JP3976691B2 - Injection device for electric injection molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection apparatus for an electric injection molding machine including a plurality of ball screw mechanisms for moving a pusher plate.
[0002]
[Prior art]
An example of this type of injection apparatus will be described with reference to FIG. 5. A front plate 2 that holds the heating cylinder 1 and a rear plate 4 that is connected between the front plate 2 by tie bars 3 (usually four). And a pusher plate 6 which is disposed between the front plate 2 and the rear plate 4 and holds the rear end of the screw 5 (one), and is installed so as to connect between the pusher plate 6 and the rear plate 4. A ball screw mechanism 7 (two in this example) driven by an injection servo motor is provided.
The screw 5 is arranged at the center of the injection device, and the ball screw mechanism 7 is arranged at symmetrical positions (horizontal direction left and right) around the axis of the screw 5. A ball screw nut 8 is fixed to the pusher plate 6, a ball screw shaft 9 is rotatably supported on the rear plate 4, and the rotational force of the injection servo motor is transmitted to the ball screw shaft 9 via a pulley 11. . In FIG. 5, reference numeral 12 denotes a pulley that is rotated by a measuring servo motor (not shown) to rotate the screw 5.
[0003]
In this injection device, when the ball screw shaft 9 is rotated at the time of injection to move the pusher plate 6 forward, and the shooting power is given to the screw 5, the pusher plate 6 is moved on both sides (location where the ball screw nut 8 is fixed). In FIG. 5, a forward shooting force F1 is received, and a reaction force F2 from the screw 5 is received at the center, whereby the pusher plate 6 is deflected.
As shown in FIG. 6, the ball screw nut 8 is accommodated in the holding portion 13 of the pusher plate 6 and fixed by the bolt 14, and the receiving surface 13 a of the holding portion 13 is in surface contact with the front end surface 8 a of the ball screw nut 8. In addition, the receiving surface 13a receives the radiation output F1 from the end surface 8a. In FIG. 6, A is the axis of the screw.
[0004]
At the time of injection, when the pusher plate 6 is deflected by the output F1 and the reaction force F2, both sides of the pusher plate 6 are inclined forward as shown in FIG. The ball screw nut 8 is inclined by the inclination of the pusher plate 6 (angle α with respect to the axis A of the screw 5), while the ball screw shaft 9 is originally supported in parallel with the axis A of the screw 5. Accordingly, as the ball screw nut 8 is inclined, a large eccentric load (moment load) is applied to the ball screw mechanism 7, and when the ball screw mechanism 7 is driven in this state, the ball is twisted inside the mechanism. The life of the ball screw mechanism 7 is significantly reduced.
[0005]
The injection device shown in FIG. 8 is of a type in which a ball screw nut 8 is fixed to the front plate 2 and a ball screw shaft 9 is rotatably supported on the pusher plate 6. Have. That is, at the time of injection, the front plate 2 is subjected to the radiation force F1 and its reaction force F2, causing the front plate 2 to bend, both sides of the front plate 2 are inclined rearward, and the ball screw nut 8 is simultaneously inclined. As a result, a large eccentric load (moment load) is applied to the ball screw mechanism 7 as described above. In the injection device shown in FIG. 5, the rear plate 4 is installed to receive the reaction force from the ball screw mechanism 7, and the front plate 2 and the rear plate 4 are connected by the tie bar 3. In the case of the device, it is not necessary to install the rear plate 4 and therefore the tie bar 3 is also unnecessary. Instead, generally, a guide bar for guiding the pusher plate 6 in the axial direction of the screw 5 is separately installed.
[0006]
An electric injection molding machine provided with a plurality of ball screw mechanisms for moving the pusher plate is described in, for example, Patent Documents 1 to 3 below.
[0007]
[Patent Document 1]
Japanese Utility Model Publication No. 7-21295 [Patent Document 2]
JP 63-77721 A [Patent Document 3]
Japanese Patent Laid-Open No. 2000-248706
To reduce the life of the ball screw mechanism based on the deflection of the pusher plate, etc., conventionally, a method has been adopted in which the deflection of the pusher plate or the like is increased (specifically, the thickness of the plate is increased) to reduce the deflection. However, the increase in the size of the injection apparatus has a problem that the cost is increased and the installation space is increased.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned problems of the prior art, and without reducing the size of the injection device, the inclination of the ball screw nut based on the deflection of the pusher plate or the like is suppressed to reduce the life of the ball screw mechanism. The purpose is to prevent.
