shift actuator

Abstract

The invention relates to a shift actuator comprising a linear drive assembly with a rotary member supported in a housing for rotation but not for movement in an axial direction defined by its axis of rotation, an electric motor for rotating the rotary member and a driven part engaged by the rotary member for converting the rotary motion into a linear axial movement of the driven part for driving a shift fork from a neutral position to a first gear engagement position and back to neutral when the rotary member is rotated in a first rotational direction and in an opposite second rotational direction, respectively, characterized in that the rotary member comprises a hollow cylindrical sleeve (4) with a first cam follower (6) on its inner wall, the driven part comprises a first cylindrical cam (10) with a helical cam groove (12) on its outer wall configured to accommodate the first cam follower (6) and is supported in the sleeve (4) for slidable movement in the axial direction but locked against rotational movement relative to the central rod (30), the central rod (30) is supported in the housing for movement in the axial direction but locked against rotational movement and carries a second end stop (34) coupled at a distance from the first cylindrical cam (10), the central rod (30) is configured to be linked to the shift fork (30), a compression mechanism (40) is configured to extend the central rod (30) from the first cylindrical cam (10) by biasing the second end stop (34) away from the first cylindrical cam (10), wherein the biasing movement is limited by a first end stop (32) on the central rod (30) and the helical cam groove is configured such that rotation of the sleeve (4) in the first rotational direction moves the first cylindrical cam (10) axially in the first direction, which movement is transmitted by the compression mechanism (40) to the central rod (30) to drive the coupled shift fork (50) from the neutral position towards the first gear engagement position and such that rotation of the sleeve (4) in the second rotational direction moves the first cylindrical cam in the opposite second direction, which movement is transmitted to the central rod (30) to drive the coupled shift fork (50) from the first gear engagement position to the neutral position.

Description

TECHNICAL FIELD

[0001] The present invention relates to a shift actuator comprising a linear drive assembly having a rotary member supported in a housing so as to be rotatable but not movable in an axial direction defined by its axis of rotation, an electric motor for rotating the rotary member, and a driven part engaged by the rotary member for transmitting the rotary motion of the rotary member into a linear motion of the driven part in the axial direction for driving a shift fork from a neutral position to a gear engagement position and back to the neutral position when the rotary member is driven to rotate in a first rotational direction and in a second rotational direction opposite to the first direction, respectively. BACKGROUND

[0002] In motor vehicles, shift actuators are used to switch a transmission between a gear engagement position, in which a rotational engagement and torque transmission between two coaxially arranged rotary shafts is established, and a neutral disengagement position, in which the two rotary shafts are disengaged from each other. A typical application scenario for shift actuators of the above-mentioned type is an actuator for a dog clutch. A dog clutch is a mechanism for connecting and disconnecting two rotary shafts. The principle of its operation is that a regularly spaced set of teeth or projections is made on one wheel connected to one of the shafts, and a set of complementary grooves is made on the other wheel connected to the second shaft. When the two wheels are moved together, the teeth of the first wheel are accommodated in the grooves, which are formed between the teeth of the second wheel, and a rotational engagement without slippage between the shafts is established. A dog clutch with a dog clutch actuator is described, for example, in US 2015 / 0107955 Al, the preamble of claim 1 being based on this document. The shift actuator comprises a linear drive assembly having a rotary member in the form of a screw spindle supported so as to be rotatable but not movable in the direction of its axis of rotation, an electric motor for rotating the screw spindle, and a driven part in the form of a nut engaged by the screw spindle. By the engagement of the nut with the screw spindle, the rotational motion of the screw spindle is transmitted into a linear motion of the nut in the axial direction of the axis of rotation of the screw spindle. When the screw spindle is driven to rotate in a first rotational direction and in a second rotational direction opposite to the first direction, respectively, the driven part in the form of a nut is connected to a shift fork for driving the shift fork from a neutral position to a gear engagement position and vice versa. When the shift fork is in the neutral position, one of the wheels with teeth is moved away from the other wheel with teeth, so that the mutual engagement between the two wheels is stopped. By moving the shift fork to the gear engagement position using the linear drive assembly, the two toothed or dog-shaped wheels are moved into a rotational mutual engagement position, in which the teeth of one wheel are accommodated in the grooves between the teeth of the other wheel. SUMMARY

[0003] For such a shift actuator, it can occur that the two teethed or claw wheels are in a relative angular position with respect to each other such that the teeth of one wheel are directly opposite the teeth of the other wheel, in which case the shift actuator cannot be shifted into the gear position engagement position until the claw wheels are rotated with respect to each other such that the recesses between the claws of one wheel are aligned with the recesses between the claws of the other wheel.

