JP2016112818A - Mold clamping device, molding machine and method for controlling the mold clamping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate the abnormality of a mold clamping force by measuring the mold clamping force with a relatively simple constitution.SOLUTION: Provided is a die clamping device comprising: a die clamping mechanism imparting die clamping force to a molding die; a servo motor of driving the die clamping mechanism; a detecting means of detecting the maximum value of the driving torque of the servo motor till the die clamping mechanism finishes the die clamping; and a determination means of determining the abnormality of the die clamping force in accordance with the maximum value of the driving torque.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a mold clamping device.

  2. Description of the Related Art Conventionally, for example, in an injection molding machine, it is necessary to fasten a mold with a predetermined clamping force so that a parting surface of the mold does not open due to a filling pressure of resin or the like. When the mold clamping force is below a predetermined mold clamping force, burrs are generated in the molded product. In Patent Document 1, as a method for detecting the mold clamping force, a sensor for detecting tie bar distortion (mainly, the amount of elongation) is attached to a tie bar to which a tensile force is applied by the mold clamping force, and the mold clamping force is determined from the amount of elongation. Techniques for detecting the are described. A strain gauge can be used as the sensor.

JP 2010-274661 A

  In the technique described in Patent Document 1, since the sensor is attached to the tie bar, it is difficult to ensure that the mold clamping force is accurately measured due to the displacement of the sensor or the slip with the tie bar. Further, when a strain gauge is attached to a tie bar as a sensor, it may be necessary to perform adhesion or additional work on the tie bar, and it takes time and effort to attach the sensor.

  The present invention provides a technique for measuring a mold clamping force with a relatively simple configuration and determining an abnormality in the mold clamping force.

  According to one aspect of the present invention, for example, a mold clamping apparatus, a mold clamping mechanism that applies a mold clamping force to a mold, a servo motor that drives the mold clamping mechanism, and the mold clamping mechanism performs mold clamping. And a detecting unit that detects a maximum value of the driving torque of the servo motor and a determining unit that determines an abnormality of the mold clamping force according to the maximum value of the driving torque. And

  ADVANTAGE OF THE INVENTION According to this invention, the technique which measures a mold clamping force with a comparatively simple structure, and determines the abnormality of a mold clamping force can be provided.

The figure which shows the mold opening state and mold closing state of the mold clamping apparatus by one Embodiment. FIG. 2 is a control diagram of the mold clamping device of FIG. 1. The figure which compares the case where a mold-clamping mechanism is normal, and the case where it is abnormal. The figure which shows the relationship between the torque of a servomotor, and a rotation position. The control flow of this embodiment.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a mold clamping device 1 according to an embodiment. In the present embodiment, the mold clamping device 1 is applied to a vertical injection molding machine, but can also be applied to a horizontal injection molding machine. 1A shows the mold opening state of the mold clamping device 1, and FIG. 1B shows the mold clamping state of the mold clamping device 1. FIG.

<Clamping device 1>
The mold clamping device 1 includes a fixed side platen 2a, a movable side platen 2b, a tie bar 3, a base plate 4, a molding die 5, a ball screw mechanism 10 and a toggle link mechanism 11 which are mold clamping mechanisms, and a servo motor 12. And the control device 13. The mold clamping device 1 includes a movable side platen 2b including a movable side mold plate 5b, and a fixed side, along a tie bar 3 standing on a base plate 4 serving as a bottom wall, from below to above the mold clamping device 1. A stationary platen 2a including a template 5a is arranged in order. The movable platen 2b and the fixed platen 2a are arranged in parallel to each other. The fixed side platen 2a is connected to the upper end of the tie bar 3 and fixed. The movable platen 2 b is movable along the tie bar 3. The base plate 4 is provided with a ball screw mechanism 10, a toggle link mechanism 11, and a servo motor 12. When the servo motor 12 is driven, the ball screw mechanism 10 is driven, and a link of a toggle link mechanism 11 described later pushes up the movable platen 2b toward the fixed platen 2a.

