JPH0716984B2 - 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 provided with a hydraulic cylinder for driving a screw forward and backward and a motor for driving a screw rotation.

[0002]

2. Description of the Related Art A screw advancing / retreating drive hydraulic cylinder having a cylinder portion and a piston portion built in the cylinder portion, in which the front of the piston body in the piston portion is a front oil chamber and the rear is a rear oil chamber, A hydraulic injection molding machine equipped with an oil motor for screw rotation drive, in which the front side of a rotary shaft that passes through the rear oil chamber from the rear end of the cylinder part is connected to the rear end of the piston part through a spline mechanism, is known. There is.

By the way, in this type of injection molding machine, when setting the molding conditions such as the injection speed and the injection pressure, the optimum value is set according to the size and shape of the molded product, but the setting range is the screw. Since it depends on the capacity of the drive mechanism, there is a weak point that the setting range is limited in the case of a single hydraulic cylinder.

For this reason, in the prior art, the actual open flat 2-146017 is used.
The use of a multi-stage hydraulic cylinder capable of extracting a plurality of outputs of different sizes as disclosed in Japanese Patent Publication No. 59-15295 and Japanese Patent Publication No. 59-15295, thereby expanding the setting range when setting molding conditions. I was trying. The former injection molding machine is one in which a plurality of pairs of single hydraulic cylinders, which are arranged in parallel at positions symmetrical to the screw shaft center, are connected to the screw, and the latter injection molding machine. Is made up of several rams with different diameters that are connected in order from the largest to the largest, and a working chamber composed of this ram and a cylinder is formed into a cylindrical shape, and an oil inflow pipe is connected to each working chamber. Then, the hydraulic cylinders are guided to the directional control valve, and the hydraulic cylinders are actuated by pressing the oil into the respective working chambers at the same time or with a time difference between the respective working chambers.

[0005]

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

First, in the former case, a plurality of different single hydraulic cylinders that are separately configured are combined, so that the number of hydraulic cylinders used increases in accordance with the number of stages, and there is a problem 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 In addition to the need for the cylinder portion, the overall shape becomes complicated, which causes a problem of increasing cost.

By the way, usually, in the injection process of filling the resin into the mold cavity, the speed control for the screw is performed, 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 the 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 in improving the molding quality.

The present invention has solved the problems existing in the prior art as described above. By utilizing the existing form of the screw drive mechanism as it is, the screw drive mechanism can be downsized and the cost can be reduced. An object of the present invention is to provide an injection molding machine capable of performing highly accurate and stable pressure control.

[0010]

The present invention has a cylinder portion 3 and a piston portion 4 built in the cylinder portion 3, and a front oil chamber C is provided in front of the piston body 4u in the piston portion 4.
n and a hydraulic cylinder 2 for driving the screw back and forth with the rear oil chamber Cd in the rear, and the rear oil chamber C from the rear end 3r of the cylinder portion 3.
The front side of the rotary shaft 5s passing through d is connected to the spline mechanism 6
When configuring the injection molding machine 1 including the screw rotation driving motor 5 that is coupled to the rear end 4r of the piston portion 4 via the, the internal oil chamber Ci is particularly provided inside the piston portion 4.
Further, inside the rotary shaft 5s, an inner oil passage Ji whose front end opening Jis faces the inside of the inner oil chamber Ci is provided, and one or more of the front oil chamber Cn, the rear oil chamber Cd, and the inner oil passage Ji are selected. A hydraulic circuit 7 capable of supplying pressure oil is provided.

In this case, an outer oil passage Jo formed by a ring groove along the circumferential direction is provided on the bearing surface 8 through which the rotary shaft 5s is inserted at the rear end 3r of the cylinder portion 3, and the inner oil passage Ji is provided in this outer oil passage Jo. It can be configured with the rear end facing up. Further, the sizes of the pressure receiving area Sd of the rear oil chamber Cd, the pressure receiving area Sn of the front oil chamber Cn, and the pressure receiving area Si of the inner oil chamber Ci are configured such that the pressure receiving area Sd> the pressure receiving area Si> the pressure receiving area Sn. It is desirable that the hydraulic circuit 7 be provided with a meter-out circuit 9 that controls the pressure of the return oil by the pressure control valves 9p and 9m.

[0012]

In the injection molding machine 1 according to the present invention, if the pressure oil is supplied only to the rear oil chamber Cd in the cylinder portion 3, the screw moves forward and the output F to the screw at this time is increased.
The size of d [kg] is the pressure receiving area Sd [c of the rear oil chamber Cd.
m ² ] and the hydraulic pressure Pi [kg / cm ² ] of the hydraulic circuit 7 (S
d × Pi).

