BATTERY PACK LOWER BOX BODY, BATTERY PACK, APPARATUS, AND ASSEMBLY METHOD OF BATTERY PACK LOWER BOX BODY

This application relates to the technical field of battery packs, and a battery pack lower box body, a battery pack, an apparatus, and an assembly method of battery pack lower box body are provided. The battery pack lower box body includes a box frame, a base plate, a stiffening beam, and a stiffener. The base plate is arranged at the bottom of the box frame; the stiffening beam is arranged inside a space enclosed by the box frame and on top of the base plate; and the stiffening beam is fixed to the box fame via the stiffener, and the stiffener is welded to the box frame to form a weld seam, where a length of the weld seam is kept greater than a sum of side lengths of a projection of the stiffening beam onto the box frame.

TECHNICAL FIELD

Embodiments of this application relate to the technical field of battery packs, and in particular, to a battery pack lower box body, a battery pack, an apparatus, and an assembly method of battery pack lower box body

BACKGROUND

In recent years, traction batter packs are increasingly in pursuit of light weight and high energy density. However, limitations of the structure of a vehicle body have led to a development trend toward maximizing grouping efficiency within limited installation space for battery packs. However, increasing the number of cells as much as possible in order to improve the grouping efficiency also has certain drawbacks, for example, less design space for other enhancement structures, challenging assurance of safety performance of the battery pack.

Therefore, a new type of battery pack lower box body, battery pack, apparatus, and assembly method of battery pack lower box body are urgently needed to solve the foregoing problem.

SUMMARY

Embodiments of this application provides a battery pack lower box body, a battery pack, an apparatus, and an assembly method of battery pack lower box body to reduce the risk of breakage of a weld seam formed between a stiffening beam and a box frame.

A first aspect of this application provides a battery pack lower box body, including:

a box frame;

a base plate arranged at the bottom of the box frame;

a stiffening beam arranged inside a space enclosed by the box frame and on top of the base plate; and

a stiffener, where the stiffening beam is fixed to the box frame via the stiffener, and the stiffener is welded to the box frame to form a weld seam: where

a length of the weld seam is kept greater than a sum of side lengths of a projection of the stiffening beam onto the box frame.

The battery pack lower box body is welded to the box frame via the stiffener, and the length of the weld seam formed by welding the two is kept greater than the sum of side lengths of the projection of the stiffening beam onto the box frame, increasing the length of the weld seam between the stiffening beam and the box frame, thus enhancing structural strength of the weld seam, and thereby reducing the risk of breakage of the weld seam formed between the stiffening beam and the box frame.

In some embodiments, the stiffening beam and the stiffener are an integral structure. Such design can reduce assembly steps.

In some embodiments, the stiffening beam and the stiffener are split structures, the stiffener is provided with a first insertion hole, and the stiffening beam is inserted into the first insertion hole. Such design can reduce manufacturing costs.

In some embodiments, the stiffener is further provided with a second insertion hole communicating with the first insertion hole, and the stiffening beam is provided with a threaded hole; and

a threaded member is provided inside the second insertion hole and the threaded hole, and the stiffening beam is fixed to the stiffener by the threaded member.

In some embodiments, along a width direction, two ends of the stiffening beam are provided with limiting faces, the stiffener has a first welding face welded to the box frame, and the limiting face abuts against the first welding face. In one aspect, providing the limiting face can ensure that the depth of insertion of the stiffening beam into the stiffener meets the requirements. To be specific, when the limiting face abuts against the first welding face, it means that the stiffening beam and the stiffener meet assembly requirements, and a next step of installation, for example, inserting the threaded member, can proceed. In another aspect, providing the limiting face can further ensure that the threaded hole is aligned with the second insertion hole in installation, thereby improving, installation efficiency.

In some embodiments, an area of the first welding face is larger than that of a projection of the stiffening beam onto the box frame. Such design can increase the area of the first welding face and thus increases the length of the weld seam.

