JP3398565B2 - Injection equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection device used for resin molding.

[0002]

2. Description of the Related Art As an injection device used for resin molding,
A cylinder having an injection port at one end, a plunger that slides in the axial direction at a position facing the injection port inside the cylinder, and a drive unit that moves the plunger forward and backward are provided. A mold cavity having a mold material supply port between a position and the injection port, and pressurizing the mold material supplied to the inside of the cylinder by advancing the plunger, and connected to the injection port. There is known an injection device adapted to inject a molding material into an injection molding machine. This injection device is classified into a pre-plastic type in which a screw for melting the molding material is provided outside the cylinder and an in-line type in which the screw is integrally provided inside the cylinder on the tip side of the plunger. In some of the pre-plastic injection devices, the plunger is provided with a large diameter portion that comes into contact with the inner peripheral wall surface of the cylinder and shuts off the inside and outside of the cylinder, and a small diameter portion provided on the tip side thereof.

The injection device of the conventional injection molding machine has the following various circumstances.

If the molding material pressure (back pressure) on the side of the plunger head is too high, when the mold is opened and the product is taken out, the molding material is extruded from the tip of the injection port and becomes a so-called bunting state, and the back pressure is too low. Since the weighing becomes unstable, the suckback is performed so that the plunger is pushed back a little further from the position where the plunger is pushed back by the back pressure to the extent that no haunting occurs.

In order to prevent the molding material from leaking out of the cylinder through the clearance (gap) between the cylinder and the plunger when supplying the molding material into the cylinder or injecting the molding material into the mold cavity. In addition, the length of the portion of the plunger that is in contact with the cylinder is increased, and the clearance between the plunger and the cylinder is made as small as possible within the slidable range of the plunger, that is, narrowed.

In the cylinder, between the liquid storage part having the injection port and the supply port, a backflow prevention valve for preventing the molding material molten liquid stored in the liquid storage part from flowing back to the supply port. (Ring valve) was placed. This check valve
When the metering is completed and the retreat of the plunger is stopped, the back pressure of the molding material melt liquid causes it to come into close contact with the valve seat of the plunger,
It is designed to prevent the melt from flowing back to the supply port.

On the other hand, in order to prevent the backflow of the molding material from the inside of the mold cavity to the inside of the cylinder after the completion of the pressure holding / compression process after the injection of the molding material into the mold cavity, After the injection of the molding material into the inside and until the holding pressure / compression step is completed, a force is applied to the plunger in the plunger forward direction so as to balance with the force of the molding material that tries to flow backward from the mold cavity into the cylinder. The pressure was controlled by adding.

[0008]

However, the above-mentioned prior art has the following problems.

Since the inside of the cylinder is in a depressurized state during the suck back, air is drawn from the outside of the cylinder at the rear end side of the plunger into the inside of the cylinder, and this air becomes a void in the product. It was mixed and was a cause of product defects. When the molding material pressure applied from the plunger head to the guide side is P ₁ , the molding material pressure (back pressure) on the plunger head tip side is P ₂ , and the pressure outside the cylinder is P ₀ (atmospheric pressure), P ₂ > P ₀ at the time of measurement, but P ₂ <P ₀ at the end of measurement. At this time, if P ₁ <P ₀ due to insufficient check of the check valve, etc. The air is drawn in from.

Even if the clearance between the plunger and the cylinder is narrowed, it is avoided that the molding material adheres to the wall surface of the plunger and the cylinder in the sliding section of the plunger and the molding material enters between the plunger and the cylinder. I can't. In addition, the molding material that has entered between the plunger and the cylinder has a very small clearance, so that it is difficult for the molding material to flow, and the molding material stays in the clearance.
The stagnant molding material is deteriorated and carbonized by frictional heat caused by sliding of the plunger. The carbide is mixed with the molding material in the cylinder and mixed in the molded product, which is one of the causes of product defects.

As shown in FIG. 7A, the plunger 2
In the pre-plastic type injection device having the large diameter portion 21 that contacts the inner peripheral wall surface of the cylinder 1 to shut off the inside and outside of the cylinder and the small diameter portion 22 provided on the tip side thereof, the molding material supply port provided in the cylinder 1 The molten liquid of the molding material entered from 12 is guided by the step surface 23 at the boundary between the large diameter portion 21 and the small diameter portion 22 toward the injection port (downward in the figure-not shown). As shown in FIG. 7B, a part of the molding material melt supplied from the molding material supply port 12 becomes two flows that go around the small diameter portion 22 of the plunger 2 to the left and right, and when viewed from the supply port 12. The collision occurs at the position on the back surface, and the retention portion 9 is generated at that position. Then, the molding material of the retention portion 9 is deteriorated by heat to become a carbide, and the carbide is separated from the wall surface of the small diameter portion 22 and mixed into the product, which is one of the causes of the product defect.

