Injection molding machine

An injection molding machine includes a belt transmission mechanism (mold opening/closing mechanism, ejector mechanism, screw drive mechanism, injection mechanism) configured to transmit drive force from a driving shaft (driving pulley) to a driven shaft (driven pulley) by means of a belt. The injection molding machine includes: a cover covering part or entirety of the belt; and a sensor attached to the cover and configured to detect an abnormality of the belt.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-158907 filed on Aug. 30, 2019, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an injection molding machine having a belt transmission mechanism that transmits drive force from a driving shaft to a driven shaft by means of a belt.

Description of the Related Art

Japanese Laid-Open Patent Publication No. 2012-161995 discloses an injection molding machine having a belt transmission mechanism that transmits drive force (power) from a driving shaft to a driven shaft by means of a belt. The injection molding machine includes a driving pulley on the driving shaft side, a driven pulley on the driven shaft side, a belt for transmitting drive force from the driving pulley to the driven pulley, and a sound-proof cover covering the driving pulley, driven pulley, and belt.

SUMMARY OF THE INVENTION

In an injection molding machine having a belt transmission mechanism, damage to the belt, such as cracks etc., reduces belt tension and causes lag in operation of the injection molding machine. Further, the injection molding machine has to be stopped if the belt has broken. It is hence desirable to find abnormalities of the belt in the early stages in order to prevent operation lag and stoppage of the injection molding machine.

Accordingly, an object of the present invention is to provide an injection molding machine that can find belt abnormalities in the early stages.

According to an aspect of the present invention, there is provided an injection molding machine having a belt transmission mechanism configured to transmit drive force from a driving shaft to a driven shaft by use of a belt. The injection molding machine includes: a cover covering part or entirety of the belt; and a sensor attached to the cover and configured to detect an abnormality of the belt.

According to the present invention, it is possible to find belt abnormalities in the early stages, to utilize the cover as part of a detection device for detecting belt abnormalities, and to prevent increase in the size of the injection molding machine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The injection molding machine according to the present invention will be described in detail below in connection with preferred embodiments while referring to the accompanying drawings.

1. Configuration of Injection Molding Machine10

FIG.1is a schematic diagram illustrating the configuration of an injection molding machine10. The injection molding machine10includes a base12, and a clamping device14, and an injection device16provided on the base12.

[1.1. Configuration of Clamping Device14]

The clamping device14includes a stationary platen18, a rear platen20, and four tie bars22. The four tie bars22couple the stationary platen18and the rear platen20. The four tie bars22are arranged so that their axial directions are parallel to each other. A movable platen24is provided between the stationary platen18and the rear platen20. The movable platen24is provided on the base12with a sliding unit26interposed therebetween. The sliding unit26can move along guide rails28provided on the base12. The movable platen24can thus move forward and backward relative to the stationary platen18along the axial direction of the tie bars22.

A mold30is provided between the stationary platen18and the movable platen24. The mold30includes a fixed mold32and a movable mold34. The fixed mold32is attached to a side of the stationary platen18that faces the movable platen24, and the movable mold34is attached to a side of the movable platen24that faces the stationary platen18.

Toggle links36are provided between the rear platen20and the movable platen24. A total of four toggle links36are provided, two on each of upper and lower sides. Each toggle link36includes a first link rod38, a second link rod40, a first toggle pin42, a second toggle pin44, and a third toggle pin46. One end of the first link rod38is pivotably connected to the movable platen24through the first toggle pin42. One end of the second link rod40is pivotably connected to the rear platen20through the second toggle pin44. The other end of the first link rod38and the other end of the second link rod40are pivotably connected to each other through the third toggle pin46.

The second link rods40are connected to a crosshead50through cross links48. The crosshead50includes arms52(an upper arm52a, a lower arm52b) extending upward and downward, and the cross links48are connected to the ends of the respective arms52. The rear platen20has guide rods (not shown). The guide rods (not shown) are arranged so that their axial direction is parallel to the axial direction of the tie bars22. The crosshead50is guided by the guide rods (not shown) to move forward and backward in the direction parallel to the axial direction of the tie bars22.

