Mold clamping device and injection molding machine

Abstract

To provide a mold clamping device which suppresses a difference in mold clamping force between upper and lower sides of a mold platen within an allowable range.SOLUTION: A mold clamping device (2) includes a fixed platen (7), a movable platen (8), and a mold clamping housing (9), and the fixed platen (7) and the mold clamping housing (9) are connected by an upper tie bar (11) and a lower tie bar (12). A toggle mechanism (13) is provided between the mold clamping housing (9) and the movable platen (8). In the mold clamping housing (9), a rigidity of a lower connection region (52) to which the lower tie bar (12) is connected is made smaller than that of an upper connection region (51) to which the upper tie bar (11) is connected.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a mold clamping device having a toggle mechanism that is placed horizontally on a bed, and an injection molding machine. [Background technology]

[0002] An injection molding machine is composed of a clamping device that clamps a mold and an injection device that injects an injection material. In a so-called horizontal injection molding machine, the clamping device is placed horizontally on a bed, and the platen is driven horizontally to open and close the mold. That is, the clamping device includes a fixed platen fixed on the bed, a movable platen slidably provided on the bed, and a clamping housing similarly slidably provided on the bed. The fixed platen and the clamping housing are connected by a plurality of tie bars, and the movable platen is slidable between them. A toggle mechanism consisting of a plurality of links and a crosshead is provided between the clamping housing and the movable platen. Therefore, when the toggle mechanism is bent and extended by driving the crosshead, the movable platen moves back and forth horizontally relative to the clamping housing. That is, the mold is opened and closed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-030075 A

[0004] Patent Document 1 proposes a mold clamping device that can apply a uniform mold clamping force to a mold during mold clamping. The mold clamping device described in this document is equipped with four tie bars, and a hydraulically driven mold clamping cylinder is provided for each tie bar. The device is configured to selectively supply pressure oil of at least two or more different pressures to each mold clamping cylinder, thereby adjusting the tension generated for each tie bar and allowing the mold clamping force to act uniformly. Summary of the Invention [Problem to be solved by the invention]

[0005] A clamping device having a toggle mechanism is excellent in that it generates a large clamping force by utilizing the magnification ratio of the toggle mechanism and can open and close the mold at high speed, thereby increasing molding efficiency. However, due to its mechanism, a toggle-type clamping device cannot control the tension for each tie bar like the clamping device described in Patent Document 1. Since the toggle-type clamping device has a toggle mechanism symmetrically arranged with respect to the platen, the design is such that a uniform clamping force is generated during clamping. However, in many models, the clamping force tends to be slightly larger on the lower side of the platen than on the upper side. If the difference between the clamping forces on the upper and lower sides is larger than the allowable range, molding defects may occur during molding.

[0006] The present disclosure provides a mold clamping device that limits the difference in mold clamping force between the upper and lower sides of the mold platen within an acceptable range.

[0007] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0008] The present disclosure is directed to a horizontally-mounted mold clamping device that includes a fixed platen, a movable platen, and a mold clamping housing, and that is equipped with a toggle mechanism. The fixed platen and the mold clamping housing are connected by a plurality of tie bars. Of these plurality of tie bars, half of the tie bars arranged on the upper side are referred to as upper tie bars, and the remaining half arranged on the lower side are referred to as lower tie bars. The present disclosure makes the rigidity of the mold clamping housing different between the upper side and the lower side. Specifically, the mold clamping housing is configured such that the rigidity of a lower connection region, which is a region in the vicinity of a connection portion to which a lower tie bar is connected, is smaller than that of an upper connection region, which is a region in the vicinity of a connection portion to which an upper tie bar is connected. Effect of the Invention

