EP1884293B1 - Masking system for masking a cylinder hole - Google Patents

Description

The invention relates to a masking system for masking a cylinder bore of an internal combustion engine during a thermal coating process, as well as the use of a marking system according to the invention according to the preamble of the independent claim of the respective category.

The thermal coating of cylinder surfaces of internal combustion engines by various thermal spraying methods is state of the art nowadays and is widely used, in particular, but not only, in engines for motor vehicles of all kinds. In doing so, usually the corresponding cylinder treads are activated by various methods prior to thermal coating, e.g. by corundum blasting, chilled cast iron, high pressure water jets or by other known activation processes. Substrates made of light metal alloys based on Al or Mg are most commonly used.

A widespread type of engines are V-type engines, that is, engines having two parallel rows of cylinders, wherein the two longitudinal axes of two adjacent cylinder liners, each belonging to one of the two rows of cylinders, are inclined by a certain angle to each other, whereby the characteristic V-shape of the engine block of a V-shaped engine is formed.

In such V-type engines, thermal coating involves the risk that, during coating of a cylinder wall of a cylinder bore of a first cylinder bank, on the cylinder wall of an adjacent cylinder of the second bank of cylinders, vapors, e.g. Metal vapors of the coating material, which are never completely avoided during thermal coating, are deposited. Due to the deposition of the metal vapors on the relatively cold walls on the cylinder wall of the cylinder of the second row of cylinders, this cylinder wall is contaminated in the second row of cylinders by the metal vapors, which, inter alia, has a negative effect on the adhesion of a later also applied to this cylinder coating , In addition, contamination by unmelted particles and overspray is to be feared.

Another problem is the heating of the engine block by the thermal coating process. Since the difference in thermal expansion coefficient between the thermal spray layer and the substrate may be relatively high, a temperature of the substrate above 120 ° C, which is essentially a kind of mean engine block temperature, has a negative effect on the residual stress level of the layers and above 150 ° C, there is even the danger that the made of a light metal alloy component, so the engine block, a distortion of the material suffers and thus unusable.

This problem becomes particularly clear when one considers the thermal expansion coefficients of typical materials used: typical expansion coefficients of thermal spray coatings of iron-based alloys are, for example, about 11 × 10 ^-6 / ° C, while typical thermal expansion coefficients of aluminum-based substrates at about 23 × 10 ^-6 / ° C and magnesium-based substrates typically at 27x10 ^-6 / ° C. This means that typical coefficients of thermal expansion of the substrates, that is to say of the material from which the engine blocks are made, are more than twice the size of the thermal expansion coefficients of the sprayed-on thermal sprayed coatings on the order of magnitude.

In the prior art, various devices are known, which in particular try to solve the problem of contamination of cylinder surfaces with the aforementioned metal vapors.

Thus, devices are known in which cylinder bores that are not coated with a kind of inflatable balloon are sealed, such as in the US 2001/0029886 A However, this can lead to heat accumulation and aggravates the above-mentioned problems with the thermal expansion coefficients. There are other systems, eg according to EP 1 136 583 A1 in use, in which by the crankshaft housing covers are introduced to protect the not to be coated cylinder bores. Again, ultimately, the thermal problems are not completely solved and, at least as important, the use of all known systems is very difficult or impossible to automate, especially in the case of motors of V-type, so that the coating process ultimately very expensive because a lot of manual work is necessary when coating a large number of engine blocks.

The EP 1 685 910 A1 discloses a device for applying a coating to an engine block, with which during the coating of a first cylinder bank to protect a second cylinder bank, a nozzle for sucking gas from the second cylinder bank is provided. However, here too, especially the cooling of the cylinder block is not sufficiently guaranteed.

The object of the invention is therefore to provide a device with which the problems known from the prior art, in particular the thermal problems and the problems with the contamination by metal vapors, are avoided in the thermal coating of cylinder bores of internal combustion engines At the same time a high degree of automation can be achieved easily and inexpensively.

The objects of the invention solving these objects are characterized by the features of the independent claim of the respective category.

The respective dependent claims relate to particularly advantageous embodiments of the invention.

The invention thus relates to a masking system for masking a cylinder bore of an internal combustion engine during a thermal coating process, comprising a masking body, which can be placed during the thermal coating process of a first cylinder of the internal combustion engine to cover a cylinder wall of a second cylinder in the cylinder bore of the second cylinder. In this case, the masking body is configured such that a flow gap of predeterminable width can be set to produce a flow of a fluid between the masking body and the cylinder wall of the second cylinder.

