JPH07100344B2 - Injection molding machine - 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 molding machine having a screw drive mechanism for driving a screw forward and backward by a multistage hydraulic cylinder.

[0002]

2. Description of the Related Art Conventionally, an injection molding machine equipped with a multi-stage hydraulic cylinder is known from Japanese Utility Model Publication No. 2-146017 and Japanese Patent Publication No. 59-15295.

The former injection molding machine is a machine in which a plurality of pairs of single hydraulic cylinders, which are arranged in parallel at positions symmetrical with respect to the axis of the screw, are connected to the screw, and the latter injection molding machine. The machine gradually connects several rams with different diameters in order of increasing diameter, and forms a working chamber composed of this ram and a cylinder into a cylindrical shape, and an oil inflow pipe is provided in each working chamber. By connecting and leading to the directional control valve, oil is press-fitted into each working chamber at the same time or with a time difference between the respective working chambers to operate the hydraulic cylinder.

[0004]

However, the conventional injection molding machine has the following problems to be solved.

First, in the former case, since a plurality of different single hydraulic cylinders which are separately configured are combined, the number of hydraulic cylinders to be used increases in accordance with the number of stages, and there is a drawback that the size is significantly increased. On the other hand, in the latter case, since the hydraulic cylinder is apparently integrated, the dimension in the width direction is smaller than in the former case, but since the cylinder parts (piston parts) are provided in series in front and rear, However, the size in the front-rear direction becomes large, and the overall shape becomes complicated, resulting in a cost increase.

By the way, normally, in the injection step of filling the resin into the mold cavity, the speed of the screw is controlled, and the magnitude of the speed is controlled based on the variable injection pressure. On the other hand, the resin that has flowed into the mold cavity is cured more rapidly toward the outside (skin layer), and the resin flow state in the mold cavity is not constant. For this reason, the magnitude of the injection pressure varies depending on the flow state of the resin, and the molding quality is greatly influenced. That is, the residual stress on the resin changes according to the flow state of the resin,
This causes molding defects such as warpage and distortion.

However, since the conventional injection molding machine employs a multi-stage hydraulic cylinder in which the pressure change is stepwise, it is not possible to perform highly accurate and stable pressure control, and there is a limit to improving the molding quality. there were.

The present invention solves the problems existing in the prior art as described above. The screw drive mechanism including a multi-stage hydraulic cylinder can be downsized and the cost can be reduced, and high-precision and stable pressure can be achieved. An object is to provide an injection molding machine that can perform control.

[0009]

According to the present invention, in constructing an injection molding machine 1 including a screw drive mechanism E for driving a screw 3 forward and backward by a multi-stage hydraulic cylinder 2, in particular, a front end 5f is set to the screw 3. The inner piston part 5 connected to the inner piston part 5 and a cylindrical outer piston arranged coaxially with the inner piston part 5 via a first gap G1 and having a front part 6t connected to the front part 5t of the inner piston part 5. The piston block 4 composed of the portion 6, the outer cylinder portion 8 and the outer cylinder portion 8 are coaxially arranged via the second gap G2, and the rear portion 9n is coupled to the rear portion 8n of the outer cylinder portion 8. A cylinder block 7 including an inner cylinder portion 9 is provided, and the inner cylinder portion 9 is inserted into the first gap G1 and the outer piston portion 6 is inserted into the second gap G2. Ca, Siri A second oil chamber Cb is provided in front of the da part 9, a third oil chamber Cc is provided behind the outer piston part 6, and a reverse pressure oil chamber Cd is provided between the outer piston part 6 and the outer cylinder part 8 in front of the outer piston part body 6u. In addition to providing each, first oil chamber C
The hydraulic circuit 10 is characterized by including one or two or more of a, the second oil chamber Cb, the third oil chamber Cc, or the reverse pressure oil chamber Cd to supply the pressure oil.

