JPH0624752B2 - Method and apparatus for detecting indirect resin pressure of injection molding machine - Google Patents

Description

The present invention relates to a method and a device for detecting resin pressure in a mold of an injection molding machine having a direct pressure type mold clamping device.

(B) Conventional Technology In the conventional injection molding method, the resin pressure in the mold is detected by installing the resin pressure sensor 8 in the mold 2 as shown in FIG.

However, in the above method, it is necessary to process the mold 2, and in the case of the multi-cavity mold 2, it is difficult to determine in which cavity 3 the resin pressure sensor 8 is provided. Therefore, an indirect resin pressure detection method is also devised. ing.

As an indirect resin pressure detecting method, as shown in FIG. 6, after the initial mold clamping force is applied, the pilot check valve 11 is closed to confine the oil in the mold clamping cylinder 1 and to inject it.
The oil pressure in the mold clamping cylinder 1 is compressed by the mold opening force A generated by the mold resin pressure at the time of holding pressure and rises. The pressure sensor 14 measures the oil pressure, and the measured value indirectly determines the mold resin. It detects the behavior of pressure.

(C) Problem to be Solved by the Invention In this conventional indirect resin pressure detection method, the hydraulic oil is confined by the pilot check valve 11. However, if the hydraulic oil leaks from the pilot check valve 11 even slightly, the hydraulic oil pressure is reduced. There is a problem that the rise is small and the detection accuracy is low.

Also, since the volume of hydraulic oil contracts when the pressure increases, if the volume inside the mold clamping cylinder is large, this compression margin will increase and the fluctuation in the hydraulic pressure in the mold clamping cylinder will be small relative to the fluctuation in the resin pressure inside the mold. However, there is also a problem that the detection accuracy decreases.

(D) Means for Solving the Problem The present invention is an injection molding machine having a direct pressure type mold clamping device, in which an initial mold clamping force is set and a mold opening force generated by a resin pressure in a mold during injection / holding pressure. The oil pressure is controlled so as to hold the position of the movable plate 9 against A, the rising oil pressure is measured for holding the position, and the measured value indirectly detects the behavior of the resin pressure in the mold. By doing so, the above problem is solved.

Further, in an injection molding machine having a direct pressure type mold clamping device, an initial mold clamping force is set, and the position of the movable platen 9 is held against the mold opening force A generated by the resin pressure in the mold during injection / pressure holding. A pressure control valve 13 for controlling the hydraulic pressure, a position holding controller 20 for sending a pressure command signal 21 for holding the position to the pressure control valve 13, and a position sensor 10 for measuring the position of the movable platen 9, The above problem is solved by the pressure sensor 14 for measuring the hydraulic pressure in the mold clamping cylinder 1 that rises to maintain the position.

(E) Action The behavior of the resin pressure inside the mold during injection / holding pressure is as shown in FIG. 2, and this resin pressure causes a mold opening force that is a force to open the mold. The behavior of the mold opening force is almost the same as the resin pressure in the mold and is as shown in FIG. The oil is compressed in order to maintain the position of the movable plate against the mold opening force, and the hydraulic pressure rises in proportion to the mold opening force, and the behavior shown in FIG. 4 is exhibited.

That is, it is possible to know the behavior of the resin pressure in the mold by measuring the hydraulic pressure in the mold clamping cylinder.

(F) Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a view showing an embodiment of the present invention. In a normal direct pressure type mold clamping apparatus, a pressure sensor 14 for measuring the hydraulic pressure in the mold clamping cylinder 1 and a position sensor for measuring the position of the movable platen 9 are provided. 1
0, a pressure control valve 13 for controlling the mold clamping oil pressure so as to maintain the position of the movable platen 9 against the mold opening force A at the time of injection / pressure holding.
The position holding controller 20 for sending the pressure command signal 21 to the pressure control valve 13 is installed. Further, since the main controller 22 issues a command for the initial mold clamping force, the directional control valve 18 is used for controlling the mold clamping cylinder 1.

The position holding controller 20 and the main controller 2
The two can be integrated.