It is essential to the invention that the masking system according to the invention comprises a masking body, which on the one hand substantially completely covers a cylinder wall of a cylinder bore which is not to be coated during the coating of another cylinder wall and which therefore covers it before the direct application of metal vapors originating from a coating jet which the other cylinder is coated protects. So prevents the cylinder wall not to be coated from being exposed directly or indirectly to the coating jet.

On the other hand, the masking body is configured in such a way that a flow gap remains free between the masking body and the cylinder wall which is currently not to be coated, so that an air flow can be generated therein on the one hand causes cooling of the engine block in the covered cylinder bore and on the other hand prevents indirectly metal dust that spread in the interior of the engine block, reflected on the currently not to be coated cylinder wall.

Considering a particular embodiment of the invention, e.g. On the opposite cylinder during the coating, a closed pipe with a controlled flow gap between pipe and cylinder surface is introduced. Through appropriate openings and adequate suction, a flow of air or other fluids is achieved, which cools the cylinder surface and at the same time prevents the deposition of metal vapors on this cylinder surface, since the flows or turbulence of the metal vapors can be effectively suppressed.

In the coating of cylinder crankcases in V-construction, a row of cylinders is preferably coated in each case. The cylinder row opposite it is protected by a masking system according to the invention such that, for example, a plasma jet of a rotating plasma spray device, which is guided in the axial direction during coating through the cylinder bore, which plasma jet at a lower reversal point in the region of the crankcase of the engine block to the opposite hole can reach, the cylinder walls not to be coated cylinder row reached. This means that it does not come to the dreaded "Overspray", so the contamination of a cylinder wall not to be coated by overspray from a cylinder bore, which is currently coated. This prevents layer delamination as known in the art, which occurs when a cylinder wall previously contaminated with metal vapors is later coated.

In addition, as already mentioned, a heating of the cylinder block that inevitably takes place during the coating process is significantly reduced by the heat transfer of molten powder to the substrate. Overheating must be avoided, especially with thin-walled components, because this can lead to overheating of the cylinder block, which can also result in harmful delamination. These harmful effects are also avoided by the use of a masking system according to the invention because, by regulating the flow of the fluid through the flow gap, the masking system of the present invention ensures intelligent temperature management during the coating process.

In a specific embodiment, the masking body is a hollow masking body or a solid masking body, preferably a hollow masking cylinder or a solid masking cylinder.

In this case, the masking body is preferably designed such that the flow gap has a width of 0.1 mm to 10 mm, preferably a width between 0.2 mm and 5 mm, in particular a width between 0.4 mm and 3 mm. This ensures at the same time that the flow gap is narrow enough so that a direct contamination of the cylinder wall of the cylinder protected by the masking body can be prevented and at the same time a sufficiently strong flow in the flow gap can be maintained, so that sufficient cooling can be achieved.

In a specific embodiment, a masking system according to the invention comprises at least two masking bodies, so that at least two cylinders, preferably two adjacent cylinders, can be masked simultaneously, wherein in a particularly important practical embodiment the masking system comprises a predeterminable number of masking bodies and is designed such that a complete cylinder row of an internal combustion engine in V-construction is simultaneously maskable.

The masking body preferably comprises a masking cover and the masking cover comprises in particular a channel which can be connected to the flow gap, in particular an outlet channel and / or an inlet channel for conveying the fluid. The channel may have openings, one or more of which may be provided in the masking cover over which the fluid, e.g. Air or another gas, for example by a suction device, which may be provided on the crankcase, is sucked, so that thereby the flow in the flow gap between masking body and cylinder wall can be produced.

It will be understood that in another embodiment, air or other gas may also be provided via the openings, several of which, for example, may be provided in the masking cover and e.g. may be arranged in the vicinity of an edge of the masking cover can be introduced under a predetermined pressure in the flow gap or sucked through the openings, wherein the flow direction of the fluid, depending on whether the fluid is injected under pressure into the openings or sucked out of these is directed either into the crankcase or out of this. It will be understood by those skilled in the art that the shape of the openings may vary depending on the requirement, e.g. circular openings, slot-shaped openings or openings of other suitable shape can be provided.

As the fluid, in particular a gas or a gas mixture, in particular air and / or nitrogen and / or a noble gas, in particular argon and / or helium for generating the flow in the flow gap is particularly well suited.

As already mentioned, a suction means may be provided on the crankshaft space of the motor housing to be coated, so that the flow of the fluid through the flow gap through the crankshaft space of the internal combustion engine can be sucked off.

Or it can also, as also already explained for a specific example, a feed means for feeding the fluid into the flow gap may be provided, so that the flow of the fluid through the flow gap can be generated under a predetermined feed pressure.