[0010]
[Means for Solving the Problems]
The present invention (Claim 1) includes a front plate for holding a heating cylinder, a rear plate connected by a tie bar between the front plate, and a rear end of a screw disposed between the front plate and the rear plate. A pusher plate that is linearly movable along the axis of the screw, and a plurality of ball screw mechanisms that are driven by an injection servo motor to move the pusher plate, the ball screw mechanism Injection of an electric injection molding machine that is arranged around the screw, a ball screw nut is fixed to the pusher plate, and a ball screw shaft is rotated by the injection servo motor to move the pusher plate. In the apparatus, the pusher plate is brought into surface contact with the end face of the ball screw nut to shoot. Is installed receiving plate for receiving the force, the outer peripheral portion is fixed to said pusher plate, further, the receiving the plate stepped portion is formed in the axial end of the screw, the end face of the ball screw nut in the stepped portion A gap is formed between the two. In this case, the ball screw shaft is generally supported by the rear plate.
In the present invention (including claim 2), the axis side of the screw means a position close to the axis side of the screw as viewed from the central axis of the ball screw nut.
[0011]
At the time of injection, the ball screw nut is inclined according to the deflection of the pusher plate. By adopting the above-described configuration, at the same time, the direction that cancels the inclination based on the deflection of the pusher plate (the direction in which the rear side of the ball screw nut approaches the axis of the screw) ) To the pusher plate. Thereby, the magnitude | size of the inclination of a ball screw nut is suppressed compared with the past.
The ball screw nut needs to be inclined in the direction with respect to the pusher plate at the time of injection. Therefore, when the holding part for accommodating the ball screw nut is formed in the pusher plate, the ball screw nut needs to be accommodated in the holding part so as to be elastically tiltable in the direction. This is because, for example, within the range of a predetermined distance from the rear end of the ball screw nut to the front side (for example, ½ or more of the length of the ball screw nut), at least the outer periphery of the ball screw nut This is easily achieved depending on whether the axial region is not accommodated in the holding portion or whether a gap is provided between the holding portion and the holding portion. When the shooting power is released, the ball screw nut returns to its original position elastically.
[0012]
The present invention (Claim 2) includes a front plate that holds the heating cylinder, a pusher plate that holds the rear end of the screw and is linearly movable along the axis of the screw, and an injection servo motor. A plurality of ball screw mechanisms that are driven to move the pusher plate, the ball screw mechanisms are arranged around the screw, a ball screw nut is fixed to the front plate, and a ball screw shaft is driven by the injection servo motor; In the injection device of the electric injection molding machine in which the pusher plate is moved by rotating, a receiving plate for receiving a radiant output in contact with the end surface of the ball screw nut is installed on the front plate. The outer peripheral portion is fixed to the front plate, and the receiving plate Is stepped portion formed on the axial side of the-menu, characterized in that a gap is formed between the end face of the ball screw nut in the stepped portion. In this case, the ball screw shaft is pivotally supported by the pusher plate.
The operation of this configuration is the same as described above, and the point is that the ball screw nut needs to be inclined in the above direction with respect to the front plate at the time of injection.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an injection apparatus according to the present invention will be described with reference to FIGS. In these examples, the present invention is applied to an injection apparatus of the type shown in FIG.
In the injection apparatus shown in FIG. 1, a holding portion 21 having a cylindrical inner surface is formed on the pusher plate 6, and the front side thereof is closed by a receiving plate 22. The holding portion 21 accommodates the ball screw nut 8 and supports the outer periphery of the ball screw nut 8 in close contact from the front side end portion to the rear side over a predetermined distance, and a gap 23 is provided between the rear side and the outer periphery.