The clamping device14includes a mold opening/closing mechanism55for opening and closing the mold30. The mold opening/closing mechanism55includes a servomotor56, a driving pulley58, a belt60, a driven pulley62, a ball screw64, and a ball screw nut66. The ball screw64is arranged so that its axial direction is parallel to the axial direction of the tie bars22.

The driving pulley58can rotate integrally with a rotary shaft132of the servomotor56(FIG.2etc.), and the driven pulley62can rotate integrally with the ball screw64. The belt60is wound around the driving pulley58and the driven pulley62, so as to transmit rotational power (rotational force) of the driving pulley58to the driven pulley62. The ball screw nut66is screw-engaged with the ball screw64and moves along the ball screw64as the ball screw64rotates. The ball screw nut66is fixed to the crosshead50.

As the servomotor56rotates, the rotational force is transmitted to the ball screw64through the driving pulley58, the belt60, and the driven pulley62, causing the ball screw64to rotate. As the ball screw64rotates, the crosshead50moves along the guide rods (not shown) together with the ball screw nut66. The movement of the crosshead50causes the movable platen24to move along the axial direction of the tie bars22, through the cross links48and the toggle links36. The ball screw64and the ball screw nut66constitute a reciprocating mechanism70for moving the crosshead50forward and backward.

As the movable platen24moves toward the stationary platen18, the movable mold34abuts on the fixed mold32to close the mold30. On the other hand, as the movable platen24moves toward the rear platen20, the movable mold34separates apart from the fixed mold32to open the mold30.

The clamping device14includes an ejector mechanism72for ejecting a molded article from the movable mold34. The ejector mechanism72includes a servomotor74, a driving pulley76, a belt78, a driven pulley80, a ball screw82, a ball screw nut84, an ejector plate86, ejector pins88, and a guide rod90. The ball screw82and the guide rod90are arranged so that their axial direction is parallel to the axial direction of the tie bars22.

The driving pulley76can rotate integrally with the rotary shaft of the servomotor74, and the driven pulley80can rotate integrally with the ball screw82. The belt78is wound around the driving pulley76and the driven pulley80, so as to transmit the rotational force of the driving pulley76to the driven pulley80. The ball screw nut84is screw-engaged with the ball screw82and moves along the ball screw82as the ball screw82rotates. The ball screw nut84is fixed to the ejector plate86having the ejector pins88.

As the servomotor74rotates, the rotational force is transmitted to the ball screw82through the driving pulley76, the belt78, and the driven pulley80, causing the ball screw82to rotate. As the ball screw82rotates, the ejector plate86and the ejector pins88move along the guide rod90together with the ball screw nut84. As the ejector pins88move toward the movable platen24, the molded article is pushed out and removed from the movable mold34.

[1.2. Configuration of Injection Device16]

The injection device16includes a nozzle92, a cylinder94, a screw96, a hopper98, and a heater100. The nozzle92, cylinder94, and screw96will be referred to as an injection unit97. The nozzle92is provided at an end of the cylinder94. The cylinder94is a hollow member through which the screw96passes. The cylinder94and the screw96extend in the direction in which the mold30opens and closes. The cylinder94is provided with the hopper98. The hopper98serves to load (supply) resin material into the cylinder94. If the resin material loaded from the hopper98is in the form of pellets, the resin pellets are melted by the heater100.

The injection device16is provided on the base12with an extruder base102interposed therebetween. The extruder base102moves the injection device16along the direction in which the mold30opens and closes. The injection device16includes a screw drive mechanism104for rotating the screw96and an injection mechanism105for injecting the resin material from the nozzle92.

The screw drive mechanism104includes a servomotor106, a driving pulley108, a belt110, and a driven pulley112.

The driving pulley108can rotate integrally with the rotary shaft of the servomotor106, and the driven pulley112can rotate integrally with the screw96. The belt110is wound around the driving pulley108and the driven pulley112so as to transmit the rotational force of the driving pulley108to the driven pulley112.