If pressure oil is supplied only to the inner oil chamber Ci, the screw moves forward and the magnitude of the output Fi to the screw at this time is determined by the pressure receiving area S of the inner oil chamber Ci.
It is the product of i and the oil pressure Pi (Si × Pi).

On the other hand, when the pressure oil is supplied to the front oil chamber Cn, the screw is pressurized in the direction of retreating, and the magnitude of the output Fn with respect to the screw is equal to the pressure receiving area Sn of the front oil chamber Cn. It becomes the product (Sn × Pi) of the oil pressure Pi and acts in the negative direction.

Therefore, the pressure receiving area Sd of the rear oil chamber Cd,
Pressure receiving area Sn of the front oil chamber Cn and pressure receiving area S of the inner oil chamber Ci
By configuring the size of i such that the pressure receiving area Sd> pressure receiving area Si> pressure receiving area Sn and controlling the hydraulic circuit 7, the inner oil passage Ji (inner oil chamber Ci) and the rear oil chamber Cd are controlled.
If one or more of the front oil chambers Cn is selected and pressure oil is supplied, the output to the screw is F1 = Fi-F.
n, F2 = Fi, F3 = Fd-Fn, F4 = Fd, F5
= Fi + Fd-Fn, F6 = Fi + Fd, that is, six sizes, in other words, six 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 constituting the meter-out circuit 9, 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 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 screw, the front end side of which is inserted into the heating cylinder 10 and the rear end of the screw 11 is coupled to the screw drive mechanism E side. In addition,
The screw drive mechanism E includes a hydraulic cylinder 2 for driving the screw forward and backward and an oil motor 5m for driving the screw rotation.
Further, 12 indicates a material supply port.

On the other hand, 13 is a cylindrical cylinder block whose rear end is closed by a rear end block 14. The second half of the cylinder block 13 constitutes the hydraulic cylinder 2. The hydraulic cylinder 2 includes a cylinder portion 3, and the cylinder portion 3 has a built-in single rod type piston portion 4. The piston rod 4b of the piston portion 4 is the cylinder portion 3
The front end 3f of the screw protrudes forward, and the rear end of the screw 11 is coupled to the front end of the piston rod 4b. This allows
The front of the piston body 4u in the piston portion 4 is the front oil chamber Cn, and the rear thereof is the rear oil chamber Cd.

An inner cylinder portion 15 is formed inside the piston portion 4. On the other hand, the screw rotation driving oil motor 5m is mounted on the rear end surface of the rear end block 14, and the rotary shaft 5s of the oil motor 5m extends forward. That is, the rotary shaft 5s is the rear end block 14
Through the bearing surface 8 and the rear oil chamber Cd provided in the
It is exposed to the inside of the inner cylinder portion 15 via a spline mechanism 6 provided at the rear end 4r. And the rotating shaft 5s
The inner piston portion 16 is attached to the tip of the. This allows
The inner cylinder portion 15 in front of the inner piston portion 16 constitutes an inner oil chamber Ci.

Furthermore, an inner oil passage Ji is formed at the center of the rotary shaft 5s along the axial center. This allows
The front end opening Jis of the inner oil passage Ji faces the inner oil chamber Ci, and the rear portion of the inner oil passage Ji is at the position of the bearing surface 8.
It is bent at a right angle in the radial direction, and its rear end opens on the peripheral surface of the rotary shaft 5s. On the other hand, an outer oil passage Jo formed by a ring groove along the circumferential direction is provided on the inner peripheral surface of the bearing surface 8, and the outer oil passage Jo is exposed to the rear end (opening) of the inner oil passage Ji. Thereby, even if the rotating shaft 5s rotates, the inner oil passage Ji and the outer oil passage Jo are always communicated with each other.

The sizes of the pressure receiving area Sd of the rear oil chamber Cd, the pressure receiving area Sn of the front oil chamber Cn, and the pressure receiving area Si of the inner oil chamber Ci are selected in the relationship of Sd>Si> Sn.

With the above structure, the operation of the hydraulic cylinder 2 for driving the screw forward / backward can control the screw 11 for forward / backward movement, and the oil motor 5 for driving the screw rotation.
The rotation of the screw 11 can be controlled by controlling the operation of m.

On the other hand, the front oil chamber Cn, the rear oil chamber Cd, and the inner oil chamber Ci (outer oil passage Jo) are connected to the hydraulic circuit 7. The hydraulic circuit 7 includes a hydraulic pump 21, an oil tank 22, four-port switching valves V1, V2, V3, a three-port switching valve V4, relief valves 23, 24, and a meter-out circuit 9, which are connected 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. 4 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 output each switching valve V1.
V4 is switched and the 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, the hydraulic circuit 7 is used to control the oil chambers Ci, C.
If one or more of d and Cn are selected and pressure oil is supplied,
As an output to the screw 11, F1 = Fi−Fn,
F2 = Fi, F3 = Fd-Fn, F4 = Fd, F5 = F
Six sizes of i + Fd−Fn and F6 = Fi + Fd can be selected. In this case, the output Fi is the product of the pressure receiving area Si of the inner oil chamber Ci and the oil pressure Pi of the hydraulic circuit 7 (Si × Pi), and the output Fd is the product of the pressure receiving area Sd of the rear oil chamber Cd and the oil pressure Pi (S
d × Pi), the output Fn is the product (Sn × Pi) of the pressure receiving area Sn of the front oil chamber Cn and the hydraulic pressure Pi, and Fn acts in the negative direction.

