WO2009112177A1

WO2009112177A1 - Cylinder crankcase, and method for the production thereof

Info

Publication number: WO2009112177A1
Application number: PCT/EP2009/001480
Authority: WO
Inventors: Erik Graf; Patrick Izquierdo; Peter Lingl; Peter Ludwig; Christian Schwarz; Guido Söll
Original assignee: Daimler Ag
Priority date: 2008-03-12
Filing date: 2009-03-03
Publication date: 2009-09-17
Also published as: DE102008013813A1

Abstract

The invention relates to a method for producing a cylinder crankcase (2) which encompasses the following steps: a core (4) is produced; the core (4) is inserted into a casting mold; the cylinder crankcase (2) is cast at an increased pressure using a light metal; the core (4) is removed from the cast cylinder crankcase (2); and a cylinder wall (6) is coated by means of a thermal spraying process. The invention also relates to a die-cast cylinder crankcase (2) that is made of an aluminum-silicon die-casting alloy, has a closed-deck design, and is characterized in that the cylinder walls (6) of the cylinder crankcase (2) are made of the same aluminum-silicon die-casting alloy as the rest of the cylinder crankcase (2) and in that the cylinder walls (6) are coated with a layer applied in an arc wire spraying process.

Description

Cylinder crankcase and method of making same

The invention relates to a method for producing a cylinder crankcase. Furthermore, the invention relates to a cylinder crankcase.

Cylinder crankcases in modern engines are exposed to high mechanical and thermal loads. Therefore, runs around a cylinder liner usually a water jacket, which is used for cooling, in particular the cylinder bore. This water jacket is in the case of crankcases, which are produced in a die-casting process above - cylinder head side - open. This is referred to as "open deck" construction.The water jacket open on the cylinder head side results in the use of movable slides in the metal die casting mold, which after casting cast the water jacket in the crankcase.The valves must be pulled out before opening the crankcase Therefore, no enclosed spaces can be represented with this technique.

The open water jacket leads to a limitation of the mechanical load capacity of the motors. It would be better, therefore, an at least partially closed water jacket ("closed deck" construction), which is not represented in the conventional die-casting process for the reasons mentioned above "Closed deck" - Crankcase in die casting basically possible. For this purpose, an additional ring is placed around the cylinder liner, which the Salt core keeps in the distance and positioned in the tool. However, this leads in practice to a high reject rate, since the salt core is exposed to high bending loads. In addition, this results in an insufficient metallic connection between the casting material and the cylinder liner. Further, an iron-based cylinder liner means a significantly increased weight.

A similar process for the production of a cylinder crankcase using a lost, so in retrospect, detachable salt core with the additional use of infiltratable ceramic inserts is described in DE 197 52 518 Al.

In DE 10 2005 043 193 Al a cylinder crankcase is described, which has a base material modified by alloying in the region of the cylinder surfaces. The base material is modified by the local introduction of suitable alloying elements so that it withstands higher tribological loads.

Object of the present invention is to produce a cylinder crankcase at high cycle times in the "closed deck" method, which has a high mechanical and tribological stability and thereby has a reduced weight.

This object is achieved by a method for producing a cylinder crankcase with the features of claim 1 and by a cylinder crankcase with the features of claim 12. Advantageous embodiments with expedient and non-trivial developments of the invention are specified in the remaining claims.

The method according to claim 1 for producing a cylinder crankcase comprises the following steps: Making a core,

Inserting the core into a casting tool, casting the cylinder crankcase under elevated pressure and using a light metal, detaching the core from the cast cylinder crankcase,

Coating of a cylinder wall by a thermal spraying process.

By inserting a detachable core, undercutting can be produced in the die casting process, which enables the representation of a cylinder crankcase in a "closed-deck" construction, resulting in a particularly high mechanical stability of the crankcase compared to conventional open-top cylinder crankcases. Since the die casting technique (or squeeze cast technique) is used, high cycle times can be realized. Compared to conventional cylinder crankcases is dispensed with the use of cylinder liners. In particular with cast-iron cylinder liners, which often can only guarantee the required mechanical stability in the cylinder area in "open-deck" designs, since they are mechanically more stable than cylinder liners based on aluminum, considerable weight savings can be achieved by eliminating the bushes applied to walls of cylinder bores a thermal spray coating having the required tribological stability.

