Actuator for an automotive vehicle transmission system

Abstract

The present invention provides an actuator (1) for a transmission system comprising a housing (2) defining an annular space with axis X, an annular piston (3) for transmitting an actuation force to a coupling device, the piston (3) being arranged coaxially with the axis X and being mounted axially about the axis X between a retracted position (R) and a deployed position (D), an annular coil (5) comprising a winding of conductive wire, the coil (5) being encapsulated by a coating (6) of polymer material, characterized in that at least one fluid guidance means (12, 14a, 14b, 24) is provided between the housing (2) and the coil (5). Figure 2

Description

Title of the invention: Actuator for an automotive vehicle transmission system

[0001] The invention relates to an actuator for a transmission system of a motor vehicle.

[0002] The invention relates more particularly to an electromagnetic actuator which is intended to be housed inside a transmission casing of the transmission chain by being linked to a coupling device.

[0003] US patent 20170159726 Al discloses an electromagnetic actuator for actuating a coupling device equipping a differential system. The coupling device has a disengaged state in which the differential is free to distribute torque from an engine to two wheel shafts of a vehicle axle, and a coupled state that disables the "differential" function so that the two wheel shafts cannot rotate at different speeds. The electromagnetic actuator includes a housing intended to be fixed in a transmission housing that also houses the differential system. Furthermore, the electromagnetic actuator includes a housing having an annular space in which are housed an overmolded coil and a piston movably mounted between a retracted and an extended position.The various movements of the piston between its retracted and extended positions cause noise or impacts when it comes into contact with metal parts. The noise is particularly undesirable for passenger comfort, and the impacts can cause vibrations in the actuator, eventually preventing proper operation or even destroying it. Furthermore, the moving parts of this actuator are not lubricated, which can lead to overheating.

[0004] The present invention aims to improve current solutions, in particular by proposing an actuator with a simple architecture and allowing lubrication of the inside of the actuator while reducing noise and shocks related to the movements of the piston between its retracted position, its deployed position and vice versa.

[0005] More particularly, the invention relates to an actuator for a transmission system comprising a housing defining an annular space with axis X, an annular piston for transmitting an actuation force to a coupling device, the piston being arranged coaxially with axis X and being mounted axially movable about axis X between a retracted position and an extended position, an annular coil comprising a winding of conductive wire, the coil being in encapsulated by a polymer material coating, at least one means for guiding a fluid is provided between the housing and the coil.

[0006] Thus, overheating of the elements constituting the actuator will be avoided, the elements will be lubricated and the noises or shocks of the piston during its movements will be reduced.

[0007] According to the invention, the coating of the annular coil is made of a polymer material, for example, epoxy resin, polyurethane, or polyamide. In other words, the coil is overmolded. Advantageously, the coating forms an annular radial extension defining an end-of-stroke stop for the piston.

[0008] According to one feature of the invention, the coil is housed in the annular space of the casing.

[0009] According to another feature of the invention, the piston is housed in the annular space of the casing. Alternatively, the piston may be located outside the casing.

[0010] According to one feature of the invention, the piston is located radially inside the coil. Alternatively, the piston can be located radially outside the coil.

[0011] Advantageously, the radial extension defines an end-of-stroke stop for the piston when it is in the retracted position. Alternatively, the radial extension defines an end-of-stroke stop for the piston when it is in the extended position.

[0012] According to the invention, the housing is U-shaped and made of a single material, preferably a magnetic material, for example steel. A single material means that the housing is a single piece. The use of a housing made of a single material simplifies the design and manufacture of the actuator.

[0013] Alternatively, the housing is U-shaped, consisting of two L-shaped parts joined together, the two parts preferably being made of a magnetic material, for example steel. The two L-shaped parts are joined, for example, by a crimping, rolling, or press-fitting operation.

[0014] According to one feature of the invention, the housing comprises a radially internal skirt, a bottom surface, and a radially external skirt. If the piston is located radially inside the coil, then the piston guiding surface is the radially internal skirt. If the piston is located radially outside the coil, then the piston guiding surface is the radially external skirt.

[0015] The piston guide surface can be coated with a thermochemical treatment in order to harden the surface of the part in sliding contact with the piston and thus facilitate sliding.

[0016] Preferably, the surfaces of the housing can be machined to obtain a good surface finish and can also be combined with a surface treatment, for example of the "DLC" type, which stands for "diamond-like carbon" or "TiN" which stands for titanium nitride or "M0S2" stands for molybdenum disulfide or nitride. These treatments optimize the tribological performance of the casing surfaces.

