JPS61237617A - Mold clamping device in injection molding machine - Google Patents

Abstract

PURPOSE:To contrive miniaturization of a ball screw mechanism, by preventing feed and discharge of a working fluid from the outside into a pressurizing chamber and boosting chamber at the time of pressure clamping of a mold. CONSTITUTION:Although capacity of a boosting chamber 56 and fluid chamber 72 can be kept constant after closing of a mold, capacity of a pressurizing chamber 54 is made to reduce with advancement of a pressurizing piston 28. When the mold closing is completed, excitation of a solenoid of a directional control valve 88 is released by an encoder 50, the excitation of a directional control valve 86 is started, a cartridge valve 78 is closed and the pressurizing chamber 54 and boosting chamber 56 are intercepted from the outside. Fluid pressure, therefore, is generated in the pressurizing chamber 54 and boosting chamber 56 and a movable platen 18 is pressed against a stationary platen 14 by a mold clamping ram 24. As a pressure receiving area of a mold clamping ram 24 side is larger than that of a pressurizing piston 28 side, force which is larger than that applied to a working fluid is acted upon the mold clamping ram 24. With this construction, mold clamping force which is capable of making sufficient resistance to resin pressure to be injected into the mold even if a ball screw mechanism is tiny can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a mold clamping device for an injection molding machine, and more particularly to a mold clamping device that employs a ball screw mechanism as a moving mechanism for a movable platen.

(Background Art) In a mold clamping device of an injection molding machine, a movable platen is moved to close a mold between it and a fixed platen, and the mold is moved to resist the injection resin pressure applied to the mold. A function to clamp the mold is required.

For this reason, conventionally, a direct pressure type mold clamping device in which a movable platen is directly moved by a hydraulic cylinder, a toggle type mold clamping device in which the movable platen is moved via a link mechanism, etc. have been generally used.

On the other hand, as a moving mechanism for the movable platen in such a mold clamping device, it has been considered to employ a ball screw mechanism used in machine tools, etc., without using a structure such as the above-mentioned hydraulic cylinder.

(Problem to be solved by the invention) However, when simply adopting a ball screw mechanism as a moving mechanism for the movable platen, the ball screw mechanism is inevitably large because a large mold clamping force is required when clamping the mold. Therefore, there is a problem that the mold clamping device as a whole becomes larger.

(Means for Solving the Problem) Here, in order to solve the problem, the mold clamping device according to the present invention includes (a> an outer cylinder member provided in a fixed position with respect to the fixed platen, and (b) ) an inner member having a movable platen fixedly attached to one end thereof, which is slidably fitted to the inner circumferential surface of the outer cylindrical member; and (C) a male screw member screwed together with a predetermined ball screw structure. one of the male screw member and the nazoto member is fitted to the other end of the inner member so as to be slidable and non-rotatable in the axial direction; a ball screw mechanism provided in the member so as to be immovable and rotatable in the axial direction with respect to the outer cylindrical member; (d) rotation drive means for rotating the other member of the ball screw mechanism; and (e) the ball screw. (f) a regulating means that prevents sliding of the one member of the mechanism relative to the inner member when the mold is closed, but allows it when the mold is clamped; (f) the one member of the ball screw mechanism; a pressurized chamber filled with a predetermined working fluid, which is formed between the member of
) The inner member is formed between the outer cylindrical member and the inner member and communicates with the pressurizing chamber, and is configured to transfer the fluid pressure generated in the pressurizing chamber based on the decrease in the volume (h) a pressure intensifying chamber that acts in a direction in which the movable platen is pressed against the fixed platen; and (h) a supply/discharge prevention block that prevents working fluid from being supplied or discharged from the outside to the pressurization chamber and the ground pressure chamber. and means.

(Function) In such a mold clamping device, when closing the mold,
Since sliding of one member of the ball screw mechanism with respect to the inner member is prevented by the restricting means, the movable platen, together with one member of the hole screw mechanism, rotates its axis as the other member of the ball screw mechanism is rotated by the rotational drive means. It will be moved towards the heart. In addition, at this time, since one member and the inner member of the hole screw mechanism are relatively fixed, the volume of the pressurizing chamber formed between them does not change, and therefore the pressurizing chamber does not change. No fluid pressure is generated.

