JP7603364B2 - Ball screw mechanism, mold clamping device, and injection molding machine - Google Patents

Description

The present invention relates to a ball screw mechanism, a mold clamping device, and an injection molding machine that are installed in industrial machinery.

There are many types of industrial machines, including injection molding machines, presses, and machine tools, and these are equipped with ball screw mechanisms that convert the rotational force of a motor into linear driving force. For example, Patent Document 1 describes a mold clamping device installed in an injection molding machine or press. This mold clamping device is composed of a fixed platen, a movable platen, four sets of ball screw mechanisms that connect the fixed platen and the movable platen, and four servo motors installed in each ball screw mechanism. When the four servo motors are driven, the four sets of ball screw mechanisms are driven and the movable platen slides relative to the fixed platen. In other words, the mold opens and closes.

Japanese Patent Application Publication No. 5-269748

The ball screw mechanism includes a ball screw and a ball nut that is screwed into the ball screw, and is rotatably mounted on a member of an industrial machine. For example, as shown in the clamping device of Patent Document 1, the ball screw is connected to a fixed platen via a bearing mechanism. Although not explained in detail in Patent Document 1, a bearing holder is provided on the fixed platen side, and a male thread is formed on the ball screw and a lock nut is provided. The bearing mechanism is sandwiched between the bearing holder on the fixed platen side and the lock nut on the ball screw side. In this way, the ball screw is rotatably connected to the fixed platen. Meanwhile, a ball nut is fixed to the movable platen side, and the ball screw mechanism connects the fixed platen and the movable platen.

Industrial machines equipped with a ball screw mechanism often have a load cell installed in association with the ball screw mechanism. For example, in the case of the clamping device described in Patent Document 1, the load cell needs to be installed between the ball nut and the movable platen to detect the clamping force. However, it is necessary to insert the load cell as a separate component between the ball nut and the movable platen, which creates the problem of a large number of parts.

This disclosure provides a ball screw mechanism, mold clamping device, and injection molding machine that can detect load and has a small number of parts.

Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

The present disclosure provides a ball screw mechanism for industrial machinery as follows. The ball screw mechanism includes a ball screw, a ball nut, a bearing stopper provided on a part of the ball screw, a bearing mechanism for rotatably supporting the ball screw, and a bearing presser provided on a member of the industrial machinery. The bearing mechanism is sandwiched between the bearing presser and the bearing stopper. The present disclosure provides a load cell on the bearing presser as follows . The bearing presser is integrally formed with a mounting and fixing part that is fixed to the member of the industrial machinery by a bolt, a bearing contact part that contacts the bearing mechanism, and a connecting part that connects the mounting and fixing part and the bearing contact part. The connecting part is formed to be thinner than at least one of the mounting and fixing part and the bearing contact part, and a strain gauge is provided on this connecting part. In other words, the load cell is formed with the connecting part and the strain gauge.

It is possible to provide a ball screw mechanism, mold clamping device, and injection molding machine with a small number of parts.

1 is a front view showing an injection molding machine according to an embodiment of the present invention; FIG. 1 is a perspective view showing a mold clamping device according to an embodiment of the present invention. 2 is a front cross-sectional view showing a part of a ball screw mechanism and a mold clamping device according to the present embodiment. FIG. FIG. 1 is a front view showing a conventional mold clamping device. FIG. 11 is a front cross-sectional view showing a part of a ball screw mechanism and a mold clamping device according to a second embodiment of the present invention.

Specific embodiments will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. To clarify the explanation, the following description and drawings have been simplified as appropriate. In each drawing, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary. In addition, hatching has been omitted in some areas to avoid cluttering the drawings.

<Injection molding machine according to the present embodiment>
As shown in FIG. 1, an injection molding machine 1 according to this embodiment is made up of a mold clamping device 2 provided on a bed B, and an injection device 4.

<Injection unit>
The injection device 4 is composed of a heating cylinder 6, a screw 7 contained in the heating cylinder 6, and a screw drive device 8 that drives the screw 7. The heating cylinder 6 is provided with a hopper 10, and an injection nozzle 11 is provided at the tip. The injection material is charged from the hopper 10, and when the injection material is melted by rotating the screw 7, it is metered to the tip of the screw 7. When the screw 7 is driven in the axial direction, the injection material is injected.