[0004] It is an object of the present invention to provide a shift actuator whose design is able to deal with the situation in which the shift fork actuated by the shift actuator is temporarily blocked in a simple and reliable manner.

[0005] This object is achieved by a shift actuator comprising the features of claim 1. Preferred embodiments of the invention are set out in the dependent claims.

[0006] According to the invention, the rotating member comprises a hollow cylindrical sleeve provided with first cam followers projecting inwardly from the inner wall of the sleeve. The driven part comprises a first cylindrical cam having helical cam grooves on its outer wall configured to accommodate the first cam followers. The first cylindrical cam is supported in the sleeve by a central rod so as to be slidable in the sleeve in the axial direction along the central rod but locked against rotational movement about the axial direction relative to the central rod. The central rod is in turn supported in the housing so as to be movable in the axial direction but locked against rotational movement about the axial direction relative to the housing. The central rod carries a second end stop coupled at a distance from the first cylindrical cam. The central rod is configured to project from the housing and to be linked to the shift fork for driving it. A compression mechanism is provided between the second end stop and the first cylindrical cam and is configured to extend the central rod from the first cylindrical cam by biasing the second end stop away from the first cylindrical cam, wherein this biasing movement of the central rod is limited by a first end stop on the central rod which abuts the first cylindrical cam on the side opposite the compression mechanism. The helical cam grooves are arranged and configured such that a rotation of the sleeve in a first rotational direction moves the first cylindrical cam axially in a first direction by the movement of the first cam followers along the helical cam grooves, wherein this movement is transmitted in the first direction by the compression mechanism and the second end stop to the central rod to drive the linked shift fork from the neutral position towards the first gear engagement position, and such that a rotation of the sleeve in a second rotational direction moves the first cylindrical cam in a second, opposite direction by the movement of the first cam followers along the helical cam grooves, the movement of the first cylindrical cam being transmitted in the second direction directly to the central rod by the first end stop to drive the linked shift fork from the first gear engagement position back to the neutral position.

[0007] The actuation feature of this shift actuator is asymmetric, when the first cylindrical cam is moved in a first direction to move the shift fork from neutral to first gear, the movement of the first cylindrical cam is transmitted to the compression mechanism and further from the compression mechanism (through the second end stop) to the center rod, while when the first cylindrical cam is moved in a second, opposite direction to move the shift fork from first gear to neutral position, the movement of the first cylindrical cam is transmitted directly from the first cylindrical cam (i.e. not through the compression mechanism) to the center rod through the first end stop. In this way, when the center rod is moved in a first direction to move from neutral to first gear, it acts in a compliant or yielding manner, meaning that when the shift fork is blocked, the movement of the first cylindrical cam is absorbed by the compression mechanism, compressing and storing actuation force without further moving the center rod; once the blocked state of the shift fork is released, the expansion movement of the compression mechanism moves the center rod to move the shift fork to the first gear engagement position. On the other hand, in the second, opposite direction, the center rod is driven by the first cylindrical cam in a rigid or direct contact manner, which exerts force directly through the first end stop of the center rod. In this way, the linear drive mechanism can be driven in a full cycle in the first direction, from the position corresponding to neutral to the first gear engagement position, where, in the case of the center rod acting on a blocked shift fork, the movement is partially absorbed by the compression mechanism. After the blocked state of the shift fork is released, the compression energy saved in the compression mechanism is released and moves the center rod, moving the shift fork to the first gear engagement position. In this way, when the first cylindrical cam is moved in the first direction, the actuation force applied by the linear drive assembly is mechanically stored in a simple and reliable manner in the compression mechanism, and as soon as the blocked state of the shift fork is released, the driving force will be released at any time.

[0008] In a preferred embodiment, a symmetrical arrangement of two cylindrical cams (one on each side of the compression mechanism) is provided on the central rod, which is capable of driving the central rod from the neutral position in the first axial direction to a first gear engagement position and from the neutral position in the second axial direction to a second gear engagement position in the opposite direction of the first. In particular, in this embodiment, a second cylindrical cam is provided between the second end stop and the compression mechanism, wherein the second cylindrical cam, like the first, is supported by the central rod for axial movement, but is locked against rotational movement about the axial direction relative to the central rod, wherein the second cylindrical cam is biased towards the second end stop by the compression mechanism. In other words, the compression mechanism biases the first cylindrical cam towards the first end stop on the central rod and the second cylindrical cam towards the second end stop on the central rod. The sleeve is provided with a second cam follower, which is arranged in the sleeve in circumferential alignment with the first cam follower and is accommodated in a helical cam groove of the second cylindrical cam. Each helical cam groove extends over about 180° around the circumference of the respective cylindrical cam, while the remaining circumferential portion of the surface of the respective one of the first and second cylindrical cam is a recessed portion, which, when it is located in the associated recessed portion, enables the respective one of the first and second cam followers to move freely in the axial direction in the recessed portion. In practice, when both the first and second cam followers are partially located within their associated cam groove, there is a small overlap area in the positioning around. Since the extension of the first and second cam followers in their associated cam groove is limited, a certain rotational movement of the sleeve is required until one of the first and second cam followers is fully in the associated cam groove and the other is fully out of its associated cam groove and fully in the associated recessed portion. For simplicity of the description, this small rotational overlap area is not mentioned in the following.

