METHOD FOR SURFACE MACHINING, METHOD FOR MANUFACTURING AN ENGINE BLOCK, DEVICE FOR SURFACE MACHINING

Description

[0001] The invention relates to a device for surface treatment of a cavity, a method for surface treatment of a cavity, in particular a piston bore of a cylinder of an internal combustion engine block, a method for producing an engine block of an internal combustion engine and a motor vehicle, in particular a passenger car.

[0002] During the production of piston bores for cylinders in internal combustion engine blocks, these are typically structured. This can be performed as a preparatory step for thermal coating. Abrasive processes, such as laser radiation, can be used to structure the surface.

[0003] In abrasive surface treatment processes, removed material typically occurs in the form of solid particles, liquid droplets, or in gaseous or vapor form. For an efficient and trouble-free process, this material must be quickly removed from the site of removal. For this purpose, suction extraction is often a suitable option. A negative pressure is used to generate a gas stream, such as an air stream, which is suitable for carrying the particles along and transporting them away from the site of removal. For this purpose, a sufficient air velocity must be achieved to keep the particles, which typically consist of metal or metal oxide, in the air stream. The air stream can then be cleaned, for example, using a filtration process.

[0004] In existing processes, very large air flows are generated by suction, which requires a large vacuum source and thus high investment costs. Furthermore, the energy consumption is high, which results in high operating costs. The equipment required to clean the air flow must also be correspondingly large.

[0005] EP 2 799 180 A2 teaches a method and a device for surface structuring of a machine element, in which structures are created on a surface in a near-surface region using electromagnetic radiation. A reflector element is inserted into a cavity within a protective tube, allowing the surface to be structured by means of a laser and the reflection of the laser. Gases or particles generated in this process can be removed by suction. For this purpose, a gas flow is generated along the outer side of the protective tube and is extracted from the cavity on the side opposite the protective tube.

[0006] DE 100 64 440 A1 describes a method and a device for machining an inner surface of a cylindrical bore of a component, in which a laser beam is also directed onto the inner surface of the cylindrical bore by means of a reflector. Extraction is carried out here in such a way that an extraction pipe is provided, the opening of which is positioned near the point of impact of the laser beam on the surface to be machined. By generating a negative pressure, gases or particles are removed from the machining point through this extraction pipe. DE 101 18 291 A1 discloses a device for laser exposure of a surface of metallic workpieces, with a deflecting mirror and with a laser beam source which emits a laser beam directed onto the deflecting mirror and deflected at the reflective surface of the deflecting mirror.

[0007] From US 2012 / 100313 A1 a device for surface treatment of a cavity is known, comprising a substantially hollow rod-shaped treatment tool with a reflector as well as a laser beam source and an extraction system which can be sealingly attached to an opening of a cavity.

[0008] The invention is based on the object of providing a method for surface treatment, a method for producing an engine block and a device for surface treatment with which purge gas can be supplied and removed material can be removed in a simple, cost-effective and efficient manner.

[0009] To achieve this object, a device for surface treatment of a cavity according to claim 1, a method for surface treatment of a cavity, in particular a piston bore of a cylinder of an internal combustion engine block according to claim 4, and a method for producing an engine block of an internal combustion engine according to claim 9 are provided. Advantageous embodiments of the device for surface treatment are specified in subclaims 2 and 3, and advantageous embodiments of the method for surface treatment are specified in subclaims 5-8.

[0010] One aspect of the invention is a device for surface machining of a cavity. This device comprises a substantially hollow rod-shaped machining tool with a reflector, a laser beam source, and an extraction system that can be sealingly attached to one side of a cavity, in particular a cylinder of an internal combustion engine block. The device is configured such that the purge gas can be extracted at the opening of the cavity, to which it was previously introduced through the interior of the machining tool.

[0011] The machining tool is preferably designed in the shape of a hollow rod. The laser beam source can include optical elements, such as a collimator.