However, when the mold is clamped, the movement of the inner member is prevented, and the restricting state by the restricting means is released, allowing one member of the ball screw mechanism to slide relative to the inner member. , one member of the ball screw mechanism is brought closer to the inner member as the other member rotates. As a result, the volume of the pressurizing chamber is reduced. On the other hand, at this time, since the outer cylinder member and the inner member are relatively fixed, the volume of the pressure increasing chamber formed between them does not change.

Therefore, if the supply and discharge blocking means prevents the supply and discharge of working fluid from the outside to the pressurizing chamber and the pressure intensifying chamber during this clamping, the rotation drive means can rotate the other member of the ball screw mechanism. As a result, fluid pressure can be generated in the pressurizing chamber and the pressure increasing chamber connected to the pressurizing chamber,
The mold clamping force applied to one member of the ball screw mechanism based on the rotational force of the rotational drive means can be amplified and applied to the inner member and, ultimately, the movable platen.

(Effects of the Invention) In other words, according to the mold clamping device according to the present invention, the mold clamping force applied to the ball screw mechanism from the rotational drive means can be amplified and applied to the inner member, and therefore the ball screw mechanism can be amplified. This makes it possible to obtain sufficient mold clamping force without increasing the size. Furthermore, as is clear from this, the rotational drive means that applies rotational force to the ball screw mechanism can also be downsized, and furthermore, the mold clamping device as a whole can also be downsized.

(Example) Hereinafter, in order to clarify the present invention more specifically,
One embodiment thereof will be described in detail based on the drawings.

FIG. 1 is a diagram showing the mold opening state of the mold clamping device according to the present invention. In this figure, reference numeral 10 denotes tie bars arranged parallel to each other in the front-rear direction, and a fixed platen 14 to which the fixed mold 12 is attached at the front end (the right end in the figure).
is fixedly supported, and a movable platen 18 to which a movable mold 16 is attached is supported at the intermediate portion so as to be slidable in the front-rear direction. Reference numeral 20 denotes a mold clamping cylinder as an outer cylindrical member, which has a cylindrical shape and supports the rear end portion of the tie bar 10 at a flange portion 22 formed on the outer peripheral surface of the front end portion.

A mold clamping ram 24, which is an inner member, is fitted to the inner circumferential surface of the mold clamping cylinder 20 so as to be slidable in the axial direction. ,
The movable platen 18 is attached. When the mold clamping ram 24 moves relative to the mold clamping cylinder 20 in the axial direction, the movable platen 18 is moved toward and away from the fixed platen 14. In addition, the mold clamping ram 24 has a bottomed hole 26 opened at its rear end surface, and a cylindrical pressure piston 28 is accommodated in the bottomed hole 26. It is fitted to the surface so as to be slidable in the axial direction and non-rotatably. Then, a hole screw nut 3 is screwed into the inside of this pressurizing piston 28 with a ball screw 30 described later and a predetermined ball screw structure.
2 is fixed. This ball screw nut 32 and the pressure piston 28 constitute a NAND member of a ball screw mechanism having a ball screw 30 as a male screw member, which will be described later.

Between the pressure piston 28 and the bottom of the bottomed hole 26,
A compression coil spring 34 is interposed, and this compression coil spring 34 constantly biases the pressurizing screw 1-28 in the direction away from the mold clamping ram 24, that is, in the direction of protruding from the bottomed hole 26. -ing Further, a stopper member 36 is provided at the opening of the bottomed hole 26, and the pressurizing piston 28 is prevented from coming out from the bottomed hole 26 by coming into contact with this stopper member 36. .

This stopper member 36 prevents the pressurizing piston 2B from being separated from the mold clamping ram 24 (more precisely, from the bottom surface of the bottomed hole 26) by more than a certain distance.