[0009] The present disclosure can suppress the difference in clamping force between the upper and lower sides of the platen within an acceptable range. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a front view of an injection molding machine according to a first embodiment. [Diagram 2] FIG. 2 is a perspective view showing a clamping housing of the clamping device according to the first embodiment. [Figure 3A] 3 is a cross-sectional view of an upper connection area of ​​the mold clamping housing according to the first embodiment, taken along the line XX in FIG. 2. [Figure 3B] 3 is a cross-sectional view of a lower connection region of the mold clamping housing according to the first embodiment, taken along the YY cross section in FIG. 2. [Figure 4A] FIG. 11 is a cross-sectional view of a lower connection region of a clamping housing according to a first modified example of the first embodiment. [Figure 4B] FIG. 11 is a cross-sectional view of a lower connection region of a clamping housing according to a second modified example of the first embodiment. [Diagram 5] 11 is a graph showing the magnitude of the difference in tension between the upper tie bar and the lower tie bar when clamping is performed in the clamping device. [Figure 6] FIG. 6 is a front view showing a part of a mold clamping unit according to a second embodiment. [Figure 7] FIG. 11 is a front view showing a mold clamping unit according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Specific embodiments will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. In order to clarify the description, the following description and drawings are appropriately simplified. In each drawing, the same elements are given the same reference numerals, and duplicated descriptions are omitted as necessary. In addition, hatching is omitted in some parts to avoid cluttering the drawings.

[0012] [First embodiment] <Injection molding machine> 1, an injection molding machine 1 according to the first embodiment includes a mold clamping unit 2 provided on a bed B, an injection unit 3 provided on the side of the mold clamping unit 2 on the bed B, and a control device 4 that controls these. The injection molding machine 1 is a so-called horizontal type.

[0013] <Mold clamping device> The mold clamping device 2 includes a fixed platen 7 fixed to the bed B, a movable platen 8 slidably provided on the bed B, and a mold clamping housing 9 slidably provided on the bed B. The mold clamping housing 9 has a structure characteristic of the first embodiment, which will be described in detail later. The fixed platen 7 and the mold clamping housing 9 are connected by a plurality of tie bars 11, 12, ..., and the movable platen 8 is disposed between the fixed platen 7 and the mold clamping housing 9. In this specification, the upper tie bars 11, 11 are referred to as upper tie bars, and the lower tie bars 12, 12 are referred to as lower tie bars. In this embodiment, there are two each of the upper tie bars 11, 11 and the lower tie bars 12, 12, but there may be one each or three each.

[0014] A toggle mechanism 13, which will be described later, is provided between the clamping housing 9 and the movable platen 8. A fixed-side mold 15 and a movable-side mold 16 are provided on the fixed platen 7 and the movable platen 8, respectively. Therefore, when the toggle mechanism 13 is driven, the molds 15, 16 are opened and closed.

[0015] <Injection device> The injection device 3 includes a heating cylinder 19, a screw 20 provided in the heating cylinder 19, and a screw drive device 22. The heating cylinder 19 is supported by the screw drive device 22, and the screw 20 is driven in the rotational direction and the axial direction by the screw drive device 22. The heating cylinder 19 is provided with a hopper 23 and an injection nozzle 24. The heating cylinder 19 is also provided with heaters 25, 25, ...

[0016] <Toggle mechanism> The toggle mechanism 13 includes a crosshead 30 and a plurality of links. The plurality of links include an upper mold clamping housing side link 31 and a lower mold clamping housing side link 32 connected to the mold clamping housing 9. These are rotatably connected to connection parts formed on the upper and lower sides of the mold clamping housing 9, i.e., an upper mold clamping housing clevis 40 and a lower mold clamping housing clevis 41. Similarly, there are an upper movable platen side link 34 and a lower movable platen side link 35 rotatably connected to connection parts formed on the upper and lower sides of the movable platen 8, i.e., an upper movable platen clevis 42 and a lower movable platen clevis 43. The upper mold clamping housing side link 31 and the upper movable platen side link 34, and the lower mold clamping housing side link 32 and the lower movable platen side link 35 are rotatably connected to each other.

[0017] Cross links 37, 38 are rotatably connected to the crosshead 30, and these cross links 37, 38 are rotatably connected to the upper mold clamping housing side link 31 and the lower mold clamping housing side link 32. When the crosshead 30 is driven by the ball screw mechanism 45, the toggle mechanism 13 bends and extends, and the movable platen 8 slides to open and close the mold.

