JPS63126658A - Direct press type mold clamping device - Google Patents

Abstract

PURPOSE:To permit high speed and powerful clamping of molds by constructing a mold clamping device for the molds of an injection molding machine as a direct press type mold clamping device which is directly coupled with cylinder rods of hydraulic cylinders, etc., to a moving die plate and opens and closes the molds directly by an oil pressure. CONSTITUTION:The stationary mold 12 and moving mold 10 of the direct press type mold clamping device for the injection molding machine are opened and closed by the movement of the respective piston rods 5, 8 of the hydraulically actuated mold opening cylinder 2 and the likewise hydraulically actuated die closing cylinder 3. The cylinders 2, 3 are disposed to a stationary plate 1 apart at a specified spacing. The piston rods 5, 8 in common use as tie bars are connected to a moving plate 7. A piston 16 sliding on the inside surface of the cylinder 2 is mounted to the top end of the mold opening piston rod 5 and a piston 18 consisting of a large diameter part 18a and small-diameter part 18b is provided to the top end of the mold closing piston rod 8 so that part of the small-diameter part 18b exists in a head cover 19 even in the mold opening state. The two cylinders 2, 3 are respectively connected to a differential pressure fluid circuit. The cylinders 2, 3 are hydraulically actuated to move the plate 7 upward and downward by which the moving mold 10 and stationary mold 12 are opened, closed and clamped.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a mold clamping device, and in particular to a mold clamping device in which a cylinder rod such as a hydraulic cylinder is directly connected to a movable guide plate to directly open and close a mold using hydraulic pressure. This relates to a pressure type mold clamping device.

C. Prior Art] Mold clamping devices used in injection molding machines and the like can be broadly classified into direct pressure type mold clamping devices and toggle type mold clamping devices.

Compared to toggle type mold clamping devices, direct pressure type mold clamping devices can be easily adjusted when replacing molds. In addition, the structure is simple and there are few wear parts, so it has excellent durability and is easy to maintain. However, the opening and closing speed of the mold is generally slow, and if the mold clamping force is increased, It becomes difficult to prevent oil leakage.

In order to eliminate these drawbacks, we developed an auxiliary cylinder system in which separate cylinders are used for opening and closing the mold and for generating mold clamping force.
Or there is a prefill valve system with a complicated hydraulic circuit.

[Problem that the invention seeks to solve]

However, all of the various direct pressure type mold clamping devices that have been proposed so far have complicated structures or hydraulic circuits, which not only lead to larger devices and higher costs, but also to ensure that the mold opening/closing speed is sufficiently high and the mold clamping speed is sufficiently high. I couldn't make the force big enough.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive direct pressure type mold clamping device that can solve the above-mentioned drawbacks of the prior art, open and close a mold at high speed, and provide a large mold clamping force.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention arranges a mold opening fluid cylinder and a mold closing fluid cylinder, which are made of, for example, a hydraulic cylinder, on a fixed plate at a predetermined interval, and the mold opening fluid cylinder and the mold closing fluid cylinder are arranged at a predetermined interval. Each piston rod serves as a tie bar and is connected to a moving plate, and the mold opening fluid cylinder and the mold closing fluid cylinder are each connected to a differential pressure fluid circuit.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Figure 1 is a front view of the direct pressure type mold clamping device, Figure 2 is a sectional view of the mold clamping device, Figure 3 is a bottom view of the mold clamping device with the oil tank removed, and Figure 4 is the mold clamping device. Fig. 5 and Fig. 6 are cross-sectional views of the mold clamping device showing the state during mold clamping and when mold clamping is completed, Fig. 7 is a block diagram for explaining the control operation, and Fig. 8 is the operation. It is an explanatory diagram.

First, the structure of a vertical direct pressure type mold clamping device according to an embodiment will be explained using FIGS. 1 to 3.

The fixed plate 1 has two mold opening cylinders 2 erected,
2 and the upper ends of the two mold-closing cylinders 3.3. As shown in FIG. 3, one mold-opening cylinder 2 and the other mold-opening cylinder 2 are arranged diagonally, and one mold-closing cylinder 3 and the other mold-closing cylinder 3 are similarly arranged diagonally. The upper ends of the winter mold cylinders 2, 2 and mold closing cylinders 3.3 are integrally connected by the aforementioned fixing plate 1, and the lower ends of each mold opening cylinder 2, 2 and mold closing cylinders 3, 3 are connected together as shown in FIG. As shown in the figure, they are each integrally connected by a connecting portion 4.