FIG. 2 is a control matrix of the switching valves V1 to V4 for switching control when selecting the outputs F1 to F6. No mark indicates a neutral position, and a mark indicates a symbol a side or symbol b side in FIG. Means to switch to. 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.
It is switched to each side. Also in other output modes, each switching valve V1 according to the control matrix shown in FIG.
Similarly, V4 is switched and controlled.

On the other hand, in FIG. 3, the vertical axis represents the injection pressure P [kg / c
m ² ], the horizontal axis represents the output F [kg] with respect to the screw 11, and shows the magnitude of the output F corresponding to the injection pressure P. That is, when the switching valves V1 to V4 are switch-controlled according to the control matrix shown in FIG. 2, the output F changes stepwise as shown in FIG. As an example, when the injection pressure P3 is specified, the output F3 is output, and at this time, each switching valve V1 corresponds to F3 in FIG.
~ V4 is switch-controlled. The magnitude of the injection pressure P3 is F3 / Ss (Ss: cross-sectional area of the heating cylinder), and is preset or selectable in the setting unit 31 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, the injection pressure Px in FIG.
4, a switching valve control command is output from the arithmetic processing unit 32 in FIG. 4, and the switching valves V1 to V4 are switched and controlled corresponding to F3 in FIG. 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 11 becomes Fx. in this way,
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.

[0033]

As described above, the injection molding machine according to the present invention has the cylinder part and the piston part built in the cylinder part, and the front part of the piston body in the piston part is the front oil chamber and the rear part is the rear oil chamber. A hydraulic cylinder for driving the screw forward and backward, which is a chamber, and a motor for driving the screw rotation that connects the front side of the rotary shaft that passes from the rear end of the cylinder part to the rear oil chamber to the rear end of the piston part via a spline mechanism. At the same time, an inner oil chamber is provided inside the piston portion, and an inner oil passage whose front end opening faces the inside of the inner oil chamber is provided inside the rotary shaft. Alternatively, since a hydraulic circuit capable of supplying pressure oil by selecting two or more is provided, the screw drive mechanism can be downsized and the cost can be reduced by using the existing form of the screw drive mechanism as it is. Also, a marked effect of being able to perform highly accurate and stable pressure control.

[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 for driving screw forward / backward 3 Cylinder part 3r Rear end of cylinder part 4 Piston part 4r Rear end of piston part 4u Piston body 5 Screw rotation drive motor 5s Rotating shaft 6 Spline mechanism 7 Hydraulic circuit 8 Bearing surface 9 Meter-out circuit 9p Pressure control valve 9m Pressure control valve Cn Front oil chamber Cd Rear oil chamber Ci Inner oil chamber Ji Inner oil passage Jis Inner oil passage front end opening Jo Outer oil passage

Claims (4)

[Claims] 1. A screw advancing / retreating drive hydraulic cylinder having a cylinder part and a piston part built in the cylinder part, wherein a front part of the piston body of the piston part is a front oil chamber and a rear part is a rear oil chamber, and a cylinder part. In an injection molding machine equipped with a screw rotation drive motor in which the front side of the rotary shaft that passes from the rear end to the rear oil chamber is connected to the rear end of the piston part through a spline mechanism, the internal oil chamber is inside the piston part. In addition, the inner end of the rotary shaft is provided with an inner oil passage whose front end opening faces the inside of the inner oil chamber, and one or more of the front oil chamber, the rear oil chamber, or the inner oil passage is selected to supply the pressure oil. An injection molding machine characterized by being provided with a possible hydraulic circuit. 2. An outer oil passage formed by a ring groove along the circumferential direction is provided on a bearing surface of the rear end of the cylinder portion through which the rotary shaft is inserted, and the outer oil passage is made to face the rear end of the inner oil passage. The injection molding machine according to claim 1, wherein: 3. The pressure receiving area of the rear oil chamber, the pressure receiving area of the front oil chamber, and the pressure receiving area of the inner oil chamber are as follows: Pressure receiving area of the rear oil chamber> pressure receiving area of the front oil chamber> pressure receiving area of the inner oil chamber The injection molding machine according to claim 1, characterized in that 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.