Wheel unit with breakable joint, hub unit and mounting method

Abstract

A wheel unit for electrically driven vehicles with a disconnectable drive comprises a wheel support (4), a wheel hub (1) rotatably supported by the wheel support (4), and a wheel pin (5) carried by a component driven by an electric motor and rotatably mounted in the wheel hub (1) by means of two rolling bearings (19, 20). A coupling device (15) releasably connects the driven component (6) to the wheel hub (1). The two rolling bearings (19, 20) rotatably supporting the wheel pin (5) have respective outer rings (19A, 20A) mounted by interference fit within a cylindrical wall (7) of a central opening of the hub and respective inner rings (19B, 20B) rigidly connected together by means of a spacer sleeve (21) having a strictly predetermined length. The wheel-hub (1) unit (M) with the two rolling bearings (19, 20) and the spacer sleeve (21) can be assembled before being mounted on the wheel pin (5).

Description

Technical Field

[0001] The invention relates to a wheel unit with a disengageable drive for an electric vehicle, of the type comprising:

[0002] - wheel supports,

[0003] - a wheel hub, which is rotatably supported by the wheel support,

[0004] - a wheel pin, which is rotatably mounted in the cylindrical wall of the central opening of the hub by means of two rolling bearings axially spaced from one another,

[0005] - wherein the wheel pin is carried by a rotatable member configured to be driven by an electric motor of the vehicle; and

[0006] - Coupling means for releasably connecting the aforementioned driven member to the wheel hub. Background Art

[0007] Solutions of the type mentioned above are already used in advanced battery electric vehicles (BEVs) that are equipped with two electric motors for driving the front and rear wheels, respectively. In electric vehicles of this type, in the case of four-wheel drive, so-called eAWD (electric all-wheel drive), four-wheel drive is generally excessive, but on the contrary is useful when the goal is to exploit the regenerative braking capabilities and the resulting battery recharging as much as possible or otherwise for driving in extreme conditions of tire adhesion. In order to enable engagement and disengagement of the drive axle (usually the front axle), corresponding wheel units are provided according to the configuration mentioned above. Thanks to the coupling device mentioned above, the component driven by the electric motor can be rotationally connected to the wheel pin or otherwise disconnected from the wheel pin by the electronic controller of the vehicle, on demand by the driver or in other cases even automatically based on detected dynamic conditions. Furthermore, transitioning from the all-wheel drive (AWD) condition to the rear-wheel drive (RWD) condition is advantageous because the passive drag of the disengaged axles (axle shafts, differential, electric motor) is substantially reduced overall to the advantage of the vehicle battery's autonomy.

[0008] Attached Figure 10 is a schematic cross-sectional view of a wheel unit with a disconnectable drive of a known type for an electric vehicle with a disconnectable front wheel drive.

[0009] exist Figure 10 In the drawing, reference numeral 1 designates as a whole the body of the wheel hub, which is rotatably mounted via rolling bearings 2 in a hub support part 3 which in turn is rigidly connected to a wheel support 4, for example by means of bolts.

[0010] Reference numeral 5 designates a wheel pin, which is carried by a driven part 6 (typically a bell-shaped body of a constant-speed universal joint) that is to be driven in rotation by an electric motor designed to drive the front wheels of the vehicle. Since the wheel unit envisages the possibility of disconnecting the rotational connection between the driven part 6 and the wheel hub 1, the pin 5 is not rigidly connected to the wheel hub 1 in rotation, as would happen in conventional solutions with a permanent drive, but is, on the contrary, rotatably mounted in the cylindrical wall 7 of the central opening of the wheel hub 1 by means of two rolling bearings 8, 9 axially spaced from each other. In this way, when the wheel hub 1 is not rotationally connected to the pin 5 and the electric drive motor is deactivated, the wheel hub 1 is free to rotate about the pin 5, as in the case of any non-driven wheel.