Note that the biasing force of the compression coil spring 34 prevents the pressure piston 28 and the mold clamping ram 24 from approaching in the axial direction at times other than when the mold is clamped; At times, when movement of the mold clamping ram 24 in the axial direction is prevented, the size is preset to allow their approach. Furthermore, as is clear from this, in this example,
The compression coil spring 34 and the stopper member 36 constitute a regulating means.

On the other hand, the ball screw 30 into which the ball screw nut 32 is screwed is rotatable and slidable in the axial direction in a deep hole 38 formed at the bottom of the bottomed hole 26 of the mold clamping ram 24 at its front end. At its rear end, it is rotatably but immovably supported in the axial direction by a closing member 40 that fluid-tightly closes the opening on the rear end side of the mold clamping cylinder 20 . And the ball screw 30
A pulley 42 is fixed to the rear end protruding from the closing member 40, and rotational power is input to the ball screw 30 from an AC servo motor 46 serving as a rotational drive means via a timing belt 44 wrapped around the pulley 42. It has become so. The AC servo motor 46 is provided with an electromagnetic brake 48 for fixing the motor shaft, and an encoder 50 for detecting the rotational position. Further, the closing member 40 and the ball screw 30
A space surrounded by the closing member 40 and the mold clamping ram 24 in the clamping cylinder 20 is maintained fluid-tight with respect to the outside space. As will be described later, this space serves as a tank 52 containing a predetermined working fluid.

Further, in such a mold clamping device, a first annular fluid chamber 54 as a pressurizing chamber is formed in the sliding portion between the pressurizing piston 28 and the mold clamping ram 24, and a first fluid chamber 54 is formed as a pressurizing chamber. An annular second fluid chamber 56 serving as a pressure increasing chamber is formed in the sliding portion between the clamping cylinder 20 and the mold clamping ram 24, and these fluid chambers 54 and 56 are filled with a predetermined working fluid. .

The working fluid filled in these fluid chambers 54 and 56 is always allowed to flow between both fluid chambers 54 and 56 through a fluid passage 58 formed in the mold clamping ram 24.

That is, the outer periphery of the pressure piston 28 and the inner periphery of the bottomed hole 26 of the mold clamping ram 24 are aligned with the stepped ζJ surfaces 60 and 6, respectively.
2, and the stepped surfaces 60 and 62
When the pressurizing piston 28 and the bottom of the bottomed hole 26 approach each other,
The pressurizing piston 28 is moved closer and further away depending on the distance.
The mold clamping ram 24 is fitted with the mold clamping ram 24, and as a result, the volume decreases when the pressure piston 28 approaches the mold clamping ram 24. A first fluid chamber 54 is formed as a pressure chamber.

On the other hand, the second fluid chamber 56 as a pressure intensifying chamber has an annular protrusion 64 formed protrudingly formed on the inner circumferential surface of the mold clamping cylinder 20 and is brought into fluid-tight sliding contact with the outer circumferential surface of the mold clamping ram 24. , an annular protrusion 66 formed protrudingly formed on the outer circumferential surface of the mold clamping ram 24 is brought into fluid-tight sliding contact with the inner circumferential surface of the mold clamping cylinder 20 at a portion on the front end side.・It has been done. As a result, when fluid pressure is generated in the second fluid chamber 56, the fluid pressure acts on the rear side surface 68 of the protrusion 66 and presses the mold clamping ram 24 and, by extension, the movable platen 18 toward the fixed platen 14. This is what we are meant to do.

Note that the fluid pressure in the fluid chambers 54 and 56 can be confirmed by a pressure gauge 69 connected to the second fluid chamber 56, and can also be detected by a pressure sensor (not shown). . Further, an annular closing member 70 is provided at the opening between the mold clamping ram 24 on the front end side of the mold clamping cylinder 20 and slidingly contacts the mold clamping ram 24 to close the opening in a fluid-tight manner. , whereby a third fluid chamber 72 is formed between the protrusion 66 and the protrusion 66 . This third fluid chamber 72 is connected to the tank 52 as described later.
It also serves as a tank for containing working fluid.

