Starter for an internal combustion engine

Abstract

A starter for an internal combustion engine may include a support, an electric motor for driving a pinion in rotation, and a solenoid drive configured to axially adjust the pinion between an active position for driving a gearwheel of an internal combustion engine, and an axially offset passive position. The solenoid drive may include a ferromagnetic solenoid housing fastened to the support, a ferromagnetic plunger stop arranged one of in and at the solenoid housing, a ferromagnetic plunger axially adjustable relative to the plunger stop extending axially through a passage opening of a face side wall of the solenoid housing, and a cylindrical coil arrangement arranged in the solenoid housing surrounding a cylindrical coil interior in a circumferential direction. The plunger stop may include a cylindrical section projecting axially into the coil interior. The cylindrical section may have a face end facing towards the face side wall.

Claims

1. A starter for an internal combustion engine, comprising: a support; an electric motor arranged on the support for driving a pinion in rotation; a solenoid drive arranged on the support configured to axially adjust the pinion between an active position for driving a gearwheel of an internal combustion engine, and a passive position axially offset with respect to the active position; wherein the solenoid drive has a ferromagnetic solenoid housing coupled to the support, a ferromagnetic plunger stop arranged one of in and at the solenoid housing, a ferromagnetic plunger axially adjustable relative to the plunger stop and extending axially through a passage opening of a face side wall of the solenoid housing, and a cylindrical coil arrangement arranged in the solenoid housing and surrounding a cylindrical coil interior of the coil arrangement in a circumferential direction; wherein the plunger stop has a cylindrical section projecting axially into the coil interior; and wherein the cylindrical section has a face end facing towards the face side wall and includes a cylindrical chamber, the plunger protruding axially into the cylindrical chamber when the pinion is in each of the active position and the passive position.

2. The starter according to claim 1, wherein: the coil interior includes a proximal half section and a distal half section, the proximal half section disposed closer to the face side wall than the distal half section; and the face end of the cylindrical section is arranged in the proximal half section of the coil interior.

3. The starter according to claim 1, wherein the cylindrical section extends over more than 50% of an axial length of the coil arrangement.

4. The starter according to claim 3, wherein the cylindrical section extends over at least 75% of the axial length of the coil arrangement.

5. The starter according to claim 1, wherein: at least when the pinion is in the passive position, an axial gap is defined between the face end of the cylindrical section and a portion of the plunger; an axial distance of the gap is reduced when the pinion is adjusted from the passive position to the active position and the portion of the plunger is adjusted towards the face end of the cylindrical section; and the gap is arranged proximal to the face side wall.

6. The starter according to claim 5, wherein the face side wall has an inner side facing towards the coil arrangement and, when the pinion is in the passive position, the gap axially overlaps at least substantially completely a radially inner edge of the inner side.

7. The starter according to claim 5, wherein: the plunger includes a protrusion section protruding axially into the cylindrical chamber, and a head section arranged in axially adjustable fashion in an edge region bordering the passage opening in a circumferential direction, the head section having a larger cross-sectional area than a cross-sectional area of the protrusion section; and the portion of the plunger is an annular step arranged between the protrusion section and the head section.

8. The starter according to claim 1, wherein the plunger is coupled via a diverting lever to a drive shaft connected rotationally conjointly to the pinion for axially adjusting the drive shaft, such that, during an adjustment of the pinion from the passive position into the active position, the plunger extends to an increasing depth into the cylindrical chamber.

9. The starter according to claim 7, wherein, when the pinion is in the passive position, the annular step is arranged axially outside of the coil interior.

10. The starter according to claim 7, wherein, when the pinion is in the active position, the annular step bears axially against the face end.

11. The starter according to claim 7, wherein an axial face side of the plunger arranged in the cylindrical chamber bears axially against a base of the plunger stop, and the base of the plunger stop axially delimits the cylinder chamber when the pinion is adjusted into the active position.

12. The starter according to claim 7, wherein the cylindrical section includes a cylindrical wall bordering the cylindrical chamber.

