JPH0698472B2 - Mold clamping method and apparatus for injection molding machine - Google Patents

Description

The present invention relates to a mold clamping method and apparatus for an injection molding machine.

(B) Conventional Technology There are two types of conventional mold clamping devices for injection molding machines: a direct pressure type mold clamping device and a toggle type mold clamping device. The direct pressure type mold clamping device directly presses the movable platen with a large diameter hydraulic cylinder, and the toggle type mold clamping device moves by pushing the pushing force of a relatively small diameter hydraulic cylinder with a toggle mechanism. It is designed to press the board. As the mold clamping device, an electric direct-acting mold clamping device as disclosed in Japanese Utility Model Laid-Open No. 61-36357 or an electric toggle-type mold clamping device as disclosed in Japanese Patent Application Laid-Open No. 61-220819. There is also. 61-363
The one disclosed in Japanese Patent Laid-Open No. 57-5819 is configured such that a movable platen is moved by a motor and a ball screw mechanism in place of the above hydraulic cylinder, and the one disclosed in Japanese Patent Laid-Open No. 61-220819 is The toggle mechanism is provided between the ball screw mechanism and the movable plate.

(C) Problems to be Solved by the Invention However, in the mold clamping device of the conventional injection molding machine as described above, pressure oil is sent to the hydraulic cylinder when the mold clamping force is generated, and the mechanism is operated under a high load. Since the components are operated, the smoothness of the mold clamping operation is lacking, there is a problem regarding durability, and there is a problem that the hydraulic oil is easily deteriorated. The present invention aims to solve such problems.

(D) Means for Solving the Problems The present invention solves the above problems by generating the mold clamping force by utilizing the deformation of the tie bar due to the magnetostriction phenomenon. That is, the mold clamping method according to the present invention, the tie bar made of a ferromagnetic material is magnetized and elongated by a magnetostriction phenomenon, and in this state the mold is closed and the mold clamping device is fixed in a state of contacting the mold, Then, the gist is to generate the mold clamping force by stopping the magnetization of the tie bar and contracting the tie bar.

A mold clamping device according to the present invention for carrying out this mold clamping method includes a fixed platen (12) and a movable platen (14) arranged so as to face the fixed platen and movable in a direction toward or away from the fixed platen (12).
And a tie bar (22) made of a ferromagnetic material, and a mold thickness adjusting mechanism (24) for connecting the movable plate and the tie bar so that the relative position can be adjusted.
And a mold opening / closing mechanism (hydraulic cylinder 42) for driving the movable plate and the tie bar toward or away from the fixed plate,
An exciting coil (50) that is provided on the outer circumference of the tie bar and can magnetize it, and a tie bar that can switch between a state in which the fixed plate side tip of the tie bar is connected to the fixed plate and a state in which it is released.
A fixed platen connecting mechanism (45). The reference numerals in parentheses indicate the corresponding members of the embodiments described later.

Further, the method of the present invention can be carried out by providing an exciting coil capable of magnetizing the tie bar in a normal direct pressure type mold clamping mechanism, a toggle type mold clamping device or the like.

(E) Action In the closed state, the tie bar is in an extended state due to the magnetostrictive phenomenon. If the mold clamping device is fixed in this state to stop the magnetization, the tie bar tends to contract. However, since the mold clamping device is fixed, the force that the tie bar tries to contract acts to clamp the mold. Thereby, the mold clamping force can be obtained. This operation will be described below in more detail with respect to the device of the present invention. That is, first, the mold opening / closing mechanism is operated from the mold open state to advance the movable plate and the tie bar toward the fixed plate.
As a result, the movable die attached to the movable plate comes into contact with the fixed die attached to the fixed plate. At this time, the tip of the tie bar on the side of the fixed plate is not advanced to a position where it can be connected to the fixed plate by the tie bar / fixed plate connecting mechanism.
In this state, the exciting coil is energized. As a result, the tie bar is magnetized and extends in the axial direction due to the magnetostriction phenomenon.
By the extension of the tie bar, the tip end of the tie bar reaches a position where it can be connected by the tie bar / fixing plate connecting mechanism. Then, the tie bar / fixing plate connecting mechanism is operated to connect the fixing plate and the tie bar. When the excitation coil is de-energized after connection with the tie bar / fixing plate connection mechanism is completed, the tie bar tries to contract because the expansion of the tie bar due to the magnetostriction phenomenon is canceled, but the tie bar / fixing plate connection mechanism causes the tie bar to contract. Since the tip portion is connected to the fixed plate, a tensile force is applied to the tie bar. This tensile force acts as a mold clamping force between the fixed mold and the movable mold. The molds may be opened in the reverse order.

