JPH0158058B2 - - 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, it is possible to minimize deflection by making the tie bar large in diameter, or by interposing a support plate between the lower surface of the movable platen and the bed. It has been carried out to support both sides.

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 standpoint. Even if we assume that the parallelism is positive, firstly,
The support plate is affected by the heat of the molding cycle, resulting in dimensional errors. Secondly, the support plate has the necessary clearance to move between it and the bed, but at the same time it wears out due to metal contact with the bed.
It must be adjusted according to the frequency of use while allowing for the above-mentioned clearance error. Third, the support plate needed to be finely adjusted each time the mold was replaced in response to the weight of the mold.

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, in injection molding,
Accuracy on the micron order is increasingly required.
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 at most 50
Since the limit is microns, it could not be applied to molds for precision parts requiring accuracy of 10 microns or less.

In view of the above circumstances, the applicant has filed a patent application filed in 1983-
149599 is provided. This is achieved by applying pressure oil to the annular oil groove provided in the bearing of the rod of the mold clamping cylinder, creating a self-aligning structure with respect to the amount of movement of the rod. The structure maintains the horizontality of the movable platen. According to this, the rod was self-centering by applying pressure oil to the oil groove and adjusting the forward and backward movement clearance, but the results of various experiments have revealed that it is not necessary to supply pressure oil. That is, if the oil groove and the chamber of the mold clamping cylinder are communicated through the clearance, the forward and backward movement of the rod can be controlled by the flow of oil in addition to the chamber pressure.

The present invention has been provided in view of the above circumstances, and is capable of increasing the accuracy of the parallelism of the platen in response to lateral pressure at two locations: the bearing portion of the rod and the outer peripheral surface of the piston. The purpose of this is to ensure parallelism without deviation over a long period of time.

[Means for Solving the Problems] In order to achieve the above object, the present invention is such that a movable platen is provided on the rod of a horizontally arranged mold clamping cylinder, and the movable platen is connected to a fixed platen via a tie bar. It is applied to a direct pressure mold clamping device such as an injection molding machine that is configured to open and close a mold.

The feature is that the rod has a large diameter to provide rigidity, and the inner peripheral surface of the bearing part is provided with a large number of annular V-shaped oil grooves in the axial direction. The oil groove communicates with the chamber of the mold clamping cylinder, and a large number of annular V-shaped oil grooves are provided in the axial direction on the outer peripheral surface of the piston in the mold clamping cylinder extending from the rod.

[Function] In each V-shaped oil groove, the oil pressure is balanced in the radial direction by acting on the average in the radial direction. On average, the clearance between the rod and the bearing is filled with a skin layer of oil film.

Further, a hydraulic balance and an oil film are 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 axially
In addition, the rigidity of the rod due to its large diameter supports the movable platen on a cantilever, and the lateral pressure on the bearing and the outer circumference of the piston due to the cantilever support is self-aligning, so the rod can be moved. The side platens maintain parallelism without eccentricity.

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

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 cylinder 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. It is. 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 bush of the bearing portion 5, and are formed in a V-shaped cross section with an appropriate gap. Further, the balancing groove 20 is not provided at one end in the axial direction of the bush, and is provided at one end in the axial direction via the clearance 21 between the outer circumferential surface of the rod 3 and the inner circumferential surface of the bearing part 5, and the balancing groove 20 is provided at one end in the axial direction of the bush. It communicates with room 11. The clearance 21 is set to a small enough gap to form a thin oil film.
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 includes, for example, a seal packing 22 and a dust seal 23.

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, ball bearings 27 are provided in the hole portions of the movable platen 12, which are sliding portions with the tie bars 16. ball bearing 2
6 and 27 can be used in a no-load state, and those with high dimensional accuracy are 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, and since the lateral 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. Due to this hydraulic equilibrium, the tie bar 1
6 is not subjected to the load of the movable platen 12 and the mold 13.

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 state close to no load, and the outer peripheral surface of the piston 4 is in a state close to no load. Therefore, Rod 3 moves forward immediately. 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. The ball bearing 27 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 moves forward, but the oil and oil film in the balancing grooves 20 and 24 self-align against the increase in lateral pressure, and at the same time are supported at two points. Because there is, Rod 3
Its levelness is still maintained accurately. The rigidity of the rod 3 is such that it 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 and the high-speed mold-closing region to the mold-closing protection region. Further, the ball bearing 27 positions the rod 3 in the radial direction. The mold 13 of the movable platen 12 is the same as that of the fixed platen 1.
The fitting surfaces of the molds 15 of No. 4 and the respective mating surfaces will fit together accurately. 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. Hydraulic pressure is supplied to the balancing groove 20 of the bearing portion 5 and the balancing groove 24 of the piston 4 via the chamber 11 or 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 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 and closes the mold. An opening is made. Of course, the parallelism of the platen continues to be maintained in the mold opening region.

In the above embodiment, the 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) Oil is replenished in the annular oil groove of the rod bearing part through a clearance communication structure to the cylinder chamber, and
Since the annular oil groove structure was added to the outer circumference of the piston, the rod was horizontally supported at two locations, and 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
The pressure around the separated oil grooves becomes equal, creating a pressure equilibrium, and this pressure equilibrium also works in the axial direction through the multiple oil film grooves, resulting in self-alignment, so the platen is always aligned. I was able to set the parallelism 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 with a large load, but since slow-speed feeding can be performed with a small pressure, there is an advantage that foreign object detection can be performed 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 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, and 4 are enlarged sectional views of the same essential parts. 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, 24...Oil groove, 21, 25...Clearance, 2
6,27...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 mold clamping device such as the above, the rod has a large diameter to give rigidity, 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 of the rod. The oil groove is communicated with the chamber of the mold clamping cylinder through the clearance with the bearing part, and a large number of annular V-shaped oil grooves are formed in the axial direction on the outer peripheral surface of the piston in the mold clamping cylinder extending from the rod. A direct pressure mold clamping device for an injection molding machine, etc., characterized in that it is provided with a mold clamping device.