In this case, the pressure receiving area Sa of the first oil chamber Ca,
The sizes of the pressure receiving area Sb of the second oil chamber Cb, the pressure receiving area Sc of the third oil chamber Cc, and the pressure receiving area Sd of the reverse pressure oil chamber Cd are as follows: Pressure receiving area Sd <pressure receiving area Sa <pressure receiving area Sb <pressure receiving area Sc
Compose the relationship. The front portion 6t of the outer piston portion 6 and the front portion 5t of the inner piston portion 5 are rotatably connected. Furthermore, the hydraulic circuit 10 is provided with a meter-out circuit 11 that controls the pressure of the return oil by the pressure control valves 11m and 11p.

[0011]

In the injection molding machine 1 according to the present invention, when the pressure oil is supplied only to the first oil chamber Ca, the screw 3 moves forward, and the magnitude of the output Fa [kg] to the screw 3 at this time is The product (Sa × P) of the pressure receiving area Sa [cm ² ] of the first oil chamber Ca and the oil pressure Pi [kg / cm ² ] of the hydraulic circuit 10.
i).

If pressure oil is supplied only to the second oil chamber Cb, the screw 3 moves forward and the magnitude of the output Fb to the screw 3 at this time is determined by the pressure receiving area Sb of the second oil chamber Cb and the hydraulic pressure. Product of oil pressure Pi of circuit 10 (Sb x Pi)
Becomes

Furthermore, if pressure oil is supplied only to the third oil chamber Cc, the screw 3 moves forward, and the magnitude of the output Fc to the screw 3 at this time is determined by the third oil chamber Cc.
Of the pressure receiving area Sc of the hydraulic pressure Pi and the hydraulic pressure Pi of the hydraulic circuit 10 (Sc ×
Pi).

On the other hand, if pressure oil is supplied to the counter pressure oil chamber Cd,
Pressure is applied in the direction in which the screw 3 is retracted, and the magnitude of the output Fd with respect to the screw 3 is the reverse pressure oil chamber Cd.
Of the pressure receiving area Sd of the hydraulic pressure Pi and the hydraulic pressure Pi of the hydraulic circuit 10 (Sd ×
Pi) and acts in the negative direction.

Therefore, the pressure receiving area S of the first oil chamber Ca
a, the pressure receiving area Sb of the second oil chamber Cb, the pressure receiving area Sc of the third oil chamber Cc, and the pressure receiving area Sd of the reverse pressure oil chamber Cd,
The configuration is such that Sd <Sa <Sb <Sc, and the first oil chamber Ca and the second oil chamber C are controlled by controlling the hydraulic circuit 10.
b, if one or more of the third oil chamber Cc and the reverse pressure oil chamber Cd is selected and pressure oil is supplied, F1 = Fa-Fd, F2 = Fa, F3 = Fb-F as outputs to the screw 3.
d, F4 = Fb, F5 = Fa + Fb−Fd, F6 = Fa
+ Fb, F7 = Fc−Fd, F8 = Fc, F9 = Fa +
Fc-Fd, F10 = Fa + Fc, F11 = Fb + Fc
-Fd, F12 = Fb + Fc, F13 = Fa + Fb + F
It is possible to select 14 sizes of c-Fd and F14 = Fa + Fb + Fc, in other words, 14 different injection pressures.

Further, at this time, if the pressure of the return oil is controlled by the pressure control valves 11m and 11p constituting the meter-out circuit 11, the back pressure can be controlled at each selected output (injection pressure), and the meter-in pressure can be controlled. Even if is constant, continuous linearity control with respect to the injection pressure can be easily performed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, the structure of the injection molding machine according to the present invention will be described with reference to FIG.

In the figure, reference numeral 1 is an injection molding machine, and in particular,
A part of an injection device is shown. Reference numeral 3 denotes a screw, the front end side of which is inserted into a heating cylinder (not shown), and the rear end of the screw 3 is supported by a screw drive mechanism E. The screw drive mechanism E includes a tubular casing block 21, and the rear end of the casing block 21 is closed by an oil motor support block 22. The casing block 2
The rear part of 1 constitutes a multistage hydraulic cylinder 2 according to the invention.

