Gear shift actuator

Abstract

The invention is directed to a gear shift actuator for driving a linear rod (30) comprising: a rotary member which is rotatable, but unmovable in an axial direction defined by its rotary axis, a motor (8) for rotating the rotary member, the linear rod (30) is driven by rotary movement of the rotary member driven by two barrel cams (1, 2) which are of the same design and which are supported to be movable in axial direction, and which are disposed oppositely oriented and rotationally aligned with respect to each other and coaxially with the rotary axis between two opposite end stops (5, 6), a spring mechanism (7) disposed between the two barrel cams (1, 2) to bias them aper, each of the two barrel cams (1, 2) being provided with an outer cam surface configuration configured to cooperate with one of two cam followers so that the two barrel cams (1, 2) and the spring mechanism (7) in between cooperate with the linear rod (30) - such that the linear rod (30) is driven in a first direction from a neutral position to an engaged position and back to neutral, when the rotary member is rotated first in a first sense of rotation and then in a second sense opposite to the first sense, and is moved in a second direction opposite to the first direction from the neutral position to another engaged position and back to neutral, when the rotary member is first driven to rotate in the second sense and then in the first sense of rotation, and - such that, when the linear rod (30) is driven from an engaged position to neutral it is driven in a stiff mode in which barrel cam and linear rod movement is coupled, and when the linear rod (30) is driven from neutral to an engaged position it is driven in a sprung mode in which barrel cam and linear rod movement is decoupled so that, in case of a blockage of the linear rod, a driving one of the two barrel cams (1, 2) is displaced in axial direction away from its end stop (5, 6) thereby compressing the spring mechanism (7) to store the drive force as long as the linear rod (30) is blocked, characterized in that the rotary member is a shaft (4) coupled to the two barrel cams in torque-proof engage- ment, but allowing them to axially move along the shaft (4); the linear rod (30) is supported radially outwardly with respect to the two barrel cams (1, 2) and is provided with the two cam followers (31, 32) projecting inwardly; the gear shift actuator is adapted to shift the linear rod (30) within a sequence of shift states in which the states first gear engaged, first neutral, second gear engaged, second neu- tral, and third gear engaged follow each other, wherein shifting in this sequence is accom- plished by the cam surface configuration of the two barrel cams (1, 2).

Description

[0001] Gear Shift Actuator

[0002] The present invention is directed to a gear shift actuator for driving a linear rod 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, wherein the linear rod is driven by rotary movement of the rotary member for linear movement parallel to the axial direction driven by two barrel cams which are of the same design and which are supported to be movable in axial direction, and which are disposed oppositely oriented to each other and rotationally aligned with respect to each other and coaxially with the rotary axis between two opposite end stops which are located at a fixed axial distance to each other, a spring mechanism disposed between the two barrel cams to bias them apart, each towards a respective one of the two end stops, wherein each of the two barrel cams is provided with an outer cam surface configuration configured to cooperate with one of two cam followers so that the two barrel cams and the spring mechanism in between cooperate such that the linear rod is driven along the axial direction in a first direction from a neutral position to an 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 is moved in a second direction opposite to the first direction from the neutral position to another 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, and such that, when the linear rod is driven from an engaged position to neutral it is driven in a stiff mode in which barrel cam and linear rod movement is coupled, and when the linear rod is driven from neutral to an engaged position it is driven in a sprung mode in which barrel cam and linear rod movement is decoupled so that, in case of a blockage of the linear rod, a driving one of the two barrel cams is displaced in axial direction away from its end stop thereby compressing the spring mechanism to store the drive force as long as the linear rod is blocked and to drive the linear rod to the engaged position by the expanding spring mechanism as soon as the blockage has sufficiently diminished.

[0003] Gear shift actuators are utilized in motor vehicles to shift transmission between two coaxially disposed, rotary shafts between an 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 make a set of regularly spaced teeth or protrusions on one wheel connected to one of the shafts to a set of complementary recesses between teeth on another wheel connected to 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. A dog clutch with a dog clutch actuator is for example described in US 2015 / 0107955 A1. A driven component in form of the nut is connected to a shift fork for driving it from neutral 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 rotary engagement between the two wheels is ceased. By moving the shift fork using gear shift to the gear engaged position the two teeth or dog wheels are moved into rotary inter engagement with the teeth of one wheel being received in the recesses between the teeth of the other wheel.

[0004] For such gear shift actuators the situation may arise that the two 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.

[0005] WO 2023 / 165705 A1 discloses a gear shift actuator which is designed to deal with a temporary blockage of a linear rod for actuating a shift fork and which forms the basis of the preamble of claim 1. This known gear shift actuator can shift the linear rod from a central neutral position in a first direction to a first gear engaged position, and from neutral in an opposite direction to a second gear engaged position. The gear shift actuator comprises a rotary member in the form of a hollow cylindrical sleeve which is supported to be rotatable, but unmovable in an axial direction defined by its rotary axis, and an electric motor for rotating the hollow sleeve. The hollow sleeve is provided with two inwardly projecting cam followers aligned and spaced apart in the axial direction. Within the hollow sleeve two barrel cams are supported to be moveable in axial direction, but not rotatable about the rotary axis. Two opposite end stops are fixed at a predetermined axial distant on the linear rod, and the two barrel cams are disposed oppositely oriented and coaxially with the rotary axis between the two opposite end stops, wherein a spring mechanism is disposed between the two barrel cams to bias them apart, each towards a respective one of the two end stops. The two barrel cams are coupled to the linear rod which is extending coaxially with the rotary axis. Each of the two barrel cams is provided with an outer cam surface configuration configured to cooperate with one of the two cam followers of the hollow sleeve so that rotation of the hollow sleeve, and thus rotational movement of the two cam followers leads to movement of the cam followers along the cam surface configurations of the two barrel cams which drives the barrel cams to move in axial direction, thereby moving the linear rod. The cam surface configuration of each of the two barrel cams comprises a helical cam groove in an outer end portion of each barrel cam facing away from the other barrel cam and climbing towards the outer end of the respective barrel cam. Towards the inner end portion the helical cam groove merges into a recessed surface sector of the respective barrel cam which leaves sufficient space such that the cam follower entering the recessed surface sector is free to axially move with respect to the respective barrel cam. The two oppositely oriented barrel cams are in angular alignment to each other such that the helical cam groove portion of one of the two barrel cams is aligned with the recessed surface sector of the other barrel cam such that when one of the cam followers is entering the helical cam groove portion of one of the barrel cams and moving along it, the other cam follower is entering the recessed surface sector of the other of the two barrel cams and moving within it. In this manner the other cam follower is, within the recessed surface sector, free to follow an axial movement of the linear rod driven by the one cam follower engaged by driven by the helical cam groove of the driving one of the barrel cams. In this way axial movement of the linear rod is decoupled from the rotational movement of the barrel cams in the sense that the linear rod does perform the axial movement driven by the rotation of the barrel cams as long as the linear rod does not experience a resistance high enough to compress the spring mechanism. On the other hand, if the linear rod is blocked by high resistance a driving one of the two cam followers which is driven by rotating the helical cam groove of the driving barrel cam along the associated cam follower, cannot be moved in axial direction because the linear rod coupled to it is blocked; in this situation the movement of the driving cam follower along the helical cam groove portion of the first barrel cam causes, because of the blocked linear rod, a movement of the driving barrel cam in axial direction away from its end stop, thereby compressing the spring mechanism between the two barrel cams, whereas the second cam follower in the recessed surface sector of the second barrel cam is free to follow this movement of the first.