(F) Embodiment (First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. 1 to 9 of the accompanying drawings.

As shown in FIG. 1, a fixed plate 12 is fixed on the bed 10. The movable platen 14 is arranged so as to face the fixed platen 12, and the movable platen 14 is movable in a direction toward or away from the fixed platen 12. A fixed die 16 is attached to the fixed platen 12, and a movable die 18 is attached to the movable platen 14. The fixed platen 12 is provided with a central hole 12a that allows the injection unit 20 to enter. Further, the fixed plate 12 is also provided with a hole 12b that allows passage of a tie bar 22 described later. Tie bars 22 are provided through the holes provided at the four corners of the movable platen 14, and the tie bars 22 are connected to the movable platen 14 by a mold thickness adjusting mechanism 24. The tie bar 22 is made of a ferromagnetic material. The mold thickness adjusting mechanism 24 includes a male screw member 26, a female screw member 28,
It has a large-diameter gear 30 and a motor 32 (see FIG. 8). The male screw member 26 is provided on the outer periphery of the tie bar 22 and
And is configured to move integrally in the axial direction. Further, by connecting the four male screw members 26 to each other by the holding plate 34, they are integrated with the tie bar 22 in the rotation direction. The male screw member 26 has a male screw 26a on the outer circumference.
The female screw member 28 has a female screw 28a that meshes with the male screw 26a in its inner diameter portion. Further, the female screw member 28 is restrained in the axial direction with respect to the movable platen 14 by a holding metal fitting 36 fixed to the movable platen 14. However, the female screw member 28 is not restricted in the rotation direction. The gear 28b formed on the outer periphery of the female screw member 28 meshes with the large diameter gear 30 as shown in FIG. Large diameter gear 30 and gear 28b of female screw member 28
A rotary drive mechanism is constituted by the above. Further, the large diameter gear 30 meshes with a drive gear 38 which is rotationally driven by a motor 32. The motor 32 is movable as shown in FIG.
Is fixed against. The above-mentioned holding plate 34 is connected to the piston rod 42a of the hydraulic cylinder 42 (mold opening / closing mechanism) fixed to the tie bar guide plate 40. Tie bar information board 40
Supports the tie bar 22 via a bush 44 so as to be movable in the axial direction. A tie bar fixing plate 46 is provided so as to be in close contact with the fixing plate 12. The tie bar fixing plate 46 has a thickness dimension that is slightly smaller than the axial dimension of the small diameter neck portion 22a (which forms the head portion 22b at the tip of the tie bar 22) formed on the tie bar 22. There is. The tie bar fixing plate 46, as shown in FIG.
There is a head passage hole 46a capable of passing the head portion 22b of the tie bar 22 and a neck portion passing slot 46b capable of passing the neck portion 22a of the tie bar 22 but not the head portion 22b. is doing. The hole 46a and the elongated hole 46b are arranged in a horizontal positional relationship with each other, one end of the elongated hole 46b reaches the outer periphery of the hole 46a, and the two form an integral hole. The tie bar fixing plate 46 is a hydraulic cylinder that is a plate moving device.
It is connected to 48 piston rods 48a. The hydraulic cylinder 48 is fixed to the fixed platen 12. The tie bar fixing plate 46 (the hole 46a and the elongated hole 46b thereof), the hydraulic cylinder 48, the neck portion 22a and the head portion 22b of the tie bar 22 constitute a tie bar / fixing plate connecting mechanism 45. An exciting coil 50 is provided on the outer periphery of the tie bar 22. The left end of the exciting coil 50 in FIG. 1 is fixed to the movable platen 14. An electric current can be supplied to the exciting coil 50 from an electric device (not shown) at a predetermined timing.

