JPH0158059B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection molding machine, and particularly to an injection molding machine capable of high-speed molding and precision molding.

[Background of the invention]

In recent years, various uses of servo motors have been considered as drive sources for injection molding machines because they allow easy feedback control of speed, pressure, and position, have good responsiveness, and have stable operation even at low speeds. . As a method for controlling the back pressure of the screw in this servo motor driven injection molding machine, for example,
A control method as described in Japanese Patent No. 58-179631 has been proposed.

This back pressure control method converts the backward movement of the screw, which occurs when the molten synthetic resin is charged by the rotation of the screw, into rotational motion using gear means, and adjusts the rotational force using brake means. This is an attempt to control the back pressure of the screw.

However, in this control method, a gear means is used to convert the backward movement of the screw into a rotational movement, and a brake means is used to control the rotational movement obtained by the conversion. It has the disadvantage that stable and accurate back pressure control is difficult.

On the other hand, toggle type mold clamping devices and direct pressure type mold clamping devices have been conventionally employed as mold clamping devices for injection molding machines. All of these devices are hydraulically driven, and the mold clamping operation is performed by switching the flow direction of the pressure oil between forward and reverse at a predetermined timing.
It requires a switching operation using a valve, and there is a delay until the hydraulic pressure reaches the specified pressure after switching.
It is a hindrance to high-speed driving.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an injection molding machine capable of high-speed molding and precision molding by eliminating the drawbacks of the prior art described above.

[Summary of the invention]

In order to achieve the above-mentioned object, a heating cylinder, an injection nozzle arranged at the tip end side of the heating cylinder, and a screw resin supply means, for example, for supplying molten resin into the injection chamber provided at the tip end of the heating cylinder, are used. and a piston, such as a plunger, which has a stop valve mechanism that closes when moving in the injection direction and opens when moving in the opposite backward direction, and injects the molten resin supplied to the injection chamber into the cavity through the injection nozzle. A sensor, such as a load cell, for detecting the resin pressure in the injection chamber applied during the movement of the piston is provided in the drive system of the piston means to maintain the resin pressure in the injection chamber constant during charging;
The retracting speed of the piston means is maintained constant, and the supply speed of molten resin by the resin supply means is feedback-controlled based on a resin pressure detection signal from the sensor. It is.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic layout diagram of the main parts of an injection molding machine viewed from the front.

First, the overall schematic configuration of the injection molding machine will be explained using FIG. 1. In the figure, reference numeral 1 denotes a base portion of an injection molding machine, and an operation/display panel portion 2 is provided on the right side of the upper front side of the base portion, and a chute 3 for discharging molded products is provided on the left side.

FIG. 2 is a front view of the operation/display panel section 2. In the figure, 4 is a teaching power switch, 5 is a connection part for a teaching box which will be described later, 6 is an operation power switch, 7 is a heater switch, and 8 is a group of operation keys. It consists of operation keys for manual operation, semi-automatic operation, automatic operation, motor on, nozzle forward, nozzle retract, mold opening/closing, injection molding, etc. 9 is a code display section consisting of 4-digit seven segments, and 10 is an emergency stop button.

Returning again to FIG. 1, the schematic structure of the injection molding machine will be explained. An injection cover 11, a safety door 12, and a crank cover 13 are provided on the upper part of the base portion 1.

A hopper 14 for charging pellet-shaped molding material is provided on the injection cover 11, and inside there are a charging servo motor 15, an injection servo motor 16, and a nozzle/touch limit switch 1.
7. In addition to the nozzle retrieval motor 18, a heating cylinder housing a screw, which will be described later, is provided.

Inside the safety door 12 is a fixed die plate 1.
9. Moving die plate 20 and tie bar 21
is provided. In addition, the crank cover 13
Inside, there is a mold thickness adjustment motor 22, a tail stock 23, and a mold opening/closing servo motor 2 below it.
4 are provided.

The main parts of the injection molding machine are arranged as shown in FIG. 1. Next, the injection mechanism and mold clamping mechanism of this injection molding machine will be explained.

First, the structure of the injection mechanism will be described in detail with reference to FIGS. 3 to 9.

3 and 4 are a plan view and a front view showing the general structure of the injection molding machine, FIG. 5 is a sectional view of the vicinity of the injection screw, FIG. 6 is a sectional view of the vicinity of the slide chamber, and FIG. 7 is a sectional view of the vicinity of the slide chamber. 6 A cross-sectional view along line I-I,
FIG. 8 is a plan view of the vicinity of the slide chamber, and FIG. 9 is a sectional view of the vicinity of the plunger tip.

