Electromagnetically-actuated dog clutch and method of mounting shift sleeve of electromagnetically-actuated dog clutch

Abstract

To reduce the space required for an electromagnetically-actuated dog clutch, particularly in the radial direction, and facilitate mounting.SOLUTION: An electromagnetically-actuated dog clutch comprises: a shift sleeve that has an internal tooth and is received axially movably on an external tooth of a transmission shaft to rotate together with the transmission shaft; an actuator that has a magnet coil and is configured to move the shift sleeve axially on the transmission shaft into a first shift position; a spring element that cooperates with the shift sleeve and acts on the shift sleeve in a direction opposite to a movement caused by the actuator in the direction of a second shift position; and a support ring that is plugged onto the transmission shaft, is disposed in an axial direction of the shift sleeve between the spring element and the internal tooth of the shift sleeve and is fixed to the transmission shaft in the axial direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electromagnetically actuated dog clutch having a shift sleeve and a method of mounting the shift sleeve of an electromagnetically actuated dog clutch to a transmission shaft. [Background technology]

[0002] In an electromagnetically actuated dog clutch, the shift sleeve is typically electromagnetically attracted to one of two shift positions by a magnetic field generated by a coil and biased to the other shift position by a spring, which must therefore be located within the clutch assembly and supported against a reaction force. DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0003] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to reduce the space required, particularly radially, for an electromagnetically actuated dog clutch while also facilitating installation. [Means for solving the problem]

[0004] This object is achieved by an electromagnetically actuated dog clutch comprising a shift sleeve having internal teeth, axially movably received on the external teeth of a transmission shaft and rotating together with the transmission shaft, an actuator having a magnetic coil and configured to move the shift sleeve axially on the transmission shaft to a first shift position, a spring element cooperating with the shift sleeve and acting on the shift sleeve in a direction towards a second shift position, the direction being opposite to the movement caused by the actuator, and a support ring inserted on the transmission shaft, arranged in the axial direction of the shift sleeve between the spring element and the internal teeth of the shift sleeve and fixed to the transmission shaft in the axial direction.

[0005] Since the support ring is fixed directly to the transmission shaft, a radially very compact assembly is achieved and can be mounted, for example, by simply pressing it axially onto the transmission shaft.

[0006] The external teeth of the transmission shaft are formed, for example, on a known clutch body that is connected to the transmission shaft and rotates together, and an idler gear having external teeth that is connected to the transmission shaft is disposed adjacent to the clutch body in the axial direction. The idler gear and the transmission shaft are connected to rotate together by the internal teeth of a shift sleeve meshing with the external teeth of the idler gear to shift the respective gears.

[0007] The dog clutch is preferably designed as a normally open clutch, with the first shift position corresponding to a closed position of the dog clutch and the second shift position corresponding to an open position of the dog clutch, but the principles of the invention can also be implemented with a normally closed dog clutch.

[0008] The support ring has a surface against which the spring element rests against the force transmitted by the shift sleeve and forms an axially oriented reaction surface for the spring element.

[0009] The support ring is, for example, an axially rigid metal ring, which is always a separate part from the transmission shaft and its external teeth. Preferably, the support ring has sufficient radial elasticity to be pressed against the external teeth of the transmission shaft. In general, the support ring may be made of a spring material to prevent plastic deformation as far as possible.

[0010] The spring element may, for example, consist of a plurality of disc springs arranged axially side by side on the external teeth of the transmission shaft.

[0011] In a preferred variant, the shift sleeve is made up of several parts fixed to each other. For example, the shift sleeve has an engagement ring on which the internal toothing is formed and a shift ring fixed to the engagement ring and cooperating with the actuator, the shift ring being arranged radially outside the engagement ring and the support ring being arranged axially next to the engagement ring. In this way, the spring element and the support ring can be easily integrated into a prefabricated assembly for mounting the shift sleeve. Furthermore, it is easy to realize a shift sleeve made of several different materials, for example having different magnetic and mechanical properties.

[0012] In particular, the shift ring should be made of a ferromagnetic material adapted to be displaced by the actuator. In a preferred variant, the magnetic field of the actuator generates a reluctance force on the shift ring, which attracts the shift sleeve to the actuator, maximizing the inductance of the magnetic circuit.