Next, the operation of this embodiment will be described. FIG. 1 shows the mold open state. From this state, mold clamping is performed as follows. First, the hydraulic cylinder 42 is operated to
The movable platen 14 and the tie bar 22 are moved to the right from the state shown in the figure. As a result, the movable mold 18 comes close to the fixed mold 16,
Finally, as shown in FIG. 2, the two are in contact with each other. At this time, the diver fixing plate 46 is positioned so that the head passage hole 46a coincides with the center position of the tie bar 22, as shown in FIG. Therefore, the tie bar 22 passes through the hole 12b of the fixed platen 12 and the head-passing hole 46a of the tie bar fixing plate 46 to be in the state shown in FIG. In this state, the right end portion of the neck portion 22a of the tie bar 22 is located on the left side of the right end surface of the tie bar fixing plate 46 by Δl. Next, the exciting coil 50 is energized to magnetize the tie bar 22. When the tie bar 22 is magnetized,
The tie bar 22 will be stretched due to the magnetostriction phenomenon. The magnetostriction phenomenon is a phenomenon in which a strain is generated when a ferromagnetic material is magnetized, and this strain extends in the magnetization direction and contracts in a direction orthogonal to the magnetization direction. This relationship is illustrated in FIG. The energization amount, the characteristics of the exciting coil 50, the material and size of the tie bar 22, etc. are set in advance so that the elongation at this time becomes Δl. Due to the elongation Δl due to the magnetostrictive phenomenon, the positional relationship between the neck portion 22a of the tie bar 22 and the tie bar fixing plate 46 becomes as shown in FIG. The hydraulic cylinder 48 is operated in the state shown in FIG. 3 to move the tie bar fixing plate 46 as shown in FIG. That is, the neck portion 22a of the tie bar 22 has the neck portion passing slot 46b.
Try to move to the side. If the excitation coil 50 is de-energized in this state, the tie bar 22 is demagnetized, and the tie bar 22 is contracted by the amount of Δ1 which was extended due to the magnetostriction phenomenon.
As shown in FIG. 4, the head portion 22a of the tie bar 22 is constrained by the tie bar fixing plate 46 and cannot return, so that the tie bar 22 is in a state of being stretched by Δl, which causes the elastic force to act on the fixing plate 12 and the fixing plate 12. It acts on the movable platen 14, and this acts as a mold clamping force between the fixed mold 16 and the movable mold 18. The mold clamping force F at this time is F = A.
It will be shown by E · Δl / l. Here, A is the cross-sectional area of the tie bar 22, E is the longitudinal elastic modulus of the tie bar 22, and l is the effective length of the tie bar 22.

In this way, injection molding is performed with the mold clamping force applied. When the cooling of the molded product is completed, the mold opening is performed as follows. First, the exciting coil 50 is energized to magnetize the tie bar 22 and extend the tie bar 22 by Δl. In this state, the hydraulic cylinder 48 is operated to move the tie bar fixing plate 46 to the sixth position.
The state shown in the figure is returned to the state shown in FIG. Then, the energization of the exciting coil 50 is stopped. In this state, since the head 22b of the tie bar 22 can pass through the head passing hole 46a of the tie bar fixing plate 46, the hydraulic cylinder 42
Is operated to move the movable platen 14 and the tie bar 22 to the left in FIG. 2, the mold can be opened as shown in FIG.