[0006] In the arrangement of the gear shift actuator of WO 2023 / 165705 A1 the spring mechanism between the two barrel cams is within the force transmission path when the linear rod is driven from neutral to gear engaged, but it is not in the force transmission path when the linear rod is moved from gear engaged to neutral. In this manner this gear shift actuator is configured such that, when the linear rod is driven from an engaged position to neutral it is driven in a stiff mode in which movement of a barrel cam and the linear rod is positively coupled, and when the linear rod is driven from neutral to an engaged position it is driven in a sprung mode (i.e. spring mechanism is in the force transmission path), in which sprung mode barrel cam and linear rod movement is decoupled so that, in case of a blockage of the linear rod, a driving one of two barrel cams is displaced in axial direction away from its end stop thereby compressing the spring mechanism to store the drive force as long as the linear rod is blocked, and to drive the linear rod to the engaged position by the expanding spring mechanism as soon as the blockage has sufficiently diminished.

[0007] It is an object of the present invention is to provide a gear shift actuator which does not use a hollow sleeve as an outer rotary member and can therefore be of more compact design. In addition, it is an object of the invention to allow shifting between more than three shift states (first gear engaged, neutral, secondly engaged), namely between five shift positions (first gear engaged, first neutral, second gear engaged, second neutral, third gear engaged) or more in a sequential manner.

[0008] According to the present invention the rotary member is a shaft with non-circular cross-section (e.g. a splined shaft having longitudinal grooves along its length), wherein the shaft is extending coaxially with the rotary axis through central openings of complementary non-circular cross-section in the two barrel cams to provide torque-proof engagement of the two barrel cams with a shaft and to allow the two barrel cams to move axially along the shaft limited by the two end stops which are stationary in axial direction with respect to the shaft. To arrange the rotary member as a central shaft radially within the two barrel cams allows a more compact design compared to an outer sleeve as rotary member which was used in the above-mentioned prior art design.

[0009] The linear rod is supported radially outwardly with respect to the two barrel cams. The linear rod is provided with two inwardly directed cam followers which are to it at axially spaced locations, wherein one of the two cam followers is received in the cam surface configuration of one of the two barrel cams, whereas the other is received in the cam surface configuration of the other one of the two barrel cams.

[0010] The gear shift actuator is adapted to shift the linear rod within a sequence of shift states in which the states first gear engaged, first neutral, second gear engaged, second neutral, and third gear engaged follow each other in the linear sequence. Shifting in this sequence is accomplished by the cam surface configuration of the two barrel cams cooperating with the two cam followers of the linear rod, wherein the cam surface configuration of each of the two barrel cams includes in circumferential sequence and extending from an outer end of the respect of one of the barrel cams to an inner end adjacent the spring mechanism the following cam surface features: a first cam groove starting at the outer end with a circumferentially extending cam groove end portion, followed by a helical drive cam portion climbing away from the outer end of the respective one of the two barrel cams, followed by a circumferentially extending cam groove end portion which terminates the first cam groove by transitioning into a first recessed surface sector of increased width in axial direction in which a respective one of the two cam followers is free to move in axial direction, which first recessed surface sector transitions into a second cam groove extending from the first recessed surface sector (18) with a circumferentially extending cam groove end portion, followed by a helical drive cam portion climbing further away from the outer end of the respective one of the two barrel cams, followed by a circumferentially extending cam groove end portion which terminates the second cam groove by transitioning into a second recessed surface sector of increased width in axial direction in which the respective one of the two cam followers is free to move in axial direction, which second recessed surface sector transitions into a circumferentially extending closed end cam groove portion having a closed end.

[0011] The sequence in the cam surface configuration of each of the two barrel cams is formed, starting at the outer end of the barrel cam remote from the spring mechanism and the other barrel cam, by a first cam groove, a first recessed surface sector, continued by a second cam groove, followed by a second recessed surface sector, and continued the circumferentially extending closed end cam groove portion which terminates the sequence. The opposite orientation and the rotational alignment of the two barrel implies that when one of the cam followers is within a helical drive cam portion, and thus is driven in axial direction, the other cam follower is in one of the recessed surface sectors such that the other cam follower is decoupled from its barrel cam and is free to follow the axial movement dictated by the one cam follower.

[0012] The two cam followers of the linear rod are in the following referred to as first and second cam followers, and the two barrel cams are referred to as first and second barrel cams, wherein the first cam follower is received in the cam surface configuration of the first barrel cam and the second cam follower is received in the cam surface configuration of the second barrel cam so that when reference is made to the first (second) cam follower in respect to cam surface configuration features it is implied that this is referring to the first (second) barrel cam. Furthermore, when in the following the movement of the first and second cam followers relative to the cam surface configuration of the first (second) barrel cam is often described as a movement of the first (second) cam follower within and along the cam surface configuration this is a description of the relative movement of the first and second cam followers and it should be clear that in the rest frame of the gear shift actuator the first and second cam followers are rotationally at rest whereas the first and second barrels cams are rotating with their cam surface configurations, and the first and second cam followers are driven for axial movement only.

[0013] In more detail the cam surface configuration of the two barrel cams and their rotational alignment with respect to the each other results in the following technical functionality. When the linear rod is with its first cam follower at the closed end of the circumferentially extending cam groove end portion of the first cam groove of the first barrel cam, the second cam follower is at the closed end of the circumferentially extending closed end cam groove portion of the second barrel cam (first gear engaged). When the shaft now is rotated with the first and second barrel cams in a first sense of rotation the first cam groove of the first barrel cam rotates along the first cam follower so that the first cam follower enters the helical drive cam portion of the first cam groove driving the linear rod in first axial direction in the direction of the second barrel cam, whereas the second barrel cam is rotated such that the second cam follower is already within the second recessed surface sector which allows axial movement of the second cam follower within the second recessed surface sector while the first cam follower is further driven by the rotating helical drive cam portion which eventually leads the first cam follower to the circumferentially extending cam groove end portion of the first cam groove which terminates the axial movement of the linear rod, while the second cam follower has passed the second recessed surface sector and reached the entry of the circumferentially extending cam groove end portion of the second cam groove (corresponding to the first neutral position).

