PRISMATIC BATTERY PACK PROVIDED WITH A THRUST UNIT

Abstract

A prismatic battery pack (20), in particular for supplying power to an electric drive motor (12) of an electric or hybrid vehicle (10), the prismatic battery pack (20) comprising: - at least one stack (22) of prismatic battery cells (24) stacked along a reference axis (100) of the prismatic battery pack (20), - a housing (26) accommodating the stack (22) of prismatic battery cells (24), - at least one end plate (28) located within the housing (26) and extending into a space between an end wall (30) of the housing and an axial end of the stack (22) of prismatic battery cells (24), and - at least one pusher device comprising at least one movable pusher member (34) in contact with a contact face of the end plate (28) opposite the stack (22) of prismatic battery cells. (24), and at least one spring (38) that directly or indirectly applies a thrust force to the thrust member towards the stack (22) of prismatic battery cells (24), such that the thrust member (34) applies a pressure force to the end plate (28) with an axial pressure force component (36) towards the stack (22) of prismatic battery cells (24), characterized in that the thrust device is a thrust unit (32) removably attached to the housing (26) and provided with a frame (40), which houses the spring (38) and guides the thrust member (34).

Description

PRISMATIC BATTERY PACK PROVIDED WITH A UNIT OF PUSH TECHNICAL FIELD The present invention relates to a prismatic battery pack, in particular for supplying power to an electric drive motor of an electric vehicle, provided with a thrust device to absorb the play that may accumulate over time between the battery cells of the prismatic battery pack, particularly due to a reduction in the volume of the battery cells. PREVIOUS TECHNIQUE A prismatic battery pack known from US patent 11894570 comprises a housing that accommodates several stacks of prismatic battery cells arranged along a reference axis of the prismatic battery pack, an end plate located within the housing and extending into a space between an end wall of the housing and an end of the prismatic battery pack, and a pusher device for applying a pushing force to the end plate toward the stack of prismatic battery cells. The pusher device comprises a pusher member in contact with the end plate and movable between a first end position and a second end position, and a spring that directly or indirectly applies a pushing force to the pusher member toward the second end position.The pusher device is located within the prismatic battery pack housing and occupies substantial space unavailable for battery cells, which is unfavorable in terms of compactness and power density. The pusher device components must be assembled into the housing individually and cannot be easily mounted or removed. Furthermore, the pressure applied to the end plate cannot be easily adjusted during assembly and may be too high or too low. DISCLOSURE OF THE INVENTION The invention aims to address at least some of the disadvantages of the prior art. According to a first aspect of the invention, a prismatic battery pack is provided, in particular for supplying power to an electric drive motor of an electric or hybrid vehicle, the prismatic battery pack comprising: - at least one stack of prismatic battery cells stacked along a reference axis of the prismatic battery pack, - a casing, which houses the stack of prismatic battery cells, - at least one end plate located within the housing and extending into a space between an end wall of the housing and an axial end of the prismatic battery cell stack and - at least one push device comprising at least one movable push member in contact with a contact face of the end plate opposite the prismatic battery cell stack, and at least one spring that directly or indirectly applies a push force to the push member towards the prismatic battery cell stack, such that the push member applies a pressure force to the end plate with an axial pressure force component towards the prismatic battery cell stack, wherein the push device is a push unit removably fixed to the housing and provided with a frame, which houses the spring and guides the push member. The thrust unit can be pre-assembled before being mounted in or onto the prismatic battery pack housing. It can also be easily removed as a unit from the housing, for example, for maintenance or recycling. The potential and kinetic energy of the spring can be transmitted directly to the thrust member, for example, if the spring is attached to the thrust member, or if the thrust member is provided with a spring seat on which one end of the spring rests. Alternatively, the force can be transmitted through one or more intermediate members, which transmit force and motion from the spring to the movable thrust member at a transmission ratio that can be selected to amplify the pressure force or the stroke of the thrust member. Various types of intermediate members can be considered, which may include, in particular, one or more of the following: - an integral spring seat with or attached to the thrust member - a lever, which pivots around a pivot axis