Internal combustion engine

A cylinder structure includes cylinders arranged inline. A cooling channel facing a first side wall of the cylinder structure includes a first inner channel and a first outer channel. The first inner channel is arranged for a first cooling medium to flow through. The first outer channel is away from the first side wall than the first inner channel is, and arranged for a second cooling medium to flow through. A cooling channel facing a second side wall of the cylinder structure includes a second outer channel and a second inner channel. An upstream part of the second outer channel is connected to a downstream part of the first outer channel. The second inner channel is close to the second side wall than the second outer channel is. Connection channels connecting between the second outer channel and the second inner channel are respectively provided at positions facing the cylinders.

BACKGROUND

Technical Field

The present disclosure relates to an internal combustion engine including a cooling channel for cooling a plurality of cylinders.

Background Art

Patent Literature 1 discloses a configuration of a water jacket of an internal combustion engine. Cooling water in the water jacket flows along a plurality of cylinders in turn. An upstream part of the water jacket is separated into an upper channel and a lower channel. Upper cooling water flowing through the upper channel cools an outer wall of the plurality of cylinders directly. Whereas, lower cooling water flowing through the lower channel is not in contact with the outer wall of the plurality of cylinders. Therefore, a rise in temperature of the lower cooling water is suppressed. The lower cooling water is guided by an upward guiding member to the upper channel to join the upper cooling water. As a result, the plurality of cylinders are sufficiently cooled also in a downstream part of the water jacket.

LIST OF RELATED ART

Patent Literature 1: Japanese Unexamined Patent Application Publication No. JP-2008-128133

SUMMARY

According to the technique disclosed in the above-mentioned Patent Literature 1, a temperature of the cooling water in the water jacket (cooling channel) rises from the upstream part towards the downstream part. That is, cooling performance decreases from the upstream part towards the downstream part. Although the cooling performance temporarily recovers due to the lower cooling water joining the upper cooling water, thereafter the cooling performance decreases again towards the downstream part. Since the cooling performance decreases towards the downstream part, a cooling effect on the plurality of cylinders becomes non-uniform. This causes variation in temperature between the plurality of cylinders, which is not preferable.

An object of the present disclosure is to provide a technique that is related to an internal combustion engine including a cooling channel for cooling a plurality of cylinders and can cool the plurality of cylinders more uniformly.

A first aspect provides an internal combustion engine.

The internal combustion engine includes:

a cylinder structure including a plurality of cylinders arranged inline; and

a cooling channel arranged around a side wall of the cylinder structure, and through which a cooling medium flows.

The side wall of the cylinder structure includes:

a first side wall on one of an intake side and an exhaust side; and

a second side wall on another of the intake side and the exhaust side.

The cooling channel includes:

an inlet to which the cooling medium is injected;

a first inner channel facing the first side wall, whose upstream part being connected to the inlet, and arranged for a first cooling medium of the injected cooling medium to flow through;

a first outer channel facing the first side wall, being away from the first side wall than the first inner channel is, whose upstream part being connected to the inlet, and arranged for a second cooling medium of the injected cooling medium to flow through;

a second outer channel facing the second side wall, whose upstream part being connected to a downstream part of the first outer channel, and arranged for the second cooling medium to flow through;

a second inner channel facing the second side wall, and being close to the second side wall than the second outer channel is; and

a plurality of connection channels connecting between the second outer channel and the second inner channel, and respectively provided at positions facing the plurality of cylinders.

A second aspect further has the following feature in addition to the first aspect.

Cross-sectional areas of the plurality of connection channels increase from the upstream part towards a downstream part of the second outer channel.

A third aspect further has the following feature in addition to the first or second aspect.

The cylinder structure and the cooling channel are arranged in a cylinder block.

The first inner channel is arranged for the first cooling medium to be drained out of the cylinder block without joining the second cooling medium.

A fourth aspect further has the following feature in addition to any one of the first to third aspects.

A cross-sectional area of the first inner channel decreases from the upstream part towards a downstream part of the first inner channel.

A fifth aspect further has the following feature in addition to any one of the first to fourth aspects.