<Servo motor 12>
The servo motor 12 is attached to the base plate 4 and connected to the ball screw mechanism 10. In the present embodiment, an electric motor is employed as the servo motor 12. Examples of the electric motor include an AC servo motor, a DC servo motor, a stepping motor, and the like, but any form can be adopted in the present embodiment. The servo motor 12 rotates the ball screw portion 10a of the ball screw mechanism 10 to drive the ball screw mechanism 10 and the toggle link mechanism 11 and move the movable platen 2b toward the fixed platen 2a. The mold opening and mold clamping of the mold clamping device 1 are performed. A position detector 14 for detecting the rotational position of the servo motor 12 such as a resolver, a potentiometer, a pulse coder or the like is attached to the servo motor 12. The control device 13 connected to the servo motor 12 controls the drive of the servo motor 12 using the output signal from the position detector 14 as a feedback signal.

<Drive mechanism>
A drive mechanism for performing mold opening and mold clamping of the mold clamping device 1 includes a ball screw mechanism 10 and a toggle link mechanism 11. The ball screw mechanism 10 includes a ball screw portion 10 a that is rotated by a servo motor 12, and a nut portion 10 b that converts rotation of the ball screw portion 10 a into a linear motion and serves as a slider of the toggle link mechanism 11. The nut portion 10b is movable along the ball screw portion 10a in the left-right direction in the drawing so as to cross the base plate 4. The toggle link mechanism 11 includes a first link 11a having one end rotatably connected to the nut portion 10b, and a second link 11b connected to the first link 11a. One end of the second link 11b is rotatably connected to the first link 11a, and the other end is fixed to the lower surface of the movable platen 2b. The second link 11b is disposed so as to hang from the lower surface of the movable platen 2b.

  When the ball screw portion 10a is rotated by the servo motor 12, the nut portion 10b moves along the ball screw portion 10a. As the nut portion 10b moves, one end of the first link 11a moves along the ball screw portion 10a, and the other end of the first link 11a connected to the second link 11b pushes the second link 11b upward. Since the second link 11b is fixed to the lower surface of the fixed platen 2b, the second link 11b pushed up pushes up the lower surface of the movable platen 2b, and the movable platen 2b moves in the direction of the fixed platen 2a. To do. Then, the movable platen 2b and the fixed platen 2a approach each other, the fixed mold plate 5a and the movable mold plate 5b of the mold 5 come into contact with each other, and clamping is performed. Finally, as shown in FIG. 1B, when the first link 11a and the second link 11b are arranged in a straight line in the vertical direction, the movable platen 2b is most strongly pressed against the fixed platen. Will be. Therefore, in the state shown in FIG. 1B, the mold clamping force is most strongly applied to the mold, and in this embodiment, the abnormality of the mold clamping force in this state is determined.

<Control device 13>
The control device 13 is connected to the servo motor 12, the position detector 14, and the notification device 15. The notification device 15 is a device that notifies the outside when an abnormality in the clamping force described later is determined. Further, a current detector 16 that detects a drive current supplied to the servomotor 12 is disposed between the control device 13 and the servomotor 12. The control device 13 controls the drive of the servo motor 12 based on the rotational position detected by the position detector 14 and detects the drive torque of the servo motor 12 from the current value detected by the current detector 16. . The drive torque of the servo motor 12 can be obtained by the product of the torque constant and the drive current. The control device 13 controls the position and speed of the servo motor 12 based on a program for controlling the mold clamping device 1 described later when a drive command is issued to the servo motor 12. Further, the control device 13 detects the positions of the toggle link mechanism 11 and the movable platen 2b based on the output signal from the position detector 14. The position of the nut portion 10b can be detected from the rotational position of the servo motor 12, and the state of the toggle link mechanism 11 can be detected from the position of the nut portion 10b. That is, since the rotational position of the servo motor 12 and the state of the toggle link mechanism 11 have a correlation, it is determined whether the toggle link mechanism 11 is disposed perpendicular to the movable platen by the rotational position of the servo motor 12. To do. In this way, it is possible to detect the state where the mold clamping shown in FIG. The detected drive torque of the servo motor 12 and the state of the toggle link mechanism 11 can be appropriately stored in the control device 13.

