GB2469825A - I.c. engine cylinder head combustion chamber cooling passage arrangement and casting mould - Google Patents

Abstract

A cylinder head 20 for a vehicular i.c. engine comprises a cooling channel 10 for cooling a front face of the upper part of the combustion chambers 18 and a separate a cooling jacket 24 for cooling a peripheral surface of the upper part of the combustion chambers 18, the cooling jacket 24 communicating with a cooling circuit (64, fig.6) of the engine block (56). Since the cooling channel core 22 and the cooling jacket core 26 are separate parts their respective casting cores 22, 26 can be designed differently for increased cooling efficiency and it is possible to place a channel core 52, eg to form an exhaust channel 54, downwards from above on to the cooling channel core 22 before applying the cooling channel core 22. The channel core 52 can thus be spaced by a small distance d1, d2from the cooling channel core 22 and the cooling jacket core 26, respectively. The cooling jacket core 26 may comprise separate cooling line cores (40, 42, fig.3) which are placed individually on a base plate 38.

Description

Cylinder head, casting mold and method for assembling a casting mold

Description

The invention relates to a cylinder head, which can be used for a combustion engine of a motor vehicle. The invention further relates to a casting mold for casting such kind of a cylinder head as well as to a method of assembling such kind of a casting mold.

It is known to cool an upper part of a combustion chamber, which is located in a cylinder head for a combustion engine of a motor vehicle, by means of a cooling channel inside the cylinder head, wherein the cooling channel is provided mainly at a front face of the upper part of the combustion chamber. A plurality of cooling pockets protrudes downwards from the cooling channel, wherein the cooling pockets are arranged along a peripheral surface of the upper part of the combustion chamber.

It is a disadvantage of such kind of a cylinder head that the cooling channel provides a low flow speed and a high pressure drop leading to a low cooling efficiency.

Further the cooling channel is complicatedly designed leading to a complicated design of a corresponding casting mold for casting such kind of a cylinder head.

For example it is difficult to provide an exhaust channel or other channel communicating with the upper part of the combustion chamber due to the complicated design of the casting mold. Particularly it is necessary to insert a curved channel core for providing the exhaust channel by a linear movement in lateral direction. This leads to a partial thick wall between the exhaust channel and the cooling channel reducing the cooling efficiency of the exhaust channel, where comparatively high temperatures occur.

It is the object of the invention to provide a cylinder head, a casting mold and a method for assembling a casting mold, by means of which a better cooling efficiency for an upper part of a combustion chamber is possible.

The solution of the object is achieved by a cylinder head with the features of claim 1, a casting mold with the features of claim 9 and a method of assembling a casting mold with the features of claim 13. Preferred embodiments are given by the dependent claims.

The cylinder head according to the invention for a combustion engine of a motor vehicle comprises at least one upper part of a combustion chamber for fuel combustion and a cooling channel for cooling at least partially a front face of the upper part of the combustion chamber. According to the invention a cooling jacket for cooling at least partially a peripheral surface of the upper part of the combustion chamber is provided, wherein the cooling jacket is adapted for communicating with a cooling circuit of a motor block.

Since the cooling channel do not cool the whole the upper part of the combustion chamber of the cylinder head by its own, the design of the cooling channel can be optimized with respect to better flow conditions, like increased flow speed and reduced pressure drop. This leads to a significantly increased cooling efficiency at the front face of the upper part of the combustion chamber, where the highest temperatures occur during the combustion. In assembled state the peripheral surface of the upper part of the combustion chamber is arranged closer to the motor block than the front face of the upper part of the combustion chamber. Particularly dead ends for the cooling medium are prevented, since cooling pockets can be omitted. The parts not cooled by the cooling channel are cooled by the cooling jacket, which is fed by cooling medium from the motor block, where the cooling circuit for cooling the motor block is provided.