A cylinder bore in "open deck" construction with a sprayed layer usually does not provide the mechanical stability, the walls of the cylinder bores are barreled by the high pressures, resulting in a flow of unburned gasoline and increases fuel consumption.The introduction of a mechanically stable and tribologically resistant cylinder liner leads to a significant increase in weight, first through the application of the "closed deck" design using a removable core and bringing a thermal spray coating with the desired tribological stability leads to the desired weight reduction while high mechanical stability.

In die casting using a lost core, it has been found that the casting piston speed in a first die casting phase is between 0.08 m / s and 0.2 m / s, preferably between 0.12 m / s and 0.15 m / s. Furthermore, in a second die-casting phase, the casting piston speed should be between 4.0 m / s and 4.5 m / s, preferably between 4.2 m / s and 4.4 m / s, in particular 4.3 m / s. At these piston speeds, the core is least mechanically stressed. It has also been found that with a piston diameter of 170 mm an advantageous pressure build-up time is more than 110 ms. The temperature of the light metal alloy is advantageously between 650 ⁰ C and 690 ⁰ C preferably between 670 ⁰ C and 680 ⁰ C.

The releasable core forms after casting in the cylinder crankcase a water jacket between a cylinder wall and the rest of the cylinder crankcase. The water jacket serves to cool the cylinder wall. The core preferably has a ring on a cylinder head side. Through-openings can be present in the core underneath the rim, which form webs between the cylinder wall and the remaining crankcase after casting.

In a further advantageous embodiment of the invention, the arc wire spraying is applied as a thermal spraying process. In principle, other spraying methods such as plasma spraying or flame spraying can also be used. The basis for the sprayed layer is a tri-logically stable iron alloy. However, it is also possible to use other tribologically stable sprayed coatings which represent an advantageous tribological mating with the material of the cylinder piston. The cylinder crankcase is made of an aluminum-silicon die-cast alloy, the cylinder crankcase being designed in a "closed-deck" construction Like the rest of the cylinder crankcase and the cylinder walls are coated with an arc wire spraying layer, such a cylinder crankcase has high mechanical strength with high tribological resistance, it is lightweight and economical to produce.

Further advantages, features and details of the invention will become apparent from the following description of a preferred Ausfϋhrungsbeispiels and with reference to the drawings; these show in:

Figure 1 is a perspective view of a removable core for insertion into a diecasting tool.

Fig. 2 is a perspective view of a cylinder crankcase with a cast-in core according to Fig.l;

3 is a perspective view of a cylinder crankcase in "closed deck" construction with dissolved out core.

4 shows a sectional view through the cylinder crankcase along the line IV in Figure 3;

5 shows a sectional view through the cylinder crankcase along the line V in Figure 3;

Fig. 6 is a schematic representation of a single core with conical taper; Fig. 7 is a sectional view through the core along the line VII in Fig. 6;

8 shows a core for a motor with four cylinder bores in three-dimensional representation; and in

9 is a sectional view of the core of FIG. 8.

In order to produce a cylinder crankcase 2 in the "closed deck" construction, sleeves (not shown) are used in accordance with the number of cylinders of the engine to be produced, which omit the cylinder bores during casting After casting, the sleeves are withdrawn from the casting mold and the cavity forming the cylinder space is released. Conventional die casting tools employ an additional slide which forms a water jacket 24 around the cylinder liners 6. However, the water jacket 24 is closed a cylinder head open, as is the case with the three left cylinder bores 36 of Figures 2 and 3. There is thus a gap in the form of the open water jacket 24 between a cylinder wall 6 and a housing wall 28, which is disadvantageous for the mechanical load capacity of the ges amten Motors is. These disadvantages must be compensated by costly countermeasures.

To solve the problem, instead of the movable water jacket slide (not shown), a core 4 according to FIG. 1 is inserted into the die casting tool. This core 4 is of course intended for all cylinder bores, in the present figures 1-3 is shown for comparison purposes, however, only a single core. For a core which is suitable for the design of the entire water jacket over all cylinder bores, reference is made to FIGS. 8 and 9. The core 4 preferably consists of a per se known inorganic granules, which is composed essentially of a salt and various binders. The core 4 is produced, for example, by a core shooting method or a pressing method. For this purpose, there are special core tools that can be configured in such a way that, according to the number of cylinders, the corresponding number of cores are pressed in an integral core component (compare FIGS. 8 and 9).

The core 4 according to FIG. 1 has a collar 12, which adjoins a core jacket in the area on the cylinder head side. The wreath is preferably inserted into a recess provided for this purpose in a fixed tool side. The core is thus (in contrast to US 4, 446, 906) supported and thus keeps the very high pressure during the casting process without breaking. A core shell 30 extends at a distance of a few millimeters concentric with the quill. At a crankshaft-side region of the core 4, the core jacket has a curved lower boundary line 16. The boundary line 16 could also be configured in stages or the like.