[0011] In order to achieve the rotational coupling, the bodies of the driven part 6 and the hub 1 carry adjacent annular gears 10, 11, both of which can be engaged by the internal toothing of a ring 12 carried by the driven part 6 and which can be actuated via actuator means (not shown). Figure 10 ) is axially displaced between: an inactive position, in which ring 12 engages only annular gear 10 of component 6, wherein wheel hub 1 is disconnected from driven component 6; and an active position, in which the inner ring gear of ring 12 meshes with both the toothings of annular gears 10, 11, so that wheel hub 1 is rotationally connected to driven component 6 and to wheel pin 5. In the latter condition, the front electric motor of the vehicle can be activated in order to rotationally drive wheel pin 5 and, consequently, wheel hub 1. In this condition, rolling bearings 8, 9 are stationary.

[0012] Reference again Figure 10 The known solutions of the type mentioned above that have been developed so far envisage the use of roller bearings 8 without an inner ring, in which the rollers are in direct contact with the surface of the wheel pin 5 and the roller cage is mounted in the cylindrical wall 7 of the central opening of the hub 1. The rolling bearing 9 is a ball bearing.

[0013] The known solutions described above present a number of disadvantages. First, the use of roller bearings in which the rollers are in direct contact with the wheel pin 5 renders the system particularly susceptible to malfunction following external infiltration of water, mud, and dirt (during installation and removal, during production, or during maintenance). Furthermore, the roller bearing 8 operates with a relatively wide and uncontrollable functional clearance, which can be the source of noise and / or rattling. A further disadvantage is that both bearings 8, 9 require adjustment operations that must be performed in the production facility, always creating the risk that optimal operating conditions for the bearings may not be achieved in all circumstances. Yet another disadvantage is that the ball bearing 9, located on the outward-facing end of the cylindrical wall 7, must be equipped with a specific seal resistant to the infiltration of water, mud, and dirt, with the attendant increase in the passive resistance of the aforementioned sealing means. Furthermore, the entire system described above also entails the use of grease in the production facility, which in turn leads to complications during production and the risk of malfunctions resulting from the application of an incorrect amount of grease.

[0014] In view of the foregoing, the need is therefore felt for a solution that will overcome the above-mentioned drawbacks and, in particular, will simplify the operations to be carried out in a production plant.

[0015] A wheel unit of the type indicated at the beginning of the description is known from WO 2006 / 035836 A1.

[0016] Purpose of the Invention

[0017] The object of the present invention is therefore to provide a wheel unit of the type described above which will enable deactivation of the drive on the wheel, substantially reducing the passive resistance of the disengaged axle (axle shaft, differential, electric motor) as a whole to the advantage of the battery autonomy of the electric vehicle and which at the same time will overcome the disadvantages of the known solutions.

[0018] In particular, the object of the present invention is to simplify the operations to be carried out in the production plant, envisaging the possibility of pre-assembling (offline) the wheel-hub unit, which can then be mounted on the wheel support in the production plant using simple operations without requiring complex setting operations and adjustment operations.

[0019] A further object of the invention is to provide a wheel unit of the above specified type which will always be in proper and reliable operation.

[0020] A further object of the present invention is to provide a wheel unit of the type specified above which will not be exposed to risks of failure due to penetration of water, mud or dirt.

[0021] Finally, a still further object of the present invention is to achieve all of the aforementioned aims with a wheel unit that is relatively simple and inexpensive to produce. Summary of the Invention

[0022] In order to achieve one or more of the aforementioned objects, the subject of the present invention is a wheel unit with a disengageable drive for an electric vehicle, comprising:

[0023] - wheel supports,

[0024] - a wheel hub, which is rotatably supported by the wheel support,

[0025] - a wheel pin, which is rotatably mounted in the cylindrical wall of the central opening of the hub by means of two rolling bearings axially spaced from one another,

[0026] - wherein the wheel pin is carried by a rotatable member configured to be driven by an electric motor of the vehicle, and

[0027] - coupling means for releasably connecting the aforementioned driven member to the wheel hub,

[0028] The wheel unit is characterized in that:

[0029] - the wheel pin is rotatably mounted in the cylindrical wall of the hub by means of two rolling bearings axially spaced from one another, the two rolling bearings having respective outer rings mounted by interference fit in said cylindrical cavity, abutting against two respective annular shoulders of said cylindrical cavity and facing the two opposite ends of the cylindrical cavity, and

[0030] - the rolling bearings have respective inner rings which are rigidly mounted on the wheel pins and are rigidly connected together by means of spacer sleeves having a length predetermined according to the axial distance between the annular shoulders,

[0031] - The unit consists of the hub with rolling bearings and spacer sleeves, which can be assembled before mounting on the wheel pin.

[0032] In a preferred embodiment, the two rolling bearings are two ball bearings. A first of the ball bearings, which is located further from the free end of the wheel pin, has its inner ring placed against the annular shoulder of the driven component. A second of the ball bearings has its inner ring axially secured by a nut screwed onto the threaded portion of the free end of the wheel pin in such a manner that the entirety of the two inner rings of the rolling bearings, together with the interposed spacing sleeve, are axially pressed against the shoulder of the driven component.

[0033] According to a further characteristic of the invention, the end of the cylindrical wall of the hub facing outwards is protected from external aggressions and isolated from the outside by a covering element which is mounted on the hub.

[0034] As is clear from the foregoing, in the solution according to the invention, the unit consisting of the wheel hub with the two aforementioned rolling bearings and the spacer sleeve rigidly interposed between the inner rings of the two rolling bearings can be preassembled outside the production line and then installed in the production facility using a simple operation that does not require any adjustment operations. The preassembled unit also already includes the grease for lubricating the bearings, without the need for any further operations in the production facility.

[0035] The outer cover protecting the central opening of the hub prevents the intrusion of foreign media such as water, mud and dirt. Preferably, the outer cover is made of a metal material in a manner that results in it also playing the role of protection against accidental impacts and collisions.

[0036] The aforementioned spacer sleeve is selected with a strictly predetermined length, which depends on the axial distance of the aforementioned annular shoulder against which the outer rings of the two rolling bearings are mounted.

[0037] The spacer sleeve is rigidly connected to the inner rings of the two rolling bearings, for example by means of a crimping operation, so as to be incorporated into the hub unit. When the nut screwed onto the threaded end of the wheel pin is tightened, the unit is automatically positioned in a manner that minimizes the residual rolling torque of each bearing and maximizes the efficiency of the unit in terms of duration and correct and reliable operation, without any risk of noise caused by undesirable play.

[0038] The subject matter of the invention is also a wheel-hub unit which, considered per se, is preassembled with two rolling bearings and a spacer sleeve interposed between the inner rings of the two bearings.

[0039] Finally, the present invention also relates to a method for assembling the hub unit described above, wherein, in a first step, the hub unit is assembled with two rolling bearings and the aforementioned spacer sleeve, and in a second step, the aforementioned hub unit assembled in the first step is mounted on a wheel pin, so that the unit is axially tightened in the installation position by means of a nut screwed on the threaded end of the wheel pin in such a manner that the entirety of the two inner rings of the rolling bearings together with the spacer sleeve interposed therebetween are axially pressed against the shoulder of the aforementioned driven part. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further characteristics and advantages of the invention will emerge from the ensuing description, made with reference to the accompanying drawings, provided purely by way of non-limiting example, and in which:

[0041] - Figure 1is a perspective view of a conventional type of steerable front wheel unit having a wheel support rotatably supporting a wheel hub which is permanently rotatably connected to an axle shaft driven by an electric motor of a vehicle;

[0042] - Figure 2 is a perspective view showing a wheel support of a steering front wheel to which a preferred embodiment of the present invention is applied;

[0043] - Figure 3 and Figure 4 are cross-sectional views of a preferred embodiment of a wheel unit according to the invention in two different operating conditions;

[0044] - Figure 5 yes Figure 3 and Figure 4 Another cross-sectional view of the wheel unit of FIG. 1 , on an enlarged scale;