The cooling channel further comprises an inter-cylinder channel arranged between adjacent cylinders of the plurality of cylinders.

The inter-cylinder channel is connected to the second outer channel.

According to the first aspect, the cooling channel facing the first side wall of the cylinder structure includes the first inner channel and the first outer channel. The cylinder structure on the side of the first side wall is effectively cooled by the first cooling medium flowing through the first inner channel. Meanwhile, cooling performance of the second cooling medium flowing through the first outer channel is maintained without deterioration, because the first outer channel is away from the first side wall than the first inner channel is.

The cooling channel facing the second side wall of the cylinder structure includes the second inner channel and the second outer channel. The upstream part of the second outer channel is connected to the downstream part of the first outer channel. Accordingly, the second cooling medium with high cooling performance flows from the first outer channel into the second outer channel. Moreover, the second outer channel is away from the second side wall than the second inner channel is. Therefore, the high cooling performance of the second cooling medium is maintained also in the second outer channel.

The connection channel connects between the second inner channel and the second outer channel. The second cooling medium in the second outer channel is supplied to the second inner channel through the connection channel. The cylinder structure on the side of the second side wall also is effectively cooled by the second cooling medium with the high cooling performance.

Furthermore, the plurality of connection channels are respectively provided at positions facing the plurality of cylinders of the cylinder structure. Therefore, the second cooling medium is supplied in parallel through the plurality of connection channels to the second inner channel at the positions facing the plurality of cylinders, respectively. It is thus possible to cool the plurality of cylinders more uniformly, as compared with a case where the second cooling medium flows along the plurality of cylinders in turn through the second inner channel. As a result, variation in temperature between the plurality of cylinders is suppressed.

According to the second aspect, the cross-sectional areas of the plurality of connection channels increase from the upstream part towards the downstream part of the second outer channel. Meanwhile, a pressure of the second cooling medium in the second outer channel decreases from the upstream part towards the downstream part. Therefore, respective flow rates of the second cooling media passing through the plurality of connection channels are equalized, and it is thus possible to further uniformly cool the plurality of cylinders.

According to the third aspect, the first inner channel is arranged for the first cooling medium to be drained out of the cylinder block without joining the second cooling medium. Since the first cooling medium whose cooling performance is lowered does not join the second cooling medium, decrease in cooling performance of the second cooling medium is suppressed.

According to the fourth aspect, the cross-sectional area of the first inner channel decreases from the upstream part towards the downstream part of the first inner channel. Therefore, a flow speed of the first cooling medium increases from the upstream part towards the downstream part of the first inner channel. Meanwhile, a temperature of the first cooling medium rises from the upstream part towards the downstream part of the first inner channel. Increase in cooling performance due to the increase in flow speed compensates the decrease in cooling performance due to the rise in temperature. It is thus possible to more uniformly cool the plurality of cylinders also on the side of the first side wall.

According to the fifth aspect, the inter-cylinder channel arranged between the adjacent cylinders is connected to the second outer channel. As a result, the second cooling medium with the high cooling performance is supplied from the second outer channel to the inter-cylinder channel. A part between the adjacent cylinders is effectively cooled by the second cooling medium with the high cooling performance.

EMBODIMENTS

Embodiments of the present disclosure will be described below with reference to the attached drawings.

1. First Embodiment

FIG. 1is a schematic diagram showing a configuration of an internal combustion engine1according to a first embodiment. The internal combustion engine1includes a cylinder10and a cooling channel100for cooling the cylinder10.

The cylinder10(a combustion chamber) is formed in a cylinder block20. More specifically, a cylinder liner21(a cylinder bore) having a cylindrical shape forms an inner side surface of the cylinder10. A piston30is provided so as to reciprocate in an axis direction of the cylinder10. An upper surface of the piston30forms a bottom surface of the cylinder10. A cylinder head40is placed on the cylinder block20. A bottom surface of the cylinder head40forms an upper surface of the cylinder10.

