Battery pack

A battery pack has a battery unit and a battery case. The battery case includes side frames and an upper frame. The upper frame includes an upper surface portion and a trailing portion that extends downward from an end portion of the upper surface portion. Each of the side frames includes a side surface portion, an intermediate portion that extends from an upper end of the side surface portion inward in the width direction so as to pass below the upper surface portion and faces the upper surface portion in an up-down direction, and a contact portion that extends upward from an end portion of the intermediate portion and is brought into contact with the upper surface portion. The trailing portion includes one or more access openings that are accessible to a space between the upper surface portion and the intermediate portion facing each other in the up-down direction.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-222638 filed on Nov. 15, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a battery pack which has a battery unit and a battery case that houses the battery unit, and is mounted in a vehicle.

2. Description of Related Art

In an electrically powered vehicle, for example, a hybrid vehicle or an electric vehicle, a battery pack that supplies electric power to a motor for traveling is mounted. Such a battery pack has a configuration in which a battery unit with a plurality of single cells, a voltage sensor, and the like combined in a unit is housed in a battery case. The battery pack is assembled outside the vehicle, transported to a designated location of the vehicle, and mounted. When no holding portion or handle is provided in the battery pack, in a case of transporting the battery pack, the battery pack has to be lifted up from the bottom, and transportability is bad.

SUMMARY

Japanese Unexamined Patent Application Publication No. 2014-013661 (JP 2014-013661 A) discloses that a handle projecting outward is provided on a side surface of a case of a battery pack. A worker holds the handle and transports the case. However, in a case where the handle projecting outward from the side surface of the case is provided as disclosed in JP 2014-013661 A, the entire battery pack increases in size. In the vehicle, since a mounting space is limited, an increase in size of the in-vehicle battery pack causes a serious problem.

The handle disclosed in JP 2014-013661 A is merely used when the worker manually transports the single case before being assembled as the battery pack. In other words, in the related art, providing a holding portion for lifting up and transporting the entire assembled battery pack in the battery pack is not considered. As a result, in the battery pack of the related art, transportability is bad.

Accordingly, the present disclosure provides a battery pack that is easy to transport and suppresses an increase in size.

An aspect of the present disclosure relates to a battery pack that includes a battery unit and a battery case that houses the battery unit, and is configured to be mounted in a vehicle. The battery case includes side frames and an upper frame. The side frames and the upper frame are prepared separately from one another and are bonded together. The upper frame includes an upper surface portion that covers an upper surface of the battery unit and a trailing portion that extends downward from an end portion in a width direction of the upper surface portion. Each of the side frames includes a side surface portion that covers a side surface of the battery unit, an intermediate portion that extends from an upper end of the side surface portion inward in the width direction so as to pass below the upper surface portion and faces the upper surface portion in an up-down direction, and a contact portion that extends upward from an end portion of the intermediate portion and is brought into contact with the upper surface portion. The trailing portion includes one or more access openings that are accessible to a space between the upper surface portion and the intermediate portion facing each other in the up-down direction.

According to the aspect of the present disclosure, the access openings are included in the trailing portion of the upper frame, whereby it is possible to suspend and hold the battery pack by hooking a part of a handle or a transport device on the upper surface portion, and to improve transportability of the battery pack. Furthermore, since the access openings are merely included in the trailing portion, and a dedicated member that projects outward in the width direction is not provided in order to suspend and hold the battery pack, it is possible to suppress an increase in size of the battery pack. In addition, since the contact portion of each of the side frames is brought into contact with the upper surface portion of the upper frame, even if the access openings are formed in the upper frame, entrance of a foreign substance or water into the battery pack is prevented.

In the battery pack according to the aspect of the present disclosure, the access opening may be a notched portion that is notched from a lower end of the trailing portion to the middle of the upper surface portion.

According to the aspect of the present disclosure, the access openings extend to the middle of the upper surface portion, whereby a contact area of a holding hook of the transport device and the upper frame increases, making it possible to more stably transport the battery pack.

In the battery pack according to the aspect of the present disclosure, the upper frame may have a pair of trailing portions that extend downward from both ends in the width direction of the upper surface portion and face each other in the width direction, and the side frames may be disposed on both sides in a width direction of the battery unit. Each trailing portion may include two access openings.

According to the aspect of the present disclosure, four access openings in total with two access openings on each side in the width direction of the battery pack are included, whereby it is possible to distribute a holding position, and to more stably transport the battery pack.

In the battery pack according to the aspect of the present disclosure, a vicinity of a lower end of the trailing portion may be brought into contact with a vicinity of an upper end of the side surface portion. The upper surface portion of the upper frame and the contact portion of each of the side frames may be bonded to each other. The trailing portion of the upper frame and the side surface portion of each of the side frames may be bonded to each other.