between the first end position and the second end position; - a cam, which rotates around a pivot axis perpendicular to the reference; - a conical slider, which slides on a translation axis perpendicular to the reference axis. The spring's thrust force and the pressure force applied to the end plate are linked by a strictly increasing relationship; that is, an increase in thrust force results in an increase in pressure force, at least within the operating range. This relationship may or may not be proportional, depending on the presence and type of intermediate member. Adjusting the thrust force allows for easy adjustment of the pressing force. In one embodiment, the thrust unit further comprises an adjustment mechanism for adjusting the thrust force, the adjustment mechanism being at least partially housed within the frame. In another embodiment, the adjustment mechanism comprises an irreversible motion transformation mechanism, preferably bidirectional, and an adjustment interface that allows a user to operate the irreversible motion transformation mechanism, such as to adjust, i.e., increase or decrease, the thrust force when the prismatic battery pack is installed in the vehicle or during maintenance. In a preferred embodiment, which minimizes the number of parts, the adjusting member and the thrust member are integral with each other and the irreversible transformation mechanism is such that it adjusts a position of a spring seat to transfer force and motion between the spring and the thrust member with respect to the thrust member. In an alternative embodiment, the adjusting member and the irreversible transformation mechanism are such that they adjust a position of a spring seat attached to the frame. In a preferred embodiment, the irreversible motion transformation mechanism comprises a screw and nut mechanism. When the thrust member is in contact with the end plate, one part of the screw and nut is rotationally fixed with respect to the housing, and the other part is translationally fixed with respect to the housing. A particularly simple thrust unit is achieved where the thrust member and the adjusting member are two sections of the same threaded rod or screw. Alternative irreversible motion transformation mechanisms can be used, such as a worm gear mechanism comprising a worm gear meshing with a worm wheel. In one embodiment, the adjustment mechanism is accessible from outside the housing. This makes it possible to adjust the thrust force without having to open the housing. In a preferred embodiment, the frame guides the translationally movable thrust member along a translation axis parallel to the reference axis. A translationally movable thrust member, such as a rod, is particularly adapted to a configuration in which the thrust unit frame is located outside the housing. Various mechanical springs can be used, including helical springs, Belleville washers, leaf springs, or combinations thereof. In one embodiment, the spring has a recoil spring with an operating stroke of at least 5 mm, preferably 10 mm, within the frame, between a fully retracted state and a released or partially released state. The recoil spring, for example, a helical spring or a set of Belleville washers, preferably has a recoil direction parallel to the reference axis. In one embodiment, the thrust unit frame is located within the housing. This configuration may be preferable if it is necessary to protect the thrust unit from shocks or other interference before the prismatic battery pack is mounted in the vehicle. To allow adjustment of the thrust force from outside the housing, the housing may have a through-hole through which the adjustment mechanism's interface is accessible from within the housing or protrudes outside the housing. Alternatively, the spring is located outside the housing, which has a through-hole through which the thrust member protrudes into the housing. This configuration offers the advantage of maximizing the volume available for the battery cells within the housing, thus maximizing the power density of the prismatic battery pack. According to another aspect of the invention, a prismatic battery pack is provided, in particular for supplying power to an electric drive motor of an electric or hybrid vehicle, the prismatic battery pack comprising: - at least one stack of prismatic battery cells stacked along a reference axis of the prismatic battery pack, - a casing, which houses the stack of prismatic battery cells, - at least one end plate located within the housing and extending into a space between an end wall of the housing and an axial end of the prismatic battery cell stack and - at least one thrust device comprising at least one movable thrust member in contact with a contact face of the end plate opposite the prismatic battery cell stack, and at least one spring directly or indirectly applying a thrust force to the thrust member towards the prismatic battery cell stack, such that the thrust member applies a pressure force to the end plate with an axial pressure force component towards the prismatic battery cell stack, wherein the spring is located outside the housing, which has a through hole through