Device for locking a drive train transmission in a motor vehicle

Abstract

The invention relates to a device for locking a drive train transmission in a motor vehicle, comprising at least one toothed wheel (8), a rod (3) with a rod axis, the rod comprising a first portion (31) having an external thread with a right-hand pitch, and a second portion (32) having an external thread with a left-hand pitch, a drive member (4) for rotating the rod, two locking members (1, 2) each comprising a sleeve (10, 20) and a projection (5, 6), the sleeve comprising an internal thread interlockingly cooperating with an external thread of the rod, the projections comprising a free end forming a stop for stopping a tooth of the toothed wheel in both directions, and guide elements (7) for preventing the locking members from rotating about the rod axis but allowing them to be translated along the rod axis.

Description

DESCRIPTION TITLE OF THE INVENTION: Device for locking a driveline transmission in a motor vehicle

[0001] The invention relates to a device for locking a driveline transmission in a motor vehicle.

[0002] This type of locking device is commonly called a parking brake and is commonly used especially on vehicles with automatic transmission. This type of locking device is also used in electric or hybrid vehicles. The transmission locking device is activated when the driver moves the transmission selector lever to the "P" position, usually when the vehicle is stationary.

[0003] The locking device in question here is distinct from and complementary to another braking system called a parking brake, also present on motor vehicles, and acting directly on the vehicle's wheels. Said parking brake also acts as an emergency brake to slow down and immobilize the vehicle. Conversely, the parking brake which is the subject of the present invention is intended and designed to be engaged only at zero or near-zero speed.

[0004] Parking brake solutions are known where a pivoting toothed element (latch or 'pawl') selectively interferes with a toothed wheel forming part of the transmission. However, it turns out that the known solutions take up a significant amount of space and, moreover, they are not free of play. An example of such a solution is known from document US2016223082.

[0005] The inventors sought to improve the situation and propose a new configuration to achieve the parking brake function.

[0006] To this end, a device is thus proposed for locking a driveline transmission in a motor vehicle, by mechanical engagement of at least one locking member in a toothed wheel of the transmission, the device comprising at least: - a toothed wheel, mounted to rotate relative to a wheel axle, - a rod mounted for rotation in a housing around a rod axis, the rod comprising a first portion equipped with an external thread with a right-hand thread and a second portion equipped with an external thread with a left-hand thread, - a motor member configured to selectively rotate the rod in one direction or the other, - a first locking member comprising a first sleeve centered on the rod axis and a first projection extending radially outward from the sleeve, the sleeve comprising an internal thread, adapted to cooperate by form complementarity with an external thread of the rod, the first projection comprising a free end forming a stop for stopping a tooth of the toothed wheel in a first direction of rotation, - a second locking member comprising a second sleeve centered on the rod axis and a second projection extending radially outward from the sleeve, the sleeve comprising an internal thread, adapted to cooperate by form complementarity with the other external thread of the rod, the second projection comprising a free end forming a stop for stopping a tooth of the toothed wheel in a second direction of rotation, - guide elements to prevent rotation of the first and second locking members around the rod axis but allow translation of the locking members along the rod axis.

[0007] By virtue of the threaded portions of the rod having opposite pitches, and the locking members with their respective corresponding internal threads engaged around the rod, when the rod rotates in one direction, the locking members move towards each other, and when the rod rotates in the other direction, the locking members move away from each other.

[0008] Thanks to these arrangements, when the locking members move towards each other, they come to surround one or more teeth of the toothed wheel, which therefore blocks the toothed wheel. Conversely, when the locking members move away from each other, the rotation of the toothed wheel is released.

[0009] The proposed configuration is compact and simple to manufacture and assemble. The proposed configuration requires fewer parts than in the solutions of the prior art and, moreover, advantageously, the proposed configuration is lighter than the configurations known in the art.

[0010] Other benefits will be seen below.

[0011] The term "powertrain" is generally understood to mean any system comprising an engine, whether internal combustion or electric, a transmission comprising a reducer with, where appropriate, several selectable reduction ratios, a differential and two axle shafts connected respectively to a left wheel and a right wheel of a vehicle axle.

