POWER TRANSMISSION DEVICE AND INDUSTRIAL MACHINE

Abstract

A power transmission device (100) comprising: a first pulley (104), a second pulley (106) with a diameter equal to or greater than a diameter (D) of the first pulley (104), a belt (108) wound around the first pulley (104) and the second pulley (106), and a detection unit (110A, 110B) designed to detect a displacement of the belt (108) in a direction which intersects a surface of the belt (108), wherein the detection unit (110A, 110B) is designed to detect the displacement of the belt (108) at a defined measuring point (112A, 112B), and wherein a distance from a boundary between a section where the belt (108) and the first pulley (104) are in contact with each other and a section where the belt (108) and the first pulley (104) are not in contact with each other to the measuring point (112A, 112B) is equal to or less than the diameter (D) of the first pulley (104), characterized in that the power transmission device (100) also has a procurement unit (120) which is configured to determine information regarding a fastening tension of the belt (108) based on the displacement and information associated with a torque of a drive source which is configured to rotate the first pulley (104) or the second pulley (106).

Description

Background of the invention; Field of the invention

[0001] The present invention relates to a power transmission device and to an industrial machine. Description of the state of the art

[0002] JP 3 416 843 B2 discloses an injection molding machine that includes a belt detection unit which detects the presence or absence of a transmission belt. According to JP 3 416 843 B2, it is possible to detect a break or similar issue with the transmission belt.

[0003] JP 2016 - 136 032 A, CN 1 09 211 455 A, SU 1 479 841 A1, JP 2004 - 137 040 A, AT 516 047 A4 and GB 2 497 100 A disclose power transmission devices from the prior art. Summary of the invention

[0004] However, the injection molding machine according to JP 3 416 843 B2 cannot detect belt irregularity that occurs before the belt breaks (tears), in particular a reduction in the belt's fastening tension.

[0005] It is therefore an object of the present invention to propose a power transmission device and an industrial machine with which a reduction in the fastening tension of a belt can be detected.

[0006] This problem is solved by the power transmission device with the features of claim 1 and the industrial machine with the features of claim 6. Preferred embodiments of the invention are evident from the dependent claims.

[0007] With the present invention it is possible to create a power transmission device and an industrial machine that can advantageously detect a reduction in the fastening tension of the belt.

[0008] The above and further tasks, features and advantages of the present invention will become even clearer from the following description in conjunction with the accompanying drawings, in which a preferred embodiment of the present invention is illustrated by way of example. Brief description of the drawings Fig. Figure 1 is a schematic representation of an industrial machine according to one embodiment, Fig. Figure 2 is a schematic representation of a power transmission device according to one embodiment, Fig. Figure 3 is a diagram showing the relationship between the torque of a drive source and the tension of a belt, and Fig. Figure 4 is a diagram showing the relationship between the torque of a drive source and the tension of a belt. Description of preferred embodiments

[0009] A power transmission device and an industrial machine according to the present invention are explained in more detail below by describing a preferred embodiment with reference to the accompanying drawings. [Version]

[0010] A power transmission device and an industrial machine according to one embodiment are described with reference to the Fig. 1 to 3 described. Fig. Figure 1 is a schematic diagram showing an industrial machine according to the present embodiment. An example is described here in which an industrial machine 10 is an injection molding machine. However, the invention is not limited to this.

[0011] The industrial machine 10 comprises a clamping device 12 and an injection device 14. The clamping device 12 and the injection device 14 are installed on a base (frame) 16. The industrial machine 10 also comprises a control unit (control device) 18, which controls the clamping device 12 and the injection device 14. The industrial machine 10 also has a display unit (display) 118.

[0012] The clamping device 12 has a rear support (tool mounting plate) 22, a movable support (tool mounting plate) 24 and a stationary support (tool mounting plate) 26. The movable support 24 can move back and forth along a tie rod 28, which is arranged between the rear support 22 and the stationary support 26.

[0013] A form 30 is provided between the movable support 24 and the stationary support 26. The form 30 has a movable form half 32 and a fixed form half 34. The movable form half 32 is attached to the movable support 24. The fixed form half 34 is attached to the stationary support 26.

[0014] A hinged rod (knee lever) 36 is arranged between the rear support 22 and the movable support 24. The hinged rod 36 is connected to a crosshead (connecting bolt) 40 via a cross connection 38.