Reference numeral 8 denotes an outer cylinder portion, and an inner cylinder portion 9 is coaxially arranged inside the outer cylinder portion 8 with a gap G2. The rear end of the inner cylinder portion 9 is integrally formed with the oil motor support block 22, so that the rear portion 8n of the outer cylinder portion 8 and the rear portion 9n of the inner cylinder portion 9 are configured as a coupled cylinder block 7.

On the other hand, 6 is a cylindrical outer piston portion, and the inner piston portion 5 is coaxially arranged inside the outer piston portion 6 via a gap G1. The front part 6t of the outer piston part 6 has bearings 23, 2 with respect to the front part 5t of the inner piston part 5.
It is rotatably coupled via 4 and thereby constitutes the piston block 4. The inner cylinder portion 9 has a gap G.
1 and the outer piston portion 6 is inserted into the gap G2.

With the above construction, the first oil chamber Ca is located behind the inner piston part 5, the second oil chamber Cb is located in front of the inner cylinder part 9, and the third oil chamber is located behind the outer piston part 6. Cc is
Reverse pressure oil chambers Cd are provided between the outer piston portion 6 and the outer cylinder portion 8 in front of the outer piston portion main body 6u. In this case, the pressure receiving area Sa of the first oil chamber Ca, the pressure receiving area Sb of the second oil chamber Cb, the pressure receiving area Sc of the third oil chamber Cc, and the pressure receiving area Sd of the reverse pressure oil chamber Cd are the same as the pressure receiving area Sd.
<Pressure receiving area Sa <pressure receiving area Sb <pressure receiving area Sc,
Desirably, the pressure receiving area Sa: pressure receiving area Sd = 2: 1, the pressure receiving area Sb: pressure receiving area Sd = 4: 1, and the pressure receiving area Sc: pressure receiving area Sd = 8: 1 are selected.

The piston block 4 projects forward from the front end 8f of the outer cylinder portion 8, and the rear end of the screw 3 is connected to the front end 5f of the inner piston portion 5. On the other hand, the oil motor 25 is provided on the rear end surface of the oil motor support block 22.
The rotation shaft 25 of the motor 25
s penetrates the center of the oil motor support block 22,
Further, the spline mechanism 26 is connected to the rear end 5r of the inner piston portion 5 through the first oil chamber Ca.

Therefore, if the hydraulic cylinder 2 constituting the injection drive system is operated and controlled, the screw 3 can be moved forward and backward, and if the oil motor 25 constituting the metering drive system is operated and controlled, the screw 3 is rotationally controlled. it can.

On the other hand, the first oil chamber Ca, the second oil chamber Cb, the third oil chamber Cc and the reverse pressure oil chamber Cd are connected to the hydraulic circuit 10.
The hydraulic circuit 10 includes a hydraulic pump 31, an oil tank 32, four-port switching valves V1, V2, V3, V4, V6, V7, a three-port switching valve V5, relief valves 33, 34, and a meter-out circuit 11, and FIG. Connect as shown in. The meter-out circuit 11 is a main relief valve (pressure control valve).
11m, pilot relief valve (electromagnetic proportional pressure control valve)
11p and an arithmetic processing unit 35, the input side of the arithmetic processing unit 35 is connected to the hydraulic pressure sensor 36 and the setting unit 37 connected to the discharge line of the hydraulic pump 31, and the output side of the arithmetic processing unit 35. Is connected to the control input side of the pilot relief valve 11p via the amplifier 38.
In this case, if the setting unit 37 sets the injection pressure P, the arithmetic processing unit 35 outputs a switching valve control command to switch and control each switching valve V1 to V7, and also outputs a pressure control command to output the meter-out circuit. The pilot relief valve 11p of 11 is variably controlled.

