JP2000218673A - Overload preventive device of driver for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an overload due to a collision or the like of a driver by constituting to restrict one direction of either a ball screw shaft or a ball nut in a linear motion direction and to conduct the linear motion in the other, and reversing mutual relationship between the restriction and the linear motion when a member for conducting the linear motion is disturbed. SOLUTION: A rotation of a rotor 3b is transmitted to a spline shaft 11 by energizing an ejector motor 3, a ball screw shaft 12 linearly moves while rotating to advance an ejector plate 2 and to project an ejector rod 16. When anything is collided with an end of the rod 16, its shock is transmitted to a ball nut 13 through the plate 2, shafts 14, 15 and a transmission shaft 6, and transmitted to a coiled spring 20 through a support plate 21. Thus, the shock is absorbed, and hence not largely transmitted to a motor plate 18. Accordingly, even when an overload is operated at the rod 16, a force for canceling the shock is operated to prevent the overloading, thereby guaranteeing safety of a machine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for an injection molding machine. In particular, in an ejector device, an ejector in which an overload caused by a collision can be prevented by a protrusion limit of the ejector, and when a molded product is a small object, the molded product can be easily dropped by the collision. The present invention relates to an overload prevention device for a device.

[0002]

2. Description of the Related Art Conventionally, a resin melted by being heated in a heating cylinder is filled at high pressure into a cavity of a mold, cooled in the cavity, and then the mold is opened to take out a molded product. In the molding machine, when the cooling step is completed, the mold is opened with the molded article left on the movable side, and the molded article is pushed down from the mold by the ejector device. Ejector devices are classified into an electric type and a hydraulic type, depending on the type of drive source of the injection molding machine, but the electric type ejector device is characterized by being superior in its high-precision position control as compared with the hydraulic type. .

FIG. 6 is a schematic view showing an example of an ejector device of a conventional electric injection molding machine. In the electric ejector shown in FIG. 6, the rotational motion of a servo motor (not shown) is transmitted to the ball nut 33 via the timing belt 31 and the pulley 32. The ball nut 33 is rotatably supported by bearings 34a and 34b, and the bearings 34a and 34b are fixed to a support member 35. Further, the support member 35 is connected to a guide bar 37 fixed to a movable platen 36. An ejector rod plate 39 is slidably attached to the guide bar 37.

On the other hand, a ball nut 3 is driven by a servomotor.
3 is converted into linear motion by a ball screw shaft 38, and an ejector rod plate 39 and an ejector rod 40 connected to the ball screw shaft 38.
Forward and backward. The ejector rod 40 pushes the ejector plate 42 inside the mold 41 attached to the movable platen 36, and the ejector pins 43a, 43b, 43c attached to the ejector plate 42 move forward and backward, thereby projecting the molded product 44. You. FIG. 7 shows a state where the ejector plate 42 has advanced to the forward limit and the ejector pins 43a, 43b, 43c have protruded the molded product 44.

However, the conventional ejector device of an injection molding machine has a problem that a molded product does not come off from an ejector pin due to static electricity or the like. One of the ways to solve this problem is for hydraulic ejector devices,
There is a method in which the ejector plate in the mold is hit against the forward end at a high speed, stopped, and the product is dropped by the impact.However, in the case of a motorized ejector device, this method may be used for the following reasons. Can not.

In the case of the electric type, the rotational motion of the servomotor is converted into a linear motion between the ball nut and the ball screw shaft, so that the inertia of the drive system becomes larger than that of the hydraulic type.
Even when the ejector plate reaches the forward limit, the inertial force remains, and this residual inertia force reduces the difference between the inertia force of the molded product and the resulting impact force. It is difficult to drop.

[0007] In both hydraulic and electric ejector devices, the ejecting speed of the ejector plate increases at a constant acceleration from the start of the stroke, and when the set speed is reached, the ejecting speed becomes constant. Next, in the case of the hydraulic type, when the forward limit is reached, the projection speed suddenly becomes zero from the set speed and the ejector plate stops, but in the case of the electric type, the inertia force remains, so the At that point, the protrusion speed cannot be suddenly reduced to zero, but is set so that it decelerates slightly before the forward limit and reaches the forward limit to become zero. In the electric ejector device, if the setting is incorrect, the components of the injection molding device are overloaded by the inertial force, resulting in mechanical damage.