As the servomotor106rotates, the rotational force is transmitted to the screw96through the driving pulley108, the belt110, and the driven pulley112, causing the screw96to rotate. As the screw96rotates, the resin material is delivered toward the nozzle92.

The injection mechanism105includes a servomotor114, a driving pulley116, a belt118, a driven pulley120, a ball screw122, a ball screw nut124, and a pusher plate126. The ball screw122is arranged so that its axial direction is parallel to the axial direction of the screw96.

The driving pulley116can rotate integrally with the rotary shaft of the servomotor114, and the driven pulley120can rotate integrally with the ball screw122. The belt118is wound around the driving pulley116and the driven pulley120, so as to transmit the rotational force of the driving pulley116to the driven pulley120. The ball screw nut124is screw-engaged with the ball screw122and moves along the ball screw122as the ball screw122rotates. The ball screw nut124is fixed to the pusher plate126.

As the servomotor114rotates, the rotational force is transmitted to the ball screw122through the driving pulley116, the belt118, and the driven pulley120, causing the ball screw122to rotate. As the ball screw122rotates, the pusher plate126moves along the axial direction of the ball screw122together with the ball screw nut124. The movement of the pusher plate126causes the screw96to move in the cylinder94along the axial direction of the ball screw122. As the screw96moves toward the nozzle92, the resin material accumulated at the end of the screw96in the cylinder94is injected from the nozzle92.

2. Configuration of Belt Transmission Mechanisms

The mold opening/closing mechanism55, ejector mechanism72, screw drive mechanism104, and injection mechanism105shown inFIG.1are belt transmission mechanisms in which the belt60,78,110,118transmits drive force (motive power) from the driving shaft to the driven shaft. The belt transmission mechanisms will be further described referring toFIG.2. The mold opening/closing mechanism55will be described below as an example of the belt transmission mechanisms.

The servomotor56on the driving shaft side is fixed to a motor bracket130. The driving pulley58(driving shaft) is fixed at an end of the rotary shaft132of the servomotor56. On the other hand, the ball screw64on the driven shaft side is rotatably supported by a holding plate134. The driven pulley62(driven shaft) is fixed to an end of the ball screw64. Though not shown graphically, the motor bracket130is coupled to the holding plate134and the holding plate134is provided on the base12(FIG.1), for example.

The belt60hung over the driving pulley58and the driven pulley62is a synchronous power transmission belt. Belt teeth140formed on the belt60mesh with driving pulley teeth136formed on the driving pulley58and driven pulley teeth138formed on the driven pulley62.

As shown inFIGS.3to5, part or entirety of the belt60of the belt transmission mechanism is covered by a cover142so as to prevent an operator from touching the belt60or for the purpose of soundproofing. For example, as shown inFIG.3, the cover142may cover the driving pulley58(FIG.2) and part of the belt60wound on the driving pulley58. Alternatively, as shown inFIG.4, the cover142may cover the driven pulley62(FIG.2) and part of the belt60wound on the driven pulley62. Alternatively, as shown inFIG.5, the cover142may cover the driving pulley58, the driven pulley62, and the belt60. The cover142is fixed to one or both of the motor bracket130and the holding plate134, but may be fixed to another part. The cover142may be made of metal, or casting or resin.

3. Configuration for Detecting Abnormalities of Belt60

As shown inFIGS.6to8, a sensor148is attached on an inner wall surface144or an outer wall surface146of the cover142. The sensor148detects a change in condition that occurs due to an abnormality of the belt60, thus detecting the abnormality occurring before the belt60breaks. For example, the sensor148can be a displacement meter, a thermometer, a microphone, a vibration meter, a rotary encoder164(FIG.9), a camera, or the like. A description will be given below about an attachment position for the sensor148.