13. The starter according to claim 12, wherein one of: the cylindrical wall includes at least one recess delimited in a circumferential direction and extending at least one of radially and axially at least over a part of the cylindrical wall; and the cylindrical wall surrounds the cylindrical chamber in a closed encircling fashion in a circumferential direction and with a constant wall thickness.

14. The starter according to claim 1, wherein the plunger is, at least in an axial section protruding into the cylindrical chamber, cylindrically hollow such that a cylindrical plunger wall surrounds a cavity.

15. The starter according to claim 14, wherein the plunger wall surrounds the cavity in a closed encircling fashion in a circumferential direction and with a constant wall thickness.

16. The starter according to claim 14, wherein the plunger wall includes at least one recess delimited in a circumferential direction and extending at least one of radially and axially at least over a part of the plunger wall.

17. The starter according to claim 7, wherein: the plunger is arranged in an axially adjustable fashion in a guide sleeve extending coaxially through the coil interior and supported radially on the cylindrical section; the coil arrangement is supported radially at an inside on the guide sleeve; and the edge region is supported radially at an inside on the guide sleeve.

18. A starter for an internal combustion engine, comprising: a support; an electric motor arranged on the support for driving a pinion in rotation; a solenoid drive arranged on the support configured to axially adjust the pinion between an active position for driving a gearwheel of an internal combustion engine, and a passive position axially offset with respect to the active position, the solenoid drive including: a ferromagnetic solenoid housing coupled to the support; a ferromagnetic plunger stop arranged one of in and at the solenoid housing; a ferromagnetic plunger axially adjustable relative to the plunger stop and extending axially through a passage opening of a face side wall of the solenoid housing; and a cylindrical coil arrangement arranged in the solenoid housing and surrounding a cylindrical coil interior of the coil arrangement in a circumferential direction; wherein the plunger stop has a cylindrical section projecting axially into the coil interior, the cylindrical section having a face end facing towards the face side wall; wherein, at least when the pinion is in the passive position, an annular gap extending axially between the face end of the cylindrical section and a portion of the plunger is defined, the gap at least partially disposed radially between the plunger and the face side wall; and wherein an axial distance of the gap is reduced when the pinion is adjusted from the passive position to the active position and the portion of the plunger is adjusted towards the face end of the cylindrical section.

19. A starter for an internal combustion engine, comprising: a support; an electric motor arranged on the support for driving a pinion in rotation; a solenoid drive arranged on the support configured to axially adjust the pinion between an active position for driving a gearwheel of an internal combustion engine, and a passive position axially offset with respect to the active position, the solenoid drive including: a ferromagnetic solenoid housing coupled to the support; a ferromagnetic plunger stop arranged one of in and at the solenoid housing; a ferromagnetic plunger axially adjustable relative to the plunger stop and extending axially through a passage opening of a face side wall of the solenoid housing, the plunger including a head section and a protrusion section protruding axially from the head section towards the plunger stop, the head section having a greater radial extent than the protrusion section defining an annular step; and a cylindrical coil arrangement arranged in the solenoid housing and surrounding a cylindrical coil interior of the coil arrangement in a circumferential direction; wherein the plunger stop has a cylindrical section projecting axially into the coil interior, the cylindrical section including a cylindrical wall projecting axially towards the plunger stop and having a face end facing towards the face side wall, at least a portion of the cylindrical wall disposed radially between the coil arrangement and the protrusion section such that the protrusion section is arranged within a cylindrical chamber defined by the cylindrical wall.

20. The starter according to claim 19, further comprising a guide sleeve extending coaxially through the coil interior, the guide sleeve arranged on a radially inner side of the coil arrangement and on a radially inner surface of an edge region of the face side wall circumferentially surrounding the passage opening, wherein the head section slides axially along the guide sleeve and the protrusion section slides axially along the cylindrical wall when the pinion is adjusted from one of the active position and the passive position to the other of the active position and the passive position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the figures, in each case schematically:

(2) FIG. 1 shows a side view, partially in longitudinal section, of a starter with a conventional solenoid drive,

(3) FIG. 2 shows a longitudinal section through a solenoid drive according to the invention.

