JPH04238012A - Injection molding machine with directly pressurizing type mold clamping device - Google Patents

Abstract

PURPOSE:To simplify and downsize the hydraulic circuit of an injection molding machine with a directly pressurizing type mold clamping device. CONSTITUTION:At mold clamping (mold closing) process, pressure oil emitted from a variable pump 2 is simultaneously supplied to the mold closing oil chambers 3b of mold clamping cylinders 3 and the accumulator oil chamber 20c of a spring type accumulator 20 so as to energize spring force by compressing the spring 20a of the spring type accumulator. After the completion of mold clamping, even when the supply of pressure oil from the variable pump to the mold clamping cylinders is stopped, the oil pressure, which is developed by the energized spring force, is applied from the spring type accumulator to the mold closing oil chambers of the mold clamping cylinders.

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 mold clamping device that directly generates mold clamping force by a mold clamping cylinder (hydraulic cylinder).

0003

0002

0004

[Prior Art] In an injection molding machine, a mold clamping cylinder (
The mold is clamped by a hydraulic cylinder, and then at an appropriate injection timing, an injection cylinder (hydraulic cylinder) injects and fills the molding space (cavity) in the clamped mold with molten resin. In addition, the hydraulic actuators such as the mold clamping cylinder and injection cylinder are normally supplied with pressure oil from the same main variable pump via a control valve, and are selectively driven. When the pressure oil is being supplied to the mold clamping cylinder, the supply of pressure oil from the main variable pump to the mold clamping cylinder is stopped.

[0005]

By the way, in an injection molding machine equipped with a direct pressure type mold clamping device, a movable die plate is directly connected to the piston rod of the mold clamping cylinder, and unlike a toggle type mold clamping device, the mold clamping force is directly applied to the mold. It is generated by the tightening cylinder. Therefore, after switching the control valve for the mold clamping cylinder to the neutral position after mold clamping is completed, it is necessary to prevent the mold clamping force (hydraulic pressure) from decreasing due to leakage, etc. Therefore, conventionally, a sub variable pump was used. It was attached to the hydraulic system of the mold clamping cylinder, and the predetermined mold clamping force was maintained even during the injection stroke by supplying auxiliary pressure oil from this auxiliary variable pump.

[0006]

FIG. 3 is a diagram showing the hydraulic circuit of such a conventional injection molding machine. In the figure, 1 is a motor, 2' is a main variable pump driven by the motor 1, and 3 and 3 are two-unit configuration. a mold clamping cylinder, 4 a control valve for the mold clamping cylinder, 5 an injection cylinder, 6 a control valve for the injection cylinder, 7 a safety door valve, 8 a mold clamping force detection (hydraulic pressure detection) sensor, 9 1 is an auxiliary motor, and 10 is a auxiliary variable pump driven by the auxiliary motor 9 and 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 in the left position (position where pressure oil can be supplied to the mold clamping cylinder), and at this time, the control valve 6 is in the neutral position and the control valve 4 is in the neutral position. By switching to the left position, the piston rod of the mold clamping cylinder 3 moves rightward, and a mold clamping (mold closing) operation is performed. Then, the movable die plate (not shown) reaches the mold clamping completion position, and the mold clamping force detection sensor 8
When it is recognized that the set mold clamping force has been reached, the control valve 4 is switched to the neutral position and the supply of pressure oil from the main variable pump 2' to the mold clamping cylinder 3 is cut off. At this time, the mold closing oil chamber of the mold clamping cylinder 3 is supplied with pressure oil from the auxiliary variable pump, so even if there is a leak between the time the mold clamping is completed and the mold opening starts, the mold closing oil chamber 3 is supplied with pressure oil from the sub variable pump. The power is not reduced. At a predetermined time after the mold clamping is completed, the control valve 5 is switched to the right position and a known injection operation is performed.

[0008]

[0006]

[0009]

[Problems to be Solved by the Invention] As mentioned above, in the conventional injection molding machine equipped with a direct pressure type mold clamping device, the control valve 4 for the mold clamping cylinder is switched to the neutral position after mold clamping is completed, so leakage etc. In order to prevent the mold clamping force (hydraulic pressure) from decreasing due to
The problem is that the construction of the hydraulic circuit becomes bulky, making it difficult to downsize the hydraulic circuit. Furthermore, 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 rate adjustment means, so the hydraulic circuit configuration There were limits to the simplification and miniaturization of the.

0010

3, the main variable pump 2' and the auxiliary variable pump 10 are simplified for convenience of illustration, but in reality, the pump discharge flow rate is as shown in FIG. 4, for example. Adjustment means is added, and the pump discharge flow rate is controlled via the regulator 13 by the electromagnetic servo valve 11 and servo valve 12, and each detection signal of the pressure gauge 14 and the tilt angle detector (flow meter) 15 is adjusted. Since servo control is performed while comparing the command signal, the addition of one sub-variable pump 10 greatly hinders the simplification and miniaturization of the hydraulic circuit configuration.

[0011]

Therefore, the technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art.
The purpose of this is to simplify and miniaturize the hydraulic circuit configuration, which has the function of reliably preventing the mold clamping force (hydraulic pressure) from decreasing due to leaks after mold clamping is completed, and to create a direct pressure type The object of the present invention is to achieve downsizing and cost reduction of an injection molding machine equipped with a mold clamping device.

