JPH0771729B2 - Direct pressure type mold clamping device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mold clamping device, and more particularly to a direct pressure type in which a cylinder rod such as a hydraulic cylinder is directly connected to a movable die plate to directly open and close a mold by hydraulic pressure. The present invention relates to a mold clamping device.

[Conventional technology]

The mold clamping devices used in injection molding machines and the like are roughly classified into a direct pressure type mold clamping device and a toggle type mold clamping device. Compared with the toggle type mold clamping device, the direct pressure type mold clamping device can be easily adjusted when changing the mold. In addition, the structure is simple and there are few worn parts, so it has excellent durability and easy maintenance management, but generally the mold opening and closing operation speed is slow, and if the mold clamping force is increased, ground packing It becomes difficult to prevent oil leaks from the parts.

In order to eliminate such drawbacks, an auxiliary cylinder system in which a cylinder for opening / closing the mold and a cylinder for generating the mold clamping force are separately provided,
Alternatively, there is a prefill valve system of a complicated hydraulic circuit.

[Problems to be solved by the invention]

However, all of the various direct pressure mold clamping devices that have been proposed so far have a complicated structure or hydraulic circuit, which not only leads to an increase in size and cost of the device, but also a sufficiently high mold opening / closing operation speed and mold clamping. I couldn't make my strength big enough.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide an inexpensive direct pressure type mold clamping device capable of performing mold opening / closing at high speed and obtaining a large mold clamping force.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides a fixed plate with a mold opening fluid cylinder and a mold closing fluid cylinder, which are, for example, hydraulic cylinders, arranged in parallel at a predetermined interval, and the mold opening fluid cylinder and the mold closing fluid are closed. Each piston rod of the cylinder is connected to the moving plate also as a tie bar, and the opening fluid cylinder and the mold closing fluid cylinder respectively constitute a part of the differential pressure fluid circuit. The piston rod diameter is almost the same, the piston rod end of the mold opening fluid cylinder is provided with a piston body that slides against the inner surface of the cylinder, the cylinder end is closed by a head cover, and the piston rod end of the mold closing fluid cylinder is It consists of a large-diameter part that is in sliding contact with the inner peripheral surface of the cylinder and a small-diameter part that is provided on the side opposite to the piston rod of the large-diameter part. A stone body is provided, a hollow head cover is arranged at the end of the cylinder, and a part of the small diameter portion is located in the hollow head cover even when the moving plate is at the maximum mold open position. It is characterized by.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view of a direct pressure type mold clamping device, FIG. 2 is a sectional view of the mold clamping device,
3 is a bottom view of the mold clamping device with the oil tank removed, FIG. 4 is a hydraulic circuit of the mold clamping device, FIG. 5 and FIG.
FIG. 7 is a sectional view of the mold clamping device showing a state during mold clamping and at the time of completion of mold clamping, FIG. 7 is a block diagram for explaining a control operation, and FIG. 8 is an operation explanatory view.

First, the structure of the vertical direct pressure type mold clamping device according to the embodiment will be described with reference to FIGS. 1 to 3.

The fixed plate 1 is integrated with the upper ends of the two mold opening cylinders 2 and 2 and the two mold closing cylinders 3 and 3 which are vertically provided.
As shown in FIG. 3, one mold closing cylinder and the other mold opening cylinder 2 are diagonally arranged, and one mold closing cylinder 3 and the other mold closing cylinder 3 are also diagonally arranged. And each mold opening cylinder 2,2 and mold closing cylinder 3,3
The upper ends of the mold opening cylinders 2 and 2 and the mold closing cylinders 3 and 3 are integrally connected by a connecting portion 4 as shown in FIG. Are linked to.

As shown in FIG. 2, the piston rod 5 of the mold opening cylinder 2 penetrates the rod cover 6 to move the moving plate 7 above.
Is stuck to. Piston rod 8 of mold closing cylinder 3
Penetrates the rod cover 9 and is similarly fixed to the upper moving plate 7. A movable die 10 is fixed to the lower surface of the movable plate 7, while a fixed die 12 is fixed above the fixed plate 1 via a die mounting plate 11 and moved with respect to the fixed die 12. Mold 10 is facing. A rack 13 is hung from one end of the moving plate 7, a pinion 14 meshing with a tooth portion of the rack 13 is rotatably fixed at a predetermined position, and an encoder 15 is connected to a rotation shaft of the pinion 14. Therefore, the rack 13, the pinion 14, and the encoder 15 constitute a position sensor for detecting the position of the moving plate 7.

As shown in FIG. 2, at the lower end of the piston rod 5 of the mold opening cylinder 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. The lower end opening is closed by a head cover 17. On the other hand, the piston rod 8 in the mold closing cylinder 3
The piston body 18 fixed to the lower end of the mold is the mold opening cylinder 2
And a large diameter portion 18a of which the outer peripheral surface is in sliding contact with the inner peripheral surface of the mold closing cylinder 3, and the large diameter portion 1 thereof.
It comprises a small diameter portion 18b provided at the lower end of 8a and having a diameter 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 has a hollow head cover 19. Has reached.