In such a mold clamping device, the tank 52
and the third fluid chamber 72 are constantly communicated through a fluid passage 74, and the fluid passage 74 and the second fluid chamber 5
A cartridge valve 78 is provided on the fluid passage 76 that connects the tank 52 and the third fluid chamber 72 and the second fluid chamber 56. There is.

The cartridge valve 78 is configured such that a piston 82 provided in a cylinder 80 is constantly biased by a compression coil spring 84 in a direction to cut off a connection between the second fluid chamber 56 and the fluid passage 74. The chamber on the side in which the coil spring 84 is housed is connected to the second fluid chamber 56 and the fluid passage 74 via directional control valves 86 and 88, respectively.

Then, when only the solenoid of the directional control valve 86 is energized, the connection between the second fluid chamber 56 and the fluid passage 74 is cut off, and conversely, when only the solenoid of the directional control valve 88 is energized, the second fluid chamber 56 and the fluid passage 74 are closed. Two fluid chambers 56 and fluid passages 7
It is designed to communicate with 4.

Note that the fluid passage 74 is provided with a throttle 89, and the fluid passage 76 is provided between the throttle 89 and the third fluid chamber 72.
is connected. As will be described later, when the mold is closed, fluid pressure is generated in the third fluid chamber 72 based on this throttle 89, and the fluid generated in the third fluid chamber 72 is pressure is piston 82
The cartridge valve 78 is
is opened, and the working fluid in the third fluid chamber 72 flows into the second fluid chamber 5.
6.

Further, a check valve 90 whose forward direction is the direction from the fluid passage 74 toward the second fluid chamber 56 is provided between the fluid passage 74 and the second fluid chamber 56 on the tank 52 side with respect to the throttle 89. .

In such a mold clamping device, when closing the mold from the mold open state shown in FIG. Rotate and drive. In this way, the ball screw 30 rotates in the normal direction, and the ball screw nut 32, that is, the pressure piston 28, is moved forward (to the right in the figure), but at this time, the mold clamping ram 24
The forward movement of the mold clamping ram 24 is not restricted.
G is moved forward while the pressurizing piston 28 is kept in contact with the stopper member 36 according to the biasing force of the compression coil spring 34. In other words, the mold is closed while the volume of the first fluid chamber 54 is maintained at its maximum.

When the mold is closed, the volume of the second fluid chamber 56 gradually increases as the mold clamping ram 24 moves forward, but a throttle is added to the third fluid chamber 72, which similarly decreases in volume as the mold clamping ram 24 moves forward. 89, the cartridge valve 78 is opened by this fluid pressure, and the working fluid is allowed to flow in from the third fluid chamber 72 through the fluid passage 76, and the working fluid is allowed to flow from the tank 52 through the check valve 90. is allowed to flow in, so that the second fluid chamber 56 does not become a negative pressure and the movement of the mold clamping ram 24 is not hindered.

Then, as the mold clamping ram 24 moves forward as described above, the movable mold 16 comes into contact with the fixed mold 12 as shown in FIG. 2, and when mold closing is completed, the mold clamping ram 24 Forward movement is blocked.

Therefore, after this, as shown in FIG. 3, the pressure piston 28 moves forward while further compressing the compression coil spring 34 as the ball screw 30 rotates.

That is, after the mold is closed, the volumes of the second fluid chamber 56 and the third fluid chamber 72 are kept constant, but the volume of the first fluid chamber 54 is decreased as the pressurizing piston 2B moves forward. It is.

On the other hand, when mold closing of the mold is completed, this is detected by the encoder 50, and based on the detection result, the solenoid of the directional valve 88 is de-energized, and the solenoid of the directional valve 86 is de-energized. will be started. Then, as shown in FIG. 2, the cartridge valve 78 is closed and the second fluid chamber 56 and the fluid passage 74 are cut off. In other words, the first fluid chamber 5
4 and the second fluid chamber 56 are isolated from the outside.

