JP2024050163A - piston - Google Patents

Abstract

To strengthen gas flow within a combustion chamber.
[Solution] The piston has a piston body including a central body portion in which an accommodation recess that opens to the crown surface side is formed, and an outer peripheral body portion in which a flange surrounding the opening of the accommodation recess and an annular crown surface are formed. The piston has a movable member that is accommodated in the accommodation recess, has a central crown surface exposed from the opening, and is movable between a first position in contact with the flange and a second position away from the flange. The piston has a spring member provided between the piston body and the movable member, and biases the movable member toward the first position. When the movable member is moved to the first position, the annular crown surface and the central crown surface are continuous with each other.
[Selected figure] Figure 5

Description

The present invention relates to a piston that is assembled into an engine.

A piston that defines a combustion chamber is attached to the cylinder of the engine (see Patent Documents 1 to 4). In order to effectively combust the air-fuel mixture in the combustion chamber, it is important to generate a gas flow, such as a tumble flow, within the combustion chamber.

JP 2000-136724 A JP 2007-224787 A JP 2013-44278 A JP 2014-43839 A

By the way, by generating a gas flow such as a tumble flow within the combustion chamber, it is possible to shorten the combustion period of the mixture and increase the thermal efficiency of the engine, but there is a demand for further improvement in this engine thermal efficiency. In other words, there is a demand for further strengthening of the gas flow within the combustion chamber in order to achieve a further improvement in engine thermal efficiency.

The object of the present invention is to enhance gas flow within the combustion chamber.

A piston according to one embodiment is a piston to be assembled in an engine, and includes a piston body including a central body portion in which a storage recess that opens to the crown surface side is formed, and an outer peripheral body portion in which a flange surrounding the opening of the storage recess and an annular crown surface are formed; a movable member that is housed in the storage recess and has a central crown surface exposed from the opening, and is movable between a first position in contact with the flange and a second position away from the flange; and a spring member that is provided between the piston body and the movable member and biases the movable member toward the first position, and when the movable member is moved to the first position, the annular crown surface and the central crown surface are continuous with each other.

According to one aspect of the present invention, when the movable member is in the first position, the annular crown surface and the central crown surface are continuous with each other. This enhances the gas flow in the combustion chamber.

FIG. 1 is a diagram illustrating an example of a vehicle equipped with an engine. FIG. 1 is a diagram illustrating an example of an engine. FIG. 2 is a diagram showing a combustion chamber of an engine and its vicinity. FIG. 4 is a diagram showing the piston as viewed from the direction of arrow α in FIG. 3 . FIG. FIG. FIG. 4 is a cross-sectional view showing the piston in an exploded state. 4A and 4B are diagrams illustrating the position of a movable head during a compression stroke and an expansion stroke. 4 is a diagram showing an example of the flow direction of intake air in a combustion chamber. FIG. 4 is a diagram showing an example of the flow direction of intake air in a combustion chamber. FIG. 1A and 1B are diagrams illustrating an example of a situation in which an intake valve or an exhaust valve comes into contact with a piston. FIG. 1 is a diagram illustrating an example of a situation in which abnormal combustion occurs. FIG. 11 is a diagram showing the position of a movable head during a compression stroke and an expansion stroke as another embodiment 1. FIG. 11 is a cross-sectional view showing a piston according to another embodiment 2. FIG. 11 is a cross-sectional view showing a piston according to another embodiment 3.

The following describes in detail an embodiment of the present invention with reference to the drawings. In the following description, identical or substantially identical configurations and elements are designated by the same reference numerals and repeated description will be omitted.

[vehicle]
FIG. 1 is a diagram showing an example of a vehicle 11 equipped with an engine 10. As shown in FIG. 1, the vehicle 11 is equipped with a power unit 12 equipped with the engine 10. Wheels 16 are connected to an output shaft 13 of the power unit 12 via a propeller shaft 14 and a differential mechanism 15. The illustrated power unit 12 is a power unit for rear-wheel drive, but is not limited thereto, and may be a power unit for front-wheel drive or all-wheel drive. In addition, as described later, the illustrated engine 10 is a horizontally opposed engine, but is not limited thereto, and may be, for example, an in-line engine, a V-type engine, or a single-cylinder engine.

