DE102022105774A1 - Method for machining a crankcase and crankcase - Google Patents

Abstract

Method for machining a crankcase, comprising the steps: - Providing a crankcase comprising at least one cylinder bore which extends along a cylinder axis; - Applying a coating to the cylinder bore along the cylinder axis via a thermal spray process; - Varying the spray parameters when coating along the Cylinder axis for creating a coating that has different properties along the cylinder axis.

Description

The present invention relates to a method for machining a crankcase and a crankcase.

It is known from the prior art to coat the cylinder bores of crankcases to create running surfaces. Thermal coating processes, such as arc wire spraying, are often used for this purpose. One challenge that arises here is to ensure that the coating lasts permanently, i.e. does not chip or anything like that. For this purpose, the surface of the cylinder bore is activated in a suitable manner before the coating is applied, which in particular means mechanical roughening. The DE 10 2006 004 769 A1 In this context, for example, discloses a method for roughening metal surfaces to improve the adhesion of layers thermally sprayed thereon. In order to further reduce fuel consumption and costs, it is important to find solutions to further optimize such treads.

It is therefore an object of the present invention to provide a method for machining a crankcase and a crankcase, whereby the known methods and crankcases are to be further optimized in order to increase operational efficiency and reduce manufacturing costs.

This object is achieved by a method according to claim 1 and by a crankcase according to claim 10. Further advantages and features result from the subclaims as well as the description and the attached figure.

• - Bereitstellen eines Kurbelgehäuses, umfassend zumindest eine Zylinderbohrung, welche sich entlang einer Zylinderachse erstreckt;
• - Aufbringen einer Beschichtung auf die Zylinderbohrung entlang der Zylinderachse über ein thermisches Spritzverfahren;
• - Variieren der Spritzparameter beim Beschichten entlang der Zylinderachse zum Erzeugen einer Beschichtung, welche entlang der Zylinderachse unterschiedliche Eigenschaften aufweist.

According to the invention, a method for machining a crankcase comprises the steps:

• - Providing a crankcase comprising at least one cylinder bore which extends along a cylinder axis;
• - Applying a coating to the cylinder bore along the cylinder axis via a thermal spray process;
• - Varying the spray parameters when coating along the cylinder axis to produce a coating that has different properties along the cylinder axis.

It has been found that many advantages can be gained by coating according to needs or load, be it in terms of the efficiency that can be achieved in operation, which is reflected in the fuel consumption of the internal combustion engine, or also in terms of the use of resources required during coating. This is achieved by varying the spray/process parameters during coating. This takes into account the fact that the piston runs through a speed profile along the cylinder axis, with a maximum speed between the piston reversal points and speed 0 in the area of the piston reversal points. It was recognized that the cylinder running surface is exposed to different loads and tribological conditions and that this should advantageously influence the design of the cylinder running surface. The use of thermal spraying processes is particularly advantageous in this context, since the coating application and thus the formation of the coating/cylinder running surface can be adjusted flexibly and quickly via the spraying parameters.

According to preferred embodiments, the aforementioned properties, which are preferably designed differently, include the hardness and/or the porosity of the coating.

Thermal coating processes, also called “thermal spraying”, are surface coating processes. Here, additional materials (also called spray additives) are melted, melted or melted inside or outside a heat source, such as a spray torch, accelerated in a gas stream in the form of spray particles and thrown onto the surface of the component to be coated.

• - Variieren der Spritzparameter derart, dass die Beschichtung im Bereich der Kolbenumkehrpunkte eine höhere Härte aufweist als dazwischen.

According to a preferred embodiment, the method comprises the step:

• - Vary the spraying parameters in such a way that the coating has a higher hardness in the area of the piston reversal points than in between.

• - Variieren der Spritzparameter derart, dass die Beschichtung im Bereich zwischen den Kolbenumkehrpunkten eine höhere Porosität aufweist als im Bereich der Kolbenumkehrpunkte.

According to a preferred embodiment, the method also includes the step:

• - Vary the spray parameters in such a way that the coating has a higher porosity in the area between the piston reversal points than in the area of the piston reversal points.

For example, it was found that it is not necessary for the coating between the piston reversal points to have the same hardness as at or in the area of the piston reversal points. Similarly, the coating conveniently does not have the same porosity along the cylinder axis. In fact, this is advantageously larger between the piston reversal points than at or in the area of the piston reversal points. Increased porosity in the area between the piston reversal points can serve to ensure a sufficient oil film precisely where the piston speeds are highest, since the porosity advantageously forms the smallest oil pockets.

