JP7310175B2 - engine - Google Patents

Description

The present disclosure relates to engines.

Conventionally, in an engine, intake air flows into a cylinder from an intake port. The intake port is provided with an intake valve that opens and closes the intake port. In the case of a structure in which the intake valve is in contact with the extension of the cylinder, a valve recess is provided at the upper end of the cylinder in order to avoid interference between the cylinder and the intake valve (for example, Patent Document 1).

JP-A-2002-188509

By the way, in the case of adopting a structure in which the intake valve is located inside the extension line of the cylinder, when the intake valve lifts into the combustion chamber, if the gap between the intake valve and the cylinder is small, the amount of air flowing into the combustion chamber cannot be secured. Sometimes I can't. In such a case, there is a problem that the amount of air flowing into the cylinder is reduced and the combustion efficiency is lowered.

An object of the present disclosure is to provide an engine capable of increasing the amount of air flowing into a cylinder and improving combustion efficiency in view of such problems.

In order to solve the above problems, an engine according to one aspect of the present disclosure includes a cylinder in which a combustion chamber is formed, a cylinder head connected to an upper end of the cylinder, an intake air formed in the cylinder head and communicating with the combustion chamber. a port, an intake valve that opens and closes the intake port, and a recess that is formed on the inner peripheral surface of the cylinder at a position that is separated from the upper end and faces the valve body of the intake valve and that is recessed radially outward of the cylinder. , the intake port has a bearing surface that expands in diameter toward the combustion chamber at the end that communicates with the combustion chamber, and the recess extends along the axial direction of the cylinder passing through the center position of the cylinder and the center position of the intake valve. On a plane, it is formed at the intersection where the extension of the bearing surface and the inner peripheral surface of the cylinder intersect, or at the lower end side of the cylinder from the intersection .

The recess may be curved along the axial direction.

The radial depth of the recess may be half or less of the lift amount of the intake valve.

According to the present disclosure, it is possible to increase the amount of air flowing into the cylinder and improve the combustion efficiency.

It is a figure which shows the schematic structure of an engine. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1; It is a figure explaining the shape of an intake hollow part. It is a figure explaining the intake hollow part of a modification.

Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding, and do not limit the present disclosure unless otherwise specified. In this specification and the drawings, elements having substantially the same functions and configurations are denoted by the same reference numerals, thereby omitting redundant description. Illustrations of elements that are not directly related to the present disclosure are omitted.

FIG. 1 is a diagram showing a schematic configuration of engine 100. As shown in FIG. As shown in FIG. 1 , engine 100 includes cylinder block 102 , cylinder head 104 and piston 106 . Cylinder head 104 is connected to the upper end of cylinder block 102 . The engine 100 is a Miller cycle gas engine that obtains power by burning fuel gas. However, the engine 100 may not be a gas engine as long as it is a reciprocating engine.

A cylinder liner 102 a is press-fitted or cast into the cylinder block 102 . A cylinder 102b is formed by the inner peripheral surface of the cylinder liner 102a. The cylinder liner 102a may not be provided, and the cylinder block 102 may form the cylinder 102b. A piston 106 is accommodated in the cylinder 102b.

A combustion chamber 108 is formed inside the cylinder 102b. Combustion chamber 108 is surrounded by cylinder liner 102 a (cylinder 102 b ), cylinder head 104 and crown surface 106 a of piston 106 .

Two intake ports 110 and two exhaust ports 112 are formed in the cylinder head 104 . Any number of intake ports 110 and exhaust ports 112 may be provided, for example, one each may be formed.

Intake port 110 and exhaust port 112 communicate with combustion chamber 108 . An intake valve 114 is provided in the intake port 110 . The intake valve 114 is supported by the cylinder head 104 so as to be slidable along the axial direction of the cylinder 102b. Intake valve 114 opens and closes a communication port of intake port 110 with combustion chamber 108 .

An exhaust valve 116 is provided in the exhaust port 112 . The exhaust valve 116 is supported by the cylinder head 104 so as to be slidable along the axial direction of the cylinder 102b. The exhaust valve 116 opens and closes the communication port of the exhaust port 112 with the combustion chamber 108 .

The intake valve 114 and the exhaust valve 116 are arranged so that they are all positioned radially inward of the inner peripheral surface of the cylinder 102b. In other words, the intake valve 114 and the exhaust valve 116 are provided at positions that do not interfere with the cylinder 102b even if they slide along the axial direction of the cylinder 102b.

A mixture of air (intake) and fuel gas is introduced to the intake port 110 . The air-fuel mixture enters combustion chamber 108 via intake port 110 . The exhaust discharged from the combustion chamber 108 to the exhaust port 112 is discharged to the outside through the exhaust port 112 .

A communication passage 118 that communicates with the combustion chamber 108 is formed in the cylinder head 104 . The communication passage 118 communicates with a sub-combustion chamber (not shown). The secondary combustion chamber is located, for example, on the opposite side of the piston 106 with respect to the combustion chamber 108 . However, as long as the combustion chamber 108 and the sub-combustion chamber communicate with each other, the sub-combustion chamber is not limited to this arrangement. Also, the number of sub-combustion chambers is not limited.

