FR3161072A1 - METHOD FOR ASSEMBLING A BATTERY PACK AND ITS JUNCTION BOX - Google Patents

Abstract

The invention relates to an assembly method for assembling a battery pack intended to equip an electric traction vehicle, the battery pack comprising a plurality of electrochemical cell modules, the battery pack comprising a junction box, the method comprising: a- assembling the modules one after the other in a sump, b- assembling, on a rear rising wall, a connector (3), c- assembling the junction box on the connector, by moving it from top to bottom (F3) relative to the connector assembly, causing, thanks to at least one centering ramp, a resetting of the junction box along the transverse axis (Y), d- screwing a first screw (V1) and a second screw (V2) to tighten respectively first and second terminals (51, 52) of the junction box on first second pins (11, 12) of the connector. Figure 2

Description

METHOD FOR ASSEMBLING A BATTERY PACK AND ITS JUNCTION BOX

The invention relates to a method for assembling a battery pack intended to equip an electric vehicle. Here, an electric vehicle is understood to mean a vehicle equipped with an electric powertrain capable of moving the vehicle in zero-emission mode.

Such a battery pack comprises one or more electrochemical cell modules, which makes it possible to provide a substantial capacity electrical energy storage function.

Such a battery pack comprises at least one power connector which makes it possible to electrically couple a positive pole of the battery pack with a positive line of a high voltage network of the vehicle and to electrically couple a negative pole of the battery pack with a negative line of the high voltage network of the vehicle.

Such a battery pack includes a junction box which includes isolation contactors to open the electrical distribution circuit which connects the battery pack to the high voltage network.

In practice, there may be two connectors, one on the front of the battery pack and one on the back of the battery pack. In other configurations, there is only one power connector for the electrical interface.

The connector passes tightly through the enclosure housing that contains the electrochemical cell modules. The junction box is also housed inside the enclosure housing in question.

The junction box is equipped with two power terminals, i.e. a positive terminal and a negative terminal. Once the battery pack is assembled, the positive terminal of the junction box is electrically coupled with the pin of the connector intended to carry the positive voltage of the high voltage network and the negative terminal of the junction box is electrically coupled with the pin of the connector intended to carry the negative voltage of the high voltage network.

The various elements contained in the battery pack casing are fixed to a lower part of the casing called here 'tray', with a positioning tolerance of a few millimeters.

Furthermore, the electrical power connections in the battery pack are made by means of bus bars which are relatively rigid parts, with little flexibility, which is also the case for the pins of the power connector.

The present invention is particularly concerned with taking into account the dispersion of positioning of the junction box relative to the power connector.

To accommodate a positioning tolerance along one direction, it is common to use an oblong hole. To accommodate a positioning tolerance along two orthogonal directions, a hole with a larger diameter than necessary must be provided, which reduces the contact surface of the screw connection that connects one bus bar to another, and which is unfavorable for the quality of the electrical contact.

The inventors therefore sought to propose an improved solution to take into account the positioning dispersions, in particular between the junction box and the power connector at the output of the battery pack, with the aim of having a good mutual contact surface between the bus bars to be coupled.

To this end, the present invention proposes an assembly method for assembling a battery pack intended to equip an electric traction vehicle, the battery pack being delimited by a casing enclosing at least one tray, the tray comprising a bottom wall and rising walls, the battery pack comprising a plurality of electrochemical cell modules, the battery pack comprising a junction box comprising at least isolation contactors, the battery pack being referenced in space with respect to an orthonormal reference frame comprising a vertical axis, a longitudinal axis corresponding to a front-rear axis of the vehicle, and a transverse axis perpendicular to the vertical axis and to the longitudinal axis and corresponding to a left-right axis of the vehicle, the method comprising:
a- assemble the modules one after the other in the tray,
b- assemble, on a rear rising wall, a connector assembly comprising a connector support and a connector body,
c- assembling the junction box on the connector assembly, by moving it from top to bottom relative to the connector assembly, causing, thanks to at least one centering ramp, a resetting of the junction box along the transverse axis relative to the connector assembly,
d- screwing a first screw to tighten a first terminal of the junction box onto a first pin of the connector body and screwing a second screw to tighten a second terminal of the junction box onto a second pin of the connector body.

Thanks to the provisions promoted above, it is possible to reduce a dispersion of a few millimeters (up to ten mm) to a positioning within a tolerance of less than 1 millimeter. It is thus possible to limit the size of the hole in the busbars, the shape of which can be simply oblong for managing the dispersion along X, and reduced to the smallest extent for the transverse direction Y.