[0012] R2 According to one aspect, each of the first and second projections is formed as a finger which extends in an extension direction (X1, X2) inclined relative to the rod axis. Whereby, the tip of the finger can be inserted between two teeth of the toothed wheel. The inclination of the finger makes it possible to absorb a force resulting from a torque exerted by the wheel, the finger works essentially in compression and the cantilever effect is minimized.

[0013] Note that the term 'arm' can also be used to refer to the projection instead of 'finger'.

[0014] R3 In one aspect, the fingers are directed towards each other. They can thus grip a tooth of the gear wheel in a vice like pliers. The functional clearance can thus be reduced to a very small value or even to zero.

[0015] R+ According to one aspect, the extension direction (X1, X2) is inclined at an angle 0 relative to the rod axis, 0 being between 35° and 60° and preferably between 40° and 50°. This gives a bracing effect for the rotation stop direction where the finger works in compression. The chosen angle (or angular range) results from a compromise between the vice-like grip effect and finesse allowing the finger to be inserted between two successive teeth of the toothed wheel.

[0016] R4 According to one aspect, the ends of the first and second projections are moved in translation along a tangent to a primary circle of the toothed wheel. It is noted that this direction of movement is a distinctive characteristic with respect to the known art in which the movable element comes radially closer to the toothed wheel. The radial size with respect to the axis of the toothed wheel is also reduced.

[0017] R5 In one aspect, the rod axis (A) is perpendicular to the wheel axis (W). As a result, there is no need to locate a rotation axis parallel to the gear axis near the gear. Other than the gear axis (W), the rod axis (A) is the only axis required in the proposed configuration of the function.

[0018] R6 According to one aspect, the first and second projections generally extend in a radial plane (PR) perpendicular to the wheel axis (W). This provides a reduced footprint with a flat configuration favorable to easy and compact integration into a transmission.

[0019] R7 According to one aspect, the first and second projections act on the same tooth of the toothed wheel. The locking system can thus be located on a reduced area relative to the toothed wheel. The chain of ribs is thus as short as possible.

[0020] R8 In one aspect, the number of teeth on the gear wheel is between 10 and 20. This maximizes the probability of being able to directly lock a tooth with the two fingers of the locking members moving closer together.

[0021] R9 According to one aspect, the rod is mounted and interposed between a bearing of the drive member and an opposite bearing connected to the transmission housing. As a result, the rod swirls in these two bearings and the assembly has good mechanical robustness and allows forces to be taken up in the axial and radial directions.

[0022] R+ According to one aspect, the internal and external threads are fine pitch threads, the pitch of the threads PF being less than 12% of the diameter of the rod D3. The external diameter D3 of the rod may be between 8 cm and 16 cm, preferably for example between 10 cm and 12 cm.

[0023] This contributes to the irreversibility of the force path. In particular, when a vehicle is parked on sloping ground, whether going uphill or downhill, gravity (i.e. the weight of the vehicle) generates a torque (static or even dynamic) on the toothed wheel which is transmitted to the locking devices and to the threads and the rod. But with a small thread pitch, the torque applied on the rod is not enough to turn the motor or the geared motor (the actuator).

[0024] The invention also relates to a transmission for a motor vehicle comprising a locking device as described above.

[0025] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.1] schematically illustrates an example of a parking brake, with a view to elevation, according to the present invention; - [Fig.2] shows a partial view of the threaded rod with opposite screw threads; - [Fig.3] shows a cross-sectional view of the rod and a locking member with the translational guide; - [Fig.4] schematically illustrates an embodiment according to the invention with the parking brake function not engaged; - [Fig.5] schematically illustrates an embodiment according to the invention with the parking brake function engaged; - [Fig.6] is similar to figure 5 and schematically illustrates a particular situation before blocking; - [Fig.7] illustrates the inclined orientation of the fingers of the locking members.

[0026] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the presentation, certain elements are not necessarily represented to scale

[0027] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the presentation, certain elements are not necessarily represented to scale

[0028] Figure 1 shows an example of an embodiment of a blocking device as proposed. The blocking device is arranged in a transmission housing marked 9. The transmission may be an automatic gearbox transmission, without however excluding the case of a manually operated gearbox. The transmission may also be an electric or hybrid vehicle transmission.