According to the aspect of the present disclosure, the upper surface portion and the contact portion are bonded to each other, whereby it is possible to more reliably eliminate the gap between both portions, and to more reliably prevent entrance of water or a foreign substance from the gap between both portions into the battery pack. Furthermore, the trailing portion and the side surface portion are bonded to each other as well as the upper surface portion and the contact portion, whereby it is possible to distribute force applied to a bonded portion at the time of suspending and holding, and to more effectively prevent separation of the upper frame and the side frames.

In the battery pack according to the aspect of the present disclosure, a plate thickness of each of the side frames and a plate thickness of the upper frame may be different from each other.

According to the aspect of the present disclosure, the plate thicknesses of the side frames and the upper frame are changed depending on requested strength or the like, whereby it is possible to further reduce the materials for the side frames and the upper frame while maintaining needed strength. Consequently, it is possible to further reduce the weight and cost of the battery pack.

According to the aspect of the present disclosure, since the access openings are included in the trailing portion of the upper frame, it is possible to suspend and hold the battery pack by hooking a part of the handle or the transport device on the upper surface portion, and to improve transportability of the battery pack. Furthermore, since the access openings are merely included in the trailing portion, and a dedicated member projecting outward in the width direction is not provided in order to suspend and hold the battery pack, it is possible to suppress an increase in size of the battery pack. In addition, since the contact portion of each of the side frames is brought into contact with the upper surface portion of the upper frame, even if the access openings are included in the upper frame, entrance of a foreign substance or water into the battery pack is prevented.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, a battery pack10of an embodiment will be described referring to the drawings.FIG. 1is a schematic perspective view of the battery pack10, andFIG. 2is an exploded perspective view of the battery pack10.FIG. 3is a sectional view taken along line III-III ofFIG. 1, andFIG. 4is a sectional view taken along line IV-IV ofFIG. 1. InFIGS. 1 to 4, for ease of understanding, the dimension of each member is changed from the actual dimension, and the shape of each member is simplified compared to the actual shape.

The battery pack10is an in-vehicle battery pack that is mounted in an electrically powered vehicle, for example, a hybrid vehicle, an electric vehicle, or the like. The battery pack10includes a battery unit12, and a battery case that houses the battery unit12. InFIG. 1, both ends of the battery case in a depth direction (Y direction) are opened, and the openings are covered with a front cover and a back cover (both are not shown). A supply duct that supplies refrigerant to the battery unit12, an exhaust duct that discharges the refrigerant to the outside, and the like are connected to the front cover and the back cover.

The battery unit12stores electric power that is supplied to a motor for traveling, and has a plurality of single cells and accessories mechanically or electrically coupled in a unit. Each single cell is a rechargeable secondary battery, and is, for example, a lithium-ion battery, a nickel-hydrogen battery, or the like. The accessories include a bus bar or a harness that electrically connects the single cells, a coupling member that mechanically couples the single cells, sensors that detect a voltage, a temperature, and the like of each single cell, a relay that relays the single cells and external equipment, a resin frame or a holder that holds the single cells, and the like. The shape of the battery unit12constituted of the single cells and the accessories is not particularly limited, and in the embodiment, is substantially a rectangular parallelepiped shape elongated in the depth direction (Y direction).

The battery unit12is housed in the battery case. The battery case includes a lower case14in which the battery unit12is placed, an upper cover16that covers an upper end opening of the lower case14, and the front cover and the back cover that cover both ends in the depth direction (Y direction). The upper cover16includes an upper frame18and side frames20. The side frames20and the upper frame18are prepared separately from one another and are bonded together. The lower case14, the upper cover16, the front cover, and the back cover are all formed by sheeting and molding a metal plate made of, for example, a metal, such as aluminum.

The lower case14is a member in which the battery unit12is placed and an upper end thereof is opened. Specifically, the lower case14has a substantially U-shaped section with both ends in a width direction (X direction) rising in a stepwise manner. However, the stepwise rising portion formed at the first end in the width direction is lower than the stepwise rising portion formed at the second end in the width direction. Hereinafter, the first end in the width direction is referred to as a “front side”, and the second end in the width direction is referred to as a “back side”. The battery unit12is assembled inside the lower case14. The assembling work is performed in a state in which the front side of the lower case14faces the front and the back side thereof faces the back. In order to prevent the assembling work from being obstructed, the rising portion on the front side of the lower case14is lower than the rising portion on the back side.

As will be apparent fromFIG. 2, the rising portion on the front side has a first step surface22and a second step surface24. The rising portion on the back side has a first step surface22, and a backwall26that stands vertically from the step surface22. The battery unit12is placed on the first step surface22. Accordingly, as shown inFIGS. 3 and 4, a space23is formed between a lower end of the battery unit12and a bottom portion21of the lower case14. The space23functions as a flow passage through which a fluid, for example, refrigerant cooling the battery unit12, smoke exhaust discharged from the battery unit12, or the like flows. A part of the upper cover16described below overlaps the second step surface24formed on the front side and the backwall26formed on the back side. Then, the lower case14and the upper cover16are screwed and fastened in the overlapped state.