The indirect resin pressure detection method and device for an injection molding machine according to the present invention are configured as described above, and the operation thereof will be described below.

An initial mold clamping force command is sent from the main controller 22 to the pressure control valve 13 via the position holding controller 20,
Apply a certain mold clamping force. The position of the movable platen 9 at that time is detected by the position sensor 10, a pressure sufficient to hold the position is calculated by the position holding controller 20, and the pressure command signal 21 is sent to the pressure control valve 13.

When the injection / pressure-holding process is started at this point, the mold opening force A is generated by the resin pressure in the mold.

This mold opening force A acts as an external force of the mold clamping cylinder 1 and tries to change the position of the movable platen 9, but the position holding controller 2
Since the pressure is controlled by 0 to maintain the position, the oil pressure supplied to the mold clamping cylinder 1 also changes according to the mold opening force (projected cavity area × resin pressure in the mold). .

When the volume of the resin cooled in the cooling step contracts and the resin pressure in the mold decreases, the mold opening force A also decreases, and the mold clamping force increases and the mold 2 is compressed in the direction of compressing the mold. However, since the position holding controller 20 is controlled to hold the position, the hydraulic pressure of the mold clamping cylinder 1 decreases.

The oil pressure controlled by the position holding controller 20 is proportional to the mold opening force A, that is, the resin pressure in the mold as described above. If this oil pressure is measured by the pressure sensor 14, the resin pressure in the mold is You can know the behavior.

Also, the behavior of the resin pressure inside the mold can be indirectly known by the pressure command signal 21 from the position holding controller 20 for holding the position.

(G) Effect of the Invention As described above, according to the present invention, it is possible to modify the mold without using an expensive resin pressure sensor in all molds that are normally used. With an inexpensive pressure sensor, the behavior of the resin pressure in the mold can be easily known with high accuracy.

Further, in the present invention, by knowing the total sum of the resin pressures of the entire molded product, it is possible to eliminate the uncertain control by the local measurement, which is the conventional method of measuring only the setting place of the resin pressure sensor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a hydraulic circuit diagram of the present invention, FIG. 2 is a diagram showing a behavior of resin pressure in a mold, and FIG. 3 is a behavior of a mold opening force. FIG. 4 is a diagram showing the behavior of the hydraulic pressure in the mold clamping cylinder, FIG. 5 is a conventional method for detecting resin pressure in a mold, and FIG. 6 is a diagram showing another conventional mold pressure. It is a hydraulic circuit diagram of a resin pressure detection method. 1 ... Mold clamping cylinder, 2 ... Mold, 3 ... Cavity,
4 ... Injection device, 7 ... Ejector pin, 8 ... Resin pressure sensor, 9 ... Movable plate, 10 ... Position sensor, 11 ...
Pilot check valve, 12 ... solenoid valve, 13 ... pressure control valve, 14 ... pressure sensor, 17 ... hydraulic pressure supply source, 1
8: Direction control valve, 20: Position holding controller, 2
1 ... Pressure command signal, 22 ... Main controller, A
…… Mold opening force.

Claims (2)

[Claims] In an injection molding machine having a direct pressure type mold clamping device, an initial mold clamping force is set, and a movable plate (A) is set against a mold opening force (A) generated by a resin pressure in a mold during injection / holding pressure. 9) The hydraulic pressure is controlled so that the position can be held, the hydraulic pressure that rises to hold the position is measured, and the behavior of the resin pressure inside the mold is indirectly detected by this measured value. Indirect resin pressure detection method for injection molding machine. 2. In an injection molding machine having a direct pressure type mold clamping device, an initial mold clamping force is set, and a movable plate is set against a mold opening force (A) generated by a resin pressure in a mold during injection / holding pressure. A pressure control valve (1 that controls the oil pressure so that the position of (9) can be maintained.
3) and a position holding controller (20) for sending a pressure command signal (21) for holding the position to the pressure control valve (13)
And a position sensor (1 for measuring the position of the movable plate (9).
0) and a pressure sensor (14) for measuring the oil pressure in the mold clamping cylinder (1) that rises to hold the position, an indirect resin pressure detection device for an injection molding machine.