An intake port50is provided for supplying intake gas to the cylinder10. An exhaust port60is provided for exhausting exhaust gas from the cylinder10. The intake port50and the exhaust port60are formed within the cylinder head40. An intake valve51is provided at an opening of the intake port50to the cylinder10. An exhaust valve61is provided at an opening of the exhaust port60to the cylinder10.

The cooling channel100(a water jacket) is formed around the cylinder10in the cylinder block20. A cooling medium (e.g. cooling water) flows through the cooling channel100, thereby cooling the cylinder10,

FIG. 2is a schematic diagram for explaining a cylinder structure10X and the cooling channel100according to the present embodiment. The cylinder structure10X is a collection of a plurality of cylinders10-i(i is an integer equal to or larger than 2). In the example shown inFIG. 2, the cylinder structure10X includes a plurality of cylinders10-1to10-3. The plurality of cylinders10-iare arranged inline in one direction.

In the description below, an X-direction is the one direction in which the plurality of cylinders10-iare arranged. A Z-direction is a direction of movement of the piston30. The X-direction is orthogonal to the Z-direction. A Y-direction is a direction orthogonal to the X-direction and the Z-direction. An upward direction is a direction of ascension of the piston30, that is, a direction from the cylinder block20towards the cylinder head40. A downward direction is a direction opposite to the upward direction.

A shown inFIG. 2, the cylinder structure10X and the cooling channel100are arranged in the cylinder block20. The cooling channel100is arranged around a side wall of the cylinder structure10X. The cylinder structure10X (i.e. the plurality of cylinders10-i) is cooled by the cooling medium flowing through the cooling channel100.

A configuration (structure) of the cooling channel100is adjustable by the use of a water jacket spacer200as shown inFIG. 2. More specifically, when assembling the internal combustion engine1, the water jacket spacer200is inserted into the cooling channel100. As a result, the cooling channel100with a desired configuration is obtained.

Hereinafter, a configuration of the cooling channel100according to the present embodiment will be described in detail.

1-2. Configuration of Cooling Channel

In order to explain a configuration of the cooling channel100, let us first explain the side wall of the cylinder structure10X with reference toFIG. 3. The side wall of the cylinder structure10X includes a first side wall11and a second side wall12. The first side wall11is the side wall on one of an intake side (i.e. a side of the intake port50) and an exhaust side (i.e. a side of the exhaust port60). The second side wall12is the side wall on the other of the intake side and the exhaust side. In the example shown inFIG. 3, the first side wall11is the side wall on the exhaust side, and the second side wall12is the side wall on the intake side.

FIGS. 4 and 5are a schematic diagram and a cross-sectional diagram, respectively, for explaining a configuration of the cooling channel100on a side of the first side wall11. The cooling channel100on the side of the first side wall11includes a “first inner channel110A” and a “first outer channel110B”. Both of the first inner channel110A and the first outer channel110B face the first side wall11.

The first inner channel110A and the first outer channel110B are separated in the Z-direction. More specifically, the first inner channel110A is arranged on the upper side, and the first outer channel110B is arranged on the lower side. For such the channel separation, the water jacket spacer200may include a first separating member210as shown inFIG. 5. The first separating member210is sandwiched between the first side wall11and the cylinder block20, and separates the cooling channel100on the side of the first side wall11into the first inner channel110A and the first outer channel110B.

As shown inFIG. 5, the first outer channel110B is away from the first side wall11than the first inner channel110A is. Conversely, the first inner channel110A is close to the first side wall11than the first outer channel110B is. For example, the first inner channel110A is in contact with the first side wall11, whereas the first outer channel110B is not in contact with the first side wall11. For forming such the first outer channel110B, the water jacket spacer200may include a first spacer member215as shown inFIG. 5. The first spacer member215is formed to be in contact with the first side wall11. Due to the first spacer member215, the first outer channel110B is formed away from the first side wall11.

The cooling channel100includes an inlet101to which the cooling medium C (e.g. cooling water) is injected (seeFIG. 4). Respective upstream parts of the first inner channel110A and the first outer channel110B are connected to the inlet101. The cooling medium C injected into the cooling channel100through the inlet101is distributed to the first inner channel110A and the first outer channel110B. The cooling medium C distributed to the first inner channel110A is hereinafter referred to as a “first cooling medium CA”. The cooling medium C distributed to the first outer channel110B is hereinafter referred to as a “second cooling medium CB”.

