JP2508060Y2 - Injection device with washer-type load cell - Google Patents

Description

[Detailed description of the device]

The present invention relates to an injection device equipped with a washer-type load cell for measuring pressure for measuring injection pressure and screw back pressure.

[Prior art]

An injection device for measuring the injection pressure, the screw back pressure, etc. by detecting the strain caused by the backward force acting on the screw at the time of measuring the molding material, the reaction force acting on the screw at the time of injection, and the like, is disclosed in JP-A-62-264924. It is known from JP-A-62-97818 and the like. The former connects a screw and a bracket that moves in the axial direction by an electric motor for injection through a load cell, and detects the resultant force of the backward force due to screw weighing and the backward force by the electric motor for injection by the load cell and However, the structure of the load cell and the specific related structure of the screw and the bracket are not disclosed. In such an injection device, since the injection pressure is transmitted to the screw through the load cell and the injection pressure is extremely strong, an excessive load is applied to the load cell at each injection, and no special measures are taken there. There is a problem that fatigue fracture occurs with a very small number of injections. In the latter, the strain gauge is interposed between the rear step of the bearing retainer in the pressure plate that supports the screw shaft and the internal partition that receives the rear step, and The strain gauge is used to detect the holding pressure and back pressure. The problem in this case is that the strain of the bearing retainer is detected electrically, so that the strain differs depending on the metal material and structure that form the bearing retainer. Since the amount is limited, it is difficult to obtain a large output, and the detection efficiency is low, so high-precision measurement cannot be expected. The improvement of strain detection accuracy is improved by adopting a load cell. As a conventional washer-type load cell, as shown in FIG. 4, strain gauges 2, 2 are attached to the inner and outer surfaces of an annular main body 1 having a drum-shaped cross section, and the strain gauges 2, 2 are used as an outer cover 3. Some are covered by the inner cover 4. In this washer-type load cell, a flange 5 for attaching both covers 3 and 4 is integrally formed on one end side of the annular body 1, and the openings of the annular body 1 and the covers 3 and 4 are closed by a diaphragm 6. is there. Such a washer-type load cell is arranged between members that are relatively movable with both end faces of the annular body 1 as action surfaces, and the strain is measured by measuring the compressive strain generated by the external force acting on both end faces. As a change in resistance in 2 and 2,
This change is detected electrically.

[Problems to be solved by the device]

In this conventional washer-type load cell, since the strain gauges 2, 2 are attached to the inner and outer surfaces of the ring-shaped body 1, the width W of the ring-shaped body 1 is reduced to reduce the distance between the working surface and the strain gauges 2, 2. There is a limit to how short it can be made, and it requires a flange 5 to attach the covers 3 and 4, which makes the structure complicated and large, and the strain gauge is difficult to attach because the attachment surface is a curved surface. Has many challenges. Therefore, it was extremely difficult to incorporate such a washer type load cell into the rear structure of the screw of the injection device for the purpose of measuring the injection pressure and the screw back pressure. It is also possible to install a load cell mounting space in the rear structure, but since the inner diameter of the load cell is formed large due to the interposition of the inner cover, the working surface will be located away from the screw axis. The detection accuracy is inferior compared to the case where the detection is performed by moving the surface closer to the axis.
Since the compression strain is measured, it is difficult to obtain a large output. As a result, in order to measure injection pressure, screw back pressure, etc. with high accuracy by using a washer-type load cell, not only the washer-type load cell was improved, but also the mounting position of the washer-type load cell in the injection device was devised. is required. Therefore, as a result of repeated research by the present inventors, the problem of the washer-type load cell is already known from Japanese Utility Model Laid-Open No. 63-63733, but the thick outer ring portion and inner ring portion are not known. Washer-type load cell consisting of a triple annular body having a strain-flexing portion of a required thickness integrally formed between both ring portions with the opposite ends of the acting surface as a working surface, and a strain gauge attached to one side surface of the strain-generating portion. We have found that it can be solved by adopting. Therefore, an object of the present invention is to provide an injection device capable of highly accurate pressure measurement by a new combination of the washer-type load cell having the triple annular body and a bearing device.

[Means for Solving the Problems]

According to the invention for the above-mentioned purpose, a space for accommodating a washer-type load cell is provided at the rear part of a bearing device in a movable body that rotatably supports a screw in a heating cylinder, and the washer-type load cell has a thick outer ring part and an inner part. Consisting of a triple annular body having a strain-flexing portion of a required thickness integrally formed between both ring portions with the opposite ends of the ring portion acting as a working surface, and a strain gauge attached to one side surface of the strain-generating portion, The washer-type load cell is installed in the space by contacting the inner ring portion with the bearing portion of the bearing device, respectively, on the inner step portion formed with the outer ring portion inside the movable body.

