JPH0818360B2 - 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 on the other hand, the metering side drive mechanism that rotationally drives the screw and the hydraulic cylinder move forward and backward. Therefore, the size in the front-rear direction becomes large and the diameter also becomes large, so that there is a problem that miniaturization cannot be achieved in the end. In addition, the shape of the cylinder portion of the hydraulic cylinder is complicated, resulting in a significant increase in 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, when the injection molding machine 1 is provided with the screw drive mechanism E for driving the screw 3 forward and backward by the multi-stage hydraulic cylinders 2x, 2y, the front end 5xf, 5yf is particularly preferable. Has built-in pistons 5x and 5y that are connected to the screw 3 side, and the piston body 5
xu and 5yu are front oil chambers 4xf and 4yf, rear portions are rear oil chambers 4xr and 4yr, and a pair of outer cylinder portions 2xo arranged symmetrically with respect to the axial center of the screw 3 are provided.
2yo and the inner oil chamber 6x inside each piston 5x, 5y,
6y is provided and the rear end 2 of the outer cylinder portion 2xo, 2yo
Inner oil chamber 6x from xr, 2yr through oil pipes 7x, 7y,
A pair of inner cylinder parts 2 configured to be capable of supplying pressure oil to 6y
xi, 2yi, front oil chambers 4xf, 4yf , rear oil chamber 4x
r, 4yr or one or more of the inner oil chambers 6x, 6y is configured to be capable of supplying pressure oil , and the pressure control valve 9
Meter-out times to control the pressure of return oil by m and 9p
By providing the passage 9, the injection pressure P is continuous.
It is characterized by comprising a hydraulic circuit 8 for performing linearity control .

[0010] In this case, the inner oil chamber 6x ... the pressure receiving area of Si,
The size of the front oil chamber 4Xf ... pressure receiving area Sf and a rear oil chamber 4Xr ... pressure receiving area Sr of the will relationship Si <Sf <Sr
To configure.

[0011]

The operation of the injection molding machine 1 according to the present invention is as follows.
If the pressure oil is supplied only to the inner oil chambers 6x, 6y of the inner cylinder portions 2xi, 2yi provided in x, 5y, the pistons 5x,
5y moves forward and the screw 3 moves forward. At this time, the magnitude Fi [kg] of the output to the screw 3 is the pressure receiving area Si [cm ² ] of both inner oil chambers 6x and 6y and the hydraulic pressure Pi [of the hydraulic circuit 8]. kg / cm ² ]. (Si × Pi).

On the other hand, if pressure oil is supplied only to the rear oil chambers 4xr and 4yr of the outer cylinder portions 2xo and 2yo, the pistons 5x and 5y move forward and the screw 3 moves forward. The output magnitude Fr is the product (Sr × Pi) of the pressure receiving areas Sr of the rear oil chambers 4xr and 4yr and the hydraulic pressure Pi of the hydraulic circuit 8.

If pressure oil is supplied to the front oil chambers 4xf and 4yf of the outer cylinder portions 2xo and 2yo, the pistons 5
In order to press x and 5y in the backward direction, screw 3
On the other hand, the output Fn is in the negative direction, and its magnitude is the pressure receiving area Sf of the front oil chambers 4xf and 4yf and the hydraulic pressure P of the hydraulic circuit 8.
It is the product of i (Sf × Pi).

Therefore, the pressure receiving area S of the inner oil chambers 6x ...
i, the pressure receiving area Sf of the front oil chamber 4xf ... And the rear oil chamber 4xr ...
The pressure receiving area Sr of the front oil chamber 4 is controlled by the hydraulic circuit 8 while the size of the pressure receiving area Sr is set to the relationship of Si <Sf <Sr.
xf ..., rear oil chamber 4xr ... or inner oil chamber 6x ... If one or two or more are selected and pressure oil is supplied, as output to the screw 3, F1 = Fi, F2 = Fr-Fn, F3 = Fi.
It is possible to select five sizes of + Fr-Fn, F4 = Fr, F5 = Fi + Fr, in other words, five different injection pressures. 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.

[0015]

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 11 denotes a heating cylinder whose rear end is supported by a heating cylinder support plate 12, which has a screw 3 built therein, and the rear end of the screw 3 has a screw drive mechanism E.
Supported by. The screw drive mechanism E includes a cylinder unit 13, and the unit 13 includes a pair of hydraulic cylinders 2x and 2y arranged symmetrically with respect to the axis of the screw 3.
The hydraulic cylinders 2x and 2y are connected by a connecting plate portion 14, and the cylinder unit 13 and the heating cylinder supporting plate 12 are connected by a plurality of tie bars 15.

