JPH09300415A - Clamping apparatus for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately control clamping force and to perform precise molding by a method wherein cylinder parts with a large diameter and a small diameter are provided in a hydraulic pressure generating cylinder apparatus and a piston is reciprocally driven and a cylinder for clamping is connected with the cylinder part with a small diameter. SOLUTION: A mold clamping cylinder apparatus 3 is provided with a cylinder 33 for mold clamping and a ram 32 for mold clamping and large and small diameter cylinder parts 58b and 58c are provided in a hydraulic pressure generating cylinder apparatus 4. In addition, in mold closing process, a movable stage 15 is forwarded by the first rotational driving source 44. In this case, a piston 51 of the hydraulic pressure generating cylinder apparatus 4 is in the large diameter cylinder part 58b and hydraulic oil in an oil reservoir 60 flows freely into a hydraulic pressure room 35 for mold clamping through a pipeline 72. Then, when a movable mold 16 is brought into touch with a fixed mold 17, the first rotational driving source 44 is stopped and the piston 51 is hooked to a small diameter cylinder part 58c by the second rotational driving source 54 to introduce pressure oil in the hydraulic pressure room 59 into the hydraulic pressure room 35 for mold clamping and a mold clamping ram 32 and the movable stage 15 are strongly pressed to push the movable mold 16 on the fixed mold 17.

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.

[0002]

2. Description of the Related Art As a mold clamping device for a conventional injection molding machine,
For example, a direct pressure type shown in FIG. 5 is known. This mold clamping device has a mold clamping cylinder device 80 and a hydraulic circuit 90. The mold clamping cylinder device 80 has a main ram 81 that is slidably fitted in the main cylinder 83 and divides a main pressure chamber 85 and a return pressure chamber 86. The main ram 81 has a moving ram at the center thereof. A small-diameter moving cylinder 82 is formed in which 84 is slidably fitted.

When performing mold closing from the illustrated mold open state, hydraulic oil from the hydraulic pump 97 flows into the moving cylinder 82 via the mold moving valve 94, and the main ram 81 and the movable ram connected to the main ram 81 are moved. Board 15 and mold (not shown)
To move forward at high speed. At that time, the prefill valve 91 opens, and the reserve tank 9 is placed in the space inside the main pressure chamber 85.
When the hydraulic oil of No. 6 flows in, the inside of the main pressure chamber 85 is prevented from becoming a negative pressure as the main ram 81 moves forward.
At the same time, the valve 98 is opened to return the hydraulic oil in the return pressure chamber 86 to the main pressure chamber 85. As a result, the mold closing operation is performed at high speed.

Next, immediately before the mold (not shown) arranged between the fixed platen 12 and the movable platen 15 is closed, the pressurizing valve 9 with the prefill valve 91 and the valve 98 closed.
Switch 5 As a result, the pressure oil acts in the main pressure chamber 85, and the main ram 81 moves forward at a low speed. When the mold is completely closed, hydraulic pressure acts on the entire area of the main ram 81, and a large mold clamping force is generated.

At the time of mold opening, the retreat valve 92 is switched, the prefill valve 91 is opened by the pilot pressure to release the pressure of the main ram 81, and the hydraulic oil from the hydraulic pump 97 is returned through the retreat valve 92. The pressure is supplied to the pressure chamber 86, and the movable platen 15 is retracted. The hydraulic oil in the moving cylinder 82 flows back to the reserve tank 96 from the oil drain valve 93. At the time of pushing out the product at the beginning and the end of the mold opening, the return speed of the movable platen 15 is reduced, and the gear shifting at this time is usually performed by switching the amount of hydraulic oil.

[0006]

However, such a conventional mold clamping device for an injection molding machine has the following technical problems. First, since all the operations of the mold clamping cylinder device 80 are performed by controlling the flow of hydraulic oil from the hydraulic pump 97 by switching the valves 92, 93, 94, 95 and 98, precise control is performed. Was difficult. That is, the hydraulic oil has a large change in viscosity and the like, and it is difficult to adjust the hydraulic oil by following the change in the environment in which the injection molding machine is placed.