When the mold is replaced with a mold having a different thickness, the relative position between the movable platen 14 and the tie bar 22 needs to be adjusted according to the thickness of the mold. Be seen. That is, when the drive gear 38 is rotated by operating the motor 32, this rotation is transmitted through the large diameter gear 30 to the female screw member.
Transmitted to drive gear 28 (drive gear 38, large diameter gear 30 and gear 28b
Constitutes a rotary drive mechanism for transmitting the rotational force of the motor 32 to the gear 28). When the female screw member 28 rotates, it is screwed to the male screw member 26, so that the male screw member 26 moves axially with respect to the female screw member 28. Female thread member 28
Is constrained to be integrated with the movable platen 14 in the axial direction, and the male screw member 26 is integrated with the tie bar 22, so that relative movement between the movable platen 14 and the tie bar 22 eventually occurs. Thereby, the position of the tie bar 22 with respect to the movable platen 14 can be adjusted according to the mold thickness.

In the first embodiment, the mold clamping operation can be smoothly performed only by stopping the energization of the exciting coil 50. However, in addition to this, a large diameter hydraulic cylinder, a toggle mechanism or the like is not required, and therefore the mold is not required. It is possible to obtain the effect that the entire fastening device can be downsized.

(Second Embodiment) FIG. 10 shows a second embodiment of the present invention. In the second embodiment, a tie bar 22 of a general direct pressure type mold clamping die including a fixed platen 12, a movable platen 14, a tie bar 22, an end housing 60, a mold clamping cylinder 62 and the like is made of a ferromagnetic material. An exciting coil 50 is provided on the outer periphery of the. The excitation coil 50 is energized to magnetize the tie bar 22, and the tie bar 22 is extended in the axial direction by the magnetostriction phenomenon.In this state, the mold is closed and the oil chamber 62a of the mold clamping cylinder 62 is closed. Contain the oil so that it does not flow backwards. Excitation coil in this state
When the power supply to 50 is stopped, the tie bar 22 tries to contract, but since the oil chamber 62a is blocked and the mold clamping mechanism is in a fixed state, the tie bar 22 is in an expanded state, which fixes the elastic force. It acts as a mold clamping force between the board 12 and the movable board 14. As a result, the same action and effect as those of the first embodiment can be obtained.

(Third Embodiment) FIG. 11 shows a third embodiment of the present invention. In the third embodiment, a tie bar 22 of a general toggle type mold clamping device including a fixed plate 12, a movable plate 14, a tie bar 22, an end housing 60, a mold clamping cylinder 62, a toggle mechanism 64 and the like is made of a ferromagnetic material. It is assumed that an exciting coil 50 is provided on the outer circumference of this,
The third embodiment is different from the second embodiment only in that the force of the mold clamping cylinder 62 is transmitted through the toggle mechanism 64.
It is obvious that the same effect as in the second embodiment can be obtained.

The direct pressure type mold clamping device of the second embodiment as described above, the third
A known electric mold clamping device other than the toggle mold clamping device of the embodiment, that is, a tie bar for an electric mold clamping device using a motor and a ball screw mechanism instead of the hydraulic cylinder as described in the prior art. A similar action can be obtained by providing an exciting coil capable of magnetizing.