Further, each hydraulic cylinder 2x, 2y has an outer cylinder portion 2xo, 2yo containing a piston 5x, 5y. As a result, the front of the piston bodies 5xu, 5yu inside the outer cylinder portions 2xo, 2yo become the front oil chambers 4xf, 4yf, and the piston bodies 5xu, 5yu are formed.
The rear oil chambers are rear oil chambers 4xr and 4xr. Further, the internal cylinders 2xi and 2yi are formed by forming the internal oil chambers 6x and 6y inside the pistons 5x and 5y, respectively. And the rear end 2x of the outer cylinder portion 2xo, 2yo
The outer cylinder portions 2xo, 2y are provided at the centers of r, 2yr.
The linear oil pipes 7x and 7y are projected inward along the axis of o, and the front ends thereof penetrate the rear ends of the pistons 5x and 5y and face the inner oil chambers 6x and 6y. As a result, the oil pipe 7
Pressure oil can be supplied into the inner oil chambers 6x and 6y through x and 7y.

The pressure receiving area Si of the inner oil chambers 6x, the pressure receiving area Sf of the front oil chambers 4xf, and the pressure receiving area Sr of the rear oil chambers 4xr ... Have a relationship of Si <Sf <Sr.

On the other hand, the piston rods 5xt and 5yt of the pistons 5x and 5y are the outer cylinder portions 2xo and 2yo.
The piston rod 5xt, 5
The tips 5xf and 5yf of yt are coupled to both ends of the movable block 16. The movable block 16 is provided with a rotating block 18 rotatably supported by a plurality of bearings 17 at the center thereof, and the screw 3 is provided at the center of the tip of the rotating block 18.
Join the rear ends of. Further, an oil motor 19 is attached to the connecting plate portion 14, and a rotating shaft of the motor 19 is connected to a rear end of the rotating block 16 via a spline mechanism 20. With such a configuration, a rational layout of each part is possible, and in particular, the screw drive mechanism E can be made compact and compact.

Therefore, when the hydraulic cylinders 2x, 2y forming the injection drive system are operated and controlled, the movable block 16,
The rotation block 18 moves back and forth, the screw 3 can be moved back and forth, and an oil motor 19 that constitutes a metering drive system is provided.
If the operation control is performed, the rotation block 18 rotates, and the rotation of the screw 3 can be controlled.

On the other hand, 8 is a hydraulic circuit, which is connected to the hydraulic circuit 8 by commonly connecting the front oil chambers 4xf and 4yf, the rear oil chambers 4xr and 4yr, and the oil pipes 7x and 7y in the outer cylinder portions 2xo and 2yo, respectively. Connecting. Hydraulic circuit 8
Is a hydraulic pump 25, an oil tank 26, a four-port switching valve V
1, V2, V3, V4, relief valve 27, cooler 28,
A meter-out circuit 9 is provided and is connected by piping as shown in FIG. The meter-out circuit 9 also includes a main relief valve (pressure control valve) 9m, a pilot relief valve (electromagnetic proportional pressure control valve) 9p, and a check valve 9c.

FIG. 5 shows an example of a simplified control system, 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 control switching of the four-port switching valves V1, V2, V3, V4, and pressure control. A 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, the front oil chamber 4xf ...
If one or more of the rear oil chamber 4xr ... or the inner oil chamber 6x ... is selected and pressure oil is supplied, the output F to the screw 3 is F1 = Fi, F2 = Fr-Fn, F3 = Fi + Fr.
Five sizes of -Fn, F4 = Fr, F5 = Fi + Fr can be selected. In this case, the output magnitude Fi is the product (Si × Pi) of the pressure receiving area Si of both the inner oil chambers 6x and 6y and the oil pressure Pi of the hydraulic circuit 8, and Fr is the pressure receiving area Sr of both the rear oil chambers 4xr and 4yr and the oil pressure. Product of oil pressure Pi of circuit 8 (Sr x Pi)
Is. Further, the output magnitude Fn is determined by the front oil chambers 4xf, 4
The product of the pressure receiving area Sf of yf and the hydraulic pressure Pi of the hydraulic circuit 8 (Sf
XPi), which means acting in the negative direction.

On the other hand, FIG. 3 shows four-port switching valves V1, V2, V for switching control when selecting each output F1 to F5.
3 is a control matrix of V4, where the blank indicates the neutral position, and the open circle indicates that the four-port switching valve V1, V2, V3, or V4 is switched to the corresponding symbol a side or symbol b side in FIG. To do. As an example, when the output F1 is selected, the four-port switching valve V2 has the symbol a.
, The four-port switching valve V3 is switched to the symbol b side, and the four-port switching valve V4 is switched to the symbol b side. In other output modes, and also in the operation of the oil motor 19 and the backward operation of the screw 3, the port switching valves V1, V2, V3, V according to the control matrix shown in FIG.
4 is similarly switch-controlled.

