JPS6345295B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a mold clamping device for an injection molding machine or a die-casting machine, and specifically relates to a structure for ensuring parallelism of a platen in a direct pressure type mold clamping device. It is.

[Prior Art] Conventionally, in direct pressure type mold clamping devices such as injection molding machines, a mold clamping cylinder is arranged horizontally on a bed, and a movable side and a fixed side are connected through tie bars in the forward and backward direction of the mold clamping cylinder. 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 to allow 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, resulting in premature loss of the life of the mold. It became.

[Problems to be solved by the invention] In order to eliminate the above drawbacks, the tie bars should be made large in diameter to minimize deflection, or a support plate should be interposed between the lower surface of the movable platen and the bed. It has been carried out to support both sides by, for example,

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 addition, in the case of the latter, the rod of the mold clamping cylinder,
The three points of the fixed platen and the movable platen with the support plate must be parallel. 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 determined, the first
Secondly, the support plate is affected by the heat of the molding cycle, resulting in dimensional errors. Secondly, the support plate has the clearance necessary for movement between it and the bed, but at the same time it wears out due to metal contact with the bed, so the support plate has to be adjusted according to the frequency of use while allowing for the above-mentioned error in clearance. must be adjusted. Thirdly,
The support plate is designed to accommodate the weight of the mold when replacing the mold.
Fine adjustments were necessary each time.

In view of the above-mentioned circumstances, a device in which a rolling bearing is provided on the lower surface of the movable platen in place of the support plate has been provided. This has a predetermined clearance necessary for rolling between it and the bed. Although this clearance is smaller than the clearance of the support plate, it is unavoidable that dust and the like are mixed in, and rattling occurs due to wear caused by long-term use.
In any case, the parallelism of the platen is at most 50
The limit was microns, and it could not be guaranteed over a long period of time. Therefore, at present, the molds are matched based on this 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 requirement, 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.

Therefore, the present invention was provided in view of the above-mentioned circumstances, and it is possible to improve the accuracy of the parallelism of the platen in response to the lateral pressure between the rod bearing part and the outer peripheral surface of the piston, and to improve the accuracy of the parallelism of the platen over a long period of time. The purpose of this is to ensure parallelism without deviation.

[Features of the Invention] To achieve the above object, the present invention includes a movable platen supported by a rod of a mold clamping cylinder, and a movable platen guided through a tie bar to a fixed platen to open and close the mold. It is applied to direct pressure mold clamping devices such as injection molding machines. In this case, a large number of annular oil grooves on the inner circumferential surface of the bearing part of the rod are provided in the axial direction on which pressure oil acts, and an annular oil groove is provided on the outer circumferential surface of the piston in the mold clamping cylinder extending from the rod. It is characterized in that a large number of are provided in the axial direction.

[Operation of the Invention] Since the pressure oil is supplied from the hydraulic source to each oil groove, it acts on the average in the radial direction of each oil groove, thereby achieving hydraulic equilibrium in each radial direction. An oil film filled with pressure oil is formed in the clearance between the rod and the bearing.

Further, an oil film is formed in the annular oil groove on the outer peripheral surface of the piston in the mold clamping cylinder, which is the extended end of the rod. As a result, the rod is held at two locations in the axial direction, and the rigidity of the rod due to its large diameter supports the movable platen in a cantilever, reducing lateral pressure on the bearing and the outer circumference of the piston. is self-aligned, so the movable platen maintains parallelism without eccentricity.

[One embodiment of the invention] Hereinafter, the present invention will be explained based on the drawings.

The drawings show an embodiment of a mold clamping device for an injection molding machine or the like according to the present invention, in which FIG. 1 is a schematic cutaway of the same part showing the mold opening limit, and FIG. 2 is a schematic cutout of the same part showing the mold closing limit. 3 are enlarged 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 a pre-fill valve, 8 is a booster ram, 9, 10, 11 are cylinder chambers where oil acts,
12 is a movable platen, 13 is a movable platen 1
2 is a mold to be attached, 14 is a fixed platen,
15 is a mold attached to the stationary platen 14;
16 is a tie bar.

The bearing portion 5 is provided with a balancing groove 20 as an oil groove. A large number of balancing grooves 20 are provided in an annular shape surrounding the rod 3 on the inner circumferential surface of the bearing portion 5, and are formed in a V-shaped cross section with an appropriate gap.

A pressure port 21 that communicates with a hydraulic power source 22 is provided at the axial center of the bearing portion 5, and a port 23 that communicates with a drain tank 24 is provided at the axial tip side. is sealed with a dust seal 25. Also,
The piston 4 of the mold clamping ram 2 has a large number of annular V-shaped grooves 26 as oil grooves on its outer circumferential surface, and a ball bearing 27 as a rolling bearing on its inner circumferential surface. Similarly, the ball bearings 28 are provided in the hole portions of the movable platen 12, which are sliding portions with the tie bars 16.