  FIG. 2 is a block diagram of the control device 13. The control device 13 includes a processing unit 13a, a storage unit 13b, and an interface unit 13c, which are connected to each other via a bus (not shown). The processing unit 13a executes a program stored in the storage unit 13b. In the present embodiment, the program is a program for performing mold opening and mold clamping of the mold clamping device 1, for example. The processing unit 13a is, for example, a CPU. The storage unit 13b is, for example, a RAM, a ROM, a hard disk, or the like. The interface unit 13c is provided between the processing unit 13b and an external device (host computer 13d, sensors such as the position detector 14 and the current detector 16, actuators of the servo motor 12, and the notification device 15). Interface and I / O interface. The control device 13 controls the mold clamping device 1 according to an instruction from the host computer and also functions as a drive circuit for the notification device 15.

<Clamping and mold opening process of mold clamping device 1>
With reference to FIG. 1 again, the mold clamping and mold opening process of the mold clamping apparatus 1 will be described. FIG. 1A is an external view of the mold clamping device 1 in the mold open state, and FIG. 1B is an external view of the mold clamping device 1 in a state where the mold clamping is completed. In the mold clamping apparatus 1, the ball screw mechanism 10 moves the nut portion 10b in the left direction in the figure by driving the servo motor 12 from the state shown in FIG. Then, the first link 11a moved at one end by the nut portion 10b pushes the second link 11b connected to the other end upward in FIG. 1 (A). The second link 11b pushed up by the first link 11a pushes up the movable platen 2b connected to the end thereof upward in FIG. 1 (A). Finally, as shown in FIG. 1B, when the first link 11a and the second link 11b are vertically arranged on a straight line, the movable side mold plate 5b and the fixed side platen mounted on the movable side platen 2b. The fixed side template 5a attached to 2a comes into contact. At this time, when the movable platen 2b pushes up the mold 5 and the fixed platen 2a, the tie bar 3 connected to the fixed platen 2a is stretched. At this time, the elastic force generated by the extended tie bar 3 becomes a mold clamping force, and the mold 5 is in a state where a predetermined mold clamping force is applied.

  After the mold clamping of the mold clamping apparatus 1 is completed, resin or the like is filled into the mold 5 from an injection cylinder of an injection molding machine (not shown), and a molded product is molded. The molded product molded in the mold 5 is taken out from the mold 5 when the mold clamping device 1 opens the mold 5. When the mold clamping device 1 opens the mold 5, the servo motor 12 is rotationally driven in the direction opposite to that during mold clamping to move the nut portion 10 b in the right direction in the figure. By doing so, the first link 11a and the second link 11b are bent, and the second link 11b lowers the movable platen 2b toward the base plate 4 side. Thus, when the fixed side mold plate 5a and the movable side mold plate 5b are separated from each other, the mold 5 is opened, and the molded product in the mold 5 can be taken out. When mass-producing a large number of molded products, this mold clamping and mold opening process is repeated.

<Decrease in clamping force>
With reference to FIG. 3, the change of the mold clamping force of the mold clamping mechanism which arises by repeating such mold clamping and mold opening is demonstrated. If the mold clamping device 1 repeats mold clamping and mold opening in order to produce a large amount of molded products, the mold clamping mechanism may change over time, and a predetermined mold clamping force may not be obtained. FIG. 3A shows a case where the mold clamping apparatus 1 has performed mold clamping at the time of shipment from the factory, that is, with no change over time, and FIG. 3B shows a case where change over time has occurred. .

  As an example of the change over time of the mold clamping mechanism, for example, there is a case where the joint portion, which is a connecting portion between the first link 11a and the second link 11b, is worn by repeatedly moving the movable platen 2b. Specifically, the length of the state in which the first link 11a and the second link 11b are vertically arranged may be shortened due to wear of the joint portion indicated by the wear spot D in FIG. This is because the sum of the lengths of the first link 11a and the second link 11b shown in FIG. 3B is the sum of the lengths of the first link 11a and the second link 11b shown in FIG. It shows that it is shorter. That is, the movable platen 2b is pressed by a link having a short length as it is worn at the wear point D due to a change with time of the toggle link mechanism 11. As shown by the distance S in FIG. 3, the tie bar 3 shown in FIG. 3B is not extended by the distance S than the tie bar 3 shown in FIG. 3B, the tie bar 3 is not sufficiently stretched and it is difficult to generate a predetermined elastic force, so it is difficult to apply a predetermined mold clamping force to the mold 5. As a result, the mold clamping force may decrease due to a change in the mold clamping mechanism over time. In the present embodiment, the wear part D of the link is illustrated as an example of the change over time of the mold clamping mechanism, but the present invention is not limited to this. For example, the mold clamping force may decrease due to deformation such as link distortion.