Next, the overall operation of the injection molding machine 1 according to the present invention will be described.

First, by the hydraulic circuit 10, each oil chamber Ca,
If one or more of Cb, Cc and Cd are selected and pressure oil is supplied, the output to the screw 3 is F1 = Fa−
Fd, F2 = Fa, F3 = Fb−Fd, F4 = Fb, F
5 = Fa + Fb−Fd, F6 = Fa + Fb, F7 = Fc
-Fd, F8 = Fc, F9 = Fa + Fc-Fd, F10
= Fa + Fc, F11 = Fb + Fc-Fd, F12 = F
b + Fc, F13 = Fa + Fb + Fc-Fd, F14 =
Fourteen sizes of Fa + Fb + Fc can be selected. In this case, the magnitude of the output Fa is the pressure receiving area S of the first oil chamber Ca.
The product of a and the hydraulic pressure Pi of the hydraulic circuit 10 (Sa × Pi), and the size of the output Fb are the pressure receiving area Sb of the second oil chamber Cb and the hydraulic pressure Pi.
(Sb × Pi), the size of the output Fc is the third oil chamber Cc
Product of the pressure receiving area Sc and the hydraulic pressure Pi (Sc × Pi), output F
The size of d is the product (Sd × Pi) of the pressure receiving area Sd of the counter pressure oil chamber Cd and the hydraulic pressure Pi, and Fd acts in the negative direction.

FIG. 2 is a control matrix of the switching valves V1 to V7 that are switched and controlled when selecting the outputs F1 to F14, and the circles indicate the switching valves V1 to V7 in FIG. This means switching to the b side. As an example, when the output F1 is selected, the switching valve V1 is on the symbol a side, the switching valve V2 is on the symbol b side, the switching valve V3 is on the symbol b side, and the switching valve V4 is on the symbol b side. V5 is switched to the symbol b side, switching valve V6 is switched to the symbol a side, and switching valve V7 is switched to the symbol b side. In the other output modes, the switching valves V1 to V7 are similarly switched and controlled according to the control matrix shown in FIG.

On the other hand, in FIG. 3, the vertical axis represents the injection pressure P [kg / c
m ² ], a horizontal axis is an output F [kg] with respect to the screw 3, and is a characteristic diagram showing the magnitude of the output F corresponding to the injection pressure P. That is, if the switching valves V1 to V7 are switch-controlled in accordance with the control matrix shown in FIG. 2, the output F changes stepwise as shown in FIG. As an example, if the injection pressure P6 is specified, the output F6 is output,
At this time, each of the switching valves V1 to V corresponding to F6 in FIG.
7 is switch-controlled. The magnitude of the injection pressure P6 is F
6 / Ss (Ss: heating cylinder cross-sectional area), and is preset or selectable in the setting section 37 together with other injection pressures P1.

The main relief valve 11m and the pilot relief valve 11p which constitute the meter-out circuit 11 are also provided.
Thus, by controlling the back pressure of the return oil, continuous linearity control can be performed with respect to the injection pressure. The linear function characteristic expressed in a straight line in FIG. 3 is a case where such control is performed. That is, as an example, the injection pressure Px shown in FIG.
2 is specified, the switching valve control command is output from the arithmetic processing unit 35, and the switching valves V1 to V corresponding to F6 in FIG.
7 is switch-controlled. On the other hand, the arithmetic processing unit 35 calculates the back pressure of the return oil in the meter-out circuit 11 according to the linear function characteristic shown in FIG. 3, and gives a corresponding pressure control command to the pilot relief valve 11p via the amplifier 37,
The relief valve 11P is variably controlled. As a result, the magnitude of the output to the screw 3 becomes Fx. Thus, if back pressure control is also used for each selected output F,
Continuous linearity control with respect to the injection pressure P can be easily performed.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment.
For example, the screw in the present invention is a concept including various injection members such as a plunger capable of injecting resin. In addition, the detailed configuration, shape, and the like can be arbitrarily changed without departing from the scope of the present invention.