The first cooling medium CA flows through the first inner channel110A. A direction from the upstream part towards a downstream part of the first inner channel110A is a direction from the cylinder10-1towards the cylinder10-3, and its principal component is the X-direction. In other words, the first inner channel110A is arranged for the first cooling medium CA to flow along the plurality of cylinders10-1,10-2, and10-3in turn.

Moreover, the first inner channel110A is arranged for the first cooling medium CA to be drained out of the cylinder block20without joining the second cooling medium CB. For example, as shown inFIG. 4, the downstream part of the first inner channel110A is connected to an outlet102. The outlet102is connected to the outside of the cylinder block20, typically to the cylinder head40. The water jacket spacer200may include a partition member202as shown inFIG. 4. The partition member202is located at the downstream part of the first inner channel110A and prevents the first cooling medium CA from flowing into a side of the second side wall12.

The cylinder structure10X on the side of the first side wall11is effectively cooled by the first cooling medium CA flowing through the first inner channel110A. Specifically, a temperature of an upper part of the cylinder structure10X (cylinder10) is high, and such the high-temperature part is effectively cooled by the first cooling medium CA. A temperature of the first cooling medium CA rises towards the downstream part of the first inner channel110A. The first cooling medium CA whose cooling performance is decreased is drained out of the cylinder block20through the outlet102without joining the second cooling medium CB.

Meanwhile, the second cooling medium CB flows through the first outer channel110B. A direction from the upstream part towards a downstream part of the first outer channel110B is the direction from the cylinder10-1towards the cylinder10-3, and its principal component is the X-direction. In other words, the first outer channel110B is arranged for the second cooling medium CB to flow along the plurality of cylinders10-1,10-2, and10-3in turn.

It should be noted here that the first outer channel110B is away from the first side wall11than the first inner channel110A is (seeFIG. 5). Although both the first cooling medium CA and the second cooling medium CB flow in the vicinity of the first side wall11, a temperature of the second cooling medium CB does not rise as much as the first cooling medium CA. The temperature of the second cooling medium CB after flowing through the first outer channel110B is lower than the temperature of the first cooling medium CA after flowing through the first inner channel110A. That is, cooling performance of the second cooling medium CB is maintained without deterioration. Such the second cooling medium CB with high cooling performance is used for cooling the cylinder structure10X on a side of the second side wall12.

FIGS. 6 and 7are a schematic diagram and a cross-sectional diagram, respectively, for explaining a configuration of the cooling channel100on the side of the second side wall12. The cooling channel100on the side of the second side wall12includes a “second inner channel120A” and a “second outer channel120B”. Both of the second inner channel120A and the second outer channel120B face the second side wall12.

The second inner channel120A and the second outer channel120B are separated in the Z-direction. More specifically, the second inner channel120A is arranged on the upper side, and the second outer channel120B is arranged on the lower side. For such the channel separation, the water jacket spacer200may include a second separating member220as shown inFIG. 7. The second separating member220is sandwiched between the second side wall12and the cylinder block20, and separates the cooling channel100on the side of the second side wall12into the second inner channel120A and the second outer channel120B.

As shown inFIG. 7, the second outer channel120B is away from the second side wall12than the second inner channel120A is. Conversely, the second inner channel120A is close to the second side wall12than the second outer channel120B is. For example, the second inner channel120A is in contact with the second side wall12, whereas the second outer channel120B is not in contact with the second side wall12. For forming such the second outer channel120B, the water jacket spacer200may include a second spacer member225as shown inFIG. 7. The second spacer member225is formed to be in contact with the second side wall12. Due to the second spacer member225, the second outer channel120B is formed away from the second side wall12.