The upper cover16is a member that covers the upper end opening of the lower case14, and is constituted by bonding a pair of side frames20to one upper frame18. The upper frame18has a substantially U-shaped section including an upper surface portion30that covers an upper surface of the battery unit12, and a pair of trailing portions28that extend downward from both ends in a width direction of the upper surface portion30. Two access openings32are formed in each trailing portion28at an interval in the depth direction. In the embodiment, the access openings32are notched portions that are notched in a substantially rectangular shape from a lower end of the trailing portion28to the middle of the upper surface portion30.

Each of the side frames20includes a side surface portion34that covers the side surface of the battery unit12, an intermediate portion36that extends from an upper end of the side surface portion34inward in the width direction, and a contact portion38that extends upward from an end portion of the intermediate portion36. The upper end of the side surface portion34is higher than the lower end of the trailing portion28. In other words, the vicinity of the upper end of the side surface portion34overlaps the trailing portion28in an up-down direction. Then, in a case of attaching the upper cover16to the lower case14, an outer surface of the side surface portion34is brought into contact with an inner surface of the trailing portion28.

The lower end of the side surface portion34is screwed and fastened to the lower case14. Specifically, the lower end of the side surface portion34on the front side is bent outward in the width direction and overlaps the step surface24of the lower case14. The lower end of the side surface portion34on the back side extends to a height position overlapping the backwall26of the lower case14and overlaps outward in the width direction of the backwall26. The lower case14and the side frames20are screwed and fastened in the overlapped location.

The intermediate portion36extends from the upper end of the side surface portion34inward in the width direction so as to pass below the upper surface portion30and faces the upper surface portion30in the up-down direction. In other words, a space42is formed between the upper surface portion30and the intermediate portion36. The access openings32permit access to the space42from the outside. The intermediate portion36is brought into contact with an upper end surface of the battery unit12. In other words, the battery unit12is brought into a state of being sandwiched vertically between the step surface22of the lower case14and the intermediate portion36of the upper cover16.

The contact portion38that rises upward and is then bent inward in the width direction, and has a substantially L-shaped section extends from an inward end portion in the width direction of the intermediate portion36. The upper end of the contact portion38is brought into contact with the upper surface portion30.

The upper frame18and the side frames20are bonded to each other by welding and integrated. InFIGS. 3 and 4, a black ellipse indicates a welding location. As will be apparent fromFIGS. 3 and 4, in the embodiment, a contact portion of the upper surface portion30and the contact portion38, and a contact portion of the vicinity of the lower end of the trailing portion28and the side surface portion34are bonded to each other by welding.

In a case of assembling the battery pack10, the battery unit12is assembled inside the lower case14. In order to facilitate the assembling work of the battery unit12, the height on the front side of the lower case14is lower than the height on the back side. In a case where the battery unit12is assembled, subsequently, the upper cover16is attached to an upper side of the lower case14. Next, the front cover and the back cover are attached to the front side and the back side of the lower case14, and in a case where various ducts and the like are attached to the covers, the battery pack10is completed. In a case where the battery pack10is assembled, the battery pack10is transported to a desired position by the transport device. The transport device is provided with holding hooks100(seeFIG. 4). The transport device moves up the holding hooks100in a state of being engaged with the upper surface portion30with the holding hooks100inserted into the access openings32, thereby suspending and holding the battery pack10.

As will be apparent from the above description, in the embodiment, the upper cover16is constituted of the upper frame18and the side frames20that are bonded together, and the access openings32are provided in a part of the upper frame18. In other words, the upper end and both end portions in the width direction of the upper cover16are formed in a double structure in which there are spaces42between an outer surface and an inner surface, and the access openings32that are accessible from the outside are provided in the spaces42. A reason for such a configuration will be described in comparison with the related art.FIG. 7is a sectional view of a battery pack10of the related art.

As shown inFIG. 7, an upper cover16of the battery pack10of the related art is constituted of a single member having a substantially U-shaped section. No openings that can become holding portions are provided in the side surfaces of the upper cover16. For this reason, in a case of suspending and holding the battery pack10with the holding hooks100of the transport device, the holding hooks100need to be engaged with the bottom portion of the battery pack10and the bottom portion needs to be suspended and held. However, in a case where the bottom portion of the battery pack10is suspended and held, since the center of gravity of the battery pack10becomes higher than the holding portions, the posture of the battery pack10being transported is hardly stable, and transportability is bad.

