Battery case for electric vehicle

A battery case for containing therein battery modules includes a tray member, cover member, and seal member. The seal member is applied to a joint part between the tray member and cover member. Insert members made of metal are embedded in the resin of the tray member. Each of the insert members is provided with an embedded bolt a threaded part of which protrudes upward, and embedded nuts. The battery case is provided with first fastening sections and second fastening sections. In the first fastening section, a nut member is screwed onto the embedded bolt from above the cover member. In the second fastening section, a bolt member is screwed into the embedded nut from above the cover members.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery case for containing battery modules of an electric vehicle which runs by means of a motor using a battery as a power source.

2. Description of the Related Art

A battery unit used for an electric vehicle includes battery modules and a battery case for containing the battery modules. An example of the battery case includes a tray member for supporting the battery modules, and a cover member for covering an upper part of the tray member.

In, for example, Jpn. Pat. Appln. KOKAI Publication No. 8-186390, a tray member and cover member are disclosed. A joint part between a peripheral edge part of the tray member and peripheral edge part of the cover member is fastened by a plurality of bolts and nuts. These bolts are inserted into bolt inserting holes formed in the peripheral edge part of the cover member from above the cover member. Further, these bolts are screwed into the nuts arranged on the underside of the peripheral edge part of the tray member.

In a battery unit requiring a high degree of waterproof property such as a lithium ion battery, the joint part between the peripheral edge part of the tray member and the peripheral edge part of the cover member is provided with a waterproof seal member. Water is prevented from entering inside from the joint part by the seal member. The seal member is, for example, a resin-based seal member having fluidity, and hardens after being applied to the joint part.

In the case where the nuts are embedded in the tray member, when the liquid seal member is applied to the joint part of the tray member, part of the seal member enters the threaded part of the nut of the tray member in some cases. When the seal member enters the threaded part and hardens, there is the possibility of the tightening torque of the bolt screwed into the nut becoming unstable. In the battery case requiring a high degree of waterproof property, it is necessary to carry out torque control of bolts for fastening the tray member and cover member to each other. However, if the seal member enters the threaded part of the nut as described above, the tightening torque of the bolt is affected by the seal member, and thus accurate torque control cannot be expected.

It has been conceivable, in order to prevent the seal member from entering the threaded parts of the nuts, that embedded bolts are provided on the tray member side, and the nuts are screwed onto the bolts from above the cover member. However, in order to provide the tray member with a plurality of embedded bolts, it is necessary to attach a plurality of embedded bolts to an insert member at predetermined positions by welding or the like. Further, it is necessary to form holes into which the embedded bolts are to be inserted inside a mold die for molding the tray member.

There is naturally a limit to manufacturing an insert member of sheet metal with a high degree of accuracy. Thus, when a plurality of embedded bolts are fixed to one insert member, relative positions of the embedded bolts are somewhat deviated from ideal positions in whatever way in some cases. In the die for molding the tray member, a plurality of holes into which the plurality of embedded bolts are to be inserted are formed. Thus, if the positions of the embedded bolts are deviated even a little, it becomes difficult to insert the embedded bolts into the holes formed at predetermined positions of the die.

SUMMARY OF THE INVENTION

The present invention provides a battery case that makes it possible to prevent a seal member to be provided at a joint part between a tray member and a cover member from adversely affecting the torque control of the threaded part, and makes it easy to set an insert member in a die for molding the tray member.

The present invention is a battery case for an electric vehicle for containing therein battery modules and comprises a tray member for supporting the battery modules, and a cover member to be put on top of the tray member, and fixed to the tray member. The tray member includes a resin section constituted of a peripheral wall and bottom wall formed of a resin, an insert structure including at least one insert member embedded in the peripheral wall, and a seal member applied to a joint part between the tray member and cover member. Further, the insert member includes an embedded bolt arranged in the peripheral wall in such a manner that a threaded part thereof protrudes from the joint part of the tray member, and embedded nuts arranged in the peripheral wall at positions different from the embedded bolt. The battery case further comprises first fastening sections each of which is formed by screwing a nut member onto the embedded bolt, and fastening the nut member in a state where the cover member is put on top of the tray member, and second fastening sections each of which is formed by screwing a bolt member into the embedded nut, and fastening the bolt member in the state where the cover member is put on top of the tray member.