Even when the backflow of the plunger is stopped after the metering is finished and the retreat of the plunger is stopped, the check valve does not sufficiently close to the valve seat of the plunger, that is, the check valve does not completely close, and the complete closing is the injection end. Due to the time, a considerable and unstable amount of the molding material melt flows back until the valve is completely closed, and as a result, the preset molding material supply amount and the actual The supply amount of the molding material did not match, and the actual supply amount varied, making it difficult to make the supply amount of the molding material into the mold cavity constant.

In the above-mentioned pressure control, the pressure of the molding material in the mold cavity at the time of holding and compressing the pressure and the force applied to the plunger in the direction of advance of the plunger should be balanced so that the position of the plunger in the cylinder should be constant. However, in reality, the position of the plunger fluctuates as a result of slight fluctuations in the balance between the two, and it has been difficult to maintain a constant holding pressure by perfectly balancing the forces of both. For this reason, the molding material enters and leaves the mold cavity during the pressure-holding / compression process, making it difficult to keep the amount of molding material supplied into the cavity constant.

Therefore, the present invention is to provide an injection device which can solve various problems such as the generation of defects of molded products due to the inclusion of carbides and voids and the difficulty of making the amount of molding material supplied to the mold cavity constant. It is an issue.

[0015]

In order to prevent the above-mentioned molded product defect, a cylinder having an injection port at one end, a plunger sliding axially at a position facing the injection port inside the cylinder, A driving means for sliding the plunger in the axial direction, wherein the cylinder has a molding material supply port between the sliding position of the plunger and the injection port, wherein the plunger is
A first diameter portion that is in contact with an inner peripheral wall surface of the cylinder, and a second diameter portion having an outer diameter smaller than an outer diameter of the first diameter portion at both ends of the first diameter portion, The outer peripheral wall surface of the first diameter portion has a groove along the circumferential direction.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In order to prevent the above-mentioned molded product defect, the present invention comprises a cylinder having an injection port at one end, and a plunger which slides in the axial direction at a position facing the injection port inside the cylinder. And a drive means for moving the plunger forward and backward, the cylinder has a supply port of the molding material between the sliding position of the plunger and the injection port, and the cylinder moves inside the cylinder when the plunger moves forward. In an injection device configured to pressurize the supplied molding material and inject the molding material into a cavity of a mold connected to the injection port, the injection device of the present invention is characterized in that the plunger has an outer periphery. It is characterized in that it has a groove along the circumferential direction on the wall surface. In this case, the injection device may be of the pre-plastic type or the in-line type.

The pressure inside the cylinder X is Px, the pressure outside the cylinder Z is Pz, and the pressure at the plunger portion Y is P
Assuming y, when there is a positive pressure (+ Px) inside the cylinder, there is a pressure gradient-a gradient where the plunger portion is (positive pressure + Py) -in the inside and outside of the cylinder, and there is air outside the cylinder. Is not drawn into the cylinder, but when the pressure inside the cylinder becomes negative (-Px), the pressure gradient inside and outside the cylinder as shown by the broken line in FIG. 6-the gradient where the plunger part becomes (negative pressure-Py) When the − is generated and there is no groove on the outer peripheral wall surface of the plunger, the air outside the cylinder is drawn into the cylinder. On the other hand, when the outer peripheral wall surface of the plunger has a groove, positive pressure (+ Py) can be temporarily maintained in the groove portion as shown by the alternate long and short dash line in FIG. Does not occur.

The number of the grooves may be one, but a plurality is preferable from the viewpoint of improving the effect of preventing the intake of air from the outside of the cylinder. Although the cross-sectional shape of the groove is arbitrary, it is preferable to round the corners of the bottom of the groove to prevent the molding material from staying at the bottom of the groove.

