Parking brake and electric machine comprising such brake

Abstract

The invention relates to a parking brake device (40) adapted to be placed in a housing (20) of an electric machine (1), which housing accommodates a rotating shaft (10) and at least one rolling bearing (32) for guiding the rotating shaft, comprising:-an annular support (47) adapted to be inserted between the rolling bearing and the housing; -an annular slide gear (45) mounted on the support, slidable between two extreme positions, the annular slide gear being fixed against rotation on the support and having a dog clutch adapted to engage with a notched wheel coupled to the rotating shaft; and-an actuator (41) adapted to move the sliding gear between the two extreme positions thereof.

Description

Technical Field

[0001] The present invention generally relates to the braking of motor vehicles.

[0002] The present invention more particularly relates to a device having a parking brake function.

[0003] The present invention also relates to an electric machine equipped with such a device, and to a motor vehicle comprising such an electric machine. Background Art

[0004] Various types of parking brakes are known.

[0005] For example, hand brakes are known, which include a handle capable of pulling a metal cable that is connected to a brake caliper capable of immobilizing the rear wheels of a vehicle.

[0006] Electric parking brakes are also known, which include an actuator that is also capable of actuating a cable connected to a brake caliper.

[0007] Although this second system saves space compared to the first system, it is still bulky and also expensive.

[0008] Thus, a differently arranged device that can be used for electric vehicles is known from document DE102017217829. In this document, the braking device includes a ratchet mechanism that can lock onto a notched wheel that is fixed to the shaft of an electric motor of a vehicle. Thus, the device makes it possible to immobilize the shaft of the electric motor in terms of rotation and thus immobilize the vehicle's wheels.

[0009] However, this device is still bulky. It also cannot reduce the noise of the electric machine. Summary of the Invention

[0010] In order to overcome the above-mentioned drawbacks of the prior art, the present invention proposes to position the parking brake as close as possible to the motor.

[0011] More particularly, according to the present invention, a parking brake device is proposed that is adapted to be arranged in a housing of an electric machine, the housing accommodating a rotating shaft and at least one rolling bearing for guiding the rotating shaft. According to the present invention, the parking brake device comprises:

[0012] - an annular support adapted to be inserted between the rolling bearing and the housing;

[0013] - An annular sliding gear, which is mounted on a support and is capable of sliding between two extreme positions, is fixed against rotation on the support, and has at least one projection (typically one or more pawls) capable of engaging, in the manner of a claw clutch, with a notched wheel coupled to the rotating shaft; and

[0014] - An actuator adapted to move the sliding gear between its two extreme positions.

[0015] The annular nature of the support and the sliding gear allows these elements to be positioned around the rotating shaft of the electric machine. Thus, by means of the present invention, the device can be positioned in the housing of the electric machine, as close as possible to the rotor, in a space that has hitherto usually remained unoccupied. Consequently, the device proves to be not very bulky and can be housed in a protected and lubricated space, thus ensuring its correct operation over a long period and at low cost.

[0016] The advantage of positioning the support between the housing and the rolling bearing is that the support can thus reduce the operating noise. Specifically, if made of a suitable material, the stiffness of the support can be greater than the stiffness that the housing may have, and this will reduce vibrations and thus the noise.

[0017] Typically, when such a support is made of grey cast iron, it is capable of damping the aperiodic behavior of the rotating shaft and ensuring good lubrication around the rolling bearing when the rolling bearing rotates at a very high speed and becomes "floating".

[0018] When the support is made of a suitable material, the support can also exhibit a coefficient of expansion closer to that of the rolling bearing than that of the housing, such that the clearance around the rolling bearing will be less sensitive to thermal variations, thus further reducing the noise.

[0019] By reducing vibrations, the support will also make it possible to ensure a long service life for the electric machine as a whole.

[0020] Finally, it should be noted that the advantage of positioning the parking brake device as close as possible to the rotor of the electric machine rather than to the vehicle wheel is that the braking torque required to immobilize the vehicle will be lower than the braking torque required to immobilize the vehicle when the parking brake device is positioned at the wheel. Specifically, this braking torque will be divided by the reduction ratio between the rotating shaft of the motor and the wheel. Thus, a smaller-sized braking device can be used.

