EP2331810A1

EP2331810A1 - Reducing gear and starter device of an internal combustion engine

Info

Publication number: EP2331810A1
Application number: EP09783455A
Authority: EP
Inventors: Samuel Billot
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-09-29
Filing date: 2009-09-28
Publication date: 2011-06-15
Also published as: US9004034B2; WO2010034829A1; AU2009295846A1; KR20110074746A; RU2011116925A; US20110168116A1; CN102165180A; JP2012504215A; DE102008042431A1

Abstract

The invention relates to a reducing gear (3), in particular for a starter device (1) of an internal combustion engine, for speed-reducing coupling of a drive shaft and a driven shaft (5, 7), said coupling accomplished by way of at least two toothed gears (11) that engage with one another. The toothed gears (11) comprise straight cogs, and the cogging (30) is extra deep cogging (31). The invention further relates to a starter device (1) of an internal combustion engine.

Description

description

Title reducer and starter device of an internal combustion engine

The invention relates to a reduction gear, in particular for a starter device of an internal combustion engine, for speed-reducing coupling of a drive and an output shaft by means of at least two gears which are engaged with each other. The invention further relates to a starter device of an internal combustion engine.

State of the art

Reducing gears of the type mentioned are known from the prior art. They are often used in starter devices of internal combustion engines to increase the torque, for example, an electric motor, whereby the size of the electric motor small and its weight are kept low. If the internal combustion engine is started or started, the electric motor is operated for this purpose

Torque on the reducer - while reducing the speed - increased and thus the internal combustion engine is set in motion. From a speed which is dependent on the internal combustion engine used, this can be transferred to independent operation. This procedure when starting the internal combustion engine is necessary because internal combustion engines are usually not self-starting. Frequently, gears with conventional toothing are used for the reduction gear, for example a planetary gear. This has the disadvantage that vibrations are excited during operation, resulting in poor acoustic properties of the reducer. The resulting noise can sometimes be relatively loud and thus annoying. In order to prevent the formation of these vibrations, a helical gear for the reduction gear is now partially provided. This measure improves the engagement conditions and prevents the development of vibrations and the associated noise level. This means improved acoustic properties. However, the helical gearing also means that axial thrust forces occur on the gears, which are equipped with helical gearing. This has the consequence that, depending on the resulting thrust forces, a corresponding mounting of the gears or the gears assigned to the gears must be provided. Also, the rigidity of the housing must be designed taking into account the thrust forces. This leads to a complex design of the bearings and the housing, which results in an increase in costs. Also, there is a higher friction on the helical gears, so that the efficiency of the reducer is degraded and thus the performance of the starter is reduced. This means that the starting capability of the starter device or the electric motor is reduced. Therefore, the power of the electric motor must be increased to obtain the necessary starting ability. This in turn means that the wear of the electric motor increases, in particular the wear of the

Commutation, and thus the life of the electric motor is reduced. Furthermore, it would be possible to provide the gears with a double helical toothing. This prevents the occurrence of axial thrust forces on a bearing, since these are absorbed by the gearing itself. However, the double helical gearing has the appearance of further frictional forces and thus a further reduction of the efficiency result. The production is also complex and therefore expensive. The advantageous vibration behavior of the helical gearing or the double helical gearing is thus opposed to a deterioration of the efficiency and a more complex construction.

Disclosure of the invention

In contrast, the reduction gear with the features mentioned in claim 1 has the advantage that the noise and vibration behavior of the reducer is improved, while the high efficiency of the spur gearing is substantially maintained. Other objects of the invention are the achievement of a compact design, a significantly increased life and a cost-effective design of the reducer. This is achieved by the gears are straight toothed and the teeth is a high toothing. It is therefore intended, the reduction gear, which is designed in particular as a planetary gear and serves to reduce the rotational speed of an electric motor and to transmit its torque to an output shaft of a starter to provide with an optimized toothing. The toothing can have a special profile in order to reduce the noise level at the reduction gear, which is formed, for example, during a starting process of the internal combustion engine. This design of the reducer has the advantage that as a result the optimized toothing is significantly quieter during operation, thus having improved acoustic properties. In addition, a compact and cost-saving design is possible. The latter is achieved in particular by the use of a straight toothing. This creates no axial forces that would have to be absorbed by structural measures of the reducer. The storage of the drive and the output shaft or the gears can therefore be designed so that no or only small axial forces are absorbed. Thus, a housing of the reducer can be constructed lighter and more space-saving. The improvement of the acoustic properties is achieved by the toothing is designed as a high toothing. Thus, the overlap of the teeth can be significantly increased, which has an improved noise and vibration behavior. Due to the reduced vibrations and the life of the resulting teeth of the reducer is positively influenced. The teeth should be designed to suit the application, in particular with regard to the torques or speeds to be transmitted. High toothing is understood as meaning a toothing in which the overlapping of the toothing is increased (greater than or equal to 2.0) by reducing the normal engagement angle (less than 20 °). This results in steeper edges, a larger profile coverage and lower radial forces acting on the bearing of the gears. The high-gearing is therefore less sensitive compared to a conventional geometry