The displacement meter can be of non-contact type, such as a laser displacement meter, for example. The displacement meter can be attached to the cover142covering part of the belt60on the driving shaft side (FIG.6), the cover142covering part of the belt60on the driven shaft side (FIG.7), and the cover142covering the entirety of the belt60(FIG.8). The displacement meter can be attached to either of the inner wall surface144and the outer wall surface146of the cover142.

The thermometer can be of contact type, such as a thermocouple or a thermistor etc., or of non-contact type, such as a radiation thermometer, for example. The thermometer can be attached to the cover142covering part of the belt60on the driving shaft side (FIG.6), the cover142covering part of the belt60on the driven shaft side (FIG.7), and the cover142covering the entirety of the belt60(FIG.8). The thermometer can be attached to either of the inner wall surface144and the outer wall surface146of the cover142.

The microphone can be attached to the cover142covering part of the belt60on the driving shaft side (FIG.6), the cover142covering part of the belt60on the driven shaft side (FIG.7), and the cover142covering the entirety of the belt60(FIG.8). The microphone can be attached to either of the inner wall surface144and the outer wall surface146of the cover142.

The vibration meter can be mechanical, electromagnetic, piezoelectric, optical, or electromagnetic wave type. The vibration meter can be attached to all of the cover142covering part of the belt60on the driving shaft side (FIG.6), the cover142covering part of the belt60on the driven shaft side (FIG.7), and the cover142covering the entirety of the belt60(FIG.8). The vibration meter can be attached to either of the inner wall surface144and the outer wall surface146of the cover142.

The rotary encoder164can be attached to the inner wall surface144of the cover142covering part of the belt60on the driven shaft side (FIG.7), and the inner wall surface144of the cover142covering the entirety of the belt60(FIG.8). The rotary encoder164is disposed on the inner wall surface144of the cover142in a position on the axis line of the driven shaft, i.e., of the ball screw64. Further, as shown inFIG.9, the shaft166(rotary shaft) of the rotary encoder164is disposed on the axis line of the driven pulley62and connected to the ball screw64. The shaft166(rotary shaft) may be connected to the ball screw64through a shaft coupling, bolt, nut, spacer, etc.

The camera can be a webcam, for example. The camera can be attached to the inner wall surface144of the cover142covering part of the belt60on the driving shaft side (FIG.6), the inner wall surface144of the cover142covering part of the belt60on the driven shaft side (FIG.7), and the inner wall surface144of the cover142covering the entirety of the belt60(FIG.8). Note that the camera is disposed so as to capture an image of a part where the belt60and the driving pulley58mesh with each other or a part where the belt60and the driven pulley62mesh with each other.

As shown inFIGS.6to8, the sensor148outputs detected information to a notification device150by wired communication or by wireless communication. The notification device150may be a controller provided in the injection molding machine10or may be a personal computer or mobile device (a tablet terminal, smartphone, etc.).

The notification device150includes an input unit (not shown), an arithmetic unit152, a storage unit154, and a notification unit156. The input unit includes a device through which the operator inputs information, such as a touchscreen panel or keyboard, for example. The arithmetic unit152includes a processor such as a CPU, for example. The arithmetic unit152functions as an abnormality determining unit158by executing a program stored in the storage unit154. The storage unit154includes various types of memory. The storage unit154stores, as well as various programs, a given range concerning the values detected by the sensor148when the belt60is normal (hereinafter referred to as a normal range) for each type of sensor148. The notification unit156includes one or both of a display device and a speaker device.

[3.3. Operations of Notification Device150]

[3.3.1. Operations of Notification Device150with Displacement Meter Used]

Referring toFIGS.6to8, operations of the notification device150in cases where a displacement meter is used as the sensor148will be described. Abnormalities of the belt60, such as wear, elongation, cracks, etc., increase the vibration of the belt60. This increases the amount of displacement of the belt60. This also increases the amount of displacement of the cover142that receives the vibration of the belt60through the motor bracket130or the holding plate134. In the case of being attached to the inner wall surface144of the cover142, the displacement meter irradiates the belt60with a laser beam to thereby detect the amount of displacement of the belt60relative to the cover142. In the case of being attached to the outer wall surface146of the cover142, the displacement meter irradiates a reference portion160provided outside of the cover142with a laser beam to thereby detect the amount of displacement of the cover142relative to the reference portion160.