[0014]
As shown in FIG. 2, the receiving plate 22 has a hole 24 through which the ball screw shaft 9 is passed at the center, and a receiving portion 25 that receives the radiant output from the ball screw nut 8 is formed around the hole 24. Further, a flange portion 26 for attaching to the pusher plate 6 is formed around the periphery. The receiving portion 25 is a ring-shaped portion having an outer diameter substantially the same as the outer diameter of the ball screw nut 8 and protrudes a predetermined distance from the rear side and is fitted into the front side of the holding portion 21. On the screw side of the receiving portion 25 (hereinafter, referred to as the axis A side), a step portion 25a that is retracted to the front side (the degree of protrusion is one step lower) is formed, and in this step portion 25a, the front side of the ball screw nut 8 is formed. A gap 27 is formed between the end surface 8a and the surface of the portion excluding the step portion 25a facing the rear side comes into surface contact with the end surface 8a of the ball screw nut 8 as a receiving surface 25b. The thickness in the front-rear direction of the step portion 25a is thinner than that of the receiving surface 25b by the amount corresponding to the step.
[0015]
In the receiving plate 22, the line 25 c at the boundary of the step portion 25 a is installed so as to be perpendicular (vertical direction) to the straight line connecting the axis A and the central axis B of the ball screw nut 8 as shown in FIG. 2. It is desirable.
Bolt holes 30 and 28 are respectively formed in the receiving portion 25 and the flange portion 26, the receiving plate 22 is fixed to the pusher plate 6 by bolts 29, and the ball screw nut 8 is fixed to the receiving plate 22 by bolts 31. In this example, the bolt hole 30 is not formed in the step portion 25a, but it may be formed and bolted at this portion.
[0016]
In this injection apparatus, when the ball screw shaft 9 is rotationally driven by an injection servo motor (not shown), the pusher plate 6 is moved forward, and an injection output is applied to the screw, as described with reference to FIG. Receives a forward projecting force F1 on both sides, and receives a reaction force F2 from the screw at the center, which causes the pusher plate 6 to bend and the ball screw nut 8 to be inclined at the same time.
In the case of the present invention, since the receiving plate 22 receives the radiant power of the ball screw nut 8, the receiving plate 22 bends in such a manner that the center protrudes to the front side as shown in FIG. The step 25a is formed in the receiving portion 25 and the thickness of the receiving plate 22 is reduced at that portion, which contributes to the deflection of the receiving plate 22.
[0017]
If the receiving portion 25 of the receiving plate 22 is not formed with the stepped portion 25a and all the surfaces facing the rear side of the receiving portion 25 are in surface contact with the end surface 8a of the ball screw nut 8 as a receiving surface, the ball screw The nut 8 has an inclination similar to that of the conventional device, but a step portion 25a is formed in the receiving portion 25, and a gap 27 is formed between the end surface 8a of the ball screw nut 8 and the receiving portion 25 on the axis A side. Therefore, the end surface 8 a of the ball screw nut 8 pressed against the receiving portion 25 enters the gap 27. As a result, the ball screw nut 8 is inclined with respect to the pusher plate 6 in a direction in which the rear side approaches the axis A, that is, in a direction to cancel the inclination based on the deflection of the pusher plate 6. Therefore, the inclination angle β of the ball screw nut 8 is smaller than the conventional inclination angle α.
In the test conducted by the applicant, the projecting power of 75 tons on one side and the inclination angle α of the ball screw nut in the conventional apparatus was 0.025 degrees, but when the present invention is applied, the inclination angle β is 0. Improved to 01 degree.
[0018]
In the receiving plate 22, the step portion 25a (or the gap 27) is formed on the axis A side of the screw. The axis A side is the axis A when viewed from the central axis B of the ball screw nut 8 as described above. It means a place that is close to the side. When the width W of the gap 27 (see FIG. 2) is large, the amount of entry into the gap 27 of the end face 8aS of the ball screw nut 8 is large, and the inclination of the ball screw nut 8 with respect to the pusher plate 6 increases, but the receiving plate 22 As a result, the ball screw nut 8 and the receiving plate 22 are damaged, and the inclination becomes small when the width W of the gap 27 is small. Taking these points into consideration, the width W of the gap 27 may be set as appropriate.
In addition, the receiving plate 22 needs to bend upon receiving a radiation output from the ball screw nut 8. It is not uncommon to use structural steel or alloy steel that can be used normally, and extremely thick steel. However, in order to ensure a certain degree of deflection, at least from the pusher plate 6 Low rigidity.
