Gear shift actuator
The gear shift actuator addresses the challenge of blocked dog clutch positions by utilizing a rotary member with barrel cams and a spring mechanism to manage blocked states and ensure reliable shifting operations.
Patent Information
- Application Number
- PCT/EP2023/072986
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-08-22
- Publication Date
- 2025-02-27
AI Technical Summary
Gear shift actuators face challenges when the teeth or dog wheels of a dog clutch are in a relative angular position that prevents the actuator from shifting to the gear engaged position until the dog wheels are aligned.
The gear shift actuator incorporates a rotary member with first and second barrel cams that allow for torque-proof engagement with a cylindrical sleeve, enabling sliding movements in the axial direction. This design includes a spring mechanism and cam followers to manage blocked states and ensure reliable shifting.
The gear shift actuator effectively handles situations where the pushrod is blocked by storing energy in a compressed spring, which is then used to overcome the blockage and achieve the desired gear position, ensuring reliable and efficient shifting operations.
Smart Images
Figure EP2023072986_27022025_PF_FP_ABST
Abstract
Description
[0001] Gear Shift Actuator
[0002] The present invention is directed to a gear shift actuator for actuating a shift fork comprising: a rotary member which is supported to be rotatable, but unmovable in an axial direction defined by its rotary axis, an electric motor for rotating the rotary member, and a driven component driven by rotary movement of the rotary member for linear movement in axial direction in a first direction from a neutral position to a first gear engaged position and back to neutral, when the rotary member is driven to rotate first in a first sense of rotation and then in a second sense of rotation opposite to the first sense of rotation, and in a second direction opposite to the first direction from the neutral position to a second gear engaged position and back to neutral, when the rotary member is first driven to rotate in the second sense of rotation and then in the first sense of rotation.
[0003] Gear shift actuators are utilized in motor vehicles, in particular in trucks and heavy-duty vehicles, to shift the transmission state of two coaxially disposed, rotary shafts between a gear engaged position in which rotary engagement between the two shafts is established and torque transmission takes place, and a neutral, disengaged position, in which the two rotary shafts are decoupled from each other. A typical case of application for a gear shift actuator of the above-described type is an actuator for a dog clutch. A dog clutch is a mechanism for connecting and disconnecting two rotating shafts. It is based on the working principle to let a set of regularly spaced teeth or protrusions on the circumference of one wheel connected to one of the shafts get engaged with a set of complementary recesses between teeth on another wheel connected to the second shaft. When the two wheels are moved together such that the teeth of the first wheel are received in the recesses formed between teeth of the second wheel a slip-free rotary engagement between the shafts is established.
[0004] A dog clutch with a dog clutch actuator is for example described in US 2015 / 0107955 A1 on which the preamble of claim 1 is based. The gear shift actuator comprises a linear drive assembly having a rotary member in the form of a lead screw which is supported to be rotatable, but not moveable in the direction of its rotary axis, an electric motor for rotating the lead screw, and a driven component in the form of a nut engaged by the lead screw. By engagement of nut and lead screw rotary movement of the lead screw is transmitted into a linear movement of the nut along the axial direction of the rotary axis of the lead screw. The driven component in form of the nut is connected to a shift fork for driving it from a neutral position to a gear engaged position and vice versa, when the lead screw is driven to rotate in a first sense of rotation and in a second sense of rotation opposite to the first sense of rotation, respectively. In the neutral position of the shift fork one of the teeth carrying wheels is moved away from the other so that the torque-transmitting engagement between the two wheels is ceased. By moving the shift fork using the linear drive assembly to the gear engaged position the one of the two teeth or dog wheels is moved into rotary engagement with the teeth of the other wheel, wherein the teeth of one wheel are received in the recesses between the teeth of the other wheel and vice versa.
[0005] For such gear shift actuators the situation may arise that the teeth or dog wheels are in a relative angular position with respect to each other such that the teeth of one wheel are facing directly opposite teeth of the other wheel, in which case the gear shift actuator cannot shift to the gear engaged position until the dog wheels have rotated relative to each other so that the dogs of one wheel are aligned with recesses between dogs of the other wheel.
[0006] It is an object of the present invention to provide a gear shift actuator designed such that it can deal with situations in which a shift fork to be actuated by the gear shift actuator is temporarily blocked in a simple and reliable manner.
[0007] This object is achieved by a gear shift actuator comprising the features of claim 1. Preferred embodiments of the invention are set out in the dependent claims.
[0008] The present invention is directed to a gear shift actuator for actuating a shift fork of a transmission. The gear shift actuator comprises: a rotary member which is supported to be rotatable, but unmovable (in the rest frame of the transmission housing) in an axial direction defined by its rotary axis, an electric motor for rotating the rotary member, and a driven component driven by rotary movement of the rotary member for linear movement parallel to the axial direction. The gear shift actuator is configured such that this linear movement is effected in a first direction from a neutral position to a first gear engaged position of the driven member and back to neutral, when the rotary member is driven to rotate first in a first sense of rotation and then in a second sense of rotation opposite to the first sense of rotation; and such that this linear movement is effected in a second direction opposite to the first direction from the neutral position to a second gear engaged position and back to neutral, when the rotary member is first driven to rotate in the second sense of rotation and then in the first sense of rotation. According to the invention the rotary member is a hollow cylindrical sleeve having an inner wall. First and second barrel cams are coaxially disposed inside the cylindrical sleeve opposite to each other in axial direction, wherein outer walls of the first and second barrel cams and the inner wall of the cylindrical sleeve are configured to provide engagement of the first and second barrel cams with the cylindrical sleeve which is torque-proof with respect to relative rotational movements about the rotary axis, but allows sliding relative movement in axial direction. Such engagement can for example be realized by outer walls of the first and second barrel cams being in cross-section non-circular, when the first and second barrel cams are received in in the cylindrical sleeve with the inner wall being of complementary non-circular shape; preferably, the first and second barrel cams have splined outer walls which are in engagement with a complementary splined inner wall of the cylindrical sleeve, wherein the splines extend parallel to the axial direction so that they allow sliding of the first and second barrel cams inside of the cylindrical sleeve, but prevent any rotational movements of the first and second barrel cams with respect to the cylindrical sleeve. The first and second barrel cams are disposed between first and second end stops which are spaced apart from each other in axial direction and which are fixed in axial direction to limit axial movement of the first and second barrel cams, respectively. A spring mechanism is disposed between the first and second barrel cams to bias them apart and towards the first and second end stops, respectively.
[0009] The driven component is a pushrod which is supported in bearings for linear movement in axial direction and for extending coaxially on the rotary axis through central openings in the first and second barrel cams. The central openings of the first and second barrel cams comprise first and second internal cam grooves on inner surfaces of the central openings, respectively, and the pushrod carries first and second cam followers spaced apart and aligned in axial direction and arranged to be received in the first and second internal cam grooves, respectively, wherein the pushrod and its bearings provide a torque-proof engagement against rotational movements of the pushrod about the rotary axis.