[0013] The shift sleeve preferably has a receiver for the support ring and the spring element. For this purpose, the shift ring can extend axially over the support ring and the spring element, i.e. the shift ring can be arranged radially outside the support ring and the spring element. Furthermore, the support ring should have a transverse axial stop for the spring element, which connects the spring element to the shift sleeve and transmits the spring force of the spring element to the shift sleeve. The spring element is preferably arranged between the axial stop and the support ring and is axially clamped between these components.

[0014] The support ring may be radially shorter than the engagement ring and radially spaced apart from the shift ring. In this manner, magnetic flux from the shift ring to the support ring may be reduced. Since the support ring does not contribute to the shift force, it is preferably made of a non-ferromagnetic material.

[0015] The internal toothing of the shift sleeve has, for example, a plurality of radial stop projections, each of which cooperates with a stop groove of the external toothing of the transmission shaft to define an end position of the shift sleeve in the second shift position of the dog clutch. For example, some of the teeth of the internal toothing each have a radial projection that is axially arranged to abut an axial end of the associated stop groove when the shift sleeve is in the second shift position.

[0016] A stop protrusion contacting an end face of the idler gear at the first shift position can be used to limit shift movement to and define the first shift position.

[0017] The actuator's magnetic coil may be surrounded by an annular actuator housing, which together with the shift ring forms the actuator's magnetic circuit.

[0018] The support ring preferably has a seating surface for the shift sleeve, which is formed with a geometric structure that reduces contact between the shift sleeve and the support ring. This structure must be designed to reduce adhesion forces between the support ring and the shift sleeve, such as due to oil films and / or magnetic forces. For example, the support ring may have an L-shaped axial cross section or may have protrusions distributed along the radial and / or circumferential direction. The surface of the shift sleeve that comes into contact with the seating surface is, for example, the side surface of the engagement ring.

[0019] The above object is also achieved by a method for mounting a shift sleeve of an electromagnetically actuated dog clutch on a transmission shaft, as described above, comprising the steps of: - forming an assembly by placing a support ring and a spring element on the shift sleeve; and - pushing the assembly onto the external teeth of the transmission shaft up to a predefined end position of the support ring, which is axially fixed to the transmission shaft in its predefined end position.

[0020] To manufacture the assembly, the engagement ring, the support ring and the spring element are aligned axially, and then the shift ring is placed radially on these elements and welded to the engagement ring. In this way, a receptacle is formed, into which the support ring and the spring element are placed at the same time. The support ring and the spring element can thus be easily preassembled on the shift sleeve and therefore can be treated together as a single component. The assembly then only needs to be pressed into the desired axial position on the external toothing of the transmission shaft. Usually, the support ring initially rests against the side of the engagement ring and is pressed into the transmission shaft by the engagement ring.

[0021] The above radial stop protrusions and stop grooves define a predetermined end position for the support ring. When the assembly is pressed into the external teeth of the transmission shaft, the sliding movement stops when the stop protrusions hit the axial ends of the stop grooves and stop. Thus, the support ring reaches the correct axial position on the transmission shaft without any further movement. Thus, the tolerances in the assembly are also automatically compensated.

[0022] In the predefined end position, the support ring is automatically fixed axially on the transmission shaft, preferably without any further work steps.

[0023] The support ring is fixed to the transmission shaft so that the frictional force of the transmission shaft alone can hold the support ring in a defined end position. For this purpose, a closed support ring is used in particular. This has the advantage that the support ring does not create an imbalance. This variant is therefore particularly suitable for high speeds.

[0024] When the dog clutch is shifted, the support ring is pressed against the transmission shaft with an axial force higher than that applied by the actuator, so that the support ring does not shift during normal operation of the clutch.

[0025] If necessary, pressing can be assisted by applying heat, which temporarily expands the support ring radially and allows it to move to its defined end position on the transmission shaft. Upon cooling, the support ring contracts again and is fixed firmly on the transmission shaft.

[0026] In a further variant, the support ring is fixed to the transmission shaft by engaging in a radial groove of the external toothing of the transmission shaft at a given end position. In this case, the support ring is slotted so that it can be sufficiently expanded radially to be pressed against the transmission shaft until it reaches the radial groove. This variant is particularly suitable for low speeds.