Therefore, after the mold is closed, as the volume of the first fluid chamber 54 decreases due to the advance of the pressurizing piston 28, the second fluid chamber 54 and the second fluid chamber 56 communicating therewith decrease. Fluid pressure is generated, and a force based on the fluid pressure is applied to the mold clamping ram 24 in a direction to press the movable platen 18 toward the fixed platen 14. In this case, as is clear from the figure, the pressure receiving area on the mold clamping ram 24 side that receives the fluid pressure (area of the stepped surface 62 + area of the rear side surface 68 of the protrusion 66) is equal to the pressure receiving area on the pressure piston 28 side. Since the area is larger than the area (area of the stepped surface 60), a force larger than the force applied to the working fluid from the pressurizing piston 28 is applied to the mold clamping ram 24. In other words, even if the ball screw mechanism is small, it is possible to obtain mold clamping force sufficient to counter the pressure of the injection resin injected into the mold. Furthermore, as is clear from this, the AC servo motor 46 that inputs rotational power to the ball screw 30 can also have a small output, making it possible to downsize the entire mold clamping device. Furthermore, as is clear from the above explanation,
In this embodiment, the cartridge valve 78 is connected to the fluid chamber 54.
56 from the outside.

Further, as described above, after the mold is closed, the pressurizing piston 28 is further advanced, the fluid pressure in the first fluid chambers 54.56 is increased, and a pressure sensor (not shown) is activated in the fluid chambers 54.56. When it is detected that the fluid pressure has reached a level sufficient to resist the injection resin pressure, the electromagnetic brake 48 is activated, the motor shaft of the AC servo motor 46 is fixed, and the mold clamping force is maintained. Ru. Then, while this mold clamping force is maintained, a predetermined resin is injected into the product cavity of the mold.

In addition, in this embodiment, as described above, the fluid chambers 54°, 56°
Since the cartridge valve 78 with little leakage is used to isolate the mold from the outside, the mold clamping force is maintained well under such mold clamping force retention state.

Furthermore, when opening the mold after the resin injected into the product cavity of the mold is cured, only the solenoid of the directional control valve 88 is energized, as in the case of closing the mold. - On the other hand, release the electromagnetic brake 48 and reverse the AC motor 46. In this way, first, the pressurizing screw 28 is retracted to the position where it contacts the stopper member 36, and 1. Thereafter, the mold clamping ram 24 is retracted integrally with the pressurizing piston 28. Then, as shown in FIG. 1, when the mold clamping ram 24 retreats to a predetermined position, this is detected by the encoder 50 and the drive of the AC servo motor 46 is stopped. Also,
The working fluid in the second fluid chamber 56 is supplied to the cartridge valve 78
It opens and flows out, and is stored in the tank 52 and the third fluid chamber 72.

Although one embodiment of the present invention has been described above, this is a literal illustration, and the present invention should not be interpreted as being limited to this specific example.

For example, in the embodiment described above, the AC servo motor 46 is provided with an encoder 50, and the encoder 50 detects the mold closing position of the mold and the retracted position of the mold clamping ram 24. Detection may be performed using other detection means such as a beam switch.

Further, in the above embodiment, the fluid chamber 54 is
．． 56 is detected to determine whether the mold clamping force of the mold has reached a level capable of resisting the injection resin pressure. It is also possible to perform this based on the output of the encoder 50.

Further, in the embodiment, the fluid chambers 54 and 56 and the tank 52
A cartridge valve 78 is interposed between the cartridge valve 78 and the fluid chambers 54.5 and 54.5.
Although the inflow/outflow of the working fluid into and out of the cartridge valve 78 is allowed and prevented, it is also possible to employ other valve mechanisms in place of the cartridge valve 78.

Further, the tank 52 does not necessarily need to be provided inside the mold clamping cylinder 20.

Furthermore, in the embodiment described above, the regulating means was constituted by the compression coil spring 34 and the stopper member 36, but the regulating means does not need to be constituted by a combination of the urging means and the stopper means, As long as it prevents sliding between the pressurizing piston 28 and the mold clamping ram 24 during mold closing, and allows the sliding during clamping,
It may be a locking mechanism that simply temporarily fixes the pressurizing piston 28 and the mold clamping ram 24.

