JP2521591B2 - Electro-hydraulic mold clamping device for injection molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold clamping device for an injection molding machine, which is an electrohydraulic mold equipped with an electric mold opening / closing mechanism using a screw mechanism and a hydraulic cylinder for generating a mold clamping force. It relates to a fastening device.

[0002]

2. Description of the Related Art As an electro-hydraulic mold clamping device of this type,
A structure as shown in FIG. 7 is known. In this structure, a ball screw 26 is fixed behind the movable platen 2, a ball screw nut 11 is pivotally supported on the support plate 3 so as to be rotatable and slightly movable in the axial direction, and an engagement provided on the ball screw nut 11 is carried out. A ring-shaped mold clamping cylinder 12 is arranged behind the flange 45, and the ball screw nut 11 is rotationally driven by a servo motor 32 via a timing belt 34. In this structure, the mold clamping force of the mold clamping cylinder 12 is transmitted to the movable platen 2 via the collar 45, the ball screw nut 11 and the ball screw 26.

In addition, as another conventional structure, an actual fair 3-33
There is one disclosed in Japanese Patent Publication No. 89. This structure is a ball screw that fixes the ram of a large-diameter, large-stroke mold clamping cylinder located in the center of the support plate directly to the movable plate, and fixes the ball screw extending through the head end of the mold clamping cylinder to the ram. The movable platen is opened and closed by screwing it onto a nut and rotating this ball screw.When the movable platen moves back and forth by a screw mechanism, oil is taken in and out from a separately placed oil container to the mold clamping cylinder, and at the time of mold clamping. After blocking the passage between the oil container and the mold clamping cylinder, high-pressure hydraulic oil is supplied to the mold clamping cylinder to perform mold clamping.

[0004]

Although the structure shown in FIG. 7 has a simple mechanism, a large mold clamping force acts on the screw mechanism, so that a thick and highly rigid ball screw is required. It was Further, there is a drawback that the ball screw 26 projects to the back surface of the support board 3 when the mold is opened.

On the other hand those disclosed in Japanese Patent actual fairness 3-3389, although the mold clamping force to the ball screw does not act, the mold clamping cylinder becomes large, and out a large amount of oil at the time of mold opening and closing the mold clamping cylinder Therefore, there is a problem that it is necessary to provide a large separate oil container or valve mechanism for controlling the movement of oil.

As a mold clamping device that opens and closes a movable plate by using a screw mechanism, a structure in which a ball screw drives a toggle and a structure in which a ball screw directly generates a mold clamping force are known. The clamping force cannot be controlled accurately, the latter requires a larger ball screw than that of FIG. There is also known a structure in which the mold is opened and closed by an electric motor, and the mold is clamped by four mold clamping cylinders arranged at the rear end of the tie bar. There is a problem that the device becomes large in size, the hydraulic circuit becomes complicated, and the device becomes expensive.

Therefore, an object of the present invention is to provide an electrohydraulic mold clamping device having a simple structure and a compact structure in which a mold clamping force does not act on a ball screw.

[0008]

The mold clamping device of the present invention comprises:
A ring-shaped mold clamping cylinder 12 is provided at the center of the support board 3, and a through hole 14 is provided in the shaft center of the mold clamping piston 13. The ball screw nut 11 of the electric mold opening / closing mechanism is fixedly provided at the tip of the mold clamping rod 8 extending from the center of the back surface of the movable plate 2 to the support plate 3 side. A cavity 10 is provided into which the ball screw 26 is inserted when opened.

The ball screw 26 is rotatably supported on the support board 3 in alignment with the axis of the mold clamping cylinder 12.
Ball screw nut 1 passing through the through hole of the mold clamping piston 13.
It is screwed to 1. The ball screw 26 is rotationally driven by a servo motor 32 mounted on the support board 3 via a power transmission mechanism 34.

An engaging / disengaging mechanism 50 is provided between the end of the mold clamping piston 13 on the movable platen 2 side and the end of the mold clamping rod 8 on the support platen 3 side so that they can be engaged at the mold closing position. Has been. As the engagement / disengagement mechanism 50, a structure utilizing the engagement of spline teeth by the rotational movement of the male spline 9 and the female spline 18, and a ball screw 26 between the tip of the mold clamping rod 8 and the tip of the mold clamping piston 13 are used. It is possible to employ a structure in which the transmission plate 38 provided with the cutout 40 through which the holes can pass is inserted.

