JPH04129719A - Injection molding machine - Google Patents

Abstract

PURPOSE:To improve durability and reliability and permit pressure to be detected with a high degree accuracy by providing a load cell (pressure detector) between a ball screw and an injection driving stand in the ball screw mechanism for driving a screw forward and rearward. CONSTITUTION:A pressure is applied from a screw 2 through a screw coupling 3, a guide coupling 5, a ball nut 3n, a ball screw 3s, a stopper 19 and a thrust bearing 20 to an inner ring part 7i. On the other hand, since an outer ring part 6c is fixed to an injection driving stand 6 and its position is restricted to the axial direction, a strain is produced at an intermediate stress liable part 7m according to the pressure being applied and this strain is detected by the bridge using a strain gage 7s at the intermediate stress liable part 7m. The output of this bridge is not affected by a preload and the existence of the guide coupling 5, but in proportion to the pressure from the screw 2. In this case, since load cell 7 is provided between the ball screw 3s and the injection driving stand 6 for freely rotatably supporting this ball screw 3s, the load cell 7 is secured in the fixed position of the injection driving stand 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection molding machine equipped with a built-in pressure detector that detects the pressure applied to a screw.

[Conventional technology]

Conventionally, an injection molding machine in which a load cell, which is a pressure detector, is built into the screw drive mechanism and the pressure applied to the screw by the load cell can be detected is known, for example, from Japanese Patent Laid-Open No. 64-27921. .

FIG. 5 shows a simplified configuration of the main parts of the injection molding machine disclosed in the publication. The injection molding machine M is slidably supported by a plurality of guide shafts 51 and includes a guide joint 53 to which linear motion is transmitted from a ball screw mechanism 52.
and a screw coupling 54 that connects the rear end of the screw 55 and transmits rotational motion, and the screw coupling 54 has an angular ball bearing 59.
It is rotatably supported by a guide joint 53 via...

Further, a washer-type load cell (pressure detector) 61 consisting of an inner ring portion 62, an outer ring portion 63, and an intermediate strain-generating portion 64 is interposed between the guide joint 53 and the pole nut 57 of the ball screw mechanism 52.

As a result, if the pressure from the screw 55 is applied to the inner ring part 62 via the screw coupling 54, the angular ball bearing 59... and the guide joint 53, the outer ring part 63
Since the position is regulated by the pole nut 57, a strain that is correlated to the pressure is generated in the intermediate strain-generating portion 64.
Pressure is detected by a strain gauge attached to the same strain section 64.

[Problem to be solved by the invention]

However, in conventional injection molding machines such as this injection molding machine M, the load cell 61 is directly attached to the guide joint 53, which causes the following problems.

First, a connection cable CO shown by a phantom line in FIG. 1 is led out from the load cell attached to the guide joint 53 (indicated by reference numeral 5 in FIG. 1), and the connection cable Co is located near the injection drive base. It is connected to amplifier A located in
Since the guide joint 53 repeatedly advances and retreats to the position indicated by the imaginary line in the figure in each molding cycle, the degree of bending of the connection cable CO changes periodically accordingly. As a result, long-term use may cause mechanical fatigue in the connecting cable Co due to bending, which may lead to poor continuity or disconnection.
There are problems with durability and reliability. In addition, connection cable C
If o is disconnected, the injection pressure for closed loop control cannot be detected in the pressure control area during the injection process, which may cause serious malfunctions such as mold damage due to excessive injection pressure. Become.

Second, since the length of the connection cable CO needs to have a certain amount of leeway to accommodate the forward and backward movement of the guide joint 53, the length of the connection cable CO becomes unnecessarily long, and during inspection work, etc. It also becomes a nuisance.

Thirdly, the load cell 6
1 itself is affected by heat. The zero point and output size of the load cell 61 change due to the influence of temperature, and as a result, highly accurate pressure detection is no longer possible.

The present invention solves the problems that exist in the conventional technology, and aims to provide an injection molding machine that has improved durability and reliability, and is also capable of highly accurate pressure detection. It is.