<Clamping device>
The mold clamping device 2 according to this embodiment is a so-called two-platen mold clamping device. That is, as shown in Fig. 2, the mold clamping device 2 is equipped with first and second mold platens 13, 14, i.e., a fixed platen 13 and a movable platen 14. The fixed platen 13 is fixed on a bed B, and the movable platen 14 is placed on linear guides 15, 15 provided on the bed B. That is, the movable platen 14 is freely slidable in a direction approaching and moving away from the fixed platen 13. As shown in Fig. 1, a fixed side mold 16 is attached to the fixed platen 13, and a movable side mold 17 is attached to the movable platen 14.

As shown in FIG. 2, in the mold clamping device 2 according to this embodiment, the fixed platen 13 and the movable platen 14 are connected by four sets of ball screw mechanisms 18, 18, .... Each ball screw mechanism 18, 18, ... includes a ball screw 19, 19, ... and a ball nut 20, 20, ... with which the ball screw 19, 19, ... is screwed.

Although not shown in FIG. 2, the movable platen 14 has through holes, and the ball nuts 20, 20, ... are fixed to these through holes. In other words, the ball screws 19, 19, ... are connected to the movable platen 14 via the ball nuts 20, 20, .... In the case of a conventional clamping device, a load cell is provided between the ball nuts 20, 20, ... and the movable platen 14 to detect the clamping force. However, in the clamping device 2 according to this embodiment, there is no load cell between the movable platen 14 and the ball nuts 20, 20, ..., and they are directly fixed.

The ball screws 19, 19, ... pass through the fixed platen 13 and are supported rotatably relative to the fixed platen 13. As will be clear from the following explanation, the function of the load cell for detecting the clamping force is provided at the connection side between the ball screws 19, 19, ... and the fixed platen 13. The fixed platen 13 is provided with servo motors 22, 22, ... and connected to the ball screws 19, 19, .... Therefore, when the servo motors 22, 22, ... are driven, the ball screws 19, 19, ... rotate and the movable platen 14 slides. In other words, the molds 16, 17 (see FIG. 1) are opened and closed.

<Connection between ball screw and fixed platen>
The connection between the ball screws 19, 19, ... and the fixed platen 13 will be described. As shown in Fig. 3, a through hole 24 is formed in the fixed platen 13, and the ball screw 19 is inserted into this through hole 24. A step 25 having a reduced outer diameter is formed in the ball screw 19, and a bearing mechanism 26 is inserted into this step 25. A bearing stopper 28 for stopping the bearing mechanism 26 is provided on the step 25. In this embodiment, the bearing stopper 28 is made of a lock nut 28. The lock nut 28 is screwed into a male thread formed in a partial area of the step 25.

An annular bearing holder 29 is fixed to the fixed platen 13 by bolts 35, 35, .... The bearing mechanism 26 is sandwiched between the bearing holder 29 and the lock nut 28. In this way, the ball screw 19 is rotatably attached to the fixed platen 13 via the bearing mechanism 26. The servo motor 22 is composed of a stator 30 and a rotor 31, and the rotor 31 is fixed to the end of the ball screw 19.

<Load cell>
The bearing holder 29 according to this embodiment is equipped with a load cell. In other words, the bearing holder 29 itself serves as a load cell and is adapted to detect the thrust load acting on the ball screw 19. The bearing holder 29 is integrally formed of three parts. That is, the bearing holder 29 is formed of an attachment/fixing part 36 that is fixed to the fixed platen 13 by bolts 35, 35, ..., a bearing contact part 37 that contacts the bearing mechanism 26, and a connection part 38 that connects the attachment/fixing part 36 and the bearing contact part 37.

As shown in FIG. 3, the connection portion 38 is formed to be thinner than the mounting and fixing portion 36 and the bearing contact portion 37. Specifically, in FIG. 3, it has a recessed shape that is cut from both the left and right end faces. Therefore, when a thrust load acts between the ball screws 19, 19, ... and the fixed platen 13 and the bearing presser 29 elastically deforms, the amount of deformation is greatest at the connection portion 38. In this connection portion 38, multiple strain gauges 41, 41, ... are attached to both the left and right recesses. Therefore, the load can be detected with high accuracy. The thrust load acting between the ball screws 19, 19, ... and the fixed platen 13 is detected by these strain gauges 41, 41, ....