[0015] The clamping device 12 also includes a mold opening / closing mechanism 42. The mold opening / closing mechanism 42 can move the movable carrier 24 forwards and backwards relative to the stationary carrier 26. The mold opening / closing mechanism 42 includes a power transmission device 100A. The power transmission device 100A comprises a drive source (mold opening / closing motor) 102A, a pulley (drive pulley, first pulley) 104A, a pulley (output pulley, second pulley) 106A, and a belt 108A. Reference numeral 100 is used to describe the power transmission devices when referring to them generally, and reference numerals 100A to 100D are used to describe individual power transmission devices.Reference numeral 102 is used to describe the drive sources in general, and reference numerals 102A to 102D are used to describe individual drive sources. Reference numerals 104 and 106 are used to describe the pulleys in general, while reference numerals 104A to 104D and 106A to 106D are used to describe individual pulleys. Reference numeral 108 is used to describe the belts in general, and reference numerals 108A to 108D are used to describe individual belts. Belt 108A is wound around pulley 104A and pulley 106A to transmit the torque from pulley 104A to pulley 106A. The drive of drive source 102A can be controlled by control unit 18.

[0016] The rotary motion of the drive source 102A is transmitted to a ball screw mechanism 46 connected to the cross link 40. The rotational force transmitted by the drive source 102A is converted by the ball screw mechanism 46 into a forward / reverse movement of the cross link 40. The forward / reverse movement of the cross link 40 is transmitted via the connecting rod 36 to the movable support 24. In this way, the movable support 24 can be moved forwards and backwards relative to the stationary support 26.

[0017] An information acquisition unit (ICU) 74A is connected to the drive source 102A. For example, a signal corresponding to the torque of the drive source 102A, in particular a signal indicating the magnitude of an electric current supplied to the drive source 102A, is input into the ICU 74A. The ICU 74A provides information indicating the torque of the drive source 102A to the control unit 18. The power transmission device 100A also includes detection units (detectors, sensors) 110A and 110B (see Figure 1). Fig. 2), which will be described later. Reference numeral 110 is used to describe the detection units in general, and reference numerals 110A and 110B are used to describe individual detection units. The detection units 110, provided in the power transmission device 100A, supply a signal corresponding to the displacement of the belt 108A in the direction that intersects the surface of the belt 108A to an information acquisition unit 75A described below. Reference numeral 75 is used to describe information acquisition units in general, while reference numerals 75A to 75D are used to describe individual information acquisition units.

[0018] The information acquisition unit 75A is connected to the detection unit 110 provided in the power transmission device 100A. The information acquisition unit 75A includes an interface board into which the signal supplied by the detection unit 110 is input. Based on the signal supplied to the power transmission device 100A by the detection unit 110, the information acquisition unit 75A determines, for example, whether the displacement of the belt 108A is equal to or greater than a displacement threshold (displacement path threshold value) or not (i.e., whether the displacement ≥ the displacement threshold value). The displacement threshold value is a threshold for determining whether the displacement of the belt 108A occurs or not. The information acquisition unit 75A delivers the information thus obtained, i.e., the information about the displacement of the belt 108A, to the control unit 18.The clamping device 12 includes an ejector mechanism 48. The ejector mechanism 48 serves to remove a molded product from the movable mold half 32. The ejector mechanism 48 has a power transmission device 100B. The power transmission device 100B comprises a drive source (ejector motor) 102B, a pulley 104B, a pulley 106B, and a belt 108B. The belt 108B is wound around the pulley 104B and the pulley 106B to transmit the rotational force from the pulley 104B to the pulley 106B. The drive of the drive source 102B can be controlled by the control unit 18.

[0019] The rotary motion of the drive source 102B is transmitted to a ball screw mechanism 54, which is connected to an ejector pin 52. The ball screw mechanism 54 converts the rotational force transmitted by the drive source 102B into the forward / reverse movement of the ejector pin 52. Thus, the ejector pin 52 can be moved backward and forward relative to the movable carrier 24. When the ejector pin 52 moves toward the movable carrier 24, the formed product is pushed out of the movable mold half 32 and removed.