[0012] The reflector, also known as a deflection prism or mirror, serves primarily to deflect the laser beam, which is guided through the machining tool along its longitudinal axis and then reflected toward the surface of the cavity. Typically, the reflector is located in the machining tool on the side designed for entry into the cavity. The laser beam exits the machining tool through an outlet, particularly one located on the side.

[0013] A purge gas stream is designed to protect the reflector from contamination and to help remove the ablated particles. In particular, at least one outlet is arranged on the machining tool to allow the purge gas stream to exit. This outlet can also be the laser's exit opening. Any contaminants that become detached from the reflector can be removed with the gas or gas mixture stream.

[0014] The extraction system comprises, in particular, an extraction sleeve, also called an extraction cup, which is suitable for application to the surface of the workpiece containing the cavity. Furthermore, the extraction system comprises sealing elements, at least one hose, and a vacuum source.

[0015] The extraction system is mounted directly or indirectly on the guide device. In the case of an indirect arrangement, intermediate elements can be provided. These could, for example, be elements that allow for angle compensation between the guide device and the extraction system.

[0016] The advantage of this device according to the invention is that it can be used to carry out the efficient method according to the invention, which enables significant savings in investment and running costs.

[0017] In one embodiment, the surface treatment device comprises a vacuum generating device.

[0018] This can be a negative pressure pump or vacuum pump. In particular, a device for treating or cleaning the exhaust air is also provided or can be provided, for example, by means of an air filter. This can also be part of the device.

[0019] In a further embodiment of the device, the suction system has a flexible element, in particular a suction sleeve, which is suitable for producing a sealing effect on the surface of the material forming the cavity in which the opening is formed.

[0020] The sleeve can be made of a flexible material so that it deforms when pressed against the surface, such as the engine block, thus achieving a tight seal. Alternatively, a rigid sleeve is possible, which is pressed against the surface by gravity or contact pressure. This can also include a seal.

[0021] The advantage of this design is that the flexible element, the suction sleeve, can be precisely adapted to the opening, such as the cylinder opening of a cylinder block, to quickly and effectively create a tight connection. The sealing effect is further enhanced by the negative pressure applied during suction.

[0022] A further aspect of the invention is a method for surface machining a cavity, in particular a piston bore of a cylinder of an internal combustion engine block, in which a cavity is provided and a described device for surface machining a cavity is made available. A machining tool is inserted into the cavity, and the surface of the cavity is machined with the machining tool. Furthermore, a purge gas is introduced into the cavity, and an extraction system is connected to an opening in the cavity to extract purge gas and any particles generated during machining.

[0023] In general, the term "cavity" refers to straight, circular-cylindrical cavities. In particular, cylindrical cavities are cylinders open on both sides in an internal combustion engine block. However, it cannot be ruled out that a blind hole or a differently shaped cavity, for example, a general cylinder with a square or irregular base, could be machined using the method according to the invention.

[0024] The machining tool, also called the internal machining head, can be guided along a guide device, such as a guide rail, along a longitudinal axis of the cylinder. This longitudinal axis runs, in particular, through the center of gravity of the surface, such as the circular area, that defines the cylinder.

[0025] In particular, the machining tool is suitable for at least partial insertion into the cavity along the longitudinal axis of the cylinder and is guided and rotatably mounted on the guide device to machine every point on the inner surface of the cylinder. In the case of an engine block, every point on the piston bore can thus be machined. Particles may be generated by the machining tool during machining, for example, by removing material from the surface.

[0026] The machining tool is suitable for surface processing, especially for surface structuring or roughening. This can be done, for example, using a laser, also as preparation for a subsequent coating process.

[0027] The purge gas to be introduced can be under excess pressure and can be nitrogen, for example. Other gases are also conceivable, for example other inert gases. Alternatively, air can also be used as the purge gas. The purge gas can be introduced into the cavity through the interior of the machining tool. Alternatively, the purge gas can be introduced into the cavity from another location and / or using a separate purge gas lance. In the case of machining based on laser beams, a reflector for deflecting the laser beam can be arranged in the machining tool, in particular at the end that can be inserted into the cavity. This allows the beam to be directed out of the machining tool and onto the surface of the cavity. The purge gas can protect the reflector from contamination by removed material. In an alternative embodiment, a protective glass is used to protect the reflector.