DETAILED DESCRIPTION

(4) In accordance with FIG. 1, a starter 1 which is provided for starting an internal combustion engine 2, of which, in FIG. 1, only a gearwheel 3 is indicated by way of dashed lines, comprises a support 4, an electric motor 5 and a solenoid drive 6. The gearwheel 3 is incorporated in a suitable manner into a drivetrain (not shown in any more detail here) of the internal combustion engine 2, such that said gearwheel is connected in terms of drive to a crankshaft of the internal combustion engine 2 if the internal combustion engine 2 is, as is preferred, a piston engine with a crankshaft. The gearwheel 3 may for example be formed on a flywheel of the drivetrain.

(5) The support 4 is designed for fastening the starter 1 to the internal combustion engine 2 or to a peripheral of the internal combustion engine 2 which may be situated for example in a vehicle which is equipped with the internal combustion engine 2.

(6) The electric motor 5 is arranged on the support 4 and serves for driving a pinion 7 in rotation. The pinion 7 serves for driving the gearwheel 3 when the internal combustion engine 2 is to be started by way of the starter 1. For this purpose, the pinion 7 can, together with a drive shaft 8 on which the pinion 7 is rotationally conjointly arranged, be adjusted bilinearly in an axial direction 9, which is defined by an axis of rotation 10 of the drive shaft 8 or of the electric motor 5, between a passive position PS, which is shown in FIG. 1 by solid lines, and an active position AS, which is indicated in FIG. 1 by dashed lines. In said active position AS, the pinion is denoted by the reference sign 7. In the active position AS, the pinion 7 serves for driving the gearwheel 3 and thus meshes with the latter such that a rotation of the pinion 7 forces a rotation of the gearwheel 3. In the passive position PS, the pinion 7 is axially offset with respect to the active position AS, specifically to such an extent that it does not mesh with the gearwheel 3. In this respect, the pinion 7 is then arranged axially spaced apart from the gearwheel 3.

(7) The electric motor 5 furthermore has, in the conventional manner, an external stator 11 and an internal rotor 12, wherein the rotor 12 is connected in terms of drive to the drive shaft 8 by way of a transfer device 13. The transfer device 13 may have a clutch, in particular a one-way friction clutch. The transfer device 13 may additionally or alternatively have a gear transmission 18, in particular a planetary gear train. The stator 11 is accommodated in a stator housing 14 which is fastened to the support 4. In the situation shown, the support 4 has a base housing 29, which serves for the fastening of the starter 1 to said peripheral, and an intermediate housing 15, which is fastened to the base housing 29. In the example shown, the stator housing 14 is now fastened to said intermediate housing 15.

(8) The drive shaft 8 is mounted by way of a main bearing 16 on the support 4 or on the base housing 29 thereof. A further bearing 17 is provided in the intermediate housing 15 for additional support of the drive shaft 8.

(9) The solenoid drive 6 has a solenoid housing 19 which is fastened to the support 4, specifically to the intermediate housing 15 thereof. The solenoid drive 6 serves for the axial adjustment of the pinion 7. For this purpose, the solenoid drive 6 has a plunger stop 20 which is static with respect to the support 4, a plunger 21 which is axially adjustable relative to the plunger stop 20, and a cylindrical coil arrangement 22. An axial direction 23 of the axial adjustability of the plunger 21 is defined by a longitudinal central axis 24 of the solenoid drive 6. The solenoid drive 6 is expediently arranged on the support 4 so as to be parallel and adjacent to the electric motor 5, such that the longitudinal central axis 24 extends parallel to the axis of rotation 10.

(10) The coil arrangement 22 is arranged on the plunger stop 20 and surrounds a cylindrical coil interior 25 in a circumferential direction about the longitudinal central axis 24. The plunger 21 is coupled by way of a diverting lever 26 to the drive shaft 8 such that, for the adjustment of the pinion 7 from the passive position PS into the active position AS, the plunger 21 is retracted into the coil interior 25. Accordingly, the coil arrangement 22 is in the form of a retraction coil which, when energized, pulls the plunger 21 into the coil interior 25. The diverting lever 26 in this case effects a reversal of the movement direction, such that the retraction of the plunger 21 toward the right in FIG. 1 effects a deployment of the pinion 7 toward the left in FIG. 1.