[0020] An information acquisition unit 74B is connected to the drive source 102B. For example, a signal corresponding to the torque of the drive source 102B, in particular a signal indicating the magnitude of an electric current supplied to the drive source 102B, is input into the information acquisition unit 74B. The information acquisition unit 74B provides information indicating the torque of the drive source 102B to the control unit 18.

[0021] The power transmission device 100B also includes a detection unit 110. The detection unit 110 in the power transmission device 100B provides a signal to the information acquisition unit 75B, which is associated with the displacement of the belt 108B in the direction which intersects the surface of the belt 108B.

[0022] The information acquisition unit 75B is connected to the detection unit 110 contained in the power transmission device 100B. The information acquisition unit 75B includes an interface board into which the signal supplied by the detection unit 110 is input. Based on the signal supplied by the detection unit 110 to the power transmission device 100B, the information acquisition unit 75B determines, for example, whether the displacement of the belt 108B is equal to or greater than a displacement threshold value (i.e., whether the displacement ≥ the displacement threshold value). The information acquisition unit 75B then supplies the acquired signal, i.e., the information about the displacement of the belt 108B, to the control unit 18.

[0023] The injection device 14 comprises a nozzle 56, a cylinder 58, a screw (feed screw) 60, a hopper 62, and a heater 64. The nozzle 56 is located at the front end of the cylinder 58. The cylinder 58 is a hollow element. The feed screw 60 is inserted into the cylinder 58. The cylinder 58 and the feed screw 60 extend in the opening / closing direction of the mold 30. The hopper 62 is connected to the cylinder 58. The hopper 62 is designed to introduce resin or plastic material into the cylinder 58. If the plastic material loaded via the hopper 62 is in the form of pellets, the heater 64 melts the plastic material.

[0024] The injection device 14 comprises a plastic conveying mechanism 66 and an injection mechanism 68. The plastic conveying mechanism 66 transports (feeds) the plastic material in the cylinder 58 to the nozzle 56 of the cylinder 58. The injection mechanism 68 injects the plastic material into the mold 30. The plastic conveying mechanism 66 has a power transmission mechanism 100C. The power transmission mechanism 100C comprises a drive source (motor for rotary motion) 102C, a pulley 104C, a pulley 106C, and a belt 108C. The belt 108C is wound around the pulley 104C and the pulley 106C to transmit rotary force from the pulley 104C to the pulley 106C. The drive of the drive source 102C can be controlled by the control unit 18.

[0025] The rotary motion of the drive source 102C is transmitted to a sleeve 72, which is connected to the auger 60, causing the auger 60 to rotate about its axis. As the auger 60 rotates about its axis, the plastic material in the cylinder 68 is conveyed to the nozzle 56 of the cylinder 58.

[0026] An information acquisition unit 74C is connected to the drive source 102C. The signal associated with the torque of the drive source 102C, in particular, for example, a signal indicating the magnitude of an electric current supplied to the drive source 102C, is input into the information acquisition unit 75C. The information acquisition unit 74C transmits the information indicating the torque of the drive source 102C to the control unit 18.

[0027] The power transmission unit 100C also includes a detection unit 110. The detection unit 110 contained in the power transmission unit 100C provides a signal, which is associated with the displacement of the belt 108C in the direction which intersects the surface of the belt 108C, to a subsequently named information acquisition unit 75C.

[0028] The information acquisition unit 75C is connected to the detection unit 110 in the power transmission device 100C. The information acquisition unit 75C includes an interface board into which the signal supplied by the detection unit 110 is input. Based on the signal supplied by the detection unit 110 to the power transmission device 100C, the information acquisition unit 75C determines, for example, whether the displacement of the belt 108C is equal to or greater than a defined displacement threshold (i.e., whether the displacement is ≥ the displacement threshold). The information acquisition unit 75C then transmits the information thus obtained, i.e., the information about the displacement of the belt 108C, to the control unit 18.

[0029] The injection mechanism 68 includes a power transmission device 100D. The power transmission device 100D comprises a drive source (motor for linear motion) 102D, a pulley 104D, a pulley 106D, and a belt 108D. The belt 108D is wound around the pulley 104D and the pulley 106D to transmit a rotational force from the pulley 104D to the pulley 106D. The drive of the drive source 102D can be controlled by the control unit 18.