[0021] Further advantageous and non-limiting features of the device according to the invention, considered individually or in any technically possible combination, are as follows:

[0022] - The support is formed from a single one-piece component;

[0023] - The support is made of cast iron;

[0024] - The support defines an inner surface, and the part of the inner surface that is a rotary cylindrical surface accommodates the rolling bearing;

[0025] - The support defines an outer surface, and the part of the outer surface that is a rotary cylindrical surface is adapted to be disposed in an opening of the housing;

[0026] - The support and the sliding gear have mating splines;

[0027] - The splines extend on the outer surface of the support and the inner surface of the sliding gear;

[0028] - An elastically deformable member is provided between the actuator and the sliding gear, and the elastically deformable member is adapted to allow the actuator to move when the sliding gear is held stationary by the notched wheel.

[0029] The present invention also provides an electric machine, which includes:

[0030] - A housing;

[0031] - A rotor, which is accommodated in the housing;

[0032] - A rotating shaft, which is fixed to the rotor, is installed in the housing and can pivot by means of at least one rolling bearing, and the rotating shaft supports the notched wheel; and

[0033] - The parking brake device as mentioned above, when the sliding gear of the parking brake device is in only one of its two extreme positions, the sliding gear engages the notched wheel in the manner of a claw clutch.

[0034] Preferably, the notched wheel is shrink-fitted onto the rotating shaft.

[0035] The present invention also provides a motor vehicle, which includes a chassis, wheels, and the electric machine as mentioned above, and the rotating shaft of the electric machine is always coupled to at least some of the wheels.

[0036] Of course, various features, variations, and embodiments of the present invention can be combined with each other in various combinations as long as they are not mutually incompatible or mutually exclusive. Detailed Description

[0037] The following description given by way of non-limiting examples with reference to the accompanying drawings will make it easy to understand the content of the present invention and how the present invention can be implemented.

[0038] In the drawings:

[0039] Figure 1 ​is a cross-sectional schematic view of an electric machine according to the present invention, the electric machine including a parking brake device shown in a non-activated position;

[0040] Figure 2 is similar to Figure 1 the view in which the parking brake device is shown in an intermediate position;

[0041] Figure 3 is similar to Figure 1 the view in which the parking brake device is shown in an activated position.

[0042] Figure 1 depicts an electric machine 1 of a motor vehicle.

[0043] The motor vehicle can be of any type.

[0044] For example, the motor vehicle is an electric or hybrid motor vehicle including a chassis and wheels, and its electric machine serves as a traction motor to drive the driven wheels. In this case, the electric machine is preferably coupled to the driven wheels via a speed reducer and a differential. This coupling is continuous in the sense that it is not possible to disconnect the driven wheels from the electric machine.

[0045] As Figure 1 shown, the electric machine 1 conventionally includes a housing 20, which is made of several components assembled to define a chamber for receiving a rotor 60 and an annular stator 70.

[0046] The electric machine can be any type of electric machine, having axial or radial flux, wound rotor or other means, etc.

[0047] Conventionally, the stator 70 is fixed to the housing, while the rotor 60 is intended to rotate about the stator 70.

[0048] The rotor 60 has a central opening through which the rotor is fixedly mounted on a rotating shaft 10, and this rotating shaft thus forms the output shaft of the electric machine 1.

[0049] Conventionally, the rotating shaft 10 is mounted in the housing 20 so as to be able to rotate relative to the housing about a rotation axis A1.

[0050] For this purpose, the rotating shaft is equipped with two rolling bearings 31, 32 (ball bearings in this example), the inner rings of these rolling bearings being shrink-fitted onto the rotating shaft 10, and the outer rings of these rolling bearings being placed in coaxial openings 21, 22 (which are formed in the housing 20 and serve as bearing seats). Thus, the rotating shaft 10 is guided to rotate about its rotation axis A1.