[0011]

In the mold clamping device having the above structure, the ball screw 26 is rotationally driven to advance the movable platen 2 by the screwing action to close the mold, and if necessary, the torque control of the servo motor 32 at the mold closing position is performed. , A mold protection pressure is generated to avoid damage to the mold due to foreign matter being caught, and then the engaging / disengaging mechanism 5
At 0, the hydraulic pressure is supplied to the mold clamping cylinder 12 in a state where the mold clamping rod 8 is prevented from retreating, and the mold clamping force is transmitted to the movable platen 2 via the mold clamping rod 8.

When the mold is opened, the mold clamping piston 13 is retracted, the engaging / disengaging mechanism 50 is opened, and the ball screw 26 is rotated in the opposite direction to retract the movable platen 2. At this time, the tip of the ball screw 26 is housed in the cavity 10 in the mold clamping rod 8, and the mold clamping rod 8 is inserted into the through hole of the mold clamping piston 13.

The mold clamping device of this structure has one mold clamping cylinder 12 in which the mold clamping and the mold opening / closing are arranged at the center of the movable platen 2.
Since it is performed by the ball screw 26 of the book, the structure is simple, and when the movable platen 2 is moved, imbalance of force, stop position and speed does not act.

[0014]

1 to 3 show an embodiment of the present invention. 1 is a fixed board, 2 is a movable board, 3 is a support board, 4
Is a tie bar, 5 is a fixed mold, 6 is a movable mold, and 7 is an ejector built-in portion integrated with the movable platen 2. Behind the center of the movable platen 2, a mold clamping rod 8 having a compressive strength that can withstand the mold clamping force.
Is provided, and a short male spline 9 is provided on the outer periphery of the tip end thereof. The mold clamping rod 8 has a hollow hole 10, and a ball screw nut 11 is fitted and fixed to the end portion of the mold clamping rod 8 on the side of the support board 3.

A ring-shaped mold clamping cylinder 12 having a large diameter and a small stroke is formed at the center of the support board 3, and a male spline 9 can pass through the shaft center of a mold clamping piston 13 fitted in this. A through hole 14 having a diameter is provided.
Reference numeral 15 denotes a cylinder flange of the mold clamping cylinder 12. Inside the mold clamping cylinder 12, a mold clamping side oil chamber 16 and a return side oil chamber 17 are provided.
Is formed.

The tip of the mold clamping piston 13, that is, the movable platen 2
A female spline 18 fitted to the male spline 9 of the mold clamping rod is rotatably attached to the end on the side by being pressed by a holding plate 19 and a lock cylinder bracket 20 whose axial movement is shown in FIG. There is. As shown in FIGS. 1 and 2, the tip of the mold clamping piston 13 projects from the cylinder flange 15, and shallow parallel chamfered parts are provided on both left and right sides of this projecting part in FIG. A guide block 21 fixed to the cylinder flange 15 is in sliding contact with the parallel chamfered portion to prevent the mold clamping piston 13 from rotating about its axis. A slide key can also be used as this rotation preventing means.

A lock cylinder 22 having a trunnion structure is attached to the lock cylinder bracket 20 fixed to the end surface of the mold clamping piston 13. The lock cylinder 22 is fixed to the tip of the rod of the lock cylinder and the end surface of the female spline 18. The tip of the arm 23 is connected by a pin 24 in a direction parallel to the spline shaft. Therefore, as the rod of the lock cylinder 22 moves back and forth, the female spline 18 reciprocally rotates. The rotation angle at this time is an angle corresponding to 1/2 of the pitch of the teeth of the splines 9 and 18. Although FIG. 3 shows a spline having six teeth with a coarse pitch,
Actually, a finer pitch is used.

A bearing housing 25 is fixed to the rear end of the central portion of the support board 3, and the base end of a ball screw 26 is rotatably and axially immovably supported by this bearing housing via a bearing 27. . The ball screw 26 extends toward the movable platen 2 at the central position of the support plate 3 and is screwed into the ball screw nut 11 at the tip of the mold clamping rod 8.

The base end of the ball screw 26 penetrates a holding flange 28 which fixes a bearing 27, and a grooved pulley 29 is fixed to the penetrating end. The gap between the bearing 27 and the grooved pulley 29 is defined by the collar 30, and the nut 31 fastens the grooved pulley 29. A servo motor 32 is mounted on the support board 3, and a drive side pulley 33 fixed to the output shaft of the servo motor and the grooved pulley 29 of the ball screw are drivingly connected by a timing belt 34.

