Patent Description:
The present invention relates to an apparatus for manufacturing an electrode assembly, an electrode manufactured therethrough, and a secondary battery.

Rechargeable batteries are classified into coin type batteries, cylindrical type batteries, prismatic type batteries, and pouch type batteries according to a shape of a battery case. In such a secondary battery, an electrode assembly mounted in a battery case is a chargeable and dischargeable power generating device having a structure in which an electrode and a separator are stacked.

The electrode assembly may be approximately classified into a jelly-roll type electrode assembly in which a separator is interposed between a positive electrode and a negative electrode, each of which is provided as the form of a sheet coated with an active material, and then, the positive electrode, the separator, and the negative electrode are wound, a stacked type electrode assembly in which a plurality of positive and negative electrodes with a separator therebetween are sequentially stacked, and a stack/folding type electrode assembly in which stacked type unit cells are wound together with a separation film having a long length.

In the case of the stacked type electrode assembly according to the related art, the electrode assembly may be manufactured through a lamination in which heat and a pressure are applied to a stack of an electrode and a separator while the stack passes between a pair of rollers.

Here, in order to adjust the pressure applied to the stack of the electrode and the separator, an upper roller moves to a lower roller to adjust the pressure. That is, a pressure actually applied to the stack changes by a distance between the rollers, a weight of each of the rollers, and a thickness of the stack. Thus, it is impossible to apply a uniform pressure to the stack always.

The reason is that the thickness of the stack is not uniform always, the distance between the rollers changes due to thermal expansion of the upper and lower rollers through heat transfer between the upper and lower rollers by the heat applied to the stack, which is applied to perform the process, and the pressure applied to the upper roller and the pressure applied to the stack change always.

For this reason, there is a problem that it is difficult to achieve the purpose of realizing the uniform quality (adhesion strength).

[Prior Art Document] : (Patent Document) <CIT>
<CIT> discloses an apparatus for manufacturing an electrode assembly.

The present invention is to provide an apparatus for manufacturing an electrode assembly.

An apparatus for manufacturing an electrode assembly is defined in the appended claim <NUM>, preferred embodiments are defined in dependent claims <NUM>-<NUM>.

According to the present invention, when the stack of the electrode and the separator is bonded through the lamination, the pressure of the portion disposed at a portion at the lower portion of the stack to adjust the pressing force applied to the stack, thereby uniformly pressing the stack, and thus, the uniform bonding of the stack may be realized.

Here, the pressures at both the sides of the lower roll disposed below the lower portion of the stack may be detected to adjust the distance between the upper roll and the lower roll in the control part. Therefore, the more uniform pressure may be applied to the stack to realize the uniform quality (adhesion strength).

The objectives, specific advantages, and novel features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

<FIG> is a conceptual block diagram of an apparatus for manufacturing an electrode assembly according to an embodiment of the present invention, and <FIG> is a front view illustrating the apparatus for manufacturing the electrode assembly according to an embodiment of the present invention.

Referring to <FIG> and <FIG>, an apparatus for manufacturing an electrode assembly according to an embodiment of the present invention may comprise an upper roll <NUM> and a lower roll <NUM>, which press upper and lower portions of a stack <NUM>, an upper support part <NUM> supporting the upper roll <NUM>, a moving part <NUM> allowing the upper support part <NUM> to move, a lower support part <NUM> supporting both sides of the lower roll <NUM>, a pressure detection part <NUM> measuring a pressure applied to the lower roll <NUM>, and a control part <NUM> adjusting a pressure applied to the stack <NUM>.

<FIG> is a perspective view exemplarily illustrating an electrode assembly manufactured through the apparatus for manufacturing the electrode assembly and a secondary battery comprising the electrode assembly according to an embodiment of the present invention.

Hereinafter, the apparatus for manufacturing the electrode assembly according to an embodiment of the present invention will be described in more detail with reference to <FIG>.

Referring to <FIG> and <FIG>, the apparatus for manufacturing the electrode assembly according to an embodiment of the present invention may be an electrode assembly manufacturing apparatus that laminates the stack <NUM> of the electrode <NUM> and the separator <NUM> to manufacture an electrode assembly <NUM>'.

The electrode assembly <NUM>' may be a chargeable and dischargeable power generation element and have a shape in which the electrode <NUM> and the separator <NUM> are alternately stacked to be assembled with each other.