Further, in the embodiment, of the male threaded member and the nut member that constitute the ball screw mechanism, the ball screw 30 forming the male threaded member is supported to be rotatable and immovable in the axial direction with respect to the mold clamping cylinder 20, The ball screw nut 32 and the pressure piston 2B, which constitute a NAND member, were provided on the mold clamping ram 24 so as to be non-rotatable but slidable in the axial direction. The ball screw 30 is fixed to the pressurizing piston 28, and the mold clamping ram 2
It is also possible to provide it so that it is not rotatable with respect to 4 but is slidable in the axial direction. In this case, the ball screw nut 32 constitutes a NAND member, and the ball screw 30
and the pressurizing piston 28 constitute a male threaded member.

Further, in the above embodiment, the mold clamping ram 24, which is an inner member, is fitted onto the outer peripheral surface of the pressure piston 28 at the inner peripheral surface of the bottomed hole 26 formed at the rear end, and the mold clamping ram 24, which is an inner member, is fitted into the outer peripheral surface of the pressurizing piston 28. One fluid chamber 54 was formed in the sliding part between them, and the pressurizing piston 28 was placed on the mold clamping ram 24 on its inner peripheral surface.
It is also possible to fit the outer peripheral surface of the rear end portion and form the first fluid chamber 54 as a pressurizing chamber in the sliding portion between them. Note that, as in the case described above, the pressurizing piston 28 is provided integrally with either the ball screw 30 or the ball screw nut 32.

Further, in the embodiment described above, the rotational drive means is the AC servo motor 46, but the invention is not limited to this.

Although not listed here, it goes without saying that the present invention can be implemented with various modifications and improvements within the scope of the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention,
2 is a diagram corresponding to FIG. 1 showing a different operating state of the embodiment device of FIG. 1 from that in FIG. 1, and FIG. 3 is a diagram showing a further different operating state of the embodiment device of FIG. It is a main part explanatory diagram. 12: Fixed mold 14: Fixed plate 16: Movable mold 18: Movable plate 20: Clamping cylinder (outer cylinder member) 24; Clamping ram (inner member) 30: Ball screw (male thread member) 46: AC servo motor (Rotation drive means) 48: Electromagnetic brake 52: Tank 54: First fluid chamber (pressurizing chamber) 56: Second fluid chamber (pressurizing chamber) 58: Fluid passage

Claims (2)

[Claims] (1) Injection molding in which the movable platen is moved to close the mold between it and the fixed platen, and the mold is further clamped so as to counteract the injection resin pressure applied to the mold. A mold clamping device for a machine, comprising: an outer cylindrical member provided in a fixed position with respect to the fixed platen; and the movable platen at one end slidably fitted to the inner circumferential surface of the outer cylindrical member. It has an inner member that is fixedly attached, and a male screw member and a nut member that are screwed together with a predetermined ball screw structure, and the inner member has a male screw member and a nut member that are screwed together with a predetermined ball screw structure. The other end is slidably and non-rotatably fitted in the axial direction, and
a ball screw mechanism provided in the other member so as to be immovable and rotatable in the axial direction with respect to the outer cylindrical member; a rotation drive means for rotating the other member of the ball screw mechanism; and one of the ball screw mechanisms. a regulating means that prevents sliding of the member relative to the inner member when the mold is closed, but allows it when the mold is clamped; and the one member of the ball screw mechanism and the inner member. a pressurized chamber filled with a predetermined working fluid, the pressurized chamber being formed between the outer cylindrical member and the inner member and whose volume is reduced by their approach; a pressure intensifying chamber communicated with the pressurizing chamber and causing fluid pressure generated in the pressurizing chamber based on the decrease in volume to act on the inner member in a direction in which the movable platen is pressed against the fixed platen; A mold clamping device for an injection molding machine, comprising: a supply/discharge preventing means for preventing supply/discharge of working fluid from the outside to the pressurizing chamber and the pressure increasing chamber. (2) The regulating means is interposed between the one member of the ball screw mechanism and the inner member, and includes a biasing means for biasing them in a direction away from each other, and one member of the ball screw mechanism. and a stopper means for preventing the inner member from being separated by a certain distance or more.
Mold clamping device as described in section.