FR3140599A1 - Parking brake device integrated into an electric machine - Google Patents

Abstract

The invention relates to a parking brake device (100) adapted to be installed in an electrical machine casing (10) which houses a rotating shaft (21) and at least one bearing (30) for guiding said rotating shaft, said device parking brake comprising: an annular support (110) which is adapted to be interposed between said bearing and said housing and which carries a parking brake mechanism (140) adapted to block the rotation of the rotary shaft, as well as measuring means (130) adapted to measure the position or angular speed of the rotating shaft and/or of the electrical conduction means (120) between the rotating shaft and the casing. Figure for abstract: Fig.1

Description

Parking brake device integrated into an electric machine Technical field of the invention

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

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

It also relates to an electric machine equipped with such a device and a motor vehicle comprising such an electric machine.

State of the art

There are different types of parking brakes.

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

We also know electric parking brakes which include an actuator allowing here again to operate cables connected to the brake shoes.

Although this second system saves space compared to the first, it is still bulky and also has a significant cost.

We then know from document DE102017217829 a device arranged differently, and usable on electric vehicles. In this document, the braking device comprises a ratchet mechanism which is adapted to lock on a toothed wheel fixed to the shaft of the electric motor of the vehicle. Thus, this device makes it possible to block the rotation of the electric motor shaft and, consequently, that of the vehicle wheels.

In this document, the toothed wheel is fixed at the end of the electric motor shaft, against the drive wheel pinion.

However, this device remains cumbersome. It also does not reduce the noise of the electric motor.

Presentation of the invention

In order to remedy 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.

More particularly, according to the invention we propose a parking brake device adapted to be installed directly in an electrical machine casing, which casing houses at least part of a rotary shaft and at least one guide bearing of said rotary shaft.

According to the invention, this parking brake device comprises an annular support which is adapted to be interposed (radially) between said bearing and said casing and which carries:
- a parking brake mechanism adapted to block the rotation of the rotary shaft relative to the casing, as well as:
- measuring means adapted to measure the position or the angular speed of the rotating shaft relative to the casing, and/or electrical conduction means adapted to conduct the electric current between the rotating shaft and the casing.

The annular nature of the support allows this support to be placed around the rotating shaft of the electric machine, between the outer ring of the bearing and an opening made in the housing.

Thus, thanks to the invention, the elements that this annular support carries can be positioned in the casing of the electric machine, as close as possible to the rotor, in a space which was until now left free. The device then takes up little space and is installed in a protected and lubricated space, which guarantees its proper functioning at lower cost and in the long term.

The advantage of placing the annular support between the housing and the bearing is that this support can then reduce rolling noise. If it is made of a suitable material, it can in fact have a greater stiffness than that which the casing would have, which will reduce vibrations and therefore noise.

Typically, when this support is made of gray cast iron, it helps cushion the acyclisms of the rotating shaft and ensures good lubrication around the bearing when the latter rotates at very high speed and enters into “levitation”.

This support, when made of a suitable material, can also have an expansion coefficient 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 the noise.

By reducing vibrations, this support will also guarantee a longer lifespan for the entire electrical machine.

Finally, note that the advantage of placing this parking brake device as close as possible to the rotor of the electric machine, and not near the wheels of the vehicle, is that the braking torque that it will have to provide to block the vehicle will be more weaker than that which it should provide if it were placed at the level of 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 smaller brake device.

Another aspect of the invention is that the annular support carries components making it possible to perform different functions. This aspect has several advantages. The first is that it makes it possible to reduce the number of components of the electrical machine since a single support carries several functions. The second is that it allows these components to be assembled outside the electrical machine, which facilitates this assembly. The third is that all the forces exerted on these components are taken up by the annular support, which is sized according only to the component generating the most effort. The third is that this assembly guarantees the coaxiality of the components and therefore ensures their proper functioning.

Finally, note that the installation of this braking device in the casing involves the installation of a toothed wheel on the rotating shaft of the electric machine to ensure the parking brake function. This toothed wheel will then advantageously increase the rigidity of the shaft and thus prevent it from bending excessively.

Other advantageous and non-limiting characteristics of the device according to the invention, taken individually or in all technically possible combinations, are as follows:

- the annular support carries measuring means and electrical conduction means;
- said electrical conduction means are adapted to be inserted between the bearing and the measuring means;

- the parking brake mechanism comprises means for hooking a toothed wheel which is fixed to said rotary shaft, and an actuator adapted to move the hooking means between a hooked position on the toothed wheel and an unhooked position of the toothed wheel ;

- the electrical conduction means comprise a ring fixed to the annular support and flexible electrical conduction elements which rest on a part of the toothed wheel;

- there is provided, between the actuator and the hooking means, an elastically deformable part adapted to allow the actuator to move when the hooking means is blocked by the toothed wheel;

- the measuring means comprise a position sensor adapted to determine the position of a washer fixed to the rotating shaft;

- the annular support is formed from a single, single piece, and is preferably made at least partly of cast iron;

- the annular support delimits an internal face of which a cylindrical part of revolution accommodates said bearing, and an external face of which a cylindrical part of revolution is adapted to be installed in an opening of the casing.