The electrode <NUM> comprises a positive electrode <NUM> and a negative electrode <NUM>. Here, the positive electrode <NUM>, the separator <NUM>, and the negative electrode <NUM> may be alternately disposed.

The positive electrode <NUM> may comprise a positive electrode collector and a positive electrode active material applied to the positive electrode collector. For example, the positive electrode collector may be provided as foil made of an aluminum material, and the positive electrode active material may be made of lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate, or a compound or mixture thereof containing at least one or more of the above-described materials.

The negative electrode <NUM> may comprise a negative electrode collector and a negative electrode active material applied to the negative electrode collector. For example, the negative electrode collector may be provided as foil made of a copper (Cu) or nickel (Ni) material. The negative electrode active material may comprise synthetic graphite, a lithium metal, a lithium alloy, carbon, petroleum coke, activated carbon, graphite, a silicon compound, a tin compound, a titanium compound, or an alloy thereof. Here, the negative electrode active material may further comprise, for example, non-graphite-based SiO (silica) or SiC (silicon carbide).

Also, the separator <NUM> may be made of an insulating material and a flexible material. Here, the separator <NUM> may be made of, for example, a polyolefin-based resin film such as polyethylene or polypropylene having micropores.

<FIG> is a conceptual front view exemplarily illustrating the apparatus for manufacturing the electrode assembly according to an embodiment of the present invention. Here, <FIG> exemplarily illustrates the moving part <NUM> when viewed from a front side.

Referring to <FIG>, the upper roll <NUM> and the lower roll <NUM> may press the upper and lower portions of the stack <NUM> of the electrode <NUM> and the separator <NUM>.

Also, the upper roll <NUM> and the lower roll <NUM> may continuously laminate a plurality of stacks <NUM> while rotating.

Furthermore, for example, each of the upper roll <NUM> and the lower roll <NUM> may be provided with a heater (not shown) therein to transfer heat heated through the heater to the stack <NUM>.

The upper roll <NUM> may be in contact with a top surface of the stack <NUM>, and the lower roll <NUM> may be in contact with a bottom surface of the stack <NUM>. Here, for example, the upper roll <NUM> may move in a direction of the lower roll <NUM> to press the stack <NUM>.

The upper support part <NUM> may support the upper roll <NUM>. Here, the upper support part <NUM> may be disposed in an upward direction of the upper roll <NUM> to rotatably support the upper roll <NUM>.

Also, the upper support part <NUM> may comprise an upper roll support body <NUM> coupled to both sides of the upper roll <NUM>, a moving block <NUM> disposed to be spaced a predetermined distance upward from the upper roll support body <NUM>, a connection part <NUM> connecting the moving block <NUM> to the upper roll support body <NUM>, and a distance adjustment means <NUM> mounted on both sides of a lower portion of the moving e block <NUM> and coupled to both sides of the upper roll support body <NUM>.

The upper roll support body <NUM> may comprise one portion 121a rotatably supporting one side <NUM> of the upper roll <NUM> and the other portion 121b rotatably supporting the other side <NUM>.

The connection part <NUM> may comprise a block connection part <NUM> disposed below the moving block <NUM> and a support connection part <NUM> disposed above the upper roll support body <NUM>.

The distance adjustment means <NUM> may comprise one-side distance adjustment means 126a coupled to the one portion 121a of the upper roll support body <NUM> and the other-side distance adjustment means 126b coupled to the other portion 121b.

Each of the one-side distance adjustment means 126a and the other-side distance adjustment means 126b may be provided as, for example, an actuator. Here, the actuator may be specifically provided as, for example, a pneumatic actuator or a hydraulic actuator.

The upper support part <NUM> may further comprise an upper support <NUM> extending upward from an upper end of the moving block <NUM> and an upper block <NUM> provided at an upper end of the upper support <NUM>.

The moving part <NUM> may move the upper support part <NUM>. Here, the moving part <NUM> may be connected to an upper side of the upper support part <NUM> to allow the upper support part <NUM> to move so that the upper roll <NUM> moves vertically.

Also, the moving part <NUM> may comprises a vertical moving means S and a pressing means P so that the upper support <NUM> moves or is pressed to allow the upper roll <NUM> to move or be pressed. Here, the upper support part <NUM> may move by the vertical moving means S to allow the upper roll <NUM> to be in contact with the stack <NUM>, and the pressure applied to the upper roll <NUM> may be adjusted by the pressing means P to adjust pressing force applied to the stack <NUM>.