[0045] - Figure 6 yes Figure 5 Further cross-sectional views of details on an enlarged scale;

[0046] - Figure 7 and Figure 8 are two perspective views of a hub unit according to the present invention;

[0047] - Figure 9 yes Figure 7 and Figure 8 a cross-sectional view of the hub unit; and

[0048] - Figure 10 is a partial schematic cross-sectional view of a wheel unit according to the prior art. DETAILED DESCRIPTION

[0049] exist Figure 1-9 Regarding the prior art described above, Figure 10 Parts that are common or correspond to the parts illustrated in FIG. 1 are designated by the same reference numerals.

[0050] Figure 1 A conventional wheel unit is shown, wherein the wheel hub 1 is rotatably supported by a wheel support (steering knuckle) 4 and is permanently rotationally connected via a constant-speed universal joint 13 to an axle shaft 14 driven by a front electric motor (not shown) of the vehicle. Figure 1 The example relates to a front wheel unit, in which the wheel support 4 is supported in a pivoting manner about the steering axis of the wheel by means of components of the vehicle suspension. Figure 1 and Figure 2-9In both cases, the suspension components to which the wheel supports 4 are connected are not shown, since they may be provided in any known manner and since, considered per se, they do not fall within the scope of the present invention.

[0051] As already mentioned above, the wheel unit according to the invention is of a type for an electric vehicle and has a disengageable drive, which electric vehicle will be operated both by means of a first electric motor permanently connected to a wheel axle (typically the rear axle) and by means of a second electric motor releasably connected to the hub of the front wheel.

[0052] Figure 2 The present invention is shown as an example of a wheel support 4 of a front steering wheel having a wheel hub 1 rotatably supported by the wheel support 4 and a coupling device 15 described in detail later, which is carried by the wheel support 4 and is provided for selectively coupling the wheel hub 1 to a driven member (not shown) of a constant speed universal joint 13. Figure 2 The constant speed universal joint 13 is connected to the wheel shaft 14 (also not shown in FIG). Figure 2 (see figure in the middle).

[0053] refer to Figure 3 、 Figure 4 and Figure 5 In the example of embodiment illustrated here, the wheel hub 1 is rotatably supported by the hub support part 3 by means of a double ball ring 16, which is rigidly connected (typically by means of bolts) to the body of the wheel support 4. It should be noted that the specific configuration of the wheel support 4, the hub support part 3, the body of the wheel hub 1 and the rolling bearing constituted by the double ball ring 16 is illustrated here purely by way of example, and these components may be provided in any other known manner.

[0054] The driven part 6 of the constant speed universal joint has an axis forming the wheel pin 5. Figure 10 As in the case of the known solution illustrated in FIG, the body of the driven part 6 and the body of the hub 1 carry ring gears 10, 11 adjacent to each other, which are connected by means of slip rings 12 (see Figure 3 and Figure 4 ) are rotatably connected together after engaging with the internal toothed portion. Figure 3 and Figure 4Also shown schematically are actuator means 15 comprising an electric motor 18 which, by means of any type of mechanical transmission, drives, in a manner known per se, the axial movement of the ring 12. Since the structural details concerning the mechanism controlled by the electric motor 18 can be obtained in any known manner and since, considered per se, they do not fall within the scope of the present invention, they are not described or illustrated herein.

[0055] Figure 3 shows an operating condition in which ring 12 has its inner ring gear meshing with both ring gear 10 and ring gear 11, wherein, Figure 4 FIG shows an operating condition in which the sleeve 12 is engaged only with the ring gear 10. Figure 3 In the case of Figure 4 In the condition of , the driven component 6 is disconnected from the wheel hub 1 and the driven component 6 is thus free to rotate on the wheel pin 5.