[0009] The helical cam grooves of the first and second cylindrical cams are offset 180° in rotational direction relative to each other, such that when the first cam follower is engaged in the cam groove of the first cylindrical cam, the second cam follower is located in the recessed portion of the second cylindrical cam, such that when the center rod is in a position corresponding to the neutral position of the coupled shift fork, rotation of the sleeve in the second rotational direction moves the second cylindrical cam in the second direction, which movement is transmitted to the center rod through the compression mechanism (through the first cylindrical cam and the first end stop) to drive the coupled shift fork from the neutral towards the second gear engagement position, and such that when the center rod is in a position corresponding to the second gear engagement position of the coupled shift fork, rotation of the sleeve in the first rotational direction moves the second cylindrical cam in the first direction, which movement is transmitted directly to the center rod through the second end stop to drive the coupled shift fork from the second gear engagement position back to the neutral position. Thus, the actuation profile for the movement of the coupled shift fork from the neutral position to the second gear engagement position is also asymmetric, in the sense that the actuation movement of the center rod to move the coupled shift fork from the neutral to the second gear engagement position is compliant, and the actuation movement of the second cylindrical cam in the opposite direction is able to be absorbed by compression of the compression mechanism in case the shift fork is blocked, wherein once the blocked state is released, the compression of the compression mechanism provides the driving force for completing the movement of the shift fork to the second gear engagement position, while the actuation movement of the second cylindrical cam in the opposite direction moves the coupled shift fork from the second gear engagement position to the neutral position is transmitted directly (through the second end stop) to the center rod, such that when the coupled shift fork is moved from the second gear engagement position back to the neutral, the force is transmitted to the center rod in a rigid manner. Thus, the actuation profile of the second cylindrical cam movement is symmetrical to the actuation movement of the first cylindrical cam as described above.

[0010] In a preferred embodiment, the compression mechanism comprises a compression spring extending in axial direction along the center rod from the first cylindrical cam towards the second end stop on the center rod to bias the second end stop away from the first cylindrical cam.

[0011] In a preferred embodiment, the center rod has a non-circular cross-sectional shape, and each of the first and second cylindrical cams has a complementary cross-sectional shape opening, such that when the center rod is accommodated in the openings of the first and second cylindrical cams, the center rod allows a sliding movement of the first and second cylindrical cams in axial direction, but locks the first and second cylindrical cams against rotational movement around the axial direction. For this purpose, for example, the non-circular cross-sectional shape can be formed by any type of keying surface of the center rod, for example, a planar surface portion adjoining a complementary planar surface portion in the opening of the cylindrical cam.

[0012] In a preferred embodiment, the compression mechanism and the sliding resistance of the axial movement on the central rod of the first barrel cam are arranged such that, once a predetermined threshold force acts between the first barrel cam and the central rod, the first barrel cam starts to move and the compression mechanism starts to compress. In this way, it is possible to achieve that the first barrel cam is held on the central rod in a less floppy manner, while the barrel cam is able to react and move relative to the central rod when the central rod is blocked by a larger counter force.

[0013] In a preferred embodiment, the second barrel cam has the same shape as the first barrel cam, but the second barrel cam is arranged 180° rotated relative to the first barrel cam such that the two corresponding end surfaces of the first and second barrel cam face each other, wherein the second barrel cam is arranged 180° rotated relative to the first barrel cam around the axial direction. With this arrangement, the helical cam grooves of the first and second barrel cam have the same shape and arrangement on the respective barrel cam and cooperate with the respective one of the first and second cam followers in a symmetrical manner for the first and second barrel cam. BRIEF DESCRIPTION OF DRAWINGS

[0014] The application will be described below with reference to the embodiments shown in the drawings, in which:

[0015] Figure 1 a cross-sectional view of a shift actuator according to the application is shown;

[0016] Figure 2 a schematic perspective view of the main components of an embodiment of a shift actuator according to the application is shown;

[0017] Figures 3 to 8 a partially cross-sectional schematic view of several actuation steps of a shift actuator is shown;

[0018] Figure 9 a schematic cross-sectional view of an alternative embodiment of a shift actuator according to the application is shown; and