[0051] ​​It should be noted here that the rotary shaft 10 has a reduced cross-section portion 11 on one side (the right-hand side in the figure), which allows it to engage in the first rolling bearing 32 in the rolling bearing, and the rotary shaft does not have such a reduced cross-section portion on the opposite side because the diameter of the second rolling bearing 31 is larger than that of the first rolling bearing.

[0052] It should also be noted that the two openings 21, 22 for accommodating the rolling bearings 31, 32 have the same diameter. Therefore, only the outer ring of the second rolling bearing 31 has a direct shrink fit into the opening 21 of the housing 20.

[0053] According to the invention, the electric machine 1 is effectively equipped with a parking brake device 40 on the same side as the first rolling bearing 32.

[0054] This device is designed to act directly on the rotary shaft 10 of the electric machine 1 in order to brake the vehicle when it is parked.

[0055] In the electric or hybrid vehicle as defined above, the electric machine is actually always kept coupled to the driven wheels of the vehicle because neither a clutch nor a gearbox is provided between the electric machine 1 and the driven wheels. In contrast, a simple speed reducer (typically a constant mesh single-speed ratio device) is provided. As a result, immobilizing the rotary shaft 10 of the electric machine 1 can immobilize the driven wheels, thus providing high-performance braking when parked.

[0056] In this regard, it can be noted that if a torque is applied to the wheels, the speed reducer will reduce the torque experienced at the rotary shaft 10, such that the requirement to brake the vehicle at the rotary shaft 10 will be lower than the requirement to brake the vehicle at the wheels.

[0057] Here, the parking brake device 40 is positioned around the rotary shaft 10. The components providing mechanical braking are located between the rotor 60 and the first rolling bearing 32 in the rolling bearing, inside the housing 20. Therefore, it is not particularly space-consuming.

[0058] To achieve the desired braking, the device includes an annular support 47 fixed to the housing 20 and an annular sliding gear 45 mounted on the support 47, which has a single degree of freedom, i.e., the mobility to slide between the following two extreme positions:

[0059] - A non-enabled position ( Figure 1 ); and

[0060] - An enabled position ( Figure 3 ), in which the sliding gear 45 is coupled to the notched wheel 12 fixed to the rotary shaft 10 in the manner of a claw clutch.

[0061] In the embodiment shown in the figures, the notched wheel 12 has an annular shape, with two planar main faces, an inner face in the form of a cylindrical surface of revolution about the axis of rotation A1, and an outer face with at least one projection (in this example, the outer face has a plurality of claws).

[0062] The notched wheel 12 is shrink - fitted onto the rotating shaft 10 in the vicinity of the rotor 60 (between the rotor and the first rolling bearing 32).

[0063] The claws have the same shape and are regularly distributed around the periphery of the notched wheel 12. These claws form, for example, serrations, the sides of which extend radially with respect to the axis of rotation A1. Thus, the claws are "non - uniform" in the sense that they have a consistent orthogonal cross - section along the axis of rotation A1.

[0064] The support 47, on which the sliding gear 45 slides in order to engage the notched wheel 12 in the manner of a claw clutch, is arranged in the opening 22 of the housing 20 such that the support is inserted between the edge of the opening 22 and the outer ring of the first rolling bearing 32.

[0065] The support is a one - piece part made by casting. The support is preferably made of grey cast iron, which imparts lubrication and damping properties to it.

[0066] Thus, the support 47 forms a high - stiffness interface between the first rolling bearing 32 and the housing 20, thereby making it possible to reduce the noise generated by the rotation of the rotating shaft 10.

[0067] Specifically, the support is made of a material with a stiffness higher than that of the material of the housing 20. Further, due to the presence of the support, the diameter of the opening 22 in the housing 20 is greater than the diameter it would have to have in the absence of the support 47, which means that the housing 20 itself has a higher stiffness than it would have in the absence of the support 47. Thus, the rotating shaft 10 is better guided, better damped, and vibrates less, all of which reduce stress and noise.

[0068] As Figure 1 shown, the support 47 has: a first end portion 47A inserted between the rolling bearing 32 and the housing 20; an opposite second end portion 47B on which the sliding gear 45 slides; and an intermediate ring flange 47C that extends between these two portions and presses against the inner face of the housing 20 to hold the support 47 stationary in the opening 22.