[engine]
FIG. 2 is a diagram showing an example of an engine 10. As shown in FIG. 2, the engine 10 has a cylinder block 20 constituting one cylinder bank, a cylinder block 21 constituting the other cylinder bank, and a crankshaft 22 supported by the pair of cylinder blocks 20, 21. A cylinder head 24 having a valve mechanism 23 and the like is attached to each of the cylinder blocks 20, 21. Intake ports 26 communicating with combustion chambers 25 are formed in the cylinder heads 24, and intake valves 27 for opening and closing the intake ports 26 are attached to the cylinder heads 24. Exhaust ports 28 communicating with the combustion chambers 25 are formed in the cylinder heads 24, and exhaust valves 29 for opening and closing the exhaust ports 28 are attached to the cylinder heads 24. An ignition plug (not shown) for igniting the air-fuel mixture in the combustion chambers 25 is provided in the cylinder head 24, and an injector (not shown) for injecting fuel toward the intake air is provided in the cylinder head 24.

A cylinder bore 30 is formed in each cylinder block 20, 21, and a piston 31 is housed in each cylinder bore 30. In this manner, a piston 31, which is one embodiment of the present invention, is assembled to the cylinder blocks 20, 21 of the engine 10. A piston pin 32 is attached to this piston 31, and a small end 34 of a connecting rod 33 is connected to the piston pin 32. In addition, a crank pin 36 that is eccentric with respect to the crank journal 35 is provided on the crankshaft 22, and a large end 37 of the connecting rod 33 is connected to the crank pin 36. In this manner, the crankshaft 22 and the piston 31 are connected to each other via the connecting rod 33.

[piston]
Fig. 3 is a diagram showing the combustion chamber 25 of the engine 10 and its vicinity, and Fig. 4 is a diagram showing the piston 31 as viewed from the direction of the arrow α in Fig. 3. Figs. 5 and 6 are cross-sectional views showing the piston 31, and Fig. 7 is a cross-sectional view showing the piston 31 in an exploded state. Figs. 5 and 6 show a cross-section of the piston 31 taken along line A1-A1 in Fig. 4 and a cross-section of the piston 31 taken along line A2-A2 in Fig. 4. Fig. 5 shows a state in which the movable head 42 has been moved to the forward position, and Fig. 6 shows a state in which the movable head 42 has been moved to the backward position.

As shown in FIG. 3, the combustion chamber 25 is defined by the cylinder bore 30, the piston 31, and the cylinder head 24. As shown in FIGS. 4 to 7, the piston 31 has a piston body 41 in which an accommodating recess 40 is formed, and a movable head (movable member) 42 accommodated in the accommodating recess 40 of the piston body 41. A disc spring (spring member) 43 is accommodated in the accommodating recess 40 of the piston body 41, and this disc spring 43 is disposed between the piston body 41 and the movable head 42. In order to accommodate the movable head 42 and disc spring 43 in the accommodating recess 40, the piston body 41 has a split structure that is split at a predetermined portion. For example, by splitting the piston body 41 into two at the portion indicated by the dashed line β in FIG. 5, it is possible to accommodate the movable head 42 and disc spring 43 in the accommodating recess 40 of the piston body 41.

As shown in FIG. 7, the piston body 41 is composed of a central body portion 44 provided at the center of the piston and an outer circumferential body portion 45 provided radially outward of the central body portion 44. The central body portion 44 of the piston body 41 is formed with a housing recess 40 that opens toward the piston crown surface (crown surface) 46, and a pin boss portion 47 for inserting the piston pin 32 is formed. The outer circumferential body portion 45 of the piston body 41 is formed with an inner flange (flange) 48 and an annular crown surface 49 that surround the opening 40o of the housing recess 40. The outer circumferential body portion 45 of the piston body 41 is formed with a land portion 51 to which the piston ring 50 is attached, and a skirt portion 52 that slidably contacts the inner circumferential surface of the cylinder bore 30. The inner flange 48 of the outer circumferential body portion 45 is formed by extending radially inward from the land portion 51. The piston crown surface 46 is also called the piston top surface, piston upper surface, or piston head.

The movable head 42 of the piston 31 has a disk-shaped head body 61 on which a central crown surface 60 is formed, and an outer flange 62 that extends radially outward from the head body 61. The movable head 42 is accommodated in the accommodation recess 40 of the piston body 41, and the central crown surface 60 of the movable head 42 is exposed from the opening 40o of the accommodation recess 40. In addition, an annular seal 63 is attached to the outer peripheral surface 61a of the head body 61, and the gap between the outer peripheral surface 61a of the head body 61 and the inner peripheral surface 48a of the inner flange 48 facing it is sealed by the annular seal 63. Furthermore, the movable head 42 accommodated in the accommodation recess 40 is movable along the piston center line CL. That is, the movable head 42 is movable between a forward position (first position) where the outer flange 62 contacts the inner flange 48 as shown in FIG. 5, and a backward position (second position) where the outer flange 62 separates from the inner flange 48 as shown in FIG. 6.

