GB2511903A

GB2511903A - Arrangement of a freewheel device

Info

Publication number: GB2511903A
Application number: GB1322465.4A
Authority: GB
Inventors: M E Anirudh Thummalapalli
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2013-12-18
Filing date: 2013-12-18
Publication date: 2014-09-17
Also published as: GB201322465D0

Abstract

A freewheel device 62 is arranged between a hub 64 and a knuckle 66 of a motor vehicle wheel, comprising at least one clamping element 68 switchable into a use position (70, fig 5), in which the freewheel device 62 and the hub 64 can independently rotate, and a non-use position 72, in which rotation between the hub 64 and the freewheel device 62 is blocked in one rotational direction 98. The device is switched by translational movement 100, preferably of an annular piston 78, between the freewheel device 62 and the knuckle 66. The device 62 may be switched by the vehicle driver. The clamping element 68 is preferably clamped in a ramp area 76 to block rotation in one direction.

Description

Arrangement of a Freewheel Device The invention relates to an arrangement of a freewheel device between a hub and a knuckle of a motor vehicle. Furthermore the invention relates to a method for operating a freewheel device between a hub and a knuckle of a motor vehicle.

A mechanical component which is capable of disengaging a drive shaft (drive) from a driven shaft (driven) when the driven shaft rotates faster than the drive shaft is known as a freewheel or a so-called overrunning clutch. Such freewheels are often used to block a relative rotation between the drive shaft and the driven shaft into one direction while allowing the relative rotation into another direction of rotation.

Such a freewheel can, for example, already be taken as known from US 2003/0226415 Al. The freewheel there is designed as an overrunning clutch assembly for an automotive transmission and comprises an outer race having a cylindrical inner surface and an inner race engaged with a drop shaft of the transmission and having a cammed outer surface coaxial with the cylindrical inner surface and defining a gap in between and a roller clutch disposed within the gap. The overrunning clutch assembly also comprises a biasing element to bias the roller clutch to a disengaged position and an actuator to selectively overcome the biasing element to engage the roller clutch and lock the outer race and inner race and prevent relative rotation between the outer race and inner race, thereby preventing rotation of the drop shaft and movement of the automobile.

If the automobile has to be halted on a hill side by means of the freewheel, which engages the transmission, an especially high surface pressure is exerted upon the engaged gears of the transmission. Since the transmission as well as the automobile is kept at standstill the lubrication of the gears is poor which results in a metallic contact of the engaged gears with each other. This can at least lead to micro-damage of the gears.

Therefore, it is the object of the present invention to provide an arrangement of a freewheel device of the initially mentioned kind by means of which a motor vehicle can be halted in an especially safe and gentle manner.

This object is solved by an arrangement having the features of claim 1 and by a method having the features of claim 5. Advantageous configurations with convenient developments of the invention are specified in the dependent claims.

In the arrangement of a freewheel device between a hub and a knuckle of a motor vehicle according to the invention the arrangement comprises at least one clamping element which is capable of being switched into a use position, in which the freewheel device and the hub are mechanically disengaged and thus the hub is independently rotatable relative to the freewheel device according to a rotational axis of the hub, and a non-use position, in which the hub and the knuckle are mechanically engaged by means of the freewheel device and thus at least a rotation about the rotational axis between the hub and the freewheel device is blocked in one rotational direction, by means of a translational movement between the freewheel device and the knuckle.

In this arrangement the freewheel device is housed between the wheel hub and the knuckle wherein there is no need to switch the freewheel device into the use position when the motor vehicle is climbing a gradient since the arrangement itself takes care of the free movement of the vehicle in the forward direction. In other words, the arrangement automatically switches into the use position, if the motor vehicle shall be accelerated from the standstill to a desired speed and there is no need for disengaging the arrangement by means of a driver input, such as pushing a button or operating a lever.

In other words and in contrast to the prior art and thus in contrast to a conventional start-stop function which uses the service brake of the motor vehicle to hold it in position accordingly, the freewheel device is automatically mechanically disengaged as soon as the motor vehicle is moved forward since then a clamping force, which is holding the clamping element in the non-use position (in which the motor vehicle is held) is released.