Axial distance deviations and concentricity errors and also smoothness is improved. The high-toothing has in comparison with a double helical toothing, which is also referred to as an arrow toothing, the advantage that the spur gears used in this case by means of Conventional manufacturing processes can be produced and thus existing assembly processes can be maintained.

A development of the invention provides that the reduction gear is a planetary gear, with a sun gear, a ring gear and at least one planet gear, which is arranged between the sun gear and the ring gear and is engaged with these. Planetary gears have the advantage that they allow large gear ratios and can transmit large torques, as this is divided by the use of multiple planet gears on them. The shafts of the sun gear, the ring gear and the planet gear are usually parallel to each other, and those of the sun gear and the ring gear may be coaxial. It is advantageous if both the sun gear, the ring gear and the at least one planetary gear have the high toothing. Sun gear, ring gear and planet form the gears of the invention.

A development of the invention provides that the sun gear on the drive shaft rotatably and / or the ring gear is fixedly arranged / are. The sun gear is thus assigned to the drive shaft and fixed on this, so that a transmission of a drive torque in the reducer is possible. Drive shaft and sun gear are thus actively connected. The ring gear can be stationary, so not rotatable, arranged. The drive of the reducer thus takes place via the drive shaft, which is connected to the sun gear. The output is provided via the at least one planetary gear which is rotatably mounted on a planet carrier. The planet carrier can be operatively connected to the output shaft, so rotatably connected, be. It can also be provided that the planet carrier is formed integrally with the output shaft.

A development of the invention provides that the sun gear is formed integrally with the drive shaft. For example, the sun gear can already be formed during the production of the drive shaft on this. In this way, no attachment mechanisms must be provided to secure the sun gear on the drive shaft. This can be one Reduction in weight of the drive shaft and thus the reducer be conducive.

A development of the invention provides that the at least one planet gear is rotatably mounted on a planet carrier. The planet carrier serves for the rotatable mounting of the at least one planetary gear. The planet carrier can be mounted stationary or rotatable. In a planetary gear, either the ring gear or the planet carrier must always be rotatably arranged. The planet carrier holds the at least one planetary gear between the sun gear and the ring gear so that the teeth of the planetary gear can engage with both the sun gear and the ring gear.

A development of the invention provides that the planet carrier rotatably mounted and rotatably connected to the output shaft, in particular integrally formed with this is. The output of the reducer, for example on the side of the internal combustion engine, thus takes place via the planet carrier. For this purpose, this is rotatably mounted and has a rotationally fixed connection with the output shaft. It may be particularly advantageous to design the planet carrier in one piece with the output shaft in order to achieve a weight reduction of the reduction gear. For example, the reduction gear may have a rotationally fixed connection between the sun gear and drive shaft and the planet carrier and output shaft, while the ring gear is arranged stationary.

A development of the invention provides that the high-toothing has an effective minimum profile coverage of about two or more than two between the sun gear and the planetary gear and / or the ring gear and the planet gear. An essential goal of the design of the high gear is to design the tooth height so that the uncorrected

Involute area an effective minimum profile coverage of> 2 each between the sun and the at least one planet and between the at least one planet and the ring gear reaches. This condition is satisfied if the shape of circle diameter dFa is chosen so that the engagement gap g _a g of the relationship _a = 2 obeys ^* p _e, where p _{e is} the (front) Engaging division referred; the profile overlap ε _α is the ratio of the engagement distance to the frontal meshing pitch p _e . The frontal meshing pitch p _e = m * π / cos (α) is the distance between two right or left flanks on the engagement line. This can also be the aim, for example, in the course of optimizing load capacity. Thus, the requirements for the one hand optimal noise and vibration behavior and on the other hand to a sufficient strength of the gears are met. The increase of the profile coverage is achieved, inter alia, by the use of a reduced module for a specific gear ratio on the gear pair, which is to be determined on the basis of the following consideration: The module used must be selected strength appropriate, so that sustainable tooth feet can be designed. The minimum usable module is found to be 0.5 mm. However, this value is to be understood only as an indicative value, since by using improved materials, a lower modulus may also be possible.