(11) As per FIG. 2, the plunger stop 20 of the solenoid drive 6 has a cylindrical section 27 which projects axially into the coil interior 25. In said cylindrical section 27 there is furthermore formed a cylindrical chamber 28 which is arranged coaxially with respect to the coil interior 25 and into which the plunger 21 protrudes axially. This relationship is not evident in the case of the conventional solenoid drive 6 shown in FIG. 1.

(12) The solenoid housing 19 has, on a side facing toward the plunger 21, a face side wall 30 which has a passage opening 31 extended through axially by the plunger 21. The plunger stop 20 and the coil arrangement 22 are accommodated in the solenoid housing 19. The face side wall 30 has an edge region 32 which surrounds the passage opening 31 in the circumferential direction. Said edge region 32 is in this case spaced apart axially from a face end 33, facing toward the face side wall 30, of the cylindrical section 27.

(13) There is thus a gap 34 between the face end 33 and the edge region 32 and thus between the plunger stop 20 and the solenoid housing 19. In the passive position PS said gap 34 results in a reduced density of field lines, which extend through the plunger 21 to the plunger stop 20, of a magnetic field that is generated when the coil arrangement 22 is energized. The density of the field lines is considerably greater within the solenoid housing 19 and within the plunger stop 20. For this purpose, the solenoid housing 19, the plunger 21 and the plunger stop 20 are expediently composed of a magnetically conductive material, preferably of a ferromagnetic material, in particular of an iron material. Owing to the reduced field line density in the plunger 21 in the passive position PS, it is the case at the start of an adjustment movement of the plunger 21 that the magnetic force which acts on the plunger 21 and which pulls the plunger 21 into the coil interior 25 is reduced.

(14) According to FIG. 2 the coil interior 25 is axially divided into two half sections, namely a proximal half section 62 and a distal half section 63, wherein said proximal half section 62 is arranged closer to the face side wall 30 of the solenoid housing 19 than the distal half section 63. Furthermore, the face end 33 of the cylindrical section 27 is arranged in the proximal half section 62 of the coil interior 25. AS can be seen in FIG. 2, at least in the passive position PS of the pinion 7, the axial gap 34 is provided between said face end 33 of the cylindrical section 27 and a portion 61 of the plunger 21. When the plunger 21 is moving in order to move the pinion 7 from the passive position PS into the active position AS said portion 61 of the plunger 21 moves towards said face end 33 of the cylindrical section 27 in order to axially reduce said gap 34. Furthermore, said gap 34 is arranged proximal to the face side wall 30 of the solenoid housing 19. Preferably, the face side wall 30 has an inner side 64 facing towards the coil arrangement 22. In the passive position PS of the pinion 7, said gap 34 axially overlaps a radially inner edge 35 of said inner side 64.

(15) To support this aspect, it is the case in FIG. 2 that the plunger 21 has a stepped design such that it has a protrusion section 36 and a head section 37 which transition into one another via an annular step 38. The protrusion section 36 is coordinated with the cylindrical chamber 28, such that said protrusion section 36 can protrude axially into said cylindrical chamber 28. To this end, the protrusion section 36 is preferably formed as a cylindrical body. By contrast, the head section 37 has a larger cross section than the protrusion section 36, wherein the annular step 38 defines a cross-sectional step. It is expediently possible for the annular step 38 to be positioned on the plunger 21 such that, in the active position AS of the pinion 7, that is to say when the plunger 21 is fully retracted, said annular step 38 is arranged axially between the edge region 32 and the face end 33. In this way, the abovementioned gap 34 is reduced in size by way of the head section 37. As a result, the field line density passed from plunger 21 to plunger stop 20 increases as the plunger 21 protrudes to an increasing extent into the cylindrical chamber 28. An embodiment is particularly advantageous in which the annular step 38 is positioned axially on the plunger 21 such that, in the active position AS, said annular step 38 comes to bear axially against the face end 33 and thus, in effect, forms an axial abutment for the plunger 21. In this case, in the active position AS, the abovementioned gap 34 is completely closed, whereby a maximum field line density is attained in said region, such that it is possible with relatively little electrical current to realize a relatively high holding force for the plunger 21 in the active position.