[0030] The rotary motion of the drive source 102D is converted into the forward / reverse motion of the sleeve 72 by a ball screw mechanism 78 and transmitted to the auger 60. This causes the auger 60 to move in the axial direction. When the auger 60 moves towards the nozzle 56, the resin material in the cylinder 58 is injected into the mold 30 via the nozzle 56.

[0031] An information acquisition unit 74D is connected to the drive source 102D. For example, a signal corresponding to the torque of the drive source 102D, in particular a signal indicating the magnitude of an electric current supplied to the drive source 102D, is input into the information acquisition unit 74D. The information acquisition unit 74D transmits the information indicating the torque of the drive source 102D to the control unit 18.

[0032] The power transmission device 100D also includes a detection unit 110. The detection unit 110, which is contained in the power transmission device 100D, transmits a signal, which is associated with the displacement of the belt 108D in the direction which intersects the surface of the belt 108D, to a subsequently named information acquisition unit 75D.

[0033] The information acquisition unit 75D is connected to the detection unit 110 contained in the power transmission device 100D. The information acquisition unit 75D includes an interface board into which the signal supplied by the detection unit 110 is input. Based on the signal supplied by the detection unit 110 to the power transmission device 100D, the information acquisition unit 75D determines, for example, whether the displacement of the belt 108D is equal to or greater than a displacement threshold value (i.e., whether the displacement is ≥ the displacement threshold value). The information acquisition unit 75D then transmits the information thus obtained, i.e., the information about the displacement of the belt 108D, to the control unit 18.

[0034] Fig. Figure 2 is a schematic diagram showing the power transmission device according to the present embodiment.

[0035] As in Fig. As shown in Figure 2, the power transmission device has 100 pulleys 104 and 106. The diameter D of pulley 104 is smaller than that of pulley 106. The belt 108 is wound around pulley 104 and pulley 106. A toothed belt with many teeth is used as belt 108. The pulleys 104 and 106 have many teeth that mesh with the teeth of the belt 108. Although this description is of an example where belt 108 is a toothed belt, the present invention is not limited to this. Furthermore, the description is based on a configuration where only one belt 108 is wound around pulleys 104 and 106, but the present invention is not limited to this configuration.

[0036] When the pulley 104 is not rotated by the drive source 102, the tension in the straight sections of the belt 108 is the same. The tension of the belt 108 when the pulley 104 is not rotated by the drive source 102 is referred to as the mounting tension.

[0037] When a clockwise torque is applied to the pulley 104 by the drive source 102, the following situation occurs. A section of the belt 108 on the right side of a line connecting the center of pulley 104 to the center of pulley 106 sags, causing the tension in this section to decrease. Conversely, a section of the belt 108 on the left side of the line connecting the center of pulley 104 to the center of pulley 106 is tensioned, causing the tension in this section to increase.

[0038] When a counterclockwise torque is applied to the pulley 104 by the driving force 102, the following situation occurs. The section of the belt 108 located on the left side of the line connecting the center of pulley 104 to the center of pulley 106 sags, causing the tension in this section to decrease. Conversely, the section of the belt 108 located on the right side of the line connecting the center of pulley 104 to the center of pulley 106 is tensioned, causing the tension in this section to increase.

[0039] The side (section) of the belt 108 where the tension decreases as the pulley 104 is rotated by the drive source 102 is called a slack side. The side (section) of the belt 108 where the tension increases as the pulley 104 is rotated by the drive source 102 is called a tensioned side. Thus, when the pulley 104 is rotated by the drive source 102, the belt 108 has a slack side and a tensioned side. The tension of the belt 108 on the slack side is called the slack tension. The tension of the belt 108 on the tensioned side is called the tensioned-side tension. The tension required to rotate the pulley 104 is called the effective tension.If the effective stress is denoted as Te, the stress on the sagging side is denoted as Ts, and the stress on the taut side is denoted as Tt, the following relationship applies, which is expressed by the following equation (1). Te=Tt−Ts

[0040] When the torque of the drive source 102 is increased, the sag on the sagging side increases, and the tension on the tensioned side increases. Therefore, when the torque of the drive source 102 is increased, the tension on the sagging side decreases, while the tension on the tensioned side increases.