A development of the invention provides that the high-toothing has a normal engagement angle of 10 ° to 20 °, preferably about 10 ° or about 16 °. Reducing the normal meshing angle for the high gear results in steeper flanks, greater profile coverage, and lower radial forces. Thus, the high-gearing is less sensitive to axial distance deviations and concentricity errors compared to a conventional geometry, and the smoothness is improved. For non-cutting teeth, the pressure angle can be reduced to about 10 °, especially if the profile coverage is> 2. If the toothing is hobbed off, the pressure angle can be reduced, for example, to 16 °. By suitable measures, for example to increase the strength by a different choice of material, the normal engagement angle can also assume values smaller than 10 °.

A further development of the invention provides that toothed feet of the high-toothed toothing have a shape deviating from a trochoidal shape. The tooth root radius of the toothing is reduced by the use of the smaller module. This will be compensated with appropriate measures. For example, the tooth root shape for improving tooth root strength may be the conventional rounding of the tooth root by a corrected version be replaced advantageously. This is preferably done while maintaining the trouble-free engagement of the gear pairs. The optimized Zahnfußform may differ from the previous Trochoidenform.

A further development of the invention provides that tooth heads of the high toothing have a modified head region. In the tooth head region, the flank can be formed, for example, by means of a (slight) head rounding adapted to the module used. Likewise, a head take-back can be provided. Both measures allow a good lubricating film structure between the force-transmitting tooth flanks. This leads to less wear and reduced noise generation.

A development of the invention provides that the high-toothing can be produced by means of a conventional manufacturing process. The gears provided with the high-toothing have the advantage, for example, of double-helical toothing, that existing assembly processes can be maintained. So no additional manufacturing steps must be carried out or used. This allows a cost-effective production of the reducer.

A development of the invention provides that the output shaft is associated with a freewheel. About the freewheel can be prevented that the already started internal combustion engine applied to the drive shaft of the reducer with a high speed and thus damaged, for example, a connected via this electric motor. By means of the freewheel so a one-sided torque transmission is realized, that is, that the torque can be transmitted only from the drive to the output shaft.

A development of the invention provides that the reduction gear has a starter pinion, in particular with helical teeth, which can be brought into engagement with a further gear wheel. The starter pinion is preferably provided on the output shaft of the reduction gear. It is therefore not intended that the reducer or its output shaft is permanently in operative connection with the internal combustion engine - which may be assigned to the other gear - or another device. It is rather, provided that the connection can be interrupted via the starter pinion. Thus, for example, during a starting operation of the internal combustion engine, a torque transmission from the drive shaft of the reduction gear may be provided on the internal combustion engine, while this connection is interrupted following the startup process. This is done via the starter pinion, which is engageable with another gear, which is assigned for example to the internal combustion engine or the other device, into engagement. The starter pinion has particularly advantageously a helical toothing to facilitate engagement during operation. The starter pinion, for example, the freewheel assigned or these two elements can be structurally integrated.

A development of the invention provides at least one damping device, which is assigned to the drive and / or the output shaft and / or the gears. In order to further improve the acoustic behavior, the reducer can be equipped with at least one damping device. The damping device serves to considerably reduce the vibration excitations caused, for example, by the internal combustion engine. Such a device can thus make a significant contribution to reducing the noise level and the vibrations. In this case, the at least one damping device of the drive and / or the output shaft and / or the gears of the reducer is assigned. Advantageously, the damping device between reduction gear and the internal combustion engine or the other device is arranged so that vibrations are damped before reaching the reducer. This is the life of the gears beneficial. A further improvement of the acoustic properties can be achieved by using a plurality of damping devices.

The invention further relates to a starter device of an internal combustion engine having an electric motor, by means of which the internal combustion engine can be started. In this case, a arranged between the electric motor and the engine reduction gear is provided, which is designed in particular according to the above statements. Brief description of the drawings

The invention will be explained in more detail below with reference to the embodiments illustrated in the drawing, without any limitation of the invention. Show it:

1 shows a starter device of an internal combustion engine with a

reducer,

Figure 2 is a perspective view of the reducer, which is designed as a planetary gear, and

Figure 3 is a side view of the planetary gear.