(G) Effect of the Invention As described above, according to the present invention, the mold contraction force is generated by using the deformation of the tie bar due to the magnetostriction phenomenon, so that a large force is applied by the hydraulic cylinder or the motor. Therefore, it is not necessary to operate the mechanical member, the smooth mold clamping operation can be performed, the durability of the mold closing device is improved, and the deterioration of the hydraulic oil can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a mold opening state of a mold clamping device of an injection molding machine according to the present invention, FIG. 2 is a diagram showing a mold closing state of the mold clamping device of the injection molding machine shown in FIG. 1, and FIG. FIG. 4 is a diagram showing a state in which a tie bar of the mold clamping device of the injection molding machine shown in FIG. 1 is extended, and FIG. 4 is a diagram showing a mold clamping state of the mold clamping device of the injection molding machine shown in FIG. 5 is a diagram showing the position of the tie bar fixing plate in the non-mold clamping state, FIG. 6 is a diagram showing the position of the tie bar fixing plate in the mold clamping state, and FIG. 7 is the first diagram.
The figure which shows the mold thickness adjusting mechanism of the mold clamping device of the injection molding machine shown in FIG. 8, FIG. 8 is sectional drawing which follows the VIII-VIII line of FIG. 7, and FIG.
FIG. 10 is a diagram showing the relationship between the strength of magnetization and magnetostriction, FIG. 10 is a diagram showing a second embodiment of the present invention, and FIG. 11 is a third diagram of the present invention.
It is a figure which shows an Example. 10 …… bed, 12 …… fixed plate, 14 …… movable plate, 16 …… fixed type, 18 …… movable type, 20 …… injection unit, 22 …… tie bar, 24 …… die thickness adjustment mechanism, 26… … Male screw member, 28 ……
Female thread member, 30 ... Large gear, 32 ... Motor, 34 ... Holding plate, 36 ... Holding metal, 38 ... Drive gear, 40 ... Tie bar guide plate, 42 ... Hydraulic cylinder, 44 ... Bush , 45 ...
… Tie bar / fixing plate connection mechanism, 46 …… Tie bar fixing plate, 48 …… Hydraulic cylinder, 50 …… Excitation coil.

Claims (5)

[Claims] 1. A tie bar made of a ferromagnetic material is magnetized and elongated by a magnetostriction phenomenon. In this state, the mold is closed and the mold clamping device is fixed in a state where the mold is in contact with the tie bar. A mold clamping method for an injection molding machine in which a mold clamping force is generated by stopping and contracting a tie bar. 2. A fixed plate, a movable plate arranged so as to face the fixed plate and movable in a direction toward or away from the fixed plate, a tie bar made of a ferromagnetic material, and a relative position adjustment between the movable plate and the tie bar. A mold thickness adjusting mechanism that can be connected as much as possible, a mold opening / closing mechanism that drives the movable platen and the tie bar toward or away from the fixed platen, an exciting coil that can magnetize the tie bar, and a fixed platen side of the fixed platen side of the tie bar. A mold clamping device for an injection molding machine having a tie bar / fixing plate connecting mechanism capable of switching between a connected state and a released state. 3. A tie bar / fixing plate connecting mechanism comprises a neck portion of a predetermined length provided at the tip of the fixing plate side of the tie bar so as to form a head, and a fixing plate for passing the tie bar. The hole provided, the tie bar fixing plate that is placed in close contact with the fixing plate and has a thickness slightly smaller than the length of the neck portion of the tie bar, the head passage hole provided in the tie bar fixing plate and this It moves between a neck passing slot that is continuously provided, a position where the head passing hole of the tie bar fixing plate is concentric with the tie bar, and a position where the neck passing slot matches the tie bar. 3. A mold clamping device for an injection molding machine according to claim 2, further comprising a plate moving device capable of moving the tie bar fixing plate. 4. A mold thickness adjusting mechanism, which is integrally connected to a tie bar and has an external thread on its outer periphery, and a male screw member which moves integrally with the movable plate in the axial direction but is rotatable relative to the movable plate. The mold clamping device for an injection molding machine according to claim 2 or 3, further comprising: an internal thread member having an internal thread that is connected and meshes with the external thread; and a rotary drive mechanism and a motor that can rotationally drive the internal thread member. . 5. A mold clamping of an injection molding machine, wherein a tie bar of a toggle type mold clamping mechanism, a direct pressure type mold clamping mechanism or an electric type mold clamping mechanism is made of a ferromagnetic material, and an exciting coil capable of magnetizing the tie bar is provided. apparatus.