[0010] Each of the first and second internal cam grooves extends from a starting point along a circumferential start portion, followed by a helical portion extending axially further towards an outer end portion of the respective one of the first and second barrel cams, which is followed by a circumferentially extending end portion. Thus, the helical portion of each of the first and second barrel cams is, in the direction from the starting point to the end portion, extending away from the other one of the first and second barrel cams. The starting points of the first and second internal cam grooves are open to recessed surface sectors of the inner surfaces of the central openings of the first and second barrel cams, respectively, which recessed surface sectors allow movement of the first and second cam followers, respectively, in a direction parallel to the axial direction in a region between the first and second internal cam grooves, respectively, and an inner end portion adjacent to the spring mechanism, wherein the first and second barrel cams are rotationally oriented with respect to each other such that the start portions of the first and second internal cam grooves are aligned so that, when the first cam follower is in the start portion of the first cam groove the second cam follower is in the start portion of the second cam groove, so that, when the rotary member in this state is rotated in the first sense of rotation, the first cam groove is moved along the first cam follower which thereby is driven by its helical portion to move the pushrod in the first direction, while the second cam follower is free to follow this movement in the recessed surface portion of the second barrel cam, is rotated in the second sense of rotation, the second cam groove is moved along the second cam follower which thereby is driven by the helical portion to move the pushrod in the second direction, while the first cam follower is free to follow this movement in the recessed surface portion of the first barrel cam.
[0011] Since the first and second internal cam grooves, when they are rotated along the start portion further through the helical portion drive the respective one of the first and second cam followers closer to the outer end portion of the respective one of the first and second barrel cams, the first internal cam groove, when it is rotated along the first cam follower, drives the latter towards its outer end portion in the first axial direction, while the second internal cam groove, when it is rotated along the second cam follower, drives the second cam follower with its helical portion in the opposite direction, towards the outer end portion of the second barrel cam and thus in the second axial direction.
[0012] With this design of the present invention the gear shift actuator can deal with situations in which the pushrod is acting against a blocked clutch. In the case of a blockage, the pushrod acts against the blocked clutch and can therefore not perform the desired linear movement. If the rotary member is rotated in this state, the respective one of the first and second barrel cams which is generating the drive force for the pushrod is forced in reaction to perform instead of the desired but blocked linear movement of the pushrod a movement of the respective barrel cam in opposite direction which moves the respective one of the first and second barrel cams away from its associated end stop; due to this movement of the respective one of the first and second barrel cams towards closer to the opposite one of the first and second barrel cams the spring mechanism acting between them is compressed. In other words the driving energy input for rotating the rotary member is in the case of a completely blocked clutch stored in the compressed spring, and after the blockage of the clutch is resolved the spring mechanism expands thereby driving the pushrod to perform the desired linear movement when the respective one of the first and second barrel cams is moved by the expanding spring mechanism back to abut against its associated end stop.
[0013] According to the present invention the pushrod is disposed coaxially with the rotary axis inside of the first and second barrel cams and the cylindrical sleeve. This arrangement is on the one hand advantageous because it requires less space than arrangements in which a pushrod is arranged parallel to but at a distance to the rotary axis of a rotatable driving component. Furthermore, the design according to the present invention is advantageous because the pushrod is extending on the rotary axis and is driven to move in axial direction for effecting the shifting operations; this arrangement is advantageous compared to designs in which the pushrod is arranged shifted with respect to the rotary axis of the rotary components because a displacement with respect to the central axis leads, when the pushrod is driven to move in axial direction, but displaced from the rotary axis, any counter acting force of the member driven by the pushrod is inducing a torque on the mechanism. Such torque is not induced in the design of the present invention in which the pushrod is extending in the axial direction on the rotary axis.
[0014] In a preferred embodiment, as mentioned above, the outer wall of each of the first and second barrel cams has in cross-section a non-circular surface structure which is received in a complementary non-circular surface structure of the inner wall of the cylindrical sleeve to provide torque-proof engagement of the first and second barrel cams with the cylindrical sleeve while allowing movement of the first and second barrel cams in axial direction within the cylindrical sleeve.
[0015] In a preferred embodiment the non-circular cross-sectional surface structure of the outer wall of each of the first and second barrel cams is formed by a splined outer wall and the non- circular cross-sectional surface structure of the inner wall of the cylindrical sleeve is formed by complementary splined inner wall of the cylindrical sleeve to provide a spline connection between the first and second barrel cams and the cylindrical sleeve which allows relative axial movement of the first and second barrel cams within the cylindrical sleeve, but is torque-proof with respect to relative rotational movements about the rotational axis.
[0016] In a preferred embodiment the first and second end stops and the first and second barrel cams with the spring mechanism in-between are arranged such that the spring mechanism is under a predetermined preload and exerts oppositely directed forces on the first and second barrel cams to bias them against the first and second end stops, respectively. In other words, the arrangement of the first and second barrel cams with the spring mechanism in-between would expand on the shaft if one or both of the first and second end stops would be removed.
[0017] In a preferred embodiment the circumferentially extending end portion of each of the first and second internal cam grooves is continued by a cam groove section having a closed end and a slope opposite to the slope of the helical portion of the respective cam groove to form a detent end section of the respective cam groove to enable the respective one of the first and second cam followers to reach a stable end position at the closed end. In this way the risk that the cam followers and thus the pushrod could leave the intended gear engaged position due to vibrations or other external interferences is minimized. For the sloping end section of the cam groove it is sufficient that the inner wall of the respective one of the first and second internal cam grooves, which inner wall separates the respective one of the first and second internal cam grooves from the respective recessed surface sector, is formed with such a slope.
[0018] In this connection it is preferred that, in the circumferential region of the closed end cam groove section of the first and second internal cam grooves, in the recessed surface sector of each of the first and second barrel cams a projecting surface is formed which is projecting away from the opposite one of the first and second barrel cams so that, when one of the first and second cam followers is reaching the detent end section of the respective one of a first and second internal cam grooves, the other one of the first and second cam followers is reaching and sliding along the projecting surface thereby pulling the one of the first and second cam followers in axial direction further into the closed end cam groove section to thereby enhance the detent effect in the first and second gear engaged end positions of the first and second barrel cams.
[0019] In a preferred embodiment, in each recessed surface portion of the first and second barrel cams a, wall of the respective point of the first and second internal cam grooves, which wall separates the respective one of the first and second internal cam groove from the recessed surface sector, is in the helical portion of the respective one of the first and second internal cam grooves arranged such that its outer surface facing the recessed surface sector forms a further helical cam surface arranged such that after a predetermined angle of rotation of the first and second barrel cams, in case of a blocked pushrod, the one of the first and second cam followers that during the rotation of the first and second barrel cams has left its associated one of the first and second internal cam grooves into the recessed surface sector slides onto the further helical cam surface and thereby actively drives the pushrod further to overcome the blockage. In this manner it can be ensured that in case of a blocked pushrod not only the spring mechanism is tensioned to store drive force, but also that eventually an additional active drive force is exerted on the pushrod as an attempt to actively overcome the blockage.