JP 2014-013661 A discloses that handles110projecting outward are provided in the side surfaces of the battery case as shown inFIG. 8. In a case where such handles110are provided in the vicinity of the upper end of the battery case, since the center of gravity of the battery pack becomes higher than the holding portions (the portions of the handles110), stability is improved. However, as shown inFIG. 8, in a case where the handles110projecting outward are provided, the size of the entire battery pack increases. In the vehicle, since a mounting space is limited, an increase in size of the in-vehicle battery pack10causes a serious problem.

In the embodiment, in order to facilitate transport and to suppress an increase in size, a part of the upper cover16is formed in a double structure in which there are the spaces42between the inner surface and the outer surface, and the access openings32that are accessible to the spaces42are provided. In the above-described case, as shown inFIG. 4, it is possible to insert the holding hooks100into the spaces42through the access openings32, and consequently, to engage the holding hooks100with the upper surface portion30. In a case where the holding hooks100are engaged with the upper surface portion30, since the center of gravity of the battery pack10becomes lower than the holding portions, it is possible to stably transport the battery pack10. In particular, in the embodiment, the four access openings32in total with the two access openings in each of the trailing portions28facing each other are provided. As described above, in a case where the access openings32are distributed and provided at four locations, since the holding positions for holding the battery pack10are distributed evenly, it is possible to more stably transport the battery pack. The positions or the number of access openings32may be suitably changed according to the mass, shape, the position of the center of gravity, or the like of the battery pack10.

According to the embodiment, it is understood that the width of the upper cover16is substantially equal to the width of the lower case14, and the size is hardly increased compared to the related art (FIG. 7). As a result, it is possible to facilitate transport and to suppress an increase in size.

Since the upper cover16has a double structure, even if the access openings32are included in the trailing portions28, an internal space and an external space of the battery case do not communicate with each other. As a result, a foreign substance or water that enters the spaces42through the access openings32is prevented from reaching the inside of the battery case. With this, the battery unit12is appropriately protected. In particular, in the embodiment, as described above, since the contact portion38and the upper surface portion30are bonded to each other by welding, entrance of a foreign substance or the like from the gap between the contact portion38and the upper surface portion30into the pack is effectively prevented.

In a case where the holding hooks100are hooked on the upper surface portion30to suspend and hold the battery pack10, force F1is applied to the bonded portion of the upper surface portion30and the contact portion38in a direction of separating the upper surface portion30and the contact portion38from each other. In order to prevent bonding of the upper surface portion30and the contact portion38from being released by the force F1, in the embodiment, the trailing portion28and the side surface portion34are bonded to each other by welding. The trailing portion28and the side surface portion34are bonded to each other, part of the force F1that is applied to the upper surface portion30and the contact portion38is distributed to the bonded portion of the trailing portion28and the side surface portion34. With this, separation of the upper surface portion30and the contact portion38is effectively prevented. When the upper surface portion30and the contact portion38are firmly bonded to each other, bonding of the trailing portion28and the side surface portion34may be omitted.

In any cases, according to the embodiment, it is possible to improve transportability while suppressing an increase in size of the battery pack10. The above-described configuration is an example, and as long as the upper cover16includes the upper frame18and the side frames20that are connected together and the access openings32are included in a part of the upper frame18, other configurations may be suitably changed. For example, in the embodiment, while the plate thickness of the upper frame18and the plate thickness of each of the side frames20are equal to each other, the plate thickness of the upper frame18and the plate thickness of each of the side frames20may be different from each other. For example, there is a case where a withstanding load requested for the upper surface portion of the battery pack10is greater than a withstanding load requested for the side surface portion against treading or the like. In the above-described case, as shown inFIG. 5, the plate thickness of the upper frame18may be greater than the plate thickness of each of the side frames20. With such a configuration, it is possible to further reduce the materials for the entire battery case while securing the withstanding load of the upper surface portion of the battery pack10, compared to a case where the plate thickness of each of the side frames20and the plate thickness of the upper frame18are equal to each other. Consequently, it is possible to further reduce the weight or cost of the battery pack10.

The access openings32may be suitably changed as long as the access openings are formed in the trailing portions28and are of such a size that at least the holding hooks100can be inserted and detached. For example, as shown inFIG. 5, the access openings32may be of a size not reaching the upper surface portion30. However, in the above-described case, since the contact area of the holding hooks100and the upper frame18becomes small, it is desirable that the access openings32extend to the middle of the upper surface portion30. As shown inFIG. 6, the access openings32are not limited to notched portions, and may be through-holes formed in the trailing portions28.

As long as the spaces42can be formed between the intermediate portion36and the upper surface portion30, and the contact portion38can be brought into contact with the upper surface portion30, the shapes of the intermediate portion36and the contact portion38may be suitably changed. For example, as shown inFIG. 5, the intermediate portion36and the contact portion38may be inclined surfaces that extend from the upper end of the side surface portion34obliquely upward.