Parking brake and electric machine comprising such a brake

Abstract

The invention relates to a parking brake device (40) suitable for being installed in a casing (20) of an electric machine (1) that houses a rotary shaft (10) and at least one rolling bearing (32) for guiding the rotary shaft, the parking brake device comprising: - an annular support (47) suitable for being inserted between the rolling bearing and the casing, - an annular sliding gear (45) which is mounted so as to slide on the support between two end positions, which is locked against rotation on the support, and which has dog clutches suitable for engaging a notched wheel coupled to the rotary shaft, and - an actuator (41) suitable for moving the sliding gear between its two end positions.

Description

DESCRIPTION TITLE OF THE INVENTION: PARKING BRAKE AND ELECTRIC MACHINE COMPRISING SAME SUCH BRAKE TECHNICAL FIELD OF THE INVENTION

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

[0002] It relates more particularly to a device having a parking brake function.

[0003] It also relates to an electrical machine equipped with such a device and a motor vehicle comprising such an electrical machine. STATE OF THE ART

[0004] There are different types of parking brakes.

[0005] For example, we know of hand brakes, which have a handle allowing you to pull a metal cable connected to a brake shoe adapted to block the rear wheels of the vehicle.

[0006] We also know electric parking brakes which include an actuator which again allows the operation of cables connected to brake shoes.

[0007] Although this second system saves space compared to the first, it is still bulky and also comes at a significant cost.

[0008] Document DE102017217829 discloses a device arranged differently, usable on electric vehicles. In this document, the braking device comprises a ratchet mechanism which is adapted to lock onto a toothed wheel fixed to the shaft of the vehicle's electric motor. Thus, this device makes it possible to block the rotation of the electric motor shaft and, consequently, that of the vehicle's wheels.

[0009] However, this device remains bulky. Furthermore, it does not reduce the noise of the electric motor. PRESENTATION OF THE INVENTION

[0010] In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes to place the parking brake as close as possible to the engine.

[0011] More particularly, the invention provides a parking brake device suitable for installation in an electrical machine casing, which casing houses a rotating shaft and at least one bearing for guiding said rotating shaft. According to the invention, this parking brake device comprises: - an annular support adapted to be interposed between said bearing and said casing, - an annular sliding gear which is mounted to slide on the support, between two extreme positions, which is locked in rotation on said support, and which has at least one relief (typically one or more dogs) adapted to engage a toothed wheel coupled to said rotating shaft, and - an actuator adapted to move the player between its two extreme positions.

[0012] The annular nature of the support and the sliding gear allows these elements to be placed around the rotating shaft of the electric machine. Thus, thanks to the invention, the device can be positioned in the casing of the electric machine, as close as possible to the rotor, in a space that was previously often left free. It is therefore compact and can be installed in a protected and lubricated space, which guarantees its proper operation at low cost and in the long term.

[0013] The advantage of placing the mount between the casing and the bearing is that it can reduce rolling noise. If it is made of a suitable material, it can have a greater stiffness than the casing would have, which will reduce vibrations and therefore noise.

[0014] Typically, when this support is made of gray cast iron, it helps to absorb the acyclisms of the rotating shaft and to ensure good lubrication around the bearing when the latter rotates at very high speed and enters into "levitation".

[0015] This support, when made of a suitable material, can also have a coefficient of expansion closer to that of the bearing than the housing, so that the clearance around the bearing will be less sensitive to thermal variations, which will further reduce noise.

[0016] By reducing vibrations, this support will also ensure a longer lifespan for the entire electrical machine.

[0017] Finally, it should be noted that the advantage of placing this parking brake device as close as possible to the rotor of the electric machine, and not near the vehicle's wheels, is that the braking torque it will have to provide to block the vehicle will be lower than that which it would have to provide if it were placed at the wheels. In fact, this braking torque will be divided by the speed reduction ratio provided between the rotating shaft of the motor and the wheels. It is therefore possible to use a brake device of smaller dimensions.

[0018] Other advantageous and non-limiting characteristics of the device according to the invention, taken individually or in all technically possible combinations, are the following: - the support is formed from a single piece; - the support is made of cast iron; - the support delimits an internal face of which a cylindrical part of revolution accommodates said bearing; - the support delimits an external face of which a cylindrical part of revolution is adapted to be installed in an opening of the casing; - the support and the player have grooves which cooperate together; - the grooves extend on an external face of the support and on an internal face of the slider; - there is provided, between the actuator and the slider, an elastically deformable part adapted to allow the actuator to move when the slider is blocked by the toothed wheel.