[0028] After machining an inner surface and retracting the machining tool from the cavity, the machining tool and the extraction system can be moved laterally to approach and subsequently machine the inner surface of another cylinder. For this purpose, the machining tool and extraction system can be designed to be movable, particularly transversely to the longitudinal axis of the cylinder, i.e., laterally. Multiple cylinders can thus be approached, meaning that, for example, multiple cylinders of an engine block or multiple engine blocks can be machined consecutively using the method according to the invention.

[0029] A key advantage of the process according to the invention is that a significant reduction in the extraction flow rate is achievable. This reduces the amount of air to be conveyed and filtered, thus reducing costs, and increases the efficiency of the process. The vacuum source and the exhaust air filter can be significantly smaller, saving on investment costs. Lower energy consumption also reduces operating costs. Compared to processes in which the removed particles are extracted through the crankshaft chamber, there is also less risk of contamination, as the particles are extracted directly through the cylinder and cannot enter the crankshaft chamber.

[0030] In one embodiment of the method, the machining tool is essentially hollow rod-shaped and the purge gas is guided into the cavity through an outlet at the end of the machining tool located in the cavity.

[0031] In other words, the machining tool is designed to be connected to a gas source so that a purge gas flow can be realized through the interior of the machining tool toward the component to be machined. The machining tool is essentially and preferably precisely hollow-rod-shaped.

[0032] The purge gas enters the hollow space through an outlet in the hollow rod. In the case of a laser-assisted machining process, this could, for example, be the same opening through which the laser beam exits. Alternatively, it could be a separate outlet, or multiple outlets could be arranged. The purge gas flow can be designed to clean the reflector, protect it from contamination, and transport the removed particles.

[0033] Typically, the essentially hollow rod-shaped machining tool has a longitudinal extension that significantly exceeds its transverse extension—in the case of a circular rod, its diameter—so that it has an elongated basic shape and can be inserted into a typically elongated cylinder. The longitudinal extension of the machining tool is, for example, a factor of 1.5 to 10 larger than the diameter of the machining tool, in particular a factor of 2 to 5.

[0034] On the side of the machining tool opposite the cavity, the tool is fastened in particular to the guide device, which enables a guided insertion of the machining tool into the cavity, for example a cylinder.

[0035] The advantage of this design is that the supply of purge gas and the device for processing, for example by means of a laser beam, are realized in one tool.

[0036] In a further embodiment of the method, the extraction system is sealingly connected to one side of the cavity at its opening.

[0037] In particular, the extraction system is directly connected. Of course, the arrangement of sealing elements, such as a gasket, is also possible. The extraction system is suitable for creating a vacuum and sucking in particles. These can be solid and / or liquid; gases or gas mixtures can also be sucked in. This is achieved, for example, by arranging a hose or pipe connected to a vacuum source. In particular, a gas or gas mixture flow is created throughout the cylinder, carrying the removed particles.

[0038] The extraction system can, for example, be designed in the form of a suction sleeve that is placed over the respective opening of the cavity and seals the opening so that, when a negative pressure is applied, only gases or gas mixtures, possibly including liquid and / or solid particles, present in the cavity are extracted. The shape of the suction sleeve can be adapted to the shape of the opening. For circular-cylindrical cavities such as engine cylinders, a round basic shape of the sleeve is possible, for example.

[0039] The extraction sleeve can be made of plastic, rubber, or sheet metal, for example. It can be rubber-elastic, or rigid, for example. It can have a seal to create a seal against the body to be machined. It can be pressed against it with contact pressure to create a tight connection, or it can create a tight connection using its weight, for example. For example, the extraction sleeve can become deformed and / or a seal located therein can be pressed against the body, thereby deforming. In particular, the extraction system is designed to be movable for this purpose and is arranged, for example, on the guide device of the machining tool. In this case, there is no movement relative to the guide device, and the machining tool can be moved into the cylinder independently of the extraction system.For example, before the machining tool is inserted into the cylinder, a movement can be carried out to position the guide device, comprising the extraction system, on the workpiece in order to establish the sealing connection.