(16) The plunger 21 has, on its protrusion section 36, an axial face side 39 which is arranged in the cylindrical chamber 28 and which is situated axially opposite a base 40, which axially delimits the cylindrical chamber 28, of the plunger stop 20. Depending on the positioning of the annular step 38, it is possible, in the active position AS, for the face side 39 to come to bear against the base 40 and form an axial abutment for the plunger 21. If the annular step 38 defines the axial abutment, the face side 39 has an axial spacing to the base 40 even in the active position AS. By contrast, if the face side 39 defines the axial stop, the annular step 38 has an axial spacing to the face end 33 in the active position AS. In a specific embodiment, it may be provided that, in the active position AS of the pinion 7, the annular step 38 bears axially against the face end 33 and the face side 39 bears axially against the base 40.

(17) The cylindrical section 27 has a cylindrical wall 41 which surrounds the cylindrical chamber 28 in the circumferential direction. Here, an embodiment is preferable in which said cylindrical wall 41 surrounds the cylindrical chamber 28 in closed encircling fashion in the circumferential direction and with a constant wall thickness. It is however alternatively also possible for an embodiment to be provided in which said cylindrical wall 41 has at least one recess which is delimited in the circumferential direction and which extends radially and/or axially over at least a part of the cylindrical wall 41. For example, the cylindrical wall 41 may thus have a varying wall thickness and/or interruptions in the circumferential direction. This duly yields a varying distribution of the magnetic field lines 35 in the circumferential direction, but the overall density of the field lines 35 in the region of the 34 can be set in targeted fashion in this way.

(18) The plunger 21 may be of hollow cylindrical form at least in an axial section which protrudes into the cylindrical chamber 28, said axial section being formed in this case by the protrusion section 36. Accordingly, in the protrusion section 36, the plunger 21 has a cylindrical plunger wall 42 which surrounds a cavity 43 in the circumferential direction. In this case, too, an embodiment is preferred in which said plunger wall 42 surrounds the cavity 43 in closed encircling fashion in the circumferential direction and with a constant wall thickness. As an alternative to this, an embodiment is also conceivable in which said plunger wall 42 has at least one recess which is delimited in the circumferential direction and which extends radially and/or axially at least over a part of the plunger wall 42. Accordingly, it is also possible in this case for said plunger wall 42 to have a varying wall thickness and/or at least one interruption in the circumferential direction. Thus, it is possible in this way, too, to realize a field line density which varies in the circumferential direction, which altogether improves a targeted setting of the field line density in the region of the gap 34.

(19) The solenoid drive 6 is furthermore equipped with a guide sleeve 44 in which the plunger 21 is mounted in axially adjustable fashion. For this purpose, the guide sleeve 44 extends coaxially through the coil interior 25. Furthermore, the guide sleeve 44 is supported radially on the cylindrical section 27. Furthermore, the coil arrangement 22 is supported radially at the inside on said guide sleeve 44. Also, the edge region 32 of the face side wall 30 is supported radially at the inside on the guide sleeve 44. The head section 37 of the plunger 21 slides along the guide sleeve 44. By contrast, the protrusion section 36 slides along the cylindrical wall 41 of the cylindrical section 27.

(20) The edge region 32 is in the form of a cylindrical sleeve. In this case, an axial length of the sleeve-shaped edge region 32 is greater than the axial adjustment travel of the plunger 21 covered by the latter between the active position AS and the passive position PS. In this case, depending on the embodiment of the abovementioned axial abutment, said adjustment travel corresponds to the axial spacing between the annular step 38 and the face end 33 and/or the axial spacing between the face side 39 and base 40.