[0019] The invention also provides an electric machine comprising: - a casing, - a rotor housed in the casing, - a rotating shaft which is fixed to the rotor, which is pivotally mounted in the housing by means of at least one bearing, and which carries a toothed wheel, and - a parking brake device as mentioned above, the sliding lever of which engages the toothed wheel when it is in one of its extreme positions only.

[0020] Preferably, the toothed wheel is shrunk onto said rotating shaft.

[0021] The invention also provides a motor vehicle comprising a chassis, wheels, and an electric machine as mentioned above, the rotating shaft of which is constantly coupled to at least part of said wheels.

[0022] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. DETAILED DESCRIPTION OF THE INVENTION

[0023] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0024] On the attached drawings:

[0025] [Fig. 1] is a schematic sectional view of an electric machine according to the invention, comprising a parking brake device shown in the inactive position;

[0026] [Fig. 2] is a view similar to that of Figure 1, in which the parking brake device is illustrated in the intermediate position;

[0027] [Fig. 3] is a view corresponding to that of Figure 1, in which the parking brake device is shown in the activated position.

[0028] In Figure 1, an electrical machine 1 of a motor vehicle is shown.

[0029] This motor vehicle could be of any type.

[0030] For example, an electric or hybrid car, comprising a chassis and wheels, whose electric machine serves as the traction motor for the drive wheels. In In this eventuality, the electric machine is preferably coupled to the drive wheels by a speed reducer and a differential. This coupling is continuous, in the sense that it is not possible to decouple the drive wheels from the electric machine.

[0031] As shown in Figure 1, the electrical machine 1 conventionally comprises an outer casing 20 which is made of several pieces assembled to delimit a chamber housing a rotor 60 and an annular stator 70.

[0032] It could be an electric machine of any type, axial or radial flux, wound rotor or not...

[0033] Conventionally, the stator 70 is fixed to the housing while the rotor 60 is provided to pivot in the stator 70.

[0034] The rotor 60 has a central opening through which it is fixedly mounted on a rotating shaft 10, which therefore forms the output shaft of the electrical machine 1.

[0035] Conventionally, this rotary shaft 10 is mounted in the casing 20 so as to be able to rotate relative to the latter around an axis of rotation A1.

[0036] For this purpose, it is equipped with two bearings 31, 32, here ball bearings, the inner rings of which are shrunk onto the rotating shaft 10 and the outer rings of which are placed in coaxial openings 21, 22 provided in the casing 20 and acting as bearings. Thus the rotating shaft 10 is guided in rotation around its axis of rotation A1.

[0037] It will be noted here that the rotating shaft 10 has on one side (the right side in the figures) a reduction in section 11 allowing it to be engaged in a first of the bearings 32 and that it is devoid of such a reduction in section on the opposite side since the second bearing 31 has a diameter greater than that of the first.

[0038] It will also be noted that the two openings 21, 22 receiving the bearings 31, 32 are of the same diameters. Then, only the second bearing 31 has an outer ring directly shrunk into the opening 21 of the casing 20.

[0039] According to the invention, the electric machine 1 is in fact equipped on the side of the first bearing 32 with a parking brake device 40.

[0040] This device is designed to act directly on the rotating shaft 10 of the electric machine 1 in order to brake the vehicle when the latter is parked.

[0041] In an electric or hybrid vehicle as defined above, the electric machine always remains coupled to the drive wheels of the vehicle since there is no clutch or gearbox provided between the electric machine 1 and the drive wheels. Instead, a simple speed reducer (typically a single-ratio constant mesh) is provided. Consequently, locking the rotating shaft 10 of the electric machine 1 makes it possible to lock the drive wheels, and therefore to ensure efficient parking braking.

[0042] In this regard, it can be noted that if a torque is exerted at the wheels, the torque felt at the rotating shaft 10 will be reduced thanks to the speed reducer, so that it will be less restrictive to brake the vehicle at the rotating shaft 10 than at the wheels.

[0043] Here, the parking brake device 40 is placed around the rotating shaft 10. The part allowing the braking to be carried out mechanically is located between the rotor 60 and the first of the bearings 32, inside the casing 20. It is therefore particularly space-saving.

[0044] To achieve the desired braking, the device comprises an annular support 47 fixed to the casing 20, and an annular sliding member 45 mounted on the support 47 with a single degree of freedom, namely sliding mobility between two extreme positions: - an inactive position (figure 1), and - an activated position (figure 3) in which the sliding gear 45 is clutched to a toothed wheel 12 which is fixed on the rotating shaft 10.