Secondly, managing the hydraulic oil to ensure precise control means managing the oil temperature at the time of starting, managing the hydraulic oil during normal operation, and further controlling the room temperature. , Management cost was high, and efficiency was poor. Thirdly, the leakage of hydraulic oil from the plurality of valves 91, 92, 93, 94, 95 and 98 deteriorates the surrounding environment, and a slight amount of hydraulic oil adheres to the molded product. Was not preferable either.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional technical problems, and has the following configuration. The structure of the invention of claim 1 is arranged between the fixed mold clamping housing 13 and the fixed platen 12, has a movable platen 15 capable of reciprocating movement, and is arranged between the fixed platen 12 and the movable platen 15. In a mold clamping device having a drive device for opening and closing the molds 16 and 17, the drive device is arranged between the mold clamping housing 13 and the movable platen 15, and the linear drive device 2 drives the movable platen 15 back and forth. , A mold clamping cylinder device 3 and a hydraulic pressure generating cylinder device 4,
The mold clamping cylinder device 3 is formed on one of the mold clamping housing 13 and the movable platen 15, and on the other of the mold clamping housing 13 and the movable platen 15. The mold clamping cylinder device 3 slides on the mold clamping cylinder 33. The hydraulic pressure generating cylinder device 4 is provided with a mold clamping ram 32 that is movably fitted to the cylinder body 58 having a large diameter cylinder portion 58b and a small diameter cylinder portion 58c, and is slidable on the small diameter cylinder portion 58c. It is characterized in that it has a piston 51 that is fitted to generate pressure oil, and a piston drive device that reciprocally drives the piston 51, and the inside of the mold clamping cylinder 33 is connected to the small diameter cylinder portion 58c. It is a mold clamping device of an injection molding machine. Claim 2
The piston drive device for reciprocatingly driving the piston 51 has a tip end portion connected to the piston 51 and a base end portion connected to the second rotary drive source 54, and is a ball screw member rotatably driven in the forward and reverse directions. 5. The mold clamping device for an injection molding machine according to claim 1, further comprising: a ball nut 53 fixed to the cylinder body 58 and engaging with the ball screw member 52 via a ball. According to a third aspect of the present invention, the linear drive device 2 is fixed to the ball screw 41 rotatably supported by the mold clamping housing 13 and the movable platen 15,
3. A movable platen moving ball nut 42 that engages with the ball screw 41 via a ball, and a first rotation drive source 44 that drives the ball screw 41 to rotate forward and backward. It is a mold clamping device of an injection molding machine. According to a fourth aspect of the present invention, there is provided a mold clamping device for an injection molding machine according to the first, second or third aspect, which has a pressure detecting means 71 for detecting a pressure in the mold clamping cylinder 33.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. In FIG.
Reference numeral 1 denotes a mold clamping device, which has a mold clamping housing 13 and a stationary platen 12 fixed on the bed 10, and a movable platen 15 arranged between the mold clamping housing 13 and the stationary platen 12. The mold clamping housing 13 and the fixed plate 12 are connected by four tie bars 11, and both ends of the tie bar 11 are fastened by tie bar nuts 23. The movable platen 15 can reciprocate forward and backward (left and right in FIG. 1) on the bed 10 via the rollers 14 between the mold clamping cylinder 33 and the fixed platen 12, and along the tie bar 11. Slide. A movable die 16 is attached to the movable platen 15, and the fixed platen 12 is attached.
A fixed mold 17 is attached to the.

A drive device for opening and closing the molds 16 and 17 arranged between the fixed plate 12 and the movable plate 15 is arranged. The drive device is arranged between the mold clamping housing 13 and the movable platen 15, and drives the movable platen 15 back and forth.
It has a mold clamping cylinder device 3 and a hydraulic pressure generating cylinder device 4 that generate a mold clamping force on the molds 16 and 17.