[0019] Figure 10 a functional diagram showing Figures 1 to 8 the actuation characteristics of the shift actuator of the embodiment shown in Fig. 6, wherein the actuation movement achieved by the shift actuator is shown as a function of the rotation angle of the rotation member of the linear drive assembly of the shift actuator. DETAILED DESCRIPTION

[0020] The application will first be described with reference to a simple embodiment shown in Figure 9 Fig. 1, Figure 9A schematic partial cross-sectional view of a shift actuator is shown, which is capable of switching a coupled shift fork 50 from a neutral position N to a first gear engagement position and back again to the neutral position. The shift actuator comprises a rotating member in the form of a cylindrical hollow sleeve 4, which is driven by an electric motor (not shown) to selectively rotate in a first rotational direction and in an opposite second rotational direction. The cylindrical sleeve 4 is supported in a housing (not shown) of the actuator to be rotatable about a defined axial rotation axis of the sleeve 4, wherein the sleeve 4 is supported such that it is not movable in axial direction relative to the housing. The sleeve 4 is provided with a first cam follower 6 protruding radially inward from the sleeve inner wall. The first cam follower 6 is shown as a short cylindrical pin.

[0021] The shift actuator further comprises a first cylindrical cam 10, which is also substantially cylindrical and accommodated inside the sleeve 4. The cylindrical cam 10 is supported by a central rod 30, which extends axially into the sleeve 4 and protrudes from the sleeve 4 to be coupled to the shift fork 50. The central rod 30 is accommodated in an opening of the first cylindrical cam 10, wherein the cross-sectional shape of the central rod is non-circular and the cross-sectional shape of the opening of the first cylindrical cam 10 has a complementary non-circular shape, such that the cylindrical cam 10 is axially slidable along the central rod 30, while it is locked against rotational movement about the rotation axis of the sleeve 4.

[0022] When the sleeve 4 is rotated in the first rotational direction, the first cam follower 6 slides along a helical cam groove 12 formed in the surface of the cylindrical cam 10. Since the axial position of the first cam follower does not change during its movement within the cam groove 12, the first cylindrical cam 10 is forced to move in a first direction, to the left in Figure 9 The movement of the first cylindrical cam 10 in the first direction is transmitted by a compression mechanism 40, here in the form of a compression spring, to a second end stop 34, which is fixed to the central rod 30 at a distance from the first cylindrical cam 10. When the shift fork 50 is free to move in the left-hand direction to the first gear engagement position, the movement of the first cylindrical cam 10 to the left is transmitted by the spring 40 to the central rod (via the second end stop 34), so that the coupled shift fork 50 moves to the first gear engagement position. Figure 9 On the other hand, if the shift fork 50 is blocked in the right-hand direction, the movement of the first cylindrical cam 10 to the right is transmitted by the spring 40 to the central rod (via the second end stop 34), so that the coupled shift fork 50 moves to the neutral position N. Figure 9The movement of the first cam 10 to the left-hand side, shown in the position, will cause the compression mechanism 40 to compress, as the shift fork 50 is blocked, the central rod 30 cannot move to the left-hand side, thus causing compression of the compression mechanism 40. When the blocking state of the shift fork 50 is released, the compressed compression mechanism 40 expands, thus moving the central rod 30 and the coupled shift fork to the left-hand side, so that the shift fork 50 comes to the first gear engagement position.

[0023] If the sleeve 4 is rotated in the opposite second rotational direction in this state, the cam 10 moves back to the right-hand side to Figure 9 the position shown, thus pulling the central rod 30 back and moving the coupled shift fork 50 from the first gear engagement position back to the neutral position. During the movement of the first cam 10 to the left-hand side, it pushes against the first end stop 32 fixed on the central rod, thus causing the force to be transmitted directly from the cam to the central rod 30.

[0024] In this way, when the shift actuator attempts to move the coupled shift fork 50 from the neutral to the first gear engagement position, the actuation characteristic of the shift actuator is compliant or yielding, whereas when it is moved from the first gear engagement position back to the neutral position, there is a non-yielding force transmitted directly from the first cam 10 to the central rod 30 and the coupled shift fork 50. Figure 9 In this way, when the shift actuator attempts to move the coupled shift fork 50 from the neutral to the first gear engagement position, the actuation characteristic of the shift actuator is compliant or yielding, whereas when it is moved from the first gear engagement position back to the neutral position, there is a non-yielding force transmitted directly from the first cam 10 to the central rod 30 and the coupled shift fork 50.

[0025] In the following, we describe a shift actuator which is able to move a coupled shift fork from the neutral in a first direction to a first gear engagement position and from the neutral in an opposite second direction to a second gear engagement position, wherein in both directions the actuation is compliant or yielding when moving from the neutral to the gear engagement position, whereas a direct, rigid force transmission is implemented when moving from one of the gear engagement positions back to the neutral position.