The storage unit154has stored therein, as the normal range, a range of the amount of displacement of the belt60in the absence of abnormality of the belt60, or a range of the amount of displacement of the cover142in the absence of abnormality of the belt60. The abnormality determining unit158compares the amount of displacement of the belt60detected by the displacement meter and the upper limit value of the amount of displacement of the belt60stored in the storage unit154. Alternatively, the abnormality determining unit158compares the amount of displacement of the cover142detected by the displacement meter and the upper limit value of the amount of displacement of the cover142stored in the storage unit154. If the amount of displacement detected by the displacement meter exceeds the upper limit value, then the abnormality determining unit158determines that an abnormality has occurred on the belt60, and outputs a notification command to the notification unit156. According to the notification command, the notification unit156notifies the operator of the occurrence of the abnormality of the belt60.

Referring toFIGS.6to8, operations of the notification device150in cases where a thermometer is used as the sensor148will be described. Abnormalities of the belt60, such as wear, elongation, cracks, etc., increase the vibration of the belt60. This increases vibrations of components coupled to the belt60and increases the amount of heat generated due to the vibrations. Accordingly, the temperature of the belt60, the temperature of the cover142, and the temperature of the atmosphere inside the cover142increase. A non-contact type thermometer attached to the inner wall surface144of the cover142detects the temperature of the belt60. A contact type thermometer attached to the inner wall surface144of the cover142detects the temperature of the inner wall surface144of the cover142or the temperature of the atmosphere inside the cover142. A contact type thermometer attached to the outer wall surface146of the cover142detects the temperature of the outer wall surface146of the cover142.

The storage unit154has stored therein, as the normal range, a range of the temperature of the belt60in the absence of abnormality of the belt60, or a range of the temperature of the cover142in the absence of abnormality of the belt60, or a range of the temperature of the atmosphere inside the cover142in the absence of abnormality of the belt60. The abnormality determining unit158compares the temperature of the belt60detected by the thermometer and the upper limit value of the temperature of the belt60stored in the storage unit154. Alternatively, the abnormality determining unit158compares the temperature of the cover142detected by the thermometer and the upper limit value of the temperature of the cover142stored in the storage unit154. Alternatively, the abnormality determining unit158compares the temperature of the atmosphere inside the cover142detected by the thermometer and the upper limit value of the temperature of the atmosphere inside the cover142stored in the storage unit154. If the temperature detected by the thermometer exceeds the upper limit value, then the abnormality determining unit158determines that an abnormality has occurred on the belt60and outputs a notification command to the notification unit156. According to the notification command, the notification unit156notifies the operator of the occurrence of the abnormality of the belt60.

[3.3.3. Operations of Notification Device150with Microphone Used]

Referring toFIGS.6to8, operations of the notification device150in cases where a microphone is used as the sensor148will be described. Abnormalities of the belt60, such as wear, elongation, cracks, etc., increase the vibration of the belt60. This increases the sound pressure level of the sound generated from the belt60, the driving pulley58, and the driven pulley62. The microphone detects the sound pressure level of the sound generated in the vicinity of the cover142.

The storage unit154has stored therein, as the normal range, a range of the sound pressure level of the sound generated in the vicinity of the cover142in the absence of abnormality of the belt60. The abnormality determining unit158converts the information concerning the sound in the vicinity of the cover142outputted from the microphone into the sound pressure level, and compares it with the upper limit value of the normal range stored in the storage unit154. If the converted sound pressure level exceeds the upper limit value, then the abnormality determining unit158determines that an abnormality has occurred on the belt60and outputs a notification command to the notification unit156. According to the notification command, the notification unit156notifies the operator of the occurrence of the abnormality of the belt60.