[0029] From a general point of view, the powertrain comprises an engine, whether internal combustion or electric, a transmission comprising a reducer with, where appropriate, several selectable reduction ratios, a differential and two axle shafts each connected to the respective wheels of an axle.

[0030] It is noted that in the proposed configuration, only one locking device is needed to lock both wheels of an axle.

[0031] In the illustrated example, the casing 9 contains various gears and pinions. In particular, Figure 1 illustrates a transmission gear marked 81 permanently engaged via its peripheral teeth 81a with a toothed wheel 8. It is the toothed wheel 8 which will be blocked in certain cases of use by the device which will be described further.

[0032] The toothed wheel 8, via the transmission gear 81, is generally rotationally fixed to the wheels of an axle or at least to a wheel shaft. The locking of the toothed wheel 8 therefore allows the wheels of the vehicle axle to be immobilized. There may be a differential (not shown) interposed between the gear 81 and the wheel shafts.

[0033] The toothed wheel 8 is mounted to rotate around a wheel axle marked W. The toothed wheel 8 is mounted on a shaft, rotating or not, connected to the casing 9.

[0034] The gear wheel 8 may comprise 10 teeth as illustrated in the figures. Generally, the number of teeth on the gear wheel 8 is between 10 and 20. For example, the number of teeth on the gear wheel may be 12, or the number of teeth on the gear wheel may be 16.

[0035] The teeth are of trapezoidal profile with steep flanks. According to one embodiment, the flanks 87 may be parallel to each other.

[0036] The outer diameter D8 of the gear wheel 8 can be between 10 cm and 25 cm, for example preferably between 16 cm and 20 cm. The gear wheel 8 is made of metal like a conventional pinion or gear.

[0037] The locking device comprises a rod 3. The rod 3 is rotatably mounted in the casing around a rod axis denoted A.

[0038] The rod 3 is made of, for example steel. The rod 3 comprises a first journal in the vicinity of its first end on the drive member side, and a second journal at its second end. The first journal is received in a bearing 34 of the drive member 4. The second journal is received in an opposite bearing 39. The bearing 39 can be connected by a support 38 to the casing or can be integrated directly into a bored shape of the casing casting 9.

[0039] The pivoting in the bearings is lubricated by the oil present in the transmission housing by splashing effect of the moving parts. The rod 3 is further immobilized along the axis A by the bearings. Thus, the only degree of freedom conferred to the rod 3 is rotation around the rod axis A.

[0040] The rod 3 comprises two threaded portions with opposite pitches. More precisely, the rod 3 comprises a first portion 31 equipped with an external thread 31a with a right-hand pitch and a second portion 32 equipped with an external thread 32a with a left-hand pitch.

[0041] The internal and external threads are preferably fine-pitch threads. As shown in Figure 2, the thread pitch, denoted PF, corresponds to the distance between two successive threads. In the example shown, the PF pitch is less than 12% of the rod diameter D3. For example, for a rod diameter of 8 millimeters, the PF pitch is less than 1 millimeter.

[0042] An unthreaded portion 30 may be interposed between the two threaded portions. It is noted that the invention covers any type of thread including standard pitch threads.

[0043] The outer diameter D3 of the rod 3 may be between 8 mm and 16 mm, for example preferably between 10 mm and 12 mm.

[0044] On each of the two threaded portions is mounted a locking member, movable along the rod axis A.

[0045] The locking device comprises a first locking member 1 and a second locking member 2.

[0046] The first locking member 1 comprises a first sleeve 10 centered on the rod axis A. The first locking member 1 comprises a projection called here first projection 5 which extends radially outward from the first sleeve 10.

[0047] The first projection is formed as a finger or an arm. This finger or arm extends from the sleeve in a direction of axis X1 inclined relative to the rod axis A. The axis X1 is inclined relative to the rod axis A at an angle 0. 0 is between 35° and 60°. Preferably 0 is between 40° and 50°.

[0048] The first sleeve 10 comprises an internal thread, adapted to cooperate by form complementarity with the external thread 31a of the rod.

