JPH07100343B2 - 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 each cylinder part is independent, the quantity corresponding to the number of stages is A cylinder portion is required, and in particular, the diameter becomes large, and the overall shape becomes complicated, which causes a problem of increasing cost.

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 4f is fixed to the screw 3. The combined inner piston 4 and the inner piston 4 are built in, the front of the inner piston main body 4u serves as the inner front oil chamber Cb, and the rear serves as the inner rear oil chamber Ca. The outer piston 5 opened at the end 5r and the outer piston 5 are built in, and the front of the outer piston body 5u is the outer front oil chamber Cd, and the rear is the outer rear oil chamber Cc.
Outer cylinder 7, inner front oil chamber Cb, inner rear oil chamber Ca,
It is characterized by including a hydraulic circuit 8 capable of supplying one or more of the outer front oil chamber Cd and the outer rear oil chamber Cc to supply pressure oil.

In this case, the pressure receiving area Sa of the inner rear oil chamber Ca and the pressure receiving area Sb of the inner front oil chamber Cb are determined by the pressure receiving area S
The relation of a> pressure receiving area Sb is established. Also, the hydraulic circuit 8
Is equipped with a meter-out circuit 9 for controlling the pressure of return oil by means of pressure control valves 9m and 9p.

[0011]

In the injection molding machine 1 according to the present invention, the relation between the pressure receiving area Sa of the inner rear oil chamber Ca and the pressure receiving area Sb of the inner front oil chamber Cb in the inner cylinder 6 is expressed by the relation of pressure receiving area Sa> pressure receiving area Sb. With this configuration, by supplying pressure oil to both the inner rear oil chamber Ca and the inner front oil chamber Cb, the inner piston 4 moves forward and the screw 3 moves forward. At this time, the magnitude of the output F1 [kg] with respect to the screw 3 is the inner rear oil chamber Ca.
The magnitude of the output acting from the side is Fa, and the inner front oil chamber Cb
If the magnitude of the output acting from the side is Fb, then Fa-F
It becomes b [kg]. In this case, Fa is the pressure receiving area Sa [c
m ² ] and the hydraulic pressure Pi [kg / cm ² ] of the hydraulic circuit 8 (S
a × Pi) and Fb are the pressure receiving area Sb [cm ² ] and the hydraulic pressure Pi.
It is the product (Sb × Pi) of [kg / cm ² ].

If pressure oil is supplied only to the inner rear oil chamber Ca, the inner piston 4 moves forward and the screw 3 moves forward. Output F2 [k for screw 3 at this time
The magnitude of g] is only the magnitude Fa of the output acting from the inner rear oil chamber Ca side.

On the other hand, the outer front oil chamber Cd in the outer cylinder 7
When pressure oil is supplied to the outer rear oil chamber Cc and the inner rear oil chamber Ca in the inner cylinder 6, the inner piston 4 and the outer piston 5 simultaneously move forward, and the screw 3 moves forward.
The magnitude of the output F3 [kg] with respect to the screw 3 at this time is the magnitude of the output acting from the outer rear oil chamber Cc side as Fc.
And the magnitude of the output acting from the outside front oil chamber Cd side is Fd.
Then, it becomes Fa + Fc−Fd [kg]. In this case, Fc is the product (Sc × P) of the pressure receiving area Sc [cm ² ] of the outer rear oil chamber Cc and the oil pressure Pi [kg / cm ² ] of the hydraulic circuit 8.
i) and Fd are the product (Sd × Pi) of the pressure receiving area Sd [cm ² ] of the outer front oil chamber Cd and the oil pressure Pi [kg / cm ² ].

Further, by supplying the pressure oil only to both the inner rear oil chamber Ca and the outer rear oil chamber Cc, the inner piston 4 and the outer piston 5 simultaneously move forward, and the screw 3 moves forward. Output F4 [kg] for screw 3 at this time
Is Fa + Fc [kg].

Therefore, if pressure oil is selectively supplied to the oil chambers Ca to Cd by the control of the hydraulic circuit 8, the output to the screw 3 is one of the four sizes F1 to F4 described above. If so, four different injection pressures can be selected. Further, at this time, if the pressure of the return oil is controlled by the pressure control valves 9m and 9p forming the meter-out circuit 9, back pressure control becomes possible at each selected output (injection pressure), and the meter-in pressure is kept constant. However, continuous linearity control with respect to the injection pressure can be easily performed.

[0016]

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 FIGS.

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 cylindrical cylinder block 11, and the rear end of the cylinder block 11 is closed by an oil motor support block 12. The rear part of the cylinder block 11 constitutes a multistage hydraulic cylinder 2 according to the present invention. An outer cylinder 7 has an outer piston 5 built therein. As a result, the front of the outer piston body 5u of the outer piston 5 becomes the outer front oil chamber Cd, and the rear of the outer piston body 5u becomes the outer rear oil chamber Cc.