[0014] When rotation of the first and second barrel cams is continued in the first sense of rotation the first cam follower is moved into the first recessed surface sector of the first barrel cam, while the second cam follower at the same time is moving along the helical drive cam portion of the second cam groove which drives the second cam follower and the linear rod further in the first axial direction, whereas the first cam follower is in the first recessed surface sector; in this phase the linear rod is driven from first neutral to second gear engaged position, while the first cam follower is in the first recessed surface sector; this would, in case of blockage of the linear rod, allow the first cam follower to be displaced in the first recessed surface sector of the first barrel cam, while the rotation of the second barrel cam with the helical drive cam portion passing along the second cam follower would cause the second barrel cam to be displaced away from its end stop, thereby compressing the spring mechanism and storing the drive force until the blockage has sufficiently diminished. With continuing rotation of the shaft the first cam follower gets from the first recessed surface sector into the entry to the second cam groove which starts with the circumferentially extending cam groove end portion, whereas the second cam follower at this stage is close to the end of the second cam groove in the circumferentially extending cam groove end portion of the second cam groove. In this position the linear rod is in the second gear engaged position.

[0015] Upon further rotation of the first and second barrel cams in the first sense of rotation from the second gear engaged position the second cam groove is rotated along the first cam follower which is thereby driven by the helical drive cam portion of the second cam in the first axial direction, while the second cam follower in this way entered the first recessed surface sector of the second barrel cam. In this stage the linear rod is driven towards the second neutral position, wherein the first barrel cam with the first cam follower in the helical drive cam portion drives the linear rod in a stiff manner towards the second neutral position. Eventually the first cam follower reaches the circumferentially extending cam groove end portion of the second cam groove while the first cam follower reaches the circumferentially extending end portion of the first cam groove (this position corresponds to the second neutral position of the linear rod).

[0016] When at this point rotation of the first and second barrel cams in the first sense of rotation is continued the first cam follower enters the second recessed surface sector, while the second cam follower is moved along the helical drive cam portion of the first cam groove, wherein this is a driving phase driving the linear rod to the third gear engaged position. In this drive phase driving the linear rod into a gear engaged position a sprung driving mode is performed (which means that in a case of a blockage of the linear rod the first barrel cam which is driving the first cam follower would be blocked by the blocked linear rod which would cause the first barrel cam to be displaced away from its end stop, whereby the spring mechanism is compressed to store the drive force of the first barrel cam on the first cam follower in the compressed state of the spring mechanism until the blockage has sufficiently diminished to allow the expanding spring mechanism to move the linear rod into the third gear engaged position. In any case rotation of the first and second barrel cams in the first sense of rotation is terminated once the first cam follower has reached the closed end of the circumferentially extending closed end cam groove portion of the first barrel cam, and the second cam follower has reached the closed end of the first cam groove, which corresponds to the third gear engaged position of the linear rod.

[0017] Due to the identical design of the first and second barrel cams, their opposite orientation and rotational alignment it is clear that, when the linear rod has been moved by rotating the barrel cams in a first sense of rotation to eventually reach the third gear engaged position as just described, rotation of the two barrel cams in a second sense of rotation opposite to the first sense of rotation will move the linear rod in a second axial direction opposite to the first axial direction from the third gear engaged position in reversed sequence through the above described intermediate positions and eventually back to the first gear engaged position.

[0018] In a preferred embodiment the shaft is a splined shaft in the form of a cylindrical shaft comprising a plurality of parallel grooves extending parallel to the axial direction on its outer surface; the complementary shaped central openings of the two barrel cams are cylindrical openings with a plurality of elongated protrusions which are arranged to be received in the plurality of grooves of the splined shaft, whereby a torque-proof engagement of the splined shaft with the two barrel cams is achieved on the one hand, while on the other hand axial movement of the barrel cams with respect to the splined shaft is permitted.

[0019] In a preferred embodiment the two end stops are fixed to the shaft. In this manner the two end stops are rotating with the shaft, as do the two barrel cams so that there is no relative rotational movement between the end stops and the two barrel cams which are biased by the spring mechanism against the two end stops.

[0020] In a preferred embodiment the distance between the two end stops, the dimensions of the two barrel cams and of the spring mechanism are arranged such that the spring mechanism is under a predetermined preload and exerts oppositely directed forces on the two barrel cams to bias them against the two end stops. By establishing a predetermined preload of the spring mechanism at which a resistance force level experienced by the linear rod, when being moved towards a gear engaged position, the driving forced generated by the gear shift actuator is, without moving the linear rod in axial direction, converted to axial movement of one of the barrel cams and thereby into an increasing spring compression to store the drive force. In other words, the resistance force experienced by the linear rod has to exceed a threshold determined by the preload for causing the axial shift movement of the linear rod which compresses the spring mechanism. As soon as the resistance force experienced by the linear rod dropped below the threshold the spring mechanism starts to expand thereby driving the linear rod to the gear engaged position.

[0021] In a preferred embodiment a detent mechanism is realized which counteracts any interfering forces on the linear rod which attempt to pull the linear rod out of one of the engaged positions. For this purpose each of the two barrel cams has an enlarged cam groove width in axial direction in the first, second, and third gear engaged positions of the linear rod, namely the circumferentially extending cam groove end portion of the first cam groove extending from the closed end, and the circumferentially extending closed end cam groove portion extending from the second recessed surface sector at the inner end of the barrel cam have a width in axial direction that is enlarged and larger than the width of the first and second cam followers; furthermore, the two circumferentially extending cam groove end portions of the second cam groove, which circumferentially extending cam groove end portions merge into the first and second recessed surface sector, respectively, have a width in axial direction that is enlarged and larger than the width of the two cam followers, which enlarged widths are configured to establish a free play for the linear rod in axial direction in the first gear, second gear and third gear engaged positions. By this arrangement a detent mechanism is realized which counteracts any interfering forces on the linear rod which attempt to pull the linear rod out of one of the engaged positions mentioned. When the linear rod is in one of the gear engaged positions mentioned a first cam follower of the linear rod is within the cam surface configuration of the first barrel cam, while the second cam follower of the linear rod is in the cam surface configuration of the second barrel cam. If the linear rod is in one of the gear engaged positions mentioned the free play of the cam followers in the defined regions with enlarged axial width as the following effect. Due to the spring mechanism acting between the first and second barrel cams, the first and second barrel cams are urged away from each other such that the first and second cam followers are pressed against inner walls in the respective cam groove areas, i.e. to the wall which is closer to the spring mechanism. If an external force is acting on the linear rod to move the linear rod away from the gear engaged position the linear rod can follow such force over a limited distance (determined by the free play a mentioned), wherein such movement caused by an external force has to overcome the force of the spring mechanism (preload of the spring mechanism) and has to compress the spring mechanism over a distance as permitted by the free play of the first and second cam followers. In other words, any external force acting on the linear rod to move it out of one of the gear positions mentioned has to compress the spring mechanisms when the linear rod is moved by the external force, and thus experiences an increasing counter force attempting to return the linear rod to the one of the gear engaged positions mentioned. When the linear rod has been moved by the external force out of one of the gear engaged positions mentioned up to the distance as permitted by the free play of the first and second cam followers, a hard end stop is reached preventing any further out of gear movement of the linear rod. Therefore, the distance the linear rod could be moved out of one of the gear engaged positioned mentioned is limited by the hard end stop created by the limits of the free play, and the additional compression of the spring mechanism caused by movement of the linear rod establishes a returning force which returns the linear rod to the one of the gear engaged positions mentioned as soon as the interfering external force diminishes.