It is used the insight that the pressure difference of the cooling medium like water provided in the cooling circuit of the motor block is sufficient to cool a part of the upper part of the combustion chamber in the cylinder head. In assembled state the upper part of the combustion chamber of the cylinder head communicates with the part of the combustion chamber provided by the cylinder of the motor block. The use of the cooling medium of the cylinder head for cooling mainly the front face of the upper part of the combustion chamber and the use of the cooling medium of the motor block for cooling mainly the peripheral surface of the upper part of the combustion chamber leads to an increased cooling efficiency for the upper part of the combustion chamber of the cylinder head. This in turn leads to an increased overall efficiency of a combustion engine and a C02-reduction by reducing C02-emissions.

Since the cooling channel and the cooling jacket may be mainly different parts of the cylinder head without interfering with each other, the design of a corresponding casting mold can simplified. The casting mold can be particularly made of several parts, so that a channel core can be placed between two parts of the casting mold without the need of a lateral insertion of the channel core rendering a constantly thin wall between a cooling medium and an exhaust channel possible. Due to the thin wall between the cooling medium and the exhaust channel a good cooling at a place, where comparatively high temperatures occur, is possible leading to a further increased cooling efficiency and a reduced component heat load.

Preferably the cooling channel and the cooling jacket are separated from each other for cooling the upper part of the combustion chamber. The cooling medium of the cooling channel and the cooling medium of the cooling jacket are not mixed with each other before cooling the upper part of the combustion chamber. The function of cooling the cylinder is distributed to at least two different parts. Due to the separation of the cooling channel and the cooling jacket different temperature levels can be provided for the cooling channel on the one hand and the cooling jacket on the other hand.

Particularly a connecting surface for contacting a motor block in assembled state is provided and the cooling jacket comprises an inlet opening and an outlet opening, wherein the inlet opening and/or the outlet opening are arranged in a plane of the connecting surface. A connection tube for connecting the cooling jacket of the cylinder head to the cooling circuit of the motor block arranged outside the cylinder head and the motor block is not necessary. The connection of the cooling jacket to the cooling circuit is provided inside the combustion engine via the connection surface between the cylinder head and the motor block.

In a preferred embodiment the cooling jacket comprises a first cooling line for cooling at least a first part of the peripheral surface of the upper part of the combustion chamber and a second cooling line for cooling at least a second part of the peripheral surface of the upper part of the combustion chamber. Particularly the first cooling line and the second cooling line are connected to each other-by a connecting channel, which is particularly provided by two drillings, wherein the connecting channel is particularly aligned such, that in assembled state the connecting channel is led between a spark plug and a fuel injector. Due to the different cooling lines it is possible to force the cooling medium from one side of the cylinder to the opposite side of the cylinder guaranteeing a cooling along mainly the whole circumference of the level, where the cooling jacket is provided. Since the connecting channel can be used for cooling, it is possible to cool at places, which are difficult to reach and becomes comparably very hot during operation of the combustion engine. In order to reach such places, particularly at the front face at the upper end of the upper part of the combustion chamber like between the spark plug and the fuel injector, it is possible to start one drilling from the first cooling line and another drilling from the second cooling line, wherein both d.rillings meet near to the upper end of the upper part of the combustion chamber within the cylinder head. Since the cooling jacket may provide a bigger volume close to the upper part of the combustion chamber, it is facilitated to drill a hole starting from this volume.

Particularly only the first cooling line is connected to an inlet opening of the cooling jacket and/or only the second cooling line is connected to an outlet opening of the cooling jacket. Due to this design the whole cooling medium of the first cooling line have to go through the second cooling line before reaching the outlet. Hence the whole heat capacity of the cooling medium can be used for cooling the upper part of the combustion chamber increasing the cooling effect.

Preferably the cooling channel and the cooling jacket are connected to a common collector channel connected to an outlet, wherein the collector channel is provided significantly spaced to the upper part of the combustion chamber. The collector channel do not have to provide a cooling effect to the cylinder, so that a larger hydraulic diameter can be provided, since a large surface with respect to the flow rate is not necessary anymore. By means of the collector channel it is possible to provide only one outlet reducing the sealing effort.