[0069] The first end portion 47A has the form of a ring, the inner face of which is shrink - fitted onto the outer ring of the first rolling bearing 32, and the outer face of which is shrink - fitted into the opening 22. These two faces are cylindrical surfaces of revolution about the axis of rotation A1.

[0070] The intermediate ring flange 47C is in the shape of a washer and has two planar main surfaces orthogonal to the rotational axis A1, with one of the planar main surfaces pressing against the inner surface of the housing 20.

[0071] The inner diameter and outer diameter of this intermediate ring flange are respectively smaller and larger than the inner diameter and outer diameter of the two end portions 47A, 47B. Accordingly, the intermediate ring flange forms an inward protrusion relative to the inner surfaces of these two end portions, and this protrusion presses against the outer ring of the first rolling bearing 32 to laterally fix it in place. The intermediate ring flange also forms an outward protrusion relative to the outer surfaces of these two end portions, and this protrusion presses against the inner surface of the housing 20. To maintain this pressure, screws are provided here for fixing the support member 47 in the housing 20.

[0072] The second end portion 47B is in the form of a ring, and its outer surface has a specific shape for guiding the translational movement of the sliding gear 45 along the rotational axis A1 and for fixing the sliding gear against rotation about this axis.

[0073] For this purpose, the outer surface is formed with profiled splines that mate with the correspondingly negative-shaped splines carried by the sliding gear 45.

[0074] The sliding gear 45 (recall that it also has an annular shape) thus has splines on its inner surface.

[0075] Here, these splines extend only over a part of the length of this inner surface. Specifically, one of the ends of the outer surface (the end facing the end of the notched wheel 12) supports at least one protruding projection. In practice, this end supports a number of identical projections that form claws adapted to mate with the claws of the notched wheel 12. For this purpose, the shape of these claws is complementary to the shape of the notched wheel 12.

[0076] Thus, the sliding gear 45 can slide from its non-activated position ( Figure 1 ) to its activated position ( Figure 3 ), in which non-activated position the claws of the sliding gear are away from the claws of the notched wheel 12 so as not to mate with them, and in which activated position the claws mate with each other.

[0077] During this sliding, the sliding gear 45 passes through Figure 2The depicted intermediate position, in which the pawls of the sliding gear 45 engage with the pawls of the notched wheel 12. This engagement requires the rotary shaft 10 to be in an exact angular position relative to the sliding gear 45 about the axis of rotation A1, which is easily achieved if the rotor 60 is controllable in terms of angular position. If not in the exact angular position, the pawl connection can be mechanically achieved as long as the pawls of the notched wheel 12 are aligned with the space provided between the pawls of the sliding gear 45.

[0078] To enable the sliding gear 45 to slide between its non-activated limit position and its activated limit position, an actuator 41 is provided.

[0079] Any type of actuator can be used, such as an electric servo motor, a moving magnet electromagnetic system, etc.

[0080] The actuator includes a support fixed to the housing 20 and a sliding arm.

[0081] Here, the moving arm supports a cage, which thus moves translationally. This cage is intended to exert a pulling or pushing force on the connecting rod 43, one end of which is hinged to the arm 44, which is adapted to slide the sliding gear. In this particular instance, the arm 44 is pivotally mounted on the housing 20 and has one end that projects towards the inside of the housing 20 and extends into a peripheral groove cut into the outside of the sliding gear 45, and one end that projects towards the outside of the housing and on which the connecting rod 43 is hinged.

[0082] Therefore, the pushing or pulling movement applied to the connecting rod 43 can force the arm 44 to pivot in one direction or the other about an axis orthogonal to the axis of rotation A1 in order to slide the sliding gear 45 between its two limit positions.

[0083] In the case where the rotor 60 is controllable in terms of angular position, an arrangement can be made such that the actuator 41 and the connecting rod 43 are hinged to each other via a simple pivot connection.