[0018] <Uneven clamping force on the platen> In the mold clamping device 2, the toggle mechanism 13 and the tie bars 11, 12 are arranged symmetrically with respect to the symmetry plane 46. That is, the toggle mechanism 13, the upper mold clamping housing side link 31 and the lower mold clamping housing side link 32, the upper movable platen side link 34 and the lower movable platen side link 35 are also arranged symmetrically with respect to the symmetry plane 46. The upper tie bars 11, 11 and the lower tie bars 12, 12 are also arranged symmetrically with respect to the symmetry plane 46. Therefore, when the crosshead 30 is driven to clamp the mold, the mold clamping force should be generated uniformly. However, the mold platens, that is, the fixed platen 7, the movable platen 8, and the mold clamping housing 9 are fixed to the bed B or slidably provided, so that the lower parts indicated by the reference numerals 47, 47, ... are slightly thick. Due to the thickness, the rigidity of the lower parts of the mold platens 7, 8, 9 is greater than the rigidity of the upper parts.

[0019] When the mold is clamped, the upper tie bars 11, 11 and the lower tie bars 12, 12 expand, and the mold platens 7, 8, 9 are slightly elastically deformed. This elastic deformation is slightly smaller at the lower parts of the mold platens 7, 8, 9 than at the upper parts due to the difference in rigidity. Since the lower parts of the mold platens 7, 8, 9 hardly undergo elastic deformation compared to the upper parts, the lower tie bars 12, 12 expand slightly more than the upper tie bars 11, 11. Since the mold clamping force is generated by the tension of the tie bars 11, 12, ..., in the mold clamping unit 2, the lower side connected to the lower tie bars 12, 12 tends to have a slightly larger mold clamping force than the upper side connected to the upper tie bars 11, 11. The mold clamping housing 9 of the mold clamping unit 2 according to the first embodiment described next has a structure that reduces the bias in the upper and lower mold clamping forces.

[0020] <Clamping housing> A clamping housing 9 of a clamping device 2 according to the first embodiment is shown in Fig. 2. The clamping housing 9 has a substantially square shape when viewed from the side, and tie bar insertion holes 48, 49, ... are provided near the four vertices of the square. Upper tie bars 11, 11 (see Fig. 1) are inserted into the upper tie bar insertion holes 48, 48, and lower tie bars 12, 12 (see Fig. 1) are inserted into the lower tie bar insertion holes 49, 49. The upper clamping housing clevises 40, 40 already described are formed on the upper side of the clamping housing 9, and lower clamping housing clevises 41, 41 are formed on the lower side.

[0021] In the mold clamping housing 9, the area near the tie bar insertion holes 48, 48 and the upper mold clamping housing clevis 40, 40 is referred to as the upper connection area 51 in this specification because the upper tie bars 11, 11 (see FIG. 1) are connected thereto. Similarly, the area near the tie bar insertion holes 49, 49 and the lower mold clamping housing clevis 41, 41 is referred to as the lower connection area 52 because the lower tie bars 12, 12 (see FIG. 1) are connected thereto. These upper connection area 51 and lower connection area 52 have a predetermined structure so as to withstand a large force acting during mold clamping while reducing the weight. Figure 3A shows the upper connection area 51 cut along the XX cross section in Figure 2, and Figure 3B shows the lower connection area 52 cut along the YY cross section in Figure 2.

[0022] First, as shown in FIG. 3A, the upper connection area 51 has a front plate 54 on the side where the upper clamping housing clevises 40, 40 are provided, that is, on the side facing the fixed platen 7 (see FIG. 1), and a rear plate 55 on the opposite side. Ribs 56, 56, ... are formed between the front plate 54 and the rear plate 55. This structure is lightweight and can withstand a large force acting during clamping. Similarly, as shown in FIG. 3B, the lower connection area 52 has a front plate 59 on the side where the lower clamping housing clevises 41, 41 are provided, and a rear plate 60 on the opposite side. Ribs 61, 61, ... are formed between the front plate 59 and the rear plate 60.