As shown in FIG. 2, the piston rod 5 of the mold opening cylinder 2 passes through a rod cover 6 and is fixed to an upper movable plate 7. The piston rod 8 of the mold-closing cylinder 3 passes through a rod cover 9 and is similarly fixed to the upper movable plate 7. A movable mold 1o is fixed to the lower surface of the movable plate 7, while a fixed mold 12 is fixed above the fixed plate 1 via a mold mounting plate 11, and the movable mold 1o is fixed to the lower surface of the movable plate 7. The molds 10 are facing each other. A rack 13 is suspended from one end of the movable plate 7, and a binion 14 that meshes with the teeth of the rack 13 is rotatably fixed at a predetermined position, and an encoder 15 is connected to the rotating shaft of the binion 14. Therefore, the rack 13, pinion 14, and encoder 15 constitute a position sensor that detects the position of the moving plate 7.

As shown in FIG. 2, a relatively short-shaft piston body 16 whose entire outer peripheral surface is in sliding contact with the inner peripheral surface of the mold opening cylinder 2 is fixed to the lower end of the piston rod 5 in the mold opening cylinder 2. The lower end opening of 2 is closed with a head cover 17. On the other hand, the piston body 18 fixed to the lower end of the piston rod 8 in the mold-closing cylinder 3 has a different shape from the piston body 16 of the mold-opening cylinder 2, and its outer peripheral surface slides against the inner peripheral surface of the mold-closing cylinder 3. A contacting large diameter portion 18a;
It consists of a small diameter part 18b which is provided at the lower end of the large diameter part 18a and whose diameter is slightly smaller than the inner diameter of the mold closing cylinder 3. As shown in the figure, the small diameter portion 18b has a long axis shape, and even when the moving plate 7 is at the uppermost position (the state shown in FIG. 2), the lower end of the small diameter portion 18b is a hollow head cover 19. It has reached this point.

A differential pressure circuit is adopted for both the mold opening cylinder 2 and the mold closing cylinder 3 to increase the speed, and in order to make the speeds of both almost the same, the piston body 18 of the mold closing cylinder 3 has a special shape as described above. There is.

An example of the dimensional relationship among the cylinders 2, 3, piston rods 5, 8, and piston bodies 16, 18 is shown in Table 1 below.

Table 1 In a differential pressure circuit, the moving speed of the piston is inversely proportional to the area on the inlet side of the pressure oil minus the area on the outlet side, so according to the design side mentioned above, the speed coefficient is as shown in Table 2 below. become.

Table 2 The aforementioned four cylinders 2, 2, 3.3 are attached above the oil tank 21 storing oil 20, and the cylinders 2, 3.
Even if oil leaks from the mold, it is collected in the tank 21, and the small diameter portion 18b of the piston body 18 is immersed in the oil 20 and adheres to the oil during mold clamping, thereby maintaining good sliding performance with the head cover 19 at all times. .

Next, the hydraulic circuit of this vertical direct pressure type mold clamping device will be explained with reference to FIG.

To explain the mold clamping operation, a variable discharge amount pump 23 is driven by a motor 22, and the amount of oil discharged is controlled by an electromagnetic throttle valve 24.

In addition, the hydraulic pressure in the main pipe line 25 is controlled by the proportional electromagnetic relief valve 2.
Controlled by 6. 27 is the variable discharge power pump 2
3, which is a load sensing valve specific to the pump discharge side, which detects the pressure in a pipe 28 on the pump discharge side, and a main pipe 25 communicating from the outlet of the electromagnetic throttle valve 24 to the pump side of each actuator.
In other words, a discharge amount equal to the amount of passing oil commanded to the electromagnetic throttle valve 24 is discharged from the variable discharge amount pump 23 so that the pressure is always constant.

4-way valve 29 based on the mold clamping command signal from the control section.
30 solenoid is energized and pressure oil is supplied to the 4-way valve 30.
29) It enters the head chamber 3H side of the mold-closing cylinder 3 via P-B→T→A. At the same time, the mold closing cylinder 30 enters the rod chamber 3R via the boat P-B of the 4-way valve 29, thereby forming a differential pressure circuit, and as a result, the movable mold 10 descends at high speed together with the movable plate 7. The mold is then clamped. Figure 5 shows the state during mold clamping,
By driving the mold-closing cylinder 3, the piston body 18 is lowered, and the small diameter portion 18b is lowered below the helad cover 19 and immersed in the oil 20.