In other words, the clamping force no longer affects the clamping element as soon as the motor vehicle is moved forward and thus the clamping element is moved from the non-use position into the use position as soon as the clamping force is removed. This arrangement only affects a small portion of the drive train (only the portion between the hub and the knuckle) which is subjected to a torsional moment due to the slope force of the motor vehicle if it is stopped on a slope. Thus, the motor vehicle is only moved by a small distance down the slope if the clamping element is switched in the non-use position, namely only the distance which is covered as a result of the torsion of the arrangement due to the slope force.

Further advantages, features and details of the invention are apparent from the following description of a preferred embodiment as well as based on the drawings.

They show in: Fig. la a schematic view of a pedal arrangement of a motor vehicle comprising a clutch pedal, a brake pedal and an accelerator pedal, wherein whilst the motor vehicle is at rest none of the pedals is actuated by the driver

according to the prior art;

Fig. lb a schematic view of the pedal arrangement wherein according to the prior art the accelerator pedal is actuated by the driver and the motor vehicle is in motion; Fig. lc a schematic view of the pedal arrangement according to the prior art wherein the clutch pedal and the accelerator pedal are alternately actuated by the driver when the motor vehicle is moved in e.g. a traffic jam; Fig. ld a schematic view of the pedal arrangement according to the prior art wherein the clutch pedal and the brake pedal are alternately actuated by the driver when the motor vehicle is moved in e.g. a traffic jam; Fig. 2a a schematic view of the motor vehicle which is stopped at an incline; Fig. 2b a schematic view of the pedal arrangement according to the prior art wherein the clutch pedal and the brake pedal are actuated by the driver to halt the motor vehicle at the incline according to Fig. 2a; Fig. 2c a schematic view of the pedal arrangement according to the prior art wherein the clutch pedal and the accelerator pedal are actuated by the driver to move the motor vehicle forward at the incline according to Fig. 2a; Fig. 3 a schematic front view of a freewheel according to the prior art, wherein the freewheel comprises an inner part which is designed as a drive shaft and an outer ring which is designed as a driven shaft as well as several rollers which are actuated by a spring; Fig. 4 a sectional view of a technical drawing showing a hub and a knuckle of a front axle of the motor vehicle according to the prior art wherein this section merely serves to explain the background of the invention; Fig. 5a a schematic view of a section according to a section line B-B of Fig. 5b of an arrangement of a freewheel device between a hub and a knuckle of the motor vehicle according to the invention wherein a clamping element of the freewheel device is in a use position; Fig. 5b a schematic front view of the arrangement wherein the rotation according to freewheel directions is allowed, since the clamping element is in its use position; Fig. 6a a schematic view of the section according to the section line C-C of Fig. 6b of the arrangement of freewheel device between the hub and the knuckle of the motor vehicle according to the invention wherein the clamping element of the freewheel device is in a non-use position; and Fig. 6b a schematic front view of the arrangement wherein the rotation according to the freewheel directions is blocked, since the clamping element is in its non-use position.

Figs. 1 a -1 d each show a pedal arrangement 10 of a motor vehicle 20 (not shown here) with an accelerator pedal 12, a brake pedal 14 and a clutch pedal 16. If one or more of the pedals 12, 14, 16 are actuated by a driver of the motor vehicle 20, they are illustrated hatched at present. Fig. la shows the pedal arrangement 10 when the motor vehicle 20 is at rest. Thus, none of the pedals 12, 14, 16 is actuated by the driver and the motor vehicle 20 is held e.g. by a hand brake (not shown here). Fig. lb shows the pedal arrangement 10 when the motor vehicle 20 is in motion and thus the accelerator pedal 12 (hatched) is actuated by the driver. Fig. ic in conjunction with Fig. ld shows the actuation of the pedal arrangement 10 when the motor vehicle 20 is moved in a stop-and-go mode e.g. when the motor vehicle 20 is moved in a traffic jam. Thus, as it is typical for vehicles with manual transmission, the pedals 12, 14, 16 of the pedal arrangement 10 are actuated in an alternating manner.