[0023] As shown in FIG. 3B with emphasis, in the first embodiment, the plate thickness t1 of the front plate 59 of the lower connection region 52 is thinner than the plate thickness T1 of the front plate 54 of the upper connection region 51 (see FIG. 3A). Since the plate thickness t1 of the front plate 59 is thinner, the rigidity of the lower connection region 52 is smaller than that of the upper connection region 51. Therefore, when the mold is clamped, the deformation due to elastic deformation of the lower connection region 52 is slightly larger than that of the upper connection region 51. This suppresses the extension of the lower tie bars 12, 12 (see FIG. 1). This reduces the bias of the mold clamping force in the platens 7, 8, 9 (see FIG. 1) described above.

[0024] <First Modification> The first embodiment can be modified. The lower connection region 52 (see FIG. 3B) according to the first embodiment is designed to have a smaller rigidity than the upper connection region 51 (see FIG. 3A) by making the plate thickness t1 of the front plate 59 thinner. By modifying this and adopting a different structure, the rigidity of the lower connection region 52 can be made smaller than that of the upper connection region 51. FIG. 4A shows the lower connection region 52' of a clamping housing 9' according to a first modified example of the first embodiment. In this first modified example, the front plate 59' has the same plate thickness T1 as the front plate 54 of the upper connection region 51 (see FIG. 3A). However, the plate thickness t2 of the ribs 61', 61', ... is thinner than the plate thickness T2 of the ribs 56, 56, ... of the upper connection region 51. As a result, the clamping housing 9' according to the first modified example of the first embodiment also has a lower rigidity in the lower connection region 52', reducing the bias in the clamping force on the platens 7, 8, and 9 (see FIG. 1) described above.

[0025] <Second Modification> FIG. 4B shows a lower connection region 52'' of a clamping housing 9'' according to a second modified example of the first embodiment. In this second modified example, the front plate 59'' and the ribs 61, 61, ... have the same plate thicknesses T1 and T2 as the front plate 54 and the ribs 56, 56, ... of the upper connection region 51 (see FIG. 3A), respectively. However, the plate thickness t3 of the rear plate 60'' is thinner than the plate thickness T3 of the rear plate 55 of the upper connection region 51. As a result, the rigidity of the lower connection region 52'' of the clamping housing 9'' according to the second modified example of the first embodiment is also reduced, and the bias in the clamping force on the platens 7, 8, 9 (see FIG. 1) described above is reduced.

[0026] <Verification of effects through numerical calculations> Numerical calculations were performed to verify the effects of the clamping housing 9 according to the first embodiment (see FIG. 3B), the clamping housing 9' according to the first modified example, and the clamping housing 9'' according to the second modified example. First, as a comparative example, the shape of the clamping housing 9 was input to a calculator so that the shape of the lower connection area 52 (see FIG. 3B) was the same as that of the upper connection area 51 (see FIG. 3A), that is, the plate thickness of the front plate 59 was the same as that of the front plate 54 of the upper connection area 51. Then, a simulation calculation was performed so that a clamping force of 30 MPa was generated in the injection molding machine 1. At this time, the tension difference obtained by subtracting the tension generated in the upper tie bar 11 from the tension generated in the lower tie bar 12 was about 40 kN, as shown in graph A in FIG. 5. In other words, it was found that a large tension difference occurs when there is no difference in the structure between the upper connection area 51 and the lower connection area 52.

[0027] Next, the shape of the mold clamping housing 9 according to the first embodiment was input into a calculator. That is, the shape of the mold clamping housing 9 has a structure in which the front plate 59 of the lower connection region 52 (see FIG. 3B) is thinner than the front plate 54 of the upper connection region 51 (see FIG. 3A). A simulation was performed so that a mold clamping force of 30 MPa was generated in the injection molding machine 1, and the tension difference obtained by subtracting the tension generated in the upper tie bar 11 from the tension generated in the lower tie bar 12 was calculated, and the tension difference was approximately 28 kN, as shown in graph B of FIG. 5. In other words, it was confirmed that the tension difference was reduced and the bias in the mold clamping force was reduced.

