1. Field of the Invention
The present invention relates to a cranking device of an internal combustion engine.
2. Description of Related Art
A cranking device for internal combustion engines of the type mentioned in the introduction is known from the published German utility model document DE 297 04 299 U1. The cranking device for internal combustion engines described therein has a cranking motor, which is disposed in a pole casing and has a drive shaft that is in operative connection to a driven shaft via a reduction gear. The driven shaft is part of a starter-pinion drive having an overrunning clutch and a starting pinion. The starting pinion is disposed on the driven shaft in a manner that allows axial displacement and engagement with the ring gear of a starter gear of the internal combustion engine by axial displacement.
The drive shaft of the cranking motor carries an armature and a commutator having carbon brushes together with a current supply. Via its end on the commutator side, the drive shaft is supported in a commutator bearing; on its opposite side, it is accommodated in an axial bore of the driven shaft with the aid of a lug. The drive shaft drives the driven shaft via a planetary gear. For this purpose, the driven shaft has an external gearing which drives planetary gears, which in turn are in comb-type engagement with a fixed internal gear. The planetary gears are supported on pins pressed into a flange of the driven shaft at the extremity. The extreme flange is facing the cranking motor. The driven shaft is supported behind the flange in a bore of the bearing of an intermediate bearing, and its other end is supported in a bearing of a housing which seals the pole casing and is clamped to it with the aid of tension rods. However, in such a system particles from the region of the commutator travel to the region of the armature and downstream components.
In contrast, the cranking device of an internal combustion engine according to the present invention has the advantage that the stator and/or the armature as well as downstream components, in particular gears, are protected against the introduction of particles with the aid of a protective element. Particles such as dust, coal dust as well as any other type of media may originate from a commutator of the electric machine, in particular a cranking motor, or also from the external environment of the cranking device. Since the aforementioned components and especially the gearing exhibit a sensitive response to the entry of particles for design-related reasons, the use of the protective element makes it possible to achieve a longer service life of the gear and adjacent mechanical components. The protective element is disposed in the region of the drive unit, particularly the stator and/or armature, in such a way that a separating effect is provided with regard to the mentioned components relative to an operating region of the commutator. Due to the positioning of the protective element and a resulting geometrical structure of the element, the technical approach in this case allows the use of a simple sealing means, i.e., a sealing means that is able to be produced and put in place at low expense, possibly in conjunction with a slight modification of existing components.
The result is an isolation of the mechanical components from harmful particles or also the trapping of such particles. Both the isolation and also the trapping subsequently create a barrier for particles, so that the service life and the quality of lubricants present in gears are able to be increased. Furthermore, the material wear is reduced, especially the wear on bearings, bushings and gear components, since particles are kept away from these components. Last but not least, by adapting the geometry of the protective element, a more advantageous air flow may be created, which in turn leads to improved cooling of heat-sensitive components. If the cranking device is monitored for wear and/or function and/or the degree of contamination with the aid of an electronic monitoring system, then a corresponding report, possibly in the form of a servicing request, will be output only at a considerably longer service life of the internal combustion engine.
In one advantageous development of the present invention, the protective element is implemented as guard ring, particularly one having an I-shaped, L-shaped, or U-shaped profile. Depending on the desired method of functioning and the design, the most suitable protective element may be used. For example, a simple separating element is able to be realized by the I-shaped design, while the L-shaped protective element may be effective as trapping element. The U-shaped design of the protective element also functions as receiving vessel for harmful particles.
In a further advantageous development of the present invention, the protective element is disposed at the level of an armature bandage on a housing. For that purpose the protective element is radially adapted in such a way that an air gap remaining with respect to the peripheral area of the armature bandage is kept as small as possible, an existing air flow is modified in the sense of an improved cooling effect, and the entry of particles and media into the mechanical region is reduced.
In one example development of the present invention, the protective element is disposed at the level of an extremity of the armature on a permanent solenoid and/or on the housing. The protective element is adapted and placed in such a way that the air gap between an inner peripheral surface area of the protective element and the armature is as small as possible, or that free spaces between segments of the permanent solenoid are closed off.
In another example development of the present invention, the protective element is disposed on the armature bandage, especially on its circumference. The protective element is radially adapted in such a way that an air gap remaining with respect to the peripheral area of a pole casing is kept as small as possible, an existing air flow is modified in the sense of an improved cooling effect, and the entry of particles and media into the mechanical region is reduced.
According to an advantageous development of the present invention, the protective element is disposed in interspaces of the permanent solenoid, the interspaces being sealed and the air gap between the circumferential area of the armature and the solenoid package being reduced.
According to a further advantageous development of the present invention, the protective element is situated in the region of an end face of the armature bandage and on the housing. The protective element is positioned in such a way that the air gap between the armature bandage and the protective element is reduced in the axial direction, and that the air gap between the armature bandage and the commutator is reduced in the radial direction. An already existing current bar, especially for six carbon brush holders, may be used as protective element for this purpose.