Fig. 2a shows the motor vehicle 20 which is held at an incline 18 and Fig. 2b shows the pedal arrangement 10 wherein both the clutch pedal 16 and the brake pedal 14 are actuated -wherein a gear of the manual transmission of the motor vehicle 20 is engaged -by the driver to prevent the motor vehicle 20 as it is shown in Fig. 2a from rolling downhill. If the motor vehicle 20 shall be accelerated and thus moved uphill it is known from the prior art that the driver both has to disengage the brake pedal 14 and to engage the accelerator pedal 12 shortly thereafter (Fig. 2c) wherein by means of carefully loosening the clutch pedal 16 (disengaging the clutch pedal 16) the torque of an internal combustion engine (not shown) is transmitted to the drive wheels of the motor vehicle 20 by friction of the clutch (not shown), when the motor vehicle 20 begins to move and thus the clutch grinds at the beginning of the movement.

Fig. 3 shows a schematic front view of a freewheel 30 according to the prior art. The freewheel 30 comprises a drive shaft 32 which corresponds to an inner part of the freewheel 30 designed as a solid shaft at present which is operated by e.g. a combustion engine by means of a transmission. The freewheel 30 also comprises a driven shaft 34 which corresponds to an outer ring of the freewheel 30 which is designed as a driven hollow shaft concentrically surrounding the drive shaft 32 at present. The drive shaft 32 and the driven shaft 34 are spaced by means of rollers 38 wherein each of the rollers 38 is arranged in a holding portion 46 of the drive shaft 32. Each of the holding portions 46 has a narrow area 48 which expands to a wide area 50. By means of a spring 36 each of the rollers 38 is pushed in a position between the narrow area 48 and the wide area 50, wherein between the narrow area 48 and the wide area 50 the rollers 38 are both in contact with the drive shaft 32 and the driven shaft 34. The radial recess of the wide area is dimensioned such as to allow the rollers 38 to unroll under especially low friction losses between the drive shaft 32 and the driven shaft 34. The radial recess of the narrow area 48 is dimensioned such as to clamp the rollers 38 in such a manner that the rollers 38 are prevented from rolling between the drive shaft 32 and the driven shaft 34 due to self-locking, wherein the friction between the rollers 38, the drive shaft 32 and the driven shaft 34 is too high to allow them to unroll. If the driven shaft 34 is rotated according to a rotation 42, which is marked with an arrow and is faster than a rotation 40 of the drive shaft 32, wherein the rotation 40 is also marked with an arrow, the rollers 38 tend to move towards the wide area 50 of the drive shaft 32 and thus the driven shaft 34 can be moved relative to the drive shaft 32 in the same rotational direction. In other words, if the driven shaft 34 rotates faster and in the same direction as the drive shaft 32 the driven shaft 34 is not inhibited. However, if the driven shaft 34 is rotated according to an opposite rotation 44 which corresponds to a rotation in the opposite direction of the rotation 42, or if the drive shaft 32 rotates in the same direction of the rotation 42, but faster than the driven shaft 34 alternatively, the rollers 38 tend to move towards the narrow area 48 of the holding portion 46. As a consequence the rollers 38 are clamped between the drive shaft 32 and the driven shaft 34 and, thus, a relative rotation between the drive shaft 32 and the driven shaft 34 is blocked.

Fig. 4 shows a section from a technical drawing of a wheel suspension 22 according to the prior art and merely serves to explain the background of the invention. The wheel suspension 22 comprises a hub 64 and a knuckle 66. The dashed region A marks an area of the wheel suspension 22, which is designed as a front wheel suspension at present, where an arrangement 60 exemplarily can be placed according to the invention correspondingly.