[0027] To simplify the mounting of the components, in particular the pressing of the support ring onto the transmission shaft, the support ring is preferably pressed against a chamfer at one axial end of the external toothing of the transmission shaft and thereby radially expanded. A chamfer may be formed at the axial end of a tooth of the external toothing of the transmission shaft, which chamfer simultaneously correctly centers the support ring on the transmission shaft when pressing the support ring. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a schematic perspective view of an assembly of an electromagnetically actuated dog clutch of the present invention prior to installation on a transmission shaft using the method of the present invention. [Diagram 2] FIG. 2 is a schematic perspective partial cross-sectional view of the dog clutch of FIG. 1 in an open position. [Diagram 3] FIG. 3 is a schematic perspective partial cross-sectional view of the dog clutch of FIG. 1 in a closed position. [Figure 4] FIG. 4 is a schematic cross-sectional view of the dog clutch of FIG. 1 shown in an open position. [Diagram 5] FIG. 5 is a schematic cross-sectional view of the dog clutch of FIG. 1 in a closed position. [Figure 6] FIG. 6 is a schematic side view of the dog clutch of FIG. [Figure 7] FIG. 7 is a schematic cross-sectional view of the dog clutch of FIG. 1 shown in an open position. [Figure 8] FIG. 8 is a schematic cross-sectional view of the dog clutch of FIG. 1 in a closed position. [Figure 9] FIG. 9 is yet another schematic cross-sectional view of the dog clutch of FIG. 1 during the installation of the shift sleeve on the transmission shaft. [Figure 10] 10A to 10C are schematic cross-sectional views of various modifications of the support ring of the dog clutch of FIG. [Figure 11] 11A to 11C are schematic cross-sectional views of various modifications of the support ring of the dog clutch of FIG. [Figure 12] 12A to 12C are schematic cross-sectional views of various modifications of the support ring of the dog clutch of FIG. [Figure 13] FIG. 13 is a schematic top view of various variations of the support ring. [Figure 14] FIG. 14 is a schematic top view of various variations of the support ring. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The invention will now be described in more detail on the basis of an embodiment with reference to the accompanying drawings, in which: FIG.

[0030] 1 to 8 show an electromagnetically actuated dog clutch 10 comprising a shift sleeve 12 mounted on a transmission shaft 14 so as to be movable in an axial direction A of the transmission shaft and to rotate therewith in a circumferential direction U of the transmission shaft. The shift sleeve 12 has internal teeth 16, the transmission shaft 14 being provided with corresponding external teeth 18.

[0031] 2 to 6, the shift sleeve 12 is surrounded in a radial direction r by an actuator 20 comprising an energizable magnetic coil 22 and an actuator housing 24. The current supply to the magnetic coil 22 is via a suitable electrical connection 26, as shown in FIG.

[0032] When the actuator 20 is actuated, a magnetic force FM acts on the shift sleeve 12, moving the shift sleeve 12 to a first shift position. In this example, the first shift position corresponds to a closed position of the dog clutch 10. This first shift position is configured with the actuator housing 24 and the actuator housing 24 as shown in Figure 6. The first shift position is shown in Figures 3, 5 and 8.

[0033] The shift sleeve 12 here consists of an engagement ring 28 and a shift ring 30 which is arranged radially outside the engagement ring 28 and fixed thereto. The internal teeth 16 are only present on the engagement ring 28. The radial inner side of the shift ring 30 is of smooth design. At a first axial end 32 remote from the engagement ring 28, the shift ring 30 is provided with a radial projection 34 which extends in the direction towards the transmission shaft 14.

[0034] Between the radial projection 34, the radial inside of the shift ring 30 and the lateral surface 36 of the engagement ring 28, a receiver 38 is formed in which a support ring 40 and a spring element 42, respectively, which are designed annularly and are pressed onto the transmission shaft 14, are accommodated (see, for example, Figures 7 and 8).

[0035] The support ring 40 is rigidly fixed in the axial direction and, optionally, also in the circumferential direction U on the transmission shaft 14 at a given end position. The spring element 42 is compressed in the axial direction A by the movement of the shift sleeve 12 and can be released to return the shift sleeve 12 axially from the first shift position to the second shift position, which here corresponds to the open position of the dog clutch 10 and is shown in Figures 2, 4 and 7.