[0020] In this connection it is preferred that the further helical cam surfaces in the recessed surface sectors of the first and second barrel cams are arranged such that the predetermined rotational angle from neutral at which additional drive force for the pushrod is generated by the further helical cam surface is larger than the rotational angle that is required to let the helical portion of the first and second internal cam grooves pass the first and second cam followers, respectively. In this manner it is ensured that the integrated drive force from the one of the first and second barrel cams is completely stored in the compressed spring mechanism before the further helical cam surface starts to actively add further drive force to the pushrod in order to overcome the blockage.
[0021] In a preferred embodiment the width of the closed end sections of the first and second internal cam grooves is enlarged and larger than the width of the first and second cam followers, respectively, thereby establishing a free play for the pushrod relative to the first and second gear engaged positions, respectively.
[0022] In this connection it is further preferred that the axial distance between a circumferentially extending end surface section forming a continuation of the further helical cam surface and the opposing projecting surface in each of the first and second recessed surface sectors is larger than the width of the first and second cam followers, respectively, thereby establishing further free play for the pushrod relative to the first and second gear engaged positions, respectively. This free play of the first and second cam followers in combination with the spring mechanism between the first and second barrel cams provides a detent mechanism for the gear shift actuator in the gear engaged position generating a returning bias force if a external force is displacing the pushrod from the gear engaged position, and provides hard stops for such displacement as will be described in more detail below.
[0023] The invention will be described in the following with reference to a preferred embodiment shown in the drawings, in which:
[0024] Fig. 1 shows a side view of the preferred embodiment of the gear shift actuator according to the present invention;
[0025] Fig. 2 is an enlarged side view of the gear shift actuator in partial cross-section, wherein an outer cylindrical sleeve is shown in cross-section to make the interior visible and also the area on the left hand side of a central spring mechanism shown in cross-section;
[0026] Fig. 3 is a side view corresponding to the side view in Fig. 2 but with the rectangle surrounding the area on the right hand side of the spring mechanism shown in cross-section;
[0027] Fig. 4 is a perspective view of the gear shift actuator with most parts of the cylindrical sleeve removed to show the arrangement of interior components;
[0028] Fig. 5 shows a perspective view of first and second barrel cams in an oppositely oriented, spaced apart and coaxial arrangement as in the interior of the gear shift actuator;
[0029] Fig. 6 shows on the right hand side a perspective view of the first barrel cam and below that a plan view of the first barrel cam, and on the left hand side a plan view of the inner wall of a central opening of the first barrel cam, the inner wall being cut and unrolled so that the vertical axis shows the inner wall from 0° (corresponding to the cutting line) to 360°;
[0030] Fig. 7 shows the unrolled plan view of the inner walls of the first and second barrel cams as they are rotationally aligned with respect to each other;
[0031] Figs. 8 a) - d) show schematic views of a sequence of rotational states of the gear shift actuator when it is driven from neutral to the first gear engaged position without obstruction of the push rod, and Fig. 8 e) shows a cross-sectional view of the gear shift actuator in the neutral position; Fig. 9 is a diagram showing the push rod displacement (arbitrary units) as a function of the rotational angle of the first and second cam barrels during the shift operation of the gear shift actuator illustrated in Fig. 8 a) - d);
[0032] Figs. 10 a) - d) show schematic views of a sequence of rotational states of the gear shift actuator when it is driven from the first gear engaged position back to neutral;
[0033] Figs. 11 a) - d) show schematic views of a sequence of rotational states of the gear shift actuator when it is driven from neutral towards the first gear engaged position in a situation in which the pushrod is temporarily blocked during this driving operation;
[0034] Figs. 12 a) - d) show schematic views of a sequence of rotational states of the gear shift actuator in a situation in which the pushrod is blocked and remains blocked up to predetermined angle of rotation, whereafter the pushrod is actively driven in a stiff actuation mode to overcome the blockage; and
[0035] Fig. 13 is a schematical view of a portion of the gear shift actuator in cross-section together with an enlarged detail in fully engaged first gear position locked by a detent mechanism.
[0036] With reference to Figs. 1 - 3 an overview over the main components of the gear shift actuator and their arrangement will be given. In Fig. 1 a side view of the gear shift actuator is shown which comprises as an outer component a rotary member in form of a cylindrical sleeve 2. The cylindrical sleeve 2 is rotatably mounted by ball bearings 3 allowing the cylindrical sleeve 2 to rotate about a rotational axis coinciding with its central longitudinal axis. The rotational axis of the cylindrical sleeve 2 defines an axial direction. The ball bearings 3 are mounted such that they are unmovable in axial direction with respect to the transmission to be actuated. In this manner the cylindrical sleeve 2 is mounted to be rotatable about its central rotational axis, but is stationary in axial direction.
[0037] The cylindrical sleeve 2 is provided on its outer wall with a gearwheel which surrounds the circumference of the cylindrical sleeve 2 in one of its outer end regions adjacent to the ball bearing 3 supporting this end region. The gearwheel is coupled to the cylindrical sleeve 2 and is engaged by a further gearwheel (not shown) connected to an electric motor (not shown). To operate the gear shift actuator to perform a shift operation the electric motor is turned on, thereby driving the cylindrical sleeve 2 to rotate, wherein the electric motor and the transmission of its rotation to the gearwheel are configured such that the cylindrical sleeve 2 can selectively be rotated in a first sense of rotation and in a second sense of rotation opposite to the first sense.
[0038] In Fig. 2 the gear shift actuator is shown partly in cross-section and partly as a side view. In particular, the outer cylindrical wall of the cylindrical sleeve 2 is shown in cross-section, whereas its gearwheel and the adjacent ball bearing 3 are still shown in a side view. In addition, an area on the left hand side of a central spring mechanism 10 in Fig. 2 is shown in crosssection. Fig. 3 differs from the view of Fig. 2 in that the area shown in cross-section is on the right hand side of the central spring mechanism 10 instead the area on the left hand side.
[0039] In the interior of the cylindrical sleeve 2 first and second barrel cams 20, 40 are disposed. The two barrel cams 20, 40 are cylindrical drums or rollers and are disposed coaxially to each other and with the cylindrical sleeve 2. The two barrel cams 20, 40 are of the same design, but are oppositely oriented such that the inner end portions 38 of the first and second barrel cams 20, 40 are facing each other (see Fig. 5).
[0040] As can be seen in Figs. 2 and 3 the inner wall of the cylindrical sleeve 2 is provided with a splined surface structure, i.e. with splines that extend parallel to the axial direction along the inner wall of the cylindrical sleeve 2.
[0041] The outer walls of the first and second barrel cams 20, 40 are provided with a complementary splined surface structure fitting into the splined surface structure of the inner wall of the cylindrical sleeve 2 such that a splined connection of the first and second barrel cams 20, 40 to the cylindrical sleeve 2 is formed which is torque-proof regarding rotational movements about the rotational axis of the cylindrical sleeve 2, but which allows sliding movements of the first and second barrel cams 20, 40 in axial direction within the cylindrical sleeve 2.