[0040] In other words, the extraction system does not move with the processing tool, but remains stationary and pressed against the workpiece, for example the engine block, while the processing tool performs a relative movement to the engine block for processing.

[0041] Typically, the machining tool also performs a relative movement to the side of the extraction system opposite the workpiece. For example, the machining tool can extend through the extraction system. In this case, a sealing element, such as a rubber seal, is arranged to create a substantially and preferably completely gas-tight seal despite the relative movement.

[0042] When the process is applied to an engine block, the suction device is placed on the top side, also called the top deck, and pressed down if necessary before the cylinder bore is machined.

[0043] The purge gas is drawn off in particular at the opening of the cavity to which it was previously introduced through the interior of the machining tool.

[0044] The advantage of this design is that a specific cylinder can be machined and extracted. The machining tool and the extraction system can then be moved to the next cylinder to be machined.

[0045] In one embodiment of the method, the surface treatment is carried out with a laser beam, wherein the laser beam exits the processing tool through the outlet of the processing tool, through which the purge gas also exits.

[0046] Surface treatment can serve, for example, as preparation for thermal coating. In particular, material is removed using a laser, resulting in the removal of solid particles, liquid droplets, and / or gas. During the removal process, the material can be liquefied, vaporized, and / or sublimated, for example. This removed material can be extracted by the extraction system.

[0047] In a further embodiment, the extraction system extracts a gas or a gas mixture, in particular ambient air mixed with purge gas, from the cavity, so that a gas or gas mixture flow is realized at the point of surface treatment.

[0048] This creates a carrier flow capable of entraining removed material and transporting it away from the removal site. To achieve this, ambient air is drawn in from a point that is fluidically upstream of the material removal site. For example, ambient air is drawn into the cavity through an opening opposite the extraction system.

[0049] In particular, in an engine block, ambient air can be drawn through at least one other cylinder and the crankshaft chamber to the site of material removal. For this purpose, the engine block is secured and sealed on its underside to carry out the process, for example, with sealing plates or rubber elements. Alternatively, air can also be drawn in only through the crankshaft chamber.

[0050] The advantage of this design is that, in addition to the introduced purge gas, another gas or gas mixture stream is created to transport the removed particles. This allows the purge gas stream to be kept minimal, allowing it to primarily fulfill the function of cleaning the reflector, while the freely available ambient air is used to transport the particles.

[0051] A further aspect of the invention is a method for producing an engine block of an internal combustion engine, in which the method according to the invention for surface treatment is carried out and a surface coating is then carried out.

[0052] In particular, a thermal coating can be carried out, for example an atmospheric plasma coating.

[0053] Various types of internal combustion engines, such as in-line engines, V-engines or W-engines, can be produced using the method according to the invention

[0054] The invention is explained below with reference to the embodiments shown in the accompanying drawings.

[0055] It shows Fig. 1 : a section through a device for surface treatment according to the invention, Fig. 2 : a section through a device for surface treatment according to the invention, partially inserted into a cylinder crankcase, Fig. 3 : a section through a device according to the invention for surface treatment before carrying out the method according to the invention, Fig. 4 : a section through a device according to the invention for surface treatment during the implementation of the method according to the invention, and Fig. 5: a perspective view of a surface treatment device according to the invention.