A flow velocity of the fluid in the flow gap is preferably greater than 1 m / s, in particular greater than 10 m / s, and in particular between 1 m / s and 150 m / s, preferably between 10 m / s and 80 m / s. This on the one hand sufficient cooling of the engine block is achieved and on the other hand generates a sufficiently strong flow in the flow gap, so that no metal vapor on a non-coated cylinder surface, which is protected by a masking system according to the invention, can settle.

In particular in order to advantageously automate the coating process of cylinder running surfaces of engine blocks for industrial mass production, a manipulator, in particular a program-controlled robot system, can be provided for positioning the masking body so that the masking body can be automatically placed in the cylinder bore according to a predefinable program startup pattern.

In addition, a supply unit for providing the fluid can advantageously be provided, which is preferably programmably controllable and / or regulatable, so that e.g. the flow rate and / or the pressure and / or the flow rate of the fluid flow in the flow gap can be controlled and / or regulated, and e.g. depending on the time, the type of engine block to be coated or depending on certain coating parameters, such as temperature, type of coating device used, type of coating material, type of coating method, etc. controllable and / or regulated.

The invention further relates to the use of a masking system according to the invention, as described in detail in this application, wherein the thermal coating process is a plasma spraying process, preferably a plasma APS process, a flame spraying process, In particular, a high-speed flame spraying method and / or another thermal spraying method such as, for example, an arc wire spraying method.

In this case, an inventive masking system is used in particular as protection against contamination of a cylinder bore and / or for cooling during the thermal coating process.

It is understood that the use of both the prevention of overspray an already coated cylinder bore of a first cylinder, but of course can also relate to the prevention of overspray a still uncoated cylinder bore.

• Fig. 1 einen Schnitt durch einen Zylinderblock eines Motors in V-Bauweise mit einem erfindungsgemässen Maskierungssystem;
• Fig. 2 einen acht Zylinder V-Motor mit einem Roboter unterstützten Maskierungssystem.

In the following the invention will be explained in more detail with reference to the drawing. In a schematic representation:

• Fig. 1 a section through a cylinder block of a motor in V-construction with a masking system according to the invention;
• Fig. 2 an eight cylinder V engine with a robot assisted masking system.

Fig. 1 shows in a representation in section a simple embodiment of a masking system according to the invention during the coating of a cylinder bore of a motor in V-construction, on which the operation of a masking system according to the invention, which is hereinafter referred to in its entirety by the reference numeral 1, is explained schematically.

In Fig. 1 is a section through an engine block of a motor shown in V-construction, whose two rows of cylinders are arranged in a conventional manner parallel to each other, at an inclination angle α.

A first cylinder 5, which according to the illustration is a right-hand cylinder, is currently being coated with a rotating plasma spray gun 1000 known per se. The plasma spray gun rotates during the coating process in the cylinder 5 about a longitudinal axis, as the arrow 1002 indicates and is guided under rotation in the axial direction through the cylinder bore during the coating process. At a lower end of the plasma spray gun 1000, a plasma jet 1003 with coating material 1004 exits from a spray opening 1001, with which coating material 1004 the cylinder wall of the cylinder 5 is coated.

As Fig. 1 shows, the plasma spray gun 1000 is just near its lower reversal point, that is, the plasma jet 1003 with coating material 1004 not only applies to the cylinder wall to be coated of the cylinder 5, but extends into the crankcase of the V-engine 3 and even into the not to be coated second cylinder 7 inside.

That is, without the use of a masking system 1 according to the invention, the cylinder wall 6 of the second cylinder 7 would be contaminated with coating material 1004 and moreover heated excessively by the plasma jet 1003.

To prevent this, a masking body 4 according to the present invention is provided in the cylinder bore 2 of the second cylinder 7, which in the present example of the Fig. 1 is designed as a hollow cylinder 4 and additionally comprises a masking cover 41. The masking cover 41, which forms a cover on the second cylinder 7 or on the marking body 4, comprises a channel 42 connected to the flow gap 10, which is formed between the masking cylinder 4 and the cylinder wall 6, with openings 421, which in the example of FIG Fig. 1 is formed as an inlet channel 42 for conveying the fluid 9 in the flow gap 10.

The flow 8 of the fluid 9 in the flow gap 10 is characterized by an in Fig. 1 not explicitly shown suction generated in a manner known to those skilled in the art in the crankcase a predetermined negative pressure, so that air is sucked through the openings 421 in the masking cover 41, which then flows through the opening 421 connected to the flow gap 10, so that the cylinder 7 and thus the complete engine block of the internal combustion engine 3 on the one hand is cooled and on the other hand, a deposition of metal vapors on the cylinder wall 6 of the second cylinder 7 is prevented.

In Fig. 2 schematically an eight-cylinder V-engine with a robot-assisted masking system is shown.