Particularly the upper part of the combustion chamber is connected to an exhaust channel, wherein the distance in radial direction between the exhaust channel and the cooling channel and/or the cooling jacket is mainly constant. Due to the mainly constant wall thickness between the exhaust channel and the cooling medium along mainly the whole circumference of the exhaust channel at a major part of the exhaust channel a defined cooling can be provided, particularly at the hottest places. Due to the simplified design for cooling the upper part of the combustion chamber a casting mold can be used, which enables a constant wall thickness between the exhaust channel or other channels communication with the upper part of the combustion chamber and the cooling medium.

The invention further relates to a combustion engine for a motor vehicle comprising a cylinder head, which may be designed as previously described, and a motor block.

The motor block comprises a cooling circuit communicating via a connecting surface, where the cylinder head contacts the motor block, with the cooling jacket of the cylinder head. The use of the cooling medium of the cylinder head for cooling mainly the front face of the upper part of the combustion chamber and the use of the cooling medium of the motor block for cooling mainly the peripheral surface of the upper part of the combustion chamber leads to an increased cooling efficiency for the cylinder.

The invention further relates to a casting mold for casting a cylinder head, which may be designed as previously described. The casting mold comprises a base core assembly for providing a lower contour of the cylinder head and for providing a cooling jacket and a cooling channel core for providing a cooling channel. The use of the cooling medium of the cylinder head for cooling mainly the front face of the upper part of the combustion chamber and the use of the cooling medium of the motor block for cooling mainly the peripheral surface of the upper part of the combustion chamber leads to an increased cooling efficiency for the upper part of the combustion chamber. Since the cooling for the upper part of the combustion chamber is distributed to different parts of the cylinder head, different cores can be used for providing the cooling channel on the one hand and the cooling jacket on the other hand. Since the weights of the base core assembly and of the cooling channel core are reduced compared to a combined core, the handling of these cores is facilitated.

Particularly at least one channel core for providing an exhaust channel is provided between the base core assembly and the cooling channel core. Due to the different cores the channel core can be easily provided between the base core assembly and the cooling channel core. Particularly the channel core can be inserted from above downwards, so that a lateral movement for providing the channel core can be prevented. This enables a thinner wall thickness between the respective channel and the cooling medium leading to an increased cooling efficiency.

Preferably the base core assembly comprises a base plate for providing the lower contour of the cylinder head and a cooling jacket core for providing the cooling jacket, whereby the base plate and the cooling jacket core are one-piece or the cooling jacket core is placed directly on the base plate. Both alternates lead to a facilitated handling of the base core assembly.

Particularly the cooling jacket core comprises a first cooling line core for providing a first cooling line and a second cooling line core for providing a second cooling line, wherein the first cooling line core and the second cooling line core are only connected via the base plate.

The base core assembly may comprise at least three independent parts, wherein each part can be easily handled for its own. Particularly the cooling jacket and/or the cooling line cores may be placed plane on the base plate. This leads to a mechanically stable arrangement for the base core assembly.

The invention further relates to a method for assembling a casting mold, which may be designed as previously described. The method comprises the steps of providing a base core assembly for providing a lower contour of the cylinder head and for providing a cooling jacket and subsequent placing a cooling channel core for providing a cooling channel. The use of the cooling medium of the cylinder head for cooling mainly the front face of the upper part of the combustion chamber and the use of the cooling medium of the motor block for cooling mainly the peripheral surface of the upper part of the combustion chamber leads to an increased cooling efficiency for the upper part of the combustion chamber.

Since the cooling for the upper part of the combustion chamber is distributed to different parts of the cylinder head, different cores can be used for providing the cooling channel on the one hand and the cooling jacket on the other hand. Since the weights of the base core assembly and of the cooling channel core are reduced compared to a combined core, the handling of these cores is facilitated.

Particularly after providing the base core assembly and prior to placing the cooling channel core a channel core is placed spaced to the base core assembly and spaced to the cooling channel core. Due to the different cores the channel core can be easily provided between the base core assembly and the cooling channel core.