This ensures good electrical coupling of the junction box with the connector pins, with, for each terminal, a substantial contact surface under clamping pressure, for example at least 1 cm².

Note that the expression “the tray” covers the case of a single-piece lower shell or the case of a multi-piece tray.

The junction box may contain, in addition to isolation contactors (for example in the form of relays), fuses, protection circuits or components, without excluding other electrical connection parts.

We note that the junction box is called in the jargon "BDU" from the Anglo-Saxon term "Battery Disconnect Unit" because of one of its functions consisting of disconnecting the battery from the voltage network external to the battery pack.

According to one embodiment, the method may further comprise:
e- mount bus bars connecting the electrochemical cell modules and the junction box,
f- mount a cover on the tray.

Thanks to these additional steps, we complete the complete assembly of the battery pack.

According to one embodiment, the centering ramp(s) is/are arranged on the connector assembly. In practice, the centering ramps in question may be provided, depending on the most relevant mechanical configuration, on the connector body or on the connector support.

For example, the connector holder has a shape that flares outward as it descends. The connector holder or connector body may have a conical or pyramidal shape.

According to one embodiment, the centering ramp(s) is/are arranged on a portion of the junction box facing downwards.

The junction box can thus include an inverted funnel shape which centers itself very naturally on elements of the connector body or the connector support.

It should be noted that centering ramps can be present on both the connector assembly side and the junction box side.

In a particular example, four centering ramps are provided.

Depending on whether the offset to be corrected is a movement to the right or a movement to the left, as will be seen later, only half of the centering ramps will be used for recentering.

In one embodiment, the first pin of the connector body is longer than the second pin of the connector body, with a length difference of at least 20 mm.

Thanks to this, although the second spindle is located above the first spindle, access to the screwing area of the first spindle is preserved. The difference in length allows the passage of screwdriver sockets. Screwing can also be done simultaneously on the first screw and on the second screw.

A particular example, the distance between the screw axes is at least 25 mm, which provides a fairly wide passage for the screwdriver sockets

The person skilled in the art will notice that the connector pins are positioned one above the other along Z, which makes it possible to have a flat wiring outlet along the transverse direction Y, thanks to the right-angle bend present in the power plug. This promotes good integration of the battery pack and its wiring into the vehicle architecture.

According to one embodiment, the inner end zone of the first pin of the connector body comprises a first orifice equipped with a first crimped nut, and the inner end zone of the second pin of the connector body comprises a second orifice equipped with a second crimped nut.

The screw cooperates with the internal thread of the nut when tightening, preventing it from turning. The crimped nut system allows for very easy assembly by simply inserting the screw and tightening it, without requiring access from below.

In one embodiment, the first and second holes are round. This is very simple to manufacture.

According to one embodiment, an oblong hole is provided in each of the first and second terminals of the junction box to accommodate the dispersion in the longitudinal direction.

Thanks to these oblong holes, we can take into account the dispersion present along the longitudinal direction X.

According to one embodiment, the connector support is made of metal and the connector body is made of plastic.

According to one embodiment, the connector support is made of aluminum alloy. According to one embodiment, for informational and non-limiting purposes, the connector body is made of polypropylene or polyethylene.

The invention further relates to a battery pack intended to equip an electric traction vehicle, characterized in that it has been assembled using an assembly method as described previously.

The invention further relates to a vehicle comprising at least one battery pack assembled using an assembly method as described above.

The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which:
FIG. 1 schematically illustrates a top view of a battery pack, intended to equip an electric vehicle;
FIG. 2 schematically illustrates, in longitudinal vertical section, the principle of electrical coupling between the terminals of the junction box and the pins of the connector according to an exemplary embodiment of the present invention;
FIG. 3 schematically illustrates in perspective view the junction box just before its assembly on the connector assembly according to an exemplary embodiment of the present invention;
FIG. 4 schematically illustrates, in a vertical cross-section view, the principle of Y-recalibration provided by the presence of the centering ramps, according to the section line IV-IV indicated in FIG. 2 ;
FIG. 5 schematically illustrates, in a vertical cross-section view, the principle of Y recalibration provided by the presence of the centering ramps, according to the section line VV indicated in FIG. 2 in the final state;
FIG. 6 shows, in schematic elevation view, an electric vehicle with the battery pack located in the lower part of the chassis;
FIG. 7 schematically illustrates, in top view, the coupling area between the terminals of the junction box and the pins of the connector;
FIG. 8 schematically illustrates the assembly movement of the junction box in an XZ plane section.