The rear end 5r of the outer piston 5 comes into contact with the oil motor support block 12 in the final retracted position.
Further, the outer piston 5 is formed in the inner hollow, and the inner piston 4 is
By incorporating the above, it also serves as the inner cylinder 6. As a result, the front of the inner piston body 4u of the inner piston 4 becomes the inner front oil chamber Cb, and the rear of the inner piston body 4u becomes the inner rear oil chamber Ca. In this case, the inner rear oil chamber Ca is opened to the rear end 5r of the outer piston 5. Therefore, the outer piston 5
Is the most retracted position, the rear end 5r contacts the oil motor support block 12, so the outer rear oil chamber Cc and the inner rear oil chamber C
Although a is cut off, if the outer piston 5 exists at a position other than the last retracted position, the outer rear oil chamber Cc and the inner rear oil chamber Ca communicate with each other. A stopper portion 6e is formed on the inner surface of the inner cylinder 6 forming the inner rear oil chamber Ca so that the rear end of the inner piston 4 is locked by the step portion.

Further, at least the sizes of the pressure receiving area Sa of the inner rear oil chamber Ca and the pressure receiving area Sb of the inner front oil chamber Cb are set in the relationship of pressure receiving area Sa> pressure receiving area Sb, and preferably,
Pressure receiving area Sa: Pressure receiving area Sb = 2: 1 is selected. Furthermore, when the pressure receiving area of the outer rear oil chamber Cc is Sc, the relationship between the pressure receiving area Sa and the pressure receiving area Sc is as follows: Pressure receiving area Sa: Pressure receiving area Sc = 1: 1 Sd
In this case, it is desirable that the relationship between the pressure receiving area Sa and the pressure receiving area Sd is selected to be pressure receiving area Sa: pressure receiving area Sd = 2: 1.

On the other hand, the outer piston 5 is made to project forward from the front end 7f of the outer cylinder 7, the inner piston 4 is made to project forward from the front end 5f of the outer piston 5, and the front end 4f of the inner piston 4 is set to the rear of the screw 3. Join the ends. Also,
The oil motor 13 is attached to the rear end surface of the oil motor support block 12, and the rotation shaft 13s of the motor 13 penetrates the center of the oil motor support block 12 and further passes through the inner rear oil chamber Ca to the rear of the inner piston 4. The end is connected by the spline mechanism 14.

Therefore, by controlling the operation of the inner cylinder 6 and the outer cylinder 7 forming the injection drive system, the screw 3 can be moved forward and backward, and the screw motor can be formed by controlling the operation of the oil motor 13 forming the measuring drive system. 3 can be controlled to rotate.

On the other hand, the inner front oil chamber Cb, the inner rear oil chamber Ca, the outer front oil chamber Cd and the outer rear oil chamber Cc are connected to the hydraulic circuit 8. The hydraulic circuit 8 includes a hydraulic pump 21, an oil tank 22, four port switching valves V1 and V3, three port switching valves V2, V4 and V5.
The relief valves 23 and 24, the four-port switching valve 25, and the meter-out circuit 9 are provided and are connected as shown in FIG. Also,
The meter-out circuit 9 is a main relief valve (pressure control valve)
9m, pilot relief valve (electromagnetic proportional pressure control valve) 9
p, including a check valve 9c.

FIG. 4 shows an example of a simplified control system, where 31 is a setting unit and 32 is an arithmetic processing unit. With such a system, if the setting unit 31 sets the injection pressure P, the arithmetic processing unit 32 outputs a switching valve control command to output each switching valve V1.
.About.V5 are switch-controlled and a pressure control command is output to variably control the pilot relief valve 9p of the meter-out circuit 9.

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

First, by the hydraulic circuit 8, the oil chambers Ca and C are
If one or more of b, Cc and Cd are selected and pressure oil is supplied, the output to the screw 3 is F1, F2, F.
There are four options: 3, F4 [kg].

F1 [kg] is the case where pressure oil is supplied to both the inner rear oil chamber Ca and the inner front oil chamber Cb, and in this case, the magnitude of the output acting from the inner rear oil chamber Ca side. Is Fa and the magnitude of the output acting from the inner front oil chamber Cb side is Fb, F1 = Fa−Fb [kg], and only the inner piston 4 moves forward.

F2 [kg] is the case where the pressure oil is supplied only to the inner rear oil chamber Ca, and in this case, only the magnitude Fa of the output acting from the inner rear oil chamber Ca side becomes the inner piston 4 Only move forward.

F3 [kg] is the case where pressure oil is supplied to the outer front oil chamber Cd and the outer rear oil chamber Cc in the outer cylinder 7, and further to the inner rear oil chamber Ca in the inner cylinder 6, and in this case. , The magnitude of the output acting from the outer rear oil chamber Cc side is F
c, and the magnitude of the output acting from the outside front oil chamber Cd side is F
If d, then F3 = Fa + Fc−Fd [kg],
Both the outer piston 5 and the inner piston 4 move forward.

