JP7069096B2 - Greasing method for mold clamping device of hydraulic injection molding machine - Google Patents

Description

The present invention relates to a greasing method for supplying grease to moving parts such as a ball screw mechanism and a toggle mechanism in a hydraulic injection molding machine.

As is well known in the past, a hydraulic injection molding machine is composed of an injection device that melts and injects a resin material, a mold clamping device that molds a mold, and the like, and these are driven by a hydraulic motor, a hydraulic cylinder, and the like. It has become. Hydraulic injection molding machines have a number of mechanically driven moving parts. For example, a toggle type clamping device is provided with a toggle mechanism, and the toggle mechanism is composed of a plurality of links, which are pivotally attached to each other by pins. The pivotal part is a movable part that moves when the toggle mechanism bends and stretches. In addition, some toggle-type mold clamping devices are designed to directly drive the crosshead of the toggle mechanism by a hydraulic cylinder, but the rotational force of the hydraulic motor is converted into axial driving force via the ball screw mechanism. Some are designed to drive a crosshead. Such a ball screw mechanism is also a movable part. Grease is supplied to these moving parts. Grease enters between metal members, that is, between solids and lubricates them, but the lubrication state changes depending on the amount of grease existing between the solids. When the amount of grease is relatively large, it is called liquid lubrication, when the amount of grease is small, it is called boundary lubrication, and when it is in an intermediate state between them, it is called mixed lubrication. Since friction between solids does not occur during liquid lubrication, wear does not occur substantially, which is ideal. However, in reality, the lubrication state in the moving part of the hydraulic injection molding machine is between the mixed lubrication and the boundary lubrication. If such a lubricated state is maintained, wear of the moving portion can be appropriately prevented, and the driving portion can be driven smoothly. However, when the hydraulic injection molding machine is operated for a long period of time, the amount of grease in the moving part decreases, and eventually the grease oil film is cut off and the dry lubrication state is reached. Then, the moving parts are easily worn. Therefore, it is necessary to lubricate the moving parts with grease before the dry lubrication state is reached, and to bring the lubrication state between the mixed lubrication and the boundary lubrication again. The hydraulic injection molding machine is provided with a grease pump and is connected to a predetermined distributor. A plurality of greasing pipes are branched from the distributor and are connected to each moving part. Therefore, when the grease pump is driven, grease is supplied to the moving parts at a plurality of locations all at once. In a conventional hydraulic injection molding machine, grease is lubricated to a moving part as follows, for example. After starting the operation of the shipped hydraulic injection molding machine, greasing is performed after 3000 molding cycles are completed. After that, greasing is performed every time the molding cycle reaches 6000 times. Alternatively, greasing is performed every predetermined operating time.

Japanese Unexamined Patent Publication No. 2011-148286

Patent Document 1 describes a greasing method in which a greasing timing is determined by another method, although it is not a hydraulic injection molding machine but an electric injection molding machine. In the injection molding machine described in Patent Document 1, the torque of the motor required to drive the moving portion is measured and multiplied by the rotation angle of the motor. That is, the amount of work is calculated. The amount of work in the moving part calculated in this way is accumulated when the electric injection molding machine is operated. The cumulative value of such work amount reaches a predetermined reference value, that is, the reference work amount, as the molding cycle is repeated. When the standard work amount is reached, the moving parts are lubricated and the cumulative work amount is reset to zero. The amount of work in the moving part is calculated and accumulated again. When the cumulative value reaches the standard work amount, lubricate the moving parts. The same applies hereinafter. In the greasing method described in Patent Document 1, when the grease is reduced and the lubrication state approaches the dry lubrication state, the work amount increases, so that the cumulative value inevitably reaches the reference work amount. Then, it is possible to lubricate before reaching the dry lubrication state. As a result, wear of the moving part can be appropriately suppressed. In addition, since the amount of grease should still be sufficient before the cumulative value of the work amount reaches the standard work amount, there is an effect that the grease is not wasted.