In the various figures, the same references designate identical or similar elements. For reasons of clarity of the presentation, certain elements are not necessarily represented to scale.

We illustrate the FIG. 1 a PB battery pack, intended to equip an electric vehicle VH shown in the FIG. 6 .

The vehicle and VH and the battery pack PB are referenced in space relative to an orthonormal reference frame comprising a vertical axis Z, a longitudinal axis X corresponding to a front-rear axis of the vehicle, and a transverse axis Y perpendicular to the vertical axis and to the longitudinal axis and corresponding to a left-right axis of the vehicle.

The power connector and junction box, which will be discussed in more detail below, are located in the rear area of the battery pack. However, it should be noted that the aforementioned elements could just as easily be located in the front area of the battery pack.

The PB battery pack comprises a plurality of modules 4, each module comprising a plurality of electrochemical cells.

The PB battery pack comprises an external casing 10 forming mechanical protection and delimiting a confined internal space.

As illustrated in the FIG. 6 , the battery pack PB is arranged in the lower part of the vehicle chassis. According to a particular embodiment, the battery pack PB is arranged under the structural floor of the vehicle VH. It occupies a large part of the floor area. The battery pack must be protected from the mechanical, physical and chemical environment, and therefore it is encapsulated in the casing called here casing envelope 10. Any entry of foreign bodies which could cause a short circuit must be avoided.

The battery pack must be replaceable and therefore must be removable from the vehicle's lower chassis structure. The battery is secured to the chassis by means of fastenings not shown in the figures in this document.

According to a particular embodiment, the casing 10 comprises a tray 8 and a cover 9.

The tray 8 comprises a bottom wall 7 and rising edges 6. The tray 8 may be a single-piece lower shell, e.g. a stamped sheet metal part. The tray may alternatively be a multi-piece type tray, e.g. with a bottom and a side perimeter assembled together. Stiffeners may be provided to support the weight of the modules 4.

According to an alternative embodiment, the rising walls 6 can be separate pieces assembled on the bottom wall 7.

The casing 10 is preferably made of a metallic material. It forms a hermetic casing. The interior volume is configured to receive the plurality of electrochemical cell modules as well as a member which will be of particular interest, namely a junction box 5 with as an auxiliary a battery management computer otherwise called in practice BMS from the Anglo-Saxon name Battery Monitoring System.

The junction box 5 comprises two isolation contactors, namely one isolation contactor for interrupting the positive voltage supply line and another isolation contactor for interrupting the negative voltage supply line. In practice, these isolation contactors may take the form of relays. The isolation devices are known in the art and therefore not described in detail here.

The junction box 5 comprises an outer casing marked 50 and fixing means 51 allowing the outer casing to be screwed onto the bottom wall 7 of the casing 10.

The junction box may further include one or more fuses and electrical protection circuits. Furthermore, the construction and functions of the BMS battery management computer are known in the art and not described here in detail. The BMS battery management computer controls the opening and closing of the isolation contactors.

An electrical interface is provided between the PB battery pack and the rest of the vehicle by means of one or two power connectors.

In this case, in the illustrated example, a first power connector is provided in the front area of the battery pack to supply power to the inverter of the electric machine of the front electromotive group. In addition, a second power connector is provided in the rear area of the battery pack to connect the battery pack to the on-board charger in the function and to manage the recharging of the vehicle from a charging station providing alternating current or direct current for the case of fast recharging.

In the configuration of interest, the junction box 5 is electrically and mechanically coupled directly to a connector assembly denoted 3 arranged on the rear portion of the battery pack.

The connector assembly 3 comprises a connector holder 2 and a connector body 1.

The connector support 2 is made of metal, for example aluminum alloy. The connector support is fixed to the tray 8 of the casing housing 10 by means of fixing screws, only one of which is visible in the figures and marked 24.

More precisely, in the example illustrated, the connector support is fixed to the rear rising wall 6 of the casing. Note that the rear rising wall is inclined relative to the vertical. The shape of the connector support 2 makes it possible to compensate for this inclination so that the connector pins are substantially horizontal.

The connector body 1 is made of plastic, in particular non-conductive plastic. For example, the connector body may be made of polypropylene or polyethylene, but not limited to. The connector body 1 includes electrical pins.

In practice, the connector body comprises a first electrical power pin 11 and a second electrical power pin 12, and each of them carries the positive or negative voltage of the battery pack.

The connector passes tightly through the rising wall 6, i.e. passes through the casing; a portion of the connector is located inside the casing and another portion is located outside the casing to receive a wiring plug 82.