[0028] Similarly, the shapes of the mold clamping housing 9' according to the first modified example of the first embodiment and the mold clamping housing 9'' according to the second modified example were input into a computer and simulated. When the tension difference between the lower tie bar 12 and the upper tie bar 11 was calculated for the first modified example and the second modified example, the results were as shown in graphs C and D in FIG. 5. In other words, it was confirmed that the bias in the mold clamping force was reduced in both the mold clamping housing 9' according to the first modified example and the mold clamping housing 9'' according to the second modified example. The effect of reducing the bias in the mold clamping force was the highest in the first embodiment in which the plate thickness of the front plate 59 (see FIG. 3B) was thinned, followed by the first modified example in which the plate thickness of the ribs 61', 61', ... (see FIG. 4A) was thinned.

[0029] [Second embodiment] <Injection molding machine according to the second embodiment> In the injection molding machine according to the second embodiment, the injection unit 3 and the control unit 4 are configured in the same manner as the injection molding machine 1 according to the first embodiment shown in Fig. 1. Therefore, the description of these will be omitted. Fig. 6 shows a part of a mold clamping device 2A according to the second embodiment, but the parts not shown are the same as those in the first embodiment (see Fig. 1), so the description will be omitted. Also, for the parts shown, the same reference numbers are used for members that perform the same functions, and the description will be omitted.

[0030] In the clamping unit 2A according to the second embodiment, the clamping housing 9A is different from that of the first embodiment. Specifically, the upper connection area 51A and the lower connection area 52A have the same structure. Although not shown in FIG. 6, the front plate, the rear plate, and the rib have the same plate thickness. In the clamping unit 2A according to the second embodiment, the interval 70 between the upper clamping housing clevis 40 and the upper movable platen clevis 42 is not the same as the interval 71 between the lower clamping housing clevis 41 and the lower movable platen clevis 43. Specifically, the upper clamping housing clevis 40 and the upper movable platen clevis 42 are provided so that the upper interval 70 is slightly shorter than the lower interval 71.

[0031] In this way, it can be said that the structure is such that, when the toggle mechanism 13 is extended to clamp the mold, the clamping force on the upper side of the mold platens 8, 9A is slightly greater than that on the lower side. However, in reality, there is a bias in the clamping force on the mold platens 7, 8, 9 (see FIG. 1) as described above. Therefore, the mold clamping device 2A according to the second embodiment also has the effect of reducing this bias in the clamping force.

[0032] [Third embodiment] <Injection molding machine according to the third embodiment> In the injection molding machine according to the third embodiment, the injection unit 3 and the control unit 4 are configured similarly to the injection molding machine 1 according to the first embodiment shown in Fig. 1. Therefore, the description of these will be omitted. Fig. 7 shows a mold clamping unit 2B according to the third embodiment. The same reference numbers are used for members that perform the same functions as in the first embodiment, and the description will be omitted.

[0033] In the clamping device 2B according to the third embodiment, the clamping housing 9B is different from that of the first embodiment. Specifically, the upper connection area 51B and the lower connection area 52B have the same structure. Although not shown in FIG. 7, the front plate, the rear plate, and the rib have the same plate thickness. The upper tie bar 11 and the lower tie bar 12 are fixed to the fixed plate 7 by fixing members 75, 75. However, in the clamping device 2B according to the third embodiment, the fixing member 75 that fixes the upper tie bar 11 to the fixed plate 7 is different from the lower fixing member 75. Specifically, the upper fixing member 75 is provided on the fixed plate via a thin shim 76. As a result, the effective length 78 of the upper tie bar 11, that is, the distance between the fixed plate 7 and the clamping housing 9B, is slightly shorter than the effective length 79 of the lower tie bar 12.