A heating tube 26 is provided at the front of the injection section main body 25, and a screw 27 is rotatably inserted into the heating tube 26. The rear end of the screw 27 is engaged with a gear 29 by a plurality of keys 28 arranged in the circumferential direction as shown in FIG. 5, so that the screw 27 rotates integrally with the gear 29. gear 29
As shown in FIG. 4, the gears 29 and 30 are in mesh with the drive gear 30 of the charge servo motor 15, and both gears 29 and 30 are supported by the injection section main body 25 via ball bearings 31. Therefore, the rotational driving force of the charge servo motor 15 is transmitted to the screw 27 via the gear 30, the gear 29, and the key 28, and the screw 27 is rotationally driven in a fixed direction.

As shown in FIG. 5, pellet charging holes 36 are formed at predetermined positions in the injection section main body 25 and the heating cylinder 26, and the hopper 14 and the hollow portion of the heating cylinder 26 communicate with each other through the pellet charging holes 36.

As shown in FIG. 6, a cylinder member 37 is fixed inside the tip of the heating cylinder 26, and this cylinder member 37 is composed of a front end 37a, an intermediate part 37b, and a rear end 37c. This front end 37
An injection chamber 38 is formed in the center of a in the axial direction, and the rear part of the front end part 37a expands into a mortar shape toward the intermediate part 37b. A plurality of passages 39 are formed in the vicinity of the outer periphery of the intermediate portion 37b in the axial direction, and a slide chamber 40 extending in a direction perpendicular to the axial direction is provided in the center of the intermediate portion 37b.
A slide hole 41 is formed from the center of this slide chamber 40 toward the front. The rear end portion 37
An introduction hole 42 is provided in the center of c in the axial direction, and the front part of the introduction hole 42 expands into a cone shape toward the intermediate part 37b.

A plunger 44 having approximately the same diameter as these is slidably inserted from the front slide hole 41 formed in the intermediate portion 37b to the injection chamber 38 of the front end portion 37a, and near the tip thereof there is a plunger 44 extending from the outer periphery toward the center. One or more elongated radial holes 4
5 (see FIG. 9), and an axial hole 46 communicating with the radial hole 45 and opening toward the distal end surface of the plunger 44. As shown in FIG. 6, the diameter of the axial hole 46 increases from the middle, and a ball 47 and a retaining pin 48 are inserted into the large diameter portion.

The rear end of the plunger 44 is screwed to a holder arm 49, and both ends of this holder arm 49 protrude outward from the heating cylinder 26, as shown in FIG. 8, and both ends are connected to an injection bar 50. An injection reaction force sensor 51 consisting of a load cell is interposed in the middle of one injection bar 50.

As shown in FIG.
A screw hole is formed along the axial direction in the center of 2, and a screw cylinder 53 is screwed into the screw hole. This threaded cylinder 53 is rotatably supported by a ball bearing 31 as shown in FIG.
A threaded portion 54 for screwing into the driving body 52 is formed on the outer periphery. As shown in FIG. 4, a gear 55 is attached to the rear end of the threaded cylinder 52, and the gear 55 meshes with a driving gear 56 of the injection servo motor 16. Therefore, the rotational driving force of the injection servo motor 16 is transmitted through the drive side gear 56 and the gear 5.
5, screw cylinder 53, driver 52, injection bar 50,
and the plunger 4 via the holder arm 49.
4, and the plunger 44 moves forward and backward by forward and reverse rotation of the injection servo motor 16.

As shown in FIG. 6, at the rear of the holder arm 49 is a needle 5 extending toward the orifice 34.
7 is arranged and is separate from the holder arm 49. A nozzle 58 is attached to the tip of the cylinder member 37, and a plurality of thermocouples 59 and heaters 60 are arranged in pairs at predetermined locations on the tip of the cylinder member 37 and the outer periphery of the heating cylinder 26. is wrapped in.

Next, the structure of the mold clamping mechanism will be explained. 1st
0 and 11 are a plan view and a front view of the mold clamping part.

Four tie bars 21 are installed between the housing 61 and the fixed die plate 19 and are arranged at predetermined intervals. The movable die plate 20 is movably arranged relative to the fixed die plate 19 using the tie bar 21 as a guide, and the fixed side mold 62 is mounted on the fixed die plate 19.
The movable molds 63 are each fixed to the movable die plate 20, so that the movable molds 63 can move toward and away from the fixed mold 62.