The outer free end of the first pin 11 is marked 61 as shown in FIG. 3 . Here it is in the form of a pin of cylindrical section, but it could have another shape. Similarly, the outer free end of the second pin 12 is marked 62.

As illustrated in Figures 1 and 2, the power connector 1 is configured to receive by coupling an electrical power plug 82 containing two conductors and two clips adapted to each respectively plug into the outer end 61, 62 of the power connector 1. The electrical conductors form a 90° bend in the electrical power plug 82.

It is noted that the power electrical harness 83 connected to the power electrical plug 82 has a path at the rear of the battery pack generally parallel to the Y direction. This facilitates the integration of the battery pack PB and the wiring connected to it into the vehicle architecture. This also explains the arrangement of the connector pins 11, 12 one above the other.

Turning to the FIG. 2 , we notice that the first pin 11 of the connector body is longer than the second pin 12 of the connector body, with a difference in length noted D1.

In practice, a value of at least 20 mm is chosen for the distance D1.

This offset allows access, from above, i.e. in the Z direction, to the end zone of the first pin on the inside, despite the presence of the second pin which is located above the first pin, but set back.

We can thus pass a screwdriver to screw or unscrew the screw marked V1 which allows the first pin 11 to be mechanically coupled with the first terminal 51 of the junction box 5.

You can also use a screwdriver socket to screw or unscrew screw V1.

The screw marked V2 makes it possible to mechanically couple the second pin 12 with the second terminal 52 of the junction box 5.

The first pin is spaced from the second pin in the vertical Z direction by a second distance denoted D2 determined by the standard of the two-way power connector. D2 can typically range from 15 mm to 30 mm without these values being limiting.

As can be seen from Figures 2 and 7, the first pin 11 comprises an orifice marked T1. Preferably, it is a round orifice. Similarly, the second pin 12 comprises an orifice marked T2. Preferably, it is a round orifice.

In the example shown, the first pin and the second pin are formed as a flat bar. Other shapes, including a round section, are also possible, provided that the end area where the holes T1 and T2 are drilled is crushed and flattened.

The first orifice T1 has an axis A1 and the second orifice T2 has an axis A2. The axes A1 and A2 are substantially parallel to the vertical axis Z, they are spaced by the aforementioned distance D1.

The junction box 5 comprises a first terminal 51 intended to be electrically coupled to the first pin 11 of the connector and comprises a second terminal 52 intended to be coupled to the second pin 12 of the connector 1.

The first terminal 51 covers the first pin 11 and the second terminal 51 covers the second pin 12.

The junction box 5 includes an access well 59 which allows a tool to descend to the screw head V1, both for initial screwing and for possible subsequent disassembly. Depending on the geometric configuration, there may also be a less deep well for access to the second screw V2

In the coupling zone, the first terminal 51 includes an oblong hole T3 visible in particular at the FIG. 7 , the second terminal 52 comprises an oblong hole T4. The large dimension of these oblong holes is parallel to X.

The oblong shape of these holes makes it possible to take into account a dispersion of positioning of the junction box 5 relative to the connector along the longitudinal direction X.

Advantageously, according to the present invention, the possible dispersion of positioning of the junction box along the transverse axis Y is cancelled by the effect of the centering ramps 26.

In fact, when the junction box 5 is assembled on the connector assembly, by moving it from top to bottom F3, this causes, thanks to the centering ramps, a resetting/recentering of the junction box along the transverse axis Y in relation to the connector assembly.

In the illustrated example, the centering ramp(s) 26 are symmetrical and are arranged on the connector assembly.

In the example illustrated, the centering ramps 26 are part of walls 22. Two walls 22 are provided on either side of the connector pins.

On either side of the pins. Expressed differently, the pins of the connector are interposed along Y between the two walls 22, which are symmetrical in the example illustrated.

As can be seen in the figures, the section of the wall decreases as it goes upwards, the wall acts as a corner.

In the example shown, there are also centering ramps 56 on a docking portion of the junction box. Here too they are symmetrical with respect to the axis of the screwing to be carried out.

The centering ramps 56 are attached to an external wall 57, these shapes being obtained by plastic molding.

The centering ramps 56 of the junction box are arranged in an interior zone of a mouth portion denoted 58. The centering ramps 56 form an inverted V, open downwards as visible in figures 3, 4 and 5.

Alternatively, the centering means could be offset to one side, away from the pin area. There could be a pyramid on the connector side and an inverted V or funnel shape on the junction box side.

In other configurations, the centering ramps could only be present on the connector part or only on the junction box part.