Embodiment (s) of the invention

1 shows a starter device 1, also referred to as starter, an internal combustion engine, not shown, with an electric motor 2. The starter device 1 is used to start the engine by means of the electric motor 2. It is therefore one, at least temporary, operative connection between the electric motor 2 and provided the internal combustion engine. The starter device 1 has a reduction gear 3, which is designed as a planetary gear 4. This is arranged between the electric motor 2 and the internal combustion engine. A drive shaft 5 of the planetary gear 4 is therefore in operative connection with the electric motor 2 or an armature shaft 6 of the electric motor 2 and can in particular be designed in one piece with this. On the side of the planetary gear 4 assigned to the internal combustion engine, an output shaft 7 is provided. The drive shaft 5 and the output shaft 7 are connected via a sun gear 8, a ring gear 9 and three planetary gears 10 in operative connection. The sun gear 8, the ring gear 9 and the planet wheels 10 thus form gears 11 of the reduction gear 3. These are characterized by the fact that they are straight toothed and have a toothing high teeth. The sun gear 8 is rotatably connected to the drive shaft 5 and executed in the example shown in one piece with her. The ring gear 9, however, is stationary, so not rotatable, in one Housing 12 of the starter device 1 fixed. For this purpose, the ring gear 9 is provided in an intermediate storage 13, which is arranged, for example, in a drive bearing 14 or a pole housing 15 stationary and rotationally fixed. The intermediate storage 13 may, for example, a plastic or metal bearing 33 and / or a bearing 34, the latter serving to guide the output shaft 7 rotatably. Drive bearing 14 and pole housing 15 form components of the housing 12. In the pole housing 15 and the electric motor 2 is provided. The ring gear 9 may be formed directly in the intermediate bearing 13 in order to realize a more cost-effective design of the planetary gear 4. However, the ring gear 9 may also be designed as a single component and introduced into the intermediate storage 13. In this case, between the ring gear 9 and intermediate bearing 13, a damping device 16 may be arranged to prevent or reduce transmission of vibrations from the planetary gear 4 to the housing 12. The damping device 16 may be formed, for example, as a damping rubber 17. In the planetary gear 4, at least one planetary gear 10, three in the present example, is provided. The number and arrangement of the planet gears 10 of the planetary gear 4 is arbitrary and depends, for example, on the torque to be transmitted. The number of planet gears 10 is selected so that the strength of a toothing of the gears 11 and a planet carrier 18 of the planet gears 10 is ensured over a required life. The planet gears 10 are rotatably mounted on the planet carrier 18. For this purpose, the planet carrier 18 forms, for example, pin-like elements 19, on which the planet gears 10 are supported. The planet carrier 18 is connected to the

Output shaft 7 rotatably connected and integrally formed in the example shown with this. In the output shaft 7, a bearing 20 is provided, which serves to support the drive shaft 5. On the output shaft 7, a driver 21 is provided, which is characterized by a tooth-Λ / Vellenverbindung 22 of the type oblique or spur toothing. The toothed shaft connection 22 interconnecting the output shaft 7 and the driver 21 constitutes a so-called single-pinion drive 23. Clamping elements, not shown, and a starter pinion 24 are installed in the driver 21. It thus forms a freewheel 25 of the starter device 1. The starter device 1 is activated via an engagement relay 26, which the freewheel 25 in the direction of Sprocket 27 presses and simultaneously activates a power supply 28 of the electric motor 2 via a contact bridge 29. The engagement relay 26 thus closes the contact bridge 29, so that the electric motor 2 is supplied with power. The sprocket 27 is assigned to the internal combustion engine, so this is therefore drivable on him. When the freewheel 25 is pressed in the direction of the ring gear 27, the starter pinion 24 can mesh with the ring gear 27 and thus establish a connection between the electric motor 2 and the internal combustion engine. In this case, the starter pinion 24 experiences upon rotation of the output shaft 7 either by the helical tooth-Λ / Vellenverbindung 22 on the output shaft 7 or on the driver 21 or by the helical toothing on the starter pinion 24 a feed.

2 shows an isometric view of the reduction gear 3 in the form of the planetary gear 4. Shown is the drive shaft 5, which simultaneously forms the armature shaft 6 of the electric motor 2, not shown here. The drive shaft 5 is formed integrally with the sun gear 8 of the planetary gear 4. It is engaged with three planet wheels 10, which are rotatably mounted on the planet carrier 18 and its pin-shaped elements 19. The planet carrier 18 is integrally formed with the output shaft 7 and thus rotatably connected to her. The planet gears 10 are also engaged with the ring gear 9, which is arranged in the intermediate bearing 13, wherein the damping rubber 17 ensures a reduction in the transmitted to the housing 12, not shown vibrations.