That is, the first fastening section is constituted of the embedded bolt, and the nut member thread-engaged with the embedded bolt. The second fastening section is constituted of the embedded nut and the bolt member thread-engaged with the embedded nut.

According to the present invention, it is possible to prevent the seal member applied to the joint part between the tray member and cover member from adhering to the threaded part of the embedded bolt. Accordingly, it is possible to accurately carry out torque control of the nut member with respect to the threaded part of the embedded bolt. Further, it is possible to fix the peripheral edge part of the cover member to the tray member by means of the embedded bolt, nut member, embedded nut, and bolt member.

In one aspect of the present invention, the seal member to be applied to the joint part between the tray member and cover member is applied to a peripheral edge part of the joint part. According to this aspect, it is possible to prevent the seal member from adhering to the embedded bolt and embedded nut provided in the tray member. As a result of this, it is possible to accurately carry out torque control of the nut member to be thread-engaged with the embedded bolt, and torque control of the bolt member to be thread-engaged with embedded nut.

In another aspect of the present invention, a first collar made of metal is arranged in a hole of a peripheral edge part of the cover member into which the embedded bolt is inserted, the first collar is interposed between the insert member and the nut member, a second collar is arranged in a hole of the peripheral edge part of the cover member into which the bolt member is inserted, and the second collar is interposed between the insert member and a head section of the bolt member. By being provided with such collars, even when the resin section fastened by the embedded bolt and nut member, and the resin section fastened by the embedded nut and bolt member deteriorate with time, the fastening torque of the bolt member or nut member never lowers.

The battery case for an electric vehicle according to a preferred aspect of the present invention, further comprises beam members arranged on the undersurface side of the tray member, and extending in the width direction of the vehicle body, embedded horizontal nuts fixed to the insert members, and extending in the horizontal direction, and bolts to be screwed into the embedded horizontal nuts, for fixing the tray member to the beam members, wherein both end parts of the beam members are fixed to a pair of side members of the vehicle body from the undersurface side of the vehicle body by means of bolts.

In another preferred aspect of the present invention, each of the insert members is provided with only one embedded bolt. According to this aspect, a hole (hole into which the embedded bolt is to be inserted) to be provided in the die for molding the tray member has only to be provided at only one position for each of the insert members. As a result of this, when the insert members are set in the die, it is easily possible to insert the embedded bolts into the holes of the die. Further, it is possible to insert the embedded bolts into the holes of the die even when the positions of the embedded bolts fixed to the insert members somewhat vary.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows an example of an electric vehicle10. This electric vehicle10is provided with a motor12for traveling, and charging equipment13which are arranged at the rear part of the vehicle body11, a battery unit14arranged under the floor of the vehicle body11, and the like. A heat exchanger unit15for air-conditioning is arranged at the front part of the vehicle body11.

The front wheels20of the vehicle10are supported by the vehicle body11by means of front suspensions (not shown). The rear wheels21are supported by the vehicle body11by means of rear suspensions (not shown). An example of the rear suspension is a trailing arm type rear suspension.

FIG. 2shows a frame structure30constituting a lower skeletal structure of the vehicle body11, and the battery unit14to be attached to the frame structure30.

The frame structure30includes a pair of right and left side members31and32extending in the back-and-forth direction of the vehicle body11, and cross members33,34, and35extending in the width direction of the vehicle body11. The cross members33,34, and35are fixed to predetermined positions of the side members31and32by welding.

Suspension arm support brackets40and41are provided at the rear parts of the side members31and32. Each of the suspension arm support brackets40and41is fixed to a predetermined position of each of the side members31and32by welding. Each of the suspension arm support brackets40and41is provided with an axis section42. Front end parts of the trailing arms are attached to these axis sections42.