[0041] If the fastening tension of the belt 108 is appropriate, the following relationship applies, which is expressed by the following equation (2): T0>Tmax / 2 where T0 is the fastening tension and T max A voltage exists when the maximum torque Tr max occurs.

[0042] Even if the torque of the drive source 102 is limited to the maximum torque Tr under normal operating conditions max As the pressure increases, the tension on the sagging side will not become zero in such a case. However, the fastening tension of the belt 108 decreases due to wear when it is frequently used. If the fastening tension of the belt 108 decreases to a certain degree, or if the initial fastening tension is insufficient, the following relationship applies according to equation (3): T0 <Tmax / 2

[0043] In this case, even under normal operating conditions, the voltage on the sagging side will be zero before the torque of the drive source 102 reaches the maximum torque Tr. max increases.

[0044] When the tension on the sagging side reaches zero, the belt 108 is displaced in the direction that intersects its surface. Continuous use of the belt 108, during which it is displaced in the direction that intersects its surface, can shorten its service life or cause premature breakage (tearing). Therefore, if the belt 108's mounting tension decreases to some degree, it is preferable that the user or other person adjust the belt 108's mounting tension. To address this, the present embodiment uses detection units 110A and 110B to determine whether the belt 108's mounting tension has decreased to a certain extent.

[0045] Detection unit 110A is located on one side of the line connecting the center of pulley 104 with the center of pulley 106. Detection unit 110B is located on the other side of the line connecting the center of pulley 104 with the center of pulley 106. Detection units 110A and 110B detect the displacement of the belt 108 in the direction that intersects the surface of the belt 108. Detection unit 110A detects the displacement of a section of the belt 108 located on one side of the line connecting the center of pulley 104 with the center of pulley 106. Detection unit 110A can detect the displacement of the belt 108 when a counterclockwise torque is applied to the pulley 104 by the drive source 102.The detection unit 110B detects the displacement of a section of the belt 108 located on the opposite side of the line connecting the center of pulley 104 to the center of pulley 106. The detection unit 110B can detect the displacement of the belt 108 when a counterclockwise torque is applied to the pulley 104 from the drive source 102. Since, in this embodiment, the detection units 110 are located on both sides of the line connecting the center of pulley 104 to the center of pulley 106, a decrease in the belt tension of the belt 108 can be detected regardless of the direction in which the torque is applied to the pulley 104. The detection unit 110A detects the displacement of the belt 108 occurring at a defined measuring point 112A.The detection unit 110B detects the displacement of the belt 108 that occurs at a defined measurement point 112B. The reference numeral 112 is used to describe measurement points when they are referred to generally, and the reference numerals 112A and 112B are used to describe individual measurement points. For example, a detector capable of emitting a laser beam onto a measurement target and detecting the displacement of the target based on the light reflected from the target is used as the detection unit 110. However, the detector should not be limited to this. In the present example, a non-contact detector is used as the detection unit 110, but the detection unit 110 can also use a contact detector. The information obtained by the detection unit 110, i.e., the information about the displacement of the belt 108, is supplied to the information acquisition unit 75 in the manner described above.

[0046] As described above, the detection units 110A and 110B supply the information acquisition unit 75 with a signal corresponding to the displacement of the belt 108 in the direction that intersects its surface. Based on the signal supplied by the detection unit 110, the information acquisition unit 75 determines, for example, whether the displacement of the belt 108 is equal to or greater than a displacement threshold. The displacement threshold is a value upon which the determination of whether a displacement of the belt 108 has occurred is based, as described above. The information acquisition unit 75 then delivers the information thus obtained, i.e., the information about the displacement of the belt 108, to the control unit 18.A condition in which the displacement of the belt 108 is greater than the displacement threshold under normal operating conditions means that the fastening tension of the belt 108 has decreased to a certain extent, i.e., that the fastening tension of the belt 108 is insufficient.

[0047] The distance from the boundary between a section where the belt 108 and the pulley 104 are in contact and a section where the belt 108 and the pulley 104 are not in contact, to measuring point 112, is specified such that it is equal to or less than the diameter D of the pulley 104. The reason why the displacement of the belt 108 is detected at measuring point 112 as defined in this embodiment is that the displacement of the belt 108 due to sagging is likely to occur at such a measuring point. Since the displacement of the belt 108 is measured at measuring point 112 as defined in this embodiment, it is possible to reliably detect the displacement of the belt 108 by a decrease in the fastening tension of the belt 108.The reason why the displacement of the belt 108 due to a decrease in the fastening tension of the belt 108 is likely to occur in the area defined above is that the contact area between the belt 108 and the pulley 104 is smaller, i.e., that the number of teeth in the area where the teeth of the belt 108 mesh with the teeth of the pulley 104 is smaller.