F4 [kg] is the case where pressure oil is supplied only to both the inner rear oil chamber Ca and the outer rear oil chamber Cc. In this case, the inner rear oil chamber Ca and the outer rear oil chamber Cc The magnitude of the output acting from is Fa + Fc, and both the inner piston 4 and the outer piston 5 move forward.

Fa is the pressure receiving area Sa of the inner rear oil chamber Ca.
[Cm ² ] and the hydraulic pressure Pi [kg / cm ² ] of the hydraulic circuit 8, Fb is the product of the internal pressure receiving area Sb [cm ² ] of the front oil chamber Cb and the hydraulic pressure Pi [kg / cm ² ], and Fc is the external The product of the pressure receiving area Sc [cm ² ] of the rear oil chamber Cc and the oil pressure Pi [kg / cm ² ],
Fd is the pressure receiving area Sd [cm ² ] of the outer front oil chamber Cd and the hydraulic pressure P.
It is the product of i [kg / cm ² ].

FIG. 2 is a control matrix of the switching valves V1 to V5 which are switched and controlled when selecting the outputs F1 to F4. The circles indicate the switching valves V1 to V5 on the side of the corresponding symbol a in FIG. This means switching to the symbol 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 a side. V5 is switched to the symbol b side. In other output modes, the switching valves V1 to V5 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, when the switching valves V1 to V5 are switch-controlled according to the control matrix shown in FIG. 2, the output F changes stepwise as shown in FIG. As an example, if the injection pressure P3 is specified, the output F3 is output,
At this time, each of the switching valves V1 to V corresponding to F3 in FIG.
5 is switch-controlled. The magnitude of the injection pressure P3 is F
3 / Ss (Ss: heating cylinder cross-sectional area), and it is set in advance in the setting unit 31 so that it can be designated or selected together with other injection pressures P1.

Further, if the back pressure of the return oil is controlled by the main relief valve 9m and the pilot relief valve 9p constituting the meter-out circuit 9, 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, if the injection pressure Px shown in FIG. 3 is specified, first, in FIG. 4, the switching valve control command is output from the arithmetic processing unit 32, and the switching valves V1 to V1 corresponding to F3 in FIG. V5 is switch-controlled. On the other hand, the arithmetic processing unit 32 calculates the back pressure of the return oil in the meter-out circuit 9 according to the linear function characteristic shown in FIG. 3, gives a corresponding pressure control command to the pilot relief valve 9p, and changes the relief valve 9P. Control. 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 (injection rate),
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.

[0036]

As described above, the injection molding machine according to the present invention includes the inner piston having the front end coupled to the screw and the inner piston, and the front of the inner piston body is the inner front oil chamber and the rear is the inner rear oil. It also serves as an inner cylinder that serves as a chamber, and incorporates an outer piston that opens the inner rear oil chamber to the rear end, and an outer piston,
Select one or more of the outer cylinder with the front of the outer piston body being the outer front oil chamber and the rear being the outer rear oil chamber, and the inner front oil chamber, inner rear oil chamber, outer front oil chamber, or outer rear oil chamber. Since a hydraulic circuit capable of supplying pressurized oil is provided, the screw drive mechanism including a multi-stage hydraulic cylinder can be downsized and the cost can be reduced, and highly accurate and stable pressure control can be performed. Has a great effect.

[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,

FIG. 4 is a block system diagram showing an example of a control system in the injection molding machine.

[Explanation of symbols]

 1 Injection Molding Machine 2 Hydraulic Cylinder 3 Screw 4 Inner Piston 4f Inner Piston Front End 4u Inner Piston Body 5 Outer Piston 5r Outer Piston Rear End 6 Inner Cylinder 7 Outer Cylinder 8 Hydraulic Circuit 9 Meter-out Circuit 9m Pressure Control Valve 9p Pressure Control Valve Ca Inner rear oil chamber Cb Inner front oil chamber Cc Outer rear oil chamber Cd Outer front oil chamber E Screw drive mechanism

Claims (3)

[Claims] 1. An injection molding machine comprising a screw drive mechanism for driving a screw forward and backward by a multistage hydraulic cylinder, and an inner piston having a front end coupled to the screw.
It has a built-in inner piston, doubles as an inner cylinder with the front of the inner piston body as the inner front oil chamber and the rear as the inner rear oil chamber.It also has an outer piston with the inner rear oil chamber open at the rear end and an outer piston. , An outer cylinder with the front of the outer piston body as the outer front oil chamber and the rear as the outer rear oil chamber, and one or more of the inner front oil chamber, the inner rear oil chamber, the outer front oil chamber, or the outer rear oil chamber An injection molding machine comprising a hydraulic circuit capable of supplying pressure oil. 2. The pressure receiving area of the inner rear oil chamber and the pressure receiving area of the inner front oil chamber are set such that the pressure receiving area of the inner rear oil chamber> the pressure receiving area of the inner front oil chamber. The injection molding machine according to claim 1. 3. 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.