[3.3.4. Operations of Notification Device150with Vibration Meter Used]

Referring toFIGS.6to8, operations of the notification device150in cases where a vibration meter is used as the sensor148will be described. Abnormalities of the belt60, such as wear, elongation, cracks, etc., vary the vibration of the belt60. This varies vibration of the cover142that receives the vibration of the belt60through the motor bracket130or the holding plate134. The vibration meter detects the vibration of the cover142.

The storage unit154has previously stored therein, as the normal range, a range of the amount of vibration (e.g., frequency or amplitude) of the cover142in the absence of abnormality of the belt60. The abnormality determining unit158compares the amount of vibration detected by the vibration meter and the upper limit value of the normal range stored in the storage unit154. If the amount of vibration detected by the vibration meter exceeds the upper limit value, then the abnormality determining unit158determines that an abnormality has occurred on the belt60and outputs a notification command to the notification unit156. According to the notification command, the notification unit156notifies the operator of the occurrence of the abnormality of the belt60.

[3.3.5. Operations of Notification Device150with Rotary Encoder164Used]

Referring toFIGS.7to9, operations of the notification device150in cases where a rotary encoder164is used as the sensor148will be described. Occurrence of abnormalities on the belt60, such as wear, elongation, cracks, etc., reduces the tension of the belt60. As a result, temporal unmeshed state of the belt60occurs on the driving shaft side and the driven shaft side, and hence the drive force transmitted from the driving pulley58to the driven pulley62is momentarily interrupted. This enlarges the phase difference (speed difference) of the driven pulley62relative to the driving pulley58. The rotary encoder164detects the rotational positions of the ball screw64and the driven pulley62.

On the other hand, the servomotor56includes a detector that detects the rotational position of the rotary shaft132of the servomotor56. This detector is referred to as a motor-side encoder162. The motor-side encoder162detects the rotational positions of the rotary shaft132of the servomotor56and the driving pulley58.

The storage unit154has stored therein, as the normal range, a range of the phase difference (speed difference) of the driven shaft relative to the driving shaft in the absence of abnormality of the belt60. The abnormality determining unit158obtains the phase difference of the driven shaft with respect to the driving shaft, on the basis of the information outputted from the motor-side encoder162and the information outputted from the rotary encoder164as the sensor148, and compares it with the upper limit value of the normal range stored in the storage unit154. If the phase difference obtained exceeds the upper limit value, then the abnormality determining unit158determines that an abnormality has occurred on the belt60and outputs a notification command to the notification unit156. According to the notification command, the notification unit156notifies the operator of the occurrence of the abnormality on the belt60.

[3.3.6. Operations of Notification Device150with Camera Used]

Referring toFIGS.6to8, operations of the notification device150in cases where a camera is used as the sensor148will be described. Occurrence of abnormalities on the belt60, such as wear, elongation, cracks, etc., reduces the tension of the belt60. As a result, temporal unmeshed state of the belt60occurs on the driving pulley58or the driven pulley62. The camera captures an image of the unmeshed state of the belt60in the position where the driving pulley58and the belt60mesh with each other, or captures an image of the unmeshed state of the belt60in the position where the driven pulley62and the belt60mesh with each other.

The information outputted from the camera is displayed in real time on a display of the notification unit156.

4. Other Embodiments

The sections [2] and [3] above have described the mold opening/closing mechanism55as an example of the belt transmission mechanisms. However, the ejector mechanism72, the screw drive mechanism104, and the injection mechanism105shown inFIG.1are also belt transmission mechanisms. Accordingly, the ejector mechanism72, the screw drive mechanism104, and the injection mechanism105may be provided with the cover142shown inFIGS.3to8and the sensor148and the notification device150shown inFIGS.6to8.

The belt60may be a friction transmission belt in place of a synchronous power transmission belt.

5. Invention Obtained from Embodiments

The invention graspable from the embodiments described above will be recited below.