[0026] Figure 1 A sectional view of this embodiment is shown, which comprises a hollow cylindrical sleeve 4 which is rotatably supported in the housing of the shift actuator, but is not movably supported in the direction defined by the rotation axis of the sleeve 4 with the corresponding movement. In Figure 1 Ball bearings are shown in the two end portions of the sleeve 4, which rotatably support the sleeve 4.

[0027] The central rod 30 extends within the sleeve and protrudes from the sleeve and the housing of the shift actuator. The central rod 30 supports the first and second barrel cams 10, 20 which are slidably supported on the central rod but are locked against rotational movement about the axial direction relative to the central rod. The central rod 30 is supported to be movable in the axial direction but rotational movement about an axis parallel to the axial direction is prevented.

[0028] The movement of the first barrel cam 10 to the left hand side is limited by a first end stop 32 fixed on the central rod 30, while the movement of the second barrel cam 20 to the right hand side is limited by a second end stop 34 fixed on the central rod 30. Between the first and second barrel cams 10, 20 a compression mechanism 40, here in the form of a compression spring, acts which pushes the first barrel cam 10 towards the first end stop 32 and the second barrel cam 20 towards the second end stop 34.

[0029] Reference will now be made to Figure 2 the cooperation of the sleeve 4 with the first and second barrel cams 10, 20, Figure 2 a schematic perspective view showing the main components of the shift actuator, wherein the outer sleeve 4 is shown in a transparent manner by means of dashed lines to make the interior of the sleeve visible. The central rod 30 extends within the sleeve 4, one end of which protrudes beyond the sleeve 4 (and indeed also from the housing of the shift actuator as Figure 1 shown). The central rod 30 supports the first and second barrel cams 10, 20 inside the sleeve 4, wherein the first and second barrel cams are slidable along the central rod 30 in the axial direction but are locked against rotational movement about the axial direction relative to the central rod. The first barrel cam 10 is provided with a helical cam groove 12 which is formed in the surface of the first barrel cam 10 and extends about 180° around the circumference of the first barrel cam. Likewise, the second barrel cam 20 is provided with a helical cam groove 22 which extends about 180° around the circumference of the second barrel cam 20, wherein in Figure 2 the figure it is seen that only the beginning or entrance of the cam groove 22 is visible, while the remainder is not visible since it is located at the back of the second barrel cam 20. The remaining circumferential surface portion of the second barrel cam outside the cam groove 22 is a recessed portion 24. The first barrel cam 10 is likewise provided with a recessed portion 14 in the circumferential portion thereof outside the first cam groove 12.

[0030] The sleeve 4 is provided with a first cam follower 6 and a second cam follower 8 which protrude from the inner wall of the sleeve to extend radially inwardly within the sleeve to a certain extent. In Figure 2In this position, the first cam follower 6 is shown as a flat pin located at the entry of the cam groove 12 of the first cylindrical cam 10 and the second cam follower 8 is in this position located at the opposite entry of the cam groove 22 of the second cylindrical cam 20.

[0031] If the sleeve 4 is rotated in a clockwise direction (when looking at the first end stop 32) the first cam follower 6 slides further along the cam groove 12 from the entry point of the cam groove 12, which causes the first cylindrical cam 10 to move in an axial direction to the right hand side, while at the same time the second cam follower 8 leaves the entry of its associated cam groove 22 and enters the recessed portion 24 of the second cylindrical cam 20. This means that, in addition to the position shown in Figure 2 Figure 2 and 3 the positioning of the first and second cylindrical cams 6, 8 is alternating, i.e. when the first cam follower 6 is engaged in the cam groove 12 of the first cylindrical cam 10, the second cam follower 8 is in the recessed portion 24 of the second cylindrical cam 20, so the second cylindrical cam 20 can move in a sliding motion along the central rod 30, because the second cam follower 8 can move freely in an axial direction with respect to the recessed portion 24 of the second cylindrical cam, and when the second cam follower 20 is engaged within its associated cam groove 22, the first cam follower 6 has reached the recessed portion 14 of the first cylindrical cam 10, so that the first cylindrical cam can slide in an axial direction on the central rod 30 with respect to the sleeve 4, because the first cam follower 6 can move freely in an axial direction within the recessed portion 14 of the first cylindrical cam 10. In other words, if one of the two cylindrical cams 10, 20 is driven by the rotation of the sleeve 4 and the engagement of the corresponding cam follower in the cam groove of the corresponding cylindrical cam and thus moves in an axial direction with respect to the sleeve 4, the other one of the first and second cylindrical cams 10, 20 is decoupled from the sleeve 4, because its associated cam follower is located in the recessed portion of the other one of the first and second cylindrical cams 10, 20. This means that, when one of the cam cylinders 10, 20 is moved axially by the rotation of the sleeve and the engagement of the associated cam follower in its cam groove, the other one of the cylindrical cams driven by the movement of the moved cylindrical cam is free to move axially with respect to the central rod by the force transmission through the compression mechanism and, therefore, in the case that the shift fork, whose axial movement should be blocked, is blocked, the other cylindrical cam can move

[0032] This alternating driving scheme of the two cylindrical cams 10, 20 will now be described with reference to the plurality of movement steps shown in Figures 3 to 8 .