As shown inFIG. 6, an upstream part of the second outer channel120B is connected to the downstream part of the above-described first outer channel110B. As a result, the above-described second cooling medium CB flows from the first outer channel110B into the second outer channel120B. A direction from the upstream part towards a downstream part of the second outer channel120B is a direction from the cylinder10-3towards the cylinder10-1, and its principal component is the −X-direction. In other words, the second outer channel120B is arranged for the second cooling medium CB to flow along the plurality of cylinders10-3,10-2, and10-1in turn.

The cooling channel100according to the present embodiment further includes a “connection channel130” connecting between the second inner channel120A and the second outer channel120B.FIG. 8is a cross-sectional diagram at a position of the connection channel130. As shown inFIG. 8, the connection channel130is achieved, for example, by a through-hole penetrating through the second separating member220. The second cooling medium CB in the second outer channel120B is supplied to the second inner channel120A through the connection channel130.

As described above, the second outer channel120B is away from the second side wall12than the second inner channel120A is. Therefore, also in the second outer channel120B, the temperature of the second cooling medium CB does not rise so much and the high cooling performance of the second cooling medium CB is maintained. Such the second cooling medium CB with the high cooling performance is supplied to the second inner channel120A through the connection channel130. Then, the cylinder structure10X on the side of the second side wall12is effectively cooled by the second cooling medium CB with the high cooling performance. Specifically, the temperature of the upper part of the cylinder structure10X (cylinder10) is high, and such the high-temperature part is effectively cooled by the second cooling medium CB.

Furthermore, according to the present embodiment, a plurality of connection channels130-i(i being an integer representing plural connection channels, such as connection channels130-1,130-2and130-3) are respectively provided at positions facing the plurality of cylinders10-i, as shown inFIG. 6. Therefore, the second cooling medium CB is supplied in parallel through the plurality of connection channels130-ito the second inner channel120A at the positions facing the plurality of cylinders10-i, respectively. It is thus possible to cool the plurality of cylinders10-imore uniformly, as compared with a case where the second cooling medium CB flows along the plurality of cylinders10-iin turn through the second inner channel120A. As a result, variation in temperature between the plurality of cylinders10-iis suppressed.

A cooling effect on the cylinder10-idepends also on a flow rate of the second cooling medium CB passing through the connection channel130-i. Therefore, it is possible to adjust the cooling effect on the cylinder10-iby adjusting a cross-sectional area of the connection channel130-i. Here, the cross-section of the connection channel130-iis perpendicular to the direction of flow of the second cooling medium CB passing through the connection channel130-i.

For example, a pressure of the second cooling medium CB in the second outer channel120B decreases from the upstream part towards the downstream part. Therefore, the cross-sectional areas of the plurality of connection channels130-imay be designed to increase from the upstream part towards the downstream part of the second outer channel120B. As a result, respective flow rates of the second cooling media CB passing through the plurality of connection channels130-iare equalized, and it is thus possible to further uniformly cool the plurality of cylinders10-i.

The second cooling medium CB in the second inner channel120A is appropriately drained out through an outlet not shown.

The cooling channel100facing the first side wall11of the cylinder structure10X includes the first inner channel110A and the first outer channel110B. The cylinder structure10X on the side of the first side wall11is effectively cooled by the first cooling medium CA flowing through the first inner channel110A. Meanwhile, the cooling performance of the second cooling medium CB flowing through the first outer channel110B is maintained without deterioration, because the first outer channel110B is away from the first side wall11than the first inner channel110A is.

The cooling channel100facing the second side wall12of the cylinder structure10X includes the second inner channel120A and the second outer channel120B. The upstream part of the second outer channel120B is connected to the downstream part of the first outer channel110B. Accordingly, the second cooling medium CB with high cooling performance flows from the first outer channel110B into the second outer channel120B. Moreover, the second outer channel120B is away from the second side wall12than the second inner channel120A is. Therefore, the high cooling performance of the second cooling medium CB is maintained also in the second outer channel120B.

The connection channel130connects between the second inner channel120A and the second outer channel120B. The second cooling medium CB in the second outer channel120B is supplied to the second inner channel120A through the connection channel130. The cylinder structure10X on the side of the second side wall12also is effectively cooled by the second cooling medium CB with the high cooling performance.