In some embodiments, the box frame has a second welding face welded to the first welding face, and the first welding face is flush with the second welding face. Such design can ensure that the stiffener is reliably fixed to the box frame and the stiffener is welded to the box frame with ease.

In some embodiments, the box frame is provided with a slot formed by the second welding face recessed inwards, and the stiffener is accommodated in the slot. Such design allows the box frame to accommodate the stiffener.

A second aspect of this application provides a battery pack, including a battery module, a battery-pack upper box body and the foregoing battery pack lower box body, where the battery-pack upper box body is fixed to the battery pack lower box body, and the battery module is accommodated in the battery-pack upper box body and the battery pack lower box body.

A third aspect of this application provides an apparatus, including a driving source and the foregoing battery pack, where the driving source is configured to provide driving force for the apparatus, and the battery pack is configured to provide electrical energy for the driving source.

A fourth aspect of this application provides an assembly method of battery pack lower box body, including:

providing a box frame including a base plate;

arranging a stiffening beam inside a space enclosed by the box frame and on top of the base plate;

fixing the stiffening beam to the box frame via a stiffener; and

welding the stiffener to the box frame to form a weld seam, with a length of the weld seam kept greater than a sum of side lengths of a projection of the stiffening beam onto the box frame.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of this application more comprehensible, the following describes this application in detail with reference to embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely used to explain this application but are not intended to limit this application.

In the descriptions of this application, unless otherwise specified and defined the terms “first” and “second” are merely intended for a purpose of description, and should not be understood as an indication or implication of relative importance, and the terms “connection” and “fastening” should be understood in their general senses. For example, the “connection” may be a fixed connection, a detachable connection, an integral connection, or an electrical connection; or may be a direct connection, or an indirect connection through an intermediate medium. A person of ordinary skill in the art can understand specific meanings of these terms in this application as appropriate to specific situations.

in the descriptions of the specification, it should be understood that the directional terms such as “above” and “under” described in the embodiments of this application are described from angles shown in the accompanying drawings, and should not be understood as a limitation on the embodiments of this application. In addition, in the context, it should be further understood that when an element is referred to as being “above” or “under” another element, the element can not only be directly connected “above” or “under” the another element, but also be indirectly connected “above” or “under” the another element through an intermediate element.

In some cases, some battery pack lower box bodies are directly welded to box frames by using solid beams or extruded aluminum beams. Due to limited installation space, the stiffening beam has a relatively small cross-sectional area, while a weld seam formed between the stiffening beam and the box frame becomes the main force-bearing part of the two. Therefore, the weld seam is prone to breakage in long-term turbulence or severe collision.

FIG. 1is a schematic structural diagram of part of a battery pack lower box body according to an embodiment of this application;FIG. 2is an enlarged view of position A inFIG. 1;FIG. 3is an exploded view of a box frame, stiffener, and stiffening beam inFIG. 1;FIG. 4is a schematic cross-sectional view of a stiffener and stiffening beam inFIG. 1; andFIG. 5is a schematic structural diagram of a battery pack according to a second aspect of the embodiments of this application.

Referring toFIG. 1(Where only part of structure of the battery pack lower box body100is shown), the battery pack lower box body100includes a box frame1, a base plate2, a stiffening beam3, and a stiffener4.

The base plate2is arranged at the bottom of the box frame1, for example, the base plate2is fixed to the bottom of the box frame1by welding; and the stiffening beam3is arranged inside a space enclosed by the box frame1and on top of the base plate2, where the stiffening beam3can be arranged along a width direction Y, along a length direction X, or along both the width direction Y and the length direction X. In this embodiment, the stiffening beam3is arranged inside a space enclosed by the box frame1and on top of the base plate2along the width direction Y. X is the length direction of the battery pack M, Y is the width direction of the battery pack M, and Z is the height direction of the battery pack M.