[0033] In the position shown in Figure 3 ​In the schematic diagram, the position of the center rod 30 of the shift actuator is shown, in which the coupled shift fork 50 is in the neutral position. If the sleeve 4 is now rotated in the first rotational direction, so that the first cam follower 6 is moved, about 180° along the cam groove 12 to the opposite end of the cam groove 12 (the end point of this movement is shown in Figure 4 ), the first cylindrical cam 10 is moved in the axial direction (shown by arrow 1 in the first direction) to the left-hand side to reach the positioning as shown in Figure 4 . If the shift fork 50 coupled to the center rod is free to move, this movement of the first cylindrical cam 10 in the first direction 1 is transmitted via the compression mechanism 40 to the second cylindrical cam 20, so that likewise the second cylindrical cam 20 is moved axially by the second end stop 34 to drive the center rod 30, the movement of which is transmitted to the shift fork 50, which is thus moved to the first gear engagement position as shown in Figure 4 .

[0034] Figure 5 and Figure 6 The same rotational movement steps of the sleeve 4 are shown, when the shift fork 50 coupled to the center rod 30 is blocked. In this case, the first cylindrical cam 10 has been driven to the same axial movement to the left-hand side in the first direction 1 as in Figure 4 , but since the center rod 30 is blocked by the blocked shift fork 50, the axial movement of the first cylindrical cam 10 in the first direction 1 cannot be transmitted to the second cylindrical cam 22, so that the first cylindrical cam is moved in a sliding manner relative to the center rod 30, so that the compression mechanism 40 is included between the first and second cylindrical cams 10, 20. During the compression movement of the compression mechanism 40 and the sliding movement of the second cylindrical cam 20 closer to the first cylindrical cam 10, the second cam follower 8 associated with the second cylindrical cam 20 is moved in the axial direction relative to the recessed portion 24 of the second cylindrical cam 20, as can be seen when comparing Figure 4 and Figure 6 .

[0035] When the shift actuator is in the situation as shown in Figure 6 , the blocked state of the shift fork 5 ends, the actuation force stored in the compressed compression mechanism 40 is released to expand the compression mechanism 40 again, which drives the axial movement of the second cylindrical cam 20 to the left-hand side in the first direction 1 Figure 6 , the movement of the second cylindrical cam 20 is transmitted to the center rod 30 via the end stop 34, so that the coupled shift fork 50 is moved to the first gear engagement position as shown in Figure 7 .

[0036] In order to move from the first gear engagement position as shown in Figure 7the sleeve 2 is rotated in a second direction opposite to the first direction, thereby causing an axial movement of the first cam cylinder 10 in the second direction, as indicated by arrow 2, and Figure 8 The first cam cylinder 10 is moved to the right-hand side by means of arrow 2. The movement of the first cam cylinder 10 to the right-hand side in the second direction is transmitted to the central rod 30 by means of the first end stop 32, thereby pulling the shift fork 50 from the Figure 7 first gear engagement position to the Figure 8 neutral position, as indicated.

[0037] When the sleeve 4 is in the state of Figure 8 , a further rotation of the sleeve in the second rotational direction, the second cam cylinder 20 is axially driven in the second direction of arrow 2 relative to the sleeve 4, which movement is transmitted to the coupled shift fork 50 by means of the central rod 30 to move it from the neutral to the second gear engagement position. If in the Figure 8 case the shift fork 50 is blocked when the sleeve 4 is rotated in the second rotational direction to move the second cam cylinder 20 in the second direction 2, the second cam cylinder 20 has to move axially relative to the central rod 40, which is blocked by the blocked shift fork 50, so that the movement of the second cam cylinder 20 to the right-hand side in the second direction 2 compresses the compression mechanism 40. If the compression mechanism 40 is already in a compressed state and the blocked state of the shift fork 50 ends, the force released by the expanding compression mechanism will pull the central rod 30 in the second direction 2 to bring the coupled shift fork 50 from the neutral position to the second gear engagement position.