The clamping device 2 according to this embodiment is provided with four ball screw mechanisms 18, 18, ..., but the bearing presser 29 equipped with a load cell may be used in all of these ball screw mechanisms 18, 18, ..., or may be used only in some of the ball screw mechanisms 18, 18, .... When the bearing presser 29, 29, ... equipped with a load cell is used in all of the four ball screw mechanisms 18, 18, ..., the clamping force can be obtained by adding up the thrust loads detected by the four bearing presser 29, 29, .... On the other hand, when the bearing presser 29 equipped with a load cell is used in only one ball screw mechanism 18 out of the four ball screw mechanisms 18, 18, ..., for example, the clamping force can be obtained by multiplying the thrust load detected by the bearing presser 29 by four.

The bearing holder 29 in this embodiment is equipped with a load cell consisting of strain gauges 41, 41, ..., so there is no need to prepare a separate load cell, and the number of parts can be reduced. Therefore, assembly of the fixed platen 13 and the ball screws 19, 19, ... is easy, and there is no risk of assembly defects.

<Conventional mold clamping device>
4 shows a conventional mold clamping device 50. The mold clamping device 50 is composed of a fixed platen 51 on which a fixed-side mold 61 is provided, a movable platen 52 on which a movable-side mold 62 is provided, and four sets of ball screw mechanisms 54, 54, ... which connect the fixed platen 51 and the movable platen 52. The ball screw mechanisms 54, 54, ... include ball screws 56, 56, ... and ball nuts 57, 57. The ball screws 56, 56 are rotatably supported with respect to the fixed platen 51 by a bearing mechanism 64, a lock nut 65, and a bearing holder 67, and are rotated by servo motors 59, 59, ....

In the conventional mold clamping device 50, the ball nuts 57, 57, ... are not directly fixed to the movable platen 52. In other words, load cells 69, 69, ... are separately required, and the ball nuts 57, 57, ... are fixed to the movable platen 52 via these load cells 69, 69, .... The mold clamping force is detected by these load cells 69, 69, .... Since the load cells 69, 69, ... are separately required and the number of parts is large, there is a problem that assembly defects may occur.

Second Embodiment
5 shows a part of the mold clamping device 2 equipped with a bearing presser 29A according to the second embodiment. The bearing presser 29A according to the second embodiment is also composed of an attachment/fixing portion 36 attached and fixed to the fixed platen 13, a bearing contact portion 37 that contacts the bearing mechanism 26, and a connecting portion 38 that connects the attachment/fixing portion 36 and the bearing contact portion 37. However, the connecting portion 38 is formed in a shape that is cut only from the right end face in FIG. 5. The strain gauges 41, 41 are attached only to the left end face side. The bearing presser 29A according to this embodiment can also accurately detect the thrust load acting between the ball screw 19 and the fixed platen 13.

<Other Modifications>
This embodiment can be modified in various ways. The bearing holder 29, 29A (see Figs. 3 and 4) has been described as being formed with a thin connection portion 38 relative to the mounting and fixing portion 36 and the bearing contact portion 37, but it is not necessarily required to form it with a thin wall. A thinner wall will increase the accuracy of thrust load detection, but a thicker wall will increase the durability of the bearing holder 29, 29A. The number of strain gauges 41, 41, ... attached to the bearing holder 29, 29A can also be modified. For example, only one strain gauge 41 may be attached. In this embodiment, the lock nut 28 is used as the bearing stopper 28 (see Fig. 3), but this can also be modified. For example, if an enlarged diameter portion with a larger radius is provided on the ball screws 19, 19, ..., the bearing mechanism 26 can be stopped at this enlarged diameter portion.

The mold clamping device 2 (see FIG. 2) according to this embodiment can also be modified. Although the mold clamping device 2 has been described as having four sets of ball screw mechanisms 18, 18, ..., the number of ball screw mechanisms 18, 18, ... may be two, three, or even five or more.

The ball screw mechanism 18 equipped with the bearing presser 29 according to this embodiment can also be applied to a conventional mold clamping device that has three mold plates and opens and closes the mold by a toggle mechanism. The ball screw mechanism 18 equipped with the bearing presser 29 according to this embodiment can be applied to the ball screw mechanism that drives the crosshead of the toggle mechanism. Furthermore, the ball screw mechanism 18 according to this embodiment can also be applied to the screw drive device 8 of the injection device 4. The ball screw mechanism 18 according to this embodiment can be applied not only to injection molding machines, but also to other industrial machines, such as presses and machine tools.

The invention made by the inventor has been specifically described above based on the embodiments, but the present invention is not limited to the embodiments already described, and it goes without saying that various modifications are possible without departing from the gist of the invention. The multiple examples described above can also be implemented in appropriate combinations.