<Abnormal judgment of clamping force>
As described in the prior art, a decrease in the clamping force is not preferable because burrs are generated in the molded product. Therefore, it is necessary to monitor the abnormality of the clamping force every time the mold 5 is clamped even during the production of the molded product. With reference to FIG. 4, a method for determining an abnormality in the mold clamping force will be described. In the present embodiment, the abnormality of the mold clamping force is determined by detecting the drive torque of the servo motor 12 that is the drive unit of the toggle link mechanism 11. FIG. 4 shows the driving torque of the servo motor 12 and the rotational position of the servo motor 12 that is the operating position of the toggle link mechanism 11 in consideration of the operating position of the toggle link mechanism 11 when detecting the driving torque of the servo motor 12. Shows the relationship.

  FIG. 4 is a graph showing the relationship between the drive torque of the servo motor 12 and the rotational position where the rotational position of the servo motor 12 during mold clamping is the X axis and the drive torque of the servo motor 12 is the Y axis. The location indicated by E on the Y axis is the position where the mold clamping ends. As described above, the operating position of the toggle link mechanism 11 can be obtained from the rotational position of the servo motor 12. Further, the driving torque that is the output of the servo motor 12 can be obtained from the current value detected by the current detector 16.

  The servomotor 12 increases the drive torque to move the toggle link mechanism 11 and the movable platen 2b from the start of mold clamping indicated by 0 on the Y axis. Next, the servo motor 12 outputs a constant driving torque to the mold touch position where the movable side mold plate 5b of the movable side platen 2b contacts the fixed side mold plate 5a of the fixed side platen 2a. Next, in order to clamp the mold 5 with a predetermined mold clamping force, the drive torque is increased so that the first link 11a and the second link 11b are in a vertical position. When the first link 11a and the second link 11b reach a vertical position, the driving torque becomes maximum. Thereafter, the first link 11a and the second link 11b further move the nut portion 10b while maintaining the vertical position, so that the servo motor 12 outputs drive torque. The driving torque at this time is gradually decreased and output. Finally, when the mold clamping indicated by E on the Y axis is completed, the servo motor 12 stops driving. As described above, in the mold clamping apparatus 1 of the present embodiment, the drive torque increases to the maximum value before the mold clamping is completed, and then the drive torque decreases, and the drive torque is completely clamped. The maximum value that is the peak value is output immediately before the operation.

  In this embodiment, each time the mold is clamped, the rotational position of the servo motor 12 and the drive torque of the servo motor 12 are detected a plurality of times, and data on the relationship between the drive torque and the rotational position is obtained, and this data is controlled. The data is stored in the storage unit of the device 13. Further, the maximum value is detected from the drive torque data and stored in the storage unit as the maximum torque. Therefore, each time the mold is clamped, the maximum torque data is compared with a reference torque described later, and when it is recognized that the mold clamping force has decreased by a predetermined value or more, an abnormality in the mold clamping force is determined. Accordingly, the control device 13 detects the maximum value of the drive torque of the servo motor 12 until the mold clamping mechanism finishes the mold clamping, and determines the abnormality of the mold clamping force according to the maximum value of the drive torque. To do.

  In FIG. 4, the solid line represents the relationship between the driving torque and the rotational position when the mold clamping is normally performed, for example, the state of the mold clamping apparatus 1 shown in FIG. Also, in FIG. 4, the dotted line shows the relationship between the driving torque and the rotational position when the mold clamping is performed in a state where the mold clamping force is reduced due to the change over time. For example, the mold clamping apparatus shown in FIG. 1 state. In this way, when the clamping force is reduced due to the change over time, the maximum value that is the peak value of the torque of the servo motor 12 is changed from the peak value indicated by the solid line (A) in FIG. 4 to the peak value indicated by the dotted line (B). descend. Accordingly, the clamping force is reduced by determining that the value of the maximum torque of the servo motor 12 is lower than a predetermined value in the data on the relationship between the driving torque and the rotational position at the time of clamping. Determine.