[0038] Figure 10 the functional diagram shows the actuation characteristics of the above-described embodiment of Figures 1 to 8 . Figure 10 The linear displacement of the central rod of the shift actuator in the axial (full line) direction is shown as a function of the rotational angle of the sleeve 4 relative to the first and second cam cylinders. There is a small angular range around 0°, in which there is no displacement as a function of the rotational angle of the sleeve (horizontal part of the full line). This is due to the fact that in the state shown in Figure 3 , a rotation of the sleeve 4 in either direction does not immediately result in an axial displacement of one of the first and second cam cylinders 10, 20, but only after the associated one of the cam followers 6, 8 has fully moved into the associated one of the cam grooves 12, 22, and once this initial rotational phase of the angle has been passed, the engagement of the associated one of the cam followers 6, 8 causes a linear displacement of the associated one of the first and second cam cylinders 10, 20, as indicated in Figure 10The linear displacement shown by the solid straight line occurs if the coupled shift fork follows the movement from the neutral state to the first or second gear engagement position freely. The linear displacement is shown by a solid line at positive angles of rotation and by a linearly descending solid line at negative angles of rotation, wherein this linear displacement occurs if the coupled shift fork follows the movement from the neutral state to the first or second gear engagement position freely.

[0039] Figure 10 Shift fork blocking situations are also shown, which are indicated in the "jaw-to-jaw scenario" region, meaning that the shift fork cannot be moved into the corresponding engagement position because of a jaw-to-jaw confrontation between the two components to be engaged, which prevents the engagement. For these situations, the movement state of the center rod is shown by a dashed line, which extends substantially horizontally at the beginning since the center rod is blocked. The development of the spring force is also shown in the region indicated by "jaw-to-jaw scenario" (in the superimposition in solid line, showing the spring force as a function of the angle of rotation), with further rotational movement of the sleeve relative to the first and second cam, wherein the spring force increases with further compression of the compression mechanism. As soon as the jaw-to-jaw confrontation ends, the blocked shift fork can be moved freely, and the center rod then moves axially due to the release of the load of the compression mechanism (indicated by a rapid drop in the spring force). The release of the compression mechanism is accompanied by an axial displacement of the center rod, as shown by the rapidly increasing (decreasing) dashed line near the end of the 180° (-180°) rotational range, which illustrates that the center rod moves the shift fork into the corresponding gear engagement position at this stage.

[0040] From Figure 10 It can also be seen that the center rod initially also moves a certain distance in the axial direction in the event of a blocking of the shift fork until its movement is blocked by the shift fork. The reason is, on the one hand, that the coupling of the center rod to the shift fork makes it necessary for the center rod to be moved first towards the shift fork until a force transmission connection is established at the interface between the center rod and the shift fork. On the other hand, the two components to be engaged must first be moved relative to each other until their respective jaws are moved into the same plane, so that a blocking situation can occur.

Claims

1. Gear shift actuator comprising a linear drive assembly having a rotary member supported within a housing, rotatable but not movable in an axial direction defined by its axis of rotation, an electric motor for rotating the rotary member, and a driven part engaged by the rotary member to convert rotational movement of the rotary member into linear movement of the driven part in the axial direction for driving a shift fork from a neutral position to a first gear position engagement position and back to the neutral position when the rotary member is driven to rotate in a first rotational direction and in a second rotational direction opposite to the first rotational direction, respectively, characterized in that the rotary member comprises a hollow cylindrical sleeve (4) provided with a first cam follower (6) protruding inwardly from an inner wall of the hollow cylindrical sleeve (4), the driven part comprises a first cylindrical cam (10) having a helical cam groove (12) in its outer wall configured to accommodate the first cam follower (6), and the first cylindrical cam is supported in the hollow cylindrical sleeve (4) by a central rod (30) to be slidably movable in the hollow cylindrical sleeve along the central rod (30) in the axial direction but locked against rotational movement relative to the central rod (30) about the axial direction, the central rod (30) is supported within the housing to be movable in the axial direction but locked against rotational movement about the axial direction, and carries a second end stop (34) coupled thereto at a distance from the first cylindrical cam (10), the central rod (30) is configured to protrude from the housing and to be linked to a shift fork for driving the shift fork, a compression mechanism (40) is configured to extend the central rod (30) from the first cylindrical cam (10) by biasing the second end stop (34) away from the first cylindrical cam (10), wherein the biasing movement is limited by the first end stop (32) on the central rod (30) abutting against the first cylindrical cam (10), and the helical cam groove is configured such that rotation of the hollow cylindrical sleeve (4) in the first rotational direction moves the first cylindrical cam (10) axially in a first direction, which movement is transmitted by the compression mechanism (40) to the central rod (30) to drive the coupled shift fork (50) from the neutral position towards the first gear position engagement position, and such that rotation of the hollow cylindrical sleeve (4) in the second rotational direction moves the first cylindrical cam in a second opposite direction, which movement is transmitted to the central rod (30) to drive the coupled shift fork (50) from the first gear position engagement position to the neutral position.