[0034] In this way, it can be said that the structure is such that, when the toggle mechanism 13 is extended to clamp the mold, the clamping force on the upper side of the mold platens 7, 8, 9B is slightly greater than that on the lower side. However, in reality, there is a bias in the clamping force on the mold platens 7, 8, 9 (see FIG. 1) as described above. Therefore, the mold clamping device 2B according to the third embodiment also has the effect of reducing this bias in the clamping force.

[0035] Although the invention made by the present inventor has been specifically described above based on the embodiment, it goes without saying that the present invention is not limited to the embodiment already described, and various modifications are possible without departing from the gist of the invention. The above-described examples may be implemented in appropriate combination. [Explanation of symbols]

[0036] 1 Injection molding machine 2 Mold clamping device 3 Injection unit 4 Control unit 7 Fixed plate 8 Movable plate 9 Clamping housing 11 Upper tie bar 12 Lower tie bar 13 Toggle mechanism 15 Fixed side mold 16 Movable side mold 19 Heating cylinder 20 Screw 22 Screw drive device 23 Hopper 24 Injection nozzle 25 Heater 30 Crosshead 31 Upper clamping housing side link 32 Lower clamping housing side link 34 Upper movable platen side link 35 Lower movable platen side link 37 Crosslink 38 Crosslink 40 Upper clamping housing clevis 41 Lower clamping housing clevis 42 Upper movable platen clevis 43 Lower movable platen clevis 45 Ball screw mechanism 48 Tie bar insertion hole 49 Tie bar insertion hole 51 Upper connection area 52 Lower connection area 54 Front plate 55 Rear plate 56 Ribs 59 Front plate 60 Rear plate 61 Rib

Claims

1. A fixed plate fixed to the bed; A movable platen slidably provided on the bed; a mold clamping housing slidably provided on the bed; a plurality of tie bars connecting the fixed platen and the mold clamping housing; a toggle mechanism provided between the mold clamping housing and the movable platen, When half of the tie bars arranged on the upper side are referred to as upper tie bars and the remaining half arranged on the lower side are referred to as lower tie bars, The clamping housing is formed in a structure such that the rigidity of a lower connection region, which is a region near the connection portion to which the lower tie bar is connected, is smaller than that of an upper connection region, which is a region near the connection portion to which the upper tie bar is connected.

2. The clamping device according to claim 1, wherein the clamping housing has a structure integrally formed from a front plate arranged on the fixed platen side, a rear plate arranged on a side away from the fixed platen, and a plurality of ribs connecting the front plate and the rear plate in the vicinity of the connection portion to which the tie bar is connected.

3. The mold clamping device according to claim 2 , wherein a plate thickness of the front plate in the lower connection region is thinner than a plate thickness of the front plate in the upper connection region.

4. The mold clamping device according to claim 2 , wherein the thickness of the rib in the lower connection region is thinner than that of the rib in the upper connection region.

5. The mold clamping device according to claim 2 , wherein a plate thickness of the rear plate in the lower connection region is thinner than a plate thickness of the rear plate in the upper connection region.

6. A fixed plate fixed to the bed; A movable platen slidably provided on the bed; a mold clamping housing slidably provided on the bed; a plurality of tie bars connecting the fixed platen and the mold clamping housing; a toggle mechanism provided between the mold clamping housing and the movable platen, When half of the tie bars arranged on the upper side are referred to as upper tie bars and the remaining half arranged on the lower side are referred to as lower tie bars, The upper tie bar is adjusted so that an effective length between the fixed platen and the clamping housing is shorter than that of the lower tie bar.

7. A fixed plate fixed to the bed; A movable platen slidably provided on the bed; a mold clamping housing slidably provided on the bed; a plurality of tie bars connecting the fixed platen and the mold clamping housing; a toggle mechanism provided between the mold clamping housing and the movable platen, the toggle mechanism includes an upper mold clamping housing link, a lower mold clamping housing link, an upper movable platen link, a lower movable platen link, a crosshead, and two cross links; the upper mold clamping housing side link and the lower mold clamping housing side link are rotatably connected to the upper and lower sides of the mold clamping housing, respectively; the upper movable platen side link and the lower movable platen side link are rotatably connected to the upper and lower sides of the movable platen, respectively; the upper mold clamping housing side link and the upper movable platen side link, and the lower mold clamping housing side link and the lower movable platen side link are rotatably connected to each other, the upper mold clamping housing side link and the lower mold clamping housing side link are each connected to the crosshead via the cross link, a distance between a connection portion of the upper clamping housing side link in the clamping housing and a connection portion of the upper movable platen side link in the movable platen is shorter than a distance between a connection portion of the lower clamping housing side link in the clamping housing and a connection portion of the lower movable platen side link in the movable platen.

