WO2010106058A1

WO2010106058A1 - Starter for an internal combustion engine

Info

Publication number: WO2010106058A1
Application number: PCT/EP2010/053366
Authority: WO
Inventors: Thomas Botzenhard; Rainer Stoeckl
Original assignee: Robert Bosch Gmbh
Priority date: 2009-03-16
Filing date: 2010-03-16
Publication date: 2010-09-23
Also published as: DE102009001562A1; CN102348887A; EP2409018A1

Abstract

The invention relates to a starter (10) for an internal combustion engine having a starter motor (13) having a drive shaft (44) that can be coupled to a starting pinion (22) via an idler (137). To improve the sliding properties and to reduce the wear of metallic parts (132, 138, 140) of the idler (137) that are movable relative to one another, coatings (242, 244, 246) are applied thereto that replace conventional lubrication in the idler and improve the durability and the sliding properties of the starter (10) overall.

Description

description

title

Starter for an internal combustion engine

State of the art

The invention is based on a starter for an internal combustion engine according to the preamble of the independent claim, as it is known for example from the Yellow Series of Bosch publications on generators and starters, Edition 2002, p. 52ff. is known. On page 71 of this document, a freewheel for a starter according to the invention is explained, which in the manner of an overrunning the rotational movements of a starter motor on the

Internal combustion engine transmits. This freewheel is located between the starter motor and a starting pinion for the internal combustion engine and has the task to take the pinion when driving the drive shaft and to solve the connection between the pinion and the drive shaft at faster running pinion. The freewheel thus prevents the armature of the starter motor is accelerated when starting the engine to an inadmissible high speed.

Starters of the type according to the invention usually have roller freewheels, wherein the frictional connection between an inner ring connected to an output shaft and an outer ring which can be driven by the starter motor is produced by cylindrical rollers can be produced, which are arranged movably along a sliding cam. At rest, this springs press the rollers in a narrowing part between the sliding curve of the freewheel outer ring and the inner ring, or the pinion shaft. The clamping angle formed on the rollers is so small that the pinion is immediately rotated when the starter motor starts up.

Occurs after the start of the separation engine overtaking, the roles are due to the friction of the

Ritzelschaftes, or the inner ring, moves in the widening part of the sliding curve, wherein the rollers due to the spring force play against the sliding curve and solve the connection between the starter motor and the engine.

In known embodiments of the freewheel whose lubrication is carried out by a special grease, which on the one hand protects the components of the freewheel from corrosion and on the other hand minimizes the temperature of the friction parameters in the freewheel. Due to large differences in the operating temperature, especially of highly stressed starters, in the range between about -40 ⁰ C and +150 ⁰ C, however, there is a risk of hardening or leakage of the lubricant. When the fat is cured, ie when the lubricating oil in the grease is lost, the freewheel locks or slips, since the fats used are generally based on silicone oil and, in the case of heat and movement, the fat is broken down into its individual components, in particular silicone oil and soaps disintegrate. The silicone oil escapes from the lubricating area while the carrier material remains as dry granules in the freewheel and impairs its function. Disclosure of the invention

The starter according to the invention with the features of the independent claim has the advantage that the functionality of its freewheel, especially with frequent use and high operating temperatures, such as those arising during start-stop operation of the engine, is maintained with certainty during the required life of the starter. This is especially true for the vulnerable friction pairings of the freewheel, namely acting as a driver outer ring with its receivers for the freewheel rollers and arranged on the output shaft of the starter inner ring as an abutment of the freewheel rollers. The fatigue of the freewheel and the hereby associated in particular at high temperatures difficulties completely eliminated, thereby reducing the assembly cost is reduced. In addition, the risk of deterioration by decomposition products of the grease is avoided at the parts adjacent to the freewheel, for example in the pinion bushings and the drive of the freewheel through the output shaft of the starter motor.

