

FIG. 2 shows a configuration diagram of the pressure control means including the fluid pressure damper 40. In FIG. 2, the pressure control means includes a piston member 42 connected to the end of the link lever 22, a fluid storage portion 44 fixed to the fixed die plate 16a and holding the piston member 42 movably, and a pipe. A relief valve 50 (unload valve) connected to the fluid storage portion 44 via the passage 46;
A hydraulic tank 54 connected to the relief valve 50 and a hydraulic tank
A check valve 52 is provided for connecting the fluid storage section 44 with the check valve 52. In this case, the oil 53 is stored in the fluid storage section 44, but a gas can be used instead of the oil 53.

As shown in FIGS. 3a and 3b, the tie bars 36a to 36a
Fluid pressure dampers 43a to 43d can be dispersedly disposed between the end of 6d and the fixed die plate 16a.

The mold clamping drive mechanism 10 according to the present embodiment is basically configured as described above, and its operation and effect will be described in detail below.

1 or 3, fixed die plates 16a and 16b are provided at both ends on a base 34, and are connected by four tie bars 36a to 36d. The movable die plate 12 moves along 36a to 36d, and the movable die plate 12 and the fixed die plate
The dies 14, 18 provided opposite to 16b can be closed.

The movement of the moving die plate 12 is performed by rotating the electric servomotor 32 so that the gear group 30 is rotated.
The rotation of 28 causes the link lever 26 having one end coupled to the link cam 28 to be displaced. This displacement has a fixed die plate at one end.
A link lever 22 movably connected to 16a and one end act on a connection point of a link lever 24 movably connected to the movable die plate 12, and this is realized by changing the angle between the two,
The molds 14 and 18 are closed and opened.

That is, the gear group 30 and the electric servomotor 32 are rotated so that the link cam 28 is rotated clockwise so that the angle formed between the link lever 22 and the link lever 24 is increased, so that the molds 14 and 18 are closed. Conversely, by rotating the gear group 30 and the electric servomotor 32 so that the link cam 28 is rotated counterclockwise so that the angle between the link lever 22 and the link lever 24 becomes small, the mold 14 and the mold The mold 18 is opened.

In the present embodiment, the control of the pressing pressure is performed by the fluid pressure damper 40. For this reason, it is not necessary to control the angle between the link lever 22 and the link lever 24 by the rotation angle position of the electric servomotor 32 as in the related art.
It is sufficient to perform control based on the rotational angle position of the electric servomotor 32 so that the link lever 22 and the link lever 24 are on a straight line, and control can be easily performed.

That is, the fluid pressure damper 40 has a cylinder structure as shown in FIG. So, link lever
When 22 and link lever 24 open and are on a straight line,
When the internal pressure of the oil 53 in the fluid storage portion 44 of the fluid pressure damper 40 becomes equal to or higher than the pressure set in the relief valve 50, the relief valve 50 is opened, and the oil 53 corresponding to the excessive pressure of the fluid pressure damper 40 is piped. It flows from the passage 46 to the hydraulic tank 54 through the relief valve 50.

This is because the clamping pressure of the mold is set in advance,
This is because the internal area of the fluid storage portion 44 of the fluid pressure damper 40 is known, so that the pressure of the release valve 50 can be set in accordance with the pressing pressure of the mold.

Next, when the link lever 22 and the link lever 24 are closed, the internal pressure of the fluid storage part 44 of the fluid pressure damper 40 becomes a negative pressure as compared with the previous time, so that the fluid storage of the fluid pressure damper 40 is reduced. Hydraulic tank in which oil 53 corresponding to the negative pressure of section 44 is reserved through check valve 52
Inflow from 54.

The fluid pressure damper 40 is not provided at the end of the fixed die plate 16a and the end of the link lever 22, but at the end of the movable die plate 12 and the end of the link lever 24, or between the movable die plate 12 and the die 14, Plate 16b and mold 18
It can also be arranged between them.

Further, the fluid pressure dampers 43a to 43d are tie bars 36a to 3d.
Instead of being disposed between the end of the fixed die plate 16a and the end of the fixed die plate 16a, the tie bars 36a to 36d and the fixed die plate 16b may be disposed separately.

Further, when gas is used instead of the oil 53, the fluid storage part, that is, the part corresponding to the hydraulic tank 54 can be omitted.

Note that, instead of using the fluid pressure damper 40 or the fluid pressure dampers 43a to 43d described above, an elastic body can be used as the pressure control means.

[Effects of the Invention] Since the mold clamping drive mechanism according to the present invention is configured as described above, the following functions and effects can be obtained.

In other words, the mold-clamping drive mechanism has low noise during operation, makes it easy to control the clamping pressure, and does not deteriorate the environment due to oil leakage even when hydraulic oil is used. It is hard to be restricted by such factors. In addition, it is possible to provide a mold clamping drive mechanism in which the sharing of functions and operations is appropriate, and there is no need to use components that shorten the life even if the mold clamping pressure increases. is there.

[Brief description of the drawings]

1a and 1b are schematic configuration diagrams of a mold clamping drive mechanism according to the present invention, FIG. 2 is a configuration diagram of pressure control means, and FIGS. 3a and 3b are diagrams of a mold clamping drive mechanism according to the invention. FIGS. 4A and 4B are schematic diagrams of a conventional mold-clamping drive mechanism, and FIGS. 4A and 5B are operation explanatory diagrams of the conventional mold-clamping drive mechanism. 10… Die clamp drive mechanism 12… Movable die plate 14… Dies 16a, 16b …… Fixed die plate 18 …… Die 20 …… Link mechanism 22, 24, 26 …… Link lever 28 …… Link cam 30 ... Gear group 32 ... Electric servo motor 34 ... Base 36a-36d ... Tie bar 40, 43a-43d ... Fluid pressure damper 50 ... Relief valve 52 ... Check valve 54 ... Hydraulic tank

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-199560 (JP, A) JP-A-2-206525 (JP, A) JP-A-56-117870 (JP, A) JP-A 62-195870 227716 (JP, A) JP-A-62-227717 (JP, A) JP-A-58-143214 (JP, U) JP-A-58-143213 (JP, U) JP-A-62-196517 (JP, U) 60-142919 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 33/20-33/24 B29C 45/66 B29C 45/82

Claims (2)

(57) [Claims] 1. A mold-clamping drive mechanism having a drive means for moving a mold provided on a movable die plate toward a mold provided on a fixed die plate, and closing and pressing the mold. In the above, the driving means comprises: a driving source; a displacing means for displacing the moving die plate with respect to the fixed die plate by transmitting a driving force from the driving source to the moving die plate; Pressure control means for absorbing a part of the pressing pressure of the mold by the above, and controlling the pressing pressure on the die to be constant, wherein the pressure control means stores a part of the pressing pressure in a fluid storage A fluid pressure damper that absorbs in the section, a relief valve connected to the fluid storage section, a fluid storage section connected to the relief valve, and is connected between the fluid storage section and the fluid storage section, The fluid A check valve that allows only the flow of fluid from the storage section to the fluid storage section. 2. The mold clamping drive mechanism according to claim 1, wherein the drive source comprises a motor, and the displacement means comprises a link mechanism for converting a rotational motion of the motor into a linear motion of the movable die plate. The mold clamping drive mechanism.