[0019]
In the injection apparatus shown in FIG. 4, the holding portion 21 is not formed on the pusher plate 6, and the receiving plate 22 is fixed to the rear surface of the pusher plate 6. The outer periphery of the receiving plate 22 is fixed around the hole 32 formed in the pusher plate 6 by bolts 29, and the ball screw nut 8 is fixed to the receiving plate 22 by the nut 31. Also in this example, the step portion 25a of the receiving portion 25 of the receiving plate 22 is formed on the axis A side, and a gap 27 is formed between the step portion 25a and the end surface 8a on the front side of the ball screw nut 8, and the receiving portion The surface of the portion excluding the 25 step portions 25a facing the rear side comes into surface contact with the end surface 8a of the ball screw nut 8 as a receiving surface 25b.
The hole 32 allows the ball screw shaft 9 to pass and allows the receiving plate 22 to bend at the time of injection (bends in such a way that the center projects to the front side). For this purpose, the diameter of the hole 32 needs to be equal to or greater than the distance R from the center of the plate 22 to the step portion 25a. The effect of the receiving plate 22 in this injection device is the same as that of the example of FIG.
[0020]
In the above example, the pusher plate type push-out device that pushes out the pusher plate by two ball screw mechanisms has been described. However, the present invention applies to an pusher device that uses a larger number (for example, four) of ball screw mechanisms. Applicable to. Further, the present invention can be similarly applied to an extrusion apparatus of the type shown in FIG.
[0021]
【The invention's effect】
According to the present invention, it is possible to suppress the inclination of the ball screw nut based on the deflection of the pusher plate or the like without increasing the size of the injection device, and to prevent the life of the ball screw mechanism from being reduced.
[Brief description of the drawings]
FIG. 1 is a plan sectional view of an essential part of an injection apparatus according to the present invention.
FIG. 2 is a side view of the receiving plate.
FIG. 3 is a plan sectional view for explaining an inclined state of a ball screw nut at the time of injection.
FIG. 4 is a plan cross-sectional view of the main part of another injection device according to the present invention.
FIG. 5 is a plan sectional view of a conventional injection apparatus.
FIG. 6 is a plan sectional view of an essential part thereof.
FIG. 7 is a cross-sectional plan view illustrating an inclined state of a ball screw nut at the time of injection in a conventional injection device.
FIG. 8 is a cross-sectional plan view of another conventional injection apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heating cylinder 2 Front plate 3 Tie bar 4 Rear plate 5 Screw 6 Pusher plate 7 Ball screw mechanism 8 Ball screw nut 8a End surface on the front side of the ball screw nut 9 Ball screw shaft 21 Holding part 22 Receiving plate 25 Receiving part 25a Step part 25b Receiving surface 26 Flange 27 Clearance

Claims (2)

A front plate that holds the heating cylinder, a rear plate that is connected to the front plate by a tie bar, and a rear end that is disposed between the front plate and the rear plate to hold the rear end of the screw. A pusher plate that is linearly movable along a plurality of ball screw mechanisms that are driven by an injection servo motor to move the pusher plate, and the ball screw mechanism is disposed around the screw, In an injection device of an electric injection molding machine, wherein a screw nut is fixed to the pusher plate, and a ball screw shaft is rotated by the injection servo motor to move the pusher plate, the ball on the pusher plate Receiving plate that receives surface output in contact with the end face of the screw nut There is installed, the outer peripheral portion is fixed to said pusher plate, further, the receiving the plate stepped portion is formed in the axial end of the screw, the gap between the end face of the ball screw nut in the stepped portion An injection device for an electric injection molding machine, characterized in that is formed. A front plate that holds the heating cylinder, a pusher plate that holds the rear end of the screw and is linearly movable along the axis of the screw, and is driven by an injection servo motor to move the pusher plate. Provided with a plurality of ball screw mechanisms, the ball screw mechanism is disposed around the screw, a ball screw nut is fixed to the front plate, and the ball screw shaft is rotated by the injection servo motor to move the pusher plate In the injection device of the electric injection molding machine configured to perform, a receiving plate for receiving a radiant output in contact with the end surface of the ball screw nut is installed on the front plate, and an outer peripheral portion of the receiving plate is disposed on the front plate. fixed, further stepped portion on the receiving plate to the axis side of the screw Made is an injection apparatus for an electric injection molding machine, wherein a gap is formed between the end face of the ball screw nut in the stepped portion.

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