[0032]

As described above, in the injection molding machine according to the present invention, the inner piston portion having the front end coupled to the screw and the inner piston portion are coaxially arranged with a first gap therebetween,
And a piston block composed of a cylindrical outer piston portion whose front portion is connected to the front portion of the inner piston portion, the outer cylinder portion and the outer cylinder portion which are coaxially arranged with a second gap therebetween, and The cylinder block is composed of an inner cylinder part whose rear part is connected to the rear part of the outer cylinder part.The inner cylinder part is inserted into the first gap and the outer piston part is inserted into the second gap. One oil chamber, a second oil chamber in front of the inner cylinder part, a third oil chamber behind the outer piston part, and a back pressure oil chamber in front of the outer piston part body between the outer piston part and the outer cylinder part, respectively. , A first oil chamber, a second oil chamber, a third oil chamber or a reverse pressure oil chamber, because it comprises a hydraulic circuit capable of supplying pressure oil by selecting one or more
The screw drive mechanism including the multi-stage hydraulic cylinder can be downsized and the cost can be reduced, and highly accurate and stable pressure control can be performed.

[Brief description of drawings]

FIG. 1 is a partial configuration diagram including a partial cross section of an injection molding machine according to the present invention,

FIG. 2 is a control matrix diagram of each switching valve with respect to output,

FIG. 3 is a characteristic diagram showing the relationship between output and injection pressure,

[Explanation of symbols]

 1 Injection Molding Machine 2 Hydraulic Cylinder 3 Screw 4 Piston Block 5 Inner Piston 5f Front End of Inner Piston 5t Front of Inner Piston 6 Outer Piston 6t Front of Outer Piston 7 Cylinder Block 8 Outer Cylinder 8n Outer Cylinder Rear part 9 inner cylinder part 9n inner cylinder part 10 hydraulic circuit 11 meter-out circuit 11m pressure control valve 11p pressure control valve E screw drive mechanism G1 first gap G2 second gap Ca first oil chamber Cb second oil chamber Cc Third oil chamber Cd Reverse pressure oil chamber

Claims (4)

[Claims] 1. An injection molding machine comprising a screw drive mechanism for advancing and retracting a screw by a multistage hydraulic cylinder, wherein an inner piston portion having a front end coupled to the screw and a first gap for the inner piston portion are provided. Via a second clearance to the outer cylinder part and this outer cylinder part, and a piston block composed of a cylindrical outer piston part that is coaxially arranged with the front part connected to the front part of the inner piston part. Equipped with a cylinder block consisting of an inner cylinder part whose rear part is connected to the rear part of the outer cylinder part.The inner cylinder part is inserted into the first gap and the outer piston part is inserted into the second gap. , A first oil chamber behind the inner piston part, a second oil chamber in front of the inner cylinder part, a third oil chamber behind the outer piston part, between the outer piston part and the outer cylinder part in front of the outer piston part body Reverse With each pressure oil chamber,
An injection molding machine comprising a hydraulic circuit capable of supplying one or more of the first oil chamber, the second oil chamber, the third oil chamber, or the reverse pressure oil chamber to supply pressure oil. 2. The pressure receiving area of the first oil chamber, the pressure receiving area of the second oil chamber, the pressure receiving area of the third oil chamber, and the pressure receiving area of the reverse pressure oil chamber are as follows: The injection molding machine according to claim 1, wherein the pressure receiving area of one oil chamber <the pressure receiving area of the second oil chamber <the pressure receiving area of the third oil chamber. 3. The injection molding machine according to claim 1, wherein a front portion of the outer piston portion and a front portion of the inner piston portion are rotatably coupled to each other. 4. The injection molding machine according to claim 1, wherein the hydraulic circuit is provided with a meter-out circuit for controlling the pressure of the return oil by a pressure control valve.