JP2849223B2 - Injection molding machine with direct pressure type mold clamping device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine having a direct pressure type mold clamping device for directly producing a mold clamping force by a mold clamping cylinder (hydraulic cylinder).

[0003]

[0002]

[0004]

2. Description of the Related Art In an injection molding machine, a mold is clamped by a mold clamping cylinder (hydraulic cylinder), and at an appropriate timing thereafter, the molten resin is clamped by an injection cylinder (hydraulic cylinder) in a mold. It is designed to inject and fill the molding space (cavity). In addition, hydraulic actuators such as the mold clamping cylinder and the injection cylinder are usually supplied with pressure oil from the same main variable pump via a control valve, and are selectively driven. , The supply of pressure oil from the main variable pump to the mold clamping cylinder is stopped.

[0005]

In an injection molding machine having a direct pressure type mold clamping device, a moving die plate is directly connected to a piston rod of a mold clamping cylinder, and unlike a toggle type mold clamping device, a mold clamping force is directly applied to a mold. It is generated by the tightening cylinder. For this reason, it is necessary to prevent the mold clamping force (oil pressure) from decreasing due to leakage or the like after switching the control valve for the mold clamping cylinder to the neutral position after the mold clamping is completed. It is attached to the hydraulic system of the mold clamping cylinder, and a predetermined mold clamping force is maintained even during the injection stroke by supplying auxiliary pressure oil from the auxiliary variable pump.

[0006]

FIG. 3 is a diagram showing a hydraulic circuit of the conventional injection molding machine. In FIG. 3, reference numeral 1 denotes a motor, 2 'denotes a main variable pump driven by the motor 1, and 3, 3 comprise a two-unit configuration. , 4 is a control valve for the mold cylinder, 5 is an injection cylinder, 6 is a control valve for the injection cylinder, 7 is a safety door valve, 8 is a mold clamping force detection (oil pressure detection) sensor, 9 Reference numeral 10 denotes a sub-variable pump which is driven by the sub-motor 9 and is directly connected to the mold closing oil chamber of the mold clamping cylinder 3.

[0007]

In the above configuration, when the safety door is closed, the safety door valve 7 is at the left position (the position where the pressurized oil can be supplied to the mold closing cylinder). At this time, the control valve 6 is set to the neutral position and the control valve 4 is set to the neutral position. By switching to the left position, the piston rod of the mold clamping cylinder 3 moves rightward to perform the mold clamping (mold closing) operation. Then, the movable die plate (not shown) reaches the mold clamping completion position, and the mold clamping force detecting sensor 8
When it is recognized that the set clamping force has been reached, the control valve 4 is switched to the neutral position, and the supply of the pressurized oil from the main variable pump 2 ′ to the clamping cylinder 3 is cut off. At this time, since the pressurized oil from the auxiliary variable pump is supplied to the mold closing oil chamber of the mold closing cylinder 3, even if there is a leak from the time of completion of the mold closing to the time of starting the mold opening, the mold closing is performed. The power is not reduced. At a predetermined time after completion of mold clamping, the control valve 5 is switched to the right position, and a known injection operation is performed.

[0008]

[0006]

[0009]

As described above, in the injection molding machine having the conventional direct pressure type mold clamping device, the control valve 4 for the mold clamping cylinder is switched to the neutral position after the mold clamping is completed. In order to prevent the mold clamping force (oil pressure) from being reduced by the
Therefore, there is a problem that the configuration of the hydraulic circuit is increased by that much, and miniaturization is difficult. Even if the main variable pump 2 'and the sub-variable pump 10 are driven by the same motor, each variable pump needs to be provided with a relatively complicated flow adjusting means. There was a limit to the simplification and miniaturization of the system.