[0022] In a preferred embodiment a boundary wall of the second recessed surface sector which limits the second recessed surface sector in axial direction away from the inner end of the respective one of the first and second barrel cams is in the region approaching the circumferentially extending closed end cam groove portion at an inner end of the respective barrel cam provided with a wall portion climbing towards the inner end of the respective barrel cam and is provided with a push projection near the entry of the circumferentially extending closed end cam groove portion and pointing towards the inner end of the respective barrel cam to exert a pushing force on the respective one of the first and second cam followers when it is passing the push projection when moving towards and into the circumferentially extending closed end cam groove portion to actively overcome a potential blockage of the linear rod when it is approaching one of the first and third gear engaged position.

[0023] The cam surface configuration of each of the two barrel cams can be extended by repeating a cam groove and a recessed surface sector so that one more neutral and one more gear engaged position is added at one end of the sequence. In principle, such extension can be repeated further so that gear shift actuators with sequences of (2n +1) shift positions with n > 3 can be realized.

[0024] The invention will now be described with reference to a preferred embodiment shown in the drawings in which:

[0025] Fig. 1 is a perspective side view of a gear shift actuator according to the invention;

[0026] Fig. 2 corresponds to Fig. 1 but is shown partially in cross-section in a region surrounded by a rectangle inbroken lines; Fig. 3 is a schematical graph showing a sequence of shift states which are available for the gear shift actuator of the invention;

[0027] Fig. 4 shows schematic side views of the gear shift actuator in the five shift states of Fig. 3;

[0028] Figs. 5a) - k) show side views of a plurality of subsequent rotational states of the gear shift actuator when shifted from first gear (G1) in Fig. 5a) to third gear (G3) in Fig. 5k);

[0029] Figs. 6a) - d) show a sequence of rotational states of the gear shift actuator when it is driven from second gear (G2) to the state second neutral;

[0030] Figs. 7a) - e) show a sequence of rotational states of the gear shift actuator when it is driven from second neutral to the third gear state while the linear rod driven by the gear shift actuator is temporarily blocked during the shift operation; and

[0031] Figs. 8 - 10 schematical side views of the gear shift actuator in the shift position second gear, third gear, and first gear, respectively, wherein an enlarged schematical detail is shown on top of the gear shift actuator.

[0032] With reference to Figs. 1 and 2 the main components of the gear shift actuator will be described, wherein Fig. 1 is a perspective side view and Fig. 2 is a side view as in Fig. 1 , but in the region surrounded by the rectangle in broken lines shown partially in cross-section. The gear shift actuator comprises a rotary member in form of a shaft 4, in the preferred embodiment shown a splined shaft 4, as can be seen best in Fig. 2 indicating the longitudinal groove extending parallel to the axial direction along the splined shaft 4. The shaft 4 is supported to be rotatable with its central axis coinciding with the rotational axis, wherein in Fig. 2 ball bearings can be seen on the left hand side indicating the rotary support for the shaft 4. The shaft 4 is further supported to be stationary in axial direction. As shown in Fig. 1 an electric motor is provided which is operable to drive the shaft 4 via a set of gear wheels to rotate about its rotary axis in a first sense of rotation or in an opposite second sense of rotation as indicated by the curved arrows in Fig. 1 and 2.

[0033] The gear shift actuator further comprises a first and a second barrel cam 1 and 2. The two barrel cams are of identical design but are arranged in an orientation opposite to each other such that like ends of the two barrel cams are at the inner end facing each other, and like outer ends of the two barrel cams are facing away from each other at the opposite outer ends of the arrangement of the two barrel cams 1 , 2. Each of the two barrel cams 1 , 2 has a throughgoing central opening for receiving the shaft 4 which extends through the central openings of the two barrel cams 1 , 2. The central openings of the two barrel cams have a complementary cross- sectional shape to the cross-sectional shape of the splined shaft 4 so that a spline engagement is formed between the shaft 4 and the two barrel cams 1 , 2. This engagement on the one hand provides a torque-proof engagement of the two barrel cams 1 , 2 on the shaft 4, while at the same time the two barrel cams are able to slide in axial direction along the shaft 4. Axial movement of the two barrel cams 1 , 2 is limited by two opposite, spaced apart end stops 5, 6 which are stationary in axial direction, wherein in the embodiment shown the two opposite end stops 5, 6 are fixed to the shaft 4. Between the two barrel cams 1 , 2 a spring mechanism 7 is acting which urges the two barrel cams 1 and 2 apart in opposite axial directions towards their associated end stops 5 and 6, respectively. Since both the barrel cams 1 , 2 and the end stops 5, 6 are rotating with the shaft 4 there is no friction between the end stops 5, 6 and the barrel cams 1 , 2 upon rotation of the shaft 4.

[0034] Each of the two barrel cams 1 , 2 has a cam surface configuration comprising a first cam groove 10, followed by a first recessed surface sector 18, continued by a second cam portion 20 which merges into a second recessed surface sector 28. This cam surface configuration of the two barrel cams cooperates with two cam followers 31 , 32 in a manner which will be described in more detail below, wherein the first cam follower 31 is received in the cam surface configuration of the first barrel cam 1 , and the second cam follower 32 is received in the surface configuration of the second barrel cam 2.

[0035] The two cam followers 31 , 32 are axially aligned and axially spaced apart from each other fixed to a linear rod 30. The linear rod 30 is supported radially exterior to the two barrel cams, wherein the linear rod 30 is supported to be moveable in axial direction parallel to the rotary axis of the shaft 4 in opposite axial directions as indicated by the two arrows in Figs. 1 and 2. The two cam followers 31 and 32 are connected to the linear rod such that they project inwardly, thereby extending into the cam surface configuration of each of the two barrel cams 1 , 2 as indicated above.