We note that it is not excluded to have a single centering ramp, starting from an off-center position always on the same side.

The inner end area of the first pin 11 of the connector body comprises a first hole T1 equipped with a first crimped nut 91, and the inner end area of the second pin 12 of the connector body comprises a second hole T2 equipped with a second crimped nut 92.

Nuts 91 92 may include a socket extension to provide sufficient internal threads to withstand screwing with substantial torque.

The crimped nut system allows for very easy assembly by bringing the screw in and tightening it, without the need for access from below.

It should be noted here that the screws can be pre-positioned in an elastomer skirt (not shown in the figures). This makes the first assembly and maintenance operations simpler and more reliable.

To reformulate the entire assembly process, the following actions are planned.

a- assemble the modules 4 one after the other in the tray 8, along X and fixed on the bottom 7.

b- assemble, on the rear rising wall 6, the connector assembly 3 comprising the connector support 2 and the connector body 1.

Note that steps a- and - can be carried out in any order.

The process continues as follows:
c- assemble the junction box 5 on the connector assembly, by moving it from top to bottom F3 relative to the connector assembly, causing, thanks to the centering ramps (26,56), a resetting of the junction box along the transverse axis Y relative to the connector assembly,

d- screw the first screw V1 to tighten a first terminal 51 of the junction box on the first pin 11 and screw the second screw V2 to tighten the second terminal 52 of the junction box on a second pin 12.

e- install bus bars 43 connecting the modules 4 and the junction box 5, which causes the electrical power to be switched on to the junction box 5,

f- mount the cover 9 on the tray and fix them together using fasteners 98.

Considering the FIG. 5 , we see that the angle of inclination β1 of the ramp 26 on the wall 22 can be between 15° and 30°.

Similarly, we see that the angle of inclination β2 of the ramp 56 on the mouth of the junction box can be between 15° and 30°.

Claims (10)

Assembly method for assembling a battery pack (PB) intended to equip an electric traction vehicle, the battery pack being delimited by an envelope casing (10) with at least one tray (8), the tray comprising a bottom wall (7) and rising walls (6), the battery pack comprising a plurality of modules (4) of electrochemical cells, the battery pack comprising a junction box (5) comprising at least isolation contactors,
the battery pack being referenced in space relative to an orthonormal reference frame comprising a vertical axis (Z), a longitudinal axis (X) corresponding to a front-rear axis of the vehicle, and a transverse axis (Y) perpendicular to the vertical axis and to the longitudinal axis and corresponding to a left-right axis of the vehicle, the method comprising:
a- assemble the modules one after the other in the tray,
b- assembling, on a rear rising wall, a connector assembly (3) comprising a connector support (2) and a connector body (1),
c- assembling the junction box on the connector assembly, by moving it from top to bottom (F3) relative to the connector assembly, causing, thanks to at least one centering ramp (26,56), a resetting of the junction box along the transverse axis (Y) relative to the connector assembly,
d- screwing a first screw (V1) to tighten a first terminal (51) of the junction box onto a first pin (11) of the connector body and screwing a second screw (V2) to tighten a second terminal (52) of the junction box onto a second pin (12) of the connector body.
The assembly method of claim 1, further comprising:
e- mount bus bars connecting the electrochemical cell modules (4) and the junction box,
f- mount a cover (9) on the tray (8).
Assembly method according to claim 1, characterized in that the centering ramp(s) is/are arranged on the connector assembly (3).
Assembly method according to claim 1, characterized in that the centering ramp(s) is/are arranged on a portion of the junction box facing downwards.
Assembly method according to any one of claims 1 to 4, characterized in that the first pin (11) of the connector body is longer than the second pin (12) of the connector body, with a length difference (D1) of at least 20 mm.
Assembly method according to any one of claims 1 to 5, characterized in that an inner end zone of the first pin (11) of the connector body comprises a first orifice (T1) equipped with a first crimped nut (91), and an inner end zone of the second pin (12) of the connector body comprises a second orifice (T2) equipped with a second crimped nut (92).
Method according to any one of claims 1 to 6, characterized in that an oblong hole (T3, T4) is provided in each of the first and second terminals (51, 52) of the junction box to accommodate the dispersion in the longitudinal direction (X).
Method according to any one of claims 1 to 7, characterized in that the connector holder (2) is made of metal and the connector body (1) is made of plastic.
Battery pack (PB) intended to equip an electric traction vehicle, characterized in that it has been assembled using an assembly method according to any one of claims 1 to 8.
Motor vehicle (VH) comprising a battery pack assembled using an assembly method according to any one of claims 1 to 8.