[Means to solve the problem]

The present invention includes a ball screw mechanism 3 that moves the screw 2 in forward and backward directions, and a ball nut 3n of the ball screw mechanism 3.
is attached to a guide joint 5 that is supported by the guide part 4 so as to be freely forward and backward, and the screw 2 is supported by the guide joint 5, and the ball screw 3s of the ball screw mechanism 3 is rotatably supported by the fixed injection drive stand 6. When configuring the injection molding machine 1 supported, in particular, a pressure detector for detecting the pressure applied to the screw 2, for example, a washer-shaped pressure detector consisting of an outer ring part 7c, an inner ring part 71, and an intermediate straining part 7m is used. The rotor self is disposed between the ball screw 3s and the injection drive stand 6, and the ball screw 3s is supported so as to be axially displaceable with respect to the injection drive stand 6. In this case, the load cell 7 is configured such that the outer ring portion 7c is fixed to the injection drive stand 6 and the pressure of the ball screw 3S can be applied to the inner ring portion 71. Further, the outer ring portion 7C can be fixed to the injection drive base 6 by bolts 8 . . . or by sandwiching it between cover plates 9. Furthermore, the injection drive table 6 is provided with a notch 6p for positioning that fits into the outer ring portion 7c, and the rotor self is provided with a notch 7p for positioning that fits into the bearing (angular contact ball bearing) 10. This is desirable.

[For production]

According to the injection molding machine 1 according to the present invention, the pressure applied to the screw 2 is transmitted to the ball screw 3s via the guide joint 5 and the pole nut 3n of the ball screw mechanism 3, and the pressure applied to the ball screw 3S is transmitted to the load cell. 7 is attached to the inner ring portion 71 of No. 7. On the other hand, since the outer ring part 7c of the rotor self is fixed to the injection drive table 6 side, a strain corresponding to the pressure is generated in the intermediate strain generating part 7m of the rotor self, and the generated strain is transferred to the intermediate strain generating part 7m. Detected by an attached strain gauge. The output of this strain gauge is screw 2
proportional to the pressure applied to the

In this case, since the load cell 7 is disposed between the ball screw 3S and the injection drive stand 6 that rotatably supports the ball screw 3S, the load cell 7 is held at the fixed injection drive stand 6, that is, at a fixed position.

Therefore, the connection cord C led out from the rotor self is held in a fixed position without being affected by the repeated forward and backward movements of the guide joint 5 during the molding cycle, and its length is sufficient. Further, the load cell 7 is held by the injection drive stand 6 which is located at a position farther away than the guide joint 5 with respect to the heating tube which is the heat generation source, so that it is not affected by heat.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings.

First, in order to clarify the present invention, the overall schematic configuration of an injection molding machine will be described with reference to FIG. 1.

1 is an injection molding machine, and particularly shows a screw drive mechanism. The injection molding machine 1 includes an injection table 11 and an injection drive table 6 arranged at a distance behind the injection table 11. Between the injection table 11 and the injection drive table 6, there are a plurality of guide shafts 4S constituting the guide section 4.
・Construct. Further, a guide joint 5 is slidably loaded onto the guide shaft 4S. On the other hand, injection table 1
1 is equipped with a heating cylinder 12, a screw 2 is inserted into this heating cylinder 12, and the rear end of the screw 2 is connected to a screw coupling 13. The screw coupling 13 is rotatably supported inside the guide joint 5,
Rotary motion for metering is transmitted via an integrally mounted transmission gear 14.

On the other hand, 3 is a ball screw mechanism consisting of a ball screw 3S and a pole nut 3n, and the ball screw 3S is connected to an injection drive base 6.
is rotatably supported by the pole nut 3.
n is coupled to the guide joint 5. And ball screw 3S
Rotational motion is transmitted to the guide joint 5 through a transmission gear 15 integrally attached to its rear end, and thereby forward and backward motion for injection is transmitted to the guide joint 5.

Next, the configuration of the main parts will be explained with reference to FIGS. 1 to 3.

