JP3414999B2 - Hydraulic device of injection molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a hydraulic tank for supplying hydraulic oil to a direct pressure type mold clamping cylinder of an injection molding machine or the like, and particularly to shortening of mold clamping pressure increasing time and mold closing and mold clamping operations. The present invention relates to a hydraulic device configured to perform quickly and smoothly.

[0002]

2. Description of the Related Art Conventionally, in a hydraulic system such as an injection molding machine, when performing mold closing and mold clamping control, a mold clamping ram is advanced by a boost cylinder during mold clamping and a negative pressure is generated in the mold clamping cylinder. A so-called prefill operation is performed in which hydraulic oil is sucked from the hydraulic tank into the mold clamping cylinder by the suction pipe that connects the clamping cylinder and the hydraulic tank.

In this case, since the hydraulic tank is generally installed at a position considerably lower than the oil chamber of the mold clamping cylinder, the hydraulic oil in the hydraulic tank is sucked into the oil chamber against the hydraulic head difference. It is necessary and is an obstacle to quick and smooth mold clamping operation of the mold clamping ram. That is, the negative pressure in the oil chamber of the mold clamping cylinder causes the hydraulic oil to be sucked up from the hydraulic tank through the suction pipe. In this case, the pressure for supplying the hydraulic oil to the oil chamber is 1 Kgf / cm. ^It cannot be ² or more, and the higher the speed when closing the mold, the larger the speed of increase of the space volume in the oil chamber of the mold clamping cylinder.Therefore, during the transition from the mold closing operation to the mold closing operation,
There is a delay in filling the oil chamber of the mold clamping cylinder with hydraulic oil, or the negative pressure in the oil chamber of the mold clamping cylinder causes the mold clamping ram to retract, which hinders quick and smooth operation. become.

Therefore, in the prior art, for a hydraulic tank, in order to maintain the pressure in the tank at a predetermined pressure, a relief valve for discharging the air in the tank when the pressure exceeds the predetermined pressure, and a pressure in the tank. When a predetermined negative pressure is reached, a suction means for sucking air into the tank is installed to keep the pressure in the hydraulic tank at a predetermined pressure, and the inflow / outflow of air in the tank is regulated to prevent the mold clamping ram from moving. A hydraulic device in an injection molding machine configured to perform a quick and smooth mold clamping operation has been proposed (JP-A-5-25).
3996 publication).

In the hydraulic system according to the above proposal, when the mold clamping ram expands and contracts, the hydraulic oil in the hydraulic tank is sucked into the oil chamber of the mold clamping cylinder via the prefill valve, and the inside of the hydraulic tank becomes negative pressure. The pressure in the hydraulic tank is compared based on the fact that air is sucked into the tank from the suction means and the hydraulic oil flows back to the hydraulic tank again, and the temperature rise of the hydraulic oil due to the expansion and contraction operation of the mold clamping ram. Boost the pressure very early. As a result, the relief valve adjusts the pressure in the hydraulic tank so that the pressure substantially corresponds to the head difference between the hydraulic tank and the oil chamber. In this state, when the mold clamping ram is extended, when the working oil in the hydraulic tank is sucked into the oil chamber, the working oil is sent to the oil chamber without causing a negative pressure in the oil chamber or the like. Further, when the pressure in the hydraulic tank becomes equal to or higher than a predetermined pressure, only the extra pressure is released, and the relief valve and the suction means prevent air from entering and leaving the hydraulic tank during normal operation. It is regulated, and the amount of oil mist released from the hydraulic tank is small.

Further, in order to completely prevent the contamination of the hydraulic oil in the hydraulic tank by the contact with the outside air and the oil mist released to the outside, a system closed by a closed hydraulic tank and an air reservoir is formed. However, there is also proposed a hydraulic device that uses a sealed hydraulic tank configured to keep clean internal pressure of the hydraulic tank by enclosing clean air therein (Japanese Utility Model Laid-Open No. 6-49802, JP-A-8-98802). No. 21403).

