JPH0735077B2 - Injection molding machine - Google Patents

Description

The present invention relates to an injection molding machine having a pressure detector for detecting 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 in a screw drive mechanism and the pressure applied to the screw by the load cell can be detected is known, for example, in Japanese Patent Laid-Open No. 64-27921. .

FIG. 5 shows a simplified configuration of the essential parts of the injection molding machine disclosed in this publication. The injection molding machine M has a plurality of guide shafts.
51 includes a guide joint 53 slidably supported by the ball screw mechanism 52 to which a linear motion is transmitted, and a screw coupling 54 that couples a rear end of a screw 55 and transmits a rotational motion, The screw coupling 54 is a guide joint via angular contact ball bearings 59 ...
It is rotatably supported by 53. Further, a washer-type load cell (pressure detector) 61 including an inner ring portion 62, an outer ring portion 63, and an intermediate strain generating portion 64 is provided with a guide joint 53 and a ball screw mechanism 52.
Is interposed between the ball nuts 57 in FIG.

As a result, if the pressure from the screw 55 is applied to the inner ring portion 2 via the screw coupling 54, the angular ball bearing 59 ... And the guide joint 53, the outer ring portion 63 becomes the ball nut 57.
Since the position is regulated at, the strain having a correlation with the pressure is generated in the intermediate strain generating portion 64, and the pressure is detected by the strain gauge attached to the strain generating portion 64.

[Problems to be Solved by the Invention]

However, the conventional injection molding machine including such an injection molding machine M has the following problems because the load cell 61 is directly attached to the guide joint 53.

First, a connection cable Co shown by an imaginary line in FIG. 1 is derived from the attached load cell having the guide joint 53 (indicated by reference numeral 5 in FIG. 1), and the connection cable Co is near the injection drive base. Although the guide joint 53 is repeatedly moved forward and backward to the position of the imaginary line in the figure in each molding cycle, the bending degree of the connection cable Co is periodically changed. Change. As a result, there is a problem in durability and reliability such that the connection cable Co may be mechanically fatigued due to bending due to long-term use, leading to poor conduction and disconnection. If the connection cable Co is broken, the injection pressure for closed-loop control cannot be detected in the pressure control area in the injection process, so that excessive injection pressure may cause damage to the mold, which is a serious problem. It may cause a failure.

Secondly, since the length of the connection cable Co needs to allow a certain amount of allowance in correspondence with the forward / backward movement of the guide joint 53, the length of the connection cable Co becomes unnecessarily long, and in the inspection work etc. Becomes an obstacle.

Thirdly, the load cell 61 itself is affected by heat because it is arranged at a position close to the heating cylinder (reference numeral 12 in FIG. 1) which is a heat source (about 400 ° C.). In the load cell 61, the zero point and the magnitude of the output change due to the influence of the temperature, which makes it impossible to detect the pressure with high accuracy.

The present invention has solved the problems existing in such conventional techniques, and an object thereof is to provide an injection molding machine capable of improving durability and reliability, and capable of performing highly accurate pressure detection. Is.

[Means for Solving the Problems]

The present invention includes a ball screw mechanism 3 for moving the screw 2 in the advancing / retreating direction, and the ball nut 3n of the ball screw mechanism 3 is used.
Is attached to a guide joint 5 that is supported by a guide portion 4 so as to be able to move back and forth, and the screw 2 is supported by the guide joint 5, and the fixed injection drive base 6 allows the ball screw 3s of the ball screw mechanism 3 to rotate freely. When constructing the injection molding machine 1 which is supported, especially the screw 2
Pressure detector for detecting the pressure applied to the outer ring
A washer-shaped load cell 7 composed of 7c, an inner ring portion 7i and an intermediate strain portion 7m is arranged between the ball screw 3s and the injection drive base 6, and the ball screw 3s can be axially displaced with respect to the injection drive base 6. It is characterized by supporting. in this case,
In the load cell 7, the outer ring portion 7c is fixed to the injection drive base 6 and the inner ring portion 7i is fixed to the ball screw 3s.
It is configured to be able to apply a pressure of 3s. Further, the outer ring portion 7c can be fixed to the injection drive table 6 by being sandwiched by the bolts 8 ... Or by the cover plate 9, and the inner ring portion can be sandwiched between the stopper provided on the ball screw and the bearing nut screwed to the ball screw. Can be fixed with. Furthermore, the injection drive base 6
It is desirable to provide a notch 6p for positioning that fits in the outer ring portion 7c, and a notch 7p for positioning that fits in the bearing (angular ball bearing) 10 in the load cell 7.

[Action]

According to the injection molding machine 1 of the present invention, the pressure applied to the screw 2 is transmitted to the ball screw 3s via the guide joint 5 and the ball nut 3n of the ball screw mechanism 3, and
The pressure applied to the ball screw 3s is the inner ring part of the load cell 7.
Granted to 7i. On the other hand, the outer ring portion 7c of the load cell 7
Is fixed to the injection drive base 6 side, strain corresponding to pressure is generated in the intermediate strain generating portion 7m of the load cell 7, and the generated strain is detected by a strain gauge attached to the intermediate strain generating portion 7m. . The output of this strain gauge is proportional to the pressure applied to the screw 2.