Fig. 5a and Fig. Ba show this region A which is marked in Fig. 4 in an enlarged view, wherein additionally and in contrast to the prior art the freewheel device 62 is arranged between the hub 64 and the knuckle 66 to prevent the motor vehicle 20 from rolling backwards, if it is stopped at the incline 18. Fig, 5a corresponds to the section B-B according to the section line B-B which is shown in Fig. Sb. However, Fig 6a corresponds to a section according to the section line C-C shown in Fig. 6b. Figs. 5a and Sb refer to a use position 70, in which the freewheel device 62 and the hub 64 are mechanically disengaged and thus the hub 64 is independently rotatable relative to the freewheel device 62 according to a rotational axis 102 of the hub 64. In contrast to this Figs. Ba and 6b refer to a non-use position, in which the hub 64 and the knuckle 66 are mechanically engaged by means of the freewheel device 62 and thus at least a rotation around the rotational axis 102 between the hub 64 and the rotation of the hub 64 is blocked in one rotational direction 98. The freewheel device 62 comprises four clamping elements 68 at present wherein it is clear that also a different number of clamping elements 68 would be possible. The freewheel device 62 comprises a sleeve 76 with several clamping areas 74 (according to the number of clamping elements 68) which at least partially surround the clamping elements 68 and thus the clamping elements 68 are each supported in one of the clamping areas 74 of the freewheel device 62. The clamping elements 68 are designed as cylindrical rolling elements at present. In other words, in each of the clamping areas 74 of the freewheel device 62 a clamping element 68 is supported. The clamping areas 74 also comprise a ramp area 76 by means of which the clamping element 68 is engaged with the hub 64. In other words, both the clamping areas 74 and the ramp areas 76 accordingly are arranged at the sleeve 82 of the freewheel device 62 in a circumferential direction of the sleeve 82.

In a fluid chamber 90 of the knuckle 66 an annular piston 78 is arranged. The fluid chamber 90 corresponds to an annular recess in the knuckle 66. The fluid chamber 90 is coupled with e.g. a steering pump (not shown) of the motor vehicle 20. By means of the steering pump the fluid chamber 90 can be filled with mineral oil to engage the annular piston 78. In doing so the annular piston 78 is pushed into the direction of the hub 64 by means of the fluid pressure. The annular piston 78 and the sleeve 82 are coupled in a force transmitting manner by means of a bearing 84. The bearing 84 is designed as an axial bearing at present. When the fluid chamber 90 is filled with hydraulic oil e.g. from the steering pump, which is especially easy if the arrangement 60 is arranged at the front wheel of the motor vehicle 20, both the annular piston 78, the bearing 84 and the sleeve 82 are pushed into the direction of the hub 64 against a spring force of spring elements which are arranged between the sleeve 82 and the hub 64. For each of the clamping elements 68 one of the spring elements 80 can be arranged, to realize a symmetric force flow within the arrangement 60 and to prevent canting. The spring element 80 is kept in position by means of a bearing 86 which is arranged at the hub 64 at present. It is clear that the bearing 86 could also be arranged at the sleeve 82 as an alternative. When the fluid pressure is exerted upon the annular piston 78 (and the fluid chamber 90 is filled with hydraulic oil which exerts a pressure upon the annular piston 78) the sleeve 82 and thus the clamping element 68 are moved according to a translational movement 100 which is marked with an arrow in Fig. 6a. In doing so the spring element 80 is pushed together and the clamping element 68 engages the hub 64. The translational movement 100 between the sleeve 82 of the freewheel device 62 and the knuckle 68 is possible, because the sleeve 82 is supported by means of a bearing 88 which is designed as a gearing at present. In other words the bearing 88 allows the translational movement 100 but not a relative rotation between the sleeve 82 and the knuckle 66. If the clamping element 68 or the clamping elements 68, respectively, are in contact with the hub 64 the clamping elements 68 and thus the freewheel device 62 are in the non-use position 72 as shown in Fig. 6a, and thus the clamping elements 68 each roll on the ramp area 76 wherein the clamping elements 68 roll until they are clamped in between the hub 64 and the sleeve 82. Since the sleeve 82 cannot rotate relative to the knuckle 66 because of the bearing 88, which is designed as a gearing, the rotation according to the rotational direction 98 which is marked with an arrow in Fig. Sb is not possible. However, the rotation according to a rotational direction 96 which is also marked with an arrow in Fig. Sb is allowed. In other words, if the hub 64 is rotated according to the rotational direction 96 the clamping of the clamping elements 68 between the hub 64 and the sleeve 82 is loosened and by means of the spring force of the spring elements 80 the clamping elements 68 are moved away and thus are disengaged from the hub 64 (Fig. 5a). It is clear that the translational movement 100 as it is shown in Fig. 5a (opposite direction of translational movement 100 as it is shown Fig. 6a) is only possible if the fluid pressure within the fluid chamber 90 is released. If the clamping elements 68 and thus the sleeve 82 is moved into the use position 70 the freewheel device 62 is no longer engaging the hub 64 and thus a rotation according to a freewheeling direction 94 of the clamping elements 68 as well as a freewheeling direction 92 of the hub 64 are allowed. In other words, if the freewheel device 62 is in its use position 70 (Fig. 5a, Fig. 5b) the hub 64 and thus a wheel of the motor vehicle 20 which is connected with the hub 64 in a momentum transmitting manner is rotatable forwards and backwards as it is also illustrated by the double arrow of the freewheeling direction 92. However, if the clamping element 68 and thus the freewheel device 62 are in their non-use position 72 (Fig. 6a, Fig. Sb) the rotation of the hub 64 according to the rotational direction 98 is blocked and only a rotation according to the rotational direction 96 (opposite direction of rotational direction 98) is possible.