Particularly the channel core can be inserted from above downwards, so that a lateral movement for providing the channel core can be prevented. This enables a thinner wall thickness between the respective channel and the cooling medium leading to an increased cooling efficiency.

In a further embodiment during the providing of the base core assembly first a base plate for providing a lower contour of the cylinder head is provided and subsequent a cooling jacket core for providing a cooling jacket is placed on the base plate. The base core assembly may comprise at least three independent parts, wherein each part can be easily handled for its own.

Particularly the cooling jacket and/or the cooling line cores may be placed plane on the base plate. This leads -10 -to a mechanically stable arrangement for the base core assembly.

The invention further relates to a cylinder head obtainable by a casting process using a casting mold, which may be designed as previously described. Preferably the used casting mold is assembled by an assembling method, which may be performed as illustrated above. The use of the cooling medium of the cylinder head for cooling mainly the front part of the upper part of the combustion chamber and the use of the cooling medium of the motor block for cooling mainly the peripheral surface of the upper part of the combustion chamber leads to an increased cooling efficiency for the upper part of the combustion chamber.

These and other aspects of the invention will be apparent from and elucidated with reference to a preferred embodiment described hereinafter.

In the drawings: Fig. 1 is a schematic perspective view of a cooling channel according to the state of the art, Fig. 2 is a schematic perspective view of an upper part of a casting mold, Fig. 3 is a schematic perspective view of a base core assembly for a casting mold, Fig. 4 is a schematic perspective detailed view of the upper part of the casting mold of Fig. 2 with additional drillings, -11 -Fig. 5 is a schematic sectional view of the casting mold of Fig. 2 and Fig. 6 is a schematic partially transparent perspective view of a cylinder head connected to a motor block.

The cooling channel 10 according to the state of the art as illustrated in Fig. 1 comprises an inlet 12 for feeding cooling medium and an outlet 14 for discharging the cooling medium. A plurality of cooling pockets 16 are connected to the cooling channel 10. The cooling pockets follow the lateral surface of an upper part of a combustion chamber 18 of a cylinder head 20, which comprises the cooling channel 10. In order to illustrate the interior of the cylinder head 20 the cylinder head 20 itself is not illustrated but only a not terminal number of hollow parts inside the cylinder head 20 for sake of clarity.

As illustrated in Fig. 2 the cylinder head 20 according to the invention comprises the cooling channel 10, which particularly cools only a front face of the upper part of the combustion chamber 18. The cooling channel 10 can be provided during the casting of the cylinder head 20 by means of a correspondingly shaped cooling channel core 22. Further a cooling jacket 24 is provided, which particularly cools only a peripheral surface of the upper part of the combustion chamber 18.

The cooling jacket 24 can be provided during the casting of the cylinder head 20 by means of a correspondingly shaped cooling jacket core 26. The cooling channel core 22 and the cooling jacket core 26 are part of a casting mold 28, which can be provided in a casting form 30 for casting the cylinder head 20. Since the cooling channel and the cooling jacket 24 are separated from each -12 -other, the cooling channel core 22 and the cooling jacket core 26 can be designed as different parts, which can be handled independently from each other. The lower end of the cooling jacket 24 terminates in a plane of a connecting surface 32 of the cylinder head 20, wherein the connecting surface 32 contacts in assembled state a not illustrated motor block. The cooling jacket 24 comprises an inlet opening 34 in the plane of the connecting surface 32, so that cooling medium from a cooling circuit of the motor block can be fed to the cooling jacket 24. If so, the cooling channel 10 and the cooling jacket 24 may be led to a common collector channel 35 for discharging both cooling mediums of the cooling channel 10 as well as of the cooling jacket 24 via a common outlet 14. The collector channel 35 is provided significantly spaced to the cylinder 18, so that the collector channel 35 provides mainly no significant cooling effect to the cylinder 18.