A bracket 64 is provided protruding from the movable die plate 20, and the free end of a crank arm 66 is connected to the bracket 64 via a pin 65.

As shown in FIG. 4, a mold opening/closing servo motor 24 is installed below the housing 61, and is connected to an eccentric shaft portion 68 of a crankshaft 67 connected to its drive shaft via a bearing 69 (see FIG. 11). A base end portion of the crank arm 66 is rotatably connected to the crank arm 66. Therefore, the servo motor 24 for opening and closing the mold
The driving force is transmitted to the movable die plate 20 via the crankshaft 67, the eccentric shaft portion 68, the crank arm 66, and the bracket 64, and the rotational motion of the servo motor 24 is converted into forward and backward movement by the crank mechanism. The movable side mold 63 is moved toward and away from the side mold 62.

As shown in FIGS. 4 and 11, a mold thickness adjustment motor 22 is mounted above the housing 61 via a bracket 70, and its driving side is connected to each diver 21 via a gear group 71. The mold thickness can be adjusted by rotating the motor 22.

FIG. 12 is a perspective view of the teaching box. On the top surface of the box body 72 is a numeric keypad 73.
, menu key 74, cursor key 75,
Input keys such as an on key 76, a reset key 77, and an entry key 78, and a display section 79 are provided. An optical fiber cable 80 and a metacon 81 are connected to this box body 72.
These are designed to be inserted into a teaching box connection portion 5 of the operation/display panel 2 shown in FIG. By using this teaching box, there is the convenience of being able to set various molding data even at a location away from the molding machine main body.

Next, the operation of this injection molding machine will be explained.
In the state shown in FIGS. 5 and 6, the charging servo motor 15 is driven to rotate the screw 27, and resin pellets from the hopper 14 are fed into the heating cylinder 26. The supplied synthetic resin 82 is plasticized and melted by the rotation of the screw 27 and is fed into the slide chamber formed by the cylinder member 37.

Further, the radial hole 45, the axial hole 46, the injection chamber 38, and the nozzle 58 are filled with the molten resin 82. The ball 47 is pushed forward by the pressure of the filled molten resin 82, but the pin 48 prevents it from coming off. In this way,
A certain amount of molten resin 82 is filled into the injection chamber 38 .

As shown in FIG. 6, the injection servo motor 16 is driven in the forward rotation direction in a state filled with the molten resin 82. As a result of this drive, the drive side gear 56, gear 55, and threaded cylinder 53 shown in FIG. Move forward towards the side.

As a result of this advancement, the ball 47 receives resin pressure and immediately retreats, and as shown in FIG.
As a result, the small diameter portion of the axial hole 46 is closed. That is, this ball 47 and the small diameter portion of the axial hole 46 constitute a stop valve mechanism. By moving the plunger 44 forward in this state, the molten resin 82 is injected from the nozzle 58 into the molds 62 and 63.

The injection amount of the molten resin 82 is determined by the stroke length of the plunger 44, and the injection servo motor 1
By changing the rotation amount of the plunger 6, the stroke length of the plunger 44 can be adjusted. It is important to determine the final injection amount by looking at the finished molded product, and to set the stroke length of the plunger 44 so as not to cause sink marks or burrs on the molded product.

The injection molding process consists of a filling process in which molten resin is filled into the cavity, and a pressure holding process in which the resin in the cavity is pressed until it solidifies within the cavity. During this pressure holding process, the molten resin 82 is supplied and filled into the above-mentioned accumulator chamber. FIG. 13 is a sectional view of the main part at the time of completion of this pressure holding process.

After this pressure holding process is completed, by rotating the injection servo motor 16 in the reverse direction, both the plunger 44 and the holder arm 49 move backward as shown in FIG. 14. As a result of this movement, the ball 47 receives resin pressure and immediately moves toward the plate fixing pin 48.
The small diameter portion of the axial hole 46 opens, and as the plunger 44 moves, a portion of the molten resin 82 passes through the radial hole 45 and the axial hole 46 and enters the injection chamber 38.
sent to.