[0036] The radial projection 34 forms an axial stop 44 for the spring element 42 and transmits the restoring force FR generated by the spring element 42 to the shift sleeve 12. Opposite the axial stop 44, the spring element 42 rests against a side surface of the support ring 40 which forms a second axial stop for the spring element 42 and absorbs and distributes the reaction force of the spring element 42 to the transmission shaft 14.

[0037] Some of the teeth of the internal toothing 16 of the engagement ring 28 of the shift sleeve 12 are each formed with a radial stop projection 46, which are distributed over the circumference of the shift sleeve 12 so as to cooperate with stop grooves 48 of the external toothing 18 of the transmission shaft 14 (see Figures 1, 7 and 8). The axial depth of the stop grooves 48 and the axial positions of the stop projections 46 limit the axial movement of the shift sleeve 12 in the direction of the second shift position and therefore also define the axial position of the second shift position.

[0038] The first shift position is here defined by the stop projection 46 abutting an end face of the idler gear 66 .

[0039] In the second shift position, the shift sleeve 12, more precisely the lateral surface 36 of the engagement ring 28, is in contact with a stationary surface 58 of the support ring 40 facing axially. In order to reduce adhesion forces between these two elements resulting from an oil film between the lateral surface 36 and the stationary surface 58 and / or magnetic forces, the stationary surface 58 may be provided with one or more geometric structures 60 which minimize as much as possible the contact between the stationary surface 58 and the lateral surface 36. These variants are shown in figures 11 and 12, with figure 10 showing a simple flat support ring 40.

[0040] In the example of FIG. 11, in cross section in radial direction r along axial direction A, rest surface 58 is L-shaped, with only a narrow ring in contact with side surface 36 of engagement ring 28 .

[0041] In the example of FIG. 12, a plurality of axial protrusions 62 are formed in different positions of the stationary surface 58 in the radial direction r and / or the circumferential direction U, and the stationary surface 58 contacts the side surface 36 only in the area of ​​the protrusions 62.

[0042] During operation of the electromagnetic shift sleeve 12, the actuator 20 is energized when closing the shift sleeve 12. The magnetic field of the magnetic coil 22 creates a reluctance force FM on the shift ring 30, which pulls the shift ring 30 radially under the actuator housing 24 to form as closed a magnetic circuit as possible, maximizing the total inductance. In this manner, the shift sleeve 12 is caused to move toward the first shift position until the shift sleeve 12 reaches the first shift position.

[0043] In this position, the internal teeth 16 of the engagement ring 28 of the shift sleeve 12 move axially to engage with the external teeth 64 of an idler gear 66 that is disposed axially immediately adjacent to the external teeth 18 of the transmission shaft 14, the external teeth 18 of the transmission shaft 14 engage with the external teeth 64 of the idler gear 66, and the transmission shaft 14 and the idler gear 66 are connected to rotate in unison with each other.

[0044] Due to the displacement of the shift sleeve 12, the spring element 42 is compressed between the axial stop 44 of the projection 34 of the shift ring 30 and the support ring 40 and accumulates a restoring force FR.

[0045] When the shift sleeve 12 is to be opened again, the magnetic coil 22 of the actuator 20 is de-energized. The force FM generated by the magnetic field is now stopped, and the shift sleeve 12 is pushed back in the opposite axial direction by the restoring force FR applied by the spring element 42, moving to the second shift position. The axial displacement ends at the second shift position when the stop projection 46 abuts against the axial end of the stopper groove 48. Thus, the internal teeth 16 of the engagement ring 28 are disengaged from the external teeth 64 of the idler gear 66, and the transmission shaft 14 and the idler gear 66 are separated again.

[0046] To mount the shift sleeve 12 on the external toothing 18 of the transmission shaft 14, an assembly 67 is first formed. For this purpose, the engagement ring 28, the support ring 40 and the spring element 42 are arranged axially adjacent to one another. The shift ring 30 is arranged radially outside the engagement ring 28 and fixed there, for example by welding. A receiving portion 38 is thus formed between the side surface 36 of the engagement ring 28 and the radial projection 34 of the shift ring 30, in which the support ring 40 and the spring element 42 are simultaneously accommodated (see Figures 1 and 9).