The stiffening beam3is fixed to the box frame1via the stiffener4, and the stiffener4is welded to the box frame1to form a weld seam5(seeFIG. 2). A length of the weld seam5is kept greater than a sum of side lengths of a projection of the stiffening beam3onto the box frame1. For example, in this embodiment, the weld seam5includes three sides that are mutually perpendicular. When the stiffening beam3is a rectangle, the projection of the stiffening beam3onto the box frame1also includes three sides that are mutually perpendicular (which are length of the weld seam in the related art). Therefore, structural strength of the weld seam5can be improved as long as the length of the weld seam5is kept greater than the sum of side lengths of the projection of the stiffening beam3onto the box frame1.

The battery pack lower box body100provided by the embodiments of this application is welded to the box frame1via the stiffener4, and the length of the weld seam5formed by welding the two is kept greater than the sum of side lengths of the projection of the stiffening beam3onto the box frame1, increasing the length of the weld seam between the stiffening beam3and the box frame1, thus enhancing structural strength of the weld seam, and thereby reducing the risk of breakage of the weld seam formed between the stiffening beam and the box frame.

It should be noted that both tensile force and shear force of the weld seam5are proportional to the length of the weld seam5, and therefore greater length of the weld seam5means greater tensile and shear force of the weld seam5, which can ensure better strength of the weld seam5, reducing the risk of breakage of the weld seam.

In addition, the stiffening beam3of this embodiment is welded to the box frame1via provision of the stiffener4, with two joints present between the three, which are, respectively, a joint between the stiffening beam3and the stiffener4and a joint (the weld seam5) between the stiffener4and the box frame1. Compared with the related art where one joint is provided between the stiffening beam and the box frame, this application provides two joints to disperse the acting force.

Specifically, when the battery pack has bumped for a long time or is subjected to severe collision, part of the acting force generated may act on the joint between the stiffening beam3and the stiffener4, and the other part of the acting force may act on the weld seam5, thus reducing the risk of breakage of the weld seam5, which in turn increases overall structural strength of the battery pack.

In addition, when part of the acting force generated acts on the joint between the stiffening beam3and the stiffener4, that part of acting force will continue to be transmitted to the stiffening beam3. Because structural strength of the stiffethng beam3is much greater than structural strength of the weld seam5, the overall structural strength of the battery pack is increased to some extent.

Referring toFIG. 1andFIG. 5, the battery pack lower box body100further includes a battery fixing portion6, where the battery fixing portion6is connected to inner sides of three adjacent box frames1. Along the height direction Z, a plurality of first connecting holes10are provided in a top surface of the box frame1, and the battery pack lower box body100is fixed to a battery-pack upper box body200via the first connecting holes10. A plurality of second connecting holes30are provided in a top surface of the stiffening beam3, and a plurality of third connecting holes60are provided in a top surface of the battery fixing portion6. The second connecting holes30and the third connecting holes60can all be configured for installing and fixing one or more battery modules300. In some embodiments, the first connecting holes10, the second connecting holes30, and the third connecting holes60may all be threaded holes, and bolts can be used to fix the battery pack lower box body100to the battery-pack upper box body200via the first connecting holes10and also fix the battery module300between the battery pack lower box body100and the battery-pack upper box body200. It can be understood that not only the battery module300but also components such as a high-voltage box, a battery management unit (Battery Management Unit, BMU), a cell supervision circuit (Cell Supervision Circuit, CSC), a high-voltage copper bar, and a low-voltage wiring harness can be fixed between the battery pack lower box body100and the battery-pack upper box body200.

In the battery pack lower box body100, the box frame1, the base plate2, the stiffening beam3, the stiffener4, and the battery fixing portion6can all be made of aluminum alloy. Using aluminum alloy can reduce overall weight of the battery pack lower box body100to meet light-weight requirement for the battery pack, thereby increasing energy density of a battery pack using the battery pack lower box body100in this embodiment.