[0048] The control unit 18 controls the entire industrial machine 10. The control unit 18 comprises a processing unit 114 and a storage unit 116. The processing unit 114 can be, for example, a CPU (central processing unit) or the like, but is not limited to this. The storage unit 116 comprises, for example, volatile memory (not shown) and non-volatile memory (not shown). Examples of volatile memory include RAM (random access memory) and the like. Examples of non-volatile memory include ROM (read-only memory) and flash memory. Programs, data, tables, etc., can be stored in the storage unit 116. Based on the information obtained from the detection unit 110, the control unit 18 provides the display unit 118 with information about the displacement of the belt 108 when the drive source 102 is rotated.Based on information supplied by the control unit 18, the display unit 118 can show information on a display screen (not shown) about the displacement of the belt 108 when the drive source 102 is rotated. The control unit 18 can also display information about the torque of the drive source 102 and the displacement of the belt 108 when the drive source 102 is rotated on the display screen of the display unit 118. Furthermore, the control unit 18 can display information on the display screen of the display unit 118 indicating whether or not an irregularity has occurred in the belt 108, in particular whether the belt tension has decreased by a specified value or more.

[0049] Based on the information displayed on the display unit 118, the user can determine whether the tension of the belt 108 has decreased. If the user determines that the tension of the belt 108 has decreased, it can be readjusted.

[0050] The processing unit 114 comprises a procurement unit (calculation unit, determination unit) 120. The procurement unit 120 can be implemented by the processing unit (processor) 114, which executes a program stored in the storage unit 116. The procurement unit 120 can obtain information about the belt tension 108 based on information related to the torque of the drive source 102, and information about the belt displacement 108.

[0051] The Fig. 3 and Fig. Figure 4 shows the relationships between the torque of the drive source and the tension of the belt. The horizontal axis represents the torque of the drive source 102. The vertical axis represents the tension of the belt 108. Fig. Figure 3 shows an example where T0 < T max / 2. Fig. 4 shows an example where T0 = T max / 2. As described above, T0 is the fastening tension, and T max is the voltage when the maximum torque Tr max is generated.

[0052] When the torque of the drive source 102 is zero, the tension of the belt 108 corresponds to the fastening tension T0 of the belt 108. The solid lines in the Fig. 3 and Fig. 4 indicate the tension generated on the sagging side of belt 108, i.e., the tension Ts on the sagging side. The dashed lines in the Fig. 3 and Fig. 4 indicate the tension generated on the tensioned side of the belt 108, i.e., the tension Tt on the tensioned side. The two-dot dashed lines in the Fig. 3 and Fig. The numbers 4 indicate the effective voltage Te.

[0053] As in the Fig. 3 and Fig. As shown in Figure 4, the tension on the sagging side gradually decreases, while the tension on the taut side gradually increases as the torque of the drive source 102 increases.

[0054] If the torque of the drive source 102 is further increased, as described in Fig. As shown in Figure 3, it begins in a case where T0 < T max / 2, the belt 108 a displacement in the direction which intersects the surface of the belt 108. Tr pointA torque is present when the belt 108 begins to register movement. If the torque of the drive source 102 is further increased, the displacement of the piston 108 in the direction that intersects the surface of the belt 108 reaches and exceeds the displacement limit. When the displacement of the belt 108 becomes equal to or greater than the displacement threshold, the information acquisition unit 75 detects the occurrence of the displacement of the belt 108 in the manner described above. If the torque of the drive source 102 is in a range between Tr point and Tr max As the torque of the drive source 102 increases, the displacement of the belt 108 in the direction that cuts the surface of the belt 108 increases.