The rack 13 also descends together with the movable plate 7, thereby rotating the pinion 14 and outputting a pulse signal from the encoder 15. The control unit counts this pulse signal and outputs a signal to return the solenoid of the 4-way valve 30 to the neutral position just before the mold clamping is completed, and the configuration of the differential pressure circuit is released. Closed series〉l
Pressure oil is heated only in the rod chamber 3R of the die 3, resulting in high-pressure mold clamping.

Incidentally, when the mold is closed and the mold is clamped under high pressure, the mold closing solenoid of the four-way valve 31 is also energized, and the pressurized oil in the head chamber 2H of the mold opening cylinder 2 is released to the tank.

In addition, during high-pressure mold clamping, it is only necessary to replenish from the hydraulic source the amount of leakage oil that escapes from the piston of the cylinder, so input a flow rate signal of "zero" to the electromagnetic throttle valve 24,
The discharge amount of the variable discharge amount pump 23 is made almost zero, and only the pressure oil from the small capacity constant discharge pump 32 driven by the same motor is used. FIG. 6 shows the state when the mold clamping is completed.

Next, the mold opening operation will be explained. Based on the mold opening command signal from the control unit, the mold opening solenoids of the 4-way valves 31 and 33 are energized, and the pressure oil passes through the boats P→B→T→A of the 4-way valves 33 and 31, and enters the mold opening cylinder 2. rod room 2R
to go into. At the same time, it also enters the head chamber 2H of the mold opening cylinder 2 through the port P→B of the 4-way valve 31, thereby forming a differential pressure circuit, and as a result, the movable mold 10 moves at high speed together with the movable die plate 7. The mold is opened by rising.

In order to further improve the mold opening/closing performance, in the embodiment of the present invention, the variable discharge amount pump 23 is controlled as described below.

As shown in FIG. 7, the control device 34 includes a central processing unit (CPU) 35, a read-only memory (ROM)
36, random access memory (RAM) 37, keyboard switch (KB) 38, analog-digital converter (A/D) 39, input interface (IN) 40
, an output interface (OUT) 41, a digital-to-analog converter (D/A) 42, and the like.

Reference numeral 43 in the figure is a pressure sensor such as a strain gauge, which detects the working oil pressure of the main pipe line 44 when the mold is opened and closed, and converts this into a DC voltage.

This hydraulic pressure signal P passes through the A/D converter 39 and the input interface 40 and is stored at a predetermined address in the RAM 37.

On the other hand, the ROM 36 stores the following logic program, and the contents of this program will be explained with reference to FIG.

(2) The operating oil pressure signal P from the pressure sensor 43 is the rated pressure P of the variable discharge amount pump 23. . p corresponding to 50% of
Until reaching so, the rated discharge of the variable discharge amount pump 23 is 1tct, o. Discharge with .

■ The operating oil pressure signal P8 from the pressure sensor 43 is P. From P. . Until then, the discharge i- of the variable discharge amount pump 23 is calculated as CP according to the following formula with respect to the working oil pressure P at that time.
Calculated by U35.

PS (1) According to the program contents, as shown in Figure 8,
The operating oil pressure signal Px from the pressure sensor 43 is P. -P.

If it is between the rated discharge amount Q of the variable discharge amount pump 23. . , to speed up the mold opening/closing time, while the operating hydraulic pressure signal Px is P. ~PIG.

According to the above formula, the discharge amount Q becomes the rated pressure P,
. . These control signals are controlled to decrease linearly toward the output interface 41 and D
The signal is input to the electromagnetic throttle valve 24 via the /A converter 42.

Of course, with this discharge amount QX as the upper limit, a speed instruction program preset according to the stroke process of mold opening/closing is also input into the ROM 36 from the keyboard switch (KB), so the actual speed output from the electromagnetic throttle valve 24 The command signal follows the speed setting value % with the discharge amount Q as the upper limit (100%). Then, by the action of the load sensing valve 27, the discharge amount of the variable discharge amount pump 23 is automatically adjusted to match the speed commanded to the electromagnetic throttle valve 24.

Therefore, by such discharge amount control, if the pressure in the main pipe 44 is low while the mold closing cylinder 3 is operating,
The hydraulic oil is fully discharged from the variable discharge amount pump 23.