Based on the above configuration, pressure oil is constantly supplied from the hydraulic source 22 to each balancing groove 20 through the pressure port 21, and the port 2 on the tip side
3 into the drain tank 24 and the chamber 11 on the proximal end side. Therefore, since the pressure oil acts on each balancing groove 20 in the radial direction on average, hydraulic pressure is balanced in the radial direction in each balancing groove 20. An oil film filled with pressure oil is formed in the clearance between the rod 3 and the bearing portion 5, so that the rod 3 slides in the axial direction almost under no load. The rod 3 supports the movable platen 12 and the mold 13 in a cantilever manner by its rigidity due to its large diameter.
Since the side pressure applied to the bearing portion 5 due to the cantilever support is self-aligned, the movable platen 12 and the mold 13 maintain parallelism without eccentricity.

Furthermore, an oil film is formed within the V-shaped grooves 26 of the piston 4 and between them and the inner circumferential surface of the cylinder. As a result, the tie bar 16 is
is not receiving any load from the movable platen 12 and the mold 13. Note that since the pressure oil on the bearing side is supplied independently from the mold clamping mechanism, the parallelism of the platen is ensured regardless of the mold opening/closing operation.

Next, when clamping the mold, when hydraulic pressure is applied to the chamber 9 of the booster ram 8 in the mold closing area, the rod 3 is in a nearly unloaded state, and the outer peripheral surface of the piston 4 is in a nearly unloaded state. Rod 3 moves forward immediately. The ball bearing 28 of the movable platen 12 is guided by the tie bar 16 and moves without being subjected to its own weight. The cantilever support distance of the rod 3 increases as it advances, but the balancing groove 2
..., 26... is self-centering, so the horizontality of the rod 3 itself is still maintained accurately. The rigidity of the rod 3 is determined by the movable platen 12 and the mold 13.
It does not affect the parallelism of Therefore,
The rod 3 always maintains the parallelism of the platen from the low-speed mold-closing area and the high-speed mold-closing area to the mold-closing protection area. Mold 13 of movable platen 12
In this case, the mold 15 of the movable platen 14 and the respective mating surfaces are accurately aligned and fitted. During this time, oil is sucked into the chamber 10 from the prefill valve 7.

Further, in the high-pressure mold clamping region, the prefill valve 7 is closed, and the pressure oil acts on the mold clamping ram 2 to generate a predetermined high-pressure mold clamping force. Along with high pressure mold clamping,
Hydraulic pressure also acts within the V-shaped grooves 26 of the piston 4. As a result, hydraulic equilibrium will work not only on the rod 3 side but also on the piston 4 side, and the parallelism of the platen will be maintained at two locations.

When opening the mold, the prefill valve 7 opens and hydraulic pressure is applied to the chamber 11. Since hydraulic pressure is also supplied from the chamber 11 to the V-shaped groove 26 of the piston 4, the piston 4 is maintained in hydraulic equilibrium. Therefore, the piston 4 and the rod 3 are in a nearly unloaded state, and since the bearing 27 is provided on the inner peripheral surface of the piston 4, the mold clamping ram 2 moves back in response to the hydraulic pressure and closes the mold. An opening is made. Of course, the parallelism of the platen continues to be maintained in the mold opening region.

[Other Embodiments of the Invention] 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.

[Effect of the invention] According to the present invention, the following effects are achieved.

(a) Since the rod bearing part and the piston outer periphery have an annular oil groove structure, the rod is horizontally supported at two places through the thin oil that occurs in the clearance at the piston sliding part in addition to the bearing part. The rigidity of the rod made it possible to accurately maintain the horizontality of the movable platen and the mold.

For lateral pressure according to the amount of advance and retreat of the rod, 2
Since self-alignment works in each of the multiple grooves, the parallelism of the platen can always be set uniformly. As a result, it is possible to maintain parallelism of approximately 10 microns or less, making precision molding possible when applied to molds for precision parts.

(b) Since an oil film acts on the rod's bearing and the tip piston, the rod is in a nearly no-load state, allowing high-speed opening and closing without backlash, as well as slow-speed feeding with very low 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.

(c) By supporting the rod at two points, the base and the tip, and using its rigidity to cantileverly support the platen, the tie bar can be made thinner and the mounting surface of the mold can be expanded.

[Brief explanation of the drawing]

The drawings show an embodiment of the mold clamping device for an injection molding machine or the like according to the present invention, in which FIG. 1 is a schematic cutaway of the same part showing the mold opening limit, and FIG. 2 is a schematic cutaway of the same part showing the mold closing limit. , FIG. 3 is an enlarged cross-sectional view of the same main part. DESCRIPTION OF SYMBOLS 1... Mold clamping cylinder, 2... Mold clamping ram, 3... Rod, 5... Rod bearing part, 12... Movable side platen, 14... Fixed side platen, 16... Tie bar, 2
0,26...Oil groove.

Claims (1)

[Claims] 1 A direct pressure type mold clamping device for an injection molding machine, etc., in which a movable platen is supported by a rod of a mold clamping cylinder, and the movable platen is guided via a tie bar to a fixed platen to open and close the mold. A large number of annular oil grooves in which pressure oil acts are provided in the axial direction on the inner circumferential surface of the bearing part of the rod, and an annular oil groove is provided on the outer circumferential surface of the piston in the mold clamping cylinder extending from the rod. A direct pressure type mold clamping device for an injection molding machine, etc., characterized in that a large number of devices are provided in multiple directions.