In order to explain the effect of the individual core features, the following figures will already deal in more detail with the cast cylinder crankcase before the casting process is subsequently described in more detail.

FIG. 2 shows a crankcase 2 in which a core 4 according to FIG. 1 is cast. The ring 12 of the core 4 can still be seen above the cylinder head end 8 of the left cylinder wall 6. After the casting process, the core 4 is replaced by a liquid medium, for. B. dissolved out with water. The core 4 decays into its granules and is washed out by the water. The core material can be washed out, for example, through the channel 26 (FIGS. 4 and 5) of the cylinder crankcase. After that out Washing remain metallic webs 22 are on the cylinder head end 8 of the cylinder liner 6, which traverse the water jacket 24 and this partially to the cylinder head (not shown) out close (Fig. 3). This is called a "closed deck" cylinder crankcase.

The metallic webs 22 are formed by casting metal in the core 4 through vertical openings 14 (FIG. 1) and solidifying. The openings 14 are arranged directly below the cylinder head end 8 of the cylinder wall 6. The geometry of the webs 22 and their number thus depends on the nature of the opening 14 in the core 4. Their design will be discussed later.

In Fig. 3, two sectional lines IV and V are shown, wherein the line IV extends through the free water jacket 24 and this section is shown schematically in Figure 4. The line V passes through two metallic webs 22, which correlates with the illustration in FIG. In the section of Fig. 4, the water jacket 24 is open to the cylinder head, allowing a connection of the water circuits from the cylinder head and the crankcase. The core is still included in the cast crankcase in this illustration. To better illustrate the arrangement of the core in the die casting or in the crankcase, the rim 12 of the core 4 is shown above the cylinder liner in dashed lines, although it has already been removed in this cut state of the crankcase 2. In the sectional view according to FIG. 5, the core 4 has already been removed from the crankcase 2, the water jacket 24 which is covered by the webs 22 on the cylinder head end 8 of the cylinder wall 6 is now exposed. The granules have passed through the channel 26. Also in this illustration, the original position of the ring 12 above the cylinder liner 6 is marked by a dashed line to further understanding. Furthermore, the geometry of the core 12 will be discussed with reference to FIGS. 6 and 7, which contributes to the advantageous stability of the core during the casting process. The vertical openings 14 are configured in the form of pendulum bores in FIGS. 6 and 7, which narrow in a manner similar to loopholes from outside to inside. However, it can also be expedient slots long vertically inwardly extending walls. The core 4 according to FIG. 1 has approximately rectangular openings 14. The recess in the region of the rim 12 are caused by the core pressing tool in this core.

It has also been found that it contributes to a better core stability during the casting process, when an outer contour 18 of the core 6 in particular of the region of the ring 12 tapers conically, as shown in Fig. 6. Furthermore, in order to avoid stress peaks, it is expedient to design a core inner contour 32 in such a way that it has a slight rounding (in the form of a radius) 34 in the transition region to the crown 12 in the form of a radius 34.

Below, the casting of the cylinder crankcase will be discussed in more detail. The core 4 in the described embodiment is inserted into the casting tool, not shown, in a receptacle provided for this purpose. The casting mold is closed and under pressure liquid casting metal, here an aluminum-based die casting alloy (ALSI12) is cast.

It comes to casting the cylinder crankcase, a die-casting process for use. Diecasting is generally understood to mean a casting process in which, compared to the gravitational pressure, an increased pressure is used for pouring the metal into the usually metallic casting tool. These methods are usually called die casting or squeeze casting, although low pressure casting can be applied. The conventional die casting process involves three phases. In the first phase, a casting piston is moved comparatively slowly until the casting metal has reached a sprue area in the casting tool. In a second phase, the casting piston is accelerated and the casting metal is injected at high speed into a mold cavity of the casting tool. In a subsequent third phase, the mold cavity is filled with casting metal, the piston speed is greatly reduced and the still liquid casting metal is densified to solidification.

In order to avoid breakage of the core 4 during the casting process, it is necessary to modify the three phases of the die casting in comparison to conventional die casting methods. There is a conflict of objectives between a good cast structure and a conservation of the core. The following pouring parameters were determined, which meet this conflict of objectives.