Accordingly, the applicant of the present application has proposed a “prior application” of the present application.
As an ejector device of an electric injection molding machine,
Even if the ejector plate is hit against the forward end as in the case of a hydraulic ejector device, an ejector device of an electric injection molding machine capable of properly separating a molded product from an ejector pin without overloading the injection molding device. Provided (Japanese Patent Application No. 9-93208).

As shown in FIG. 8, a spring 53 is provided as a buffer member on an ejector rod 51 and an ejector rod plate 52. In FIG. 8, reference numeral 54 denotes a ball nut which converts the rotation transmitted by a servo motor (not shown) into a linear motion and transmits it to a ball shaft screw 59. Reference numeral 55 denotes a rotatable supporting member 56 for the ball nut 54.
It is a bearing to be fixed to. The support member 56 is connected to a guide bar 58 fixed to a movable platen 57. On the other hand, the ball screw shaft 59, the ejector rod plate 52, and the ejector rod 51 are connected in series, and further connected to an ejector plate and an ejector pin (not shown) to form a linearly movable member.

As described above, the ejector rod plate 5
Between the ejector rod 51 and the ejector rod 51 as a resilient member.
3 are interposed. The fixing of the spring 53 is performed by a bolt 60 embedded from the ejector rod plate 52 to the ejector rod 51. This bolt 60
By adjusting the tightening, the pressure (preload) applied to the spring 53 in advance can be controlled.
Since the spring 53 is preloaded equivalent to the rated output,
When the ejector plate protrudes, the spring 53 moves without bending, and the protruding output (inertial force) generated at the time of a collision in the forward limit is absorbed by the spring 53. At this time, if an overload equal to or greater than the rated sudden output occurs, the spring 53 contracts by the amount of the overload, and the bolt 60 moves relatively rearward, so that the overload can be absorbed.

In the conventional belt drive system, the belt serves as a buffer, but this shortens the life of the belt. Further, in the prior invention by the present applicant, a cushioning material is provided on the output shaft. However, it is difficult to cope with a case where a large number of different output shafts are used for the output shaft depending on the mold, and the setting of the adjustment mechanism Is difficult.

[0012]

A drive device, for example, an overload caused by a collision at a projecting limit of an ejector can be prevented.
It is another object of the present invention to enable a molded article to be easily dropped by collision.

[0013]

Means for Solving the Problems (1) In a drive device of an injection molding machine having a movement direction conversion mechanism for converting a rotational movement of a motor into a linear movement by a combination of a ball screw shaft and a ball nut, a linear movement direction is provided. In, the position of one of the ball screw shaft or the ball nut is constrained, the other is configured to perform a linear motion, if the member performing the linear motion is prevented from linear motion for any reason, By reversing the relationship between the constraint and the linear motion, the occurrence of overload on the ball screw or the ball nut is prevented. (2) A movable platen movably arranged with respect to the fixed platen, an ejector plate movably arranged with respect to the movable platen, a ball screw for moving the ejector plate, and a ball nut screwed to the ball screw. And a buffer member is provided for a support member that supports an axial load acting on the ball screw or the ball nut. (3) It has a guide rod that slidably supports the ejector plate, a motor fixing plate fixed to the guide rod, and a ball nut support plate that supports a ball nut. A buffer member was arranged between them. (4) In the above (3), the buffer member is a spring. (5) In the above (4), the spring was compressed and incorporated with a preset amount of preload. (6) In the above (5), the spring is provided with an adjusting mechanism for adjusting the amount of preload.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below with reference to FIGS. FIG. 1 is a diagram showing an ejector device of an injection molding machine embodying the present invention. FIG. 2 is a diagram showing a state in which the ejector rod of FIG. 1 is advanced. FIG. 3 is a view showing a state in which the ejector rod has collided and slightly retreated in the state of FIG. 2. FIG. 4 is a sectional view taken along the arrow A of FIG. 1, and FIG. 5 is a sectional view taken along the arrow B of FIG.