The pressing means P may comprise a cylinder <NUM> to press the upper support part <NUM> through a pressure of the cylinder <NUM>, thereby pressing the stack <NUM> through the upper roll <NUM> supported on the upper support part <NUM>. Here, the pressing means P may further comprise a moving shaft provided at a lower end of the cylinder <NUM> to allow the moving shaft <NUM><NUM> to vertically move through the pressure of the cylinder <NUM>, thereby adjusting the pressing force. Here, for example, the cylinder <NUM> and the moving shaft <NUM> may constitute an actuator.

The vertical moving means S may allow the upper support part <NUM> to move in the vertical direction or support the upper support part <NUM> to be disposed at a predetermined height. Here, the vertical moving means S may perform only the function of the moving means for allowing the upper support part <NUM> to move in the vertical direction or may additionally perform the function of adjusting the pressing force while the upper support part <NUM> moves in the vertical direction.

The vertical moving means S may comprise, for example, a driving motor <NUM>, a pinion gear <NUM> coupled to a rotation shaft 113a of the drive motor <NUM>, and a rack gear <NUM> engaged with the pinion gear <NUM>. Here, the driving motor <NUM> may be provided as a servo-motor or a step motor. Here, when the rotation shaft 113a rotates by an operation of the drive motor <NUM>, the pinion gear <NUM> mounted on the rotation shaft 113a rotates. As a result, the rack gear <NUM> may move vertically to allow the upper support part <NUM> to move. Also, a seating part <NUM> on which an end of the upper block <NUM> is seated may be disposed to protrude from an end of the rack gear <NUM> and support the upper block <NUM>, thereby supporting the upper support part <NUM>. Here, when the rack gear <NUM> moves upward, the upper block <NUM> of which the end is seated on the seating part <NUM> may move upward to allow the upper support part <NUM> to move.

Also, for another example, the vertical moving means S may comprise a rotation motor (not shown), a screw shaft (not shown) rotating by the rotation motor and having an outer circumferential surface on which a screw part is disposed, and a coupling block coupled to the screw shaft and having a screw groove, which corresponds to the screw part of the screw shaft, in an inner circumferential surface thereof. Here, the upper support part <NUM> may be connected to the coupling block. Thus, when the screw shaft rotates by the rotation motor, the coupling block may move vertically to allow the upper support part <NUM> to move vertically. Here, in the upper support part <NUM>, the upper block <NUM> may be connected to the coupling block. (Since a technique in which the screw shaft rotates by the rotation motor to allow the coupling block coupled to the screw shaft to rotate is the well-known technique, detailed description thereof will be omitted.

<FIG> is a right view illustrating a third support part and a fourth support part in the apparatus for manufacturing the electrode assembly according to an embodiment of the present invention.

Referring to <FIG> and <FIG>, the lower support part <NUM> may support both sides of the lower roll <NUM>.

The lower support part <NUM> comprises a first support part <NUM> supporting one side <NUM> of the lower roll <NUM> and a second support part <NUM> supporting the other side <NUM> of the lower roll <NUM>. Also, the lower support part <NUM> further comprises a third support part <NUM> supporting lower portions of the first support part <NUM> and the second support part <NUM>. The lower support part <NUM> may further comprise a fourth support part <NUM> supporting a lower portion of the third support part <NUM>.

The fourth support part <NUM> may further comprise a base block <NUM> disposed under the third support part <NUM> and a guide means <NUM> provided in plurality between the base block <NUM> and the third support part <NUM> to guide vertical movement of the third support part <NUM>.

The guide means <NUM> may be provided as a guide block in which a guide hole 155c is defined in a vertical direction. Here, a guide protrusion 155c protruding from an end of the third support part <NUM> may be coupled to the guide hole 155c so that the guide protrusion 155c is guided to move along the guide hole 155c.

The pressure detection part <NUM> may be disposed on the lower support part <NUM> to measure a pressure applied to the lower roll <NUM>, thereby detecting a pressure applied to the stack <NUM>.

The pressure detection part <NUM> comprises a first pressure detection part <NUM> detecting a pressure applied to one side of the lower roll <NUM> and a second pressure detection part <NUM> detecting a pressure applied to the other side of the lower roll <NUM>.

The pressure detection part <NUM> further comprises a third pressure detection part <NUM> extracting the total pressure applied to the stack <NUM> through the detection of the pressure applied to the third support part <NUM>.