  FIG. 5 is a flowchart in which the control device 13 performs a process for detecting change over time based on the driving torque and the rotational position. First, it waits until the mold clamping apparatus 1 starts mold clamping by the process of S401. Examples of detection of the start of mold clamping include detection by an operator pressing a switch or the like that starts driving the mold clamping device, or detection of removal of a molded product after mold opening. It is not limited. When the mold clamping device 1 starts mold clamping, the process of S402 is performed. The process of S402 is a process of recording the drive torque of the servo motor 12 from the start of mold clamping to the end of mold clamping, and storing it in the storage unit (400a) of the control device 13 as a torque log. As a timing for taking a log of the drive torque, the drive torque may be detected a plurality of times at a predetermined rotational position of the servo motor 12, or the drive torque may be detected continuously until the end of mold clamping.

  Next, in the process of S403, it is detected from the rotational position of the servo motor 12 whether the first link 11a and the second link 11b of the toggle link mechanism 11 are vertical. When it is detected that the first link 11a and the second link 11b are in the vertical position, the completion of the operation of recording the drive torque is confirmed in S403 processing. As a method for detecting whether the first link 11a and the second link 11b are vertical, in this embodiment, the servo motor 12 is rotated to a position where the first link 11a and the second link 11b are vertical. However, it is not limited to this. For example, it may be detected by a switch that operates when the first link 11a and the second link 11b are aligned with each other.

  In the process of S404, the maximum value of torque is detected from the torque log stored in 400a, and this maximum value is temporarily stored in the storage unit (400b). In the process of S405, the maximum torque value temporarily stored in 400b and the reference torque to be used as a reference when a predetermined mold clamping force prepared in advance in the storage unit (400c) at the time of factory shipment or the like is generated. Compare the value of. The reference torque is a value with a range from the maximum value of torque when clamping is performed before time-dependent changes such as factory shipment to the torque at which a predetermined clamping force can be applied. Is set. That is, S405 is equivalent to comparing the torque that can give a predetermined mold clamping force with the current maximum torque. At this time, if the maximum value of the torque is lower than the reference torque, it is determined that a change with time has occurred and it is determined that there is an abnormality (S406). If the maximum value of the torque is not lower than the reference torque, it is determined that there is no change over time and it is determined that there is no abnormality (S407). Finally, the process ends.

  According to the present embodiment, the maximum value of the drive torque of the servo motor 12 is detected before the mold clamping mechanism finishes the mold clamping, and the abnormality of the mold clamping force is determined according to the maximum value of the drive torque. Therefore, there is no need to attach a sensor such as a strain sensor used for conventional mold clamping force detection to the tie bar 3. Further, since the decrease in the mold clamping force is detected based on the drive torque of the servo motor 12, the sensor mounting position does not deviate from the tie bar 3 and the sensor does not slide with the tie bar 3. The decrease can be accurately detected. Therefore, it is possible to measure the mold clamping force with a relatively simple configuration and determine abnormality of the mold clamping force.

  In the present embodiment, the peak value of the drive torque output by the servo motor 12 before the toggle link mechanism 11 finishes the mold clamping is set as the maximum value of the drive torque. By doing so, it is possible to determine the state in which the toggle link mechanism 11 has completed the mold clamping, and it is possible to accurately detect the maximum value of the driving torque until the mold clamping is completed. That is, when the maximum value until the mold clamping is finished without considering the peak value, for example, even when the movable side platen 2b is caught by the tie bar 3 for some reason and cannot move, It will be detected as a value. However, by considering the peak value in the maximum value of the torque, it can be determined that the movable side platen 2b has normally contacted the fixed side platen 2a and the mold clamping has been completed normally.

  Moreover, the mold clamping apparatus 1 of this embodiment is provided with the alerting | reporting apparatus 15 which alert | reports abnormality, when the abnormality of mold clamping force is determined. When the lowering of the mold clamping force is recognized by the notification device 15 while the mold clamping device 1 is performing the molding operation, it is possible to stop the mold clamping device 1 by notifying an operator or the like of an abnormality. The production of defective products can be stopped quickly. Alternatively, the mold clamping device 1 may be automatically stopped based on a signal output from the notification device 15.

  In the present embodiment, a single toggle link mechanism driven by a ball screw mechanism is employed as the drive mechanism, but the present invention is not limited to this. For example, a drive mechanism that includes a pair of toggle link mechanisms and connects the joints connecting the connection points of the first and second links with a cross member and drives the cross member with a ball screw mechanism or the like. May be.