The invention also proposes an electric machine comprising a casing, a rotor housed in the casing, a rotating shaft which is fixed to the rotor and which is pivotally mounted in the casing by means of at least one bearing, and a brake device parking as mentioned above.

It also concerns a motor vehicle comprising a chassis, wheels and an electric machine as mentioned above, the rotating shaft of which is coupled to at least part of said wheels.

Of course, the different characteristics, variants and embodiments of the invention can be associated with each other in various combinations as long as they are not incompatible or exclusive of each other.

Detailed description of the invention

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 carried out.

On the attached drawings:

is a schematic exploded perspective view of a part of an electrical machine according to the invention;

is a schematic perspective view of the annular support and the grounding washer of the electrical machine of the ;

is a sectional view of a detail of the electrical machine of the ;

is a schematic exploded perspective view of the annular support, the position sensor, the toothed wheel and the target of the electric machine of the ;

is a schematic exploded perspective view of a part of the parking brake device of the electric machine of the .

On the , an electric machine 10 of a motor vehicle has been shown.

This motor vehicle could be of any type. This is, for example, a car classically comprising a chassis and wheels.

This car has an electric or hybrid engine. It is therefore equipped with at least one electric machine serving as a traction motor for the drive wheels. This electric machine is preferably coupled to the drive wheels by a gear reducer and a differential. This coupling is preferably permanent, in the sense that it is not possible to decouple the drive wheels from the electric machine.

Conventionally, the electric machine 10 comprises an outer casing which is made of several pieces assembled to delimit a chamber housing a rotor 20 and an annular stator.

It could be an electrical machine of any type, with axial or radial flow, with a wound rotor or not…

The stator is fixed to the casing while the rotor 20 is designed to pivot in the stator and the casing.

The rotor 20 has a central opening through which it is fixedly mounted on a rotating shaft 21, which therefore forms the output shaft of the electrical machine 10.

Conventionally, this rotating shaft 21 is mounted in the casing so as to be able to rotate relative to it around an axis of rotation A1.

For this, it is equipped, near its ends, with two bearings 30, only one of which is shown here and will be described below (the other being arranged in a standard manner in an opening in the housing).

This is a ball bearing, the inner ring of which is fitted onto the rotating shaft 21 and the outer ring of which is placed in an opening provided for this purpose in the housing. Thus the rotating shaft 21 is guided in rotation around its axis of rotation A1.

It will be noted here that the outer ring of bearing 30 is not directly fixed in the opening of the casing but that an intermediate part is provided which is interposed between them. This intermediate part, which therefore acts as a “replaced bearing”, will hereinafter be called annular support 110.

The rotating shaft 21 has at its free end, beyond the bearing 30 and outside the casing, a pinion 24 allowing it to be coupled to the drive wheels of the motor vehicle.

The electric machine 10 here integrates within its casing a parking brake device 100 which notably comprises this annular support 110.

According to the invention, this parking brake device 100 is multifunctional in the sense that it provides a parking brake function, but also at least one other function. The annular support 110 is then specially designed to carry the components enabling all of these different functions to be performed.

A first function of the device is therefore a brake function making it possible to block any rotation of the rotary shaft 21 relative to the casing. A second of its functions is a grounding function of the rotating shaft 21. A third of its functions is a function of measuring the position and/or the angular speed of the rotating shaft 21.

If the first function is essential, it could alternatively be provided that the parking brake device 100 only ensures one or the other of the second and third functions.

The components that the annular support 110 carries to ensure the first parking brake function are designed to act directly on the rotating shaft 21 of the electric machine 10 in order to brake the vehicle when the latter is parked. This rotating shaft 21 carries a toothed wheel 22 for this purpose.

In an electric or hybrid vehicle as defined above, the electric machine 10 in fact always remains coupled to the drive wheels of the vehicle since neither clutch nor gearbox is provided between the electric machine 1 and the drive wheels. . On the contrary, a simple speed reducer is provided (typically single-speed constant mesh). Consequently, blocking the rotating shaft 21 of the electric machine 10 makes it possible to block the drive wheels, and therefore to ensure efficient parking braking.