which the thrust member protrudes into the housing. This configuration offers the advantages of maximizing the volume available for the battery cells within the housing, thus maximizing the power density of the prismatic battery pack and making it possible to adjust the thrust force without having to open the housing. According to another aspect of the invention, an electric or hybrid vehicle is provided comprising an electric drive motor and at least one prismatic battery pack according to one or more of the previous aspects of the invention, to supply power to the electric drive motor. BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and features of the invention will become more apparent from the following description of specific embodiments of the invention given only as non-restrictive examples and depicted in the accompanying drawings, in which: - Figure 1 is a schematic view of an electric or hybrid motor vehicle provided with a prismatic battery pack according to one embodiment of the invention; - Figure 2 is an isometric view of a prismatic battery pack according to one embodiment of the invention; - Figure 3 is an isometric cross-sectional view through a pair of thrust units of the prismatic battery pack of Figure 2; - Figure 4 is another isometric cross-sectional view through one of the thrust units of Figure 3; - Figure 5 is a cross-sectional view of the thrust unit of Figure 4; - Figure 6 is an isometric view of the thrust unit of Figure 3, with a cover removed to show an interior space of a thrust unit frame; - Figure 7 is a schematic view of an electric or hybrid motor vehicle provided with a prismatic battery pack according to another embodiment of the invention; - Figure 8 is a schematic view of an electric or hybrid motor vehicle provided with a prismatic battery pack according to another embodiment of the invention; - Figure 9 is a schematic view of an electric or hybrid motor vehicle provided with a prismatic battery pack according to another embodiment of the invention: - Figure 10 is a schematic view of an electric or hybrid motor vehicle provided with a prismatic battery pack according to another embodiment of the invention. The corresponding reference numbers refer to the same or corresponding parts in each of the figures. DESCRIPTION OF THE MODES OF REALIZATION An electric or hybrid motor vehicle 10 with an electric drive motor 12, which drives the drive wheels 14 through a mechanical transmission 16 is illustrated schematically in Figure 1. The electric motor 12 is powered by one or more prismatic battery packs 20, each of which includes at least one stack 22 of prismatic battery cells 24 stacked along a reference axis 100 of the prismatic battery pack 20, housed in a casing 26. One or more end plates 28 are located within the housing 26 in a space between an end wall 30 of the housing and an axial end of each stack 22 of prismatic battery cells 24. The one or more end plates 28 are translationally movable parallel to the reference axis 100 at least in a thrust direction 200 towards the stack 22 of prismatic battery cells 24. The prismatic battery pack 20 is provided with at least one pusher unit 32 to push the end plate(s) 28 towards the stack(s) 22 of battery cells 24 and maintain a pressure force throughout the lifetime of the prismatic battery pack 20 to absorb the play that would otherwise accumulate between the battery cells 24 as their volume decreases over time. In Figure 1, only two thrust units 32 are schematically illustrated, each with a movable thrust member 34 in contact with a contact face 36 of the end plate 28 opposite the stack 22, at least one spring 38 applying a thrust force directly or indirectly to the thrust member 34 towards the stack 22, such that the thrust member 34 applies a pressure force to the end plate 28 with an axial component 36 towards the stack 22 of prismatic battery cells 24. Each thrust unit 32 is housed in a frame 40, which is removably attached to the housing 26, outside the housing 26, by means of fasteners 42. An adjustment mechanism 44 comprising an adjustment interface 46 allows adjustment of the thrust force of the spring 38. In an embodiment disclosed in more detail in Figures 2 to 6, several end plates 28 can be provided, each pushed by one or more thrust units 32 acting in parallel. More specifically, each thrust unit 32 is provided with a frame 40, which houses a nut 48 and a compression spring 38 compressed between the nut 48 and the frame 40. The frame 40 can be made in two parts, with a body 50 and a threaded cap 52 fixed to the body 50. Optionally, two parallel thrust units 32 can share a common frame, as shown in Figures 3 to 6. The movable thrust member 34 is a rod, which passes through a through-hole 54 in the body 50 of the frame 40, and another through-hole 56 in the cap 52 at an opposite end of the frame 40, so that the rod is guided in translation parallel to a translation axis 300 and free to rotate about the translation axis 300. The rod has a threaded intermediate portion engaged in the nut 48 to provide a threaded connection 58. The nut 48 has a radial protrusion 60, which engages in a groove 62 in the body of the frame 