In this case, since the load cell 7 is disposed between the ball screw 3s and the injection drive base 6 that rotatably supports the ball screw 3s, the load cell 7 is fixed to the injection drive base 6, that is,
It is held in a fixed position. Therefore, the connection cord C led out from the load cell 7 is held in a fixed position without being affected by the reciprocating movement of the guide joint 5 which is repeated in the molding cycle, and the length is sufficient. Further, since the load cell 7 is held by the injection drive table 6 which is located at a position farther from the guide joint 5 with respect to the heating cylinder as the heat source, it is not affected by heat.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

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

Reference numeral 1 is an injection molding machine, and in particular, shows a screw drive mechanism. The injection molding machine 1 includes an injection table 11 and an injection drive table 6 which is arranged behind the injection table 11, and a plurality of guide shafts 4s forming a guide section 4 are installed between the injection table 11 and the injection drive table 6. . A guide joint 5 is slidably mounted on the guide shafts 4s. On the other hand, the injection table 11 is equipped with a heating cylinder 12, the screw 2 is inserted into the heating cylinder 12, and the rear end of the screw 2 is screw-coupled.
Combine to 13. Screw coupling 13 is a guide joint 5
Transmission gear that is rotatably supported inside and attached integrally
The rotary movement for weighing is transmitted via 14.

On the other hand, 3 is a ball screw mechanism composed of a ball screw 3s and a ball nut 3n. The ball screw 3s is rotatably supported by the injection drive base 6, and the ball nut 3n is coupled to the guide joint 5. Then, the rotational movement is transmitted to the ball screw 3s via a transmission gear 15 integrally attached to the rear end thereof, whereby the advancing / retreating movement for injection is transmitted to the guide joint 5.

Next, the configuration of the main part will be described with reference to FIGS.

Reference numeral 7 is a load cell (pressure detector). As shown in FIGS. 2 and 3, the load cell 7 has a relatively thick inner ring portion 7i.
The outer ring portion 7c and the intermediate straining portion 7m which is relatively thin are integrally formed in a washer shape, and a notch recess 7p for positioning is provided on one end face. Further, the intermediate strain generating portion 7m is provided with a plurality of (a multiple of 4) strain gauges 7s .... Strain gauge 7s
Are bridge-connected, and the connection cable C is led out to the outside 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 portion 7i and the outer ring portion 7c of the load cell 7. However, in the load cell 7 of the present embodiment, both end surfaces are formed into parallel surfaces by cutting the entire surface without providing such a step, thereby improving workability and parallelism.

On the other hand, the load cell 7 is disposed between the ball screw 3s and the injection drive base 6 according to the present invention. The arrangement method is as follows.

First, a supporting hole 6s is provided in the center of the injection drive table 6, and a positioning notch 6p having a relatively large diameter is provided at the rear of the supporting hole 6s. The load cell 7 is provided in the notch 6p.
To house. As a result, the load cell 7 and the injection drive table 6 are accurately positioned by fitting. Further, the outer fitting portion 7c is fixed to the notch recess 6p by a bolt 8 inserted into the mounting hole 7h. In this case, the fixing force does not affect the intermediate flexure portion 7m. On the other hand, a stopper 19 protruding radially outward is provided on the outer peripheral portion of the ball screw 3s located in 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 7i of the load cell 7, and the rear end surface of the inner ring portion 7i is screwed to the ball screw 3s via the angular ball bearing 10. It is held and fixed by the bearing nut 22. The outer ring portion 10 of the angular contact ball bearing 10
c is fitted into the cutout recess 7p of the load cell 7 and positioned accurately, and the inner ring portion 10i abuts on the bearing nut 22. Therefore, when the bearing nut 22 is tightened, the angular ball bearing 10 is preloaded. In this case, the preload should not affect the intermediate strain generating portion 7m that detects the pressure. As a result, even if the injection pressure changes, the linearity of load and output does not change.
The zero point does not change even if loosening occurs. In addition, the front surface of the stopper 19 is fixed to the angular contact ball bearing 24.
Hold through 25 and fix. On the other hand, the load cell 7 is covered with a cover plate 9 attached to the injection drive base 6. The cover plate 9 is formed integrally with a motor mounting plate for mounting a drive motor (not shown). The shape of the cover plate 9 is selected such that the inner ring portion 7i of the load cell 7 and the outer ring portion 10c of the angular ball bearing 10 are allowed to be displaced in the axial direction with respect to the injection drive base 6, and the inner shape of the cover plate 9 Consideration should be given to forming a predetermined gap between the ring portion 7i and the angular ball bearing 10. Further, an amplifier A is attached near the injection drive table 6, a connection cable C derived from the load cell 7 is connected to the amplifier A, and the amplifier A is connected to a central controller (not shown).