8. a mold clamping device that clamps the mold; an injection device for injecting the injection material; The mold clamping device includes a fixed platen fixed to a bed, A movable platen slidably provided on the bed; a mold clamping housing slidably provided on the bed; a plurality of tie bars connecting the fixed platen and the mold clamping housing; a toggle mechanism provided between the mold clamping housing and the movable platen, When half of the tie bars arranged on the upper side are referred to as upper tie bars and the remaining half arranged on the lower side are referred to as lower tie bars, an injection molding machine, wherein the mold clamping housing is structured so that a lower connection region, which is a region in the vicinity of the connection portion to which the lower tie bar is connected, has smaller rigidity than an upper connection region, which is a region in the vicinity of the connection portion to which the upper tie bar is connected.

9. 9. The injection molding machine according to claim 8, wherein the mold clamping housing has a structure integrally formed from a front plate arranged on the fixed platen side, a rear plate arranged on a side spaced away from the fixed platen, and a plurality of ribs connecting the front plate and the rear plate in the vicinity of a connection portion to which the tie bars are connected.

10. 10. The injection molding machine according to claim 9, wherein a plate thickness of the front plate in the lower connection region is thinner than a plate thickness of the front plate in the upper connection region.

11. 10. The injection molding machine according to claim 9, wherein the thickness of the ribs in the lower connection region is thinner than the thickness of the ribs in the upper connection region.

12. 10. The injection molding machine according to claim 9, wherein a plate thickness of the rear plate in the lower connection region is thinner than a plate thickness of the rear plate in the upper connection region.

13. a mold clamping device that clamps the mold; an injection device for injecting the injection material; The mold clamping device includes a fixed platen fixed to a bed, A movable platen slidably provided on the bed; a mold clamping housing slidably provided on the bed; a plurality of tie bars connecting the fixed platen and the mold clamping housing; a toggle mechanism provided between the mold clamping housing and the movable platen, When half of the tie bars arranged on the upper side are referred to as upper tie bars and the remaining half arranged on the lower side are referred to as lower tie bars, an injection molding machine, wherein the upper tie bar is adjusted so that an effective length, which is the length between the fixed platen and the mold clamping housing, is shorter than that of the lower tie bar.

14. a mold clamping device that clamps the mold; an injection device for injecting the injection material; The mold clamping device includes a fixed platen fixed to a bed, A movable platen slidably provided on the bed; a mold clamping housing slidably provided on the bed; a plurality of tie bars connecting the fixed platen and the mold clamping housing; a toggle mechanism provided between the mold clamping housing and the movable platen, the toggle mechanism includes an upper mold clamping housing link, a lower mold clamping housing link, an upper movable platen link, a lower movable platen link, a crosshead, and two cross links; the upper mold clamping housing side link and the lower mold clamping housing side link are rotatably connected to the upper and lower sides of the mold clamping housing, respectively; the upper movable platen side link and the lower movable platen side link are rotatably connected to the upper and lower sides of the movable platen, respectively; the upper mold clamping housing side link and the upper movable platen side link, and the lower mold clamping housing side link and the lower movable platen side link are rotatably connected to each other, the upper mold clamping housing side link and the lower mold clamping housing side link are each connected to the crosshead via the cross link, an injection molding machine in which a distance between a connection portion of the upper clamping housing side link in the clamping housing and a connection portion of the upper movable platen side link in the movable platen is shorter than a distance between a connection portion of the lower clamping housing side link in the clamping housing and a connection portion of the lower movable platen side link in the movable platen.

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