As shown inFIG. 3, the battery unit14is provided with a battery case50. The battery case50includes a tray member51positioned on the lower side, and a cover member52positioned on the upper side.

The tray member51is constituted of a resin section53integrally formed of a resin having electrical insulating properties, and insert structure200(shown inFIGS. 6 and 7) to be described later. The resin which is a material of the resin section53is a resin obtained by reinforcing a base material constituted of, for example, polypropylene with short glass fibers having a length of about several mm to several cm.

The tray member51includes a front wall51a, rear wall51b, a pair of right and left side walls51cand51d, bottom wall51e, and partition walls51fand51g. The tray member51is formed into a box-like shape opened at its top surface. The front wall51ais positioned on the front side with respect to the back-and-forth direction of the vehicle body11. The rear wall51bis positioned on the rear side. The partition walls51and51gextend in the back-and-forth direction. The peripheral wall54of the tray member51is constituted of the front wall51a, rear wall51b, and both side walls51cand51d. This tray member51is formed by stamping forming to be described later. An insert structure200is embedded in the resin section53at a predetermined position.

A front battery containing section55is formed at the front half part of the battery case50. A rear battery containing section56is formed at the rear half part of the battery case50. A center battery containing section57, an electric circuit containing section58, and the like are formed between the front battery containing section55and rear battery containing section56.

A battery module60(only part thereof is shown by two-dot chain lines inFIG. 3) is contained in each of the battery containing sections55,56, and57. The battery module60is supported by the bottom wall51eof the tray member51. An example of the battery module60is formed by connecting, in series, a plurality of cells each of which is constituted of a lithium ion battery.

Electric components61(part of them are schematically shown inFIGS. 3 and 6) and the like are contained in the electric circuit containing section58. The electric components61have a function of managing a monitor for detecting a state of the battery module60, and control and the like. The electric components61are electrically connected to the battery modules60.

As shown inFIG. 4, the battery unit14is arranged on the undersurface side of a floor panel70. The floor panel70extends in the back-and-forth direction and width direction of the vehicle body11. The floor part of the vehicle body11is constituted of the floor panel70. The floor panel70is fixed to predetermined positions of the frame structure30including the side members31and32by welding.

Front seats71(shown inFIG. 1) and rear seats72are arranged above the floor panel70. The front battery containing section55of the battery unit14is arranged below the front seats71. The rear battery containing section56of the battery unit14is arranged below the rear seats72. The floor panel70includes a concave portion70a. The concave portion70aof the floor panel70is formed between the front battery containing section55and rear battery containing section56. This concave portion70ais positioned in the vicinity of the feet of the occupants seated on the rear seats72.

A cover fitting surface80(shown inFIGS. 3 and 7) is formed at a peripheral edge part of the tray member51. The cover fitting surface80is continuous over the whole circumference of the tray member51. A waterproof seal member81is provided at a peripheral edge part of a joint part82between the tray member51and cover member52. This seal member81is a resin-based liquid seal member, and hardens after being applied to the cover fitting surface80. The seal member81is applied to only the peripheral edge part of the joint part82, and hence it is possible to prevent the seal member81from adhering to the embedded bolt204and embedded nut205to be described later.

As shown inFIG. 6, the insert structure200includes three insert members200a,200b, and200carranged at the front half part of the tray member51, and three insert members200d,200e, and200farranged at the rear half part of the tray member51. These insert members200ato200fare sheet metal (for example, steel sheet) stampings.

The insert members200a,200b, and200con the front side are embedded in the front wall51a, and both the side walls51cand51dof the tray member51, respectively. The front wall51a, and both the side walls51cand51dof the tray member51are reinforced by these insert members200a,200b, and200c. The rear wall51band both the side walls51cand51dof the tray member51are reinforced by the insert members200d,200e, and200fembedded in the rear half part of the tray member51.