[0042] The first and second barrel cams 20, 40 have throughgoing central openings 21 , 41 (see Fig. 5) through which a pushrod 4 (shown in Figs. 1 - 4) is extending coaxially with the rotary axis of the cylindrical sleeve 2. The pushrod 4 is mounted in linear bearings 5 which allow pushrod 4 to move in axial direction, but prevent rotary movements of the pushrod 4 about the rotary axis of the cylindrical sleeve 2 A circlip or snap ring 9 is in engagement with the cylindrical sleeve 2 close to each of its opposite ends (as can best be seen on one of the ends in Fig. 4), and the two circlips 9 at the opposite ends of the cylindrical sleeve 2 support a first end stop 22 on one end and a second end stop 42 on the opposite end. The first and second end stops 22, 42 have the shape of washers, i.e. discs with central openings through which the pushrod 4 extends. The first and second end stops 22, 42 are coupled to the circlips 9 such that they rotate with the cylindrical sleeve 2.
[0043] Between the oppositely disposed first and second cam barrels 20, 40 in the interior of the cylindrical sleeve 2 a spring mechanism 10 is located which biases the first and second cam barrels 20, 40 apart and against respective end stops 22, 42 which limit axial movement of the first and second barrel cams 20, 40 in axial direction beyond the opposite ends of the cylindrical sleeve 2. Since the first and second end stops 22, 42 are supported via the circlips 9 by the cylindrical sleeve 2, the first and second end stops 22, 42 are likewise stationary in axial direction.
[0044] Fig. 4 shows a perspective view of the interior components of the cylindrical sleeve 2, wherein the cylindrical sleeve 2 itself has been omitted to show the arrangement of the interior components; however, please note that nevertheless the gearwheel surrounding the cylindrical sleeve 2 near one of its ends is also shown in Fig. 4. When in the arrangement of Fig. 4 the gearwheel is driven by an electric motor (not shown) the cylindrical sleeve is rotating with the gearwheel and the first and second barrel cams 20, 40 are rotating with the cylindrical sleeve because of their rotational engagement with the cylindrical sleeve 2; also the second end stop 42 and the circlip 9 supporting it are likewise rotated (in the same manner as a circlip and the first end stop 22 on the opposite end which are not visible in Fig. 4). On the other hand, the pushrod 4 is supported in linear bearings 5 which prevent any rotational movement of the pushrod 4 about the rotary axis of the cylindrical sleeve. The linear bearings 5 are supported to be stationary.
[0045] In the following it will be described how rotational movement of the cylindrical sleeve and the first and second barrel cams 20, 40 which are in rotational engagement with the cylindrical sleeve 2 is transmitted to linear movement of the pushrod 4. In Fig. 5 the first and second barrel cams 20, 40 are shown as they are disposed coaxially and opposite to each other in the interior of the cylindrical sleeve (wherein the spring mechanism 10 between them has been omitted). The first and second barrel cam 20, 40 are oriented with respect to each other such that their inner end portions 38 are facing each other and such that their central, cylindrical openings 21 , 41 are coaxially aligned to allow the pushrod 4 to extend therethrough.
[0046] Now with reference to Figs. 2 and 3 again it is noted that the pushrod 4 is provided with first and second cam followers 6, 8 which are axially spaced apart from each other and circumferentially aligned and fixed to the pushrod 4. The first and second cam followers 6, 8 are threaded bolts which are screwed into bores in the pushrod 4 and which have enlarged head portions to form projecting cam followers 6, 8 projecting from the surface of the pushrod 4. As can be seen in the portions of Figs. 2 and 3 which are shown in cross-section the first and second cam followers 6, 8 are received in internal cam grooves 24, 44 of the first and second cam barrels 20, 40, respectively. As can be seen in the perspective view of the first barrel cam 20 on the right hand side of Fig. 6 the internal cam groove 24 is formed in the inner wall of the central opening 21 and extends along this inner wall in a manner as will be described now with reference to the plan view shown on the left hand side of Fig. 6. For the plan view of the inner wall of the central opening 21 the first barrel cam 20 has been cut in a circumferential position designated as 0 deg (or 360 deg) and then unrolled to extend in a plane from 0° (0 deg) to 360° (360 deg) in vertical direction in the presentation on the left hand side of Fig. 6.
[0047] As can be seen on the left hand side of Fig. 6 the inner wall of the central opening 21 is formed with two main structures which are recessed compared to the remaining inner wall portions (i.e. are extending to a larger radial distance to the rotary axis than the neighboring inner wall portions), namely an internal cam groove 24 and a recessed surface sector 23 extending into the inner wall of the first barrel cam 20. The first internal cam groove 24 of the first barrel cam 20 starts from a starting point 26, which is open to the recessed surface sector 23, and is continued by a circumferentially extending start portion 28. The circumferentially extending start portion 28 is followed by a helical portion 30 which, when it is passing along the first cam follower 6 when the first barrel cam 20 is rotated, drives the first barrel cam 6 and consequently the pushrod 4 in a first axial direction towards the outer end portion 36 of the first barrel cam 20. The helical portion 30 is followed by a circumferentially extending end portion 32 of the first internal cam groove 24 which is ultimately terminated by a closed end cam groove section 34. As can be seen on the left hand side of Fig. 6, this closed cam groove section 34 has a slightly sloped inner wall of the internal cam groove 24 which is inclined towards the inner end portion 38 in an opposite sense compared to the helical portion 30 of the first internal cam groove 24. This slightly oppositely sloping closed end cam groove section 34 provides for a detent effect when the first cam follower 6 is reaching the first gear engaged position at the closed end cam groove section 34 to safely hold the pushrod in the gear engaged position as will be described in more detail below.
[0048] At the starting point 26 the first internal cam groove 24 opens into the recessed surface sector 23 which is sufficiently recessed (i.e. is sufficiently deep) to accommodate the cam follower and therefore allows movement of the first cam follower 6, in particular in axial direction towards the outer end portion 38 of the first barrel cam 20.
[0049] In order to describe how the first internal cam groove 24 and the associated recessed surface sector 23 are oriented circumferentially with respect to the respective second internal cam groove 44 and the associated recessed surface sector 43 of the second barrel cam 40 reference is made to Fig. 7. In this Fig. 7 the inner walls of the first and second barrel cams 20, 40 are again shown in the unrolled plan view as has been described in connection with Fig. 6 for the first barrel cam 20. The second internal cam groove 44 also has a starting point 46, a circumferentially extending start portion 48, followed by a helical portion 50, followed by circumferentially extending end portion 52 and is terminating in closed end cam groove section 54. The first and second internal cam groove 24, 44 are circumferentially aligned to each other in such manner that their circumferentially extending start portions 28, 48 are aligned and sightly overlap in their angular extension about the rotary axis of the first and second barrel cams 20, 40. This arrangement ensures that there is a rotational state of the first and second barrel cams 20, 40 in which the first cam follower 6 is, after entering the first internal cam groove 24 by passing the starting point 26, within the circumferentially extending start portion 28 of the first internal cam groove, while the second cam follower 8 is still in the start portion 48 of the second internal cam groove 44, wherein this state corresponds to the neutral position of the pushrod 4. This arrangement ensures that, when the first and second barrel cams 20, 40 are rotated from the neutral state in a first sense of rotation such that the first internal cam follower 6 is moving further into the circumferentially extending start portion 28 of the first internal cam groove, the second internal cam groove 44 is moved towards and through the starting point 46, thereby leaving the second internal cam groove 44 and entering the recessed surface sector 43 of the second barrel cam 40 before the first cam follower 6 reaches the helical portion 30 of the first internal cam groove 24. In the recessed surface sector 43 of the second barrel cam 40 the second cam follower 8 is free to move in the first axial direction and allows movement of the second cam follower 8 in axial direction within the region between the second cam groove 44 and an inner end portion 38 of the second barrel cam 40 adjacent to the spring mechanism 10. This arrangement of internal cam grooves and recessed surface sectors ensures that, when the helical portion 30 is passing along the first cam follower 6 and moves the cam follower 6, and accordingly also the pushrod 4, in the first axial direction towards the outer end portion 36 of the first barrel cam 20, the second cam follower 8 is free to follow this movement in the recessed surface sector 43 of the second barrel cam 40.