2. Gear shift actuator according to claim 1, characterized in that ​ ​ ​ ​ ​ Between the second end stop (34) and the compression mechanism (40), a second cylindrical cam (20) is supported by the central rod (30) for axial movement but locked against rotational movement about the axial direction relative to the central rod, the second cylindrical cam (20) being biased by the compression mechanism (40) towards the second end stop (34), The hollow cylindrical sleeve (4) is provided with a second cam follower (8) which is circumferentially aligned with the first cam follower (6) and accommodated in a helical cam groove (22) of the second cylindrical cam (20), Each helical cam groove (12, 22) extends 180° around the circumference, while the remaining circumferential portion of the respective cylindrical cam surface is a recessed portion (14, 24), such that the respective cam follower (6, 8) is free to move in the axial direction in the recessed portion (14, 24), The helical cam grooves (12, 22) of the first and second cylindrical cams (10, 20) are offset 180° in the rotational direction relative to each other, such that when the first cam follower (6) enters the helical cam groove (12) of the first cylindrical cam (10), the second cam follower (8) exits its helical cam groove and enters the recessed portion (24) of the second cylindrical cam (20), such that when the central rod (30) is in a position corresponding to the neutral position of a coupled shift fork, rotation of the hollow cylindrical sleeve (4) in the second rotational direction moves the second cylindrical cam (20) in the second direction (2), which movement is transmitted by the compression mechanism (40) to the central rod (30) to drive a coupled shift fork (50) from the neutral position towards a second gear engagement position, and such that, when the central rod (30) is in a position corresponding to the second gear engagement position of a coupled shift fork, rotation of the hollow cylindrical sleeve (4) in the first rotational direction moves the second cylindrical cam (20) in the first direction (1), which movement is transmitted to the central rod (30) to drive a coupled shift fork (50) from the second gear engagement position back to the neutral position.

3. The shift actuator of claim 1, wherein The compression mechanism (40) is formed by a compression spring extending in the axial direction from the first cylindrical cam (10) along the central rod in a direction away from the second end stop (34) of the first cylindrical cam (10) on the central rod (30) to bias the second end stop (34) away from the first cylindrical cam (10).

4. The shift actuator of claim 2, wherein, The compression mechanism (40) is formed by a compression spring extending in the axial direction from the first barrel cam (10) along the center rod in a direction towards the center rod (30) away from the second end stop (34) of the first barrel cam (10) to bias the second end stop (34) away from the first barrel cam (10).

5. The shift actuator of claim 2, wherein, The center rod has a non-circular cross-sectional shape and each of the first barrel cam (10) and the second barrel cam (20) has a complementary cross-sectional shape opening such that when the center rod (30) is received in the openings of the first barrel cam (10) and the second barrel cam (20), the center rod allows sliding movement of the first barrel cam (10) and the second barrel cam (20) in the axial direction but locks the first barrel cam (10) and the second barrel cam (20) to prevent any rotational movement thereof about the axial direction.

6. The shift actuator of claim 5, wherein, The compression mechanism (40) is formed by a compression spring extending in the axial direction from the first barrel cam (10) along the center rod in a direction towards the center rod (30) away from the second end stop (34) of the first barrel cam (10) to bias the second end stop (34) away from the first barrel cam (10).

7. The shift actuator according to any one of claims 2, 4, 5 and 6, characterized by, The sliding resistance of the compression mechanism (40) and the first barrel cam (10) to axial movement on the center rod (30) is arranged such that once a predetermined threshold force acts between the first barrel cam (10) and the center rod (30), the first barrel cam begins to move along the center rod and begins to compress the compression mechanism (40).

8. The shift actuator of any one of claims 1 and 3, wherein, The sliding resistance of the compression mechanism (40) and the first barrel cam (10) to axial movement on the center rod (30) is arranged such that once a predetermined threshold force acts between the first barrel cam (10) and the center rod (30), the first barrel cam begins to move along the center rod and begins to compress the compression mechanism (40).

9. The shift actuator of any of claims 2, 4, 5, and 6, wherein, The second barrel cam (20) has the same shape as the first barrel cam (10) but is rotated 180° relative to the first barrel cam (10) such that their respective front faces face each other, wherein the second barrel cam is further rotated 180° about the axial direction relative to the first barrel cam (10).

10. The shift actuator of claim 7, wherein, The second barrel cam (20) has the same shape as the first barrel cam (10) but is rotated 180° relative to the first barrel cam (10) such that their respective front faces face each other, wherein the second barrel cam is further rotated 180° about the axial direction relative to the first barrel cam (10).

Images