REFERENCE SIGNS LIST 1 injection molding machine 2 mold clamping device 4 injection device 6 heating cylinder 7 screw 8 screw drive device 10 hopper 11 injection nozzle 13 fixed platen 14 movable platen 15 linear guide 16 fixed mold 17 movable mold 18 ball screw mechanism 19 ball screw 20 ball nut 22 servo motor 24 through hole 25 step portion 26 bearing mechanism 28 lock nut 29 bearing presser 30 stator 31 rotor 35 bolt 36 mounting fixing portion 37 bearing contact portion 38 connection portion 41 strain gauge B bed

Claims (10)

A ball screw mechanism for industrial machinery, comprising:
A ball screw;
a ball nut screwed onto the ball screw;
a bearing stopper means provided on a part of the ball screw;
a bearing mechanism that rotatably supports the ball screw;
Bearing holder and
A load cell ,
the ball screw is inserted through a through hole formed in a member constituting the industrial machine via the bearing mechanism and is rotatably supported with respect to the member,
the bearing holder is fixed to the member, and the bearing mechanism is sandwiched between the bearing stopper and the bearing holder;
the bearing presser is integrally formed of an attachment/fixing part which is fixed to the member by a bolt, a bearing contact part which contacts the bearing mechanism, and a connection part which connects the attachment/fixing part and the bearing contact part, the connection part being formed to be thinner than at least one of the attachment/fixing part and the bearing contact part,
The load cell is composed of a strain gauge provided at the connection portion . 2. The ball screw mechanism according to claim 1 , wherein the bearing locking means is a lock nut provided on a male thread formed on a part of the ball screw. 3. The ball screw mechanism according to claim 1 , wherein the industrial machine is an injection molding machine. 4. The ball screw mechanism according to claim 3 , wherein the injection molding machine includes a mold clamping device, and the ball screw mechanism is provided in the mold clamping device. The first and second mold plates,
a plurality of ball screw mechanisms connecting the first and second mold plates;
The ball screw mechanism includes a ball screw and
a ball nut screwed onto the ball screw;
a bearing stopper means provided on a part of the ball screw;
a bearing mechanism that rotatably supports the ball screw;
Bearing holder and
A load cell ,
the ball screw is inserted into a through hole formed in the first platen via the bearing mechanism and is supported rotatably with respect to the member;
the bearing holder is fixed to the first platen, and the bearing mechanism is sandwiched between the bearing stopper means and the bearing holder;
the bearing presser is integrally formed of an attachment/fixing part that is fixed to the first platen by a bolt, a bearing contact part that contacts the bearing mechanism, and a connection part that connects the attachment/fixing part and the bearing contact part, the connection part being formed to be thinner than at least one of the attachment/fixing part and the bearing contact part,
The load cell is composed of a strain gauge provided at the connection portion . 6. The mold clamping device according to claim 5 , wherein the bearing locking means is a lock nut provided on a male thread formed on a part of the ball screw. 7. The mold clamping device according to claim 5 , wherein the number of the ball screw mechanisms connecting the first and second mold plates is four. a mold clamping device that clamps the mold;
an injection device for injecting the injection material;
The mold clamping device includes first and second mold plates,
a plurality of ball screw mechanisms connecting the first and second mold plates;
The ball screw mechanism includes a ball screw and
a ball nut screwed onto the ball screw;
a bearing stopper means provided on a part of the ball screw;
a bearing mechanism that rotatably supports the ball screw;
Bearing holder and
A load cell ,
the ball screw is inserted into a through hole formed in the first platen via the bearing mechanism and is supported rotatably with respect to the member;
the bearing holder is fixed to the first platen, and the bearing mechanism is sandwiched between the bearing stopper means and the bearing holder;
the bearing presser is integrally formed of an attachment/fixing part that is fixed to the first platen by a bolt, a bearing contact part that contacts the bearing mechanism, and a connection part that connects the attachment/fixing part and the bearing contact part, the connection part being formed to be thinner than at least one of the attachment/fixing part and the bearing contact part,
The load cell is composed of a strain gauge provided at the connection portion . 9. The injection molding machine according to claim 8 , wherein the bearing stopper means is a lock nut provided on a male thread formed on a part of the ball screw. 10. The injection molding machine according to claim 8 , wherein the number of the ball screw mechanisms connecting the first and second platens is four.

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