Engine 100 is, for example, a four-cycle engine. During the intake stroke, the piston 106 moves toward bottom dead center. Also, the intake valve 114 is opened and the exhaust valve 116 is closed. A mixture of fuel gas and air enters combustion chamber 108 through intake port 110 .

During the compression stroke, the piston 106 moves toward top dead center. Also, the intake valve 114 and the exhaust valve 116 are closed. The air-fuel mixture compressed by piston 106 is led from combustion chamber 108 to the sub-combustion chamber.

In the expansion (explosion) stroke, the air-fuel mixture in the sub-combustion chamber is ignited by an ignition device (not shown), and flame is ejected into the combustion chamber 108 . The air-fuel mixture is combusted in the combustion chamber 108, and the piston 106 is pushed toward the bottom dead center.

During the exhaust stroke, the piston 106 moves toward top dead center. Also, the intake valve 114 is closed and the exhaust valve 116 is opened. Exhaust gases exit combustion chamber 108 through exhaust port 112 .

By the way, in the engine 100, it is desired to increase the amount of air flowing into the cylinder 102b and improve the combustion efficiency. Therefore, in the engine 100, a recess is formed in the inner peripheral surface of the cylinder 102b. In addition, below, the recessed portion facing the intake valve 114 is referred to as an intake recessed portion 120a. Also, the hollow portion facing the exhaust valve 116 is referred to as an exhaust hollow portion 120b.

FIG. 2 is a sectional view taken along line II-II of FIG. Note that the cylinder block 102 is omitted in FIG. As shown in FIGS. 1 and 2, the intake recess 120a is provided at a position facing the valve body 114a of the intake valve 114 in the radial direction of the cylinder 102b. The exhaust recess portion 120b is provided at a position facing the valve body 116a of the exhaust valve 116 in the radial direction of the cylinder 102b. Two intake recessed portions 120a and two exhaust recessed portions 120b are provided.

As shown in FIG. 1, the intake recess 120a and the exhaust recess 120b are formed at positions spaced apart from the upper end of the cylinder 102b by a predetermined distance. The intake recessed portion 120a and the exhaust recessed portion 120b are recessed radially outward from the inner peripheral surface side of the cylinder 102b.

As shown in FIG. 2, the intake recesses 120a are formed in a predetermined range on both sides of the cylinder 102b in the circumferential direction with reference to the position closest to the valve element 114a of the intake valve 114 in the cylinder 102b. The exhaust recessed portion 120b is formed in a predetermined range on both sides in the circumferential direction of the cylinder 102b with reference to the position closest to the valve body 116a of the exhaust valve 116 in the cylinder 102b.

The detailed shape of the intake recess 120a will be described below. Since the exhaust recess 120b has the same shape as the intake recess 120a, the description thereof will be omitted.

FIG. 3 is a diagram for explaining the shape of the intake recess 120a. 3 is a cross-sectional view along the axial direction passing through the center position of the cylinder 102b and the center position of the intake valve 114 (communication port of the intake port 110). In FIG. 3, the closed intake valve 114 is indicated by a solid line, and the intake valve 114 lifted to the lowest position is indicated by a dashed line.

As shown in FIG. 3, a communication port of the intake port 110 is provided with a valve seat 110a. The valve seat 110a is formed with a seat surface 110b that is inclined radially inward as the distance from the combustion chamber 108 increases (upward in FIG. 3). It should be noted that the intake port 110 may not be provided with the valve seat 110a, and the intake port 110 may be formed with the seat surface 110b. In other words, the intake port 110 has a bearing surface 110b that expands toward the combustion chamber 108 at the end that communicates with the combustion chamber 108 .

The intake valve 114 is formed with a valve body 114a having an enlarged diameter at the end on the combustion chamber 108 side. A contact surface 114b that contacts the valve seat 110a is formed on the valve body 114a. The contact surface 114b is inclined with respect to the axial direction at the same inclination angle as the seat surface 110b of the valve seat 110a.

The intake recessed portion 120a extends along an extension line L1 of the seat surface 110b and the inner wall surface of the cylinder 102b on an axial plane that passes through the center position of the cylinder 102b and the center position of the intake valve 114 (communication port of the intake port 110). is formed at the intersection point P1 with The intake recess 120a may be formed closer to the lower end of the cylinder 102b than the intersection point P1. In other words, the upper end of the intake recessed portion 120a is located at the intersection point P1 or at a position further away from the intake port 110 than the intersection point P1.

The lower end of the intake recessed portion 120a is positioned at the position P2 where the intake valve 114 is lifted to the lowest position in the axial direction, or at the lower end side of the cylinder 102b from the position P2.

The radial depth of the intake recess 120a is a length H2 that is less than half the lift amount H1 of the intake valve 114. As shown in FIG.

The intake recess 120a is curved along the axial direction of the cylinder 102b and has a bowl-shaped cross section. That is, the cross section of the intake recessed portion 120a has a curvature centered on the radially inner side of the cylinder 102b.