The first pressure detection part <NUM> may detect a pressure applied to the first support part <NUM>, and the second pressure detection part <NUM> may detect a pressure applied to the second support part <NUM>.

The first pressure detection part <NUM> may be disposed between the first support part <NUM> and the third support part <NUM> in the vertical direction, and the second pressure detection part <NUM> may be disposed between the second support part <NUM> and the third support <NUM> in the vertical direction.

The third pressure detection part <NUM> may be disposed between the third support <NUM> and the base block <NUM>.

Each of the first pressure detection part <NUM>, the second pressure detection part <NUM>, and the third pressure detection part <NUM> may comprise a load cell. Here, the load cell may be deformed to be compressed or stretched when a weight is applied thereto, and an amount of deformation may be detected to measure a pressure.

Referring to <FIG> and <FIG>, the control part <NUM> may adjust the pressure applied to the stack <NUM> by reflecting the pressure detection value detected by the pressure detection part <NUM>.

Also, for example, the control part <NUM> may allow the upper roll <NUM> to move vertically through the moving part <NUM> so as to adjust the pressure applied to the stack <NUM> disposed between the upper roll <NUM> and the lower roll <NUM>. Here, for a specific example, the control part <NUM> may adjust the pressing force applied to the upper roll <NUM> through the pressing means P after the upper roll <NUM> moves vertically through the vertical moving means S of the moving part <NUM> to contact the stack, thereby adjusting the pressure applied to the stack <NUM> disposed between the upper roll <NUM> and the lower roll <NUM>.

Here, the control part <NUM> may control an operation of the driving motor <NUM> of the vertical moving means S and control an operation of the cylinder <NUM> of the pressing means P to control pressing force of the upper roll <NUM>.

For example, the control part <NUM> may control the vertical movement and the pressing force of the upper roll <NUM> through the moving part <NUM> on the basis of data stored in a memory <NUM> according to the pressure detection value transmitted from the pressure detection part <NUM> so that a uniform pressure is applied to the stack <NUM> through the upper roll <NUM>.

Furthermore, for example, the control part <NUM> may receive the pressure value from the third pressure detection part <NUM> to adjust the pressure applied to the stack <NUM> through the moving part <NUM> so that the uniform pressure is applied to the stack <NUM>. Here, the control part <NUM> may determine a pressure except for a self-weight of each of devices (structures) disposed above the third pressure detection part <NUM> as the pressing force applied to the stack <NUM> to control the moving part <NUM> on the basis of the pressing force, thereby the pressure applied to the stack <NUM>.

Also, the control part <NUM> may receive one-side pressure value and the other-side pressure value of the lower roll <NUM>, which are detected from the first pressure detection part <NUM> and the second pressure detection part <NUM>, to control the one-side distance adjustment means 126a and the other-side distance adjustment means 126b so that the uniform pressure is applied to the stack <NUM>, thereby adjusting distances h between the one side and the other sides of the upper roll <NUM> and the lower roll <NUM>. That is, a distance between the one side <NUM> of the upper roll <NUM> and the one side <NUM> of the lower roll <NUM> may be adjusted through the one-side distance adjustment means 126a and a distance between the other side <NUM> of the upper roll <NUM> and the other side <NUM> of the lower roll <NUM> may be adjusted through the others-side distance adjustment means 126b.

The control part <NUM> may compare a reference position storage value, which is stored in the memory <NUM>, with respect to a reference position at which the upper roll <NUM> and the lower roll <NUM> contact each other with a reference position detection value, which is detected in the pressure detection part <NUM>, at a time point, at which the upper roll <NUM> and the lower roll <NUM> contact each other to increase in pressure, to reset and correct the reference position detection value to the reference position at which the upper roll <NUM> and the lower roll <NUM> contact each other. Here, for example, the reference position at which the upper roll <NUM> and the lower roll <NUM> contact each other may be a position at which the stack <NUM> is not disposed between the upper roll <NUM> and the lower roll <NUM>, but the upper roll <NUM> and the lower roll <NUM> directly contact each other.

The apparatus for manufacturing the electrode assembly according to an embodiment of the present invention may be further provided with a pressing force detection sensor <NUM> between the moving part <NUM> and the upper support part <NUM> to detect pressing force applied from the moving part <NUM> to the upper support part <NUM>, thereby transmitting the detected value to the control part <NUM>. Here, the pressing force detection sensor <NUM> may be provided as, for example, a load cell.