[0036] Fig. 3 is a schematical diagram showing a linear sequence of shift positions of the linear rod corresponding to the shift states first gear G1 , first neutral N1 , second gear G2 second neutral G2, and third gear G3. The gear shift actuator can be operated to move the linear rod from one of the shift positions mentioned to any of the adjacent shift positions as indicated by the arrows. There are two kinds of horizontal arrows, namely arrows which are completely filled with black color, and arrows shown with black outer lines only. The two different types of arrows represent different shift characteristics. The completely black arrows are assigned to shift movements from one of the gear engaged positions to one of the neutral positions, and these shift movements are performed in a “stiff” shift mode in which the axial movement of the linear rod is strictly coupled to the rotary movement of the two barrel cams. The shift movements indicated by the arrows with black outer lines are associated with shift movements from one of the neutral positions to one of the gear engaged positions, and these shift movements are performed in a “sprung” or “compliant” shift mode in which the axial movement of the linear rod is not strictly coupled to the rotary movement of the barrel cams, but is partially decoupled in the following sense: If the linear rod encounters a low resistance with a force resisting its linear movement below a threshold the linear movement of the rod is carried out, whereas in case of a resistance force above the threshold the linear rod is blocked (stuck) and does not move in axial direction; the consequence of this blocked state is that the one of the two barrel cams which is attempting to drive the movement of the linear in axial direction is - in reaction to the blocked state of the linear rod - forced by the driving force to move in opposite axial direction along the shaft, thereby moving away from its associated end stop and moving closer to the opposite other barrel cam, thereby compressing the spring mechanism 7 between the two barrel cams 1 , 2. In other words, in this sprung or compliant shift mode the spring mechanism 7 is in the force transmission path between the shaft 4 and the linear rod 3. If the resistance or blocking force experienced by the linear rod is above the threshold, the linear rod does not move in axial direction and instead the driving force of the mechanism is redirected by the driving one of the barrel cams 1 , 2 into its axial displacement which compresses the spring mechanism 7, thereby storing the integrated driving force for the linear rod in the compressed state of the spring mechanism 7. As soon as the resistance or blocking force diminishes below the threshold the spring mechanism 7 expands, thereby driving the linear rod 30 to the intended gear engaged position. In other words, the blocked axial movement of the linear rod into the intended gear engaged position is converted into a compression of the spring mechanism, thereby storing the drive force, and the intended linear movement of the linear rod 30 is performed in a delayed manner as soon as the resistance or blocking force sufficiently dropped to allow the compressed spring mechanism 7 to expand again which then moves the linear rod to the intended gear engaged position, thereby making up for the previously blocked movement. How the two different shift mode characteristics is realized by the cam surface configuration of the two barrel cams will be described in more detail below. Figs. 4 a) - e) show schematical side views of the gear shift actuator in the five shift states GIGS described before. In Fig. 4a) the linear rod 30 is in the first gear engaged position in which the first cam follower 31 is in the circumferentially extending cam groove end portion 12 of the first cam groove which extends from a closed end 11. The second cam follower 32 is in a circumferentially extending closed end cam groove portion 29 which merges into a second recessed surface sector 28 of the cam surface configuration of the second barrel cam 2.

[0037] In Fig. 4 b) the shaft and the two barrel cams 1 , 2 have been rotated in a first sense of rotation such that the linear rod 30 has been moved in axial direction to the shift position corresponding to first neutral. In the course of this rotation the first cam follower 31 has moved from the closed end 11 of the first cam groove 10 along the circumferentially extending cam groove end portion 12 and further along a helical drive cam portion 13 (see Fig. 4 c)) of the first cam groove. Upon further rotation of the barrel cams the first cam follower 31 has reached a circumferentially extending cam groove end portion 14 of the first cam groovelO. At the same time the second cam follower 32 has been moved out of the circumferentially extending closed end cam groove portion 29 and into the second recessed surface sector 28 of the second barrel cam 2. The second recessed surface sector 28 allows axial movement of the second cam follower 32 such that the second cam follower 32 could be displaced in axial direction within the second recessed surface sector 28 while the first cam follower 31 was climbing along the helical drive cam portion 13. When the first cam follower 38 passed the helical drive cam portion 13 and reached the following circumferentially extending cam groove end portion 14 of the first cam groove the second cam follower 32 passed through the second recessed surface sector 28 and entered the adjoining circumferentially extending cam groove end portion 24 of the second cam groove 20 of the second barrel cam as shown in Fig. 4 b).

[0038] For the next shift operation from first neutral (Fig. 4 b)) to second gear engaged (Fig. 4 c)) the shaft 4 and the two barrel cams are again rotated in the same sense of rotation as before, wherein this rotation lets the second cam groove of the second barrel cam 2 pass along the second cam follower 32 with its helical drive cam portion 23 of the second cam groove, whereas the first cam follower 31 moves through the first recessed surface sector 18. In this manner the second cam follower 32 is driven by the rotating helical cam drive portion 23 of the second cam groove of barrel cam 2 to move an axial direction, whereas the first cam follower 31 in this phase is in the first recessed surface sector 18 of barrel cam 1 and is thus free to follow the axial movement driven by the second cam follower 32. After having passed along the helical drive cam portion 23 the second cam follower 32 reaches upon further rotation the following circumferentially extending cam groove end portion 22 of the second cam groove of barrel cam 2. In this rotational state shown in Fig. 4 c) the first cam follower 31 has passed through the first recessed surface sector 18 of barrel cam 1 and has entered the circumferentially extending cam groove end portion 22 of the second cam groove of barrel cam 1 so that the linear rod 30 has reached the second gear engaged position as shown in Fig. 4c). In case that this rotational movement operation for the shift from Fig. 4b) to Fig. 4c) from first neutral to second gear engaged the linear rod 30 would have been blocked the drive force exerted due to the rotation of barrel cam 2 with its helical drive cam portion 23 passing along the second cam follower 32, the drive force would have been converted to displace barrel cam 2 in opposite direction, thereby compressing spring mechanism 7. Thus, the shift operation from neutral 1 to second gear engaged from Fig. 4b) to Fig. 4c) is performed in a sprung or compliant manner as described before. A shift operation from a neutral to a gear engaged position will be described in more detail below with reference to Figs. 7 a) - e).

[0039] When the next shift operation from second gear engaged G2 in Fig. 4 c) to second neutral N2 in Fig. 4 d) is performed by rotating barrel cams 1 , 2 in the same sense of rotation a further step, the drive force is created by the helical drive cam portion 23 of the second cam groove of barrel cam 1 passing along the first cam follower 31 which drives the first cam follower in axial direction, while at this time the second cam follower 32 is in the first recessed surface sector 18 of barrel cam 2 and is thus free to follow the axial movement driven by the first barrel cam 31 . After the helical drive cam portion 23 has passed along the first cam follower 31 the circumferentially extending cam groove end portion 24 of the second cam groove has reached the first cam follower 31 while the second cam follower 32 has entered the circumferentially extending cam groove end portion 14 of the first cam groove of barrel cam 2, as shown in Fig. 4 d), and thus the linear rod 30 has reached the position corresponding to second neutral. This shift operation from a gear engaged to a neutral position was performed in a stiff manner, i.e. was driven by the second cam follower 32 passing along the helical drive cam portion 23 of the second cam groove of barrel cam 2 without the spring mechanism 7 in the force transmission path.

