Method of manufacturing adhered components

A method of manufacturing adhered components includes a process of applying adhesive to application areas on a surface of a first component, a process of placing a second component above the first component, and a process of pressurizing the second component toward the first component. In the pressurization process, the load applied to a pressurizer changes while sequentially undergoing a curvilinear increase period in which the load increases in a curved line as the compression amount of the adhesive increases, and a rapid increase period in which the load increases in a polygonal line with respect to the trajectory of the load in the curvilinear increase period as the compression amount increases. During pressurization by the pressurizer, the load is detected by a load sensor, the rapid increase period is detected based on the detection value of the load sensor, and the pressurization is stopped during the rapid increase period.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2021-127426 filed on Aug. 3, 2021, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The technology disclosed in the specification relates to a method of manufacturing adhered components.

2. Description of Related Art

Japanese Unexamined Patent Application Publication No. 2019-119147 (JP 2019-119147 A) discloses a technology for bonding two components with an adhesive. In this technology, initially, the adhesive is applied in the form of beads to two or more locations on a surface of a first component. Then, a second component is placed above the first component so that the adhesive is sandwiched between the first component and the second component. Then, a pressurization process of pressurizing the second component toward the first component is performed. When the pressurization process is performed, the adhesive is compressed and expanded in the lateral direction. The expanded adhesives are connected to each other, so that the adhesive is applied to a wide area. Thus, in this technology, the adhesive is distributed and applied to two or more locations, and then the adhesives at the locations are compressed and expanded, to be connected to each other. According to this technology, the adhesive can be applied to a wide area, using a relatively low load as the load of the pressurization process. Accordingly, it is possible to apply the adhesive to a wide area, without applying a high load to the first component and the second component. Then, the adhesive is cured, so that the first component and the second component are bonded to each other.

SUMMARY

In the technology of JP 2019-119147 A, it is difficult to grasp the expanded area of the adhesive in the pressurization process. Thus, in the pressurization process, the adhesives applied to the two or more locations may not be connected to each other. When the adhesives are not connected to each other, and a gap exists between the adhesives, the adhesive strength is reduced. In the technology for applying adhesives to two or more locations and then performing a pressurization process, a technology for surely connecting the adhesives to each other during the pressurization process is proposed in this specification.

A first method of manufacturing adhered components disclosed in the specification has an application process, a component placement process, and a pressurization process. In the application process, an adhesive is applied to a plurality of application areas extending linearly and spaced in a direction intersecting an extending direction in which the application areas extend linearly, on a surface of a first component. In the component placement process, a second component is placed above the first component such that the adhesive is sandwiched between the first component and the second component. In the pressurization process, a pressurizer pressurizes the second component toward the first component, to compress the adhesive. In the pressurization process, a load applied to the pressurizer changes such that the load goes through a curvilinear increase period in which the load increases in a curved line as an amount of compression of the adhesive increases, and a rapid increase period in which the load increases in a polygonal line with respect to a trajectory of the load in the curvilinear increase period as the amount of compression of the adhesive increases, in the order of description. The pressurization process includes performing pressurization by the pressurizer while detecting the load by a load sensor, detecting the rapid increase period based on a detection value of the load sensor, and stopping the pressurization by the pressurizer during the rapid increase period.

In the manufacturing method, after the adhesive is applied to the application areas of the first component, and the second component is placed such that the adhesive is sandwiched between the first component and the second component, the pressurization process is performed. In the pressurization process, the pressurizer pressurizes the second component toward the first component to compress the adhesive, so that the adhesive expands in the lateral direction. While the adhesives on the application areas are not connected to each other, the load applied to the pressurizer increases in a curved line as the amount of compression of the adhesive increases. Namely, the period in which the adhesives are not connected to each other corresponds to the curvilinear increase period. Then, once the adhesives are connected to each other due to expansion of the adhesives, the adhesive is less likely or unlikely to flow in the lateral direction in an area where the adhesives are connected to each other. Thus, the adhesive is less likely or unlikely to be compressed, and the load applied to the pressurizer rapidly increases. At this time, the load applied to the pressurizer increases in a polygonal line with respect to the trajectory of the load in the curvilinear increase period. Namely, the period after the time when the adhesives are connected to each other corresponds to the rapid increase period. In this manufacturing method, the pressurizer performs pressurization while the load applied to the pressurizer is detected by the load sensor, the rapid increase period is detected based on the detection value of the load sensor, and the pressurization by the pressurizer is stopped during the rapid increase period. Accordingly, the pressurization can be stopped in a condition where the adhesives are connected to each other. Namely, according to the manufacturing method, the adhesives can be surely connected to each other during the pressurization process.