In practical applications, stiffening beams3of different widths can be selected as appropriate to specific requirements. Provided that the stiffening beam3is able to support the battery assembly, the stiffening beam3should have a smallest possible width to meet the light-weight requirement for the battery pack lower box body100. Designing stiffening beams3of different widths can have corresponding impact on the size of the stiffener4and the length of the weld seam5, which in turn affects the structural strength of the weld seam5. Therefore, it is also very important to select stiffening beams3of different widths.

In some embodiments, the stiffening beam3and the stiffener4may be split structures or an integral structure. Being split structures, the stiffening beam3and the stiffener4need to be joined, increasing assembly steps but with low manufacturing costs; while being an integral structure, the stiffening beam3and the stiffener4need to be cast integrally, reducing assembly steps but with high manufacturing costs. For example, when the stiffening beam3and the stiffener4are split structures, the two can be joined using fastening methods such as threaded connection, welding, or plugging. In some embodiments, the assembly method of plugging followed by threaded connection allows the stiffening beam3and the stiffener4to be joined more reliably at lower costs.

Specifically, referring toFIG. 3, the stiffener4is provided with a first insertion hole41, and the stiffening beam3is inserted into the first insertion hole41. In such manner, an end portion of the stiffening beam3can be designed to be gradually narrowed to facilitate insertion of the stiffening beam3into the first insertion hole41. In some embodiments, further, a part of the stiffening beam3that is inserted into a rear part of the first insertion hole41can be designed to be slightly larger than the first insertion hole41in size, allowing the stiffening beam3to be in interference fit with the stiffener4, even sparing the subsequent threaded connection. Nevertheless, for reliability of the overall structure, a threaded connection is still adopted subsequently for further fixing.

The first insertion hole41can be a square hole or a round hole. In some embodiments, the first insertion hole41is a square hole, because a round hole is prone to relative rotation of the stiffening beam3and the stiffener4, causing structural instability. When the first insertion hole41is a square hole, a cross section of the stiffening beam3is also square, allowing the stiffening beam3to fit more tightly in the first insertion hole41.

In some embodiments, when the stiffening beam3and the stiffener4are connected threadedly, specifically, the stiffener4is further provided with a second insertion hole42communicating with the first insertion hole41, the stiffening beam3is provided with a threaded hole31, a threaded member40is provided inside the second insertion hole42and the threaded hole31, and the stiffener4is fixed to the stiffening beam3by the threaded member40. Referring toFIG. 4, the second insertion hole42may be a stepped hole, to facilitate insertion and fitting of the threaded member40. For example, the threaded member40is a bolt with a flange face that can abut against a limiting face of the stepped hole to provide preload for the stiffening, beam3and the stiffener4.

The second insertion hole42may rim through up and down, or may only run to the first insertion hole41. When the second insertion hole42runs through up and down, a longer threaded member40can be inserted and fitted into the second insertion hole42. In the same way, the first insertion hole41can run through back and forth or nm slightly deeper than the second insertion hole42. Either way is possible as long as the stiffening beam3and the stiffener4can fit together through plugging and threaded connection. It can be understood that when the first insertion hole41runs through back and forth and the second insertion hole42runs through up and down, the stiffener4is easier to process.

In some embodiments, along the width direction Y, two ends of the stiffening beam3are provided with limiting faces32, the stiffener member4has a first welding face43welded to the box frame1, and the limiting face32abuts against the first welding face43. Providing the limiting face32can ensure that the depth of insertion of the stiffening beam3into the stiffener4meets the requirement. To be specific, when the limiting face32abuts against the first welding face43, it means that the stiffening beam3and the stiffener4meet assembly requirements, and a next installation step, for example, inserting the threaded member40, can proceed. In some embodiments, providing the limiting face32can further ensure that the threaded hole31is aligned with the second insertion hole42in installation, improving the installation efficiency.