According to a preferred embodiment, the spraying process in the present case is arc spraying (also: arc wire spraying). Here, an arc is ignited between several, for example two, three or four, wire-shaped spray materials of the same or different types. The wire tips are melted at a temperature of around 4000 °C and blown onto the workpiece surface using a gas stream. According to a preferred embodiment, an iron material (FeC) is used as the wire material. The following statements relate primarily to arc wire spraying. However, it is possible for the person skilled in the art to also carry out other spraying processes, such as cold gas spraying, high-speed flame spraying or atmospheric plasma spraying, although this list is not intended to be exhaustive, along the cylinder axis with different process parameters, so that arc wire spraying is to be understood as an example in which However, the variation is easily feasible.

The aforementioned process parameters, which can expediently be varied/changed, are general or, in the case of arc wire spraying, in particular: the pressure of the gas stream, the volume flow of the gas stream, the power of the heat source, in particular, for example, the electrical voltage and the electrical current, as well as the speed (m /s) the supply of the spray material, in other words the wire feed, such as the wire material in arc wire spraying.

It was found that it is particularly advantageous to coat along the cylinder axis with different temperatures and/or impact speeds of the spray particles in order to achieve the desired properties of the coating. The aforementioned coating properties can advantageously be changed, particularly at the same time, via the temperature/impact speed of the spray particles.

In particular, the porosity and lamellarity as well as the hardness of the coating can be influenced. When coating along the cylinder axis, different parameter sets are expediently used.

According to one embodiment, there is a set of parameters for top (upper piston reversal point), intermediate and bottom (lower piston reversal point). According to one embodiment, fewer or more parameter sets can also be provided in order to adjust the properties of the coating along the cylinder axis in a targeted and needs-based manner.

• - Beschichten im Bereich der Kolbenumkehrpunkte mit höherer Temperatur und/oder mit höheren Auftreffgeschwindigkeiten als dazwischen.

The method expediently includes the step:

• - Coating in the area of the piston reversal points with higher temperatures and/or with higher impact speeds than in between.

Increasing the temperature (and/or the impact speed) results in a more compact, harder layer. Accordingly, coating with a comparatively lower temperature/impact speed results in a looser, more porous layer.

The temperature, as well as the speed of the spray particles, can be varied via the temperature/speed of the gas stream, which in turn can be influenced via the pressure and/or the volume flow. When arc wire spraying, the temperature of the spray particles is expediently set via the temperature of the arc.

• - Variieren der elektrischen Leistung, insbesondere der Stromstärke und/oder der Spannung, zum bedarfsgerechten Ändern der Temperatur der Spritzpartikel.

According to a preferred embodiment, the method comprises the step:

• - Varying the electrical power, in particular the current and/or the voltage, to change the temperature of the spray particles as needed.

The variation in the temperature of the spray particles can expediently be brought about quickly and efficiently by varying the current intensity and/or the voltage. By changing the temperature of the spray particles, the hardness, porosity and layer thickness of the coating can be adjusted as required.

When arc wire spraying, for example, the current intensity (or the voltage) is preferably varied via the power source.

• - Erhöhen der Stromstärke beim Beschichten im Bereich der Kolbenumkehrpunkte.

The method expediently includes the step:

• - Increasing the current strength when coating in the area of the piston reversal points.

A more compact, denser and harder coating can expediently be produced by increasing the current intensity. Accordingly, the current intensity in the area is reduced creates a less hard, more porous layer between the piston reversal points.

Reducing the current intensity causes a change in the resulting arc, which changes the impact temperature of the jet particles. The temperature typically decreases as the current intensity decreases.

The parameters current and voltage are preferably not changed at the same time. According to a preferred embodiment, the current intensity is changed at a constant voltage, or vice versa. According to one embodiment, the wire feed is expediently kept constant.

• - Variieren einer Geschwindigkeit des Gasstroms zum Beeinflussen eines Auftreffwinkels der Spritzpartikel.

According to one embodiment, the method comprises the step:

• - Varying a speed of the gas flow to influence an impact angle of the spray particles.

The speed of the gas flow can be adjusted by varying the pressure of the propellant gas (for example nitrogen in arc wire spraying). Lower speeds result in a flatter impact angle of the spray particles, which in turn results in a higher porosity of the coating. Higher speeds result in a steeper impact angle of the spray particles, which results in a lower porosity of the coating.

According to one embodiment, the travel speed of the coating tool is also varied along the cylinder axis. This can be used, for example, to create a uniformly thick layer along the cylinder axis. The creation of the looser, more porous layer is typically accompanied by the fact that it becomes relatively thicker. By adjusting the travel speed, the thickness of the coating along the cylinder axis can be advantageously adjusted. According to one embodiment, coating is also carried out multiple times, at least in areas or sections.

• - Nacharbeiten der Beschichtung zum Einstellen eines Durchmessers, insbesondere also eines entlang der Zylinderachse gleichmäßigen Durchmessers.