In this regard, it can be noted that if a torque is exerted at the level of the wheels, the torque felt at the level of the rotating shaft 21 will be reduced thanks to the speed reducer, so that it will be less restrictive to brake the vehicle at the level of the rotating shaft 21 than at the level of the wheels.

Here, the parking brake device 100 is placed around the rotating shaft 21. The toothed wheel 22 on which it is possible to rely to mechanically achieve braking is for its part located between the rotor 20 and the bearing 30 , inside the housing. It is therefore particularly space-saving.

We can now describe in more detail the annular support 110 and the components of the parking brake device 100 making it possible to ensure the three aforementioned functions.

The annular support 110 is shown in detail on the .

As shown in the , it is therefore installed in an opening 12 of the casing 11, so as to be interposed between the edge of this opening 12 and the outer face of the outer ring 31 of the bearing 30. We recall here that the inner ring 32 of this bearing 30 is directly fitted onto the rotating shaft 21.

The annular support 110 is a one-piece part resulting from a foundry operation. It is preferably made of gray cast iron (for example of the GL04S type), which gives it good lubricating, electrically conductive and damping properties, at a low cost.

It therefore forms a high stiffness interface between the bearing 30 and the casing 11, which makes it possible to reduce the noise generated by the rotation of the rotary shaft 21.

It is in fact made of a material which has a stiffness greater than that of the material of the casing 11. Furthermore, due to its presence, the opening 12 of the casing 11 has a diameter greater than that which it should have in l absence of annular support 110, so that the casing 11 itself has a stiffness greater than that which it would present in the absence of annular support 110. In this way, the rotating shaft 21 is better guided, better damped and it vibrates less, which reduces stress and noise.

As shown in the , this annular support 110 has a first part 111 which is interposed between the bearing 30 and the casing 11, a second part 112, facing the side of the rotor 20, on which the components ensuring the three aforementioned functions can be fixed.

The first part 111 has the shape of a ring, with a cylindrical internal face of revolution hooped on the external ring of the bearing 30, and an external cylindrical face of revolution hooped in the opening 12. These hooping operations can be implemented under press.

The second part 112 forms a sort of flange extending in a plane orthogonal to this axis of rotation A1, on one side of the first part 111. It has threaded bores and threaded wells along axes parallel to the axis of rotation A1, which makes it possible to secure the components ensuring the three aforementioned functions.

On the , we have also shown the electrical conduction means 120 which make it possible to electrically connect the rotating shaft 21 to the casing 11 so that this shaft does not become charged with electric current and generates destructive electric arcs in the bearing 30 or in the pinion 24.

These means are therefore designed to put this rotating shaft 21 to electrical ground. They are also positioned as close as possible to the bearing 30 to protect it as best as possible.

They could come in various forms, typically in the form of felt incorporating metal wires.

Here, it is more of a grounding ring, of the eyelash type.

It therefore comprises a ring body 121 which is designed to be locked in position on the annular support 110, and flexible electrical conduction elements 122 designed to rest on the rotating shaft 21 or, as is the case here , on an element fixed to this shaft, namely on the toothed wheel 22.

The flexible electrical conduction elements 122 are here curved metal cilia which extend all around the axis of rotation A1 in order to together present good electrical conductance.

As shown in the , the ring body 121 is designed to rest directly against one side of the outer ring 31 of the bearing 30, that side oriented towards the inside of the casing 11.

It has an exterior diameter slightly greater than or equal to the interior diameter of the annular support 110, so as to ensure electrical contact from the rotating shaft 21 to the casing 11 via this annular support 110 which we recall is made of cast iron, which gives it good electrical conduction properties.

The flexible electrical conduction elements 122 are provided projecting inside the ring body 121 such that their ends extend in a circle of diameter less than the diameter of the part of the toothed wheel 22 on which they fit. support.

Mounting this grounding ring directly on the annular support 110 reduces the risk of misalignment and therefore the risk of eyelash breakage.

On the , we observe that a groove 124 is dug in the internal face of the annular support 110, at the level of this ring 121, so as to provide a space between the ring 121 and the annular support 110 through which the oil can flow towards the bottom of the casing 11. This groove 124 therefore makes it possible to reduce the risk of bubbling of the bearing 30 and to limit the quantity of oil found on the rotating shaft 21 (reducing the electrical conductivity of the latter).

On the , the means 130 for measuring the position and/or the angular speed of the rotating shaft 21 have been shown.

These measuring means comprise in practice here an inductive position sensor which is adapted to determine the position of a target washer 23 fixed to the rotating shaft 21.