[0050] From the above description it is also clear that, when the first cam follower 6 is at the beginning of the start portion 28 and the second cam follower 8 is at the beginning of the start portion 48 of the second barrel cam 40 (neutral position of the pushrod), and when the first and second barrel cams 20, 40 are rotated in a second sense of rotation opposite to the first sense of rotation, the relative movement of the second cam follower 8 is further into the second internal cam groove 44 and along the helical portion 50, while at that stage the first cam follower 6 has already left the first internal cam groove 24 and entered the recessed surface sector 23 of the first barrel cam such the first cam follower 6 is free to follow the axial movement in the second axial direction which is driven by the helical portion 50 passing along the second cam follower 8 which drives the second cam follower 8, and thus the pushrod 4, in the second axial direction opposite to the first axial direction.
[0051] In the following the operation of the gear shift actuator will be described when the pushrod is to be moved from the position corresponding to neutral to the first gear engaged position, wherein there is no obstruction or blockage of this movement of the pushrod. Figs. 8 a) - d) show schematical views of a sequence of rotational states of the gear shift actuator, wherein the schematical views show rotational states of the first and second barrel cams 20, 40 by using the unrolled plan views of their inner walls when they are rotated with respect to the pushrod 4 with its first and second cam followers 6, 8. For simplicity, the cam followers are shown by circles which are connected by a thick line indication the pushrod 4. Also for simplicity of the drawing reference numerals are included in the view of Fig. 8 a) only, but are omitted for the following movement steps in Figs. 8 b) - d). In the views of Figs. 8 a) - d), also the spring mechanism 10 between the first and second barrel cams 20, 40, and the first and second end stops 22, 42 are shown. It should be noted that Figs. 8 a) - d), as also Figs. 10 -12, show sequences of rotational states of the first and second barrel cams by illustrating the relative movement of the first and second cam followers 6, 8 of the pushrod 4 with respect to internal cam groves and recessed surface sectors of the inner walls of the first and second barrel cams 20, 40; however, it should be kept in mind that the pushrod 4 in fact is stationary with respect to rotational movement, while the first and second barrel cams are rotated which causes the relative rotational movement of the first and second cam followers in the internal cam grooves and the recessed surface sectors of the first and second barrel cams.
[0052] Fig. 8 a) shows the state when the pushrod 4 is in the position corresponding to neutral, and this state is also shown in the cross-sectional view of the gear shift actuator in Fig. 8 e). In the neutral position the first and second cam followers 6, 8 are both in the respective internal cam grooves 24, 44 of the first and second barrel cams, in particular in the circumferentially extending start portions 28, 48. When the first and second barrel cams 20, 40 are now rotated by the cylindrical sleeve to rotate in the first sense of rotation the circumferentially extending start portion 28 of the first internal cam groove 24 is moved along the first cam follower 6 towards the helical portion 30 thereof, whereas this rotation moves the second internal cam groove 44 along the second cam follower 8 such that the latter leaves the second internal cam groove 44 and enters the recessed surface sector 43 of the second barrel cam 40. In this state the second cam follower 8 is free to follow the axial movement of the pushrod 4 which is caused by rotating the helical portion 30 of the first internal cam groove 24 along the first cam follower 6 which causes the first cam follower 6 to move in axial direction closer to the first end stop 22 as shown in the state of Fig. 8 b) in which the first cam follower 6 is approaching the end of the helical portion 30.
[0053] In the further rotational state of Fig. 8 c) the first and second barrel cams 20, 40 have been rotated further such that the first cam follower 6 has reached the circumferentially extending end portion 32 of the first internal cam groove while the second cam follower 8 is still in the recessed surface sector 43 of the second barrel cam 40; in this state the movement of the pushrod 4 in the first axial direction to the first gear engaged position is already completed. Upon further rotation of the first and second barrel cams 20, 40 to the state of Fig. 8 d) the first cam follower 6 reaches the closed end cam groove section 34 and the second cam follower 8 has passed along a projecting surface 59 in the recessed surface sector 43 of the second barrel cam 40, wherein the projecting surface 59 is projecting away from the first barrel cam 20 such that, when the second cam follower 8 slides along the projecting surface 59 the second cam follower 8 pulls on the pushrod 4 to the opposite direction compared to the movement of the pushrod from neutral to the first engaged position to thereby pull the first cam follower 6 further onto the bottom of the sloped closed end cam groove section 34 against the counteracting preloaded spring mechanism 10 to thereby enhance the detent effect in the first gear engaged position. This detent function by the oppositely sloped closed end cam groove section 34 compared to the helical portion 30 holds the pushrod safely in the first gear engaged position even if vibrations or other interferences are acting on the pushrod. This detent function will be described in more detail below with reference to Fig. 13.
[0054] Fig. 9 is a diagram illustrating the movement of the first cam follower (and thus the pushrod) from neutral to the first gear engaged position as a function of the rotational angle for the unobstructed operation of the gear shift actuator as has been described and as is illustrated in Figs. 8 a) - d). After a first short rotational phase with no linear movement of the first cam follower 6 (the first cam follower 6 in this phase is in the circumferentially extending start portion 28 of the first internal cam groove 24) a steep linear rise of the shifted position the first cam follower as a function of the rotational angle follows when the helical portion 30 of the first internal cam groove passes along the first cam follower 6 which movement phase lasts up to a rotational angle of about 155°. In the following phase the circumferentially extending end portion 32 of the first internal cam groove 24 passes along the first cam follower 6 which consequently is not moving anymore until a rotational angle of about 230° is reached, whereafter a slide backward movement of the first cam follower 6 occurs, when the closed end section 34 of the first internal cam groove 24 passes along the first cam follower 6 which has a bottom wall with a slightly opposite slope to the slope of the helical portion 30 of the first internal cam groove 24 to create the above described detent effect when the first gear engaged position of the gear shift actuator has been reached, wherein this detent effect is enhanced by the second cam follower 8 when it is in the last phase of the rotation into the first gear engaged position sliding along the projecting surface 59, thereby pulling the pushrod 4 and the first cam follower 6 slightly backwards into the oppositely slope bottom of the closed end cam groove section 34 to enhance the detent effect, as described above. Please note that in the diagram of Fig. 9 the backward movement between 225° and about 280° due to the detent effect is exaggerated compared to the shift movement distance from neutral to the first gear engaged position.