[0084] However, as a safety measure, it is preferable to provide elastic connection means between the actuator 41 and the connecting rod 43 such that if the sliding gear 45 is held stationary by the notched wheel 12 (due to their respective pawls not being correctly positioned relative to each other), these elastic connection means allow the actuator to slide the cage without causing damage and without forcing.

[0085] In this instance, these elastic connection means include a spring that is housed in the cage and is clamped between one of the inner faces of the cage and a disc-shaped member fixed to the end of the connecting rod 43.

[0086] At this stage, it can be noted that, conventionally, a dielectric lubricant is used to lubricate the rolling bearings 31, 32. This lubricant will naturally provide lubrication for the connection between the sliding gear 45 and its support 47, which will ensure the correct operation and extended service life of the parking brake device 40.

[0087] It should also be noted that when the vehicle is stationary on a slope and the parking brake device 40 is enabled, it may be found difficult to move the device to the non-enabled position due to the force applied to the parking brake device.

[0088] Therefore, in order to make it easier to move the sliding gear 45, the electric machine 1 can be operated in such a way that the rotary shaft 10 rotates a small stroke (about 1 degree) in a relatively short time, during which the stress applied to the device will be low.

[0089] More generally, before each deactivation of the parking brake device 40, the rotary shaft 10 can be pivoted in one direction and then in the other direction in order to ensure that the sliding gear can slide quickly and without difficulty on its support 47.

[0090] The present invention does not limit the described and depicted embodiments in any way, but can be varied by those skilled in the art in any way according to the present invention.

Claims

1. A parking brake device (40) adapted to be arranged in a housing (20) of an electric machine (1), the housing accommodating a rotating shaft (10) and at least one rolling bearing (32) for guiding the rotating shaft (10), the parking brake device comprising: - an annular support (47) adapted to be inserted between said rolling bearing (32) and said housing (20); - an annular sliding gear (45) mounted on the support (47) and able to slide between two extreme positions, the annular sliding gear being immobilized against rotation on the support (47) and having at least one protrusion able to engage in the manner of a dog clutch with a notched wheel (12) coupled to the rotary shaft (10); as well as - an actuator (41) suitable for moving the sliding gear (42) between its two extreme positions.

2. The parking brake device (40) according to claim 1, wherein, The support member (47) is formed from a single one-piece component.

3. The parking brake device (40) according to one of claims 1 and 2, wherein, The support (47) is at least partially made of cast iron.

4. The parking brake device (40) according to any one of claims 1 to 3, wherein, The support member (47) defines an inner surface and an outer surface, wherein the inner surface, which is a cylindrical surface of revolution, accommodates the rolling bearing (32), and the outer surface, which is a cylindrical surface of revolution, is suitable for being placed in the opening of the housing (20).

5. The parking brake device (40) according to one of claims 1 to 4, wherein, The support member (47) and the sliding gear (45) have splines that fit each other.

6. The parking brake device (40) according to claim 5, wherein, The splines extend on the outside of the support (47) and on the inside of the sliding gear (45).

7. The parking brake device (40) according to any one of claims 1 to 6, wherein, An elastically deformable component (42) is provided between the actuator (41) and the sliding gear (45), the elastically deformable component being adapted to allow the actuator (41) to move when the sliding gear (45) is immobilized by the notched wheel (12).

8. An electric machine (1), comprising a housing (20), a rotor (60) received in the housing (20), and a rotating shaft (10) fixed to the rotor (60), the rotating shaft being mounted in the housing (20) so as to be pivotable by means of at least one rolling bearing (32), and the rotating shaft supporting a notched wheel (12), characterized in that, The electric machine further comprises a parking brake device (40) as claimed in one of claims 1 to 7, wherein a sliding gear (45) of the parking brake device engages the notched wheel (12) in the manner of a dog clutch when the sliding gear is in only one of its two extreme positions.

9. The electric machine (1) according to claim 8, wherein, The notched wheel (12) is shrink-fitted onto the rotating shaft (10).

10. A motor vehicle comprising a chassis and wheels, characterized in that, The motor vehicle further comprises an electric machine (1) as claimed in one of claims 8 and 9, the rotary shaft (10) of which is always coupled to at least some of the wheels.

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