[0055] The following relationships apply between torque, tension, and pulley pitch radius. Torque = Voltage × Pulley pitch radius

[0056] If the torque of the drive source 102 equals Tr point If the voltage Tt on the tensile side is equal to 2T0, as shown... Fig. 3 is evident. If one assumes that the pitch diameter of the pulley 104 is equal to D', then the following equation (4) applies. Trpoint=2T0⋅(D' / 2)

[0057] Equation (4) can be rewritten as the following equation (5). T0=Trpoint / D'

[0058] Therefore, the above relationship between the fastening stress T0 and the torque Tr applies. point , when belt 108 begins to shift.

[0059] In one case, when T0 = T max / 2, the voltage Ts on the sagging side becomes zero, as shown in Fig. Figure 4 shows that when the torque of the drive source 102 is the maximum torque Tr max achieved. In the case of T0 = T max / 2 Thus, the belt 108 begins to displace in the direction that intersects the surface of the belt 108 when the torque of the drive source 102 reaches the maximum torque Tr max reached.

[0060] Procurement unit 120 can obtain information about the belt tension of belt 108 based on the torque of the drive source 102 when a displacement equal to or greater than the displacement threshold value begins to occur in belt 108. Specifically, procurement unit 120 can, for example, obtain the belt tension of belt 108 based on the torque of the drive source 102 when the displacement of belt 108 becomes equal to or greater than the displacement threshold value.

[0061] For example, when determining the fastening tension of the belt 108, a table can be used which shows the relationship between the torque of the drive source 102 and the fastening tension of the belt 108 when a displacement equal to or greater than the displacement threshold value begins to occur on the belt 108. This table is stored, for example, in the memory unit 116.

[0062] Procurement unit 120 can procure the fastening tension of belt 108 by appropriate use of this table.

[0063] The case in which the belt tension of the belt 108 is obtained using a table has been described here as an example. However, the present invention is not limited to this. For example, the belt tension of the belt 108 can be calculated by the procurement unit 120 based on the torque of the drive source 102 when a displacement equal to or greater than the displacement threshold value in the belt 108 begins to occur, the diameter of the pulleys 104 and 106, the distance between the axis of rotation of the pulley 104 and the axis of rotation of the pulley 106, and the like.

[0064] Furthermore, the case described above, in which the belt tension of the 108 was obtained, was described as an example. However, the present invention is not limited to this. If a certain amount of torque is generated by the drive source 102, it may be sufficient to detect whether a displacement of the 108 is equal to or greater than a threshold value. As long as it is possible to detect that the belt tension of the 108 has dropped to a certain extent, it is possible to prompt the user to adjust the belt tension of the 108, even without actually obtaining the belt tension of the 108 itself.

[0065] As described above, in the present embodiment, the displacement of the belt 108 at the defined measuring point 112 is detected by the detection unit 110. The distance from the boundary between the section where the belt 108 and the pulley 104 are in contact and the section where the belt 108 and the pulley 104 are not in contact, to the measuring point 112, is equal to or less than the diameter D of the pulley 104. It is likely that the displacement of the belt 108 will occur at such a measuring point 112. In the present embodiment, it is therefore possible to provide a power transmission device 100 that can advantageously detect a decrease in the fastening tension of the belt 108. [Modified embodiment]

[0066] Although the preferred embodiment of the present invention has been described above, the present embodiment is not intended to be limited to the embodiment described above. Various modifications can be made without departing from the scope of the present invention.

[0067] For example, the embodiment described above was given by providing an example in which the industrial machine 10 is an injection molding machine. However, the invention is not limited to this. The present invention can be used in various other industrial machines 10 besides an injection molding machine, for example, machine tools, robots, mining machines, woodworking machines, agricultural machines, and construction machines.

[0068] The above embodiment was described by giving an example in which the power transmission device 100 is provided in the industrial machine 10. However, the present invention is not limited to this. The power transmission device 100 can be included in any device. For example, the power transmission device 100 can be provided in a vehicle or the like.

[0069] The above embodiment was described by giving an example in which pulley 104 is a drive pulley and pulley 102 is a driven pulley. Thus, the example was described by considering a case in which pulley 104, which has a relatively small diameter, is a drive pulley, while pulley 106, with a relatively large diameter, is a driven or output pulley. However, the present invention is not limited to this. Pulley 106, with its relatively large diameter, can be a drive pulley, while pulley 104, with its relatively small diameter, can be a driven pulley.