[0055] With reference to Figs. 10 a) - d) now the disengagement operation from the first gear engaged position to the neutral position will be described. In Fig. 10 a) the pushrod is in the first gear engaged position. To start disengagement the cylindrical sleeve 2 and the first and second barrel cams 20, 40 are rotated in the second sense of rotation opposite to the first sense of rotation. In Fig. 10 b) the first internal cam groove is already rotated such that the first cam follower 6 made a relative movement away from the closed end cam groove section 34 and is approaching the end of the circumferentially extending end portion 32, while the second cam follower 8 is still in the recessed surface sector 43 of the second barrel cam 40. With continuing rotation the helical portion 30 of the first internal cam groove is moving along the first cam
[0056] RECTIFIED SHEET (RULE 91 ) ISA / EP follower 6, as shown in Fig. 10 c), which causes a linear movement of the first cam follower 6 and consequently of the pushrod 4 in the second axial direction which is directed from the first gear engaged position to the neutral position. Eventually, the circumferentially extending start portion 48 of the second internal cam groove reaches the second cam follower 8, while the first cam follower 6, after having passed the helical portion 30 and a large part of the circumferentially extending start portion 28, is close to the starting point 26 of the first internal cam groove. In this state, as it is illustrated in Fig. 10 d) the first and second cam follower 6, 8 are in the entry portions of the first and second internal cam grooves 24, 44 close to the starting point 26, 46, respectively, which corresponds to the neutral position of the pushrod 4.
[0057] In the following an operation scenario of the gear shift actuator is described in which the pushrod experiences a temporary obstruction during the driving phase which is intended to move the pushrod from the neutral to the first gear engaged position, wherein reference is made to Figs. 11 a) - d). In Fig. 11 a) the pushrod 4 is in the neutral position, and the cylindrical sleeve with the engaged first and second barrel cams 20, 40 is about to start rotation in the first sense of rotation. In Fig. 11 b) the first and second barrel cams 20, 40 have already been rotated to an extent such that the major part of the helical portion 30 of the first internal cam groove 24 has already moved along the first cam groove 6. Because the pushrod 4 was blocked in this case the pushrod and consequently also the first cam follower 6 could not be driven for a linear movement in the first direction because of the blockage. Due to the blocked movement of the pushrod 4 and the first cam follower 6 the first barrel cam 20 had to compensate the passage of the helical portion 30 along the first cam follower 6 by a linear movement in the second direction closer to the second barrel cam 40 and away from the associated first end stop 22 which resulted in a compression of the spring mechanism 10 as shown in Fig. 11 b), and resulted in a gap between first barrel cam 20 and the associated end stop 22. In other words the gear shift actuator reacts to the blocked pushrod 4 by, instead of moving the pushrod 4 in the first direction, moving the first barrel cam 20 in the opposite second direction, thereby compressing the spring mechanism 10. In this manner the blocked state of the pushrod 4 causes that the integrated driving force generated by rotation of the helical portion 30 of the first barrel cam 20 with respect to the cam follower 6 is not transmitted into movement of the blocked pushrod 4, but instead in an oppositely directed movement of the first barrel cam 20 which compressed the spring mechanism 10 and thereby stored the integrated drive force.
[0058] In the scenario of Figs. 11 a) - d) it is assumed that the blockage is released by itself shortly after the rotational state of Fig. 11 b). When the blockage is released the compressed spring
[0059] RECTIFIED SHEET (RULE 91 ) ISA / EP mechanism 10 expands again, and thereby urges the first barrel cam 20 to move in the first direction back to abut against the first end stop 22, wherein the expanding spring mechanism after release of the blockage makes up for the originally intended drive in the first axial direction during the blocked phase so that the pushrod 4 is moved to the intended first gear engaged position as shown in Fig. 11 c). After release of the blockage and expansion of the spring mechanism 10 in Fig. 11 c) it follows a final rotation phase until the first cam follower 6 reaches the closed end cam groove section 34, and insofar, regarding the final rotational phase and the detent effect, reference can be made to the description in connection with Fig. 8 d).
[0060] With reference to Figs. 12 a) - d) now an operation scenario of the gear shift actuator will be described in which the blockage of the pushrod is not released by itself. During the initial rotation from Fig. 12 a) to Fig. 12 b) the helical portion 30 of the first internal cam groove 24 already almost completely passed along the first cam follower 6, wherein due to the blocked pushrod 4 no pushrod movement in the first axial direction took place so that the first barrel cam 20 reacted to the drive force created by the helical portion 30 passing along the first cam follower 6 by moving in the opposite second direction, thereby moving away from the associated first end stop 22 and compressing the spring mechanism as shown in Fig. 12 b). But unlike the situation in Fig. 11 c) the blockage is not released so that the first and second barrel cams 20, 40 rotate further, wherein in Fig. 12 c) the first cam follower 6 is already in the circumferentially extending end portion 32, but the pushrod 4 is still blocked. In this situation the second cam follower 8 gets effective in the following manner. In the recessed surface sector 43 of the second barrel cam 40 a wall of the second cam groove 44, which is the wall separating the second cam groove 44 from the recessed surface sector 43, is in the helical portion 50 of the second cam groove 44 arranged such that its outer surface facing the recessed surface sector 43 forms a further helical cam surface 60 such that after a predetermined angle of rotation which has been reached in Fig. 12 c), the second cam follower 8 slides onto the further helical cam surface 60. Upon further rotation of the second barrel cam 40 the further helical cam surface 60 actively drives the second cam follower 8 and thus the pushrod 4 with additional force in the first direction, which force adds to the force of the compressed spring mechanism 10 in the first direction, in an attempt to actively overcome the blockage. In the scenario illustrated in Figs. 12 a) - d) it is assumed that due to this further push on the second cam follower 8 by the helical cam surface 60 providing additional drive force to the pushrod 4, the blockage is overcome, whereafter the spring mechanism 10 expands to bring the first barrel cam 20 in first axial direction back into abutment against the first end stop 22, whereafter rotation continues for a last rotation phase until the first and second cam follower 6, 8 have reached their stable end position (first gear engaged) as shown in Fig. 12 d). This final phase of the rotation including the detent effect corresponds to the situation described with reference to Fig. 8 d).
[0061] As can be seen in Fig. 7 and Fig. 12 a) the further helical cam surface 60 is continued by a circumferentially extending surface end section 62. The second cam follower 8 reaches the gap between the circumferentially extending surface end section 62 and the opposing projecting surface 59 when the gear shift actuator reaches the first gear engaged position.