0012

[0009]

[0013]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a direct pressure type mold in which a movable die plate is directly connected to the 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 equipped with a clamping device, the same variable pump is used to selectively supply pressure oil to at least the mold clamping cylinder and the injection cylinder, and a spring-type accumulator that is charged by hydraulic pressure is connected to the mold clamping cylinder. The spring of the spring-type accumulator is stored with pressure oil supplied at the same time during the mold clamping (mold closing) stroke of the mold clamping cylinder, and after the mold clamping is completed, the spring force stored in this accumulator is The mold clamping force of the mold clamping cylinder is maintained by hydraulic pressure via the mold clamping cylinder.

[0014]

0010

[0015]

[Operation] The mold-closing oil chamber of the mold-clamping cylinder and the accumulator oil chamber of the spring-type accumulator are connected through an oil passage, and during the mold-clamping (mold-closing) stroke, pressure oil from the variable pump is transferred to the mold-closing oil chamber. and the accumulator oil chamber at the same time. As a result, the piston rod of the mold clamping cylinder is driven in the mold closing direction, and the spring body in the form of a multistage disc spring of the spring type accumulator is compressed to store spring force. Then, 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, the control for the mold clamping cylinder is activated. Although the valve is switched to the neutral position and the supply of pressure oil from the variable pump to the mold-clamping cylinder is cut off, hydraulic pressure from the stored spring force is added from the spring-type accumulator to the mold-closing oil chamber of the mold-clamping cylinder. This reliably prevents the mold clamping force from decreasing due to leakage.

[0016]

[0011]

[0017]

[Embodiment] The present invention will be explained below with reference to an embodiment shown in FIGS. 1 and 2. FIG. 1 is an explanatory diagram showing a main hydraulic circuit in an injection molding machine having a direct pressure mold clamping device, and FIG. 2 is a partially cutaway explanatory diagram of the 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 is a mold clamping cylinder having a two-unit configuration, and 4 is a corresponding mold clamping 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 (hydraulic pressure detection) sensor; these members are shown in FIG. It is completely equivalent to the member. Further, 20 is a spring type accumulator attached to the mold clamping cylinders 3, 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 piston body 20b whose one end side is in contact with a, and an accumulator oil chamber 2 where the other end side of the piston body 20b is located.
It is mainly composed of 0c. The accumulator oil chamber 20c communicates with the mold closing oil chambers 3b, 3b of the pair of mold clamping cylinders 3 via oil passages 21, respectively.

[0020]

As shown in FIG. 2, the mold clamping cylinder 3,
3 and the spring-type accumulator 20 are installed on a fixed die plate 22 to which a fixed mold 23 is attached. Further, one ends of the piston rods 3a, 3a of the mold clamping cylinders 3, 3 are fixed and connected to a movable die plate 24 to which a movable mold 25 is attached. In addition, in Figures 1 and 2, 3c
is the 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 in the left position in FIG. 1 (position where pressure 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, pressure oil is supplied from the variable pump 2.
It is simultaneously supplied to the mold closing oil chamber 3b and the accumulator oil chamber 20c. As a result, the piston rod 3a of the mold clamping cylinder 3 moves to the right in FIGS. 1 and 2, the movable die plate 24 is driven in the same direction in FIG. 2, and a mold clamping (mold closing) operation is performed. The piston body 20b of the spring-type accumulator 20 moves against the spring body 20a, compressing the spring body 20a and storing spring force. Then, 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 The supply of pressure oil from the mold clamping cylinder 3 to the mold clamping cylinder 3 is cut off.

[0022]

After this, although the pressure oil supply from the variable pump 2 to the mold clamping cylinder 3 is cut off, the hydraulic pressure due to the stored spring force is transferred from the spring type accumulator 20 to the mold clamping cylinder 3 for mold closing. Since the oil is added to the oil chamber 3b, there is no risk of the mold clamping force being reduced due to leakage, and the control valve 5 is switched to the right position at a predetermined time after the mold clamping is completed, and the injection operation is started. will be carried out without any problems.

[0023]

[0017] In this embodiment having such a configuration, compared to the prior art which required a sub-variable pump and accompanying servo valves, the simple configuration of the spring-type accumulator 20 is added. Therefore, the configuration of the hydraulic circuit can be made simple and compact.

[0024]

[0018]

[0025]

[Effects of the Invention] As described above, according to the present invention, the hydraulic circuit configuration, which has the function of reliably preventing the mold clamping force (hydraulic pressure) from decreasing due to leakage etc. after mold clamping is completed, is simplified and miniaturized. As a result, it is possible to downsize and reduce costs of an injection molding machine having a direct pressure mold clamping device, which is of great value.

[Brief explanation of the drawing]

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

FIG. 2 is a partially cutaway explanatory diagram of a 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 diagram showing a main hydraulic circuit in an injection molding machine having a direct pressure mold clamping device according to the prior art.

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

[Explanation 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

Claims (2)

[Claims] Claim 1: In an injection molding machine having a direct pressure type mold clamping device in which a movable die plate is directly connected to the piston body of a mold clamping cylinder consisting of a hydraulic cylinder, and mold clamping force is directly generated by the mold clamping cylinder, A variable pump selectively supplies pressurized oil to at least the mold clamping cylinder and the injection cylinder consisting of the hydraulic cylinder, and
An injection molding machine having a direct pressure type mold clamping device, characterized in that a spring type accumulator that stores energy by hydraulic pressure is attached to the mold clamping cylinder. 2. In the spring-type accumulator according to claim 1, a spring is stored with pressure oil supplied at the same time during the mold clamping (mold closing) stroke by the mold clamping cylinder, and after the mold clamping is completed, this spring-type accumulator is loaded with pressure oil. An injection molding machine having a direct pressure type mold clamping device, characterized in that the mold clamping force of a mold clamping cylinder is maintained by hydraulic pressure via a spring force stored in an accumulator.