The linear drive device 2 is composed of a servomotor, and has a first rotary drive source 44 fixedly mounted on the upper portion of the mold clamping housing 13, and a ball that is rotationally driven in the forward and reverse directions by the first rotary drive source 44. The ball screw 41 has a screw 41 and a movable platen moving ball nut 42 fixed to the upper part of the movable platen 15. The ball screw 41 has a thrust load and a radial load by a bearing 43 fixedly fixed to the upper part of the mold clamping housing 13. Both are supported and only rotation is allowed. Further, the front end portion of the ball screw 41 engages with the movable platen moving ball nut 42 via a ball (not shown) to form a ball screw mechanism. As a result, the ball screw 41 is rotationally driven in the forward and reverse directions by the first rotary drive source 44, whereby the movable platen 15 reciprocates at high speed back and forth due to the function of the movable platen moving ball nut 42. The linear drive device 2 may be configured by a rack and pinion instead of the ball screw mechanism.

The mold clamping cylinder device 3 comprises a mold clamping housing 1
3, a mold clamping cylinder 33 fixed to the movable platen 15, and a mold clamping ram 32 fixed to the movable plate 15 and slidably fitted to the mold clamping cylinder 33 via a seal ring 34. A mold clamping hydraulic chamber 35 is defined inside the clamping cylinder 33. Then, since the movable platen 15 and the movable mold 16 are pushed out by propagating the hydraulic pressure to the hydraulic oil in the mold clamping hydraulic chamber 35, a mold clamping force can be generated between the molds 16 and 17. it can. The mold clamping cylinder 33 can be formed integrally with the mold clamping housing 13 or can be fixed to the mold clamping housing 13 by fixing means such as bolts and nuts. Further, the mold clamping ram 32 can be formed integrally with the movable platen 15 or can be fixed to the movable platen 15 by fixing means such as bolts and nuts.

The hydraulic pressure generating cylinder device 4 has a cylinder body 58 in which an upper large-diameter cylinder portion 58b and a lower small-diameter cylinder portion 58c are connected by a taper portion 58a, and a ball screw member 52. It has a piston 51 slidably fitted in the cylinder portion 58c, the large diameter cylinder portion 58b forms an oil reservoir 60, and the small diameter cylinder portion 58c forms a hydraulic chamber 59. The lower end of the ball screw member 52 is rotatably connected to the piston 51,
The upper end is connected to the drive shaft of the second rotary drive source 54 which is a servomotor. The large-diameter cylinder portion 58b herein may have a cross-sectional shape including the small-diameter cylinder portion 58c in plan view, and includes a cross-sectional shape other than a circular shape.

A screw is formed in the intermediate portion of the ball screw member 52, and the screw of the ball screw member 52 is inserted into a ball nut 53 fixed to the central portion of the upper lid 57 of the cylinder body 58 through a ball (not shown). Engaged. The lower portion of the hydraulic chamber 59 of the hydraulic pressure generating cylinder device 4 communicates with the mold clamping hydraulic chamber 35 of the mold clamping cylinder device 3 via a pipe 72. 58d is a large diameter cylinder portion 58
It is an air vent hole formed in the upper part of b. The ball screw mechanism having the ball screw member 52 and the ball nut 53, and the second rotary drive source 54 constitute a piston drive device that reciprocally drives the piston 51.

The second rotary drive source 54 is attached to a guide bar 56 fixed to an upper lid 57 via a bearing 55, and is vertically movable. Then, if the ball screw member 52 is rotationally driven in the forward and reverse directions by the second rotary drive source 54, the ball screw 53 causes the ball screw member 52, the piston 51, and the second rotary drive source 54 to be integrated. Move up and down. The vertical movement of the second rotary drive source 54 is guided by the guide bar 56 via the bearing 55. The second rotary drive source 54 is provided with a position sensor 61 for detecting the vertical position of the second rotary drive source 54 and thus the piston 51. However, the vertical position of the piston 51 can also be detected from the rotation angle of an encoder (not shown) for detecting the rotation angle of the second rotary drive source 54.

When the piston 51 is located in the large diameter cylinder portion 58b above the tapered portion 58a of the cylinder body 58, the oil reservoir 60 and the hydraulic chamber 59 communicate with each other. Therefore, the oil reservoir 60 communicates with the mold clamping hydraulic chamber 35 of the mold clamping cylinder device 3 via the pipe 72.