[0017] According to the invention, the fluid guidance means is at least an annular groove located on the bottom surface of the housing opposite a surface of the coil.

[0018] According to an additional feature of the invention, the fluid guidance means is at least a groove located on a surface of the coil opposite the bottom surface of the housing.

[0019] According to the invention, the fluid guidance means is at least one groove located on the external surface of the coil opposite the radially external skirt of the housing.

[0020] According to one feature of the invention, the fluid guidance means is at least one groove located on the internal surface of the coil opposite the radially internal skirt of the housing.

[0021] According to one feature of the invention, the fluid guidance means is at least one groove located on the surface of the radial extension opposite the piston

[0022] According to the invention, the housing includes an opening located in the radially external skirt, this opening allows the passage of fluid from the outside to the inside of the housing as well as the passage of an electrical connector of the coil.

[0023] According to another feature of the invention, the housing is made of a material with a carbon content of less than 0.2%, for example, steel. This steel is thus called low-carbon steel. This feature makes it possible to reduce the mass of the actuator.

[0024] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings:

[0025] Fig. 1 illustrates an actuator according to the invention in front view;

[0026] [Fig.2] illustrates the actuator of [Fig.1] in section along axis AA;

[0027] Figure [Fig. 3a] illustrates an annular coil of the actuator according to a first mode of realization ;

[0028] Figure 3b illustrates an annular coil of the actuator according to a second mode of realization ;

[0029] [Fig.4] illustrates the annular coil of the actuator in rear view;

[0030] [Fig.5] illustrates a variant embodiment of the actuator;

[0031] Figure 6 illustrates a perspective view of the actuator housing according to the variant of the [Fig.5].

[0032] In relation to [Fig. 1], an actuator 1 is described according to an embodiment of the invention which is suitable for being housed in a transmission housing. The housing of The transmission can consist of any housing in a vehicle's drivetrain, including a differential housing. The actuator 1 is an electromagnetic actuator designed to be connected to a coupling device (not shown) of a motor vehicle transmission. It comprises a housing 2 intended to be attached to a transmission housing (not shown). Within this housing 2 are arranged an annular coil 5 and an annular piston 3, which will be described in relation to the following figures.

[0033] The actuator 1 includes an electrical connector 10 for connecting the coil 5 to a control device located outside the housing. The electrical connector 10 is connected to the coil 5 by at least one flexible cable and provides electrical power to the coil 5.

[0034] Fig. 2 allows for a better visualization of the constituent elements of actuator 1. The actuator 1 thus comprises a housing 2 defining an annular space with axis X in which are housed the annular piston 3 intended to transmit an actuation force to a coupling device and the annular coil 5. The piston 3 is arranged coaxially with the axis X and is mounted to move axially along the axis X between a retracted position R and a deployed position D. The piston 3 is located radially inside the coil 5.

[0035] In the embodiment shown in [Fig. 2], the housing 2 is U-shaped and made of a single material, preferably magnetic steel. This steel has a carbon content of less than 0.2%. The housing 2 comprises a radially internal skirt 21 serving as a guiding surface for the piston 3, a bottom surface 22, and a radially external skirt 23. On the bottom surface 22 on the external side of the housing 2 are projections 26 distributed angularly around the X-axis, enabling contact with a transmission element, for example, a bearing. In the present embodiment, four projections 26 are present.

[0036] The annular coil 5 consists of a winding of conductive wire and is hermetically encapsulated by a coating 6 made of polymer material, for example, epoxy resin, polyurethane, or polyamide. The coating 6 forms an annular radial extension 7 that defines an end-of-stroke stop for the piston 3 when it is in the retracted position R. The radial extension 7 is located axially along the X-axis on the side of the bottom surface 22 of the housing 2. In other words, the radial extension 7 is in contact with the bottom surface 22 of the housing 2.

[0037] The piston 3 is mounted movably in a housing 11 defined between the coil 5 and the inner skirt 21 of the housing 2. The radial extension 7 of the coil 5 extends inside this housing 11. The radial extension 7 extends radially in the direction of the X axis.

[0038] The annular space of the housing 2 is closed by a magnetic cover 8; the magnetic cover 8 defines an end-of-stroke stop for the piston 3 when the piston 3 is In the deployed position D, the magnetic cover 8 is attached to the housing 2 by means of tabs 9 belonging to the outer skirt 23 of the housing 2. These tabs 9 are folded towards the magnetic cover 8 during assembly. The piston 3 has a shoulder designed to abut against a shoulder of the magnetic cover 8 when the piston 3 is in the deployed position D.