A pair of right and left reinforcement plates201is provided at both ends of the insert member200apositioned at the front-center of the tray member51. The reinforcement plates201are embedded in the partition walls51fof the tray member51. As shown inFIG. 7, the front end201aof the reinforcement plate201is attached to the insert member200a. The rear end201bof the reinforcement plate201extends toward the rear side of the vehicle body11.

In order to enhance the anchorage strength of the reinforcement plate with respect to the resin section53, a plurality of holes202are formed in the reinforcement plate201. The holes202penetrate the reinforcement plate201in the thickness direction. Part of the resin of the resin section53enters the holes202, and hardens. As a result of this, it is possible to enhance the anchorage strength of the reinforcement plate201with respect to the resin section53.

The bottom wall51e, partition walls51fand51g, and peripheral wall54of the tray member51are integrally formed by pressurizing the material of the resin section53by using the die (lower die260and upper die261) schematically shown inFIG. 12. A cavity265is formed between the lower die260and upper die261. The insert structure200is set inside the cavity265along the lower die260. A plurality of holes266are formed in the lower die260. Threaded parts204aof the embedded bolts204to be described later are inserted into the holes266.

As shown inFIG. 6, each of the insert members200ato200fis provided with embedded horizontal nuts203extending in the horizontal direction, an embedded bolt204protruding upward, and embedded nuts205in the vertical direction. A first fastening section310(shown inFIGS. 7 to 10) is constituted of the embedded bolt204, and a nut member97.

The embedded bolt204is fixed to an upper wall311of the insert structure200in such a manner that the threaded part204athereof protrude upward from the cover fitting surface80. The cover fitting surface80is formed at the joint part82between the tray member51and cover member52, and extends in the horizontal direction.

A second fastening section320(shown inFIGS. 7,8, and11) is constituted of the embedded nut205and a bolt member96. The embedded nut205is fixed in the upper wall311of the insert structure200in a state where the nut205is embedded inside with respect to the joint part82of the tray member51. The embedded bolt204and embedded nut205described above are each provided on the insert members200ato200f. Furthermore, the embedded bolt204and embedded nut205are provided at positions separate from each other in the horizontal direction.

The cover member52is constituted of an integrally molded product of a synthetic resin reinforced by fibers. An opening85for service plug and cooling air introduction opening86are formed at a front part of the cover member52. A bellows-like boot87is attached to the opening85for service plug. A bellows-like boot88is also attached to the cooling air introduction opening86. A bypass flow path90for causing part of the cooling air to flow therethrough, cooling fan containing section91, and the like are provided on the top surface of the cover member52.

A flange portion95is formed at a peripheral edge part of the cover member52. The flange portion95is continuous over the whole circumference of the cover member52. As shown inFIGS. 9 and 10, in the flange portion95, a first collar330made of metal is fitted in a hole into which the embedded bolt204is inserted. The collar330is interposed between the upper wall311of the insert structure200and the nut member97when the nut member97is screwed onto the embedded bolt204. A washer332made of sheet metal is arranged on the top surface of the flange portion95.

As shown inFIG. 11, in the flange portion95, a second collar331made of metal is fitted in a hole into which the bolt member96is inserted. The collar331is interposed between the upper wall311of the insert structure200and a head section96aof the bolt member96when the bolt member96is screwed into the embedded nut205. The tray member51and cover member52are fastened to each other through the collars330and331made of metal. As a result of this, even when the resin section of the fastening section deteriorates with time, the fastening torque never lowers.

When the tray member51and cover member52are fastened to each other, the seal member81is applied to the cover fitting surface80of the tray member51. That is, the liquid seal member81is applied to the peripheral edge part of the joint part82between the tray member51and cover member52. The threaded part204a(shown inFIG. 9) of the embedded bolt204protrudes upward from the cover fitting surface80. Thus, it is possible to prevent the seal member81from adhering to the threaded part204a. After the seal member81has hardened to a certain degree, the cover member52is placed on the tray member51. After that, the flange portion95of the cover member52is put on top of the cover fitting surface80of the tray member51.