[0047] This assembly 67 is pressed in the axial direction A against the external toothing 18 of the transmission shaft 14. This movement is supported by chamfers 68 at the axial ends of the external toothing 18 (see Figures 1 and 9). The chamfers 68 cause the support ring 40 to be centrally located and to expand radially so that it presses against the external toothing 18 under radial tension. During this movement, the support ring 40 is moved in the axial direction A by the flanks 36 of the engagement ring 28. This movement ends when the stop projections 46 of the internal toothing 16 of the engagement ring 28 reach the axial ends of the respective stop grooves 48. The support ring 40 is now in a predetermined end position. For this mounting, the predetermined end position is precisely aligned with the position of the shift sleeve 12 at the end of the shift movement in the direction of the second shift position.

[0048] In a first variant shown in Fig. 13, the support ring 40 is closed in the circumferential direction U. In this case, the support ring 40 is fixed to the transmission shaft 14 only by frictional forces. The attachment can be supported, for example, by heating the part, which causes the support ring 40 to temporarily expand in the radial direction r.

[0049] In a second variant shown in figure 14, the support ring 40 is open in the circumferential direction U, i.e. is provided with slots, which facilitates the expansion of the support ring 40 when it is pressed onto the transmission shaft 14. In this case, the external teeth 18 of the transmission shaft 14 are provided with radial grooves 70 at predetermined end positions of the support ring 40 (shown in figure 9), into which the support ring 40 fits tightly.

Claims

1. a shift sleeve (12) having internal teeth (16) and axially movably received on the external teeth (18) of the transmission shaft (14) and rotating together with the transmission shaft (14); an actuator (20) having a magnetic coil (22) and configured to move the shift sleeve (12) axially on the transmission shaft (14) to a first shift position; a spring element (42) cooperating with the shift sleeve (12) and acting on the shift sleeve (12) in a direction opposite to the movement caused by the actuator (20) toward a second shift position; a support ring (40) inserted on the transmission shaft (14), disposed between the spring element (42) and the internal teeth (16) of the shift sleeve (12) in the axial direction (A) of the shift sleeve (12), and fixed to the transmission shaft (14) in the axial direction (A); An electromagnetically actuated dog clutch (10) comprising:

2. The shift sleeve (12) has an engagement ring (28) on which the internal teeth (16) are formed, and a shift ring (30) fixed to the engagement ring (28) and interacting with the actuator (20), 2. The dog clutch of claim 1, wherein the shift ring is disposed radially outward of the engaging ring and the support ring is disposed axially adjacent the engaging ring.

3. The shift sleeve (12) has a receiver (38) for the support ring (40) and the spring element (42), 3. The dog clutch (10) of claim 2, wherein said shift ring (30) extends axially over said support ring (40) and said spring element (42) and includes an axial stop (44) for said spring element (42).

4. 4. The dog clutch (10) of claim 1, wherein the internal teeth (16) of the shift sleeve (12) have a plurality of radially extending stop projections (46), each of which interacts with a stop groove (48) of the external teeth (18) of the transmission shaft (14) to define an end position of the shift sleeve (12) in the second shift position of the dog clutch (10).

5. 5. The dog clutch (10) of claim 4, wherein in said first shift position, said stop projection (46) contacts an end face of an idler gear (66).

6. 6. The dog clutch (10) of claim 1, wherein the support ring (40) has a stationary surface (58) for the shift sleeve (12), and a geometric structure (60) is formed on the stationary surface (58) to reduce contact between the shift sleeve (12) and the support ring (40).

7. A method for mounting the shift sleeve (12) of the electromagnetically actuated dog clutch (10) to the transmission shaft (14) comprising the steps of: - forming an assembly (67) by placing said support ring (40) and said spring element (42) on said shift sleeve (12); - pushing said assembly (67) onto said external teeth (18) of said transmission shaft (14) up to a predetermined end position of said support ring (40) so that said support ring (40) is axially fixed on said transmission shaft (14) in said predetermined end position; The method includes:

8. 8. The method of claim 7, wherein the support ring (40) is held in the predetermined end position on the transmission shaft (14) by frictional forces only.

9. 8. The method according to claim 7, wherein in said predetermined end position, said support ring (40) engages in radial grooves (70) of said external teeth (18) of said transmission shaft (14).

10. 10. The method according to claim 7, wherein the support ring (40) is pressed against a chamfer (68) at the axial end of the external teeth (18) of the transmission shaft (14) and thereby expanded radially.

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