Furthermore, the plurality of connection channels130-iare respectively provided at positions facing the plurality of cylinders10-iof the cylinder structure10X. Therefore, the second cooling medium CB is supplied in parallel through the plurality of connection channels130-ito the second inner channel120A at the positions facing the plurality of cylinders10-i, respectively. It is thus possible to cool the plurality of cylinders10-imore uniformly, as compared with a case where the second cooling medium CB flows along the plurality of cylinders10-iin turn through the second inner channel120A. As a result, variation in temperature between the plurality of cylinders10-iis suppressed.

The cooling effect on the cylinder10-idepends also on the flow rate of the second cooling medium CB passing through the connection channel130-i. The pressure of the second cooling medium CB in the second outer channel120B decreases from the upstream part towards the downstream part. Therefore, the cross-sectional areas of the plurality of connection channels130-imay increase from the upstream part towards the downstream part of the second outer channel120B. As a result, respective flow rates of the second cooling media CB passing through the plurality of connection channels130-iare equalized, and it is thus possible to further uniformly cool the plurality of cylinders10-i.

Moreover, the first inner channel110A is arranged for the first cooling medium CA to be drained out of the cylinder block20without joining the second cooling medium CB. Since the first cooling medium CA whose cooling performance is lowered does not join the second cooling medium CB, decrease in cooling performance of the second cooling medium CB is suppressed.

2. Second Embodiment

FIG. 9is a cross-sectional diagram for explaining a configuration of the cooling channel100according to a second embodiment. In particular,FIG. 9shows a cross-sectional configuration of the cooling channel100on the side of the first side wall11, as in the case ofFIG. 5in the first embodiment. An overlapping description with the first embodiment will be omitted as appropriate.

According to the second embodiment, a cross-sectional area of the first inner channel110A is smaller than that in the case of the first embodiment shown inFIG. 5. Here, the cross-section of the first inner channel110A is perpendicular to the direction of flow of the first cooling medium CA. For example, the water jacket spacer200includes a narrowing member230as shown inFIG. 9. The cross-sectional area of the first inner channel110A becomes smaller due to the narrowing member230arranged in the first inner channel110A.

Since the cross-sectional area of the first inner channel110A becomes smaller, a flow speed of the first cooling medium CA flowing through the first inner channel110A increases, and thus cooling performance of the first cooling medium CA increases. As a result, it is possible to further effectively cool the cylinder structure10X on the side of the first side wall11.

The temperature of the first cooling medium CA rises from the upstream part towards the downstream part of the first inner channel110A. In consideration of decrease in cooling performance due to the rise in temperature, the cross-sectional area of the first inner channel110A may decrease from the upstream part towards the downstream part of the first inner channel110A (This is equivalent to the narrowing member230becoming thicker from the upstream part towards the downstream part of the first inner channel110A). In this case, the flow speed of the first cooling medium CA increases from the upstream part towards the downstream part of the first inner channel110A. Increase in cooling performance due to the increase in flow speed compensates the decrease in cooling performance due to the rise in temperature. It is thus possible to more uniformly cool the plurality of cylinders10-ialso on the side of the first side wall11. As a result, variation in temperature between the plurality of cylinders10-iis suppressed.

FIG. 10is a schematic diagram for explaining a configuration of the cooling channel100according to a third embodiment. In particular,FIG. 10shows a configuration of the cooling channel100on the side of the second side wall12, as in the case ofFIG. 6in the first embodiment. An overlapping description with the first embodiment will be omitted as appropriate.

As shown inFIG. 10, the cooling channel100further includes an inter-cylinder channel140(a drill path) arranged between adjacent cylinders10. The inter-cylinder channel140is provided for cooling a part between the adjacent cylinders10. The inter-cylinder channel140is connected to the second outer channel120B through a connection hole150. As a result, the second cooling medium CB with the high cooling performance is supplied from the second outer channel120B to the inter-cylinder channel140. The part between the adjacent cylinders10is effectively cooled by the second cooling medium CB with the high cooling performance.

It should be noted that it is also possible to combine the second embodiment and the third embodiment.