At the first fastening section310, the nut member97is screwed onto the embedded bolt204from above the cover member52. The nut member97is fastened at predetermined torque. No seal member81adheres to the threaded part204aof the embedded bolt204, and hence it is possible to accurately carry out the fastening torque control of the nut member97. On the other hand, at the second fastening section320, the bolt member96is screwed into the embedded nut205from above the cover member52, and is fastened. In this way, the tray member51and cover member52are fastened to each other through the seal member81in a watertight manner.

As shown inFIGS. 9 to 11, an insulating member340having electrical insulating properties is provided on the inner surface side of the tray member51at a part at which the insert structure200is exposed. An example of the insulating member340is an insulating tape. It should be noted that the entire insert structure200may be embedded in the resin section53having the electrical insulating properties. In this case, the insulating member340can be omitted.

A plurality of (for example, four) beam members101,102,103, and104are provided on the undersurface side of the tray member51. As shown inFIGS. 3 and 5, the beam members101,102,103, and104respectively include beam bodies111,112,113, and114extending in the width direction of the vehicle body11. The beam members101,102,103, and104are constituted of a metallic material (for example a steel sheet). These beam members are each provided with strength sufficient to support the weight of the battery unit14.

The first beam body111from the front is provided with joining portions121and122at both ends thereof. The second beam body112from the front is provided with joining portions123and124at both ends thereof. The third beam body113from the front is provided with joining portions125and126at both ends thereof. The fourth (rearmost) beam body114from the front is provided with joining portions127and128at both ends thereof. A pair of right and left front support members130and131is provided at a front end part of the battery unit14.

A bolt inserting hole143(shown inFIGS. 2 and 3) is formed in each of the joining portions121and122provided at both the ends of the first beam member101from the front. The bolt inserting hole143penetrates the joining portion121or122in the vertical direction. The side members31and32are provided with battery unit fitting portions145and146at positions opposed to the joining portions121and122. The battery unit fitting portions145and146are provided with nut members. A bolt147(shown inFIGS. 2 and 4) is inserted into the bolt inserting hole143from below the joining portion121or122. The bolt147is screwed into the nut member of the battery unit fitting portion145or146to be fastened. As a result of this, the joining portions121and122of the first beam member101are fixed to the side members31and32.

InFIGS. 8 to 10, the joining portion121of the beam member101is shown. Bolts350extending in the horizontal direction are screwed into the embedded horizontal nuts203, whereby the beam member101is fixed to the tray member51. The embedded horizontal nut203is fixed to a vertical wall312of the insert structure200. As described previously, the embedded bolt204is fixed to the upper wall311of the insert structure200. The cover member52is fixed to the tray member51through the collar330made of metal and washer332. The joining portion121of the beam member101is fixed to the side member31by means of the bolt147.

That is, the tray member51and cover member52are fixed to the side member31through the collars330and331made of metal, bolt member96and nut member97made of metal, insert structure200made of metal, embedded nut203and embedded bolt204made of metal, and beam member101made of metal. Accordingly, the anchorage strength of the battery case50is high with respect to the vehicle body11, and the cover member52hardly loosens during the running of the vehicle. Further, it is possible to maintain the waterproofness of the battery case50. The same is true of the joining portions122to128other than the joining portion121.

A bolt inserting hole153(shown inFIGS. 2 and 3) is formed in each of the joining portions123and124provided at both the ends of the second beam member102from the front. The bolt inserting hole153penetrates the joining portion123or124in the vertical direction. The side members31and32are provided with battery unit fitting portions155and156at positions opposed to the joining portions123and124. The battery unit fitting portions155and156are provided with nut members. A bolt157(shown inFIGS. 2 and 4) is inserted into the bolt inserting hole153from below the joining portion123or124. The bolt157is screwed into the nut member of the battery unit fitting portion155or156to be fastened. As a result of this, the joining portions123and124of the second beam member102are fixed to the side members31and32.