This target washer 23 comprises an annular body 25 which is mounted directly on the rotating shaft 21 or, as is the case here, on an element fixed to this shaft, namely on the toothed wheel 22.

It also includes fins 26 projecting outwards from the annular body 25, which are regularly distributed around the axis of rotation A1.

The target washer 23 is angularly indexed on the rotating shaft 21, so that the control computer of the electric machine knows its exact angular position.

The inductive position sensor comprises an annular body 131 with interior and exterior diameters substantially equal to those of the annular support 110. It also comprises three lugs projecting radially outwards, which allow its attachment to the annular support 110, here by screwing. Three screws 132 are used here in this regard.

Fixing this inductive position sensor directly on the annular support 110 ensures good centering of this sensor in relation to the axis of rotation A1. Thus, these measuring means 130 are adapted to determine the angular position of the rotating shaft 21 with a precision of the order of a tenth of a degree.

Note that this sensor, once fixed, makes it possible to block the grounding ring against the bearing 30 in order to block it axially (see ).

The inductive position sensor finally comprises a radial bulge 133 which extends outwards from the annular body 131, and which houses data communication means connected to the control computer of the electrical machine 10. Here, this radial bulge 133 therefore has a terminal block allowing it to be connected by wire to the computer.

As shown in Figures 1 and 5, to achieve the desired braking, namely here complete blocking of the rotating shaft 21 relative to the casing 11, the parking brake mechanism 140 comprises:
- a hooking means 141 of the toothed wheel 22 which we recall is fixed to the rotating shaft 21, and
- an actuator 142 adapted to move the hooking means 141 between a hooked position on the toothed wheel 22 and an unhooked position of the toothed wheel 22.

As shown in the , the toothed wheel 22 comprises a tubular body 27 and, projecting from the external face of this tubular body 27, at least one relief. Here it comprises several forming claws 28. The claws 28 have identical shapes and are regularly distributed around the periphery of the tubular body 27 of the toothed wheel 22. They thus delimit slots whose lateral faces extend radially relative to the axis of rotation A1.

These claws 28 are here located halfway along the tubular body 27 and therefore extend at a distance from the ends of this body. Thus, the tubular body 27 has a length such that it makes it possible to stiffen the rotating shaft 21 on which it is fitted.

The target washer 23 is then mounted on the tubular body 27 of this toothed wheel 22, on the side of the bearing 30. The eyelashes of the grounding ring also rest on this side of the tubular body 27.

The hooking means 141 of the parking brake mechanism 140 could be in various forms.

As shown in the , here, it is presented here in the form of a lever 141, one end of which is shaped to engage between two dogs of the toothed wheel 22 in order to block any rotational movement of the rotary shaft 21. This end of the lever 141 carries for this purpose a tooth 141A whose shape is identical, in negative, to the space between two dogs of the toothed wheel 22.

This lever 141 has an opening at mid-length through which it is mounted movable in tilting on the annular support 110.

In practice, a cylindrical axis 144 is fixed on one side to the annular support 110 and it accommodates at its opposite end the lever 141, which is mounted to rotate freely on this end of the cylindrical axis 144.

The lever 141 is thus mounted on the annular support 110 with a single degree of freedom, namely pivoting mobility around an axis strictly parallel to the axis of rotation A1, between two extreme positions called hooked (in which the tooth 141A is housed between two dogs) and unhooked (in which the tooth is located at a distance from the dogs).

We understand that when the lever 141 blocks the rotation of the rotating shaft 21 and the vehicle is stopped on a slope, significant forces are exerted on the cylindrical axis 144.

Consequently, to prevent the latter from bending and the lever 141 from letting the toothed wheel 22 escape, means are provided for fixing the free end of this cylindrical axis 144. These means are presented here in the form of a plate 144A pierced in its center to accommodate the free end of this cylindrical axis 144 and at its ends to allow its fixing, here by means of screws 146, on the annular support 110.

The lever 141 has, at its end opposite the tooth 141A, a bearing end on which the actuator 142 can exert a force.

When activated, the actuator 142 is here provided to force the movement of this lever 141 towards one of the two aforementioned positions. Elastic return means 145 are provided to return it to the other of these two positions when the actuator is inactive.

In practice, the actuator is designed to force the lever to switch to the hooked position.

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

As shown in the , this actuator 142 here comprises a support 147 fixed to the casing 20 (inside it) and a sliding arm 148 adapted to slide relative to the support 147 towards a deployed position when activated, and to return in initial position otherwise.

In the event that the rotor 20 can be controlled in an angular position with great precision, the hooking of the toothed wheel 22 will be facilitated and will therefore make it possible to use an actuator 142 of reduced power (saving and inexpensive).