In the proposed hydraulic system of this type, a closed tank for storing hydraulic oil and an air reservoir are connected to each other so that gases can be exchanged with each other to form a closed system. Even if the amount of hydraulic oil in the tank increases or decreases, the internal pressure can be adjusted only within the sealed hydraulic system, and contact between the hydraulic oil and the outside air can be eliminated altogether.
No foreign matter is mixed into the hydraulic oil, and no oil mist is ejected to the outside.Therefore, the manufacturing environment of molded products by injection molding machines driven and controlled by this type of hydraulic system is always clean. It has the advantage that it can be kept at.

[0008]

However, in the conventional hydraulic system described above, in which the closed hydraulic tank is used, since the inside of the hydraulic system is set to a pressure higher than atmospheric pressure, it is sealed after long-term use. It is assumed that the generated gas leaks. In this case, the volume of the gas stored in the bag of the air reservoir decreases, and it becomes impossible to replenish the required amount of gas when the amount of hydraulic oil in the tank decreases. It is also expected that the pressure inside the hydraulic system will rise abnormally when cooling water enters the tank due to damage to the cooler or the like and the contents of the tank increase. As a safety measure in such a case, it is necessary to provide an intake / exhaust valve in the closed system.

However, in this intake / exhaust valve, when the internal pressure of the hydraulic system decreases and falls below the set pressure, the external pressure overcomes the elastic force of the first spring urging the vacuum valve in the closing direction. The vacuum valve is configured to be pushed open so that outside air can enter the intake / exhaust pipe through the filter from the intake / exhaust port. When the internal pressure of the hydraulic system rises and exceeds the set pressure, the elastic force of the second spring that biases the spool via the spring holder is overcome by the pressure of the sealed gas in the hydraulic system, and Is configured to be pushed open so that the enclosed gas is released from the intake / exhaust pipe through the filter to the outside through the intake / exhaust port.

Therefore, the hydraulic system has an advantage that it can prevent the hydraulic oil from being contaminated and the oil mist from being discharged to the outside. However, not only does the system structure become complicated, but also unexpectedly. As a safety measure against the situation, it is required to attach a safety valve mechanism having a complicated configuration as described above, which increases the manufacturing cost and requires frequent maintenance, which makes handling difficult.

Further, in the conventional hydraulic system, when an accumulator is used as the air reservoir, the pressure in the hydraulic tank is increased to a certain pressure or more even during the mold opening operation. When the ram retreats, it becomes a resistance, so a large retreating force is required when opening the mold.

[0012] Therefore, as a result of intensive research and trial production, the present inventor pressurizes the inside of the hydraulic tank only during the mold closing (forward) operation, and during the mold opening (reverse) operation. It was found that by opening the air inside and setting it so as not to generate residual pressure, the mold opening / closing operation can be achieved with a small mold opening force (retraction force) without resistance during the mold opening operation.

Further, in this case, immediately before the mold closing, the supply of hydraulic oil from the hydraulic pressure circuit is stopped, and while the pressure in the mold clamping cylinder is detected by the required pressure sensor, the hydraulic tank is controlled by the air pressure adjusting valve. By controlling the air pressure in the inside, it is possible to reduce the final mold closing force as compared with the case of performing only the control of the hydraulic pressure circuit,
It was also found that the mold clamping force generated by the subsequent supply of high-pressure hydraulic oil can be reduced, and high-precision low-pressure mold clamping control can be realized.

Therefore, it is an object of the present invention to supply sufficient hydraulic oil into the oil chamber of the mold clamping cylinder to shorten the time for increasing the mold clamping pressure even when the mold closing speed is high in the mold closing operation. And to provide a hydraulic device of an injection molding machine capable of rapidly and smoothly shifting from a mold closing operation to a mold closing operation.

[0015]

In order to achieve the above object, a hydraulic system of an injection molding machine according to the present invention is a mold clamping oil for performing a mold clamping operation of a mold clamping ram on a mold clamping cylinder of the injection molding machine. In a hydraulic system of an injection molding machine in which a suction chamber for hydraulic oil is connected to the oil chamber through a prefill valve and the suction pipe is connected to the hydraulic tank, the hydraulic chamber is externally connected to the hydraulic tank. In addition to providing a release / sealing switching valve for switching between opening and closing and closing, the air pressure introducing pipe for supplying and shutting off the air pressure from the required air pressure source is connected in communication, and at the time of mold closing operation by the mold clamping ram. When the release / sealing switching valve is closed, air pressure is introduced from the air pressure introduction pipe into the hydraulic tank to maintain the mold clamping oil chamber of the mold clamping cylinder at atmospheric pressure or higher, and when opening the mold by the mold clamping ram. The above The clamping oil chamber of the air pressure mold clamping cylinder by blocking the introduction of the air pressure introduction pipe to the hydraulic tank while release operation of releasing a sealing changeover valve, characterized in that configured to release the air.