Switching the freewheel device 62 from the use position 70 to the non-use position 72 is done in dependency on a driver input. The driver input can correspond to actuating a button or a lever or other actuators by means of which the clamping element 68 and thus the freewheel device 62 is moveable from the use position 70 to the non-use position 72.

In this example, by means of the driver input the fluid chamber 90 is filled with mineral oil exerting a pressure upon the annular piston to move the clamping elements 68 and thus the freewheel device 62 in the non-use position 72.

List of reference characters pedal arrangement 12 accelerator pedal (A) 14 brake pedal (B) 16 clutch pedal (C) 18 incline motor vehicle 22 wheel suspension freewheel 32 drive shaft 34 driven shaft 36 spring 38 roller rotation 42 rotation 44 opposite rotation 46 holding portion 48 narrow area wide area arrangement 62 freewheel device 64 hub 66 knuckle 68 clamping element use position 72 non-use position 74 clamping area 76 ramp area 78 annular piston spring element 82 sleeve 84 bearing 86 bearing 88 bearing fluid chamber 92 freewheeling direction 94 freewheeling direction 96 rotational direction 98 rotational direction translational movement 102 rotational axis

Claims

Claims An arrangement (60) of a freewheel device (62) between a hub (64) and a knuckle (66) of a motor vehicle (20), the arrangement (60) comprising at least one clamping element (68) which is switchable into -a use position (70), in which the freewheel device (62) and the hub (64) are mechanically disengaged and thus the hub (64) is independently rotatable relative to the freewheel device (62) according to a rotational axis (102) of the hub (64), and -a non-use position (72), in which the hub (64) and the knuckle (66) are mechanically engaged by means of the freewheel device (62) and thus at least a rotation around the rotational axis (102) between the hub (64) and the freewheel device (62) is blocked in one rotational direction (98), by means of a translational movement (100) between the freewheel device (62) and the knuckle (66).
2. The arrangement (60) according to claim 1, characterized in that the freewheel device (62) comprises a clamping area (74) by means of which the clamping element (68) is supported.
3. The arrangement (60) according to claim 2, characterized in that the clamping area (74) comprises a ramp area (76) by means of which the clamping element (68) engages the hub (64).
4. The arrangement (60) according to any one of claims 1 to 3, characterized in that the arrangement (60) comprises an annular piston (78) by means of which the clamping element (68) is switchable from the use position (70) to the non-use position (72).
5. A method for operating a freewheel device (62) between a hub (64) and a knuckle (66) of a motor vehicle (20), the freewheel device (62) comprising at least one clamping element (68) which is switched into -a use position (70), in which the freewheel device (62) and the hub (64) are mechanically disengaged and thus the hub (64) is independently rotatable relative to the freewheel device (62) according to a rotational axis (102) of the hub (64), or -a non-use position (72), in which the hub (64) and the knuckle (66) are mechanically engaged by means of the freewheel device (62) and thus at least a rotation about the rotational axis (102) between the hub (64) and the freewheel device (62) is blocked in one rotational direction (98), by means of a translational movement (100) between the freewheel device (62) and the knuckle (66) in dependency on a driver input.