In FIG. 1, reference numeral 1 denotes a movable platen, to which a movable mold (not shown) is attached at the front end. A fixed platen (not shown) is provided to the movable platen 1 so as to face the movable platen 1. 2 is an ejector plate,
The movable platen 1 can move. An ejector motor 3 has a stator 3a and a rotor 3b built in a motor casing. Reference numeral 4 denotes a rotation transmitting unit that transmits the rotation of the rotor 3b, and reference numeral 5 denotes a movement direction conversion unit that converts the rotation of the rotation transmission unit 4 into a forward-backward movement. Reference numeral 6 denotes a transmission shaft of the rotation transmitting unit 4.

Reference numeral 7 denotes a hollow rotor shaft fixed inside the rotor 3b, and both ends of the rotor shaft 7 are provided with bearings 8 and 9 respectively.
And is rotatably mounted in the motor casing. Reference numeral 10 denotes a spline nut fixed to the hollow rotor shaft 7 with bolts 28, and a spline shaft 11 provided at the end of the transmission shaft 6 is slidably engaged with the spline nut. Conduction shaft 6
Is composed of the spline shaft 11 and the ball screw shaft 12, and the ball screw shaft 12 is screwed with the ball nut 13, so that the rotational motion is converted into a linear motion.

The ball nut 13 is screwed with the ball screw shaft 12 of the transmission shaft 6. One end (left side in the figure) of the transmission shaft 6 is rotatably supported in the ejector plate 2 by bearings 14 and 15. An ejector rod 16 is screwed to the ejector plate 2. A guide rod 17 connects the movable platen 1 and the motor plate 18, and guides the ejector plate 2 to move left and right. Therefore, the ejector plate 2 is interposed between the movable platen 1 and the motor plate 18 and slidably supported by the guide rod 19 via the hole 2A.

Reference numeral 19 denotes a spring support bar for supporting a buffer member such as a coil spring 20. One end of the spring support bar is screwed to the motor plate 18, and the other end is fixed to a support bar plate 22 via a ball nut support plate 21 with screws 23. Have been. Therefore, the coil spring 20 as a buffer member is inserted into the spring support bar 19, is sandwiched between the ball nut support plate 21 and the washer 24 on the motor plate 18 side, and a preload adjusting nut provided outside the washer 24. At 25, the preload is held so as to be adjustable. The ball nut 13 is inserted into the ball nut support plate 21 and its flange portion 13a is
It is fixed with. The preload adjusting nut 25 is screwed into a thread provided on the motor plate 18 side of the spring support bar 19.

The ball nut 13 includes a ball nut support plate 21, a coil spring 20, and a washer 2.
4, the spring support bar 19 and the motor plate 1
8 supported. At the rear end of the rotor shaft 7 of the rotation transmission unit 4, an encoder 27 as a rotation speed sensor is provided. The rotation speed of the rotor 3b is directly detected by the encoder 27.

When the ball screw shaft 12 is rotated, the ejector rod 16 at the front end of the ejector plate 2 is converted into forward and backward movement by a ball nut 13. When the ejector plate 2 is advanced, the ejector rod 16
To extrude the molded product (FIG. 2).

(Operation) 1) When the ejector motor 3 is energized, the rotor 3b rotates. This rotation is transmitted to the spline shaft 11 via the spline nut 10. 2) When the spline shaft 11 rotates, it is transmitted to the integral ball screw shaft 12 in front of the spline shaft. 3) Since the ball nut 13 is fixed to the motor plate 18 and screwed with the ball nut 13, the ball screw shaft 12 makes a linear motion while rotating. 4) The ejector plate 2 is moved forward by the linear motion of the ball screw shaft 12 and the ejector rod 16
Stick out. 5) In this operation, due to the preload applied to the coil spring 20 as a shock absorber, even if a collision occurs at the projecting limit of the ejector, the spring damping action prevents occurrence of overload on the ball nut and the bearing. it can. 6) When it is desired to shake down a small molded product due to a collision, the preload of the coil spring works effectively and the dropping property of the product is improved.