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

Cylinders 2, 3, piston rods 5, 8 and piston body 1
Table 1 below shows an example of the dimensional relationship of 6,18.

In the differential pressure circuit, the moving speed of the piston is inversely proportional to the area obtained by subtracting the area on the outlet side from the area on the inlet side of the pressure oil. Therefore, according to the above-mentioned design example, the speed coefficient is as shown in Table 2 below. .

The above-mentioned four cylinders 2, 2, 3, 3 are skirted above the oil tank 21 storing the oil 20, and even if oil leaks from the cylinders 2, 3, they are stored in the tank 21 and at the time of mold clamping. The small-diameter portion 18b of the piston body 18 is immersed in the oil 20 so that the oil adheres to the piston 20 and always maintains good slidability with the head cover 19.

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

First, the mold clamping operation will be described. The motor 22 drives the variable discharge pump 23, and the discharge amount of oil is controlled by the electromagnetic throttle valve 24. The hydraulic pressure in the main conduit 25 is controlled by the proportional electromagnetic relief valve 26. 27 is a load sensing valve unique to the variable discharge force pump 23,
The pressure of the pipe 28 on the discharge side of the pump and the electromagnetic throttle valve 24
So that the pressure in the main conduit 25 communicating with the pump side of each actuator from the outlet of the actuator is always constant, in other words, the discharge amount equal to the amount of oil passing through which is commanded to the electromagnetic throttle valve 24 is the variable discharge pump 23. It is supposed to be discharged from.

Based on the mold clamping command signal from the control unit, the 4-way valve 29,30
The solenoid is excited and the pressure oil enters the rod chamber 3R of the mold clamping cylinder 3 through the port P → B of the 4-way valve 29. At the same time, port P → B → T → A of 4-way valve 30,29
Through the head chamber 3H of the mold clamping cylinder 3, thereby forming a differential pressure circuit based on the cross-sectional area difference of the mold clamping cylinder 3, and as a result, the movable mold 10 moves together with the movable plate 7 at high speed. The mold is lowered and the mold is clamped. FIG. 5 shows a state in the middle of mold clamping, in which the piston body 18 is lowered by driving the mold closing cylinder 3, and the small diameter portion 18b is immersed in the oil 20 below the head cover 19.

The rack 13 also moves down together with the moving plate 7, whereby the pinion 14 rotates and the encoder 15 outputs a pulse signal. The control unit counts this pulse signal and outputs a signal for returning the solenoid of the 4-way valve 30 to the neutral position immediately before the completion of mold clamping, and the differential pressure circuit is released. Therefore, only the 4-way valve 29 is used. In the meantime, only the rod chamber 3R of the mold closing cylinder 3 is pressurized with the pressure oil, which causes high-pressure mold clamping.

When the high pressure mold is clamped, the mold closing solenoid of the 4-way valve 31 is also excited to release the pressure oil in the head chamber 2H of the mold opening cylinder 2 to the tank.

Also, at the time of high-pressure mold clamping, it is sufficient to replenish from the hydraulic pressure source by the amount of leak oil that escapes from the piston body of the cylinder.
A signal of flow rate "zero" is input to the electromagnetic throttle valve 24, the discharge amount of the variable discharge pump 23 is set to almost zero, and only pressure oil from a 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 described. The mold closing solenoids of the 4-way valves 31, 33 are excited based on the mold opening command signal from the control unit, and the pressure oil passes through the ports P → B of the 4-way valve 31 and enters the head chamber 2H of the mold opening cylinder 2. . At the same time, it also enters the mold opening cylinder 2 and the rod chamber 2R through the ports P → B → T → A of the four-way valves 33, 31 and thereby creates a differential pressure circuit based on the difference in cross-sectional area of the mold opening cylinder 2. As a result, the moving die 10 is moved up at a high speed together with the moving die plate 7 to open the die.

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

As shown in FIG. 7, the control device 34 includes a central processing unit (CPU) 35, a read only memory (ROM) 36, a random access memory (RAM) 37, and a keyboard switch (K).
B) 38, analog-digital converter (A / D) 39, input interface (IN) 40, output interface (OUT) 4
1 and a digital-analog converter (D / A) 42.

43 in the figure is a pressure sensor such as a strain gauge,
By detecting the hydraulic pressure of the main pipeline 44 when opening and closing the mold,
This is converted into a DC voltage. This hydraulic signal P _x is A /
R through D converter 39 and input interface 40
It is stored in the prescribed address of AM37.

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

The variable discharge pump 23 discharges at the rated discharge amount Q ₁₀₀ until the operating hydraulic signal P _x from the pressure sensor 43 reaches P ₅₀ corresponding to 50% of the rated pressure P ₁₀₀ of the variable discharge pump 23.

The hydraulic signal P _x from the pressure sensor 43 changes from P ₅₀ to P _100.
Until that time, the discharge amount Q _x of the variable discharge amount pump 23 is calculated by the CPU 35 according to the following equation with respect to the operating oil pressure P _{x at} that time.