A second method of manufacturing adhered components disclosed in the specification has an application process, a component placement process, and a pressurization process. In the application process, an adhesive is applied to a plurality of application areas extending linearly and spaced in a direction intersecting an extending direction in which the application areas extend linearly, on a surface of a first component. In the component placement process, a second component is placed above the first component such that the adhesive is sandwiched between the first component and the second component. In the pressurization process, a pressurizer pressurizes the second component toward the first component, to compress the adhesive. In the pressurization process, a compression speed of the adhesive changes such that the compression speed goes through a curvilinear decrease period in which the compression speed decreases in a curved line as an amount of compression of the adhesive increases, and a rapid decrease period in which the compression speed decreases in a polygonal line with respect to a trajectory of the compression speed in the curvilinear increase period as the amount of compression of the adhesive increases, in the order of description. The pressurization process includes performing pressurization by the pressurizer while detecting the compression speed by a compression speed sensor, detecting the rapid decrease period based on a detection value of the compression speed sensor, and stopping the pressurization by the pressurizer during the rapid decrease period.

In the manufacturing method, after the adhesive is applied to the application areas of the first component, and the second component is placed such that the adhesive is sandwiched between the first component and the second component, the pressurization process is performed. In the pressurization process, the pressurizer pressurizes the second component toward the first component to compresses the adhesive, so that the adhesive expands in the lateral direction. While the adhesives on the application areas are not connected to each other, the compression speed of the adhesive decreases in a curved line as the amount of compression of the adhesive increases. Namely, the period in which the adhesives are not connected to each other corresponds to the curvilinear decrease period. Then, once the adhesives are connected to each other due to expansion of the adhesives, the adhesive is less likely or unlikely to flow in the lateral direction in an area where the adhesives are connected to each other. Thus, the adhesive is less likely or unlikely to be compressed, and the compression speed of the adhesive rapidly decreases. At this time, the compression speed of the adhesive decreases in a polygonal line with respect to the trajectory of the compression speed in the curvilinear decrease period. Namely, the period after the time when the adhesives are connected to each other corresponds to the rapid decrease period. In the manufacturing method, the pressurizer performs pressurization while the compression speed of the adhesive is detected by the compression speed sensor, the rapid decrease period is detected based on the detection value of the compression speed sensor, and the pressurization by the pressurizer is stopped during the rapid decrease period. Accordingly, the pressurization can be stopped in a condition where the adhesives are connected to each other. Namely, according to the manufacturing method, the adhesives can be surely connected to each other during the pressurization process.

DETAILED DESCRIPTION OF EMBODIMENTS

In one example of the first manufacturing method described above, in the pressurization process, the pressurization by the pressurizer may be stopped when the detection value of the load sensor reaches a threshold value. The threshold value may be set to a value of the load during the rapid increase period.

With this arrangement, the pressurization by the pressurizer can be stopped during the rapid increase period.

In one example of the first manufacturing method described above, the adhesive may have thixotropic properties.

With this arrangement, the viscosity of the adhesive increases when the adhesives are connected to each other; therefore, the load applied to the pressurizer rises more sharply during the rapid increase period. Accordingly, the rapid increase period can be easily detected.

In one example of the first manufacturing method described above, the first component may be a battery pack, and the second component may be a cooler.

In one example of the first manufacturing method described above, the stiffness of one of the first component and the second component may be lower than the stiffness of the other of the first component and the second component.

With this arrangement, when the component having the higher stiffness is distorted, the component having the lower stiffness can deform according to the distortion. Accordingly, the components are likely to be more properly bonded together.

In one example of the first manufacturing method described above, ceramic powder may be dispersed in the adhesive.

With this arrangement, the thermal conductivity of the adhesive can be improved.

In the following description, a method of manufacturing a module of a battery pack for an electrified vehicle and a cooler, by bonding the cooler to the battery pack.

First Embodiment

In a manufacturing method of a first embodiment, an adhesive application process, a component placement process, and a pressurization process are carried out in this order.

In the adhesive application process, adhesive20is applied to a surface of a case14of a battery pack12, as shown inFIG.1. The adhesive20is applied to two application areas21a,21bthat are spaced apart from each other in the x direction. The adhesive20is applied such that the adhesive20extends in a straight line in the y direction (i.e., the direction perpendicular to the x direction) in each of the application areas21a,21b. As shown inFIG.2, the adhesive20is applied such that the cross-sectional shape of the adhesive20is a generally circular shape. The adhesive20is jelly-like and has thixotropic properties. In this specification, the thixotropic properties mean properties where the viscosity decreases in a condition where shear stress is applied, and the viscosity gradually increases in static conditions. Also, ceramic powder is dispersed within the adhesive20. In the following description, the adhesive20in the application area21amay be referred to as “adhesive20a”, and the adhesive20in the application area21bmay be referred to as “adhesive20b”. In the conditions ofFIG.1andFIG.2, there is a gap22between the adhesive20aand the adhesive20b.