(21) The plunger 21 is furthermore coupled to a switching rod 45 which, for this purpose, at least partially extends through the plunger 21. The switching rod 45 serves for the axial adjustment of a contact element 46 which, in turn, serves for the electrical connection of two electrical contacts 47. By way of said electrical contacts 47, the electric motor 5 is connected to a main electrical supply 48. In other words, when the contact element 46 electrically connects the two electrical contacts 47 to one another, the electric motor 5 can be supplied, by way of the main electrical supply 48, with a rated electrical power in order that the electric motor 5 can output a rated torque at the pinion 7. To realize a so-called soft-start process, it is possible for a considerably lower level of electrical power to be supplied to the electric motor 5 in order for the pinion 7 to be driven with a considerably lower torque for as long as it has not yet reached its active position AS. To this end usually the electrical power supply (not shown here) of the coil arrangement 22 is also used to operate the electric motor 5.

(22) The switching rod 45 is led coaxially through the plunger stop 20. Accordingly, the plunger stop 20 is ultimately situated axially between the plunger 21 and the contact element 46. The plunger 21 is assigned at least one restoring spring 49 which, in the example, extends coaxially around the switching rod 45. In this case, the restoring spring 49 is supported at one side on the plunger 21 and at the other side on the plunger stop 20. In this case, the restoring spring 49 protrudes into the cavity 43. In this way, it is possible overall for an axially larger restoring spring 49 to be accommodated, whereby in particular, it is possible to realize a spring characteristic curve which is linear over the entire adjustment travel of the plunger 21. The maximum of said adjustment travel is the axial spacing between the plunger end 39 and the base 40.

(23) The switching rod 45 is also assigned a restoring spring 50 which is supported at one side on the switching rod 45 and at the other side on a contact housing 51 on which the electrical contacts 47 are situated. Furthermore, a preload spring 52 may be provided which drives the contact element 46 in the direction of the contacts 47. Said preload spring 52 is in this case supported on the switching rod 45. As can be seen, an axial spacing between the contact element 46 and the contacts 47 is smaller than the overall travel of the plunger 21 between the passive position PS and the active position and AS. Thus, the contact element 46 comes into contact with the contacts 47 shortly before the active position AS is reached. When the active position AS is reached, the preload spring 52 then effects preloaded abutment of the contact element 46 against the contacts 47. Owing to the capacitive action of the coils/windings of the electric motor 5, the rated torque is built up after a time delay. Coordination is preferably performed such that the rated torque is present approximately at the same time as the active position AS is reached.

(24) It can also be seen that, in the passive position PS, the contact element 46 bears axially against a face end 53, facing away from the plunger 21, of the plunger stop 20.

(25) In the example shown here, the coil arrangement 22 has a coil carrier 54 which has a cylindrical body 55 and two end discs 56. The cylindrical body 55 extends coaxially with respect to the longitudinal central axis 24. The end discs 56 are expediently of planar form and extend annularly and perpendicular to the longitudinal central axis 24. Radially at the outside around the cylindrical body 55 and axially between the end discs 56, the coil arrangement 22 has at least one electrical coil 57. For example, it is possible for at least two different electrical coils 57 to be provided, specifically at least one retraction coil and at least one holding coil.

(26) The coil arrangement 22 expediently performs a pre-assemblable coil structural unit in which the respective coil 57 is wound on the coil carrier 54. Furthermore, the plunger stop 20, guide sleeve 44 and coil arrangement 22 likewise form a pre-assemblable plunger stop structural unit which can be inserted in the preassembled state into the solenoid housing 19. Said plunger stop structural unit can also comprise the plunger 21, the switching rod 45, the contact element 46 and the respective springs 49, 52. Subsequently, the contact housing 51 can also be inserted and fixed for example by means of a flange connection 58 and/or by means of an adhesive connection 59.

(27) In the assembled state, the coil carrier 54 bears by way of its end disc 56, shown on the right in FIG. 2, against an annular step 60 of the plunger stop 20.

(28) According to FIG. 2 the cylindrical section 27 of the plunger stop 20 extends over more than 50% of an axial length 65 of the coil arrangement 22. Preferably, the cylindrical section 27 extends over more than 75% of the axial length 65 of the coil arrangement 22. In the depicted example, the cylindrical section 27 extends over more than 90% of the axial length 65 of the coil arrangement 22. The axial length 65 of the coil arrangement 22 is the distance between axial outer sides of the two end discs 56 of the coil carrier 54 which is a part of the coil arrangement 22, said axial outer sides of the two end discs 56 are axially turned away from each other.