The injection device of the present invention is of a pre-plastic type, and the plunger has a small diameter part at the front part and a large diameter part at the rear part, and the outer peripheral wall surface of the large diameter part is the inner circumference of the cylinder. The cylinder is contacted with the wall surface to block the inside and outside of the cylinder, and the stepped surface at the boundary between the small diameter portion and the large diameter portion guides the molding material toward the injection port, and the plunger has one groove. In the case of, the clearance between the outer peripheral wall surface of the large diameter portion of the plunger and the inner peripheral wall surface of the cylinder is such that η is the viscosity of the molding material and P is the back pressure during measurement (k
gf / cm ² ), Q is the amount of molding material supplied (cm ³ / s),
R is the inner radius of the cylinder, r ₁ is the outer radius of the small diameter portion, r ₂ is the outer radius of the portion of the large diameter portion before the groove, r ₃ is the outer radius of the bottom surface of the groove, r ₄ Is the outer radius of the portion of the large diameter portion after the groove, l ₁ is the axial length of the small diameter portion, l ₂ is the axial length of the portion of the large diameter portion before the groove, l ₃ is an axial length (width) of the groove, l ₄ is an axial length of a portion of the large diameter portion after the groove, and the axial length (width) of the plunger into the cylinder with respect to the total amount of the molding material supplied. When the ratio of the flow rate from the molding material supply port to the upper part is k, it is characterized by the following formula 1.

[0020]

[Equation 1]

By providing the plunger with a small-diameter portion and a large-diameter portion and guiding the molding material toward the injection port at the step surface of the boundary between them, it becomes difficult for the molding material melt to flow backward. In order to make the guide smooth, when a molding material is supplied from the molding material supply port,
It is preferable that the large diameter portion is in a state of slightly closing the molding material supply port.

When the clearance between the outer peripheral wall surface of the large diameter portion of the plunger and the inner peripheral wall surface of the cylinder is set as described above, the molding material melt flows more easily than before in the clearance, and the molding material melts more easily. Since the both wall surfaces are washed, the molding material is less likely to stay. This prevents deterioration and carbonization of the molding material.

From the viewpoint of preventing the molding material from staying, it is preferable to shorten the length of the large diameter portion of the plunger to increase the clearance, but to prevent the air outside the cylinder from being drawn into the cylinder. From a viewpoint, it is preferable to lengthen the length of the large diameter portion of the plunger to reduce the clearance, and the two have a close relationship, and the inventors, as a result of research, obtain the optimum value of the clearance,
We have come to find Equation 1 above.

The above equation 1 can be derived from the following equation. That is, as shown in FIG. 4, the pressure loss at each portion A, B, C, D in the section where the plunger 2 slides in the cylinder 1 is P _A , P _B ,
When P _C and P _D are set, the following Expression 2 is established.

[0025]

[Equation 2]

Therefore, the following equation 3 is established.

[0027]

[Equation 3]

Here, Q = Q ₁ + Q ₂ , P + P _A
= P _B + P _C + P _D , and in order to satisfy Q ₂ = kQ, the following equation 4 is established from Q ₁ = (1-k) Q.

[0029]

[Equation 4]

Therefore, the formula 1 at the beginning is derived.

The injection device according to the present invention is also of a pre-plastic type, and the injection device reaches the rear surface position by wrapping around the small diameter portion to a position which is the rear surface when viewed from the supply port of the small diameter portion of the plunger. A guide part is provided for guiding the two molding material melts toward the injection port without collision. The guide portion is not particularly limited, but it is preferable that the top end of the guide portion has a substantially triangular shape toward the injection port. In this case, if the two opposing hypotenuses of the triangle are curved, the flow of the melt becomes smoother.

From the viewpoint of preventing the molding material from staying around the guide portion, it is sufficient that the shape of the projection is convex toward the forward direction of the plunger so as to be along the flowing direction of the molding material. However, the shape of the molding material retention region is similar to a triangle, and xy = c
(X is the base of the triangular shape of the molding material retention region (a part of the bottom surface of the plunger), y is the height of the triangular shape, and c is different depending on the viscosity of the molding material). The shape is preferably the above triangle, and most preferably the shape satisfying the above expression. In addition, it is preferable that the convex portion becomes thinner toward the apex thereof, and that the apex has no thickness.

The back position of the small diameter portion is not particularly limited, but from the viewpoint of preventing backflow of the molding material and easiness of flow in the direction of the plunger head, the position occupying the upper half of the molding material supply port is set. preferable.

In order to make the amount of the molding material supplied into the mold cavity constant, the injection device of the present invention also includes, in the cylinder, between the reservoir part having the injection port and the supply port. A backflow prevention valve is arranged to prevent the molding material molten liquid stored in the liquid storage portion from flowing back to the supply port. The backflow prevention valve is a spring provided on a connecting shaft extending forward from the plunger. Is always urged in a direction of contacting a valve seat provided on the plunger. In this case, the injection device may be either a pre-plastic type or an in-line type.