40, which runs parallel to the rod, so that the nut 48 is free in translation parallel to the rod but cannot rotate about the translation axis 300 with respect to the frame 40. The frame 40 can be detachably attached to the end wall 30 of the housing 26 by means of detachable fasteners 42 such as threaded fasteners, in a position where the through holes 54, 56 of the frame 40 align with a through hole 64 in the end wall 30 of the housing 26. In this position, the rod protrudes through hole 64 into the housing 26 and comes into contact with the associated end plate 28, and the translation axis 300 of the rod is parallel to the reference axis 100 of the housing, so that the rod rests against the associated end plate 28. A free end of the rod opposite the end plate 28 is provided with a user interface, here a hexagonal hole, which constitutes the adjustment interface 46. With the rod supported against the end plate 28, the threaded connection 58 between the rod and the nut 48 provides an irreversible, bidirectional mechanical motion transformation mechanism. This allows a user to screw the rod, which rotates about its axis 300 without translational movement, by driving the nut 48 in a direction opposite to the thrust direction 200, in order to adjust the load of the recoil spring 38 to a desired level. Therefore, the screw and nut mechanism between the nut 48 and the rod constitutes an adjustment mechanism 44 for adjusting the thrust force of the recoil spring 38. Once loaded, spring 38 rests on nut 48, which acts as a spring seat attached to the rod, and pushes the nut 48, which transfers a thrust force to the rod. The rod acts as a thrust member and applies a pressure force to the end plate 28, which is approximately equal to the thrust force applied by the spring, except for friction. The translation of nut 48 in the frame 40 is limited in one direction by the maximum retraction of spring 38 and in the opposite direction by cap 50, which acts as a stop. The stroke of spring 38 is preferably sufficient to remain in contact with nut 48 when the latter rests on cap 50.The force applied by spring 38 to nut 48 and rod decreases when the rod moves in the push direction 200, but is set so that the axial pressure force applied to end plate 28 at the end of the prismatic battery pack 20's service life is sufficient when the maximum expected decrease in the volume of the prismatic battery cells 24 has occurred. The thrust unit 32 of the embodiment shown in Figures 2 to 6 has the advantage of combining a number of functions in a small number of parts and in a very compact design, including - the function of storing potential mechanical energy thanks to spring 38, - the function of transferring this energy to the end plate 28 thanks to the threaded connection 58 between the rod and the nut 48, - the function of adjusting the thrust force thanks to the adjustment interface 46 of the rod, the threaded connection 58 between the rod and the nut and the sliding connection between the nut 48 and the frame 40, and - the function of keeping the parts of the push unit 32 together in a detachable unit of the housing 26, thanks to the frame 40 and the fasteners 42. The prismatic battery pack schematically illustrated in Figure 7 differs from the prismatic battery pack of the embodiment of Figures 2 to 6 in that the load of spring 38 is applied to a cam 148, which rotates about an axis perpendicular to the reference axis and pushes a thrust member 34, in this case a push rod, on a translational axis parallel to the reference axis 100. The thrust force of spring 38 can be adjusted by means of an irreversible adjustment mechanism 144, which includes a lever 146 and a ratchet wheel 158. In this embodiment, the adjustment interface is formed by the lever 146, which is a separate part of the thrust member 34. Furthermore, the motion of spring 38 is not transferred 1:1 to the thrust member 34, meaning that the shape of the cam 148 can be optimized to provide a desired transmission ratio between spring 38 and the thrust member. 34. The prismatic battery pack of Figure 8 differs from previous embodiments in that the load of spring 38 is applied to a conical slider 248, which slides in a direction perpendicular to the reference axis, and pushes a thrust member, in this case a thrust rod fixed to another conical slider 234, on a translation axis 300 parallel to the reference axis 100. The thrust force of spring 38 can be adjusted by means of an irreversible adjustment mechanism 244, which includes a screw 258 and a nut 248.2. The prismatic battery pack in Figure 9 differs from previous embodiments in that the thrust unit 32 is located within the housing 26 of the prismatic battery pack 10, except for the adjustment interface 46, which protrudes from the housing 26 to remain accessible from the outside of the housing 26. Although the thrust member 34 is depicted as a rod, it could alternatively be a cam similar to cam 148 in Figure 7, or a slider similar to slider 234 in Figure 8. The prismatic battery pack in Figure 10 differs from previous embodiments in that the thrust unit 32 is pre-charged and is not provided with an adjustment mechanism.