  In the present embodiment, as an example to which the mold opening / closing mechanism according to the present invention is applied, an example applied to a vertical injection molding machine has been described, but the present invention is not limited to this. The mold opening / closing mechanism according to the present invention can be applied to, for example, a horizontal injection molding machine, a two-color or multi-material injection molding machine, a rotary injection molding machine, etc. as an injection molding machine. Furthermore, the present invention can be applied to, for example, a mold used for casting such as die casting, and a mold opening / closing mechanism used for blow molding or compression molding. The material used for the molding machine in the present embodiment is not particularly limited, and examples thereof include thermoplastic resins such as plastics, molten metals such as iron and magnesium, and composite materials to which these inorganic materials are added.

DESCRIPTION OF SYMBOLS 1 Clamping device, 2a Fixed side platen 2a, 2b Movable side platen, 3 Tie bar, 4 Base plate, 5 Mold, 10 Ball screw mechanism, 11 Toggle link mechanism, 12 Servo motor, 13 Control device, 14 Position detector, 15 Notification device, 16 current detector

Claims (10)

A mold clamping device,
A mold clamping mechanism that applies a mold clamping force to the mold; and
A servo motor for driving the mold clamping mechanism;
Detection means for detecting the maximum value of the drive torque of the servo motor until the mold clamping mechanism finishes mold clamping;
Determination means for determining abnormality of the clamping force according to the maximum value of the driving torque;
A mold clamping device comprising: The detection means includes a current detection means for detecting a drive current supplied to the servo motor,
The mold clamping device according to claim 1, wherein the maximum value of the driving torque is detected based on the driving current. The mold clamping mechanism includes a ball screw mechanism and a toggle link mechanism,
The ball screw mechanism converts the rotation of the servo motor into a linear motion, drives the toggle link mechanism,
The toggle link mechanism is connected to the movable mold plate of the mold, moves the movable mold plate to the fixed mold plate, and clamps the mold.
2. The mold clamping device according to claim 1, wherein a peak value of the drive torque output by the servo motor is set as a maximum value of the drive torque until the toggle link mechanism finishes mold clamping.   The determination means determines an abnormality when a maximum value of the drive torque is lower than a reference torque value that is a drive torque of the servo motor that applies a predetermined clamping force to the mold. The mold clamping device according to any one of claims 1 to 3.   The mold clamping apparatus according to any one of claims 1 to 4, wherein the mold clamping device further includes notification means for notifying abnormality when the determination means determines abnormality of the mold clamping force. apparatus. The mold clamping device further includes storage means for storing the maximum value of the driving torque detected by the detection means,
The mold according to any one of claims 1 to 5, wherein the determination unit determines an abnormality of the mold clamping force with reference to a maximum value of the driving torque stored in the storage unit. Fastening device. The detecting means detects a rotational position of the servo motor,
The mold clamping device according to any one of claims 3 to 6, wherein the determination unit detects an operation position of the toggle link mechanism from the rotation position and determines the end of the mold clamping.   A molding machine comprising the mold clamping device according to any one of claims 1 to 7. A method for controlling a mold clamping device, comprising: a mold clamping mechanism that applies a mold clamping force to a molding die; and a servo motor that drives the mold clamping mechanism,
A detection step of detecting a maximum value of the drive torque of the servo motor until the mold clamping mechanism finishes mold clamping;
A determination step of determining abnormality of the mold clamping force according to the maximum value of the driving torque;
A method for controlling a mold clamping device, comprising: The mold clamping mechanism includes a toggle link mechanism and a ball screw mechanism,
The ball screw mechanism converts the rotation of the servo motor into a linear motion, drives the toggle link mechanism,
The toggle link mechanism is connected to the movable mold plate of the mold, moves the movable mold plate to the fixed mold plate, and clamps the mold.
A storage step of storing the maximum value of the driving torque by setting the peak value of the driving torque output by the servo motor as the maximum value of the driving torque until the toggle link mechanism finishes clamping; ,
10. The method of controlling a mold clamping device according to claim 9, wherein the determination step determines an abnormality of the mold clamping force with reference to a maximum value of the driving torque stored in the storage step.

Images