Further, an oil pressure sensor for detecting the oil pressure in the mold clamping oil chamber of the mold clamping cylinder is provided, and the air in the hydraulic tank is adjusted so that the oil pressure is equal to or higher than the atmospheric pressure during the mold closing operation. The pressure can be adjusted.

In this case, the air pressure in the hydraulic tank can be adjusted by connecting the air pressure adjusting valve to the air pressure introducing pipe and adjusting the air pressure adjusting valve based on the detection signal of the oil pressure sensor. It is preferable to configure the above.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a hydraulic system for an injection molding machine according to the present invention will be described in detail below with reference to the accompanying drawings.

1 and 2 show an embodiment of a hydraulic system for an injection molding machine according to the present invention. FIG. 1 shows an operating state of a hydraulic system during a mold closing operation, and FIG. The operation state of the hydraulic system at the time of mold opening operation is shown.

However, in FIGS. 1 and 2, reference numeral 10 indicates a mold clamping cylinder which constitutes a hydraulic device of an injection molding machine, and a mold clamping ram 12 is inserted through the mold clamping cylinder 10 so as to be movable back and forth. There is. In addition, the mold clamping ram 12
A movable plate 14 for mounting a moving die (not shown) is provided at the tip of the. Further, the rear end of the mold clamping ram 12 is annularly expanded to form a piston portion 12a, and the cylinder chamber of the mold clamping cylinder 10 formed on the rear surface side of the piston portion 12a is connected to the mold clamping oil chamber. 16 and the cylinder chamber of the mold clamping cylinder 10 formed on the outer periphery of the mold clamping ram 12 on the front side of the piston portion 12a is configured as a mold oil opening chamber 17. Further, a hole 18 that extends in the axial direction is provided in the center of the rear end side of the mold clamping ram 12, and a boost cylinder 20 that protrudes from one side of the mold clamping cylinder 10 is provided in the hole 18. Has been inserted.

The mold clamping cylinder 10 configured as described above
Is provided with a suction pipe 22 that communicates with the mold clamping oil chamber 16, and connects the suction pipe 22 to the inside of a hydraulic tank 30 so that the inside of the mold clamping oil chamber 16 and the suction pipe 22 are inside the hydraulic tank 30. It is configured to be filled with the hydraulic oil 32. A prefill valve 24 is provided in a portion of the suction pipe 22 that communicates with the mold clamping oil chamber 16. Further, an oil passage 28 for supplying hydraulic oil for performing mold closing by the mold clamping ram 12 into the boost cylinder 20 is connected to the mold clamping cylinder 10, and the mold clamping operation is performed. A high pressure oil passage 26 for supplying high pressure hydraulic oil into the mold clamping oil chamber 16 is connected and arranged. An oil pressure sensor 29 is provided for the high pressure oil passage 26.

However, the hydraulic tank 30 is composed of a hermetically sealed casing in which the hydraulic oil 32 is filled to a predetermined level, and the upper surface 30a of the hydraulic tank 30 is controlled so as to be opened and closed to the outside. An open / close switching valve 34 is provided, and an air pressure introducing pipe 36 for introducing air pressure from the outside is connected and connected. An air pressure sensor 38 for detecting the air pressure in the hydraulic tank 30 is provided.

The open / close switching valve 34 is equipped with appropriate filters 40a, 40b, 40c, 40d in the valve passage portion for communicating the inside and the outside of the hydraulic tank 30.
The oil mist generated in the hydraulic tank 30 is absorbed by the filters 40a, 40b, 40c and 40d and is not discharged directly to the outside. In addition, the air pressure source 4 is provided in the valve operation portion of the opening / closing switching valve 34.
By supplying the air pressure supplied from 2 via the first switching valve 44, the opening / closing switching valve 34 is switched.