It can be understood that a distance of the stiffening beam3to an outer end face along the width direction Y to the limiting face32should not exceed the depth of the first insertion hole41, otherwise the assembly of the two may be difficult or impossible to be mounted to the box frame1.

In some embodiments, an area of the first welding face43is larger than that of the projection of the stiffening beam3onto the box frame1, so as to increase the length of the weld seam5by increasing the area of the first welding face43. Certainly, when the area of the first welding face43is smaller than that of the projection of the stiffening beam3onto the box frame1, the length of the weld seam5may not necessarily be reduced. For example, the projection of the stiffening beam3onto the box frame1is a square, the projection of the first welding face43onto the box frame1is a shape, a sum of whose side lengths is greater than a sum of side lengths of the square (which is a sum of side lengths of three sides). For example, at least one of the right-angled sides may be changed to an arc.

However, it can be understood that an increased area of the first welding face43can increase the length of the weld seam5and increase an contact area between the stiffener4and the box frame1, thereby increasing strength of connection between the stiffener4and the stiffening beam3and connection between the stiffener4and the box frame1.

Still referring toFIG. 2, the box frame1has a second welding face11welded to the first welding face43, and the first welding face43is substantially flush with the second welding face11, so that the stiffener4are reliably fixed to the box frame1and the stiffener4is welded to the box frame1with ease. For example, welding is more difficult when the first welding face43is not flush with the second welding face11. Certainly, the first welding face43may also slightly protrude with respect to the second welding face11.

Referring toFIG. 2andFIG. 3, the box frame1is provided with a slot13formed by the second welding face11recessed inwards, and the stiffener4is accommodated in the slot13, allowing the box frame1to acconunodate the stiffener4.

In some embodiments, along the height direction Z, the box frame1has a bottom face12, and the slot13runs through the bottom face12and the second welding face11. Certainly, the slot13can alternatively be directly formed in the middle of the second welding face11without running through the bottom face12. In this embodiment, the slot13runs through the bottom face12and the second welding face11, thus increasing volumetric capacity of the battery pack lower box body100.

It can be understood that the stiffener4provided in this embodiment is a rectangular solid, which facilitates the ease of processing the stiffener4. Certainly the stiffener4may alternatively be of other regular of irregular shapes. For example, a side of the stiffener4close to the first welding face43may be designed as an enclosure structure that goes beyond the main body of the stiffener4(not shown in the figure), thus increasing an area of the first welding face43, and further increasing the length of the weld seam5.

When the stiffener4is a rectangular solid, the depth of the slot13is the same as the length of the stiffener4in an insertion direction; and when the stiffener4has an enclosure structure close to the first welding face43, the enclosure structure abutting against the second welding face11can indicate that the stiffener4is completely inserted into the slot13.

As shown inFIG. 5, another aspect of this application further provides a battery pack M, where the battery pack M includes a battery module300, a battery-pack upper box body200, and the battery pack lower box body100described above. After a battery module300is installed and fixed to the battery pack lower box body100, the battery-pack upper box body200and the battery pack lower box body100are fixed to form the battery pack M. The battery pack M provides the same beneficial effects as the foregoing battery pack lower box body100, which will not be repeated herein.

Still another aspect of this application further provides an apparatus, which can be mobile devices such as a vehicle, a ship, or a small aircraft. A vehicle is used as an example. The vehicle in this embodiment of this application may be a new energy vehicle. The new energy vehicle may be a battery electric vehicle, or may be a hybrid electric vehicle or an extended-range electric vehicle. The apparatus includes a driving source (not shown in the figure) and the battery pack M described above, where the driving source is configured to provide driving force for the apparatus, and the battery pack M is configured to provide electrical energy for the driving source. In some embodiments, the driving source may be an electric motor, and the electric motor is connected to wheels of the vehicle through a transmission mechanism to drive the vehicle.

An embodiment of this application further provides an assembly method of battery pack lower box body100. A battery pack lower box body assembled using this assembly method is the foregoing battery pack lower box body100.