[0045] In the embodiment illustrated in the figures, the toothed wheel 12 has a ring shape, with two main flat faces, a cylindrical internal face of revolution around the axis of rotation A1 and an external face having at least one relief (here this external face has several dogs).

[0046] This toothed wheel 12 is shrunk onto the rotating shaft 10, close to the rotor 60 (between the latter and the first bearing 32).

[0047] The dogs have identical shapes and are regularly distributed around the circumference of the toothed wheel 12. They form, for example, notches whose lateral faces extend radially relative to the axis of rotation A1. They are thus “profiled” in the sense that they have uniform orthogonal sections along the axis of rotation A1.

[0048] The support 47, on which the sliding gear 45 slides in order to engage this toothed wheel 12, is installed in the opening 22 of the casing 20, so as to be interposed between the edge of this opening 22 and the external ring of the first bearing 32.

[0049] It is a single-piece part produced by a foundry operation. It is preferably made of gray cast iron, which gives it lubricating and shock-absorbing properties.

[0050] This support 47 therefore forms a high stiffness interface between the first bearing 32 and the casing 20, which makes it possible to reduce the noise generated by the rotation of the rotary shaft 10.

[0051] It is in fact made of a material which has a stiffness greater than that of the material of the casing 20. Furthermore, due to its presence, the opening 22 of the casing 20 has a diameter greater than that which it would have in the absence of support 47, so that the casing 20 itself has a stiffness greater than that which it would have in the absence of support 47. would present in the absence of support 47. In this way, the rotating shaft 10 is better guided, better damped and it vibrates less, which reduces stresses and noise.

[0052] As shown in Figure 1, this support 47 has a first end portion 47A which is interposed between the bearing 32 and the casing 20, a second opposite end portion 47B on which the sliding sleeve 45 slides, and an intermediate ring 47C which extends between these two portions and which bears against the internal face of the casing 20 in order to block the support 47 in the opening 22.

[0053] The first end portion 47A has a ring shape, with an internal face shrunk onto the external ring of the first bearing 32, and an external face shrunk into the opening 22. These two faces are cylindrical in revolution around the axis of rotation A1.

[0054] The intermediate crown 47C has a washer shape, with two main faces which are flat and orthogonal to the axis of rotation A1, one of which bears against the internal face of the casing 20.

[0055] It has inner and outer diameters that are respectively smaller and larger than those of the two end portions 47A, 47B. It thus forms an inward projection relative to the inner faces of these two end portions, which bears against the outer ring of the first bearing 32 to block it laterally. It also forms an outward projection relative to the outer faces of these two end portions, which bears against the inner face of the casing 20. To maintain this support, screws are provided here for fixing the support 47 in the casing 20.

[0056] The second end portion 47B has a ring shape, with an external face of particular shape to guide the translation of the slider 45 along the axis of rotation A1 and block the rotation of this slider around this axis.

[0057] This external face forms profiled grooves for this purpose, which cooperate with grooves of corresponding negative shapes, carried by the sliding member 45.

[0058] This 45 player, which we recall also has an annular shape, then has grooves on its inner face.

[0059] Here, these grooves extend over only part of the length of this inner face. Indeed, one of the ends of this outer face, the one facing the toothed wheel 12, carries at least one projecting relief. In practice, it carries several identical ones which form dogs adapted to cooperate with those of the toothed wheel 12. These dogs therefore have shapes complementary to those of the toothed wheel 12.

[0060] Thus, the sliding gear 45 can slide from its inactive position (figure 1), in which the dogs of the sliding gear are located at a distance from those of the toothed wheel 12 so as not to cooperate with them, to its activated position (figure 3) in which the dogs cooperate with the with each other.

[0061] During this sliding, the sliding gear 45 passes through an internal position shown in Figure 2, in which the dogs of the sliding gear 45 engage with those of the toothed wheel 12. This engagement requires that the rotary shaft 10 has a precise angular position around the axis of rotation A1 relative to the sliding gear 45, which is done without difficulty when the rotor 60 can be controlled in an angular position. Otherwise, the dog engagement can be done mechanically, at the moment when the dogs of the toothed wheel 12 align with the spaces provided between the dogs of the sliding gear 45.

[0062] In order to slide the slider 45 between its extreme inactive and activated positions, an actuator 41 is provided.

[0063] Any type of actuator could be used, for example an electric servomotor, a moving magnet electromagnetic system, etc.

[0064] This actuator comprises a support fixed to the housing 20 and a sliding arm.