Next, the operation of the mold clamping device will be described. FIG. 1 shows the state when the mold is clamped, and FIG. 2 shows the state when the mold is opened. The ball screw 26 is rotated from the mold opened state of FIG. 2, and the movable plate is moved by the screwing action with the ball screw nut 11. 2 is advanced to close the mold. The position of the movable platen 2 (or movable mold) at the time of mold closing is detected by an encoder (not shown). When the movable platen 2 reaches near the mold closing position, the servo motor 32 is torque-controlled to set the mold. The movable platen 2 is driven by a force corresponding to the mold protection pressure. When the fixed mold 5 and the movable mold 6 come into contact with each other and the movable platen 2 stops, when the movable mold 2 does not reach the regular mold closing position,
It is determined that foreign matter has been caught in the mating surface of the mold, and the mold clamping operation is not performed to protect the mold.

During the mold closing operation, the hydraulic pressure is supplied to the return side oil chamber 17 of the mold clamping piston, the mold clamping piston 13 is moved to the side opposite to the movable platen, and the teeth of the male spline 9 are in the groove of the female spline 18. The female spline 18 is rotated to the passing angle. Therefore, the male spline 9 passes through the female spline 18 without being blocked by the female spline 18,
When the movable platen 2 reaches the mold closing position, the mold clamping rod 8
Between the tip of the female spline 18 and the end surface of the female spline 18
_{A 0} is formed.

Next, the hydraulic pressure is supplied to the lock cylinder 22 to rotate the female spline 18 so that the teeth of the male spline 9 and the teeth of the female spline 18 are in the same phase.
And the hydraulic pressure is supplied to the mold clamping side oil chamber 16 of the mold clamping cylinder 12. A large mold clamping force generated by the large-diameter mold clamping cylinder 12 is transmitted to the movable platen 2 via the female spline 18, the male spline 9 and the mold clamping rod 8.

After the molding work is performed in this mold clamping state, hydraulic pressure is supplied to the return side oil chamber 17 of the mold clamping cylinder 12 to retract the mold clamping piston 13, and the tip of the mold clamping rod 8 and the female spline 18 are retracted. After the pressing force with the end surface of the female spline is released, the lock cylinder 22 causes the female spline 18 to rotate in a phase in which the teeth of the male spline 9 and the groove of the female spline 18 match, and then the ball screw 26 rotates in the opposite direction. Then movable plate 2
Moves backward and returns to the mold opening state shown in FIG.

Female spline 18 for disengagement
Rotation of, when being molded product without a mold clamping force with less necessary, it goes without saying that can be performed during cooling of the product in the mold. This is because if the mold clamping cylinder is depressurized while the movable platen is pressed against the fixed platen by the ball screw for mold opening and closing, the mold opening operation can be promptly performed after cooling.

It should be noted the driving mechanism of the ball screw, servo motor is fixed to the rear end of the support plate 3, it can be consolidated by placing the output shaft and the ball screw servo motor on the same axis.
At this time, no overhang load is applied to the shaft end of the ball screw.

Although the engagement / disengagement mechanism 50 of the first embodiment uses the splines 9 and 18, the engagement / disengagement mechanism having the structure shown in FIGS. 4 to 6 can be adopted as a simpler structure. The engagement / disengagement mechanism shown in FIGS. 4 to 6 inserts a transmission plate 38 from the side between the end surface 36 of the mold clamping rod 8 and the tip surface 37 of the mold clamping piston 13 that have advanced to the mold closing position. The clamping force of the mold clamping piston 13 via the movable plate 2
Is to be transmitted to. In the structure of the present invention, since the ball screw 26 extending from the tip of the mold clamping rod 8 to the through hole of the mold clamping piston 13 is present, the transmission plate 38 has a notch for avoiding interference with the ball screw 26. It is necessary to provide 40.

As a structure for advancing and retracting the transmission plate 38 between the mold clamping piston 13 and the mold clamping rod 8, as shown in FIG. 5, the transmission plate 38 pivotably mounted on the support plate 3 is rocked. Various structures such as a structure in which the cylinder 41 swings and a structure in which the transmission plate 38 is connected to the rod of the direct acting cylinder 42 to move back and forth by linear movement as shown in FIG. 6 can be adopted.

When mounting molds having different thicknesses between the fixed platen and the movable platen in the mold clamping device having the above-mentioned structure,
A known mold thickness adjusting device for moving the support plate and the movable plate relative to the fixed plate may be provided on the support plate. That is, a trapezoidal screw is formed from the portion of the tie bar that is inserted into the support plate to the rear end, and an adjusting nut equipped with a gear or roller chain sprocket is rotatably attached to the support plate and is screwed into the trapezoidal screw. Is synchronously rotated by a hydraulic motor or an electric motor mounted on the support plate, thereby moving the support plate and the movable plate connected to the support plate with respect to the fixed plate.