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

First, the pressure (backward pressure) applied from the screw 2 is applied to the inner ring portion 7i via the screw coupling 13, the guide joint 5, the ball nut 3n, the ball screw 3s, the stopper 19, and the thrust bearing 20. It On the other hand, since the outer ring portion 7c is fixed to the injection drive table 6 and is axially regulated in position, a strain corresponding to the pressure is generated in the intermediate strain generating portion 7m,
This strain is detected by the bridge using the strain gauges 7s ... Of the intermediate strain portion 7m. 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 table 6, the distance between the load cell 7 and the amplifier A arranged in the vicinity thereof is small and the length of the connection cable C is short. Further, 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. Further, since the load cell 7 can be completely separated from the heating cylinder 12 which is a heat source to a position where it is not affected by heat, the load cell 7 (strain gauge 7s ...) Is not affected by heat.

On the other hand, FIG. 4 shows a modified embodiment of the injection molding machine 1. The modified embodiment is different in that the outer ring portion 7c is fixed to the injection drive table 6 by being sandwiched and fixed by the cover plate 9 instead of screwing. That is, the axial length of the cutout recess 6p in the support hole 6s is set to the outer ring portion 7c of the load cell 7.
The thickness is selected to be the same as or slightly smaller than the thickness of the inner ring portion 7i, and a concave portion 9e that allows displacement of the inner ring portion 7i is provided on the surface of the cover plate 9 facing the inner ring portion 7i. In the modified embodiment, since the load cell 7 is not provided with the mounting holes 7h, there is an advantage that the load cell 7 can be downsized. The rest of the configuration is the same as in FIG. Therefore, the same parts in FIG. 4 as those in FIG. 1 are designated by the same reference numerals to clarify the configuration thereof, and detailed description thereof will be omitted.

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 scope of the present invention.

〔The invention's effect〕

The injection molding machine according to the present invention is provided with a pressure detector using a washer-shaped load cell including an outer ring portion, an inner ring portion, and an intermediate strain portion, and the pressure detector is disposed between the ball screw and the injection drive base to provide Since the ring part is fixed to the injection drive base and the inner ring part is fixed to the ball screw respectively so that the ball screw pressure can be applied to the inner ring part, and the ball screw is supported so as to be axially displaceable with respect to the injection drive base, It has a remarkable effect.

Since the load cell is attached to the injection drive base on the fixed side, there is no fear of disconnection due to bending fatigue of the connection cable, and durability and reliability can be improved.

Since the length of the connecting cable connecting the load cell and the amplifier is short, it is possible to contribute to cost reduction as well as to improve workability such as inspection work because it is not an obstacle.

Since the load cell is separated from the heating cylinder, which is a heat source, to a position where it is not affected by heat, it is possible to detect pressure with high accuracy.

The load cell can be securely fixed, and since the preload at the time of fixing does not affect the intermediate strain section, the linearity of the load and output does not change even if the injection pressure changes, improving the accuracy of pressure detection. it can.

Both ends of the load cell used can be formed into parallel surfaces by cutting the entire surface, improving workability and parallelism,
The cost and the flattening of the load cell can be achieved, and the accuracy and quality can be improved.

[Brief description of drawings]

1 is a side view including a cross section of an essential part of an injection molding machine according to the present invention, FIG. 2 is a sectional side view of a load cell used in the injection molding machine, FIG. 3 is a rear view of the load cell, and FIG. FIG. 5 is a side view including a cross section of an essential part of an injection molding machine according to a modified embodiment of the present invention, and FIG. 5: a side sectional view showing the principle of the injection molding machine according to the prior art. In the drawing, 1: injection molding machine, 2: screw 3: ball screw mechanism, 3s: ball screw 3n: ball nut, 4: guide part 5: guide joint, 6: injection drive base 6p: notch recess, 7: load cell 7i: Inner ring part, 7c: Outer ring part 7m: Intermediate flexure part, 7p: Notch recess 8 ...: Bolt, 9: Cover plate 10: Bearing

Claims (6)

[Claims] 1. A ball screw mechanism for moving a screw in an advancing / retreating direction, 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 able to advance and retreat, and the screw is supported and fixed by the guide joint. In an injection molding machine in which a ball screw of a ball screw mechanism is rotatably supported by an injection drive table, a pressure detector using a washer type load cell including an outer ring portion, an inner ring portion and an intermediate strain portion is By arranging between the ball screw and the injection drive table, the outer ring portion is fixed to the injection drive table and the inner ring portion is fixed to the ball screw, and the ball screw pressure is applied to the inner ring portion. An injection molding machine, which supports an injection drive base so as to be displaceable in the axial direction. 2. The injection molding machine according to claim 1, wherein the outer ring portion is fixed to the injection drive table by bolts. 3. The injection molding machine according to claim 1, wherein the outer ring portion is sandwiched by cover plates and fixed to the injection drive table. 4. The injection molding machine according to claim 1, wherein the inner ring portion is fixed by being sandwiched between a stopper provided on the ball screw and a bearing nut screwed on the ball screw. 5. The injection molding machine according to claim 1, wherein the injection drive table has a notch for positioning which is fitted to the outer ring portion of the load cell. 6. The injection molding machine according to claim 1, wherein the load cell has a notch recess for positioning that fits into the bearing.