JPH0114855B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a mold clamping device for an injection molding machine or a die casting machine, and more specifically, to a structure for ensuring parallelism of a platen in a horizontal direct pressure mold clamping device. It is related to.

(2) Prior art and its problems Traditionally, direct pressure type mold clamping devices such as injection molding machines have a mold clamping cylinder placed horizontally on a bed, and the mold clamping cylinder is movable in the forward and backward directions via tie bars. side and fixed side platens are arranged. Further, the rod of the mold clamping cylinder is provided with a movable platen, and the bearing portion of the rod is constituted by a bush having a clearance of at least about 30 microns that allows the rod to move forward and backward. Therefore, the weight of the movable platen and the mold attached to it causes the rod to become eccentric within the range of the bearing clearance, and at the same time causes the tie bar to bend, which in turn causes the platen to become out of parallelism. It was something that made me want to do something. If the parallelism of the platen is out of alignment, the guide pins of the mold will be subjected to uneven loads and wear out, and the molds will not be properly aligned, which will lead to the premature end of the mold's life. It happened.

In order to overcome the above drawbacks, the tie bars have been made large in diameter to minimize deflection, or a sliding plate has been interposed between the lower surface of the movable platen and the bed. In the former case, there is a limit to how large the tie bar can be made.
When the tie bar is made larger in diameter, the mold mounting surface of the platen is narrowed by the larger diameter. Therefore, enlarging the area of the platen is not preferable because the overall load increases. The tie bar could only have a large diameter within a range not restricted by the mold mounting surface.

In the latter case, it is necessary to ensure parallelism at three points: the rod of the mold clamping cylinder, the stationary platen, and the movable platen provided with the sliding plate. Since the bed of the main body is not necessarily horizontal and there is a clearance in the bearing section, the parallelism of the three points mentioned above cannot be achieved strictly from a machining perspective. Even assuming that the parallelism is accurately achieved, firstly, the sliding plate is affected by the heat of the molding cycle,
Dimensional errors occur. Secondly, the sliding plate has the clearance necessary for sliding between it and the bed, but at the same time it wears out due to metal contact with the bed, so it is necessary to allow for the above clearance error while adjusting the frequency of use. must be adjusted accordingly. Thirdly,
The sliding plate needed to be finely adjusted each time the mold was replaced in response to the weight of the mold. In any case, the maximum parallelism of the platen is 50 microns, and it cannot be guaranteed over a long period of time. Therefore, at present, the molds are matched on the assumption that there is an error in the parallelism of the platen.

By the way, with the development of engineering plastics in modern times, precision on the order of microns has been required in injection molding. In order to meet this demand, the mold must have an absolute condition that the dividing surfaces match accurately. No matter how precisely the mold is finished, if there is an error in mold matching, molding on the micron order is impossible. In this sense, the parallelism of the conventional platen mentioned above is limited to a maximum of 50 microns, and therefore cannot be applied to molds for precision parts requiring accuracy of 10 microns or less.

In view of the above circumstances, the applicant filed the patent application No. 57-149599.
The company provides equipment related to this issue. By applying pressure oil to the annular oil groove provided in the bearing of the rod of the mold clamping cylinder, a self-aligning structure is created with respect to the amount of movement of the rod, and a cantilevered structure is created due to the rigidity of the rod. This is to maintain the horizontality of the movable platen. According to this, the rod was self-aligned by applying pressure oil to the oil groove and adjusting the forward and backward movement clearance, but the results of various experiments have shown that it is possible to utilize the skin layer of oil without necessarily supplying pressure oil. found. That is, in the viscous region, the skin layer is formed into an extremely thin oil film. The clearance between the bearing portion and the rod is set to a minute enough to form a skin layer, and the oil groove and the chamber of the mold clamping cylinder are brought into communication via this clearance. In this case, the forward and backward movements of the rod can function as oil flow, and a skin layer as a boundary layer can be formed in the clearance.

(3) Purpose of the Invention The present invention was developed in view of the above-mentioned circumstances, and is capable of achieving high accuracy in the parallelism of the platen and maintaining the parallelism without deviation over a long period of time. The purpose is to do what is done.

(4) Features of the Invention The feature of the present invention to achieve the above object is that there are many annular V-shaped oil grooves in the axial direction on the inner peripheral surface of the bearing portion of the large diameter and rigid rod of the mold clamping cylinder. The rod and the bearing are provided with a clearance sufficient to form an oil film, and the oil groove communicates with the chamber of the mold clamping cylinder via this clearance. Hereinafter, the present invention will be explained based on the drawings.