Then, in the component placement process, the cooler16is placed above the battery pack12, as shown inFIG.3. The cooler16is placed above the battery pack12, such that the adhesive20is sandwiched between the case14of the battery pack12and an outer wall18of the cooler16. The stiffness of the case14of the battery pack12is higher than that of the outer wall18of the cooler16.

Then, the pressurization process is carried out. In the pressurization process, the cooler16is pressurized toward the battery pack12by the pressurizer30as indicated by arrows100inFIG.4. As a result, the adhesive20is compressed. Namely, the thickness t1of the adhesive20is reduced. As shown inFIG.4, the pressurizer30has a load sensor40and a controller42. The load sensor40detects the load N1applied to the pressurizer30(namely, the load applied to the adhesive20). The controller42controls the pressurizer30according to the detection value of the load sensor40. In the pressurization process, the adhesive20is compressed while the load N1applied to the pressurizer30is detected by the load sensor40. As the adhesive20is compressed, the adhesive20flows in the x direction as indicated by arrows102inFIG.5. As a result, the width W1of the adhesives20a,20bexpands. As the adhesive20is further compressed from the state ofFIG.5, the width W1of the adhesives20a,20bfurther expands, and the adhesive20aand the adhesive20bcontact with each other, as shown inFIG.6andFIG.7. In this manner, the adhesive20aand the adhesive20bare connected to each other, so that the adhesive20is spread over the entire major area of the surface of the case14(i.e., the area having the width W2inFIG.6andFIG.7).

In the pressurization process, the pressurizer30compresses the adhesive20in such a manner that the load N1applied to the pressurizer30(i.e., the load applied to the adhesive20) can be changed. For example, the pressurizer30compresses the adhesive20at a constant work rate or at a constant compression speed. Thus, during the pressurization process, the load N1applied to the pressurizer30changes.

FIG.8shows changes in the load N1applied to the pressurizer30during the pressurization process. As shown inFIG.8, the load N1applied to the pressurizer30at the start of the pressurization process is low. Immediately after the start of the pressurization process, the adhesive20aand the adhesive20bare separated from each other as shown inFIG.4andFIG.5. In this condition, as the width W1of each adhesive20a,20bexpands, the load required to expand the width W1increases. Thus, as shown inFIG.8, immediately after the start of the pressurization process, the load N1applied to the pressurizer30increases slowly in a curved line as the thickness t1of the adhesive20decreases. Then, when the adhesive20aand the adhesive20bcontact with each other as shown inFIG.6, the adhesives20a,20bbecome unable to flow in the x direction at the contact position J1. Thus, after that, the load required to expand the width W2of the adhesive20rapidly increases. As a result, as shown inFIG.8, the load N1applied to the pressurizer30rises rapidly from the bending point P1. In the first embodiment, in particular, the adhesive20has the thixotropic properties. Thus, when the adhesive20stops flowing in the x direction at the contact position J1, the viscosity of the adhesive20increases at around the contact position J1. Thus, the load N1applied to the pressurizer30rises extremely steeply from the bending point P1. In the following description, the period in which the load N1increases slowly in a curved line will be referred to as “curvilinear increase period T1”, and the period in which the load N1increases rapidly will be referred to “rapid increase period T2”. In the rapid increase period T2, the load N1increases at a higher rate of increase than the rate of increase of the load N1in the curvilinear increase period T1. In the rapid increase period T2, the load N1increases in a polygonal line with respect to the trajectory of the load N1in the curvilinear increase period T1. Namely, at the bending point P1, the load N1changes in an indifferentiable manner. As described above, the adhesive20aand the adhesive20bare separated from each other during the curvilinear increase period T1, and the adhesive20aand the adhesive20bare connected to each other during the rapid increase period T2.

During the pressurization process, the controller42of the pressurizer30monitors the detection value of the load sensor40. When the detection value of the load sensor40reaches a threshold value Nth shown inFIG.8, the controller42stops pressurization by the pressurizer30. The threshold value Nth is set to a value of the load N1applied to the pressurizer30during the rapid increase period T2. Namely, the threshold value Nth is set to a higher value than the load N1applied at the bending point P1. Thus, at the time when the controller42stops pressurization (namely, at the time when the load N1reaches the threshold value Nth), the adhesive20aand the adhesive20bare in contact with each other as shown inFIG.6andFIG.7. Thus, it is possible to surely make the adhesive20aand the adhesive20bcontact with each other, by stopping the pressurization after the time of transition from the curvilinear increase period T1to the rapid increase period T2. Then, the adhesive20is cured while a condition where the battery pack12and the cooler16are sandwiched by the pressurizer30is maintained. With the adhesive20thus cured, the battery pack12is bonded to the cooler16. In this manner, the module of the battery pack12and the cooler16is completed.