A bolt inserting hole163(shown inFIGS. 2 and 3) is formed in each of the joining portions125and126provided at both the ends of the third beam member103from the front. The bolt inserting hole163penetrates the joining portion125or126in the vertical direction. As shown inFIGS. 4 and 5, load transmission members170and171are fixed to the side members31and32by means of bolts172. The load transmission members170and171are provided above the joining portions125and126of the third beam member103from the front. The one load transmission member170is welded to one suspension arm support bracket40. The other load transmission member171is welded to the other suspension arm support bracket41.

That is, the load transmission members170and171are joined to the side members31and32, and suspension arm support brackets40and41. These load transmission members170and171constitute part of the frame structure30. The load transmission members170and171are provided with battery unit fitting portions175and176including nut members.

A bolt177is inserted into the bolt inserting hole163from below the joining portion125or126. The bolt177is screwed into the nut member of the battery unit fitting portion175or176to be fastened. As a result of this, the joining portions125and126of the third beam member103are fixed to the side members31and32through the load transmission members170and171.

A bolt inserting hole193(shown inFIGS. 2 and 3) is formed in each of the joining portions127and128of the fourth beam member104from the front. The bolt inserting hole153penetrates the joining portion127or128in the vertical direction. The side members31and32are provided with extension brackets194and195at positions opposed to the joining portions127and128. The extension brackets194and195extend to positions beneath kick-up frame portions31band32bof the side members31and32. The extension brackets194and195constitute part of the frame structure30. These extension brackets194and195are provided with battery unit fitting portions196and197including nut members.

A bolt198(shown inFIGS. 2 and 4) is inserted into the bolt inserting hole193from below the joining portion127or128. The bolt198is screwed into the nut member of the battery unit fitting portion196or197to be fastened. As a result of this, the joining portions127and128of the fourth beam member104are fixed to the side members31and32through the extension brackets194and195.

As shown inFIG. 4, undersurfaces of the beam members101,102,103, and104are positioned on the same plane L extending in the horizontal direction along the flat undersurface of the tray member51. The first and second beam members101and102are directly fixed to the battery unit fitting portions145,146,155, and156provided at the horizontal portions31aand32aof the side members31and32.

The third and fourth beam members103and104are fixed to the battery unit fitting portions175,176,196, and197provided beneath the kick-up frame portions31band32bof the side members31and32. That is, the third and fourth beam members103and104are located at positions downwardly offset from the kick-up frame portions31band32b. Accordingly, the third beam member103is fixed to the battery unit fitting portions175and176through the load transmission members170and171each of which has a certain thickness in the vertical direction. The fourth beam member104is fixed to the battery unit fitting portions196and197by means of the extension brackets194and195extending to the positions beneath the kick-up frame portions31band32b.

The front support members130and131which are located at the front end of the battery unit14protrude forward from the first beam member101from the front. The front support members130and131are joined to the beam member101. As shown inFIG. 2, joining portions210and211provided to the front support members130and131are fixed to the battery unit fitting portions213and214of the cross member33by means of bolts212.

As described above, the beam members101,102,103, and104of the electric vehicle of this embodiment are provided between the right and left side members31and32. The side members31and32are joined to each other by the beam members101,102,103, and104. Thus, the beam members101,102,103, and104of the battery unit14can function as rigid members corresponding to the cross members.

Further, the load transmission members170and171are fixed to the suspension arm support brackets40and41. The load in the transverse direction input to the suspension arm support brackets40and41is input to the beam member103through the load transmission members170and171.

It is possible to enhance the rigidity of the parts around the suspension arm support brackets40and41by the beam member103even when a cross member is not arranged near the suspension arm support brackets40and41. Accordingly, the steering stability and ride quality of the electric vehicle10are improved. In other words, it is possible to arrange part of the large-sized battery unit14in a space between the pair of right and left suspension arm support brackets40and41. As a result of this, it becomes possible to mount the large-sized battery unit14on the electric vehicle, and prolong the travel distance of the electric vehicle.