[0062] In Fig. 13 a schematic view of the gear shift actuator is shown, again in the cut and unrolled plan view of the first and second barrel cams, with the pushrod in the first gear engaged position, the first cam follower 6 being in the closed end section 34 of the first internal cam groove, and the second cam follower 8 being located in the gap between the projecting surface 59 of the second barrel cam 40 and the circumferentially extending surface end section 62 which is forming a continuation of the further helical cam surface 60 in the recessed surface sector 43 of the second barrel cam. Above the first and second barrel cams 20, 40 an enlarged detail is shown in a rather schematic manner, namely the closed end section 34 of the first barrel cam 20 on the left hand side and on the right hand side the space formed in the gap between the projecting surface 59 formed in the recessed surface sector 43 and the opposite circumferential surface section 62 forming a continuation of the further helical cam surface 60 in the recessed surface sector 43 of the second barrel cam 40. With reference in particular to this schematic detail in Fig. 13 the detent mechanism which keeps the gear shift actuator in the currently engaged gear position will now be described.
[0063] Under normal conditions, when the gear shift actuator is in the first gear engaged position as shown in in Fig. 13, the preload of the spring mechanism 10 urges the first barrel cam 20 and the second barrel cam 40 apart so that the first cam follower 6 and the second cam follower 8 are in the positions indicated by the full circles in the detail in the middle of Fig. 13. As shown, the first cam follower 6 and the second cam follower 8 have some free play in axial direction in their respective positions between the opposing surfaces in the first barrel cam 20 and the second barrel cam 40. If some external force is acting on the pushrod 4 trying to pull the pushrod out of the first gear engaged position towards neutral, this force has to overcome the preload of the spring mechanism 10, thereby pulling the first barrel cam 20 closer to the second barrel cam 40. If such force is acting on the pushrod 4 and pulls the first barrel cam 20 closer to the second barrel cam 40 the second cam follower 8 will be displaced by the same distance in its gap of the second barrel cam 40. Eventually the second cam follower 8 will contact the circumferential surface end section 62 which forms a hard stop (which is supported by end stop 42) so that the pushrod 4 cannot be pulled any further away from the first gear engaged position towards neutral. This position of the second cam follower 8 is schematically indicated by the dashed line circle in the gap between the surfaces 59 and 62. Any further displacement of the pushrod 4 from the close neighborhood of the first gear engaged position is thus in any case prevented (wherein the extent of this neighborhood is determined by the degree of free play of the cam follower 8 in axial direction in the described position).
[0064] As soon as the interfering force on the pushrod stops to act on the pushrod the additional compression of the spring mechanism 10 will be released by expansion of the spring mechanism 10 so that the pushrod 4 with its first and second cam followers 6, 8 again reaches the position as indicated by the cam followers 6, 8 in full circles, which corresponds to the first gear engaged position of the pushrod.
[0065] The same operation principle applies when the gear shift actuator is in the second gear engaged position and an interfering force is trying to pull the push rod out of the second gear engaged position towards neutral. Then the second barrel cam 40 will be pulled closer to the first barrel cam 20 to follow the movement of the push rod away from the second gear engaged position. Such movement of the push rod pulling the second barrel cam 40 closer to the first barrel cam 20 then reaches a hard end stop when the first cam follower 6, due to the displacement of the push rod, reaches the opposite wall of the closed end section 34 of the first cam groove, as indicated by the dashed line circle.
[0066] From the description of the design and the operation of the detent mechanism as described above for an interfering force directed such that it attempts to pull the pushrod out of the gear engaged position towards neutral, it is clear that the same functionality is achieved for an interfering force oppositely directed such that it attempts to push the pushrod further into and beyond the respective gear engaged position, which will also result in reaching a hard stop when the free play of the cam follower 6 has been used up, which prevents further compression of the spring mechanism 10 and thereby prevents any further movement of the pushrod away from the gear engaged position; when the interfering force ceases to act on the pushrod the expanding spring mechanism 10 moves the pushrod back to the gear engaged position.
[0067] The diagram including springs and lines in the upper part of Fig. 13 illustrates the described detent function with the hard end stops as described, wherein the hard stops are indicated by a left vertical full line and a right vertical full line, wherein in-between there is a spring-loaded zone which allow movement of the push rod out of the first gear engaged position (central full line) to a certain extent towards neutral or in the opposite direction, but in any case limited by one of the two hard stops indicated by the left and right full lines. The horizontal axis in this diagram represents the displacement of the pushrod from the first gear engaged position (indicated by the central line), wherein the right full line indicates the hard stop when the force is trying to pull the pushrod out of the first gear engaged position, the left full line indicates the hard stop when the force is trying to push the pushrod further into and beyond the first gear engaged position, and the central full line represents the rest state of the pushrod (with no interfering force acting on it) in the first gear engaged position. This spring biased detent mechanism ensures that the pushrod is retained in the region between the two hard stops indicated by the leftmost and rightmost vertical line, and is always returned to the original engaged gear position (indicated by the central vertical line) as soon as the interfering force on the pushrod has ceased.
[0068] It is noted here that in some of the Figures, namely Figs. 8 and 10-12, the space between the circumferential surface end section 62 and the projecting surface 59 is shown in such a manner as if there is no or little free play for the second cam follower in axial direction, but this is only for simplifying the illustrations. In principle, the free play as explained here in connection with Fig. 13 can also be realized in the embodiment shown in the remaining Figures such as Figs. 8, and 10-12.
[0069] As a general comment it is noted that in the present description the main focus was on describing the operation of the gear shift actuator for shifting from neutral to first gear engaged position and back to neutral. The opposite shift operation from neutral to second gear engaged position is not described in detail here, but it should be apparent that this operation works in the same manner as described herein in the opposite direction with the roles of the first and second barrel cams 20, 40 interchanged when the gear shift actuator is shifting from neutral to second gear engaged position and back to neutral.