On the other hand, in FIG. 4, the vertical axis represents the injection pressure P [kg / c
m ² ], the horizontal axis is an output F [kg] with respect to the screw 3, and a characteristic diagram showing the magnitude of the output F corresponding to the injection pressure P. That is, when the four-port switching valves V1, V2, V3, and V4 are switching-controlled according to the control matrix shown in FIG. 3, the output F changes stepwise as shown in FIG. As an example, when the injection pressure P4 is designated, the output F4 is output, and at this time, the four-port switching valves V1 and V4 are switching-controlled corresponding to F4 in FIG. The magnitude of the injection pressure P4 is F4 / Ss (F4: Sr ×
Pi, Ss: heating cylinder cross-sectional area) and other injection pressure P1
Together with ... Are set in advance in the setting section 31 so as to be designated or selectable.

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 represented by a straight line in FIG. 4 is a case where such control is performed. That is, as an example, if the injection pressure Px shown in FIG. 4 is designated, first, the switching valve control command is output in FIG. 5, and the four-port switching valve V1, V4 corresponds to F4 in FIG.
V4 is switch-controlled. On the other hand, the arithmetic processing unit 32 calculates the back pressure Po of the return oil in the meter-out circuit 9 according to the linear function characteristic shown in FIG. In this case, the back pressure Po is obtained by Po = {(Pi * Sr)-(P4 * Ss)} / Sf. Therefore, a corresponding pressure control command is given to the pilot relief valve 9p, and the relief valve 9P is variably controlled. To do. As a result, the magnitude of the output to the screw 3 is F
x. In this way, 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.

[0030]

As described above, in the injection molding machine according to the present invention, the piston whose front end is connected to the screw side is built in, the front of the piston body is the front oil chamber, the rear is the rear oil chamber, and A pair of outer cylinders arranged symmetrically with respect to the shaft center and an inner oil chamber inside each piston, and pressure oil can be supplied to the inner oil chamber from the rear end of the outer cylinder through an oil pipe. Pressure oil can be supplied by selecting one or more of the pair of inner cylinder parts and the front oil chamber , the rear oil chamber, or the inner oil chamber.
And the pressure of the return oil is adjusted by the pressure control valve.
By providing a meter-out circuit to control the injection pressure
Since a hydraulic circuit that performs continuous linearity control with respect to force is provided, it is possible to reduce the size and cost of a screw drive mechanism including a multi-stage hydraulic cylinder, and to perform highly accurate and stable pressure control. There is a remarkable 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 when viewed from a plane direction;

FIG. 2 is a partial configuration view of the injection molding machine seen from a side direction,

FIG. 3 is a control matrix diagram of a four-port switching valve for output,

FIG. 4 is a characteristic diagram showing a relationship of output with respect to injection pressure,

FIG. 5 is a block system diagram showing an example of a control system in the injection molding machine,

[Explanation of symbols]

 1 injection molding machine 2x ... hydraulic cylinder 2xo ... outer cylinder part 2xi ... inner cylinder part 2xr ... rear end of outer cylinder part 3 screw 4xf ... front oil chamber 4xr ... rear oil chamber 5x ... piston 5xf ... piston front end 5xu ... piston body 6x ... Inner oil chamber 7x ... Oil pipe 8 Hydraulic circuit E Screw drive mechanism 9 Meter-out circuit 9m Pressure control valve (main relief valve) 9p Pressure control valve (pilot relief valve)

Claims (2)

[Claims] 1. An injection molding machine comprising a screw drive mechanism for driving a screw forward and backward by a multi-stage hydraulic cylinder, wherein a piston having a front end coupled to the screw side is built-in, and a front of the piston body is a front oil chamber and a rear side. Is a rear oil chamber, and a pair of outer cylinders symmetrically arranged with respect to the screw shaft center and an inner oil chamber inside each piston are provided. A pair of inner cylinders configured to supply pressure oil to the chambers, and one or more front oil chambers , rear oil chambers, or inner oil chambers are configured to supply pressure oil, and a pressure control valve By return oil
By providing a meter-out circuit to control the pressure of
In addition, the injection molding machine is provided with a hydraulic circuit that continuously controls linearity with respect to the injection pressure . 2. The size of the pressure receiving area of the inner oil chamber, the pressure receiving area of the front oil chamber, and the pressure receiving area of the rear oil chamber are such that the pressure receiving area of the inner oil chamber <the pressure receiving area of the front oil chamber <the pressure receiving area of the rear oil chamber. The injection molding machine according to claim 1, characterized in that