7 is a load cell (pressure detector). As shown in FIGS. 2 and 3, the rotor self has a relatively thick inner ring portion 7.
1, an outer ring portion 7c, and a relatively thin intermediate strain-inducing portion 7m.
Thus, it is integrally formed into a washer shape, and one end face is provided with a notch recess 7p for positioning. In addition, the intermediate strain part 7m
is equipped with a plurality of strain gauges 7s (multiple of 4). The strain gauges 7s are bridge-connected, and the connection cable C is led out through a guide groove 17 formed at a predetermined position of the outer ring portion 7c. By the way, a relative step in the axial direction is usually provided between the inner ring part 71 and the outer ring part 70 of the load cell 7. However, the load cell 7 of this embodiment does not have such a step (both end faces are formed into parallel surfaces by flat-cutting the entire surface to improve workability and parallelism).

On the other hand, according to the present invention, the rotor self is a ball screw 3s
and the injection drive table 6. The arrangement method is as follows.

First, a support hole 6s is provided in the center of the injection drive table 6, and a positioning notch 6p formed with a relatively large diameter is provided at the rear of the support hole 6s, and the funnel self is accommodated in this notch recess 6p. . As a result, the load cell 7 and the injection drive table 6 are accurately positioned by fitting together. Further, the external fitting portion 7c is fixed to the notch recess 6p by bolts 8 inserted into the mounting holes 7h. In this case, the fixing force does not affect the intermediate strain-generating portion 7m. On the other hand, a stopper 19 protruding radially outward is provided on the outer periphery of the ball screw 3S located within the support hole 6S. Further, a thrust bearing 20 is interposed between the rear surface of the stopper 19 and the front end surface of the inner ring portion 71 of the load cell 7, and the rear end surface of the inner ring portion 71 is screwed to the ball screw 3S via the angular ball bearing 10. It is held and fixed by a bearing nut 22. Note that the outer ring portion 10c of the angular contact ball bearing 10
is fitted into the notch recess 7p of the load cell 7 and positioned accurately, and the inner ring portion 10i is fitted into the bearing nut 2.
2. Therefore, when the bearing nut 22 is tightened, a preload is applied to the angular contact ball bearing 10. In this case, the preload is designed not to affect the intermediate strain-generating portion 7m that detects pressure.

As a result, even if the injection pressure changes, the linearity of the load and output will not change, and even if the bearing nut 22 becomes loose, the zero point will not change. Further, the front surface of the stopper 19 is held and fixed by a fixing plate 24 via a angular ball bearing 25.

On the other hand, the rotor self is covered by a cover plate 9 attached to the injection drive base 6. This cover plate 9 is formed integrally with a motor mounting plate to which a drive motor (not shown) is mounted. Note that the shape of the cover plate 9 is selected so that the inner ring part 71 of the rotor self and the outer ring part 10c of the angular contact ball bearing 10 are allowed to be displaced in the axial direction with respect to the injection drive table 6. Consideration is given to forming a predetermined gap between the ring portion 71 and the angular ball bearing 10.

Further, an amplifier A is installed near the injection drive table 6, and a connection cable C led out from the load cell 7 is connected to the amplifier A, and the amplifier A is connected to a central controller (not shown).

Next, a pressure detection function in the screw drive mechanism in the injection molding machine 1 will be explained.

First, the pressure (rearward pressing force) applied from the screw 2 is applied to the screw coupling 3, the guide joint 5, the ball nut 3n, and the ball screw 3s.

It is attached to the inner ring portion 71 via the stopper 19 and the thrust bearing 20. On the other hand, since the outer ring portion 6C is fixed to the injection drive base 6 and its position is regulated in the axial direction, the intermediate strain-generating portion 7m
A strain corresponding to the pressure occurs, and this strain occurs in the intermediate strain-generating portion 7.
It is detected by a bridge using strain gauges 7S... The output of the bridge is not affected by the preload and the presence of the guide joint 5, and is proportional to the pressure from the screw 2.

In this case, since the load cell 7 is attached to the injection drive stand 6, the distance between it and the amplifier A disposed nearby is small, and the length of the connection cable C can be short. Furthermore, since the injection drive table 6 is fixed, the degree of bending of the connection cable C does not change, and therefore bending fatigue does not occur. Furthermore, the rotor self is equipped with a heating cylinder 12 which is a heat generation source.
Since it can be completely separated from the point where it is not affected by the heat, it is possible to completely separate the rotor self (strain gauge 7s...
) are not affected by heat.