The operation when the ejector rod 16 collides with something will be described with reference to FIGS. First, in the state of FIG.
When something collides with the tip of the motor, the impact is transmitted to the transmission shaft 6 via the ejector plate 2 and the bearings 14 and 15. Since the transmission shaft 6 is freely slidable in the axial direction with respect to the spline nut 10, the impact is transmitted to the ball nut 13. The ball nut 13 transmits the impact to the coil spring 20 via the ball nut support plate 21.

The coil spring 20 is compressed by a distance a by the impact (see FIG. 3). As a result, the impact is absorbed by the coil spring 20 and is not largely transmitted to the motor plate 18. Therefore, the ejector rod 16 and the ball screw shaft 12 are not damaged.

[0024]

According to the first aspect of the present invention, the relationship between the rotational motion and the linear motion is reversed even when a constraint force such as an impact force acts in the linear motion direction in the mechanism for converting the rotary motion into the linear motion. As a result, for example, even if an overload acts on the ejector, a force acts in a direction to cancel the overload, and the overload can be prevented, and the safety of the mechanical device is guaranteed. According to the second aspect of the present invention, the load on the ball nut or the ball screw shaft can be prevented by the presence of the shock absorber. The overload can be prevented by the cushioning member according to the third aspect of the invention and the buffering action of the spring according to the fourth aspect of the invention. According to the fifth aspect, the preload can be applied by compressing the spring, and the preload can be adjusted according to the sixth aspect. Therefore, the amount of the preload can be converted according to the molding conditions, and the overload prevention function can be finely controlled. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a driving device according to the present invention.

FIG. 2 is a view showing a state where an ejector rod is advanced in FIG. 1;

FIG. 3 is a view showing a state in which the ejector rod collides and slightly retreats in the state of FIG. 2;

FIG. 4 is a sectional view taken in the direction of arrow A in FIG. 1;

FIG. 5 is a view taken in the direction of arrow B in FIG. 1;

FIG. 6 is a cross-sectional view of a known ejector.

FIG. 7 is a diagram showing a state when the ejector of the ejector device of FIG. 5 is ejected.

FIG. 8 shows a prior invention disclosed by the present applicant.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Movable platen 2 Ejector plate 2A (Guide rod insertion) hole 3 Ejector motor 3a Stator 3b Rotor 4 Rotation transmission part 5 Motion direction conversion part 6 Conduction shaft 7 (hollow) rotor shaft 8,9 Bearing 10 Spline nut 11 Spline shaft 12 Ball screw shaft 13 Ball nut 14, 15 Bearing 16 Ejector rod 17 Guide rod 18 Motor plate 19 Spring support bar 20 Coil spring 21 Ball nut support plate 22 Support bar plate 23 Screw 24 Washer 25 Preload adjustment nut 26, 28 Bolt 27 Encoder

Claims (6)

[Claims] 1. A driving device for an injection molding machine having a movement direction converting mechanism for converting a rotational movement of a motor into a linear movement by a combination of a ball screw shaft and a ball nut. The position of one of the nuts is restricted, and the other is configured to perform a linear movement. If the member performing the linear movement is prevented from performing the linear movement for some reason, the relationship between the restriction and the linear movement A device for preventing an overload from occurring in a drive device in an injection molding machine, wherein an overload is prevented from being applied to a ball screw or a ball nut by reversing the rotation. 2. A movable platen movably arranged with respect to a fixed platen, an ejector plate movably arranged with respect to the movable platen, a ball screw for moving the ejector plate, and screwed with the ball screw. An overload prevention device for a driving device in an injection molding machine, comprising a ball nut, and a buffer member provided to a support member for supporting an axial load acting on the ball screw or the ball nut. 3. A motor fixing plate comprising a guide rod slidably supporting an ejector plate, a motor fixing plate fixed to the guide rod, and a ball nut supporting plate for supporting a ball nut. 3. An overload prevention device for a driving device in an injection molding machine according to claim 2, wherein a buffer member is arranged between the driving device and the shock absorber. 4. The apparatus according to claim 2, wherein the buffer member comprises a spring. 5. The apparatus according to claim 4, wherein the spring is compressed and incorporated with a preset preload amount. 6. The apparatus according to claim 5, wherein the spring is provided with an adjusting mechanism for adjusting an amount of preload.