In this eventuality, it could be envisaged that the actuator 142 is connected to the lever 141 by a simple link or that it presses directly on the lever.

However, as a safety measure, it will be preferable to provide elastic connection means 143 between the actuator 142 and the lever 141, so that if the lever 141 is blocked by the toothed wheel 22 (because its tooth is not exactly in facing a space delimited by dogs), these elastic connection means allow the actuator to slide the sliding arm 148 without damage and without forcing.

In practice, as shown in , there is provided here at the end of the sliding arm 148 a cap 148A which is fixed to the latter and which carries, as elastic connection means 143, a torsion spring. This hat 148A also carries a shaft 149.

This shaft 149 is mounted so as to be able to pivot in the cap 148A around the axis of the sliding arm 148. It carries a cam 149A which forms a slope inclined with respect to this axis and which rests under the free end of the lever.

Thus, the sliding movement of the sliding arm 148 can force the lever to tilt, but if the latter is blocked, the shaft 149 will be able to pivot thanks to the cam 149A and avoid any damage to the mechanism. The torsion spring 143 will allow the shaft 149 to be returned to its initial position as soon as possible.

At this stage, it can be noted that, conventionally, a dielectric lubricant is used to lubricate the bearings 30. This lubricant will naturally lubricate the junction between the lever 141 and its cylindrical axis 144, which will guarantee the parking brake device a good operation and a long lifespan.

It will also be noted that when the vehicle is stationary on a slope and the parking brake device 100 is activated, it may prove difficult to move this device to the inactive position due to the forces exerted on it. him.

Consequently, to facilitate the movement of the lever, the electric machine 10 can be controlled to rotate the rotary shaft 21 over a short stroke (of the order of 1 degree) and in a fairly short period of time during which the constraints exerting on the device will be reduced.

More generally, it will be possible, before each deactivation of the parking brake device 100, to rotate the rotary shaft 21 in one direction then in the other, in order to ensure that the lever can at some point return to position removed without difficulty.

Claims (10)

Parking brake device (100) adapted to be installed in a casing (11) of an electric machine (10) which houses a rotary shaft (21) and at least one bearing (30) for guiding said rotary shaft (21), said parking brake device (100) comprising an annular support (110) which is adapted to be interposed between said bearing (30) and said casing (11) and which carries:
- a parking brake mechanism (140) adapted to block the rotation of the rotary shaft (21) relative to the casing (11), as well as:
- measuring means (130) adapted to measure the position or angular speed of the rotating shaft (21) relative to the casing (11), and/or electrical conduction means (120) adapted to conduct the electric current between the rotating shaft (21) and the housing (11). Parking brake device (100) according to claim 1, in which, the annular support (110) carrying measuring means (130) and electrical conduction means (120), said electrical conduction means (120) are adapted to be inserted between the bearing (30) and the measuring means (130). Parking brake device (100) according to claim 1 or 2, wherein the parking brake mechanism (140) comprises means (141) for hooking a toothed wheel (22) which is fixed to said rotary shaft (21). ), and an actuator (142) adapted to move the hooking means (141) between a hooked position on the toothed wheel (22) and an unhooked position of the toothed wheel (22). Parking brake device (100) according to claims 2 and 3, in which the electrical conduction means (120) comprise a ring (121) fixed to the annular support (110) and flexible electrical conduction elements (122) which are 'press on part of the toothed wheel (22). Parking brake device (100) according to one of claims 3 and 4, in which there is provided, between the actuator (142) and the hooking means (141), an elastically deformable part (143) adapted to allow for the actuator (142) to move when the hooking means (141) is blocked by the toothed wheel (22). Parking brake device (100) according to one of claims 1 to 5, in which the measuring means (130) comprise a position sensor adapted to determine the position of a washer (23) fixed to the rotating shaft (21). Parking brake device (100) according to one of Claims 1 to 6, in which the annular support (110) is formed in one single piece, and is preferably made at least partly of cast iron. Parking brake device (100) according to one of claims 1 to 7, in which the annular support (110) delimits an internal face of which a cylindrical part of revolution accommodates said bearing (30), and an external face of which a part cylindrical revolution is adapted to be installed in an opening in the housing (11). Electric machine (10) comprising a housing (11), a rotor (20) housed in the housing (11), and a rotating shaft (21) which is fixed to the rotor (20) and which is pivotally mounted in the housing (11) ) by means of at least one bearing (30),
characterized in that it further comprises a parking brake device (100) according to one of claims 1 to 8. Motor vehicle comprising a chassis and wheels, characterized in that it further comprises an electric machine (10) according to claim 9, the rotary shaft (21) of which is coupled to at least part of said wheels.