According to one embodiment, the method also includes the step:

• - Reworking the coating to set a diameter, in particular a diameter that is uniform along the cylinder axis.

During this, in particular mechanical, reworking, a constant or essentially constant diameter is set along the cylinder axis. In a further step, (shape) honing is expediently carried out to finalize the cylinder surface.

The invention also relates to a crankcase, in particular a crankcase which has been machined according to the method according to the invention, comprising at least one cylinder bore, the cylinder bore having a coating which is produced via a thermal spraying process, and the cylinder bore having different properties along the cylinder axis. The coating is expediently produced in accordance with needs or load.

According to a preferred embodiment, the coating has a higher hardness in the area of the piston reversal points than in between.

The coating expediently has a higher porosity between the piston reversal points than in the area of the piston reversal points.

It should be mentioned at this point that the advantages mentioned in connection with the process apply analogously and accordingly to the crankcase, and vice versa. As already mentioned, it was found that the two aforementioned target variables can expediently be set simultaneously using the “temperature” parameter. Increasing the temperature during coating results in a more compact, harder coating, while a decrease in temperature results in a looser, more porous structure. Additionally or alternatively, you can also work with a different impact angle of the jet particles in order to influence the properties of the coating.

Further advantages and features result from the following description of an embodiment of the method with reference to the attached figure.

• 1: eine schematische Ansicht einer Ausführungsform eines Kurbelgehäuses zur Veranschaulichung einer Ausführungsform eines Verfahrensablaufs.

It shows:

• 1 : a schematic view of an embodiment of a crankcase to illustrate an embodiment of a process sequence.

1 shows a schematic view of a section of a crankcase 10, comprising a cylinder bore 12 which extends along a cylinder axis Z. Reference numeral 40 denotes a schematically illustrated device for coating, in particular for arc wire spraying. The cylinder bore 12 has a coating 20 which is applied via the device 40. The cylinder bore is 12 divided into three areas along the cylinder axis Z. Reference numeral 30 designates the areas of piston reversal points, while reference numeral 32 outlines the area in between. The coating 20 is expediently formed with different properties along the cylinder axis Z. The coating 20 was expediently applied differently along the cylinder axis Z. In particular, the spraying process was carried out differently along the cylinder axis Z. The coating 20 is preferably carried out at an elevated temperature in the area of the piston reversal points 30, resulting in a coating 20 which has a higher compactness and a higher hardness in these areas than in the intermediate area 32, in which the coating was carried out at a lower temperature. For example, the temperature is varied by adjusting the current strength during coating.

Reference symbol list

10

crankcase

12

Cylinder bore

20

Coating

30

Piston reversal points

32

Intermediate area

40

Coating device

Z

Cylinder axis

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006004769 A1 [0002]

Claims (12)

Method for machining a crankcase (10), comprising the steps: - Providing a crankcase (10) comprising at least one cylinder bore which extends along a cylinder axis (Z); - Applying a coating (20) to the cylinder bore (12) along the cylinder axis (Z) via a thermal spray process; - Varying the spray parameters when coating along the cylinder axis (Z) to produce a coating (20) which has different properties along the cylinder axis (Z). Procedure according to Claim 1 , where the spraying process is arc wire spraying. Procedure according to Claim 1 or 2 , comprising the step: - varying the spraying parameters such that the coating (20) in the area (32) between the piston reversal points (30) has a higher porosity than in the area of the piston reversal points (30) and / or the coating (20) in the area the piston reversal points (30) have a higher hardness than in the area (32) in between. Method according to one of the preceding claims, comprising the step: - Coating along the cylinder axis (Z) with different temperatures and/or impact speeds of the spray particles. Method according to one of the preceding claims, comprising the step: - Coating in the area of the piston reversal points (30) with a higher temperature and/or a higher impact speed of the spray particles. Method according to one of the preceding claims, comprising the step: - Varying the electrical power, in particular the current and/or the voltage, to change the temperature of the spray particles as needed. Procedure according to Claim 6 , comprising the step: - Increasing the current strength during coating in the area of the piston reversal points. Method according to one of the preceding claims, comprising the step: - Varying a speed of the gas flow during coating to influence the spray angle of the spray particles. Method according to one of the preceding claims, comprising the step: - Reworking the coating (20) to set a diameter. Crankcase (10), in particular processed according to a method according to one of the preceding claims, comprising at least one cylinder bore (12), the cylinder bore (12) having a coating (20) which is produced via a thermal spray process, and wherein the cylinder bore (12) has different properties along its cylinder axis (Z). crankcase Claim 10 , wherein the coating (20) has a higher hardness in the area of the piston reversal points (30) than in between. Crankcase according to one of the Claims 10 - 11 , wherein the coating (20) between the piston reversal points (30) has a higher porosity than in the area of the piston reversal points (30).

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