In engine 100, intake valve 114 is lifted downward to open intake port 110 during an intake stroke. Then, the air-fuel mixture is led to the combustion chamber 108 through between the valve seat 110 a of the intake port 110 and the valve body 114 a of the intake valve 114 . At this time, part of the air-fuel mixture passes between the valve body 114a of the intake valve 114 and the cylinder 102b.

Here, when the intake recess 120a is provided, the distance between the intake valve 114 and the cylinder 102b is larger than when the intake recess 120a is not provided.

By increasing the distance between the intake valve 114 and the cylinder 102b, the pressure loss when the air-fuel mixture flows into the combustion chamber 108 can be reduced. As a result, the intake recess portion 120a can increase the inflow amount (air amount) of the air-fuel mixture flowing into the combustion chamber 108, thereby improving the combustion efficiency. In addition, the intake recessed portion 120a can increase the expansion ratio with respect to the compression ratio due to the effect of increasing the amount of air, and can improve the thermal efficiency. This is particularly effective in the Miller cycle engine 100 because the timing at which the intake valve 114 closes is early (the lift amount is small).

Further, since the intake recessed portion 120a is curved along the axial direction, the air-fuel mixture passing through the intake recessed portion 120a flows along the wall surface of the intake recessed portion 120a. As a result, the intake recess 120a promotes a tumble flow that rotates the combustion chamber 108 in the vertical direction (axial direction). By promoting the tumble flow, the combustion propagation of the air-fuel mixture is promoted, so the intake recess 120a can improve the combustion efficiency.

In addition, the upper end of the intake hollow portion 120a is located at the intersection point P1 or on the lower end side of the intersection point P1. As a result, the air-fuel mixture flowing into the combustion chamber 108 from the intake port 110 is linearly guided to the intake recess 120a. Therefore, the intake recess 120a can rectify the flow of the air-fuel mixture in the combustion chamber 108. As shown in FIG. Further, the intake recess portion 120a can ensure a flow rate between the intake valve 114 and the cylinder 102b when the valve lift amount just before the intake valve 114 is closed is small.

Further, since the radial depth of the intake recess portion 120a is the length H2 which is half or less of the lift amount H1 of the intake valve 114, it is possible to suppress a decrease in the compression ratio.

Further, the provision of the exhaust recess 120b allows the distance between the exhaust valve 116 and the cylinder 102b to be larger than in the case where the exhaust recess 120b is not provided. As a result, the exhaust gas that is led from the combustion chamber 108 to the exhaust port 112 can be efficiently led to the exhaust port 112 with reduced pressure loss. Therefore, the exhaust recess portion 120b can reduce the amount of exhaust gas remaining in the combustion chamber 108 during the exhaust stroke, thereby improving combustion efficiency.

4A and 4B are diagrams illustrating an intake recess portion 220a of a modified example. In the embodiment described above, the cross section of the intake recessed portion 120a is formed in a bowl shape curved in the axial direction. However, as shown in FIG. 4, the cross-section of the intake recess 220a may be a non-curved rectangle. Similarly, the exhaust recess may also be rectangular in cross-section.

Although the embodiments have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such embodiments. It is obvious that a person skilled in the art can conceive of various modifications or modifications within the scope of the claims, and it is understood that these also belong to the technical scope.

For example, in the embodiments and modifications described above, a mixture of air and fuel gas flowed into the combustion chamber 108 from the intake port 110 . However, the air may flow into the combustion chamber 108 from the intake port 110 and the fuel gas may be directly injected into the combustion chamber 108 .

Further, in the above-described embodiment and modification, an auxiliary combustion chamber is provided, and the air-fuel mixture is ignited in the auxiliary combustion chamber. However, the auxiliary combustion chamber may not be provided and the mixture may be ignited in the combustion chamber 108 .

Further, in the above-described embodiment, the exhaust recess portion 120b is provided at a position facing the exhaust valve 116. As shown in FIG. However, the exhaust recess 120 b may not be formed at the position facing the exhaust valve 116 . That is, the exhaust recess 120b may not be formed in the cylinder 102b.

The present disclosure can be applied to engines.

100 Engine 102b Cylinder 104 Cylinder head 110 Intake port 114 Intake valve 120a Intake recess (recess)

Claims (3)

a cylinder in which a combustion chamber is formed;
a cylinder head connected to the upper end of the cylinder;
an intake port formed in the cylinder head and communicating with the combustion chamber;
an intake valve that opens and closes the intake port;
a recess formed on the inner peripheral surface of the cylinder at a position that is separated from the upper end and faces the valve body of the intake valve and that is recessed radially outward of the cylinder;
with
The intake port is
At the end communicating with the combustion chamber, a bearing surface that expands in diameter toward the combustion chamber is provided,
The recess is
An intersection point where the extension of the seat surface and the inner peripheral surface of the cylinder intersect on a plane along the axial direction of the cylinder passing through the center position of the cylinder and the center position of the intake valve, or from the intersection point is also formed on the lower end side of the cylinder . 2. An engine according to claim 1 , wherein said recessed portion is curved along the axial direction. 3. The engine according to claim 1 , wherein the radial depth of the recess is half or less of the lift amount of the intake valve.

Images