JP3426992B2 - Device for preventing overload of drive unit in 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 drive device for an injection molding machine. Particularly, in the ejector device, an ejector that can prevent an overload from being generated due to a collision at the protrusion limit of the ejector and can easily drop the molded product due to the collision when the molded product is a small product. The present invention relates to an overload prevention device for a device.

[0002]

2. Description of the Related Art Conventionally, injection is carried out in which a molten resin heated in a heating cylinder is filled in a cavity of a mold at high pressure and cooled in the cavity, and subsequently the mold is opened to take out a molded product. In the molding machine, when the cooling process is completed, the mold is opened with the molded product left on the movable side, and the molded product is pushed down by the ejector device. The ejector device is 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 excellent in 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 device of FIG. 6, the rotational movement of the 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 the movable platen 36. An ejector rod plate 39 is slidably attached to the guide bar 37.

On the other hand, the servomotor drives the ball nut 3
The rotation transmitted to 3 is converted into a linear motion by the ball screw shaft 38, and the ejector rod plate 39 and the ejector rod 40 which are connected to the ball screw shaft 38.
Move 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 to project the molded product 44. You FIG. 7 shows a state in which the ejector plate 42 has advanced to the forward limit and the ejector pins 43a, 43b, 43c project the molded product 44.

However, the ejector device of the conventional injection molding machine has a problem that the molded product does not come off the ejector pin due to the influence of static electricity or the like. As one of the methods to solve this problem, in the case of a hydraulic ejector device,
There is a method of hitting the ejector plate in the mold at a high speed at the forward limit, stopping it, and dropping the product due to the impact, but in the case of an electric ejector device, this method can be taken for the following reasons. Can not.

In the case of the electric type, since the rotational movement of the servo motor is converted into the linear movement between the ball nut and the ball screw shaft, the inertia of the drive system becomes larger than that of the hydraulic type.
Even if the ejector plate reaches the forward limit, the inertial force remains, and the residual inertial force reduces the difference from the inertial force of the molded product. Difficult to drop.

In both hydraulic and electric ejector devices, the ejection speed of the ejector plate increases at a constant acceleration from the start of the stroke, and the projection speed becomes constant at the set speed. Next, in the case of the hydraulic type, when the forward limit is reached, the protrusion speed suddenly becomes zero from the set speed, and the ejector plate stops, but in the case of the electric type, inertia force remains, so the forward limit is reached. The protrusion speed cannot be suddenly set to zero when it reaches, and it is set so that it decelerates a little before the forward limit and reaches the forward limit and becomes zero. In the electric ejector device, if an erroneous setting is made, the component of the injection molding device will be overloaded with this inertial force component and will be mechanically damaged.

[0008] Therefore, the applicant of the present invention, the "prior application" of the present application
As an ejector device for an electric injection molding machine,
Even if the ejector plate is hit at the limit of forward movement like a hydraulic ejector device, an ejector device for an electric injection molding machine that can remove the molded product from the ejector pin without overloading the injection molding device is provided. It was provided (Japanese Patent Application No. 9-93208).

As shown in FIG. 8, the ejector rod 51 and the ejector rod plate 52 are provided with springs 53 as cushioning members. In FIG. 8, reference numeral 54 is a ball nut that converts the rotation transmitted by a servo motor (not shown) into a linear movement to the ball shaft screw 59 and transmits the linear movement. 55 is a support member 56 for rotatably supporting the ball nut 54.
It is a bearing that is 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.

In this way, the ejector rod plate 5
2 and the ejector rod 51, the spring 5 as an elastic member.
3 intervenes. 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
The pressure (preload) applied in advance to the spring 53 can be controlled by adjusting the tightening by.
Since the spring 53 is preloaded corresponding to the rated rush output,
When the ejector plate is projected, the spring 53 moves without bending, and the spring 53 absorbs the collision force (inertial force) generated at the time of a collision in the forward limit. At this time, if an overload of the rated rush output or more occurs, the spring 53 contracts by the amount of the overload, and the bolt 60 relatively moves in the backward direction, so that the overload can be absorbed.

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

[0012]

SUMMARY OF THE INVENTION It is possible to prevent an overload due to a collision of a drive device, for example, an ejector, at a protruding limit,
Moreover, it is an object of the present invention to make it possible to easily drop a molded product due to a collision.

[0013]

[Means for Solving the Problems] (1) In a drive unit of an injection molding machine equipped with a motion direction conversion mechanism for converting a rotational motion of a motor into a linear motion by a combination of a ball screw shaft and a ball nut, a linear motion direction In the case where, in the ball screw shaft or the ball nut, one of the positions is constrained and the other is configured to perform a linear motion, and the member performing the linear motion is hindered from the linear motion for some reason, By reversing the mutual relationship between the restraint and the linear motion, the overload on the ball screw or the ball nut is prevented from occurring. (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 with the ball screw. And a buffer member is provided for the support member that supports the axial load acting on the ball screw or ball nut. (3) A guide rod that slidably supports the ejector plate, a motor fixing plate fixed to the guide rod, and a ball nut supporting plate that supports a ball nut are provided. A buffer member was placed in between. (4) In the above (3), the buffer member is a spring. (5) In (4) above, the spring is assembled by compressing it with a preset amount of preload. (6) In the above (5), the spring is provided with an adjusting mechanism for adjusting the preload amount.

[0014]

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

In FIG. 1, reference numeral 1 denotes a movable platen, to the front end of which a movable mold (not shown) is attached. A fixed platen (not shown) is provided facing the movable platen 1 with respect to the movable platen 1. 2 is an ejector plate,
It is movable with respect to the movable platen 1. An ejector motor 3 has a stator 3a and a rotor 3b built in a motor casing. Reference numeral 4 denotes a rotation transmission 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 movement in the front-back direction. Reference numeral 6 is a conduction shaft of the rotation transmission unit 4.