In this case, the material of the spring is not particularly limited, and examples thereof include metal springs, and the shape thereof is not particularly limited. For example, coil springs are used. At least one spring is required.

Finally, in the injection device of the present invention, the drive means has a position detector of the plunger within the cylinder, and the drive of the drive means is controlled based on the detection signal of the position detector to drive the plunger. It is also characterized in that it is also provided with control means for fixing the position to the position at the end of injection. In this case, the injection device may be either a pre-plastic type or an in-line type.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is
The present invention is not limited to the following embodiments, and the materials, shapes, and the like of the constituent parts described in the following embodiments are intended to limit the scope of the present invention to them unless otherwise specified. It is not an example, but merely an example of explanation.

1 to 5 show an injection device according to an embodiment of the present invention. The injection device according to this embodiment is a screw pre-plastic injection molding machine.

FIG. 1 shows an injection device 100 according to the embodiment of the present invention, a pre-plasticizing device 200 for supplying a plasticized molding material to the injection device 100, and an injection device 10.
Mold 300 for injection injection of plasticizing molding material from scratch
The whole relation of is expressed in cross section.

The injection device 100 has a cylinder 1 having an injection port 11 at one end, a plunger 2 sliding in the axial direction of the cylinder at a position facing the injection port 11 inside the cylinder 1, and moving the plunger 2 forward and backward. Drive means 3
The cylinder 1 also has a supply port 12 of the molding material between the sliding position of the plunger 2 and the injection port 11.

As shown in FIGS. 2 to 4, the plunger 2 has a large-diameter portion 21 and a small-diameter portion 22 integrally formed on the tip side thereof, and the molding material supply port 12 of the small-diameter portion 22. A guide portion 24, which has a substantially triangular shape with its top tip facing the ejection port 11, is also provided at a position which is the rear surface when viewed from above.

A groove 211 is provided on the outer peripheral wall surface of the large diameter portion 21 of the plunger so as not to draw air from the outside of the cylinder. In order to prevent the molding material from staying in the depression of the groove 211, the bottom corner of the groove 211 is rounded as shown in the figure.

The guide portion 24 is at least a pair of inclined guide surfaces 24a, 24b facing each other, and the two molding material molten liquids flowing around the small diameter portion and reaching the back surface position are well balanced. In order to guide toward the outlet, it is preferable that the inclination angles of the guide surfaces 24a and 24b with respect to the axial direction of the plunger 2 be substantially the same. Furthermore, it is preferable that the guide portion 24 has a substantially equigonal trapezoidal shape having the pair of inclined guide surfaces 24a and 24b. Further, the molding material melt is retained in a lower portion of the lower end of the trapezoidal shape. In order to prevent the above-mentioned problem more reliably, it is preferable that the guide portion is a substantially isosceles triangle with the tip of the apex facing the ejection port. More preferably,
If the guide portion 24 is an equilateral triangle, the molding material melt can be guided more efficiently.

In this case, the clearance between the outer peripheral wall surface of the large-diameter plunger portion 21 and the inner peripheral wall surface of the cylinder 1 is designed to be an optimum value in relation to the axial length of the large-diameter plunger portion 21 according to the equation (1). Has been done.

The driving means 3 has a slide guide shaft 31 extending from the rear end of the cylinder 1, a servo motor 33 installed on a support base 32 at the other end of the slide guide shaft 31, and one end connected to the servo motor 33. Rotating screw shaft 3
4 and the screw shaft 34 mesh with the screw shaft 34
And a transmission member 35 that moves forward and backward along the slide guide shaft 31 by the forward and reverse rotations. One end of the transmission member 35 is connected to the rear end of the plunger 2, and its back-and-forth movement is transmitted to the plunger 2 to move the plunger 2 back and forth.

As shown in FIG. 1, the molding material molten liquid stored in the liquid storage portion 13 is provided between the liquid storage portion 13 and the supply port 12 provided in the front stage of the injection port 11 in the cylinder 1. A check valve 4 is arranged to prevent backflow to the supply port 12. The check valve 4 has a cylindrical shape as shown in FIG. 5C, and a connecting shaft extending from the small diameter portion 22 of the plunger toward the injection port 11 (see FIG. 1) as shown in FIG. 5A. 25 is inserted and slides in the cylinder 1 in the vertical direction as viewed in the drawing. A valve seat 22 corresponding to the tapered valve portion 41 of the check valve 4 is provided at the tip of the small diameter portion 22 of the plunger.
1 is provided.