The above-mentioned configuration further has the following functions. Upon initial mold closing, so that a gap d _o to the end portion and the female spline of the clamping rod can occupy perform known injection compression. Injection filling is performed by applying a weak preliminary mold clamping force to the extent that the mold is opened by the resin pressure filled in the mold cavity (not shown) by the torque control of the servo motor, and by keeping the engagement / disengagement device in the engaged state. Resin in the mold cavity
This is because the amount of opening the mold can be regulated by the pressure . At this time, the servo motor is rotated in the reverse direction, but there is no problem because the position of the movable plate with respect to the support plate is fed back by a known position detector. Then, the resin is cooled and the mold clamping and compression operation is performed.

[0030]

According to the structure of the present invention described above,
Since the movable platen is linearly driven by the ball screw mechanism which is rotationally driven by the electric motor to open and close the mold, the controllability of the opening and closing operation of the mold is improved. The mold is opened and closed by a ball screw mechanism driven by an electric motor, and after the mold is closed, the mold clamping cylinder exerts a mold clamping force on the movable plate via an engagement / disengagement mechanism, so the stroke of the mold clamping piston can be small and large capacity can be achieved. No pump or separate oil container and valve mechanism is required. Since the ball screw only needs to bear the load when the mold is opened and closed, the ball screw can be made thin. Furthermore, since the ball screw is inserted in the hollow part of the mold clamping rod and the ball screw mechanism is coaxially arranged in the hollow part of the mold clamping cylinder, the whole structure can be made compact, and behind the support plate at the time of mold opening. The ball screw does not project.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view showing a mold clamping state.

FIG. 2 is a partial cross-sectional side view showing a mold open state.

FIG. 3 is a front view showing an engagement / disengagement mechanism.

FIG. 4 is a partial cross-sectional side view of a main part showing another example of the engagement / disengagement mechanism.

5 is a view on arrow A of FIG.

FIG. 6 is a view on arrow A of FIG. 4 showing another structural example.

FIG. 7 is a partial cross-sectional side view showing an example of a conventional structure.

[Explanation of symbols]

 2 Movable plate 8 Mold clamping rod 9 Male spline 11 Ball screw nut 12 Mold clamping cylinder 13 Mold clamping piston 14 Through hole 18 Female spline 22 Lock cylinder 26 Ball screw 32 Servo motor 34 Timing belt 38 Transmission plate 40 Notch 41 Swing cylinder 42 Direct acting cylinder 50 Engagement mechanism 60 Electric type opening / closing mechanism

Claims (3)

(57) [Claims] 1. An electrohydraulic mold clamping device for an injection molding machine, which comprises a hydraulically driven mold clamping cylinder and an electric mold opening / closing mechanism, wherein the mold clamping cylinder (12) has a through hole (14) in its axis. Equipped with a mold clamping piston (13), the electric mold opening / closing mechanism (60)
Rotate the ball screw nut (11) fixed on the movable platen (2) side, the ball screw (26) mounted on the support platen (3) so as to be rotatable and immovable in the axial direction, and the ball screw (26). And a driving means (32) for driving, and a ball screw (2
6) is arranged coaxially with the center axis of the mold clamping cylinder (12), and when the mold is closed, the end of the mold clamping piston (13) on the movable plate (2) side and the movable plate.
An engagement / disengagement mechanism (50) that disengages the end of the mold clamping rod (8) protruding from the rear of (2) and selectively transmits the mold clamping force to the movable platen (2) when engaged. An electro-hydraulic mold clamping device for injection molding machines, which is characterized by 2. A male spline (9) having an engagement / disengagement mechanism (50) formed on the tip peripheral surface of a mold clamping rod (8), and a mold clamping piston (13).
The mold clamping device according to claim 1, comprising a female spline (18) rotatably mounted on the female spline and a rotational drive device (22) for the female spline (18). 3. The mold clamping rod when the engagement / disengagement mechanism (50) closes the mold.
A transmission plate (38) inserted between the tip surface of (8) and the end surface of the mold clamping piston (13) on the movable platen side, and an advance / retreat drive device (41) or (42) for this transmission plate (38). The mold clamping device according to claim 1, wherein the transmission plate (38) is provided with a notch (40) through which the ball screw (26) of the electric mold opening / closing mechanism can pass in the advancing direction. .