The coefficient of friction (μ) of the coating is preferably in the range of 0.02 to 1, in particular in the range of 0.04 to 0.4, wherein the coating expediently has a thickness of 2 to 10 μ. A galvanically deposited hard chrome layer has proven to be a particularly advantageous coating with an application of a solid lubricant, in particular a solid lubricant of PTFE (polytetrafluoroethylene) or MoS ₂ (molybdenum disulfide). Such an electrodeposited hard chrome layer preferably has a Thickness of 5 to 10μm. Other coatings are expediently applied in a smaller thickness, for example diamond-like carbon layers (DLC layers) in a layer thickness of 2 to 4 μm. A galvanically deposited hard chrome layer has the further advantage that the coated part is heated only very little, as a rule only to temperatures of about 50 ° C, at which deformations of the coated workpiece can be excluded with certainty. When applying DLC coatings in a PVD and / or CVD method, the coating temperature in the plasma is preferably limited to a value of approximately 250 ⁰ C, in order here also to exclude deformation of the coated workpiece and / or a deterioration in its hardness.

Further details and advantageous embodiments of the invention will become apparent from the subclaims and the embodiments in the description, in particular also to the possibility of incorporation of the solid lubricant as a finely divided, disperse phase in the base layer or in a separately applied, additional coating. The figures show:

1 shows an overall view of a starter for an internal combustion engine,

Figure 2 is an enlarged view of the

Output range of the starter with a freewheel according to the invention and

3 is an enlarged sectional view of the freewheel according to the invention along the line III-III in Figure 2. Embodiments of the invention

FIG. 1 shows a starter 10 in longitudinal section. This has a starter motor 13 and an engagement relay 16. The starter motor 13 and the engagement relay 16 are attached to a common drive bearing plate 19. The starter motor 13 is functionally to drive a starter pinion 22 when it is meshed in the ring gear 25 of the internal combustion engine, not shown here.

The starter motor 13 has a pole tube as a housing 28, which carries on its inner circumference pole pieces 31, which are each wrapped by a field winding 34. The pole shoes 31 in turn surround an armature 37, which has an armature packet 43 constructed from fins 40 and an armature winding 49 arranged in grooves 46. The armature package 43 is pressed onto a drive shaft 44. At the end remote from the starting pinion 22 end of the drive shaft 44, a commutator 52 is further attached, the u.a. from single

Commutator blades 55 is constructed. The commutator bars 55 are so electrically connected in a known manner with the armature winding 49, that upon energization of the commutator fins 55 by carbon brushes 58, a rotational movement of the armature 37 in the pole tube 28 results. A arranged between the contactor 16 and the starter motor 13 power supply 61 supplies in the on state, both the Kohlbürsten 58 and the field winding 34 with power.

The drive shaft 44 is commutator side supported with a shaft journal 64 in a sliding bearing 67, which in turn is held stationary in a commutator bearing plate 70. The end shield 70 is in turn by means of tie rods 73, which are arranged distributed over the circumference of the pole tube 28 (screws, for example, 2, 3 or 4 pieces) in the drive end plate 19 is attached. The pole tube 28 is supported on the drive bearing plate 19 and the commutator bearing plate 70 on the pole tube 28th

In the drive direction, a so-called sun gear 80 connects to the armature 37, which is part of a planetary gear 83. The sun gear 80 is surrounded by a plurality of planet gears 86, usually three

Planetary gears 86 which are supported by means of rolling bearings 89 on journals 92. The planet gears 86 roll in a ring gear 95, which is mounted outside in the pole tube 28. Towards the output side, the planetary gears 86 are followed by a planet carrier 98, in which the

Achszapfen 92 are included. The planet carrier 98 is in turn stored in an intermediate storage 101 and a slide bearing 104 arranged therein. The intermediate bearing 101 is designed cup-shaped, that in this both the planetary carrier 98 and the planet gears 86 are added. Furthermore, the ring gear 95 is arranged in the cup-shaped intermediate bearing 101, which is ultimately closed by a cover 107 relative to the armature 37. Also, the intermediate bearing 101 is supported with its outer circumference on the inside of the pole tube 28. The armature 37 has on the end facing away from the commutator 52 end of the drive shaft 44 has a further shaft journal 110, which is also received in a sliding bearing 113, from. The sliding bearing 113 in turn is received in a central bore of the planet carrier 98. The planetary carrier 98 is integrally connected to the output shaft 116. This output shaft 116 is supported with its end 119 facing away from the intermediate bearing 101 in a further bearing 122 which is fixed in the drive bearing plate 19. The output shaft 116 is divided into several sections. Thus, the section which is arranged in the sliding bearing 104 of the intermediate bearing 101 is followed by a section with a straight toothing 125 (internal toothing), which is part of a shaft-hub connection. This shaft-hub connection 128 in this case allows the axially rectilinear sliding of a driver 131. This driver 131 is a sleeve-like extension which is integral with a cup-shaped outer ring 132 of the freewheel 137. This freewheel 137 (Richtgesperre) further consists of the inner ring 104 which is disposed radially within the outer ring 132. Between the inner ring 140 and the outer ring 132 clamping body 138 are arranged. These designed as cylindrical rollers clamp body 138 prevent in cooperation with the inner and outer ring relative rotation between the outer ring and the inner ring in a second direction. In other words, the freewheel 137 allows a relative movement between inner ring 140 and outer ring 132 in one direction only. In this embodiment, the inner ring 140 is formed integrally with the starter pinion 22 and its helical teeth 143 (external helical teeth).