For example, the pressing force detection sensor <NUM> may be disposed between an upper end of the moving block <NUM> at the upper support part <NUM> and an end of the moving shaft <NUM> moving by the cylinder <NUM> at the moving part <NUM>. Here, for example, the control part <NUM> may adjust the pressing force applied to the stack <NUM> with reference to the pressure value applied from the moving part <NUM> to the upper support part <NUM> through the pressing force detection sensor <NUM>.

Referring to <FIG>, in the apparatus for manufacturing the electrode assembly having the above-described configuration according to an embodiment of the present invention, when the electrode <NUM> and the separator <NUM> are bonded to each other by applying heat and a pressure while passing between the upper roll <NUM> and the lower roll <NUM>, the pressure detection part detecting the pressure may be mounted on the lower support part <NUM> supporting the lower roll <NUM> to detect the pressure transmitted to the lower roll <NUM> through the stack by pressing the stack <NUM> through the upper roll <NUM>. Thus, the control part <NUM> may control the moving part <NUM> that transmits the pressing force to the upper roll <NUM> so that the uniform pressure is applied, thereby realizing the uniform bonding between the electrode <NUM> and the separator <NUM>.

Also, pressures at both sides of the lower roll <NUM> disposed below the stack <NUM> may be detected through the pressure detection part <NUM>, and the detected value may be reflected in the control part <NUM> to adjust the distance h between the upper roll <NUM> and the lower roll <NUM> through the distance adjustment means <NUM>, thereby realizing remarkably uniform bonding and thus realizing uniform quality (adhesion strength). As a result, an electrode assembly <NUM>' in which the uniform bonding of the stack <NUM> of the electrode <NUM> and the separator <NUM> is enabled may be manufactured to prevent the separator <NUM> from being damaged due to nonuniform bonding, thereby preventing short circuit from occurring in the electrode due to the damage of the separator <NUM>. Therefore, when the electrode assembly <NUM>' is accommodated in a battery case <NUM> to manufacture a secondary battery <NUM>, impregnation of an electrolyte may increase to manufacture the secondary battery <NUM> having high quality.

Hereinafter, the electrode assembly manufactured according to an embodiment of the present invention will be described.

Referring to <FIG> and <FIG>, an electrode assembly <NUM>' may be the electrode assembly <NUM>' manufactured through the apparatus for manufacturing the electrode assembly according to the foregoing embodiment.

Thus, in this embodiment, contents duplicated with those of the apparatus for manufacturing the electrode assembly according to the foregoing embodiment will be omitted.

The electrode assembly <NUM>' may be a chargeable and dischargeable power generation element and have a structure in which an electrode <NUM> and a separator <NUM> are stacked to be combined with each other. Here, the electrode assembly <NUM>' may have, for example, a shape in which a positive electrode <NUM>, a separator <NUM>, and a negative electrode <NUM> are alternately stacked to be combined with each other.

Hereinafter, a secondary battery manufactured according to an embodiment of the present invention will be described.

Referring to <FIG> and <FIG>, a secondary battery <NUM> comprises an electrode assembly <NUM>' and a battery case <NUM> accommodating the electrode assembly <NUM>'.

The secondary battery according to an embodiment of the present invention may be a secondary battery <NUM> comprising the electrode assembly <NUM>' manufactured through the method for the electrode assembly according to the foregoing embodiment. Thus, contents of this embodiment, which are duplicated with those according to the forgoing embodiment, will be omitted or briefly described, and also, differences therebetween will be mainly described.

In more detail, the electrode assembly <NUM>' may be the electrode assembly <NUM>' manufactured through the apparatus for manufacturing the electrode assembly according to the foregoing embodiment. In the electrode assembly <NUM>', an electrode <NUM> and a separator <NUM> may be alternately stacked. Here, the electrode assembly <NUM>' may have a shape in which a positive electrode <NUM>, a separator <NUM>, and a negative electrode are alternately stacked to be combined with each other through lamination.

The battery case <NUM> may comprise an accommodation part <NUM> in which the electrode assembly <NUM>' is accommodated.

Hereinafter, an apparatus for manufacturing an electrode assembly according to another embodiment of the present invention will be described.

Referring to <FIG>, <FIG>, and <FIG>, an apparatus for manufacturing an electrode assembly according to another embodiment of the present invention may comprise an upper roll <NUM> and a lower roll <NUM>, which press upper and lower portions of a stack <NUM> in which an electrode <NUM> and a separator <NUM> are stacked, an upper support part <NUM> supporting the upper roll <NUM>, a moving part <NUM> allowing the upper support part <NUM> to move, a lower support part <NUM> supporting both sides of the lower roll <NUM>, a pressure detection part <NUM> measuring a pressure applied to the lower roll <NUM>, and a control part <NUM> adjusting a pressure applied to the stack <NUM>.