On the other hand, the air pressure introducing pipe 36 is configured to supply or cut off the air pressure supplied from the air pressure source 42 via the second switching valve 46. In this case, an air pressure adjusting valve 48 is connected to the air pressure introducing pipe 36 so that the air pressure in the hydraulic tank 30 can be adjusted. Note that reference numeral 5
Reference numeral 0 indicates a control unit of the air pressure adjusting valve 48.

Next, the operation of the hydraulic system of this embodiment having the above construction will be described.

First, at the time of mold closing and mold closing operations, as shown in FIG. 1, the opening / closing switching valve 34 is closed by the first switching valve 44, and the second switching valve 46 is operated. From the air pressure introducing pipe 36 to the air pressure source 4
The required air pressure is supplied from 2 into the hydraulic tank 30.
Then, by supplying hydraulic oil of a required pressure from the oil passage 28 into the boost cylinder 20, the mold clamping ram 12 can be moved in the mold closing direction indicated by the arrow.

In this case, according to the present embodiment, by supplying a required air pressure from the air pressure source 42 into the hydraulic tank 30, the pressure in the mold clamping oil chamber 16 of the mold clamping cylinder 10 is increased. By adjusting and setting the pressure to be equal to or higher than the atmospheric pressure, the mold closing operation by the movement of the mold clamping ram 12 by the boost cylinder 20 can be achieved quickly and smoothly. That is, during the mold closing operation,
The mold pressure oil chamber 1 of the mold clamping cylinder 10 is controlled by the hydraulic pressure sensor 29.
6, the air pressure adjusting valve 48 is controlled via its control unit 50 based on this detection signal, and the air pressure in the hydraulic tank 30 is controlled to the atmospheric pressure or the oil pressure sensor 29.
The pressure can be adjusted to be equal to or higher than the pressure detected in. The air pressure in the hydraulic tank 30 at this time can be detected by the air pressure sensor 38.

Therefore, immediately before the mold closing due to the movement of the mold clamping ram 12, the supply of hydraulic oil from the oil passage 28 is stopped, and the mold pressure oil chamber 29 of the mold clamping cylinder 10 is stopped by the hydraulic pressure sensor 29.
By controlling the air pressure in the hydraulic tank 30 by the air pressure adjusting valve 48 while detecting the pressure in the inside, the final mold closing force can be reduced, and then the prefill valve 24 is closed to increase the high pressure. The mold clamping force (advancing force) of the high pressure hydraulic oil supplied from the oil passage 26 into the mold clamping oil chamber 16 can also be reduced, and highly accurate low pressure mold clamping control can be achieved. That is, with the hydraulic device configured as described above, it is possible to easily achieve the protection of the mold at the time of mold closing and mold clamping.

On the other hand, in the mold opening operation, as shown in FIG. 2, after opening the prefill valve 24, the opening / closing switching valve 34 is opened via the first switching valve 44, and at the same time, the second switching valve is opened. Through the switching valve 46 of the air pressure introducing pipe 36
Shut off the air pressure derived from. Then, by supplying hydraulic oil of a required pressure into the mold opening chamber 17 of the mold clamping cylinder 10, the mold clamping ram 12 can be moved in the mold opening direction indicated by the arrow.

In this case, according to this embodiment, the inside of the hydraulic tank 30 communicates with the outside through the open / close switching valve 34, the air in the tank 30 is released, and the residual pressure is reduced. Does not happen. Therefore, there is no resistance during the mold opening operation of the mold clamping ram 12, and quick and smooth mold opening control can be achieved with a small mold opening force (retraction force).

The movement of the mold clamping ram 12 in the mold opening direction causes the hydraulic oil 32 in the mold clamping oil chamber 16 to move to the hydraulic tank 30.
When the oil level of the hydraulic oil 32 in the hydraulic tank 30 rises, the compressed air in the hydraulic tank 30 becomes
Filters 40a to 40d from the open / close switching valve 34
It is released to the outside (atmosphere) via. At this time, the oil mist generated in the hydraulic tank 30 is generated by the filters 4
There is no fear that the oil mist will be directly absorbed to the outside (atmosphere) in a large amount by being absorbed by 0a to 40d.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and many design changes can be made without departing from the spirit of the present invention.