[0056] Figure 1shows a section through a surface processing device 10 according to the invention. This device comprises a processing tool 20, also referred to as an internal processing head, which is designed in the form of a hollow rod. The processing tool 20 can be guided vertically by means of a guide device 28 in order to insert it into a cavity, for example, into a cylinder 54 of an engine block. A purge gas flow is realized inside the processing tool 20, which is directed along the longitudinal axis of the processing tool 20 and runs from top to bottom toward the side of the processing tool 20 that can be inserted into the cylinder.At the lower end of the machining tool 20, a reflector 26, also referred to as a deflection prism, is arranged. This reflector is suitable for reflecting a laser beam, which is also guided from top to bottom through the machining tool 20, and for directing it through the outlet to the surface of the piston track 52 inside the cylinder 54 (not shown here). A lateral outlet 22 is arranged at the end region of the machining tool 20 for the exit of both the laser beam 24 (not shown here) and the purge gas 30.

[0057] This outlet 22 is positioned such that it is located along the longitudinal direction of a laser beam directed into the processing tool between the reflector 26 and a suction sleeve 40 arranged opposite it, so that a laser beam reflected by the reflector 26 runs with a directional component in the direction of the suction sleeve 40. This means that when the processing tool 20 is arranged vertically, the laser beam reflected by the reflector 26 runs obliquely upwards, as shown in the figures, and can exit the processing tool 20 through an outlet 22 located there. This prevents contamination of the reflector 26 by vapors and / or particles occurring at the operating point of the laser beam.

[0058] In an alternative embodiment not shown here, the reflector 26 and the outlet 22 can be arranged and designed such that the reflected laser beam is deflected obliquely downwards.

[0059] At its upper end, the machining tool 20 is connected by flange connections to a hollow shaft 76, which can be set in rotation by a belt drive 72. Thus, the entire machining tool 20 rotates about its longitudinal axis, and all points on the piston track 52 of the cylinder 54 can be reached for machining.

[0060] At the lower end of the guide device 28, a suction sleeve 40 of an extraction system 41 is arranged, which is fixed to the guide device 28. The processing tool 20 extends through the upper side of the suction sleeve 40. During a vertical movement of the processing tool 20, the suction sleeve 40 remains stationary. For this purpose, a seal 46 is arranged between the suction sleeve 40 and the processing tool 20, which enables a substantially and in particular completely gas-tight connection even during relative movement of the two elements. A suction hose 42 is arranged on the suction sleeve 40, to which a negative pressure generating device 44, for example a vacuum pump, can be connected. This is capable of generating a gas or gas mixture flow 34, which can comprise the purge gas 30, any removed particles, and possibly ambient air 32, shown in the lower part of the image.The underside of the suction sleeve 40 is straight and is suitable for being placed on the top side, also called top deck, of a cylinder crankcase.

[0061] Figure 2 shows a section through a surface treatment device 10 according to the invention, which is partially inserted into a cylinder crankcase, i.e., an internal combustion engine block 50. For reasons of clarity, the purge gas 30 and the ambient air 32 are not shown in this illustration.

[0062] The laser beam 24 runs vertically from top to bottom through the longitudinal axis of the machining tool 20 and is guided by the reflector 26 arranged below through the lateral outlet 22 at the end of the machining tool 20 onto the inner surface of the piston bore 52 of the internal combustion engine block 50. In the figure shown, the machining tool 20 is fully retracted into the cylinder 54. The suction sleeve 40, made of flexible material here, is slightly compressed to create a sealing effect with the surface of the internal combustion engine block 50. The internal combustion engine block 50 is fixed to a support 60 and sealed by means of external sealing plates 62. This prevents ambient air from penetrating, for example, through the crankshaft chamber. A suction hose 42 is arranged on the suction sleeve 40, to which a vacuum generating device 44 can be arranged.

[0063] Figure 3shows a section through a surface treatment device according to the invention prior to carrying out the method according to the invention. The purge gas flow runs vertically through the processing tool 20 and exits at its lateral outlet 22. The vacuum generation device 44 generates a gas or gas mixture flow 34 comprising the purge gas and ambient air 32. Here, too, the combustion engine block 50 is fixed and sealed by means of external sealing plates 62.