Next, the opening/closing operation of the mold will be explained. FIG. 15 is a front view showing the mold opening state of the mold clamping section. In this state, the movable die plate 20 is moved back the most, and a sufficient distance between the movable die 63 and the fixed die 62 is maintained. When the mold opening/closing servo motor 24 (see FIG. 4) is driven to rotate the crankshaft 67 based on a mold clamping signal from the control section, the eccentric shaft portion 68 rotates around the crankshaft 67. With this rotation, the movable die plate 20 moves to the tie bar 2 via the crank arm 66.
1, the movable mold 63 approaches the fixed mold 62. Then, when the mold opening/closing servo motor 24 has rotated 180 degrees, as shown in FIG. 10, the central axis P of the crank arm 66 coincides with the rotation center O of the crankshaft 67, and the crank arm 66 is in the most extended state. , the movable mold 63 is brought into pressure contact with the stationary mold 62, and strong mold clamping is performed. In this state, the mold opening/closing servo motor 2
4 is stopped, the movement of the movable die plate 20 is stopped, and the resin is filled into the cavity and the pressure is maintained as described above.

When the injection molding process is completed in this manner, when the mold opening/closing servo motor 24 is driven again and the crankshaft 67 is rotated in the same direction, the movable die plate 20 (movable side mold 63) is transferred to the fixed die plate 1.
9 (fixed side mold 62) and the mold is opened. In connection with this mold opening operation, the ejection rod 83, which had been retracted until now, moves forward and ejects the molded product inside the movable mold 63, and the molded product passes through the chute 3 (see Figure 1) and exits the machine. is discharged. After the molded product is taken out in this way, the crankshaft 67 rotates in the same direction to clamp the mold, and the ejection rod 83 retreats as the spring 92 (see Figure 3) is compressed. .

FIG. 16 is a characteristic diagram showing the relationship between the rotation angle θ of the crankshaft 67 and the moving speed V of the movable die plate 20.

The movable die plate 20 is the fixed die plate 19
The mold opening/closing servo motor 24 is driven from the position farthest from the crankshaft 67, that is, the state where the eccentric portion 68 of the crankshaft 67 is directly behind as shown in FIG. Rotate. As shown in the figure, the moving speed V is slow at the beginning of rotation, but increases as the rotation angle θ approaches 90 degrees, and after that, the moving speed V gradually slows down. When the rotation angle θ approaches 180 degrees, the movable mold 63 comes into contact with the stationary mold 62, and as the rotation angle θ increases, the contact force also increases. Then, a motor attached to the drive shaft of the servo motor 24 for mold opening/closing indicates that the rotation angle is within the range of ±0.1 degrees (in Fig. 16, the hatched part is enlarged). Angle sensor 84 such as an encoder
(See Fig. 4), the control unit determines that the rotation angle θ of the crankshaft 67 has reached the dead center of 180 degrees, stops the rotation of the mold opening/closing servo motor 24, and moves the movable die plate 20. Stop moving. In this state, the injection and pressure holding described above are performed.

When injection and pressure holding are completed, the crankshaft 67 further rotates 180 degrees to open the mold, and the movable die plate 20 returns to its original position, completing one cycle of mold opening and closing.

As described above, in the injection molding machine of the present invention, the movable die plate is reciprocated by rotational drive in one direction using a crank system, and the mold is clamped to and opened from the fixed die plate. Therefore, the structure is simple, and the movable die plate can smoothly reciprocate, making it possible to increase the cycle of the injection molding machine. Furthermore, by using a servo motor as the drive source for the mold opening/closing operation, the accuracy of stopping the crank at its dead center can be improved.

FIG. 17 is a control system block diagram of the charging servo motor 15. In the figure, 51 is an injection reaction force sensor, 85 is an AD converter, 86 is a charge pressure setting device, and 88 is the control unit main body (not shown), but I/O
It has built-in ports, μ-CPU, RAM, ROM, etc. Further, 89 is a DA converter, 90 is a servo amplifier, and 15 is a charge servo motor.

When charging the molten resin 82 into the injection chamber 38,
The injection servo motor 16 is rotated at a constant speed at a relatively low speed, and the retraction speed of the plunger 44 is kept constant. Therefore, resin pressure is applied to the injection reaction force sensor 51 interposed in the middle of the injection bar 50, and the resin pressure detection signal is inputted to the control unit main body 88 through the AD converter 85. In addition, this control unit main body 88
A desired charge pressure (resin pressure) in the injection chamber 38 is input to the RAM through a charge pressure setting device 86. Therefore, the resin pressure actually measured by the injection reaction force sensor 51 and the set charge pressure are cpu
If there is a deviation between the set charge pressure and the measured charge pressure, a control signal calculated to achieve the set charge pressure is sent from the control unit main body 88 to DA.
The signal is input to the servo motor 15 through a converter 89 and a servo amplifier 90. Servo motor 15
The rotational speed is adjusted by the input control signal, thereby controlling the charge pressure in the injection chamber 38 to be always constant.
Although not shown, the injection servo motor 16
The rotational speed is self-controlled by an attached rotational speed detection means such as a tachometer generator so that the rotational speed is always constant. As described above, the charge density of the molten resin 82 can always be maintained constant by feedback control using the injection reaction force sensor 51.