Grease can be appropriately lubricated by the greasing method in the conventional hydraulic injection molding machine or by the greasing method in the electric injection molding machine described in Patent Document 1. However, there are some issues that need to be resolved. First, in the conventional greasing method, when the amount of grease in the moving portion is large, the dry lubrication state may be reached before the predetermined number of molding cycles or the predetermined operating time is reached. In other words, there is a danger that lubrication will be delayed and wear of moving parts cannot be prevented. In order to avoid this danger, the frequency of greasing may be high, and the greasing may be performed while the number of molding cycles is small, that is, while the operating time is short. However, if this is done, grease will be wasted when the grease is slowly reduced. In this case, there is a problem that the molded product is contaminated by the excess grease, and there is a problem that the periphery of the movable portion is contaminated by the excess grease. Generally, the rate of grease reduction in moving parts is not constant and varies depending on room temperature, molding conditions, etc., but problems occur regardless of whether the grease reduction is fast or slow. In the greasing method described in Patent Document 1, the amount of work for driving the moving part is accumulated, and when the accumulated value reaches the standard work amount, the greasing is performed, so that the greasing method is similar to the conventional greasing method. Problems are unlikely to occur. In other words, if the rate of decrease in grease in the moving part is fast, the cumulative amount of work reaches the standard work amount early, so grease can be supplied early, and if the rate of decrease in grease is slow, the cumulative amount of work becomes the standard work amount. This is because the time to reach it is delayed, so the timing of lubrication can be delayed. However, there is a problem with the greasing method described in Patent Document 1. For example, in this method, it is necessary to determine the standard work amount in advance, but there is a problem in that no specific method has been proposed as to what value should be set. If the standard work amount is set to a large value, grease lubrication may be delayed even if the moving parts are in a dry lubrication state, and if the value is set to a small value, grease will be wasted. It is not clear how to set the standard work load. Even if the standard work amount can be determined to an appropriate value, there is a problem. Specifically, there is a problem when the rate of decrease of grease in the moving part suddenly increases. At this time, the moving part becomes a dry lubrication state at an early stage, but it is necessary to wait for lubrication until the cumulative value of the work amount reaches the standard work amount. Then, wear of the moving parts cannot be prevented.

An object of the present invention is to provide a grease-lubricating method in a hydraulic injection molding machine that solves the above-mentioned problems. Specifically, the present invention is to lubricate moving parts so that the lubrication state does not become a dry lubrication state. Hydraulic injection that can be lubricated or quickly lubricated when approaching dry lubrication, and does not over-grease and pollute the surrounding environment or stain the part. It is an object of the present invention to provide a lubrication method in a molding machine.

In order to achieve the above object, the present invention comprises the following configuration for a greasing method for simultaneously greasing grease from a grease pump to a plurality of moving parts via a distributor in a hydraulic injection molding machine. Perform the molding cycle multiple times in advance. Then, the drive required time, which is the time required for driving in each step of the molding cycle, is measured for at least one monitored device from each device such as an injection device and a mold clamping device. Then, the average standard drive time is obtained. After that, every time the molding cycle is carried out, the drive time required for each process of the monitored device is monitored. Then, when the required time for driving exceeds a predetermined threshold value and becomes larger, grease is supplied.

Thus, in the present invention, a greasing pipe is connected from one or a plurality of grease pumps to a plurality of movable parts in a mold clamping device of a hydraulic injection molding machine via a distributor to drive the grease pump. This is a method of greasing the mold clamping device of a hydraulic injection molding machine in which grease is simultaneously lubricated to the movable parts of the plurality of locations, and the movable parts of the mold clamping device are lubricated in advance . The molding cycle is carried out a plurality of times in the hydraulic injection molding machine, the drive required time, which is the time required for driving in each step of the molding cycle, is measured, and the standard drive required time, which is the average thereof, is obtained. Every time the molding cycle is carried out, the drive time required for each step of the mold clamping device is monitored, and when it is detected that the drive time required is larger than the standard drive time exceeding a predetermined threshold, grease is added. It is configured as a greasing method for a mold clamping device of a hydraulic injection molding machine.
According to the second aspect of the present invention, in the greasing method according to the first aspect, the threshold value is the variation of the required driving time when the required driving time is measured by performing the molding cycle a plurality of times in advance. It is configured as a greasing method for a mold clamping device of a hydraulic injection molding machine, which comprises obtaining a certain standard deviation and determining the standard deviation based on the standard deviation.