For the sake of completeness, I would like to mention the

Einspurmechanismus received. The engagement relay 16 has a bolt 150, which is an electrical contact and which is connected to the positive terminal of an electric starter battery, which is not shown here. This bolt 150 is passed through a relay cover 153. This relay cover 153 terminates a relay housing 156, which is fastened by means of a plurality of fastening elements 159 (screws) on the drive bearing plate 19. In the engagement relay 16 are still a pull-in winding 162 and a Holding winding 165 arranged. The pull-in winding 162 and the holding winding 165 both generate an electromagnetic field in the switched-on state, which flows through the relay housing 156 (made of electromagnetically conductive material), a linearly movable armature 168 and an armature return 171. The armature 168 carries a push rod 174, which is moved in the direction of linear retraction of the armature 168 in the direction of a switching pin 177. With this movement of the push rod 174 to the shift pin 177 this is from its rest position in the direction of two

Contacts 180 and 181 moves so that a mounted at the end of the switching pin 177 contact bridge 184 connects both contacts 180 and 181 electrically. As a result, electrical power is conducted from the bolt 150 across the contact bridge 184 to the power supply 61 and thus to the carbon brushes 58. The starter motor 13 is energized.

However, the engagement relay 16 or the armature 168 also has the task, with a tension member 187 to move a drive plate 19 rotatably mounted lever. This lever 190, usually designed as a fork lever, engages with two tines, not shown here, on its outer circumference two discs 193 and 194 to a clamped between them

Driving ring 197 to the freewheel 137 to move against the resistance of the spring 200 and thereby einzura the starter pinion 22 in the ring gear 25.

Figure 2 shows a detail of an enlargement of

Drive bearing plate 19 with the starter pinion 22. This has a helical toothing 143, which is arranged on the toothed rim 25 facing the end of a sleeve-like extension 203. This sleeve-like extension 203 provides a Type pipe, which has a total of two sections. A first portion is that on whose axial length the helical gear 143 is mounted. The second section is that on which the inner ring 140 is pushed. This inner ring 140 in turn has three contours, which have different functions. Thus, on the one hand, a clamping surface or clamping web 210 is present, which has a machined, preferably ground surface, on which the clamping bodies 138 are clamped. In the direction of the helical gearing 143, a shoulder 213 can be seen, which separates the clamping track 210 from a starting collar 216.

The inner ring 140 is pushed or shrunk onto the sleeve-like extension 203, so that a frictional connection between the sleeve-like extension 203 and the inner ring 140 is made. Under normal load conditions, this inner ring 140 of the sleeve-like extension 203 is not wegschiebbar. However, the inner ring 140 can also be fastened, for example, by material engagement (welding, soldering) or by means of a shaft-hub connection.