On the other hand, the piston 51 descends and the piston 5
When 1 passes through the tapered portion 58a of the cylinder body 58 and enters the small diameter cylinder portion 58c, the communication between the hydraulic chamber 59 and the oil reservoir 60 is cut off, and the hydraulic chamber 59 and the mold clamping hydraulic chamber 35 are pressurized. Oil is generated.

In the pipe 72, a hydraulic chamber 59 of the hydraulic pressure generating cylinder device 4 and a hydraulic chamber 35 for mold clamping of the mold clamping cylinder device 3.
A pressure detecting means 71 for detecting the internal pressure is connected. The pressure detecting means 71 is a hydraulic pressure sensor, a pressure gauge, or the like. The oil pressure in the mold clamping hydraulic chamber 35 of the mold clamping cylinder device 3 is controlled by the detection value of the pressure detecting means 71.

Next, the operation will be described. In the mold closing step, the movable platen 15 is moved at high speed by the linear drive device 2. That is, the ball screw 41 is rotated in one direction by the first rotary drive source 44, and the movable platen 15 is moved forward by the action of the movable platen moving ball nut 42 (see FIG. 1).
Move it to the right). At that time, the hydraulic pressure generation cylinder device 4
The piston 51 is held in the large-diameter cylinder portion 58b of the cylinder body 58. As a result, the oil reservoir 6
0 and the hydraulic chamber 59 are communicated with each other so that the working oil in the oil reservoir 60 can freely flow into the mold clamping hydraulic chamber 35 of the mold clamping cylinder device 3 via the pipe 72. Prevents negative pressure inside.

Next, the movable platen 15 moves forward to move the movable mold 16.
Touches the fixed mold 17, the first rotation drive source 44
Is stopped and the mold clamping process is started. The movable mold 16 touches the fixed mold 17 because the torque of the first rotary drive source 44 (motor) increases, or the first rotary drive source 44
It can be detected from the rotation angle of a rotation angle detection sensor (not shown) attached to the (motor). In the mold clamping process, the movable platen 15 is strongly advanced by the hydraulic pressure generation cylinder device 4. That is, the ball screw member 52 is rotationally driven in one direction by the second rotary drive source 54, and the ball nut 53 functions to lower the ball screw member 52, the piston 51, and the second rotary drive source 54 as a unit. By engaging the piston 51 with the small diameter cylinder portion 58c, pressure oil is generated in the hydraulic chamber 59. The pressure oil generated in the hydraulic chamber 59 is introduced into the mold clamping hydraulic chamber 35 through the pipe 72, strongly presses the mold clamping ram 32 and the movable platen 15, and the movable mold 16 is pressed against the fixed mold 17. Be clamped.

In the mold opening step, first, the second rotary drive source 5
4, the ball screw member 52 is rotationally driven in the other direction, and the hydraulic pressure generating cylinder device 4 is driven in a loosening direction. Subsequently, the piston 51 of the oil pressure generating cylinder device 4 is returned to a position above the taper portion 58a of the cylinder body 58, that is, to the large diameter cylinder portion 58b, and the mold clamping hydraulic chamber 35 of the mold clamping cylinder device 3 is connected to the pipe 72 and The hydraulic oil is allowed to freely flow into the oil reservoir 60 via the hydraulic chamber 59, and the linear drive device 2 is driven. That is, the ball screw 41 is rotated in the other direction by the first rotation drive source 44, and the function of the movable platen moving ball nut 42 causes
The movable platen 15 is moved backward to the mold opening position. In the mold clamping process and the mold opening process, when the movable platen 15 moves due to the operation of the hydraulic pressure generation cylinder device 4, the first rotary drive source 44 is appropriately rotated to move the ball screw 41. It is desirable to avoid that an overload acts on the board moving ball nut 42.