[0039] The piston 3 is made of a ferromagnetic material, such as iron or steel. The piston 3 also has a non-magnetic tip 4, also annular in shape, which is attached to the piston 3 and through which the actuation force is transmitted to the coupling device. Non-magnetic means a material having no magnetic properties. The non-magnetic tip 4 of the piston 3 thus prevents unwanted leakage of magnetic flux to the other components of the coupling device. The non-magnetic tip 4 is, for example, made of bronze or aluminum.

[0040] When the actuator 1 is located in a differential housing, as in the present invention, this actuator 1 is partially immersed in a hydraulic fluid, such as oil. This oil lubricates the contacting elements in the differential housing and also limits heating. In the case of the present invention, it is particularly useful to take advantage of this humid environment to lubricate and cool the components of the actuator 1. To this end, the housing 2 includes an opening 25 located in the radially external skirt 23; this opening 25 allows the passage of fluid from the outside to the inside of the housing 2. This opening also allows the passage of the electrical connector 10 of the coil 5. In order to conduct the fluid inside the housing 2, there is at least one fluid guidance means 12a, 12b, 14a, 14b, 24 provided between the housing 2 and the coil 5.

[0041] Figure 3a shows a first means of guiding this fluid. The internal surface 51 of the coil 5 is provided with grooves 12a for guiding a fluid between the coil and the piston 3. These grooves 12a are distributed angularly and at regular intervals around the entire circumference of the internal surface 51 of the coil 5. These grooves 12a extend axially along the X-axis. The surface 71 of the radial extension 7 opposite the piston 3 is also provided with grooves 12b for guiding the fluid. These grooves 12b are distributed angularly and at regular intervals around the entire circumference of the radial extension 7 of the coil 5 opposite the piston 3. These grooves 12b extend perpendicularly to the grooves 12a. Grooves 12a and 12b thus form a continuous groove. Grooves 12b have a direction that converges towards a point located on the X-axis.

[0042] The radial extension 7 of the coil 5 comprises at least one axial slot 11. This axial slot 11 separates two sections 13. According to the embodiment shown in [Fig. 4], there are three sections 13 separated by three axial slots 11. This axial slot 11 allows indexing of the coil 5 on a tool to facilitate the winding operation of the conductor wire.

[0043] The embodiment of the coil 5 shown in [Fig. 3b] is a variant of the embodiment shown in [Fig. 3a]. The identical features of the two embodiments are designated by the same numerical references. Unlike [Fig. 3a], [Fig. 3b] shows the external surface 52 of the coil 5 provided with grooves 14a. These grooves 14a are aligned with the radially external skirt 23 of the housing 2 and allow the fluid to flow between the housing 2 and the coil 5. These grooves 14a are distributed angularly and at regular intervals around the entire circumference of the external surface 52 of the coil 5. These grooves 14a extend axially along the X-axis.

[0044] Of course, it is also possible, while remaining within the scope of the present invention, to propose a coil 5 having only grooves on the external surface 52 of the coil 5 without having grooves on the internal surface 51 or on the radial extension 7.

[0045] The grooves 12a, 12b, 14a, 14b also serve to contribute to the reinforcement of the mechanical strength of the overmolding of the coil 5.

[0046] Fig. 4 shows the surface 53 of the coil 5 facing the bottom surface 22 of the housing 2. This surface 53 has grooves 14b allowing fluid guidance between the coil and the bottom surface 22 of the housing 2. These grooves 14b extend parallel to an axis Y orthogonal to the axis X.

[0047] Fig. 5 represents an alternative embodiment of the housing 2. In this embodiment, the bottom surface 22 of the housing 2 includes an annular groove 24 opposite the surface 53 of the coil 5. Only one groove 24 is shown, but it is entirely possible to make several concentric grooves 24.

[0048] Figure 6 shows, by means of a perspective view, this groove 24 located on the bottom surface 22 of the housing 2. This groove 24 is concentric with the X-axis and is radially close to the radially internal skirt 21 of the housing 2. At least one opening 27 is provided in this groove 24 to allow fluid to flow between the outside and inside of the housing 2 and vice versa. In this case, three openings 27 are provided in the groove 24. More generally, the opening 27 is located on the bottom surface 22 of the housing 2.