[0070] The above embodiment was described by giving an example in which the diameter of pulley 104 and the diameter of pulley 106 are different. However, the present invention is not limited to this. Pulleys 104 and 106 can have the same diameter. In this case, either pulley 104 or pulley 106 is a drive pulley.

[0071] Furthermore, the above embodiment was described by using an example in which the signal output from the detection unit 110 was input into the information acquisition unit 75, and in which the information indicating whether or not a displacement of the piston 108 has occurred is supplied by the information acquisition unit 75 to the control unit 18. However, the present invention is not limited to this. The signal output from the detection unit 110 can be supplied to the control unit 18. In this case, the control unit 18 comprises an information acquisition unit 75 that determines whether or not a displacement of the piston 108 has occurred that is equal to or greater than the displacement threshold.

[0072] The above embodiments can be summarized as follows: The power transmission device (100) comprises a first pulley (104), a second pulley (106) with a diameter equal to or greater than the diameter (D) of the first pulley, a belt (108) wound around the first and second pulleys, and a detection unit (110A, 110B) configured to detect a displacement of the belt in a direction intersecting the belt surface. The detection unit is configured to detect the displacement of the belt at a defined measuring point (112A, 112B). The distance from the boundary between the section where the belt and the first pulley are in contact and the section where the belt and the first pulley are not in contact, to the measuring point, is equal to or greater than the diameter (D) of the first pulley.The belt displacement will likely occur at the measurement position defined above. Therefore, this configuration advantageously reduces the reduction in belt tension.

[0073] The detection unit can be located on one side of the line connecting the center point of the first pulley to the center point of the second pulley.

[0074] The detection unit can be positioned on either side of the line connecting the center of the first pulley to the center of the second pulley. This configuration allows for the reliable detection of a drop in belt tension when a clockwise torque is applied to the first pulley, and also when a counterclockwise torque is applied.

[0075] The power transmission device may also include a display unit (118) configured to display information about the displacement based on the information obtained from the detection unit. This configuration enables the operator to make appropriate adjustments to the fastening tension and the like based on the information displayed on the display unit.

[0076] The power transmission device can also include a procurement unit (120) configured to obtain information about the belt tension based on the displacement and information corresponding to the torque of a drive source configured to rotate the first or second pulley. This configuration advantageously enables the procurement of belt tension information.

[0077] The procurement unit can be designed to determine the belt tension based on the displacement and information corresponding to the torque of the drive source. This configuration allows for advantageous belt tension determination.

[0078] An industrial machine (10) includes the above power transmission device.

Claims

[1] A power transmission device (100) comprising: a first pulley (104), a second pulley (106) with a diameter equal to or greater than a diameter (D) of the first pulley (104), a belt (108) wound around the first pulley (104) and the second pulley (106), and a detection unit (110A, 110B) designed to detect a displacement of the belt (108) in a direction which intersects a surface of the belt (108), wherein the detection unit (110A, 110B) is designed to detect the displacement of the belt (108) at a defined measuring point (112A, 112B), and wherein a distance from a boundary between a section where the belt (108) and the first pulley (104) are in contact with each other and a section where the belt (108) and the first pulley (104) are not in contact with each other, to the measuring point (112A, 112B) is equal to or less than the diameter (D) of the first pulley (104), characterized by , that the power transmission device (100) also has a procurement unit (120) which is configured to determine information regarding a fastening tension of the belt (108) based on the displacement and information associated with a torque of a drive source which is configured to rotate the first pulley (104) or the second pulley (106). [2] The power transmission device (100) according to claim 1, wherein the detection unit (110A, 110B) is arranged on one side of a line connecting a center point of the first pulley (104) with a center point of the second pulley (106). [3] The power transmission device (100) according to claim 1, wherein the detection unit (110A, 110B) is arranged on each of both sides of a line connecting a center point of the first pulley (104) with a center point of the second pulley (106). [4] The power transmission device (100) according to one of claims 1 to 3, furthermore comprising a display unit (118) which is designed to display information about the displacement on the basis of the information obtained by the detection unit (110A, 110B). [5] The power transmission device (100) according to one of claims 1 to 4, wherein the procurement unit (120) is configured to provide the fastening tension of the belt (108) on the basis of the displacement and the information associated with the torque of the drive source. [6] An industrial machine (10) with a power transmission device (100) according to any one of claims 1 to 5.

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