By the way, the mold clamping force is determined by the pressure detecting means 71.
The position can be increased or decreased by controlling the position of the piston 51 of the hydraulic pressure generation cylinder device 4 by the pressure detection signal from the position sensor or the position detection signal of the piston 51 by the position sensor 61. That is, the mold clamping force is controlled by the feedback of the pressure detection signal by the pressure detection means 71 or the feedback of the position detection signal by the position sensor 61 based on the control block diagrams shown in FIGS. For example, when the pressure detecting means 71 and the position sensor 61 are provided, the signal from the pressure detecting means 71 is fed back as shown in FIG. 2 and compared with the signal indicating the target mold clamping force B to determine a predetermined transfer function. After being converted by G ₁ , compared with the signal from the position sensor 61, converted by a predetermined transfer function G ₂ , and then appropriately rotated by the signal from the controller A to rotate the second rotary drive source 54. Drive it. When the pressure detecting means 71 is not provided, the control is performed based on the control block diagram shown in FIG. That is, the signal from the position sensor 61 is fed back, compared with the signal indicating the target mold clamping force B, converted by the predetermined transfer function G _2, and then the second rotation drive is performed by the signal from the controller A. The source 54 is appropriately rotated. As described above, the rotation of the second rotary drive source 54 is converted into the linear movement of the ball screw member 52 and the piston 51 by the function of the ball nut 53, whereby the pressure in the hydraulic chamber 59 is changed. It

In this way, the hydraulic pressure generating cylinder device 4
By precisely controlling the piston 51, the actual mold clamping force of the molds 16 and 17 can be freely increased or decreased according to the passage of time. That is, as shown in FIG. 4, after the mold clamping force is gradually increased, the mold clamping force B ₁ is once maintained, and then the mold clamping force B ₂ is rapidly increased to maintain the mold clamping force B ₂ , and then the mold opening process is performed. , The mold clamping forces B ₂ to B ₃ and B ₄ can be gradually released to release them. By precisely controlling the mold clamping force in this manner, it is possible to perform precision molding by the molds 16 and 17.

By the way, in the above-mentioned first embodiment,
Although the second rotary drive source 54 is attached by the bearing 55 so as to be movable up and down, if the ball screw member 52 is split by a spline so as to be extendable and retractable, the second rotary drive source 54 is divided.
It is also possible to fix. When the second rotary drive source 54 is fixed, the position sensor 61 is arranged so as to detect the position of the part that moves up and down together with the piston 51. However, when the second rotary drive source 54 is fixed, the vertical position of the piston 51 can be detected from the rotation angle of the second rotary drive source 54.

The mold clamping cylinder device 3 includes a mold clamping cylinder 33 formed in the mold clamping housing 13 and a movable platen 15.
And a mold clamping ram 32 slidably fitted in a mold clamping cylinder 33. However, the mold clamping cylinder 3
3 is formed on the movable platen 15, the mold clamping ram 32 is formed on the mold clamping housing 13, and even when the mold clamping ram 32 is slidably fitted to the mold clamping cylinder 33, the mold clamping force is generated. It is possible to obtain the same operation as that of the above-described one embodiment. However, when the mold clamping cylinder 33 is formed on the movable platen 15, since the mold clamping cylinder 33 moves, it is necessary to give flexibility to the pipe 72 connected to the mold clamping cylinder 33. The position of the movable platen 15 can be detected from the rotation angle of the first rotary drive source 44 or by a position sensor attached to the movable platen 15.

[0026]

As can be understood from the above description, according to the present invention, the following effects can be obtained. (1) During the mold opening process, the mold clamping force is controlled at the piston position of the hydraulic pressure generating cylinder device without opening and closing the prefill valve to loosen the mold as in the conventional case. It is possible to control the clamping force. As a result, the defective rate of the product generated when the mold was opened was reduced. (2) Regarding the mold clamping process, it has been difficult to control the mold clamping force by adjusting the hydraulic oil amount from the hydraulic pump in the related art. However, according to the present invention, the hydraulic pressure is controlled. The pressure can be controlled only by the driving amount of the piston of the generating cylinder device, and the mold clamping force can be easily controlled in conjunction with the injection process. As a result, it is possible to control the mold clamping force with high accuracy and perform precision molding.