(5) One Embodiment of the Invention The drawings show an embodiment of the mold clamping device for an injection molding machine or the like according to the present invention. 3 and 4 are enlarged cross-sectional views of the same essential parts. The drawing shows a booster ram type implementation.

In the figure, 1 is the mold clamping cylinder, 2 is the mold clamping ram, 3 is the rod of the mold clamping ram 2, 4 is the piston of the mold clamping ram 2, 5 is the bearing part of the rod 3, 6 is the flange of the bearing part 5, 7 is the valve, 8 is the booster ram, 9,1
0 and 11 are chambers where oil acts, 12 is a movable platen, 13 is a mold that is attached to the movable platen 12, 14 is a fixed platen, 15 is a die that is attached to the fixed platen 14, and 16 is a tie bar. be. This horizontal structure direct pressure mold clamping device is known.

The bushing of the bearing portion 5 is made of carbon fiber or the like having high wear resistance, and a balancing groove 20 as an oil groove is provided on the inner circumferential surface of the bushing. A large number of balancing grooves 20 are provided in an annular shape surrounding the rod 3 on the inner circumferential surface of the bushing, and are formed in a V-shaped cross section with appropriate gaps. Further, the balancing groove 20 is not provided at one end in the axial direction of the bush, and a clearance 21 between the outer peripheral surface of the rod 3 and the inner peripheral surface of the bearing part 5 is provided at one end in the axial direction.
It communicates with the chamber 11 of the mold clamping cylinder 1 via. The clearance 21 is set to a minute gap size that allows a thin oil film to be formed. Although it depends on the machining accuracy, it is specifically set to about 15 microns or less, preferably about 5 microns or less. The other axial end of the bushing is sealed. The seal is
For example, a seal packing 22 and a tasto seal 23 are provided.

Similarly, another balancing groove 24 is provided on the outer circumferential surface of the piston 4 of the clamping ram 2. The balancing groove 24 is not provided at both ends of the piston 4 in the axial direction, and communicates with each chamber 10, 11 via a clearance 25. The clearance 25 is set to such an extent that a thin oil film can be formed.

Further, the piston 4 is provided with a ball bearing 26 as a rolling bearing on its inner peripheral surface.
Similarly, a ball bearing 27 is provided in the hole portion where the tie bar 16 and the movable platen 12 slide. Ball bearings 26, 27
can be used under no-load conditions, so one with high dimensional accuracy is selected.

To explain the operation based on the above configuration, the balancing groove 20 of the bearing portion 5 is filled with oil in an annular shape, and a thin oil film is formed in the clearance 21. Similarly, the balancing groove 24 of the piston 4 and the clearance 2 at both ends thereof
Since the annular oil and oil film are also formed on the rods 5 and 25, the thrust of the rod 3 in the axial direction is in a state close to no load. The rod 3 supports the movable platen 12 and the mold 13 in a cantilever manner due to its rigidity due to its large diameter.
2 and the mold 13 maintain parallelism without eccentricity due to the oil film. Due to this hydraulic balance, the tie bar 16 is not subjected to the load of the movable platen 12 and the mold 13.

Next, when the mold is clamped, when hydraulic pressure is applied to the chamber 9 of the booster ram 8 in the mold closing area, the rod 3 immediately moves forward since it is in a nearly unloaded state. As the rod 3 moves forward, the oil film in the clearance 21 acts as a boundary layer, and the balancing groove 20 is replenished with oil entrained therein. Similarly, in the balancing groove 24 and the clearance 25 of the piston 4, a thin oil film acts as a boundary layer. Movable platen 1
The second ball bearing 27 is guided by the tie bar 16 and moves without being subjected to its own weight. Rod 3
, the cantilever support distance increases as the lateral pressure increases, but the oil and oil film in the balancing grooves 20 and 24 self-align as the lateral pressure increases.
Since it is point supported, the horizontality of the rod 3 itself is still maintained accurately. The rigidity of Rod 3 is
This does not affect the parallelism between the movable platen 12 and the mold 13. Therefore, the rod 3 always maintains the parallelism of the platen from the low speed mold closing region to the high pressure mold closing region. Further, the ball bearing 27 positions the rod 3 in the radial direction. The mold 13 of the movable platen 12 is fitted with the mold 15 of the stationary platen 14 with their mating surfaces accurately aligned. During this time,
Oil is drawn into the chamber 10 from the valve 7.