Specifically, the assembly method includes the following steps:

S1. Fix the stiffening beam3to the stiffener4.

S11. Insert the stiffening beam3into the first insertion hole41of the stiffener4.

Specifically, an end portion of the stiffening beam3can be designed to be gradually narrowed to facilitate insertion of the stiffening beam3into the first insertion hole41. In some embodiments, further, a part of the stiffening beam3that is inserted into a rear part of the first insertion hole41can be designed to be slightly larger than the first insertion hole41in size, so that the stiffening beam3is in interference fit with the stiffener4.

S12. Connect the stiffening beam3to the stiffener4threadedly.

Specifically, the stiffener4is further provided with a second insertion hole42communicating with the first insertion hole41, the stiffening beam3is provided with a threaded hole31, a threaded member40is provided inside the second insertion hole42and the threaded hole31, and the stiffener4is fixed to the stiffening beam3by the threaded member40. Referring toFIG. 4, the second insertion hole42may be a stepped hole, to facilitate insertion and fitting of the threaded member40. For example, the threaded member40is a bolt with a flange face that can abut against a limiting face of the stepped hole to provide preload for the stiffening beam3and the stiffener4.

The second insertion hole42may run through up and down, or may only run to the first insertion hole41. When the second insertion hole42runs through up and down, a longer threaded member40can be inserted and fitted into the second insertion hole42. In the same way, the first insertion hole41can run through back and forth or run slightly deeper than the second insertion hole42. Either way is possible as long as the stiffening beam3and the stiffener4can fit together through plugging and threaded connection. It can be understood that when the first insertion hole41runs through back and forth and the second insertion hole42runs through up and down, the stiffener4is easier to process.

S2. Place the stiffener4in the slot13of the box frame1and then perform welding.

This may be implemented by first placing the stiffener4in the slot13of the box frame1, and then simultaneously welding the stiffener4to the box frame1and welding the base plate2to the box frame1; or by first placing the stiffener4in the slot13of the box frame1, then welding the stiffener4to the box frame1, and then welding the base plate2to the box frame1; or by first placing the stiffener4in the slot13of the box frame1, and then welding the base plate2to the box frame1, and then welding the stiffener4to the box frame1.

Specifically, the box frame1is provided with the slot13formed by the second welding face11recessed inwards, and the stiffener4is accommodated in the slot13, allowing the box frame1to accommodate the stiffener4.

In some embodiments, along the height direction Z, the box frame1has a bottom face12, and the slot13runs through the bottom face12and the second welding face11. Certainly, the slot13can alternatively be directly formed in the middle of the second welding face11without running through the bottom face12. In this embodiment, the slot13runs through the bottom face12and the second welding face11, thus increasing volumetric capacity of the battery pack lower box body100.

It can be understood that the stiffener4provided in this embodiment is a rectangular solid, which facilitates the ease of processing the stiffener4. Certainly, the stiffener4may alternatively be of other regular or irregular shapes. For example, a side of the stiffener4close to the first welding face43may be designed as an enclosure structure that goes beyond the main body of the stiffener4(not shown in the figure), thus increasing an area of the first welding face43, and further increasing the length of the weld seam5.

When the stiffener4is a rectangular solid, the depth of the slot13is the same as the length of the stiffener4in an insertion direction; and when the stiffener4has an enclosure structure close to the first welding face43, the enclosure structure abutting against the second welding face11can indicate that the stiffener4is completely inserted into the slot13.

In summary, the battery pack lower box body100assembled using the foregoing assembly method has a much stronger weld seam, reducing the risk of breakage of the weld seam formed between the stiffening beam and the box frame.

The foregoing descriptions are merely some embodiments of this application, but are not intended to limit this application. Any modification, equivalent replacement, or improvement made without departing from the spirit and principle of this application shall fall within the protection scope of this application.