Fig. 2 shows an eight-cylinder V-engine 3 with a lower cylinder row according to the illustration, in which just the cylinder 5 is coated by means of a plasma spray gun 1000 by a plasma jet with coating material 1004.

The upper row of cylinders 11 of the internal combustion engine 3 according to the illustration are simultaneously completely masked by a masking system 1 according to the invention and therefore protected from the dangerous overspray from the coating jet 1003 with which the cylinder 5 of the lower row is coated and at the same time cooled by the fluid 9 ,

The particularly important for practice special embodiment of an inventive masking system 1 of Fig. 2 comprises four masking cylinders 4 each having a masking cover 41 which Masking cylinder 4 are placed in the cylinder bores 2 of the second cylinder 7.

When more than one masking cylinder 4 is provided in one and the same masking system simultaneously, it is self-evident, for example, that one or more of the masking cylinders is hollow and one or more of the other masking cylinders are solid.

The four masking cylinders 4 are supported via the 4 masking covers 41 on a support arm 141 of a robot system 14, so that all second cylinder bores 7 can be masked or demasked at the same time by the robot system 14, by means of an in Fig. 2 not explicitly shown drive the support arm 141 is moved so that the masking cylinder can be sunk or pulled out into the second cylinder 7.

In or on the support arm 141, a feed means 13 in the form of a feed line 13 is provided, through which the fluid 9 can be supplied to the flow gaps via the masking covers 41.

If, after the coating of the lower row of cylinders according to the illustration, the upper row of cylinders is subsequently to be coated, all masking cylinders 4 can be simultaneously pulled out of the upper row of cylinders by means of the robot system 14 and subsequently placed in the lower row of cylinders to protect the cylinder walls of the lower row of cylinders. The engine block of the engine 3 may be e.g. be arranged on a strip line, so that automatically successively the cylinder bores of several engine blocks can be coated. In this case, it is also possible that the motor blocks are additionally mounted on a manipulator or on a movable robot, so that e.g. in order to place the masking system 1 according to the invention, the motor 3 can be pivoted, rotated or aligned in any other suitable way.

Claims (14)

1. A masking system for masking a cylinder bore (2) of a combustion engine (3) during a thermal coating procedure, including a masking body (4) which can be placed during the thermal coating process of a first cylinder (5) of the combustion engine (3) in the cylinder bore (2) of a second cylinder (7) to cover a cylinder wall (6) of the second cylinder (7), characterised in that the masking body (4) is designed in such a way that a flow gap (10) of predeterminable breadth can be set between the masking body (4) and the cylinder wall (6) of the second cylinder (7) for the generation of a flow (8) of a fluid (9).
2. A masking system in accordance with claim 1, wherein the flow gap (10) has a width of 0.1 mm to 10 mm.
3. A masking system in accordance with one of the previous claims, wherein the masking system includes at least two masking bodies (4) so that at least two cylinders (7) can be masked simultaneously.
4. A masking system in accordance with one of the previous claims, wherein the masking system includes a predeterminable number of masking bodies (4) and is designed in such a way that a complete row of cylinders (11) of a V-type combustion engine (3) can be masked simultaneously.
5. A masking system in accordance with any one of the previous claims, wherein the masking body (4) includes a masking cover (41).
6. A masking system in accordance with any one of the previous claims, wherein the masking cover (41) includes a passage (42) connected to the flow gap (10 for conveying the fluid (9).
7. A masking system in accordance with any one of the previous claims, wherein the fluid (9) is a gas or a gas mixture.
8. A masking system in accordance with any one of the previous claims wherein a suction means is provided so that the flow of the fluid (9) can be sucked away through the flow gap (10) through a crank space (12) of the combustion engine (3).
9. A masking system in accordance with any one of the previous claims, wherein a feed means (13) is provided for feeding the fluid (9) into the flow gap (10) so that the flow (8) of the fluid (9) through the flow gap (10) can be produced at a predeterminable feed pressure.
10. A masking system in accordance with any one of the previous claims, wherein a flow speed of the fluid (9) in the flow gap (10) is higher than lm/s.
11. A masking system in accordance with any one of the previous claims, wherein a manipulator (14) is provided so that the masking body can be placed automatically in the cylinder bore (2) in accordance with a predetermined programme starting scheme.
12. A masking system in accordance with any one of the previous claims, wherein a programme controlled supply unit is provided for the provision of the fluid (9).
13. Use of a masking system (1) in accordance with any one of the claims 1 to 12, wherein the thermal coating procedure includes a plasma spraying method, a plasma APS method, a flame spraying method, a high speed flame spraying method or another thermal spraying method such as an arc wire spraying method for example.
14. Use in accordance with claim 13, wherein the masking system (1) is used as protection against contamination of a cylinder bore (2) and/or for cooling during the thermal coating procedure.

Images