The apparatus for manufacturing the electrode assembly according to another embodiment of the present invention is different from the apparatus for manufacturing the electrode assembly according to the foregoing embodiment in that an upper roll <NUM> moves through a control part <NUM>. Thus, contents of this embodiment, which are duplicated with those according to the forgoing embodiment, will be omitted or briefly described, and also, differences therebetween will be mainly described.

In more detail, in the apparatus for manufacturing the electrode assembly according to another embodiment of the present invention, the pressure detection part <NUM> is disposed on the lower support part <NUM> to measure the pressure applied to the lower roll <NUM>, thereby detecting the pressure applied to the stack <NUM>.

A control part <NUM> may adjust the pressure applied to the stack <NUM> by reflecting a pressure detection value detected by the pressure detection part <NUM>.

Also, the control part <NUM> may allow an upper roll <NUM> to move vertically through the moving part <NUM> so as to adjust the pressure applied to the stack <NUM> disposed between the upper roll <NUM> and the lower roll <NUM>. Here, for a specific example, the control part <NUM> may adjust the pressing force applied to the upper roll <NUM> through the pressing means P after the upper roll <NUM> moves vertically through the vertical moving means S of the moving part <NUM> to contact the stack, thereby adjusting the pressure applied to the stack <NUM> disposed between the upper roll <NUM> and the lower roll <NUM>.

For example, the control part <NUM> may control the vertical movement and the pressing force of the upper roll <NUM> in real time through the moving part <NUM> according to the pressure detection value transmitted from the pressure detection part <NUM> so that a uniform pressure is applied to the stack <NUM> through the upper roll <NUM>. That is, the control part <NUM> may control the pressing force of the upper roll <NUM> so that the pressure detection value detected by the pressure detection part <NUM> is constant, not according to a movement value of the moving part, which is inputted in a memory <NUM>. Therefore, the pressing force of the upper roll <NUM> may be more easily adjusted through the control part <NUM>.

Furthermore, for example, the control part <NUM> may receive the pressure value from the third pressure detection part <NUM> to adjust the pressure applied to the stack <NUM> through the moving part <NUM> so that the uniform pressure is applied to the stack <NUM>.

Claim 1:
An apparatus for manufacturing an electrode assembly, which is configured to laminate a stack of an electrode and a separator to manufacture an electrode assembly, the apparatus comprises:
an upper roll (<NUM>) and a lower roll (<NUM>), which are configured to press upper and lower portions of the stack (<NUM>), respectively;
an upper support part (<NUM>) configured to support the upper roll (<NUM>);
a moving part (<NUM>) configured to allow the upper support part (<NUM>) to move;
a lower support part (<NUM>) configured to support both sides of the lower roll (<NUM>);
a pressure detection part (<NUM>) provided on the lower support part (<NUM>) to measure a pressure applied to the lower roll (<NUM>), thereby detecting a pressure applied to the stack; and
a control part (<NUM>) configured to adjust the pressure applied to the stack (<NUM>) by reflecting a pressure detection value detected in the pressure detection part (<NUM>),
wherein the pressure detection part (<NUM>) comprises a first pressure detection part (<NUM>) configured to detect a pressure applied to one side of the lower roll (<NUM>); and a second pressure detection part (<NUM>) configured to detect a pressure applied to the other side of the lower roll (<NUM>);
wherein the lower support part (<NUM>) comprises a first support part (<NUM>) configured to support the one side (<NUM>) of the lower roll (<NUM>) and a second support part (<NUM>) configured to support the other side (<NUM>) of the lower roll (<NUM>), and
the first pressure detection part (<NUM>) detects a pressure applied to the first support part (<NUM>), and the second pressure detection part (<NUM>) detects a pressure applied to the second support part (<NUM>); and
wherein the lower support part (<NUM>) further comprises a third support part (<NUM>) configured to support lower portions of the first support part (<NUM>) and the second support part (<NUM>), and
the pressure detection part (<NUM>) further comprises a third pressure detection part (<NUM>) configured to extract the total pressure applied to the stack (<NUM>) by detecting a pressure applied to the third support part (<NUM>).