As described above, in the manufacturing method of the first embodiment, a value of the load N1in the rapid increase period T2is set as the threshold value Nth, and the pressurization is stopped when the detection value of the load sensor40reaches the threshold value Nth. Accordingly, the adhesive20ain the application area21aand the adhesive20bin the application area21bcan be surely brought into contact with each other. During the pressurization process and after the pressurization process, it is impossible to visually determine whether the adhesive20aand the adhesive20bare in contact with each other. However, according to the above manufacturing method, it is possible to surely make the adhesive20aand the adhesive20bin contact with each other, without the need to visually check the adhesives20a,20b. Accordingly, with this manufacturing method, the gap22can be prevented from remaining between the adhesive20aand the adhesive20b, and shortage of the adhesive strength can be prevented.

The cross-sectional area S1 of the adhesive20before compression is the sum of the cross-sectional area of the adhesive20aand that of the adhesive20b. Where R denotes the diameter of the cross section of each adhesive20a,20bshown inFIG.2, the cross-sectional area S1 satisfies the relationship that S1=2×(R/2)2. As is apparent fromFIG.6, the cross-sectional area S2 of the adhesive20after compression satisfies the relationship that S2=W2×t1. The cross-sectional area S1 of the adhesive20before compression is substantially equal to the cross-sectional area S2 of the adhesive20after compression. Accordingly, the relationship that R=((4×W2×t1)/(2×π))1/2is established. As is apparent fromFIG.2andFIG.6, the distance L1between the center of the adhesive20aand the center of the adhesive20bbefore compression is substantially equal to a half of the width W2of the adhesive20after compression. Namely, the relationship that L1=W2/2 is established. Accordingly, where W2tdenotes the design value of the width W2, and t1tdenotes the design value of the thickness t1, the distance L1and the diameter R at the time of application of the adhesive20can be set to satisfy the relationships that L1=W2t/2, and R=((4×W2t×t1t)/(2×π))1/2. With the distance L1and the diameter R set in this manner, the width W2and thickness t1of the adhesive20at the time when the load N1rapidly increases (i.e., at the bending point P1) substantially coincide with the width W2tand thickness t1tas designed. Accordingly, it is possible to make the width W2and thickness t1of the adhesive20substantially equal to the width W2tand thickness t1tas designed, by stopping the pressurization by the pressurizer30immediately after the transition from the curvilinear increase period T1to the rapid increase period T2as in the first embodiment. Thus, according to the manufacturing method of the first embodiment, the width W2and thickness t1of the adhesive20after compression can be accurately controlled.

In the first embodiment, the stiffness of the case14of the battery pack12is higher than that of the outer wall18of the cooler16. Thus, concentration of the load in the pressurization process and shortage of the adhesive strength can be prevented. Namely, while the case14is designed to have flat surfaces, the surface of the case14may be slightly distorted (e.g., warped) as shown inFIG.9. In this case, the outer wall18of the cooler16elastically deforms in accordance with the shape of the case14as shown inFIG.9in the pressurization process, since the stiffness of the outer wall18of the cooler16is lower than that of the case14. Thus, even in the case where the surface of the case14is distorted, high load can be prevented from being locally applied to a part of the case14and a part of the outer wall18. When the adhesive20is cured under this condition, the outer wall18is fixed in a deflected state to the case14because the adhesive strength of the adhesive20is stronger than the force with which the outer wall18tries to return to its original shape. Thus, the outer wall18is fixed in the shape that conforms to distortion of the case14, so that the cooler16can be fixed to the case14with high strength.

In the first embodiment, the ceramic powder is dispersed within the adhesive20; therefore, the adhesive20has a high thermal conductivity. Accordingly, the battery pack12can be efficiently cooled by the cooler16.

In the first embodiment, a value of the load N1during the rapid increase period T2is set as the threshold value Nth, and the rapid increase period T2is detected by checking whether the detection value of the load sensor40reaches the threshold value Nth. However, the rapid increase period T2may be detected by another method. For example, the rate of increase of the load N1may be calculated from the detection value of the load sensor40, and the rapid increase period T2may be detected based on the rate of increase of the load N1.