[0010]

In FIG. 3, the periphery of the main variable pump 2 'and the auxiliary variable pump 10 are simplified for convenience of illustration, but in actuality, for example, the pump discharge flow rate as shown in FIG. An adjusting means is added to control the pump discharge flow rate through the regulator 13 by the electromagnetic servo valve 11 or the servo valve 12, and to detect each detection signal of the pressure gauge 14 and the tilt angle detector (flow meter) 15. Since the servo control is performed while comparing with the command signal, the simplification and downsizing of the hydraulic circuit configuration is greatly impeded by adding only one sub-variable pump 10.

[0011]

Accordingly, a technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art.
The purpose is to simplify and downsize the hydraulic circuit configuration having a function of reliably preventing the mold clamping force (oil pressure) from being reduced due to leakage or the like after the mold clamping is completed. An object of the present invention is to achieve downsizing and cost reduction of an injection molding machine having a mold clamping device.

[0012]

[0009]

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a direct pressure type mold in which a movable die plate is directly connected to a piston body of a mold clamping cylinder and a mold clamping force is directly generated by the mold clamping cylinder. In an injection molding machine having a clamping device, the same variable pump is used to selectively supply pressurized oil to at least a mold clamping cylinder and an injection cylinder, and a spring-type accumulator charged by hydraulic pressure is used for a mold clamping cylinder. And accumulates the spring of the spring-type accumulator by pressurized oil supplied simultaneously with the mold clamping (mold closing) process by the mold clamping cylinder, and after the mold clamping is completed, the spring force accumulated in the accumulator. It is configured to maintain the mold clamping force of the mold clamping cylinder by the hydraulic pressure through.

[0014]

[0010]

[0015]

[Function] The oil chamber for closing the mold of the mold cylinder and the accumulator oil chamber of the spring-type accumulator communicate with each other by an oil passage. Chamber and the accumulator oil chamber. As a result, the piston rod of the mold clamping cylinder is driven in the mold closing direction, and the multi-stage disc spring-shaped spring body of the spring-type accumulator is compressed to accumulate the spring force. When the movable die plate directly connected to the piston rod of the mold clamping cylinder reaches the mold clamping completion position and the mold clamping force detection sensor recognizes that the set mold clamping force has been reached, control for the mold clamping cylinder is performed. The valve is switched to the neutral position and the supply of pressurized oil from the variable pump to the mold clamping cylinder is cut off, but the hydraulic pressure due to the stored spring force is applied from the spring-type accumulator to the mold closing oil chamber of the mold clamping cylinder. Therefore, it is possible to reliably prevent the mold clamping force from being reduced by leakage.

[0016]

[0011]

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to one embodiment shown in FIGS. FIG. 1 is an explanatory diagram showing a main hydraulic circuit in an injection molding machine having a direct pressure type mold clamping device, and FIG. 2 is an explanatory diagram of a partly cut mold clamping device.

[0018]

In FIG. 1, 1 is a motor, 2 is a variable pump driven by the motor 1 (corresponding to the main variable motor 2 '), 3 and 3 are mold clamping cylinders having a double structure, and 4 is A control valve for a mold closing cylinder, 5 is an injection cylinder, 6 is a control valve for the injection cylinder, 7 is a safety door valve, and 8 is a mold clamping force detection (oil pressure detection) sensor. It is completely equivalent to the above member. Reference numeral 20 denotes a spring accumulator provided with the mold clamping cylinders 3 and 3.

[0019]

The spring type accumulator 20 includes a spring body 20a in which a large number of disc springs are stacked in multiple stages, and a spring body 20a.
a, and an accumulator oil chamber 2 in which the other end of the piston body 20b is located.
0c. The accumulator oil chamber 20c communicates with the pair of mold-closing oil chambers 3b of the mold-clamping cylinder 3 via oil passages 21, respectively.

[0020]

As shown in FIG.
3 and the spring-type accumulator 20 are installed on a fixed die plate 22 to which a fixed mold 23 is attached. One end of each of the piston rods 3a, 3a of the mold clamping cylinders 3, 3 is connected to a movable die plate 24 to which a movable mold 25 is attached.
Fixed and connected to In FIGS. 1 and 2, 3
c denotes a mold opening oil chamber of the mold clamping cylinder 3.