As described above, in the present invention, one or more grease pumps are connected to a greasing pipe via a distributor to a plurality of moving parts in a mold clamping device of a hydraulic injection molding machine to provide a grease pump. This method is intended for the mold clamping device of a hydraulic injection molding machine that is driven to lubricate moving parts at a plurality of locations all at once. Then, in the present invention, the movable part of the mold clamping device is lubricated in advance , the molding cycle is carried out a plurality of times in the hydraulic injection molding machine, and the driving time required for driving in each step of the molding cycle is measured. , The standard drive required time, which is the average thereof, is obtained, and thereafter, the drive required time of each process of the mold clamping device is monitored every time the molding cycle is performed, and the drive required time is predetermined from the standard drive required time. If it is detected that it exceeds the threshold and is large, grease is added. When the amount of grease in the moving part decreases, the frictional force increases. Since the driving force of the hydraulically driven device is substantially constant, the driving speed is reduced. Then, the drive time will inevitably increase. In the case of a mold clamping device, the time required for the mold clamping process and the mold opening process becomes large. According to the present invention, when the required driving time becomes larger than the standard driving required time by more than a predetermined threshold value, the greasing is performed. Therefore, the timing at which the greasing is required can be promptly detected and the greasing can be swiftly performed. When the required driving time is not long, the necessary lubrication is secured, but in such a case, grease is not wasted and there is no risk of contaminating the surrounding environment. According to another invention, the threshold value is configured to obtain a standard deviation, which is a variation in the required driving time, and to determine based on the standard deviation when the required driving time is measured by performing a plurality of molding cycles in advance. ing. The method of determining the threshold value is clear, and the manager of the hydraulic injection molding machine does not have to wonder what value the threshold value should be.

It is a front view which shows the hydraulic injection molding machine which concerns on embodiment of this invention. It is a graph which shows the change of the drive speed of the mold clamping device in the molding cycle about the hydraulic injection molding machine which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention will be described. As shown in FIG. 1, the hydraulic injection molding machine 1 according to the present embodiment is also configured in the same manner as the conventional hydraulic injection molding machine, and the mold clamping device 2 for molding the molds 5 and 6. It is roughly composed of an injection device 3 for injecting resin, and the like. As is well known, the mold clamping device 2 includes a fixing plate 8, a mold clamping housing 9, a plurality of tie bars 10, 10, ... That connect the fixing plate 8 and the mold clamping housing 9, and the fixing plate 8. It is composed of a movable platen 12 slidably provided between the mold clamping housings 9 and a toggle mechanism 13 provided between the mold clamping housing 9 and the movable platen 12. The toggle mechanism 13 is composed of a plurality of links and a crosshead 14, which are rotatably connected to each other by pins. The crosshead 14 is driven by a hydraulic cylinder 16. That is, a hydraulic cylinder 16 is provided in the mold clamping housing 9, and the rod 18 of the hydraulic cylinder 16 is connected to the crosshead 14. Therefore, when pressure oil is supplied from a hydraulic unit (not shown in the figure) to drive the hydraulic cylinder 16, the toggle mechanism 13 bends and stretches, and the mold clamping device 2 is opened and closed.