[0056] Special reference Figure 5 and Figure 6 The rotatable support of the hub 1 on the wheel pin 5 is provided by means of two rolling bearings 19, 20 with a single ball ring. In a preferred example, both rolling bearings 19, 20 are ball bearings. The two ball bearings 19, 20 respectively have an outer ring 19A, 20A, which is mounted so as to press on a corresponding annular shoulder 1A facing the opposite end of the cylindrical wall 7 of the central opening of the hub 1 and is defined by the widened end portion of the aforementioned wall.

[0057] Furthermore, the ball bearings 19 , 20 have respective inner rings 19B, 20B mounted on the wheel pin 5 .

[0058] A spacer sleeve 21 is provided between the inner rings 19B, 20B of the two ball bearings 19, 20. The spacer sleeve 21 is preferably made of steel and has a length that is strictly predetermined according to the axial distance H between the two shoulders 1A, taking into account the configuration of the two bearings 19, 20. In the example, the length of the sleeve 21 is equal to the distance H.

[0059] The spacer sleeve 21 is rigidly connected to the inner rings 19B, 20B of the two bearings 19, 20, respectively, for example by means of a crimping operation. Figure 9The wheel-hub unit designated as a whole by the reference symbol M can be preassembled offline and mounted on the wheel pin 5 in a single operation in a production facility. The wheel-hub unit comprises a hub support part 3 in which the body of the hub 1 is rotatably mounted by means of a bearing comprising: a double ball ring 16; two rolling bearings 19, 20 with their outer ring, inner ring and corresponding balls, the outer ring being mounted in the cylindrical wall 7 by interference fit; and a spacer sleeve 21 rigidly connected to the inner ring of the bearings 19, 20. During the above mounting step, the two bearings 19, 20 are fitted on the wheel pin 5 together with the spacer sleeve 21 until the rolling bearing 19 further from the free end of the wheel pin 5 comes to bear against the pin 5 ( Figure 6 ) of the enlarged diameter portion defined by the annular shoulder 5A ( Figure 6 )until. Figure 7 and Figure 8 Show Figure 9 Two perspective views of the hub unit M before it is mounted on the wheel pin.

[0060] Reference again Figure 6 Once the hub unit M has been mounted on the wheel pin 5, it is axially tightened by screwing the nut 22 onto the threaded portion 5B of the wheel pin 5. Tightening the nut 22 causes the entirety formed by the inner rings 19B, 20B of the two bearings 19, 20 together with the spacer sleeve 21 to be axially pressed against the annular shoulder 5A of the driven part 6.

[0061] Thus, the final mounting operation of the hub unit can be carried out in a fast and efficient manner, wherein no complicated adjustment operations are required to ensure that a proper operation of the wheel unit is obtained.

[0062] Another important characteristic of the present invention is the fact that a cover 23 is rigidly mounted on the body of the hub 1, the cover 23 having the purpose of protecting the central opening of the hub 1, in which the bearings 19 and 20 are mounted, from external aggressions and isolating it from the outside, thus preventing any penetration of water, mud or dirt. Preferably, the cover 23 is made of a metal material so as to also perform the function of protection against impacts.

[0063] In the illustrated example (see Figure 5 ), the body of the hub 1 includes a cylindrical wall 1B that projects axially from the end surface of the hub 1, onto which the cylindrical wall 7 extends. Furthermore, in this example, the cover 23 is in the form of a dome-shaped element made of sheet metal, having a circumferential wall 23A that fits within the cylindrical wall 1B by an interference fit. Of course, any other configuration of the cover 23 is possible, as can any technique for rigidly connecting the cover 23 to the body of the hub 1 in a removable manner.

[0064] Of course, without prejudice to the principle of the invention, the structural details and the embodiments may vary widely with respect to what has been described and illustrated herein purely by way of example, without thereby departing from the scope of the invention, as defined in the appended claims.