[0049] The first projection comprises a free end 51 forming a stop for stopping a tooth of the toothed wheel in a first direction of rotation S1 (see figure 4). The first projection comprises a part furthest from the rod axis called the dorsal portion of the finger noted 52, the use of which we will see later.

[0050] The second locking member 2 comprises a second sleeve 20 centered on the rod axis A. The second locking member 2 comprises a projection called here second projection 6 which extends radially outwards from the second sleeve 20.

[0051] The second sleeve 20 comprises an internal thread, with left-hand pitch, adapted to cooperate by form complementarity with the external thread 32a of the rod.

[0052] The second projection 6 comprises a free end 61 forming a stop for stopping a tooth of the toothed wheel (the same tooth or another) in a second direction of rotation S2.

[0053] We notice that the fingers are directed towards each other, as in the case of pliers or a pair of pincers.

[0054] As illustrated in Figure 7, the rod axis A is separated from the wheel axis W by a distance denoted D6. When the locking members are in the locking position, the axes X1 and X2 intersect at a point P 12, separated from the rod axis A by a distance D7.

[0055] D7 can be between 25% of D6 and 50% of D6 depending on the wheel diameter.

[0056] Furthermore, the device comprises guide elements 7. As illustrated in Figure 3, the finger 5 extends between a first bearing surface 71 which prevents it from turning to the left and a second bearing surface 72 which prevents it from turning to the right. Other types of guidance are not excluded, such as, for example, tabs arranged diametrically opposite the fingers.

[0057] In a generic manner, the guide elements 7 prevent the rotation of the locking members 1, 2 around the rod axis A but allow the translation of the locking members 1, 2 along the rod axis A.

[0058] The first and second projections 5,6 generally extend in a radial plane denoted PR perpendicular to the wheel axis W. The plane PR passes through the axis A.

[0059] As can be seen in Figure 3, the configuration of the assembly of the elements is substantially flat along the Y direction. Indeed, the toothed wheel 8 and the fingers 5 and 6 extend on either side of the radial median plane PR. In addition, the grip of the elements, rod 3 and locking members (1 and 2), does not exceed the external diameter D1 of the sleeves. Such an assembly is therefore easy to install in a narrow space of a transmission.

[0060] The locking members have internal threads corresponding to the thread of the rod. The first locking member contains an internal thread with a right-hand thread while the second locking member contains an internal thread with a left-hand thread.

[0061] Even if the first thread is a right-hand thread and the second thread is a left-hand thread, of course the reverse is possible, with the corresponding reverse on the threads of the rod portions.

[0062] It is noted that the rod diameter can be reduced (< D3) beyond the threaded portions in order to be able to insert the sleeves of the locking members from the end of the rod to their position in the threaded portions 31, 32.

[0063] Thanks to the threaded portions 31a, 32a of the rod with opposite pitches, when the rod 3 rotates in a first direction T1, the locking members 1, 2 move towards each other. When the rod 3 rotates in the other direction T2, the locking members 1, 2 move away from each other.

[0064] The motor member 4 may be, for example, an electric motor. The motor member may comprise a reducer, in which case the member is a geared motor. The output shaft, e.g., the rotor of the motor or the output shaft of the reducer, is engaged with the rod 3, for example, by a splined interface. A female sleeve is secured to the rotor of the motor 4. The end of the rod on this side is of the male splined type. Other solutions, such as keying or the use of a through pin, are also possible.

[0065] It is noted that the driving member 4 can be arranged outside the casing 9, the rod 3 can be more or less long depending on the integration configurations. This flexibility of positioning of the driving member facilitates the possibilities of integrating the proposed solution into a given transmission configuration.

[0066] The drive unit is controlled by a control unit not shown in the figures. Said control unit receives the vehicle speed information and can control the engagement of the parking brake when the vehicle speed is zero or alternatively when the vehicle speed is below a very low threshold, for example below 3 km / h.

[0067] We start from the situation shown in Figure 4 where the toothed wheel can rotate freely around the W axis. When the conditions are met, the control unit can command the engagement of the parking brake.

[0068] For this purpose, the control unit controls, by means of the electric motor 4, the rotation of the rod in the direction T1 so that the locking members move closer to each other. Figure 5 represents the final situation where the tooth 8a is framed from above by the finger 5 of the first locking member 1 and from below by the finger 6 of the second locking member 2.