Claims
Claims1 . Gear shift actuator for actuating a shift fork comprising: a rotary member which is supported to be rotatable, but unmovable in an axial direction defined by its rotary axis, an electric motor for rotating the rotary member, and a driven component driven by rotary movement of the rotary member for linear movement in axial direction in a first direction from a neutral position to a first gear engaged position and back to neutral, when the rotary member is driven to rotate first in a first sense of rotation and then in a second sense of rotation opposite to the first sense of rotation, and in a second direction opposite to the first direction from the neutral position to a second gear engaged position and back to neutral, when the rotary member is first driven to rotate in the second sense of rotation and then in the first sense of rotation, characterized in that the rotary member is a hollow cylindrical sleeve (2) having an inner wall, first and second barrel cams (20, 40) are coaxially disposed inside the cylindrical sleeve (2) opposite to each other in axial direction, wherein outer walls of the first and second barrel cams (20, 40) and the inner wall of the cylindrical sleeve (2) are configured to provide engagement of the first and second barrel cams (20, 40) with the cylindrical sleeve (2) which is torque-proof with respect to rotational movements about the rotary axis, but allows sliding relative movement in axial direction, and first and second end stops (22, 42) are mounted spaced apart and stationary in axial direction to limit axial movement of the first and second barrel cams (20, 40), respectively, wherein a spring mechanism (10) is disposed between the first and second barrel cams (20, 40) to bias them apart and towards the first and second end stops (22, 42), respectively, the driven component is a pushrod (4) which is supported in bearings for linear movement in axial direction and for extending coaxially on the rotary axis through central openings in the first and second barrel cams (20, 40) comprising first and second internal cam grooves (24, 44) on inner surfaces of the central openings, respectively, and the pushrod (4) carries first and second cam followers (6, 8) spaced apart and aligned in axial direction and arranged to be received in the first and second internal cam grooves (24, 44), respectively, wherein the pushrod (4) and its bearings provide a torque-proof engagement against rotational movements of the pushrod about the rotary axis, each of the first and second internal cam grooves (24, 44) extends from a starting point (26, 46) along a circumferential start portion (28, 48), followed by a helicalportion (30, 50) extending axially further towards an outer end portion (36, 56) of the respective one of the first and second barrel cams (20, 40), which is followed by a circumferentially extending end portion (32, 52), wherein the starting points (26, 46) of the first and second internal cam grooves (24, 44) are open to recessed surface sectors (23, 43) of the inner surfaces of the central openings of the first and second barrel cams (20, 40), respectively, which recessed surface sectors (23, 43) allow movement of the first and second cam followers (6, 8), respectively, in a direction parallel to the axial direction in a region between the first and second internal cam grooves (24, 44), respectively, and an inner end portion (38) adjacent to the spring mechanism (10), wherein the first and second barrel cams (20, 40) are rotationally oriented with respect to each other such that the start portions (28, 48) of the first and second internal cam grooves (24, 44) are aligned so that, when the first cam follower (6) is in the start portion (28) of the first cam groove (24) the second cam follower (8) is in the start portion (48) of the second cam groove (44), so that when the cylindrical sleeve (2) in this state is rotated in the first sense of rotation the first internal cam groove (24) is moved along the first cam follower (6) which thereby is driven by the helical portion (30) to move the pushrod (4) in the first direction, while the second cam follower (8) is free to follow this movement in the recessed surface sector (43) of the second barrel cam (40), is rotated in the second sense of rotation the second internal cam groove (44) is moved along the second cam follower (8) which thereby is driven by the helical portion to move the pushrod (4) in the second direction, while the first cam follower (6) is free to follow this movement in the recessed surface sector (23) of the first barrel cam (20).
2. Gear shift actuator according to claim 1 , characterized in that the outer wall of each of the first and second barrel cams (20, 40) has in cross-section a non-circular surface structure which is received in a complementary non-circular surface structure of the inner wall of the cylindrical sleeve (2) to provide torque-proof engagement of the first and second barrel cams (20, 40) with the cylindrical sleeve (2) while allowing movement of the first and second barrel cams (20, 40) in axial direction within the cylindrical sleeve3. Gear shift actuator according to claim 2, characterized in that the non-circular cross- sectional surface structure of the outer wall of each of the first and second barrel cams (20) is formed by a splined outer wall and that the non-circular cross-sectional surface structure of the inner wall of the cylindrical sleeve is formed by complementary splined inner wall of the cylindrical sleeve (2) to provide a spline connection between the first and second barrel cams (20, 40) and the cylindrical sleeve (2) which allows relative axial movement of the first and second barrel cams (20, 40) within the cylindrical sleeve (2), but is torque-proof with respect to relative rotational movements about the rotational axis.
4. Gear shift actuator according to any of the preceding claims, characterized in that the distance between the first and second end stops (22, 42) and the first and second barrel cams (20, 40) and the spring mechanism (10) in between are arranged such that the spring mechanism (10) is under a predetermined preload and exerts oppositely directed forces on the first and second barrel cams (20, 40) to bias them against the first and second end stops (22, 42), respectively.
5. Gear shift actuator according to any of the preceding claims, characterized in that the circumferentially extending end portion (32, 52) of each of the first and second internal cam grooves (24, 44) is continued by a closed end cam groove section (34, 54) which has a slope opposite to the slope of the helical cam groove portion (30, 50) to form a detent end section to enable the respective one of the first and second cam followers (6, 8) to reach a stable end position in the respective closed end cam groove section (34, 54).
6. Gear shift actuator according to claim 5, characterized in that, in the circumferential region of the closed end cam groove section (34, 54) of the first and second internal cam grooves (24, 44), in the recessed surface sectors (23, 43) of each of the first and second barrel cams (20, 40), a projecting surface (59) is formed projecting away from the opposite one of the first and second barrel cams (20, 40) so that, when one of the first and second cam followers (6, 8) is reaching the closed end cam groove section (34, 54) of the respective one of the first and second internal cam grooves (24, 44), the other one of the first and second cam followers (6, 8) is reaching and sliding along the projecting surface (59) so that the other one of the first and second cam followers (6, 8) is pulling the one of the first and second cam followers (6, 8) in axial direction intothe closed end cam groove section (34, 54) to enhance the detent effect of the first and second cam followers (6, 8) in the first and second gear engaged end positions.
7. Gear shift actuator according to any of the preceding claims, characterized in that in each recessed surface sector (23, 43) of the first and second barrel cams (20, 40) a wall of the respective one of the first and second internal cam grooves (24, 44), which wall separates the respective one of the first and second internal cam grooves (24, 44) from the recessed surface sector (23, 43), is in the helical portion (30, 50) of the respective one of the first and second internal cam grooves (24, 44) arranged such that its outer surface facing the recessed surface sector (23, 43) forms a further helical cam surface (60) such that after a predetermined angle of rotation of the first and second barrel cams, in case of a blocked pushrod (4), the one of the first and second cam followers (6, 8) that during the rotation of first and second barrel cams has left its associated one of the first and second internal cam grooves (24, 44) into the recessed surface sector (23, 43) slides onto the further helical cam surface (60) and thereby drives the pushrod (4) to overcome the blockage.
8. Gear shift actuator according to claim 7, characterized in that the further helical cam surfaces (60) in the recessed surface sectors (23, 43) of the first and second barrel cams (20, 40) are arranged such that the predetermined rotational angle from neutral at which additional drive force for the pushrod (4) is generated by the further helical cam surface (60) is larger than the rotational angle that is required to let the helical portion (30, 50) of the first and second internal cam grooves (24, 44) pass the first and second cam followers (6, 8), respectively.
9. Gear shift actuator according to any of the preceding claims, characterized in that the width of the closed end sections (34, 54) of the first and second internal cam grooves (24, 44) is enlarged and larger than the width of the first and second cam followers (6, 8), respectively, thereby establishing a free play for the pushrod (4) relative to the first and second gear engaged positions, respectively.
10. Gear shift actuator according to claim 9, characterized in that the axial distance between a circumferentially extending end surface section (62) forming a continuation of the further helical cam surface (60) and the opposing projecting surface (59) in each of the first and second recessed surface sectors (23, 43) is larger than the width of thefirst and second cam followers (6, 8), respectively, thereby establishing further free play for the pushrod (4) relative to the first and second gear engaged positions, respectively.
Citation Information
Patent Citations
manual transmission
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Actuator with face dog clutch
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