[0040] In the final shift operation from second neutral (Fig. 4 d)) to third gear engaged (Fig. 4 e)) the barrel cams 1 , 2 are once again rotated in the first sense of rotation. In this case barrel cam 2 is rotated first with the circumferentially extending cam groove end portion 14 along the second cam follower 32 and then with the helical drive cam portion 13 of the first cam groove of barrel cam 2 along the second cam follower 32 which moves the linear rod further in axial direction, wherein the first cam follower 31 in this phase is in the second recessed surface sector 28 of barrel cam 1 and can thus follow the axial movement driven by the second cam follower 32. Eventually, further rotation of barrel cams 1 , 2 lets the second cam follower 32 pass along circumferentially extending cam groove end portion 12 to the closed end 11 of the first cam groove of barrel cam 2, while the first cam follower 31 has passed through the second recessed surface sector 28 of the barrel 1 and eventually reached the circumferentially extending closed end cam groove portion 29 adjoining the second recessed surface sector 28 at the inner end of barrel cam 1 . In this manner the linear rod 30 has reached the third gear engaged position G3 shown in Fig. 4 e). Again, it should be noted that this shift operation from a neutral to a gear engaged position was performed in a sprung or compliant shift mode because when the helical drive cam portion 13 of the first cam groove of barrel cam 2 was rotated along the second cam follower 32 for driving the linear rod 11 , the spring mechanism 7 was in the force transmission path in the sense that when linear rod would have been in a blocked state in this drive phase while barrel cam 2 rotated with the helical drive cam portion 13 along the second cam follower, barrel cam 2 could have reacted to a blocked state of linear rod 30 by being displaced in opposite axial direction accompanied by compression of spring mechanism 7 which would have resulted in the elastic storing of the drive force in the compressed spring mechanism which would have been released after the blockage of the linear rod has sufficiently diminished, whereafter the expanding spring mechanism would have completed the intended shift operation to third gear engaged G3 position.

[0041] It is, because of the identical design of the barrel cams 1 , 2, apparent that, when starting from the third gear engaged state shown in Fig. 4 e), when shift operations are performed by rotating barrel cams 1 , 2 in a second, opposite sense of rotation the linear rod 30 would be shifted in opposite axial direction through the shift states N2, G2, N1 and G1 in an opposite manner to eventually reach the shift position corresponding the first gear engaged G1 shown in Fig. 4 a). Likewise, it is apparent that instead of a sequential sequence of shift operation in one axial direction, shift operations could also be combined such that the linear rod is shifted from any of the shift positions shown in Fig. 4b) - d) in either of the two axial directions towards an adjacent shift position. Therefore, any series of subsequent shift positions selected out of the shift positions G1 , N1 , G2, N2, and G3 can be realized by the gear shift actuator when probably controlling the senses of rotation of the barrel cams 1 , 2 in the subsequent shift operations. Fig. 5 a) - k) shows a sequence of rotational steps of the gear shift actuator, wherein one or two intermediate steps of rotation are shown between the adjacent shift positions G1 , N1 , G2, N2, and G3. In particular Fig. 5 a) corresponds to first gear engaged G1 as in Fig. 4 a), Fig. 5 d) corresponds to first neutral N1 as in Fig. 4 b), Fig. 5 f) corresponds to second gear engaged G2 as in Fig. 4 c), Fig. 5 h) corresponds to second neutral N2 as in Fig. 4d), and Fig. 5 k) corresponds to third gear engaged G3 as in Fig. 4 e). The above description of the shift operations with reference to Figs. 4a) - e) can also be read in connection with the sequence of Fig. 5a) - k) to obtain a better impression of the cam surface configuration of barrel cams 1 and 2.

[0042] With reference to Fig. 6 a) - d) a single shift operation from second gear G2 to second neutral N2 will now be described. In Fig. 6 a) the linear rod is in the second gear engaged position, wherein in this state the first cam follower 31 is in the circumferentially extending cam groove end portion 22 of the second cam groove 20, whereas the second cam follower 32 is in the circumferentially extending cam groove end portion 24 of the second cam groove 20. Upon rotation of the shaft with barrel cams 1 , 2 first barrel cam 1 rotates with its helical drive cam portion 23 of the second cam groove along the first cam follower 31 , thereby driving cam follower 31 in axial direction. At the same time the second cam follower 32 has left the circumferentially extending cam groove end portion 24 and entered the first recessed surface sector 18, as shown in Fig. 6 b). As can be seen in Figs. 6 b) and c) a wall 35 which forms a boundary of the first recessed surface sector 18 has a helical shape climbing towards the outer end of barrel cam 2, thereby forming a helical track on which the second cam follower 32 slides, wherein this helical wall 35 and the helical drive cam portion 23 of the second cam groove have the same slope so that both cam followers 31 and 32 are driven. With continuing rotation the first cam follower 31 has passed through the helical drive cam portion 23 and reached in Fig. 6 d) the circumferentially extending cam groove end portion 24 of the second cam groove, whereas the second cam follower 32 has left the helical wall 35 and entered the first cam groove of barrel cam 2 by reaching the circumferentially extending cam groove end portion 14 of the first cam groove so that at the end of the rotational movement when approaching the end position in Fig. 6d) cam followers 31 , 32 are no longer driven in axial direction and linear rod 30 reached the second neutral N2 position. This shift process from second gear to second neutral is a stiff shift operation because the first cam follower is driven by the helical cam drive portion 23 directly, without the spring mechanism 7 in the force transmission path.

[0043] The next shift operation in the same axial direction from second neutral to third gear engaged will now be described with reference to Figs. 7 a) - e), wherein in this example linear rod 30 is temporarily blocked. At the beginning of the shift operation the first cam follower 31 is in the circumferentially extending cam groove end portion 24 of the second cam groove of barrel cam 1 , and the second cam follower 32 is in the circumferentially extending cam groove end portion 14 of the first cam groove of barrel cam 2. Soon after start of the rotation of barrel cams 1 , 2 the second cam follower 32 has reached the helical drive cam portion 13 of the first cam groove (see Fig. 7 b)), whereas the first cam follower 31 has reached the second recessed surface sector 28 of barrel cam 1 . Upon continued rotation of barrel cams 1 , 2 helical drive cam portion 13 continues to be rotated along the second cam follower 32 (Fig 7 c)), wherein in this case there is a blockage of linear rod 30 which is therefore stuck and cannot move an axial direction. The driving force of the helical drive cam portion 13 rotating against the second cam follower 32 is therefore not transmitted into axial movement of linear rod, but into an axial movement of barrel cam 2 in the opposite axial direction, thereby moving barrel cam 2 away from its end stop 6, as can be seen by the gap between the outer end of barrel cam 2 and end stop 6. This axial displacement of barrel cam 2 compresses spring mechanism 7, thereby storing the drive force by continued compression of the spring mechanism 7. The first cam follower 31 is in this phase in the first recessed surface sector, and because of the blocked axial movement of the linear rod the first cam follower stayed close to the lower wall of the second recessed surface sector 28 and moved along this circumferentially extending lower wall during further rotation from 7 c) to 7 d), wherein in this movement phase the linear rod 30 is still blocked so that the spring mechanism 7 is further compressed and the gap between the outer end of barrel cam 2 and end stop 6 increased further. In Fig. 7 d) the second cam follower 32 has reached the circumferentially extending cam groove end portion 12 of the first cam groove. It is now assumed that the blockage of linear rod ceased by itself at some time of the movement between the stats of Fig. 7d) and e). In this case the compressed spring mechanism expands, thereby pushing barrel cam 2 in axial direction towards its end stop 6, thereby closing the previously formed gap and driving the linear rod to the third gear engaged position of Fig. 7 e). To support release of a blockage of the linear rod in the last phase of the rotation towards the third gear engaged position of Fig. 7e) the second recessed surface sector 28 of barrel cam 1 is provided with a push projection 40 closed to the entry of circumferentially extending closed end cam groove portion 29. In the last phase of the rotation of barrel cams 1 , 2 from 7 d) to 7 e) the second cam follower 32 slides onto the lower wall of the second recessed surface sector 28 and slides along push projection 40 and is thereby pushed in axial direction towards the third engaged position thereby actively supporting release of the blockage of linear rod 30. In the finally reached third gear engaged position the first cam follower 31 in this manner reached the circumferentially extending closed end camp groove portion 29 of barrel cam 1 while the second cam follower 32 reached the closed end 11 of the first cam groove 10 at the outer end of barrel cam 2.