[Action]

In the above configuration, in material measurement, the material resin is melted by the rotation of the screw and accumulated in front of the screw,
When the screw retracts accordingly, the retracting force (back pressure) is directly transmitted from the bearing portion of the bearing device to the inner ring portion of the washer-type load cell, and the strain generating portion between the screw ring and the outer ring portion is deformed. Also, when the measured material resin is pressed and injected by the screw that moves forward with the movable body, the reaction force at this time is directly transmitted from the bearing part to the inner ring part, and the strain between the outer ring part and The part is deformed. A resistance change occurs in the strain gauge according to the amount of deformation of the strain generating portion, and this is electrically detected as the amount of strain, and is measured as the injection output and the screw back pressure.

【Example】

1 and 2 show an example of a washer-type load cell that can be adopted in the present invention, with lead wires omitted.
The washer-type load cell 10 includes a thick outer ring portion 11 and an inner ring portion 12 with opposite end faces alternately positioned outwardly, and a flexure portion having a required thickness integrally formed between the both ring portions. The main body is a triple ring body formed from 13 and. Both sides of the strain-flexing portion 13 are formed into annular grooves 14 and 15, the surface of the strain-flexing portion 13 facing the one annular groove 14 is flat, and the surface facing the other annular groove 15 is a concentration of stress in the connecting portion. In order to avoid this, it is formed in an arc shape. In the annular groove 14, four strain gauges 16, 16 of the same length are located at equal intervals by being attached to the surface of the strain-flexing portion 13, thereby forming a known Wheatstone bridge circuit. There is. The number of strain gauges 16 is not limited to four, and a multiple of that number is provided to form multiple sets of Wheatstone bridge circuits, and the average value of the outputs from each bridge is taken to reduce the measurement error. You can also Reference numeral 17 is a diaphragm that closes the opening of the annular groove 14. FIG. 3 shows an embodiment of the injection device of the present invention equipped with the above washer type load cell. In the figure, 20 is a screw in the heating cylinder 21, 22 is a member that connects the screw 20 and the rotary shaft 23, and is rotatably supported by a bearing device 26 inside the movable body 25 that moves forward and backward with the tie bar 24 as a guide. It is provided. This bearing device 26 is configured by housing a thrust bearing 27 that supports the rear portion of the connecting member 22 and a radial bearing 28 that supports the front portion of the connecting member 22 in a bearing support tube 29, and the bearing support tube 29 is a movable body. It is inserted in the hole formed in 25 and fixedly attached to the inside of the movable body 25. Further, an inner step portion 25a located rearward of the bearing device 26 is formed in the hole of the movable body 25, and the washer-type load cell 10 is housed between the inner step portion 25a and the bearing device 26. It has a space of 25b. Before inserting the bearing device 26 into the space 25b, the washer-type load cell 10 is inserted with the working end of the outer ring portion 11 as the inner side, and by the subsequent insertion of the bearing device 26, the working end of the outer ring portion 11 becomes It comes into contact with the inner stepped portion 25a, and the working end of the inner ring portion 12 comes into contact with the end surface of the thrust ring 27 at the rear portion of the bearing device 26. As described above, in the washer-type load cell 10 provided between the rear portion of the bearing device 26 and the movable body 25, the opposed end surfaces of the two annular portions protruding from each other serve as working surfaces, and the pressing force from the screw side is applied from the bearing portion to the inner ring. Acts directly on part 12. Further, since the outer ring portion 11 receives the pressing force, stress concentrates on the strain-flexing portion 13 between both ring portions, and the strain-generating portion 13 is deformed corresponding to the stress. Along with this change in strain, the resistance of the strain gauge also changes, so the output voltage of the Wheatstone bridge circuit also changes, and the pressure is electrically measured. The pressing force from the bearing portion acting on the strain-flexing portion 13 is such that the end surface of the inner ring portion 12 annularly contacts the rear surface of the bearing portion and the end surface of the outer ring portion 11 annularly contacts the front surface of the inner step portion 25a. Therefore, even if the pressing force is transmitted in an unbalanced manner depending on how it is assembled, one of the portions acts to cause strain in the strain-flexing portion 13. The rotary shaft 23 penetrates a nut-shaped receiving member 30 connected to the rear end of the movable body 25 and a screw shaft 31 screwed through a ball, and extends to the outer end with a drive gear 33 of a measuring motor 32. The driven gear 34 of the timing belt is spline-connected. The drive gear of the injection motor 35 is attached to the outer end of the screw shaft 31.
A driven gear 37 of a timing belt extending over 36 is attached. In the above injection device, when the metering motor 32 is normally rotated,
The rotational force is applied to the screw via the rotary shaft 23 and the connecting member 22.
It is transmitted to the screw 20, and the screw 20 rotates forward. As a result, the material resin in the hopper is melted and transferred forward along the screw groove, and is accumulated and measured in front of the screw. With the accumulation of this material, the screw 20 is pushed back by the material pressure, and the retracting force (back pressure) at this time is the screw 20-connecting member 22-thrust bearing 27-washer type load cell 10-movable body 25 in this order. Because of the transmission, the washer-type load cell 10 is deformed as described above, which is detected as a strain and the back pressure is measured. This measured value is used for feedback control of the back pressure (adjustment of output torque of the injection motor 35). After the measuring process is completed, the measuring motor 32 is stopped and the injection motor 35 is driven in the normal direction, so that the rotational force is the screw shaft.
The forward force of the movable body 25 is converted by 31 and the receiving member 30, and the forward force is transmitted in the order of the movable body 25-bearing device 26-connecting member 22-screw 20. Due to the formation of such a transmission route, the forward force of the injection motor 35 does not directly act on the washer-type load cell 10, and the measured material is pressed by the screw 20 and injected. At this time, a reaction force of the pressing force of the material by the screw 20 acts on the washer type load cell 10. The reaction force directly acts on the inner ring part 12 of the above 10 from the bearing part, the deformation generated there is detected as a strain, and it is measured as the injection output, and the measured value is feedback control of injection pressure (for injection) It will be used for adjusting the output torque of the motor 35).