As shown in FIGS. 3 and 8, the injection bar 5
An injection reaction force sensor 51 is interposed in the middle of zero, and pressure holding control is also performed by this. Next, this pressure holding control will be briefly explained.

In order to improve the dimensions and surface accuracy of the molded product and to prevent molding distortion and cracks, an injection molding system is used in which the injection speed and holding pressure of the molten resin are varied in multiple stages. .
FIG. 18 is a diagram showing an example of this pressure holding pattern.

In this figure, the horizontal axis shows time T, and the vertical axis shows pressure P. In the figure, point G is the time when pressure holding is switched, point H is the time when holding pressure is completed, and the period between point G and point H is the pressure holding process. becomes. In this example, the pressure during the holding pressure process is set to be gradually lowered over time in three stages: first holding pressure P ₁ , second holding pressure P _{2 ,} and third holding pressure P ₃ . ing. Such a holding pressure pattern is appropriately set depending on the shape, size, dimensional accuracy, surface accuracy of the molded product, and molding conditions such as the molding material used.

Setting of such a holding pressure pattern is performed by a holding pressure setting device, and is stored in the RAM of the control unit main body. During the pressure holding process, pressure is applied to the resin in the cavity by the injection bar 50 via the plunger 44, and the pressurizing force at this time, in other words, the reaction force transmitted by the plunger 44 by the resin is applied to the injection bar. The injection reaction force sensor 51 provided in the middle of the injection reaction force sensor 50 electrically detects the injection reaction force.

This detection signal is input to the control unit main body through the AD converter, and the holding pressures set as described above (first holding pressure P ₁ , second holding pressure P ₂ , third holding pressure P ₃ ) and They are compared from time to time, and if there is a deviation between the set holding pressure and the measured holding pressure, a control signal calculated to achieve the set holding pressure is input from the control unit to the servo motor 16 through the DA converter and servo amplifier. be done.
In the servo motor 16, the supplied current, that is, the output torque is adjusted by the input control signal, thereby controlling the holding pressure by the plunger 44 to the set holding pressure.

According to the so-called double-supported structure in which the injection bar 50 is connected to both ends of the holder arm 49 that supports the plunger 44 as in this embodiment,
The reciprocating movement of the plunger 44 is smoother than that of a cantilever type, and the operation reliability is high. Further, by using two injection bars 50, the injection reaction force transmitted by one injection bar 50 from the plunger 44 can be reduced by half, so that the injection reaction force attached to either one injection bar 50 can be reduced by half. Force sensor 5
1 may be an inexpensive load cell with low pressure sensing capability.

Data from the above-mentioned injection reaction force sensor 51 is read by a sampling signal periodically output from the control section main body 88.

FIG. 19 and FIG. 20 are injection force characteristic diagrams of the molding machine of the present invention and a conventional molding machine. In these figures, curve X is the actual measurement curve when the injection force is set to 1200Kg/ ^cm2 , and curve Y is the actual measurement curve when the injection force is set to 2900Kg/ ^cm2 .
The graph shows the variation in the injection force after repeated injections.

In the conventional injection molding machine, as shown in FIG. 20, when the injection force is set to 1200 Kg/cm ² , the difference in the variation in actual measured values is about 83 Kg/cm ² , and the degree of variation is about 7%. Further, when the injection force is set to 2900 Kg/cm ² , the difference in the variation in the actual measured values is about 250 Kg/cm ² , the degree of variation is about 9%, and the difference in variation becomes larger as the injection force increases.

In comparison, the injection molding machine of the present invention performs pressure feedback control as described above, so as shown in Fig. 19, the difference in the variation in actual measured values when the injection force is set to 1200 kg/cm ² is only 14Kg/cm ²
The degree of variation is approximately 1.1%. Furthermore, when the injection force is set to 2900Kg/cm ² , the difference in the variation in the actual measured values is only about 30Kg/cm ² , and the degree of variation is approximately 1.
%. As is clear from these results, even when the injection force becomes high, the injection molding machine according to the present invention has small variations in injection force, and it can be proven that it is a highly reliable injection molding machine.