[0044] In the following a detent mechanism will be described which holds the linear rod in a gear engaged position and urges the linear rod to return to the centered gear engaged position in case an interfering force attempted to move it out of the gear engaged position. In the lower part of Fig. 8 a side view of the gear shift actuator is shown in a schematic manner, wherein the gear shift actuator is in the second gear engaged position, the first cam follower 31 being in the circumferentially extending cam groove end portion 22, and the second cam follower 32 being in the circumferentially extending cam groove end portion 22 of barrel cam 2. As indicated in Fig. 8 in the gear engaged position of the first and second cam followers 31 , 32 the circumferentially extending cam groove end portions 22 are at their outwardly lying wall provided with a depression or trough 22' so that the circumferentially extending cam groove end portion 22 in this region of the depression 22' has an enlarged width.

[0045] In Fig. 8 an enlarged detail is shown in a rectangle bounded by broken lines above the gear shift actuator. In this detail the two opposing barrel cams 1 , 2, the first and second barrel cams 31 and 32, and the spring mechanism 7 are shown in a very schematic manner. Also the depressions 22' in the circumferentially extending cam groove end portions 22 in the second gear engaged position are shown, for illustration in an exaggerated manner. Under normal circumstances, when the gear shift actuator is in the second gear engaged position as shown in Fig. 8, the preload of the spring mechanism 7 urges the first barrel cam 1 and the second barrel cam 2 apart so that the first and second cam followers 31 , 32 are in the positions indicated by the full circles in the detail in the middle of Fig. 8. As shown the first cam follower 31 and the second cam follower 32 have some free play an axial direction created by the depressions 22'. If some external force is acting on the linear rod trying pull the linear rod out of the second gear engaged position towards first or second neutral, this force has to overcome the preload of the spring mechanism 7, thereby pulling one of the first and second barrel cams 1 and 2 closer to the other. If such force is acting on the linear rod and pulls the first barrel cam 1 closer to the second barrel cam 2 the second cam follower 32 will be displaced by the same distance and moved into the depression 22', this displaced position is indicated in the detail of Fig. 8 by a dashed line circle (if the linear rod is pulled in the opposite direction which pulls the second barrel cam 2 closer to the first barrel cam 1 the first cam follower 31 is moved into the depression 22’ to the position shown by the dashed lined circle in the depression 22’ of barrel cam 1). Eventually the second cam follower 32 will contact the bottom of the depression 22' which forms a hard end stop so that the linear rod cannot be pulled any further away from the second gear engaged position. Further displacement of the linear rod from the close neighborhood of the second gear engaged position is thus in any case prevented (the extent of this neighborhood is determined by the degree of free play of the cam followers in axial direction).

[0046] As soon as the interfering force on the linear rod stops the compression of the spring mechanism 7 caused by pulling the barrels cams 1 , 2 closer together will be released by expansion of the spring mechanism 7 so that the push rod with its first and second cam followers 31 , 32 again reaches the position is indicated by the first and second cam followers 31 , 32 in full circles which corresponds to the centered second gear engaged position of the linear rod.

[0047] The function of the detent mechanism is schematically illustrated in the enlarged detail of Fig. 8 by a spring between two spaced apart vertical lines and a central line between them. The central vertical line indicates the axial position of the linear rod. If the linear rod is subject to an external interfering force and is thereby displaced the spring mechanism 7 is compressed if the force pulled the two barrel cams 1 , 2 closer together. Therefore, any external force causing a displacement of the linear rod from the central position has to act against the spring force of spring mechanism 7 which is indicated by the springs on both sides of the central vertical line when it is displaced in either direction. The two outer vertical lines illustrate the hard end stop which is reached when one of the two cam followers 31 , 32 which is displaced into the depression 22' contacts the bottom of the depression 22' thereby stopping any further displacement of the linear rod as a hard end stop. As soon as the interfering external force diminishes the compressed spring mechanism 7 will release, thereby returning the linear rod to the centered second gear engaged position.

[0048] Fig. 9 is an illustration corresponding to Fig. 8 but for the first gear engaged position. In this case the first cam follower 31 is located at the closed end 11 of the first cam groove at the outer end of barrel cam 1. The second cam 32 follower is located at the circumferentially extending closed end cam groove portion 29 adjoining the second recessed surface sector 28 of barrel cam 2. The closed end 11 comprises in its wall directed to the outer end of barrel cam 1 a depression or bulge 11' which provides extra space in axial direction. Similarly, closed end cam groove portion 29 comprises in its wall towards the outer end of barrel cam 2 a depression or bulge 29' which creates a free play in axial direction for the second cam follower. Again an enlarged detail is shown in the upper part of Fig. 9, wherein the depressions or bulges 11' and 29' are exaggerated compared to the illustration in the lower part of Fig. 9. The functionality of the detent mechanism in this position is the same as describe with reference to Fig. 8. That is, the preload of spring mechanism 7 holds the linear rod centered in the first gear engaged position, and the spring mechanism 7 generates an increasing counter-force against any interfering external force urging the linear rod away from its centered position, and eventually any further displacement of the linear rod from the neighborhood of a centered position is limited by a hard stop when one of the first and second cam followers 31 , 32 contacts the bottom of a respective one of the depression 11 ' and 29'.

[0049] Fig. 10 illustrates the detent mechanism for the third engaged position in which the first cam follower 31 is in the circumferentially extending closed end cam groove portion 29 a barrel cam 1 , and second cam follower 32 is at the closed end 11 of the first cam groove at the outer end of barrel cam 2. The situation is symmetrical to the first gear engaged position shown in Fig. 9, and it is apparent that the functionality of the detent mechanism is the same as described before for the first and second gear engaged positions.