A spring 27 is provided on the arrowhead-shaped head 26 provided on the tip side of the connecting shaft 25, and the check valve 4 is provided by the spring 27 as shown in FIG. 5B. The plunger small-diameter portion 22 is always urged in the direction of contacting the valve seat 221.

As shown in FIG. 1, the drive means 3 is provided with an encoder 51 for detecting the rotation angle of the servomotor 33 in the servomotor 33 thereof. This encoder 51
Detects the position of the plunger 2 in the cylinder 1 from the detected rotation angle. The drive means 3 includes a control means 5 for controlling the drive thereof, and the control means 5 obtains a detection signal from the encoder 51 and controls the drive of the servo motor 33 of the drive means 3.

As shown in FIG. 1, the pre-plasticizing device 200 comprises a hopper 201 and a screw portion 202, and the molding material plasticized by the screw portion 201 is supplied to the supply port 1 of the cylinder 1.
It is sent into the cylinder 1 through 2. When the melt of the molding material enters the cylinder 1, the large diameter portion 21 of the plunger 2
As shown in FIG. 4, the step surface 23 at the boundary between the small-diameter portion 22 and the small-diameter portion 22 is guided toward the injection port 11 and, at the same time, a part thereof is divided into two flows as shown in FIG. 7B. When it reaches the back position as seen from the supply port 12 around the small-diameter portion 22, it is smoothly guided toward the ejection port 11 along the shape of the guide portion 24 as shown in FIG. No stagnant part is generated.

At the time of supplying the molding material into the cylinder 1,
As shown in FIG. 4, when the large-diameter plunger portion 21 closes the molding material supply port 12 to about half, the molding material is generated between the outer peripheral wall surface of the large-diameter plunger portion 21 and the inner peripheral wall surface of the cylinder 1. It does not easily leak to the outside of the cylinder through the clearance, making it easier to face the injection port 11.

The molding material in the cylinder 1 is fed into the liquid storage portion 13 ahead of the plunger head 26 and measured. The molding material sent to the liquid storage portion 13 causes the plunger 2 to retract slightly due to the reaction that has been sent during the measuring process, but when a preset amount (1 shot) of the molding material is stored in the liquid storage portion 13. The plunger 2 stops moving backward, and the weighing process ends. The plunger 2 advances to pressurize the molding material supplied into the cylinder 1. The fixed amount of the molding material molten liquid stored in the liquid storage portion 13 in the cylinder 1 has a positive pressure due to the pressurization, and the positive pressure causes the injection port 1 to have a positive pressure.
It is injected and injected into the cavity 301 of the mold 300 connected to 1. The molding material pushed into the mold cavity 301 under high pressure at a high speed holds the injection pressure by the plunger 2 and hardens during that time.

The check valve 4 is pressed against the valve seat 221 of the small diameter portion 22 of the plunger during injection, during injection completion, and during holding pressure, and closes the passage of the molding material as shown in FIG. 5 (b). However, when the molding material is fed in from the start of weighing to the beginning of weighing, the feeding pressure of the molding material overcomes the spring force, so the path is opened as shown in FIG. 5 (a). Spring 2
When there is not 7, the valve tries to open by receiving a negative pressure at the time of sucking back. However, in this injection device, the check valve 4 is always biased by the spring 27, so that even if a negative pressure is received. It does not open and keeps the molding material passage closed. Thereby, the backflow of the molding material can be prevented and the amount of the molding material supplied to the mold cavity 301 can be made constant.

The molding material tends to flow backward from the mold cavity 301 into the cylinder 1 after the injection into the mold cavity 301 and before the pressure holding / compression process is completed. At this time, the control means 5 of the drive means 3 detects the position of the plunger 2 in the cylinder 1 by the encoder 51, controls the rotation of the servo motor 33 based on the detection signal, and determines the position of the plunger 2 at the time of injection completion. Be sure to fix it in the proper position. By this position control, the injection amount can be adjusted more stably than the conventional pressure control.

In the above injection device, the plunger has the small diameter portion and the large diameter portion, and the clearance between the large diameter portion outer peripheral wall surface and the cylinder inner peripheral wall surface is defined by a predetermined formula. By so doing, it is possible to prevent the molding material from staying between the outer peripheral wall surface of the large-diameter portion and the inner peripheral wall surface of the cylinder, so that it is possible to manufacture a high-quality molded product in which no carbide of the molding material is mixed.