[Effect of device]

As described above, the present invention integrates the thick outer ring portion and the inner ring portion with the opposite ends of the bearing device as the working surface at the rear portion of the bearing device in the movable body that rotatably supports the screw in the heating cylinder. A space for accommodating a washer-type load cell consisting of a triple annular body having a strain-flexing portion having a required thickness formed and a strain gauge attached to one side surface of the strain-defining portion is provided. The inner ring portion is brought into contact with the bearing portion of the bearing device to the inner step portion formed with the outer ring portion inside the movable body, the washer type load cell is installed in the space, and the inner ring portion is pressed by the bearing portion. Since the washer-type load cell is configured to generate strain, a larger output is obtained than when a load cell that detects pressure strain and uses it as the measured value is obtained, and injection pressure and back pressure can be measured with high accuracy. It is possible. Further, since the contact position of the inner ring portion is close to the axis of the screw, the transmission loss of the pressing force is reduced, and the strain of the strain generating portion due to the pressing force directly acting on the inner ring portion from the bearing portion is detected. Therefore, the influence of the frictional force is much less than that in the case of detecting the strain of the thrust bearing retainer, and the detection can be performed more efficiently than before, so that highly accurate measurement can be performed. Furthermore, in the above configuration, since only the pressing force from the screw side acts on the washer type load cell, the forward force at the time of injection does not directly act on the washer type load cell and an excessive load does not occur, and its performance is maintained for a long time. Can be maintained. Moreover, since the washer-type load cell need only be installed in the space inside the movable body, there is no need to significantly change the structure related to the bearing device and the movable body in order to install the washer-type load cell, and the bearing device can be replaced simply by removing it. It has features such as easy operation.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a washer-type load cell included in the injection device of the present invention, FIG. 2 is an end view thereof, FIG. 3 is a vertical sectional view of the injection device of the present invention, and FIG. 4 is a conventional washer-type load cell. FIG. 10 …… washer type load cell 11 …… outer ring part 12 …… inner ring part 13 …… strain element 14,15 …… annular groove 16 …… strain gauge 20 …… injection screw 22 …… connecting member 25 …… movable Body 25a …… Inner step 25b …… Space 26 …… Bearing device 27 …… Thrust bearing 28 …… Radial bearing

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 62-264924 (JP, A) JP 62-97818 (JP, A) JP 63-63733 (JP, U)

Claims (1)

(57) [Scope of utility model registration request] 1. A space for accommodating a washer-type load cell is provided at a rear portion of a bearing device in a movable body that rotatably supports a screw in a heating cylinder, and the washer-type load cell has a thick outer ring portion and an inner ring portion. Consisting of a triple annular body having a strain-flexing portion of a required thickness integrally formed between both ring portions with the opposite end of the acting surface as a working surface, and a strain gauge attached to one side surface of the strain-generating portion. The washer-type load cell is characterized in that the ring-shaped portion is formed in the movable body, and the inner ring portion is brought into contact with the bearing portion of the bearing device, and the washer-type load cell is installed in the space. Injection device.