When opening the mold, the valve 7 opens and hydraulic pressure is applied to the chamber 11. The balancing groove 20 of the bearing part 5 and the balancing groove 24 of the piston 4 are supplied with hydraulic pressure from the chamber 11 through the respective clearances 21 and 25, and a thin oil film is formed thereon. Therefore, the piston 4 and the rod 3 are in a nearly unloaded state, and since the ball bearing 26 is provided on the inner peripheral surface of the piston 4, the mold clamping ram 2 moves back in response to the hydraulic pressure. The mold is opened. As the oil film acts as a boundary layer during the retreat, the parallelism of the platen continues to be maintained even in the mold opening region.

(6) Another Embodiment of the Invention In the above embodiment, the outer circumferential surface of the piston 4 may have a sliding contact structure without providing the balancing groove 24 on the outer circumferential surface.

Further, in the above embodiment, a booster ram type was illustrated and explained, but it goes without saying that the invention is not limited to this. As long as it is a direct pressure type mold clamping device consisting of a mold clamping cylinder, a platen, and a tie bar, it can also be implemented as an auxiliary cylinder type, a pressure increase cylinder type, etc., for example.

Further, in the above embodiment, the ball bearing 2
7 is shown as an example, but it can also be implemented by configuring it as a sliding bearing. In this case, an oil groove 24 may be provided on the inner peripheral surface of the bearing hole of the sliding bearing.

(7) Effects of the invention According to the present invention, the following effects are achieved.

(a) An annular oil groove is provided in the bearing part of the rod, and the clearance of the bearing part is set to such an extent that an oil film can be formed, and the oil groove is communicated with the mold clamping cylinder chamber through this clearance. The oil film can be applied as the rod advances and retreats, and there is no need to provide a special pressure oil supply structure, which greatly simplifies the structure and reduces manufacturing costs.

(b) The rod is supported horizontally by the oil groove and the small clearance that allows this oil film to form, and the rigidity of the rod makes it possible to accurately maintain the horizontality of the movable platen and the mold. Ta. For lateral pressure according to the amount of advance and retreat of the rod,
The pressure around the oil grooves is equalized, creating pressure equilibrium, and self-alignment occurs when this pressure equilibrium works in the axial direction through multiple oil grooves, so the parallelism of the platen is always maintained evenly. I was able to set it up. As a result, it is possible to maintain parallelism of approximately 10 microns or less, which enables precision molding when applied to the gold diameter of precision parts.

(c) Since an oil film is acting on the rod and bearing,
The rod is in a nearly no-load state, allowing high-speed opening and closing without backlash, and allows for very fast feeding with very little pressure. In particular, in the conventional closed protection area, low-speed feeding was performed under a large load, but since slow-speed feeding can be performed with low pressure, there is an advantage in that foreign matter can be detected accurately.

(d) Since the platen is cantilever-supported by the rigidity of the rod, the tie bar can be made thinner and the mounting surface of the mold can be expanded.

(E) Since there is no metal contact between the rod and the bearing, there will be no wear even after long-term use.
It is possible to maintain the parallelism of the platen without deviation over a long period of time. Furthermore, even if the weight of the mold changes, it is self-centering, so fine adjustments are not necessary.

[Brief explanation of drawings]

The drawings show an embodiment of the mold clamping device for an injection molding machine or the like according to the present invention, and FIG. 1 is a schematic cutaway diagram of the same part showing the mold opening limit, and FIG. 2 is a schematic cutaway diagram of the same part showing the mold closing limit. , FIG. 3, and FIG. 4 are enlarged sectional views of the same essential parts. 1...Mold clamping cylinder, 2...Mold clamping ram, 3...
Rod, 5... Rod bearing part, 12... Movable platen, 14... Fixed side platen, 16... Tie bar, 20, 24... Oil groove, 21, 25... Clearance, 27, 28... Rolling bearing.

Claims (1)

[Claims] 1. An injection molding machine in which a movable platen is provided on the rod of a horizontally arranged mold clamping cylinder, and the movable platen opens and closes the mold to the fixed platen via tie bars. In the direct pressure type mold clamping device such as the above, the rod is made rigid with a large diameter, and a large number of annular V-shaped oil grooves are provided in the axial direction on the inner peripheral surface of the bearing part, and the rod and the bearing part are A direct pressure type mold clamping device for an injection molding machine or the like, characterized in that the oil groove is set to a clearance sufficient to form an oil film, and the oil groove is communicated with a chamber of the mold clamping cylinder through the clearance.