[0065] Here, this movable arm carries a cage, which is therefore movable in translation. This cage is designed to exert a traction or thrust force on a connecting rod 43, one end of which is articulated on an arm 44 adapted to slide the sliding gear. In this case, this arm 44 is pivotally mounted on the casing 20 and it has one end projecting towards the inside of the casing 20 which extends into a peripheral groove provided in a hollow in the external face of the sliding gear 45, and one end projecting towards the outside of the casing, on which the connecting rod 43 is articulated.

[0066] Thus, the pushing or pulling movement exerted on the connecting rod 43 makes it possible to force the arm 44 to pivot in one direction or another, around an axis orthogonal to the axis of rotation A1, in order to slide the sliding lever 45 between its two extreme positions.

[0067] In the event that the rotor 60 can be controlled in an angular position, it could be provided that the actuator 41 and the connecting rod 43 are articulated to each other by a simple pivot connection.

[0068] However, for safety reasons, it will be preferable to provide elastic connection means between the actuator 41 and the connecting rod 43, so that if the sliding gear 45 is blocked by the toothed wheel 12 (because their dogs are not correctly positioned relative to each other), these elastic connection means allow the actuator to slide the cage without damage and without forcing.

[0069] Here, these elastic connecting means comprise a spring which is housed in the cage and which is sandwiched between one of the internal faces of this cage and a disc fixed to the end of the connecting rod 43.

[0070] At this stage, it can be noted that, conventionally, a dielectric lubricant is used to lubricate the bearings 31, 32. This lubricant will naturally lubricate the junction between the sliding gear 45 and its support 47, which will guarantee the parking brake device 40 good operation and extended service life.

[0071] It will also be noted that when the vehicle is stationary on a slope and the parking brake device 40 is activated, it may prove difficult to move this device into the inactive position due to the forces exerted on it.

[0072] Consequently, to facilitate the movement of the sliding gear 45, the electrical machine 1 can be controlled to rotate the rotary shaft 10 over a short stroke (of the order of 1 degree) and in a fairly short period of time during which the stresses exerted on the device will be reduced.

[0073] More generally, before each deactivation of the parking brake device 40, it will be possible to pivot the rotary shaft 10 in one direction then in the other, in order to ensure that the sliding gear can at some point slide without difficulty on its support 47.

[0074] The present invention is in no way limited to the embodiment described and shown, but those skilled in the art will be able to provide any variation in accordance with the invention.

Claims

CLAIMS

1. Parking brake device (40) adapted to be installed in a casing (20) of an electric machine (1) which houses a rotating shaft (10) and at least one bearing (32) for guiding said rotating shaft (10), comprising: - an annular support (47) adapted to be interposed between said bearing (32) and said casing (20), - an annular sliding gear (45) which is slidably mounted on the support (47), between two extreme positions, which is locked in rotation on said support (47), and which has at least one relief adapted to engage a toothed wheel (12) coupled to said rotary shaft (10), and - an actuator (41) adapted to move the slider (42) between its two extreme positions.

2. A parking brake device (40) according to claim 1, wherein the bracket (47) is formed from a single piece.

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

4. Parking brake device (40) according to one of claims 1 to 3, in which the support (47) delimits an internal face of which a cylindrical part of revolution accommodates said bearing (32), and an external face of which a cylindrical part of revolution is adapted to be installed in an opening of the casing (20).

5. Parking brake device (40) according to one of claims 1 to 4, in which the support (47) and the sliding member (45) have grooves which cooperate together.

6. A parking brake device (40) according to claim 5, wherein the grooves extend on an external face of the support (47) and on an internal face of the sliding member (45).

7. Parking brake device (40) according to one of claims 1 to 6, in which there is provided, between the actuator (41) and the sliding member (45), an elastically deformable part (42) adapted to allow the actuator (41) to move when the sliding member (45) is blocked by the toothed wheel (12).

8. An electrical machine (1) comprising a housing (20), a rotor (60) housed in the housing (20), and a rotating shaft (10) which is fixed to the rotor (60), which is pivotally mounted in the casing (20) by means of at least one bearing (32), and which carries a toothed wheel (12), characterized in that it further comprises a parking brake device (40) according to one of claims 1 to 7, the sliding lever (45) of which engages the toothed wheel (12) when it is in one of its two extreme positions only.

9. An electrical machine (1) according to claim 8, wherein the toothed wheel (12) is shrunk onto said rotating shaft (10).

10. Motor vehicle comprising a chassis and wheels, characterized in that it further comprises an electric machine (1) according to one of claims 8 and 9, the rotating shaft (10) of which is constantly coupled to at least part of said wheels.

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