[0050] Reference numerals:

[0051] 1 First barrel cam

[0052] 2 Second barrel cam

[0053] 4 Shaft

[0054] 5, 6 End stops

[0055] 7 Spring mechanism

[0056] 8 Electric motor

[0057] 10 First cam groove

[0058] 11 Closed end of the first cam groove at the outer end of the barrel cam

[0059] 12 Circumferentially extending cam groove end portion of the first cam groove extending from the closed end

[0060] 13 Helical drive cam portion of the first cam groove

[0061] 14 Circumferentially extending cam groove end portion of the first cam groove merging into a first recessed surface sector

[0062] 18 First recessed surface sector

[0063] 20 Second cam groove

[0064] 22 Circumferentially extending cam groove end portion of the second cam groove extending from the first recessed surface sector

[0065] 23 Helical drive cam portion of the second cam groove 24 Circumferentially extending cam groove end portion of the second cam groove merging into the second recessed surface sector

[0066] 28 Second recessed surface sector

[0067] 29 Circumferentially extending closed end cam groove portion adjoining the second re- cessed surface sector at an inner end of the barrel cam

[0068] 30 Linear rod

[0069] 31 First cam follower

[0070] 32 Second cam follower

[0071] 35 Helical wall track 40 Push projection

Claims

Claims1. Gear shift actuator for driving a linear rod (30) 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 (8) for rotating the rotary member, wherein the linear rod (30) is driven by rotary movement of the rotary member for linear movement parallel to the axial direction driven by two barrel cams (1 , 2) which are of the same design and which are supported to be movable in axial direction, and which are disposed oppositely oriented to each other and rotationally aligned with respect to each other and coaxially with the rotary axis between two opposite end stops (5, 6) which are located at a fixed axial distance to each other, a spring mechanism (7) disposed between the two barrel cams (1 , 2) to bias them apart, each towards a respective one of the two end stops (5,6), wherein each of the two barrel cams (1 , 2) is provided with an outer cam surface configuration configured to cooperate with one of two cam followers so that the two barrel cams (1 , 2) and the spring mechanism (7) in between cooperate with the linear rod (30) such that the linear rod (30) is driven along the axial direction in a first direction from a neutral position to an 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 is moved in a second direction opposite to the first direction from the neutral position to another 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, and such that, when the linear rod (30) is driven from an engaged position to neutral it is driven in a stiff mode in which barrel cam and linear rod movement is coupled, and when the linear rod (30) is driven from neutral to an engaged position it is driven in a sprung mode in which barrel cam and linear rod movement is decoupled so that, in case of a blockage of the linear rod, a driving one of the two barrel cams (1 , 2) is displaced in axial direction away from its end stop (5, 6) thereby compressing the spring mechanism (7) to store the drive force as long as the linear rod (30) is blocked and to drive the linear rod to the engaged position by the expanding spring mechanism as soon as the blockage has sufficiently diminished, characterized in that the rotary member is a shaft (4) with non-circular cross-section which is extending coaxially with the rotary axis through central openings of complementary non-circular cross-section in the two barrel cams (1 , 2) to provide torque-proof engagement of thetwo barrel cams (1 , 2) with the shaft (4) and to allow them to axially move along the shaft (4) limited by the two end stops which (5, 6) are stationary in axial direction with respect to the shaft; the linear rod (30) is supported radially outwardly with respect to the two barrel cams (1 , 2) and is provided with the two cam followers (31 , 32) fixed to it at axially spaced locations and projecting inwardly, one (31) of the two cam followers being received in the cam surface configuration of one (1) of the two barrel cams, the other one (32) being received in the cam surface configuration of the other one (2) the two barrel cams; the gear shift actuator is adapted to shift the linear rod (30) within a sequence of shift states in which the states first gear engaged, first neutral, second gear engaged, second neutral, and third gear engaged follow each other, wherein shifting in this sequence is accomplished by the cam surface configuration which for each of the two barrel cams (1 , 2) includes in circumferential sequence and extending from an outer end of the respective one of the two barrel cams (1 , 2) to an inner end adjacent the spring mechanism (7): a first cam groove (10) starting at the outer end from a closed end (11) with a circumferentially extending cam groove end portion (12), followed by a helical drive cam portion (13) climbing away from the outer end of the respective one of the two barrel cams (1 , 2), followed by a circumferentially extending cam groove end portion (14) which terminates the first cam groove (10) by transitioning into a first recessed surface sector (18) of increased width in axial direction in which a respective one of the two cam followers (31 , 32) is free to move in axial direction, which first recessed surface sector (18) transitions into a second cam groove (20) extending from the first recessed surface sector (18) with a circumferentially extending cam groove end portion (22), followed by a helical drive cam portion (23) climbing further away from the outer end of the respective one of the two barrel cams (1 ,2), followed by a circumferentially extending cam groove end portion (24) which terminates the second cam groove by transitioning into a second recessed surface sector (28) of increased width in axial direction in which the respective one of the two cam followers (31 , 32) is free to move in axial direction, which second recessed surface sector (28) transitions into a circumferentially extending closed end cam groove portion (29) having a closed end.

2. Gear shift actuator according to claim 1 , characterized in that the shaft (4) is a splined shaft in the form of a cylindrical shaft comprising a plurality of parallel grooves extending parallel to the axial direction, and in that the complementary shaped central openings of the two barrel cams (1 , 2) are cylindrical openings with a plurality of elongated protrusions that are arranged to be received in the plurality of grooves of the splined shaft to provide torque-proof engagement of the splined shaft (4) with the two barrel cams (1 , 2) and to allow axial movement of the barrel cams with respect to the splined shaft.

3. Gear shift actuator according to claim 1 or 2, characterized in that the two end stops (5, 6) are fixed to the shaft (4).

4. Gear shift actuator according to any of the preceding claims, the distance between the two end stops (5, 6), the dimensions of the two barrel cams (1 , 2) and of the spring mechanism (7) in-between are arranged such that the spring mechanism (7) is under a predetermined preload and exerts oppositely directed forces on the two barrel cams (1 , 2) to bias them against the two end stops (5, 6).

5. Gear shift actuator according to any of the preceding claims, characterized in that for each of the two barrel cams (1 , 2) the circumferentially extending cam groove end portion (11) of the first cam groove (10) extending from the closed end (11) and the circumferentially extending closed end cam groove portion (29) extending from the second recessed surface sector (28) at the inner end of the barrel cam have a width in axial direction that is enlarged and larger than the width of the first and second cam followers (31 , 32), and in that the circumferentially extending cam groove end portions (22, 24) of the second cam groove (20), which circumferentially extending cam groove end portions adjoin the first and second recessed surface sector (18, 28), respectively, have a width in axial direction that is enlarged and larger than the width of each of the two cam followers (31 , 32), which enlarged widths are configured to establish a free play for the linear rod in axial direction in the first gear, second gear and third gear engaged positions.

6. Gear shift actuator according to any of the preceding claims, characterized in that a boundary wall of the second recessed surface sector (28) which limits the second recessed surface sector (28) in axial direction away from the inner end of the respective one of the first and second barrel cams (1 , 2) is in the region approaching the circumferentially extending closed end cam groove portion (29) at an inner end of the respectivebarrel cam provided with a wall portion climbing towards the inner end of the respective barrel cam and is provided with a push projection (40) near the entry of the circumferentially extending closed end cam groove portion (29) and pointing towards the inner end of the respective barrel cam (1 , 2) to exert a pushing force on the respective one of the first and second cam followers (31 , 32) when passing the push projection (40) when moving towards and into the circumferentially extending closed end cam groove portion (29) to actively overcome a potential blockage of the linear rod when it is approaching one of the first and third gear engaged position (G1 , G3).

Images