Claims

1. A wheel unit with a disengageable drive for an electric vehicle, comprising: - wheel support (4), - a wheel hub (1), which is rotatably supported by the wheel support (4), - a wheel pin (5) rotatably mounted in the cylindrical wall (7) of the central opening of the hub (1) by means of two rolling bearings (19, 20) axially spaced from one another, - wherein the wheel pin (5) is carried by a rotatable driven member (6) configured to be driven by an electric motor of the vehicle, and - coupling means (15) for releasably connecting the driven member (6) to the hub (1), The wheel unit is characterized in that: - the wheel pin (5) is rotatably mounted in the cylindrical wall (7) of the wheel hub (1) by means of two rolling bearings (19, 20) axially spaced from one another and having respective outer rings (19A, 20A) mounted in the cylindrical wall (7) by interference fit against two respective annular shoulders (1A) of the cylindrical wall (7) at two opposite ends facing the cylindrical wall (7), and - the rolling bearings (19, 20) have respective inner rings (19B, 20B) which are rigidly mounted on the wheel pin (5) and rigidly connected together by means of a spacer sleeve (21) having a length predetermined according to the axial distance (H) between the annular shoulders (1A), - The unit (M) is composed of the hub (1) with the rolling bearings (19, 20) and the spacer sleeve (21), and can be assembled before being mounted on the wheel pin (5).

2. The wheel unit according to claim 1, characterized in that The rolling bearings (19, 20) are ball bearings, the first ball bearing (19) of the ball bearings being further from the free end of the wheel pin (5) having its inner ring (19B) placed against the annular shoulder (5A) of the driven part (6), and the second ball bearing (20) of the ball bearings having its inner ring (20B) axially tightened by a nut (22) screwed onto the threaded portion (5B) of the free end of the wheel pin (5) so as to press the entirety of the two inner rings (19B, 20B) of the rolling bearing together with the spacer sleeve (21) interposed therebetween axially against the shoulder (5A) of the driven part (6).

3. The wheel unit according to claim 1, characterized in that The end of the cylindrical wall (7) of the central opening of the hub (1) facing outwards is protected from external aggressions and isolated from the outside by a covering element (23) which is rigidly connected to the hub (1).

4. A wheel-hub unit (M) for a wheel unit with a disengageable drive according to any one of the preceding claims, comprising: - a hub support member (3) configured to be rigidly connected to the wheel support member (4), and - a wheel hub (1) rotatably supported by the hub support member (3) and having a central opening with a cylindrical wall (7) configured to receive and rotatably support a wheel pin (5) carried by a driven member (6), The wheel-hub unit (M) is characterized by: - two rolling bearings (19, 20) axially spaced apart from each other are assembled in the cylindrical wall (7) of the central opening of the hub (1), - the two rolling bearings (19, 20) have respective outer rings mounted by interference fit inside the cylindrical wall (7), against two respective annular shoulders (1A) of the cylindrical wall at two opposite ends facing the cylindrical wall (7), and - the rolling bearings (19, 20) have respective inner rings (19B, 20B) which are rigidly connected together by means of a spacer sleeve (21) having a length predetermined according to the axial distance (H) between the annular shoulders (1A), - The wheel-hub unit (M) with the rolling bearings (19, 20) and the spacer sleeve (21) is configured to be assembled on the wheel pin (5).

5. The wheel-hub unit (M) according to claim 4, characterized in that The end of the cylindrical wall (7) of the central opening of the hub (1) facing outwards is protected from external aggressions and isolated from the outside by a covering element (23) which is rigidly mounted on the hub (1).

6. A method for mounting a wheel-hub unit (M) according to claim 4 on a wheel pin (5), characterized in that In a first step, the wheel-hub unit (M) is assembled, wherein the rolling bearings (19, 20) and the spacer sleeve (21) are included in the wheel-hub unit (M), and in a second step, the wheel-hub unit (M) assembled in the first step is mounted on a wheel pin (5), and the hub unit (M) is axially fastened in the mounting position by means of a nut (22) screwed onto the threaded end (5B) of the wheel pin (5) so that the entirety of the two inner rings (19B, 20B) of the rolling bearings (19, 20) with the spacer sleeve (21) interposed therebetween are axially pressed against the shoulder (5A) of the driven component (6).

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