[0033]

As described above, the hydraulic system of the injection molding machine according to the present invention is provided with the mold clamping oil chamber for performing the mold clamping operation of the mold clamping ram in the mold clamping cylinder of the injection molding machine. In a hydraulic system of an injection molding machine in which a suction pipe for hydraulic oil is connected to the oil chamber through a prefill valve and the suction pipe is connected and arranged in a hydraulic tank, the hydraulic tank is opened and closed to the outside. In addition to providing a release / sealing switching valve that switches the air pressure, an air pressure introducing pipe that supplies and shuts off the air pressure from the required air pressure source is connected in communication, and the release / sealing switching is performed during mold closing operation by the mold clamping ram. The valve is closed and the air pressure is introduced from the air pressure introduction pipe into the hydraulic tank to keep the mold clamping oil chamber of the mold clamping cylinder above atmospheric pressure, and the release / sealing is switched during the mold opening operation by the mold clamping ram. Valve By releasing the air pressure and shutting off the introduction of air pressure from the air pressure introducing pipe into the hydraulic tank to release the atmosphere in the mold clamping oil chamber of the mold clamping cylinder, the mold closing speed is high during the mold closing operation. Is sufficient to supply sufficient hydraulic oil to the oil chamber of the mold clamping cylinder,
It is possible to shorten the time for increasing the mold clamping pressure and to quickly and smoothly shift from the mold closing operation to the mold clamping operation.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional side view showing an operation state of a hydraulic apparatus of an injection molding machine according to an embodiment of the present invention during a mold closing operation.

2 is a schematic cross-sectional side view showing an operation state during a mold opening operation in the hydraulic device of the injection molding machine shown in FIG.

[Explanation of symbols]

10 Mold clamping cylinder 12 Mold clamping ram 12a Piston part 14 Movable plate 16 mold clamping chamber 17 type oil open chamber 18 holes 20 boost cylinder 22 Suction pipe 24 prefill valve 26 High-pressure oil passage 28 oil passage 29 Oil pressure sensor 30 hydraulic tank 30a upper surface 32 hydraulic oil 34 Open / closed switching valve 36 Air pressure introduction pipe 38 Air pressure sensor 40a-40d filter 42 Air pressure source 44 First switching valve 46 Second switching valve 48 Air pressure control valve 50 control unit

Claims (3)

(57) [Claims] 1. A mold clamping cylinder of an injection molding machine is provided with a mold clamping oil chamber for performing a mold clamping operation of a mold clamping ram, and a hydraulic oil suction pipe is connected to this oil chamber through a prefill valve. In addition, in the hydraulic system of the injection molding machine in which this suction pipe is connected and arranged in the hydraulic tank, the hydraulic tank is provided with a release / sealing switching valve for switching between opening and closing with the outside and a required air pressure source. The air pressure introducing pipe that supplies and shuts off the air pressure from the
The closed switching valve is closed and air pressure is introduced from the air pressure introduction pipe into the hydraulic tank to keep the mold clamping oil chamber of the mold clamping cylinder above atmospheric pressure. An injection molding machine characterized in that the closed switching valve is operated to be released, and the introduction of air pressure from the air pressure introduction pipe into the hydraulic tank is shut off to open the atmosphere in the mold clamping oil chamber of the mold clamping cylinder. Hydraulic system. 2. An air pressure sensor for detecting an oil pressure in a mold clamping oil chamber of a mold clamping cylinder, and air pressure in a hydraulic tank so that the oil pressure is equal to or higher than atmospheric pressure when a mold closing operation is performed. The hydraulic system for an injection molding machine according to claim 1, wherein the hydraulic system is configured to adjust the pressure. 3. The air pressure in the hydraulic tank is arranged such that an air pressure adjusting valve is connected to the air pressure introducing pipe and the air pressure adjusting valve can be adjusted based on a detection signal of an oil pressure sensor. The hydraulic system for an injection molding machine according to claim 2.