The starting collar 216 has the following function: If by means of the contactor 16 the starter pinion 22 is pushed in the direction of the ring gear 25 and inserted into the helical teeth of the Andrehritzels 22 adapted or coordinated helical teeth of the ring gear 25, it is in Andrehlauf, so after transfer a drive torque from the starter pinion 22 on the sprocket 25 causes an axial force between the ring gear 25 and the starter pinion 22. This axial force acts in such a way that the starting pinion 22 moves with its helical toothing 143 further in the direction of meshing wants to be. In this left movement in FIG. 2, this ultimately leads to the toothed rim 25, with its end face 220, coming into contact with the starting collar 216 or its contact surface 223. This contact surface 223 or the starting collar 216 then prevents any further axial movement of the Andrehritzels 22 in the ring gear 25. It is thus a system of starting device 10 and internal combustion engine disclosed, wherein the starting device 10 has a starter pinion 22, which is adapted to a ring gear 25 of the internal combustion engine to be eingespurt. Both the ring gear 25 and the starting pinion 22 are each provided with a coordinated helical gears 143 and 240, respectively. At the starter pinion 22 while a means (start-up collar 216, contact surface 223) is present, which receives at a starting operation due to the helical teeth 143, 240 between the ring gear 25 and the starter pinion 22 acting axial forces.

In addition to the helical teeth 143 of the drive pinion 22 so that a contact surface 223 is present, which allows a system of at least one tooth of the ring gear 25. By this contact surface 223 and this start-up collar 216 between the ring gear 25 and the starter 22 acting axial forces are canceled such that these axial forces outside the teeth, or helical teeth 143 of Andrehritzels 22 and helical teeth 240 including a short radial portion below the helical teeth 240 of the ring gear 25 and the contact surface 223 or the start-up collar 216 are not effective. Only within this relatively narrow range are material stresses effective. In the case of an embodiment according to FIG. 2, that is to say with the design according to which the inner ring 140 rests on the sleeve-like extension 203 deferred, these two sections are also covered by this statement. In other words, an axial force which acts on the starting collar 216 naturally leads to stresses in the joining surface between the inner ring 140 and the sleeve-like extension 203. The tensions do not continue otherwise. In the ring gear 25 caused by the axial force stresses act on the helical gears 240 and in a narrow radial region below the helical gear 240.

As already explained for the description of the inner ring 140, this is integrally connected to the contact surface 223 and the start-up collar 216, wherein the inner ring 140 is designed with a running surface or clamping surface or clamping track 210 for the clamping body 138 of the freewheel 137. The starter pinion 22 is supported by means of a plate spring or plate-spring-like spring 139 relative to the outer ring 132 resiliently.

It is envisaged that the system of internal combustion engine and starter is operated as a so-called start-stop system. This means that the internal combustion engine is switched off as often as possible or sensibly for consumption optimization, for example at traffic lights or level crossings or in traffic jams. For this purpose, the starter pinion 22 is already meshed in the ring gear of the internal combustion engine in this case, when the speed of the Kurbelbeziehungsweise drive shaft is reduced because of switching off the engine. The starter motor is only started when the start request is signaled by actuating an actuator (eg accelerator pedal). In this mode of operation of the starter 10, the mechanical load and the heating, in particular of the freewheel 137, are particularly high. In order to achieve the predetermined operating time is therefore proposed according to the invention that at least some of the strongest by wear and

Heating stressed metal parts of the freewheel 137 are provided with a sliding and wear protection coating. These highly stressed parts are, in particular, the outer ring 132, the inner ring 140 and the clamping bodies 138, for example in the form of the illustrated cylindrical freewheel rollers. However, spherical or barrel-shaped freewheel bodies can also be used as clamping body 138. A coating with particularly good sliding properties and very high wear resistance is therefore applied to the inner clamping surface 212 of the outer ring 132, on the surface of the clamping body 138 and on the outer clamping surface 210 of the inner ring 140 to optimal and permanently good sliding and wear properties of the freewheel 137th to ensure. Hereinafter, the coating on the inside of the outer ring 132 is denoted by 242, 244 the coating on the outside of the inner ring 140 and 246 the coating on the clamping bodies 138th

Figure 3 shows the freewheel 137 in a sectional view along the line III-III in Figure 2. The same parts are provided with the same reference numerals as in Figure 2. The illustration clearly shows in the upper part the shape of the recesses 248 for receiving the clamping body 138 and coil springs 250, which bias the clamping body in the idle state of the freewheel and in the narrowing part of the recesses 248 between the sliding curve 252 of the outer ring 132nd and press the surface of the inner ring 140. Which At the so-called freewheel rollers forming clamping angle is in this case so small that the output shaft 116 is rotated about the inner ring 140 at starting starter motor 13 immediately. In the lower part of Figure 3, the executed in a known manner helical gear 240 of Andrehritzels 22 can be seen.