As shown in FIG. 5, a disc spring 43 is provided between the piston body 41 and the movable head 42, so that the movable head 42 is biased to the forward position by the spring force of the disc spring 43. On the other hand, as shown in FIG. 6, when a thrust force Fa exceeding a predetermined value acts on the movable head 42, the movable head 42 moves to the backward position against the spring force of the disc spring 43. Here, FIG. 8 is a diagram showing the position of the movable head 42 in the compression stroke and the expansion stroke. As shown in FIG. 8, the spring force of the disc spring 43 is set so that the movable head 42 maintains the forward position in both the compression stroke and the expansion stroke. In other words, even when the cylinder pressure in the compression stroke acts on the movable head 42, that is, when the cylinder pressure that rises due to the compression of the intake air acts on the movable head 42, the movable head 42 is maintained in the forward position by the spring force of the disc spring 43. In addition, even when the cylinder pressure during the expansion stroke acts on the movable head 42, that is, when the cylinder pressure that rises due to the combustion of the air-fuel mixture acts on the movable head 42, the movable head 42 is held in the forward position by the spring force of the disc spring 43.

As shown in Figures 4 and 5, when the movable head 42 of the piston 31 is moved to the forward position, the annular crown surface 49 of the piston body 41 and the central crown surface 60 of the movable head 42 are continuous with each other. In other words, there is no step between the annular crown surface 49 and the central crown surface 60, and the annular crown surface 49 and the central crown surface 60 are smoothly connected. In other words, the annular crown surface 49 and the central crown surface 60 are flush with each other without any step. In addition, the annular crown surface 49 and the central crown surface 60 are flat surfaces without any valve recesses. In this way, when the movable head 42 of the piston 31 is moved to the forward position, the piston crown surface 46 consisting of the annular crown surface 49 and the central crown surface 60 is a smooth flat surface without any unevenness. The valve recess is a recess formed in the piston crown surface to avoid contact with the intake valve 27 and the exhaust valve 29.

[Gas flow]
Next, the gas flow of the air-fuel mixture in the combustion chamber 25 will be described. Figures 9 and 10 are diagrams showing an example of the flow direction of intake air in the combustion chamber 25. As shown by the arrow Fa in Figure 9, during the intake stroke of the engine 10, most of the intake air flows into the gap G between the intake port 26 and the intake valve 27, and a tumble flow Ft, which is a vertical vortex gas flow, is generated in the cylinder bore 30. Then, as shown in Figure 10, the tumble flow Ft is maintained in the combustion chamber 25 even at the end of the compression stroke when the piston 31 reaches near the top dead center.

As described above, even at the end of the compression stroke, the movable head 42 of the piston 31 is held in the forward position, and the piston crown surface 46 is a smooth flat surface without any irregularities. As a result, even when the tumble flow Ft comes into contact with the piston crown surface 46, as shown by symbols X1 and X2 in Figures 9 and 10, the momentum of the tumble flow Ft can be maintained because the piston crown surface 46 is a flat surface without a valve recess. As a result, even at the end of the compression stroke, a strong tumble flow Ft can be generated in the combustion chamber 25, improving the combustion efficiency of the mixture and the thermal efficiency of the engine 10.

[Fail-safe]
As described above, the piston crown surface 46 consisting of the annular crown surface 49 and the central crown surface 60 is a flat surface on which no valve recess is formed, and therefore it is possible to strengthen gas flow such as tumble flow. However, removing the valve recess from the piston crown surface 46 causes the piston 31 to approach the intake valve 27 and the exhaust valve 29. For this reason, in the unlikely event that a malfunction of the variable valve mechanism causes a deviation in valve timing, there is a risk that the intake valve 27 and the exhaust valve 29 will come into contact with the piston 31. However, since the piston 31 is provided with the movable head 42 in a movable manner, it is possible to prevent excessive damage to the engine 10 even if the intake valve 27 and the exhaust valve 29 come into contact with the piston 31.

Figure 11 shows an example of a situation in which the intake valve 27 and exhaust valve 29 come into contact with the piston 31. As shown by symbol X3 in Figure 11, even if the intake valve 27 comes into contact with the movable head 42 of the piston 31, the intake valve 27 pushes in the movable head 42, so excessive damage to the intake valve 27 and piston 31 can be prevented. Also, as shown by symbol X4 in Figure 11, even if the exhaust valve 29 comes into contact with the movable head 42 of the piston 31, the exhaust valve 29 pushes in the movable head 42, so excessive damage to the exhaust valve 29 and piston 31 can be prevented.