(3) An electric servomotor is used as a drive source for the linear drive device and the hydraulic pressure generation cylinder device, and the movement of the movable platen can be controlled by this electric servomotor, and precise control is possible. Becomes Further, since the mold clamping force is generated by the hydraulic pressure generating cylinder device and the hydraulic pump is not used, it is not necessary to manage the hydraulic oil in order to ensure precise control, and the efficiency is high. (4) Since it is not a general hydraulic machine using various valves, it is difficult to cause stains due to leakage of hydraulic oil, and the periphery of the mold clamping device is clean. (5) Since the mold clamping device has higher rigidity than the toggle type, vibration such as rattling is less likely to occur.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a mold clamping device of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a diagram showing a control block diagram of the mold clamping force.

FIG. 3 is a diagram similarly showing a control block diagram of the mold clamping force.

FIG. 4 is a diagram showing the same mold clamping force-time characteristics.

FIG. 5 is a sectional view showing a mold clamping device of a conventional injection molding machine.

[Explanation of symbols]

1: Clamping device, 2: Linear driving device, 3: Clamping cylinder device, 4: Hydraulic pressure generating cylinder device, 10: Bed, 1
1: tie bar, 12: fixed plate, 13: mold clamping housing,
15: movable plate, 32: mold clamping ram, 33: mold clamping cylinder, 35: mold clamping hydraulic chamber, 41: ball screw, 42: movable plate moving ball nut, 43: bearing, 44: first rotary drive Source, 51: Piston, 52: Ball screw member, 53: Ball nut, 54: Second rotation drive source, 5
5: bearing, 56: guide bar, 57: upper lid, 5
8: Cylinder body, 58a: Tapered portion, 58b: Large diameter cylinder portion, 58c: Small diameter cylinder portion, 59: Hydraulic chamber, 6
0: oil reservoir, 61: position sensor, 71: pressure detecting means, 72: piping.

Claims (4)

[Claims] 1. A movable plate (15), which is arranged between a fixed mold clamping housing (13) and a fixed plate (12) and is capable of reciprocating movement, is provided with the fixed plate (12) and the movable plate (1).
5) In a mold clamping device having a drive device for opening and closing the mold (16, 17) arranged between the drive device and the mold,
A linear drive device (2) arranged between the mold clamping housing (13) and the movable platen (15) to reciprocate the movable platen (15), a mold clamping cylinder device (3) and a hydraulic pressure generation cylinder device (4). ) And the mold clamping cylinder device (3)
Is formed on one of the mold clamping housing (13) or the movable platen (15) and the other mold clamping housing (13) or the movable platen (15). Mold clamping ram (3 that slidably fits into the cylinder (33)
2), and the hydraulic pressure generating cylinder device (4) slides on a cylinder body (58) having a large diameter cylinder portion (58b) and a small diameter cylinder portion (58c), and the small diameter cylinder portion (58c). It has a piston (51) that freely fits to generate pressure oil and a piston drive device that reciprocally drives the piston (51), and the inside of the mold clamping cylinder (33) has a small diameter cylinder part (58c). A mold clamping device for an injection molding machine, which is characterized by being connected to. 2. A piston drive device for reciprocally driving a piston (51), wherein a tip portion is connected to the piston (51),
A ball screw member (52), whose base end is connected to the second rotary drive source (54) and is rotationally driven in the forward and reverse directions, and a ball screw member (52), which is fixed to the cylinder body (58). The mold clamping device for an injection molding machine according to claim 1, further comprising a ball nut (53) engaged therewith. 3. A ball screw (41) rotatably supported on a mold clamping housing (13) by a linear drive device (2),
A ball nut (42) for moving the movable plate, which is fixed to the movable plate (15) and engages with the ball screw (41) via a ball.
And a first rotary drive source (44) for rotationally driving the ball screw (41) in the forward and reverse directions, the mold clamping device of the injection molding machine according to claim 1 or 2. 4. The mold clamping device for an injection molding machine according to claim 1, further comprising a pressure detecting means (71) for detecting a pressure in the mold clamping cylinder (33).