The coatings 242, 244 and 246 are generally similar running with a coefficient of friction (μ) of 0.02 to 1, preferably from 0.04 to 0.5, and with a layer thickness between 2 and 10 microns. In principle, however, different coatings for the running surfaces of the outer ring 132 and the inner ring 140 as well as for the surface of the clamping body 138 can be selected, if different loads should be specifically taken into account. Such different loads can result, for example, from different rolling radii as well as from different materials for the production of the individual parts of the freewheel 137.

A preferred coating for the friction and sliding surfaces on the outer ring 132 on the inner ring 140 and on the clamping body 138 consists of a galvanically deposited hard chrome layer with a layer thickness of 5 to 10 μm and an additionally applied solid lubricant. As such, in particular polytetrafluoroethylene (PTFE) is suitable, since it is very temperature-resistant and allow temperatures up to approximately 250 ⁰ C during operation of the freewheel. Such a solid lubricant, for example made of PTFE or MoS ₂ , can be incorporated both as a disperse phase in the coatings 242, 244 and / or 246 or form the coating as an additional layer together with a base layer. As an alternative to electrodeposited layers, it is possible to chemically deposit the coatings 242, 244 and / or 246, for example as nickel-phosphorus layer, into which non-metallic hard-material particles may additionally be incorporated to increase the wear resistance, preferably SiC, B ₄ C, Se ₃ N ₄ and / or DLC (Diamond Like Carbon) particles. However, a DLC film may also be as a single layer, the coatings 242, 244 and / or 246 to form and be deposited in a plasma-assisted PVD and / or CVD method at temperatures up to approximately 250 ⁰ C.

Before the coating according to the invention to be coated metallic parts of the freewheel 137 are mechanically smoothed in a known manner, preferably by

Sanding and / or polishing. In addition, a hardening of the parts takes place in basically also known manner by a heat treatment. The greases used in conventional starters to improve the sliding properties and to reduce wear accounts for.

Claims

claims

1. starter (10) for an internal combustion engine, with a starter motor (13) with a drive shaft (44), which via a freewheel (137) with a starter pinion (22) can be coupled, characterized in that at least one of the mutually movable metallic parts (132,138,140) of the freewheel (137) with a sliding and anti-wear coating (242,244,246) are provided.

2. A starter according to claim 1, characterized in that the coating (242,444,246) has a coefficient of friction (μ) of 0.02 to 1, preferably from 0.04 to 0.5.

3. A starter according to claim 1 or 2, characterized in that the coating (242.244.246) consists of a galvanically deposited hard chromium layer and a solid lubricant.

4. Starter according to one of the preceding claims, characterized in that the coating (242,244,246) a

Thickness of 2 to 10 microns.

5. Starter according to one of the preceding claims, characterized in that in the coating (242,244,246) a solid lubricant is incorporated as a disperse phase.

6. A starter according to claim 1 or 2, characterized in that the coating (242,244,246) has at least two individual layers with a base layer and a further layer with inclusions of solid lubricant, preferably of PTFE

(Polytetrafluoroethylene, teflon) or from MoS ₂

(Molybdenum disulfide).

7. A starter according to claim 1 or 2, characterized in that the coating (242.244.246) consists of a chemically deposited nickel-phosphorus layer.

8. The starter according to claim 1 or 2, characterized in that the coating (242,244,246) of a nickel-phosphorus layer with embedded non-metallic particles of hard material, preferably made of SiC (silicon carbide) and / or B ₄ C (boron carbide) and / or Si ₃ N ₄ (silicon nitride) and / or DLC (Diamond Like Carbon).

9. A starter according to claim 1 or 2, characterized in that the coating (242.244.246) consists of a DLC (Diamond Like Carbon) layer.

10. A starter according to claim 9, characterized in that the DLC layer is applied in a plasma-assisted PVD / CVD method at temperatures below 250 ⁰ C.

11. Starter according to one of the preceding claims, characterized in that the metallic parts to be coated (132,138,140) of the freewheel (137) are hardened by heat treatment.

12. Starter according to one of the preceding claims, characterized in that the metallic parts to be coated (132,138,140) of the freewheel (137) are mechanically smoothed, preferably by grinding and / or polishing.