[Abnormal Combustion]
In addition, since the movable head 42 is movably provided on the piston 31, even if abnormal combustion such as knocking or pre-ignition occurs, damage to engine parts due to such abnormal combustion can be avoided. Here, Fig. 12 is a diagram showing an example of a situation in which abnormal combustion occurs. As shown by the symbol X5 in Fig. 12, when the pressure inside the cylinder rises suddenly due to abnormal combustion such as knocking, the movable head 42 is pushed to the retracted position by the increased pressure inside the cylinder. This makes it possible to increase the volume of the combustion chamber 25 and reduce the pressure inside the cylinder, thereby avoiding damage to engine parts due to abnormal combustion such as knocking.

[Another embodiment 1]
In the above description, the movable head 42 is held in the forward position during both the compression stroke and the expansion stroke, but this is not limited thereto, and the movable head 42 may be moved to the backward position during the expansion stroke. Here, Fig. 13 is a diagram showing the position of the movable head 42 during the compression stroke and the expansion stroke as another embodiment 1. In Fig. 13, the same parts and members as those shown in Fig. 8 are denoted by the same reference numerals, and their description will be omitted.

As shown in FIG. 13, the spring force of the disc spring 70, which is a spring member, may be set so as to hold the movable head 42 in the forward position during the compression stroke and move the movable head 42 to the retracted position during the expansion stroke. That is, when the cylinder pressure during the compression stroke acts on the movable head 42, that is, when the cylinder pressure that rises due to the compression of the intake air acts on the movable head 42, the movable head 42 is held in the forward position by the spring force of the disc spring 70. Also, when the cylinder pressure during the expansion stroke acts on the movable head 42, that is, when the cylinder pressure that rises due to the combustion of the air-fuel mixture acts on the movable head 42, the movable head 42 moves from the forward position to the retracted position against the spring force of the disc spring 70.

In this way, even if the movable head 42 is moved to the retreated position during the expansion stroke, the movable head 42 is held in the advanced position during the compression stroke, so that the tumble flow in the combustion chamber 25 can be strengthened. In other words, as shown in Figures 9 and 10, a strong tumble flow Ft can be maintained in the combustion chamber 25 even at the end of the compression stroke, and the combustion efficiency of the air-fuel mixture can be improved, thereby improving the thermal efficiency of the engine 10.

[Other embodiments 2 and 3]
In the example shown in Fig. 5, the annular crown surface 49 and the central crown surface 60 are formed as flat surfaces, but the present invention is not limited thereto, and the annular crown surface 49 and the central crown surface 60 may be formed as curved surfaces. Fig. 14 is a cross-sectional view showing a piston 80 according to another embodiment 2, and Fig. 15 is a cross-sectional view showing a piston 90 according to another embodiment 3. Note that Figs. 14 and 15 show cross sections cut at the same portions as in Fig. 5. In Figs. 14 and 15, portions and members similar to those shown in Fig. 5 are denoted by the same reference numerals, and description thereof will be omitted.

14, the piston 80 has a piston body 81 in which a storage recess 40 is formed, and a movable head (movable member) 82 that is stored in the storage recess 40 of the piston body 41. The annular crown surface 83 of the piston body 81 and the central crown surface 84 of the movable head 82 are formed as convex curved surfaces that do not have valve recesses. As shown in the figure, when the movable head 82 of the piston 80 is moved to the forward position, the annular crown surface 83 of the piston body 81 and the central crown surface 84 of the movable head 82 are continuous with each other. In other words, there is no step between the annular crown surface 83 and the central crown surface 84, and the annular crown surface 83 and the central crown surface 84 are smoothly connected. In other words, the annular crown surface 83 and the central crown surface 84 are flush with each other without any steps. In this way, when the movable head 82 of the piston 80 is moved to the forward position, the piston crown surface (crown surface) 85 consisting of the annular crown surface 83 and the central crown surface 84 is a smooth curved surface without any unevenness.

In this way, even if the piston crown surface 85 consisting of the annular crown surface 83 and the central crown surface 84 is a curved surface without a valve recess, it is possible to strengthen the tumble flow in the combustion chamber 25. In other words, even if the tumble flow comes into contact with the piston crown surface 85, the momentum of the tumble flow can be maintained because the piston crown surface 85 is a curved surface without a valve recess. This makes it possible to generate a strong tumble flow in the combustion chamber 25 even at the end of the compression stroke, thereby increasing the combustion efficiency of the mixture and improving the thermal efficiency of the engine 10.