The mold clamping device 2 has a plurality of so-called movable parts that are mechanically driven, such as each pin of the toggle mechanism 13. Grease is supplied to these multiple moving parts. A grease pump 20 is provided in the hydraulic injection molding machine 1, and a greasing pipe 21 extends from the grease pump 20 and is connected to the distributor 23. The distributor 23 is branched into a plurality of branch pipes 25, 25, ..., And the branch pipes 25, 25, ... Are connected to the respective movable portions. Therefore, when the grease pump 20 is operated by the command from the controller 26, the grease from the grease cartridge (not shown in the figure) is supplied to the distributor 23, and the grease is supplied to the respective movable parts via the branch pipes 25, 25, .... It will be greased. Although only one distributor 23 is shown in FIG. 1, a plurality of distributors 23 are provided, and grease is supplied to each movable portion all at once. Although the description of the injection device 3 is omitted, the injection device 3 also has many movable parts, and these movable parts are also lubricated. If the hydraulic injection molding machine 1 is small, one grease pump 20 is sufficient, but if it is large, the number of moving parts increases and the amount of grease to be greased at one time becomes large. , For the mold clamping device 2, the injection device 3, etc., a plurality of grease pumps 20, 20, ... Are provided. When there are a plurality of grease pumps 20, 20, ..., Only one grease pump 20 may be driven if necessary. In this case, among all the movable parts existing in the hydraulic injection molding machine 1, the range in which the grease is supplied all at once is only the movable part connected to one grease pump 20 that is naturally driven.

The greasing method in the hydraulic injection molding machine 1 according to the present embodiment will be described. In implementing the greasing method according to the present embodiment, at least one monitored device, that is, a monitored device is selected. For example, the mold clamping device 2 is used as a monitoring target device. In the greasing method according to the present embodiment, roughly, the monitored device is monitored to determine whether or not greasing is necessary. Then, when it is determined that it is necessary, the grease pump 20 that supplies grease to the movable portion of the mold clamping device 2 is driven. How to monitor the monitored device will be described below.

In the hydraulic injection molding machine 1, the molding conditions are adjusted in order to mold a predetermined molded product. After the adjustment of the molding conditions is completed, the trial run of the molding cycle is performed a plurality of times, for example, several hundred times. In the trial run, the necessary lubrication is performed so that the lubrication state is sufficiently maintained. In the trial run, the time required to drive the monitored device, that is, the driving time is measured for each process of the molding cycle, that is, the mold clamping process, the injection process, the pressure holding process, the mold opening process, and the projecting process. Then, the required driving time for each process is averaged and used as the standard driving time for each process. When the mold clamping device 2 is a monitored device, the mold clamping device is generally driven only in the mold clamping step and the mold opening process, but when a molding method such as injection compression molding is carried out. Includes a compression step between the injection step and the pressure holding step. In this way, in the steps related to the driving of the mold clamping device, the standard driving time required for each is obtained. FIG. 2 shows a graph showing how the drive speed of the hydraulic cylinder 16 changes when the drive unit of the mold clamping device 2 which is the monitored device, for example, the hydraulic cylinder 16 is driven in each step of the molding cycle. It is shown. Reference numeral 31 is a graph of an average change in the drive speed of the hydraulic cylinder 16 in the mold clamping process, and reference numeral 32 is a graph of an average change in the drive speed of the hydraulic cylinder 16 in the mold opening process. The standard drive time required for the mold clamping device 2 in the mold clamping process is indicated by reference numeral 33, and the standard drive time required for the mold clamping device 2 in the mold opening process is indicated by reference numeral 34.