As shown inFIGS. 1,4, and5, an under cover400is arranged under the battery unit14. A top surface of the under cover400is opposed to the undersurfaces of the beam members101,102,103, and104. An example of a material of the under cover400is a synthetic resin reinforced with glass fibers. The under cover400is fixed to at least part of the frame structure30and beam members101,102,103, and104from below the vehicle body11by means of bolts (not shown).

An overall length of the under cover400is larger than that of the battery unit14. That is, the under cover400has a length sufficient to cover from the front end50ato the rear end50bof the battery case50. A width of the under cover400is larger than that of the battery unit14.

As described previously, the battery case50of this embodiment includes the tray member51for supporting the battery modules60, cover member52put on top of the tray member51, and seal member81provided to the joint part82between the tray member51and cover member52. The tray member51includes the resin section53, and the plurality of insert members200ato200fembedded in the resin section53.

Further, each of the insert members200ato200fis provided with the embedded bolt204shown inFIG. 9, and embedded nut205shown inFIG. 11. The threaded part204aof the embedded bolt204protrudes from the top surface of the joint part82of the tray member51. The embedded nut205is embedded in the joint part82of the tray member51at a position different from the embedded bolt204.

The battery case50of this embodiment includes the first fastening section310(shown inFIGS. 9 and 10), and second fastening section320(shown inFIG. 11). At the first fastening section310, the nut member97is screwed onto the embedded bolt204from above the cover member52, and is fastened in a state where the cover member52is put on top of the tray member51. At the second fastening section320, the bolt member96is screwed into the embedded nut205from above the cover member52, and is fastened.

According to the battery case50configured as described above, it is possible to prevent the liquid seal member81applied to the joint part82between the tray member51and cover member52from adhering to the threaded part204a(shown inFIG. 9) of the embedded bolt204. This makes it possible to accurately carry out the fastening torque control of the nut member97to be screwed onto the embedded bolt204, and accurately carry out the control of the waterproofness of the joint part82. Further, it is possible to securely fasten the entire circumference of the cover member52by the plurality of first fastening sections310and the plurality of second fastening sections320.

Furthermore, the insert structure200includes the plurality of insert members200ato200fmade of sheet metal, and each of the insert members200ato200fis provided with one embedded bolt204and a plurality of embedded nuts205.

That is, each of the insert members200ato200fis provided with only one embedded bolt204. Accordingly, the hole266to be provided in the lower die260(partly shown inFIG. 12) has only to be provided at only one position for each of the insert members200ato200f. The threaded part204aof the embedded bolt204is inserted into this hole266. As a result of this, it becomes easy to set the insert members200ato200fin the lower die260, and the structure of the lower die260is simplified.

As shown inFIGS. 9 and 10, the flange portion95of the cover member52is provided with the first collars330made of metal. The flange portion95is prevented, by the collars330, from being crushed in a state where the nut members97are fastened to the bolts204. As a result of this, the predetermined fastening torque can be maintained. As shown inFIG. 11, the flange portion95of the cover member52is provided with the second collars331made of metal. The flange portion95is prevented, by the collars331, from being crushed in a state where the bolt members96are fastened to the nuts205. As a result of this, it is possible to prevent the waterproofness of the joint part82between the tray member51and cover member52from being lowered.

It should be noted that in the above embodiment, an electric vehicle in which a motor for running is mounted on the rear part of the vehicle body has been described. However, the present invention can also be applied to an electric vehicle in which a motor for running is mounted on the front part of the vehicle body. Further, as for the insert members to be embedded in the tray member, it is sufficient if at least one insert member is provided. Further, in carrying out the present invention, it goes without saying that the structures and arrangements of the constituent elements of the present invention such as the motor, tray member, cover member, insert member, embedded bolt, embedded nut, and the like can be appropriately modified and implemented.