15, the piston 90 has a piston body 91 in which a storage recess 40 is formed, and a movable head (movable member) 92 that is stored in the storage recess 40 of the piston body 41. The annular crown surface 93 of the piston body 91 and the central crown surface 94 of the movable head 92 are formed as concave curved surfaces that do not have a valve recess. As shown in the figure, when the movable head 92 of the piston 90 is moved to the forward position, the annular crown surface 93 of the piston body 91 and the central crown surface 94 of the movable head 92 are continuous with each other. In other words, there is no step between the annular crown surface 93 and the central crown surface 94, and the annular crown surface 93 and the central crown surface 94 are smoothly connected. In other words, the annular crown surface 93 and the central crown surface 94 are flush with each other without any step. In this way, when the movable head 92 of the piston 90 is moved to the forward position, the piston crown surface (crown surface) 95 consisting of the annular crown surface 93 and the central crown surface 94 is a smooth curved surface without any unevenness.

In this way, even if the piston crown surface 95 consisting of the annular crown surface 93 and the central crown surface 94 is a curved surface without a valve recess, it is possible to strengthen the tumble flow in the combustion chamber 25. In other words, even if the tumble flow comes into contact with the piston crown surface 95, the momentum of the tumble flow can be maintained because the piston crown surface 95 is a curved surface without a valve recess. This makes it possible to generate a strong tumble flow in the combustion chamber 25 even at the end of the compression stroke, thereby increasing the combustion efficiency of the mixture and improving the thermal efficiency of the engine 10.

The present invention is not limited to the above-described embodiment, and can be modified in various ways without departing from the spirit of the present invention. The engine 10 shown in the figure is an engine mounted on a vehicle 11, but the present invention is not limited to this, and the pistons 31, 80, and 90 of the present invention may be applied to engines used as power sources for other devices, etc. In addition, the engine 10 shown in the figure is a gasoline engine that uses gasoline as fuel, but the present invention is not limited to this, and the pistons 31, 80, and 90 of the present invention may be applied to engines that use diesel, hydrogen, or other fuels. In addition, in order to further strengthen the tumble flow in the combustion chamber 25, a tumble valve that controls the flow direction of the intake air may be attached to the cylinder head 24.

In the above description, the gas flow is enhanced by a tumble flow, which is a swirling flow around an axis perpendicular to the central axis of the cylinder bore, but this is not limited to this, and a swirl flow, which is a swirling flow around the central axis of the cylinder bore, may also be enhanced. In the illustrated example, two disc springs 43 are used, but this is not limited to this, and one disc spring may be used, or three or more disc springs may be used. In the above description, disc springs 43 are used as the spring member, but this is not limited to this, and a compression coil spring may be used as the spring member.

10 Engine 31 Piston 40 Storage recess 40o Opening 41 Piston body 42 Movable head (movable member)
43 Disc spring (spring member)
44 Central body portion 45 Outer circumferential body portion 46 Piston crown surface (crown surface)
48 Inner flange (flange)
49 Annular crown surface 60 Central crown surface 70 Disc spring (spring member)
80 Piston 81 Piston body 82 Movable head (movable member)
83 Annular crown surface 84 Central crown surface 85 Piston crown surface (crown surface)
90 Piston 91 Piston body 92 Movable head (movable member)
93 Annular crown surface 94 Central crown surface 95 Piston crown surface (crown surface)

Claims (4)

A piston to be assembled into an engine,
a piston body including a central body portion having an accommodating recess that opens to a crown surface side, and an outer peripheral body portion having a flange surrounding an opening of the accommodating recess and an annular crown surface;
a movable member that is accommodated in the accommodation recess, has a central crown surface exposed from the opening, and is movable between a first position in contact with the flange and a second position away from the flange;
a spring member provided between the piston body and the movable member and configured to bias the movable member toward the first position;
having
When the movable member is moved to the first position, the annular crown surface and the central crown surface are continuous with each other.
piston. 2. The piston according to claim 1,
The annular crown surface and the central crown surface are flat surfaces on which no valve recesses are formed.
piston. 2. The piston according to claim 1,
The annular crown surface and the central crown surface are curved surfaces in which no valve recess is formed.
piston. 2. The piston according to claim 1,
The spring member holds the movable member at the first position even when the cylinder internal pressure during the compression stroke acts on the central crown surface.
piston.

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