Piston speed 1. 0, 12 m / s - - 0.15 phase m / s

Piston speed 2. 4.1 m / s - 4.4 phase m / s

Pressure build-up time at 170 mm> 1 10 ms piston diameter

Pinolentemperatur 130 ⁰ C to 160 ⁰ C.

Water flow Pinolen- 200 - 250 l / h tempering

Temperature of the melt 670 ⁰ C - 680 ⁰ C.

The thus cast cylinder crankcase whose geometric features are already described in detail to the figures 2-5 is now ejected from the casting mold and placed in a bath in which the core 4 is purged. The cylinder crankcase is further processed, z. B. deburred and surface-treated. Subsequently, in the region of the cylinder bore 36, a tribologically favorable spray coating is applied to the cylinder wall 6 in a thermal spraying process. As a thermal spray process, the arc wire spraying has been found to be particularly favorable. In electric arc wire spraying, an iron-based layer can be applied in an economically favorable manner. This iron layer corresponds approximately to the commonly used gray cast cylinder liners of the material composition. Advantageously, the alloy used in the arc wire spraying can be adapted to the tribological requirements.

The sprayed layer generally has a precisely set porosity which forms open pores on the layer surface after further mechanical treatment of the sprayed layer. These open pores serve as so-called lubricant pockets in which lubricant reservoirs are formed during the piston movement during engine operation, which ensure optimum lubrication of the piston and avoid abrasion.

Claims

claims

A method of manufacturing a cylinder crankcase comprising the steps of:

Producing a core (4),

Inserting the core (4) into a casting tool, casting the cylinder crankcase (2) under elevated pressure and using a light metal, detaching the core (4) from the cast cylinder crankcase (2),

Coating a cylinder wall (6) by a thermal spraying process.

2. The method according to claim 1, characterized in that the cylinder crankcase (2) is produced in a die-casting.

3. The method according to claim 2, characterized in that the casting piston speed in a first die-casting phase is between 0.08 m / s and 0.2 m / s.

4. The method according to claim 3, characterized in that the casting piston speed in the first die-casting phase is between 0.12 m / s and 0.15 m / s.

5. The method according to any one of the preceding claims, characterized in that the casting piston speed in a second die casting phase is between 4 m / s and 4.5 m / s.

6. The method according to claim 5, characterized in that the casting piston speed in the second die-casting phase is between 4.2 m / s and 4.4 m / s, in particular 4.3 m / s.

7. The method according to any one of the preceding claims, characterized in that at a piston diameter of 170 mm, a pressure build-up time is more than 110 ms.

8. The method according to any one of the preceding claims, characterized in that the temperature of the light metal alloy between 650 ⁰ C and 690 ⁰ C is preferably between 670 ° C and 680 ⁰ C.

9. The method according to any one of the preceding claims, characterized in that the coating of the cylinder wall (6) takes place by a Lichtbo- gendrahtspritzverfahren.

10. Die-cast cylinder crankcase according to claim 9, characterized in that the sprayed layer is based on iron.

11. The method according to any one of the preceding claims, characterized in that the coating of the cylinder wall (6) takes place with an iron-based alloy.

12. Die-cast cylinder crankcase (2) made of an aluminum-silicon die-cast alloy, which is designed in a "closed-deck" construction, characterized in that Cylinder walls (6) of the cylinder crankcase (2) made of the same aluminum-silicon die-cast alloy as the rest of the cylinder crankcase (2) and the cylinder walls (6) are sprayed with a Lichtbogendraht- sprayed layer.

13. Die-cast cylinder crankcase according to claim 12, characterized in that the cylinder crankcase (2) cylinder head side metallic webs (22) between the cylinder wall (6) and a housing wall (28) having a cylinder wall (6) surrounding water jacket (24). run through.

14. Die-cast cylinder crankcase according to one of claims 12 or 13, characterized in that a lower boundary line (16) of the core (4) crankshaft side has a curved or stepped shape.

15. Die-cast cylinder crankcase according to one of claims 12 to 14, characterized in that an outer contour (18) of the core (4) in the cylinder head side direction (20) tapers conically.

16. Die-cast cylinder crankcase according to one of claims 12 to 15, characterized in that the openings (14) in the core (4) narrow from the outside to the inside.

17. Die-cast cylinder crankcase according to one of claims 12 to 16, characterized in that the removable core (4) has a ring (12), and the core (4) below the ring (12) has vertically extending openings (14).

18. Die-cast cylinder crankcase according to claim 17, characterized in that the rim (12) rests against a tool inner wall.