An aspect of the present invention provides an injection molding machine10including a belt transmission mechanism (mold opening/closing mechanism55, ejector mechanism72, screw drive mechanism104, injection mechanism105) configured to transmit drive force from a driving shaft (driving pulley58,76,108,116) to a driven shaft (driven pulley62,80,112,120) by use of a belt60,78,110,118. The injection molding machine10includes: a cover142covering part or entirety of the belt60,78,110,118; and a sensor148attached to the cover142and configured to detect an abnormality of the belt60,78,110,118.

According to the configuration above, the sensor148detects a change in condition caused by an abnormality of the belt60,78,110,118, so that abnormalities of the belt60,78,110,118can be found in the early stages. Further, according to the configuration above, the sensor148is attached to the cover142covering the belt60,78,110,118, so that the cover142can be utilized as part of the detection device for detecting abnormalities of the belt60,78,110,118. Moreover, according to the configuration above, it is possible to prevent increase in the size of the injection molding machine10.

In the aspect of the invention, the sensor148may be one of: a displacement meter configured to detect displacement of the cover142or displacement of the belt60,78,110,118; a thermometer configured to detect temperature; a microphone configured to detect a sound pressure level; and a vibration meter configured to detect vibration of the cover142.

In the aspect of the invention, the sensor148may be a rotary encoder164configured to detect a rotational position of the driven shaft (driven pulley62,80,112,120), and the rotary encoder164may have a rotary shaft (shaft166) aligned in the same straight line with an axis line of the driven shaft.

In the aspect of the invention, the sensor148may be a camera configured to capture an image of the belt60,78,110,118.

In the aspect of the invention, the injection molding machine10may further include a notification unit156configured to give notification of a result detected by the sensor148.

The configuration above enables the operator to recognize presence/absence of an abnormality of the belt60,78,110,118without directly monitoring the belt60,78,110,118.

In the aspect of the invention, the injection molding machine10may further include: an abnormality determining unit158configured to determine that an abnormality has occurred on the belt60,78,110,118if a value detected by the sensor148is out of a given range; and a notification unit156configured to give notification when the abnormality determining unit158detects an abnormality of the belt60,78,110,118.

The configuration above enables the operator to recognize the occurrence of an abnormality on the belt60,78,110,118.

In the aspect of the invention, the injection molding machine10may further include: a servomotor56,74,106,114configured to rotate the driving shaft (driving pulley58,76,108,116) and detect a rotational position of the driving shaft; an abnormality determining unit158configured to obtain a phase difference between the driving shaft and the driven shaft (driven pulley62,80,112,120) from the rotational position of the driving shaft detected by the servomotor56,74,106,114and the rotational position of the driven shaft detected by the rotary encoder164, and to determine that an abnormality has occurred on the belt60,78,110,118if the phase difference is out of a given range; and a notification unit156configured to give notification when the abnormality determining unit158detects an abnormality of the belt60,78,110,118.

The configuration above enables the operator to recognize the occurrence of an abnormality on the belt60,78,110,118.

In the aspect of the invention, the belt transmission mechanism (mold opening/closing mechanism55) may be a mechanism that moves a crosshead50of a toggle link36forward and backward by rotation of the driven shaft (driven pulley62) to thereby open and close a mold30.

In the aspect of the invention, the belt transmission mechanism (ejector mechanism72) may be a mechanism that moves forward and backward an ejector pin88for ejecting a molded article from a movable mold34by rotation of the driven shaft (driven pulley80).

In the aspect of the invention, the belt transmission mechanism (screw drive mechanism104) may be a mechanism that rotates a screw96of an injection unit97by rotation of the driven shaft (driven pulley112) to thereby supply a resin material into a cylinder94.

In the aspect of the invention, the belt transmission mechanism (injection mechanism105) may be a mechanism that moves a screw96of an injection unit97forward and backward by rotation of the driven shaft (driven pulley120) to thereby inject a resin material from a cylinder94into a mold30.

In the aspect of the invention, the belt60,78,110,118may be a synchronous power transmission belt.

The configuration of the injection molding machine according to the present invention is not limited to those of the embodiments described above but can of course adopt various configurations without departing from the essence and gist of the present invention.