According to such program contents, as shown in FIG.
If hydraulic pressure signal Px from the pressure sensor 43 is between the P ₀ to P ₅₀ is expedited mold opening and closing time is ejected at a rated discharge amount Q ₁₀₀ of the variable discharge pump 23 while the hydraulic pressure signal Px is P ₅₀ ~ P
_{When it} is between _100, the discharge rate Q is the rated pressure P according to the above formula.
Controlled to decrease linearly toward ₁₀₀ , these control signals are output interface 41 and D /
It is input to the electromagnetic throttle valve 24 via the A converter 42.

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

Therefore, by such discharge amount control, when the pressure in the main pipe line 44 is low while the mold closing cylinder 3 is operating, the variable discharge pump 23 fully discharges the hydraulic oil. Then, when the mold parting surface is touched and the pressure in the main pipe line 44 increases, the discharge amount of the variable discharge pump 23 gradually and automatically decreases, and the variable discharge pump 23 does not become overloaded at high speed. The mold can be opened and closed.

In the above embodiment, the so-called vertical type direct pressure type mold clamping device in which the mold opening fluid cylinder and the mold closing fluid cylinder are erected so that the moving plate moves in the direction of gravity is explained, but the present invention is not limited to this. However, the present invention can be applied to a so-called horizontal type direct pressure type mold clamping device in which the mold opening fluid cylinder and the mold closing fluid cylinder are laterally arranged so that the moving plate moves in the horizontal direction.

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

〔The invention's effect〕

As described above, according to the present invention, the mold opening fluid cylinder and the mold closing fluid cylinder are arranged in parallel at a predetermined interval on the fixed plate, and the piston rods of the mold opening fluid cylinder and the mold closing fluid cylinder each have a tie bar. The mold opening fluid cylinder and the mold closing fluid cylinder respectively form a part of the differential pressure fluid circuit, and the piston opening diameters of the mold opening fluid cylinder and the mold closing fluid cylinder are almost the same, The piston rod end of the open fluid cylinder is provided with a piston body that is in sliding contact with the cylinder inner peripheral surface, and the cylinder end is closed by a head cover.
The piston rod end of the closed mold cylinder is provided with a piston body consisting of a large diameter part that is in sliding contact with the inner peripheral surface of the cylinder and a small diameter part on the side opposite to the piston rod of the large diameter part. A hollow head cover is arranged, and a part of the small diameter portion is located in the hollow head cover even when the moving plate is at the maximum mold open position.

Therefore, unlike the conventional case, a prefill valve, an auxiliary cylinder, etc. are not required, the structure is simple and the size is small, and the cost can be reduced. In addition, the mold opening / closing operation speed can be sufficiently high, and the mold clamping force can be sufficiently large.

[Brief description of drawings]

The drawings are all for explaining a direct pressure type mold clamping device according to an embodiment of the present invention. 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. Is a bottom view of the mold clamping device with the hydraulic tank removed, FIG. 4 is a hydraulic circuit of the mold clamping device, and FIGS. 5 and 6 are mold clamping devices showing a condition during mold clamping and at the time of completion of mold clamping. 7 is a block diagram for explaining the control operation, and FIG. 8 is an operation explanatory view. 1 ... Fixed plate, 2 ... Mold open cylinder, 3 ... Mold closed 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.

Claims (5)

[Claims] 1. A mold opening fluid cylinder and a mold closing fluid cylinder are arranged in parallel on a fixed plate at a predetermined interval, and the piston rods of the mold opening fluid cylinder and the mold closing fluid cylinder also act as tie bars. The mold opening fluid cylinder and the mold closing fluid cylinder each constitute a part of a differential pressure fluid circuit, and the mold opening fluid cylinder and the mold closing fluid cylinder have substantially the same piston rod diameter. The piston rod end of is provided with a piston body that is in sliding contact with the inner peripheral surface of the cylinder,
The cylinder end is closed by a head cover, and at the piston rod end of the mold-closed fluid cylinder, there is a piston body consisting of a large diameter portion that is in sliding contact with the inner peripheral surface of the cylinder and a small diameter portion that is provided on the side opposite to the piston rod of the large diameter portion. A hollow head cover is provided at the end of the cylinder so that a part of the small diameter portion is located inside the hollow head cover even when the moving plate is at the maximum mold open position. Direct pressure type mold clamping device. 2. In the claim (1),
A direct pressure type mold clamping device, wherein the fluid cylinder is a hydraulic cylinder. 3. In the claim (1),
A direct pressure type mold clamping device, wherein two mold opening fluid cylinders are arranged on one diagonal of the fixing plate and two mold closing fluid cylinders are arranged on the other diagonal. 4. In the claim (1),
A direct pressure type mold clamping device in which a mold opening fluid cylinder and a mold closing fluid cylinder are erected so that the moving plate can move in the direction of gravity. 5. In the claim (4),
A direct pressure type mold characterized in that the mold opening fluid cylinder and the mold closing fluid cylinder are hydraulic cylinders, an oil tank is arranged below each cylinder, and at least an upper surface of the oil tank facing each cylinder is open. Fastening device.