Now, 7 is a hollow rotor shaft fixed inside the rotor 3b, and both ends of this rotor shaft 7 are bearings 8 and 9
Is rotatably mounted in the motor casing. Reference numeral 10 is a spline nut fixed to the hollow rotor shaft 7 with a bolt 28, and a spline shaft 11 provided at the end of the transmission shaft 6 is slidably engaged with the spline nut. Transmission shaft 6
Is composed of the spline shaft 11 and the ball screw shaft 12, and the ball screw shaft 12 is screwed into the ball nut 13 to convert the rotary motion into a linear motion.

The ball nut 13 is screwed onto the ball screw shaft 12 of the transmission shaft 6. One end (the 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. Reference numeral 17 denotes a guide rod that connects the movable platen 1 and the motor plate 18 to guide the lateral movement of the ejector plate 2. Therefore, the ejector plate 2 is interposed between the movable platen 1 and the motor plate 18, and is slidably supported by the guide rod 19 through the hole 2A.

A spring support bar 19 supports 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 the support bar plate 22 with a screw 23 via a ball nut support plate 21. Has been done. Therefore, the coil spring 20 as a cushioning member is fitted into the spring support bar 19, is sandwiched between the ball nut support plate 21 and the washer 24 on the side of the motor plate 18, and the preload adjustment nut provided outside the washer 24. It is held at 25 so that the preload can be adjusted. The ball nut 13 is fitted and inserted in the ball nut support plate 21, and the flange portion 13a of the ball nut 13 has a bolt 26.
It is stuck in. The preload adjusting nut 25 is screwed into a screw portion 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, spring support bar 19, motor plate 1
It is supported by 8. An encoder 27 as a rotation speed sensor is provided at the rear end of the rotor shaft 7 of the rotation transmitting section 4. The encoder 27 directly detects the rotation speed of the rotor 3b.

The ejector rod 16 at the front end of the ejector plate 2 is converted into forward and backward movement by the ball nut 13 when the ball screw shaft 12 is rotated. When the ejector plate 2 is moved forward, the ejector rod 16
To advance 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 integrated ball screw shaft 12 in front of it. 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 ball screw shaft 12 moves linearly to move the ejector plate 2 forward to move the ejector rod 16
Stick out. 5) In this operation, even if there is a collision at the ejecting limit of the ejector due to the preload applied to the coil spring 20 as a shock absorber, the shock absorbing action of the spring prevents the occurrence of overload on the ball nut and bearing. it can. 6) Further, when it is desired to shake off a small molded product due to a collision, the preload of this coil spring effectively acts, and the product falling property is improved.

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

The coil spring 20 is compressed by the distance a by the impact (see FIG. 3). As a result, the shock 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 movement and the linear movement is reversed even if a constraint force such as an impact force acts in the linear movement direction in the mechanism for converting the rotational movement into the linear movement. As a result, even if an ejector is overloaded, a force acts in a direction to cancel the ejector, the overload can be prevented, and the safety of the mechanical device is ensured. According to the invention of claim 2, due to the existence of the shock absorber, it is possible to prevent a load load on the ball nut or the ball screw shaft. An overload can be prevented by the cushioning member according to the invention of claim 3 and the cushioning effect by the spring of the invention of claim 4. According to the fifth aspect, the spring is compressed to apply the preload, and the preload can be adjusted according to the sixth aspect. Therefore, the preload amount can be converted according to the molding condition, and the overload prevention function can be finely controlled. .

[Brief description of drawings]

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

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

FIG. 3 is a view showing a state where the ejector rod collides with the state of FIG. 2 and is slightly retracted.

FIG. 4 is a sectional view taken along arrow A in FIG.

5 is a view on arrow B of FIG.

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

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

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

[Explanation of symbols]

1 Movable Platen 2 Ejector Plate 2A (For Guide Rod Insertion) Hole 3 Ejector Motor 3a Stator 3b Rotor 4 Rotation Transmission Unit 5 Motion Direction Converter 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 (5)

(57) [Claims] 1. A drive device of an injection molding machine comprising a motion direction conversion mechanism for converting a rotational motion of a motor into a linear motion by a combination of a ball screw shaft and a ball nut, wherein a ball screw shaft or a ball is used in the linear motion direction. Fix either one of the nuts through a cushioning member
Restrained with a toe and providing one of the above on the support plate,
The other is configured to perform a linear movement, the cushioning member,
When disposed between the fixed plate and the support plate
Both the preload is applied, if the member performing the linear movement hindered linear motion for some reason, the cushioning member
An overload prevention device for a drive unit in an injection molding machine, which is configured to prevent an overload from occurring on a ball screw or a ball nut by a cushioning action . 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 a screw screwed to the ball screw. A buffer member is provided on a fixed plate having a ball nut and supporting an axial load acting on the ball screw or the ball nut , and the buffer member supports the fixed plate and the fixed plate.
It is arranged between the plate and a preload,
Any one of the ball screw shaft or the ball nut
One is provided on the support plate, and an overload preventing device for a driving device in an injection molding machine is provided . 3. A guide rod for slidably supporting an ejector plate is provided, and said fixed rod is attached to said guide rod.
The ball nut is fixed to the support plate and the ball nut is supported on the support plate.
Overload prevention device of the drive unit in an injection molding machine according to claim 2, wherein the the. 4. The overload prevention device for a drive unit in an injection molding machine according to claim 2, wherein the buffer member is a spring. 5. An adjusting mechanism for adjusting a preload amount on a spring.
The injection molding machine according to claim 4, further comprising:
Drive device overload prevention device. That
Characterize.