Claims

1. A prismatic battery pack (20), in particular for supplying power to an electric drive motor (12) of an electric or hybrid vehicle (10), the prismatic battery pack (20) comprising: - at least one stack (22) of prismatic battery cells (24) stacked along a reference axis (100) of the prismatic battery pack (20), - a housing (26) accommodating the stack (22) of prismatic battery cells (24), - at least one end plate (28) located within the housing (26) and extending into a space between an end wall (30) of the housing and an axial end of the stack (22) of prismatic battery cells (24), and - at least one pusher device comprising at least one movable pusher member (34) in contact with a contact face of the end plate (28) opposite the stack (22) of prismatic battery cells. (24),and at least one spring (38) that directly or indirectly applies a thrust force to the thrust member towards the stack (22) of prismatic battery cells (24), such that the thrust member (34) applies a pressure force to the end plate (28) with an axial pressure force component (36) towards the stack (22) of prismatic battery cells (24), characterized in that the thrust device is a thrust unit (32) removably attached to the housing (26) and provided with a frame (40), which houses the spring (38) and guides the thrust member (34).

2. The prismatic battery pack (20) of claim 1, further comprising at least one intermediate member (48, 148, 248) between the spring (38) and the movable thrust member (34), for transmitting force and motion from the spring (38) to the movable thrust member (34).

3. The prismatic battery pack (20) of claim 2, wherein the intermediate member (48, 148,248) includes at least one of: - a spring seat (48) integral with or attached to the thrust member (34); - a lever pivoting about a pivot axis between the first end position and the second end position; - a cam (148) rotating about a pivot axis perpendicular to the reference axis; - a conical slider (248) sliding on a translation axis perpendicular to the reference axis.

4. The prismatic battery pack (20) of any one of the preceding claims, wherein the thrust unit (32) further comprises an adjustment mechanism (44) for adjusting the thrust force, the adjustment mechanism (44) being at least partially housed in the frame (40).

5. The prismatic battery pack (20) of claim 4, wherein the adjustment mechanism (44) comprises an irreversible motion transformation mechanism,6. The prismatic battery pack (20) of claim 4 or 5, wherein the adjustment member (44) and the thrust member (34) are integral with each other and the irreversible transformation mechanism (58) is such that it adjusts a position of a spring seat (48) to transfer force and motion between the spring (48) and the thrust member (34) with respect to the thrust member (34).

7. The prismatic battery pack of any one of claims 4 to 6, wherein the adjustment mechanism is accessible from outside the housing.

8. The prismatic battery pack (20) of any one of the preceding claims,wherein the frame (40) guides the movable thrust member (34) in translation about a translation axis (300) parallel to the reference axis (100).

9. The prismatic battery pack of any one of the preceding claims, wherein the spring (38) is a retraction spring with an operating stroke of at least 5 mm, preferably 10 mm, in the frame (40), between a fully retracted state and a released or partially released state.

10. The prismatic battery pack of claim 9, wherein the spring (38) has a retraction direction parallel to the reference axis.

11. The prismatic battery pack of any one of claims 1 to 7, wherein the frame (40) of the thrust unit (32) is located in the housing (26).

12. A prismatic battery pack according to the preamble of claim 1 or any one of the preceding claims,characterized in that the spring (38) is located outside the housing (26), which has an opening (64) through which the thrust member (34) protrudes into the housing (26).

13. An electric or hybrid motor vehicle (10) comprising an electric drive motor (12) and at least one prismatic battery pack (20) according to any one of the preceding claims, for supplying power to the electric drive motor (12).