[0069] The fingers grip tooth 8a like pliers.

[0070] It is noted that if tooth 8a is not exactly in the correct position at the time of tightening, one of the fingers can bring tooth 8a and therefore the entire wheel 8 into the correct position in its travel. The fineness of the pitch of the threaded portions makes it possible to provide a significant force along axis A.

[0071] Note that the fingers are moved in translation along a tangent TG to the primary circle of the toothed wheel. This configuration is ideal for the finger to push a tooth of the wheel 8 by its flank 87 in a circumferential direction and turn the wheel 8.

[0072] This provides a re-centering function if the tooth is not positioned correctly.

[0073] According to another case shown in Figure 6, in the hypothesis where the fingers 5 and 6 do not grip a tooth when they approach each other, then as soon as the wheel 8 turns a little, a tooth of the wheel can erase one of the fingers to come and lodge in the gap between the free ends of the fingers. The first tooth which passes into the gap is thus trapped,

[0074] For this, a bending of the finger is provided by pressure on the back 52 of the finger. As illustrated in Figure 6, it is the second finger 6 of the second locking member 2 which bends upwards when a tooth passes into contact with it, the wheel 8 rotating clockwise.

[0075] Depending on the rigidity of the finger and the rod, the rod may also buckle a little when a tooth passes over the back of a finger. Such flexibility may be sought to result in the trapping of a tooth even if the fingers in their approach stroke have not already gripped a tooth.

[0076] The rod and locking members are made of metal, e.g. steel.

[0077] It is noted that the helical interface between the rod 3 and the sleeves 10, 20 is lubricated by the splashing of oil from the transmission.

Claims

CLAIMS 1. Device for locking a driveline transmission in a motor vehicle, by mechanical engagement of at least one locking member in a toothed wheel of the transmission, the device comprising at least: - a toothed wheel (8), mounted to rotate relative to a wheel axle (W), - a rod (3) mounted for rotation in a casing around a rod axis (A), the rod comprising a first portion (31) equipped with an external thread with a right-hand thread and a second portion (32) equipped with an external thread with a left-hand thread, - a motor member (4) configured to selectively rotate the rod in one direction or the other (T1, T2), - a first locking member (1) comprising a first sleeve (10) centered on the rod axis and a first projection (5) extending radially outward from the sleeve, the sleeve comprising an internal thread, adapted to cooperate by form complementarity with an external thread of the rod, the first projection comprising a free end forming a stop for stopping a tooth of the toothed wheel in a first direction of rotation (S1), - a second locking member (2) comprising a second sleeve (20) centered on the rod axis and a second projection (6) extending radially outward from the sleeve, the sleeve comprising an internal thread, adapted to cooperate by form complementarity with the other external thread of the rod, the second projection comprising a free end forming a stop for stopping a tooth of the toothed wheel in a second direction of rotation (S2), - guide elements (7) to prevent rotation of the first and second locking members around the rod axis but to allow translation of the locking members along the rod axis.

2. Locking device according to claim 1, wherein each of the first and second projections is formed as a finger which extends in an extension direction (X1, X2) inclined relative to the rod axis.

3. A locking device according to claim 2, wherein the respective fingers of the first and second projections are directed towards each other.

4. A locking device according to any one of claims 1 to 3, wherein the ends of the first and second projections are moved in translation along a tangent to a primary circle of the toothed wheel.

5. Locking device according to any one of claims 1 to 4, in which the rod axis (A) is perpendicular to the wheel axis (W).

6. A locking device according to any one of claims 1 to 5, wherein the first and second projections extend generally in a radial plane (PR) perpendicular to the wheel axis (W).

7. A locking device according to any one of claims 1 to 5, wherein the first and second projections act on the same tooth of the gear wheel.

8. Locking device according to any one of claims 1 to 6, wherein the number of teeth on the toothed wheel (8) is between 10 and 20.

9. Locking device according to any one of claims 1 to 7, in which the rod is mounted and interposed between a bearing (34) of the driving member and an opposite bearing (39) connected to the transmission casing (9).

10. Transmission for a vehicle comprising a locking device according to any one of claims 1 to 9.

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