When each device of the hydraulic injection molding machine 1 is driven by hydraulic pressure, if the lubrication of the movable portion in each device becomes insufficient, the driving speed of each device decreases. If it decreases, the drive time will increase. For example, as shown in FIG. 2, the drive speed of the hydraulic cylinder 16 of the mold clamping device 2 decreases as shown in Graph 36 in the mold clamping process and Graph 37 in the mold opening process. As a result, the drive time required in the mold clamping process and the mold opening process becomes large as shown in reference numerals 39 and 40. Subsequently, the controller 26 monitors such an increase in the required driving time when the molding cycle is carried out, and determines whether or not lubrication is necessary. More specifically, when the molding cycle is carried out, the controller 26 monitors the drive time required in each step of the molding cycle with respect to the monitored device. Then, when it is detected that the required time for driving exceeds a predetermined threshold value, it is determined that the lubrication of the moving portion is insufficient. Grease pumps 20, 20, ... Are driven to lubricate. The threshold value used as the reference for determining greasing may be given in a fixed number of seconds, for example, 2 seconds, or may be given in a fixed ratio to the standard drive time, such as 0.3 times. .. In this way, it can be determined that lubrication is necessary when the time required for standard driving exceeds 2 seconds or exceeds 1.3 times the required time for standard driving. However, in this embodiment, the threshold value is determined from the standard deviation. Specifically, the standard deviation σ of the required driving time is obtained based on the required driving time for a plurality of times obtained by measuring for each of a plurality of molding cycles in the trial run. Then, a value 3 times the standard deviation σ of the drive required time, 3σ is adopted as a threshold value. The drive time obtained by performing multiple molding cycles in the test run should theoretically fall within the range of the standard drive time ± 3σ with a probability of 99.73%. In this way, it is a range that should be entered with most probability when the molding cycle is carried out in a normal state of lubrication, but in the present embodiment, when the lubrication exceeds such a range and deviates in the upper limit direction, lubrication is performed. That's why. Since the necessity of grease is determined in this way, it is possible to quickly lubricate the grease when it is needed, and it is possible to prevent the problem of excessive grease lubrication.

Various modifications can be made to the greasing method according to the present embodiment. For example, if the mold is slid or rotated, a slide device or a turntable device will be provided. When the turntable device is used as a monitoring target device, the drive time required for driving the turntable may be measured and monitored. Instead of monitoring the drive time required, the drive speed may be monitored. The drive speed of the hydraulic cylinder 16 of the mold clamping device 2 is measured using a predetermined sensor. Multiple molding cycles are performed by trial run to obtain a graph of average drive speed changes, i.e., standard drive speed changes, in each step, as shown by reference numerals 31 and 32 in FIG. Next, the threshold is determined. For example, in each step, the drive speed changes as shown in graphs 31 and 32, but only the speed at a specific timing is sampled. Then, in each step, the speeds sampled by the number of molding cycles of the trial run are obtained. The standard deviation σ is obtained from these velocities. Then, the value obtained by multiplying this standard deviation σ by 3 may be set as the threshold value. In the normal molding cycle after the test run, the drive speed is monitored in each step, and it is determined that lubrication is necessary when the threshold value is lower than the standard drive speed change shown in graphs 31 and 32. The controller 26 drives the grease pump 20 to lubricate.

1 Hydraulic injection molding machine 2 Mold clamping device 3 Injection device 5 Mold 6 Mold 8 Fixed plate 9 Mold clamping housing 10 Tie bar 12 Movable plate 13 Toggle mechanism 14 Crosshead 16 Hydraulic cylinder 18 Rod 20 Gris pump 21 Grease pipe 23 Distributor 25 Branch pipe 26 Controller

Claims (2)

A grease pipe is connected from one or more grease pumps to a plurality of movable parts in the mold clamping device of the hydraulic injection molding machine via a distributor, and the grease pumps are driven to drive the grease pumps at the plurality of locations. It is a method of lubricating the mold clamping device of a hydraulic injection molding machine that greases moving parts all at once.
The movable part of the mold clamping device is lubricated in advance , the molding cycle is carried out a plurality of times in the hydraulic injection molding machine, the driving time required for driving in each step of the molding cycle is measured, and the average thereof is measured. Obtain the standard drive time required,
After that, every time the molding cycle is performed, the drive time required for each step of the mold clamping device is monitored, and when it is detected that the drive time required is larger than the standard drive time exceeding a predetermined threshold value, grease is supplied. A method of supplying grease to a mold clamping device of a hydraulic injection molding machine, which is characterized by grease. In the greasing method according to claim 1, the threshold value obtains a standard deviation, which is a variation in the required driving time, when the required driving time is measured by performing the molding cycle a plurality of times in advance. A greasing method for a mold clamping device of a hydraulic injection molding machine, which is characterized by determining based on.

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