[0021]

In the above configuration, when the safety door is closed, the safety door valve 7 is at the left position in FIG. 1 (a position where the pressurized oil can be supplied to the mold clamping cylinder), and at this time, the control valve 6 is in the neutral position. By switching the control valve 4 to the left position, the pressure oil from the variable pump 2
The oil is supplied simultaneously to the mold closing oil chamber 3b and the accumulator oil chamber 20c. Thereby, the piston rod 3a of the mold clamping cylinder 3 moves rightward in FIGS. 1 and 2, and the movable die plate 24 is driven in the same direction in FIG. 2 to perform the mold clamping (mold closing) operation. The piston body 20b of the spring type accumulator 20 is a spring body 20a.
, The spring body 20a is compressed, and the spring force is accumulated. When the movable die plate 24 reaches the mold clamping completion position and the mold clamping force detection sensor 8 recognizes that the set mold clamping force has been reached, the control valve 4 is switched to the neutral position and the variable pump 2 is switched to the neutral position. Supply of pressurized oil to the mold clamping cylinder 3 is cut off.

[0022]

After that, although the supply of the pressure oil from the variable pump 2 to the mold clamping cylinder 3 is cut off, the hydraulic pressure by the accumulated spring force is transmitted from the spring type accumulator 20 to the mold closing cylinder 3 for closing the mold. Since the pressure is applied to the oil chamber 3b, there is no danger that the mold clamping force is reduced due to leakage, and the control valve 5 is switched to the right position at a predetermined time after the completion of mold clamping, and the injection operation is performed. Will be performed without hindrance.

[0023]

In this embodiment having such a configuration, a spring-type accumulator 20 having a simple configuration is simply added as compared with the prior art which requires a sub-variable pump and an associated servo valve. Therefore, the configuration of the hydraulic circuit can be made simple and small.

[0024]

[0018]

[0025]

As described above, according to the present invention, the hydraulic circuit configuration having a function of reliably preventing the mold clamping force (oil pressure) from decreasing due to leakage or the like after the completion of mold clamping is simplified and downsized. As a result, it is possible to reduce the size and cost of the injection molding machine having the direct pressure type mold clamping device, and its value is great.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a main part hydraulic circuit in an injection molding machine having a direct pressure type mold clamping device according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a partly cut mold clamping device of an injection molding machine having a direct pressure type mold clamping device according to an embodiment of the present invention.

FIG. 3 is an explanatory view showing a main part hydraulic circuit in an injection molding machine having a direct pressure type mold clamping device according to a conventional technique.

FIG. 4 is an explanatory diagram showing details of a hydraulic circuit around a variable pump in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motor 2 Variable pump 3 Mold clamping cylinder 4 Control valve 5 Injection cylinder 6 Control valve 8 Mold clamping force detection sensor 20 Spring type accumulator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 45/64-45 / 68,45 / 82,33 / 20-33/28 B22D 17/26

Claims (2)

(57) [Claims] 1. An injection molding machine having a direct-pressure type mold clamping device in which a moving die plate is directly connected to a piston body of a mold clamping cylinder comprising a hydraulic cylinder and a clamping force is directly generated by the mold clamping cylinder. The variable pump selectively supplies pressure oil to at least the injection cylinder including the mold clamping cylinder and the hydraulic cylinder, and a spring-type accumulator that is charged by hydraulic pressure is attached to the mold clamping cylinder. Injection molding machine with a direct pressure type mold clamping device. 2. The spring accumulator according to claim 1, wherein a spring is stored in the accumulator by pressurized oil which is simultaneously supplied during a mold clamping (mold closing) process by the mold clamping cylinder. An injection molding machine having a direct pressure type mold clamping device, wherein a mold clamping force of a mold clamping cylinder is maintained by hydraulic pressure through a spring force accumulated in an accumulator.