On the other hand, FIG. 4 shows a modified embodiment of the injection molding machine 1. In FIG. The modified embodiment differs in that when fixing the outer ring part 7C to the injection drive base 6, it is fixed by sandwiching it between cover plates 9 instead of being screwed. That is, the axial length of the notch recess 6p in the support hole 6s is selected to be the same as or slightly smaller than the thickness of the outer ring part 7c of the load cell 7, and the inner ring is placed on the surface of the cover plate 9 facing the inner ring part 71. A concave portion 9e is provided to allow displacement of the portion 71.

In the modified embodiment, since the load cell 7 is not provided with the mounting holes 7h, there is an advantage that the rotor self can be made smaller. Note that the other configurations are the same as in FIG. 1.

Therefore, the same parts in FIG. 4 as in FIG. 1 are designated by the same reference numerals to clarify the structure and omit detailed explanation thereof.

Although the embodiments have been described in detail above, the present invention is not limited to such embodiments, and the detailed configuration,
The shape, quantity, etc. can be arbitrarily changed without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, the injection molding machine according to the present invention has a load cell (pressure detector) disposed between the ball screw and the injection drive base in the ball screw mechanism that moves the screw in the forward and backward directions, and therefore has the following remarkable problems. It has a great effect.

■ Since the load cell is attached to the injection drive stand, which is the fixed side, there is no risk of disconnection of the connection cable due to bending fatigue, and improved durability and reliability can be achieved.

■ The length of the connection cable that connects the load cell and amplifier can be short enough, which contributes to cost reduction, and since it does not get in the way, it can contribute to improving the workability of inspection work, etc.

■ The load cell is located away from the heating tube, which is the source of heat, to a position where it is not affected by heat, making it possible to detect pressure with high precision.

[Brief explanation of the drawing]

Fig. 1 2 A side view including a cross section of the main parts of the injection molding machine according to the present invention, Fig. 2 2 A sectional side view of a load cell used in the injection molding machine, Fig. 3 2 A rear view of the load cell, Fig. 4 2 A side view including a cross section of a main part of an injection molding machine according to a modified embodiment of the present invention. FIG. 5: A principle cross-sectional side view of an injection molding machine according to a prior art. In the drawings, 1: Injection molding machine 2 Screw 3: Ball screw mechanism 3S two-ball screw 3n: Ball nut 4 Two-guide portion 5 Two-guide joint 6. Injection drive stand 6p: Notch recess 7: Load cell 71 inner ring 7C.
Outer ring part 7m, middle strain-generating part 7p, notch recess 8...: Bolt 9: Copper plate 10: Bearing Patent applicant Nissei Jushi Kogyo Co., Ltd., agent Patent attorney 1) Shigeru Figure 2 Figure 3 Figure 4 Figure p

Claims (1)

[Scope of Claims] [1] A ball screw mechanism is provided for moving the screw in forward and backward directions, a ball nut of the ball screw mechanism is attached to a guide joint that is supported by a guide portion so as to be freely forward and backward, and the screw is supported by the guide joint. In addition, in an injection molding machine in which a ball screw of a ball screw mechanism is rotatably supported by a fixed injection drive stand, a pressure detector for detecting the pressure applied to the screw is installed between the ball screw and the injection drive stand. An injection molding machine characterized in that the ball screw is disposed on the injection drive base and is supported so as to be movable in the axial direction with respect to the injection drive base. [2] As a pressure detector, a washer-shaped load cell consisting of an outer ring part, an inner ring part, and an intermediate strain-generating part is used, and the outer ring part is fixed to the injection drive table, and the pressure of the ball screw is applied to the inner ring part. The injection molding machine according to claim 1, characterized in that the injection molding machine is configured such that the injection molding machine can perform the injection molding process. [3] The injection molding machine according to claim 2, wherein the outer ring portion is fixed to the injection drive stand with bolts. [4] The injection molding machine according to claim 2, wherein the outer ring portion is sandwiched between cover plates and fixed to the injection drive table. [5] Claim 2, wherein the injection drive base has a positioning notch recess that fits into the outer ring of the load cell.
The injection molding machine described. [6] The injection molding machine according to claim 2, wherein the load cell has a notch for positioning that fits into the bearing.