[0064] Figure 4shows a section through a device according to the invention for surface treatment during implementation of the method according to the invention. In this next step, the treatment tool 20 is now fully retracted into the cylinder 54 of the internal combustion engine block 50. The laser beam 24, which undergoes a change of direction by the reflector 26, leaves the treatment tool 20 through its outlet 22 arranged at the end and treats the piston bore 52 of the cylinder 54. At the same time, a purge gas 30, for example nitrogen, is introduced through the treatment tool 20 and the outlet 22 into the cylinder 54 of the internal combustion engine block 50. The purge gas flow created protects the reflector 26 from contamination on the one hand by blowing away any particles that may have accumulated. On the other hand, the vacuum generation device 44 creates a vacuum in the gas orA gas mixture stream 34 is realized, comprising ambient air 32, which is drawn in through the exposed cylinders 54 and / or the crankshaft chamber and has sufficient velocity in the area of ​​material removal to entrain removed particles and keep them suspended for removal. The gas or gas mixture stream 34, comprising ambient air and purge gas 30, is drawn through the suction hose 42 to the vacuum generation device 44.

[0065] Figure 5shows a perspective view of a surface treatment device 10 according to the invention. At its lower end, this device comprises a treatment tool connected to a hollow shaft 76 by means of a flange connection. This hollow shaft 76 is rotatably mounted by two bearings 74 and can be driven into rotation by a motor 70 via a belt drive 72. This also rotates the outlet 22 (not shown here) at the end of the treatment tool 20, allowing every point on the piston path 52 to be reached. Optical devices, for example, as shown here, a collimator 78, are arranged above the hollow shaft 76.

Claims

1. Device for surface treatment of a cavity, comprising a substantially hollow-rod-shaped machining tool (20) with a reflector (26) as well as a laser beam source and an extraction system (41) which can be applied in a sealing manner to an opening of a cavity, in particular a cylinder (54) of an internal combustion engine block (50), wherein the device is designed in such a way that the purge gas (30) can be removed at the opening of the cavity at which it was previously introduced through the interior of the machining tool (20).

2. Device for surface treatment of a cavity according to claim 1, characterized in that the extraction system (41) has a negative-pressure generating means (44).

3. Device for surface treatment of a cavity according to at least one of claims 1 and 2, characterized in that the extraction system (41) has a flexible element, in particular an extraction sleeve (40), which is suitable for producing a sealing effect with respect to a surface of the material forming the cavity, in which the opening is formed.

4. Method for surface treatment of a cavity, in particular a piston path (52) of a cylinder (54) of an internal combustion engine block (50), in which: - the cavity is provided, - a device for surface treatment of a cavity according to one of claims 1 to 3 is provided, - a machining tool (20) of the device is inserted into the cavity and the surface of the cavity is machined with the machining tool (20), - a purge gas (30) is introduced into the cavity and an extraction system (41) of the device is connected to an opening of the cavity in order to extract purge gas (30) and any particles that may have been produced during the machining, wherein the purge gas (30) is removed at the opening of the cavity at which it was previously introduced through the interior of the machining tool (20).

5. Method for surface treatment according to claim 4, characterized in that the machining tool (20) is substantially hollow-rod-shaped and the purge gas (30) is guided into the cavity through an outlet (22) at the end of the machining tool (20) located in the cavity.

6. Method for surface treatment according to at least one of claims 4 and 5, characterized in that the extraction system (41) is connected to the opening in a sealing manner on one side of the cavity.

7. Method for surface treatment according to at least one of claims 4 to 6, characterized in that the surface treatment is carried out with a laser beam (24), wherein the laser beam (24) exits the machining tool (20) through the outlet (22) of the machining tool (20) through which the purge gas (30) also exits.

8. Method for surface treatment according to at least one of claims 4 to 7, characterized in that the extraction system (41) extracts a gas or a gas mixture, in particular ambient air, from the cavity, so that a gas or gas mixture stream (34) is realized at the point of surface treatment.

9. Method for producing an engine block of an internal combustion engine (70), in which the method according to at least one of claims 4 to 8 is carried out and a surface coating is then implemented.