In the injection device, since the guide portion for directing the molding material toward the injection port is provided at the back surface of the small diameter portion of the plunger, it is possible to prevent the molding material from staying at that position. It is possible to manufacture high quality molded products without contamination.

In the injection device, the guide portion is a pair of inclined guide surfaces facing each other, and the inclination angles of the guide surfaces with respect to the axial direction of the plunger are substantially the same, thereby smoothly guiding the molding material. Therefore, the retention can be further prevented.

In the injection device, since the guide portion has the pair of inclined guide surfaces and the apex of the apex is a substantially isosceles triangle facing the injection port, the molding material can be smoothly guided, The retention can be prevented further.

In the injection device, since the guide portion is an equilateral triangle, the molding material can be smoothly guided, and stagnation can be further prevented.

In the injection device, since the check valve is always urged in the closing direction by the spring, the time until the valve is closed can be shortened, and the check valve can be effectively prevented, and the check valve can be effectively moved into the mold cavity. The amount of molding material supplied can be kept constant and high quality molded products can be manufactured.

In the injection device, since the amount of the molding material supplied into the mold cavity can be made constant by controlling the position of the plunger, a high quality molded product can be manufactured.

[0061]

Since the present invention is configured as described above, it has the following effects.

In the injection device of the first aspect, since the plunger outer peripheral wall surface has the groove extending in the circumferential direction, it is possible to prevent air from being drawn from the outside of the cylinder into the cylinder and to prevent the occurrence of voids. Can produce high quality molded products.

In the injection apparatus of the first aspect, the plunger has the second diameter portion and the first diameter portion, so that the molding between the outer peripheral wall surface of the first diameter portion and the inner peripheral wall surface of the cylinder is performed. Since it is possible to prevent the material from staying, it is possible to manufacture a high-quality molded product in which no carbide of the molding material is mixed.

In the injection device of claim 2, the second
Since the guide portion is provided at the position on the opposite side of the supply port of the diameter portion of the mold, it is possible to prevent the molding material from staying at that position, and thus it is possible to manufacture a high-quality molded product free from the inclusion of carbide of the molding material. .

In the injection device of the third aspect, since the check valve is always biased in the closing direction by the spring,
The time until the valve is closed can be shortened, backflow can be effectively prevented, the amount of molding material supplied into the mold cavity can be made constant, and high-quality molded products can be manufactured.

[Brief description of drawings]

FIG. 1 is an overall schematic cross-sectional view showing the relationship between an injection device, a pre-plasticizing device, and a mold according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a plunger used in the embodiment of the present invention.

FIG. 3 is a rear view showing the shape of the plunger.

FIG. 4 is a side view showing the relationship between the shape and the dimension of the plunger.

FIG. 5 is an explanatory diagram for explaining the vicinity of the check valve.

FIG. 6 is a graph for explaining how air is drawn into the cylinder and how it is eliminated.

FIG. 7 is an explanatory view of forming a retention portion at the back surface position of the small diameter portion of the plunger.

[Explanation of symbols]

100 injection device 200 Pre-plasticizer 300 mold 1 cylinder 2 Plunger 3 drive means 4 Check valve 5 Control means 11 Exit 12 Supply port 13 Liquid storage part 21 Large diameter part 22 Small diameter part 23 Step 24 Guide 25 connecting shaft 27 spring 33 Position detector encoder 211 groove 221 valve seat

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadao Murata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-6-166072 (JP, A) JP-A-Hei 4- 173314 (JP, A) JP-A-8-52774 (JP, A) US Pat. No. 5450502 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (3)

(57) [Claims] 1. A cylinder having an injection port at one end, a plunger that slides in the axial direction at a position facing the injection port inside the cylinder, and a drive unit that slides the plunger in the axial direction, In the injection device, wherein the cylinder has a supply port for the molding material between the sliding position of the plunger and the injection port, the plunger has a first diameter part that contacts an inner peripheral wall surface of the cylinder. , A second diameter portion having an outer diameter smaller than an outer diameter of the first diameter portion at both ends of the first diameter portion, and in a circumferential direction on an outer peripheral wall surface of the first diameter portion. An injection device characterized by having a groove along it. 2. The injection device according to claim 1, wherein a guide portion is provided at a position of the second diameter portion opposite to the supply port. 3. The check valve is arranged on a connecting shaft extending forward from the plunger, and a spring is provided between the check valve and a tip of the connecting shaft extending forward from the plunger. The injection device described in 1.