Second Embodiment

Next, a manufacturing method of a second embodiment will be described. In the manufacturing method of the second embodiment, too, the adhesive application process and the component placement process are performed in the same manner as in the first embodiment. In the second embodiment, the pressurization process is performed by using a pressurizer30ashown inFIG.10. The pressurizer30aofFIG.10has a compression speed sensor44in place of the load sensor40. The other configuration of the pressurizer30aofFIG.10is identical with that of the pressurizer30ofFIG.4. The compression speed sensor44detects the compression speed V1of the adhesive20in the pressurization process. The compression speed V1is equal to the rate of reduction dt1/dt of the thickness t1of the adhesive20. In the pressurization process of the second embodiment, the pressurizer30compresses the adhesive20in such a manner that the compression speed V1can be changed. For example, the pressurizer30compresses the adhesive20at a constant work rate or at a constant load. Thus, during the pressurization process, the compression speed V1changes.

FIG.11shows changes in the compression speed V1during the compression process of the second embodiment. As shown inFIG.11, the compression speed V1at the start of the pressurization process is high. As the thickness t1of the adhesive20a,20bdecreases, the width W1expands, and the load required to expand the W1increases. Thus, immediately after the start of the pressurization process, the compression speed V1decreases slowly in a curved line as the thickness t1of the adhesive20decreases. Then, when the adhesive20aand the adhesive20bcontact with each other, the adhesives20a,20bstop flowing in the x direction at the contact position. Thus, after that, the load required to expand the width W2of the adhesive20rapidly increases. As a result, the compression speed V1rapidly drops from the bending point P2as shown inFIG.11. In particular, the adhesive20has the thixotropic properties; therefore, the compression speed V1drops extremely steeply from the bending point P2. In the following description, the period in which the compression speed V1decreases slowly in a curved line will be referred to as “curvilinear decrease period T3”, and the period in which the compression speed V1decreases rapidly will be referred to as “rapid decrease period T4”. In the rapid decrease period T4, the compression speed V1decreases in a polygonal line with respect to the trajectory of the compression speed V1in the curvilinear decrease period T3.

During the pressurization process, the controller42of the pressurizer30monitors the detection value of the compression speed sensor44. When the detection value of the compression speed sensor44decreases to a threshold value Vth shown inFIG.11, the controller42stops pressurization by the pressurizer30. The threshold value Vth is set to a value of the compression speed V1during the rapid decrease period T4. Namely, the threshold value Vth is set to a lower value than the compression speed V1at the bending point P2. Thus, at the time when the controller42stops pressurization (namely, at the time when the compression speed V1decreases to the threshold value Vth), the adhesive20aand the adhesive20bare in contact with each other. Thus, it is possible to surely make the adhesive20aand the adhesive20bin contact with each other, by stopping the pressurization after the time of transition from the curvilinear decrease period T3to the rapid decrease period T4. Then, the adhesive20is cured so that the case14is bonded to the cooler16. In this manner, the module of the battery pack12and the cooler16is completed.

As described above, in the manufacturing method of the second embodiment, too, the adhesive20aand the adhesive20bcan be surely brought into contact with each other. In the second embodiment, a value of the compression speed V1during the rapid decrease period T4is set as the threshold value Vth, and the rapid decrease period T4is detected by checking whether the detection value of the compression speed sensor44is reduced to the threshold value Vth. However, the rapid decrease period T4may be detected by another method. For example, the rate of reduction dV1/dt of the compression speed V1may be calculated from the detection value of the compression speed sensor44, and the rapid decrease period T4may be detected based on the rate of reduction dV1/dt.

In the first and second embodiments, the adhesive20is applied to the two application areas21a,21b. However, the adhesive20may be distributed and applied to three or more application areas.FIG.12shows the value of the load N1required to expand the adhesive20using the pressurizer over the same range as that of the first and second embodiments. InFIG.12, the results of measurement of the required load N1while the number “n” of the application areas is changed are indicated. As shown inFIG.12, the required load N1can be reduced as the number “n” of the application areas increases. When the number of the application areas is larger than two, the distance L1and diameter R of the adhesives20when applied can be set to satisfy the relationships that L1=W2t/n, and R=((4×W2t×t1t)/(n×π))1/2, and the thickness t1and width W2of the adhesive20after compression can be accurately controlled to the design values.

While the embodiments have been described in detail, these embodiments are merely exemplary, and do not limit the appended claims. The technologies described in the claims include those obtained by modifying or changing the illustrated specific examples in various ways. The technical elements described in the specification or drawings exhibit the technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims as filed. The technologies illustrated in the specification or drawings achieve two or more objects at the same time, and have the technical usefulness if they achieve one of the objects.