[0049] The operation of the actuator 1 will now be described. When the coil 5 is energized with a current exceeding a threshold current, this allows the piston 3 to move from the retracted position R to the extended position D. When the piston 3 is in the extended position D, the magnetic cover 8 exerts an attraction on the piston 3, which allows it to be held in the extended position D. The supply current to the coil 5 can then be decreased as long as it remains above said threshold current. When the coil 5 is switched off or energized with an intensity lower than the threshold intensity, an elastic return means (not shown) returns the coupling device to the uncoupled position, which makes it possible to counter the attractive force between the magnetic hood 8 and the piston 3 and returns the piston 3 from the deployed position D to the retracted position R.

[0050] The fluid path inside the actuator 1 will now be described. The fluid enters the actuator 1 through the opening 25 and is guided by the external surface 52 of the coil 5 (via the grooves 14a when present) towards the bottom surface of the housing 2. The grooves 14b then guide the fluid along the bottom surface of the housing 2. When groove 24 is present, this groove contributes to guiding the fluid between the coil 5 and the housing 2. The fluid then passes through the passage located between the radial extension 7 and the radially internal skirt 21 of the housing 2. The fluid is then in the housing 11 in which the piston 3 is located. The fluid is then guided in this housing 11 by the grooves 12a which are located on the internal surface 51 of the coil. When the fluid is in housing 11, it participates in the lubrication of the contact surfaces between the piston 3 and the radially internal skirt 21 of the housing 2.The fluid also participates in hydraulic damping when the piston 3 reaches the end of its stroke, whether in the deployed position D or the retracted position R. The fluid is then evacuated from the actuator 1 through the passage located between the magnetic cover 8 and the radially internal skirt 21 of the housing 2 or through the opening 27.

[0051] Generally, the width of the grooves 12a, 12b, 14a, 14b, 24 is between 1 mm and 5 mm, preferably 2 mm. The depth of the grooves 12a, 12b, 14a, 14b, 24 is between 1 mm and 3 mm.

[0052] In general, the grooves 12a, 12b, 14a, 14b, 24 also have the function of participating in the filtration of the fluid during its passage inside the actuator 1.

[0053] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0054] In the claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

Demands

1. Actuator (1) for a transmission system comprising a housing (2) defining an annular space with axis X, an annular piston (3) for transmitting an actuation force to a coupling device, the piston (3) being arranged coaxially with the axis X and being mounted axially movable about the axis X between a retracted position (R) and a deployed position (D), an annular coil (5) comprising a winding of conductive wire, the coil (5) being encapsulated by a coating (6) of polymer material, characterized in that at least one means for guiding a fluid (12, 14a, 14b, 24) is provided between the housing (2) and the coating (6) of the coil (5).

2. Actuator (1) according to claim 1 characterized in that, seen in cross-section, the housing (2) is U-shaped and is made of a single material, preferably a magnetic material.

3. Actuator (1) according to claim 1 characterized in that, seen in cross-section, the housing (2) is in the shape of a “U” made up of two assembled “L” shaped parts, the two parts preferably being made of a magnetic material.

4. Actuator (1) according to any one of the preceding claims characterized in that the housing (2) comprises a radially internal skirt (21), a bottom surface (22) and a radially external skirt (23).

5. Actuator (1) according to claim 4 characterized in that the fluid guidance means is at least one annular groove (24) located on the bottom surface (22) of the housing (2) opposite a surface (53) of the coating (6) of the coil (5).

6. Actuator (1) according to claim 4 or 5 characterized in that the fluid guiding means is at least one groove (14b) located on a surface (53) of the coating (6) of the coil (5) opposite the bottom surface (22) of the housing (2).

7. Actuator (1) according to any one of claims 4 to 6 characterized in that the fluid guiding means is at least one groove (14a) located on the external surface (52) of the coating (6) of the coil (5) opposite the radially external skirt (23) of the housing (2).

8. Actuator (1) according to any one of claims 4 to 7 characterized in that the fluid guiding means is at least one groove (12a) located on the internal surface (51) of the coating (6) of the coil (5) opposite the radially internal skirt (21) of the housing (2).

9. Actuator (1) according to any one of claims 4 to 8 characterized in that the housing (2) includes an opening (25) located in the outer radial skirt (23), this opening (25) allows the passage of fluid from outside to inside the housing (2) as well as the passage of an electrical connector (10) of the coil (5).

10. Actuator (1) according to any one of the preceding claims characterized in that the housing (2) is made of material having a carbon content of less than 0.2%.

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