Figure 3 shows a side view of the planetary gear 4 from the perspective of the electric motor 2. Recognizable are again the drive shaft 5 with the sun gear formed thereon 8 and the planet carrier 18 with attached pin-shaped elements 19, on soft the planet gears 10 are rotatably arranged. Shown is further arranged in the intermediate bearing 13 ring gear 9 with the damping rubber 17. The planet carrier 18 is formed integrally with the output shaft 7. In this illustration, it can be seen that the gears 11 have a toothing 30, which is designed as a high toothing 31. The high toothing 31 is characterized in that it has an effective minimum profile coverage of> 2 which is realized by a normal locking angle of 10 ° to 20 °. In this case, a tooth root 32 deviate from a Trochoidenform. The tooth root 32 is shown here as belonging to the ring gear 9, but may be provided on each of the gears 11.

This results in the following function of the starter device 1: For starting the internal combustion engine, first the engagement relay 26 is turned on, which energizes the electric motor 2 of the starter device 1 via a contact bridge 29. This has the consequence that a torque is generated by the electric motor 2, which sets the armature shaft 6 in a rotational movement. The armature shaft 6 forms the drive shaft 5 of the planetary gear 4, so that this is driven. This is done by the drive shaft 5, the sun gear 8 drives, which is in engagement with three planetary gears 10. These in turn are in engagement with the ring gear 9 and are mounted on the planet carrier 18, which is set in rotation in rotation. The planet carrier 18 is formed integrally with the output shaft 7, so that it is driven. The engagement relay 26 continues to move the freewheel 25 in the direction of the ring gear 27, so that the starter pinion 24 can mesh with the ring gear 27. In this way, an operative connection between the electric motor 2 and the engine is established and the torque of the electric motor 2 can drive this. In this way, the internal combustion engine is started and then the operative connection between the electric motor 2 and internal combustion engine is interrupted by the starter pinion 24 from the ring gear 27 again, as soon as the engagement relay 26 is deactivated.

Claims

claims

1. reducer (3), in particular for a starter device (1) of an internal combustion engine, for speed-reducing coupling of a drive and an output shaft (5,7), by means of at least two gears (11) which engage with each other, characterized in that the gears (11) are straight toothed and the toothing (30) is a high toothing (31).

2. reduction gear according to claim 1, characterized in that the reduction gear (3) is a planetary gear (4), with a sun gear (8), a ring gear (9) and at least one planet gear (10) which between the sun gear (8) and Ring gear (9) is arranged and is engaged with these.

3. reducer according to one or more of the preceding claims, characterized in that the sun gear (8) on the drive shaft (5) rotatably and / or the ring gear (8) is arranged stationary / are.

4. reducer according to one or more of the preceding claims, characterized in that the sun gear (8) is formed integrally with the drive shaft (5).

5. reducer according to one or more of the preceding claims, characterized in that the at least one planet gear (10) on a planet carrier (18) is rotatably arranged.

6. reducer according to one or more of the preceding claims, characterized in that the planet carrier (18) rotatably mounted and rotatably connected to the output shaft (7), in particular integrally formed therewith, is.

7. reducer according to one or more of the preceding claims, characterized in that the high toothing (31) has an effective minimum profile coverage of about two or greater than two between the sun gear (8) and the planetary gear (10) and / or the ring gear (9) and the planet gear (10).

8. reducer according to one or more of the preceding claims, characterized in that the high toothing (31) has a normal engagement angle of 10 ° to 20 °, preferably about 10 ° or about 16 °.

9. reducer according to one or more of the preceding claims, characterized in that toothed feet (32) of the high-toothing (31) have a shape deviating from a Trochoidenform.

10. reducer according to one or more of the preceding claims, characterized in that tooth heads of the high-toothing (31) have a modified head portion.

11. reducer according to one or more of the preceding claims, characterized in that the high-toothing (31) can be produced by means of a conventional manufacturing process.

12. reducer according to one or more of the preceding claims, characterized in that the output shaft (7) is associated with a freewheel (25).

13. reduction gear according to one or more of the preceding claims, characterized in that the reduction gear (3) has a starter pinion (24), in particular with helical teeth, which can be brought into engagement with a further gear (27).

14. reduction gear according to one or more of the preceding

Claims, characterized by at least one damping device (16) which is associated with the drive and / or the output shaft (5,7) and / or the gears (11).

15. Starter device (1) of an internal combustion engine, with an electric motor (2), by means of which the internal combustion engine can be started, characterized by a between electric motor (2) and internal combustion engine provided reduction gear (3), in particular according to one or more of the preceding claims.