In one exemplary embodiment of the present invention, the protective element is provided with a supplementary contour and is disposed on the permanent solenoid and/or on the housing, in particular at the level of the extremity of the armature. A labyrinth or also a vessel is provided in the process. Using these constructive measures, media flowing about are able to be collected and possibly removed in the course of servicing.
In one further exemplary embodiment of the present invention, the protective element having the supplementary contour is disposed in the region of a housing opening. In this embodiment, the protective element in conjunction with part of the housing, particularly the pole casing, forms a labyrinth whose end terminates in an outlet of the housing in order to carry off the collected particles.
Equipping a start-stop system with the cranking device according to the present invention is also advantageous because such a system makes higher demands on the stability and service life of the associated gear due to more frequent startup operations. The system automatically switches the internal combustion engine off whenever the vehicle is stopped and restarts the internal combustion engine without a delay as soon as the vehicle driver engages a gear, for instance, and/or whenever the brake pedal is released.
Furthermore, it is advantageous to provide an internal combustion engine with the cranking device according to the present invention and/or with the aforementioned start-stop system because this makes it possible, for one, to have an even more reliable component start the internal combustion engine and, for another, to obtain considerable savings in fuel when driving inside city limits.
During the startup operation of the internal combustion engine, the solenoid switch briefly connects electric machine 11 to the internal combustion engine via a gear wheel drive.
Due to the typically high rotational speed of electric motor 11 and a torque required for the startup operation, a high translation ratio of approximately 13:1, in particular, is required. The desired translation ratio is achieved by a pinion, especially a starter pinion, on the starter, and by a pinion of an associated flywheel that is relatively large in comparison with the starter pinion. The starter pinion is axially displaceable on armature shaft 16 in an infinitely variable manner, and is brought into engagement with the gearing of the flywheel by the solenoid switch or also the electromagnet. Then, electric motor 11 is switched on by closing a contact switch, which is part of the solenoid switch, or engagement solenoid. The starter pinion is equipped with an overrunning clutch, which prevents the started internal combustion engine from driving electric machine 11 at an excessively high rotational speed via the still engaged starter pinion and thereby damages or destroys the electric machine. Such starters generally have a series-wound motor or a permanent-magnet-energized motor as electric machine.
In the case at hand, electric machine 11 is an internal rotor whose armature 13 defines the inner part, and whose stator 12 defines the outer part of electric machine 11. A coil, in particular an armature coil, of armature 13 is controlled via commutator 18. Via two fixed carbon brushes, which are pressed against a drum rotating together with armature 13, commutator 18 provides an indirect line connection to the windings of armature 13. The surface of the drum is subdivided into segments that are insulated with respect to each other. As is common in a DC electric machine, armature 13 has half as many windings as there are segments on commutator 18. Each winding is connected at its ends to two segments lying opposite one another. Because of the special demands on the torque and the current flow, the cross-section between the segments and the associated carbon brushes is particularly broad. In the case of four carbon brushes, two windings must be effective at the same time.
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In summary, the presence of an additionally placed component, in particular protective element 19 or a protective ring, in the border region between stator 12 or armature 13 and commutator 18 prevents the entry of particles and/or media of all types into gear 14, in particular planetary gears, and into downstream mechanical components, which increases the service life of said components. The focus is placed on reducing the size or abolishing existing air gaps and transitions between the placement and operating region of commutator 18 and the placement and operating region of stator 12, armature 13, the permanent solenoid, gear 14 and the like.
The affixation of protective element 19 on the various components of cranking device 10 may be implemented by a snap closure, bonding connection, by superficial fusing, pressing, by clamping, a welding joint, surface vulcanization, or with the aid of an injection molding process and the like. In addition, the entry of particles may be reduced by an adapted length of protective element 19 with respect to armature 13 or commutator 18. In general, protective element 19 may have a straight or curved design or a combined geometry. In addition, protective element 19 may have a geometry that is similar to a fan wheel, having a wavy or slotted form, or also any combination of the aforementioned variants, in order to influence the air flow and/or the component cooling.
Furthermore, an additional sealing lip may be disposed on protective element 19 or on armature 13, on armature bandage 21, or on commutator 18. Both the components that are assigned in pairs, such as protective element 19 together with armature 13 or armature bandage 21 or commutator 18, and the components in connection with the sealing lip may be designed to slide against each other. Both a single component material, in particular steel or plastic, and also a multi-component material may be used as materials. A combination of the previously described variants of embodiments with each other is possible as well, in particular in order to influence the air flow in a manner that allows the media and particles to be trapped and/or carried away. With the aid of the aforementioned constructive measures, the increased demands on stability and service life in gears used in cranking devices are satisfied, which has a positive effect, particularly in a start-stop system.
Number | Date | Country | Kind |
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10 2007 051 595.4 | Oct 2007 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2008/064514 | 10/27/2008 | WO | 00 | 8/17/2010 |