Then, the mold parting surface touches the main conduit 44.
When the pressure increases, the discharge amount of the variable discharge amount pump 23 is gradually automatically reduced, so that high-speed mold opening and closing can be performed without overloading the variable discharge amount pump 23.

In the above embodiment, a so-called vertical type direct pressure type mold clamping device was described in which a mold opening fluid cylinder and a mold closing fluid cylinder were installed upright so that the movable plate moved in the direction of gravity, but the present invention is not limited to this. The present invention can also be applied to a so-called horizontal direct pressure type mold clamping device in which a mold opening fluid cylinder and a mold closing fluid cylinder are arranged horizontally so that the movable plate moves horizontally.

In the above embodiment, a direct pressure type mold clamping device was described in which two mold opening fluid cylinders were arranged on one diagonal of the fixed plate and two mold closing fluid cylinders were arranged on the other diagonal. If the device is relatively small, a mold opening fluid cylinder and a mold closing fluid cylinder may be placed on one diagonal of the fixed plate, and a regular tie bar may be placed on the other diagonal. It is possible.

〔Effect of the invention〕

As described above, the present invention arranges a mold opening fluid cylinder and a mold closing fluid cylinder on a fixed plate at a predetermined interval,
The piston rods of the mold opening fluid cylinder and the mold closing fluid cylinder are connected to a moving plate and also serve as tie bars, and the mold opening fluid cylinder and the mold closing fluid cylinder are each connected to a differential pressure fluid circuit. That is.

Therefore, there is no need for a prefill valve or auxiliary cylinder as in the conventional case, and the structure is simple and compact, resulting in cost reduction. Further, the operation speed of opening and closing the mold can be made sufficiently fast and the mold clamping force can be made sufficiently large.

[Brief explanation of the drawing]

The drawings are all for explaining the direct pressure type mold clamping device according to the embodiment of the present invention, and FIG. 1 is a front view of the direct pressure type mold clamping device, FIG. 2 is a sectional view of the mold clamping device, and FIG. 3 is a sectional view of the mold clamping device. is a bottom view of the mold clamping device with the hydraulic tank removed, Figure 4 is the hydraulic circuit of the mold clamping device, and Figures 5 and 6 are the mold clamping device showing the state during mold clamping and when mold clamping is completed. 7 is a block diagram for explaining the control operation, and FIG. 8 is a diagram for explaining the operation. l... Fixed plate, 2... Mold opening cylinder, 3... Mold closing cylinder, 5.8...
・Piston rod, 7...Moving plate, 16
．． 18...Piston body, 18a...Small diameter part, 18b...Large diameter part, 17°19...
...Head cover, 21...Oil tank. Figure 8 Pressure

Claims (6)

[Claims] (1) A mold opening fluid cylinder and a mold closing fluid cylinder are arranged at a predetermined interval on a fixed plate, and the piston rods of the mold opening fluid cylinder and mold closing fluid cylinder are connected to the movable plate by serving as tie bars. A direct pressure type mold clamping device characterized in that a mold opening fluid cylinder and a mold closing fluid cylinder are each connected to a differential pressure fluid circuit. (2) A direct pressure type mold clamping device according to claim (1), wherein the fluid cylinder is a hydraulic cylinder. (3) In claim (1), two mold-opening fluid cylinders are disposed on one diagonal of the fixing plate, and two mold-closing fluid cylinders are disposed on the other diagonal. A direct pressure mold clamping device characterized by: (4) In claim (1), the mold-opening cylinder and the mold-closing cylinder have substantially the same piston rod diameter, and the end of the piston rod of the mold-opening cylinder has a piston in sliding contact with the inner circumferential surface of the cylinder. The end of the cylinder is closed with a head cover, and the end of the piston rod of the mold-closed cylinder has a large diameter part that slides on the inner peripheral surface of the cylinder and a small diameter part provided on the side opposite to the piston rod of the large diameter part. A hollow head cover is arranged at the end of the cylinder, and a part of the small diameter part reaches the hollow part of the head cover even when the movable plate is in the most open position. Features a direct pressure mold clamping device. (5) Claim (1) or (4), characterized in that a mold opening cylinder and a mold closing cylinder are erected so that the movable plate can move in the direction of gravity. Direct pressure mold clamping device. (6) Claim (5), wherein the mold opening cylinder and the mold closing cylinder are comprised of hydraulic cylinders, an oil tank is arranged below both cylinders, and at least an upper surface of the oil tank facing both cylinders. A direct pressure mold clamping device characterized by being open.