As illustrated in Fig. 3 the casting mold 28 can be arranged in a casting form 30 for casting the cylinder head 20. The casting mold 28 comprises a base core assembly 36, which comprises a base plate 38 for providing a lower contour of the cylinder head and the cooling jacket core 26. In the illustrated embodiment the cooling jacket core 26 is divided into a first cooling line core 40 and a second cooling line core 42, which are placed individually on the base plate 38. The first cooling line core 40 and the second cooling line core 42 are only connected with each other via the base plate 38.

By means of the first cooling line core 40 a first cooling line 44 can be provided inside the cylinder head 20, wherein the first cooling line 44 is particularly adapted to cool a first part of the peripheral surface of the upper part of the combustion chamber 18.

Correspondingly by means of the second cooling line core -13 - 42 a second cooling line 46 can be provided inside the cylinder head 20, wherein the second cooling line 46 is particularly adapted to cool a second part of the peripheral surface of the upper part of the combustion chamber 18. The second part of the peripheral surface of the upper part of the combustion chamber 18 is particularly provided opposing to the first part of the peripheral surface of the upper part of the combustion chamber 18.

As illustrated in Fig. 4 the first cooling line 44 and the second cooling line 46 of the cooling jacket 24 can be connected by a connecting channel 48 consisting of two drillings 40. Each drilling 40 starts near to the connection surface 32 inside the respective cooling line 44, 46 and meet each other near to a front face of the upper part of the combustion chamber 18, where comparatively high temperatures occur for an additional cooling effect.

Since the cooling channel core 22 and the cooling jacket core 26 are different parts it is possible to provide a channel core 52 between the cooling channel core 26 and the cooling jacket core 26 without the need of a lateral movement of the channel core 52 as illustrated in Fig. 5. By means of the channel core 52 an exhaust channel 54 or other channel communicating with the upper part of the combustion chamber 18 can be provided. After providing the cooling jacket core 26 the channel core 52 can be provided from above downwards.

Subsequently the cooling channel core 22 can be provided from above downwards. Due to this arrangement it is possible to provide between the channel core 52 and the cooling channel core 22 a thin distance d1.

Correspondingly it is possible to provide between the channel core 52 and the cooling jacket core 22 a thin -14 -distance d2. Particularly the distance d1 and the distance d2 are mainly equal leading to a constantly thin wall between the exhaust channel 54 and the cooling medium of the cooling channel 10 and/or of the cooling 5:iacket 24.

In assembled state as illustrated in Fig. 6 the cylinder head 20 is connected to a motor block 56. The motor block 56 comprises several cylinders 58, each of which providing a part of the combustion chamber 18. The cylinders 58 are cooled on the peripheral surface by cylinder cooler 60, which are connected by a cylinder cooling channel 62. The cylinder cooler 60 and the cylinder cooling channel 62 can be provided on opposite sides of the motor block 56. By means of the cylinder coolers 60 and the cylinder cooling channels 62 a cooling circuit 64 of the motor block 56 is given. The cooling circuit 64 is fed via a cooling feed opening 66 for instance by means of a not illustrated water pump feeding cooling water. The cooling feed opening 66 is connected also with the inlet 12 of the cooling channel of the cylinder head 20. In the illustrated embodiment all cylinder cooler 60 communicate with its respective cooling jacket 24, so that the cylinder cooler 60 and the respective cooling jacket 24 provides a common cooling volume.

References i gn s cooling channel 12 inlet 14 outlet 16 cooling pocket 18 cylinder cylinder head 22 cooling channel core 24 cooling jacket 26 cooling jacket core 28 casting mold casting form 32 connecting surface 34 inlet opening collector channel 36 base core assembly 38 base plate first cooling line core 42 second cooling line core 44 first cooling line 46 second cooling line 48 connecting channel drilling 52 channel core 54 exhaust channel 56 motor block 58 cylinder cylinder cooler 62 cylinder cooling channel 64 cooling circuit 66 cooling feed opening d1 distance d2 distance