〔Effect of the invention〕

As described above, the present invention provides a sensor such as an injection reaction force sensor for detecting the resin pressure in the diagonal chamber during the movement of the piston in the drive system of the piston means, so that the resin pressure in the injection chamber is kept constant during charging. In order to maintain the temperature, the retraction speed of the piston means is held constant, and the supply speed of the molten resin by the resin supply means is feedback-controlled based on the resin pressure detection signal from the sensor. .

In an injection molding machine, it is very important to keep the charge pressure in the injection chamber constant in order to uniformly plasticize the resin. To this end, the retraction speed of the plunger is adjusted by keeping the rotation speed of the charge motor constant and controlling the rotation speed of the injection servo motor based on the detection signal from the injection reaction force sensor. It is conceivable to keep the charge pressure constant.

However, with this configuration, the range in which the retraction speed of the plunger can be adjusted is extremely narrow, making it impossible to properly control the plunger and making it difficult to maintain a constant charge pressure.

In this regard, the present invention has a control system as described above, in which the retraction speed of the plunger, which can be adjusted within an extremely narrow range, is kept constant, and the resin supply means such as a screw is rotated based on the detection signal from the sensor. Since the number is adjusted, it is easy to control and the charge pressure can be kept constant at all times, allowing for more precise molding.

[Brief explanation of drawings]

1 to 19 are for explaining an injection molding machine according to an embodiment of the present invention.
The figure is a front view of the operation/display panel section, Figures 3 and 4 are a plan view and front view showing the schematic configuration of the injection molding machine, Figure 5 is a cross-sectional view of the vicinity of the injection screw, and Figure 6 is the slide. Sectional view near the chamber, No. 7
The figure is a sectional view taken along line I-I in Fig. 6, Fig. 8 is a plan view of the vicinity of the slide chamber, Fig. 9 is a sectional view of the vicinity of the plunger tip, and Figs. 10 and 11 are plan views of the mold clamping section. 12 is a perspective view of the teaching box, FIG. 13 is a sectional view of the main part at the time of completion of the pressure holding process, FIG. 14 is a sectional view of the main part showing the operation after the pressure holding process is completed, and FIG. 15 is a front view. 16 is a characteristic diagram showing the relationship between the rotation angle of the crankshaft and the moving speed of the moving die plate. FIG. 17 is a block diagram of the servo motor control system. FIG. 18 is a pressure holding pattern diagram, and FIGS. 19 and 20 are injection force characteristic diagrams of the injection molding machine of the present invention. 15...Charge servo motor, 16...Injection servo motor, 19...Fixed die plate,
20... Moving die plate, 24... Servo motor for mold opening/closing, 26... Heating tube, 27... Screw, 37... Cylinder member, 38... Injection chamber,
39... Passage, 44... Plunger, 45... Radial hole, 46... Axial hole, 47... Ball, 4
9... Holder arm, 50... Injection bar, 51...
... Injection reaction force sensor, 52 ... Drive body, 53 ... Threaded cylinder, 58 ... Nozzle, 66 ... Crank arm, 67 ... Crank shaft, 68 ... Eccentric shaft section, 8
2... Molten resin, 87... Holding pressure setting device, 88...
Control unit body.

Claims (1)

[Scope of Claims] 1. A heating cylinder, an injection nozzle disposed at the tip of the heating cylinder, and a resin supply means for supplying molten resin to an injection chamber provided at the tip of the heating cylinder;
piston means having a stop valve mechanism that closes when moving in the injection direction and opens when moving in the backward direction, and injects the molten resin supplied to the injection chamber into the cavity through the injection nozzle; A sensor is provided in the drive system to detect the resin pressure in the injection chamber applied when the piston moves, and in order to keep the resin pressure in the injection chamber constant during charging, the retraction speed of the piston means is kept constant, and the An injection molding machine characterized in that the injection molding machine is configured to feedback control the supply speed of molten resin by the resin supply means based on a resin pressure detection signal from a sensor. 2. An injection molding machine according to claim 1, wherein the resin supply means is a screw that rotates in one direction and whose rotation speed can be adjusted. 3. The injection molding machine according to claim 1, wherein the drive source of the screw is a servo motor. 4. The injection molding machine according to claim 1, wherein the piston means has a plunger that reciprocates at the rear of the injection nozzle, and the plunger is equipped with the stop valve mechanism. 5. An injection molding machine according to claim 1, wherein the piston means has a plunger that reciprocates at the rear of the injection nozzle, and the stroke length of the plunger is adjustable. 6. The injection molding machine according to claim 1, wherein the piston means includes a plunger that reciprocates at the rear of the injection nozzle, and a holder arm that supports the plunger and reciprocates together.